Climate change and crop production: foundations for agroecosystem resilience 9781315391830, 131539183X, 9781315391847, 1315391848, 9781315391854, 1315391856, 9781315391861, 1315391864, 9781138032347

Table of contents :
Content: Introduction: Set the stage / Noureddine Benkeblia, Rachel E. Schattman, Sarah Wiener, and Gabrielle Roesch-McNally --
Crop species responses and adaptation to rise in carbon dioxide and temperature / Noureddine Benkeblia and Charles A. Francis --
Physiological and morphological mechanisms mediating plant tolerance to osmotic stress: balancing tolerance and productivity / Md. Hasanuzzaman, Meixue Zhou and Sergey Shabala --
Physiological mechanisms of crops mediating defense response under elevated CO2 / Xin Li and Kai Shi --
Wild relative species and genetic engineering: improving crops in response to climate change / Noureddine Benkeblia --
Tropical crops and resilience to climate change / Noureddine Benkeblia, Melinda McHenry, Jake Crisp, and Philippe Roudier --
Climate change and resilience of agrosystems: mitigation through agroforestry, permaculture, and perennial polyculture systems / Noureddine Benkeblia and Donka Radeva --
Dynamics of crop production in a heterogeneous landscape: what are the opportunities for enhancing communal farmers' resilience to climate change impacts? / Munyaradzi Chitakira and Luxon Nhamo --
The pulse of pulses under climate change: from physiology to phenology / Archana Joshi-Saha and Kandali S. Reddy --
Diversifying agriculture with novel crop introductions to abandoned lands with suboptimal conditions / Sarah C. Davis, Jacqueline Kloepfer, Jesse A. Mayer and John C. Cushman --
Agroecology education to sustain resilient food production / Charles A. Francis, Tor Arvid Breland, Geir Hofgaard Lieblein, Anna Marie Nicolaysen.

Citation preview

Climate Change and Crop Production Foundations for Agroecosystem Resilience

Climate Change and Crop Production Foundations for Agroecosystem Resilience

Edited by

Noureddine Benkeblia

CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2019 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed on acid-free paper International Standard Book Number-13: 978-1-138-03234-7 (Hardback) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http:// www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Names: Benkeblia, Noureddine, editor. Title: Climate change and crop production : foundations for agroecosystem resilience / editor: Noureddine Benkeblia. Other titles: Advances in agroecology. Description: Boca Raton, FL : Taylor & Francis, 2018. | Series: Advances in agroecology Identifiers: LCCN 2018031117| ISBN 9781138032347 (hardback : alk. paper) | ISBN 9781315391854 (pdf) | ISBN 9781315391847 (epub) | ISBN 9781315391830 (mobi/kindle) Subjects: LCSH: Agricultural ecology. | Climatic change. Classification: LCC S589.7 .C55 2018 | DDC 577.4--dc23 LC record available at https://lccn.loc.gov/2018031117 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com

“The real threats of climate change are not those predicted by our models and scenarios, but those that are unpredictable” To my daughter Faten Zahra for her big passion for science

Contents Series Preface.....................................................................................................................................ix Preface...............................................................................................................................................xi Contributors.................................................................................................................................... xiii Chapter 1 Climate Change and Crop Production: Set the Stage for Resilience..................................................1 Noureddine Benkeblia, Rachel E. Schattman, Sarah Wiener, and Gabrielle Roesch-McNally Chapter 2 Crop Species Responses and Adaptation to Rise in Carbon Dioxide and Temperature.................. 19 Noureddine Benkeblia and Charles A. Francis Chapter 3 Physiological and Morphological Mechanisms Mediating Plant Tolerance to Osmotic Stress: Balancing Tolerance and Productivity.............................................................................................. 35 Md. Hasanuzzaman, Meixue Zhou, and Sergey Shabala Chapter 4 Physiological Mechanisms of Crops’ Mediating Defense Response under Elevated CO2............... 59 Xin Li and Kai Shi Chapter 5 Wild Relative Species and Genetic Engineering: Improving Crops in Response to Climate Change................................................................................................................................ 71 Noureddine Benkeblia Chapter 6 Tropical Crops and Resilience to Climate Change........................................................................... 83 Noureddine Benkeblia, Melinda McHenry, Jake Crisp, and Philippe Roudier Chapter 7 Climate Change and Resilience of Agroecosystems: Mitigation through Agroforestry, Permaculture, and Perennial Polyculture Systems......................................................................... 105 Noureddine Benkeblia and Donka Radeva Chapter 8 Dynamics of Crop Production in a Heterogeneous Landscape: What Are the Opportunities for Enhancing Communal Farmers’ Resilience to Climate Change Impacts?............................... 131 Munyaradzi Chitakira and Luxon Nhamo vii

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CONTENTS

Chapter 9 The Pulse of Pulses under Climate Change: From Physiology to Phenology................................ 143 Archana Joshi-Saha and Kandali S. Reddy Chapter 10 Diversifying Agriculture with Novel Crop Introductions to Abandoned Lands with Suboptimal Conditions................................................................................................................... 163 Sarah C. Davis, Jacqueline E. Kloepfer, Jesse A. Mayer, and John C. Cushman Chapter 11 Agroecology Education to Sustain Resilient Food Production...................................................... 173 Charles A. Francis, Tor Arvid Breland, Geir Lieblein, and Anna Marie Nicolaysen Index............................................................................................................................................... 187

Series Preface The reality of climate change confronts humankind more directly every day, with extremes in weather conditions becoming more the norm rather than only rare events. Global CO2 levels in the atmosphere continue to rise, and global shifts in temperature are becoming more evident. Weather seems to have become more unpredictable despite the advances in observation and forecasting. Farmers are especially susceptible to the vagaries of weather, from drought to floods, from high temperatures to frosts, and to pest and disease outbreaks associated with changing conditions. But farmers are also innovators, trying new varieties, inputs, and practices as they transition their farming systems for increased adaptability and resiliency. Professor Benkeblia provides the reader with many of the foundational elements researchers are currently using to provide farmers with more options to confront the challenges of climate change. Contributed chapters from around the world with different climates provide the reader with up-to-date examples of the approaches being taken to expand the ecological, physiological, morphological, and productive potential of a range of crop types. By understanding the mechanisms of plant resilience to climate change, not only can the productivity of an individual crop species be improved, but the opportunity for bringing resistance and resiliency to the entire agroecosystem is also increased. Multiple chapters deal with the basic ecophysiology of adaptation to increased drought stress, higher temperatures, elevated atmospheric CO2, and other stressors in the environment. Other chapters look more holistically at diverse farming systems, such as agroforestry and perennial polycultures, and how they can provide even greater resistance to change. Even the larger issue of climate change mitigation is dealt with in one chapter where moving carbon into biomass for bioenergy production can lessen the dependence on non-renewable fossil fuel. Ultimately, however, the success of any adaptive process to address climate change will depend on how well we develop education programs that provide the understanding of how climate change can impact our food systems. The chapter linking education and climate change does this. From the perspective of agroecology, this book provides a strong foundation for changing research and education programs so that they think and act beyond maximization of yields and instead build both the resistance and resilience that will be needed for the uncertain climate future ahead. Ultimately, these programs will help us move beyond the farm and reach all parts of the food system, creating the multiple elements of resilience we need for change to occur. Stephen R. Gliessman Professor Emeritus of Agroecology University of California, Santa Cruz

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Preface In the twenty-first century, our planet is experiencing profound and serious climatic, environmental, and socio-economic upheavals. The consequences will affect ecosystems, biodiversity, and food security of many countries, particularly in the developing countries, and everyone’s way of life. Among these upheavals, climate change may be the most serious threat affecting agroecosystems and global food security. One large challenge facing humanity is to understand the extent to which climates will change and the effects on ecosystem, particularly agroecosystem, resilience. The role of scientists will be to inform the search for strategies on how to mitigate these effects and ensure sustainability of food production systems. Because diverse impacts on agroecosystems are anticipated under a scenario of climate change, it is crucial to decipher how changing temperature and water availability will affect crop growth and productivity, and consequently the production of food. Also critical is the spatial distribution of change and how this will impact those with limited resources. Curbing, coping with, and mitigating change are all key factors that will shape the future severity of climate change impacts on agroecosystems and food production. To achieve these goals, radical and creative strategies such as permaculture, polycultures, agroforestry, crop-livestock mixed systems and crops diversification, soil management, water conservation and harvesting, and general enhancement of agrobiodiversity will likely strengthen resilience and sustainability of agroecosystems. Understanding features underlying agroecosystem resilience is the first challenge. This can provide a foundation and support integrative responses for designing adapted agroecosystems, building resilience into food systems, and developing smarter agriculture and novel strategies for climate-resilient agroecosystems. In this book, the authors describe responses of crops to climate change and examples of climate-resilient strategies for minimizing and mitigating its effects. The goal is to enhance and inform the search for resilience and sustainability of food production systems. Noureddine Benkeblia University of the West Indies Kingston, Jamaica

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Contributors Noureddine Benkeblia Department of Life Sciences The Biotechnology Centre University of the West Indies Kingston, Jamaica

Md. Hasanuzzaman School of Land and Food University of Tasmania Tasmania, Australia

Tor Arvid Breland Department of Plant Sciences Norwegian University of Life Sciences Ås, Norway

Department of Agronomy Faculty of Agriculture Sher-e-Bangla Agricultural University Dhaka, Bangladesh

Munyaradzi Chitakira Department of Environmental Sciences School of Ecological and Human Sustainability Gauteng, South Africa

Archana Joshi-Saha Nuclear Agriculture and Biotechnology Division Bhabha Atomic Research Centre and Homi Bhabha National Institute Mumbai, India

Jake Crisp Geography and Spatial Science School of Technology, Environments and Design University of Tasmania Newnham, Australia John C. Cushman Department of Biochemistry and Molecular Biology University of Nevada Reno, Nevada Sarah C. Davis Voinovich School of Leadership and Public Affairs Ohio University Athens, Ohio Charles A. Francis Department of Agronomy and Horticulture University of Nebraska Lincoln, Nebraska and Department of Plant Sciences Norwegian University of Life Sciences Ås, Norway

and

Jacqueline E. Kloepfer Voinovich School of Leadership and Public Affairs Ohio University Athens, Ohio Xin Li Key Laboratory of Tea Quality and Safety Control Ministry of Agriculture Tea Research Institute Chinese Academy of Agricultural Sciences Hangzhou, China Geir Lieblein Department of Plant Sciences Norwegian University of Life Sciences Ås, Norway Jesse A. Mayer Department of Biochemistry and Molecular Biology University of Nevada Reno, Nevada

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Melinda McHenry Geography and Spatial Science School of Technology, Environments and Design University of Tasmania Tasmania, Australia Luxon Nhamo International Water Management Institute Pretoria, South Africa Anna Marie Nicolaysen Department of Plant Sciences Norwegian University of Life Sciences Ås, Norway Donka Radeva Economics of Natural Resources Department (independent researcher) University of National and World Economy Sofia, Bulgaria Kandali S. Reddy Nuclear Agriculture and Biotechnology Division Bhabha Atomic Research Centre and Homi Bhabha National Institute Mumbai, India Gabrielle Roesch-McNally United States Department of Agriculture Forest Service and Northwest Climate Hub Corvallis, Oregon

CONTRIBUTORS

Philippe Roudier CIRED Campus du Jardin Tropical Nogent-sur-Marne Cedex, France Rachel E. Schattman University of Vermont Extension United States Department of Agriculture Forest Service and Northeast Climate Hub South Burlington, Vermont Sergey Shabala School of Land and Food University of Tasmania Tasmania, Australia Kai Shi Department of Horticulture Zhejiang University Hangzhou, China Sarah Wiener United States Department of Agriculture Forest Service and Southeast Climate Hub Raleigh, North Carolina Meixue Zhou School of Land and Food University of Tasmania Tasmania, Australia

CHapTer  1

Climate Change and Crop Production Set the Stage for Resilience Noureddine Benkeblia, Rachel E. Schattman, Sarah Wiener, and Gabrielle Roesch-McNally CONTENTS 1.1 Introduction...............................................................................................................................1 1.2 Background................................................................................................................................2 1.2.1 Driving Causes of Climate Change...............................................................................2 1.2.2 Direct and Indirect Effects of Climate Change on Cropping Systems.........................2 1.2.2.1 Effects of Climate Change on Agricultural Economies................................. 4 1.2.2.2 Socioeconomic Impacts of Climate Change on Agricultural Production...... 5 1.3 Climate Change Adaptation and Crop Production Agroecosystems........................................ 6 1.3.1 Technology and Development.......................................................................................7 1.3.2 Policy Mechanisms and Programs................................................................................8 1.3.3 Resilience in Agroecosystems.......................................................................................9 1.4 Future Directions and Research Priorities............................................................................... 10 1.5 Conclusions.............................................................................................................................. 11 References......................................................................................................................................... 12 1.1 INTRODUCTION According the Intergovernmental Panel on Climate Change (IPCC), climate change is defined as “any change in climate over time, whether due to natural variability or as a result of human activities” (IPCC 2007). The standard period over which climate-related variables (e.g., temperature, precipitation, and wind) are observed is 30 years. Because of agroecosystems’ inherent vulnerability to changes in weather patterns, climate change can have profound effects on these systems. While some effects of climate change may have positive implications in some regions and agricultural sectors, it is estimated that climate change will have a progressively negative net impact on global agriculture between now and the end of the century (Hatfield and Takle 2014; Went 1957). These impacts will likely challenge farmer livelihoods, rural agricultural communities, and global food security. In this chapter, we summarize the driving causes of climate change, as well as the effects that climate change currently has and will continue to have on cropping systems, socioeconomic factors, and agriculture and biodiversity in agroecosystems. We also discuss some climate change adaptation strategies relevant to agroecosystems including conservation practices, support for biodiversity, tools and technology development, and policies and programs used to mitigate climate risk. We will end

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with a review of agroecological resilience to climate change and propose some future research priorities to enable greater agroecosystem resilience in the future. 1.2 BACKGROUND 1.2.1  Driving Causes of Climate Change Global climate change is caused by the release and accumulation of greenhouse gas (GHG) emissions into the Earth’s atmosphere. The concentration of GHGs such as carbon dioxide (CO2), methane (NH4), nitrous oxide (N2O), and other trace gases influences how much heat is captured in the atmosphere, also known as the radiation balance of the Earth (Hardy 2003). This leads to several important changes at a global level: warming of the oceans, sea level rise, acidification of ocean water, an increase in average air temperatures, changes in minimum and maximum daily temperatures, and shifting precipitation patterns (IPCC 2014a,b). These changes are already occurring. For example, the second half of the twentieth century was notably the warmest on record at that time (Mann et al. 1999), and average temperatures continue to set records into the first half of the twenty-first century. Anthropogenic contributions to GHG emissions have dramatically increased since the Industrial Revolution, driven by both population growth and increasing industrialization (Crowley 2000; IPCC 2014a,b). As anthropogenic emissions have increased, positive feedback loops have accelerated the warming process. For example, a warmer atmosphere caused by increased GHG concentrations leads to increased amounts of water vapor, which contributes to further warming in addition to more extreme weather events (Archer 2007). A second example is when warming leads to thawing in arctic regions, which in turn releases previously captured sinks of methane and thus accelerates warming and release of additional NH4 (Walter et al. 2006). Due to these positive feedback cycles, if all human contributions to GHGs stopped today, climate change trends would continue for decades to come (Hansen et al. 2017). Agriculture, including crop and animal production systems, contributes to the total global anthropogenic GHG emission rates that drive modern climate change. Some estimates say that agricultural land use is responsible for up to 25%–33% of GHG emissions globally (Clark and Tilman 2017). Though overall GHG contributions from agriculture increased over the past 50 years, agricultural production increased at a greater rate, meaning that the contributions per unit of production have decreased. Per-unit reductions also vary significantly between global regions (Bennetzen et al. 2016). Additionally, not all agricultural sectors contribute equally to GHG emissions: in a recent review of agriculture in China, animal production systems were found to have a significantly higher carbon footprint than vegetable production systems, but there are notable variations within these systems depending on production approaches (e.g., open field versus greenhouse production) (Yue et al. 2017). 1.2.2  Direct and Indirect Effects of Climate Change on Cropping Systems Anthropogenic climate change is already altering biological systems, including plant and animal communities, on a global scale (Horton et al. 2014; Parmesan and Yohe 2002). This has both direct and indirect implications for agroecosystems and specifically for agricultural businesses and communities. Direct impacts include changes in average, minimum, and maximum temperatures, precipitation patterns, and frequency of extreme weather events. All of these changes are expected to lead to varying crop yield decreases in some, though not all, cropping systems, especially nearing the end of the twenty-first century (Hatfield et al. 2011). Temperature plays an especially important and complex role in crop yield, profitability, and food security. All plant species, including agricultural crops, have temperature thresholds above which they will not develop properly. For example, a 1°C

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increase in average temperature will lead to an 8%–10% decrease in corn yield and a 9% decrease in rice yield (Abrol and Ingram 1996). In addition to increasing average temperatures, climate change also leads to increasing minimum temperatures. The effects of increasing minimum temperatures on perennial crops (such as apples) can include early bud break in temperate regions, which can lead to yield decreases if a late frost follows. These crops require an accumulation of cold temperatures (i.e., chilling hours) in order to produce at rates that are profitable in commercial production systems (Hatfield and Takle 2014; Horton et al. 2014; Wolfe et al. 2008). Some annual crops are also affected by warming minimum temperatures. For example, warmer temperatures can lead to decreased rates of carbohydrate accumulation in corn crops and consequently lower yields (Ruiz-Vera et al. 2015; Wolfe et al. 2017). Meanwhile, increasing maximum temperatures can lead to lower marketable yields due to disruption of pollination and fruit development. For example, corn (Zea maize) experiences decreased pollen viability in temperatures above 35°C, and kernel growth can be delayed in temperatures above 30°C (Hatfield et al. 2011; Hatfield and Prueger 2015). Of course, temperature is not the only climate change factor that influences crop fitness, and changes in environmental conditions caused by climate change do not affect all crops equally. Crop responses to CO2, temperature, and precipitation changes vary, and these responses are further complicated by other differences such as crop family and variety, regional topography, and more (Cutforth et al. 2007; Hatfield et al. 2011; Morgan et al. 2005). For example, two groups of crop plants, C4 plants (i.e., grasses such as corn, sugarcane, amaranth, and many weeds) and C3 plants (i.e., beans, rice, wheat, potatoes), use different cellular processes for photorespiration (Ghannoum 2009; Hamilton et al. 2008; Sage and Pearcy 1987). Of the two, C4 plants are more efficient in high CO2 environments because they minimize photorespiration (Taylor et al. 2009; Ziska 2000, 2001). This makes C4 plants less sensitive to high ambient air temperature, while C3 plants are relatively more sensitive. As CO2 levels continue to rise, it is likely that C4 plants will experience preferential benefits, while C3 plants struggle to thrive. It has been found that the accumulated influence of temperature and precipitation since 2008 has already led to a decrease in median yields of four major food crops: soy, rice, maize, and wheat. Some exceptions include regional increases in these crops including Argentina (soy), China (rice and maize), and some parts of the United States (wheat). It is likely that these trends will continue into the future (Lobell and Gourdji 2012; Lobell et al. 2011). Indirect effects of climate change on agroecological systems also impact crop production. Lengthening growing seasons can disrupt plant and insect relationships, which can both decrease the harm to crops from herbivorous insects while also interrupting the benefits crops derive from pollinators (Hegland et al. 2009). Severe weather events (which will become more frequent and severe because of climate change) are important drivers of disease emergence in crops (Anderson et al. 2004). Since environmental factors (e.g., temperature, humidity, precipitation, and soil conditions) play a major role in plant pathology (Sutherst 1990), it is assumed that new plant diseases and increased severity of these diseases will be observed as weather patterns continue to shift over the coming decades (Elad and Pertot 2014; Pautasso et al. 2012). However, crop systems will be affected differently by infectious agents depending on host susceptibility to these diseases, the infection mechanisms, as well as the geographical distribution of these diseases (Chakraborty and Newton 2011; Luck et al. 2011; Elad and Pertot 2014). It is well established that climate change poses a serious threat to biodiversity on a global scale, specifically through the potential of climbing extinction rates (Heller and Zavaleta 2009; Thomas et al. 2004). On the regional scale, climate change also puts pressure on ecological communities, in some cases reducing biodiversity as species’ responses change through “time (e.g., phenology), space (e.g., range), and self (e.g., physiology)” (Altieri 1999; Bellard et al. 2012; Bolton and Brown 1980; Ehleringer et al. 1991). Evidence suggests that diversity in agroecological systems has a positive impact on crops both in terms of pest resistance and crop yield (Letourneau et al. 2011), but this relationship is threatened by the negative impacts of climate change on biodiversity. The loss of

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both global and local biodiversity is anticipated to have serious negative impact on agroecosystems in the future (Sala et al. 2000; Thomas et al. 2004). Because diversity (including biodiversity) is a well-established approach in production-oriented agroecological systems (Amekawa 2011; Lin 2011), further efforts to support biodiversity in these systems may have the added benefits of reducing harm caused by climate change. The direct and the indirect effects of climate change will likely manifest in heterogeneous ways depending on the region and characteristics of cropping systems. For example, increasing atmospheric CO2 concentrations and rising temperatures may cause shifts in thermal and moisture limits of different crops, which may be further complicated by increasing severity and persistence of regional droughts (García et al. 2015). The increased frequency and severity of heat stress would be compounded by the degree to which climate change influences changes in dispersal and range of pests, weeds, diseases, and changes in nutrient availability (Parry 1992). Clearly, climate change and the variation of meteorological factors such as warming temperatures and shifting precipitation patterns have important effects on crop production systems (Parry et al. 2004). Adapting agroecological systems to a changing climate is therefore of great importance (Schattman et al. 2018). 1.2.2.1  Effects of Climate Change on Agricultural Economies Climate change will affect the economies of countries around the globe, with the most direct impacts on those nations whose economies rely heavily on natural resources and agriculture. Three major agricultural economic concerns related to climate change exist. First, potential yield decreases because of climate change are of great concern. For example, predictions show that climate change will likely decrease the yields of rice, wheat, and corn in China by 36%, 18%, and 45%, respectively (Zhang et al. 2017). This will undoubtedly affect the international trade and prices of these staple foods around the globe. In the United States, projections show significant decreases in yield and associated economic declines in corn and soybeans, two crops widely grown in the Midwestern agricultural region (Burke and Emerick 2015). In Asia, models predict small effects on agricultural economies from a 1.5°C increase of temperature but an increase in economic damage with temperature increases of 3°C or more. Damages at this level are estimated at $84 billion USD, with India noted as the most vulnerable country in the region (Mendelsohn 2014). The second concern is the impact of shifting environmental conditions on global and national gross domestic product (GDP). Costinot et al. (2016) analyzed ten crops important to agriculture globally and found that current projected yield decreases will likely lead to a 0.25% reduction in global GDP. Importantly, this study also took into account several other factors that contribute to global and local economic impacts of climate change on agricultural production. These factors include, but are not limited to, the degree of elasticity in the world market between crop varieties or species (i.e., red wheat versus white wheat, both triticum species) and crop families (i.e., wheat versus rice). In the United States, Hsiang et al. (2017) found each 1°C increase in average temperature is associated with a 1.2% decrease in national GDP, with disproportionate negative economic impacts affecting the southern United States and slight increases in GDP expected for the Pacific Northwest and New England. Third, socioeconomic impacts of climate change include job loss in the agricultural sector (Mestre-Sanchís and Feijóo-Bello 2009). For example, the 2016 drought in the United States led to an estimated loss of 1,815 full and part-time agricultural jobs in the state of California. The ripple effects in agriculture-related sectors of the state economy broadened the job loss estimates to 4,700 full and part-time jobs (Medellín-Azuara et al. 2016), not including undocumented agricultural workers. A counter example to this is the long-term increase in earnings for workers in the agricultural sector following Hurricanes Katrina and Rita (which hit the U.S. Gulf Coast in 2005). A study conducted by the U.S. Census Bureau (Groen et al. 2016) found that agricultural wages increased by 12.3% by 2011. It is clear that short- and long-term agricultural employment and earning impacts associated

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with climate change require further study. It is likely that loss of jobs would likely have the greatest negative impact in countries that do not have robust social safety nets and those with high child to adult ratios (Hanna and Oliva 2016). However, there is not sufficient research on the employment and long-term earning impacts of climate change specific to agriculture, either in developed or developing countries. 1.2.2.2  Socioeconomic Impacts of Climate Change on Agricultural Production Climate change exacerbates “existing social, economic, political, and environmental trends, problems, issues, tensions, and challenges, and hence increases vulnerability of different regions” (Upadhyay 2016). Therefore, it is clear that climate vulnerability is not driven by climatic forces alone but is and will continue to be shaped by complex interactions between social, political, and economic factors. These factors have long provided structure to society, but they also drive vulnerability among certain populations, many of whom lack the political power or economic wealth required to respond to climatic changes (Ribot 2014). Two clear manifestations of these inequities are food insecurity and the livelihood stability of smallholder farmers. First, increased temperatures, changes in precipitation, and more extreme and variable weather driven by anthropogenic climate change will impact food security across the globe (Lipper et al. 2014). Food security is defined as “when all people at all times have physical, social, and economic access to sufficient, safe, and nutritious food to meet their dietary needs and food preferences for an active and healthy life” (Brown et al. 2015). The goal of food security is to establish food access, availability, and stability as a human right (Beuchelt and Virchow 2012; FAO 2006). However, the ability to achieve food security is influenced by complex interactions between social, ecological, political, and economic factors that vary across spatial, temporal, and human institutional scales and can be negatively influenced by global climate change dynamics. Overall, climate change is expected to have a negative impact on food security and food production (Brown et al. 2015). The effects of climate change will reverberate across local, regional, and global food supply and distribution systems driven by both acute and chronic impacts associated with increased temperatures and more extreme and variable precipitation events (e.g., from floods to longer periods of drought). With the world’s population likely growing to 9 billion people by mid-century (2050), it is clear that we will have to produce more food in both environmentally and socially sustainable ways (Godfray et al. 2010), with an emphasis on meeting the needs of the most marginalized and food insecure. These needs will be exacerbated by the challenges of climate change, which are expected to reduce the global food supply through decreased yield, resulting in decreased food availability and increased prices. In addition, it is probable that extreme weather events, increasing temperatures, and other shifts in weather patterns caused by climate change will lead to interruptions in transportation of agricultural commodities and inputs, reductions in food safety and storage (Ziska et al. 2016), and diminished nutritional value (Brown et al. 2015). Food insecurity also has broader physical and mental health impacts, with severe and notable effects in agricultural communities and low-resource households (Solanki 2016). Climate change has been shown to exacerbate chronic disease (Brown et al. 2015) and affect children’s academic performance in school (Jyoti et al. 2005), illustrating a cascading effect on social systems, from public health to education. Furthermore, climate change will disproportionately affect agricultural producers, particularly smallholder agrarian communities, who produce food for global markets and household subsistence, while many of whom did little to cause this climate change (Klinsky et al. 2017). Without support from outside organizations or programs, smallholder and subsistence agricultural producers, as well as migrant farmworkers, may be more vulnerable to climate change impacts due to their limited capacity to respond to changes. They lack access to capital for investing in changes to their production system or the ability to negotiate fair wages and safe and healthy working conditions.

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Contrary to this school of thought, some argue that smallholder farms are buffered from impacts, particularly because many of them deploy a high level of biodiversity in the management of their farms. Additionally, they are often more diversified in terms of what they produce and who they produce it for (e.g., household, local, and/or global markets) (Altieri et al. 2017). Despite the insulating effects of diversified systems, localized disasters that destroy smallholder farms can have serious impacts on food security in these communities. This is largely because smallholder farmers and their families lack resources to purchase food when local supplies are destroyed or temporarily unavailable (Méndez et al. 2010; Niles and Brown 2017). Second, residents of rural, place-based communities may find their ability to maintain their way of life challenged by the effects of climate change. This is especially true for those who may need to migrate in order to feed themselves and their communities but lack the resources and often the desire to relocate. Relocation breaks ties to traditional livelihoods and homelands (Upadhyay 2016), which normally would help place-based communities achieve food security through hunting and foraging (Berman and Kofinas 2004). Many members of place-based communities retain traditional knowledge of their environment, which “enables them to monitor, observe, and manage environmental change” (Adger et al. 2011). This awareness of their ecological surroundings is important for guiding targeted adaptations to climate change, much of which is lost when communities are forced to relocate. When broadly considering the socioeconomic impacts of climate change, one must couple the potential impacts on systems of production with the place-based communities who manage them and the inherent knowledge systems they rely upon to guide effective adaptation when considering the choice to relocate or adapt in situ. Indigenous, place-based communities, and subsistence smallholder agrarian communities in particular, will experience climate change in ways that amplify existing issues such as poverty, marginalization, and non-inclusion in national and international policy processes and agreements. 1.3  CLIMATE CHANGE ADAPTATION AND CROP PRODUCTION AGROECOSYSTEMS Successful adaptation of agroecological systems to climate change will require a multi-faceted approach (Altieri et al. 2015). In this section, we review three categories of interventions that support agricultural adaptation at multiple scales: conservation practices, tool and technology use, and policy and programs to support climate change responses. A discussion of resilience in agroecological systems ties these approaches together and points the way toward future research priorities. They are designed to address many different resource concerns related to agroecosystems and can include (but are not limited to) practices that preserve water quality (such as vegetative riparian buffers or manure holding areas), limit soil erosion and improve soil health (such as shelterbelts or cover cropping), or address air quality (such as air filtration or scrubbing). It is likely that, with increasing pressure on agriculture systems resulting from climate change, there will be an increased need to implement regionally- and sector-specific conservation practices. When conservation practices are applied with the intent to protect farms and the natural resources they depend on from the intensified negative effects of climate change, they are referred to as climate change best management practices or CCBMPS (Schattman et al. 2015, 2018). Though many proposed CCBMPS are not yet rigorously evaluated, examination of what farmers are currently doing to adapt to an already-shifting climate is an important first step in developing our understanding about which practices hold most promise (Schattman et al. 2018). Many factors are positively associated with farmer adoption of conservation practices, including access to and quality of information, financial capacity, and connections to agency or local networks of farmers or watershed groups (Baumgart-Getz et al. 2012). Not all conservation practices are equally accessible to farmers, however. Financial cost and access to economic resources are often

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limiting factors, especially for capitally intensive conservation practices (Helling et al. 2015) such as manure containment or fencing and irrigation systems. While farmers often bear the full cost of implementing conservation practices, in some countries there are mechanisms that incentivize use of specific practices through either private conservation initiatives (PCIs) (Hamilton 2017), or publically funded programs, such as in the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) and Farm Service Agency (FSA) programs (Hellerstein 2017). A critique of many conservation programs is that they fail in some regions to effectively encourage adoption of conservation practices because they do not have the capacity to address social and other economic barriers faced by farmers, insecure land tenure, a basic lack of infrastructure, and incompatibility with regional farming systems (Rodriguez et al. 2009). Despite these criticisms, programs that support conservation practices have a notable impact when successfully implemented, as with the Shelterbelt Project (also called the Prairie States Forestry Project) implemented by the USDA Forest Service in the United States following the Dustbowl of the 1930s (Karle and Karle 2017). A more recent example is the reforestation project in the Sahel region of western Africa, implemented in response to severe and damaging droughts in the 1960–1980s which led to chronic and widespread food insecurity (Stith et al. 2016). 1.3.1 Technology and Development The role of technology in agricultural adaptation to climate change is critical for success and involves a wide diversity of strategies. These technologies can support farmers as they make daily decisions (such as irrigation and nutrient applications informed by weather forecasts and seasonal outlooks), seasonal decisions (such as selecting crop varieties and breeds), or longer-term decisions (such as using a decision aid application or program to understand the costs and benefits of installing irrigation or switching to a no-till system). Four important technological developments stand out: improvements in weather forecasting, improvements in climate- and weather-related tools, precision agriculture technology, and improvements in crop varieties. First, in a changing and increasingly variable climate, improved forecasts can help farmers develop better seasonal plans and adapt those plans as conditions change. Seasonal forecasts are still only moderately reliable, but improvements in forecasts related to El Niño Southern Oscillation (ENSO) have strengthened predictability in certain years and seasons. Global dynamic prediction models can help those farmers in regions where there are fewer established weather stations or a less reliable National Meteorological or Hydrometeorological Service (Goddard et  al. 2010). However, incorporating this information into agroecological decision-making requires access to the information, willingness to use it, data literacy, and familiarity with the limitations of the data. Second, improved climate and weather tools can help bridge the gaps between the existence of improved weather data and on-the-ground decision-making. Complex weather data becomes valuable to farmers only when it is contextualized in terms of real-life management decisions, and recent years have seen a proliferation of decision support tools that are designed to help farmers harness climate and weather data and interpretive resources to improve their operations. Decision support tools range from simple tools, such as extreme weather alerts and growing degree day (GDD) calculators, to complex programs that require a suite of farm data to derive specific recommendations for a plethora of operational variables. All can play a role in daily to long-term decision-making, and increased access to Internet, mobile phones, and improved technology in general can broaden the reach of these technologies beyond the developed world. Third, as climate change challenges agricultural yields and growing populations increase demand for agricultural goods, precision agriculture can be used to increase input efficiency while minimizing waste. In regions across the globe, large differences exist between observed yields and attainable yields, with these “yield gaps” reaching 45% to 70% for many crops (Mueller et al. 2012).

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Changes in water and nutrient management can help close these yield gaps, while reductions in over-application of water and nutrients can reduce costs, nutrient runoff, and water waste. Advances such as unmanned aerial vehicles (UAVs) and remote sensing technologies improve the accuracy and extent of precision agriculture (Gómez-Candón et al. 2014; Mulla 2013), though these technologies are prohibitively expensive for many of the world’s farmers and typically require an economy of scale not realistic for smallholder farmers. Fourth, development of crop varieties and genetic materials that are better suited for the regional weather patterns anticipated in coming decades is an important tool for agroecological adaptation. For example, access to stress tolerant crop varieties increases farmers’ ability to grow these crops under adverse conditions, such as drought, high temperature, and pests (Dinesh et al. 2017). These varieties can be developed through selective breeding for desirable genes or through creation of genetically modified (GM) crops. Recent advances in genetic modification through clustered regularly interspaced short palindromic repeats (CRISPR) have dramatically lowered barriers to entry for this type of technology (Miao and Fernandez 2017). Using these technologies, farmers can potentially reduce crop losses due to pests, diseases (Chen and McCarl 2001; Declour et al. 2015), and extreme events. There is also great potential to improve production on land previously considered marginal for agricultural production (Tester and Langridge 2010). However, access to GM seed stock and markets is limited by expense, patent laws, and regulatory restrictions due to controversy over the safety of consuming GM crops (Tester and Langridge 2010). 1.3.2  Policy Mechanisms and Programs Myriad policies and programs exist to help farmers prevent and recover from disasters and other climate change-related stressors. Crop insurance is one mechanism for mitigating financial risk to extreme climate and weather events. Crop insurance, like most insurance, spreads risk across participants so that agricultural disasters and low-yield years do not financially ruin a farm. Participants pay a premium and receive payments for their losses in eligible years. Markets for crop insurance often include government subsidies and players from both the public and private sector. Four types of crop insurance, as described by Roberts (2005), are commonly used in agricultural systems. First, damage-based insurance covers losses from specific threats such as hail, wildfire, and frost, though not threats that can affect wide areas such as drought and disease. Second, yield-based or multi-peril crop insurance (MPCI) protects against low yields but is not limited to specific threats. Third, crop-revenue insurance combines the risk from production and price, covering any shortfalls in years where revenue generated from both does not meet a predetermined standard. Lastly, indexbased insurance avoids the expensive need for insurance adjusters to verify an actual loss by instead using a meteorological threshold to prompt payments. As useful as crop insurance programs are in mitigating the risks farmers face due to natural disasters and negative climate change impacts, they are concentrated in the developed world. Their limited reach in the developing world has a few exceptions with those programs often only covering a few crops and/or a few types of risk (Roberts 2005). In some places where more traditional crop insurance is unavailable, other options such as microinsurance occasionally exist. While definitions for microinsurance vary, most agree that microinsurance involves relatively small premiums for relatively large groups of people and differs from traditional insurance in that it serves low-income individuals (Clarke and Grenham 2013). Currently, microinsurance has limited reach and scaling up would require significant investment in outreach and education (Clarke and Grenham 2013). Insurance is not the only type of policy or program that supports farmers. When a natural disaster strikes and causes damage beyond the realm of traditional crop insurance, other policy mechanisms are applied in some countries. Aid such as disaster recovery can be available through domestic aid, the United Nations and/or foreign aid, or private aid by means of non-profit organizations. Agricultural extension services can also play a role in disaster recovery in countries where those

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organizations are active. One example is the Extension Disaster Education Network (EDEN) in the United States, which focuses on disaster preparation, mitigation, and recovery (Black et al. 2012). Specific policy mechanisms and programs such as those explored here can help farmers recover from losses caused by natural disasters that would otherwise threaten their livelihoods. While losses are inevitable in agroecosystems, and increasingly so under climate change, adjustments in land management practices toward more sustainable and climate smart options can help reduce those risks. Resource management programs attempt to influence adoption of these practices through subsidies and incentives, regulations, or some combination of both (Smit and Skinner 2002). For example, in the United States certain farm activities are regulated through the Clean Water Act (Kopocis 2015), while others flow through voluntary incentive programs within the USDA’s NRCS (NRCS 2016). Under the Obama administration, certain practices that make farms more climateresilient or promote reduction or mitigation of greenhouse gas emissions were given an increased priority in the Building Blocks for Climate Smart Agriculture (USDA 2016). Such programs attempt to shift the policy and financial burden from loss recovery to loss prevention. Finally, national-scale vulnerability assessments of agroecological systems are useful tools in planning for climate-related natural disasters. The conclusions of such assessments will help guide policies and programs that support agroecological resilience systems in the coming century (Ezra 2016). 1.3.3  Resilience in Agroecosystems The term resilience has been applied widely, often without clarity about the definition of the term. Holling (1973) importantly deviated from historical use of the term and identified resilience as a fundamental descriptor of ecological systems. Specifically, Holling pointed to resilience as the ability of an ecological system to “absorb changes of state variables, driving variables, and parameters, and still persist” (p. 73). Since Holling introduced this concept, resilience theory has been applied to contexts beyond ecological systems, finding a home in socioecological disciplines such as disaster relief, international development, and responses to climate change. Many social scientists have challenged the use of these ecological definitions of resilience because they can mask the social context of resilience, which includes governance, economics, and issues of power and social change (Olsson et al. 2015). While resilience is a contested and complex concept, we propose the definition laid out by the Intergovernmental Panel on Climate Change (IPCC). The IPCC states that resilience is the “capacity of social, economic, and environmental systems to cope with a hazardous event or trend or disturbance, responding or reorganizing in ways that maintain their essential function, identity, and structure, while also maintaining the capacity for adaptation, learning, and transformation” (IPCC 2014a,b). In extending this definition to agroecosystems, agroecosystem resilience is thus an emergent property of agricultural systems that are driven by an interaction between farmers, farms, and the broader social-ecological context (Altieri et al. 2015; Heckelman et al. 2018; Méndez et al. 2013; Wezel et al. 2009). In order to build greater agroecological resilience in the face of projected climate change, it will be necessary for farmers and other stakeholders in agrifood systems to adapt to and respond to climate change. Adaptation can occur in response to both actual and projected climate changes and these actions can range from short-term coping with extreme events or longer-term transformation to meet multiple goals, which may or may not moderate harm or exploit benefits (Moser and Ekstrom 2010). Brooks (2003) writes that the direct function of adaptation is the reduction in vulnerability, which Adger (2006) defines as “the state of susceptibility to harm from exposure to stresses associated with environmental and social change and from the absence of capacity to adapt.” Cutter et al. (2008) further clarifies that vulnerability is reflective of pre-disruption characteristics of a system. It should be noted that a decrease in vulnerability is not synonymous with an increase in resilience (Manyena 2006), but that a high degree of vulnerability describes the increased likelihood that a system will

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need to draw upon its ability to be resilient. Additionally, adaptive responses at the farm-level can build farm-level or local resilience but may be contrary to resilience at a larger landscape scale. In other words, individual-level adaptations at the farm scale may ultimately hinder others’ ability to adapt, thus leading to greater vulnerability at a landscape scale (Roesch-McNally et al. 2017). There are social limits to adaptation based on community goals, values, risk, and social choices (Adger et al. 2009) in addition to ecological limits and climatic consequences. Resilient agroecological systems require adaptive capacity, which is defined as the preconditions that enable adaptation including social, physical, and ecological elements (Nelson et al. 2007). Indeed, adaptive actions can often favor individuals with more social, economic, and political capital as they are often better poised to take advantage of new policy and/or economic opportunities, which can lead to further marginalization of vulnerable groups (Nelson et al. 2007). Therefore, any approaches to assessing future sustainability of social and ecological systems must be based on a broader understanding of the sociopolitical processes that influence adaptive capacity and vulnerability (Ribot 2014) to ensure an equitable approach to adaptation. Cabell and Oelofse (2012) developed thirteen indicators of resilience at the agroecosystem level. These indicators help define when an agroecosystem is resilient by assessing social, ecological, agronomic, and economic elements and are generally relevant and applicable within the context of climate change (Heckelman et al. 2017). These indicators are intended to be assessed in the context of local agroecosystems. They have been utilized by the Food and Agricultural Organization (FAO) of the United Nations to support participatory climate resilience assessments using the SHARP (Self-evaluation and Holistic Assessment of climate change Resilience of farmers and Pastoralists) tool to enable community scale assessments of climate resilience and identify areas for improvement and intervention (Choptiany et al. 2017). Other organizations have also adopted an indicator-based approach to determining the degree to which agroecosystems are resilient to climate change. The CGIAR (formerly called Consultative Group on International Agricultural Research) Research Program on Climate Change, Agriculture, and Food Security suggests key strategies for building “climate smart” agriculture systems which can be utilized to build a robust and resilient agricultural system (Dinesh et al. 2017). These strategies include the promotion of agricultural practices such as agroforestry, aquaculture, and development of stress-tolerant crop varieties. Other climate smart activities include diversifying income streams (e.g., smallholder dairy projects), supporting infrastructure development (e.g., solar irrigation efforts), digital agriculture, climate informed advisories, weather index-based agricultural insurance, and broader financial support for adaptation. While climate adaptation is a clear focus of this programing, GHG mitigation is also an important goal. The work of the CGIAR program includes efforts toward creating climate-smart agricultural solutions that reduce greenhouse gas emissions associated with agricultural production. 1.4  FUTURE DIRECTIONS AND RESEARCH PRIORITIES Scientific evidence shows that the climate is changing. Among other outcomes experienced on a global scale in coming decades, it is likely that we will see reduced food production, vulnerable agroecosystems, and a reduced global food supply. To cope with climate change, we propose that research should be prioritized in the following areas. First, the development of agroecological measures to strengthen crop resilience should be further explored. While agroecological systems encompass social, political, and biophysical dimensions (Guzmán and Woodgate 2013; Hecht 1995), this need directly refers to development of indicators relevant to ecologically-sound production. These indicators should be selected and monitored based on regional vulnerabilities to climate change. For example, the development and success of new crop varieties resistant to disease outbreaks, drought, and high temperatures, or the development of new varieties that may lead to biodiverse agroecosystems (Mijatović et al. 2013; Redden 2013; Rosenthal

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et al. 2012). In particular, we advocate for research that will lead to development of diversified agroecosystems, which we hypothesize will be less susceptible to production variability caused by climate change. Second, water quality, availability, and access should be a focus of the scientific community. Under changing climatic conditions, water suitable for agriculture and for consumption will likely become increasingly scarce in some regions (Di Falco and Chavas 2008). This situation will likely be worse in Asia and Africa where more than 80% of groundwater is withdrawn for agriculture uses, and projections indicate that climate change will have a significant impact on the future availability of water. For successful agroecological adaptation to climate change, it is crucial to develop regionally appropriate technologies for water harvesting and management. Investments in integrated water resource management (IWRM) should be targeted, specifically water harvesting systems for supplemental irrigation. Agroecosystems will likely become increasingly dependent upon currently underutilized water sources in the future. This is especially true in those regions impacted heavily by drought. It is likely that major investments in water infrastructure and equipment will be required to maintain yields and food supplies. Further development of best practices in this area are needed. Third, further investigation of how diversified agroecosystems (including agroforestry and mixed crop-livestock systems) might contribute to agroecosystem resilience should be conducted. Mixeduse land management has great potential to generate alternative sources of income for farmers while protecting individuals and communities from some negative impacts associated with climate change. For example, riparian buffers can reduce runoff from cultivated land, while also potentially producing agroforestry crops for commercial sale. Diversified production can help to diffuse the market risks associated with single-commodity production. In theory, shifting from largely monoculture cropping systems to agroecological, diversified cropping systems may lead to greater climate resilience. The practical steps of shifting large-scale production systems to more diversified systems need to be further explored through targeted research. Lastly, diversity in agroecosystems should further be broadened to include social dimensions. Specifically, inclusion of a diversity of perspectives regarding what constitutes healthy agroecosystems in the context of climate change is an important sociological endeavor. Greater inclusion of traditionally excluded groups (e.g., smallholder farmers) in research and development would address some of the strongest critiques leveled at transnational movements such as Climate Smart Agriculture (Taylor 2017). As inclusion in research and policy decision-making is associated with access to technology, finance, and institutional support (Newell and Taylor 2017), efforts to include historically excluded groups could help to address the humanitarian issues associated with climate change and agriculture (e.g., food insecurity, human migration, and resource competition). While this does not constitute a specific research recommendation, it is a recommendation for a research approach that can be applied widely. 1.5 CONCLUSIONS Climate change is currently affecting and will continue to affect agroecological systems around the globe. The causes of modern climate change are largely anthropogenic, while the effects are amplified by social-ecological feedbacks (Collins et al. 2011). Agricultural systems both contribute to modern climate change and are vulnerable to the negative impacts of climate change. Changing climate and weather patterns will alter crop photosynthesis and photorespiration processes, drive changes in plant and animal communities, and will likely lead to decreases in agricultural yields around the world. The economic results of these declining yields will strain our economic and social systems, disproportionately affecting food insecure populations and communities who remain dependent on subsistence agriculture. Adapting to climate change will be a necessity in agroecosystems, including increased use of conservation practices, improvement in tools and technologies, and development

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of supportive policies. Future research priorities include (1) agroecological measures to enhance crop resilience; (2) best practices in maintaining water quality, access, and availability; and (3) investigations in agroecosystem diversity and resilience to climate change. Lastly, bringing diverse perspectives to the table to inform research and programming can address issues of equity in agroecological systems. This is of increasing importance as climate change puts ever more pressure on the social, economic, and ecological aspects of global and regional agroecological systems. REFERENCES Abrol, Y. P., and K. T. Ingram. 1996. Effects of higher day and night temperatures on growth and yields of some crop plants. In Global Climate Change and Agricultural Production: Direct and Indirect Effect of Changing Hydrological, Pedological and Plant Physiological Processes, ed. F. A. Bazzaz, and W. G. Sombroek, 123–140. New York, NY: Food and Agriculture Organization. Adger, N. W. 2006. Vulnerability. Global Environ Chang 16:268–81. Adger, W. N., J. Barnett, F. S. Chapin III, and H. Ellemor. 2011. This must be the place: Underrepresentation of identity and meaning in climate change decision-making. Global Environ Polit 11:1–25. Adger, W. N., S. Dessai, M. Goulden et al. 2009. Are there social limits to adaptation to climate change? Climatic Change 93:335–54. Altieri, M. A. 1999. The ecological role of biodiversity in agroecosystems. Agr Ecosyst Environ 74:19–31. Altieri, M. A., C. I. Nicholls, A. Henao, and M. A. Lana. 2015. Agroecology and the design of climate changeresilient farming systems. Agron Sustain Dev 35:869–90. Altieri, M. A., C. I. Nicholls, and R. Montalba. 2017. Technological approaches to sustainable agriculture at a crossroads: An agroecological perspective. Sustainability 9:349. DOI:10.3390/su9030349. Amekawa, Y. 2011. Agroecology and sustainable livelihoods: Towards an integrated approach to rural development. J Sustain Agric 35:118–62. Anderson, P. K., A. A. Cunningham, N. G. Patel, F. G. Morales, P. R. Epstein, and P. Daszak. 2004. Emerging infectious diseases of plants: Pathogen pollution, climate change and agrotechnology drivers. Trends Ecol Evol 19:534–44. Archer, D. 2007. Global Warming: Understanding the Forecast. Malden, MA: Blackwell Publishing. Baumgart-Getz, A., L. S. Prokopy, and K. Floress. 2012. Why farmers adopt best management practice in the United States: A meta-analysis of the adoption literature. J Environ Manag 96:17–25. Bellard, C., C. Bertelsmeier, P. Leadley, W. Thuiller, and F. Courchamp. 2012. Impacts of climate change on the future of biodiversity. Ecol Lett 15:365–77. Bennetzen, E. H., P. Smith, and J. R. Porter. 2016. Agricultural production and greenhouse gas emissions from world regions—The major trends over 40 years. Global Environ Chang 37:43–55. Berman, M., and G. Kofinas. 2004. Hunting for models: Grounded and rational choice approaches to analyzing climate effects on subsistence hunting in an Arctic community. Ecol Econ 49:31–46. Black, L., T. D. Beuchelt, and D. Virchow. 2012. Food sovereignty or the human right to adequate food: Which concept serves better as international development policy for global hunger and poverty reduction? Agric Human Values 29:259–73. Bolton, J. K., and R. H. Brown. 1980. Photosynthesis of grass species differing in carbon dioxide fixation pathways. 5. Response of Panicum maximum, Panicum milioides and tall fescue (Festuca arundinacea) to nitrogen nutrition. Plant Physiol 66:97–100. Brooks, N. 2003. Vulnerability, risk and adaptation: A conceptual framework. Tyndall Centre Working Paper No. 38. Tyndall Centre for Climate Change Research. Norwich, UK: University of East Aglia. Brown, M. E., J. M. Antle, P. Backlund et al. 2015. Climate Change, Global Food Security, and the U.S. Food System. Available online at http://www.usda.gov/oce/climate_change/FoodSecurity2015Assessment/ FullAssessment.pdf. (Accessed: December 10, 2017). Beuchelt, T. D., and D. Virchow. 2012. Food sovereignty or the human right to adequate food: Which concept serves better as international development policy for global hunger and poverty reduction? Agric Human Values 29:259–73. Burke, M., and K. Emerick. 2015. Adaptation to climate change: Evidence from U.S. agriculture. Am Econ J-Econ Polic 8:106–40.

CLIMATE CHANGE AND CROP PRODUcTION: SET THE STAGE FOR RESILIENcE

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Cabell, J., and M. Oelofse. 2012. An indicator framework for assessing agroecosystem resilience. Ecol Soc 17:18. http://dx.doi.org/10.5751/ES-04666-170118. Chakraborty, S., and A. C. Newton. 2011. Climate change, plant diseases and food security: An overview. Plant Pathol 60:2–14, Chen, C., and B. A. McCarl. 2001. An investigation of the relationship between pesticide usage and climate change. Climatic Change 50:475–87. Choptiany, J. M. H., S. Phillips, B. E. Graeu et  al. 2017. SHARP: integrating a traditional survey with participatory self-evaluation and learning for climate change resilience assessment. Clim Dev 9:505–17. Clark, M., and D. Tilman. 2017. Comparative analysis of environmental impacts of agricultural production systems, agricultural input efficiency, and food choice. Environ Res Lett 12:64016. DOI: https://doi. org/10.1088/1748-9326/aa6cd5. Clarke, D. J., and D. Grenham. 2013. Microinsurance and natural disasters: Challenges and options. Environ Sci Policy 27, S89–S98. Collins, S. L., S. R. Carpenter, S. M. Swinton et al. 2011. An integrated conceptual framework for long-term social-ecological research. Front Ecol Environ 9:351–7. Costinot, A., D. Donaldson, and C. Smith. 2016. Evolving comparative advantage and the impact of climate change in agricultural markets: Evidence from 1.7 million fields around the world. J Polit Econ 124:205–48. Crowley, T. 2000. Causes of climate change over the past 1,000 years. Science 289:270–7. Cutforth, H. W., S. M. McGinn, K. E. McPhee, and P. R. Miller. 2007. Adaptation of pulse crops to the changing climate of the northern great plains. Agron J 99:1684–99. Cutter, S. L., L. Barnes, M. Berry, C. Burton, E. Evans, E. Tate, and J. Webb. 2008. A place-based model for understanding community resilience to natural disasters. Global Environ Chang 18:598–606. Declour, I., P. Spanoghe, and M. Uyttendaele. 2015. Literature review: Impact of climate change on pesticide use. Food Res Int 68:7–15. Di Falco, S., and J. P. Chavas. 2008. Rainfall shocks, resilience, and the effects of crop biodiversity on agroecosystem productivity. Land Econ 84:83–96. Dinesh, D., B. Campbell, O. Bonilla-Findji, and M. Richards. 2017. 10 best bet innovations for adaptation in agriculture: A supplement to the UNFCCC NAP Technical Guidelines. CCAFS Working Paper no. 215. Wageningen, The Netherlands: CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS). Available online at: www.ccafs.cgiar.org. (Accessed: December 17, 2017). Ehleringer, J. R., R. F. Sage, L. B. Flanagan, and R. W. Pearcy. 1991. Climate change and the evolution of C4 photosynthesis. Trends Ecol Evol 6:95–9. Elad, Y., and I. Pertot. 2014. Climate change impacts on plant pathogens and plant diseases. J Crop Improvem 28:99–139. Ezra, M. C. A. 2016. Climate change vulnerability assessment in the agriculture sector: Typhoon Santi experience. Procedia Soc Behav Sci 216:440–5. FAO. 2006. The Right to Adequate Food. Sheet no: 34. Rome: Food and Agriculture. DOI: ISSN N014-5567. García, G. A., M. F. Dreccer, D. J. Miralles, and R. A. Serrago. 2015. High night temperatures during grain number determination reduce wheat and barley grain yield: A field study. Glob Change Biol 21:4153–64. Ghannoum, O. 2009. C-4 photosynthesis and water stress. Ann Bot 103:635–44. Goddard, L., Y. Aitchellouche, W. Baethgen et al. 2010. Providing seasonal-to-interannual climate information for risk management and decision-making. Procedia Environ Sci 1:81–101. Godfray, H. C. J., J. R. Beddington, I. R. Crute et al. 2010. Food security: The challenge of feeding 9 billion people. Science 327:812–8. Gómez-Candón, D., A. I. De Castro, and F. López-Granados. 2014. Assessing the accuracy of mosaics from unmanned aerial vehicle (UAV) imagery for precision agriculture purposes in wheat. Precis Agric 15:44–56. Groen, J. A., M. J. Kutzbach, and A. E. Polivka. 2016. Storms and jobs: The Effect of Hurricanes On Individuals’ Employment and Earnings Over the Long Term. Washington, DC: U.S. Census Bureau Center for Economic Studies. Guzmán, E. S., and G. Woodgate. 2013. Foundations in agrarian social thought and sociological theory agroecology. Agroecol Sust Food 37:32–44.

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Hamilton, E. W. III, S. A. Heckathorn, P. Joshi, D. Wang, and D. Barua. 2008. Interactive effects of elevated CO2 and growth temperature on the tolerance of photosynthesis to acute heat stress in C3 and C4 species. J Integr Plant Biol 50:1375–87. Hamilton, N. 2017. Evaluating how private conservation initiatives may increase farmer adoption of conservation practices. Iowa State University Leopold Center for Sustainable Agriculture, Competitive Grant Report P2016–01. http://lib.dr.iastate.edu/leopold_grantreports/528. (Accessed: November 30, 2017). Hanna, R., and P. Oliva. 2016. Implications of climate change for children in developing countries. Future Child 26:115–32. Hansen, J., M. Sato, P. Kharecha et al. 2017. Young people’s burden: Requirement of negative CO2 emissions. Earth Syst Dynam 8:577–616. Hardy, J. T. 2003. Climate Change: Causes, Effects, and Solutions. Hoboken, NJ: John Wiley & Sons. Hatfield, J., G. Takle, R. Grotjahn et al. 2014. Chapter 6: Agriculture. Climate change impacts in the United States: The third national climate assessment. In U.S. Global Change Research Program, eds. J. M. Melillo, T. C. Richmond, and G. W. Yohe, 150–174. DOI: 10.7930/J02Z13FR. http://nca2014. globalchange.gov/report/sectors/agriculture. (Accessed: June 30, 2017). Hatfield, J. L., K. J. Boote, B. A. Kimball et al. 2011. Climate impacts on agriculture: Implications for crop production. Agron J 103:351–70. Hatfield, J. L., and J. H. Prueger. 2015. Temperature extremes: Effect on plant growth and development. Weather Clim Extrem 10:4–10. Hecht, S. 1995. The evolution of agroecological thought. In Agroecology: The Science of Sustainable Agriculture, ed. M. A. Alteiri, 2nd Ed., 1–19. Boulder, CO: Westview Press. Heckelman, A., S. Smukler, and H. Wittman. 2018. Cultivating Climate Resilience: A participatory assessment of organic and conventional rice systems in the Philippines. Renew Agr Food Syst 1–13. DOI: 10.1017/ S1742170517000709. Hegland, S. J., A. Nielsen, A. Lázaro, A. L. Bjerknes, and Ø. Totland. 2009. How does climate warming affect plant-pollinator interactions? Ecol Lett 12:184–95. Heller, N. E., and E. S. Zavaleta. 2009. Biodiversity management in the face of climate change: A review of 22 years of recommendations. Biol Conserv 142:14–32. Hellerstein, D. 2017. The U.S. conservation reserve program: The evolution of an enrollment mechanism. Land Use Policy 63:601–10. Helling, A., D. Conner, S. Heiss, and L. Berlin. 2015. Economic analysis of climate change best management practices in Vermont agriculture. Agriculture 5:879–900. Holling, C. S. 1973. Resilience and stability of ecological systems. Annu Rev Ecol Syst 4:1–23. Horton, R., G. Yohe, W. Easterling et al. 2014. Climate change impacts in the United States: Northeast. In U.S. Global Change Research Program, eds. J. M. Melillo, T. C. Richmond, and G. W. Yohe, 371–395. DOI: 10.7930/J02Z13FR. http://nca2014.globalchange.gov/report/sectors/agriculture. (Accessed: June 17, 2017). Hsiang, S., R. Kopp, A. Jina et al. 2017. Estimating economic damage from climate change in the United States. Science 1369:1362–9. IPCC. 2007. Appendix I: Glossary, Climate Change 2007: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. DOI: 10.1016/0197-2456(95)90487-5. IPCC. 2014a. Climate Change 2014: Synthesis Report. Geneva, Switzerland: Intergovernmental Panel on Climate Change. IPCC. 2014b. Summary for policymakers. In Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects, eds. C. B. Field, V. R. Barros, D. J. Dokken et al., 1–32. Cambridge, MA: Cambridge University Press. Jyoti, D. F., E. A. Frongillo, and S. J. Jones. 2005. Food insecurity affects school children’s academic performance, weight gain, and social skills. J Nutr 135:2831–9. Karle, S. T., and D. Karle. 2017. Conserving the dust bowl: The New Deal’s Prairie States Forestry Project. Baton Rouge, LA: Louisiana State University Press. Klinsky, S., T. Roberts, S. Huq et al. 2017. Why equity is fundamental in climate change policy research. Global Environ Chang 44:170–3. Kopocis, K. 2015. The facts about the clean water rule and agriculture. https://blog.epa.gov/blog/2015/06/ clean-water-rule-and-agriculture/. (Accessed: June 30, 2017).

CLIMATE CHANGE AND CROP PRODUcTION: SET THE STAGE FOR RESILIENcE

15

Letourneau, D. K., I. Armbrecht, B. S. Rivera et al. 2011. Does plant diversity benefit agroecosystems? A synthetic review. Ecol Appl 21:9–21. Lin, B. B. 2011. Resilience in agriculture through crop diversification: Adaptive management for environmental change. BioScience 61:183–93. Lipper, L., P. Thornton, B. M. Campbell et al. 2014. Climate-smart agriculture for food security. Nat Clim Change 4:1068–72. Lobell, D. B., and S. M. Gourdji. 2012. The Influence of climate change on global crop productivity. Plant Physiol 160:1686–97. Lobell, D. B., W. Schlenker, and J. Costa-Roberts. 2011. Climate trends and global crop production since 1980. Science 333:616–20. Luck, G., M. Spackman, A. Freeman, P. Trebicki, W. Griffiths, K. Finlay, and S. Chakraborty. 2011. Climate change and diseases of food crops. Plant Pathol 60:113–21. Mann, M. E., R. S. Bradley, and M. K. Hughes. 1999. Northern hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophys Res Lett 26:759–62. Manyena, S. 2006. The concept of resilience revisited. Disasters 30:433–51. Medellín-Azuara, J., D. Macewan, R. E. Howitt et  al. 2016. Economic analysis of the 2016 California drought on agriculture. A report for the California Department of Food and Agriculture, Center for Watershed Science. Davis, CA: University of California, https://watershed.ucdavis.edu/files/ DroughtReport_20160812.pdf. (Accessed: November 14, 2017). Mendelsohn, R. 2014. The impact of climate change on agriculture in Asia. J Integr Agric 13:660–5. Méndez, V., C. Bacon, and R. Cohen. 2013. Agroecology as a transdisciplinary, participatory, and actionoriented approach. Agroecol Sust 37:37–41. Méndez, V. E., C. M. Bacon, M. Olson, K. S. Morris, and A. Shattuck. 2010. Agrobiodiversity and shade coffee smallholder livelihoods: A review and synthesis of ten years of research in central America. Prof Geogr 62:357–76. Mestre-Sanchís, F., and M. L. Feijóo-Bello. 2009. Climate change and its marginalizing effect on agriculture. Ecol Econ 68:896–904. Miao, Z., and D. Fernandez. 2017. Intellectual property protection of CRISPR related technologies. Int J Bioeng Life Sci 11:569–74. Mijatović, D., F. Van Oudenhoven, P. Eyzaguirre, and T. Hodgkin. 2013. The role of agricultural biodiversity in strengthening resilience to climate change: Towards an analytical framework. Int J Agric Sustain 11:95–107. Morgan, P. B., G. A. Bollero, R. L. Nelson, F. G. Dohleman, and S. P. Long. 2005. Smaller than predicted increase in aboveground net primary production and yield of field-grown soybean under fully open-air [CO2] elevation. Global Change Biol 11:1856–65. Moser, S. C., and J. A. Ekstrom. 2010. A framework to diagnose barriers to climate change adaptation. Proc Natl Acad Sci USA 107:22026–31. Mueller, N. D., J. S. Gerber, M. Johnston, D. K., Ray, N. Ramankutty, and J. A. Foley. 2012. Closing yield gaps through nutrient and water management. Nature 490:254–7. Mulla, D. J. 2013. Twenty five years of remote sensing in precision agriculture: Key advances and remaining knowledge gaps. Biosyst Eng 114:358–71. Natural Resources Conservation Service. 2016. Incentive programs and assistance for producers. https:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/climatechange/resources/?cid=stelprdb1043608. (Accessed: November 17, 2017). Nelson, D. R., W. N. Adger, and K. Brown. 2007. Adaptation to environmental change: Contributions of a resilience framework. Annu Rev Environ Resour 32:395–419. Newell, P., and O. Taylor. 2017. Contested landscapes: The global political economy of climate-smart agriculture. J Peasant Stud 0:1–22. Niles, M. T., and M. E. Brown. 2017. A multi-country assessment of factors related to smallholder food security in varying rainfall conditions. Sci Rep 7:1627. DOI: 10.1038/s41598-017-16282-9. Olsson, L., A. Jerneck, H. Thoren, J. Persson, and D. O’Byrne. 2015. Why resilience is unappealing to social science: Theoretical and empirical investigations of the scientific use of resilience. Sci Adv 1:e1400217. DOI: 10.1126/sciadv.1400217. Parmesan, C., and G. Yohe. 2002. A globally coherent fingerprint of climate change impacts across natural systems. Nature (London) 421:37–42.

16

CLIMATE CHANGE AND CROP PRODUcTION

Parry, M. 1992. The potential effect of climate changes on agriculture and land use. Adv Ecol Res 22:63–91. Parry, M. L., C. Rosenzweig, A. Iglesias, M. Livermore, and G. Fischer. 2004. Effects of climate change on global food production under SRES emissions and socio-economic scenarios. Global Environ Change 14:53–67. Pautasso, M., T. F. Döring, M. Garbelotto, L. Pellis, and M. J. Jeger. 2012. Impacts of climate change on plant diseases—opinions and trends. Eur J Plant Pathol 133:295–313. Redden, R. 2013. New approaches for crop genetic adaptation to the abiotic stresses predicted with climate change. Agronomy 3:419–32. Ribot, J. 2014. Cause and response: Vulnerability and climate in the Anthropocene. J Peasant Stud 41:667–705. Roberts, R. A. 2005. Insurance of Crops in Developing Countries. Vol. 159. Rome, Italy: Food and Agriculture Organization. Rodriguez, J. M., J. J. Molnar, R. A. Fazio, E. Sydnor, and M. J. Lowe. 2009. Barriers to adoption of sustainable agriculture practices: Change agent perspectives. Renew Agri Food Syst 24:60–71. Roesch-McNally, G. E., J. G. Arbuckle, and J. C. Tyndall. 2017. What would farmers do? Adaptation intentions under a Corn Belt climate change scenario. Agric Human Values 34:333–46. Rosenthal, D. M., R. A. Slattery, R. E. Miller et al. 2012. Cassava about-FACE: Greater than expected yield stimulation of cassava (Manihot esculenta) by future CO2 levels. Global Change Biol 18:2661–75. Ruiz-Vera, U. M., M. H. Siebers, D. W. Drag, R. D. Ort, and C. J. Bernacchi. 2015. Canopy warming caused photosynthetic acclimation and reduced seed yield in maize grown at ambient and elevated [CO2]. Global Biol Change 21:4237–49. Sage, R. F., and R. W. Pearcy. 1987. The nitrogen use efficiency of C3 and C4 plants. 2. Leaf nitrogen effects on the gas exchange characteristics of Chenopodium album (L.) and Amaranthus retroflexus (L.). Plant Physiol 84:959–63. Sala, O. E., F. S. Chapin, J. J. Armesto et al. 2000. Biodiversity—global biodiversity scenarios for the year 2100. Science 287:1770–4. Schattman, R., V. E. Méndez, K. Westdijk et al. 2015. Vermont agricultural resilience in a changing climate: A transdisciplinary and participatory action research (PAR) process. In Agroecology, Ecosystems, and Sustainability, ed. N. Benkeblia, 326–346. Boca Raton, FL: CRC Press. Schattman, R. E., V. E. Mendez, S. C. Merrill, and A. Zia. 2018. A mixed methods approach to understanding farmer and agricultural advisor perceptions of climate change and adaptation in Vermont, United States. Agroecol Sustain Food Syst 42:121–48. Smit, B., and M. W. Skinner. 2002. Adaptation options in agriculture to climate change: A typology. Mitig Adapt Strat Gl 7:87–114. Solanki, R. P. 2016. Effect of climate change on mental health. Int J Indian Psychol 3:129–35. Stith, M., A. Giannini, J. Corral, S. del Adamo, and A. de Sherbinin. 2016. A quantitative evaluation of the multiple narratives of the recent Sahelian regreening. Weather Clim Soc 8:67–83. Sutherst, R. W. 1990. Impact of climate change on pests and diseases in Australasia. Search 21:230–2. Taylor, M. 2017. Climate-smart agriculture: What is it good for? J Peasant Stud 45:89–107. Taylor, S. H., S. P. Hulme, M. E. Rees, B. S. Ripley, F. I. Woodward, and C. P. Osborne. 2009. Ecophysiological traits in C3 and C4 grasses: A phylogenetically controlled screening experiment. New Phytol 185:780–91. Tester, M., and P. Langridge. 2010. Breeding technologies to increase crop production in a changing world. Science 327:818–22. Thomas, C. D., A. Cameron, A. R. E. Green et al. 2004. Extinction risk from climate change. Nature 427:145–8. Upadhyay, P. 2016. Climate change as ecological colonialism: Dilemma of innocent victims. Himalayan J Soc Anthropol 7:111–40. U.S. Department of Agriculture. 2016. USDA building blocks for climate smart agriculture and forestry: Implementation plan and progress report. Washington, DC: USDA. https://www.usda.gov/sites/default/ files/documents/building-blocks-implementation-plan-progress-report.pdf. (Accessed: June 1, 2016). Walter, K. M., S. A. Zimov, J. P. Chanton, D. Verbyla, and F. S. Chapin. 2006. Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming. Nature 443:71–5. Went, F. W. 1957. Climate and agriculture. Sci Am 196:82–98. Wezel, A., S. Bellon, T. Doré, C. Francis, D. Vallod, and C. David. 2009. Agroecology as a science, a movement, and a practice. A Review Agron Sustain Dev 29:503–15. Wolfe, D. W., A. T. DeGaetano, G. M. Peck et al. 2017. Unique challenges and opportunities for northeastern U.S. crop production in a changing climate. Climatic Change. https://doi.org/10.1007/s10584-017-2109-7.

CLIMATE CHANGE AND CROP PRODUcTION: SET THE STAGE FOR RESILIENcE

17

Wolfe, D. W., L. Ziska, C. Petzoldt, A. Seaman, L. Chase, and K. Hayhoe. 2008. Projected change in climate thresholds in the Northeastern U.S.: Implications for crops, pests, livestock, and farmers. Mitig Adapt Strat Gl 13:555–75. Yue, Q., X. Xu, J. Hillier, K. Cheng, and G. Pan. 2017. Mitigating greenhouse gas emissions in agriculture: From farm production to food consumption. J Clean Prod 149:1011–9. Zhang, P., J. Zhang, and M. Chen. 2017. Economic impacts of climate change on agriculture: The importance of additional climatic variables other than temperature and precipitation. J Environ Econ Manag 83:8–31. Ziska, L., A. Crimmins, A. Auclair et al. 2016. Food safety, nutrition, and distribution. In The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment, 189–216. Washington, DC: U.S. Global Change Research Program. DOI: http:// dx.doi.org/10.7930/J0ZP4417. Ziska, L. H. 2000. The impact of elevated CO2 on yield loss from a C3 and C4 weed in field-grown soybean. Global Change Biol 6:899–905. Ziska, L. H. 2001. Changes in competitive ability between a C4 crop and a C3 weed with elevated carbon dioxide. Weed Sci 49:622–7.

CHapTer  2

Crop Species Responses and Adaptation to Rise in Carbon Dioxide and Temperature Noureddine Benkeblia and Charles A. Francis CONTENTS 2.1 Introduction............................................................................................................................. 19 2.2 Climate Change (CC): What Is Changing and How?..............................................................20 2.3 How Plants Respond to Climate Change?............................................................................... 22 2.4 Effects of CO2.......................................................................................................................... 22 2.5 Effects of Temperature............................................................................................................ 23 2.6 Effects of Drought...................................................................................................................24 2.7 Gene Expression......................................................................................................................25 2.8 Phenotype Plasticity................................................................................................................26 2.9 Climate Change and Physiological Responses in Photosynthesis...........................................26 2.10 Climate Change and Crop Quality.......................................................................................... 27 2.11 Conclusions and Future Directions.......................................................................................... 27 2.12 Summary.................................................................................................................................28 Acknowledgments.............................................................................................................................28 References.........................................................................................................................................28 2.1 INTRODUCTION Agriculture is a vital sector in the economies of many countries. In providing food for the human population, feed for livestock, and raw material for agroprocessing, agriculture contributes substantially to the GDP worldwide. In less developed countries it occupies a proportionally higher role in national economies. However, agriculture is greatly dependent on prevailing climate conditions, especially the variability of weather, and it is therefore important to understand the impacts of any climate or weather change on crop growth and production (Antle and Capalbo 2010; Darnhofer 2014; Dwivedi et al. 2013; Porter and Semenov 2005). Both rise in average temperature and increase in atmospheric carbon dioxide (CO2) over the past two decades are well documented (IPCC 2001). Many studies and reports have shown that increases in temperature and CO2 could be beneficial for some crops, depending on other interacting climatic conditions. Thus it is crucial to understand how different crop species will respond to increasing CO2 and global warming, and how crops in general will respond to changes in the future (CGCR 1999; Fuhrer 2003; Idso and Idso 1994; Nemecek et al. 2012; Singh-Chauhan et al. 2014).

19

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The effects of climate change should also be evaluated by considering other interacting emergent properties that result from current successful agricultural systems (Howden et al. 2007). These consequences include widespread soil degradation, deforestation, biodiversity loss, pollution, and natural system destruction. Understanding these unintended results can inform our choices of how to design new technologies and farming practices that contribute to mitigating climate and weather changes (Goglio et al. 2014; Holloway and Ilbery 1996; Lal et al. 2011; Tausz et al. 2013). It is anticipated that climate change will make crop production more difficult and solutions more complex compared to the recent past, as we emerge from several centuries of relatively “benign and stable climate;” frequent extreme weather conditions now markedly affect crop yields and quality (Gregory et al. 2005; Kang et al. 2009; Lobell and Burk 2010; Mattos et al. 2014; Mayes et al. 2012; Parry et al. 1999, Parry et al. 2004; Schmidhuber and Tubiello 2007; Supit et al. 2012). Recent research reveals that crop yields will be negatively affected by climate change much sooner than predicted, and importantly the impacts will vary both from year to year and from place to place (Walsh 2014; Wheeler and von Braun 2013; Yang 2009). Therefore, there is an urgent need to look at the problem of climate change not only in terms of its overall effects on agriculture and agroecosystems (Walker and Schulze 2008), but also for impacts at different levels of spatial scale, for example at the watershed, field, and plant levels. The increases in CO2 levels, global temperatures, and more frequent extreme weather events will not affect plants, insects and other fauna, soil biota, and their interactions equally throughout the ecosystem (Eastburn et al. 2011; Lake and Wade 2009). Likewise, abiotic components such as soil nutrients will be differentially impacted, and thus it is difficult to predict the response of ecosystems including agroecosystems to such changes (Reeves 1997; Seybold et al. 1999). But first we need to understand individual species’ responses to change (Goudriaan and Zadoks 1995). Recognizing the scarcity of available data and the importance of needed additional research, we present this review to describe responses—at both macro- and microlevels—of crops to the different manifestations of climate change. 2.2  CLIMATE CHANGE (CC): WHAT IS CHANGING AND HOW? There is no doubt that the global climate is changing, as described in detail in Chapter 1. The most measurable changes in our modern era began during the industrial revolution. This period marked the beginning of significant human contributions to greenhouse gas emissions. Multiple studies consistently report that atmospheric CO2, a major greenhouse gas, has increased worldwide since the 1800s. For example, it was noted that pre-industrial atmospheric CO2 levels ranged between 275 and 284 ppm, with the lowest levels recorded between 1550 and 1800 ad. However, major CO2 increases have occurred since the period of the industrial revolution (Etheridge et al. 1996). Extensive literature is available on the corollary relationship between atmospheric levels of CO2 and rising temperatures in the Earth’s atmosphere. Research indicates that CO2 increased by approximately 30%, while average temperature increased by 0.3°–0.6°C, over the past two centuries. Researchers predict that global temperature will rise by 0.9°–3.5°C by the end of the twenty-first century (Table 2.1) (Anonymous 2014; Lawlor 2005). In this context, the problem of climate change should be interpreted within the context of two different but likely ecological impacts at the global scale. The first impact will be on the carbon cycle itself (Follett et al. 2012; Lal 2004), the second will affect biodiversity, and these two impacts will be manifested in the redistribution of plant species. In agriculture, both will affect individual crop changes. The frequency of climatic events is illustrated more by changes in the variability of temperature and CO2 than in their means, and results to date show that experiments using climate models need to be further developed to more accurately detect climate variability changes (Katz and Brown 1992). Their impacts are more difficult to understand in the physiological effects on plants and to model for either crops or systems (Figure 2.1).

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Table 2.1 Projected Global Average Surface Warming and Sea Level Rise at the End of the Twenty-First Century Temperature Change (°C at 2090–2099 Relative to 1980–1999)a Case Constant Year 2000 concentrationsb B1 scenario A1T scenario B2 scenario A1B scenario A2 scenario A1F1 scenario

Sea Level Rise (m at 2090–2099 Relative to 1980–1999). Model-Based Range Excluding Future Rapid Dynamical Changes in Ice Flow

Best Estimate

Likely Range

0.6

0.3–0.9

NA

1.8 2.4 2.4 2,8 3.4 4.0

1.1–2.9 1.4–3.8 1.4–3.8 1.7–4.4 2.0–5.4 2.4–6.4

0.18–0.38 0.20–0.45 0.20–0.43 0.21–0.48 0.23–0.51 0.26–0.59

Source: IPCC (2007). a These estimates are assessed from a hierarchy of models that encompass a simple climate model, several Earth System Models of Intermediate Complexity and a large number of Atmosphere-Ocean General Circulation Models (AOGCMs). b Year 2000 constant composition is derived from AOGCMs only.

Figure 2.1 Anthropogenic emissions of CO2, CH4, N2O, and sulphur dioxide for the six illustrative SRES scenarios, A1B, A2, B1 and B2, A1F1 and A1T. For comparison the IS92a scenario is also shown. (Based on IPCC (Intergovernmental Panel on Climate Change). 2000. IPCC special report. Emissions scenarios. Policy makers. A Special Report of IPCC Working Group III. IPCC. https:// ipcc.ch/pdf/special-reports/spm/sres-en.pdf. Accessed: February 18, 2018.)

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2.3 HOW PLANTS RESPOND TO CLIMATE CHANGE? The responses of plants to past climate changes indicate that migration of plant communities was the most frequent reaction, and individual species response has led to changes in vegetative composition of natural ecosystems (Huntley 1991). Current climate change is characterized by a decrease in frost, snow and ice cover, and an increase in rainfall in many areas, particularly at high latitudes. Some areas will suffer more from drought in the future. Climate change is impacting cloud formation and consequently solar radiation. These results are relevant to predicting the future adaptation of crop species. Because climate change may alter the timing and severity of stress and disturbance in many systems (Wolkovich and Cleland 2014), plants as components of agroecosystems adapt to these changes through modifications in their growth patterns as a result of both natural and guided genetic selection (Ainsworth and Long 2005; Lawlor 2005; Tubiello et  al. 2007; Walther et  al. 2002; Wullschleger and Norby 2001). Modified crop species have been tested by plant breeders and incorporated by farmers into better-adapted systems to keep up with climate change. For thousands of years, many crops have been modified to thrive in new conditions, but as the climate is changing faster everyone who now depends on agroecosystems for food is increasingly challenged to keep pace with new developments. Each crop species will manifest different responses, growing and yielding less where the climate is becoming too stressful and hostile, and prospering where the climate is becoming more favorable (Tylianakis et al. 2008). Predominant food crops as well as cropping systems in each area will have to be designed and managed to adapt to new realities, and the most desirable species and systems in which they are grown will have to be modified accordingly (DaMatta 2004; Lin 2011; Lin et al. 2008). 2.4  EFFECTS OF CO2 The responses of plants to Free-Air Carbon dioxide Enrichment (FACE) have been actively researched, and different effects have been observed and reported in different species. In general, the effects are likely to cause major consequences in both natural environments and agroecosystems (Drake et al. 1997). Drake et al. (1997) provide examples that show yields for some crops such as wheat and soybeans potentially increasing by 30% or more under a doubling of CO2 concentrations. On the other hand, yields for other major crops such as maize exhibit less response and could potentially increase by only 10%. The first response of plants to rising atmospheric CO2 (Ca) is to increase the efficiency of other resource use such as water and nutrients (Rockström 2003). Generally, increases are seen in water use efficiency (WUE) and instantaneous transpiration efficiency (ITE), although a decline in rate may be observed with time (Eamus 1991; Nogueira et al. 2004; Norby et al. 2001). Researchers report that WUE and ITE increase considerably with elevated CO2, however the magnitude of this boost varies from no effect (Field et al. 1997) to +180% (De Luis et al. 1999), and the increase of WUE is greater in plants and ecosystems under drought (Arp et al. 1998; Field et al. 1997). Long-term exposure to Ca elicits acclimatization mechanisms such as changes in key enzymes active in the photosynthetic carbon reduction cycle, causing an increase of nutrient use efficiency (NUE), and this may result in changes in leaf conductance (Vico et al. 2013). On the other hand, the responses of leaf conductance and photosynthesis rate were found to be highly correlated, suggesting a simultaneous response to Ca, but differing over time at high temperatures (Del Pozo et al. 2005). Furthermore, Ca also enhanced greater carbon to nitrogen ratio (C/N) in plants due to negative relations between WUE, the root mass ratio, and nitrogen use efficiency (NUE). Declines in plant nitrogen (N) concentration and/or content under CO2 enrichment were, in part, associated with stomatal conductance and reduction in transpiration (McDonald et al. 2002). However, WUE was

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enhanced with higher N application under high Ca, but greater increase of NUE was noted with lower N application (Hunsaker et al. 2000; Li et al. 2003; Schapnedonk et al. 1997). Carbon dioxide enrichment was also reported to improve soil-water balance as soil moisture is less depleted under elevated CO2 (Robredo et al. 2007). This leads to increased soil wetness (Manabe and Wetherald 1987) and deep soil moisture storage (Nelson et al. 2004). Little is known about the direct effect of Ca and the concentration of secondary compounds in higher plants. According to Lambers (1993), an accumulation of phenolic compounds was noted in plants exposed to elevated CO2, however this accumulation is rather due to limitation of nutrients (nitrogen supply) than to direct Ca. One key question that arises from these observations is whether the response of plants exposed to a single-step Ca increase will be similar to a gradual exposure over several decades. Although the two approaches have not yet been investigated, a response in a model plant–soil system suggests that the response of some communities to Ca might be overestimated because the biota may be more sensitive to ecosystem changes resulting from abrupt CO2 increases (Klironomos et al. 2005). From the critical point of view, all predicted responses of crops to Ca are based on developing predictive models, for example, correlating CO2 increases with the growth and yield of crops. Therefore, the future responses of crops, including predictions of their distribution, were defined and redrawn based on this changing Ca. However, these models are subject to many larger-scale uncertainties such as land uses effects, deforestation rate and tree dieback, differential availability of seeds, and the growth of plants, as well as changes in design of cropping systems which are discussed in Chapter 7. Net overall effect can become either a source of additional CO2 (quickening the warming) or a lowering of CO2 (reducing the warming). According to these models, the capacities of crops to support atmospheric CO2 should be greater, and Ca in agricultural systems should be intensively implemented at higher latitudes to reduce the capacity of soils to store carbon below the current capacity. 2.5  EFFECTS OF TEMPERATURE The effects of projected global warming on crop growth and yield have in most cases been estimated using simulation models and mathematical projections (Challinor et al. 2005; Wheeler et  al. 2000). Appropriate and robust models can help researchers understand the interactions of genetics, physiology, and the environment, as well as assist in understanding how to modify practices, make management decisions, and create recommendations for appropriate cultivars. These include fertilization, tillage, and irrigation practices that are most beneficial under changing climate conditions. Such models also assist policy-makers in understanding the potential effects of climatic change using large-area yield forecasts. Nevertheless, the use of these models should be considered with caution. It is necessary to determine whether current models that start with plant responses have been tested in different environments and are appropriate for larger systems and also whether their complexity is appropriate for a particular purpose. If such factors are considered, the use of models can potentially play an important role in research and crop management as well as in addressing important policy questions (Boote et al. 1996). Any modeling work can help identify gaps in current research and provide understanding of model components. Practical applications of temperature studies have been used in the revision of maps of zones of adaptation for horticultural crops in the United States (Dobroski et al. 2013). These maps are similar to the assisted migration of forest species and are also analogous to northward changes in geographic areas of different maturities of soybean that illustrate an agronomic adaptation to increasing temperatures (Dobroski et al. 2013). Additional studies would provide more reliable information that could make assessing the impact of climate change on crop production more accurate and could then inform the practical adaptation

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process for crops needed to fit into this new climate reality. Investigating climate-yield relationships is fundamental for forecasting crop growth and development within the cropping season, as well as for projecting the impact of future climate changes (Lobell et al. 2007, 2008). Global warming and increase of temperatures could induce greater vegetative growth of some crops but might also reduce yields. Under warmer environments, for example, crops tend to grow faster, and in cereals this extra growth may reduce the filling period, speed maturation, and cause yield reduction (Ferris et al. 1998; Muchow et al. 1990; Stone and Nicolas 1995). Peng et al. (2004) analyzed weather data over 24 years (1979–2003) to assess the relationship between rice yield and temperatures; they found that grain yield decreased by 10% for each 1°C increase. In addition, direct evidence was reported of decreased rice yields from increased nighttime temperature, no doubt due to higher respiration rates. Similar results reported by Gibson and Paulsen (1999) showed that high temperature reduced grain yield by 18%. In some regions, temperature increases might benefit crops that originate there. Nonetheless, for any specific crop, the effect of temperature increase will depend on the optimal temperature for growth and reproduction (Chen et al. 1982). Temperatures above the optima may be very harmful to crops (Schlenker and Roberts 2009), and in cases where temperatures exceed optimum growing temperatures, yields can decline (Deutsch et al. 2008; Muchow et al. 1990). Indeed, temperature increase driven by increase in atmospheric CO2 is a key driver of change, and most reports showed that such an increase could also directly alter crop phenology. Responses of crop species to elevated CO2 have shown accelerated phenological development, although crop species respond more to elevated CO2 than do wild species, perhaps because their growth is not limited by other resources such as nutrients, water, and light (Hill and Li 2016). It is likely that the managed populations and intraspecific competition are different in current monocultures than the interspecific competition from other species growing simultaneously on the same land (Beer et al. 1998; Francis 1986). 2.6  EFFECTS OF DROUGHT The term “drought” is considered too “labile” because it is difficult to make predictions about ecosystem reactions to this condition. Purists define drought as “a meteorological condition characterized by a substantial period of low or no rainfall,” while crop scientists consider drought rather as “an environmental circumstance during which plants show reduced growth or yield because of insufficient water supply or a high humidity deficit” (Passioura 1997; Wilhite and Glantz 1985). In addition to the constraints of elevated CO2 and warming, attention should also be paid to the impact of variable water supply on crop yields and productivity. It is necessary to have a comprehensive picture of crop performance during water shortage and assess as accurately as possible the effects of drought on crop growth, development, and final yields. Drought is a stress that affects crops at various times and degrees of severity, and the responses of crops to drought are more complex than appear at first glance (Blum 1996). Blum et al. (1985) investigated multiple wheat genotypes under different moisture conditions and found a positive correlation between the “drought-susceptibility index” and canopy temperatures. On the other hand, Leakey et al. (2006) reported that in the absence of drought, photosynthesis and yield of maize were unaffected even under rising CO2, and recently Lobell et al. (2014) reported that drought tolerance of crops is translated into higher average yields in maize and soybeans. With global warming and concurrent climate change, dealing with drought will likely become a serious and challenging issue in regions where temperatures are increasing and precipitation decreasing, hence reducing water supply to crops. As described in previous sections, under warmer temperature conditions and as climate change progresses, drought is projected to intensify in many regions and at a larger scale, such that even regions of high precipitation will be affected. When

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compared to other climate changes, predictions of drought-induced triggers and their impacts on crops remain full of uncertainties. Limited available observations suggest that the recent drought was more extensive than that observed during previous periods, and in the future drought events might be more severe under warmer conditions. 2.7  GENE EXPRESSION The development of molecular biology, and more recently omics technologies, is helping scientists to better understand and predict to some degree how climate change can affect crops and how crops differ in their acclimation capacities by modifying their tolerances to rising CO2, warming temperatures, and increasing drought (Benkeblia 2014; Somero 2010). The analyses at genome, transcriptome, proteome, and metabolome levels will contribute to revealing the types and levels of change needed to adapt molecular and regulatory mechanisms to changing climate. Additional information will provide insights into potential rates of adaptive evolution and capacities for modifying crops to address acute and long-term environmental changes (Ahuja et  al. 2010; Habash et al. 2009; Somero 2010). The real challenge is not only to predict climate changes over the long term, but also to understand the trends of natural crop evolution as well as manipulation by plant breeders in this changing climate, and to identify which crops can acclimate without being affected and which crops are living near their physiological limits; the latter may be considered “losers” in the future (Hoffmann and Sgrò 2011). Climate change can rapidly shift allele frequencies in populations with relatively short generation times, and many such shifts have now been linked to global warming (Hoffmann and Willi 2008). Therefore, it was suggested that to understand gene expression and predict crop responses to the changing climate, gene functions such as genetic control of flowering time and phenotypic plasticity should be investigated in naturally varying conditions (gene-by-environment interaction) (Shimizu et al. 2011). Flowering of crops is affected by climate change, and the onset of flowering is controlled by photo- and thermo-periods. Recent studies have reported that floral regulator genes, thought to act independently of the environment, were found to be involved in mediating the effects of temperature that were shown to affect floral pathway expression (Aikawa et al. 2010; Blázquez et al. 2003). Consequently, earlier onset of crop flowering, often associated with warmer spring temperatures, affects the rate of plant development by shortening early development stages, affecting the grain fill period, and reducing crop yields (Craufurd and Wheeler 2009). Similar earlier onset of flowering caused by drought was also reported in several annual crops, thus confirming the genetic basis of evolutionary shifts driven by climate change (Franks et al. 2007). In order to mitigate the negative impacts of climate change on early flowering, a range of adaptation options exists such as changing the timing of cultivation, selecting other crop species and cultivars (Olesen et al. 2011), modifying time of planting (Matthews et  al. 1997), and using protected cultivation for many crops. Much remains unknown in the field of gene expression in response to climate change, but research on crop responses to abiotic stresses is making substantial progress. Advances at the genomic level, as well as results of other high throughput technologies, began making it possible to distinguish between responses to different abiotic stressors. Although results of some experiments have advanced the understanding of the effects of climate variables on gene expression at the scale of the individual plant, these effects on a global scale remain uncertain. However, at the population level the existing models have started to incorporate more sophisticated climate predictions to reliably discern the acclimation potential of crops. Modern agroecology is now one of the disciplines addressing the role of changing climate and the responses of crop ecosystems, as well as informing the challenge to scaling up from individual response to population and ecosystem levels.

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2.8  PHENOTYPE PLASTICITY While extensive research has focused on the genetic responses of plants to climatic change, phenotypic plasticity is also an important aspect of these responses. In this context, “phenotypic plasticity” describes the differences in the physiology, morphology, and development of crops that arise in response to changes in their close environment, including reversible (acclamatory) and nonreversible phenotypic changes (Bradshaw 1965; Callahan et al. 1997; Jump and Peñuelas 2005). Because plants are sessile, cannot seek out optimal environmental conditions to complete their biological cycles, and must therefore function completely wherever they are growing, they must be remarkably plastic. A single genotype has potential to give rise to a wide range of phenotypes. Thus, phenotypic plasticity has numerous implications for the evolution and the ecology of plants and could contribute substantially to improving yields, total production, and resilience in agriculture (de Jong and Leyser 2012). However, adaptation by plasticity has evolved differently in different species, and the mechanisms involved are varied (Bradshaw 1965; Matesanz et al. 2010). Traits enabling plants to adapt to changing climate can be tissue turnover, transpiration rate, and root/shoot ratio, and these are physiologically linked to key growth-related traits such as photosynthesis rates, leaf area, nutrient uptake, and growth rate (Chapin and Kellar 1993; Gimeno et al. 2009). Consequently, plants have the ability to modify their phenotypes to adapt to different environmental conditions (Mercer and Perales 2010; Sultan 1995). The occurrence of phenotypic plasticity is ubiquitous, and even though it has a genetic basis, very few studies have reported on the molecular mechanisms of phenotypic plasticity (Zhang et al. 2012). Plastic response does not require “evolution” (i.e., changes in gene frequencies), and many “adapting” plants continue yielding similarly because of greater or lesser plastic responses to specific elements of changing conditions (Scheiner 1993). In response to warming, a crop plant will probably respond through shifts in its morphology, phenology, or development, which may help it maintain fitness (Stearns 1989). The phenotypic changes that have been observed are surface leaf area (SLA), root development, and vessel distribution (von Arx et al. 2012). Anderson et al. (2012) combined data from a continuous 38 years’ field survey to assess adaptation of Drummond’s rockcress (Boechera stricta) to climate change and found that flowering phenology was strongly correlated to warmer temperatures and earlier snowmelt dates. Drought also increased stomatal density, and research showed that abaxial stomatal density and leaf area are plastic in their response to water and temperature manipulations; however, the potential to adapt and respond to a combination of drought and warming is limited (Fraser et al. 2009). It is clear that many areas lack long-term, ground-based phenological observations. Therefore, robust phenological models are recommended to simulate future species phenology. It would be particularly desirable to advance the ability of phenological models to predict SLA potential to influence carbon balance, growth, and yield. Even though much is known on the physiological pathways that underlie plant phenology, not much is known about how environmental changes influence or interact with endogenous cues to developmental events. By incorporating newly understood physiological pathways, phenological models might further our understanding about whether phenological response to warming is more consistent, versus less consistent responses to other global changes such as elevated CO2. 2.9  CLIMATE CHANGE AND PHYSIOLOGICAL RESPONSES IN PHOTOSYNTHESIS Results from recent research reflect the direct effects of increasing CO2 concentration on photosynthesis, with the prediction that increasing plant activity and biomass production will

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result from changes in the CO2 concentration gradient between atmosphere and leaf (DaMatta et  al. 2010). This is due to saturation of the RuBisCO (ribulose-1.5-bisphosphate carboxylase) pathway, which is the CO2-fixing enzyme for primary carboxylation, the metabolic process that drives photosynthesis in C3 plants such as many major crops. This process would not have as much effect on other photosynthetic systems, C4, and CAM (Crassulacean Acid Metabolism), due to their compartmented CO2 fixation and photosynthesis features. However, one question that arises is: to what extent would overall agroecosystems be impacted? It is certain that the interacting effects of CO2 concentration and temperature on crop growth will become more complex and difficult to research. Understanding these interactions would contribute substantially to models of how climate change will affect agroecosystems and thus improve models to predict outcomes of individual crops, future agricultural systems, and future food supply. 2.10  CLIMATE CHANGE AND CROP QUALITY There is extensive literature on the impacts of climate change on crop productivity, but few studies have focused on how climate change would impact the nutritional qualities of crops and few examples have been reported (DaMatta et al. 2010). Ahmed et al. (2014) investigated the direct and interactive effects of water availability on tea growth and functional quality, including phytochemical content. They found that higher water availability significantly increased total phenolic content and methylxanthine, but lower concentrations of epicatechin 3-gallate were observed. The analysis of rice quality indicated that high-CO2-grown rice showed better firmness, but iron and zinc levels were lower, suggesting the need to select more productive cultivars able to maintain suitable quality characteristics under rising CO2 levels (Seneweera and Conroy 1997). Another issue raised is the impact of climate change on the microbiological and toxicological pre- and post-harvest qualities of crops. The review of Magan et al. (2011) examined information on the possible impacts of climate change on pre- and post-harvest mycotoxin contamination of food crops. From the available literature, environmental stress conditions might stimulate toxin production (Schmidt-Heydt and Geisen 2007), and combined interaction of high CO2, temperature, and water availability may also stimulate growth of some mycotoxigenic species (Cairns-Fuller et al. 2005). 2.11  CONCLUSIONS AND FUTURE DIRECTIONS Climate change issues should be considered as a “multidisciplinary problem that requires multidisciplinary solutions.” Any consideration of system dynamics and impact on food supply must be based on clear understanding of the responses of plants to past climatic changes, as well as predicted future weather and climate patterns. Despite our knowledge of crop responses to varying environmental factors, we still need to understand better how such responses change over a shorter time period and in response to rapid changes in weather. There is no doubt that we know very little about how crops will interact with many extreme changes or how they will adapt to major events such as rising CO2, global warming, and drought. Understanding this is difficult because weather events vary with time and location, and their interactions are even more complex. Therefore, our understanding should start with focus on individual environmental factors, and this can contribute to comprehensive models of plant reactions. By learning about potential effects of climate change on plants, it will be possible to build on this foundation to provide data to construct viable models to predict more reliably the changes that are likely in the future. This is essential for scaling up to construct better understanding of plant communities and agroecosystems. The real challenge lies in synthesizing across different scales of inference and making reliable predictions about future global change impacts on individual crops.

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Several other chapters present details on the impacts of climate change on specific crop species, and relevant information can be synthesized into meaningful data sets that can be applied to agroecosystems. It is essential not just to adapt to future changes in weather and climate changes, but also to inform the design and proactively implement more resilient and sustainable future agroecosystems. 2.12 SUMMARY Agriculture is the most important sector in many countries’ economies, and it is widely recognized that sustainable production is greatly dependent on long-term climate as well as short-term, unpredictable weather. Average global temperature and atmospheric CO2 are currently increasing, and it is ever more crucial that we understand how different crop plants respond (Streck 2005). It is essential that we observe how crops are likely to cope with these changes in the future, and the individual species’ performance can inform how agroecosystems can be designed for greater resilience (Naylor 2009). Climate change is location specific, characterized by a decrease in frost, snow, and ice cover in some places and by increase in rainfall in others. Some regions will suffer from more frequent drought. Trends in global warming, rising CO2 levels, their combined impacts on ecosystems, and the responses of plants are already clearly visible. Impacts include changes in timing and severity of stress and disturbance, affecting growth and yield of crops. It has been widely demonstrated that frequency of weather events is manifested more in changes in variability and frequency than in long-term means (Porter and Semenov 2005). Thus, research should contribute to climate models that reflect changes in climate variability. Climate change issues should be considered “multidisciplinary problems that require multidisciplinary solutions.” Considering the responses of plants to past climatic changes, the role of adaptation should not be underestimated. We should thus concentrate on accurately predicting responses of crop species to potential future climatic changes. Our current capacity to generate useful predictions remains limited by lack of knowledge of plant responses to varying environmental factors. It is essential to understand better what plant responses will be in the short and long terms, especially in the face of rapidly changing frequency and severity of extreme climate elements. This information will contribute to preparing for unexpected weather through choice of crops and design of cropping systems to mitigate extreme weather impacts. In this review, we describe the responses at the plant level to multiple contributing forces and effects of climate change. ACKNOWLEDGMENTS The authors thank Dr. Rachel Schattman, Center for Sustainable Agriculture, The University of Vermont, for her comments and critical reading of the manuscript. REFERENCES Ahmed, S., C. Orians, T. S. Griffin et al. 2014. Effects of water availability and pest pressures on tea (Camellia sinensis) growth and functional quality. AoB Plants 6:plt054. DOI:10.1093/aobpla/plt05. Ahuja, I., R. C. H. de Vos, A. M. Bones, and R. D. Hall. 2010. Plant molecular stress responses face climate change. Trends Plant Sci 15:664–74. Aikawa, S., M. J. Kobayashi, A. Satake, K. K. Shimizu, and H. Kudoh. 2010. Robust control of the seasonal expression of the Arabidopsis FLC gene in a fluctuating environment. Proc Natl Acad Sci USA 107:11632–7. Ainsworth, E. A., and S. P. Long. 2005. What have we learned from 15 years of free-air CO2 enrichment (FACE)? A meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2. New Phytol 165:351–72.

CROP SPEcIES RESPONSES AND ADAPTATION TO RISE IN CARBON DIOXIDE

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Anderson, J. T., D. W. Inouye, A. M. McKinney, R. I. Colautti, and T. Mitchell-Olds. 2012. Phenotypic plasticity and adaptive evolution contribute to advancing flowering phenology in response to climate change. P Roy Soc B 22 279:3843–52. Anonymous. 2014. Rising global temperatures and CO2. Climate Central. http://www.climatecentral.org/. (accessed: May 13, 2017). Antle, J. M., and S. M. Capalbo. 2010. Adaptation of agricultural and food systems to climate change: An economic and policy perspective. App Econ Persp Policy 32:386–416. Arp, W. J., J. E. M. Van Mierlo, F. Berendse, and W. Snijders. 1998. Interactions between elevated CO2 concentration, nitrogen, and water: Effects on growth and water use of six perennial species. Plant Cell Environ 21:1–11. Beer, J., R. Muschler, D. Kass, and E. Somarriba. 1998. Shade management in coffee and cacao plantations. Agroforest Syst 38:134–64. Benkeblia, N. 2014. Omics Technologies and Crops Improvement. Boca Raton, FL: CRC Press. Blázquez, M. A., J. H. Ahn, and D. Weige. 2003. A thermosensory pathway controlling flowering time in Arabidopsis thaliana. Nat Genet 33:168–71. Blum, A. 1996. Crop responses to drought and the interpretation of adaptation. Plant Growth Reg 20:135–48. Blum, A., L. Shpiler, G. Golan, and J. Mayer. 1985. Yield stability and canopy temperature of wheat genotypes under drought-stress. Field Crops Res 22:289–96. Boote, K. J., J. W. Jones, and B. Nigel-Pickering. 1996. Potential uses and limitations of crop models. Crop Sci 88:704–16. Bradshaw, A. D. 1965. Evolutionary significance of phenotypic plasticity in plants. Adv Genet 13:115–50. Cairns-Fuller, V., D. Aldred, and N. Magan. 2005. Water, temperature, and gas composition interactions affect growth and ochratoxin A production by isolates of Penicillium verrucosum on wheat grain. J Appl Microbiol 99:1215–21. Callahan, H. S., M. Pigliucci, and C. D. Schlichting. 1997. Developmental phenotypic plasticity: Where ecology and evolution meet molecular biology. Bio Essays 9:519–25. Challinor, A. J., T. R. Wheeler, P. Q. Craufurd, and J. M. Slingo. 2005. Simulation of the impact of high temperature stress on annual crop yields. Agr Forest Meteorol 135:180–9. Chapin, F., and S. Kellar. 1993. Autumn and Francisco pugnaire. Evolution of suites of traits in response to environmental stress. Am Nat 142:S78–92. Chen, H. H., Z. Y. Shen, and P. H. Li. 1982. Adaptability of crop plants to high temperatures stress. Crop Sci 22:719–25. CGCR (Committee on Global Change Research). 1999. Global Environmental Change: Research Pathways for the Next Decade. Washington, DC: National Academy Press. Craufurd, P. Q., and T. R. Wheeler. 2009. Climate change and the flowering time of annual crops. J Exp Bot 60:2529–39. DaMatta, F. M. 2004. Ecophysiological constraints on the production of shaded and unshaded coffee: A review. Field Crops Res 84:99–114. DaMatta, F. M., A. Grandis, B. C. Arenque, and M. S. Buckeridge. 2010. Impacts of climate changes on crop physiology and food quality. Food Res Int 43:1814–23. Darnhofer, I. 2014. Resilience and why it matters for farm management. Eur Rev Agric Econ 41:461–84. de Jong, M., and O. Leyser. 2012. Developmental plasticity in plants. Cold SH S B 77:63–73. Del Pozo, A., P. Pérez, R. Morcuende, A. Alonso, and R. Martínez-Carrasco. 2005. Acclimatory responses of stomatal conductance and photosynthesis to elevated CO2 and temperature in wheat crops grown at varying levels of N supply in a Mediterranean environment. Plant Sci 169:908–16. De Luis, I., J. J. Irigoyen, and M. Sanchez-Diaz. 1999. Elevated CO2 enhances plant growth in droughted N2-fixing alfalfa without improving water status. Physiol Plant 107:84–9. Deutsch, C. A., J. J. Tewksbury, R. B. Huey et al. 2008. Impacts of climate warming on terrestrial ectotherms across latitude. Proc Natl Acad Sci USA 105:6668–72. Dobroski, S. Z., J. Abatzoglou, A. K. Swanson et al. 2013. The climate velocity of the contiguous United States during the 20th century. Global Change Biol 19:241–51. Drake, B. G., M. A. Gonzàlez-Meler, and S. P. Long. 1997. More efficient plants: A consequence of rising atmospheric CO2? Annu Rev Plant Physiol Plant Mol Biol 48:609–39. Dwivedi, S., K. Sahrawat, H. Upadhyaya, and R. Ortiz. 2013. Food, nutrition, and agrobiodiversity under global climate change. Adv Agron 120:1–128.

30

CLIMATE CHANGE AND CROP PRODUcTION

Eamus, D. 1991. The interaction of rising CO2 and temperatures with water use efficiency. Plant Cell Environ 14:843–52. Eastburn, D. M., A. J. McElrone, and D. D. Bilgin. 2011. Influence of atmospheric and climatic change on plant–pathogen interactions. Plant Pathol 60:54–69. Etheridge, D. M., L P. Steele, R. L. Langenfelds, R. J. Francey, J. M. Barnola, and V. I. Morgan. 1996. Natural and anthropogenic changes in atmospheric CO2 over the last 1,000 years from air in Antarctic ice and firn. J Geophys Res-Atmos 101:4115–28. Ferris, R., R. H. Ellis, T. R. Wheeler, and P. Hadley. 1998. Effect of high temperature stress at anthesis on grain yield and biomass of field-grown crops of wheat. Ann Bot 82:631–9. Field, C. B., C. P. Lund, N. R. Chiariello, and B. E. Mortimer. 1997. CO2 effects on the water budget of grassland microcosm communities. Global Change Biol 3:197–206. Follett, R. F., C. E. Stewart, E. G. Pruessner, and J. M. Kimble. 2012. Effects of climate change on soil carbon and nitrogen storage in the U.S. Great Plains. J Soil Water Conserv 67:331–42. Francis, C. A. 1986. Multiple Cropping Systems. New York, NY: Macmillan Publishers. Franks, S. J., S. Sim, and A. E. Weis. 2007. Rapid evolution of flowering time by an annual plant in response to a climate fluctuation. Proc Natl Acad Sci USA 104:1278–82. Fraser, L. H., A. Greenall, C. Carlyle, R. Turkington, and C. Ross-Friedman. 2009. Adaptive phenotypic plasticity of Pseudoroegneria spicata: Response of stomatal density, leaf area, and biomass to changes in water supply and increased temperature. Ann Bot 103:769–75. Fuhrer, J. 2003. Agroecosystem responses to combinations of elevated CO2, ozone, and global climate change. Agr Ecosyst Environ 97:1–20. Gibson, L. R., and G. M. Paulsen. 1999. Yield components of wheat grown under high temperature stress during reproductive growth. Crop Sci 39:1841–6. Gimeno, T. E., B. Pías, J. P. Lemos-Filho, and F. Valladares. 2009. Plasticity and stress tolerance override local adaptation in the responses of Mediterranean holm oak seedlings to drought and cold. Tree Physiol 29:87–98. Goglio, P., B. B. Grant, W. N. Smith et al. 2014. Impact of management strategies on the global warming potential at the cropping system level. Sci Total Environ 490:921–33. Goudriaan, J., and J. C. Zadoks. 1995. Global climate change: Modelling the potential responses of agroecosystems with special reference to crop protection. Environ Pollut 87:215–24. Gregory, P. J., J. S. I. Ingram, and M. Brklacich. 2005. Climate change and food security. Phil T Roy Soc B 360:2139–48. Habash, D. Z., Z. Kehel, and M. Nachit. 2009. Genomic approaches for designing durum wheat ready for climate change with a focus on drought. J Exp Bot 60:2805–15. Hill, C. B., and C. Li. 2016. Genetic architecture of flowering phenology in cereals and opportunities for crop improvement. Front Plant Sci 19:1906. DOI:10.3389/fpls.2016.01906. Hoffmann, A. A., and C. M. Sgrò. 2011. Climate change and evolutionary adaptation. Nature 470:479–85. Hoffmann, A. A., and Y. Willi. 2008. Detecting genetic responses to environmental change. Nat Rev Genet 9:421–32. Holloway, L. E., and B. W. Ilbery. 1996. Farmers’ attitudes towards environmental change, particularly global warming, and the adjustment of crop mix and farm management. Appl Geogr 16:159–71. Howden, S. M., J. F. Soussana, F. N. Tubiello, N. Chhetri, M. Dunlop, and H. Meinke. 2007. Adapting agriculture to climate change. Proc Natl Acad Sci USA 104:19691–6. Hunsaker, D. J., B. A. Kimball, P. J. J. Jr. Pinter et al. 2000. CO2 enrichment and soil nitrogen effects on wheat evapotranspiration and water use efficiency. Agr Forest Meteorol 104:85–105. Huntley, B. 1991. How plants respond to climate change: Migration rates, individualism, and the consequences for plant communities. Ann Bot 67(Suppl. 1):15–22. Idso, K.E., and S.B. Idso. 1994. Plant responses to atmospheric CO2 enrichment in the face of environmental constraints: A review of the past 10 years’ research. Agr Forest Meteorol 69:153–203. IPCC (Intergovernmental Panel on Climate Change). 2000. IPCC special report. Emissions scenarios. Policy makers. A Special Report of IPCC Working Group III. IPCC. https://ipcc.ch/pdf/special-reports/spm/ sres-en.pdf. (accessed: February 18, 2018). IPCC (Intergovernmental Panel on Climate Change). 2001. Climate change 2001: The scientific basis. In Contribution of Working Group I to the Third Assessment Report of the IPCC, eds. J. T. Houghton, Y. Ding, D. J. Griggs et al. Cambridge, MA: Cambridge University Press.

CROP SPEcIES RESPONSES AND ADAPTATION TO RISE IN CARBON DIOXIDE

31

Jump, A. S., and J. Peñuelas. 2005. Running to stand still: Adaptation and the response of plants to rapid climate change. Ecol Lett 8:1010–20. Kang, Y., S. Khan, and M. Xiaoyi. 2009. Climate change impacts on crop yield, crop water productivity and food security—A review. Prog Nat Sci 19:1665–74. Katz, R. W., and B. G. Brown. 1992. Extreme events in a changing climate: Variability is more important than averages. Clim Change 21:289–302. Klironomos, J. N., M. F. Allen, M. C. Rillig et  al. 2005. Abrupt rise in atmospheric CO2 overestimates community response in a model plant–soil system. Nature 433:621–4. Lake, J., and R. Wade, 2009. Plant–pathogen interactions and elevated CO2: Morphological changes in favour of pathogens. J Exp Bot 60:3123–31. Lal, R. 2004. Soil carbon sequestration to mitigate climate change. Geoderma 123:1–22. Lal, R., J. A. Delgado, P. M. Groffman, M. C. Dell, and A. Rotz. 2011. Management to mitigate and adapt to climate change. J Soil Water Conserv 66:276–85. Lambers, H. 1993. Rising CO2, secondary plant metabolism, plant-herbivore interactions, and litter decomposition. Vegetatio 104–105:263–71. Lawlor, D. W. 2005. Plant responses to climate change: Impacts and adaptation. In Plant Responses to Air Pollution and Global Change, eds. K. Omasa, I. Nouchi, and L. J. De Kok, 81–8. Tokyo, Japan: Springer-Verlag. Leakey, A. D. B., M. Uribelarrea, A. Ainsworth et al. 2006. Photosynthesis, productivity, and yield of maize are not affected by open-air elevation of CO2 concentration in the absence of drought. Plant Physiol 140:779–90. Li, F., S. Kang, J. Zhang, and S. Cohen. 2003. Effects of atmospheric CO2 enrichment, water status, and applied nitrogen on water- and nitrogen-use efficiencies of wheat. Plant Soil 254:279–89. Lin, B. B. 2011. Resilience in agriculture through crop diversification: Adaptive management for environmental change. Bioscience 61:183–93. Lin, B. B., I. Perfecto, and J. Vandermeer. 2008. Synergies between agricultural intensification and climate change could create surprising vulnerabilities for crops. Bioscience 58:847–54. Lobell, D. B., C. Bonfils, and P. B. Duffy. 2007. Climate change uncertainty for daily minimum and maximum temperatures: A model inter-comparison. Geophys Res Lett 34:L05715. DOI:10.1029/2006GL028726. Lobell, D. B., and M. B. Burk. 2010. On the use of statistical models to predict crop yield responses to climate change. Agr Forest Meteorol 150:1443–52. Lobell, D. B., M. B. Burke, C. Tebaldi, M. D. Mastrandrea, W. P. Falcon, and R. L. Naylor. 2008. Prioritizing climate change adaptation needs for food security in 2030. Science 319:607–10. Lobell, D. B., M. J. Roberts, W. Schlenker et al. 2014. Greater sensitivity to drought accompanies maize yield increase in the U.S. Midwest. Science 344:516–9. Magan, N., A. Medina, and D. Aldred. 2011. Possible climate-change effects on mycotoxin contamination of food crops pre- and postharvest. Plant Pathol 60:150–63. Manabe, S., and R. T. Wetherald. 1987. Large-scale changes of soil wetness induced by an increase in atmospheric carbon dioxide. J Atmos Sci 44:1211–36. Matesanz, S., E. Gianoli, and F. Valladares. 2010. Global change and the evolution of phenotypic plasticity in plants. Ann NY Acad Sci 1206:35–55. Matthews, R. B., M. J. Kropff, T. Horie, and D. Bachelet. 1997. Simulating the impact of climate change on rice production in Asia and evaluating options for adaptation. Agr Syst 54:399–425. Mattos, L. M., C. L. Moretti, S. Jan, S.A. Sargent, C. E. P. Lima, and M. R. Fontenelle. 2014. Climate changes and potential impacts on quality of fruit and vegetable crops. In Emerging Technologies and Management of Crop Stress Tolerance, Volume 2—A Sustainable Approach, eds. P. Ahmad, and S. Rasool, 467–86. Amsterdam, The Netherlands: Academic Press. Mayes, S., F. J. Massawe, P. G. Alderson, J. A. Roberts, S. N. Azam-Ali, and M. Hermann. 2012. The potential for underutilized crops to improve security of food production. J Exp Bot 63:1075–9. McDonald, E. P., J. E. Erickson, and E. L. Kruger. 2002. Can decreased transpiration limit plant nitrogen acquisition in elevated CO2? Funct Plant Biol 29:1115–20. Mercer, K. L., and H. R. Perales. 2010. Evolutionary response of landraces to climate change in centers of crop diversity. Evol Appl 3:480–93. Muchow, R. C., T. R. Sinclair, and J. M. Bennett. 1990. Temperature and solar radiation effects on potential maize yield across locations. Crop Sci 82:338–43.

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Naylor, R.L. 2009. Managing food production systems for resilience. In Principles of Ecosystem Stewardship, eds. C. Folke, G. P. Kofinas, and F. S. Chapin, 259–80. New York, NY: Springer. Nelson, J. A., J. A. Morgan, D. R. LeCain, A. R. Mosier, D. G. Milchunas, and B. A. Parton. 2004. Elevated CO2 increases soil moisture and enhances plant water relations in a long-term field study in semi-arid shortgrass steppe of Colorado. Plant Soil 259:169–79. Nemecek, T., K. Weiler, K. Plassmann et al. 2012. Estimation of the variability in global warming potential of worldwide crop production using a modular extrapolation approach. J Clean Prod 31:106–17. Nogueira, A., C. A. Martinez, L. L. Ferreira, and C. H. B. A. Prado. 2004. Photosynthesis and water use efficiency in twenty tropical tree species of differing succession status in a Brazilian reforestation. Photosynthetica 42:351–6. Norby, R. J., D. E. Todd, J. Fults, and D. W. Johnson. 2001. Allometric determination of tree growth in a CO2enriched sweetgum stand. New Phytol 150:477–87. Olesen, J. E., M. Trnka, K. C. Kersebaum et al. 2011. Impacts and adaptation of European crop production systems to climate change. Eur J Agron 34:96–112. Parry, M., C. Rosenzweig, C. Iglesias, G. Fischer, and M. Livermore. 1999. Climate change and world food security: A new assessment. Global Environ Chang 9(Suppl. 1):S51–67. Parry, M. L., C. Rosenzweig, A. Iglesias, M. Livermore, and G. Fischer. 2004. Effects of climate change on global food production under SRES emissions and socio-economic scenarios. Global Environ Chang 14:53–67. Passioura, J. B. 1997. Drought and drought tolerance. In Drought Tolerance in Higher Plants: Genetical, Physiological, and Molecular Biological Analysis, ed. E. Belhassen, 1–5. Amsterdam, The Netherlands: Springer. Peng, S., J. Huang, J. E. Sheehy et al. 2004. Rice yields decline with higher night temperature from global warming. Proc Natl Acad Sci USA 101:9971–5. Porter, J. R., and M. A. Semenov. 2005. Crop responses to climatic variation. Philos TR Soc B 360:2021–35. Reeves, D. W. 1997. The role of soil organic matter in maintaining soil quality in continuous cropping systems. Soil Till Res 43:131–67. Robredo, A., U. Pérez-López, H. Sainz de la Maza et al. 2007. Elevated CO2 alleviates the impact of drought on barley improving water status by lowering stomatal conductance and delaying its effects on photosynthesis. Environ Exp Bot 59:252–63. Rockström, J. 2003. Resilience building and water demand management for drought mitigation. Phys Chem Earth 28:869–77. Schapnedonk, A. H. C. M., P. Dijkstra, J. Groenwold, C. S. Pot, and S. C. Van de Geij. 1997. Carbon balance and water use efficiency of frequently cut Lolium perenne L. swards at elevated carbon dioxide. Glob Change Biol 3:207–16. Scheiner, S. M. 1993. Genetics and evolution of phenotypic plasticity. Annu Rev Ecol Syst 24:35–68. Schlenker, W., and M. J. Roberts. 2009. Nonlinear temperature effects indicate severe damages to U.S. crop yields under climate change. Proc Natl Acad Sci USA 37:15594–8. Schmidhuber, J., and F. N. Tubiello. 2007. Global food security under climate change. Proc Natl Acad Sci USA 104:19703–8. Schmidt-Heydt, M., and R. Geisen. 2007. A microarray for monitoring the production of mycotoxins in food. Int J Food Microbiol 117:131–40. Seneweera, S. P., and J. P. Conroy. 1997. Growth, grain yield, and quality of rice (Oryza sativa L.) in response to elevated CO2 and phosphorus nutrition. In Plant Nutrition for Sustainable Food Production and Environment, eds. T. Ando, K. Fujita, T. Mae, H. Matsumoto, S. Mori, and J. Sekiya, 873–8. Amsterdam, The Netherlands: Springer. Seybold, C. A., J. E. Herrick, and J. J. Brejda. 1999. Soil resilience: A fundamental component of soil quality. Soil Sci 164:224–34. Shimizu, K. K., H. Kudoh, and M. J. Kobayashi. 2011. Plant sexual reproduction during climate change: Gene function in natura studied by ecological and evolutionary systems biology. Ann Bot 108:777–87. Singh-Chauhan, B. S., K. Prabhjyot-Kaur, G. Mahajan, R. K. Randhawa, H. Singh, and M. S. Kang. 2014. Global warming and its possible impact on agriculture in India. Adv Agron 123:65–121. Somero, G. N. 2010. The physiology of climate change: How potentials for acclimatization and genetic adaptation will determine ‘winners’ and ‘losers’. J Exp Biol 213:912–20. Stearns, S. C. 1989. The evolutionary significance of phenotypic plasticity. Bioscience 39:436–45.

CROP SPEcIES RESPONSES AND ADAPTATION TO RISE IN CARBON DIOXIDE

33

Stone, P. J., and M. E. Nicolas. 1995. A survey of the effects of high temperature during grain filling on yield and quality of 75 wheat cultivars. Aust J Agr Res 46:475–92. Streck, N. A. 2005. Climate change and agroecosystems: The effect of elevated atmospheric CO2 and temperature on crop growth, development, and yield. Sci Rural Santa Maria 35:730–40. Sultan, S. E. 1995. Phenotypic plasticity and plant adaptation. Acta Bot Neerl 44:363–83. Supit, I., C. A. van Diepen, A. J. W. de Wit et al. 2012. Assessing climate change effects on European crop yields using the Crop Growth Monitoring System and a weather generator. Agr Forest Meteorol 164:96–111. Tausz, M., S. Tausz-Posch, R. M. Norton, G. J. Fitzgerald, M. E. Nicolas, and S. Seneweera. 2013. Understanding crop physiology to select breeding targets and improve crop management under increasing atmospheric CO2 concentrations. Environ Exp Bot 88:71–80. Tubiello, F. N., J. F. Soussana, and S. M. Howden. 2007. Crop and pasture response to climate change. Proc Natl Acad Sci USA 104:19686–90. Tylianakis, J. M., R. K. Didham, J. Bascompte, and D. A. Wardle. 2008. Global change and species interactions in terrestrial ecosystems. Ecol Lett 11:1351–63. Vico, G., S. Manzoni, S. Palmroth, M. Weih, and G. Katul. 2013. A perspective on optimal leaf stomatal conductance under CO2 and light co-limitations. Agr Forest Meteorol 182-183:191–9. von Arx, G., S. R. Archer, and M. K. Hughes. 2012. Long-term functional plasticity in plant hydraulic architecture in response to supplemental moisture. Ann Bot 109:1091–100. Walker, N. J., and R. E. Schulze. 2008. Climate change impacts on agro-ecosystem sustainability across three climate regions in the maize belt of South Africa. Agr Ecosyst Environ 124:114–24. Walsh, B. 2014. Climate change could cause the next great famine. Time March:17. Walther, G. R., E. Post, P. Convey et al. 2002. Ecological responses to recent climate change. Nature 416:389–95. Wheeler, T. R., P. Q. Craufurd, R. H. Ellis, J. R. Porter, and P. V. Vara-Prasad. 2000. Temperature variability and the yield of annual crops. Agr Ecosyst Environ 82:159–67. Wheeler, T., and J. von Braun. 2013. Climate change impacts on global food security. Science 341:508–13. Wilhite, D. A., and M. H. Glantz. 1985. Understanding the drought phenomenon: The role of definitions. Water Int 10:111–20. Wolkovich, E. M., and E. E. Cleland. 2014. Phenological niches and the future of invaded ecosystems with climate change. AoB Plants 6:plu013. DOI:10.1093/aobpla/plu01. Wullschleger, S. D., and R. J. Norby. 2001. Sap velocity and canopy transpiration in a sweetgum stand exposed to free-air CO2 enrichment (FACE). New Phytol 150:489–98. Yang, C. M. 2009. Climate change and food security. J Crop Environ Bioinform 6:134–40. Zhang, C. C., W. Y. Yuan, and Q. F. Zhang. 2012. RPL1, a gene involved in epigenetic processes regulates phenotypic plasticity in rice. Mol Plant 5:482–93.

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Physiological and Morphological Mechanisms Mediating Plant Tolerance to Osmotic Stress Balancing Tolerance and Productivity Md. Hasanuzzaman, Meixue Zhou, and Sergey Shabala CONTENTS 3.1 Introduction............................................................................................................................. 36 3.2 Major Constraints Imposed by Osmotic Stress....................................................................... 37 3.3 Physiological Mechanisms to Deal with Osmotic Stress: Osmitic Adjustment...................... 38 3.3.1 De novo Synthesis of Compatible Solutes................................................................... 39 3.3.1.1 Proline........................................................................................................... 39 3.3.1.2 Glycinebetaine..............................................................................................40 3.3.2 Uptake and Sequestration of Inorganic Ions............................................................... 41 3.4 Physiological Mechanisms to Deal with Osmotic Stress: Transpirational Control................. 42 3.4.1 Stomatal Transpiration under Water Stress................................................................. 43 3.4.2 Cuticular Transpiration under Water Stress................................................................ 43 3.5 Morphological and Anatomical Mechanisms to Deal with Osmotic Stress...........................44 3.5.1 Leaf Anatomical Changes...........................................................................................44 3.5.1.1 Leaf Succulence............................................................................................44 3.5.1.2 Leaf Pubescence........................................................................................... 45 3.5.1.3 Stomatal Density and Size............................................................................ 45 3.5.1.4 Sunken Stomata............................................................................................46 3.5.1.5 Mesophyll and Epidermis Thickness of Leaves...........................................46 3.5.1.6 Bulliform Cells.............................................................................................46 3.5.1.7 Leaf Surface Cuticular Wax......................................................................... 47 3.5.2 Root and Stem Anatomical Change............................................................................ 47 3.5.2.1 Sclerenchyma................................................................................................ 47 3.5.2.2 Aerenchyma.................................................................................................. 47 3.5.2.3 Connective Tissue......................................................................................... 47 3.6 Conclusions.............................................................................................................................. 48 Acknowledgments............................................................................................................................. 48 References......................................................................................................................................... 48

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3.1 INTRODUCTION The world population is projected to increase by more than one billion people within the next 15 years, reaching 8.5 billion in 2030, and to increase further to 9.7 billion in 2050 and 11.2 billion by 2100. This will result in a need to increase the food production by 70% by 2050 to meet the demand (UN 2015). At the same time, global agricultural sustainability is jeopardized by a wide range of abiotic stress conditions; of these, drought and salinity are undoubtedly the most critical. The negative effect of both stresses is exacerbated by the current trends in climate change. Drought and salinity affect more than 10% of arable land, and desertification and salinization are rapidly increasing on a global scale, reducing average yields for most major crop plants by more than 50% (Bray et al. 2000). Therefore, future food security cannot be achieved without a major breakthrough in crop breeding for salinity and drought stress tolerance. The initial responses of plants to drought and salinity are common, and both stresses are attributed to water deficit which induces osmotic stress and inhibits plant growth and development. During the evolutionary shift from water to land, plants had to acquire the tolerance and many strategies to survive exposure to osmotic stress. Drought may occur as a result of both decreased precipitation and/ or increased evaporation over an extended period of time, which are associated with other climatic factors such as high temperatures, high winds, and low relative humidity. In contrast to the permanent aridity in arid regions, drought is a temporary dry period over most parts of the planet which is also related to the occurrence (i.e., principal season of occurrence, delays in the start of the rainy season, occurrence of rains in relation to principal crop growth stages), distribution, the effectiveness of the rains (i.e., rainfall intensity, number of rainfall events), evaporating demand, and moisture storing capacity of soils (McWilliam 1986). Drought severity is enhanced not only by the duration, intensity, and geographical extent of a specific drought episode but also on the demands made by human activities, poor water management, erosion, and vegetation on a region’s water supplies (Dai 2011). Salinity can occur naturally (primary salinity) in soils from long-term chemical and physical weathering of parent materials, rocks, and other geological and organic materials, aerial deposition of ocean salts via wind or rain containing soluble salt compounds like Cl−, Na+, Ca2+, and Mg2+, and sometimes SO42− and CO32− (Rengasamy 2002). Soil salinization also occurs as a result of anthropogenic activities (secondary salinity) including overexploitation of irrigation schemes by low quality irrigation water to crop fields without sustainable drainage systems which triggers the accumulation of salts in the root zone of the plant, affecting soil properties. Salinity is becoming more extensive due to bringing marginal land into production and replacing deep-rooted native perennial vegetation with shallow-rooted annual crops or pastures with less evapotranspiration (Shabala and Munns 2012). It has been estimated that climate change along with warming temperatures will create increasingly severe and prolonged drought episodes in the next 30–90 years that will affect over a third of the Earth, including the world’s best food production areas (Cook et al. 2014; Dai 2011, 2013). This is expected to result in significant (more than 75%) losses in agricultural production worldwide, costing approximately $23.5 billion per year and posing a major risk to the global food security (FAO 2015). On the other hand, salinity affected area is increasing day by day and cutting crop yields by 20%–50% in many regions in the world (Shrivastava and Kumar 2015). Over the last 20 years, the world has been losing about 2,000 ha of irrigated farmland in arid and semi-arid regions across 75 countries every day due to salinity (Qadir et al. 2014). Globally, total cultivable irrigated land is equivalent to 310 million ha producing 36% of the world’s food demand; among them 20% of the area (ca. 62 million ha) is negatively affected by salinity, costing approximately $27.3 billion each year (Qadir et al. 2014). Physiological water deficit or osmotic stresses are the common major physiological mechanisms for salinity and drought stress to reduce the growth and yield of plants as both stresses lower the soil water potential. Early responses of plants to drought and salt stress are largely identical except for

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the ionic component. Exposure to drought or salt stress triggers many common reactions in plants. Both stresses may lead to various physiological changes, such as compromised membrane integrity, nutrient imbalance, impaired ability to detoxify reactive oxygen species (ROS), reduced rate of cell expansion in growing tissue, stomatal closure, and decreased photosynthetic activity (Munns and Tester 2008; Rahnama et al. 2010). Reduction of yield is the ultimate effect of plant growth under osmotic stress conditions. The degree of plant growth and yield restriction due to osmotic stress depends on the severity, duration, and time scale of the osmotic stress response and how the stress treatment was given (rapid or gradual). Mild osmotic stress leads rapidly to growth inhibition of leaves and stems, whereas roots may continue to elongate (Nonami and Boyer 1990; Sharp et al. 1988; Spollen et al. 1993; Westgate and Boyer 1985). In cereals, water stress imposed by salinity and drought reduces yield by more than 60% in their different growth episodes by reducing the growth- and yield-contributing attributes (Farooq et al. 2009; Hakim et al. 2014). As water and salt stresses occur frequently and can affect most habitats, plants have developed several strategies to cope with these challenges: either adaptation mechanisms, which allow them to survive the adverse conditions, or specific growth habits to avoid stress conditions. However, attempts to improve yield under stress conditions by plant improvement have been largely unsuccessful, primarily due to the multigenic origin of the adaptive mechanisms. Therefore, a well-focused approach combining the molecular, physiological, anatomical, biochemical, and metabolic aspects of salt tolerance is essential to develop osmotic stress tolerant crop varieties to meet the upcoming food demand globally. This chapter provides a comprehensive review of the major responses of plants to osmotic stresses caused by salinity and drought, and the physiological and morpho-anatomical mechanisms to adapt the osmotic stress environment. 3.2  MAJOR CONSTRAINTS IMPOSED BY OSMOTIC STRESS Water deficit in the soil generates a low water potential zone around the root making it increasingly difficult for the plant to take up both water and nutrients. As a result, the water absorption capacity of root systems decreases, and water loss from leaves is accelerated due to osmotic stress (Munns 2005). The osmotic phase of salinity stress starts immediately when the electrical conductivity (EC) of the soluble salt concentration around the roots increases to a threshold level 4 dS m−1, equivalent to approximately 40 mM NaCl, and generates an osmotic pressure about −0.2 MPa. The first osmotic phase is a rapid response to the increase in external osmotic pressure and occurs due to the reduction of osmotic potential of the soil solution outside the roots which immediately reduces leaf expansion, cell membrane permeability, and stomatal conductance (Maggio et al. 2007). Drought stress induces different responses in plants depending on three distinct stages of soil dehydration (Serraj and Sinclair 2002). Leaf gas exchange including stomatal conductance, transpiration rate, and leaf growth are inhibited late in stage I and in stage II of soil dehydration when the rate of water uptake from the soil cannot match the potential transpiration rate due to osmotic stress. Under the osmotic stress phase of salinity, the rate of leaf expansion reduces and the emergence of new leaves and lateral bud development either slows down or arrests, leading to fewer branches or lateral shoots and rapid and severe reduction in total leaf area (Fricke 2004; Munns et al. 1995; Yeo et al. 1991). In dicotyledonous species, the major effect is the dramatic decrease of the size of individual leaves or the numbers of branches. Generally, leaf growth is more sensitive to osmotic stress than root growth. For example, mild osmotic stress inhibits the growth of stems and leaves, a phenomenon that also occurs under drought stress conditions (Bartels and Sunkar 2005; Nonami and Boyer 1990). Osmotic stress affects cell division and elongation. Cell division is the key factor of meristem activity and regulates the overall plant growth rate. The growth rate is regulated by cyclin-dependent

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kinase (CDK) activity and cell division (Cockcroft et  al. 2000; West et  al. 2004). CDKs are emerging as key players in the regulation of cell division and are likely to be regulated at both transcriptional and post-translational levels in response to stress. The decrease in the cell division in response to water stress is characterized by lower CDK activity, which is correlated with tyrosine phosphorylation (Schuppler et al. 1998). Cell expansion is a coordinated, controlled process at the whole plant level and is influenced by external stimuli including water availability. The rate of cell expansion is mainly determined by two parameters: cell wall extensibility and cellular osmotic potential. The enlargement of plant cells involves control of wall synthesis and expansion, solute and water transport, membrane synthesis, Golgi secretion, ion transport, and some other processes (Cosgrove 1997). However, the effect of osmotic stress on cell enlargement may also involve other hormones such as auxin, cytokinin, or gibberellins. A sudden increase in soil salinity and water deficit decreases cell volume and turgor due to loss of cell water (Passioura and Munns 2000). Cells regain their original volume and turgor owing to osmotic adjustment within hours, but despite this, cell elongation rates are reduced (Cramer 2002; Fricke and Peters 2002; Passioura and Munns 2000). Over days, reductions in the cell elongation and cell division rates lead to slower leaf appearance and smaller leaf size. With more reduction in area than depth in cell dimension, leaves are smaller and thicker (Shabala and Munns 2012). Osmotic stress reduces the photosynthetic leaf area and the flow of assimilates to the meristematic and growing tissues of both leaves and root. At a cellular level the osmotic stress caused by salinity and drought leads to different consequences depending on the severity of the stress applied. Under severe stress, cell dehydration is a consequence of water removal from the cytoplasm into the extracellular space, thereby decreasing cytosolic and vacuolar volumes and causing plasmolysis (Bartels and Sunkar 2005). These osmotic stresses limit plant growth due to photosynthetic decline and result in the production of ROS leading to membrane damage, nutrient imbalance, altered level of growth regulators, enzymatic inhibition and metabolic dysfunction, DNA damage, enhanced lipid peroxidation, and ultimately plant death (Hasanuzzaman et al. 2012; Mahajan and Tuteja 2005). Another consequence of osmotic stress involves autophagy, an intracellular degradation process that delivers cytoplasmic constituents to the vacuole (Han et al. 2011); this is considered to be a central component in the integrated stress response (Kroemer et al. 2010). Under osmotic stress, cytosolic and organelle proteins show reduced activity or even undergo complete denaturation. The ability of autophagy to scavenge oxidized proteins and to regulate ROS levels suggests its probable role in plant tolerance to salt and drought stresses. 3.3  PHYSIOLOGICAL MECHANISMS TO DEAL WITH OSMOTIC STRESS: OSMITIC ADJUSTMENT Osmotic stress reduces the capacity of roots to extract water from soil leading to decreased cell turgor. This affects plant growth, development, and survival capacity. To deal with this issue, plants need to undergo osmotic adjustment that is achieved by either accumulating a range of organic osmolytes (so-called compatible solutes) or de novo synthesis of compatible solutes within the cytoplasm; the alternative option is increased uptake and sequestration of inorganic ions (Na+, Cl−, and K+) (Shabala and Shabala 2011). Compatible solutes (also known as organic osmolytes) are a group of chemically diverse organic small compounds which have low molecular weight and are highly water soluble, uncharged, polar, and uniformly neutral with respect to the perturbation of cellular functions, even when present at high concentrations (Sakamoto and Murata 2002). The major role of compatible solutes is in mediating osmotic adjustment and sub-cellular structures through maintaining the turgor of cells under water deficit and counteracting the effects of rapid decline in leaf water potential (Wani et al. 2013). These molecules increase the osmotic pressure in the cytoplasm, thereby maintaining a driving gradient for

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both water uptake and turgor pressure. Apart from adaptive roles in mediating osmotic adjustment, these compounds are reported to function as natural scavengers of reactive oxygen species (ROS), having chaperone-like activity, helping in metabolic detoxification, protecting enzymes/proteins from denaturation, stabilizing the membrane or macromolecules, protecting membrane integrity during oxidative damage by stress-induced ROS outbursts, protecting and repairing photosystem 2 (PSII), sourcing of N and C, and improving ionic relations by controlling ion-transport processes (Ashraf and Foolad 2007; Serraj and Sinclair 2002; Shabala and Shabala 2011). Compatible solutes accumulated by plants vary significantly between plant species and belong to one of four major categories: sugars (fructose and glucose), amino acids (proline), polyols (mannitol, sorbitol, glycerol, D-ononitol, trehalose, raffinose, and fructans), and quaternary amines (glycine betaine, β-alanine betaine, pipecolatebetaine). Creating transgenic plants with higher rates of compatible solute production has been found to be a useful strategy to increase osmotic stress tolerance in some species (Ashraf and Foolad 2007; Dörffling et al. 2009; Knipp and Honermeier 2006). 3.3.1  De novo Synthesis of Compatible Solutes 3.3.1.1 Proline Higher plants accumulate more proline than any other amino acid. In addition to acting as an outstanding osmolyte for osmotic adjustment, proline contributes to stabilization of sub-cellular structures (e.g., membranes and proteins), scavenging free radicals, and buffering cellular redox potential under stress conditions. It may also function as a protein-compatible hydrotrope (Srinivas and Balasubramanian 1995), alleviating cytoplasmic acidosis, maintaining appropriate NADP+/ NADPH ratios compatible with metabolism, and supporting mitochondrial oxidative phosphorylation and generation of ATP for recovery and repairing of stress-induced damages (Hare and Cress 1997; Hare et al. 2003). Furthermore, proline can act as a signalling molecule to modulate mitochondrial functions, influence cell proliferation or cell death, and trigger specific gene expression, which can be essential for plant recovery from stress (Szabados and Savouré 2010). Proline may also serve as a source of organic nitrogen, carbon, and energy during recovery from stress (Sairam and Tyagi 2004). Proline accumulation normally occurs in the cytosol where it contributes substantially to the cytoplasmic osmotic adjustment (Ketchum et al. 1991). Accumulation of proline in many plant species under salt stress has been correlated with salinity stress tolerance, and its concentration has been shown to be generally higher in salt-tolerant than in salt-sensitive plants (Fougère et al. 1991; Madan et al. 1995). However, a negative correlation has also been observed between proline accumulation and salt tolerance in tomato plants (Aziz et al. 1998) and Aegiceras corniculatum (Parida et al. 2004), respectively. In plants, proline is synthesized by two pathways, namely the glutamate pathway and the orinithine pathway. The glutamate pathway accounts for major proline accumulation during osmotic stress. The proline is synthesized from glutamatic acid via intermediate Δ′-pyrroline-5-carboxylate (P5C). The reaction is catalyzed by two enzymes, namely Δ′-pyrroline-5-carboxylate synthetase (P5CS) and Δ′-pyrroline-5-carboxylate reductase (P5CR) (Sekhar et al. 2007). First, glutamate is converted to glutamic-γ-semialdehyde (GSA) and Δ′-pyrroline-5-carboxylate (P5C) by the action of P5CS, and then P5CR catalyzes the conversion of P5C to proline. P5CS is encoded by two genes whereas P5CR is encoded by only one in most plant species (Armengaud et  al. 2004). Proline catabolism occurs in mitochondria by means of the chronological action of proline dehydrogenase or proline oxidase (PDH or POX) producing P5C from proline and P5C dehydrogenase (P5CDH) which converts P5C to glutamate. Two genes encode PDH, whereas a single P5CDH gene has been identified in Arabidopsis and tobacco (Nicotiana tabacum) (Verbruggen and Hermans 2008). In an alternative pathway proline can be synthesized from ornithine, which is transaminated to P5C by

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orinithine-δ-aminotransferase. It has been suggested that the ornithine pathway is important during seedling development and in some plants for stress-induced proline accumulation (Armengaud et al. 2004; Xue et al. 2009). Proline accumulation in plants is mediated by both ABA-dependent and ABA-independent signalling pathways (Zhu 2002). ABA is known to mediate signals in plant cells under stresses that can bring about expression of stress-related genes (P5CS) followed by synthesis of compatible osmolytes such as proline (Kishor et al. 2005; Xiong et al. 2001). Proline biosynthesis under stress conditions is known to be regulated by phospholipase D along with calcium and ABA (Thiery et al. 2004). Whether MAP kinases have any role in the regulation of proline biosynthesis is not fully understood (Kishor et al. 2005). Transgenic plants modified by transgene P5CS gave higher tolerance under osmotic stress conditions by promoting proline content. The overexpression of the P5CS gene has ensured a higher survival rate, ameliorated tolerance, and higher yield under osmotic stresses in important crops such as wheat, rice, tobacco, and potato (Amini et al. 2015; Kishor et al. 1995; Zhu et al. 1998). Exogenous application of proline can play an important role in improving plant stress tolerance and may help to reduce the effects of environmental stresses (Oukarroum et al. 2012). The most noticeable affect of exogenous application of proline on plants was a decreased accumulation of Na+ and Cl− (Heuer 2003), better K+ retention in roots (Cuin and Shabala 2005, 2007), and increased K+:Na+ ratio in salt-affected plants (Abdelhamid et al. 2013). Foliar application of proline alleviated the inhibition of salt stress-induced catalase and peroxidase activities in tobacco (Hoque et al. 2007), activated a complex antioxidative defense system by increasing of activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX), and decreased activity of polyphenol oxidase (PPO) in Chemlali olive and rice plants under salt stress (Ben et al. 2010; Hasanuzzaman et al. 2014; Hossain and Fujita 2010). 3.3.1.2 Glycinebetaine Nitrogenous compound glycinebetaine (N, N, N-trimethylglycine) is a quaternary amine widely available in various plants as a compatible solute (Rhodes and Hanson 1993). Physiologically, it is a zwitterionic nature but electrically neutral molecule. It is a small organic metabolite which is soluble in water and non-toxic at high concentrations. Glycinebetaine (GB) can potentially play an important role in effective protection against salt, drought, and extreme temperature stress (Ashraf and Foolad 2007; Ashraf and Harris 2013; Chen and Murata 2008; Giri 2011). GB is ample mainly in chloroplast where it plays a vital role in the adjustment and protection of thylakoid membrane, thereby maintaining photosynthetic efficiency (Genard et al. 1991; Robinson and Jones 1986). It plays an adaptive role in mediating osmotic adjustment, protecting the sub-cellular structures in stressed plants and operating as a molecular chaperone in the refolding of enzymes (Wani et al. 2013) and mediated protein disaggregation (Diamant et al. 2003). The major role of GB under osmotic stress conditions is inhibiting ROS accumulation, detoxification of ROS, reduction of oxygen radical scavengers, macromolecular protection, and activation of some stress related genes (Giri 2011). It has been reported that GB also protects the reproductive organ of plants under abiotic stresses (Chen and Murata 2011). GB is synthesized either by oxidation of choline or N-methylation of glycine by three known pathways (Chen and Murata 2002). In plants, the enzyme choline monooxygenase (CMO) first converts choline into betaine aldehyde and then a NAD+-dependent enzyme, betaine aldehyde dehydrogenase (BADH), produces glycinebetaine. These enzymes are mainly found in chloroplast stroma, and their activity is increased in response to salt stress. GB accumulates naturally in response to stress in many crop plants such as sugar beet (Beta vulgaris), spinach (Spinacia oleracea), barley (Hordeum vulgare), wheat (Triticum aestivum), sorghum (Sorghum bicolor), cotton (Gossypium hirsutum), and maize (Zea mays) (Ashraf and Foolad 2007). In these species, tolerant genotypes normally accumulate more GB than sensitive genotypes in response to stress. Some economically

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important plant species such as rice (Oryza sativa), mustard (Brassica spp.), tobacco (Nicotiana tabacum), potato (Solanum tuberosum), and tomato (Solanum lycopersicum) are naturally unable to produce GB under stress or non-stress conditions (Rhodes and Hanson 1993). In these species, transgenic plants with over-production of GB synthesizing genes (BADH and CMO gene) exhibit an increase in the production of GB and an enhancement in tolerance to salt, cold, drought, or high temperature stresses (Niu et al. 2007; Rhodes and Hanson 1993). Identification of genes of GB biosynthetic pathways has made it easy to engineer GB biosynthesis into non-accumulators by transgenic approach for improved stress tolerance. The transgenic approach has been successfully used in a broad range of plant species to improve their abiotic stress tolerance (Giri 2011). Among the different GB biosynthetic genes, choline oxidase (codA) has been widely used for GB production in transgenic plants (Giri 2011). Exogenous application of GB to low-accumulating or non-accumulating plants can improve the tolerance to the adverse effects of environmental stresses of numerous plant species, such as tobacco (Agboma et al. 1997), bean (Xing and Rajashekar 1999), soybean (Mohammad et al. 2012; Rezaei et al. 2012), Brassica (Athar et al. 2009), maize (LiXin et al. 2009; Maqsood et al. 2006; Reddy et al. 2013), tomato (Rezaei et al. 2012), rice (Chaum and Kirdmanee 2010; Hasanuzzaman et al. 2014; Mohammed and Tarpley 2011), cotton (Meek et al. 2003), barley (Cuin and Shabala 2007; Oukarroum et al. 2012; Wahid and Shabbir 2005), wheat (Aldesuquy et al. 2012), cumin (Armin and Miri 2014), sunflower (Hussain et al. 2008), sorghum (Ibrahim 2004), and tomato (Yin et al. 2008). 3.3.2  Uptake and Sequestration of Inorganic Ions De novo synthesis of compatible solutes is an energetically costly option for osmotic adjustment, with 50–70 moles of ATP needed to synthesize 1M of compatible solute (Shabala and Shabala 2011). The concentrations of organic osmolytes are often far too low for conventional osmotic adjustment, and synthesis of compatible solutes requires hours to days and cannot contribute to rapid turgor recovery a plant requires. While many previous studies have stated a positive correlation between the accumulation of compatible solutes and plant stress tolerance, some have indicated the lack of consistent relationship between accumulation of these compounds and osmotic stress tolerance (Ashraf and Foolad 2007). A sustainable alternative to the energy-costly and relatively slow process of biosynthesis of osmoprotectants for cell osmotic adjustment is via the uptake of inorganic ions (Bohnert et al. 1995). Shabala and Lew (2002) revealed that 90% of the turgor recovery in Arabidopsis roots’ epidermal cells was achieved within 40 min by means of increased uptake of K+, Na+, and Cl− ions. It was shown that bean mesophyll cells responded to hyperosmotic stress by increased uptake of K+ and Cl− (Shabala et al. 2000). In 50 bread and durum wheat varieties, the major bulk of shoot sap osmotic adjustment was achieved by using K+, Na+, and Cl− (Cuin et al. 2010). A low concentration of these ions should not interfere significantly with cell metabolism and act as a cheap osmotica to maintain normal turgor of cells, but high concentration of Na+ and Cl− can cause severe disruptions to cell metabolism and have toxic effects (Shabala and Munns 2012). In nearly all durum and bread wheat genotypes, K+ made a major contribution (63%) towards osmotic adjustment in shoot cells under control conditions and increased significantly in shoot sap under salt-stress conditions (Cuin et al. 2010). Inorganic ions are sequestered in the vacuoles while organic solutes are compartmentalized in the cytoplasm to balance the low osmotic potential in the vacuole (Rontein et al. 2002). Vacuolar sequestration of Na+ not only lowers Na+ concentration in the cytoplasm but also contributes to osmotic adjustment and Na+ detoxification to maintain water uptake from saline solutions. Other organelles, such as plastids and mitochondria, may also accumulate some Na+ and thus contribute to the overall sub-cellular compartmentalization of Na+. Na+/H+ antiporters move potentially harmful ions from cytosol into large and internally acidic tonoplast-bounded vacuoles driven by the electrochemical gradient of protons generated by the

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vacuolar H+-translocating enzymes such as H+ ATPases and the H+ pyrophosphatase (H+-PPase). These ions act as an osmoticum within vacuoles by maintaining water flow into the cell and allowing plants to grow in saline environments. It has been reported that constitutive overexpression of the vacuolar transporters increases salt tolerance of a variety or species. AtNHX1 is an Arabidopsis vacuolar Na+/H+ antiporter involved in the control of vacuolar osmotic potential to increase salinity tolerance significantly in yeast (Aharon et al. 2003), Arabidopsis (Apse et al. 1999), tomato (Zhang and Blumwald 2001), Brassica napus (Zhang et al. 2001), alfalfa (Bao-Yan et al. 2008), and cotton (Wu et al. 2004). Similarly, constitutive overexpression of various cereal homologs has been reported to improve salinity tolerance of Arabidopsis (Brini et al. 2007), rice (Fukuda et al. 2004a,b; Ohta et al. 2002; Zhao et al. 2006), wheat (Xue et al. 2004), and barley (Fukuda et al. 2004a,b). The overexpression of NHX1 and AVP1 in Arabidopsis led to a small increase in shoot Na+ accumulation possibly allowing the cells to maintain a favorable osmotic balance, yet maintaining low cytoplasmic Na+ levels due to sequestration of Na+ within the vacuole (Apse et al. 1999). AtNHX2 and AtNHX5 could be important salt-tolerant determinants, and between them AtNHX2 has a major function in vacuolar Na+ sequestration (Yokoi et al. 2002). Overexpression of AmNHX2 (an AtNHX2-like vacuolar Na+/H+ antiporter) from Ammopiptanthus mongolicus resulted in enhanced tolerances to both drought and salt stresses in transgenic Arabidopsis plants and accumulated lower Na+ content in their leaves, showing healthier root systems in salt stress, and retained more water during the drought stress (Wei et al. 2011). Overexpression of AeNHX1 (a root-specific vacuolar Na+/H+ antiporter) from Agropyron elongatum promoted salt tolerance of Arabidopsis plants and improved osmotic adjustment and photosynthesis which might be responsible for normal development of transgenic plants under salt stress (Qiao et al. 2007). Functional characterization of wheat Na+/H+ antiporter TNHX1 and vacuolar pyrophosphatase TVP1 has been reported by Brini et al. (2007). Overexpressing of TNHX1 or TVP1 in transgenic Arabidopsis is much more resistant to high concentrations of NaCl and drought than the wild-type plants (Brini et al. 2005). Yu et al. (2007) implied that a vacuole Na+/H+ antiporter gene TaNHX2 from wheat plays an important role in salt and osmotic stress tolerance in yeast cells. The expression of a vacuolar Na+/H+ antiporter gene (OsNHX1, OsNHX2, OsNHX3, and OsNHX5) from rice is regulated differently in rice tissues and increased by salt stress. In barley, the expression of H+-PPase HVP1, and vacuolar Na+/H+ antiporter NHX1, was similarly upregulated by salt stress (Fukuda et al. 2004a,b). The simultaneous expression of NHX and AVP genes in rice was found to increase salinity tolerance to a greater extent than expression of the genes individually (Zhao et al. 2006). 3.4  PHYSIOLOGICAL MECHANISMS TO DEAL WITH OSMOTIC STRESS: TRANSPIRATIONAL CONTROL Plants need water for biochemical response and cell enlargement which is obligatory for growth and development. Plants transpire about 90% of the water absorbed by roots, and less than 1%–5% is retained by the plant for growth and biochemical reactions (Hopkins and Hüner 1999). Transpiration is determined by the vapor pressure difference of water between the inside and outside of the leaf. The primary pathway of water and CO2 movement is through stomata; plant cuticle and lenticels also contribute to water transpiration. Stomatal opening is stimulated by the response of blue and red light, low CO2 concentration, and high humidity whereas closing is promoted by darkness, high CO2 concentration, low humidity, and abscisic acid. Most plants maintain a diurnal cycle for stomatal opening and closing in response to light and dark, respectively. Depending on the species, C3 and C4 plants transpire 70%–90% water during the day and 5%–30% at night of the total diurnal water loss (Yoo et al. 2009). Transpiration is vital to keep plant water status, maintain leaf temperatures, and uptake mineral nutrients from the soil. The stoma is responsible for CO2 uptake which is essential for carbon

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assimilation into biomass and yield. The relationship between transpiration and CO2 uptake is called the transpiration ratio or water use efficiency. Optimum water use efficiency restricts stomatal control of leaf transpiration to the time when evaporative demand is highest. Plant water use efficiency can be improved by increasing CO2 assimilation relative to transpiration or reducing transpiration relative to CO2 assimilation (Chaves et al. 2004). Water use efficiency can also be improved by decreasing daytime and night-time transpiration (Sinclair et al. 2005). Under water stress conditions, the relative contribution of cuticular transpiration towards water loss may be relatively high as compared with the stomatal one, due to stomata closure. However, water stress resistance can be enhanced by increasing water use efficiency, which can be achieved by decreasing cuticular transpiration when stomata are fully or partially closed (Petcu et al. 2009). 3.4.1  Stomatal Transpiration under Water Stress Stomatal transpiration control is an important physiological trait of plants under stressed conditions. Under physiological drought conditions, CO2 must be able to enter the leaf to allow photosynthesis, yet water loss must be minimized to prevent dryness and plant death. Transpiration provides the driving force for the transport of water and nutrients from the roots to the aerial tissues, and the evaporation of water from the sub-stomatal cavity cools the plant and forms a major component of the leaf energy balance (Lambers et  al. 2008). Plants affected by osmotic stress close their stomata for reducing transpiration water loss thus increasing water use efficiency. Closed stomata may cause a dramatic increase in leaf temperature up to 7°C above the ambient air temperature (Blum 2015). Long duration of this condition enhances photo damage and/or xylem embolism, resulting in defoliation and plant death. In such conditions, tolerant genotypes are able to maintain high water use efficiency by stomata opening and transpiring water for leaf cooling. Transpiration rates normally reduce with increasing rhizosphere salinity in plants due to lower water potentials in the root zone. Additionally, transpiration is reduced by apoplastic Na+ concentrations which directly inhibit the stomatal opening under saline conditions. However, under drought conditions, the plant hormone ABA accumulates in the shoot, and that plays an important role in both inhibiting stomatal opening and promoting stomatal closure, resulting in reduced water loss from the plant. Under water deficit conditions, stomatal transpiration is controlled by stomatal conductance which is mainly determined by tissue water status at a given vapor pressure difference between the leaf surface and the air (Xu et al. 1995). 3.4.2  Cuticular Transpiration under Water Stress Cuticular transpiration is the main way of water loss through the cuticle of the leaf surface during the night when stomata are closed completely and/or partially under well-irrigated conditions. However, under stressed environmental conditions, a relatively large portion of evaporated water may bypass the stomata and occur through the cuticle at daytime when the stomata are closed. Depending on the plant species, cuticular transpiration may account for 5%–15% of day-time transpiration and could be even higher (up to 25%–30%) under stressed environmental conditions (Caird et al. 2007; Howard and Donovan 2007). Cuticular transpiration involves a significant water loss without allowing CO2 uptake by an impermeable cuticle of leaf surface, resulting in a major reduction of water use efficiency under osmotic stress conditions (Boyer 2015). Therefore, a reduction of non-stomatal transpiration (cuticular transpiration) or residual transpiration is a potentially useful mechanism for improving plant performance under stress conditions. It has been suggested as a selection trait in cereal genotypes adapted to dry environments and breeding for stress conditions (Clarke et al. 1991; Petcu 2005). Tolerant genotypes deposited cuticular wax on the epidermis of the leaves under different osmotic stress conditions. Cuticular transpiration is affected by the characteristics of the leaf surface,

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thickness of the wax layer, chemical composition of the wax, orientation of physical properties of waxes, and morphological structure of the plant (Richards et  al. 1986). Cuticular waxes are embedded in the cutin matrix and cover the outer surface of the leaf cuticle. The increase in waxes deposited in and on the leaf cuticle is one of the most obvious forms of stress acclimation (Jordan et al. 1984). The amount of cuticular waxes is increased by different stress conditions such as high light intensity, high temperature, low humidity, and soil water deficit (Baker 1982; Svenningsson and Liljenberg 1986). 3.5  MORPHOLOGICAL AND ANATOMICAL MECHANISMS TO DEAL WITH OSMOTIC STRESS Plants can minimize the detrimental effects of different abiotic stresses by modifying their morphological, anatomical, and physiological attributes (Hameed et al. 2009). The most obvious morpho-anatomical adaptations of plants under salinity and drought stress conditions are their relatively deep and robust root system for water uptake from deeper soil level, smaller and thicker leaves, lower stomatal size and density on adaxial or abaxial leaf surfaces, increased succulence, dense pubescence, thickness of leaf cuticle by deposition of wax on leaf, well-developed water-storing tissues in the cortex of stem, and reduced cortical area, intensive sclerification, large metaxylem vessel, widening of casparian band, and enhanced development of root endodermis that play a crucial role in conserving water for sustained plant growth under stress conditions (Al-maskri et al. 2014; Hameed et al. 2010; Naskar and Palit 2014; Naz et al. 2014a,b; Wahid 2003). 3.5.1  Leaf Anatomical Changes Progressive water stress reduces the expansion of young leaves, decreases total leaf area, and increases the shedding of old leaves. Thickness of epidermis, thickness of mesophyll tissue, diameter and length of palisade tissue, diameter of spongy parenchyma cell, and diameter of vascular bundle all increase with increasing salinity and drought stress (Makbul et al. 2011; Xu et al. 2014a,b). Increasing salinity resulted in greater leaf succulence and greater mesophyll thickness for Phaseolus vulgaris and Gossypium hirsutum and Atriplex patuls (Longstreth and Nobel 1979). A substantially smaller increase in mesophyll leaf surface area to leaf area was found in Atriplex patuls than that of Phaseolus vulgaris and Gossypium hirsutum (Longstreth and Nobel 1979). Increased salinity resulted in generally thicker leaves of Distichlis spicata but no significant differences in the ratio of mesophyll cell surface area to leaf area (Kemp and Cunningham 1981). It is a tendency of Atriplex and Distichlis to maintain constant mesophyll area for photosynthesis and adaptation from the harmful effect of salinity. 3.5.1.1  Leaf Succulence Leaf succulence is an important strategy to drought avoidance and salinity tolerance of plants growing in drought-prone areas and saline soils. Succulence is a common constitutive feature of certain xerophytic and halophytic plants whereas it is a facultative trait in glycophytes during waterlimited environmental conditions (Ogburn and Edwards 2010). Succulent leaves are deciduous in response to drought stress, maintain high water potentials to avoid cellular drought during drought periods, and use their stored water in large central vacuoles to facilitate water homeostasis and as a buffer for maintaining metabolic activity. Succulent features of salt tolerant plants provide more cavity for dumping off the toxic Na+ and Cl− ions intracellularly and also increasing the plant water content for balancing out ion toxicity and osmotic adjustment (Hameed et al. 2010, 2011). Leaf succulence increased with moderate increasing salinity of plants in both halophyte and glycophyte

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species (Hameed et al. 2009; Kemp and Cunningham 1981; Longstreth and Nobel 1979; Parida et al. 2004) which might have resulted from increases in water uptake and turgor pressure as a result of cells having higher solute concentration. Increasing leaf succulence is an additional salt regulation mode inside leaf tissue, achieved by salt sequestration into hypodermal tissue (Werner and Stelzer 1990). Succulence in terms of leaf thickness (which is mainly due to mesophyll and cortical cells) is an infrequent phenomenon in monocots, especially in grasses (Flowers and Colmer 2008; Hameed et al. 2010, 2011). 3.5.1.2  Leaf Pubescence Leaf pubescence is an adaptive mechanism to drought-prone environments that reduces photoinhibition and amount of heat absorbed by leaves, affecting their energy balance, reflectance, water repellence, reducing transpiration, and helping the plant to maintain a favorable water balance (Konrad et al. 2015; Skelton et al. 2012). Leaf covering with trichomes is a characteristic feature of xerophytes enabling their adaptation to drought conditions, because it potentially decreases temperature of leaves by absorbing heat and/or reflectance from the leaf surface (Ehleringer et al. 1976). Leaf pubescence of Encelia farinosa acts as a blanket reflector which reduces the absorption to solar radiation under drought (Ehleringer and Björkman 1978). Leaf pubescence of many species from hot, arid habitats reduces the absorption of solar radiation and leaf temperature, increases boundary layer resistance to diffusion, and thus lowers transpirational water losses (Ehleringer and Björkman 1978; Ehleringer et al. 1981; Savé et al. 2000; Smith and Nobel 1977). 3.5.1.3  Stomatal Density and Size Stomata play an important role in the control of transpiration and CO2 gas exchange of the leaf. Total stomatal pores occupy about 5% of the leaf surface, but plants lose approximately 70% of the water through the stomatal pores (Hetherington and Woodward 2003). Depending on the growth environment and the species, stomatal size and density varies between 10–80 µm in length and 5–1,000 cells per mm−2, respectively (Hetherington and Woodward 2003). Plant leaves have the capacity to adjust the stomatal density and patterning of stomata in response to stress environment conditions for adaptation (Zarinkamar 2006). Transpirational water loss affects the stomatal density and positively correlates without the influence of photosynthesis. Thus, plants increase their water use efficiency with decreasing stomatal density by a minimum amount for sufficient CO2 uptake (Yoo et al. 2009). Although salt tolerant barley genotypes contain naturally lower stomata density under irrigated conditions, stomatal density of salt-tolerant genotypes increase under salinity stress conditions, which is an important strategy to improve their water use efficiency (Zhu et al. 2015). The increase in stomata density in saline-treated barley leaves may be due to the smaller leaf area, resulting in a larger number of stomata per unit area of leaf. It has been suggested that salinity-induced reduction in stomatal density in quinoa leaves represents a fundamental mechanism by which plants optimize water use efficiency under saline conditions (Shabala et  al. 2012). Low concentration of salinity causes a remarkable decrease in stomatal density, which is an acute stress tolerance factor that may allow plants to adapt more effectively to salinity (Orsini et al. 2012). Adaxial and abaxial stomatal density decreased with increasing salinity in different halophytes (Boughalleb et al. 2009; Sobrado 2007), dicots (Jafri and Ahmad 1995; Romero-Aranda et al. 2001), and monocots (Hameed et al. 2009; Naz et al. 2010), which may be accountable for reducing water loss through leaf surfaces and would therefore be critical under physiological drought. A positive correlation has been reported between stomatal density and plant salt tolerance in barley whereas a negative correlation has been found for some amaranth species (Omamt et al. 2006; Zhu et al. 2015). Low stomatal density improved water use efficiency and was beneficial in terms of drought tolerance in

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Arabidopsis thaliana (Yu et al. 2008) and Panicum antidotale (Hameed et al. 2012). Under waterlimiting conditions, small sized stomata may be more useful to improve water use efficiency (WUE) than the stomatal density (Yang et al. 2004). Reduced stomatal conductance and transpiration help plants to respond to high salinities (Flanagan and Jefferies 1989). 3.5.1.4  Sunken Stomata Sunken stomata are an anatomical modification of leaves under water stress conditions to reduce transpiration water loss of certain plants such as Nerium oleander, Ficus, and Pinus canariensis. The guard cells of stomata are depressed below the epidermis layer, creating a moist microclimate in the boundary layer (Manavalan and Nguyen 2012). Small and sunken stomata have a role in reducing loss of water to avoid drought in grape leaves (Zhihua et al. 1992). Sunken stomata below the remaining epidermal cells play an important role to prevent dehydration by transpiration (Tomlinson 1969). Several plant families, such as Bromeliaceae (Faria et al. 2012), Agavaceae (Fahn and Cutler 1992), Cactaceae (Calvente et al. 2008), from drought prone areas, particularly succulents, have stomata deeply sunken in depressions in the epidermis. 3.5.1.5  Mesophyll and Epidermis Thickness of Leaves The thickness of mesophyll and the epidermis is generally the most effective mechanism of drought- and salt-tolerant plants to defend against water loss through the leaf surface under limited moisture conditions (Jenks and Ashworth 1999; YuJing et al. 2000). Adaxial and abaxial epidermis thickness and the palisade and spongy mesophyll ratio of the salt-tolerant ecotype increased under salinity stress conditions, which indicated the potential to adapt to prevent water loss through leaf surface (Boughalleb et  al. 2009; Hameed et  al. 2009). Palisade layer and thickness of the leaf increased under salt-stressed conditions compared to control conditions mainly because of increasing cell density (Omamt et al. 2006). Increased mesophyll thickness may have contributed to reduced mesophyll conductance in cotton (Brugnoli and Björkman 1992), Suaeda maritime (Hajibagheri et al. 1984), and Phaseolus vulgaris (Bray and Reid 2002). Structural modifications of leaves like increased leaf and epidermis thickness can be directly related to drought tolerance of plants by conserving water (Al-maskri et al. 2014; Hameed et al. 2012; Ristic and Cass 1991). Increasing leaf thickness due to storing parenchymatous cells in the leaf is extremely vital under moisture-limiting conditions (Abdel and Al-Rawi 2011). 3.5.1.6  Bulliform Cells Bulliform cells, or rolling cells, on the upper surface of the leaf’s mid rib are large, thin-walled, bubble-shaped, and highly vacuolated, which makes them responsible for controlling leaf blade rolling under water stress to avoid water loss (Abernethy et al. 1998; Alvarez et al. 2008; Balsamo et  al. 2006; Zhang et  al. 2015a,b). The mechanism of leaf rolling controlled by bulliform cells depends on cell turgor and cell flaccidity during leaf unrolling and rolling, respectively. Bulliform cells respond rapidly to water stress by losing their turgor and become flaccid, resulting in leaf blade rolling and vice versa under optimal water conditions. Under continuous stress condition, plants adapt by developing a large number of bulliform cells to induce more rolling of the leaf blade (Ola et al. 2012). Extensive leaf rolling is an important adaptive mechanism against salt stress which was observed in Lasiurus scindicus (Naz et al. 2014a,b), Imperata cylindrical (Hameed et al. 2009), Deschampsia antarctica (Giełwanowska et al. 2005), and in Festuca novae-zelandiae (Abernethy et al. 1998) and Leptochloa fusca (Ola et al. 2012). In addition, well developed bulliform cells were observed in different plants under drought stress condition, such as blue panic grass (Hameed et al. 2012), wheat (Al-maskri et al. 2014), sugarcane (Zhang et al. 2015a,b), and maize (Lindsey 2015).

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3.5.1.7  Leaf Surface Cuticular Wax Among the morphological adaptations, leaf surface cuticular wax is thought to play a critical role in plant drought tolerance by reducing cuticular water loss and thus improve plant water use efficiency during water deficit (Ni et al. 2012). Water deficit conditions lead to increase the amount of leaf cuticular wax, particularly the total cutin monomer and cuticular thickness, which is associated with decreased cuticle permeability and reduced cuticular transpiration in plant adaptation to limited water conditions such as drought and salinity (Kosma et al. 2009; Seo and Park 2011; Xu et al. 2014a,b; Yang et al. 2011). Physical properties and chemical compositions of cuticles may be affected by different environmental stress conditions. Drought increases long chain aliphatic components, alkanes, and aldehydes and decreases primary alcohol, which leads to higher hydrophobicity of the cuticular transpiration barrier and reduces cuticular water loss (Macková et al. 2013; Ni et al. 2012). It was reported that many plant species such as mulberry trees (Ni et al. 2015), sesame (Kim et al. 2007a), soybean (Kim et al. 2007b), Arabidopsis (Zhu et al. 2014), alfalfa (Ni et al. 2012) and tomato (Haliński et al. 2015) increased total cuticular wax deposition per unit area of leaf under water deficit conditions. 3.5.2  Root and Stem Anatomical Change 3.5.2.1 Sclerenchyma Sclerenchyma development in the outer cortex and outside the epidermis is a critical strategy for controlling the movement of water through root, thereby storing water, preventing desiccation, and supporting mechanical strength under osmotic stress conditions (Akcin et al. 2014; Hameed et al. 2011; Naz et al. 2014a,b; Ola et al. 2012). Increased sclerenchyma in the stem of the plant under salinity stress provides rigidity to these organs and generally rises with increasing osmotic stress in different species (Ola et al. 2012). The increase of sclerenchyma cells appeared to be useful for diminution of water loss in Imperata cylindrical (Hameed et al. 2009), Panicum antidotale (Hameed et al. 2012), wheat (Al-maskri et al. 2014), Festuca nove – zelandiae (Abernethy et al. 1998), Spartina alterniflora (Walsh 1990), Kandelia candel (Hwang and Chen 1995), cotton (Reinhardt and Rost 1995), Puccinellia tenuiflora (YuJing et al. 2000), and Prosopis strombulifera (Reinoso et al. 2004). 3.5.2.2 Aerenchyma Increased aerenchyma in root and stem and periderm thickness of the root is crucial for increasing water storage capacity in plants in a saline environment (Akcin et al. 2014). Root aerenchyma formed at lower to moderate salt levels (50 and 100 mM NaCl), but at higher salinity stress aerenchyma converted into compact parenchyma (Hameed et al. 2009). Thus, the area of storage tissue increases with air cavity (succulence) to store toxic ions and represents an important strategy to adapt to high salinity stress (Akhtar et al. 1998; Ola et al. 2012). Root cortical aerenchyma is beneficial for drought tolerance in maize as it reduces root metabolic costs, allowing for greater root growth and water gain from drying soil (Zhu et al. 2010). 3.5.2.3  Connective Tissue Formation of the connective tissue such as xylem and phloem is an important adaptive strategy to controlling the movement of water and solutes from source to sink for better survival capacity under osmotic stress conditions (Akcin et al. 2014). Vascular bundles, root metaxylem, and phloem area of root and stem increased under water stress condition to provide an adequate supply of water from root and stem to leaf in tolerant plants (Hameed et al. 2009, 2012; Xu et al. 2014a,b). The xeric plants usually have succulent stems which are characterized by well-developed water-storing tissue

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in the cortex and pith (Dickison 2000). Under saline conditions plants reduced the cortex thickness to reduce the distance between epidermis and stele, developed water-storing tissues in the cortex stem, enlarged the casparian band, promoted root epidermis, and decreased xylem vessel diameter (Akcin et al. 2014; Wahid 2003), resulting in a wider casparian strip that prevented redial flow of water and ions from cortex to the stele (Hose et al. 2001; Taiz and Zeiger 2002). In some cases, the walls of root epidermal and root hair cells developed protuberances on the inner side in response to high salinity, thus the epidermal cells became transfer cells (Kramer et al. 1978). 3.6 CONCLUSIONS Osmotic stress has a devastating effect on the growth, development, and yield of plants. The predicted increase in world population calls on scientists to develop more efficient strategies for boosting crop production in order to ensure food security under such hostile environmental conditions. The response to osmotic stress varies greatly among different plant species, growth stage of crops, and the levels of stress, as well as environmental conditions. However, tolerant genotypes mediate osmotic stress tolerance by efficient osmotic adjustment, water-saving strategies, and transpiration control. In a way of defense, plants considerably change their anatomical and morphological structure to cope with the osmotic stress induced by salinity and drought, which can be important genetic resources for development of new tolerant crops. The rapid progress in molecular biology and development of various “omics” technologies provide efficient platforms for breeding plants for osmotic stress tolerance. However, many physiological and anatomical traits identified in this work have never been manipulated by breeders. This may open unique and previously unexplored avenues for developing drought and salinity tolerance in crops. ACKNOWLEDGMENTS This work was supported by a Grains Research and Development Corporation (GRDC) grant (UT00027) to Sergey Shabala and Meixue Zhou. REFERENCES Abdel, C. G., and I. M. T. Al-Rawi. 2011. Anatomical alteration in response to irrigation and water stress in some legume crops. Am J Exp Agri 1:231–264. Abdelhamid, M. T., M. M. Rady, A. S. Osman, and M. A. Abdalla. 2013. Exogenous application of proline alleviates salt-induced oxidative stress in Phaseolus vulgaris L. plants. J Hortic Sci Biotechnol 88:439–446. Abernethy, G. A., D. W. Fountain, and M. T. McManus. 1998. Observations on the leaf anatomy of Festuca novae-zelandiae and biochemical responses to a water deficit. New Zealand J Bot 36:113–123. Agboma, P. C., T. R. Sinclair, K. Jokinen, P. Peltonen-Sainio, and E. Pehu. 1997. An evaluation of the effect of exogenous glycinebetaine on the growth and yield of soybean: Timing of application, watering regimes, and cultivars. Field Crops Res 54:51–64. Aharon, G. S., M. P. Apse, S. Duan, X. Hua, and E. Blumwald. 2003. Characterization of a family of vacuolar Na+/H+ antiporters in Arabidopsis thaliana. Plant Soil 253:245–256. Akcin, T. A., A. Akcin, and E. Yalcin. 2014. Anatomical adaptations to salinity in Spergularia marina (caryophyllaceae) from Turkey. Proceedings of the National Academy of Sciences, India Section B: Biological Sciences 85:625–634. Akhtar, J., J. Gorham, R. H. Qureshi, and M. Aslam. 1998. Does tolerance of wheat to salinity and hypoxia correlate with root dehydrogenase activities or aerenchyma formation? Plant and Soil 201:275–284.

MEcHANISMS OF OSMOTIc STRESS TOLERANcE

49

Aldesuquy, H. S., S. A. Abo-Hamed, M. A. Abbas, and A. H. Elhakem. 2012. Role of glycine betaine and salicylic acid in improving growth vigour and physiological aspects of droughted wheat cultivars. J Stress Physiol Biochem 8:149–171. Al-maskri, A., M. Hameed, M. Ashraf et al. 2014. Structural features of some wheat (Triticum Spp.) landraces/ cultivars under drought and salt stress. Arid Land Res Manag 28:355–370. Alvarez, J. M., J. F. Rocha, and S. R. Machado. 2008. Bulliform cells in Loudetiopsis chrysothrix (Nees) Conert and Tristachya leiostachya Nees (Poaceae): Structure in relation to function. Brazilian Arch Biol Tech 51:113–119. Amini, S., C. Ghobadi, and A. Yamchi. 2015. Proline accumulation and osmotic stress: An overview of P5CS gene in plants. J Plant Mol Breeding 3:44–55. Apse, M. P., G. S. Aharon, W. A. Snedden, and E. Blumwald. 1999. Salt tolerance conferred by overexpression of a vacuolar Na+/H+ antiport in Arabidopsis. Science 285:1256–1258. Armengaud, P., L. Thiery, N. Buhot, G. Grenier-de March, and A. Savouré. 2004. Transcriptional regulation of proline biosynthesis in Medicago truncatula reveals developmental and environmental specific features. Physiol Plantarum 120:442–450. Armin, M., and H. R. Miri. 2014. Effects of glycine betaine application on quantitative and qualitative yield of cumin under irrigated and rain-fed cultivation. J Essent Oil Bear Plants 17:708–716. Ashraf, M., and M. Foolad. 2007. Roles of glycine betaine and proline in improving plant abiotic stress resistance. Environ Exp Bot 59:206–216. Ashraf, M., and P. J. C. Harris. 2013. Photosynthesis under stressful environments: An overview. Photosynthetica 51:163–190. Athar, H. R., M. Ashraf, A. Wahid, and A. Jamil. 2009. Inducing salt tolerance in canola (Brassica napus L.) by exogenous application of glycinebetaine and proline: Response at the initial growth stages. Pakistan J Bot 41:1311–1319. Aziz, A., J. M. Tanguy, and F. Larher. 1998. Stress-induced changes in polyamine and tyramine levels can regulate proline accumulation in tomato leaf discs treated with sodium chloride. Physiol Plantarum 104:195–202. Baker, E. A. 1982. Chemistry and morphology of plant epicuticular waxes. In The Plant Cuticle, ed. D. F. Cutler, K. L. Alvin, and C. E. Price, 139–165. London, UK: Academic Press. Balsamo, R. A., C. V. Willigen, A. M. Bauer, and J. Farrant. 2006. Drought tolerance of selected Eragrostis species correlates with leaf tensile properties. Ann Bot 97:985–991. Bao-Yan, A. N., L. U. O. Yan, L. I. Jia-Rui, Q. I. A. O. Wei-Hua, X. Zhang, and G. A. O. Xin-Qi. 2008. Expression of a vacuolar Na+/H+ antiporter gene of alfalfa enhances salinity tolerance in transgenic Arabidopsis. Acta Agron Sin 34:557–564. Bartels, D., and R. Sunkar. 2005. Drought and salt tolerance in plants. Crit Rev Plant Sci 24:23–58. Ben, A. C., B. B. Rouina, S. Sensoy, M. Boukhriss, and F. B. Abdullah. 2010. Exogenous proline effects on photosynthetic performance and antioxidant defense system of young olive tree. J Agric Food Chem 58:4216–4222. Blum, A. 2015. Towards a conceptual ABA ideotype in plant breeding for water limited environments. Funct Plant Biol 42:502–513. Bohnert, H. J., D. E. Nelson, and R. G. Jensen. 1995. Adaptations to environmental stresses. Plant Cell 7:1099–1111. Boughalleb, F., M. Denden, and B. B. Tiba. 2009. Anatomical changes induced by increasing NaCl salinity in three fodder shrubs, Nitraria retusa, Atriplex halimus, and Medicago arborea. Acta Physiol Plant 31:947–960. Boyer, J. S. 2015. Turgor and the transport of CO2 and water across the cuticle (epidermis) of leaves. J Exp Bot 66:2625–2633. Bray, E. A., J. Bailey-Serres, E. Weretilnyk. 2000. Responses to abiotic stresses. In Biochemistry and Molecular Biology of Plants, ed. W. Gruissem, B. Buchannan, and R. Jones, 1158–1249. Rockville, MD: American Society of Plant Physiologists. Bray, S., and D. M. Reid. 2002. The effect of salinity and CO2 enrichment on the growth and anatomy of the second trifoliate leaf of Phaseolus vulgaris. Canadian J Bot 80:349–359. Brini, F., R. A. Gaxiola, G. A. Berkowitz, and K. Masmoudi. 2005. Cloning and characterization of a wheat vacuolar cation/proton antiporter and pyrophosphatase proton pump. Plant Physiol Bioch 43:347–354.

50

CLIMATE CHANGE AND CROP PRODUcTION

Brini, F., M. Hanin, I. Mezghani, G. A. Berkowitz, and K. Masmoudi. 2007. Overexpression of wheat Na+/ H+ antiporter TNHX1 and H+-pyrophosphatase TVP1 improve salt- and drought-stress tolerance in Arabidopsis thaliana plants. J ExpBot 58:301–308. Brugnoli, E., and O. Björkman. 1992. Growth of cotton under continuous salinity stress: Influence on allocation pattern, stomatal and non-stomatal components of photosynthesis and dissipation of excess light energy. Planta 187:335–347. Caird, M. A., J. H. Richards, and L. A. Donovan. 2007. Nighttime stomatal conductance and transpiration in C3 and C4 plants. Plant Physiol 143:4–10. Calvente, A. M., R. H. Andreata, and R. C. Vieira. 2008. Stem anatomy of Rhipsalis (Cactaceae) and its relevance for taxonomy. Plant Syst Evol 276:271–277. Chaum, S., and C. Kirdmanee. 2010. Effect of glycinebetaine on proline, water use, and photosynthetic efficiencies, and growth of rice seedlings under salt stress. Turk J Agric For 34:517–527. Chaves, M. M., J. Osório, and J. S. Pereira. 2004. Water use efficiency and photosynthesis. In Water Use Efficiency in Plant and Biology, ed. M. A. Bacon, 42–74. Boca Raton, FL: CRC Press. Chen, T. H., and N. Murata. 2002. Enhancement of tolerance of abiotic stress by metabolic engineering of betaines and other compatible solutes. Curr Opin Plant Biol 5:250–257. Chen, T. H., and N. Murata. 2008. Glycinebetaine: An effective protectant against abiotic stress in plants. Trends Plant Sci 13:499–505. Chen, T. H., and N. Murata. 2011. Glycinebetaine protects plants against abiotic stress: Mechanisms and biotechnological applications. Plant Cell Environ 34:1–20. Clarke, J., R. Richards, and A. Condon. 1991. Effect of drought stress on residual transpiration and its relationship with water use of wheat. Canadian J Plant Sci 71:695–702. Cockcroft, C. E., B. G. W. den Boer, J. M. S. Healyy, and J. A. H. Murray, 2000. Cyclin D control of plant growth rate in plants. Nature 405:575–579. Cook, B. I., J. E. Smerdon, R. Seager, and S. Coats. 2014. Global warming and 21st century drying. Clim Dynam 43:2607–2627. Cosgrove, D. J. 1997. Relaxation in a high stress environment: The molecular basis of extensible cell walls and cell enlargement. Plant Cell 9:1031–1041. Cramer, G. R. 2002. Response of abscisic acid mutants of Arabidopsis to salinity. Funct Plant Biol 29:561–567. Cuin, T. A., D. Parsons, and S. Shabala. 2010. Wheat cultivars can be screened for NaCl salinity tolerance by measuring leaf chlorophyll content and shoot sap potassium. Funct Plant Biol 37:656–664. Cuin, T. A., and S. Shabala. 2005. Exogenously supplied compatible solutes rapidly ameliorate NaCl-induced potassium efflux from barley roots. Plant Cell Physiol 46:1924–1933. Cuin, T. A., and S. Shabala. 2007. Amino acids regulate salinity-induced potassium efflux in barley root epidermis. Planta 225:753–761. Dai, A. 2011. Drought under global warming: A review. Wiley Interdisciplinary Reviews: Climate Change 2:45–65. Dai, A. 2013. Increasing drought under global warming in observations and models. Nature Climate Change 3:52–58. Diamant, S., D. Rosenthal, A. Azem, N. Eliahu, A. P. Ben-Zvi, and P. Goloubinoff. 2003. Dicarboxylic amino acids and glycine-betaine regulate chaperone-mediated protein-disaggregation under stress. Mol Microbiol 49:401–410. Dickison, W. C. 2000. Integrative Plant Anatomy. San Diego, CA: Academic Press. Dörffling, K., H. Dörffling, and E. Luck. 2009. Improved frost tolerance and winter hardiness in proline overaccumulating winter wheat mutants obtained by in vitro-selection is associated with increased carbohydrate, soluble protein and abscisic acid (ABA) levels. Euphytica 165:545–556. Ehleringer, J., and O. Björkman. 1978. Pubescence and leaf spectral characteristics in a desert shrub, Encelia farinosa. Oecologia 36:151–162. Ehleringer, J., O. Björkman, and H. A. Mooney. 1976. Leaf pubescence: Effects on absorptance and photosynthesis in a desert shrub. Science 192:376–377. Ehleringer, J., H. A. Mooney, S. L. Gulmon, and P. W. Rundel. 1981. Parallel evolution of leaf pubescence in Encelia in coastal deserts of North and South America. Oecologia 49:38–41. Fahn, A., and F. D. Cutler. 1992. Xerophytes. Encyclopedia of plant anatomy XIII 3. Berlin/Stuttgart, Germany: Borntraeger. FAO (Food and Agriculture Organisation). 2015. The impact of natural disasters on agriculture and food security and nutrition. In UN World Conference on Disaster Risk Reduction. Sendai, Japan, March 14–18, 2015. pp. 5–12.

MEcHANISMS OF OSMOTIc STRESS TOLERANcE

51

Faria, A. P. G. D., A. C. M. Vieira, and T. Wendt. 2012. Leaf anatomy and its contribution to the systematics of Aechmea subgenus Macrochordion (de Vriese) Baker (Bromeliaceae). An Acad Bras Cienc 84:961–971. Farooq, M., A. W. N. Kobayashi, D. Fujita, and S. M. A. Basra. 2009. Plant drought stress: Effects, mechanisms and management. In Sustainable Agriculture, 153–188. The Netherlands: Springer. Flanagan, L. B., and R. L. Jefferies. 1989. Effect of increased salinity on CO2 assimilation, O2 evolution and the δ13C values of leaves of Plantago maritima L. developed at low and high NaCl levels. Planta 178:377–384. Flowers, T. J., and T. D. Colmer. 2008. Salinity tolerance in halophytes. New Phytol 179:945–963. Fougère, F., D. L. Rudulier, and J. G. Streeter. 1991. Effects of salt stress on amino acid, organic acid, and carbohydrate composition of roots, bacteroids, and cytosol of alfalfa (Medicago sativa L.). Plant Physiol 96:1228–1236. Fricke, W. 2004. Rapid and tissue-specific accumulation of solutes in the growth zone of barley leaves in response to salinity. Planta 219:515–525. Fricke, W., and W. S. Peters. 2002. The biophysics of leaf growth in salt-stressed barley. A study at the cell level. Plant Physiol 129:374–388. Fukuda, A., K. Chiba, M. Maeda, A. Nakamura, M. Maeshima, and Y. Tanaka. 2004a. Effect of salt and osmotic stresses on the expression of genes for the vacuolar H+-pyrophosphatase, H+-ATPase subunit A, and Na+/H+ antiporter from barley. J Exp Bot 55:585–594. Fukuda, A., A. Nakamura, A. Tagiri et al. 2004b. Function, intracellular localization and the importance in salt tolerance of a vacuolar Na+/H+ antiporter from rice. Plant Cell Physiol 45:146–159. Genard, H., J. L. Saos, J. P. Billard, A. Tremolieres, and J. Boucaud. 1991. Effect of salinity on lipid composition, glycine betaine content, and photosynthetic activity in chloroplasts of Suaeda maritima. Plant Physiol Bioch 29:421–427. Giełwanowska, I., E. Szczuka, J. Bednara, and R. Gorecki. 2005. Anatomical features and ultrastructure of Deschampsia antarctica (Poaceae) leaves from different growing habitats. Ann Bot 96:1109–1119. Giri, J. 2011. Glycinebetaine and abiotic stress tolerance in plants. Plant Signal Behav 6:1746–1751. Hajibagheri, M. A., J. L. Hall, and T. J. Flowers. 1984. Stereological analysis of leaf cells of the halophyte Suaeda maritima (L.) Dum. J Exp Bot 35:1547–1557. Hakim, M. A., A. S. Juraimi, M. M. Hanafi et al. 2014. Biochemical and anatomical changes and yield reduction in rice (Oryza sativa L.) under varied salinity regimes. Biomed Res Int 2014:11. Haliński, Ł. P., M. Kalkowska, M. Kalkowski, J. Piorunowska, A. Topolewska, and P. Stepnowski. 2015. Cuticular wax variation in the tomato (Solanum lycopersicum L.), related wild species and their interspecific hybrids. Biochem Syst Ecol 60:215–224. Hameed, M., M. Ashraf, M. S. A. Ahmad, and N. Naz. 2010. Structural and functional adaptations in plants for salinity tolerance. In Plant Adaptation and Phytoremediation, 151–170. Springer. Hameed, M., M. Ashraf, and N. Naz. 2009. Anatomical adaptations to salinity in cogon grass [Imperata cylindrica (L.) Raeuschel] from the Salt Range, Pakistan. Plant and Soil 322:229–238. Hameed, M., M. Ashraf, and N. Naz. 2011. Anatomical and physiological characteristics relating to ionic relations in some salt tolerant grasses from the Salt Range, Pakistan. Acta Physiol Plant 33:1399–1409. Hameed, M., S. Batool, N. Naz, T. Nawaz, and M. Ashraf. 2012. Leaf structural modifications for drought tolerance in some differentially adapted ecotypes of blue panic (Panicum antidotale Retz.). Acta Physiol Plant 34:1479–1491. Han, S., B. Yu, Y. Wang, and Y. Liu. 2011. Role of plant autophagy in stress response. Protein Cell 2:784–791. Hare, P. D., and W. A. Cress. 1997. Metabolic implications of stress-induced proline accumulation in plants. Plant Growth Regul 21:79–102. Hare, P. D., W. A. Cress, and J. V. Staden. 2003. A regulatory role for proline metabolism in stimulating Arabidopsis thaliana seed germination. Plant Growth Regul 39:41–50. Hasanuzzaman, M., M. M. Alam, A. Rahman, M. Hasanuzzaman, K. Nahar, and M. Fujita. 2014. Exogenous proline and glycine betaine mediated upregulation of antioxidant defense and glyoxalase systems provides better protection against salt-induced oxidative stress in two rice (Oryza sativa L.) varieties. BioMed Res Int 2014:17. Hasanuzzaman, M., M. A. Hossain, J. A. T. da Silva, and M. Fujita. 2012. Plant response and tolerance to abiotic oxidative stress: Antioxidant defense is a key factor. In Crop Stress and Its Management: Perspectives and Strategies, 261–315. The Netherlands: Springer. Hetherington, A. M., and F. I. Woodward. 2003. The role of stomata in sensing and driving environmental change. Nature 424:901–908.

52

CLIMATE CHANGE AND CROP PRODUcTION

Heuer, B. 2003. Influence of exogenous application of proline and glycinebetaine on growth of salt-stressed tomato plants. Plant Sci 165:693–699. Hopkins, W. G., and N. P. A. Hüner. 1999. Introduction to Plant Physiology. 2nd Edition. NewYork, NY: John Wiley & Sons. Hoque, A., E. Okuma, N. A. Banu, Y. Nakamura, Y. Shimoishi, and Y. Murata. 2007. Exogenous proline mitigates the detrimental effects of salt stress more than exogenous betaine by increasing antioxidant enzyme activities. J Plant Physiol 164:553–561. Hose, E., D. T. Clarkson, E. Steudle, L. Schreiber, and W. Hartung. 2001. The exodermis: A variable apoplastic barrier. J Exp Bot 52:2245–2264. Hossain, M. A., and M. Fujita. 2010. Evidence for a role of exogenous glycinebetaine and proline in antioxidant defense and methylglyoxal detoxification systems in mung bean seedlings under salt stress. Physiol Mol Biol Plants 16:19–29. Howard, A. R., and L. A. Donovan. 2007. Helianthus nighttime conductance and transpiration respond to soil water but not nutrient availability. Plant Physiol 143:145–155. Hussain, M., M. Farooq, K. Jabran, H. Rehman, and M. Akram. 2008. Exogenous glycinebetaine application improves yield under water-limited conditions in hybrid sunflower. Arch Agron Soil Sci 54:557–567. Hwang, Y., and S. Chen. 1995. Anatomical responses in Kandelia candel (L.) Druce seedlings growing in the presence of different concentrations of NaCl. Bot Bull Acad Sin 36:181–188. Ibrahim, A. H. 2004. Efficacy of exogenous glycine betaine application on sorghum plants grown under salinity stress. Acta Bot Hung 46:307–318. Jafri, A. Z., and R. Ahmad. 1995. Effect of soil salinity on leaf development, stomatal size and its distribution in cotton. Pak J Bot 27:297–303. Jenks, M. A., and E. N. Ashworth. 1999. Plant epicuticular waxes: Function, production, and genetics. Hortic Rev 23:1–68. Jordan, W. R., P. J. Shouse, A. Blum, F. R. Miller, and R. L. Monk. 1984. Environmental physiology of sorghum. II. Epicuticular wax load and cuticular transpiration. Crop Sci 24:1168–1173. Kemp, P. R., and G. L. Cunningham. 1981. Light, temperature and salinity effects on growth, leaf anatomy and photosyntesis of Distichlis spicata (L.) greene. Am J Bot 68:507–516. Ketchum, R. E., R. S. Warren, L. J. Klima, F. Lopez-Gutiérrez, and M. W. Nabors. 1991. The mechanism and regulation of proline accumulation in suspension cell cultures of the halophytic grass (Distichlis spicata L.). J Plant Physiol 137:368–374. Kim, K. S., S. H. Park, and M. A. Jenks. 2007a. Changes in leaf cuticular waxes of sesame (Sesamum indicum L.) plants exposed to water deficit. J Plant Physiol 164:1134–1143. Kim, K. S., S. H. Park, D. K. Kim, and M. A. Jenks. 2007b. Influence of water deficit on leaf cuticular waxes of soybean (Glycine max [L.] Merr.). Int J Sci 168:307–316. Kishor, P. B. K., Z. Hong, G. Miao, C. A. Hu, and D. P. S. Verma. 1995. Overexpression of [delta]-pyrroline5-carboxylate synthetase increases proline production and confers osmotolerance in transgenic plants. Plant Physiol 108:1387–1394. Kishor, P. K., S. Sangam, R. N. Amrutha et al. 2005. Regulation of proline biosynthesis, degradation, uptake and transport in higher plants: Its implications in plant growth and abiotic stress tolerance. Curr Sci 88:424–438. Knipp, G., and B. Honermeier. 2006. Effect of water stress on proline accumulation of genetically modified potatoes (Solanum tuberosum L.) generating fructans. J Plant Physiol 163:392–397. Konrad, W., J. Burkhardt, M. Ebner, and A. Roth-Nebelsick. 2015. Leaf pubescence as a possibility to increase water use efficiency by promoting condensation. Ecohydrology 8:480–492. Kosma, D. K., B. Bourdenx, A. Bernard et al. 2009. The impact of water deficiency on leaf cuticle lipids of Arabidopsis. Plant Physiol 151:1918–1929. Kramer, D., W. P. Anderson, and J. Preston. 1978. Transfer cells in the root epidermis of Atriplex hastata L. as a response to salinity: A comparative cytological and X-ray microprobe investigation. Funct Plant Biol 5:739–747. Kroemer, G., G. Mariño, and B. Levine. 2010. Autophagy and the integrated stress response. Mol Cell 40:280–293. Lambers, H., F. S. Chapin, and T. L. Pons. 2008. Plant water relations. In Plant Physiological Ecology, 163– 223. New York, NY: Springer. Lindsey, A. J. 2015. Agronomic and Physiological Responses of Modern Drought-Tolerant Maize (Zea mays L.) Hybrids to Agronomic Production Practices. PhD diss., The Ohio State University.

MEcHANISMS OF OSMOTIc STRESS TOLERANcE

53

LiXin, Z., L. ShengXiu, and L. ZongSuo. 2009. Differential plant growth and osmotic effects of two maize (Zea mays L.) cultivars to exogenous glycinebetaine application under drought stress. Plant Growth Regul 58:297–305. Longstreth, D. J., and P. S. Nobel. 1979. Salinity effects on leaf anatomy consequences for photosynthesis. Plant Physiol 63:700–703. Macková, J., M. Vašková, P. Macek, M. Hronková, L. Schreiber, and J. Šantrůček. 2013. Plant response to drought stress simulated by ABA application: Changes in chemical composition of cuticular waxes. Environ Exp Bot 86:70–75. Madan, S., H. S. Nainawatee, R. K. Jain, and J. B. Chowdhury. 1995. Proline and proline metabolising enzymes in in-vitro selected NaCl-tolerant Brassica juncea L. under salt stress. Ann Bot 76:51–57. Maggio, A., G. Raimondi, A. Martino, and S. de Pascale. 2007. Salt stress response in tomato beyond the salinity tolerance threshold. Environ Exp Bot 59:276–282. Mahajan, S., and N. Tuteja. 2005. Cold, salinity, and drought stresses: An overview. Arch Biochem Biophys 444:139–158. Makbul, S., N. S. Güler, N. Durmuş, and S. Güven. 2011. Changes in anatomical and physiological parameters of soybean under drought stress. Turk J Bot 35:369–377. Manavalan, L. P., and H. T. Nguyen. 2012. Drought tolerance in crops: Physiology to genomics. In Plant Stress Physiology, ed. S. Shabala, 1–13. Wallingford, UK: CAB International. Maqsood, A., M. Shahbaz, and N. A. Akram. 2006. Influence of exogenously applied glycinebetaine on growth and gas exchange characteristics of maize (Zea mays L.). Pak J Agri Sci 43:1–2. McWilliam, J. R. 1986. The national and international importance of drought and salinity effects on agricultural production. Funct Plant Biol 13:1–13. Meek, C., D. Oosterhuis, and J. Gorham. 2003. Does foliar-applied glycine betaine affect endogenous betaine levels and yield in cotton? Crop Manage 2, DOI:10.1094/CM-2003-0804-02-RS. Mohammad, A. R., K. Behzad, and J. Hadi. 2012. Application of exogenous glycine betaine on some growth traits of soybean (Glycine max L.) cv. DPX in drought stress conditions. Sci Res Essays 7:432–436. Mohammed, A. R., and L. Tarpley. 2011. Characterization of rice (Oryza sativa L.) physiological responses to a-tocopherol, glycine betaine or salicylic acid application. J Agri Sci 3:3. Munns, R., 2005. Genes and salt tolerance: Bringing them together. New Phytol 167:645–663. Munns, R., D. P. Schachtman, and A. G. Condon. 1995. The significance of a two-phase growth response to salinity in wheat and barley. Funct Plant Biol 22:561–569. Munns, R., and M. Tester. 2008. Mechanisms of salinity tolerance. Annu Rev Plant Biol 59:651–681. Naskar, S., and P. K. Palit. 2014. Anatomical and physiological adaptations of mangroves. Wetl Ecol Manag 23:1–14. Naz, N., R. Batool, S. Fatima et al. 2014a. Adaptive components of tolerance to salinity in a saline desert grass Lasiurus scindicus Henrard. Ecol Res 30:429–438. Naz, N., M. Hameed, M. Ashraf, F. Al-Qurainy and M. Arshad. 2010. Relationships between gas-exchange characteristics and stomatal structural modifications in some desert grasses under high salinity. Photosynthetica 48:446–456. Naz, N., T. Rafique, M. Hameed, M. Ashraf, R. Batool, and S. Fatima. 2014b. Morpho-anatomical and physiological attributes for salt tolerance in sewan grass (Lasiurus scindicus Henr.) from Cholistan Desert, Pakistan. Acta Physiol Plant 36:2959–2974. Ni, Y., Y. J. Guo, L. Han, H. Tang, and M. Conyers. 2012. Leaf cuticular waxes and physiological parameters in alfalfa leaves as influenced by drought. Photosynthetica 50:458–466. Ni, Y., Z. Sun, X. Huang, C. Huang, and Y. Guo. 2015. Variations of cuticular wax in mulberry trees and their effects on gas exchange and post-harvest water loss. Acta Physiol Plant 37:1–9. Niu, X., W. Zheng, B. Lu et al. 2007. An unusual posttranscriptional processing in two betaine aldehyde dehydrogenase loci of cereal crops directed by short, direct repeats in response to stress conditions. Plant Physiol 143:1929–1942. Nonami, H., and J. S. Boyer. 1990. Primary events regulating stem growth at low water potentials. Plant Physiol 93:1601–1609. Ogburn, R. M., and E. J. Edwards. 2010. The ecological water-use strategies of succulent plants. Adv Bot Res 55:179–225. Ohta, M., Y. Hayashi, A. Nakashima et al. 2002. Introduction of a Na+/H+ antiporter gene from Atriplex gmelini confers salt tolerance to rice. FEBS Lett 532:279–282.

54

CLIMATE CHANGE AND CROP PRODUcTION

Ola, H., A. Elbar, E. Reham, S. Farag, S. Eisa, and S. A. Elabib. 2012. Morpho-anatomical changes in salt stressed kallar grass (Leptochloa fusca L. Kunth). Res J Agric Biol Sci 8:158–166. Omamt, E. N., P. S. Hammes, and P. J. Robbertse. 2006. Differences in salinity tolerance for growth and wateruse efficiency in some amaranth (Amaranthus spp.) genotypes. New Zealand J Crop Hort Sci 34:11–22. Orsini, F., M. Alnayef, S. Bona, A. Maggio, and G. Gianquinto. 2012. Low stomatal density and reduced transpiration facilitate strawberry adaptation to salinity. Environ Exp Bot 81:1–10. Oukarroum, A., S. E. Madidi, and R. J. Strasser. 2012. Exogenous glycine betaine and proline play a protective role in heat-stressed barley leaves (Hordeum vulgare L.): A chlorophyll a fluorescence study. Plant Biosyst 146:1037–1043. Parida, A. K., A. B. Das, and P. Mohanty. 2004. Investigations on the antioxidative defence responses to NaCl stress in a mangrove, Bruguiera parviflora: Differential regulations of isoforms of some antioxidative enzymes. Plant Growth Regul 42:213–226. Passioura, J. B., and R. Munns. 2000. Rapid environmental changes that affect leaf water status induce transient surges or pauses in leaf expansion rate. Funct Plant Biol 27:941–948. Petcu, E. 2005. The effect of water stress on cuticular transpiration and relationships with winter wheat yield. Rom Agric Res 22:15–19. Petcu, E., M. Schitea, and V. E. Cîrstea. 2009. The effect of water stress on cuticular transpiration and its association with alfalfa yield. Rom Agric Res 26:53–56. Qadir, M., E. Quillérou, V. Nangia et al. 2014. Economics of salt-induced land degradation and restoration. Nat Resour Forum 38:282–295. Qiao, W. H., X. Y. Zhao, W. Li, Y. Luo, and X. S. Zhang. 2007. Overexpression of AeNHX1, a root-specific vacuolar Na+/H+ antiporter from Agropyron elongatum, confers salt tolerance to Arabidopsis and Festuca plants. Plant Cell Rep 26:1663–1672. Rahnama, A., R. A. James, K. Poustini, and R. Munns. 2010. Stomatal conductance as a screen for osmotic stress tolerance in durum wheat growing in saline soil. Funct Plant Biol 37:255–263. Reddy, K. R., W. B. Henry, R. Seepaul, S. Lokhande, B. Gajanayake, and D. Brand. 2013. Exogenous application of glycinebetaine facilitates maize (Zea mays L.) growth under water deficit conditions. Am J ExpAgric 3:1–13. Reinhardt, D. H., and T. L. Rost. 1995. Developmental changes of cotton root primary tissues induced by salinity. Int J Plant Sci 156:505–513. Reinoso, H., L. Sosa, L. Ramírez, and V. Luna. 2004. Salt-induced changes in the vegetative anatomy of Prosopis strombulifera (Leguminosae). Can J Bot 82:618–628. Rengasamy, P. 2002. Transient salinity and subsoil constraints to dryland farming in Australian sodic soils: An overview. Anim Prod Sci 42:351–361. Rezaei, M. A., I. Jokar, M. Ghorbanli, B. Kaviani, and A. Kharabian-Masouleh. 2012. Morpho-physiological improving effects of exogenous glycine betaine on tomato (Lycopersicum esculentum Mill.) cv. PS under drought stress conditions. Plants Omics J 5:79–86. Rhodes, D. F., and A. D. Hanson. 1993. Quaternary ammonium and tertiary sulfonium compounds in higher plants. Annu Review Plant Biol 44:357–384. Richards, R. A., H. M. Rawson, and D. A. Johnson. 1986. Glaucousness in wheat: Its development and effect on water-use efficiency, gas-exchange and photosynthetic tissue temperatures. Aust J Plant Physiol 13:465–473. Ristic, Z., and D. D. Cass. 1991. Leaf anatomy of Zea mays L. in response to water shortage and high temperature: A comparison of drought-resistant and drought-sensitive lines. Botl Gaz 152:173–185. Robinson, S. P., and G. P. Jones. 1986. Accumulation of glycinebetaine in chloroplasts provides osmotic adjustment during salt stress. Funct Plant Biol 13:659–668. Romero-Aranda, R., T. Soria, and J. Cuartero. 2001. Tomato plant-water uptake and plant-water relationships under saline growth conditions. Plant Sci 160:265–272. Rontein, D., G. Basset, and A. D. Hanson. 2002. Metabolic engineering of osmoprotectant accumulation in plants. Metab Eng 4:49–56. Sairam, R. K., and A. Tyagi. 2004. Physiology and molecular biology of salinity stress tolerance in plants. Curr Sci Bangalore 86:407–421. Sakamoto, A., and N. Murata. 2002. The role of glycine betaine in the protection of plants from stress: Clues from transgenic plants. Plant Cell Environ 25:163–171. Savé, R., C. Biel, and F. D. Herralde. 2000. Leaf pubescence, water relations and chlorophyll fluorescence in two subspecies of Lotus creticus L. Biol Plantarum 43:239–244.

MEcHANISMS OF OSMOTIc STRESS TOLERANcE

55

Schuppler, U., P. H. He, P. C. L. John, and R. Munns. 1998. Effect of water stress on cell division and celldivision-cycle 2-like cell-cycle kinase activity in wheat leaves. Plant Physiol 117:667–678. Sekhar, P. N., R. N. Amrutha, S. Sangam, D. P. S. Verma, and P. B. Kishor. 2007. Biochemical characterization, homology modeling and docking studies of ornithine δ-aminotransferase-an important enzyme in proline biosynthesis of plants. J Mol Graph Model 26:709–719. Seo, P. J., and C. Park. 2011. Cuticular wax biosynthesis as a way of inducing drought resistance. Plant Signal Behav 6:1043–1045. Serraj, R., and T. R. Sinclair. 2002. Osmolyte accumulation: Can it really help increase crop yield under drought conditions? Plant Cell Environ 25:333–341. Shabala, L., A. Mackay, Y. Tian, S. Jacobsen, D. Zhou, and S. Shabala. 2012. Oxidative stress protection and stomatal patterning as components of salinity tolerance mechanism in quinoa (Chenopodium quinoa). Physiol Plant 146:26–38. Shabala, S., O. Babourina, and I. Newman. 2000. Ion-specific mechanisms of osmoregulation in bean mesophyll cells. J Exp Bot 51:1243–1253. Shabala, S., and R. Munns. 2012. Salinity stress: Physiological constraints and adaptive mechanisms. In Plant Stress Physiology, ed. S. Shabal, 59–93. Oxfordshire, UK: CAB International. Shabala, S., and L. Shabala. 2011. Ion transport and osmotic adjustment in plants and bacteria. Biomol Concepts 2:407–419. Shabala, S. N., and R. R. Lew. 2002. Turgor regulation in osmotically stressed Arabidopsis epidermal root cells. Direct support for the role of inorganic ion uptake as revealed by concurrent flux and cell turgor measurements. Plant Physiol 129:290–299. Sharp, R. E., W. K. Silk, and T. C. Hsiao. 1988. Growth of the maize primary root at low water potentials I. Spatial distribution of expansive growth. Plant Physiol 87:50–57. Shrivastava, P., and R. Kumar. 2015. Soil salinity: A serious environmental issue and plant growth promoting bacteria as one of the tools for its alleviation. Saudi J Biol Sci 22:123–131. Sinclair, T. R., G. L. Hammer, and E. J. V. Oosterom. 2005. Potential yield and water-use efficiency benefits in sorghum from limited maximum transpiration rate. Funct Plant Biol 32:945–952. Skelton, R. P., J. J. Midgley, J. M. Nyaga, S. D. Johnson, and M. D. Cramer. 2012. Is leaf pubescence of Cape Proteaceae a xeromorphic or radiation-protective trait? Aust J Bot 60:104–113. Smith, W. K., and P. S. Nobel. 1977. Influences of seasonal changes in leaf morphology on water-use efficiency for three desert broadleaf shrubs. Ecol 58:1033–1043. Sobrado, M. A. 2007. Relationship of water transport to anatomical features in the mangrove Laguncularia racemosa grown under contrasting salinities. New Phytol 173:584–591. Spollen, W. G., R. E. Sharp, I. N. Saab, and Y. Wu. 1993. Regulation of cell expansion in roots and shoots at low water potentials. In Water Deficits: Plant Responses from Cell to Community, ed. J. A. C. Smith, and H. Griffiths, 37–52. Oxford, UK: Bios Scientific Publishers. Srinivas, V., and D. Balasubramanian. 1995. Proline is a protein-compatible hydrotrope. Langmuir 11:2830–2833. Svenningsson, M., and C. Liljenberg. 1986. Changes in cuticular transpiration rate and cuticular lipids of oat (Avena sativa) seedlings induced by water stress. Physiol Plant 66:9–14. Szabados, L., and A. Savouré. 2010. Proline: A multifunctional amino acid. Trends Plant Sci 15:89–97. Taiz, L., and E. Zeiger. 2002. Photosynthesis: Physiological and ecological considerations. Plant Physiol 171–191. Thiery, L., A. Leprince, D. Lefebvre, M. A. Ghars, E. Debarbieux, and A. Savouré. 2004. Phospholipase D is a negative regulator of proline biosynthesis in Arabidopsis thaliana. J Biol Chem 279:14812–14818. Tomlinson, P. B. 1969. Anatomy of the Monocotyledons. Oxford, UK: Clarendon Press. UN (United Nations). 2015. World population prospects: The 2015 revision, key findings and advance tables. United Nations Department of Economic and Social Affairs/Population Divisions, p. 2. https://esa. un.org/unpd/wpp/publications/files/key_findings_wpp_2015.pdf (accessed December 20, 2016). Verbruggen, N., and C. Hermans. 2008. Proline accumulation in plants: A review. Amino Acids 35:753–759. Wahid, A. 2003. Physiological significance of morpho-anatomical features of halophytes with particular reference to Cholistan Flora. Int J Agric Biol 5:207–212. Wahid, A., and A. Shabbir. 2005. Induction of heat stress tolerance in barley seedlings by pre-sowing seed treatment with glycinebetaine. Plant Growth Regul 46:133–141. Walsh, G. E. 1990. Anatomy of the seed and seedling of Spartina alterniflora L. (Poaceae). Aquatic Botany 38:177–193.

56

CLIMATE CHANGE AND CROP PRODUcTION

Wani, S. H., N. B. Singh, A. Haribhushan, and J. I. Mir. 2013. Compatible solute engineering in plants for abiotic stress tolerance-role of glycine betaine. Curr Genomics 14:157. Wei, Q., Y. J. Guo, H. M. Cao, and B. K. Kuai. 2011. Cloning and characterization of an AtNHX2-like Na+/H+ antiporter gene from Ammopiptanthus mongolicus (Leguminosae) and its ectopic expression enhanced drought and salt tolerance in Arabidopsis thaliana. Plant Cell Tiss Org 105:309–316. Werner, A., and R. Stelzer. 1990. Physiological responses of the mangrove Rhizophora mangle grown in the absence and presence of NaCl. Plant Cell Environ 13:243–255. West, G., D. Inze, and G. T. S. Beemster. 2004. Cell cycle modulation in the response of the primary root of Arabidopsis to salt stress. Plant Physiol 135:1050–1058. Westgate, M. E., and J. S. Boyer. 1985. Osmotic adjustment and the inhibition of leaf, root, stem, and silk growth at low water potentials in maize. Planta 164:540–549. Wu, C., G. Yang, Q. Meng, and C. Zheng. 2004. The cotton GhNHX1 gene encoding a novel putative tonoplast Na+/H+ antiporter plays an important role in salt stress. Plant Cell Physiol 45:600–607. Xing, W., and C. B. Rajashekar. 1999. Alleviation of water stress in beans by exogenous glycine betaine. Plant Sci 148:185–192. Xiong, L., Z. Gong, C. D. Rock et al. 2001. Modulation of abscisic acid signal transduction and biosynthesis by an Sm-like protein inArabidopsis. Dev Cell 1:771–781. Xu, H., L. Gauthier, and A. Gosselin. 1995. Stomatal and cuticular transpiration of greenhouse tomato plants in response to high solution electrical conductivity and low soil water content. J Am Soc Hortic Sci 120:417–422. Xu, H. M., N. F. Y. Tam, Q. J. Zan et al. 2014a. Effects of salinity on anatomical features and physiology of a semi-mangrove plant Myoporum bontioides. Mar Pollut Bull 85:738–746. Xu, X., J. Feng, S. Lü et al. 2014b. Leaf cuticular lipids on the Shandong and Yukon ecotypes of saltwater cress, Eutrema salsugineum, and their response to water deficiency and impact on cuticle permeability. Physiol Plant 151:446–458. Xue, X., A. Liu, and X. Hua. 2009. Proline accumulation and transcriptional regulation of proline biothesynthesis and degradation in Brassica napus. BMB Rep 42:28–34. Xue, Z., D. Zhi, G. Xue, H. Zhang, Y. Zhao, and G. Xia. 2004. Enhanced salt tolerance of transgenic wheat (Tritivum aestivum L.) expressing a vacuolar Na+/H+ antiporter gene with improved grain yields in saline soils in the field and a reduced level of leaf Na+. Plant Sci 167:849–859. Yang, H. M., X. Y. Zhang, and G. X. Wang. 2004. Relationships between stomatal character, photosynthetic character and seed chemical composition in grass pea at different water availabilities. J Agr Sci 142:675–681. Yang, J., M. I. Ordiz, J. G. Jaworski, and R. N. Beachy. 2011. Induced accumulation of cuticular waxes enhances drought tolerance in Arabidopsis by changes in development of stomata. Plant Physiol Biochem 49:1448–1455. Yeo, A. R., P. Izard, P. J. Boursier, and T. J. Flowers. 1991. Short-and long-term effects of salinity on leaf growth in rice (Oryza sativa L.). J Exp Bot 42:881–889. Yin, Y., Q. Luo, C. Ma, and H. Liu. 2008. Effects of sprayed betaine on tomato seedlings in drought conditions. Northern Hort 10:24. Yokoi, S., R. A. Bressan, and P. M. Hasegawa. 2002. Salt stress tolerance of plants. JIRCAS Working Rep 23:25–33. Yoo, C. Y., H. E. Pence, P. M. Hasegawa, and M. V. Mickelbart. 2009. Regulation of transpiration to improve crop water use. Crit Rev Plant Sci 28:410–431. Yu, H., X. Chen, Y. Hong et al. 2008. Activated expression of an Arabidopsis HD-START protein confers drought tolerance with improved root system and reduced stomatal density. Plant Cell 20:1134–1151. Yu, J. N., J. Huang, Z. N. Wang, J. S. Zhang, and S. Y. Chen. 2007. An Na+/H+ antiporter gene from wheat plays an important role in stress tolerance. J Biosci 32:1153–1161. YuJing, Z., Z. Yong, H. ZiZhi, and Y. ShunGuo. 2000. Studies on microscopic structure of Puccinellia tenuiflora stem under salinity stress. Grassl Chin 5:6–9. Zarinkamar, F. 2006. Density, size and distribution of stornata in different monocotyledons. Pak J Biol Sci 9:1650–1659. Zhang, F., K. Zhang, C. Du et al. 2015a. Effect of drought stress on anatomical structure and chloroplast ultrastructure in leaves of sugarcane. Sugar Tech 17:41–48.

MEcHANISMS OF OSMOTIc STRESS TOLERANcE

57

Zhang, H., and E. Blumwald. 2001. Transgenic salt-tolerant tomato plants accumulate salt in foliage but not in fruit. Nat Biotechnol 19:765–768. Zhang, H., J. N. Hodson, J. P. Williams, and E. Blumwald. 2001. Engineering salt-tolerant Brassica plants: Characterization of yield and seed oil quality in transgenic plants with increased vacuolar sodium accumulation. Proc Natl Acad Sci 98:12832–12836. Zhang, S. Wu, L. Jiang et al. 2015b. A detailed analysis of the leaf rolling mutant sll2 reveals complex nature in regulation of bulliform cell development in rice (Oryza sativa L.). Plant Biol 17:437–448. Zhao, F., Z. Wang, Q. Zhang, Y. Zhao, and H. Zhang. 2006. Analysis of the physiological mechanism of salttolerant transgenic rice carrying a vacuolar Na+/H+ antiporter gene from Suaeda salsa. J Plant Res 119:95–104. Zhihua, L. X. L. L. Liu, and Z. Luchang. 1992. A study of stomata on grapeleaves 11-stomata and ecological adaptability. J Inner Mongolia Inst Agric Anim Husb 4:11. Zhu, B., J. Su, M. Chang, D. P. S. Verma, Y. Fan, and R. Wu. 1998. Overexpression of a Δ 1-pyrroline-5carboxylate synthetase gene and analysis of tolerance to water-and salt-stress in transgenic rice. Plant Sci 139:41–48. Zhu, J. K. 2002. Salt and drought stress signal transduction in plants. Annu Rev Plant Biol 53:247. Zhu, J., K. M. Brown, and J. P. Lynch. 2010. Root cortical aerenchyma improves the drought tolerance of maize (Zea mays L.). Plant, Cell & Environment 33:740–749. Zhu, L., J. Guo, J. Zhu, and C. Zhou. 2014. Enhanced expression of EsWAX1 improves drought tolerance with increased accumulation of cuticular wax and ascorbic acid in transgenic Arabidopsis. Plant Physiol Biochem 75:24–35. Zhu, M., M. Zhou, L. Shabala, and S. Shabala. 2015. Linking osmotic adjustment and stomatal characteristics with salinity stress tolerance in contrasting barley accessions. Funct Plant Biol 42:252–263.

CHapTer  4

Physiological Mechanisms of Crops’ Mediating Defense Response under Elevated CO2 Xin Li and Kai Shi CONTENTS 4.1 Introduction............................................................................................................................. 59 4.2 Responses of the Physical Barriers: The Role of Stomata.......................................................60 4.3 Phytohormone-Mediated Defenses: Cross Talk of Salicylic Acid (SA), Jasmonic Acid (JA), and Ethylene (ET) Signaling.................................................................................. 61 4.4 Influence of the Secondary Metabolism: Flavonoids and Caffeine........................................ 63 4.5 Redox-Mediated Resistance: Hydrogen Peroxide (H2O2) and Nitric Oxide (NO)..................64 4.6 Conclusions and Perspectives.................................................................................................. 65 References.........................................................................................................................................66 4.1 INTRODUCTION Global climate change due to increasing anthropogenic emissions is markedly affecting natural ecosystems (Kerr 2007). Rising CO2 levels, among other factors, are thought to be responsible for climate change. The global atmospheric concentration of carbon dioxide (CO2) has increased from 280 µmol mol−1 during the pre-industrial period to 388.5 µmol mol−1 in 2010 (Dr. Pieter Tans, NOAA/ESRL, http://www.esrl.noaa.gov/gmd/ccgg/trends/) and is projected to increase to 700 µmol mol−1 by the end of the twenty-first century (Aranjuelo et al. 2011). Additionally, the rise in CO2 is often projected to increase the production and quality of agroecosystems, particularly in C3 crops (Dion et al. 2013; Uprety, 1998). Many studies have investigated the likely impacts of rising CO2 concentration on crop growth and production (Aranjuelo et al. 2013; Leakey et al. 2006; Soares et al. 2008; Tubiello et al. 2000), and there has been general agreement on the beneficial effects of elevated CO2 on yield, probably due to increased photosynthesis, C:N ratio, and water use efficiency from the CO2 “fertilization effect” (Ainsworth and Long 2005; Drake et al. 1997; Slattery et al. 2013). However, yield-limiting factors such as pathogens have been ignored in most of those studies (Juroszek and von Tiedemann 2013; Pangga et al. 2011). Plants consistently face challenges from a wide array of pathogens, including fungal, bacterial, and viral attacks (Singh et al. 2000). Furthermore, disease symptoms are influenced by three main components: (i) host, (ii) pathogen, and (iii) environmental conditions (McElrone et al. 2005). Thus, the altered environmental conditions associated with elevated CO2 will potentially modify plant disease susceptibility. However, knowledge of the effects of climate change on diseases and related plant responses is still lacking. Pathogens reduce plant productivity worldwide, and billions of dollars in plant yield are lost to 59

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diseases each year. Therefore, more work is needed to elucidate how plant diseases will respond to the interacting factors of elevated CO2 climatic conditions (McElrone et al. 2010; Runion et al. 2010). Understanding such relationships is essential for predicting disease pressure and managing agricultural and natural ecosystems under changing climatic conditions. Recent studies conducted in free-air CO2 enrichment sites, open-top chambers, and growth chambers involving plant diseases have shown that responses to elevated CO2 may vary with the hostpathogen system, and thus the severity and/or incidence of disease may either increase, decrease, or remain unaffected (Eastburn et al. 2011; Melloy et al. 2010; West et al. 2012; Zhang et al. 2015). For example, the plant fungal pathogen Colletotrichum gloeosporiodes exhibited increased fecundity and aggressiveness over 25 infection cycles in the host Stylosanthes scabra under elevated CO2 (Chakraborty and Datta 2003). However, investigations into the systemic responses of tomato to Tomato yellow leaf curl virus (TYLCV) and of tobacco to Potato virus Y found that elevated CO2 decreased disease incidence and severity (Huang et al. 2012; Matros et al. 2006). Furthermore, some previous reviews (Garrett et al. 2006) have summarized research on the effect of predicted changes in environmental conditions on the development of plant diseases. However, not much about defense response of crops to pathogens was reviewed. More recent studies reported accurate determination of defense responses of crops from the molecule levels. Summarizing the physiological mechanisms of crops’ mediating defense response under elevated CO2 will be helpful to better understand, predict, and prepare for the effects of global climate change. Previous studies revealed that the effect of elevated CO2 on plants, which includes C and N assimilation, secondary metabolism, plant stomatal conductance, as well as leaf temperature, could in turn affect the interactions of crops and biotic stress (Ainsworth and Long 2005; May et al. 2013). For this review, we intended to highlight the recent advances on how elevated CO2 affects the physical barriers, phytohormones, secondary metabolites and redox status, and how these effects alter the interactions of crops and pathogen attacks. 4.2  RESPONSES OF THE PHYSICAL BARRIERS: THE ROLE OF STOMATA Pathogen entry into hosts is a critical step before the onset of the infection and disease progression. Crops have a complex array of defense mechanisms. For example, the cell wall is covered with a waxy cuticle that serves as a potent physical barrier. Successful cell wall associated defenses can halt invading pathogens at an early stage, before the establishment of disease, and can eliminate the need for more costly defense responses (Underwood, 2012). The changes in the structures and thickness of the cell wall in response to CO2 are still idiosyncratic (Ainsworth and Long 2005). Furthermore, although some pathogenic fungi infect plants by penetrating the cell wall, many foliar bacterial plant pathogens invade plants primarily through natural surface openings, namely, through the stomata (Kumar et al. 2012). Stomata are small pores in the leaf epidermis, formed by a pair of guard cells that have developed mechanisms to sense and respond to various endogenous and environmental stimuli. By changing the size of the stomatal pores, stomata can regulate gas exchange between the plant and environment, as well as control water loss (Melotto et al. 2008). There is evidence indicating that plant pathogens use the leaf surface stomata for entry into the host tissue (Boureau et al. 2002). Arabidopsis thaliana stomata closed in response to live bacteria and purified pathogen-/microbe-associated molecular patterns (PAMPs/MAMPs) in a solution system; thus, Melotto et al. (2006) suggested that stomata played an active role in restricting bacterial invasion as part of the innate immune response, but not only as a passive port of entry. It has also been reported that bacterium-induced stomatal closure requires PAMPs signaling, homeostasis of the defense hormone salicylic acid, and is upstream of signaling regulated by abscisic acid in the guard cell (Melotto et al. 2006, 2008). In Populus, the clones that opened their stomata late in the morning were more resistant to Melampsora larici-populina Kleb., compared with those that opened

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their stomata earlier (Siwecki and Przyuyl 2010). Manning and Vontiedemann (1995) speculated that reducing the stomatal conductance and the size of the stomatal aperture could inhibit the entry of bacterial pathogens through the stomata. Notably, reduced stomatal conductance is one of the primary effects of rising atmospheric CO2 on plants (Drake et al. 1997; Long et al. 2004); however, it is not clear whether the elevated CO2-induced alterations in the stomatal characteristics are associated with foliar bacterial pathogenic infections. Lake and Wade (2009) found that infection of Arabidopsis thaliana by the biotrophic pathogen Erysiphe cichoracearum resulted in fewer stomata produced on the infected leaf surfaces, and this effect was enhanced in environments with elevated levels of CO2. Similarly, in a study involving oilseed Brassica juncea, the decrease in the disease index of downy mildew caused by the stomatainvading pathogen Hyaloperonospora brassicae was suggested to be associated with a decrease in stomatal density, pore size, and stomatal conductance in response to elevated CO2 (Mathur et al. 2013). By contrast, there are also reports suggesting that stomatal conductance and stomatal density are not correlated with pathogenic infection (O’Keefe et al. 2013; Riikonen et al. 2008). Furthermore, to counter host defenses during infection and in the apoplast, plant pathogens have evolved a variety of virulence factors to subvert host defenses or to obtain nutrients (Nomura and He 2005). P. syringae pv. tomato DC3000 can produce polyketide toxin coronatine (COR) to promote stomatal opening and disrupt plant defense responses (Melotto et al. 2006; Zeng et al. 2011). A recent study revealed that under elevated CO2, the stomatal aperture was constantly smaller than the ambient counterpart and did not show any evident transient changes in response to P. syringae inoculation. Furthermore, COR-induced stomatal opening was effectively counteracted by elevated CO2 compared with an ambient counterpart, which might partly contribute to defense against pathogen infection under elevated CO2. The differences in P. syringae- and COR-induced stomatal movement between ambient and elevated CO2 treatment may contribute to the different behavior of P. syringae bacteria in these plants; namely, the concentrated distribution of P. syringae around the reopened stomata in ambient CO2-treated plants might allow pathogens to enter the intercellular space more successfully compared with the elevated CO2 plants, in which bacteria were dispersed on the surface of tomato epidermal cells among the closed stomata (Li et al. 2015). In addition, COR-induced decrease in photosynthetic efficiency at ambient CO2 was found to be eliminated by supplementation of plants with high CO2, suggesting atmospheric CO2 had fundamental effects on COR-mediated function (Attaran et al. 2014). Thus, further studies will be necessary to determine the precise effect of elevated CO2 on COR-mediated stomatal movement (Li et al. 2015). 4.3  PHYTOHORMONE-MEDIATED DEFENSES: CROSS TALK OF SALICYLIC ACID (SA), JASMONIC ACID (JA), AND ETHYLENE (ET) SIGNALING The effects of elevated CO2 on plant pathogen interactions are expected to occur both directly through plant physiological responses and indirectly through effects on microbes that associate with plants (Malmstrom and Field 1997; Rua et al. 2013). The in vitro pathogen microbe growth studies clearly showed that the bacteria P. syringae and the necrotrophic fungus B. cinerea were not affected by elevated CO2 (Zhang et al. 2015). Most scientists thus speculated that changes in plant physiology, that is, biochemical profiles of pathogen-infected plants under elevated CO2, may result in increased resistance or susceptibility to specific pathogens (Matros et al. 2006). Phytohormones are small molecules produced in crops that govern diverse physiological processes, including defense response. Among them, JA, SA, and ET are major defense-related phytohormones (Shigenaga and Argueso 2016). Signaling pathways mediated by these phytohormones will intimately interact antagonistically or synergistically. The regulatory mechanisms determine induction of downstream responses (Lu et al. 2016). Generally, JA is a positive regulator of immunity against necrotrophic pathogens that actively kill hosts to acquire nutrients and herbivore defense, whereas SA

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is a positive regulator of immunity against biotrophic pathogens that feed on living hosts as well as against hemibiotrophs that show a biotrophic phase in the early stage of infection (Glazebrook 2005). As reported, positive roles of ET in resistance against necrotrophs seem widespread in angiosperms. ET also contributes to resistance against biotrophic and hemibiotrophic pathogens in Arabidopsis, soybean, and rice (Helliwell et al. 2013; Hoffman et al. 1999; Tintor et al. 2013). In a recent study, the involvement of the phytohormones SA and JA was examined under elevated CO2 with and without pathogen inoculation (Zhang et al. 2015). Regardless of the pathogen type, elevated CO2 generally increased constitutive levels of SA and SA-related transcripts in both uninfected and infected plants, especially in the additive treatments of elevated CO2 and pathogen infection. In contrast to the universal increase in SA, JA concentrations and the transcripts of genes involved in JA signaling were not increased by elevated CO2 in uninfected plants. TMV and P. syringae infection had little or no effect on the JA contents or transcripts of genes involved in JA signaling, although these genes were induced by B. cinerea. Furthermore, the B. cinerea-induced increases in JA contents, as well as PI I and PI II transcript levels, were much lower in plants grown under elevated CO2 compared with those grown under ambient CO2. These results suggest that elevated CO2 favors the SA pathway but represses the JA pathway in plants. Along with the direct effect of elevated CO2 on plant physiology and growth, elevated CO2 may cause plants to re-allocate resources to synthesize secondary metabolites, which might contribute to SA synthesis and SA/JA cross talk (Matros et al. 2006; Runion et al. 2010). Previous studies have also suggested that elevated CO2 induces SA accumulation and that NPR1 may be activated by the altered redox status in the cytosol through increased thioredoxin and glutathione-S-transferase production (Casteel et al. 2012; Zavala et al. 2013). In view of the potential for cross talk between the SA and JA signaling pathways, it might be expected that the elevated CO2-induced accumulation of SA is related to the suppression of JA signaling, which underlies the variation in plant defenses against different pathogen types under elevated CO2. It should be noted that the cross talk between the JA and SA signaling pathways might also be modified by the pathogens’ infection to some extent (Zhang et al. 2015). However, whether the impact of elevated CO2 on SA/JA cross talk and the associated pathogen defenses is a general response is an open question. Many previous studies have reported that under elevated CO2 conditions, lower levels of disease are caused by biotrophic pathogens such as downy mildew caused by Peronospora manshurica on soybean (Eastburn et al. 2010) and virus disease caused by Potato virus Y on tobacco (Matros et al. 2006). Conversely, some studies have reported that higher levels of disease under elevated CO2 conditions are caused by necrotrophic pathogens such as brown spot caused by Septoria glycines (Eastburn et al. 2010) and powdery mildew caused by Podosphaera xanthii on zucchini (Pugliese et al. 2012). However, there are also examples of necrotrophic, biotrophic, and hemibiotrophic pathogens having reduced, increased, or no effects on disease upon increased CO2 (Eastburn et al. 2011; Lake and Wade 2009; Oehme et al. 2013). These might be explained by the other hormone player(s). ET has been shown to act synergistically with JA in the response to B. cinerea in Arabidopsis (Thomma et al. 1999). In tomato plants, JA-mediated responses seem to act independently from ethylene-induced resistance against B. cinerea, and plants pre-treated with ethylene showed a decreased susceptibility toward B. cinerea, whereas pre-treatment with 1-methylcyclopropene (an inhibitor of ethylene perception), resulted in increased susceptibility (Díaz et al. 2002). Furthermore, previous studies also indicated that elevated CO2 suppresses the ethylene signaling pathway in soybean and Medicago truncatula (Guo et al. 2014; Zavala et al. 2009). Thus, ET might be involved in the susceptibility to B. cinerea under elevated CO2. Additionally, in a previous study with Arabidopsis, elevated CO2 attenuated the SA-dependent runaway cell death in lesion simulating disease 1 (lsd1) mutant, which has been implicated in defense following avirulent or virulent pathogen challenge (Mateo et al. 2004). Given the complexity of the interactions between plants, plant pathogens, and the environment, it is not surprising that the understanding of how elevated CO2 influences plant pests and disease agents is still incomplete and requires further study.

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4.4  INFLUENCE OF THE SECONDARY METABOLISM: FLAVONOIDS AND CAFFEINE Plant secondary metabolites are major defense elements of plants against pathogen and herbivore attacks (Wang and Wu 2005). Rising atmospheric CO2 has a profound effect on plant primary and secondary metabolisms (Ghasemzadeh and Jaafar 2011; Li et al. 2008, 2017). In Arabidopsis, elevated CO2 causes a metabolic perturbation that compels plants to increase their functions or activity by consuming or storing photoassimilates (Li et al. 2008). A recent study found that elevated CO2 might also increase production and consumption of photoassimilates in crops by enhancing net photosynthesis and respiration rate, respectively (Li et al. 2013, 2017). It is to be noted that an enhancement in photosynthesis under elevated CO2 could provide increased levels of substrates for glycolysis, and a significant increase in tricarboxylic acid (TCA) cycle intermediates might contribute to increased C-partitioning to respiration or for other relevant anabolic pathways (Li et al. 2008, 2017). As per carbon-nutrient balance theory, CO2 enrichment increases the carbon-tonitrogen ratio, and thus a greater amount of carbohydrates can be allocated to secondary metabolism in plants (Ibrahim and Jaafar 2011). In addition, many experimental studies have shown that elevated conditions increase carbon-rich structural compounds and secondary metabolites in a range of plant species (Ghasemzadeh and Jaafar 2011; Matros et al. 2006). In the current study, CO2 enrichment remarkably increased contents of polyphenols, including catechins. The biosynthesis of catechins through phenylpropanoid and flavonoid pathways is dependent on the primary metabolism that supplies initial compounds required to run phenylpropanoid pathways (Li et al. 2017). The crops grown under elevated CO2 usually possess high activity of phenylalanine ammonialyase (PAL), which results in increased production and accumulation of secondary metabolites, which affect the interactions of crop defense to pathogens. PAL is the key enzyme involved in the synthesis of flavonoid compounds. Elevated CO2 might directly or indirectly influence the transcription of all key genes of flavonoid biosynthetic pathways, including CsPAL, and thus result in increased levels of flavonoid such as catechin levels in tea leaves (Li et al. 2017). On average, elevated CO2 increases total phenolics in plants by an average of 19%, condensed tannins by 22%, and flavonoids by 27% (Robinson et al. 2012). A previous study revealed that elevated CO2 could induce production of scopolin and 4- and 5-O-caffeoyl-D-quinic acid. The increase in these compounds elevates resistance against Tobacco mosaic virus (TMV) and the fungus Cercospora nicotianae in tobacco (Matros et al. 2006; Shadle et al. 2003). Similiarly, elevated CO2 reduced the levels of leaf necrosis caused by late blight in potato, and that was linked to increased β-1,3-glucanase activity, which plays a role in disease resistance, in the leaves under elevated CO2 (Plessl et al. 2007). By way of contrast, previous studies also showed that elevated CO2 sharply decreased the levels of N-rich secondary metabolites such as nicotine at limited N-supply in tobacco (Matros et al. 2006). In addition, Li et al. (2017) reported that caffeine content was dramatically decreased following exposure of tea plants to elevated CO2. Caffeine is a N-rich secondary metabolite, and its biosynthesis depends on the flow of N-based compounds toward the secondary metabolic pathway. This effect was presumably related to changes in primary nitrogen metabolism, as elevated CO2 typically decreased nitrate, ammonium, amino acids, and protein under low and intermediate N-supply. It becomes evident that elevated CO2 sharply down-regulated key genes involved in the biosynthesis of caffeine (Li et al. 2017). Given that caffeine functions as a component of chemical defense in tea plants, its content is generally increased upon pest attacks (Ashihara et al. 2008). Li et al. (2016) reported that elevated CO2 increased susceptibility of tea plants to Colletotrichum gloeosporioides, which was closely associated with the reduction of endogenous concentration of caffeine in tea leaves. Exogenous application of caffeine significantly decreased susceptibility of tea plants to C. gloeosporioides, which was attributed to a significant increase in JA content under elevated CO2. It revealed that application of caffeine could be a potential solution for efficient disease control in the climate change environment.

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Those findings lead to an assumption that elevated CO2 will absolutely change the defense mechanism of crops to pathogens by influencing secondary metabolism in the face of climate change. However, further studies should be carried out to prove the precise affect and mechanisms that elevated CO2 alters secondary metabolites of the crops to pathogen attack. 4.5  REDOX-MEDIATED RESISTANCE: HYDROGEN PEROXIDE (H2O2) AND NITRIC OXIDE (NO) The redox gradient across the plasma membrane is a key indicator of global change and a crucial regulator of redox signaling (Foyer and Noctor 2009). Elevated atmospheric CO2 levels have a stimulating effect on photosynthesis because of decreased photorespiration, particularly in C3 crops, which will in turn favor a decline in photorespiratory H2O2 production relative to oxidative signals produced by other processes, particularly photosynthetic and respiratory electron transport (MunnéBosch et  al. 2013). In alfalfa plants (Medicago sativa L.), ascorbate was more affected by CO2 enrichment than glutathione, and an interaction between CO2 and drought prevented a decrease in the AsA/DHA ratio and increased the ratio of reduced glutathione (GSH) and glutathione disulfide (GSSG) compared with ambient CO2 (Sgherri et al. 1998, 2000). Redox homeostasis is one of the most essential reliable markers for the defense responses of the crops. One of the earliest host plant responses to pathogen invasion is an oxidative burst, in which the levels of reactive oxygen species (ROS) increase rapidly (Graves, 2012). ROS are believed to perform multiple roles during plant defense responses to pathogen attack by acting directly in the initial defense and, possibly, serving as central cellular signaling molecules (Dietz 2008, Klessig et al. 2000). The overproduction of ROS resulted in an imbalanced redox status in plant cells. In particular, H2O2 is the most attractive candidate for a ROS signal because of its relatively long half-life and high permeability across membranes (Klessig et al. 2000; Van Camp et al. 1998). In addition to H2O2, other reactive compounds are also involved in signaling in plants. NO is an emerging essential redox signal in plant immunity and has been well studied. It is also an important regulatory molecule for the disease resistance of crops (Van Camp et al. 1998). Often, the production of NO and H2O2 overlaps both spatially and developmentally (Asai and Yoshioka 2009; Cui et al. 2011). Importantly, H2O2 and NO can react with each other and may influence the activities of enzymes that alter each other’s levels. Accordingly, under elevated CO2 conditions, the cross talk between H2O2 and NO may play a critical role in maintaining redox homeostasis and, subsequently, in the movement of stomata (Joudoi et al. 2013; Shi et al. 2015; Song et al. 2014). H2O2 content of chickpea plants was higher at 750 ppm of CO2 in different genotypes (Sharma et al. 2016), which proved that the H2O2 is involved in plant defense against biotic stress through signaling plant defensive pathways and by causing oxidative damage to pathogen or herbivory attack (Bittner et al. 2017; Maffei et al. 2007). Transcriptomics results showed that elevated CO2 would change the expression of genes related to cell redox homeostasis (Niu et al. 2016). However, the relationship between elevated CO2 and redox signaling remains unclear. It is noteworthy that the accumulation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent H2O2 and NR-dependent NO plays a critical role in the plant stress responses (Cui et al. 2011; Guo et al. 2003). As CO2 enrichment induces the accumulation of H2O2 and NO, it would be of great interest to investigate whether other responses in plants that are triggered by elevated CO2 also involve H2O2 and NO. As previously revealed, NO plays a pivotal role in elevated CO2-induced guard cell movement and stomatal closure (Shi et al. 2015). In addition, NO-related physiological events other than stomatal closure also contribute to the elevated CO2-induced resistance. NO is recognized as a crucial player in plant defense against pathogens. Alternatively, the role of H2O2 and NO involved in the interactions of crops and pathogens under elevated CO2 is underscoring the need for further investigation.

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4.6  CONCLUSIONS AND PERSPECTIVES Free-Air Carbon dioxide Enrichment (FACE) facilities, which have been established over the past two decades, enable researchers to study plant responses to the changing atmospheric environments under field conditions. In this way, interactions of plants suffering with other biotic and abiotic environmental variables can been examined (Eastburn et al. 2011). Plants are the targets of continuous attempts of attack by biotic stress factors such as fungi, viruses, and herbivores. In a sense, rising atmospheric CO2 not only improves plant growth, but also modifies behavior of plant pathogens that eventually affect crop productivity (Ahmed et al. 2017; Runion et al. 2010; Zhang et al. 2015). Therefore, it is important to assess the defense of crops to the virulence of pathogens under elevated CO2 in order to understand the mechanisms of crop defense in the face of climate change. The alteration in plant-pathogen interaction under elevated CO2 is principally dependent on the host plant’s physiology (Matros et al. 2006; Zhang et al. 2015). In the current review, we described how defense changes in crops are mediated by physical barriers, phytohormones, secondary metabolites, and also redox status. Stomatal response, cross talk between SA, JA, and ET signaling, secondary metabolic response, and redox status changes could be associated with the interactions between pathogens and crops grown under elevated CO2. Increasing atmospheric CO2 is creating novel environments for plants and is likely to have significant consequences with regard to the relationship between plant pathogens and their hosts. Previous studies on the effects of elevated CO2 on plant-pathogen interactions have produced conflicting results (Lake and Wade 2009, Newton et al. 2011). In addition, development in techniques for monitoring responses at the molecular level and gene regulation tools are making it possible to more precisely determine fine-scale mechanisms for the interactions between crops and pathogens under elevated conditions. Recent studies have made efficient use of “omics” approaches to distinguish transcriptional, proteomic, and metabolic networks linked to stress perception and response, not only in the model plant Arabidopsis but also in crop, garden, and woody species (Bulgakov et al. 2017; Eastburn et al. 2011; Urano et al. 2010). Transcriptomic evidence revealed that elevated CO2 has a wide range of effects on plant metabolism (including C and N assimilation, secondary metabolism, and transportation), all of which may affect interactions between crops and biotic stress (Ainsworth and Long 2005; May et al. 2013). These variations in molecular mechanisms determine crop defense responses to elevated CO2. Systems biology approaches could provide more beneficial ideas which may finally generate models showing the contribution of different biological pathways or chemicals determining defense responses in relation to elevated CO2. More accurate determination of responses on the molecular level are allowing scientists to better understand, predict, and prepare for the effects of global climate change on crop defense to pathogen attack. As we have reviewed, most of the studies on the effects of elevated CO2 have focused on physical or biochemical composition of plants, and very few studies have been carried out about the effects of elevated CO2 on the co-evolution between plant and pathogen (Rao et al. 2006; Zavala et al. 2013). Environmental changes can also have direct effects on pathogens, as well as host plants. Furthermore, we paid attention to only one factor, namely elevated CO2, which means our conclusions are not applicable over a range of various environments and conditions. More climatic factors, including temperature and precipitation levels, need to be examined to improve our understanding on the interaction between crops and pathogens (Eastburn et al. 2011). As plant-pathogen interactions under increasing CO2 have the potential to interrupt both agricultural and natural systems significantly, additional work is required to understand the extent and mechanisms through which elevated CO2 affects plant diseases. In addition, FACE facilities should incorporate some subplots with natural variation in air temperature and precipitation regimes as predicted by climate change in the future (Eastburn et al. 2011). Such studies will be essential for making accurate predictions regarding future plant disease dynamics and proper management of agricultural and natural ecosystems under changing climatic conditions.

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REFERENCES Ahmed, M., C. O. Stöckle, R. Nelson, and S. Higgins. 2017. Assessment of climate change and atmospheric CO2 impact on winter wheat in the Pacific Northwest using a multimodel ensemble. Front Ecol Evol 5:51. https://doi.org/10.3389/fevo.2017.00051. Ainsworth, E. A., and S. P. Long. 2005. What have we learned from 15 years of free-air CO2 enrichment (FACE)? A meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2. New Phytol 165:351–71. Aranjuelo, I., L. Cabrera-Bosquet, R. Morcuende et al. 2011. Does ear C sink strength contribute to overcoming photosynthetic acclimation of wheat plants exposed to elevated CO2? J Exp Bot 62:3957–69. Aranjuelo, I., A. Sanz-Saez, I. Jauregui et al. 2013. Harvest index, a parameter conditioning responsiveness of wheat plants to elevated CO2. J Exp Bot 64:1879–92. Asai, S., and H. Yoshioka. 2009. Nitric oxide as a partner of reactive oxygen species participates in disease resistance to necrotrophic pathogen Botrytis cinerea in Nicotiana benthamiana. Mol Plant Microbe In 22:619–29. Ashihara, H., H. Sano, and A. Crozier. 2008. Caffeine and related purine alkaloids: Biosynthesis, catabolism, function and genetic engineering. Phytochemistry 69:841–56. Attaran, E., I. T. Major, J. A. Cruz et al. 2014. Temporal dynamics of growth and photosynthesis suppression in response to jasmonate signaling. Plant Physiol 165:1302–14. Bittner, N., U. Trauer-Kizilelma, and M. Hilker. 2017. Early plant defence against insect attack: Involvement of reactive oxygen species in plant responses to insect egg deposition. Planta 245:993–07. Boureau, T., J. Routtu, E. Roine, S. Taira, and M. Romantschuk. 2002. Localization of hrpA-induced Pseudomonas syringae pv. tomato DC3000 in infected tomato leaves. Mol Plant Pathol 3:451–60. Bulgakov, V. P., T. V. Avramenko, and G. S. Tsitsiashvili. 2017. Critical analysis of protein signaling networks involved in the regulation of plant secondary metabolism: Focus on anthocyanins. Crit Rev Biotechnol 37:685–00. Casteel, C. L., L. M. Segal, O. K. Niziolek, M. R. Berenbaum, and E. H. DeLucia. 2012. Elevated carbon dioxide increases salicylic acid in Glycine max. Environ Entomol 41:1435–42. Chakraborty, S., and S. Datta. 2003. How will plant pathogens adapt to host plant resistance at elevated CO2 under a changing climate? New Phytol 159:733–42. Cui, J. X., Y. H. Zhou, J. Ding et al. 2011. Role of nitric oxide in hydrogen peroxide-dependent induction of abiotic stress tolerance by brassinosteroids in cucumber. Plant CellEnviron 34:347–58. Díaz, J., A. ten Have, and J. A. L. van Kan. 2002. The role of ethylene and wound signaling in resistance of tomato to Botrytis cinerea. Plant Physiol 129:1341–51. Dietz, K. J. 2008. Redox signal integration: From stimulus to networks and genes. Physiol Plantarum 133:459–68. Dion, L. M., M. Lefsrud, V. Orsat, and C. Cimon. 2013. Biomass gasification and syngas combustion for greenhouse CO2 enrichment. Bioresources 8:1520–38. Drake, B. G., M. A. Gonzalez-Meler, and S. P. Long. 1997. More efficient plants: A consequence of rising atmospheric CO2? Annu Rev Plant Biol 48:609–39. Eastburn, D. M., M. M. Degennaro, E. H. Delucia, O. Dermody, and A. J. McElrone. 2010. Elevated atmospheric carbon dioxide and ozone alter soybean diseases at SoyFACE. Global Change Biol 16:320–30. Eastburn, D. M., A. J. McElrone, and D. D. Bilgin. 2011. Influence of atmospheric and climatic change on plant-pathogen interactions. Plant Pathol 60:54–69. Foyer, C. H., and G. Noctor. 2009. Redox regulation in photosynthetic organisms: Signaling, acclimation, and practical implications. Antioxid Redox Sign 11:861–05. Garrett, K. A., S. P. Dendy, E. E. Frank, M. N. Rouse, and S. E. Travers. 2006. Climate change effects on plant disease: Genomes to ecosystems. Annu Rev Phytopathol 44:489–09. Ghasemzadeh, A., and H. Z. Jaafar. 2011. Effect of CO2 enrichment on synthesis of some primary and secondary metabolites in ginger (Zingiber officinale Roscoe). Int J Mol Sci 12:1101–14. Glazebrook, J. 2005. Contrasting mechanisms of defense against biotrophic and necrotrophic pathogens. Annu Rev Phytopathol 43:205–27. Graves, D. B. 2012. The emerging role of reactive oxygen and nitrogen species in redox biology and some implications for plasma applications to medicine and biology. J Phys D Appl Phys 45:1–42. Guo, F. Q., J. Young, and N. M. Crawford. 2003. The nitrate transporter AtNRT1.1 (CHL1) functions in stomatal opening and contributes to drought susceptibility in Arabidopsis. Plant Cell 15:107–17.

CROP DEFENSE RESPONSE TO CHANGING CO2 CONDITIONS

67

Guo, H. J., Y. C. Sun, Y. F. Li, X. H. Liu, W. H. Zhang, and F. Ge. 2014. Elevated CO2 decreases the response of the ethylene signaling pathway in Medicago truncatula and increases the abundance of the pea aphid. New Phytol 201:279–91. Helliwell, E. E., Q. Wang, and Y. Yang. 2013. Transgenic rice with inducible ethylene production exhibits broad-spectrum disease resistance to the fungal pathogens Magnaporthe oryzae and Rhizoctonia solani. Plant Biotechnol J 11:33–42. Hoffman, T., J. S. Schmidt, X. Zheng, and A. F. Bent. 1999. Isolation of ethylene-insensitive soybean mutants that are altered in pathogen susceptibility and gene-for-gene disease resistance. Plant Physiol 119:935–50. Huang, L., Q. Ren, Y. Sun, L. Ye, H. Cao, and F. Ge. 2012. Lower incidence and severity of tomato virus in elevated CO2 is accompanied by modulated plant induced defense in tomato. Plant Biology 14:905–13. Ibrahim, M. H., and H. Z. Jaafar. 2011. Enhancement of leaf gas exchange and primary metabolites under carbon dioxide enrichment up-regulates the production of secondary metabolites in Labisia pumila seedlings. Molecules 16:3761–77. Joudoi, T., Y. Shichiri, N. Kamizono et  al. 2013. Nitrated cyclic GMP modulates guard cell signaling in Arabidopsis. Plant Cell 25:558–71. Juroszek, P., and A. von Tiedemann. 2013. Plant pathogens, insect pests and weeds in a changing global climate: A review of approaches, challenges, research gaps, key studies and concepts. J Agr Sci 151:163–88. Kerr, R. A. 2007. Global warming is changing the world. Science 316, 188–90. Klessig, D. F., J. Durner, R. Noad et al. 2000. Nitric oxide and salicylic acid signaling in plant defense. Proc Natl Acad Sci USA 97:8849–55. Kumar, A. S., V. Lakshmanan, J. L. Caplan et al. 2012. Rhizobacteria Bacillus subtilis restricts foliar pathogen entry through stomata. Plant J 72:694–06. Lake, J. A., and R. N. Wade. 2009. Plant-pathogen interactions and elevated CO2: Morphological changes in favour of pathogens. J Exp Bot 60:3123–31. Leakey, A. D. B., M. Uribelarrea, E. A. Ainsworth et al. 2006. Photosynthesis, productivity, and yield of maize are not affected by open-air elevation of CO2 concentration in the absence of drought. Plant Physiol 140:779–90. Li, P., E. A. Ainsworth, A. D. Leakey et al. 2008. Arabidopsis transcript and metabolite profiles: Ecotypespecific responses to open-air elevated CO2. Plan, Cell Environ 31:1673–87. Li, X., G. J. Ahammed, Z. X. Li, M. J. Tang, P. Yan, and W. Y. Han. 2016. Decreased biosynthesis of jasmonic acid via lipoxygenase pathway compromised caffeine-induced resistance to Colletotrichum gloeosporioides under elevated CO2 in tea seedlings. Phytopathology 106:1270–77. Li, X., G. J. Ahammed, Y. Q. Zhang et al. 2015. Carbon dioxide enrichment alleviates heat stress by improving cellular redox homeostasis through an ABA-independent process in tomato plants. Plant Biology 17:81–89. Li, X., G. Q. Zhang, B. Sun et al. 2013. Stimulated leaf dark respiration in tomato in an elevated carbon dioxide atmosphere. Sci Rep 3:3433. DOI: 10.1038/srep03433. Li, X., L. Zhang, G. J. Ahammed et al. 2017. Stimulation in primary and secondary metabolism by elevated carbon dioxide alters green tea quality in Camellia sinensis L. Sci Rep 7:7937. DOI: 10.1038/ s41598-017-08465-1. Long, S. P., E. A. Ainsworth, A. Rogers, and D. R. Ort. 2004. Rising atmospheric carbon dioxide: Plants face the future. Annu Rev Plant Biol 55:591–28. Lu, H., J. T. Greenberg, and L. Holuigue. 2016. Salicylic acid signaling networks. Front Plant Sci 7:238. https:// doi.org/10.3389/fpls.2016.00238. Maffei, M. E., A. Mithofer, and W. Boland. 2007. Insects feeding on plants: Rapid signals and responses preceding the induction of photochemical release. Phytochemistry 68:2946–59. Malmstrom, C. M., and C. B. Field. 1997. Virus-induced differences in the response of oat plants to elevated carbon dioxide. Plant Cell Environ 20:178–88. Manning, W. J., and A. Vontiedemann. 1995. Climate change: Potential effects of increased atmospheric carbon dioxide (CO2), ozone (O3), and ultraviolet-B (UV-B) radiation on plant diseases. Environ Pollut 88:219–45. Mateo, A., P. Mühlenbock, C. Rustérucci et al. 2004. Lesion simulating disease 1 is required for acclimation to conditions that promote excess excitation energy. Plant Physiol 136:2818–30. Mathur, P., E. Sharma, S. D. Singh, A. K. Bhatnagar, V. P. Singh, R. Kapoor. 2013. Effect of elevated CO2 on infection of three foliar diseases in oilseed Brassica juncea. J Plant Pathol 95:135–44.

68

CLIMATE CHANGE AND CROP PRODUcTION

Matros, A., S. Amme, B. Kettig, G. H. Buck-Sorlin, U. Sonnewald, and H. P. Mock. 2006. Growth at elevated CO2 concentrations leads to modified profiles of secondary metabolites in tobacco cv. SamsunNN and to increased resistance against infection with potato virus Y. Plant. Cell Environ 29:126–37. May, P., W. Liao, Y. Wu et al. 2013. The effects of carbon dioxide and temperature on microRNA expression in Arabidopsis development. Nat Commun 4:2145. DOI: 10.1038/ncomms3145. McElrone, A. J., J. G. Hamilton, A. J. Krafnick, M. Aldea, R. G. Knepp, and E. H. DeLucia. 2010. Combined effects of elevated CO2 and natural climatic variation on leaf spot diseases of redbud and sweetgum trees. Environ Pollut 158:108–14. McElrone, A. J., C. D. Reid, K. A. Hoye, E. Hart, and R. B. Jackson. 2005. Elevated CO2 reduces disease incidence and severity of a red maple fungal pathogen via changes in host physiology and leaf chemistry. Global Change Biol 11:1828–36. Melloy, P., G. Hollaway, J. Luck, R. Norton, E. Aitken, and S. Chakraborty. 2010. Production and fitness of Fusarium pseudograminearum inoculum at elevated carbon dioxide in FACE. Global Change Biol 16:3363–73. Melotto, M., W. Underwood, and S. Y. He. 2008. Role of stomata in plant innate immunity and foliar bacterial diseases. Annu Rev Phytopath 46:101–22. Melotto, M., W. Underwood, J. Koczan, K. Nomura, and S. Y. He. 2006. Plant stomata function in innate immunity against bacterial invasion. Cell 126:969–80. Munné-Bosch, S., G. Queval, and C. H. Foyer. 2013. The impact of global change factors on redox signaling underpinning stress tolerance. Plant Physiol 161:5–19. Newton, A. C., S. N. Johnson, and P. J. Gregory. 2011. Implications of climate change for diseases, crop yields and food security. Euphytica 179:3–18. Niu, Y. F., G. J. Ahammed, C. X. Tang, L. B. Guo, and J. Q. Yu. 2016. Physiological and transcriptome responses to combinations of elevated CO2 and magnesium in Arabidopsis thaliana. PLoS One 11:e0149301. https:// doi.org/10.1371/journal.pone.0149301. Nomura, K., and S. Y. He. 2005. Powerful screens for bacterial virulence proteins. Proc Natl Acad Sci USA 102:3527–28. Oehme, V., P. Hoegy, J. Franzaring, C. P. W. Zebitz, and A. Fangmeier. 2013. Pest and disease abundance and dynamics in wheat and oilseed rape as affected by elevated atmospheric CO2 concentrations. Funct Plant Biol 40:125–36. O’Keefe, K., C. Del Cid, C. A. Pinedo, W. Puetz, and C. J. Springer. 2013. Elevated CO2 does not ameliorate the negative consequences of infection with the xylem-limited bacteria Xylella fastidiosa in Quercus rubra seedlings. Castanea 78:216–26. Pangga, I. B., J. Hanan, and S. Chakraborty. 2011. Pathogen dynamics in a crop canopy and their evolution under changing climate. Plant Pathol 60:70–81. Plessl, M., E. F. Elstner, H. Rennenberg, J. Habermeyer, and I. Heiser. 2007. Influence of elevated CO2 and ozone concentrations on late blight resistance and growth of potato plants. Environmen Exp Bot 60:447–57. Pugliese, M., J. Liu, P. Titone, A. Garibaldi, and M. L. Gullino. 2012. Effects of elevated CO2 and temperature on interactions of zucchini and powdery mildew. Phytopathol Mediterr 51:480–87. Rao, M. S., M. A. M. Khan, K. Srinivas, M. Vanaja, G. G. S. N. Rao, Y. S. Ramakrishna. 2006. Effects of elevated carbon dioxide and temperature on insect-plant interactions: A review. Agric Rev 27:200–07. Riikonen, J., L. Syrjälä, I. Tulva et al. 2008. Stomatal characteristics and infection biology of Pyrenopeziza betulicola in Betula pendula trees grown under elevated CO2 and O3. Environ Pollut 156:536–43. Robinson, E. A., G. D. Ryan, and J. A. Newman. 2012. A meta-analytical review of the effects of elevated CO2 on plant-arthropod interactions highlights the importance of interacting environmental and biological variables. New Phytol 194:321–36. Rua, M. A., J. Umbanhowar, S. Hu, K. O. Burkey, and C. E. Mitchell. 2013. Elevated CO2 spurs reciprocal positive effects between a plant virus and an arbuscular mycorrhizal fungus. New Phytol 199:541–49. Runion, G. B., S. A. Prior, H. H. Rogers, and R. J. Mitchell. 2010. Effects of elevated atmospheric CO2 on two southern forest diseases. New Forest 39:275–85. Sgherri, C. L., P. Salvateci, M. Menconi, A. Raschi, and F. Navari-Izzo. 2000. Interaction between drought and elevated CO2 in the response of alfalfa plants to oxidative stress. J Plant Physiol 156:360–66. Sgherri, C. L. M., M. F. Quartacci, M. Menconi, A. Raschi, and F. Navari-Izzo. 1998. Interactions between drought and elevated CO2 on alfalfa plants. J Plant Physiol 152:118–24.

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Shadle, G. L., S. V. Wesley, K. L. Korth, F. Chen, C. Lamb, and R. A. Dixon. 2003. Phenylpropanoid compounds and disease resistance in transgenic tobacco with altered expression of L-phenylalanine ammonia-lyase. Phytochemistry 64:153–61. Sharma, H. C., A. R. War, M. Pathania, S. P. Sharma, S. M. Akbar, and R. S. Munghate. 2016. Elevated CO2 influences host plant defense response in chickpea against Helicoverpa armigera. Arthropod-Plant Inte 10:171–81. Shi, K., X. Li, H. Zhang et al. 2015. Guard cell hydrogen peroxide and nitric oxide mediate elevated CO2induced stomatal movement in tomato. New Phytol 208:342–53. Shigenaga, A. M., and C. T. Argueso. 2016. No hormone to rule them all: Interactions of plant hormones during the responses of plants to pathogens. Semin Cell Dev Biol 56:174–89. Singh, P. K., A. L. Schaefer, M. R. Parsek, T. O. Moninger, M. J. Welsh, and E. P. Greenberg. 2000. Quorumsensing signals indicate that cystic fibrosis lungs are infected with bacterial biofilms. Nature 407:762–64. Siwecki, R., and K. Przyuyl. 2010. Water relations in the leaves of poplar clones resistant and susceptible to Melampsora larici-populina. Forest Pathol 11: 348–57. Slattery, R. A., E. A. Ainsworth, and D. R. Ort. 2013. A meta-analysis of responses of canopy photosynthetic conversion efficiency to environmental factors reveals major causes of yield gap. J Exp Bot 64:3723–33. Soares, A. S., S. P. Driscoll, E. Olmos, J. Harbinson, M. C. Arrabaca, and C. H. Foyer. 2008. Adaxial/abaxial specification in the regulation of photosynthesis and stomatal opening with respect to light orientation and growth with CO2 enrichment in the C4 species Paspalum dilatatum. New Phytol 177:186–98. Song, Y. W., Y. C. Miao, and C. P. Song. 2014. Behind the scenes: The roles of reactive oxygen species in guard cells. New Phytol 201:1121–40. Thomma, B. P. H. J., K. Eggermont, K. F. M. J. Tierens, and W. F. Broekaert. 1999. Requirement of functional ethylene-insensitive 2 gene for efficient resistance of Arabidopsis to infection by Botrytis cinerea. Plant Physiol 121:1093–01. Tintor, N., A. Ross, K. Kanehara et al. 2013. Layered pattern receptor signaling via ethylene and endogenous elicitor peptides during Arabidopsis immunity to bacterial infection. Proc Natl Acad Sci 110:6211–16. Tubiello, F. N., M. Donatelli, C. Rosenzweig, and C. O. Stockle. 2000. Effects of climate change and elevated CO2 on cropping systems: Model predictions at two Italian locations. Eur J Agron 13:179–89. Underwood, W. 2012. The plant cell wall: A dynamic barrier against pathogen invasion. Front Plant Sci 3:85. DOI: 10.3389/fpls.2012.00085. Uprety, D. C. 1998. Carbon dioxide enrichment technology: Open top chambers a new tool for global climate research. J Sci Ind Res 57:266–70. Urano, K., Y. Kurihara, M. Seki, and K. Shinozaki. 2010. ‘Omics’ analyses of regulatory networks in plant abiotic stress responses. Curr Opin Plant Biol 13:132–38. Van Camp, W., M. Van Montagu, and D. Inzé. 1998. H2O2 and NO: Redox signals in disease resistance. Trends Plant Sci 3:330–34. Wang, J. W., and J. Y. Wu. 2005. Nitric oxide is involved in methyl jasmonate-induced defense responses and secondary metabolism activities of Taxus cells. Plant Cell Physiol 46:923–30. West, J. S., J. A. Townsend, M. Stevens, and B. D. L. Fitt. 2012. Comparative biology of different plant pathogens to estimate effects of climate change on crop diseases in Europe. Eur J Plant Pathol 133:315–31. Zavala, J. A., C. L. Casteel, P. D. Nabity, M. R. Berenbaum, and E. H. DeLucia. 2009. Role of cysteine proteinase inhibitors in preference of Japanese beetles (Popillia japonica) for soybean (Glycine max) leaves of different ages and grown under elevated CO2. Oecologia 161:35–41. Zavala, J. A., P. D. Nabity, and E. H. DeLucia. 2013. An emerging understanding of mechanisms governing insect herbivory under elevated CO2. Annu Rev Entomol 58:79–97. Zeng, W., A. Brutus, J. M. Kremer et al. 2011. A genetic screen reveals Arabidopsis stomatal and/or apoplastic defenses against Pseudomonas syringae pv. tomato DC3000. PLoS Pathog 7: e1002291. https://doi. org/10.1371/journal.ppat.1002291. Zhang, S., X. Li, Z. H. Sun et al. 2015. Antagonism between phytohormone signalling underlies the variation in disease susceptibility of tomato plants under elevated CO2. J Exp Bot 66:1951–63.

CHapTer  5

Wild Relative Species and Genetic Engineering Improving Crops in Response to Climate Change Noureddine Benkeblia CONTENTS 5.1 Introduction............................................................................................................................. 71 5.2 Genetics and Responses of Plants to Climate Change............................................................ 72 5.2.1 Genetic Biodiversity as Strategic Mitigation of Climate Change............................... 72 5.2.2 Carbon Fixation Engineering of Plants as Strategic Mitigation of Climate Change....... 73 5.2.3 Water Use Efficiency (WUE) Engineering of Plants as Strategic Mitigation of Climate Change........................................................................................................... 75 5.2.4 Nutrients Management Engineering of Plants as Strategic Mitigation of Climate Change........................................................................................................... 77 5.3 Epigenetics, Phenotypic Plasticity and Responses to Climate Change................................... 77 5.4 Conclusions and Perspectives.................................................................................................. 78 Acknowledgments............................................................................................................................. 78 References......................................................................................................................................... 78 5.1 INTRODUCTION In the 1990s, the Intergovernmental Panel on Climate Change (IPCC) developed different scenarios of gas emissions for the long-term, and these scenarios were considered useful tools in analyzing climate change, its impacts, and options to mitigate this change. In 1995, these scenarios were evaluated and the outcomes of this evaluation led to some recommendations such as significant changes in the understanding of driving forces of emissions and methodologies that should be addressed. In 1996, IPCC reached a decision to develop a new set of scenarios which were reported in 2000 (see also Chapter 3) (IPCC 2000, 2007). Indeed, from the turn of the last century and the beginning of the twenty-first century different scenarios of changes in climate, biodiversity, and ecosystems were developed based on models of changes in temperatures, atmospheric carbon dioxide, climate, forests and vegetation, water withdrawal, and land use, as well as their sensitivity to these changes in the future. Many of these studies attempted to elucidate the drivers of these climate changes, decipher their effects, and identify the major sources of uncertainties (Sala et al. 2000). Food security will be one of the major concerns of the population, governments, and policymakers, and by the end of this century it will become a serious challenge to feed billions of people. According to the United Nations, the world population in 2017 was estimated to be 7.6 billion, and 71

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with roughly 83 million additional people every year the world population is expected to reach 8.6 billion in 2030, 9.8 billion in 2050, and 11.2 billion in 2100 (UN 2017). Therefore, the whole system of food production should be prepared to cover the needs of the growing population and preserve food production systems in the face of climate change. For thousands of years, humans have domesticated plants that they depend on for food, and farmers have always tried to improve their crops by traditional techniques to increase yields and crop performance. With the development of modern biotechnologies, including molecular biology, genetics, and genomics, plant breeding by enhancing certain plant traits has made a huge contribution to increase yields and build resistance to drought and diseases (Borlaug 1983; Tester and Langridge 2010). Indeed, crop scientists should not only focus on traits with the potential to increase yields, but also to improve traits to cope with challenges such as drought, high temperatures, and higher carbon dioxide that will arise as the result of the changing climate. Selecting for increased photosynthetic rate or resistance to the outbreak of diseases and pests are examples of such improvements (Atkinson and Urwin 2012; Cattivelli et al. 2008; Iba 2002; Mitra 2001; Passioura 2002; Varshney et al. 2011; Wahid et al. 2007; Zhang et al. 2000). Because improving food crops is essential for improving food security, plant breeders and scientists need to develop new genotypes with increased growth and yield in novel environments resulting from the changing climate as the combination of the different climatic factors are expected to average 30% of the known climates (Williams et al. 2007). These newly bred crops should also be made available to farmers globally, particularly small farmers of the most impacted regions. These new genotypes should be accessible and well disseminated throughout the world, particularly in developing countries and where hunger is predicted to affect vulnerable populations. This chapter aims to describe how genetics and related disciplines might be a useful tool to improve crops, aiming to increase their resistance and ability to withstand changing climates and ensure food security for future generations without affecting lands, forests, and water resources. 5.2  GENETICS AND RESPONSES OF PLANTS TO CLIMATE CHANGE Several scenarios are predicting that novel climates will develop essentially in the tropics and subtropics, while tropical montane regions and the poleward portions of continents will experience a disappearance of their climates (McCarthy et al. 2001). Estimates predict that 12%–39% of the terrestrial surface may experience novel climates, while 10%–48% of the current climates may disappear by 2100 (Williams et al. 2007). Predictions of extinction are variable from region to region; for example, 2%–12% (Thuiller et al. 2005), and 25%–67% (McClean et al. 2005) of plant species are predicted to become extinct in Europe and Africa, respectively, with an increase in temperature of 2°C. Consequently, plant genetic resources for food and agriculture will likely be negatively affected. By 2050, and depending on the migration scenarios, it is estimated that extinction will affect 16%–22% of the PGRFA (Plant Genetic Resources for Food and Agriculture); specifically, 24–31 of the 51 species of wild peanuts, 7–13 of the 108 species of potato, and 2 of the 48 species of Vigna (Jarvis et al. 2008). 5.2.1  Genetic Biodiversity as Strategic Mitigation of Climate Change Climate change is predicted to first threaten wild relatives of cultivated crops and, therefore, the diverse germplasm that could provide more resistance to additional abiotic and biotic stresses caused by the changing environment. To protect the total genetic diversity of cultivated species and their wild relatives, many of which are valuable for breeding and molecular engineering, gene banks should ensure that the genetic diversity present in species in the PGRFA is adequately conserved and available (Figure 5.1). The real challenge is characterizing the germplasm for traits and characteristics

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Figure 5.1 An integrated approach to developing crops that are better adapted to abiotic stresses. Germplasm collections including tolerant crops, landraces, and wild relatives of crops can be used to identify or isolate QTL(s), gene(s), or allele(s) that confer tolerance to abiotic stresses such as drought and high temperature by using modern genomics approaches. Although candidate QTL(s) can be deployed through MB approaches such as MABC, MARS, and GS, the most promising candidate genes along with appropriate promoters can be used by following a GE approach in conventional breeding programs. It is anticipated that the use of an integrated approach, as suggested here, should facilitate the development of designer crops that are better adapted to abiotic stresses and thereby better able to tolerate future climate variability. (Reprinted from Trends Plant Sci, 16, Varshney et al., Agricultural biotechnology for crop improvement in a variable climate: Hope or hype? 363–71, Copyright 2011, with permission from Elsevier.)

useful for crop improvement (Ford-Lloyd et al. 2011; Jackson and Ford-Lloyd 1990). The PGRFA should be utilized for crop improvement in order to help resist climate change, improve food security, and protect against the extinction of wild species (Govindaraj et  al. 2015). Numerous studies reported a significant relationship between genetic diversity and services to agroecosystems, and this biological diversity contributes to agroecosystem functioning and agricultural production (Duru et al. 2015; Hajjar et al. 2008). In fact, increased genetic crop diversity can enhance agroecosystem functions and has been shown to be a useful tool for the management of pests and diseases (Hajjar et  al. 2008). On the other hand, we also need to amalgamate biological diversity, conventional breeding, and genomics by involving the entire process from bioreserves to genes and cultivars (Banga and Kang 2014). Breeding and molecular engineering to increase crop resilience will be important for developing new varieties. Efforts should target enhancing CO2 assimilation, water and nutrient use efficiency, and resistance to heat stress, diseases, and pests (Figure 5.2) (Wu et al. 2016). 5.2.2 Carbon Fixation Engineering of Plants as Strategic Mitigation of Climate Change One of the strategies used in molecular engineering is to increase biotic carbon sequestration by either improving carbon assimilation of C3 plants by transgenic engineering using non-C4 genes or overexpressing C4-cycle photosynthetic genes in transgenic C3 plants (Ruan et al. 2012). In C3 plants, elevated CO2 increases biomass production, however, this increase in biomass due to a higher photosynthesis rate is temporary because this photosynthetic system cannot sustain high CO2 for

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Figure 5.2 Schematic diagram of the emerging cross-scale modelling framework connecting biochemical/leaflevel photosynthesis and canopy/crop-level growth and development dynamics. Crop growth and development is driven by the development of canopy leaf area and canopy biomass growth, both of which are influenced by the prevailing environment and the photosynthesis output of individual leaves in the canopy. The canopy captures resources from the environment. Leaf photosynthesis is driven by the attributes of the crop canopy and leaves. LAI, SLN, and crop water status are determined by crop scale growth and development dynamics, while light, leaf temperature, and CO2 experienced by leaves are influenced by canopy attributes, LAI, and k. This two-way connection between biochemical and crop level (the two thick arrows) is an important consideration in the cross-scale modeling framework. PAR: photosynthetic active radiation; LAI: leaf area index; k: canopy light extinction coefficient; SLN: specific leaf nitrogen; PCR: photosynthetic carbon reduction cycle; PCO: photorespiratory carbon oxidation cycle; CHO: carbohydrates synthesized by photosynthesis. (From Wu, A. et al. 2016. Front Plant Sci 13:1518. DOI: 10.3389/fpls.2016.01518, with permission from Frontiers Publisher.)

long and plants become acclimatized to this CO2-enriched atmosphere. On the other hand, because ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is the limiting factor in CO2 fixation and its activity is largely affected by nitrogen availability, research has focused on maintaining an optimal C/N ratio by raising plant nitrogen pools and enhancing nitrogen use efficiency (NUE) (Kant et al. 2012). Because photosynthesis is the fundamental anabolic activity, RuBisCO was the first target studied intensively for engineering plants with a surcharged photosynthesis and a highly efficient use of resources (Parry et al. 2013). Metabolically, synthesis and degradation of the RuBisCO protein are correlated with temperature, light intensity, soil N, and atmospheric CO2, and studies showed that when the protein is exposed to high CO2 levels for a long time, its content and activity decrease (Moore et al. 1999; Seneweera et al. 2011). This decrease of RuBisCO and photosynthesis might result from the inhibiting effect of high CO2 on the assimilation of nitrate into organic nitrogen compounds (Bloom et al. 2010). Other suggestions have been made to overcome this issue of limited capacity of RuBisCO to assimilate CO2 in an enriched atmosphere. Zhu et al. (2004, 2007) suggest that RuBisCO could have a lower affinity for CO2 and a high catalytic rate, thus increasing carbon gain in an enriched atmosphere, or that transgenic plants could be developed that express a different RuBisCO (Whitney et al. 2011a; Zhu et al. 2004, 2007). However, molecular engineering of improved forms of the RuBisCO protein has not been altogether successful even though significant progress in engineering hybrid RuBisCO

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enzymes on the basis of C4-RuBisCOs has been achieved (Ishikawa et al. 2011; Whitney et al. 2011b); incorporating engineered genes into DNA of photosynthetic organelles also remains a challenge (Maliga and Bock 2011). To enhance the photosynthesis in C3 plants, another strategy was envisioned by biologists which was to implement a C4 system in C3 plants because C4 plants sustain high level of CO2 and have better water and nitrogen use efficiency (Ghannoum et al. 2011). Attempts were conducted to transfer C4 traits to C3 plants to improve their photosynthetic performance (Häusler et al. 2001, 2002), however, results reported were of limited success. Research conducted by Suzuki et al. (2000, 2006) and Miyao et al. (2011) on carbon metabolism of newly generated transgenic rice plants expressing either phosphoenolpyruvate carboxylase (PEPC) or both PCK and PEPC, showed that PEPC/PCK-transgenic rice showed a low chlorophyll concentration but normal phenotypes, while overexpression of PEPC did not enhance the initial carbon fixation of the C4-like photosynthetic pathway. Indeed, molecular engineering attempts targeted engineering a single-cell C4 carbon-concentrating mechanism in a C3 plant (Häusler 2002; Schuler et al. 2016), however, engineering C4 cycle basic enzymatic reaction without the rest of the C4 pathway steps limited the success of enhancing C3 crop photosynthesis (Miyao et al. 2011). In fact, the limited success of this latter strategy is that metabolic networks in plants are quite complex and pathways are highly compartmentalized, thus biochemical steps of a single pathway may occur in different subcellular locations or organelles, and very few studies have considered the criteria of subcellular localization in plant metabolic engineering attempts (Heinig et al. 2013). Another strategy might consist of engineering the overexpression of glycine decarboxylase complex (GDC) in the C3 species to increase the metabolic flux through the photorespiratory pathway, leading to more efficient photosynthesis and therefore enhanced biomass production of the transformed C3 plants (Schulze et al. 2016). In C3 plants, photorespiration is a pathway used to compensate for low concentration of atmospheric CO2, and control of this process has emerged as one of the strategies to enhance crop acclimation to carbon dioxide increases and sustain or improve the productivity of crops (Ogren 1984). Some attempts have also been undertaken on C3 plants to bypass this pathway by diverting photorespiratory fluxes and circumvent the release of CO2 in mitochondria (Carvalho et al. 2011; Maier et al. 2012). First, Kebeish et al. (2007) engineered the chloroplasts of Arabidopsis thaliana by introducing the glycolate catabolism of Escherichia coli and observed higher CO2 assimilation rates and reduced photorespiratory fluxes. Another study conducted by Maier et al. (2012) reported that glycolate is completely oxidized to two molecules of CO2 within the chloroplast in engineered A. thaliana plants expressing an alternative chloroplast glycolate catabolic cycle. Interestingly the two pathways are compartmentalized in the chloroplasts, and the product CO2 released can be fixed by RuBisCO without affecting its compensation point. These two pathways also have the advantage of not producing ammonia, and therefore this might open the potential for improving nitrogen use efficiency of plants (Maurino and Weber 2012). 5.2.3 Water Use Efficiency (WUE) Engineering of Plants as Strategic Mitigation of Climate Change Globally, studies are predicting that drought will increase with the rising temperatures by 2100, particularly among the most affected regions is Africa. Yields of major crops will decrease significantly, with the decrease being possibly greater than 50% in 2050 and almost 90% in 2100 for the major crops (Li et al. 2009). Therefore, improving water use efficiency (WUE) of crops is an imperative and needs to be addressed urgently, as this plant trait is seen as one important solution to address water scarcity and drought (Hamdy et al. 2003). Because there is a pressing need to improve WUE of either rain-fed or irrigated crops, breeding new varieties with optimal water use efficiency by using either conventional breeding or molecular engineering seems to be the most environmentally friendly and sustainable solution to face water shortage and drought caused by

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the future climate (Chaerle et al. 2005). Other strategies such as nutrient management might help improve WUE of plants (Waraich et al. 2011). Gas emissions might be reduced by using water more efficiently in smarter agricultural approaches, such as conservation agriculture (Bush 2018). The need for breeding for efficient WUE was proposed by Eslick and Hockett (1974) who highlighted the need to determine the plant traits that contribute to water use efficiency, for example, by increasing carbon sequestration by plants per unit of transpired water (Condon et  al. 2004), identifying the mechanisms underlying plant resilience to water deficits (Chaves and Oliveira 2004), and understanding the regulatory networks and specific metabolites involved in crop drought tolerance (Valliyodan and Nguyen 2006). Because water use and tolerance to drought involve many gene functions regulated by water availability, and in order to generate opportunities and tailor new genotypes, these two mechanisms should be fully understood and the knowledge of the molecular and physiological processes influencing tolerance to drought should be investigated in depth (Tuberosa and Salvi 2006). Some attempts have been undertaken, by overexpressing high C4-PEPC maize, whereby WUE was increased by 30% and dry weight by 20% under moderate drought conditions, thus opening possibilities to develop maize varieties more tolerant to drought (Jeanneau et al. 2002). Other studies reported similar conclusive results; for example transgenic wheat expressing the barley HVA1 gene had significantly higher WUE, greater total dry mass, root fresh and dry weights, and shoot dry weights (Sivamani et al. 2000). The HARDY gene introduced in rice also improved WUE and biomass by enhancing photosynthetic assimilation and reducing transpiration, coinciding with better drought resistance (Karaba et al. 2007). In overexpressing the maize C4-PEPC gene in transgenic rice plants, Qian et al. (2015) noticed a particular molecular mechanism of drought tolerance related to the signaling processes via NO and Ca2+ involving the protein kinase, resulting in PEPC activity up-regulation, thereby conferring drought tolerance. One approach to sustain plant productivity is to improve water use efficiency (WUE) by engineering crassulacean acid metabolism (CAM) into C3 crops. CAM improves WUE by shifting stomatal opening and primary CO2 uptake and fixation to the night-time when leaf:air vapor pressure deficit (VPD) is low. CAM members of the tree genus Clusia exemplify the compatibility of CAM performance within tree species and highlight CAM as a mechanism to conserve water and maintain carbon uptake during drought conditions. The introduction of bioengineered CAM into short rotation forestry (SRF) bioenergy trees is a potentially viable path to sustaining agroforestry production systems in the face of a globally changing climate (Borland et al. 2015). There are two main possible approaches to achieve this goal: (i) improve CO2 diffusion to the sites of carboxylation without increasing stomatal conductance; and (ii) improve the carboxylation efficiency of RuBisCO. The first goal could be attained by increasing mesophyll conductance to CO2, which partly depends on aquaporins. The second approach could be achieved by replacing RuBisCO with those from other C3 species with higher specificity for CO2. In summary, the physiological bases and future prospects for improving yield and WUE under drought are established (Flexas et al. 2010). Despite the spectacular progress in molecular approaches over the past decade, there is little evidence that these studies are having an impact on the production of drought-tolerant cultivars. This notwithstanding, research on fundamental aspects of the genetic basis and physiological basis of the adaptive response to drought should be encouraged and integrated with conventional breeding studies (Tuberosa et al. 2007). However, there is a wealth of traditional breeding that has resulted in increased WUE in plants, and this traditional approach might be seen as providing part of the solution. As reported by Condon et al. (2004) and Passioura (2006), WUE might be improved by (i) increasing water uptake rather than to be wasted or evaporated by soils; (ii) increasing the biomass production as related to water evaporated by plants, that is, improving crop transpiration efficiency; and/or (iii) partitioning more of the achieved biomass into the harvested product. However, yield potential (YP), drought resistance (DR), and water use efficiency (WUE) association is often misunderstood, leading to wrong decisions in implementing breeding programs (Blum 2005). Indeed, potential for further improvements in understanding the physiological responses of plants to water supply exists,

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and by looking across the disciplines from genes to crops it is possible to improve water productivity contributing to sustainability (Morison et al. 2008). 5.2.4 Nutrients Management Engineering of Plants as Strategic Mitigation of Climate Change Aside from impacts on biodiversity and crop productivity, climate change will increase the unpredictability of rainfall events. This may threaten soils with the potential for accelerated erosion and reduced soil quality. Nutrient management has shown the potential to contribute significantly to mitigating climate change as well as adapting to this change (Lal 2014; Lal et al. 2011). However, climate-crop production interactions are very complex to assess, and computed simulation is the best approach for such an assessment (Stockle et al. 1992). Although all nutrients play significant roles in soil management, quality, fertility, and plant growth, two major nutrients, namely carbon (C) and nitrogen (N), will be discussed because of their importance in soils and for plants. In 2006, atmospheric CO2 was linked to the SOCRATES model (Soil Organic Carbon Resources And Transformations in EcoSystems) in order to develop a soil organic carbon (SOC) map for the North Central Region of the United States between the years 1850 and 2100 in response to climate conditions. Results showed that by 2100, SOC storage in the region will decline by 11.5% and 2% for conventional and conservation tillage scenarios, respectively (Grace et al. 2006). Sequestration of organic carbon by soils depends on many factors including soil management, and in order to increase this process, different strategies might be used, among them soil restoration and nutrient management (Canadell and Schulze 2014; Lal 2004; Marland et al. 2003). ÁlvaroFuentes and Paustian (2011) investigated the effects of climate change on SOC dynamics in semiarid Mediterranean conditions in order to identify the more efficient practices that increase SOC. Their findings showed that continuous cropping management systems yielded greater carbon inputs and SOC compared to cereal-fallow rotation systems. Indeed, different methods have been suggested in managing soils in order to increase carbon sequestration (Powlson et al. 2011). Among these methods are the conversion of arable lands to forests or grassland (Goulding and Poulton 2005; Johnston et al. 2009) and re-implementing new agroecosystems involving forests, grass, or perennial shrubs (including perennial biofuel crops if they can grow successfully) on land of limited agricultural value. Similar trends were reported by Lugato and Berti (2008) who found strong effects of the recommended management practices on carbon compared to climate change; however, they indicated that conversion to grassland was the most promising practice for sequestering C, while manure application can potentially contribute into C sequestration. Reduced tillage is considered as the least effective in comparison to the two previous approaches. 5.3  EPIGENETICS, PHENOTYPIC PLASTICITY AND RESPONSES TO CLIMATE CHANGE One of the strategies developed by plants throughout many eras is their capacity to respond to environmental changes through phenotypic plasticity (Nicotra et al. 2010), and it is thought that phenotypic plasticity might play a significant role in mitigating adaptive trade-off under changing environmental conditions (Reuter et al. 2017). However, findings suggest that, for a given plant species, the magnitude of trait responses to climate change may vary by location (Pfennigwerth et al. 2017). Phenotypic plasticity in plants and animals, as well, have been linked to epigenetic mechanisms (Turck and Coupland 2014; Weinhold 2006). However, how these mechanisms respond to rapid climate change is yet to be fully understood and deciphered. Therefore, it is imperative to understand how epigenetic variation responds to climate change to predict and manage its effects on crops and overall all plant species (Balao et al. 2018; Nicotra et al. 2010).

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In crop production, plasticity plays a key role in the plant species’ responses and adaptation to the changing environmental conditions and, therefore, potential resilience of varieties to growing environments (Bloomfield et al. 2014). Although numerous studies have been reported on the effects of genotype-environment interactions on plant growth, development, and responses to stresses, studies quantifying the relationship between plasticity and productivity in agriculture and crop production are very scarce (Aspinwall et al. 2015). Kumar et al. (2017) studied twelve rice genotypes for the plasticity under different season/site environments, and the results showed different patterns of phenotypic plasticity. From the ecological point of view, some studies strive to merge ecological experiments and epigenetic analyses to decipher how epigenetics might contribute to plant phenotypic plasticity in response to biotic and abiotic stresses and environmental changes. Nevertheless, very few of these studies consider non-model plants such as edible crops (Richards et al. 2017). Epigenetics might trap phenological plant development. For example, the alteration of sex ratios by epigenetically regulated environmental sex determination leads to natural populations collapsing and therefore impacting negatively farmed plant species (Consuegra and Rodríguez López 2016). Interestingly, some source environments likely produce more plastic genotypes than others, and a study conducted on perennial bunchgrass (Poa secunda) seeds collected from warm and dry locations produced plants with more plasticity in phenology, panicle number, and biomass; while seeds collected from cool and wet locations produced plants with more plasticity in leaf size, panicle length, plant habit, and survival (Espeland et al. 2018).

5.4  CONCLUSIONS AND PERSPECTIVES There is unquestionable scientific evidence that climatic conditions are changing, and plants are responding to these changes. These changes are raising numerous questions, and studies are being conducted in an attempt to address them. Among the topics to be addressed are the abilities of plants to cope with climate change, their survival capacities, and the factors influencing these responses. However, future studies should focus on using systematic methodologies and holistic approaches to assess plants’ responses to climate change over the next few decades. These methodologies and approaches would have to decipher the sophisticated genetic, epigenetic, and phenotypic plasticity regulatory systems of plants to respond to unfavorable environmental conditions and how they adapt to these changes through genetic diversity and adaptation. Many species will be “losers” because of their inability to evolve or migrate and thus will be more susceptible to face extinction. These species require particular consideration. Therefore, the research outcomes will undoubtedly facilitate better predictions of the capacity for plant populations to respond to rapid climate change.

ACKNOWLEDGMENTS The author thanks Dr. Christine E. Edwards, Centre for Conservation and Sustainable Development, Missouri Botanical Garden, St. Louis, MO, for her critical reading of this chapter and comments.

REFERENCES Álvaro-Fuentes, J., and K. Paustian. 2011. Potential soil carbon sequestration in a semiarid Mediterranean agroecosystem under climate change: Quantifying management and climate effects. Plant Soil 338:261–72.

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Aspinwall, M. J., M. E. Loik, V. R. De Dios, M. G. Tjoelker, P. R. Payton, and D. T. Tissue. 2015. Utilizing intraspecific variation in phenotypic plasticity to bolster agricultural and forest productivity under climate change. Plant Cell Environ 38:1752–64. Atkinson, N. J., and P. E. Urwin. 2012. The interaction of plant biotic and abiotic stresses: From genes to the field. J Exp Bot 63:3523–43. Balao, F., O. Paun, and C. Alonso. 2018. Uncovering the contribution of epigenetics to plant phenotypic variation in Mediterranean ecosystems. Plant Biol 20:38–49. Banga, S. S., and M. S. Kang. 2014. Developing climate-resilient crops. J Crop Improv 28:57–87. Bloom, A. J., M. Burger, J. S. Asensio, and A. B. Cousins. 2010. Carbon dioxide enrichment inhibits nitrate assimilation in wheat and Arabidopsis. Science 328:899–903. Bloomfield, J. A., T. J. Rose, and G. J. King. 2014. Sustainable harvest: Managing plasticity for resilient crops. Plant Biotechnol J 12:517–33. Blum, A. 2005. Drought resistance, water-use efficiency, and yield potential—are they compatible, dissonant, or mutually exclusive? Aust J Agr Res 56:1159–68. Borland, A. M., S. D. Wullscheger, D. J. Weston et al. 2015. Climate-resilient agroforestry: Physiological responses to climate change and engineering of crassulacean acid metabolism (CAM) as a mitigation strategy. Plant Cell Environ 38:1833–49. Borlaug, N. E. 1983. Contributions of conventional plant breeding to food production. Science 219:689–93. Bush, M. J. 2018. Adapting to a changing climate. In Climate Change Adaptation in Small Island Developing States. Chichester, UK: John Wiley & Sons, Ltd. DOI: 10.1002/9781119132851.ch3. Canadell, J. G., and E. Detlef-Schulze. 2014. Global potential of biospheric carbon management for climate mitigation. Nature Comm 5:5282. DOI: 10.1038/ncomms6282. Carvalho, J., P. J. Madgwick, S. J. Powers, A. J. Keys, P. J. Lea, and M. A. J. Parry. 2011. An engineered pathway for glyoxylate metabolism in tobacco plants aimed to avoid the release of ammonia in photorespiration. BMC Biotechnol 11:111. https://doi.org/10.1186/1472-6750-11-111. Cattivelli, L., F. Rizza, F. W. Badeck et al. 2008. Drought tolerance improvement in crop plants: An integrated view from breeding to genomics. Field Crops Res 105:1–14. Chaerle, L., N. Saibo, and D. Van Der Straeten. 2005. Tuning the pores: Towards engineering plants for improved water use efficiency. Trends Biotechnol 23:308–15. Chaves, M. M., and M. M. Oliveira. 2004. Mechanisms underlying plant resilience to water deficits: Prospects for water-saving agriculture. J Exp Bot 55:2365–84. Condon, A. G., R. A. Richards, G. J. Rebetzke, and G. D. Farquhar. 2004. Breeding for high water-use efficiency. J Exp Bot 55:2447–60. Consuegra, S., and C. M. Rodríguez López. 2016. Epigenetic-induced alterations in sex-ratios in response to climate change: An epigenetic trap? BioEssays 38:950–8. Duru, M., O. Therond, G. Martin et al. 2015. How to implement biodiversity-based agriculture to enhance ecosystem services: A review. Agron Sust Dev 35:1259–81. Eslick, R. F., and E. A. Hockett. 1974. Genetic engineering as a key to water-use efficiency. Agricultural Meteorology 14:13–23. Espeland, E. K., R. C. Johnson, and M. E. Horning. 2018. Plasticity in native perennial grass populations: Implications for restoration. Evol Appl 11:340–9. Flexas, J., J. Galmes, A. Galle. et al. 2010. Improving water use efficiency in grapevines: Potential physiological targets for biotechnological improvement. Aust J Grape Wine Res 16:106–21. Ford-LLoyd, B. V., M. Schmidt, S. J. Armstrong et al. 2011. Crop wild relatives—Undervalued, underutilized and under threat? BioScience 61:559–65. Ghannoum, O., J. R. Evans, S. von Caemmerer. 2011. Nitrogen and water use efficiency in C4 plants. In: C4 Photosynthesis and Related CO2 Concentrating Mechanisms, A. S. Raghavendra, and R. F. Sage, eds, 129–146. Dordrecht, The Netherlands: Springer. Goulding, K. W. T., and P. R. Poulton, 2005. The missing link. Geoscientist, 15:4–7. Govindaraj, M., M. Vetriventhan, and M. Srinivasan. 2015. Importance of genetic diversity assessment in crop plants and its recent advances: An overview of its analytical perspectives. Genet Res Int ID 431487. http:// dx.doi.org/10.1155/2015/431487. Grace, P. R., M. Colunga-Garcia, S. H. Gage, G. P. Robertson, and G. R. Safir. 2006. The potential impact of agricultural management and climate change on soil organic carbon of the north central region of the United States. Ecosystems 9:816–27.

80

CLIMATE CHANGE AND CROP PRODUcTION

Hajjar, R., D. I. Jarvis, and B. Gemmill-Herren. 2008. The utility of crop genetic diversity in maintaining ecosystem services. Agr Ecosyst Environ 123:261–70. Hamdy, A., R. Ragab, and E. Scarascia-Mugnozza. 2003. Coping with water scarcity: Water saving and increasing water productivity. Irrig Drain 52:3–20. Häusler, R. E. 2002. Overexpression of C4-cycle enzymes in transgenic C3 plants: A biotechnological approach to improve C3-photosynthesis. J Exp Bot 53:591–607. Häusler, R. E., H-J. Hirsch, F. Kreuzaler, C. Peterhänsel. 2002. Overexpression of C4-cycle enzymes in transgenic C3 plants: A biotechnological approach to improve C3-photosynthesis. J Exp Bot 53:591–607. Häusler, R. E., T. Rademacher, J. Li et al. 2001. Single and double overexpression of C4-cycle genes had differential effects on the pattern of endogenous enzymes, attenuation of photorespiration and on contents of UV protectants in transgenic potato and tobacco plants. J Exp Bot 52:1785–803. Heinig, U., M. Gutensohn, N. Dudareva, and A. Aharoni. 2013. The challenges of cellular compartmentalization in plant metabolic engineering. Curr Opin Biotechnol 24:239–46. Iba, K. 2002. Acclimative response to temperatures stress in higher plants: Approaches of gene engineering for temperature tolerance. Annu Rev Plant Biol 53:225–45. IPCC. 2000. IPCC special report. Emissions scenarios. Policy makers. A Special Report of IPCC Working Group III. IPCC. https://ipcc.ch/pdf/special-reports/spm/sres-en.pdf. (Accessed: February 18, 2018). IPCC. 2007. IPCC Fourth Assessment Report: Climate Change 2007: Working Group I: The Physical Science Basis. IPCC. https://www.ipcc.ch/publications_and_data/ar4/wg1/en/spmsspm-projections-of.html. (Accessed: February 18, 2018). Ishikawa, C., T. Hatanaka, S. Misoo, C. Miyake, and H. Fukayama. 2011. Functional incorporation of sorghum small subunit increases the catalytic turnover rate of Rubisco in transgenic rice. Plant Physiol 156:1603–11. Jackson, M. T., and B. V. Ford-Lloyd. 1990. Plant genetic resources—A perspective. In Climatic Change and Plant Genetic Resources, M. T. Jackson, B. V. Ford-Lloyd, and M. L. Parry, eds, 1–17. London, UK: Belhaven Press. Jarvis, A., H. Upadhyaya, C. L. L. Gowda, P. K. Aggarwal, S. Fujisaka, B. Anderson. 2008. Climate change and its effect on conservation and use of plant genetic resources for food and agriculture and associated biodiversity for food security. Food and Agriculture Organisation. Available at: http://www.fao.org/ docrep/013/i1500e/i1500e16.pdf. (Accessed: January 17, 2018). Jeanneau, M., D. Gerentes, and X. Foueillassar. 2002. Improvement of drought tolerance in maize: Towards the functional validation of the Zm-Asr1 gene and increase of water use efficiency by over-expressing C4–PEPC. Biochimie 84:1127–35. Johnston, A. E., Poulton, P. R. & Coleman, K. 2009. Soil organic matter: Its importance in sustainable agriculture and carbon dioxide fluxes. Adv Agron 101:1–57. Kant, S., S. Seneweera, J. Rodin et al. 2012. Improving yield potential in crops under elevated CO2: Integrating the photosynthetic and nitrogen utilization efficiencies. Front Plant Sci 3:162. DOI: 10.3389/fpls.2012.00162. Karaba, A., S. Dixit, and R. Greco. 2007. Improvement of water use efficiency in rice by expression of HARDY, an Arabidopsis drought and salt tolerance gene. Proc. Natl Acad Sci USA 104:15270–5. Kebeish, R., M. Niessen, K. Thiruveedhi et  al. 2007. Chloroplastic photorespiratory bypass increases photosynthesis and biomass production in Arabidopsis thaliana rong. Nat Biotechnol 25:593–9. Kumar, U., M. R. Laza, J. C. Soulié, R. Pasco, K. V. S. Mendez, and M. Dingkuhn. 2017. Analysis and simulation of phenotypic plasticity for traits contributing to yield potential in twelve rice genotypes. Field Crops Res 202:94–107. Lal, R. 2004. Soil carbon sequestration impacts on global climate change and food security. Science 304:1623–7. Lal, R. 2014. Soil carbon management and climate change. Crop Managm 4:439–62. Lal, R., J. A. Delgado, P. M. Groffman, N. Millar, C. Dell, and A. Rotz. 2011. Management to mitigate and adapt to climate change. J Soil Water Managm 66:276–82. Li, Y., W. Ye, M. Wang, and X. Yan. 2009. Climate change and drought: A risk assessment of crop-yield impacts. Climate Res 39:31–46. Lugato, E., and A. Berti. 2008. Potential carbon sequestration in a cultivated soil under different climate change scenarios: A modelling approach for evaluating promising management practices in north-east Italy. Agr Ecosyst Environ 128:97–103. Maier, A., H. Fahnenstich, S. Von Caemmerer et al. 2012. Glycolate oxidation in A. thaliana chloroplasts improves biomass production. Front Plant Sci 3:38. DOI: 10.3389/fpls.2012.00038.

WILD RELATIVE SPEcIES AND GENETIc ENGINEERING

81

Maliga, P., and R. Bock. 2011. Plastid biotechnology: Food, fuel, and medicine for the 21st century. Plant Physiol 155:1501–10. Marland, G., R. A. Pielke, S. Mapps et al. 2003. The climatic impacts of land surface change and carbon management, and the implications for climate-change mitigation policy. Climate Policy 3:149–57. Maurino, V. G., and A. P. M. Weber. 2012. Engineering photosynthesis in plants and synthetic microorganisms. J Exp Bot 64:743–51. McCarthy, J. J., O. F. Canziani, N. A. Leary, D. J. Dokken, and K. S. White. 2001. Climate change 2001: Impacts, adaptation, and vulnerability. Cambridge, MA: University Press. McClean, C. J., L. Hannah, W. Barthlott et al. 2005. African plant diversity and climate change. J Exp Bot 62:3021–9. Mitra, J. 2001. Genetics and genetic improvement of drought resistance of crop plants. Curr Sci 80:758–63. Miyao, M., C. Masumoto, S-I. Miyazawa, and H. Fukayama. 2011. Lessons from engineering a single-cell C4 photosynthetic pathway into rice. J Exp Bot 62:3021–9. Moore, B. D., S. H. Cheng, D. Sims, and J. R. Seemann. 1999. The biochemical and molecular basis for photosynthetic acclimation to elevated atmospheric CO2. Plant Cell Environ 22:567–82. Morison, J. I. L., N. R. Baker, P. M. Mullineaux, and W. J. Davies. 2008. Improving water use in crop production. Phil Trans R Soc B 363:639–58. Nicotra, A. B., K. Atkin, S. P. Bonser et al. 2010. Plant phenotypic plasticity in a changing climate. Trends Plant Sci 15:684–92. Ogren, W. L. 1984. Photorespiration: Pathways, regulation, and modification. Annu Rev Plant Physiol 35:415–42. Parry, M. A. J., P. J. Andralojc, J. C. Scales et al. 2013. RuBisCO activity and regulation as targets for crop improvement. J Exp Bot 64:717–30. Passioura, J. 2006. Increasing crop productivity when water is scarce—from breeding to field management. Agr Water Manag 80:176–96. Passioura, J. B. 2002. Review: Environmental biology and crop improvement. Func Plant Biol 29:537–46. Pfennigwerth, A. A., J. K. Bailey, and J. A. Schweitzer. 2017. Trait variation along elevation gradients in a dominant woody shrub is population-specific and driven by plasticity. AoB Plants 9. https://doi. org/10.1093/aobpla/plx027. Powlson, D. S., A. P. Whitmore, and K. W. T. Goulding. 2011. Soil carbon sequestration to mitigate climate change: A critical re-examination to identify the true and the false. Eur J Soil Sci 62:42–55. Qian, B., X. Li, X. Liu, P. Chen, C. Ren, and C. Dai. 2015. Enhanced drought tolerance in transgenic rice over-expressing of maize C4 phosphoenolpyruvate carboxylase gene via NO and Ca 2+. J Plant Physiol 175:9–2. Reuter, M., M. F. Camus, M. S. Hill, F. Ruzicka, and K. Fowler. 2017. Evolving plastic responses to external and genetic environments. Trends Genet 33:169–70. Richards, C. L., C. Alonso, C. Becker et al. 2017. Ecological plant epigenetics: Evidence from model and nonmodel species, and the way forward. Ecol Lett 20:1576–90. Ruan, C. J., H. B. Shao, and J. A. Teixeira da Silva. 2012. A critical review on the improvement of photosynthetic carbon assimilation in C3 plants using genetic engineering. Crit Rev Biotechnol 32:1–21. Sala, O. E., F. S. Chapin, J. J. Armesto et al. 2000. Global biodiversity scenarios for the year 2100. Science 287:1770–4. Schuler, M. L., O. Mantegazza, and A. P. M. Weber. 2016. Engineering C4 photosynthesis into C3 chassis in the synthetic biology age. Plant J 87:51–65. Schulze, S., P. Westhoff, and U. Gowik. 2016. Glycine decarboxylase in C3, C4, and C3–C4 intermediate species. Curr Opin Plant Biol 31:29–35. Seneweera, S., A. Makino, N. Hirotsu, R. Norton, and Y. Suzuki. 2011. New insight into photosynthetic acclimation to elevated CO2: The role of leaf nitrogen and ribulose-1,5-bisphosphate carboxylase/ oxygenase content in rice leaves. Environ Exp Bot 71:128–36. Sivamani, E., A. Bahieldin, J. M. Wraith et al. 2000. Improved biomass productivity and water use efficiency under water deficit conditions in transgenic wheat constitutively expressing the barley HVA1 gene. Plant Sci 155:1–9. Stockle, C. O., J. R. Williams, N. J. Rosenberg, and C. A. Jones. 1992. A method for estimating the direct and climatic effects of rising atmospheric carbon dioxide on growth and yield of crops: Part I—Modification of the EPIC model for climate change analysis. Agr Syst 38:225–38.

82

CLIMATE CHANGE AND CROP PRODUcTION

Suzuki, S., N. Murai, J. N. Burnell, and M. Arai. 2000. Changes in photosynthetic carbon flow in transgenic rice plants that express C4-type phosphoenolpyruvate carboxykinase from Urochloa panicoides. Plant Physiol 124:163–72. Suzuki, S., N. Murai, K. Kasaoka et  al. 2006. Carbon metabolism in transgenic rice plants that express phosphoenolpyruvate carboxylase and/or phosphoenolpyruvate carboxykinase. Plant Sci 170:1010–19. Tester, M., and P. Langridge. 2010. Breeding technologies to increase crop production in a changing world. Science 327:818–22. Thuiller, W., S. Lavorel, M. B. Araújo, M. T. Sykes, and I. C. Prentice. 2005. Climate change threats to plant diversity in Europe. Proc Natl Acad Sci USA 102:8245–50. Tuberosa, R., S. Giuliani, M. A. J. Parry, and J. L. Araus. 2007. Improving water use efficiency in Mediterranean agriculture: What limits the adoption of new technologies?. Ann Appl Biol 150:157–62. Tuberosa, R., and S. Salvi 2006. Genomics-based approaches to improve drought tolerance of crops. Trends Plant Sci 11:405–12. Turck, F., and G. Coupland. 2014. Natural variation in epigenetic gene regulation and its effects on plant development traits. Evolution 68:620–31. United Nation. 2017. World population projected to reach 9.8 billion in 2050, and 11.2 billion in 2100. United Nation. https://www.un.org/development/desa/en/news/population/world-population-prospects-2017. html. (Accessed: February 17, 2018). Valliyodan, B., and H. T. Nguyen. 2006. Understanding regulatory networks and engineering for enhanced drought tolerance in plants. Curr Opin Plant Biol 9:189–95. Varshney, R. K., K. C. Bansal, P. K. Aggarwal, S. K. Datta, and P. Q. Craufurd. 2011. Agricultural biotechnology for crop improvement in a variable climate: Hope or hype? Trends Plant Sci 16:363–71. Wahid, A., S. Gelani, M. Shraf, and M. R. Foolad. 2007. Heat tolerance in plants: An overview. Environ Exp Bot 61:199–223. Waraich, E. A., R. Ahmad, M. Y. Ashraf, and S. M. Ahmad. 2011. Improving agricultural water use efficiency by nutrient management in crop plants. Acta Agric Scand B 61:291–304. Weinhold, B. 2006. Epigenetics: The science of change. Environ Health Perspect 114:A160–7. Whitney, S. M., R. L. Houtz, and H. Alonso. 2011a. Advancing our understanding and capacity to engineer nature’s CO2-sequestering enzyme, Rubisco. Plant Physiol 155:27–35. Whitney, S. M., R. E. Sharwood, D. Orr, S. J. White, H. Alonso, and J. Galmés. 2011b. Isoleucine 309 acts as a C4 catalytic switch that increases ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) carboxylation rate in Flaveria. Proc Natl Acad Sci USA 108:14688–93. Williams, J. W., S. T. Jackson, and J. E. Kutzbach. 2007. Projected distributions of novel and disappearing climates by 2100 ad. Proc Natl Acad Sci USA 104:5738–42. Wu, A., Y. Song, E. J. van Oosterom, and G. L. Hammer. 2016. Connecting biochemical photosynthesis models with crop models to support crop improvement. Front Plant Sci 13:1518. DOI: 10.3389/fpls.2016.01518 Zhang, J., N. Y. Klueva, Z. Wang, R. Wu, T-H. D. Ho, and H. T. Nguyen. 2000. Genetic engineering for abiotic stress resistance in crop plants. In Vitro Cell Dev Biol Plant 36:108–14. Zhu, X. G., A. R. Portis, and S. P. Long. 2004. Would transformation of C3 crop plants with foreign RuBisCO increase productivity? A computational analysis extrapolating from kinetic properties to canopy photosynthesis. Plant Cell Environ 27:155–65. Zhu, X. G., E. de Sturler, and S. P. Long. 2007. Optimizing the distribution of resources between enzymes of carbon metabolism can dramatically increase photosynthetic rate: A numerical simulation using an evolutionary algorithm. Plant Physiol 145:513–526.

CHapTer  6

Tropical Crops and Resilience to Climate Change Noureddine Benkeblia, Melinda McHenry, Jake Crisp, and Philippe Roudier CONTENTS 6.1 Introduction............................................................................................................................. 83 6.2 Tropical Agriculture Systems.................................................................................................. 85 6.3 Generalized Impacts of Climate Change on Agriculture in the Tropics................................. 85 6.3.1 Climate Variability...................................................................................................... 85 6.3.2 Impacts on Soils........................................................................................................... 87 6.3.3 Pests and Diseases....................................................................................................... 88 6.3.4 Crop and Varietal Impacts........................................................................................... 89 6.4 Vulnerabilities of Tropical Crops and Production Systems to Climate Change..................... 91 6.4.1 Vulnerability of Tropical Crops to Climate Change................................................... 91 6.4.2 Impacts and Consequences of Climate Changes on Tropical Crop Production Systems..................................................................................................... 93 6.4.2.1 Climate Changes and Crop Productivity...................................................... 93 6.4.2.2 Future Climate Change and Crop Quality (Nutrients).................................94 6.4.2.3 Other Types of Impacts.................................................................................94 6.5 Adaptation and Mitigation Measures for Curbing Negative Impacts of Climate Change on Tropical Agriculture Systems................................................................................94 6.6 Conclusions and Perspectives..................................................................................................97 References.........................................................................................................................................97 6.1 INTRODUCTION It is anticipated that agricultural output will have to increase by 70% to feed a global population of more than 9 billion by the year 2050 (Benkeblia 2012). The capacity of global high-intensity farming systems to continue to guarantee productive returns while maintaining system stability will eventually decline, and thus new opportunities for agriculture are being realized in tropical environments. As population growth is greatest in tropical regions, and commensurate with rapid industrialization and change in traditional land use practices, it is presumed that equatorial production systems will be some of the most vulnerable to climate change. The pressure on tropical agricultural systems is two-fold. First, tropical agricultural systems are located primarily in areas of political instability, with high populations vulnerable to the impacts of climate change and with lesser organizational or community knowledge to be able to plan and implement sustainable and intensive food production systems. Second, tropical agricultural land 83

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Figure 6.1 Distribution and variation in global tropical climates. Savanna lands have distinct wet-dry cycles and can be subject to drought conditions, whereas monsoon and rainforest tropics may get wetter and rainy, more sporadic, with climate change.

managers and researchers are challenged to assess and strengthen the adaptive capacity of food crops to the predicted rise in temperature and carbon dioxide, which might be above the goal of 2°C by the end of this century and which now appears to be a conservative estimate of temperature increase (Challinor et al. 2014). Temperature and rainfall fluctuations, deficits, and efficacy are suitable indicators of climate change as they both reflect a general increase or decrease in climate variables over time (Christensen et al. 2013; Nwagbara 2008, 2015; Uguru et al. 2011). Typically, tropical regions are characterized by a limited variation in temperature but a wide variation in rainfall. Therefore, the tropics contain some of the wettest and driest locations on Earth subject to variations in these conditions (Xue et al. 2013). Total warming in the tropics is estimated to be about 0.7–0.8°C. Regions within the tropics such as the Sahara, the Sahel, and the Arabian Peninsula have been among the most rapidly warming across the globe (Trewin 2017). Tropical agricultural systems are located between the latitudes of 22.5° North and 22.5° South (Figure 6.1). These systems are characterized by high levels of solar, relatively high and consistent temperatures throughout the year, high numbers of storm systems such as cyclones, hurricanes, and thunderstorms, and air pressure distribution producing varying patterns of wind and air mass movement. According to Köppen (1900a,b), two main agricultural tropical systems fall into this classification. The first are humid tropics (HT), characterized by constant warmth and high annual rainfall supporting dense tropical rainforests, while high rainfall and good soil moisture maintain evergreen forests. These systems are well adapted with low soil erosion and good fertility, therefore more adapted to perennial and forest crops. The second are the wet-dry tropics (WDT) with greater variation and contrasting rainfall in specific seasons during the year. However, the latter are considered the most fragile and most in need of novel production approaches (Läderach et al. 2013). In this chapter, we assess the vulnerability and resilience of tropical agricultural systems to the hypothesized, modelled, and actually measured impacts of a changing climate (Malhi and Wright 2004; Moss et  al. 2010). We examine potential system vulnerabilities associated with soils, biosecurity, and crop productivity, highlighting risks and opportunities associated with an increasingly warm, yet variable climate (Rosenzweig et al. 2014).

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6.2 TROPICAL AGRICULTURE SYSTEMS The tropics provide important environmental services, resources, and productive lands that are essential to meeting future global food supply (Goldsmith and Cohn 2017; Parry et al. 1999). The tropics are also the site of increased commercial agricultural expansion (Laurance et al. 2014). There is a lack of standardized and widely accepted definitions relating to farming systems, which can impose serious limitations on the adaptability of farmers in the face of climate change (Morton, 2007). In this section, we attempt to clarify nomenclature pertaining to agricultural systems by distinguishing between crop production systems (the series of processes involved in the growing of crops) and the farming system, which in turn is an integral part of the broader agroecosystem and landscape (FAO 2017). A hierarchical approach to farming systems allows one to consider impacts and opportunities across a broad spectrum of land management approaches in turn. Farming systems of the tropics include arable systems, pastoral approaches, mixed approaches, subsistence dependencies, and commercial, intensive, extensive, sedentary, and nomadic farming (Figure  6.2). Primarily, however, tropical farming systems are typically small family holdings (some semi-commercial, many subsistence farming system), which comprise 85% of the world’s farms (Harvey et al. 2014a) and are the backbone of agricultural commodities trading in developing countries (IFPRI 2017). Traditional farming is characterized by methods such as slash-and-burn agriculture which requires clear-felling and fire techniques to establish a suitable area for crop production. Traditional agriculture, simply put, adopts farming systems that require the least input. It is a farming system that enables farmers to meet the economic demand of feeding the modern world with minimal physical effort. Minimizing physical effort sees modern machinery like tractors and harvesters used, as well as chemically engineered herbicides, pesticides, and fungicides to conquer soil-borne diseases (Bodin 2017). 6.3  GENERALIZED IMPACTS OF CLIMATE CHANGE ON AGRICULTURE IN THE TROPICS The vulnerability of tropical crops to climate change is primarily influenced by four factors: (1) the changes that will occur in the climate in tropical regions; (2) the capacity of agricultural soils and growing media to continue to provide water, nutrients, and stability to agricultural crops; (3) the inherent capacity of the crop or variety to withstand variation in rainfall, nutrients, CO2, and modified management practices; and (4) the governability and management of farming systems and the adaptive capacity of tropical agricultural communities. 6.3.1  Climate Variability Recent climate simulation exercises grouped into international projects such as CMIP5 or Cordex, and using Global Circulation Models (GCMs) and sometimes Regional Climate Models, have provided improved results on the future evolution of climate variables (temperatures, rainfall, wind) at regional and sometimes local scales (Bagley et  al. 2014; Chang 2002). However, even though these models have dramatically improved, there still is—and will always be—uncertainty on future climate change due to (i) differences among climate models, (ii) uncertainties on data, and (iii) assumptions on future greenhouse gases (GHG) emissions. This third type of uncertainty is generally taken into account using GHG emission scenarios (like the former “SRES” scenarios) or concentration pathways (called RCP and used for the last IPCC report) that represent several potential world futures in terms of emission (Table 6.1).

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Figure 6.2 Hierarchical framework depicting the interaction between the farming and production systems in the tropics.

Uncertainty in future climate projections is a very important parameter that should not be forgotten in order to avoid maladaptation. For some regions of the world (e.g., Mediterranean or Southern Africa), the models’ agreement is high for temperature increase and precipitation decrease, even if the magnitude differs among them. For other regions like West Africa, the situation is more challenging, and the climate models project contrasted cumulated rainfall evolution, except for some regions like Senegal where a significant decrease could occur in the future (Sylla et al. 2016). So, in West Africa, it is difficult to conclude whether the cumulated annual rainfall will decrease or not. However, studies like Déqué et al. (2016) project that there will be fewer rainy days but more

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Table 6.1 Global Mean Temperature Increases Projected for the 2090s Compared to Years 1986–2005 for 4 RCPs, According to CMIP5 Results Representative Concentration Pathway

Global Mean Temperature Increase

RCP2.6

+1°C

RCP4.5

+1.8°C

RCP6.0

+2.2°C

RCP8.5

+3.7°C

Source: Stocker T. F. et  al. 2013. Technical summary. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, eds. T. F. Stocker et al. 33–115, Cambridge, MA: Cambridge University Press.

intense rainfall in the future. More intense rainy events are also projected by Sylla et al. (2016) for a pessimistic pathway (RCP8.5). In this region, like in many regions of the world, the future warming is projected to be significant and range between +1°C and +3.2°C in the year 2100 for a medium concentration pathway (RCP4.5). With more pessimistic pathways (RCP8.5), and as shown in some models, the temperature increase could even reach +6°C. These climatic changes may have several impacts on cropping systems. Taking them into account is necessary in order to design relevant public policies and to reach sustainable development goals. Climate changes will impact crop production, especially in areas of the world like the Sahel, where agriculture is rain-fed and thus depends a lot on rainfall variations. Temperature increase also plays a non-negligible role as it increases potential evapotranspiration and can shorten the crop cycle for cereals in West Africa (Sultan et al. 2013). Global warming caused by the increase in temperature is expected to cause a serious perturbation of hydrological cycle elements like increase in atmospheric water vapor, shifting precipitation patterns, and changes in precipitation in the tropics. These phenomena are causing much debate and uncertainty on the temporal and spatial variabilities of rainfall events (Challinor and Wheeler 2008; Adhikari et al. 2015). Thus, climate impacts on crop productivity are expected to be negative in many tropical regions like East or West Africa for major crops like maize, sorghum, millet, and groundnuts (Schlenker and Lobell 2010; Roudier et al. 2011: Sultan et al. 2013; Yates and Strzepek 1998), while regions such as northern Australia and Indonesia may be able to expand and diversify production due to the relative stability of rainfall in these regions and the expansion of the tropics into areas that are currently unable to support tropical crops to the south (Park 2008). 6.3.2  Impacts on Soils Fifty percent of the world’s agricultural soils are degraded, yet there is a need to rapidly increase food production to satisfy a growing population (Khush 2005). Most of the acceleration in agricultural production is expected to occur in tropical regions, where tensions between increasing urbanization, nature conservation, and land clearing for agriculture are especially high. It has long been known that land clearing for agriculture increases nitrous oxide emissions from soils (Luizão et al. 1989) and is commensurate with increased soil acidification due to ion pumping interruptions (Tighe et al. 2009) and soil structure decline (Guo and Gifford 2002). Tropical horticultural soils have primarily developed under conditions of high rainfall, and hence are liable to leaching and increased availability of iron, aluminum, and manganese. Climate change will increase storms and rainfall events in many parts of the tropics, leading to localized leaching and waterlogging of clay and volcanic soils. These soils, which are moderately acidic, will thus experience further declines in pH, and as such, there is an increased risk of ion toxicity to crops. Substantial addition of lime and other soil conditioners will be required to reverse soil acidification due to increased rainfall events and waterlogging.

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Soil erosion and depletion will be a further consequence of climate change, and estimated mean annual soil erodibility has shown a clear climate effect (Salvador Sanchis et al. 2008), with distinctly different erosional patterns affecting soils in wet and dry tropics, as opposed to those in temperate areas. Possible explanations for distinctly different erosion patterns include soil laterization and sesquioxide dynamics in tropical soils, as well as the larger infiltration rates of clay soils due to year-round warm temperatures (Borselli et al. 2012). In regions of the tropics that are becoming increasingly arid, a switch from chemical weathering and fluvial erosion to physical weathering and aeolian erosion is expected. As climate change will result in increased wind speeds, farmers will need to reconsider clearing all available areas for food production, lest there be no windbreaks or soil coverage by plastic sheeting, cover crops, or residue to prevent wind erosion. Soil compaction is exacerbated by frequent wet-dry oscillations which cause structural decline in tropical soils. Consequently, soils become increasingly impermeable to oxygen and the movement of water, both of which increase risks of soil-borne fungal and bacterial diseases in warm climates (Ishak et al. 2013). The disease-soil-plant cycle is poorly understood, but certainly in the context of wet-dry oscillations, the negative effects of climate change on the quantity and distribution of freshwater are expected to outweigh the benefits of overall increases in global precipitation (Thornton et al. 2014). Central-West Asia, North Africa, and North America are likely to be particularly affected by reduced freshwater availability (Rosegrant et al. 2009) as severe water constraints become apparent by 2050 (Rockström et al. 2009). Organic carbon sequestration will be significantly affected depending on soil texture and structure, rainfall, and temperature (Lal 2004a). Soil temperature might affect carbon decomposition of soils, and even though much work has been conducted, a consensus still has to emerge on the temperature sensitivity of soil carbon decomposition (Davidson and Janssens 2006). Potentially, tropical soils could also lose fertility in a shorter time caused by the destruction of the tropical forest. In the tropics, cropland suitability will be lost consequently to climate (Ramankutty et al. 2002), while organic soils (peats) drying caused by higher temperatures might result in high loss rates of soil carbon (Schimel et al. 1994). This high loss of organic matter has been shown to be correlated to a low maintenance of availability of some mineral nutrients in soils (Maranguit et al. 2017). On the other hand, climate change and global warming have also been shown to affect soil respiration in the tropics, and this increased respiration likely provides a positive feedback to the greenhouse effect (Raich and Schlesinger 1992). Thus, while frequent tillage will cause a net loss of C (Bajgai et al. 2015a,b), residue incorporation to increase organic matter content can also enhance and accelerate soil respiration rates (Bajgai et al. 2013). In this context, it is admitted that soil C sequestration plays a major role in the carbon cycle and contributes to restore degraded soils, biomass production, and water purification, as well as reducing CO2 atmosphere enrichment (Batjest 1996; Lal 2004b). Therefore, increasing soil C sequestration through improving the productivity and sustainability of existing agricultural lands might be considered as a significant mitigation (Paustian et  al. 1997). Importantly, the role of microbial biomass carbon in the aggregation of soil, the transformation of C, and the availability of nutrients is significant in the labile pool of tropical agricultural soils, and can be efficiently conserved and manipulated for its functional attributes when conservation tillage practices are implemented in farming systems (Li et al. 2018). Nonetheless, soil organic carbon (SOC) increases require careful interpretation to assess whether or not they represent genuine climate change mitigation as opposed to redistribution of organic C within the landscape or soil profile (Powlson et al. 2016). 6.3.3  Pests and Diseases The expansion of the wet tropics into the northern and southern hemispheres as the global climate changes will result in range expansion of many tropical pests and diseases and their vectors (Bebber et al. 2013). Northern Australia is vulnerable to invasion from weeds, pests, and diseases given

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its close proximity to New Guinea and the Indonesian archipelago which are both “true” tropical environments (Australian Government 2017; Scott et al. 2014). The frequency and wind speeds of tropical cyclones in northern Australia could accelerate as much as 10% (Ash 2007), potentially increasing the likelihood of wind-borne weeds, pests, and pathogens from countries farther north (Scott et al. 2014). Anticipated impacts and therefore the vulnerability of production systems depend largely on species mixes, crops grown in the savanna, feed resources for livestock-cropping systems, and feeding strategies (Thornton et al. 2009). Rainfall and temperature interactions and their impacts on disease transmission are complex. However, major diseases of smallholder crops in Africa are likely to be associated with changes in rainfall—Maize Streak Virus and Cassava Mosaic Virus will predominate areas with increased rainfall, and Sorghum Head Smut (a fungal disease) will be likely in areas where rainfall decreases (Chancellor and Kubiriba 2006). Even in areas where rainfall is far less of a problem, intense heat and insolation are likely to enhance the vulnerability of coffee plantations, but also leave these and other crops susceptible to increased disease burden (Fain et al. 2017). Finally, increased levels of atmospheric carbon dioxide have a part to play in Fusarium spp. pathogenesis in grain crops such as wheat (Tiedemann and Firsching 2000), which are already marginal in most parts of the tropics due to the dramatically shrinking “cold” season that allows some staple crops to be grown in India and Australia. When an acute spike in temperature and atmospheric CO2 occurred between the Paleocene and Eocene epochs, the linked climatic shifts resulted in an increased percentage of damaged leaves and diversity of damage by insect herbivores (De Lucia et al. 2008). Decreases in native agrobiodiversity could substantially increase the risk of crop failure from extreme climatic events and increase crop vulnerability to disease (Garrett 2008). In fact, even a short change in seasonal link can dramatically increase the proportion of parasitic insects, leading to increased defoliation of tree and fodder crops by insect pests. Because we are not yet able to fully appreciate the relationship between the changing climate and the likelihood of disease (Chakraborty and Newton 2011), some researchers have considered reporting impacts using indirect methods, such as farmer surveys. In the context of rice production, diseases that arose due to increased and unexpected waterlogging carried through into storage facilities were shown to impact up to a quarter of the harvested yield almost 90% of the time, whilst the risk of losing between one-half to three-quarters of household income due to a significant disease outbreak was double that of risks associated with cyclones and severe flooding (Table 6.2). Plant pests and diseases could potentially reduce yields of major crops by 50%. These losses are even more significant in developing regions or regions heavily dependent on subsistence livelihoods. Average losses of rice in the period 2001–2003 totaled 37.5%, of which 15.1% was due to invertebrate pests, 10.8% because of fungal and bacterial pathogens, 10.2% from weeds, and 1.4% due to viruses (Oerke 2006). Each year an estimated 10%–16% of global harvest (Strange and Scott 2005; Oerke 2006) is lost to plant diseases. 6.3.4  Crop and Varietal Impacts Climate change is also constraining regional production, productivity, and yield of major crops, and plants have been categorized into two groups: (i) plants that will be affected negatively by CC and considered “losers,” and (ii) plants that will benefit from CC and be considered “winners.” Any significant yield decrease in tropical agricultural zones is primarily due to the temperature rise in more arid regions like the Mediterranean and the Middle East, versus the impacts of soil structural decline and poor root system development in regions that will experience more extreme rainfall events such as northern Australia, Southeast Asia, and the Gulf of Mexico (Pandey et al. 2016). It is important to emphasize that these general statements about crop productivity cannot be extended to all crops without in-depth analysis; however, it is acknowledged that yield decreases will be more

539

539

524

524

524

Loss of crops during storage

Cyclones

Severe flooding

Severe drought

68

44

51

36

81

47

% of Farmers Affected

1.8 (±0.1)

1.2 (±0.1)

1.2 (±0.1)

1.3 (±0.09)

3.1 (±0.09)

1.6 (±0.08)

23

40

30

88

–

56a

75%

% of Crop Yields Lost Due to Risks

35

40

39

–

–

10a

75%

% Reduction in Household Income Due to Risk

Source: Redrawn from Chakraborty, S., and A. C. Newton. 2011. Plant Pathol 60:2–14. Note: Numbers represent the percent of farmers experiencing this problem or the means (±SE). a Impacts of pests and diseases on crop yields and income levels were assessed jointly, owing to difficulties of attributing impacts to one or the other. b These numbers (for crop storage) refer to losses of more than 50%.

539

Severe pest damage

n

Significant disease outbreak

Agricultural Risk

Frequency of Risks (Mean Number of Occurrences in Last 5 Years)

Table 6.2 Summary of the Risks to Rice Production Experienced by Smallholder Farmers and the Impacts of These Risks on Rice Yields and Household Income (as Reported by Farmers)

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significant in the tropical regions compared to the temperate ones, even though these will undergo similar impact on yields later (Berg et al. 2012). Globally, different scenarios have been developed to predict the decline in crop production and yields. As shown in Table 6.2, decline in yield varies, and it is clear that some regions will be more affected than others, and the decline in cereals is more significant than other crops. However, some crops have been reported to be more resilient and the decline is predicted to be much less than in non-resilient crops such as cereals. In their review on the impact of climate change on major crops in eastern Africa, Adhikari et al. (2015) reported that wheat yield will decline by 72%, and maize, rice, and soybean by ca. 45%, while millet and sorghum yield, considered as more resilient, will decline by less than 20%. In their review, the same authors reported that sweet potato, potato, and cassava will be less affected by climate change and will have their yield varying from −15% to +10%. Other crops such as tea and coffee will have their yield declining by up to 40%, and similar loss will be observed in banana and sugarcane production. Similar results have been reported by Tito et al. (2018) who indicated increased risk of crop yield losses and food insecurity in the tropical Andes. They indicated that an increase by 1.3°C and 2.6°C, will cause a decline of maize and potato yield by more than 87%. Even though these crops are cultivated at higher altitudes, the maize production decline ranged between 21% and 29% in response to new soil conditions. Consequently, it is urgent to think about how (i) to sustainably increase farm productivity in order to secure enough food for our growing population, (ii) to strengthen resilience to climate change and variability, since climatic disruption needs coping and resilient agroecosystems, (iii) to alleviate global warming by reducing greenhouse gas emissions (Howden et al. 2007; Challinor et al. 2009), and (iv) to plan adaptations in agricultural water management (Cai et al. 2015a,b). 6.4  VULNERABILITIES OF TROPICAL CROPS AND PRODUCTION SYSTEMS TO CLIMATE CHANGE 6.4.1  Vulnerability of Tropical Crops to Climate Change Vulnerability of a tropical crop production system or of farming practices can be described as the net difference between the impacts driven by climate change and the ability to adapt. Or, as described by Kelly and Adger (2000), vulnerability is the capacity of people and social groups to respond to, recover from, and adapt to stresses placed on their livelihoods and well-being. Environmental pressures on tropical agroecosystems driven by increased agricultural demand will result in asymmetrical declines in ecosystem services depending on future management trajectories and adaptive capacity of land managers (Williams and Jackson 2007; Schlenker and Lobell 2010; Goldsmith and Cohn 2017). Ultimately, the vulnerability and sensitivity of tropical farming to climate change depends on the type of production system used, with tropical agricultural systems being more vulnerable due to a high concentration of developing nations and populations primarily dependent on rain-fed systems (Battisti and Naylor 2009). The climate in northern Australia is highly varied, ranging from arid in the south to monsoonal in the far north and humid tropical in the east (Willcocks and Young 1991). Given the high variability of tropical cyclones in northern Australia, the region compared to other continents in the tropics receives the highest variation in annual rainfall from less than 100 millimeters to over 2,000 millimeters (Dewar and Wallis 1999). This variability in climate across the north Australian tropics has facilitated the emergence of various tropical crop production systems from cattle grazing to tropical fruits and sugarcane. These industries are now facing unprecedented challenges as the effects of climate change continue to rise—many stakeholders within Australia and elsewhere in the tropics are autonomously adjusting to climate change (Parry and Carter 1998).

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Australia provides a suitable example of how livestock grazing and cropping cycles have benefited from tropical climates, but Australia is also faced with challenging circumstances driven by extremes in the climate within the tropics. The expected impact of climate change on the pastoral production system in the savannas of northern Australia includes changes in weed and increased woody vegetation distribution (O’Rourke et al. 1992; Burrows 1995; McHenry et al. 2009), which reduce farm productivity due to invading and smothering crops or poisoning livestock in these areas (Tothill and Gillies 1992; Hall et al. 1998). To feed the current world population, more than 8,000 km3 yr−1 of freshwater is used in rain-fed and irrigation agricultural production systems (Rost et al. 2008), which are commonly used in arable, mixed, subsistence, and commercial farming systems. It is estimated that about 5,000 km3 yr−1 more freshwater will be required by the year 2050 (Grubler 2007). There has been an increase in cultivated land in tropical to tropical-arid regions based on a rising population (Mongi et al. 2010). Other production systems such as rain-fed or irrigation agricultural methods are also affected by a changing climate. Rain-fed agriculture suffers more severely from the influence of climate change compared to irrigated agriculture (Xie et al. 2011). About 80% of total agriculture is carried out using the rain-fed production method, and today this production system provides about 62% of the world’s staple foods (Bhattacharya 2008). Therefore, current challenges facing rain-fed agriculture are a serious concern in agriculture. Ongoing droughts, seasonal shift, and increasing temperatures are described by farmers as being imminent challenges facing production in rain-fed agricultural systems (Mongi et al. 2010). Agriculture, as compared to other sectors, is the largest in terms of its water consumption and accounts for more than 70% of water withdrawn from freshwater storage points (Ashour and Al-Najar 2012). Therefore, changes in water availability likely increase the exposure of rain-fed farming methods to climate change vulnerability in the tropics. Rice requires large volumes of water to grow in that it receives about 35%–45% of the world’s irrigation water. Although evidence suggests that while rice is water demanding, with good water conservation strategies water can be preserved in times of need, like drought, and can re-enter the hydrological cycle in tropical regions (Bouman n.d.). Rain-fed agriculture already struggles to meet agricultural demands, particularly in commercial farming systems, producing a lower yield than is needed to feed an increasing population largely attributed to a global climate change and a shortage of water available for irrigation (Anderson et al. 2016). However, in the Central Highlands and Southern Delta of Vietnam there is a good example of how water conservation strategies in the face of climate change can aid both commercial and smallholder farmers in overcoming problems associated with drought. In recent years this region of Vietnam has been suffering an unprecedented drought, and the coffee plant yields have dropped considerably. Established water-saving technology providing individual coffee plants with automatically adjusted volumes of water in drought conditions has not only conserved water, but has saved considerable coffee yields for farmers in these affected tropical regions (World Bank 2016). Maize production in tropical Mexico is another example where extensive drought conditions have resulted in decreased yields in one of the most important rain-fed agricultural production systems in Mexico (Conde and Ferrer 2006). Climate change has been identified as a potential culprit in the intensification of El Niño events (Cho 2016) and therefore the onset of drought conditions in the tropics (Conde and Ferrer 2006). In Indonesia projected delays in monsoons of up to 30 days are resulting in a reduction in the yield of rice varieties (Naylor et al. 2007) due to drought. Other issues farmers are facing in the tropics for rice production include intrusion of sea water in dry seasons and increased salinity in the soil as a result (United Nations 2014). As an example, farmers in Vietnam’s Mekong Delta have seen hectares of watermelon, peanuts, rice, and sweet potatoes become inundated with intruding sea water contaminating irrigation canals (United Nations 2014). The intruding saline water has caused reductions in yield by as much as 50% (United Nations 2014) (Figure 6.3).

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Figure 6.3 Different tropical crop production systems are more resilient than others, whereas conversely, production systems also show different vulnerabilities to a changing climate.

6.4.2 Impacts and Consequences of Climate Changes on Tropical Crop Production Systems These climatic changes may have several impacts on cropping systems. Taking them into account is necessary in order to design relevant public policies and to reach sustainable development goals. 6.4.2.1  Climate Changes and Crop Productivity Climate changes will impact crop productivity, especially in areas of the world like the Sahel where agriculture is rain-fed and thus depends a lot on rainfall variations. Temperature increase also plays a non-negligible role as it increases potential evapotranspiration and can shorten the crop cycle for cereals in West Africa (Sultan et al. 2013). Thus, climate impacts on crop productivity are expected to be negative in many tropical regions like East or West Africa for major crops like maize, sorghum, millet, and groundnuts (Schlenker and Lobell 2010; Roudier et al. 2011; Sultan et al. 2013; Challinor et al. 2014). The significant yield decrease is mainly due to the temperature rise (Challinor et al. 2014); a rainfall decrease would of course aggravate this change, but an increase could not completely offset this negative effect due to warming (Sultan et al. 2013). It is fundamental to underline that these results cannot be extended to all crops without in-depth analysis. Indeed, another parameter—namely the carbon fertilization effect—plays a major role for future crop production assessment (Leakey 2009). For C3 crops (like soybean, rice, and wheat), higher CO2 concentrations in the future could be physiologically beneficial for some crops through the stimulation of photosynthesis and reduction of drought stress resulting from lower stomatal conductance (Tubiello et al. 2007), thus offsetting the negative effect of climate change. This positive CO2 effect is, however, controversial in the scientific community as some researchers underline that it could also be beneficial for weeds. Others show that the projected atmospheric ozone increase could also offset this CO2 effect (but ozone is currently not taken into account in crop models). Finally, it is necessary for C3 crop assessment to include both scenarios: with and without CO2 effect. This unfortunately increases considerably the uncertainty of future projections (Roudier et al. 2011; Müller et al. 2015b). For example, McGrath and Lobell (2013) demonstrate that in Southern Africa the carbon fertilization effect on sweet potato yields is over 20% for a 100 ppm increase in CO2 concentration. However, Challinor et al. (2014) in a meta-analysis covering all tropical areas of the world show that there will be a significant yield decrease, even for rice and wheat, after a certain warming threshold (close to +2°C of local warming) if there are no adaptation plans. Concerning tuber crops, some articles highlight that cassava will suffer less from future climate change as it is well known to be drought- and heatwave-tolerant (Jarvis et al. 2012). However, cassava is very sensitive to diseases (cassava brown streak virus, cassava mosaic disease, etc.) and to excess

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of water. As emphasized by Hershey et al. (2012), future climate change could have a positive effect on both parameters and therefore decrease cassava yields (but losses due to diseases and excess of water are more difficult to simulate in crop models typically used for climate impact studies). It is important to note that most studies do not explicitly take adaptation into account. It means that they make the assumption that farmers will not change their current cropping practices with a changing climate (except sometimes changing sowing dates). Nevertheless, Challinor et al. (2014) highlight that adaptation in tropical regions could offset the effect of CC for rice (but not for maize). These papers also do not give details about the cultivars that are studied. They focus generally on maize or rice while hundreds of cultivars with contrasted characteristics do exist. Sultan et al. (2013) show for example that traditional millet and sorghum varieties are less impacted by rising temperature than improved ones, because of their photoperiod sensitivity. There are fewer studies about the impact of future CC on tropical cash crops like cocoa than on staple crops. They are indeed more challenging to model and most of the existing crop models focus on rice, wheat, millet, etc. Still, some papers on specific tropical areas (e.g., West Africa) demonstrate that the overall suitability to grow cocoa in the region will decrease because of higher maximum temperatures during the dry season (Schroth et al. 2016). 6.4.2.2  Future Climate Change and Crop Quality (Nutrients) In a global meta-analysis, Myers et al. (2014) considered many different cases (countries, crops, years) that focused on the impact of rising CO2 concentration on nutrients (Zn, Fe, Protein, Phytate). They show that there is a significant decrease with elevated CO2 for wheat, rice (only for Zn, Fe, protein), field peas, and soybeans (only for Zn and Fe). For C4 crops like maize and sorghum the results are not statistically significant. In a recent paper combining high CO2 concentration and increased temperature during FACE experiments, Usui et al. (2016) conclude that this also leads to a decrease in rice proteins. These results could have important implications for future food security. 6.4.2.3  Other Types of Impacts As described previously, several research papers have focused on the impacts of climate change on crop yields or productivity. But little is known about the rest of the value chain like post-harvest losses or pests and diseases. This is an interesting aspect for future research. Moreover, indirect impacts such as sea-level rise (loss of land availability and soil salinization) are difficult to include even if their effects are already visible in some coastal areas like the Niayes in Senegal (Fare et al. 2017). Finally, weather shocks (at different scales) can also impact commodities prices and, therefore, farming systems. 6.5  ADAPTATION AND MITIGATION MEASURES FOR CURBING NEGATIVE IMPACTS OF CLIMATE CHANGE ON TROPICAL AGRICULTURE SYSTEMS The twenty-first century is marked by an unprecedented human demographic explosion and climate change, resulting in the acceleration in demand for food and pressures on the land in tropical as well as other regions. As described in other chapters, these climatic changes are having different negative impacts on soils, crops, and agroecosystems. In order to reduce risks of climate change to tropical crop production, land management strategies must include the capability to resist impacts of disease, explore new varieties, and reduce dependency on water. Though strategies to combat climate change impacts in agriculture are often viewed through the separate lenses of adaptation and mitigation, the more often both strategies are combined, the less likely it is that agricultural systems and the humans who depend on them will be vulnerable.

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Options to adapt span a wide variety of approaches designed to reduce system vulnerabilities and enhance the adaptive capacity of these systems to a changing climate (Harvey et al. 2014a). Sophisticated solutions are still quite expensive to implement and are largely restricted to developed and rapidly industrializing nations and include modified agroengineering practices for irrigation and soil integrity, breeding for different environmental stresses, developing early warning systems, and establishing crop insurance systems. More broadly, all nations in the tropics may realize substantial production security via soil and water conservation practices, crop diversification, and improved tillage practices (Howden et al. 2007). One of the issues of foremost importance in rain-fed agriculture is reduced soil moisture and therefore low soil fertility in agricultural soils, the result of poor rainfall distribution and prolonged drought periods (Barron et al. 2003; Gowing et al. 2003; Mongi et al. 2010). Poor soil moisture and increased temperature have been linked to increased soil salinity, another factor reducing crop yield and increasing irrigated water demand (Ashour and Al-Najar 2012). Coping strategies employed by farmers using rain-fed methods include varying planting dates, planting more resistant maize varieties, changing cultivars, and applying agrochemicals (Conde and Ferrer 2006). Innovation in rice farming is necessary to ensure ongoing security for one of the most important cereal crops in the tropics. Shifts to salt-tolerant or drought-tolerant varieties are becoming common, alongside deep-water rice varieties to advance global rice production in regions affected by sea-level rise. The Three-Tier Rice Production System is an example of such an adaptation strategy. Tier I facilitates a more sustainable farming system whereby minimal tillage and cover cropping is used to promote crop rotation techniques (Nath and Lal 2017). Tier I of this production system also utilizes the littoral zone of the wetland system where agroforestry techniques to grow other species such as bamboo are used to create diversity in cash flow and product. This technique also allows farmers to make the most of available moisture in soils to promote higher yield. Tier II utilizes the sublittoral zone of the wetland where there has been a notable increase in the ability to better manage and control weeds, and Tier III is where deep water species are adopted in this production system. This system provides a prolonged tolerance to flood waters, a common issue associated with climate change, and it also provides an option for seedling transplantation without the need for tillage. This Tier III system commonly used in Cambodia, Thailand, and India also provides opportunity for a conjunction with an aquaculture-based production system (Nath and Lal 2017). Rising seawaters have been particularly destructive to rice crops, and some government agencies and private groups have responded by planting mangroves to prevent seawater inundating costal crops (Nguyen et  al. 2014). Investments from the Vietnamese government also aim to improve irrigation canals and dikes. As temperatures continue to increase and relative sea level continues to rise, farmers producing crops in coastal or low-lying regions may need to transition to more salttolerant species. Aquaculture has even been suggested as a viable alternative for farmers currently subject to intrusion of saline waters resulting from sea-level rise (United Nations 2014). Mitigation options in tropical agriculture focus on actions, including those that increase carbon stocks above and below ground, reduce greenhouse gas emissions, and/or actively avoid the deforestation and degradation of high-carbon natural systems for agricultural production (Smith et al. 2007; Wollenberg et al. 2012). Although tropical agroecosystems were less investigated compared to temperate systems, often these agroecosystems are misunderstood and, therefore, not as well managed as the temperate agroecosystems (Janzen 1973). Different approaches have been reported to curb negative impacts of climate changes on the tropical agroecosystems. As these systems have higher levels of biodiversity conservation, this trait might mitigate changes in temperature and precipitation when combined with environmentally friendly and sustainable land use agroforestry systems which have potential to enhance biodiversity conservation (Perfecto et al. 2007). The conversion of agriculture to crop-pasture rotation (CPR) showed that the implementation of this CPR model proved to be a good strategy to mitigate soil GHG emissions in the tropics (Carvalho et al. 2013). For example, erosion caused by high rainfall has

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been mitigated by implementing sound practices of soil and vegetation management such as contour planting, no-till farming, and use of vegetative buffer strips. These practices can reduce erosion by up to 99% (Labrière et al. 2015) and reduce CO2 soil emission (La Scala et al. 2005). In some tropical areas, negative impacts of climate change on tropical agroecosystems might also be mitigated by reforestation, planting fruit trees, or expanding small plantations; however, more research is needed to determine the advantages of agroecosystems that combine trees with crops and crops with animals, because these systems are increasingly recognized and promoted to improve sustainable use of tropical lands (Nicholas 1988; Labrière et al. 2015; Locatelli et al. 2015). Moreover, appropriate management strategies of tropical agroforestry systems might mitigate climate change by adopting climate-smart approaches, especially when used in parallel with comprehensive system rehabilitation plans, and also if these systems are designed in a larger landscape context and appropriately managed (Harvey et al. 2014b; Ramakrishnan 1998). There are many definitions of resilience to climate change. In this chapter, we use the following one, as suggested by the IPCC: the “ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of a hazardous event in a timely and efficient manner.” Furthermore, and as detailed by Douxchamps et al. (2017), resilience is generally defined by its three capacities: absorptive (for a cropping system, for example, its capacity to absorb a rainfall deficit without changing its fundamental structure), adaptive (capacity to adapt the cropping practices to the changing climate based on experience and observations), and transformative (capacity to change the cropping system to something different because the initial system cannot work anymore). In Sahelian farming systems, there are diverse local practices and innovations that are increasing their resilience to CC. Examples illustrating the three types of capacities are: • Water harvesting techniques (WHT) (absorptive capacity): In many areas where agriculture is rainfed and dry spells are frequent, farmers have designed in-field WHT in order to mitigate drought effects (see e.g., Biazin et al. [2012] for a review). One well-known WHT is Zai pits, initially used in Burkina Faso, that collect on-field runoff water. Generally, these WHT can increase the root zone soil water content by up to 30% (Biazin et al. 2012) as well as the soil organic matter content (Olaleye et al. 2006). These practices therefore lead to improved yields and lower risks of bad harvest (or crop failure) in case of dry spell. • Cultivar diversity (adaptive capacity): As already detailed, for a specific type of crop (e.g., millet), there are many different cultivars with specific characteristics: drought and disease resistance, cycle length, sensitivity to photoperiod, etc. Farmers generally have many cultivars available and choose the relevant one (or a mix of different types) in order to lower the risk of crop failure. For example, in the historical peanut basin of Senegal, Müller et al. (2015a,b) report that long-term millet cultivars (Sanio) that disappeared after the 70’s and 80’s droughts were once again grown by farmers in order to benefit from wetter conditions occurring during the past years. The cultivar choice is also based on traditional seasonal forecast systems that focus on the observation of natural phenomenon or on scientific forecasts when they are available (Roudier et al., 2014). • Crops and income diversification (transformative capacity): This is another option close to cultivar choice but it implies more structural changes in crop diversification. Indeed, farmers may grow new types of crops. For instance, in the former example in Senegal, some of them decided to start growing rain-fed rice to benefit from the more humid years; in Côte d’Ivoire and Ghana, farmers growing cocoa can start planting trees in order to provide shade (beneficial for cocoa under warming conditions) and to provide another source of income. Generally, crop diversification is beneficial because it creates many co-benefits: climate risk mitigation, pest and disease management, increased nutrient storage, increased yield stability,  etc. (Lin 2011). In a recent analysis focusing on Zimbabwe, Makate et al. (2016) demonstrate that (i) 82% of the surveyed farmers practice crop diversification, and (ii) increasing crop diversification has a positive significant impact on crop productivity and income. More broadly, income diversification (including non-agricultural work) is another well-known risk management strategy for farmers. In Zimbabwe, Ersado (2003) highlights that income diversification is particularly high in rural areas and comprises essential tools to mitigate price and weather shocks on the agricultural sector.

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Many of the previous practices (as well as others like the use of meteorological and seasonal forecasts) are grouped under the terminology of agroecological practices (Altieri et al. 2015) that is recognized (i) to increase farming system resilience to climate change, but also (ii) to reduce GHG emissions coming from agriculture (close to 25% of global CO2 emissions). Agroecological practices are, however, often put in place at a very small scale and could be difficult to promote in areas where intensive agriculture is the dominant model. It is therefore necessary to (i) continue demonstrating what the benefits of agroecology are in terms of income, food security, and environmental externalities, (ii) broadcast evidence of such practices’ usefulness (workshops, education), and (iii) design appropriate regional and national policies in order to scale up local good practices (Parmentier 2014). 6.6  CONCLUSIONS AND PERSPECTIVES Evidence shows that the climate is significantly changing on a global scale and this will, if it has not already, have significant impacts on tropical agroecosystems and consequently affect food supply in the tropics, and in particular will thus make some countries in the tropics more vulnerable. Unless measures and decisions are taken to mitigate the negative effects of climate change on these vulnerable agroecosystems, food production in the tropics will be under threat. In the tropics, the temperature is going to rise significantly because of GHG emissions, and rainfall changes are expected in many regions of the world (e.g., decrease in Southern Africa) even if the uncertainty is high for some areas (West Africa). These changes will impact crop production and crop nutrients concentration. Some crops like maize are expected to be significantly negatively impacted. For C4 crops like rice, the situation is more uncertain but their nutrients concentration will probably decrease because of elevated CO2. Therefore, resilience of these systems could be strengthened by agroecological practices, and agroecology which is often localized at the project scale must be scaled-up through appropriate public policies. The future prospect is (i) focus on studying more widely the impacts of future climate change on the whole value chain (not only production), (ii) assess the impacts of agroecological practices on income, food security, and GHG emissions, (iii) focus on inequalities (especially gender inequalities), and (iv) design relevant policies to scale up agroecology, including education. Furthermore, we also need to adopt specific strategies to not only mitigate the negative impacts of climate changes on the tropical agroecosystems, but also to partly reverse the negative impacts and the degradation process caused by the climate change factors. REFERENCES Adhikari, U., P. A. Nejadhashemi, and S. A. Woznicki. 2015. Climate change and eastern Africa: A review of impact on major crops. Food Energy Sec 4:110–32. Altieri, M. A., C. I. Nicholls, A. Henao et al. 2015. Agroecology and the design of climate change-resilient farming systems. Agron Sustain Dev 35:869–90. Anderson, W., C. Johansen, and K. Siddique. 2016. Addressing the yield gap in rainfed crops: A review. Agron Sustain Dev 36:18. https://doi.org/10.1007/s13593-015-0341-y. Ash, A. 2007. Climate Change Impacts and Adaptation in Northern Queensland. Australia: CSIRO. https:// www.planning.org.au/documents/item/160. (Accessed: January 14, 2018). Ashour, E., and H. Al-Najar. 2012. The impact of climate change and soil salinity in irrigation water demand in the Gaza strip. J Earth Sci Clim Change 3:2. https://doi.org/10.4172/2157-7617.1000120. Australian Government. 2017. Weeds in Australia. http://www.environment.gov.au/biodiversity/invasive/ weeds/weeds/why/impact.html. (Accessed: January 17, 2018). Bagley, J., A. Desai, K. Harding, P. Synder, and J. Foley. 2014. Drought and deforestation: Has land cover change influenced recent precipitation extremes in the Amazon? J Clim 27:345–61.

98

CLIMATE CHANGE AND CROP PRODUcTION

Bajgai, Y., Hulugalle, N., Kristiansen, P., and McHenry, M. 2013. Developments in fractionation and measurement of soil organic carbon: A Review. Open Journal Soil Sci 3(08): 356–360. http://dx.doi. org/10.4236/ojss.2013.38041. Bajgai, Y., P. Kristiansen, N. Hulugalle, M. McHenry, and B. McCorkell. 2015a. Soil organic carbon and microbial biomass carbon under organic and conventional vegetable cropping systems in an Alfisol and a Vertisol. Nut Cycl Agroecosyst 101:1–15. Bajgai, Y., P. Kristiansen, and M. McHenry. 2015b. Comparison of organic and conventional managements on yields, nutrients, and weeds in a corn-cabbage rotation. Renew Agr Food Syst 30:132–42. Barron, J., J. Rockstrom, F. Gichuki, and N. Hatibu. 2003. Dry spell analysis and maize yields for two semi-arid locations in East Africa. Agric Meteorol 117:23–37. Batjest, N. H. 1996. Total carbon and nitrogen in the soils of the world. Eur J Soil Sci 47:151–63. Battisti, D. S., and R. L. Naylor. 2009. Historical warnings of future food insecurity with unprecedented seasonal heat. Science 323:240–4. Bebber, D. P., M. A. Ramotowski, and S. J. Gurr. 2013. Crop pests and pathogens move polewards in a warming world. Nature Clim Chang 3:985–88. Benkeblia, N. 2012. Sustainable Agriculture and New Biotechnologies. Boca Raton, FL: CRC Press. Berg, A., N. de Noblet-Ducoudré, B. Sultan, M. Lengaigne, and M. Guimberteau. 2012. Projections of climate change impacts on potential C4 crop productivity over tropical regions. Agr Forest Meteorol 170:89–102. Bhattacharya, A. 2008. Sustainable Livelihood Based Watershed Management—Watershed Plus Approach. Presented at the 2nd Working Group meeting of ERIA, IGES, Japan. Biazin, B., G. Sterk, M. Temesgen, A. Abdulkedir, and L. Stroosnijder. 2012. Rainwater harvesting and management in rainfed agricultural systems in sub-Saharan Africa—a review. Phys Chem Earth 48:139–51. Bodin, G. 2017. Traditional agriculture. https://www.dahu.bio/en/knowledge/agriculture/traditional-agriculture. (Accessed: June 6, 2017). Borselli, L., D. Torri, J. Poesen, and P. Iaquinta. 2012. A robust algorithm for estimating soil erodibility in different climates. CATENA 97:85–94. Bouman, D. B. n.d. Does rice really use too much water? International Rice Research Institute. http://irri. org/blogs/bas-bouman-s-blog-global-rice-science-partnership/does-rice-really-use-too-much-water. (Accessed: January 14, 2018). Burrows, W. 1995. Greenhouse revisited—land-use change from a Queensland perspective. Clim Chang Newslett 7:6–7. Cai, W., G. Wang, A. Santoso et al. 2015b. Increased frequency of extreme La Niña events under greenhouse gas warming. Nat Clim Chang 5:132–7. Cai, X., X. Zhang, P. H. Noël, and M. Shafiee-Jood. 2015a. Impacts of climate change on agricultural water management: A review. WIRES Water 2:439–55. Carvalho, J. J. N., G. S. Raucci, L. A. Frazão, C. E. P. Cerri, M. Bernoux, and C. C. Cerri. 2013. Crop-pasture rotation: A strategy to reduce soil greenhouse gas emissions in the Brazilian Cerrado. Agr Ecosyst Environ 183:167–75. Chakraborty, S., and A. C. Newton. 2011. Climate change, plant diseases, and food security: An overview. Plant Pathol 60:2–14. Challinor, A. J., F. Ewert, S. Arnold, E. Simelton, and E. Fraser. 2009. Crops and climate change: Progress, trends, and challenges in simulating impacts and informing adaptation. J Exp Bot 60:2775–89. Challinor, A. J., J. Watson, D. B. Lobell, S. M. Howden, D. R. Smith, and N. Chhetri. 2014. A meta-analysis of crop yield under climate change and adaptation. Nat Clim Chang 4:287–91. Challinor, A. J., and T. R. Wheeler. 2008. Crop yield reduction in the tropics under climate change: Processes and uncertainties. Agr Forest Meteorol 148:343–56. Chancellor, T., and K. Kubiriba. 2006. The Effects of Climate Change on Infectious Diseases of Plants. Review for UK Government Foresight Project, Infectious Diseases—Preparing for the Future. London, UK: Department of Trade and Industry. Chang, C. 2002. The potential impact of climate change on Taiwan’s agriculture. Agric Econ 27:51–64. Cho, R. 2016. El Niño and global warming—what’s the connection? State Planet—Earth Institute, Columbia University. http://blogs.ei.columbia.edu/2016/02/02/el-nino-and-global-warming-whats-the-connection/. (Accessed: October 25, 2017).

TROPIcAL CROPS AND RESILIENcE TO CLIMATE CHANGE

99

Christensen, J. H., K. Krishna Kumar, E. Aldrian et al. 2013. Climate phenomena and their relevance for future regional climate change. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, eds. T. F. Stocker, D. Qin, G. K. Plattner et al. Cambridge, MA: Cambridge University Press. https://www.ncdc. noaa.gov/sotc/global/201704. (Accessed: June 9, 2017). Conde, C., and R. Ferrer. 2006. Climate change and climate variability impacts on rainfed agricultural activities and possible adaptation measures: A Mexican Case Study. Atmosfera 19:181–94. Davidson, E. A., and I. A. Janssens. 2006. Temperature sensitivity of soil carbon decomposition and feedbacks to climate change. Nature 440:165–73. De Lucia, E. H., C. L. Casteel, P. D. Nabity, and B. F. O’Neill. 2008. Insects take a bigger bite out of plants in a warmer, higher carbon dioxide world. Proc Natl Acad Sci USA 105:1781–2. Déqué, M., S. Calmanti, O. B. Christensen et al. 2016. A multi-model climate response over tropical Africa at +2 °C. Clim Serv 7:87–90. Dewar, R., and J. Wallis. 1999. Geographic patterning of interannual rainfall variability in the tropics and near-tropics. J Clim 12:3457–66. Douxchamps, S., L. Debevec, M. Giordano, and J. Barron. 2017. Monitoring and evaluation of climate resilience for agricultural development—A review of currently available tools. World Dev Persp 5:10–23. Ersado, L. 2003. Income diversification in Zimbabwe: Welfare implications from urban and rural areas. Food Consumption and Nutrition Division Discussion Paper No. 152. International Food Policy Research Institute. https://ageconsearch.umn.edu/bitstream/16467/1/fc030152.pdf. (Accessed: June 6, 2017). Fain, S. J., M. Quiñones, N. L. Álvarez-Berríos, I. K. Parés-Ramos, and W. A. Gould. 2017. Climate change and coffee: Assessing vulnerability by modeling future climate suitability in the Caribbean island of Puerto Rico. Clim Chang 146:175–86. FAO. 2017. Module 4: Crop Production Systems. Rome, Italy: FAO. Fare, Y., M. Dufumier, M. Loloum et al. 2017. Analysis and Diagnosis of the Agrarian System in the Niayes Region, Northwest Senegal (West Africa). Agriculture 7:59. DOI: 10.3390/agriculture7070059. Garrett, K. A. 2008. Climate change and plant disease risk. In Global Climate Change and Extreme Weather Events: Understanding the Contributions to Infectious Disease Emergence, eds. D. A. Relman, M. A. Hamburg, E. R. Choffnes, and A. Mack, 143–155, Washington, DC: National Academies Press. Goldsmith, P., and A. Cohn. 2017. Commercial agriculture in tropical environments. Trop Conserv Sci 10:1–4. Gowing, J., M. Young, N. Hatibu, H. Mahoo, F. Rwehumbiza, and O. Mzirai. 2003. Developing improved dryland cropping systems for maize in semi-arid Tanzania. Exp Agric 9:293–306. Grubler, A. 2007. Regional, national, and spatially explicit scenarios of demographic and economic change based on SRES. Technol Forecast Soc 74:980–1029. Guo, L. B., and R. M. Gifford. 2002. Soil carbon stocks and land use change: A meta-analysis. Glob Chang Biol 8:345–60. Hall, W., G. McKeon, J. Carter et al. 1998. Climate change in Queensland’s grazing lands: II. An assessment of the impact on animal production from native pastures. Rangel J 20: 177–205. Harvey, C., Z. Lalaina Rakotobe, N. Rao et  al. 2014b. Extreme vulnerability of smallholder farmers to agricultural risks and climate change in Madagascar. Philos T R Soc B 369:20130089. http://dx.doi. org/10.1098/rstb.2013.0089. Harvey, C. A., M. Chacón, C. I. Donatti et al. 2014a. Climate-smart landscapes: Opportunities and challenges for integrating adaptation and mitigation in tropical agriculture. Conserv Lett 7:77–90. Hershey, C. H., E. Alvarez, T. Maung Aye et al. 2012. Eco-Efficient Interventions to Support Cassava’s Multiple Roles in Improving the Lives of Smallholders. Cali, Colombia: Centro Internacional de Agricultura Tropical (CIAT). Howden, M. S., J. F. Soussana, F. N. Tubiello, N. Chhetri, M. Dunlop, and H. Meinke. 2007. Adapting agriculture to climate change. Proc Natl Acad Sci USA 104:19691–6. IFPRI. 2017. Smallholder farming. International Food Policy Research Institute. http://www.ifpri.org/topic/ smallholder-farming. (Accessed: April 10, 2017). Ishak, L., M. McHenry, and P. Brown. 2013. Soil compaction and its effects on soil microbial communities in Capsicum growing soil. Acta Hortic 1123:123–30. Janzen, D. H. 1973. Tropical agroecosystems. Science 182:1212–9. Jarvis, A., J. Ramirez-Villegas, B. V. H. Campo, and C. Navarro-Racines. 2012. Is cassava the answer to African climate change adaptation? Trop Plant Biol 5:9–29.

100

CLIMATE CHANGE AND CROP PRODUcTION

Kelly, P., and W. Adger. 2000. Theory and practice in assessing vulnerability to climate change and facilitating adaptation. Clim Chang 14:325–52. Khush, G. 2005. What it will take to feed 5.0 billion rice consumers in 2030. Plant Mol Biol 59:1–6. Köppen, W. 1900a. Versuch einer Klassifikation der Klimate, vorzugsweise nach ihren Beziehungen zur Pflanzenwelt. Geogr Zeitschr 6:593–611. Köppen, W. 1900b. Versuch einer Klassifikation der Klimate, vorzugsweise nach ihren Beziehungen zur Pflanzenwelt. Geogr Zeitschr 6:657–79. Labrière, N., B. Locatellia, Y. Laumonier, V. Freycon, and M. Bernoux. 2015. Soil erosion in the humid tropics: A systematic quantitative review. Agr Ecosyst Environ 203:127–39. Läderach, P., A. Martinez-Valle, G. Schroth, and N. Castro. 2013. Predicting the future climatic suitability for cocoa farming of the world’s leading producer countries, Ghana and Côte d’Ivoire. Clim Chang 119:841–54. Lal, R. 2004a. Soil carbon sequestration impacts on global climate change and food security. Science 304:1623–7. Lal, R. 2004b. Soil carbon sequestration to mitigate climate change. Geoderma 123:1–22. La Scala, N., Jr. D. Bolonhezi, and G. T. Pereira. 2005. Short-term soil CO2 emission after conventional and reduced tillage of a no-till sugar cane area in southern Brazil. Soil Till Res 91:244–8. Laurance, W., Sayer, J., Cassman, K. 2014. Agricultural expansion and its impacts on tropical nature. Trends Ecol Evol 29:107–116. Leakey, A. D. B. 2009. Rising atmospheric carbon dioxide concentration and the future of C4 crops for food and fuel. Proc R Soc B Biol Sci 276:2333–43. Li, J., X. Wu, M.T. Gebremikael, H. Wu, D. Cai, B. Wang, B. Li, J. Zhang, Y. Li, J. Xi. 2018. Response of soil organic carbon fractions, microbial community composition and carbon mineralization to high-input fertilizer practices under an intensive agricultural system. PLoS One 13(4): DOI: https://doi.org/10.371/ journal.pone.0195144 Lin, B. 2011. Resilience in agriculture through crop diversification: Adaptive management for environmental change. BioScience 6:183–93. Locatelli, B., C. P. Catterall, P. Imbach et al. 2015. Tropical reforestation and climate change: Beyond carbon. Restor Ecol 23:337–43. Luizão, F., P. Matson, G. Livingston, R. Luizão, and P. Vitousek. 1989. Nitrous oxide flux following tropical land clearing. Global Biogeochem Cy 3:281–5. Makate, C., R. Wang, M. Makate, and N. Mango. 2016. Crop diversification and livelihoods of smallholder farmers in Zimbabwe: Adaptive management for environmental change. SpringerPlus 5:1135. DOI: 10.1186/s40064–016–2802–4. Malhi, Y., and J. Wright. 2004. Spatial patterns and recent trends in the climate of tropical rainforest regions. Philos T R Soc B Biol Sci 359:311–29. Maranguit, D., T. Guillaume, and Y. Kuzyakov. 2017. Land-use change affects phosphorus fractions in highly weathered tropical soils. Catena 149:385–93. McGrath, J. M., and D. B. Lobell. 2013. Regional disparities in the CO2 fertilization effect and implications for crop yields. Environ Res Lett 8:014054. DOI: 10.1088/1748–9326/8/1/014054. McHenry, M. T., B. R. Wilson, P. V. Lockwood et al. 2009. The impact of individual Callitris glaucophylla (White Cypress Pine) trees on agricultural soils and pastures of the north-western slopes of NSW. Aust Rangel J 31:321–8. Mongi, H., A. Majule, and J. Lyimo. 2010. Vulnerability and adaptation of rain fed agriculture to climate change and variability in semi-arid Tanzania. Afr J Environ Sci Technol 4:371–81. Morton, J. 2007. The impact of climate change on smallholder and subsistence agriculture. Proc Natl Acad Sci USA 104:9680–5. Moss, R. H., J. A. Edmonds, K. A. Hibbard et al. 2010. The next generation of scenarios for climate change research and assessment. Nature 463:747–56. Müller, B., R. Lalou, P. Kouakou et al. 2015a. Le retour du mil sanio dans le Sine: Une adaptation raisonnée à l’évolution climatique. In Les sociétés rurales face aux changements climatiques et environnementaux en Afrique de l’Ouest, eds. B. Sultan, R. Lalou, S. Amadou, A. Oumarou, and M. A. Soumaré, 377–401. Marseille, France: IRD Publications. Müller, C., J. Elliott, J. Chryssanthacopoulos et  al. 2015b. Implications of climate mitigation for future agricultural production. Environ Res Lett 10:125004. DOI: 10.1088/1748-9326/10/12/125004.

TROPIcAL CROPS AND RESILIENcE TO CLIMATE CHANGE

101

Myers, S. S., A. Zanobetti, I. Kloog et al. 2014. Increasing CO2 threatens human nutrition. Nature 510:139–42. Nath, A., Lal, R. 2017. Managing tropical wetlands for advancing global rice production: Implications for land-use management. Land Use Pol 68:681–5. Naylor, R. L., D. S. Battisti, D. J. Vimont, W. P. Falcon, and M. B. Burke. 2007. Assessing risks of climate variability and climate change for Indonesian rice agriculture. Proc Natl Acad Sci USA 104:7752–7. Nguyen, A. L., Dang, V. H., Bosma, R. H., Verreth, J. A. J., Leemans, R., and De Silva, S. S. 2014. Simulated impacts of climate change on current farming locations of Striped Catfish (Pangasianodon hypophthalmus; Sauvage) in the Mekong Delta, Vietnam. Ambio 43(8): 1059–1068. http://doi.org/10.1007/ s13280-014-0519-6 Nicholas, I. D. 1988. Plantings in tropical and subtropical areas. Agr Ecosyst Environ 22/23: 465–82. Nwagbara, M. 2008. Landcover change in relation to climate change in northern Nigeria using GIS techniques. PhD Dissertation. Uturu, Nigeria: Abia State University. Nwagbara, M. 2015. Climate change and soil conditions in the tropical rainforest of Southeastern Nigeria. Am Res Inst Policy Dev 3:99–106. Oerke, E. C. 2006. Crop losses to pests. J Agric Sci 144:31–43. Olaleye, B., A. O. Barry, A. I. Adeoti, and D. Fatondji. 2006. Impact of Soil Water Conservation and Rainwater Harvesting Technologies on Improving Livelihoods Sahelian zone of West Africa. Sydney, Australia: Australian Society of Agronomy. O’Rourke, P., L. Winks, and A. Kelly. 1992. North Australia Beef Producer Survey 1990. Brisbane, Australia: Queensland Department of Primary Industries. Pandey, S., P. H. Brown, and M. T. McHenry. 2016. Plant root development as a measure of soil health. Acta Hortic 1123:41–6. Park, S. 2008. A review of climate change impact and adaptation assessments on the Australian sugarcane industry. Proc Aust Soc Sugar Cane Technol 30:1–9. Parmentier, S. 2014. Scaling-up agroecological approaches: What, why and how? Oxfam Discussion Paper. Belgium: Oxfam-Solidarity. https://ag-transition.org/wp-content/uploads/2014/01/201401-Scaling-upagroecology-what-why-and-how-OxfamSol-FINAL.pdf. (Accessed: October 26, 2017). Parry, M., and T. Carter. 1998. Climate Impact and Adaptation Assessment. London, UK: Earthscan Publication Ltd. Parry, M., C. Rosenzweig, A. Iglesias, G. Fischer, and M. Livermore. 1999. Climate change and world food security: A new assessment. Glob Environ Change 9:S51–7. Paustian, K., O. Andrén, H. H. Janzen et al. 1997. Agricultural soils as a sink to mitigate CO2 emissions. Soil Use Manag 13:229–44. Perfecto, I., I. Armbrecht, S. M. Philpott, L. Soto-Pinto, and T. M. Dietsch. 2007. Shaded coffee and the stability of rainforest margins in northern Latin America. In The Stability of Tropical Rainforest Margins, Linking Ecological, Economic and Social Constraints of Land Use and Conservation, eds. T. Tscharntke, C. Leuschner, M. Zeller, E. Guhadja, and A. Bidin, 227–264. Environmental Science Series. Berlin, Germany: Springer Verlag. Powlson, D. S., C. M. Stirling, C. Thierfelder, R. P. White, and M. L. Jat. 2016. Does conservation agriculture deliver climate change mitigation through soil carbon sequestration in tropical agro-ecosystems? Agric Ecosyst Environ 220:164–74. Raich, J. W., and W. H. Schlesinger. 1992. The global carbon dioxide flux in soil respiration and its relationship to vegetation and climate. Tellus B 44:81–99. Ramakrishnan, P. S. 1998. Sustainable development, climate change and tropical rain forest landscape. Climatic Change 39:583–600. Ramankutty, N., F. A. Foley, J. Norman J, and K. McSweeney. 2002. The global distribution of cultivable lands: Current patterns and sensitivity to possible climate change. Global Ecol Biogeo 11:377–92. Rockström, J., M. Falkenmark, L. Karlberg, H. Hoff, S. Rost, and D. Gerten. 2009. Future water availability for global food production: The potential of green water for increasing resilience to global change. Water Res Res 45:1–16. Rosegrant, M. W., M. Fernandez, A. Sinha, et al. 2009. Looking into the future for agriculture and AKST (Agricultural Knowledge Science and Technology). In Agriculture at a Crossroads, eds. B. D. McIntyre, H. R. Herren, J. Wakhungu, and R. T. Watson, 307–376, Washington, DC: Island Press. Rosenzweig, C., J. Elliott, D. Deryng et al. 2014. Assessing agricultural risks of climate change in the 21st century in a global gridded crop model intercomparison. Proc Natl Acad Sci USA 111:3268–73.

102

CLIMATE CHANGE AND CROP PRODUcTION

Rost, S., D. Gerten, A. Bondeau, W. Lucht, J. Rohwer, and S. Schaphoff. 2008. Agricultural green and blue water consumption and its influence on the global water system. Water Res 44:W09405. DOI: 10.1029/2007WR006331. Roudier, P., A. Muller, P. d’Aquino et al. 2014. The role of climate forecasts in smallholder agriculture: Lessons from participatory research in two communities in Senegal. Clim Risk Manag 2:42–55. Roudier, P., B. Sultan, P. Quirion, and A. Berg. 2011. The impact of future climate change on West African crop yields: What does the recent literature say? Glob Environ Change 21:1073–83. Salvador Sanchis, M. P., D. Torri, L. Borselli, and J. Poesen. 2008. Climate effects on soil erodibility. Earth Surf Proc Land 33:1082–97. Schimel, D. S., B. H. Braswell, E. A. Holland et al. 1994. Climatic, edaphic, and biotic controls over storage and turnover of carbon in soils. Global Biogeiochem Cy 8:279–93. Schlenker, W., and D. B. Lobell. 2010. Robust negative impacts of climate change on African agriculture. Environ Res Lett 5:014010. DOI: 10.1088/1748-9326/5/1/014010. Schroth, G., P. Läderach, A. I. Martinez-Valle, C. Bunn, and L. Jassogne. 2016. Vulnerability to climate change of cocoa in West Africa: Patterns, opportunities and limits to adaptation. Sci Total Environ 556:231–41. Scott, J., B. Webber, H. Murphy, N. Ota, D. Kriticos, and B. Loechel. 2014. AdaptNRM Weeds and Climate Change: Supporting weed management adaptation (Technical Guide). Available at: www.AdaptNRM.org Smith, P., D. Martino, Z. Cai et al. 2007. Agriculture. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, eds. B. Metz, O. R. Davidson, P. R. Bosch, R. Dave, and L. A. Meyer, 498–540, Cambridge, MA: Cambridge University Press. Stocker, T. F., D. Qin, G. K. Plattner et al. 2013. Technical summary. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, eds. T. F. Stocker, D. Qin, G. K. Plattner et al. 33–115, Cambridge, MA: Cambridge University Press. Strange, R. N., and P. R. Scott. 2005. Plant disease: A threat to global food security. Annu Rev Phytopathol 43:83–116. Sultan, B., P. Roudier, P. Quirion et  al. 2013. Assessing climate change impacts on sorghum and millet yields in the Sudanian and Sahelian savannas of West Africa. Environ Res Lett 8:014040. DOI: 10.1088/1748-9326/8/1/014040. Sylla, M. B., P. M. Nikiema, P. Gibba, I. Kebe, and N. A. B. Klutse. 2016. Climate change over West Africa: Recent trends and future projections. In Adaptation to Climate Change and Variability in Rural West Africa, eds. J. A. Yaro, and J. Hesselberg, 25–40, Cham, Switzerland: Springer International Publishing. Thornton, P., J. van de Steeg, A. Notenbaert, and M. Herrero. 2009. The impacts of climate change on livestock and livestock systems in developing countries: A review of what we know and what we need to know. Agric Syst 101:113–27. Thornton, P. K., P. J. Ericksen, M. Herrero, and A. J. Challinor. 2014. Climate variability and vulnerability to climate change: A review. Global Change Biol 20:3313–28. Tiedemann, A. V., and K. H. Firsching. 2000. Interactive effects of elevated ozone and carbon dioxide on growth and yield of leaf rust-infected versus non-infected wheat. Environ Pollut 108:357–63. Tighe, M., N. Reid, B. Wilson, and S. V. Briggs. 2009. Invasive native scrub and soil condition in semi-arid south-eastern Australia. Agr Ecosyt Environ 132:212–22. Tito, R., H. L. Vasconcelos, and K. J. Feeley. 2018. Global climate change increases risk of crop yield losses and food insecurity in the tropical Andes. Global Change Biol 24:e592–602. DOI: 10.1111/gcb.13959. Tothill, J., and C. Gillies. 1992. The Pasture Lands of Northern Australia: Their Condition, Productivity and Sustainability. St Lucia (Qld.), Australia: Tropical Grasslands Society of Australia. Trewin, B. 2017. Essay 1: The climates of the Tropics, and how they are changing. https://www.jcu.edu.au/stateof-the-tropics/publications/2014/2014-essay-pdfs/Essay-1-Trewin.pdf. (Accessed: October 26, 2017). Tubiello, F. N., J. S. Amthor, K. J. Boote et al. 2007. Crop response to elevated CO2 and world food supply: A comment on “Food for Thought.” by Long et al., Science 312:1918–1921, 2006. Eur J Agron 26:215–23. Uguru, M., K. Baiyeri, and S. Aba. 2011. Indicators of climate change in the derived savannah niche of Nsukka, south-eastern Nigeria. Agro-Science 10:17–26. United Nations. 2014. Vietnam: Climate change threatens rice production. https://videos.un.org/en/2014/10/07/ vietnam-climate-change-threatens-rice-production-2/. (Accessed: October 26, 2017).

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Usui, Y., H. Sakai, T. Tokida, H. Nakamura, H. Nakagawa, and T. Hasegawa. 2016. Rice grain yield and quality responses to free-air CO2 enrichment combined with soil and water warming. Global Change Biol 22:1256–70. Willcocks, J., and P. Young, 1991. Queensland’s Rainfall History: Graphs of Rainfall Averages: 1880–1988. Emerald, Australia: CSIRO, Pasture Management Branch, Queensland Department of Primary Industries Williams, J., and Jackson. 2007. Novel climates, no-analog communities, and ecological surprises. Front Ecol Environ 5:475–82. Wollenberg, E., S. Higman, H. Seeberg-Elverfeldt, C. Neely, M. L. Tapio-Bistrom, and H. Neufeldt. 2012. Helping Smallholder Farmers Mitigate Climate Change. Copenhagen, Denmark: CCAFS Policy Brief #5. World Bank. 2016. Vietnam: Sustainable farming for higher productivity and a better environment. https:// olc.worldbank.org/content/vietnam-sustainable-farming-higher-productivity-and-better-environment-0. (Accessed: October 26, 2017). Xie, L., Y. Li, and M. Lin. 2011. Response and adaptation to climate change of agriculture and environment in Northeast China. Chin J Eco Agric 19:197–201. Xue, F., P. Amilcare, and R. Ignacio. 2013. Changes in rainfall seasonality in the tropics. Nat Clim Change 3:811815. DOI: 10.1038/NCLIMATE1907. Yates, D. N., and K. M. Strzepek. 1998. An assessment of integrated climate change impacts on the agricultural economy of Egypt. Climatic Change 38:261–87.

CHapTer  7

Climate Change and Resilience of Agroecosystems Mitigation through Agroforestry, Permaculture, and Perennial Polyculture Systems Noureddine Benkeblia and Donka Radeva CONTENTS 7.1 Introduction........................................................................................................................... 105 7.2 Resilience, Sustainability, and Climate Change: Fate and Issues......................................... 106 7.3 Climate Change and Agroecosystems................................................................................... 107 7.3.1 Climate Change Mitigation through Agroforestry Systems...................................... 107 7.3.2 Climate Change Mitigation through Permaculture................................................... 108 7.3.2.1 Water Management in Agroecosystems under Permaculture..................... 112 7.3.2.2 Soil Protection and Rebuilding................................................................... 112 7.3.2.3 No Waste Production.................................................................................. 113 7.3.2.4 Agroecosystems Diversity.......................................................................... 113 7.3.2.5 Design of Microclimates............................................................................. 114 7.3.2.6 Conservation of Energy and Resources...................................................... 114 7.3.2.7 Forests and Food Forests in Permaculture.................................................. 114 7.3.2.8 Design for Catastrophe............................................................................... 115 7.3.2.9 Urban Permaculture Agroecosystems........................................................ 115 7.3.2.10 Social Processes, Food, and Economic Localization................................. 115 7.3.3 Climate Change Mitigation through Perennial Polyculture Systems........................ 116 7.4 Agroecosystems for Resilience and Sustainability................................................................ 119 7.4.1 Resilience................................................................................................................... 120 7.4.2 Sustainability............................................................................................................. 121 7.5 Agroecosystems, Local Plant Genetics, and Renewable Energy Resources......................... 123 7.6 Recommendations and Conclusion........................................................................................ 125 References....................................................................................................................................... 125 7.1 INTRODUCTION To face climate change threats and ensure food security of the growing population, agriculture around the world is making plans, innovating, and developing strategies and approaches for a sustainable agriculture and agroecosystems resilience. However, it is necessary to clarify ambiguities existing between the definition of the two concepts of resilience and sustainability, 105

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particularly what is meant by resilience in agriculture, because it is becoming apparent that the term resilience is not clear to many of us. We think that resilience is what makes an agricultural system sustainable. Indeed, there is a significant overlap in defining resilience and sustainability, therefore making less evident the power of resilience in improving agroecosystems and agriculture (Schewenius et al. 2014). In fact, going back to the 1970s, Holling (1973) introduced the concept that resilience aims “to help understand the capacity of ecosystems with alternative attractors to persist in the original state subject to perturbations.” Walker et al. (2004) defined resilience as “the capacity of a system to absorb disturbance and reorganize while undergoing change so as to still retain essentially the same function, structure, identity, and feedbacks.” Thus, and from the purely ecological point of view, resilience should be understood as the “ability of an agroecosystem to acclimate, experience shocks while retaining function, structure, feedbacks and, therefore, identity” (McPhearson 2014). Conceptually, sustainability was defined as “the methods used to manage resources in a way that guarantees welfare and promotes equity of current and future generation.” (Folke et  al. 2010; Tuvendal and Elmqvist 2012). Sustainability and resilience, rather than being purely ecological concepts, are becoming necessary tools to address environmental threats including climate change (CC). Because CC impacts are becoming more evident, it is urgent to start addressing the adaptation of the agroecosystems in a more coherent and efficient manner (Howden et al. 2007). By the end of the twenty-first century, CC is predicted to severely affect crop production, agroecosystems, and food security, and the impacts will be more or less severe depending on the vulnerability of the systems. Predictions are also indicating that small-scale farming systems would be more affected than large-scale ones. Scientists and farmers have started to realize that it is urgent to prepare for how to cope with CC by minimizing crop yield losses through agroecological practices such as climate-smart agriculture (CSA), agriculture resiliency, and crop diversification (Altieri and Nicholls 2017). Indeed, resilience and sustainability of agroecosystems under the CC models are reliant on both traditional management and agroecological strategies which include crop biodiversification, soil and water management, and CSA (Altieri and Nicholls 2017). It is therefore urgent to address agroecosystem resilience and sustainability in a more coherent manner because the existing options might be efficient for marginal changes of the climate, but they might not be efficient under extreme climate changes (Howden et al. 2007). 7.2  RESILIENCE, SUSTAINABILITY, AND CLIMATE CHANGE: FATE AND ISSUES The scale and diversity of human activities, including agriculture on agroecosystems, are increasing to the extent that our food production systems are under threat and therefore at risk of hunger, poverty, and even political instability throughout the different regions of the world. Extensive literature is readily available on CC and the potential resilience of our ecosystems by either incremental or transformational adaptation. However, rather than focus on accommodating the changes, it is more efficient to deliberate and think about how to mitigate these changes (O’Brien 2012). Model-predicted increases in temperature and carbon dioxide by the end of the twenty-first century will likely exceed the CO2 uptake capacity of the ecosystems, and plants will be much less able to cope with the increase of temperatures compared to the warming and glaciation under which they grew over millions of years. Until recently, it had been considered that the responses of ecosystems to human activities were linear and therefore could be predicted and controlled. There was also a strong assumption that natural systems could be treated independently from human ones (Folke et al. 2002, 2010). However, recent scientific evidence shows that ecosystems are undergoing

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challenging environmental conditions and are facing uncertain sustainability which can lead to unpredictable catastrophic climate events. Intensive cropping, harvest rates, and expansion of additional cropping systems have the potential to increase the undermining resilience of resource systems in the long term (Adger et al. 2011; Davoudi 2012). With the higher and increasing demand of food under the changing climate, agroecosystems are under high pressure to persist in the future if no actions are taken to reduce global warming and CO2 rise. Fundamental to coping with this change, it is crucial to develop approaches that possess abilities to mitigate risks and uncertainties by examining the ecological risks and build resilience for better sustainability (Dovers and Handmer 1992). Consequently, agroecosystems will likely change rather than disappear entirely, and some species will be more resilient than others and will show greater tolerance to the changing climate. International integration of management strategies that support reef resilience needs to be rigorously implemented and complemented by strong policy decisions to reduce the rate of global warming (Klein et al. 2005). Because sustainability relies to a great extent on resilience, this should then be translated to a real ability to mitigate perturbations with less damages to the systems, adapt to the resources of the systems, and develop and innovate positive changes (Holling 1973, 1986). 7.3  CLIMATE CHANGE AND AGROECOSYSTEMS CC may affect agroecosystems in many ways, and the increasing temperatures and CO2 levels, precipitation, and soil properties might impact plant growth and development, nutrient cycles, plantweed interaction, and pest and disease occurrence and biology (Fuhrer 2003). The response of agroecosystems to elevated CO2 and its associated changes depends on the magnitude of these changes and their impacts on plant species. As reported in other sections of this book (see also Chapters 2 and 3), elevated CO2 concentration on plant growth may lead to increasing crop yields as its concentration between atmosphere and leaf will increase. However, agroecosystems’ responses should be considered under different points of view, as each system might have a specific response. Therefore, it is necessary to consider CC impacts on the prevalence of environmental constraints to crop agriculture; the impact of CC on crop production potential, climate variability, and the variability of rain-fed crop production; changes in crop production patterns and changes in potential agricultural land (Fischer et al. 2002); as well as the effects of these changes on pests and diseases (Goudriaan and Zadoks 1995). However, to assess the impacts of CC on agroecosystems, long-term agroecosystem large-scale field experiments should be conducted for a period of at least 20 years. These studies should cover crop production, nutrient cycling, and environmental impacts of agriculture and crop production. The results will be valuable resources to evaluate biological, biogeochemical, and environmental dimensions of agricultural sustainability, and will be helpful in predicting future global changes (Rasmussen et al. 1998). 7.3.1  Climate Change Mitigation through Agroforestry Systems Agroforestry systems may offer CC mitigation as trees are considered a critical component of agriculture in many systems. Forests play a role in regulating atmospheric moisture, thus moderating drought or heavy precipitation, and also regulating soil temperature. Forests also enhance soil fertility with their role in the nutrient cycle, and increasing soil organic carbon (SOC) on agricultural lands through agroforestry could contribute to food security and improve biodiversity, the quality of water, and even positively impact hydrological cycles (Luedeling et al. 2014; Mbow et al. 2014a,b). Therefore, agroforestry systems, which consist of intentionally integrated trees and shrubs into crop and animal production systems, might be considered as potential means to manage land in and mitigate consequences of the changing climate (Schoeneberger et al. 2012). Several studies have

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Table 7.1 Examples of Positive or Negative Implications of Agroforestry Practices for Adaptation or Mitigation to Climate Change

Positive

Negative

Positive

• • • • •

Soil carbon sequestration Improved water-holding capacities Use of manure instead Mixed agroforestry for commercial products Income diversification with trees, reduced nitrogen fertilizer • Fire management

• Dependence on biomass energy • Overuse of ecosystem services; increased use of mineral fertilizers • Poor management of nitrogen and manure • Over extraction of non-timber products • Timber extraction

Negative

Adaptation

Mitigation

• Integral protection of forest reserves • Limited rights to agroforestry trees • Forest plantation excluding harvest

• Use of forest fires for pastoral and land management • Tree exclusion in farming lands

Source: From Mbow, C. et al. 2014b. Curr Opin Environ Sust 6:61–7, with open permission for use.

confirmed the potentials of agroforestry systems in mitigating CC by boosting synergetic actions between mitigation of and adaptation to CC (Table 7.1). Different studies suggested that adaptation to and mitigation of CC might be enhanced through agroforestry in different ways (Duguma et al. 2014; Matocha et al. 2012; Smith and Olesen 2010). The increase of atmospheric carbon dioxide might be mitigated and reduced by the agroforestry systems through carbon sequestration (Nair et  al. 2009; Powlson et  al. 2011), biomass increase (Gustavsson et al. 2007; Nowak et al. 2004), adopting recommended management practices (RMP) (Lal 2004; Lal et al. 2011), increase of soil organic matter (SOM) (Batjes 1998; Lal 1997; Paustian et al. 1997), biochar (Gurwick et al. 2013; Lorenz and Lal 2014; Woolf et al. 2010), and diversified agroecosystems and multi-cropping species (Bangwayo-Skeete et al. 2012; Lin 2011; Thornton and Herrero 2015). Indeed, agroforestry systems offer double potential in addressing CC: First is the greater capacity of the systems to capture resources compared to single or other species (Le Maire et al. 2013; Nair et al. 2009). Second, agroforestry systems are considered perennial farming systems, that is they provide energy, vegetation cover, and food, while simultaneously growing and developing their woody biomass and root system over the seasons (Forrester 2014). Nevertheless, agroforestry systems should not be considered as the tool of choice to mitigate CC, for numerous reasons. For example, there are many crops–trees–animals associations (Altieri 1999; Khumalo et al. 2012; Tores 1983), some of which match while others do not and might fail (Bolwig et al. 2006; Nair 2007; Pardini and Nori 2011; Torquebiau 2000; Wilkinson et al. 2000). On the other hand, the selection of the appropriate tree species and crops to establish this association is critical and should be done with care to ensure the success of the agroforestry systems (Fernandes et al. 1984; Jose 2009; Kater et al. 1992; Schaller et al. 2003; Schroth et al. 2002). 7.3.2  Climate Change Mitigation through Permaculture CC effects and their mitigation have influenced a complex network of areas and stakeholders— from concepts such as sustainable development and equity through transformation of energy systems, transport, buildings, industry, agriculture and forestry, human settlements, infrastructure and spatial planning, to international cooperation and regional development, national policies, investments, and finance. All these issues have been thoroughly elaborated on by Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Smith et al. 2014). The Intergovernmental Panel on Climate Change (IPCC) has declared that “warming of climate system is unequivocal” (Bernstein et al. 2007). This is based on analysis of the evolution of global temperatures, snow and ice covers, and sea-level rise. However, emissions during recent years have

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matched or even exceeded the IPCC’s most pessimistic forecasts (Torre et al. 2009). Socioeconomic damages from CC could be significant. Agriculture is one of the economic sectors which is suffering the most directly and with the greatest impact from gradual changes in temperature and precipitation. In a study about South American farms, average estimated revenue losses from climate change in 2100 ranges from 12% for a mild CC to 50% for a severe scenario, even with adaptive measures undertaken from farmers (Torre et al. 2009). The same estimations for Mexico forecast loss in productivity from 30% to 85% for all farmers in different climate scenarios. According to this study, losses are forecasted to be higher nearer the equator with some exceptions on the Pacific and in the south of Latin America, where some gains are expected. For example, Caribbean nations are likely to suffer more from climate changes due to hits from multiple fronts, intense natural disasters, and the decline of marine ecosystems. This will be connected with permanent economic losses (Torre et al. 2009). Scientists from this study reckon that for the Latin American and Caribbean regions there is a great climate mitigation potential for agriculture if practices for agronomic and livestock management are improved and carbon storage in soils or vegetative cover are enhanced. Prasad et al. (2009) pointed out in their study that human-induced greenhouse gases (GHG) emissions are main factors in the evident global CC. The largest contributors to GHG emissions are the USA, China, Indonesia, Brazil, Russia, and India, while East Asia is the major emitter. Energy, agriculture, forestry, and waste are the core sectors causing emissions. In the chapter “Agriculture, Forestry, and Other Land Use” from Climate Change 2014: Mitigation of Climate Change, the main role of agriculture and forestry sectors is underlined as critical because the mitigation potential is on two levels—enhancement of removals of greenhouse gases (GHG) and reduction of emissions through management of land and livestock. The authors point out the importance of land as provider of food for the human population. Agriculture has a central role for sustainable development and for the livelihoods of many social groups, especially in developing countries (Smith et al. 2014). Emission of GHGs in the agriculture and forestry sectors increased by 20% from 1970 to 2010, contributing about 20%–25% of global emissions in 2010 (JRC-PBL 2013). Drivers of emissions from these sectors are increased livestock numbers, areas under agriculture, deforestation, use of fertilizer, areas under irrigation, per capita food availability, consumption of animal products, and increased human and animal populations (Blanco et al. 2014). According to Blanco et al. (2014) possible mitigation activities in agriculture and forestry can reduce climate forcing such as: • Reduction of emissions from croplands, grazing lands, and livestock; • Conservation of existing carbon stocks through conservation of forest biomass, peatlands, and soil carbon; • Reduction of carbon losses from biota and soils through management changes (e.g., reducing soil carbon loss by switching from tillage to no-till cropping) or by reducing losses of carbon-rich ecosystems (e.g., reduced deforestation, rewetting of drained peatlands); • Enhancement of carbon sequestration in soils, biota, and long-lived products through increases of carbon-rich ecosystems such as forests (afforestation, reforestation), increased carbon storage per unit area (increased stocking density in forests, carbon sequestration in soils), and wood use in construction activities; • Changes in albedo resulting from land-use and land-cover change that increase reflection of visible light; • Provision of products with low GHG emissions replacing products with higher GHG emissions for delivering the same service (e.g., replacement of concrete and steel in buildings with wood or some bioenergy options).

However, it should be mentioned that whether a particular ecosystem is functioning as sink or source of GHG, its emissions may change over time, depending on its vulnerability to CC and other stressors and disturbances. Therefore, mitigation options available today (and described previously) for agriculture and forestry may not be available in the future (Blanco et al. 2014).

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In addition, mitigation potential in the agricultural sector is highly site-specific, even within the same region or cropping system (Baker et al. 2007; Chatterjee and Lal 2009). Limited resources can also become an ecological barrier, and the decision of how to use them should balance ecological and societal needs (Jackson 2009). In our discussion about climate change mitigation measures, we will have in mind both measures for reducing GHG emissions for slowing down global warming and other climate trends, reducing the severity of future disasters, as well as adaptation actions for humans and agroecosystems for less damages or possible benefits from CC. There are climate changes that cannot be reduced, but suitable adaptation measures should be considered for them. As an example, sea level rise cannot be reduced. Instead, flood-control systems could be implemented in risky regions (Prasad et al. 2009). Other climate changes like increase in temperatures and precipitation could be mitigated with different measures. It is important to understand the connection between global warming and precipitation. Higher temperatures and evaporation increases lead to more precipitation. However, precipitation has increased significantly in eastern parts of North and South America, northern Europe, and northern and central Asia. At the same time, it has become drier in the Sahel, the Mediterranean, southern Africa, and parts of southern Asia. Mostly, precipitation decreased over the tropics since the 1970s. The number of heavy precipitation events increased over many areas, while droughts increased predominantly in the tropics and subtropics (Prasad et al. 2009). According to the authors of Climate Resilient Cities: A Primer on Reducing Vulnerabilities to Disasters, sound mitigation practices for temperature changes from CC seem to be greenery projects (e.g., rooftop gardens), improved building design, and insulation. Among mentioned mitigation practices for precipitation changes are redesigning stormwater drainage canal systems, holding ponds under roads and parks for avoiding floods, and dike systems for protections from typhoons and rising sea levels. The authors also consider that changes in lifestyle, behavior patterns, and management practices have a significant potential to mitigate climate changes in all sectors. In his book World on the Edge: How to Prevent Environmental and Economic Collapse, Brown (2011) refers to the subject of CC by introducing the term “ecological refugees” as one of the major problems of the ecological collapse on the planet. The first group of ecological refugees is that affected by an increase in sea levels. The most vulnerable countries in this group are China, India, Bangladesh, Vietnam, Indonesia, Japan, Egypt, and the USA. The second group of climate refugees is affected by global warming—mainly people from Central America, the Caribbean, the Atlantic Ocean and the Gulf of Mexico coastlines of the USA, as well as Japan, China, Taiwan, Philippines, Vietnam, the Bay of Bengal, and especially Bangladesh. The third group of refugees is affected by the expansion of deserts with most at-risk groups being from Morocco, Tunisia and Algeria, Iran, Brazil, Mexico, and China. The fourth group is affected by lack of water, and this creates refugees from northern and western China, northern Mexico, and the Middle East. The fifth group of refugees is affected by toxic waste materials, radiation, and “cancer settlements.” This group includes people from the USA, China, Ukraine, Belarus, and Russia. There is a long list of 124 fragile states classified under warning to very high alert (in the past called “failed” states or index for failed states), elaborated from the Fund for Peace (Messner et al. 2017). Of these countries, 15 are in the group with high and very high alert, like Sudan, Syria, Yemen, Central African Republic, Somalia, South Sudan, Ethiopia, Nigeria, Zimbabwe, Guinea, Haiti, Iraq, Afghanistan, Chad, and Congo (D.R.). Other reports state that the number of chronically undernourished people on the planet increased in 2016 by about 40 million to 815 million (from 777 million in 2015). After a prolonged decline, this recent increase shows a reversal of trends. The food security has worsened mostly in parts of sub-Saharan Africa, Southeastern Asia, and Western Asia. Observations indicate that reasons for this trend are mainly conflicts combined with climate change, like droughts or floods (FAO 2017). Reasons for the recent collapse of the governments of these countries include their inability to provide food security. This is not due to incompetence of their governments, but because providing food security is

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becoming increasingly difficult now. The fragile countries with the highest risk deplete their natural resources—forests, pastures, soils, and water-bearing layers—and they lose land fertility due to high erosion (Brown 2011). Based on all these alerts, Brown (2011) has developed a plan as a response to the challenges for the planet. The plan includes four components of activity—stabilizing of climate, recovering the supporting systems of the planet, stabilizing the world population, and eliminating poverty. All four goals of this plan are interrelated. It became evident how important the connection is between CC, recovering of the ecosystem functions on the planet, removing of poverty, and governance of the agroecosystems in a sustainable way. One concept which is finding solutions for all these issues is permaculture. And this is because it is based on system thinking. Very often in the permaculture literature, readers will come across Mollison’s main principle: the “problem is the solution.” Permaculture (first known as “permanent agriculture”) was theoretically elaborated in the 1970s and first created in Australia by Bill Mollison and David Holmgren. In Permaculture: A Practical Guide for a Sustainable Future, Mollison states, “Permaculture (permanent agriculture) is the conscious design and maintenance of agriculturally productive ecosystems which have the diversity and resilience of natural ecosystems. It is the harmonious integration of landscape and people providing their food, energy, shelter, and other material and non-material needs in a sustainable way.” (Mollison, 1990). Permanent agriculture or permaculture is an ecological concept for sustainable design and sustainable agriculture as an approach in agroecology, which is connected to production of ecological food in diversified farming systems. The main focus of permaculture is production of food, but the concept is further expanding to many other fields of life such as ecological building, local economies, development of local communities, etc., using theoretical and practical applications. Permaculture is also a philosophy of life, based on principles and on ethical frame of mind. It is also an international ecological movement, which is popular in more than 100 countries and is constantly growing. Achieving permanence in agriculture has a positive ecological effect in the long-term. It is connected with maintenance and rebuilding of agroecosystems, with the opportunity to practice farming under all conditions including in deserted lands, depleted and polluted soils, or under unfavorable climates. The goal is building permanent relationships between people as well as achieving the recovery of small communities. This is a process of complex acquisition and development of knowledge, practices, and ethics, and future generations will be able to evaluate its overall effect (Radeva 2017). Permaculture is constantly developing worldwide. Nowadays, permaculture has followers on all continents—individual practitioners, teachers, formal and informal groups of people, institutes, colleges, and business organizations. Permaculture is a design tool to help you take all the garden elements you want (e.g., greenhouse, vegetables, shed, small fruits, pond) and integrate them in such a way that they become more than the sum of their parts. The core for practicing permaculture is studying and implementing its basic design principles and the three ethics. The principles are detailed, explained, and elaborated by David Holmgren (2002) in his book Permaculture: Principles and Pathways Beyond Sustainability. The principles include maxims such as: observe and interact, catch and store energy, obtain a yield, apply selfregulation and accept feedback, use and value renewable resources and services, produce no waste, design from patterns to details, integrate rather than segregate, use small and slow solutions, use and value diversity, use edges and value the marginal, creatively use and respond to change. The three ethics are earth care, people care, and fair share. Care for the earth means care for the soils as living ecosystems, care for the forests, and care for the rivers and water systems of the planet. Care for people means care for the family, for neighbors, for the local community, and for the greater community and the whole planet. It is taking responsibility for the greater community and sharing knowledge for increasing its self-sufficiency. Fair share means first recognizing the limits to population growth and consumption. After recognizing these

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limits, it directs to share abundance with the community—sharing abundance in production or pollution (pollution in permaculture “language” means “resource in excess, which is not utilized productively”), investing profit in resilient projects, and sharing knowledge. The permaculture ethics are appealing in that everybody takes personal responsibility for their actions. We can either “choose to be part of the problem or part of the solution!” (Deep Green Permaculture 2018) The authors of Permaculture and Climate Change Adaptation (Henfrey and Penha-Lopes 2015) determine different strategies for coping with climate change, based on common patterns at a general level, and applied where similar problems appear and can be solved with a suitable strategy. In general, the set of strategies cover a wide array of topics, which can be classified within the three ethics of permaculture. Strategies set for achieving care for the earth are water management, soil protection, revegetation, agrodiversity and agroecology, microclimates and bioclimatic building, and energy descent. Strategies for achieving care for people are bioregionalism and economic localization, regenerative enterprise, conflict transformation, personal resilience, and changing worldviews. Strategies for realization of fair share are governance of commons, indigenous and local knowledge sharing, and permaculture education. The identified strategies at the same time serve as tools for climate change adaptation and for implementation of permaculture ethics. Here the complexity in implementation and the interdisciplinary nature of the permaculture concept becomes visible. Permaculture is suitable for all climate conditions and zones, can be practiced on land plots with depleted or polluted soils, and it gives solutions for deserted regions. There are successful examples everywhere in the world. With some exceptions, the core of permaculture is in small decisions, practicing on small scales and under small-scale risks—often a permaculture training course emphasizes to “keep it slow, keep it local.” This is hidden in the permaculture principle “small and slow solutions.” 7.3.2.1  Water Management in Agroecosystems under Permaculture Permaculture provides different solutions for preserving fresh water in agroecosystems, for coping with excess rainfalls, run-off reduction, and erosion. Keeping in mind the increased precipitation on the planet (differently distributed on the planet) as a consequence of climate change, water management turns out to be of high significance. Techniques like rainwater catchment vary from discovering of main ridges (defines catchment of water courses) and key points (the point of collection and concentration of water on a landscape) to building of swales and garden ponds, constructing of dry composting toilets, and systems for purifying of collected water with water plants and other tools for safe greywater usage. Soil storage of water is another key strategy for in-ground storage. Building up of humus and organic matter levels in soil and using mechanical methods for decompaction of overgrazed or compacted soils is of great importance (Francis 2007–2008). There are also practices like mulching with straw and adding of organic material in beds, used for decreasing evapotranspiration and keeping moisture in the soil. On the other hand, high raised beds are designed for rainy and damp areas for good water drainage. Water management design of permaculture agroecosystems depends on the local climate conditions like annual precipitation (average and maximum) and duration of the driest periods of the year. 7.3.2.2  Soil Protection and Rebuilding Permaculture emphasizes soil protection and techniques for its rebuilding. In his calculations, Yeomans showed to Esalen Congress on Sustainable Agriculture in 1990 that a net rise of 1.6% in the organic matter content of the soils would sequester excess atmospheric CO2. Currently, according to him, 2% is probably closer to the mark because of the rise in human population numbers (Yeomans 1990, 2018).

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Another study claims that croplands worldwide could sequester between 26% and 53% of the target of the Paris Climate Agreement, and there is general agreement on the significance of carbon sequestration potential of soil. Moreover, an extensive body of research has shown that land management practices can increase soil carbon stocks on agricultural lands with practices like addition of organic manures, cover cropping, mulching, conservation tillage, fertility management, agroforestry, and rotational grazing (Zomer et al. 2017). The practices mentioned previously, namely addition of animal manures, cover cropping, mulching, no tillage, fertility management of soil, and others like adding compost, compost tea, biochar, and rock dust for improving fertility and structure of the soil are widespread in permaculture agroecosystems. 7.3.2.3  No Waste Production Reuse, recycle, repair, refill, and the usage of one output as input into another thing are principles set in the concept of permaculture and its practitioners’ culture. Pollution in permaculture means unutilized productivity, that is why in a permaculture agroecosystem there is negligible small waste to be found. Organic waste and animal manures are composted, weeds are either food for the animals in the system or composted, and pests are food for their predators in the designed natural agroecosystems. All the elements in the agroecosystem support each other’s functions, and this creates a synergy effect. The system functions like a small circle economy. Only a small quantity of external resources is imported into the system, and there is no need of chemical fertilizers and pesticides. Overall decreased consumption in a permaculture system and no usage of chemical inputs generally could lead to decrease in demand and production process of polluting industries for conventional agriculture, and thus help to tackle increased GHG and climate change. 7.3.2.4  Agroecosystems Diversity Permaculture agroecosystems are characterized by high diversification of crops, usually integrated with trees and animals in the system. The goal is achieving resilience to climate extremes and damages from pests, and also guarding against market fluctuations and ensuring availability of healthy food in a greater variety of products. All the integrated elements in the agroecosystem support each other’s functions in efficient ways. This is demonstrated in the following definition of permaculture: “A method of establishing permanent, self-sustaining systems of agriculture, adaptable to both rural and urban locations, designed to produce an efficient, low-maintenance, optimally productive integration of trees, plants and animals, structures and human activities within a specific environment” (Elkington and Hailes 1988). Diversification of agroecosystems is important, keeping in mind that the majority of the world’s arable land is under monoculture systems, which are particularly vulnerable to climate change. This applies even to some large organic monoculture fields (Kazakova and Radeva 2015). Ehrmann and Ritz (2014) point out multiple studies that examine the advantages in mixed cropping systems compared to single crops. They include more efficient use of available resources and niches, facilitation via the roots, enhanced soil fertility by intercropping nitrogen-fixers, increased resilience against pests and diseases, and increased abiotic stress resistance due to higher levels of functional diversity within the system. These are serious advantages when working towards resilience and climate change. Altieri and Koohafkan (2013) demonstrate in their studies the significance of the agroecological development paradigm against poverty, based on the revitalization of small farms, which emphasizes diversity, synergy, recycling, and integration. The authors reckon that “traditional agroecosytems have the potential to bring solutions to many uncertainties in an era of climate change, energy, and financial crisis” (Altieri and Koohafkan 2013).

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7.3.2.5  Design of Microclimates One of the aims of permaculture design is to control and adapt agroecosystems to specific climate conditions such as heat, cold, sun, shade, wind, or frost. This could be achieved by using a large variety of practices. Some widely used practices are sector analysis of the land plot and cold air drainage, controlling soil temperature and moisture through mulching, forest vegetation for creating of mild climate or windbreaks. Others include options for stabilizing the local climate, temperatures, and creating reflection of heat and light through water masses or building of greenhouses, usage of shadow nets over the planting beds for resisting the heat, utilizing of “sun pockets” and “sun traps,” and many other design techniques. Through microclimates, local climate can be controlled and adaptation to climate changes like resistance to increased heat or rainfall or climate extremes (storms, flood) becomes achievable. Creating of microclimates additionally allows higher diversification and growing of crops untypical for the local climate. Especially poor regions with bad climate conditions and suboptimal food nutrition intake can benefit a lot from microclimates. 7.3.2.6  Conservation of Energy and Resources Two major permaculture principles stand behind the goal for conservation of energy and resources in permaculture agroecosystems, namely the principle catch and store energy and the principle use and value renewable resources and services. There are three key strategies for achieving conservation through permaculture design (Francis 2007–2008):





1. Behavioral—choosing the active time of the day for work, use of natural daylight in production processes, reducing footprint (“think globally and act locally”), developing new habits, for example, for conserving water, waste recycling, etc. 2. Bio-climatic—building of residential structures, water and waste water structures, gazebos, nurseries, toolsheds, animal structures, paths, and roads. Designs should take into consideration features for tropics, subtropics, or temperate climate. Orientation, shade, ventilation, and insulation of structures should be considered. Using renewable building materials when possible, building of greenhouses and ponds, creating of microclimates, which are measures for mitigation of climate changes (reduce climate forcing through fossil energy conservation and changes in albedo). 3. Technological—including choice of appropriate technologies for: (a) climate control (e.g., usage of radiant heat, compost heat, gasification); (b) hot water supply (e.g., solar water heaters, thermal water); (c) renewable electricity generation (photovoltaics, wind power); (d) refrigeration and cooling with solar fridges, usage of cool storages; (e) strategies for conservation of water (water tanks, building of rainwater catchment systems, ponds and hydraulic systems, dry compost toilets, grey water recycling irrigation).

The strategies for energy and resource conservation through permaculture design are diverse. One disadvantage for some of the practices is the high investment costs they require. Also, scientists argue about the environmental costs for producing some solar technologies and the uncertainty of the rate of energy conservation compared to some fossil fuel technologies. 7.3.2.7  Forests and Food Forests in Permaculture The role of forests in climate change mitigation is significant and so is their importance for permaculture agroecosystems, especially when designing a food forest. This subject has much in common with agroforestry systems and at the same time with the perennial polycultures, whose impact on climate change matters is comprehensively discussed later in this chapter.

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7.3.2.8  Design for Catastrophe In regions with high potential of catastrophes like floods, fire, land movements, hurricanes, cyclones, storms, tides, or volcanic eruption, historical information such as frequency, severity, duration, and risks for such extremes should be collected to assess the resistance of agroecosystems. Local disaster response strategies and authorities’ procedures should be studied. Through permaculture design, location of building structures and cropped areas should be carefully considered, and plantings should be chosen to be able to withstand these extraordinary energies. Strategies include considering of topography, vegetation type, access and roads location, designing of protected areas for houses, machinery, stock areas, fodder reserves, water storage, securing irrigated areas, orchards, and food forest. Wind breaks, stone walls, green summer crops, and planting fireresistent trees and shrubs are some practices against risks from fire (Francis 2007–2008). 7.3.2.9  Urban Permaculture Agroecosystems Considering that cities and metropolitan areas have a huge impact on the pollution and greenhouse effect on the planet, they represent a great potential to be developed as transition towns (Transition Network 2018), where circle economies should be developed for maximizing ecological, social, and economic benefits. In cities, urban permaculture design principles are widely applicable, for example, in city building, infrastructure, for social and educational goals, and for creation of urban agroecosystems for food production and greening effect. Transition towns projects are being developed everywhere in the world, and though they are still mainly small projects, their impact is impressive, as they serve as sustainable models for behavioral change of the city residents. Urban permaculture is widely developed not only in transition towns, but it appears in many big cities on all continents in different forms and scales. Comprehensive research by twenty-six scientists from eleven European Union countries within the COST (European Cooperation in Science & Technology) network was conducted, where more than one hundred case studies of urban agriculture were analyzed for a three-year period (Lohrberg et al. 2016). The social, ecological, and economic impacts of urban agriculture were studied. Urban permaculture agroecosystems may include urban backyards, rooftop and balcony gardens, community gardens, and permaculture educational gardens in kindergartens (The Organic Gardens of Learning—First Steps in Bulgaria 2012–2013) and schools, and small gardens with business goals. 7.3.2.10  Social Processes, Food, and Economic Localization Food and economic localization are some of the influential social phenomena that have spread worldwide and impacted the new alternative agriculture.* These processes represent the main factors for emergence and drive of such alternative forms as the permaculture agroecosystem. The last decades showed forced world tendencies toward movements like Slow Food (Slow Food 2015), preferences for local products (Local Food), taking part in the production of food (“eating is an agricultural act”), and development of local economies (Local Economies Project of the New World Foundation 2018). Their emergence is connected with new attitudes of people to nature and biodiversity and with growing importance of healthy food. These processes forced the establishment of new ethical attitudes toward different social groups in society and toward groups in isolation. Followers of the permaculture concept and ecological networks emphasize the uniting of local communities and restoring local economies (Radeva 2017). For instance, according to studies * More about the phenomenon “new alternative agriculture” can be found in Radeva, D. 2017. Economics of the New Alternative Agriculture in Bulgaria. Permaculture. Dissertation, defended on June 12, 2017 at the University of National and World Economy, Sofia.

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conducted with the support of the European Association for Information on Local Development, at least 2,000 community-based initiatives directly engaged in withstanding climate change were discovered in Europe (Eamon 2013). The organization Slow Food connects the food process with many other aspects of life—culture, politics, agriculture, and environment. The Local Food network also has a significant role, in that it aims to develop connections between producers and consumers of food within same geographical region in order to achieve sustainable and self-reliant food systems. Local Food systems improve local economies and support their independence from import of external products and services. Moreover, they influence health, ecology, and building of communities in a particular region (Feenstra 2002). Economic localization aims to shift focus on production of food to more sustainable regional and farm economies. Some of the goals are emergence of economically viable farms and supporting businesses which produce and process local food, create employment on a local level, and improve the ecological footprint. Another social process connected with the idea of food and economic localization is the growing negative attitude toward corporations and monopolies (OccupyWallStreet) striving to win (Slow Money 2018). The political, economic, and social movement of degrowth in the economy is based on ecological economics and anti-consumerism. Agriculture nowadays is influenced by ideas like promotion of small companies and even those “without wins,” attracting people for volunteer work, decreasing the exploitation of natural resources, preserving biodiversity, implementing of co-working spaces and even co-housing, and minimizing waste from production (Terziev and Radeva 2016). The commons movement (The Commons Network 2016) is another social phenomenon, devoted to the “community spirit” as an alternative, complete, sustainable, and social worldview. This worldwide network in the past few years has followed Elinor Ostrom—a 2009 Nobel laureate in Economics, for her work in the field of governing the commons. In some aspects, their ideas fall in the scope of the work of social, solidarity, and sharing economy, peer-to-peer economy, degrowth movements, and also the permaculture movement. All above-mentioned social phenomena are significant drivers of behavioral and economic changes and are from-the-bottom-up initiatives that are very influential and have high potential to spread rapidly and to tackle climate changes from the deep levels of personality transition to a better future of this planet. 7.3.3  Climate Change Mitigation through Perennial Polyculture Systems Perennial polyculture systems have been increasingly studied in the last decade in the search of new pathways to tackle global problems like environmental degradation and poverty. The permaculture concept with its origin in the 70s strongly embraces the idea of building perennial polyculture systems, while intercropping them with annual polycultures. Despite its forward-looking conceptual practices and the increase of academic studies in recent years, formal evidence on the impacts of permaculture is still limited. And in spite of the limitations, permaculture impact as a grassroots movement with few or no financial resources is impressive in spreading climate change solutions across the planet (Henfrey and Penha-Lopes 2015). Annual plants represent about 80% of the food crops in the world just after the Green Revolution. Perennial food plants are a minority in terms of their share in humans’ nutrition. Perennial polyculture has a lot of advantages like saving efforts in digging, sowing seeds, and cleaning up at the end of the season. Perennial plants have very deep roots, and they are better adaptable to extreme conditions. Annual plants, on the other hand, require large amounts of available soil nutrients to support their rapid growth rates. This is because the nutrients lying deeper in the soil are inaccessible to them, as their roots do not reach deep enough. Annual plants need more irrigation and water resources, as the water seeps deeper into the soil and they are unable to access it. Perennial polyculture systems need less fertilizers and water due to their slow growth and deep root systems and in some way

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are more productive than annual ones. In warmer climates, perennial plants can grow continually, while in colder climates they become dormant in winter and resume growth after the cold season. The very long roots of perennials are also important for stabilizing steep slopes and river banks, and this makes them valuable in design for floods. Perennial plants create stable ecosystems such as forests or edible forests and create habitats for flora and fauna. Growing perennial food plants is more sustainable and energy efficient and requires much less work overall (Eliades 2012). Most of the cereals that people consume, like wheat, rice, oats, corn, and maize, are grown as annual plantings and mostly in monocultures. Cereals account for at least half of the dietary energy worldwide (World Health Organization 2003). That is why a transition to perennial polycultures with mixed intercropping would be a significant change in agriculture globally (Dewar 2007). Well-developed perennial polyculture agroecosystems should include vegetables, nuts, fruits, and grains. The effect of perennial polyculture systems is to tackle environmental problems that are evident in current annual monoculture systems. Some of these global problems are soil erosion and degradation, water resources depletion and pollution from fertilizers, herbicides, and pesticides. This is of particular significance with respect to Africa, which is the continent that could most benefit from perennial polycultures (Dewar 2007). Cultivating perennial cereal grains that can be harvested continuously for 4 to 5 years without tilling and replanting—in place of annual grains whose energy-intensive spring and fall tilling exposes soil to wind and water erosion—could reduce erosion by as much as 50%, saving $20 billion worth of soil and $9 billion in tractor fuel every year in the United States. Genes for perennial cereal grains already exist in wild plant species (Pimentel et al. 1997). According to Jackson (2002), there is a new paradigm called natural systems agriculture (NSA), which emphasizes perennial food-grain-producing systems, where soil erosion is near zero and chemical contamination from agrochemicals and agriculture’s dependence on fossil fuels increasingly drops. Some authors claim that perennial polyculture crops offer the highest potential of any food production system to sequester carbon. However, the greatest challenges are their establishment and management, and also the willingness of consumers to adapt their diets to unpopular perennial crops. Perennial crop plantings can provide a balanced diet consisting of proteins (e.g., perennial beans), carbohydrates (e.g., bananas, peach palms, air potatoes), and fats (e.g., macadamia), and they also serve as building materials and energy. The best perennial crops are native to and grown in the tropics, where the highest carbon sequestration options are concentrated (Toensmeier 2016). A study from Oaxaca (Mexico) analyzed adaptation practices of small farmers and their preparation for climate challenges and how they deal with recent increases in temperature and rainfall intensity and later rainfall onset (Rogé et al. 2014). Farmers from the case study observed that vegetated borders and perennial vegetation with multiple uses mitigated exposure to extreme climatic events. Similar results of another group of farmers from this research showed that heterogeneous and forested landscapes protected fields by bringing rain, retaining groundwater, accumulating soil organic matter, and controlling insect pests. At the Land Institute in Kansas (USA), researchers for more than 30 years have developed herbaceous perennial grains to be grown in mixed species polycultures. The result is crops with deep root structures able to survive the winter and stay in the soil for many years. This reduces the largest energy input in agroecosystems, as there is no need to crop, turn, and plant seeds each year. Additionally, carbon is kept in the ground, the harmful runoff with no-tilling is reduced, and biodiversity loss is prevented by restoring systems. According to the scientists from the Land Institute, “perennialization of the 70% of cropland now growing grains has the potential to extend the productive life of our soils from the current tens or hundreds of years to thousands or tens of thousands” (Jackson 2010). Resilience of the new perennial crops to climate change is indisputable, as they will increase sequestration of carbon and will reduce the land runoff that is creating coastal dead zones and

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affecting fisheries. The Land Institute has developed a 50-year plan for change based on the transition to perennial agriculture with the goal to move the United States to sustainable agricultural production. An eight-year period for developing of perennial grain, legume, oilseed crops, and other needs of these agronomic systems is included in the plan, with a proposal for federal funding sponsorship. Additionally, the Land Institute funded a breeding project of the Yunnan Academy of Agricultural Sciences in southwestern China for perennial upland rice. Keeping in mind that millions of people in Asia depend on annual rice production, which causes erosion, use of perennial systems could turn into huge opportunity for mitigating climate change and hunger. Scientists from the Institute hybridized grain sorghum and produced large plant populations from this crop, whose annual relative is currently a drought-hardy feed grain in North America and a staple human food crop in Asia and Africa. Sunflower is another annual crop that was hybridized with perennial species. Illinois Bundleflower is a native legume that fixes atmospheric nitrogen and produces protein-rich seed, and this plant could be a partial substitute for the soybean. Wheat has also been hybridized by the Land Institute with different perennial species. Scientists from this research group believe that the same American approach to improving agriculture that led to the first worldwide Green Revolution could lead to a sustainable green revolution. Perennial plants are able to tackle many of the problems of annual grains and at the same time maintain agricultural production, but more research is required (Jackson 2010). Extended scientific research was conducted with examples of perennial polycultures, based on sufficient evidence of the ecosystem functions of legume—on grass mixtures and on case studies from Germany for wildflower mixtures. The results from the study point out that perennial polycultures enhance soil fertility, soil protection, climate regulation, pollination, pest and weed control, and landscape aesthetics compared with maize. The authors claim that perennial polycultures potentially will contribute to the sustainable management of agricultural systems, and the integration of perennial polycultures in crop rotation effectively provides diverse ecosystem services (Weibhuhn et al. 2017). On the whole, compared with monocultures, polyculture systems are potentially more complex to manage and require substantial farmer skills and specific research efforts (Malézieux et al. 2009). Perennial polycultures are mainly of three types—nuts and other food trees; oil palm, coconut, and other oil-producing plants for fuel and food; and fast-growing perennials such as poplar and eucalyptus for rapid production of wood biomass. Tree nuts are considered a successful substitute of meat diet because of their content of proteins and beneficial fats. A decrease in meat consumption globally will lead to smaller amounts of released GHG, decreased overgrazing and soil compaction, and a step toward mitigation of climate changes. Perennial grasses and legumes are rich in nitrogen, and as previously mentioned are also perennial grains for forage and food. An example of a largescale perennial planting with sea buckthorn from northwest China on 1.2 million ha has counteracted the soil erosion, land degradation, and has created a sustainable local business. Another advantage of perennials is that fuel from biomass is not only carbon neutral, but it also fertilizes the soil while fixing carbon into it. Furthermore, producing biofuels from perennials would lead to less dependence on fossil fuels and has potential to create employment and decrease poverty especially in developing countries (Kahn et al. 2011). As mentioned already, permaculture strongly emphasizes the importance of using perennial plants in our food production systems. Through the extensive use of annual crop-based agriculture, we are systematically destroying living ecosystems which support many living organisms, flora, and fauna, and replacing them with artificial systems composed solely of annuals, which cannot exist naturally in this state without excessive inputs of energy. The end result is that we are also destroying the soil as a consequence, losing it to salinity and erosion, at a time when the planet’s demand for arable soil for food production is increasing due to population growth. By decreasing usable land and increasing food production, we are exponentially increasing the demands on the planet, pushing it to a breaking point at an ever-increasing rate. In 2015 at the International Permaculture Convergence in London a new organization was created under the permaculture movement—Permaculture Climate Change Solutions. A Climate Change

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Statement and an Action Plan were adopted by the General Assembly of the Convergence (Henfrey and Penha-Lopes 2015). The Climate Change Statement includes a petition that permaculture is an integration of knowledge and practices drawn from many disciplines and linked to solutions for satisfying human needs and ensuring a resilient future. Permaculturists claim that human-caused climate change should be tackled systemically. According to the Statement, efforts for mitigating climate change must secure social, economic, and ecological justice. Identified barriers in that goal are political and social, but not technical. Solutions to climate change mitigation and adaptation are protection, restoration, and regeneration of ecosystems and small communities. Strategies for action were also developed during the International Permaculture Convergence (Permaculture Solutions for Climate Change 2015). Permaculture is not about any particular type of food production, although it helped to develop and popularize the notion of perennial polycultures. The simple elegance of this idea has captivated me for the last 17 years. Whenever I am driving, walking, or riding my bike, I imagine the landscape around me converted to perennial polycultures. Try to imagine polycultures of useful plants growing in public spaces everywhere. Vibrant ecosystems would surround our homes and neighborhoods, producing a diverse array of foods, from staple protein and carbohydrates to fruits, leaves, and roots; timber, bamboo, and other construction materials; grazing, browsing, and fodder for livestock; medicinal and culinary herbs; outdoor habitat for humans and wildlife; fuelwood for heat and cooking; fertilizers, compost feedstocks, and botanical pesticides; biofuels like vegetable oils to run diesel engines; and plant-based petroleum and plastic substitutes. We are not there yet. In fact, while some tropical areas have farmed this way for centuries, it is not yet certain that this vision is possible on larger scales for the frostier climates most readers of this book might live in. But there is only one way to find out—to start experimenting on whatever land we have access to. It is not enough to grow food sustainably—it has to be distributed equitably as well, and that is going to take a lot more than perennial polycultures. We need political and economic systems that prioritize human beings and the environment over short-term greed and oppression. In such a scenario, permaculture systems could provide the abundant basis of life in a “post-scarcity” agriculture. Perennial food systems could mean less work, less petroleum use, and more free time to enjoy life—that is, after the first few decades of working the bugs out and getting those trees to grow to maturity! Ultimately, permaculture offers a vision of how humanity can participate in—rather than damage—our planet’s ecosystems and the process of evolution itself. When seen in this context, perennial vegetables are not just a novelty for the garden: They may just have a humble role to play in the future of our species and its relationship to the planet it calls home. 7.4  AGROECOSYSTEMS FOR RESILIENCE AND SUSTAINABILITY As discussed already in this chapter, there is a conceptual distinction between the term sustainability and resilience. Sustainability is meant to “manage resources in a way that guarantees welfare and promotes equity of current and future generation,” while resilience should mark “the capacity to absorb disturbance and reorganize change in order to maintain identical traits before disturbance” (Folke et al. 2010; Tuvendal and Elmqvist 2012). Agroforestry, permaculture, and perennial polyculture agroecosystems are considered to be alternatives to the mass, monoculture, industrial, mainly large-scale, capital intensive, and most often ecology damaging agriculture. Moreover, there is evidence (Radeva 2017; Terziev and Radeva 2016), that permaculture is part of a phenomenon, called new alternative agriculture, which goes beyond just an alternative to conventional agriculture. The new alternative agriculture is an alternative

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also to so-called “conventionalized” organic agriculture, which is often practiced in monocultures, often happening only due to administrative stimulus, and due to available “beneficial” public financial support. The concepts of permaculture, biodynamics, regenerative agriculture, and urban agriculture appeared with a new generation of people who influenced the whole food sector. They exist as a result of social processes globally and due to the willingness of many grassroots efforts. They grow from the bottom up and sustain, not only without administrative support, but often in hostile administrative conditions. Most probably and intuitively, agroforestry and “pure” perennial polyculture agroecosystems will belong to this group of “new alternatives” among agroecosystems, just more research is required on this matter. 7.4.1 Resilience The ability of previously mentioned alternative agroecosystems such as agroforestry, permaculture, and perennial polycultures to reveal resilience in coping with climate changes is indisputable. There is much evidence of “smart agricultural” techniques applied by agroecosystems that, when practiced in a holistic manner, successfully lead to climate change mitigation. Examined under a purely ecological-environmental lens, resilience of these agroecosystems toward new climate challenges is unarguable. It is, however, necessary to study the socioeconomical aspect of resilience. The Resilience Alliance, focused on research of resilience in social-ecological systems as a basis for sustainability (Resilience Alliance 2010) undertook such a scientific approach. According to the scientists from the Alliance, key components of the social-ecological system assessment might include both the biophysical properties of a system and the social properties (e.g., residential development, available monitoring programs, and economic incentives). In addition, for assessing the resilience of a system to specific issues, it is necessary to account for general system resilience to determine whether actions taken to address this specific issue could unintentionally degrade general system resilience. General resilience applies to the system as a whole. Identifying the key components of social (economic, political, and cultural) and ecological factors towards resilience requires a variety of approaches. Therefore, integration of scientific and local knowledge in understanding the key components of the agroecosystem is needed. A study, based on literature review and experience worldwide, attempts a similar approach and concludes that diversified systems where a variety of crops, trees, and animals occurs, increase the resilience of agroecosystems to climate change and environmental pressures. At the same time these measures lead to improvement of economic results with low-input decisions and stability in yields. The study refers to man-made agricultural systems and claims that resembling naturally diverse systems through appropriate design and management decisions simultaneously provides economic and environmental efficiency (Kazakova and Radeva 2015). Political and cultural aspects are not taken into consideration in this study, though they are recognized as being important for assessing all aspects of social-ecological resilience. Another recent empirical study (Benjamin and Gallic 2017) about the effects of climate change on European agriculture was conducted under four different climate scenarios. Seasonal weather variables on mean yields and the variance of wheat and corn yields were in the scope of this research. The projections of greenhouse gas concentration until the end of the twenty-first century were reflected. Results show that wheat yields would increase at the European scale under most scenarios, but the gains would decrease in the north in the long term. It is not the same case, however, for projected corn yields under the four climate scenarios. Even if some small gains in corn yields would be experienced temporally in northern regions, they would become losses in the long-term perspective. Losses would be even higher for regions in southern Europe. This and other similar studies lead to significant considerations. Europe or any other region in the world cannot afford to stand by and watch the global climate crisis. When assessing resilience potential of a particular agroecosystem, not only should its socio-ecological impact on a specific

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region be considered, but also the general resilience for the whole system and for the planet. Moreover, keeping in mind that all regions and systems are interconnected, nothing can stop the spreading of poverty and migration of people from climate affected regions to less affected areas of the world. Therefore, urgent work towards gradual transition to alternative agroecosystems is necessary nationwide for providing food security and peace. The social aspect (economic, political, and cultural) of resilience of alternative agroecosystems like agroforestry, permaculture, and perennial polyculture could be achieved. It depends on the availability of clear political will for transition, the creation of appropriate institutional frameworks internationally and locally, which will allow the alternative agroecosystems to become economically viable, and on the slow cultural transition of nations towards an ecological mindset and better consumption models to pursue the goals of social resilience. The Paris Agreement on climate change from 2015 is a global agreement for response to climate changes and is a hopeful sign for global political will for change. However, the Common Agriculture Policy of Europe, aside from slight changes in direction of support for agroecology practices, does not reflect clear willingness for agricultural transition. There are, however, many grassroots movements and networks, for example, ECOLISE (the European Network for Community-Led Initiatives on Climate Change and Sustainability, which also includes international networks); the European Commons Assembly (for governing the Commons, for support of small and local communities, and against social injustice); the network COST (European Cooperation in Science and Technology with extensive research in urban agriculture across Europe); Slow Food Organization; the Local Food Network; Slow Money initiative; and Degrowth movement. These and many other national and international bottom-up initiatives are engaged on different levels—research, training, economic solutions, creating of models, and communications to support community-led actions on climate change and resilience. For example, ECOLISE brings many organizations together and seeks to establish a common, Europe-wide agenda and a platform for collective action. The Commons Network succeeded to receive publicity at the European Parliament in 2016. The Land Institute from Kansas has proposed a 50-year plan for transition to perennial agriculture to the U.S. Congress. In contrast to these grassroots initiatives, a pure political decision is the example of China. The Chinese government has recently decided to conduct large-scale research on soil pollution and to form pilot zones for testing technologies for preventing pollution and recovering of polluted soils. Their goal is transforming 90% of polluted Chinese agricultural systems into safe crop planting and food production areas by the end of 2020. The role of these bottom-up initiatives is not only to bring progressive solutions to global problems, but also to create new cultural models and values in society with information dissemination, training, formal and informal education, and using the great impact of social media to influence behavior. 7.4.2 Sustainability Reaching resilience is the only pathway of agroecosystems to further develop as sustainable systems; sustainable meaning the guarantee of welfare and equity for the current and future generations. Sustainability is a highly used term in different aspects and provokes many scientific debates. According to Bachev (2018), understanding sustainability as an “approach in farming” is not always useful when considering the “direction for changes in agriculture.” The author emphasizes the high importance of non-ignorance of the economic aspects when determining the level of sustainability, because even “the most ecological farm in the world cannot be sustainable for [the] long-term, if [it is] not able to self-sustain economically.” Furthermore, it is important for sustainability to assess the impact of factors external to the agroecosystem—the institutional environment like social standards, limitations, social support, development of markets (e.g., new alternative channels for ecological products), and current macroeconomic environments. Finally, it is necessary to assess the specific socioeconomic environment and available natural resources for the particular agroecosystem.

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To achieve sustainability, not only ecological perspectives but also the economic and social sustainability of the agroecosystems should be considered. Sustainability requires more than resilience of agroecosystems. Agroecosystems should be resilient in order to follow the goals of sustainability. However, sustainability means more than being resilient to disturbance. It is also connected with poverty eradication, equality, fair democracy, rebuilding of communities and values, and ethics. The definition of agrarian sustainability has another weakness. It is often understood in politics as the ability for satisfying requirements of external criteria, for example, measures for economic sustainability with financial indexes for covering quantity goals while ignoring the quality of production or measures for covering ecological requirements only because of high political sensibility. If we rethink what sustainable means for us in terms of personal values, like traditions, beliefs, and feelings, we easily discover that they are sustainable—independent from availability or lack of support (public, financial, etc.); they are independent of the end result (financial or other); people have willingness to pass these values on to next generations. Thus, these personal or social values survive; they are resilient and sustainable. That is why some authors (Terziev and Radeva 2018) prefer to use the term economic viability, in order to differentiate from weaknesses in the conception of sustainability. The approach towards sustainability/viability of alternative agroecosystems, elaborated in a research work about the new alternative agriculture and permaculture in Bulgaria,* includes studying five dimensions:









1. Ability to provide a satisfying level of earnings and personal satisfaction. This is based on the ideas of Herbert Simon, a Nobel Prize laureate from 1978. According to him, people normally seek options (or economic results) that are “sufficiently good” and do not seek by all means the best alternatives or options, leading to maximization; 2. Ability to self-sustain an existence (relative financial independence). An economic unit or an alternative agroecosystem could be sustainable when it is able to survive and evolve without subsidies, tax concessions or other public financial support, and with a low level of dependence on bank financing; 3. Engagement in practiced activity or project (e.g., crop cultivation, restoring of agroecosystem, etc.). When an activity like crop cultivation is practiced, it carries satisfied earnings and satisfaction, and it is fulfilled with engagement to its future development; 4. Ability to transfer the generated viability of agroecosystems to next generations. This could happen when interconnection and cooperation with local communities is realized, when models for sustainable ways of working and living are created, with training, sharing, employment creation, building of philosophy for healthy living, and spreading the ideas to young people and their families; 5. Keeping of ecological and ethical principles that care for the earth and care for people while preserving, rebuilding, and regenerating natural and human resources.

In the cited study about Bulgarian permaculture, the economic viability/sustainability of these alternative agroecosystems is demonstrated by the adherence of permaculture farms to all five dimensions of viability. Finally, it could be concluded that the described alternative agroecosystems (agroforestry, permaculture, and perennial polyculture) in this chapter appear to be resilient to climate changes in the socio-ecological sense (see Plate 7.1). However, more work and time is needed, in order for agroecosystems to fully manifest their resilience regarding their recognition in politics all over the planet. Inarguably, more work is needed for changing mentality, worldviews, and behavior towards new climate challenges. The concept of sustainability, no matter the weaknesses in its definition or interpretation, and no matter if denoted as economic viability or simply viability, is a more profound concept than * More about the economic viability approach and its application in studying permaculture and other forms of the new alternative agriculture (case study Bulgaria) can be found in dissertation of Radeva (2017).

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Plate 7.1 A 6-acre permaculture farm in Venaura (North Carolina, USA) with arugula, spinach, collards, turnip greens, cilantro crops (left) and integrated poultry in the system (right). (Credit to: Lawrence London, farmer.)

resilience, consisting of many invisible values and structures. It seems as if at the moment only permaculture fully reflects concepts and all goals of sustainability—ecological, economic, social, and ethical. Of course, the future will show if permaculture practitioners will justify expectations to fully integrate their knowledge, techniques, and ethics into practice in order to achieve overall effect on sustainability of agroecosystems and to further spread this experience to other alternative and perspective agroecosystems. 7.5  AGROECOSYSTEMS, LOCAL PLANT GENETICS, AND RENEWABLE ENERGY RESOURCES The sustainability of agroecosystems depends greatly on how agriculture is ecologically approached (Plates 7.2 and 7.3), and an efficient approach is needed especially where agroecosystems

Plate 7.2 Officina Walden (Piedmont, Italy): Free-range farm husbandry (left) and a straw house and part of the market garden of a 3-acre permaculture farm (right). (Credit to: Nicola Savio, farmer.)

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Plate 7.3 Organic Gardens (Organic Gardens Oreshak, Varna, Bulgaria). Microclimate with shadow net over diversified cropping (top left), part of the autumn harvest variety of 0.25-acre permaculture farm (bottom), and measuring of soil temp (top right). (Credit to: Konstantin Yanev, farmer.)

function more on the use of renewable and locally available resources (Gliessman 1992). With climate change and to address better food security, a new vision should be developed on how to manage natural and local resources in order to address agroecosystems’ sustainability and resilience. Thus, adapted management systems might be tailored to producing biodiverse agroecosystems able to support and sustain their own functioning (Altieri 2002). On the other hand, traditional farming agroecosystems rely on local genetic resources and energy, and the development of peasant agroecosystems is seen as most sustainable and resilient because they constitute a “natural gene bank” of wild and domesticated species (Alcorn 1984; Altieri et al. 1987; Altieri 2004; Bisht et al. 2006; Jarvis and Hodgkin 1999; Tengö and Belfrage 2004). With global warming and climate change, the utilization of renewable or bio-energy became an inevitable strategy to limit carbon dioxide and rising temperatures. (Chen and Chen 2012). One of the priorities is the development of bioenergy because sustaining biomass production might contribute significantly in this production (Souza et al. 2017). On the other hand, studies have also shown that bioenergy cropping systems might contribute in addressing environmental issues associated with fossil fuels usage and negative impacts of intensive food production systems and urbanization (Kline et al. 2016; Nogueira et al. 2015; Osseweijer et al. 2015). For example, in China, Chen and Chen (2012) investigated the economic and environmental performance of biogas-linked agroecosystems

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(BLAS) with a special focus on efficiency, emission mitigation effect and sustainability. BLAS and its four subsystems, that is, planting, breeding, aquaculture, and biogas, were evaluated, and their findings showed BLAS featured high biogas production efficiency and significant emission mitigation effects. However, attention should be paid to the fact that demand for both food and energy is rising, and more pressure will be on both within the next decades. Therefore, greater consideration should be given to reduce pressure on the agroecosystems and how they can best be used for a better sustainability and the greater benefit of society (Hill 2007). 7.6  RECOMMENDATIONS AND CONCLUSION From the different concepts described in this chapter, it is obvious that agriculture is creating huge pressure on agroecosystems. Therefore, talking about agroecosystems, resilience, and climate change is one thing, and addressing their issues resulting from climate change is another, which might be more complex than it seems. Designing and managing agroecosystems for sustainability and resilience of climate change is one challenge, and mitigating the impacts of climate changes on these agroecosystems will be another challenge to take into account. Of course, the combination of different systems such as agroforestry, permaculture, and perennial crop systems might be one of the solutions in managing and mitigating climate change impacts, and this might have a significant role in developing strategies for the transition to more sustainable and resilient agroecosystems and agriculture more generally. To achieve these goals, we need to study and understand further the background of the different ecosystems and their responses to the changing environment for better resilience and sustainability. Indeed, it is necessary to define the concept of an agroecosystem and its sustainability based on their dependence on the local plant genetic resources, their dependence on local resources such as water, and also the conservation of these agroecosystems in terms of the local genetic resources, soil preservation, and water availability. We also need to assess, monitor, and scale-up the synergism or the antagonism of the different organisms of the components of the agroecosystems from individual to the entire system. REFERENCES Adger, W. N., K. Brown, D. R. Nelson et al. 2011. Resilience implications of policy responses to climate change. Wires Clim Chang 2:757–66. Alcorn, J. B. 1984. Development policy, forests, and peasant farms: Reflections on Huastec-managed forests’ contributions to commercial production and resource conservation. Econ Bot 38:389–406. Altieri, M., and P. Koohafkan. 2013. Strengthening resilience of farming systems: A prerequisite for a sustainable agricultural production (Commentary X). In Wake Up before It Is Too Late, Make Agriculture Truly Sustainable Now for Food Security in a Changing Climate. United Nations, pp. 56–60. Available at: http://unctad.org/en/PublicationsLibrary/ditcted2012d3_en.pdf. (Accessed: January 14, 2018). Altieri, M. A. 1999. The ecological role of biodiversity in agroecosystems. In Invertebrate Biodiversity as Bioindicators of Sustainable Landscapes. Practical Use of Invertebrates to Assess Sustainable Land Use, ed. M. G. Paoletti, pp. 19–31. Amsterdam, The Netherlands: Elsevier. Altieri, M. A. 2002. Agroecology: The science of natural resource management for poor farmers in marginal environments. Agric Ecosyst Environ 93:1–24. Altieri, M. A. 2004. Linking ecologists and traditional farmers in the search for sustainable agriculture. Front Ecol Environ 2:35–42. Altieri, M. A., M. K. Anderson, and L. C. Merrick. 1987. Peasant agriculture and the conservation of crop and wild plant resources. Conserv Biol 1:49–58. Altieri, M. A., and C. I. Nicholls. 2017. The adaptation and mitigation potential of traditional agriculture in a changing climate. Clim Change 140:33–45.

126

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Bachev, H. 2018. Approach for analysis and assessment of the governance system and the level of agrarian sustainability. Defining of agrarian sustainability. In Governing and Assessment of Agrarian Sustainability—Experiences, Challenges, and Lessons from Bulgaria and China, eds. H. Bachev, B. Ivanov, D. Toteva et al., pp. 8–9. Institute of Agricultural Economics, Sofia, University of National and World Economy, Sofia, Communication University of China, Shanghai Jiao Tong University. Baker, J. M., T. E. Ochsner, R.T. Venterea, and T. J. Griffis. 2007. Tillage and soil carbon sequestration—What do we really know? Agric Ecosyst Environ 118:1–5. Bangwayo-Skeete, P. F., M. Bezabih, and P. Zikhali. 2012. Crop biodiversity, productivity, and production risk: Panel data micro-evidence from Ethiopia. Nat Resour Forum 36:263–73. Batjes, N. H. 1998. Mitigation of atmospheric CO2 concentrations by increased carbon sequestration in the soil. Biol Fert Soils 27:230–5. Benjamin, C., and E. Gallic. 2017. Effects of Climate Change on Agriculture: A European Case Study. https://ecm.univ-rennes1.fr/nuxeo/site/esupversions/c289e497-8186-47bc-a46a-54762533ecd1?inline. (Accessed: February 7, 2018). Bernstein, L., P. Bosch, O. Canzia et al. 2007. Climate change 2007: Synthesis Report to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. http://www.ipcc.ch/pdf/assessment-report/ ar4/syr/ar4_syr.pdf. (Accessed: January 17, 2018). Bisht, I. S., K. S. Rao, D. C. Bhandari, S. Nautiyal, R. K. Maikhuri, and B. S. Dhillon. 2006. A suitable site for in situ (On-farm) management of plant diversity in traditional agroecosystems of western Himalaya in Uttaranchal state: A case study. Genet Resour Crop Ev 53:1333–50. Blanco, G., R. Gerlagh, S. Suh et  al. 2014. Drivers, trends and mitigation. In Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, eds. O. Edenhofer, R. Pichs-Madruga, Y. Sokona et al., Cambridge, United Kingdom and New York, NY: Cambridge University Press. Bolwig, S., D. Pomeroy, H. Tushabe, and D. Mushabe. 2006. Crops, trees, and birds: Biodiversity change under agricultural intensification in Uganda’s farmed landscapes. Geografisk Tidsskrift-Dan J Geogr 106:115–30. Brown, L. R. 2011. World on the Edge: How to Prevent Environmental and Economic Collapse. New York, NY: W. W. Norton & Company. Chatterjee, A., and R. Lal. 2009. On farm assessment of tillage impact on soil carbon and associated soil quality parameters. Soil Till Res 104:270–7. Chen, S., and Chen, B. 2012. Sustainability and future alternatives of biogas-linked agrosystem (BLAS) in China: An energy synthesis. Renew Sust Energ Rev 16:3948–59. Davoudi, S. 2012. Resilience: A bridging concept or a dead end? Plan Theor Prac 13:299–307. Deep Green Permaculture. 2018. Permaculture Ethics. https://deepgreenpermaculture.com/permaculture/ permaculture-ethics/. (Accessed: January 22, 2018). Dewar, J. 2007. Perennial Polyculture Farming. Seeds of Another Agricultural Revolution? Santa Monica (CA): Rand Pardee Center. Available at: https://www.rand.org/content/dam/rand/pubs/occasional_ papers/2007/RAND_OP179.pdf. (Accessed: January 12, 2018). Dovers, S., and J. Handmer. 1992. Uncertainty, sustainability, and change. Global Environ Chang 24:262–76. Duguma, L. A., P. A. Minang, and M. van Noordwijk. 2014. Climate change mitigation and adaptation in the land use sector: From complementarity to synergy. Environ Manag 54:420–32. Eamon, O. 2013. Europe in Transition. Local Communities Leading the Way to a Low-Carbon Society. European Association for Information on Local Development, AEIDL. Available at: http://base.socioeco. org/docs/transition-final.pdf. (Accessed: January 4, 2018). Ehrmann, J., and K. Ritz. 2014. Plant: Soil interactions in temperate multi-cropping production systems. Plant Soil 376:1–29. Eliades, A. 2012. Perennial Plants and Permaculture. Permaculture Research Institute. https:// permaculturenews.org/2012/06/06/perennial-plants-and-permaculture/. (Accessed: January 29, 2018). Elkington, J., and J. Hailes, 1988. The Green Consumer Guide, Choice magazine and the Australian Conservation Foundation. Victoria, Australia: Penguin Books. FAO (Food and Agriculture Organization of the United Nations), IFAD (International Fund for Agricultural Development), UNICEF (the United Nations Children’s Fund), WFP (World Food Programme) and WHO (World Health Organization). 2017. The State of Food Security and Nutrition in the World 2017. Building Resilience for Peace and Food Security. Rome: FAO. http://www.fao.org/3/a-I7695e.pdf. (Accessed: January 19, 2018).

CLIMATE CHANGE AND RESILIENcE OF AGROEcOSySTEMS

127

Feenstra, G. 2002. Creating space for sustainable food systems: Lessons from the field. Agr Hum Val 19:99–106. Fernandes, E. C. M., A. Oktingati, and J. Maghembe. 1984. The Chagga homegardens: A multistoried agroforestry cropping system on Mt. Kilimanjaro (Northern Tanzania). Agroforest Syst 2:73–86. Fischer, G., M. Shah, and H. van Velthuizen. 2002. Climate change and agricultural vulnerability. Vienna: International Institute for Applied Systems Analysis, RimaPrint. Available at: http://adapts.nl/perch/ resources/climateagri.pdf. (Accessed: January 7, 2018). Folke, C., S. Carpenter, T. Elmqvist, L. Gunderson, C. S. Holling, and B. Walker. 2002. Resilience and sustainable development: Building adaptive capacity in a world of transformations. Ambio 35:437–40. Folke, C., S. R. Carpenter, B. Walker, M. Scheffer, T. Chapin, and J. Rockström. 2010. Resilience thinking: Integrating resilience, adaptability and transformability. Ecol Soc 15:20. http://www.ecologyandsociety. org/vol15/iss4/art20/. (Accessed: December 22, 2017). Forrester, D. I. 2014. The spatial and temporal dynamics of species interactions in mixed-species forests: From pattern to process. Forest Ecol Manag 312:282–92. Francis, R. 2007–2008. Permaculture Design Course Handbook. Permaculture Education. Australia: Djanbung Gardens, Permaculture Education Center. Fuhrer, J. 2003. Agroecosystem responses to combinations of elevated CO2, ozone, and global climate change. Agr Ecosyst Environ 97:1–20. Gliessman, S. R. 1992. Agroecology in the tropics: Achieving a balance between land use and preservation. Environ Manag 16:681–9. Goudriaan, J., and J. C. Zadoks. 1995. Global climate change: Modelling the potential responses of agroecosystems with special reference to crop protection. Environ Pollut 87:215–24. Gurwick, N. P., L. A. Moore, C. Kelly, and P. Elias. 2013. A systematic review of biochar research, with a focus on its stability in situ and its promise as a climate mitigation strategy. PLoS One 8:e75932. https://doi. org/10.1371/journal.pone.0075932. Gustavsson, L., J. Holmberg, V. Dornburg et al. 2007. Using biomass for climate change mitigation and oil use reduction. Energ Policy 35:5671–91. Henfrey, T., and G. Penha-Lopes. 2015. Permaculture and Climate Change Adaptation. Inspiring ecological, social, economic and cultural responses for resilience and transformation. Bristol: Permanent Publications, Hyden House Ltd. The Sustainability Center/Good Works Publishing Cooperative, The Schumacher Institute. Hill, J. 2007. Environmental costs and benefits of transportation biofuel production from food- and lignocellulose-based energy crops. A review. Agron Sust Dev 27:1–12. Holling, C. S. 1973. Resilience and stability of ecological systems. Annu Rev Ecol Syst 4:1–23. Holling, C. S. 1986. Resilience of ecosystems: Local surprise and global change. In Sustainable Development and the Biosphere, eds. W. C. Clark, and R. E. Munn, pp. 292–317. Cambridge, MA: University Press. Holmgren, D. 2002. Permaculture: Principles and pathways beyond sustainability. Holmgren Design Services. Howden M.S., Soussana J.F., Tubiello, F. N., Chhetri, N., Dunlop, M. and Meinke, H. 2007. Adapting agriculture to climate change. Proc Natl Acad Sci USA 104:19691–6. Jackson, T. 2009. Prosperity without Growth: Economics for a Finite Planet. London: EarthScan. Jackson, W. 2002. Natural systems agriculture: A truly radical alternative. Agr Ecosyst Environ 88:111–7. Jackson, W. 2010. The 50-year farm bill. Solutions 1:28–35. Jarvis, D. I., and T. Hodgkin. 1999. Wild relatives and crop cultivars: Detecting natural introgression and farmer selection of new genetic combinations in agroecosystems. Mol Ecol 8:S159–73. Jose, S. 2009. Agroforestry for ecosystem services and environmental benefits: An overview. Agroforest Syst 76:1–10. JRC/PBL. 2013. Emission Database for Global Atmospheric Research (EDGAR). Release Version 4.2 FT2010. European Commission, Joint Research Centre (JRC)/PBL. Netherlands Environmental Assessment Agency. http://edgar.jrc.ec.europa.eu/overview.php?v=42FT2010. (Accessed: January 17, 2018). Kahn, P., T. Molnar, G. Zhang, and C. Funk. 2011. Investing in perennial crops to sustainably feed the world. Issues Sci Technol 27:75–81. Kater, L. J. M., S. Kante, and A. Budelman. 1992. Karité (Vitellaria paradoxa) and néré (Parkia biglobosa) associated with crops in South Mali. Agroforest Syst 18:89–105. Kazakova-Mateva, Y., and D. Radeva-Decheva. 2015. The role of agroecosystems diversity towards sustainability of agricultural systems. Paper Prepared for Presentation at the 147th EAAE Seminar ‘CAP Impact on Economic Growth and Sustainability of Agriculture and Rural Areas’, Sofia, Bulgaria.

128

CLIMATE CHANGE AND CROP PRODUcTION

Khumalo, S., P. W. Chirwa, B. H. Moyo, and S. Syampungani. 2012. The status of agrobiodiversity management and conservation in major agroecosystems of Southern Africa. Agr Ecosyst Environ 157:17–23. Klein, R. J. T., E. L. F. Schipper, and S. Dessai. 2005. Integrating mitigation and adaptation into climate and development policy: Three research questions. Environ Sci Policy 8:579–88. Kline, K. L., S. Msangi, V. H. Dale et al. 2016. Reconciling food security and bioenergy: Priorities for action. GCB-Bioenergy 9:557–63. Lal, R. 1997. Residue management, conservation tillage and soil restoration for mitigating greenhouse effect by CO2-enrichment. Soil Till Res 43:81–107. Lal, R. 2004. Soil carbon sequestration to mitigate climate change. Geoderma 123:1–22. Lal, R., J.A. Delgado, P.M. Groffman, N. Millar, C. Dell, and A. Rotz. 2011. Management to mitigate and adapt to climate change. J Soil Water Conserv 66:276–85. Le Maire, G., Y. Nouvellon, M. Christina et al. 2013. Tree and stand light use efficiencies over a full rotation of single- and mixed-species Eucalyptus grandis and Acacia mangium plantations. Forest Ecol Manag 288:31–42. Lin, B. B. 2011. Resilience in agriculture through crop diversification: Adaptive management for environmental change. Bioscience 61:183–93. Local Economies Project of the New World Foundation. 2018. Food Economy. Ensuring the economic viability of equitable and ecologically resilient practices in the food system. http://localeconomiesproject.org/ food-economy-4/. (Accessed: January 26, 2018). Lohrberg, F., L. Licka, L. Scazzosi, and A. Timpe. 2016. Urban Agriculture Europe. COST (European Cooperation in Science & Technology). Berlin, Germany: Jovis Verlag GmbH. Lorenz, K., and R. Lal. 2014. Biochar application to soil for climate change mitigation by soil organic carbon sequestration. J Plant Nutr Soil Sci 177:651–70. Luedeling, E., R. Kindt, N. I. Huth, and K. Koenig. 2014. Agroforestry systems in a changing climate— Challenges in projecting future performance. Curr Opin Environ Sust 6:1–7. Malézieux, E., Y. Crozat, C. Dupraz et al. 2009. Mixing plant species in cropping systems: Concepts, tools and models: A review. Agron Sustain Dev 29:43–62. Matocha, J., G. Schroth, T. Hills, and D. Hole. 2012. Integrating climate change adaptation and mitigation through agroforestry and ecosystem conservation. Adv Agroforest 9:105–26. Mbow, C., P. Smith, D. Skole, L. Duguma, and M. Bustamante. 2014a. Achieving mitigation and adaptation to climate change through sustainable agroforestry practices in Africa. Curr Opin Environ Sust 6:8–14. Mbow, C., M. Van Noordwijk, E. Luedeling, H. Neufeldt, P. A. Minang, and G. Kowero. 2014b. Agroforestry solutions to address food security and climate change challenges in Africa. Curr Opin Environ Sust 6:61–7. McPhearson, T. 2014. The Rise of resilience: Linking resilience and sustainability in city planning. The nature of the cities, https://www.thenatureofcities.com/2014/06/08/the-rise-of-resilience-linking-resilienceand-sustainability-in-city-planning/. (Accessed: November 13, 2017). Messner, J.J., N. Haken, H. Blyth et al. 2017. Fragile States Index 2017—Annual Report. The Fund for Peace. http:// fundforpeace.org/fsi/2017/05/14/fragile-states-index-2017-annual-report/. (Accessed: January 19, 2018). Mollison, B. 1990. Permaculture: A Practical Guide for a Sustainable Future. 1st Edition. Washington, DC: Island Press. Nair, P. K. R. 2007. The coming of age of agroforestry. J Sci Good Agric 67:1613–9. Nair, P. K. R., B. M. Kumar, and V. D. Nair. 2009. Agroforestry as a strategy for carbon sequestration. J Plant Nutr Soil Sci 172:12–23. Nogueira, L., A.H. Leal, M.R.L.V. Fernandes et  al. 2015. Sustainable development and innovation. In Bioenergy & Sustainability: Bridging the Gaps 72, pp. 184–217. Paris, France: SCOPE, http:// bioenfapesp.org/scopebioenergy/images/chapters/bioen-scope_chapter06.pdf. (Accessed: December 14, 2011). Nowak, R.S., Ellsworth, D.S. and Smith S.D. 2004. Functional responses of plants to elevated atmospheric CO2—Do photosynthetic and productivity data from FACE experiments support early predictions. New Phytol 162:253–80. O’Brien, K. 2012. Global environmental change II: From adaptation to deliberate transformation. Prog Hum Geog 36:667–76. Osseweijer, P., H. K. Watson, F. X. Johnson et  al. 2015. Bioenergy and food security. In Bioenergy & Sustainability: Bridging the Gaps 72, pp. 90–137. Paris, France: SCOPE. http://bioenfapesp.org/ scopebioenergy/images/chapters/bioen-scope_chapter04.pdf. (Accessed: December 14, 2017).

CLIMATE CHANGE AND RESILIENcE OF AGROEcOSySTEMS

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Pardini, A., and M. Nori. 2011. Agro-silvo-pastoral systems in Italy: Integration and diversification. Pastoralism: Res Policy Pract 1:26. https://doi.org/10.1186/2041-7136-1-26. Paustian, K., O. Andrén, H. H. Janzen et al. 1997. Agricultural soils as a sink to mitigate CO2 emissions. Soil Use Manag 13:230–44. Permaculture Solutions for Climate Change. 2015. Permaculture Climate Change Statement. http://www. permacultureclimatechange.org/. (Accessed: February 2, 2018). Pimentel, D., C. Wilson, C. McCullum et al. 1997. Economic and environmental benefits of biodiversity. Bioscience 47:75547–57. Powlson, D. S., A. P. Whitmore, and K. W. T. Goulding. 2011. Soil carbon sequestration to mitigate climate change: A critical re-examination to identify the true and the false. Eur J Soil Sci 62:42–55. Prasad, N., F. Ranghieri, F. Shah, Z. Trohanis, E. Kessler, and R. Sinha. 2009. Climate Resilient Cities: A Primer on Reducing Vulnerabilities to Disasters. Washington, DC: The World Bank. Radeva, D. 2017. Economics of the new alternative agriculture in Bulgaria. Permaculture. PhD thesis, University of National and World Economy, Sofia. Rasmussen, P. E., K. W. T. Goulding, J. R. Brown, P. R. Grace, H. H. Janzen, and M. Körschens. 1998. Long-term agroecosystem experiments: Assessing agricultural sustainability and global change. Science 282:893–6. Resilience Alliance. 2010. Assessing resilience in social-ecological systems: Workbook for practitioners. Version 2.0. http://www.resalliance.org/3871.php. (Accessed: February 7, 2018). Rogé, P., A. Friedman, M. Astier, and M. Altieri. 2014. Farmer strategies for dealing with climatic variability: A case study from the Mixteca Alta Region of Oaxaca. Agroecol Sust Food Syst 38:786–811. Schaller, M., G. Schroth, J. Beer, and F. Jiménez. 2003. Species and site characteristics that permit the association of fast-growing trees with crops: The case of Eucalyptus deglupta as coffee shade in Costa Rica. Forest Ecol Manag 175:205–15. Schewenius, M., T. McPhearson, and T. Elmqvist. 2014. Opportunities for increasing resilience and sustainability of urban social-ecological systems: Insights from the URBES and the cities and biodiversity outlook projects. Ambio 43:434–44. Schoeneberger, M., G. Bentrup, H. de Gooijer et al. 2012. Branching out: Agroforestry as a climate change mitigation and adaptation tool for agriculture. J Soil Water Cons 67:128A–36A. Schroth, G., S. A. D’Angelo, W. G. Teixeira, D. Haag, and R. Lieberei. 2002. Conversion of secondary forest into agroforestry and monoculture plantations in Amazonia: Consequences for biomass, litter and soil carbon stocks after 7 years. Forest Ecol Manag 163:131–50. Slow Food. 2015. About us. http://www.slowfood.com/about-us/. (Accessed: January 26, 2018). Slow Money. 2018. Mission and Progress. https://slowmoney.org/what-we-do/. (Accessed: January 26, 2018). Smith, P., M. Bustamante, H. Ahammad et al. 2014. Agriculture, forestry and other land use (AFOLU). In Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, eds. O. Edenhofer, R. PichsMadruga, Y. Sokona et al., pp. 816–922. Cambridge, MA: Cambridge University Press. Smith, P., and J. E. Olesen. 2010. Synergies between the mitigation of, and adaptation to, climate change in agriculture. J Agric Sci 148:543–52. Souza, G. M., M. V. R. Ballesterb, C. H. de Brito Cruz et al. 2017. The role of bioenergy in a climate-changing world. Environ Dev 23:57–64. Tengö, M., and K. Belfrage. 2004. Local management practices for dealing with change and uncertainty: A cross-scale comparison of cases in Sweden and Tanzania. Ecol Soc 9:4. http://www.ecologyandsociety. org/vol9/iss3/art4/. Terziev, D., and D. Radeva. 2016. Studying the new agriculture. Paper Presented on the 2nd International Conference in Development and Economics (I.CO.D.ECON.), Thessaloniki, Greece. Terziev, D., and D. Radeva. 2018. Level and factors for agrarian sustainability in Bulgaria. Sustainability of alternative agriculture. In Governing and Assessment of Agrarian Sustainability—Experiences, Challenges, and Lessons from Bulgaria and China, eds. H. Bachev, B. Ivanov, D. Toteva et al., pp. 208–15. Institute of Agricultural Economics, Sofia, University of National and World Economy, Sofia, Communication University of China, Shanghai Jiao Tong University. The Commons Network. 2016. http://commonsnetwork.eu/on-the-rise-european-commons-assembly/. (Accessed: January 26, 2018). The Organic Gardens of Learning—First steps in Bulgaria. 2012–2013. http://gradinka.zaedno.net/taxonomy/ term/29. (Accessed: January 25, 2018).

130

CLIMATE CHANGE AND CROP PRODUcTION

Thornton, P. K., and M. Herrero. 2015. Adapting to climate change in the mixed crop and livestock farming systems in sub-Saharan Africa. Nat Climate Chang 5:830–6. Toensmeier, E. 2016. The Carbon Farming Solution: A Global Toolkit of Perennial Crops and Regenerative Agriculture Practices for Climate Change Mitigation and Food Security. White River Junction, VT: Chelsea Green Publishing. Tores, F. 1983. Role of woody perennials in animal agroforestry. Agroforest Syst 1:131–63. Torquebiau, E. F. 2000. A renewed perspective on agroforestry concepts and classification. Cr Acad Sci III 323:1009–17. Torre, A., P. Fajnzylber, and J. Nash. 2009. Low Carbon, High Growth: Latin American Responses to Climate Change. Washington, DC: World Bank Latin American and Caribbean Studies, The World Bank. Transition Network. 2018. What is transition. https://transitionnetwork.org/about-the-movement/what-istransition/. (Accessed: January 24, 2018). Tuvendal, M., and T. Elmqvist. 2012. Response strategy assessment: A tool for evaluating resilience for the management of social-ecological systems. In Resilience and the Cultural Landscape, eds. T. Plieninger, and C. Bieling, pp. 224–41. Cambridge, MA: Cambridge University Press. Walker, B., C. S. Holling, S. R. Carpenter, and A. Kinzig. 2004. Resilience, adaptability and transformability in social–ecological systems. Ecol Soc 9:5. http://www.ecologyandsociety.org/vol9/iss2/art5/. Weibhuhn, P., Orcid, M. Reckling, U. Stachow, and H. Wiggering. 2017. Supporting agricultural ecosystem services through the integration of perennial polycultures into crop rotations. Sustainability 9:2267. DOI:10.3390/su9122267. Wilkinson, K. M., C. R. Elevitch, and R. R. Thaman. 2000. Choosing timber species for pacific island agroforestry. In Agroforestry Guides for Pacific Islands, eds. C. R. Elevitch, and K. M. Wilkinson, pp. 3–25. Holualoa, HI: Permanent Agriculture Resources Publisher. Woolf, D., J. E. Amonette, F. A. Street-Perrott, J. Lehmann, and S. Joseph. 2010. Sustainable biochar to mitigate global climate change. Nat Comm 1:56. DOI:10.1038/ncomms1053. World Health Organization. 2003. Diet, Nutrition and the Prevention of Chronic Diseases. Geneva, Switzerland: WHO. Yeomans, A. 1990. The agricultural solution to the greenhouse effect. Presentation to Esalen Congress on Sustainable Agriculture. California. Yeomans, A. 2018. 10. “Carbon still” Soil Test System. Australia: Yeomans Plow Co Pty Ltd. http:// yeomansplow.com.au/10-carbon-still-soil-test-system/. (Accessed: January 23, 2018). Zomer, R., D. Bossio, R. Sommer, and L. Verchot. 2017. Global sequestration potential of increased organic carbon in cropland soils. Sci Rep 7:15554. DOI:10.1038/s41598-017-15794-8.

CHapTer  8

Dynamics of Crop Production in a Heterogeneous Landscape What Are the Opportunities for Enhancing Communal Farmers’ Resilience to Climate Change Impacts? Munyaradzi Chitakira and Luxon Nhamo CONTENTS 8.1 Introduction........................................................................................................................... 131 8.2 Description of the Case Study............................................................................................... 132 8.3 Soil Variation Across Altitudinal Zones............................................................................... 133 8.4 Dynamics of Cropped Land Area Across Zones................................................................... 134 8.5 Land Use Change Over Time................................................................................................ 136 8.6 Climate Change Related Challenges and Opportunities for Adaptation............................... 138 8.7 Potential Adaptation Strategies............................................................................................. 140 8.8 Summary............................................................................................................................... 140 8.9 Conclusion............................................................................................................................. 140 References....................................................................................................................................... 141 8.1 INTRODUCTION Globally, the vulnerability and plight of smallholder farmers is predicted to worsen as a result of climate change and the associated variable rainfall and increased temperatures (Eitzinger et al. 2014; Yanda and Mubaya 2011). While considerable work has been done on the impact of climate change on crop production at large scales, more intensive research is required to provide information about the situation at the local level and to establish sustainable ways of enhancing the smallholder farming sector’s resilience to the impact of climate change and variability. Resilience refers to the tendency of a system to maintain or regain its configuration and productivity after some disturbance (Lin 2011). Resilient agricultural systems continue to provide vital services such as food production even after suffering a severe drought or significant reduction in rainfall. Research has shown that more landscape diversity supports more varied ecosystem services, promotes higher yields, and enhances the resilience of the rural economies (Letourneau et al. 2011; Lin 2011; Schippers et al. 2015). Biodiversity-agriculture integrating cropping systems have the capacity to promote the sustainability of crop production systems, ecosystem services, and enhance local livelihoods (Chitakira et al. 2015). Studies of the determinants of crop diversification and factors influencing the extent of crop diversification within the smallholder farming sector in southern 131

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Zambia revealed that the size of landholding, amount of fertilizer used, distance to market, and the type of tillage mechanism had strong influence on crop diversification (IFPRI 2014). For instance, the bigger the landholding, the more likely the farmer is to diversify, and farmers further away from the market are more likely to diversify crop production because such farmers tend to grow only for subsistence rather than for sale. A very small proportion of South Africa (13%) is arable while the greater part of the country is unsuitable for crop production as a result of low rainfall and poor soils (ARC 2016). The average maize yield in smallholder farming areas in the country is as low as 1.0 t/ha, and this has been attributed to factors such as a lack of fertilizer application, poor pest and disease management, and the exposure of crops to moisture stress during periodic droughts (ARC 2016). The knowledge of the spatial variability and distribution of crop yield is used to tailor practices to specific locations and is a useful input for precision agriculture as yields can be mapped in detail (Huang et al. 2008; Lamb et al. 1997). Crop yields are highly variable across farming lands as a result of complex interactions among different factors such as topography, soil properties, climatic conditions, and management practices (Doerge 1999; Jaynes et al. 2003; Jiang and Thelen 2004; Kravchenko et al. 2005). Previous studies noted that topography determines the level of influence of the other factors as it explains a substantial portion of crop yield variability (Changere and Lal 1997; Jiang and Thelen 2004; Kaspar et al. 2003; Kravchenko and Bullock 2000; Schepers et al. 2004; Timlin et al. 1998). As much as 60% or even more of crop yield variability can be explained by a combination of soil properties and topographic features (Jiang and Thelen 2004; Kravchenko and Bullock 2000). The relationship between yield and topography varies substantially from year to year and from field to field as a result of the prevailing weather conditions during the growing season of each particular year (Kaspar et al. 2003; Machado et al. 2002). Topography refers to landscape features such as altitude, slope gradient, slope aspect, and surface curvature of a farmland (Jiang and Thelen 2004; Zhang et al. 2014). Topography affects crop growth and yield by redirecting and changing soil water availability, and it indirectly influences the distribution of certain soil chemical and physical properties such as organic matter content, base saturation, soil temperature, and particle size distribution (Bennett et al. 1972; Yong et al. 2009). Ovalles and Collins (1986) demonstrated that content levels of soil properties on three topographic positions of summit, shoulder, and back-slope have a significant dependence on the topographic position of a field. A study by Yang et al. (1998) showed that three topographic variables, elevation, slope, and aspect, alone can explain 15% to 35% of wheat yield variability at the whole-field scale. Jiang and Thelen (2004) observed that topography explains approximately 60% of crop yield variability of a cropland and that it will be helpful to incorporate slope information when developing field management zones. Results of farm demonstration trials in the northwest Himalaya region in India have revealed that elevation and slope aspect have a significant influence on crop productivity and soil quality (Ghosh et al. 2014). The current chapter assesses the dynamics of crop production based on a case study of smallholder farming communities in the KwaZulu-Natal Province of South Africa. It examines the pattern of crop production and land use change in relation to topographic or altitudinal zones (or velds) and explores the opportunities for enhancing the resilience of smallholder farmers to the impacts of climate change. The chapter makes a comparative analysis of the factors that impact on productivity in different altitudinal zones. It is based on information from household questionnaire surveys, Remote Sensing and Geographic Information Systems (GIS) tools, as well as secondary sources (Dijkshoorn et al. 2008). 8.2  DESCRIPTION OF THE CASE STUDY Wards 15 and 16 of Jozini Local Municipality in the uMkhanyakude District of KwaZulu-Natal Province in South Africa share borders with Swaziland to the west and Mozambique to the north (Figure 8.1). The area has an altitude ranging from 20 m to 710 m above sea level. The temperatures

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Figure 8.1 Elevation, altitudinal zones, and location of the study area.

range from 23° to 40° in summer and from 16° to 26° in winter, and the mean annual rainfall ranges from 450 mm in the low-lying areas to over 800 mm on the Lebombo highlands (Jozini Local Municipality 2017). The area experiences an annual average evaporation of about 1,660 mm and a mean annual runoff of 40 × 106 m3 a−1 (Jozini Local Municipality 2017; Midgley et al. 1994; Schulze 2007). The population of Jozini municipality showed a slow growth from 184,206 in 2001 to 186,502 in 2011, and the growth rate dropped from 2.6% to 0.9% over this period (Statistics South Africa 2014). The proportion of households with no income has been decreasing steadily from 49% in 2001 to 47% in 2007 and 43% in 2011 (Jozini Local Municipality 2017; Statistics South Africa 2014). Almost two thirds (58.6%) of the agricultural households in the municipality rear animals only, 12.3% grow crops only, while 26.9% practice mixed farming (Statistics South Africa 2014). The landscape is divided into three topographical or altitudinal zones: the gentle high veld, steep middle veld, and flat low veld (Figure 8.1). The Lubombo Mountains on the western side form the gentle high veld and the Makhatini Flats on the eastern side form the flat low veld. A steep and rocky middle veld forms a transitional zone between these two extreme landscapes, creating an aesthetic, heterogeneous terrain rich in natural resources. 8.3  SOIL VARIATION ACROSS ALTITUDINAL ZONES The soil types in the study area directly relate to specific physiographic regions, each with particular climatic and hydrological conditions (Figure 8.2). The topography and the soils are

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Figure 8.2 Relationship between soil types and cultivated land.

shaped by the underlying geology while the topography influences the local climate and overall land use across the altitudinal zones. The high veld is mainly composed of acid rhyolitic lavas while the low veld is underlain by marine limestone and calcareous mudstones of lower and middle to upper Cretaceous age (Alcock 1999). While in the high veld there are relatively deep and rich soils favorable for crop production, the steep gradient and rocky soils in the middle veld do not seem to favor expanded agriculture. The soils in the low veld are derived from alluvium river terraces and the Cretaceous sediments (Midgley et al. 1994; Schulze 2007). As such they are generally fertile. Also predominant in the low veld are deep, acidic, well drained sands of Fernwood and Clovelly forms (Schulze 2007). 8.4  DYNAMICS OF CROPPED LAND AREA ACROSS ZONES The gentle high veld was more predominantly under crop cultivation compared to the other two zones (Figure 8.2). An observable pattern is that the cultivated fields become fewer and smaller with decreasing altitude. The average size of cultivated land per household in the high veld was 2.57 ha while it was 2.09 ha in the middle veld and 1.9 ha in the lower veld (Figure 8.3).

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(a)

(b)

Figure 8.3 (a) Size of land cultivated by households. (b) Means of farm sizes.

A  comparison of means for the farm sizes across the three zones (one way ANOVA) shows significant difference between groups (sig. 0.005). The farmers in the high veld had generally larger farms than their counterparts in the middle and lower velds. The notable difference in farm sizes and land under cultivation in the three altitudinal zones can be explained by varying topographic properties. The rich soils, higher mean annual rainfall, and cooler temperatures explain why the high veld was the most settled and cultivated zone. The predominantly rocky and poor shallow leptosols in the steep middle veld (Figure 8.4) do not favor rain-fed crop cultivation (FAO 2015) and present tillage and weeding challenges. In the low veld cultivation is in few

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(a)

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(b)

Figure 8.4 (a) Typical stony and shallow soils in the steep middle veld. (b) Famers have adapted by minimizing tillage and terracing the cultivated land.

patches and tends to be limited to places where the soils are more fertile and moist, especially on alluviums. Richer cambisols are mainly along river valleys. The low veld is very hot and dry and is also susceptible to flooding in wet periods. Such conditions do not favor dry land crop farming but livestock rearing (FAO 2015). 8.5  LAND USE CHANGE OVER TIME The spatio-temporal changes in cultivated land area over the period under focus are shown in maps (a), (b), and (c) (Figure 8.5). Generally, between 2005 and 2015 there was an increase in the land area under cultivation in all three zones although there was a decrease between 2010 and 2015 (Table 8.1). Although the cultivated area increased in all the zones, more significant changes are noted in the middle veld and the low veld. In the middle veld the land under cultivation continued to change both in size and location resembling subsistence and shifting cultivation patterns. The imagery shows that some fields cultivated in 2005 in the low veld were abandoned or reduced in size by 2015. According to information gathered through the questionnaire survey, the decrease in cultivated land area could be due to some families relocating from the area in response to increasing water scarcity, hotter temperature conditions, and successive seasons of crop failure which rendered crop cultivation a less and less reliable source of livelihood. The challenge of declining crop yields was being experienced by over 85% of the respondents in each of the zones (Table 8.2). The stability in the size of cultivated area in the high veld is most probably due to gentle slopes which promote accumulation of humus from vegetation and crop residue and rainfall and temperature conditions that are more favorable for human settlement. The increases in cultivated land in rural communities is normally in response to human population growth (IUCN 1990). It can be observed that the population growth rate for the municipality under focus dropped from 2.6% to 0.9% over the decade between 2001 and 2011 (Statistics South Africa 2014). These population dynamics probably slowed down the rate of expansion of cultivated land in the study area. The decrease in cultivated area in 2015 compared to 2010 can be attributed to the El Niño and La Niña—Southern Oscillation (ENSO) episode that took place during the 2015/16 cropping season causing one of the most severe droughts which resulted in reduced cultivated area and crop yields in the whole of southern Africa (Gizaw and Gan 2016; SADC 2016).

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Figure 8.5 (a–c) Spatio-temporal changes in cultivated land area from 2005 to 2015 in the three altitudinal zones of the study area.

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Table 8.1 Spatio-Temporal Changes in Cultivated Land Area between 2005 and 2015 Cultivated Land 2005

Zone High veld Middle veld Low veld Total

Area (km2)

Area (km2)

% of zone area

69.02 68.43 62.63 200.08

25.03 1.82 0.49 27.34

36.26 2.66 0.78 13.66

Cultivated Land 2010 Area (km2)

% of zone area

30.65 5.85 2.14 38.64

44.41 8.55 3.42 19.31

Cultivated Land 2015 Area (km2)

% of zone area

% change 2005 to 2015

26.69 4.40 3.06 34.15

38.67 6.43 4.89 17.07

2.41 3.77 4.10 3.40

Not Faced

Total

Table 8.2 Challenge of Declining Crop Yields Experienced by Farmers

No. of respondents

Total

Minor

Average

Major

Low veld

2 (3.5%)

2 (3.5%)

  48 (86%)

4 (7%)

Middle veld High veld

2 (5%) 3 (4%) 7 (4.1%)

1 (2.6%) 6 (8%) 9 (5.3%)

  36 (92.4%)   64 (85.3%) 148 (87.1%)

0 2 (2.7%) 6 (3.5%)

56 39 75 170

8.6  CLIMATE CHANGE RELATED CHALLENGES AND OPPORTUNITIES FOR ADAPTATION Apart from the declining crop yields, the farmers in the study area were experiencing challenges such as frequent droughts and crop failure, limited access to sufficient amounts and right quality of water (Figures 8.6, 8.7, and Table 8.3). These challenges are indicators of the impacts of climate change and variability and attest to the necessity of measures for enhancing the resilience of the farmers to the impacts. This chapter identifies some opportunities for adaptation to the challenges being experienced. For instance, the farmers adapted to the steep terrain and erosion challenge by terracing the farmland and minimizing tillage (Figure 8.4). There was also evidence of mixed

Figure 8.6 Challenge of frequent droughts and crop failure.

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Figure 8.7 Challenge of access to sufficient water quantity. Table 8.3 Challenge of Access to Clean Water Responses Minor Area

Low veld Middle veld High veld

Total

Average

4 1 2 7

1 2 7 10

Major

Not Experienced

Total

40 28 58 126

11 8 8 27

56 39 75 170

Table 8.4  Decision-Making for Household Farming Activities Who Decides Head alone Involve family No farm Total

Respondents 75 94 1 170

Percent 44.1 55.3 0.6 100

Cumulative % 44.1 99.4 100

farming, intercropping, and use of more drought tolerant crops such as millet, sorghum, and cassava. These strategies are important for cushioning the farmers against the effects of prolonged droughts. Drought tolerance in maize, pearl millet, cowpea, groundnut, and sorghum is reported to have significantly averted the effects of severe droughts in the Sahel region (Hall 2007). In the wake of climate change and variability, the farmers need to place more and more focus on growing earlymaturing crops and drought tolerant crop varieties, in particular, millet and sorghum. The latter are regarded key cereal grain crops in dry areas and have the capacity to provide food for humans, livestock feed, domestic fuel, as well as construction material (Shiferaw et al. 2014). The question about who normally makes decisions for household farming activities is of interest in this chapter. Table 8.4 shows that while in 44% of the households the decision rested solely on the household head, in 55% of the households the family members were consulted. Involvement of family members in decision-making should be the way forward because family members need to pool together knowledge and information about short- and long-term climatic predictions. The threats posed by climate change and variability demand that smallholder farmers be proactive and make

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necessary changes in farming and land management decisions in response to the new challenges (Wood et al. 2014). Climate information is an essential tool for enhancing the farmers’ resilience to climate change. Such information empowers smallholder farmers and provides them with the knowledge to predict environmental risks. The information assists the farmers when deciding on the most appropriate technologies and adaptation mechanisms to choose in response to threats (Wood et al. 2014). 8.7  POTENTIAL ADAPTATION STRATEGIES The heterogeneity of the landscape under focus had a distinct influence on the dynamics of crop production and land use change in the area. Like their counterparts in other areas around the world, the smallholder farmers in the study area were experiencing the impact of climate change and variability. It is necessary for the farmers to adopt strategies to ensure that the smallholder farming systems remain an important livelihood for these communities. Climate smart agricultural production strategies that integrate indigenous knowledge systems are recommended to enhance resilience of the farming communities (Mafongoya and Ajayi 2017). For instance, intercropping rain-fed maize with cowpea and soybean was found to enhance crop yield by between 8% and 17% (Ghosh et al. 2014). Mixed farming, crop diversification, conservation agriculture, and agriculturebiodiversity integration strategies such as ecoagriculture, agroecology, agroforestry, and permaculture are recommended. Such approaches have the potential to increase the agricultural productivity in smallholder farming systems and improve the farmers’ buffer capacity against climate risks like droughts and water scarcity (Giller et al. 2011; Speranza 2013). 8.8 SUMMARY This chapter presented a case study of the dynamics of agricultural production in smallholder farming communities in southern Africa, and examined the pattern of crop production and land use change in relation to topographic zones. Geographic Information System (GIS) was used to delineate the study area cross section and to determine altitudinal and slope changes. Land use change in three altitudinal zones of the study area over the years 2005 to 2015 was detected from satellite imageries and analyzed to establish the dynamics in relation to topography. Household questionnaire surveys were conducted to gather information about the farmers’ experiences across the heterogeneous landscape. The analysis showed that topography is an important factor in the dynamics of crop production and land use change. The chapter discussed a number of climate change and variability related challenges experienced by the local farmers. It also highlighted several opportunities for enhancing the resilience of smallholder farmers to the impacts of climate change and variability. The opportunities include the adoption of agriculture-biodiversity integration strategies, growing of early-maturing and drought tolerant crop varieties, involvement of family members in decisionmaking, climate information dissemination and sharing, as well as utilization of local indigenous knowledge systems. Apparently, there are several adaptation strategies available for adoption by the smallholder farmers. Further research is however necessary to inform the selection of the most appropriate strategy for implementation in a given context. 8.9 CONCLUSION This chapter provides policy-makers with necessary information on how altitudinal differences influence productivity and land use patterns in smallholder communities. This information is important for resource planning and allocation. Further research work could investigate the

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appropriateness of specific adaptation strategies in different parts of heterogeneous landscapes. It could also focus on the identification and monitoring of new and invasive crop pests and diseases associated with climate change and variability in relation to topography in order to reduce the risks of crop loss and improve food security in the smallholder farming sector. REFERENCES Agricultural Research Council (ARC). 2016. Annual report 2015–16. Pretoria: ARC. Alcock, P. G. 1999. A water resources and sanitation systems source book with special reference to KwaZuluNatal. Part 6. Water Research Commission. WRC Report No. 384/6/99. Bennett, O. L., E. L. Mathias, and P. R. Henderlong. 1972. Effects of north and south facing slopes on yield of Kentucky Bluegrass (Poa pratensis L.) with variable rate and time of nitrogen application. Agron J 64:630–5. Changere, A., and R. Lal. 1997. Slope position and erosional effects on soil properties and corn production on a Miamian soil in Central Ohio. J Sustain Agric 11:5–21. Chitakira, M., E. Torquebiau, W. Ferguson, and K. Mearns. 2015. Suggesting an interdisciplinary framework for the management of integrated production and conservation landscapes in a transfrontier conservation area of Southern Africa. In Agroecology, ecosystems and sustainability, ed. N. Benkeblia, 265–77. Boca Raton, FL: CRC Press. Dijkshoorn, J. A., V. W. P. van Engelen, and J. R. M. Huting. 2008. Soil and landform properties for LADA partner countries (Argentina, China, Cuba, Senegal and The Gambia, South Africa and Tunisia). ISRIC report 2008/06 and GLADA report 2008/03. Wageningen, The Netherlands: ISRIC – World Soil Information and FAO. Doerge, T. 1999. Yield map interpretation. J Prod Agric 12:54–61. Eitzinger, A., Läderach, P., Bunn, C. et al. 2014. Implications of a changing climate on food security and smallholders’ livelihoods in Bogotá, Colombia. Mitigation and Adaptation Strategies for Global Change 19:161. Food and Agriculture of the United Nations (FAO). 2015. World reference base for soil resources 2014: International soil classification system for naming soils and creating legends for soil maps. FAO: Rome. Ghosh, B. N., N. K. Sharma, N. M. Alam et al. 2014. Elevation, slope aspect and integrated nutrient management effects on crop productivity and soil quality in north-west Himalayas, India. J Mt Sci 11:1208–17. Giller, K. E., M. Corbeels, J. Nyamangara et al. 2011. A research agenda to explore the role of conservation agriculture in African smallholder farming systems. Field Crop Res 124:468–72. Gizaw, M. S., and T. Y. Gan. 2016. Impact of climate change and El Niño episodes on droughts in sub-Saharan Africa. Clim Dynam 47:1–18. Hall, A. E. 2007. Sahelian droughts: A partial agronomic solution. www.plantstress.com (accessed: March 1, 2018). Huang, X., L. Wang, L. Yang, and A. N. Kravchenko. 2008. Management effects on relationships of crop yields with topography represented by wetness index and precipitation. Agron J 100:1463–71. International Food Policy Research Institute (IFPRI). 2014. The determinants and extent of crop diversification among smallholder farmers: A case study of Southern Province, Zambia. Washington, DC: IFPRI. IUCN. 1990. Population and Resources: Workshop report, 18th session of the General Assembly of the IUCN, Perth, Australia. Jaynes, D. B., T. C. Kaspar, T. S. Colvin, and D. E. James. 2003. Cluster analysis of spatiotemporal corn yield patterns in an Iowa field. Agron J 95:574–86. Jiang, P., K. D. Thelen. 2004. Effect of soil and topography properties on crop yield in a North-Central cornsoybean cropping system. Agron J 96:252–8. Jozini Local Municipality. 2017. Integrated development plan (IDP): 2017/18–2021/22. Jozini, South Africa: Jozini Local Municipality. Kaspar, T. C., T. S. Colvin, D. B. Jaynes, D. L. Karlen, D. E. James, and D. W. Meek. 2003. Relationship between six years of corn yields and terrain attributes. Precis Agric 4:87–101. Kravchenko, A. N., and D. G. Bullock. 2000. Correlation of corn and soybean grain yield with topography and soil properties. Agron J 92:75–83.

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Kravchenko, A. N., G. P. Robertson, K. D. Thelen, and R. R. Harwood. 2005. Management, topographical, and weather effects on spatial variability of crop grain yields. Agron J 97:514–23. Lamb, J. A., R. H. Dowby, J. L. Anderson, and G. W. Rehm. 1997. Spatial and temporal stability of corn grain yields. J Prod Agric 10:410–14. Letourneau, D. K., I. Armbrecht, B. S. Rivera et al. 2011. Does plant diversity benefit agroecosystems? A synthetic review. Ecol Appl 21:9–21. Lin, B. B. 2011. Resilience in agriculture through crop diversification: Adaptive management for environmental change. BioScience 61(3):183–93. Machado, S., E. D. Bynum, T.L. Archer et al. 2002. Spatial and temporal variability of corn growth and grain yield implications for site-specific farming. Crop Sci 42:1564–76. Mafongoya, P. L., and O. C. Ajayi. 2017. Indigenous knowledge and climate change: Overview and basic propositions. In Indigenous knowledge systems and climate change management in Africa, eds. P. L. Mafongoya and O. C. Ajayi, 17–28. Wageningen, The Netherlands: CTA. Midgley, D. C., W. V. Pitman, and B. J. Middleton. 1994. Surface water resources of South Africa, Volumes I, II, III, IV, V and VI. Pretoria, South Africa: Water Research Commission. Ovalles, F. A., and M. E. Collins. 1986. Soil-landscape relationships and soil variability in North Central Florida. Soil Sci Soc Am J 50:401–8. SADC. 2016. SADC regional humanitarian appeal. Gaborone, Botswana: SADC Secretariat. Schepers, A. R., J. F. Shanahan, M. A. Liebig, J. S. Schepers, S. H. Johnson, and A. Luchiari, Jr. 2004. Appropriateness of management zones for characterizing spatial variability of soil properties and irrigated corn yields across years. Agron J 96:195–203. Schippers, P., van der Heide, C. M., Koelewijn, H. P. et al. 2015. Landscape diversity enhances the resilience of populations, ecosystems and local economy in rural areas. Landscape Ecol 30:193–202. Schulze, RE 2007, Soils: Agrohydrological information needs, information sources and decision support, in South African Atlas of climatology and agrohydrology. WRC Report 1489/1/06. Pretoria, South Africa: Water Research Commission. Shiferaw, B., K. Tesfaye, M. Kassie, T. Abate et al. 2014. Managing vulnerability to drought and enhancing livelihood resilience in sub-Saharan Africa: Technological, institutional and policy options. Weather Clim Extrem 3:67–79. Speranza, C. I. 2013. Buffer capacity: Capturing a dimension of resilience to climate change in African smallholder agriculture. Reg Environ Change 13:521–35. Statistics South Africa. 2014. Census 2011. http://www.statssa.gov.za. (accessed: March 1, 2018). Timlin, D. J., Y. Pachepsky, V. A. Snyder, and R. B. Bryant. 1998. Spatial and temporal variability of corn grain yield on a hillslope. Soil Sci Soc Am J 62:764–73. Wood, S. A., A. S. Jina, M. Jain, P. Kristjanson, and R. S. DeFries. 2014. Smallholder farmer cropping decisions related to climate variability across multiple regions. Global Environ Chang 25:163–72. Yanda, P. Z., and C. P. Mubaya. 2011. Managing climate change in Africa: Local level vulnerabilities and adaptation experiences. Dar Es-Salaam, Tanzania: Mkuki na Nyota Publishers Ltd. Yong, X., Y. Bo, L. Guobin, and L. Puling. 2009. Topographic differentiation simulation of crop yield and soil and water loss on the Loess Plateau. J Geogr Sci 19:331–9. Zhang, Z., F. van Coillie, X. Ou, and R. de Wulf. 2014. Integration of satellite imagery, topography and human disturbance factors based on canonical correspondence analysis ordination for mountain vegetation mapping: A case study in Yunnan, China. Remote Sens 6:1026–56.

CHapTer  9

The Pulse of Pulses under Climate Change From Physiology to Phenology Archana Joshi-Saha and Kandali S. Reddy CONTENTS 9.1 Introduction........................................................................................................................... 143 9.2 Grain Legumes and Sustainable Agriculture........................................................................ 144 9.3 Multiple Lines of Evidence for Climate Change and Impact on Pulses................................ 146 9.4 Plant Strategies to Tackle Water Stress under Climate Change Scenarios: From Physiology to Phenology........................................................................................................ 147 9.4.1 A Primer on Plant-Water Relation............................................................................. 147 9.4.2 Strategies of Avoidance and Tolerance: Traits of Importance for Breeding............. 147 9.4.2.1 Root Architecture: Traditional and Novel Root Traits................................ 147 9.4.2.2 Transpiration and its Regulation................................................................. 149 9.4.3 Hormones, Antinutrients, and Stress Tolerance........................................................ 151 9.5 Strategy for Stress Escape: Climate Change and Phenology................................................ 153 9.6 Concluding Remarks............................................................................................................. 154 References....................................................................................................................................... 154 9.1 INTRODUCTION “Daffodils” that once filled the heart of William Wordsworth with pleasure and “bliss of solitude” in the musings of his famous poem once again were referred to in publications, finding themselves in the center of a fierce debate on climate change due to their early unseasonal bloom (https:// www.theguardian.com/global-development/2015/dec/20/global-warming-weather-environmentel-nino; https://www.thenation.com/article/daffodil-delusion-sensationalizing-global-warming/; Sparks 2014; Vaz et al. 2016). “Climate” is defined as weather conditions prevailing in a particular region over a period of time. Changes in these conditions are mainly attributed to the anthropogenic activities and extensive use of fossil fuels post-industrial revolution and are described as “climate change.” If the early bloom of daffodils is due to climate change is not clear, yet climate change is real with widespread consequences. Climate change can adversely affect agriculture, particularly in low- to mid-latitude countries like India that are heavily dependent on rain-fed agriculture and exhibit limitations with respect to the arable land (Crosson 1989; Gornall et al. 2010). Edible grain legumes, also known as pulses, are the largest single source of vegetable protein in the human diet and are considered the backbone of sustainable agriculture (Araújo et al. 2015; Rubiales and Mikic 2014). Legumes are grown in almost every climatic region with wide ranges of soil, yet most of the 143

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Figure 9.1 Share of various pulse producing countries in total world pulse production. (From E-pulses data book; www.iipr.res.in/e-pulse-data-book-country-wise.html.)

grain legume production is in developing countries of the semi-arid tropics (Daryanto et al. 2015; Nedumaran et al. 2015). These areas contribute a vast diversity of pulses like dry beans, chickpeas, and dry peas to the world production. Like cereals, pulses are also susceptible to various abiotic stresses, particularly drought and heat that are predicted to exacerbate under the climate change scenario. However, unlike cereals, pulses are often grown in marginal lands with resource poor farmers, and that adds to the effects of these stresses. Almost half of the global pulse production is from India, Canada, China, Myanmar, Brazil, and Australia, of which India contributes highest with an almost 25% share in production (Figure 9.1). The present chapter deals with the effect of climate change on physiology and phenology particularly pertaining to the grain legumes with special emphasis on the Indian subcontinent, which is the highest producer and consumer of these grain legumes. India is divided into 7 climatic zones, which are further divided into 15 major agroclimatic zones (online agriculture research data book 2016, http://www.iasri. res.in/agridata/16data/HOME_16.HTML). The major pulse producing states lie in semi-arid tropics that are highly stress prone particularly for drought and rising heat (Krishnamurthy et al. 2011). There is ample evidence in support of climate change, which is discussed in this chapter particularly with respect to its impact on pulses. Water deficit (drought stress) is one of the most important abiotic stresses affecting the yield of pulses particularly in the semi-arid drought prone regions. Therefore, the primary focus of the present chapter is on drought stress and the effects of increasing CO2 and temperature either singly or in combination with drought stress, with respect to the major pulse crops that are grown in the intrinsically stressful conditions of semi-arid tropics. 9.2  GRAIN LEGUMES AND SUSTAINABLE AGRICULTURE Among the myriad of plant families, Fabaceae/leguminosase consists of a group of plants that are important for food (pulses) or feed for animals and is only second to Poaceae that contains the cereals. Legumes are not only important for food and feed but are also important from an environmental perspective in that they have the ability to biologically fix atmospheric nitrogen and contribute towards sustainable agriculture. It is to commemorate this substantial contribution of food grain legumes that the United Nations declared the year 2016 as the “year of pulses” (UN 2013).

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The Food and Agriculture Organization (FAO) of the United Nations (UN) defines pulses as the annual legumes harvested solely for dry grains (FAO 2016). Pulses are grown worldwide in an area of 81 Mha, with a total production of 73.21 Mt (year 2013). Almost 50% of the pulse producing area (40.66 Mha) and production (34.09 Mt) is in Asia, with India being the major pulse producing country with a production of 19.98 Mt from an area of about 30.5 Mha (year 2013) (E pulse databook, http://www.iipr.res.in/e-pulse-data-book-country-wise.html). The Indian subcontinent is also the major consumer of pulses, as these serve as an affordable and rich source of protein to a substantial population that is vegetarian by choice. Grain legumes are not only important from the perspective of consumption but are also important for agricultural sustainability. Their cultivation as a sole crop or as intercrop can enhance quality, yield, productivity, and nutrient use efficiency (Belel et al. 2014; Gan et al. 2015; Ghosh et al. 2007). Due to their capacity to fix atmospheric nitrogen (N) they not only supply N to the next crop but also reduce the emission of greenhouse gases like CO2 and N2O fluxes compared to cropping and pasture systems that are fertilized with industrial N (Jensen et al. 2012). In addition, use of legumes for diversification of cereal based cropping systems reduces weed incidences and breaks pest and disease cycles (Krupinsky et al. 2002; Lithourgidis et al. 2011; Stagnari et al. 2017). Pulses that are included in the larger group of papilionoid legumes are broadly categorized into two groups: warm season legumes and cool season legumes. They constitute the two sister clades often referred to as the millettioids/phaseoloid and galegoid clades respectively (Cronk et al. 2006). In general, species within the phaseoloid clade (e.g., soybean, cowpea, pigeonpea, common bean) originate from lower latitudes and are short-day plants (SDPs), while those in the galegoid clade (e.g., pea, lentil, chickpea, fava bean) are from temperate regions and with respect to flowering time control are vernalization-responsive long-day plants (LDPs) (Summerfield and Roberts 1985). Of the total pulse producing area and production of the world almost 85% is covered by 5 main pulse crops, namely chickpea, dry peas, lentil (galegoid clade) dry bean, cowpeas, and pigeonpeas (phaseoloid clade), both in terms of area and production (Figure 9.2). India is the major pulse

Figure 9.2 Major pulses in terms of area (MHa) and average production (2004–2013) worldwide. (From E-pulses data book; www.iipr.res.in/e-pulse-data-book-country-wise.html.)

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producing country in the world and ranks first in production of dry beans, chickpeas, and pigeonpeas and second to Canada in production of lentils. Dry peas and cowpeas are majorly produced by Canada and Nigeria respectively (E pulse databook, http://www.iipr.res.in/e-pulse-data-bookcountry-wise.html). 9.3  MULTIPLE LINES OF EVIDENCE FOR CLIMATE CHANGE AND IMPACT ON PULSES Increase in greenhouse gases (GHG), particularly CO2 levels in the troposphere, is one of the key indicators of climate change (IPCC 2013). Multiple lines of evidence indicate that during the past few decades, most of the increasing atmospheric burden of CO2 is from fossil fuel combustion (Tans 2009). From 1980 to 2011, the average annual increase in globally averaged CO2 (from 1 January in one year to 1 January in the next year) was 1.7 ppm yr−1. Despite an interannual variability in the CO2 growth rate due to small changes in the balance between photosynthesis and respiration on land, since 2001, CO2 has increased at 2.0 ppm yr1 (IPCC 2013). The recently measured CO2 levels are around 405.61 ppm (https://climate.nasa.gov/vital-signs/carbon-dioxide/, March 17, 2017). Associated with the increasing CO2 levels is the increase in temperature often termed as “global warming” due to trapping of infrared rays by the GHGs, particularly CO2. As per a recent synthesis report on climate change by the IPCC, the earth surface temperatures have shown an increasing trend in the last three decades since 1850, with the globally averaged combined land and ocean surface temperature data as calculated by a linear trend showing a warming of 0.85 [0.65–1.06]°C from 1880–2012 (IPCC 2014). Presently this temperature anomaly is at 0.99°C (https://climate.nasa. gov/). The IPCC (2014) also predicts that the global mean surface temperature change for 2016–2035 as compared to 1986–2005 will likely be in the range of 0.3–0.7°C, while a number of ranges are predicted for the end of the twenty-first century (2081–2100) depending on various parameters and socioeconomic scenarios or representative concentration pathways (RCPs). Yet, more frequent hot and fewer cold temperature extremes over most land areas on daily and seasonal timescales and heat waves of higher frequency and duration are predicted (IPCC 2014). A negative impact of climate change on crop yields is also reported (Daryanto et al. 2015; IPCC 2014). Pulses are grown in diverse climatic regions and range of soil types, yet the major pulse crops are grown in arid to semi-arid environments or drylands of the Mediterranean (Daryanto et al. 2015). The major pulse producing regions of India—the highest pulse producer in the world—fall under the semi-arid tropics characterized by dry climates with less precipitation that are already stressful to the crop cultivation (Vadez et al. 2012). The arid and semi-arid regions account for approximately 30% of the world’s total area and are inhabited by approximately 20% of the total world population (Sivakumar et al. 2005). Under the scenario of climate change with prediction of rise in temperature from 2–4°C (year 2020–2080) and a high uncertainty in projection of precipitation (Roxy et al. 2015; Sivakumar et al. 2005), the production of grain legumes is likely to be affected particularly in the semi-arid tropics. High temperature and/or less precipitation (drought) are two main abiotic stresses that will challenge the production. A recent metadata analysis showed significant differences among different species of pulses with respect to their adaptability to drought. In the same study, no difference in yield reduction was observed between legumes planted in tropical versus non-tropical environments (Daryanto et al. 2015). Yet, there are several socioeconomic differences in addition to environmental factors in the agricultural scenario of the two regions, with low productivities in the developing countries of the tropics as compared to the developed countries that are mostly present in the non-tropical regions (Gallup and Sachs 2000). Although nutritionally very important, compared to wheat and rice grain, legumes are grown as minor crops, on marginal soils of low rain fall without irrigation, or in dry seasons of residual soil moisture postharvest of cereals with minimal inputs (Andrews and Hodge 2010; Nedumaran et al. 2015). Therefore, it is imperative to

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study the effect of these two stresses on grain legumes particularly grown in semi-arid tropics and the strategies to develop climate resilience in them pertaining to these two stresses either individually or in combination. 9.4  PLANT STRATEGIES TO TACKLE WATER STRESS UNDER CLIMATE CHANGE SCENARIOS: FROM PHYSIOLOGY TO PHENOLOGY The majority of the grain legumes have their center of origin in the dry lands of Asia, the Middle East, the Mediterranean, and Africa, with significant differences in their ability to withstand drought stress (Daryanto et al. 2015). Like other plants they also have the two basic strategies to counter drought stress that include (a) drought avoidance and (b) drought tolerance through osmotic adjustments, however, the strategies used by a particular species will depend on their environment and growth requirements (Beebe et al. 2013; Hall 2012; Nemeskeri et al. 2012; Upadhayaya et al. 2012). Each of these is discussed in the following sections with specific emphasis on grain legumes. 9.4.1  A Primer on Plant-Water Relation To devise strategies to mitigate the effects of drought stress and to understand the mechanisms of drought stress tolerance, first one must understand the plant-water relation. The uptake of water by plants takes place via the process of osmosis, which is the diffusion of water molecules through semipermeable membranes (cell membranes) from a place of higher concentration of water molecules to one of lower concentration. Water can enter roots either apoplastically where it moves freely around the cells of the root epidermis and cells of the root cortex until it reaches the endodermis (with highly suberized cells of casparian strip beyond which the only way to move further is to enter the cells of the endodermis) or symplastically, where the epidermal and root hair cells can directly take up water. However, water cannot traverse the cell membrane without the help of water conducting channels called aquaporins that are non-gated channels selectively allowing water molecules to diffuse across the membrane depending on the osmotic gradient. Traversing the casparian strip and the endodermis, the water reaches the xylem and is loaded to the xylem via osmosis as the water potential of xylem is kept lower than that of the surrounding cells. Further water movement in the plant is primarily regulated by negative pressure created by transpiring leaves sucking water upwards, or in some plants also through root hydraulic pressure pushing water upwards (Taiz and Zeiger 2010). 9.4.2  Strategies of Avoidance and Tolerance: Traits of Importance for Breeding The genetics of drought tolerance has been studied in many pulse crops and is found to be a quantitative trait (Agbicodo et al. 2009; Iglesias-García et al. 2015; Montero-Tavera et al. 2008; Varshney et al. 2014) with many contributing characters (Tardieu 2012) that include larger or deeper rooting systems, regulation of stomatal opening/closing to regulate transpiration, higher water use efficiency, leaf chlorophyll content and leaf size, and production of metabolites for osmotic adjustments, which can contribute to drought avoidance or tolerance. Some of these contributing traits are discussed in the following sections. 9.4.2.1  Root Architecture: Traditional and Novel Root Traits The architecture of roots is an important factor for uptake of water and other nutrients from soil. Root architecture refers to the arrangement of the root system in space, that is, how the root axes are geometrically arranged (Lynch 1995). The topology (connection of individual root axes to each other through branching) and distribution (presence of roots in a particular position) of roots are

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two important descriptors of root architecture that are mostly studied for their role in drought stress tolerance in various plant species and are considered as the “traditional” root traits contributing to drought adaptation (Vadez 2014). However, root architecture is highly diverse and plastic and needs novel phenotyping tools. Among the topology and distribution, more profuse root length density (RLD) and deep rooting are often considered as important and desirable traits for drought adaptation, and a large genotypic variability has been observed in various grain legumes for these traits (Bandhopadhayay 2014; Jongrungklang et al. 2012; Kashiwagi et al. 2006; Mia et al. 1996; Polania et al. 2017; Songsri et al. 2008). Roots of cereals and pulse crops were found to be more evenly distributed as compared to oil seeds, and among pulses chickpeas and peas were found to have deeper roots than lentils (Fan et al. 2016). However, root architecture has been found to be a positive trait for selection for drought adaptation only in certain cases particularly in deep soils and/or in presence of a water table (Tardieu 2012). Moreover, many times differences in RLD and/or rooting depth are not correlated with the yield under drought stress conditions. In chickpeas 20 genotypes with similar phenology but contrasting for field-derived drought tolerance index based on yield were compared for stomatal conductance and different root growth parameters, and it was concluded that a conservative pattern of water use, rather than deep or profuse rooting is critical for terminal drought tolerance of chickpeas (Zaman-Allah et al. 2011). Similar observations have been made in groundnuts (Koolachart et al. 2013; Ratnakumar and Vadez 2011). These often contradictory observations on correlation of RLD or rooting depth with plant performance under drought stress even for the same crop may be due to several reasons, including: (1) type of drought stress imposed (preflowering vs. mid-season vs. terminal drought), (2) severity of water stress (mild vs. high), (3) availability of extractable water in the deeper layers of soil, (4) type of soil (shallow vs. sandy vs. clay), and (5) environmental conditions (Mediterranean within season rainfall vs. arid/semi-arid with crop depending solely on residual soil moisture). Thus, many times development of high RLD can be an unnecessary biomass partitioning (Passioura 1983) and/or energy loss through root respiration, which is positively correlated with relative growth rate of roots (Poorter et al. 1991; Van der Werf et al. 1988). Various studies have shown that rather than taking up more water, it is the water extraction at the reproductive stage and pod filling that is more crucial for plant performance under drought stress conditions (Daryanto et al. 2015; Schoppach et al. 2013; Vadez 2014; Vadez et al. 2013; Zaman-Allah et al. 2011). This is contributed by several factors, most of which are shoot traits, as discussed in the next section. Several root anatomical “phenes” (phenes: for phenotype, as genes: genotypes, Burridge et al. 2016) also affect water acquisition from soil and hence may prove promising under drought scenarios (Feng et al. 2016; Lynch et al. 2014). Several root traits like small root diameters, long root length, and root length density, are responsible for maintaining plant productivity under drought. Seminal roots with small xylem diameters save water in deep soil where water deficit is seen in late season and thus help in crop maturation and improve yield. Comparatively less “leaky” xylem structures hold promise to improve plant productivity in water-limited environments without affecting yield (Comas et al. 2013). However, many of these “plant water budget” altering traits are regulated by root hydraulic mechanisms (Vadez 2014). There are limited studies on species variations in root hydraulic conductivity that include model species Arabidopsis (Sutka et al. 2011) and woody species (Costa-Saura et al. 2016; George et al. 2015). The various factors that influence root hydraulic conductivity include xylem vessel size and abundance (wheat: Schoppach et al. 2013; rice: Bashar 1990, Henry et al. 2012; lupin: Bramley et al. 2009; wheat and rice comparative: Kadam et al. 2015), root cortical aerenchyma (maize: Zhu  et al. 2010), root cell size and root cell file number (maize: Chimungu et al. 2014a,b; Lynch 2013), and aquaporins (lotus: Henzler et al. 1999; rice: Henry et al. 2012). Many of these traits are affected by drought, however, they may not always contribute to tolerance mechanisms; for example, although formation of root cortical aerenchyma is induced in drought stress and contributes towards drought tolerance in maize (Zhu et al. 2010), there may be a trade-off of reduced radial transport of nutrients

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due to reduction in living cortical tissues in some genotypes of maize (Hu et al. 2014). In rice, root cortical aerenchyma has shown to reduce hydraulic conductivity under certain conditions (Yang et al. 2012). There are limited studies and validation of these “root phenes” in legumes (legumes and Pennisetum comparison: Purushothaman et al. 2013; soybean metaxylem number: Prince et al. 2017), and there is a need to explore these traits in the wide germplasm collection of important legume species. Root architecture referring to the three-dimensional arrangements of roots in space is also important for the uptake of nutrients and water resources from soil (Lynch 1995). However, phenotyping root architecture is the major limiting factor in utilizing this trait in breeding programs. Although several attempts have been made to study root architecture using digging (shovelomics) (Burridge et al. 2016), custom made imaging systems and software (Clark et al. 2011), root core sampling systems and software (Wu and Guo 2014), X-ray computed tomography (Pfeifer et al. 2015; Roger et al. 2016), and MRI (van Dusschoten et al. 2016), each method has their own advantages and disadvantages with limitations on their usage in regular breeding programs (Metzner et al. 2015; Paez-Garcia et al. 2015). 9.4.2.2  Transpiration and its Regulation While the root traits are related to water uptake, this water is lost by the plants through transpiration that is mostly regulated through the opening and closing of the stomatal pores. Since these pores are also the site of exchange of CO2 from the atmosphere, regulation of stomatal aperture to reduce transpirational water loss leads to a trade-off of reduced photosynthesis affecting growth (Joshi-Saha et al. 2011a). It is estimated that about 300 × 1015 g of carbon pass through stomata (40% of the carbon in the atmosphere), and 120 × 1015 g are assimilated as gross primary production per year (Ciais et al. 1997). At the same time, about 30–40 × 1018 g of water is lost through transpiration annually (Peixoto and Oort 1992). Certain plant species have tried to resolve this paradox by adapting to crassulacean acid metabolism (CAM) that itself shows great plasticity (Cushman 2001). However most of the nutritionally important crops are either C3 or C4 plants that have to manage the balance between water loss through transpiration and carbon gain through photosynthesis. Since stomata are the major site of water loss and gas exchange, apart from number/density of stomates, the factors regulating stomatal opening/closing will in turn regulate both rate of transpiration and photosynthesis. These include plant factors such as hormonal/molecular signals and environmental factors such as relative humidity and vapor pressure deficit, temperature, light, CO2 levels, and water availability in soil. In this section some of these important factors are discussed, particularly with respect to the climate change scenario. Carbon dioxide: The increase in CO2 can affect plant metabolism, growth, and development with a consequent effect on plant productivity under changing climate scenarios. Since CO2 is the primary carbon source for the plants, providing additional carbon from elevated CO2 levels can lead to increased biomass accumulation particularly in C3 plants, through stimulation of photosynthesis (termed as “fertilization effect”) (Kant et al. 2012). Increased CO2 has also shown to mitigate the effects of abiotic stresses possibly by an increase in antioxidant production and a decrease in reactive oxygen species (ROS) production by reducing photorespiration (AbdElgawad et al. 2016). However, the carbon fertilization effect has led to only a marginal increase in grain yields in large-scale “free-air CO2 enrichment” (FACE) experiments that allow the exposure of plants to elevated CO2 concentration under natural and fully open-air conditions as compared to closed chamber experiments (Ainsworth and Long 2005; Kim et al. 2003; Kimball et al. 1995). Due to increased photosynthesis, there is an increase in C status that increases the C/N ratio, with lowered N content affecting the grain yield and quality (Lawlor 2002). The “fertilization effect” of elevated CO2 levels is temporal, and over longer exposure there is partial reversal or stabilization at a lower rate as compared to the initial stimulation, which is termed as “CO2” or “photosynthesis acclimation” (Ghildiyal and Sharma-Natu 2000). This is accompanied by a decrease in carboxylation of RuBisCO, a decrease in N concentration, reduced stomatal conductance

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and an increase of starch accumulation (Kant et al. 2012). A recent study involving temperate grassland grown under FACE conditions, showed that the carbon fertilization effect on above-ground biomass is strongest under local average environmental conditions and was reduced or disappeared under wetter, drier, and/or hotter conditions (Obermeier et al. 2016). Grain legumes that are often grown in such harsh environments balance the increased fixed carbon with increased fixed nitrogen due to nitrogen fixation as compared to the other non-leguminous C3 plants in response to elevated CO2 levels, given that there are no constraints of nutrient availability, low temperature, or drought. In addition, rising CO2 may offer some protection from drought-induced reduced nitrogen fixation (Rogers et al. 2009). In a recent FACE experiment with peas, elevated CO2 was found to alleviate the inhibitory effect of soil NO3– on nodulation and N2 fixation (Butterly et al. 2016). Elevated CO2 levels in the intercellular spaces affects stomatal conductance by closing the stomatal aperture (Mott 1988; Xu et al. 2016) and reducing the stomatal density (Lake et al. 2002; Woodward 1987). Temperature: Increase in temperature is foreseen due to climate change and will be an important determinant of crop productivity under climate change scenarios. Although all the stages of plant growth are susceptible to high temperature, the reproductive phase development of male gamete, female fertility and pollen-pistil interactions are especially vulnerable (Bita and Gerats 2013). High temperatures adversely affect respiration and photosynthesis and shoot net assimilation rates that impact on total dry weight of plants, shortening of plant life cycle, and overall reduced productivity (Barnabas et al. 2008; Wahid et al. 2007). Cool season crops including legumes are affected by high temperatures, particularly at the flowering stage, also called the terminal heat stress, and can cause severe yield losses (Jha et al. 2014a, b). In addition, a warm season legume like cowpea was reported to undergo yield reduction when exposed to high night temperatures (Thiaw and Hall 2004). Reports on screening of legume germplasms for thermo-tolerance indicate that sensitivity to high temperature particularly during/post-anthesis with more effect on pollen as compared to the female structures is common in many major food legumes including chickpeas (Devasirvatham et al. 2013; Kaushal et al. 2013), peas (Ali et al. 1994; Guilioni et al. 1997), beans (Bishop et al. 2016; Monterroso and Wien 1990), lentils (Kumar et al. 2016), and cowpeas (Hall 2004). Temperature also affects membrane fluidity, thereby affecting transport across it. The membrane stability is another trait closely associated with heat tolerance and has been studied in a number of legumes (Bhandari et al. 2017; Ibrahim 2011; Srinivasan et al. 1996). Temperature is known to regulate stomatal aperture movements (Hofstra and Hesketh 1969). Stomatal apertures were measured after exposing bean (Phaseolus vulgaris) leaves kept in the dark to varying temperatures. Irrespective of the CO2 assimilation, the elevated temperatures stimulated the stomatal opening (Feller 2006). Evolution and/or domestication have also led to phenological changes in the cool season legumes for “heat escape” with respect to the environment as discussed in the section on phenology. Soil water status: Most of the semi-arid agriculture and pulse production is rain-fed (Aggarwal 2003) and is prone to drought. Therefore, stomatal response with respect to water deficit is of prime importance to plant productivity under such environments. Under drought stress conditions, accumulation of abscisic acid (ABA) leads to triggering of gene cascade that leads to ion efflux and inhibition of sugar uptake by the guard cells that lead to stomatal closure (Daszkowska-Golec and Szarejko 2013). Many of the Mediterranean and semi-arid crops face water deficit post-anthesis or during the seed filling stage called the terminal drought. In such a scenario, a crop with conservative water use will perform better (Zaman-Allah et al. 2011). The genotypes with inherently lower water conductance will conserve soil moisture, however, if such genotypes are grown in well-watered conditions, there may be a yield penalty due to reduced photosynthesis (Vadez 2012). When occurring individually, drought and heat act in opposite manner in regulating stomatal movement, however, they are often encountered simultaneously, and the outcome depends on several factors as discussed in the following sections.

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Combined stresses: Response of plants to combinations of two or more stresses is different from that of stresses when individually applied. In addition, there are shared responses common to individual and combined stresses (Pandey et al. 2015; Zandalinas et al. 2017). Combination of stresses, mainly high temperature and/or drought in combination with high atmospheric CO2, mimics the present-day scenario of global warming particularly in the arid/ semi-arid regions. Maintenance of soil water status is critical for crop performance especially in the reproductive phase; however, it becomes limiting for grain legume production particularly in arid and semi-arid tropics that are accompanied by heat stress simultaneously (Farooq et al. 2017). Stomatal response to heat and drought is complex. In legumes like Phaseolous vulgaris and Trifolium pratense, when water is not limiting, stomata open in the dark under temperature stress to cool the canopy temperature, while in presence of low photosynthetically active radiation, there is temperature oscillation due to stomatal opening and closing in non-water limiting conditions. However, with added imposed drought, stomata close and leaf temperature increases (ReynoldsHenne et al. 2010). In addition, abscisic acid (ABA) produced under stress can shift the heat induced stomatal opening to a higher temperature (Feller and Vaseva 2014). The shared responses common to different stresses include generation of reactive oxygen species (ROS) and its consequences (Carvalho 2008; Signorelli et al. 2013; Suzuki et al. 2012). Among other factors, the overall response depends on relative severity of the different stresses, and is majorly decided on the more severe stress (dominant stressor) and the plant combination (Pandey et al. 2015). The combined effect of drought and heat leads to stomatal closing, increased leaf surface temperature, decreased photosynthesis, increased respiration, with an induction of some genes of glycolysis and pentose phosphate pathway that cause utilization of sugars in tobacco (Rizhsky et al. 2002). In chickpeas, drought and heat act synergistically to increase the severity of damage for most of the parameters like membrane damage, reduced stomatal conductance and PSII function, and leaf chlorophyll content. However, drought was the dominant stressor for RuBisCO activity that increased with heat stress, decreased with drought stress, and severely decreased with combined stress. Drought stress had a greater effect than heat stress on yield and the biochemical seed-filling mechanisms (Awasthi et  al. 2014). In terms of molecular responses, drought was the dominant stressor in case of Arabidopsis with increased drought specific gene expression and more overlap in drought and combined responses, while for wheat and sorghum heat was the dominant stressor with increased heat specific gene expression. However, in wheat, the response was more unique with genes expressed in combined stress far more than genes expressed in individual stresses as compared to sorghum (Pandey et al. 2015). A recent study compared the chemical composition of legumes and grasses under water deficit in combination with high temperature in ambient as well as elevated CO2. Non-structural carbohydrates, phenolics, and lignin were found to be increased while protein, phosphorus, and magnesium contents were found to be reduced. The effects were larger and more ubiquitous in combination with elevated CO2, and the quality of legumes was more affected than the grasses under such conditions (AbdElgawad et al. 2014). 9.4.3 Hormones, Antinutrients, and Stress Tolerance Involvement of phytohormones, particularly ABA regulating stress tolerance, and the molecular mechanisms involved in its sensing and signaling have been well worked out in the model plant species Arabidopsis and are reviewed extensively (Hubbard et al. 2010; Joshi-Saha et al. 2011b; Nakashima and Yamaguchi-Shinozaki 2013). In response to abiotic stress, there is an accumulation of ABA that causes rapid stomatal closure to limit water loss by transpiration (Wilkinson and Davies 2002), and over a long term ABA also modulates gene expression of many ABA responsive genes under drought and heat stress conditions (Rizhsky et al. 2004). When subjected to water deficit or suboptimal growth conditions, ABA was found to be accumulated in a genotype-dependent manner

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in different legumes including lupin, chickpeas, Phaseolus, and peas (Bertrand et al. 1991; Gallardo et al. 1994; Jain and Chattopadhyay 2010; Zdunek and Lips 2001). Abscisic acid perception and signal transduction in Arabidopsis has been extensively worked out, although such studies in legumes are limiting. Recently the PYR/PYL/RCAR family of ABA receptors was characterized in soybeans for their interaction with type 2C protein phosphatase (Bai et al. 2013). A few PYL-like receptor genes (in particular PYL4-like) were shown to be upregulated in chickpeas in response to wounding indicating the role of ABA (Pandey et al. 2017). Another interesting but less studied role of ABA is in development of plant-microbe interactions, where it positively regulates the establishment of arbuscular mycorrhiza (AM) and negatively regulates the legume–rhizobium symbiosis (Stec et al. 2016). This is also important in view of the climate change scenario, as nitrogen fixation is very sensitive to environment stresses, particularly temperature and soil water deficit (Zahran 1999). Climate change can directly affect legume-rhizobium symbiosis by reducing the survival of rhizobia, their competitiveness, nodule formation, growth or activity, or can act indirectly by modifying the carbon supply to the nodules (Vadez et al. 2012). In addition to ABA, the roles of salicylic acid (SA) and ethylene (ET) in regulating drought and heat stress tolerance are well documented (Bita and Gerats 2013; Khan et al. 2015; Ozga et al. 2016). The adverse effect of heat stress on photosynthesis is reduced by salicylic acid through changes in proline production in wheat (Khan et al. 2013). In grapevine the decrease in photosynthetic rate at high temperature was countered by SA by maintaining higher RuBisCO activation state and partly enhancing the level of HSP21 (Wang et al. 2010). Salicylic acid treatment also increased the antioxidant system in grapevine (Wang and Li 2006). In addition to its role in ameliorating abiotic stress response, SA also plays an important role in nodulation of legumes. Application of SA reduces nodule primodium formation and the number of nodules formed. Accumulation of SA has been proposed as a defense mechanism associated with the establishment of rhizobium-legume symbiosis. The suppression of defense response only occurs when the plant recognizes its correct partner, producing a compatible nod factor (Martínez-Abarca et al. 1998; Stacey et al. 2006). Endogenous accumulation of SA was found to play an important role in stomatal closure and drought tolerance in Arabidopsis (Miura et al. 2013). Grain legumes or pulses contain several metabolites that are considered as antinutritional factors with respect to their use as food or feed. Two such important metabolites include phytic acid (PA) and the raffinose family of oligosaccharides (RFOs). Phytic acid (or Myo-inositol hexakisphosphate (InsP6), PA) is synthesized by almost all the eukaryotic cells, however, in plants as compared to other vegetative tissues, its abundance is almost 1,000 times more in the seeds where it gets accumulated during seed development and serves as a main form of storage for phosphorus (Sparvoli and Cominelli 2015). It is a strong chelating agent that limits the bioavailability of divalent mineral micronutrients for monogastric animals including humans. Worldwide, efforts are being made to primarily develop low phytic acid lines in many crop plants (Cichy and Raboy 2009), however, levels of phytic acid have been found to be associated with biotic and abiotic stress tolerance (Dhole and Reddy 2016; Joshi-Saha and Reddy 2015). Recently many novel roles for phytic acid or its derivatives have been identified in plants (Joshi-Saha and Reddy 2016; Williams et al. 2015). Many breeding lines/mutants with perturbations in the phytic acid biosynthesis are compromised in their yield and are susceptible to biotic and abiotic stresses particularly in more stress-prone semi-arid tropical climates (Meis et al. 2003; Murphy et al. 2008; Naidoo et al. 2012; Oltmans et al. 2005; Raboy et al. 2015). Raffinose families of oligosaccharides (RFOs), widely present in legumes, are a group of watersoluble carbohydrates derived from sucrose by addition of galactosyl moieties (Frias et al. 1999; Peterbauer et al. 2001; Tahir et al. 2012). They are present in legumes in high amounts and cannot be digested by monogastric animals including humans and can cause flatulence (Jones et al. 1999). However, reducing these RFOs can have adverse effects on seed germination and stress response (ElSayed et al. 2014; Gangl and Tenhaken 2016).

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The breeding programs for developing low antinutrients should be carefully considered in view of the present climate change scenario. In this context there is a need for extensive characterization of the vast germplasm collections with respect to such antinutrient compounds like PA and RFOs for the identification of suitable accessions with low or moderate levels of these compounds adapted to a particular agroclimatic zone. 9.5  STRATEGY FOR STRESS ESCAPE: CLIMATE CHANGE AND PHENOLOGY Phenology is the study of the timing of life cycle events at the population level. As discussed previously, increasing temperature alone or in combination with elevated CO2 levels can be detrimental particularly in aggravating the heat damage, which is very pronounced in sexual reproduction, particularly the development of male gametophyte and flowering response (Bita and Gerats 2013; Hedhly 2011; Hedhly et al. 2009). Correct time of flowering is critical for reproductive success of plants and yields as it can lead to escape from biotic and/or abiotic stresses, affect “fitness” of species in an ecosystem, and/or in case of cross-pollinated species may influence the synchrony of pollination with respect to pollinator distribution or availability (Jagadish et al. 2016). The transition from vegetative to reproductive meristem is the hallmark of time to flower and is regulated by a large number of environmental and internal developmental cues including temperature, photoperiod, hormonal, and metabolic signals among others (Poethig 2003; Putterill et al. 2004; Zeiger and Taiz 2002). Analysis of effects of global warming on various species reveals a consistent temperaturerelated shift, or “fingerprint,” across different taxa including plants (Khanduri et al. 2008; Root et al. 2003), and it is predicted that relative changes in seasonal timing are likely to be greatest for primary consumers, particularly in the terrestrial environment (Thackeray et al. 2016). Various meta-analyses in a wide range of plant species have shown phenological changes with an early onset of spring for mid- and higher latitudes and an extension of growing periods (Khanduri et al. 2008; Menzel et al. 2006). Warm season legumes adapted to tropical climates (mostly of phaseoloid clade) and cool season legumes adaptable to temperate climate (mostly of galegoid clade) respond differently to environmental cues for flowering. Most of the tropical and subtropical legumes do not require an exposure to low temperature (vernalization) for floral induction, while the temperate and Mediterranean crops mostly require such an exposure (Summerfield and Roberts 1985; Weller and Ortega 2015). The predicted increase in temperature can affect vernalization by reducing the duration of “safe-winter-chill” in warmer regions resulting in reduced flowering and seed production in case of fruit and nut production from perennial crops (Luedeling 2012). However, in annuals the changes in flowering time can also be due to changes in cultivation practices and/or development of cultivar through breeding for adaptation of a particular agroclimate (Jagadish et al. 2016). For example, in chickpeas, a cool season legume, the alleles for vernalization requirement were selected against, which helped the adaptation of chickpea as a spring sown crop in west Asia, the Mediterrranean type climate in southern Australia, and as post-rainy season crop with moderate winter in low latitude regions of India and east Africa (Abbo et al. 2002; Vadez et al. 2012). An ambient growth temperature also triggers a thermosensory pathway to control flowering (Capovilla et al. 2015). Plants require certain “thermal time” as development cue to progress to the next phase. There are very limited studies on cardinal temperatures (base, optimum, and maximum) and thermal time for most of the legumes, and these parameters are still ill-defined especially with respect to transition to flowering (Covell et al. 1986; Kaushal et al. 2016). There is a need to define these parameters and how they influence legume growth and development especially under the predicted global rise in temperature. There is also a need to identify heat tolerant genotypes and incorporate this trait in cultivars in grain legumes (Gaur et al. 2015). In addition to identifying and developing heat stress tolerant breeding material, developing early flowering and early maturing genotypes has become an important breeding strategy to “escape” the

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terminal drought and/or heat stress faced by cool season legumes (Gaur et al. 2008). Such genotypes can be selected from screening of large germplasm collections, pre-breeding to incorporate novel traits from wild germplasm, or can be developed through induced mutagenesis (Joshi-Saha et al. 2015; Sharma et al. 2013). Early maturing genotypes are found to be suitable for regions with short winter or late sown conditions or in newer niches like rice fallow cultivation. However, such genotypes will have yield penalty if the crop is exposed to intermittent drought during the vegetative or reproductive stages and will also be at a disadvantage if suitable conditions for crop growth are available for longer period (Agbicodo et al. 2009; Ludlow and Muchow 1990). Therefore, it is imperative to develop both early maturing phenology and heat tolerant genotypes depending on the agroclimatic niche.

9.6  CONCLUDING REMARKS Drought is one of the major abiotic stresses that cause severe yield losses in crops including grain legumes. Drought tolerance is a complex trait and increasing global temperature and high levels of CO2 will add to its complexity and plant adaptation strategies. So far most of the breeding efforts have been made using single traits and/or single stress scenarios. However, there is a need to study and screen for the multiple stresses, particularly heat and drought, and select for suitable genotypes based on the agroclimatic region of interest. There are various drought contributing traits yet many of them are not readily used by plant breeders due to several reasons including their low heritability, measurements being labor intensive, and not always being positively correlated with the yield under stress conditions due to several reasons. Therefore, there is a need to develop welldefined traits and high throughput screening methodologies for particular agroecological niche. In addition to food security and climate resilience there are also concerns regarding the assurance of food quality. There are many breeding efforts for improving the nutritional quality of crops including pulses, particularly in context with mineral bioavailability and digestibility. Breeding efforts to reduce different antinutrients especially PA and RFOs are also underway. However, many of these antinutrients play an important role in plant growth and development and reducing them would lead to compromised growth especially under stressful environments. Therefore, there is a need to critically assess the effect of these antinutrients on legume biology and to screen the large germplasm collections for genotypes with lower antinutritional factors adapted to a particular agroclimatic zone such that the growth and/or yields are not compromised.

REFERENCES Abbo, S., S. Lev-Yadun, and N. W. Galwey. 2002. Vernalization response of wild chickpea. New Phytol 154:695–701. AbdElgawad, H., D. Peshev, G. Zinta et al. 2014. Climate extreme effects on the chemical composition of temperate grassland species under ambient and elevated CO2: A comparison of fructan and non-fructan accumulators. PLoS One 9:e92044. AbdElgawad, H., G. Zinta, G. T. S. Beemster, I. A. Janssens, and H. Asard. 2016. Future climate CO2 levels mitigate stress impact on plants: Increased defense or decreased challenge? Front Plant Sci 7:556. Agbicodo, E. M., C. A. Fatokun, S. Muranaka, R. G. F. Visser, and C. G. van der Linden. 2009. Breeding drought tolerant cowpea: Constraints, accomplishments, and future prospects. Euphytica 167:353–70. Aggarwal, P. K. 2003. Impact of climate change on Indian agriculture. J Plant Biol 30:189–98. Ainsworth, E. A., and S. P. Long. 2005. What have we learned from 15 years of free-air CO2 enrichment (FACE)? A meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2. New Phytol 165:351–71. Ali, S. M., B. Sharma, and M. J. Ambrose 1994. Current status and future strategy in breeding pea to improve resistance to biotic acid abiotic stresses. Euphytica 73:115–26.

THE PULSE OF PULSES UNDER CLIMATE CHANGE

155

Andrews, M., and S. Hodge. 2010. Climate change, a challenge for cool season grain legume crop production. In Climate Change and Management of Cool Season Grain Legume Crop, eds. S. S. Yadav, and R. Redden, 1–10. Dordrecht, The Netherlands: Springer. Araújo, S. S., S. Beebe, M. Crespi et al. 2015. Abiotic stress responses in legumes: Strategies used to cope with environmental challenges. Crit Rev Plant Sci 34:237–80. Awasthi, R., N. Kaushal, V. Vadez et al. 2014. Individual and combined effects of transient drought and heat stress on carbon assimilation and seed filling in chickpea. Funct Plant Biol 41:1148–67. Bai, G., D. H. Yang, Y. Zhao et al. 2013. Interactions between soybean ABA receptors and type 2C protein phosphatases. Plant Mol Biol 83:651–64. Bandhopadhayay, P. K. 2014. Root distribution pattern of pulses in response to water availability. In Resource Conservation Technology in Pulses, eds. P. K. Ghosh, K. K. Hazra, N. Kumar, N. Nadarajan, and M. Venkatesh, 512–520. Jodhpur, India: Scientific Publishers. Barnabas, B., K. Jager, and A. Feher. 2008. The effect of drought and heat stress on reproductive processes in cereals. Plant Cell Environ 31:11–38. Bashar, M. K.. 1990. Xylem vessel variability at three positions of rice root (Oryza sativa L.). Bangladesh Rice J 1:64–72. Beebe, S. E., I. M. Rao, M. W. Blair, and J. A. Acosta-Gallegos. 2013. Phenotyping common beans for adaptation to drought. Front Physiol 4:35–6. Belel, M. D., R. A. Halim, M. Y. Rafii, and H. M. Saud. 2014. Intercropping of corn with some selected legumes for improved forage production: A review. J Agric Sci 6: 48–62. Bertrand, A., Y. Castonguay, and P. Nadeau. 1991. Leaf gas exchange and ABA accumulation in Phaseolus vulgaris genotypes of contrasting drought tolerance. Plant Physiol Suppl 96:1; Conference: Annual meeting of the American Society of Plant Physiology, Albuquerque, NM (United States), July 28–August 1, 1991. Bhandari, K., K. D. Sharma, B. H. Rao et al. 2017. Temperature sensitivity of food legumes: A physiological insight. Acta Physiol Plant 39:1–22. Bishop, J., S. G. Potts, and H. E. Jones. 2016. Susceptibility of Faba Bean (Vicia faba L.) to heat stress during floral development and anthesis. J Agron Crop Sci 202: 508–17. Bita, C. E., and T. Gerats. 2013. Plant tolerance to high temperature in a changing environment: Scientific fundamentals and production of heat stress-tolerant crops. Front Plant Sci 4:273. Bramley, H., N. C. Turner, D. W. Turner, and S. D. Tyerman. 2009. Roles of morphology, anatomy, and aquaporins in determining contrasting hydraulic behavior of roots. Plant Physiol 150: 348–64. Burridge, J., C. N. Jochua, A. Bucksch, J. P. Lunch. 2016. Legume shovelomics: High-throughput phenotyping of common bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata subsp. Unguiculata) root architecture in the field. Field Crops Res 192:21–32. Butterly, C. R., R. Armstrong, D. Chen, and C. Tang. 2016. Free-air CO2 enrichment (FACE) reduces the inhibitory effect of soil nitrate on N2 fixation of Pisum sativum. Ann Bot 117:177–85. Capovilla, G., M. Schmid, and D. Posé. 2015. Control of flowering by ambient temperature. J Exp Bot 66:59–69. Carvalho, M. H. C. 2008. Drought stress and reactive oxygen species. Plant Signal Behav 3:156–65. Chimungu, J. G., K. M. Brown, and J. P. Lynch. 2014a. Large root cortical cell size improves drought tolerance in maize. Plant Physiol 166:2166–78. Chimungu, J. G., K. M. Brown, and J. P. Lynch. 2014b. Reduced root cortical cell file number improves drought tolerance in maize. Plant Physiol 166:1943–55. Ciais, P., A. S. Denning, P. P. Tans et al. 1997. A three-dimensional synthesis of vegetation feedbacks in doubled CO2 climate experiments. J Geophys Res Atmos 102:5857–72. Cichy, K. and Raboy, V. 2009. Evaluation and development of low phytate crops. In: Modification of Seed Composition to Promote Health and Nutrition. Agron Monograph 51. Clark, R. T., R. B. MacCurdy, J. K. Jung, 2011. Three-dimensional root phenotyping with a novel imaging and software platform. Plant Phys 156:455–65. Comas, L. H., S. R. Becker, V. M. V. Cruz, P. F. Byrne, and D. A. Dierig. 2013. Root traits contributing to plant productivity under drought. Front Plant Sci 4:442. DOI: 10.3389/fpls.2013.00442. Costa-Saura, J. M., J. Martínez-Vilalta, A. Trabucco, D. Spano, and S. Mereu. 2016. Specific leaf area and hydraulic traits explain niche segregation along an aridity gradient in Mediterranean woody species. Perspect Plant Ecol Evol Syst 21:23–30.

156

CLIMATE CHANGE AND CROP PRODUcTION

Covell, S., R. H. Ellis, E. H. Roberts, and R. J. Summerfield. 1986. The influence of temperature on seed germination rate in grain legumes: I. A comparison of chickpea, lentil, soybean and cowpea at constant temperatures. J Exp Bot 37:705–715. Cronk, Q., I. Ojeda, and R. T. Pennington. 2006. Legume comparative genomics: Progress in phylogenetics and phylogenomics. Curr Opin Plant Biol 9:99–103. Crosson, P. 1989. Climate change and mid-latitudes agriculture: Perspectives on consequences and policy responses. Clim Change 15:51–73. Cushman, J. S. 2001. Crassulacean acid metabolism. A plastic photosynthetic adaptation to arid environments. Plant Physiol 127:1439–48. Daryanto, S., L. Wang, and P. A. Jacinthe. 2015. Global synthesis of drought effects on food legume production. PLoS One. https://doi.org/10.1371/journal.pone.0127401. Daszkowska-Golec, A., and I. Szarejko. 2013. Open or close the gate—Stomata action under the control of phytohormones in drought stress conditions. Front Plant Sci 4:138. DOI: 10.3389/fpls.2013.00138. Devasirvatham, V., P. Gaur, N. Mallikarjuna, T. N. Raju, R. M. Trethowan, and D. K. Y. Tan. 2013. Reproductive biology of chickpea response to heat stress in the field is associated with the performance in controlled environments. Field Crop Res 142:9–19. Dhole, V. J., and K. S. Reddy. 2016. Association of phytic acid content with biotic stress tolerance in mungbean (Vigna radiata L. Wilezek). Phytoparasitica 44:261–7. ElSayed, A., M. S. Rafudeen, and D. Golldack. 2014. Physiological aspects of raffinose family oligosaccharides in plants: Protection against abiotic stress. Plant Biol 16:1–8. Fan, J., B. Mc Conkey, H. Wang, and H. Janzen. 2016. Root distribution by depth for temperate agricultural crops. Field Crop Res 189:68–74. FAO. 2016. Pulses: Nutritious Seeds for a Sustainable Future. Document published in 2016. www.fao.org/3/ai5528e.pdf Farooq, M., N. Gogoi, S. Barthakur et al. 2017. Drought stress in grain legumes during reproduction and grain filling. J Agron Crop Sci 203:81–102. Feller, U. 2006. Stomatal opening at elevated temperature: An underestimated regulatory mechanism? Gen Appl Plant Phys 32:19–31. (special issue). Feller, U., and I. I. Vaseva. 2014. Extreme climatic event: Impacts of drought and high temperature on physiological processes in agronomically important plants. Front Envion Sci 2:39. https://doi.org/10.3389/ fenvs.2014.00039. Feng, W., H. Linder, N. E. Robbins, and J. R. Dinneny 2016. Growing out of stress: The role of cell- and organscale growth control in plant water-stress responses. Plant Cell 28:1769–82. Frias, J., A. Bakhsh, D. Jones et al. 1999. Genetic analysis of the raffinose oligosaccharide pathway in lentil seeds. J Exp Bot 50:469–76. Gallardo, M., N. C. Turner, and C. Ludwig. 1994. Water relations, gas exchange and abscisic acid content of Lupinus cosentinii leaves in response to drying different proportions of the root system. J Exp Bot 45:909–18. Gallup, J. L., and J. D. Sachs. 2000. Agriculture, climate, and technology: Why are the tropics falling behind? Am J Agric Econ 82:731–7. Gan, Y., C. Hamel, J. T. O’Donovan et al. 2015. Diversifying crop rotations with pulses enhances system productivity. Sci Rep 5:14625. DOI: 10.1038/srep14625. Gangl, R., and R. Tenhaken. 2016. Raffinose family oligosaccharides act as galactose stores in seeds and are required for rapid germination of Arabidopsis in the dark. Front Plant Sci 7:1115–6. DOI: 10.3389/fpls.2016.01115. Gaur, P. M., J. Kumar, C. L. L. Gowda et al. 2008. Breeding chickpea for early phenology: Perspectives, progress and prospects. In Food Legumes for Nutritional Security and Sustainable Agriculture: Proceedings of the Fourth International Food Legumes Research Conference, eds. M. C. Kharkwal, 39–48, New Delhi, India: Indian Society of Genetics and Plant Breeding. Gaur, P. M., S. Samineni, L. Krishnamurthy et al. 2015. High temperature tolerance in grain legumes. Legume Perspectives 7:24–5. George, J. P., S. Schueler, S. Karanitsch-Ackerl, K. Mayer, R. T. Klumpp, M. Grabner 2015. Inter- and intraspecific variation in drought sensitivity in Abies spec. and its relation to wood density and growth traits. Agric For Meteorol 214/215:430–43. Ghildiyal, M. C., and P. Sharma-Natu 2000. Photosynthetic acclimation to rising atmospheric carbon dioxide concentration. Indian J Exp Biol 38:961–6.

THE PULSE OF PULSES UNDER CLIMATE CHANGE

157

Ghosh, P. K., K. K. Bandyopadhyay, R. H. Wanjari et al. 2007. Legume effect for enhancing productivity and nutrient use-efficiency in major cropping systems—an Indian perspective: A review. J Sustainable Agric 30:59–86. Gornall, J., R. Betts, E. Burke et al. 2010. Implications of climate change for agricultural productivity in the early twenty-first century. Philos Trans R Soc Lon B Biol Sci 365:2973–89. Guilioni, L., J. Wery, and F. Tardieu. 1997. Heat stress-induced abortion of buds and flowers in pea: Is sensitivity linked to organ age or to relations between reproductive organs? Ann Bot 80:159–68. Hall, A. E. 2004. Breeding for adaptation to drought and heat in cowpea. Eur J Agron 1:447–54. Hall, A. E. 2012. Phenotyping cowpeas for adaptation to drought. Front Physiol 3:155–6. DOI: 10.3389/ fphys.2012.00155. Hedhly, A. 2011. Sensitivity of flowering plant gametophytes to temperature fluctuations. Environ Exp Bot 74:9–16. Hedhly, A., J. I. Hormaza, M. Herrero. 2009. Global warming and sexual plant reproduction. Trends Plant Sci 14:30–6. Henry, A., A. J. Cal, T. C. Batoto, R. O. Torres, and R. Serraj. 2012. Root attributes affecting water uptake of rice (Oryza sativa) under drought. J Exp Bot 63:4751–63. Henzler, T., R. N. Waterhouse, A. J. Smyth et al. 1999. Diurnal variations in hydraulic conductivity and root pressure can be correlated with the expression of putative aquaporins in the roots of Lotus japonicus. Planta 210:50–60. Hofstra, G., and J. D. Hesketh. 1969. The effect of temperature on stomatal aperture in different species. Can J Botany 47:1307–10. Hu, B., A. Henry, K. M. Brown, and J. P. Lynch. 2014. Root cortical aerenchyma inhibits radial nutrient transport in maize (Zeas mays). Ann Bot 113:181–9. Hubbard, K. E., N. Nishimura, K. Hitomi, E. D. Getzoff, and J. I. Schroeder. 2010. Early abscisic acid signal transduction mechanisms: Newly discovered components and newly emerging questions. Genes Dev 24:1695–708. Ibrahim H. M. 2011. Heat stress in food legumes: Evaluation of membrane thermostability methodology and use of infra-red thermometry. Euphytica 180:99–105. Iglesias-García R., E. Prats, S. Fondevilla, Z. Satovic, D. Rubiales. 2015. Quantitative trait loci associated to drought adaptation in pea (Pisum sativum L.). Plant Mol Biol Rep 33:1768–78. DOI: 10.1007/ s11105-015-0872-z. IPCC. 2013. Climate change 2013: The physical science basis. In Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, eds. T. F. Stocker, D. Qin, G. K. Plattner et al., 1535 pp. Cambridge, MA: Cambridge University Press. IPCC. 2014. Climate change 2014: Synthesis report. In Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, eds. R. K. Pachauri, and L. A. Meyer, 151 pp. Geneva, Switzerland: IPCC. Jagadish, S. V. K., R. V. Bahuguna, M. Djanaguiraman, R. Gamuyao, P. V. V. Prasad, P. Q. Craufurd. 2016. Implications of high temperature and elevated CO2 on flowering time in plants. Front Plant Sci 7: 913. https://dx.doi.org/10.3389%2Ffpls.2016.00913. Jain, D., and D. Chattopadhyay. 2010. Analysis of gene expression in response to water deficit of chickpea (Cicer arietinum L.) varieties differing in drought tolerance. BMC Plant Biol 10:24. https://doi. org/10.1186/1471-2229-10-24. Jensen, E. S., M. B. Peoples, R. M Boddey et al. 2012. Legumes for mitigation of climate change and the provision of feedstock for biofuels and biorefineries. A review. Agron Sustain Dev 32:329–64. Jha, U. C., A. Bohra, N. P. Singh. 2014b. Heat stress in crop plants: Its nature, impacts and integrated breeding strategies to improve heat tolerance. Plant Breed 133:679–701. Jha, U. C., S. K. Chaturvedi, A. Bohra, P. S. Basu, and M. S. Khan. 2014a. Abiotic stresses, constraints and improvement strategies in chickpea. Plant Breed 133:163–78. Jones, D. A., M. S. DuPont, M. J. Ambrose, J. Frias, C. L. Headley. 1999. The discovery of compositional variation for the raffinose family of oligosaccharides in pea seeds. Seed Sci Res 9:305–10. Jongrungklang, N., B. Toomsan, N. Vorasoot et  al. 2012. Classification of root distribution patterns and their contributions to yield in peanut genotypes under mid-season drought stress. Field Crops Res 127:181–90.

158

CLIMATE CHANGE AND CROP PRODUcTION

Joshi-Saha, A., and K. S. Reddy. 2015. Repeat length variation in the 5′UTR of myo-inositol monophosphatase gene is related to phytic acid content and contributes to drought tolerance in chickpea (Cicer arietinum L.). J Exp Bot 66:5683–90. Joshi-Saha, A., and K. S. Reddy. 2016. Phytic acid: Boon or bane? Conflict between animal/human nutrition and plant health. J Food Legumes 29:163–73. Joshi-Saha, A., K. S. Reddy, V. C. Petwal, and J. Dwivedi. 2015. Identification of novel mutants through electron beams and gamma irradiation in chickpea (Cicer aritinum L). J Food Legumes 28:99–104. Joshi-Saha, A., C. Valon, J. Leung. 2011a. A brand new START: Abscisic acid perception and transduction in the guard cell. Sci Signal 4:re4. DOI: 10.1126/scisignal.2002164. Joshi-Saha, A., C. Valon, and J. Leung. 2011b. Abscisic acid signal off the STARTing block. Mol Plant 4:562–80. Kadam, N. N., X. Yin, P. S. Bindraban, P.C. Struik, and K. S. Jagadish. 2015. Does morphological and anatomical plasticity during the vegetative stage make wheat more tolerant of water deficit stress than rice? Plant Phys 167:1389–401. Kant, S., S. Seneweera, J. Rodin et al. 2012. Improving yield potential in crops under elevated CO2: Integrating the photosynthetic and nitrogen utilization efficiencies. Front Plant Sci 3:162. DOI: 10.3389/fpls.2012.00162. Kashiwagi, J., L. Krishnamurthy, J. H. Crouch, and R. Serraj. 2006. Variability of root length density and its contributions to seed yield in chickpea (Cicer arietinum L.) under terminal drought stress. Field Crops Res 95:171–81. Kaushal, N., R. Awasthi, K. Gupta, P. Gaur, K. H. M. Siddique, and H. Nayyar. 2013. Heat-stress-induced reproductive failures in chickpea (Cicer arietinum) are associated with impaired sucrose metabolism in leaves and anthers. Funct Plant Biol 40:1334–49. Kaushal, N., K. Bhandari, K. H. M. Siddique, H. Nayyar, and M. T. Moral. 2016. Food crops face rising temperatures: An overview of responses, adaptive mechanisms, and approaches to improve heat tolerance. Cogent Food Agric 2:1134380. https://doi.org/10.1080/23311932.2015.1134380. Khan, M. I. R, M. Fatma, T. S. Per, N. A. Anjum, and A. Nafees. 2015. Salicylic acid-induced abiotic stress tolerance and underlying mechanisms in plants. Front Plant Sci 6:462. DOI: 10.3389/fpls.2015.00462. Khan, M. I. R., N. Iqbal, A. Masood, T. S. Per, and N. A. Khan. 2013. Salicylic acid alleviates adverse effects of heat stress on photosynthesis through changes in proline production and ethylene formation. Plant Signal Behav 8:e26374. DOI: 10.4161/psb.26374. Khanduri, V. P., C. M. Sharma, and S. P. Singh. 2008. The effects of climate change on plant phenology. Environmentalist 28:143–7. Kim, H. Y., M. Lieffering, K. Kobayashi, M. Okada, and S. Miura. 2003. Seasonal changes in the effects of elevated CO2 on rice at three levels of nitrogen supply: A free air CO2 enrichment (FACE) experiment. Global Change Biol 9:826–837. Kimball, B. A., P. J. Pinter, R. L. Garcia et al. 1995. Productivity and water use of wheat under free-air CO2 enrichment. Global Change Biol 1:429–42. Koolachart, R., S. Jogloya, N. Vorasoota et al. 2013. Rooting traits of peanut genotypes with different yield responses to terminal drought. Field Crops Res 149:366–78. Krishnamurthy, L., M. Zaman-Allah, R. Purushothaman, M. Irshad Ahmed, and V. Vadez. 2011. Plant biomass productivity under abiotic stresses in SAT agriculture. In Biomass—Detection, Production, and Usage, ed. D. Matovic, 247–264. London, UK: Intech. Krupinsky, J. M., K. L. Bailey, M. P. McMullen, B. D. Gossen, and T. K. Turkington. 2002. Managing plant disease risk in diversified cropping systems. Agron J 94:198–209. Kumar, J., R. Kant, S. Kumar, P. S. Basu, A. Sarker, N. P. Singh. 2016. Heat tolerance in lentil under field conditions. Legume Genomics and Genet 7:1–11. Lake, J. A., F. I. Woodward, and W. P. Quick. 2002. Long-distance CO2 signalling in plants. J Exp Bot 53:183–193. Lawlor, D. W. 2002. Carbon and nitrogen assimilation in relation to yield: Mechanisms are the key to understanding production systems. J Exp Bot 53:773–787. Lithourgidis, A. S., C. A. Dordas, C. A. Damalas, and D. N. Vlachostergios 2011. Annual intercrops: An alternative pathway for sustainable agriculture. Aust J Crop Sci 5:396–410. Ludlow, M. M., and R. C. Muchow. 1990. A critical evaluation of traits for improving crop yields in waterlimited environments. Adv Agron 43:107–53.

THE PULSE OF PULSES UNDER CLIMATE CHANGE

159

Luedeling, E. 2012. Climate change impacts on winter chill for temperate fruit and nut production: A review. Sci Hortic 144:218–29. Lynch, J. P. 1995. Root architecture and plant productivity. Plant Physiol 109:7–13. Lynch, J. P. 2013. Steep, cheap and deep: An ideotype to optimize water and N acquisition by maize root systems. Ann Bot 112:347–57. Lynch, J. P., J. G. Chimungu, and K. M. Brown. 2014. Root anatomical phenes associated with water acquisition from drying soil: Targets for crop improvement. J Exp Bot 65:6155–66. Martínez-Abarca, F., J. A. Herrera-Cervera, P. Bueno, J. Sanjuan, and T. Bisseling. 1998. Involvement of salicylic acid in the establishment of the Rhizobium meliloti-Alfalfa symbiosis. Mol Plant Microbe Inter 11:153–5. Meis, S. J., W. R. Fehr, and S. R. Schnebly. 2003. Seed source effect on field emergence of soybean lines with reduced phytate and raffinose saccharides. Crop Sci 43:1336–9. Menzel, A., T. H. Sparks, N. Estrella et al. 2006. European phenological response to climate change matches the warming pattern. Global Change Biol 12:1969–76. Metzner, R., A. Eggert, D. van Dusschoten et al. 2015. Direct comparison of MRI and X-ray CT technologies for 3D imaging of root systems in soil: Potential and challenges for root trait quantification. Plant Methods 11:1–11. Mia, Md. W., A. Yamauchi, and Y. Kono. 1996. Root system structure of six food legume species: Inter- and intra-specific variations. Jpn J Crop Sci 65:131–40. Miura, K., H. Okamoto, E. Okuma et al. 2013. SIZ1 deficiency causes reduced stomatal aperture and enhanced drought tolerance via controlling salicylic acid-induced accumulation of reactive oxygen species in Arabidopsis. Plant J 73:91–104. Montero-Tavera, V., R. Ruiz-Medrano, and B. Xoconostle-Cázares. 2008. Systemic nature of drought-tolerance in common bean. Plant Signal Behav 3:663–6. Monterroso, V. A., and H. C. Wien. 1990. Flower and pod abscission due to heat stress in beans. J Am Soc Hortic Sci 115:631–4. Mott, K. A. 1988. Do stomata respond to CO2 concentrations other than intercellular. Plant Physiol 86:200–3. Murphy, A. M., B. Otto, C. A. Brearley, J. P. Carr, and D. E. Hanke. 2008. A role for inositol hexakisphosphate in the maintenance of basal resistance to plant pathogens. Plant J 56:638–52. Naidoo, R., P. Tongoona, J. Derera, M. Laing, and G. M. F. Watson. 2012. Combining ability of low phytic acid (lpa1-1) and quality protein maize (QPM) lines for seed germination and vigour under stress and non-stress conditions. Euphytica 185:529–41. Nakashima, K., and K. Yamaguchi-Shinozaki. 2013. ABA signaling in stress-response and seed development. Plant Cell Rep 32:959–70. Nedumaran, S., P. Abinaya, P. Jyosthnaa, B. Shraavya, P. Rao, and C. Bantilan. 2015. Grain legumes production, consumption and trade trends in developing countries. Working Paper Series No 60. ICRISAT Research Program, Markets, Institutions and Policies. Patancheru-502 324, 64 pp. Telangana, India: International Crops Research Institute for the Semi-Arid Tropics. Nemeskeri, E., K. Molnar, R. Víg, A. Dobos, and J. Nagy. 2012. Defence strategies of annual plants against drought. In: Advances in Selected Plant Physiology Aspects, ed. G. Montanaro. London, UK: Intech, available at: http://cdn.intechopen.com/pdfs/35826/InTech-Defence_strategies_of_annual_plants_ against_drought.pdf. (Accessed: October 23, 2017). Obermeier, W. A., L. W. Lehnert, C. I. Kammann et al. 2016. Reduced CO2 fertilization effect in temperate C3 grasslands under more extreme weather conditions. Nat Clim Change 7:137–41. Oltmans, S. E., W. R. Fehr, G. A. Welke, V. Raboy, and K. L. Peterson. 2005. Agronomic and seed traits of soybean lines with low–phytate phosphorus. Crop Sci 45:593–8. Ozga, J. A., H. Kaur, R. P. Savada, and D. M. Reinecke. 2016. Hormonal regulation of reproductive growth under normal and heat-stress conditions in legume and other model crop species. J Exp Bot 68:1885–94. Paez-Garcia, A., C. M. Motes, W. R. Scheible, R. Chen, E. B. Blancaflor, M. J. Monteros. 2015. Root traits and phenotyping strategies for plant improvement. Plants 4:334–55. Pandey, P., V. Ramegowda, and M. Senthil-Kumar. 2015. Shared and unique responses of plants to multiple individual stresses and stress combinations: Physiological and molecular mechanisms. Front Plant Sci 6:723. DOI: 10.3389/fpls.2015.00723.

160

CLIMATE CHANGE AND CROP PRODUcTION

Pandey, S. P., S. Srivastava, R. Goel et al. 2017. Simulated herbivory in chickpea causes rapid changes in defense pathways and hormonal transcription networks of JA/ethylene/GA/auxin within minutes of wounding. Sci Rep 7:44729. DOI: 10.1038/srep44729. Passioura, J. B. 1983. Roots and drought resistance. Agric Water Manag 7:265–80. Peixoto, J. P., and A. H. Oort. 1992. Physics of Climate Change. New York, NY: American Institute of Physics Press. Peterbauer, T., L. B. Lahuta, A. Blöchl et al. 2001. Analysis of the raffinose family oligosaccharide pathway in pea seeds with contrasting carbohydrate composition. Plant Physiol 127:1764–72. Pfeifer, J., N. Kirchgessner, T. Colombi, and A. Walter. 2015. Rapid phenotyping of crop root systems in undisturbed field soils using X-ray computed tomography. Plant Methods 11:41. https://doi.org/10.1186/ s13007-015-0084-4. Poethig, R. S. 2003. Phase change and the regulation of developmental timing in plants. Science 301:334–6. Polania, J., I. M. Rao, C. Cajiao et al. 2017. Shoot and root traits contribute to drought resistance in recombinant inbred lines of MD 23–24 × SEA 5 of common bean. Front Plant Sci 8:296. DOI: 10.3389/fpls.2017.00296. Poorter, H., A. Van der Werf, O. K. Atkin, and H. Lambers. 1991. Respiratory energy requirements of roots vary with potential growth rate of a plant species. Physiol Plant 83:469–75. Prince, S. J., M. Murphy, R. N. Mutava et al. 2017. Root xylem plasticity to improve water use and yield in water-stressed soybean. J Exp Bot 68:2027–38. Purushothaman, R., M. Zaman-Allah, N. Mallikarjuna, R. Pannirselvam, L. Krishnamurthy, and C. L. L. Gowda. 2013. Root anatomical traits and their possible contribution to drought tolerance in grain legumes. Plant Prod Sci 16:1–8. Putterill, J., R. Laurie, and R. Macknight. 2004. It’s time to flower: The genetic control of flowering time. BioEssays 26:363–73. Raboy, V., K. Peterson, C. Jackson et al. 2015. A substantial fraction of barley (Hordeum vulgare L.) low phytic acid mutations have little or no effect on yield across diverse production environments. Plants 4:225–39. Ratnakumar, P., and V. Vadez. 2011. Ground nut (Arachis hypogaea) genotypes tolerant to intermittent drought maintain a high harvest index and have small leaf canopy under stress. Funct Plant Biol 38:1016–23. Reynolds-Henne, C. E., A. Langenegger, J. Mani, N. Schenk, A. Zumsteg, and U. Feller. 2010. Interactions between temperature, drought and stomatal opening in legumes. Environ Exp Botany 68:47–3. Rizhsky, L., H. Liang, R. Mittler. 2002. The combined effect of drought stress and heat shock on gene expression in tobacco. Plant Physiol 130:1143–51. Rizhsky, L., H. Liang, J. Shuman, V. Shulaev, S. Davletova, and R. Mittler. 2004. When defense pathways collide, the response of Arabidopsis to a combination of drought and heat stress. Plant Physiol 134:1683–96. Roger, E. D., D. Monaenkova, M. Mijar, A. Nori, D. J. Goldmann, and P. N. Benfey. 2016. X-ray computed tomography reveals the response of root system architecture to soil texture. Plant Physiol 171:2028–40. Rogers, A., E. A. Ainsworth, and A. D. B. Leakey. 2009. Will elevated carbon dioxide concentration amplify the benefits of nitrogen fixation in legumes? Plant Physiol 151:1009–16. Root, T. L., J. T. Price, K. R. Hall, S. H. Schneider, C. Rosenzweig, and J. A. Pounds. 2003. Fingerprints of global warming on wild animals and plants. Nature 421:57–60. Roxy, M. K., R. Kapoor, T. Pascal, M. Raghu, A. Karumuri, and B. N. Goswami. 2015. Drying of Indian subcontinent by rapid Indian Ocean warming and a weakening land-sea thermal gradient. Nat Commun 6:7423. DOI: 10.1038/ncomms8423. Rubiales, D., and A. Mikic. 2014. Introduction: Legumes in sustainable agriculture. Crit Rev Plant Sci 34:2–3. Schoppach, R., D. Wauthelet, L. Jeanguenin, and W. Sadok. 2013. Conservative water use under high evaporative demand associated with smaller root metaxylem and limited trans-membrane water transport in wheat. Funct Plant Biol 41:257–69. Sharma, S., H. D. Upadhyaya, R. K. Varshney, and C. L. L. Gowda. 2013. Pre-breeding for diversification of primary gene pool and genetic enhancement of grain legumes. Front Plant Sci 4:309. https://dx.doi.org /10.3389%2Ffpls.2013.00309. Signorelli, S., E. Casaretto, M. Sainz, P. Díaz, J. Monza, and O. Borsani. 2013. Antioxidant and photosystem II responses contribute to explain the drought—heat contrasting tolerance of two forage legumes. Plant Physiol Biochem 70:195–203. Sivakumar, M. V. K., H. P. Das, and O. Brunini. 2005. Impacts of present and future climate variability and change on agriculture and forestry in the arid and semi-arid tropics. Clim Change 70:31–72.

THE PULSE OF PULSES UNDER CLIMATE CHANGE

161

Songsri, P., S. Jogloy, N. Vorasoot, C. Akkasaeng, A. Patanothai, and C. C. Holbrook. 2008. Root distribution of drought-resistant peanut genotypes in response to drought. J Agron Crop Sci 19:92–103. Sparks, T. H. 2014. Local-scale adaptation to climate change: The village flower festival. Clim Res 60:87–9. Sparvoli, F., and E. Cominelli. 2015. Seed biofortification and phytic acid reduction: A conflict of interest for the plants? Plants 4:728–55. Srinivasan, A., H. Takeda, and T. Senboku. 1996. Heat tolerance in food legumes as evaluated by cell membrane thermostability and chlorophyll fluorescence techniques. Euphytica 88:35–45. Stacey, G., C. B. McAlvin, S. Y. Kim, J. Olivares, and M. J. Soto. 2006. Effects of endogenous salicylic acid on nodulation in the model legumes Lotus japonicus and Medicago truncatula. Plant Physiol 141:1473–81. Stagnari, F., A. Maggio, A. Galieni, and M. Pisante. 2017. Multiple benefits of legumes for agriculture sustainability: An overview. Chem Biol Technol Agric 4:2. DOI: 10.1186/s40538-016-0085-1. Stec, N., J. Banasiak, and M. Jasiński. 2016. Abscisic acid—an overlooked player in plant-microbe symbioses formation? Acta Biochim Pol 63:53–5. Summerfield, R. J., and E. H. Roberts. 1985. Grain legume species of significant importance in world agriculture. In Handbook of Flowering, eds. A. H. Halevy, 61–73. Boca Raton, FL: CRC Press. Sutka, M., G. Li, J. Boudet, Y. Boursiac, P. Doumas, and C. Maurel. 2011. Natural variation of root hydraulics in Arabidopsis grown in normal and salt-stressed conditions. Plant Physiol 55:1264–76. Suzuki, N., S. Koussevitzky, R. O. N. Mittler, and G. A. D. Miller. 2012. ROS and redox signalling in the response of plants to abiotic stress. Plant Cell Environ 35:259–70. Tahir, M., M. Baga, A. Vandenberg, and R. N. Chibbar. 2012. An assessment of raffinose family oligosaccharides and sucrose concentration in genus Lens. Crop Sci 52:1713–20. Taiz, L., and E. Zeiger. 2010. Water balance of plants. In: Plant Physiology, 5th Edition, 85–102. Sunderland, MA: Sinauer Associates. Tans, P. 2009. An accounting of the observed increase in oceanic and atmospheric CO2 and an outlook for the future. Oceanography 22:26–35. Tardieu, F. 2012. Any trait or trait-related allele can confer drought tolerance: Just design the right drought scenario. J Exp Bot 63:25–31. Thackeray, S. J., P. A. Henrys, D. Hemming et al. 2016. Phenological sensitivity to climate across taxa and trophic levels. Nature 535:241–5. Thiaw, S., and A. E. Hall. 2004. Comparison of selection for either leaf electrolyte leakage or pod set in enhancing heat tolerance and grain yield of cowpea. Field Crops Res 86:239–53. UN (United Nations). 2013. Resolution 68/231. International Year of Pulses, 2016. Available at: http://www. un.org/en/ga/68/resolutions.shtml (Accessed: December 11, 2017). Upadhayaya, H. D., J. Kashiwagi, R. K. Varshney et al. 2012. Phenotyping chickpeas and pigeonpeas for adaptation to drought. Front Physiol 3:179. DOI: 10.3389/fphys.2012.00179. Vadez, V. 2014. Root hydraulics: The forgotten side of roots in drought adaptation. Field Crops Res 165:15–24. Vadez, V., J. D. Berger, T. Warkentin et al. 2012. Adaptation of grain legumes to climate change: A review. Agron Sustain Dev 32:31–44. Vadez, V., J. Kholova, R. S. Yadav, and C. T. Hash. 2013. Small temporal differences in water uptake among varieties of pearl millet (Pennisetum glaucum (L.) R.Br.) are critical for grain yield under terminal drought. Plant Soil 371:447–62. Van der Werf, A., A. Kooijman, R. Welschen, H. Lambers. 1988. Respiratory energy costs for the maintenance of biomass, for growth and for ion uptake in roots of Carexdiandra and Carexacutiformis. Physiol Plant 72:483–91. van Dusschoten, D., R. Metzner, J. Kochs et al. 2016. Quantitative 3D analysis of plant roots growing in soil using magnetic resonance imaging. Plant Physiol 170:1176–88. Varshney, R. K., M. Thudi, S. N. Nayak et al. 2014. Genetic dissection of drought tolerance in chickpea (Cicer arietinum L.). Theor Appl Genet 127:445–62. Vaz, A. S., D. Silva, P. Alves et al. 2016. Evaluating population and community structure against climate and land-use determinants to improve the conservation of the rare Narcissus pseudonarcissus subsp. Nobilis. Anales Jard Botá Madrid 73:e027. Wahid, A. S., M. A. Gelani, and M. R. Foolad 2007. Heat tolerance in plants: An overview. Environ Exp Bot 61:199–223.

162

CLIMATE CHANGE AND CROP PRODUcTION

Wang, L. J., L. Fan, W. Loescher et  al. 2010. Salicylic acid alleviates decreases in photosynthesis under heat stress and accelerates recovery in grapevine leaves. BMC Plant Biol 10:34. https://doi. org/10.1186/1471-2229-10-34. Wang, L. J., and S. H. Li. 2006. Salicylic acid-induced heat or cold tolerance in relation to Ca2+ homeostasis and antioxidant systems in young grape plants. Plant Sci 170:685–94. Weller, J. L., and R. Ortega. 2015. Genetic control of flowering time in legumes. Front Plant Sci 6:207. DOI: 10.3389/fpls.2015.00207. Wilkinson, S., and W. J. Davies. 2002. ABA-based chemical signaling: The coordination of responses to stress in plants. Plant Cell Environ 25:195–210. Williams, S. P., G. E. Gillaspy, and I. Y. Perera. 2015. Biosynthesis and possible functions of inositol phyrophosphates in plants. Front Plant Sci 6:1–9. Woodward, F. I. 1987. Stomatal numbers are sensitive to increases in CO2 from pre-industrial levels. Nature 327:617–8. Wu, J., and Y. Guo. 2014. An integrated method for quantifying root architecture of field-grown maize. Ann Bot 114:841–51. Xu, Z., Y. Jiang, B. Jia, and G. Zhou. 2016. Elevated-CO2 response of stomata and its dependence on environmental factors. Front Plant Sci 7:657. DOI: 10.3389/fpls.2016.00657. Yang, X., Y. Li, B. Ren et al. 2012. Drought induced root aerenchyma cell formation restricts water uptake in rice seedlings supplied with nitrate. Plant Cell Physiol 53:495–504. Zahran, H. H. 1999. Rhizobium-legume symbiosis and nitrogen fixation under severe conditions and in an arid climate. Microbiol Mol Biol Rev 63:968–89. Zaman-Allah, M., D. M. Jenkinson, and V. Vadez. 2011. A conservative pattern of water use, rather than deep or profuse rooting, is critical for the terminal drought tolerance of chickpea. J Exp Bot 62:4239–52. Zandalinas, S., R. Mittler, D. Balfagon, V. Arbona, and A. Gomez-Cadenas. 2017. Plant adaptations to the combination of drought and high temperatures. Physiol Plant 162:2–12. Zdunek, E., and S. H. Lips. 2001. Transport and accumulation rates of abscisic acid and aldehyde oxidase activity in Pisum sativum L. in response to suboptimal growth conditions. J Exp Bot 52:1269–76. Zeiger, E., and L. Taiz. 2002. The control of flowering. In Plant Physiology, 3rd edition, 559–590. Sunderland, MA: Sinauer Associates Inc. Zhu, J. M., K. M. Brown, and J. P. Lynch. 2010. Root cortical aerenchyma improves the drought tolerance of maize (Zea mays L.). Plant Cell Environ 33:740–9.

CHapTer  10

Diversifying Agriculture with Novel Crop Introductions to Abandoned Lands with Suboptimal Conditions Sarah C. Davis, Jacqueline E. Kloepfer, Jesse A. Mayer, and John C. Cushman CONTENTS 10.1 Introduction........................................................................................................................... 163 10.2 Perennial Crops..................................................................................................................... 164 10.2.1 Examples of Perennial Crops.................................................................................... 164 10.2.2 Potential Production of Perennial Crops on Abandoned Lands................................ 165 10.3 Opportunities for Diversified Crops on Abandoned Lands................................................... 165 10.4 Improving Agricultural Resilience in Semi-Arid Regions with CAM Crops....................... 167 10.5 Conclusion............................................................................................................................. 169 References....................................................................................................................................... 169 10.1 INTRODUCTION Abandoned agricultural lands represent opportunities for new management strategies that promote agroecosystem resilience without disrupting the economic welfare of current agricultural producers. Recently abandoned lands or degraded lands, in particular, where there has not yet been reestablishment of native habitats, provide opportunities for novel agricultural solutions that promote both rural economies and improved ecosystem services. This chapter describes crops suited to abandoned lands that are otherwise considered suboptimal for typical commodities. In some cases, suboptimal conditions are the product of a legacy of intensive management or mining activities. In other cases, however, suboptimal conditions are characterized by an ecosystem with lower nutrient or water availability that cannot support typical commodity crops. Here we discuss examples of crops that thrive in suboptimal conditions, imparting greater resiliency in agroecosystems, and avoiding competition for prime agricultural land that is already exploited. In the United States, there is an estimated 179 Mha of abandoned agricultural land (Campbell et al. 2013), and between 59 and 127 Mha that is still available for production (Emery et al. 2017). The gradual abandonment of agricultural land over the last half-century coincided with increasing farm size as mechanization led to more efficient management of a single crop over larger areas. This recent history of landscape simplification has not necessarily supported ecosystem or crop resilience and has in many cases resulted in increased greenhouse gas (GHG) emissions and chemical inputs (Meehan et al. 2011). 163

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Increased resource demands from agriculture can be met either by improving yields or expansion of cropland. Greater yields have been accomplished with increased fertilizer application and with the introduction of hybridized and genetically modified crop varieties. With these changes, the agricultural landscape in the United States has become increasingly less diverse. While biotechnology afforded some benefits in crop resistance to pests (e.g., Bt corn), there were unintended costs in the loss of crop varieties. A similar trend in the loss of genetic diversity has been observed in agriculture globally (Giovannucci et al. 2012). There are many examples of novel agricultural opportunities on abandoned lands that would diversify the landscape and promote ecological resilience. Cropland expansion to meet increased resource demand can lead to unintended losses of ecosystem services. Even diversified cropping strategies will have a negative impact on biodiversity if they replace native forest and grasslands. There is, however, an opportunity to divert agricultural expansion onto abandoned and reclaimed mine lands that are underservicing the ecosystem in terms of both habitat provision and carbon sequestration relative to other land uses. Abandoned mine lands are frequently characterized by poor soil quality, and even when reclaimed, these lands have low biodiversity. Yet there is growing evidence that advanced perennial crops can sequester soil carbon on mine lands (Guzman et al. 2016; Guzman and Lal 2014; Mukhopadhyay et al. 2016) and potentially improve habitats (e.g., Werling et al. 2014). There is little evidence that agricultural producers or landowners currently realize this opportunity or the associated economic incentives afforded by reclamation of such abandoned areas. In this chapter, we will first review opportunities for diversifying crop ecosystems using perennial plants in the United States. We highlight examples in the central United States for introducing alternative crops that promote agricultural resilience on abandoned land that was either previously planted for agriculture or previously mined for coal and gas or other minerals. Then, we will review the opportunity for alternative crops that use crassulacean acid metabolism (CAM) on abandoned lands in semi-arid regions, where conditions are typically poorly suited to common commodity crops. 10.2  PERENNIAL CROPS There is strong evidence to suggest that perennial crops, when compared with current annual crop commodities, sequester more carbon, emit less greenhouse gas (GHG), and leach less dissolved inorganic nitrogen to sensitive watersheds, especially if managed according to best practices (Davis et al. 2012; Sartori et al. 2006; VanLoocke et al. 2016). Some of these same crops are tolerant of suboptimal conditions, including degraded soils that resulted from previous mining activity to extract fossil fuels (e.g., Marra et al. 2013). Despite the benefits of perennial plants, adoption of alternative perennial crops that have been introduced as advanced biofuels has been slow because of market uncertainty in the advanced biofuel and bioproduct industries. 10.2.1  Examples of Perennial Crops Switchgrass is a native perennial grass that has been grown in a wide range of soils and environmental conditions (Arundale et al. 2013; Heaton et al. 2008; Sartori et al. 2006; Skousen et al. 2014). It has similar yield to that of maize in the United States, but greater potential for soil carbon sequestration (Davis et al. 2012; Sartori et al. 2006), and it supports a higher biodiversity of birds, mammals, insects, and microbiota (Evans et al. 2015; Harrison and Berenbaum 2013; Mao et al. 2013; Robertson et al. 2011; Werling et al. 2014). Yields of switchgrass in the United States are 10 Mg ha−1 y−1 on average (Arundale et al. 2013), and a modest quantity of fertilizer is required relative to row crops like maize.

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Table 10.1 Dry Biomass Yields of Miscanthus x giganteus in (Mg ha−1) on Abandoned Agricultural Lands and Abandoned Mine Lands Relative to Yield Reported in Prime Agricultural Soils Yield after 3rd Growing Season

Yield after 4th Growing Season

Abandoned agricultural landa

19.7 (±11.6)

17.4 (±4.0)

Abandoned mine landb

15.5 (±10.4)

11.4 (±6.8)

Prime agricultural landc

25.4 (±11.8)

25.8 (±6.1)

Note: Values in parentheses indicate standard deviation. a Davis, unpublished. b Skousen et al. 2014. c Heaton et al. 2008.

Miscanthus x gigantheus (Mxg) is a non-native perennial grass that frequently achieves higher yields than switchgrass with lower fertilizer application (Arundale et al. 2013; Heaton et al. 2008). The most studied genotype of Mxg is a sterile hybrid of two species native to Asia that is selfincompatible and has a low risk of invasion relative to other Miscanthus species (Matlaga and Davis 2013; Quinn et al. 2011). This grass has the potential to increase soil carbon stocks on degraded agricultural lands (Davis et al. 2012; Emery et al. 2017; Hudiburg et al. 2015) and average yield in field trials that span a range of soil types in the United States is 23.4 Mg (Arundale et al. 2013). 10.2.2  Potential Production of Perennial Crops on Abandoned Lands Recent yield estimates on abandoned agricultural lands with suboptimal soils in Ohio indicate that biomass production of Mxg reaches 19.7 Mg ha−1 in the third growing season (Table 10.1), almost twice the average yield of maize (∼10 M ha−1 y−1 including grain and stover) on prime agricultural land (Somerville et al. 2010). Yields reported for Mxg on abandoned mine lands with degraded soils were 15 Mg ha−1 in the third growing season (Skousen et al. 2014). While these yields are lower than those reported for Mxg on prime agricultural soils (e.g., Arundale et al. 2013; Heaton et al. 2008), these rates of production are commercially viable. Therefore, a crop of Mxg could potentially produce biomass feedstock for fuel while also improving soil quality, increasing carbon sequestration, and reducing soil erosion on degraded lands. 10.3  OPPORTUNITIES FOR DIVERSIFIED CROPS ON ABANDONED LANDS In 2016, maize occupied 38 Mha (94 million acres) of land, soybean occupied 34 Mha (83 million acres), and wheat occupied 20 Mha (50 million acres) of land in the United States, with these three crops comprising 68% of total cropland in the nation (USDA 2017). The increasing lack of diversity in the agricultural landscape poses risks to the resilience of crop products. Both economic and environmental risks are associated with monoculture plantings across wide geographic ranges, and recent reports suggest that yields of major commodity crops will decline in response to climatic change (Challinor et  al. 2014). Based on a preliminary assessment of data from the National Agricultural Statistics Service (NASS) and the Cropland Data Layer (CDL) that describes agriculture in growing zone 6 of the United States, there has been a decline in winter wheat as well as winter wheat plantings in rotation with soybean (a net reduction of 0.49 Mha, or 1.2 million acres, in seven years). While there is evidence of an increase in the area planted in maize, there is also evidence that up to 28 alternative crops were introduced across the region. Many of these newly introduced crops were produced on far fewer acres than the major commodities, reflecting what is likely to be localized diversification rather than widespread landscape changes.

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Figure 10.1 Agricultural land and abandoned mine land that intersects with plant hardiness zone 6 and unglaciated soils in the central United States.

Growing zone 6 provides a useful example of the potential opportunities for promoting agricultural resilience on abandoned lands (Figure 10.1). This agricultural region lies at mid-latitudes within the United States from Ohio to Colorado in a transitional zone for both plant hardiness classification (USDA 2012) and plant heat tolerance (AHS 1997). This region supports major commodity crops in a continental climate characterized by extreme seasonal fluctuations. Agricultural suitability ranges from prime at the center to suboptimal at the southern, eastern, and western margins of this region. Intermixed in this landscape are abandoned mine lands, some of which are not successfully reclaimed and offer the potential for agricultural expansion. With climate change, greater drought is expected during the growing season (Kirtman et al. 2013; US National Climate Assessment 2014), with consequences for crop production; while higher precipitation is predicted in the off-season (Kirtman et al. 2013; US National Climate Assessment 2014), with consequences of soil erosion and flooding within the central United States. Some cropland may be abandoned when yields decline, but there is also the potential that agricultural expansion will occur to meet demands for crops that have higher value. For these higher value crops with consistent demand, reduced yields lead to an increased footprint on the land. Such agricultural expansion affects ecosystem services like carbon sequestration, nutrient retention, and biodiversity by reducing native perennial habitats. There are almost 3.2 Mha (8 million acres) in zone 6 that were converted from non-agricultural land uses (including forests, wetlands, developed lands, idle cropland, and barren lands) to agriculture between 2008 and 2015. This land use change might suggest increased demand for agricultural products, shifting economic markets, a need to compensate for crop losses, labor force transitions, or a combination of these and other factors. In total, abandoned agricultural lands comprise an estimated 26% of all marginal land in the United States (Emery et al. 2017), suggesting that abandonment in some cases is due to soil degradation. Perennial crops like switchgrass and Miscanthus can be introduced in these locations to enhance resilience of the agricultural economy, improve soil quality, and diversify crops. Perennial crops can also be used to diversify agricultural lands, improve resilience, and increase production on lands where yields are declining.

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10.4  IMPROVING AGRICULTURAL RESILIENCE IN SEMI-ARID REGIONS WITH CAM CROPS The examples described thus far addressed agricultural resilience on abandoned land where the soil has either been degraded due to resource exploitation, or the land has lost value due to yield or market changes. In some cases, agriculture resilience may depend upon more discrete climatic events, like prolonged drought. This section provides examples of emerging crops that are specifically suited to survive, and even thrive, despite extreme drought events. Crassulacean acid metabolism (CAM) is the photosynthetic pathway with the greatest water use efficiency (WUE) (e.g., Borland et al. 2009; Davis et al. 2014) because it affords a plant the ability to keep stomata closed during part or all of the day when radiative heat and evaporative demand are highest. CAM plants instead open stomata during cooler nighttime conditions, losing less water and storing the carbon assimilated mainly as malic acid in the large vacuoles. After daybreak, stomata close and decarboxylation converts this stored carbon to CO2 that can then be fixed by ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) while light energy is available. The CAM system in plants is defined by four phases (Osmond 1978), where phase I is the period of nighttime carbon assimilation by phosphoenolpyruvate (PEP) carboxylase and build-up of malic acid, and phase III is defined by RuBisCO fixation of decarboxylated CO2 while the stomata are closed during the day. Phases II and IV are characterized by the shift in enzymatic activities and stomatal apertures that occur at dawn and dusk, respectively. The magnitude of carbon assimilation during phases II and IV is usually dependent on moisture availability. Some plants, like some Clusia and Mesembryanthemum species, are facultative CAM and operate with C3 photosynthesis while shifting into CAM only due to changes in environmental conditions, such as reduced water availability (Winter and Holtum 2014). Other species, such as Agave and Opuntia species, are obligate CAM plants and present tremendous potential for crops in arid and semi-arid conditions. Many CAM plants can survive long periods of drought by virtue of tissue succulence (Males 2017) and are common in desert ecosystems with low productivity. Other CAM species are found in moist and even saturated environments and are also tolerant of flooding conditions under which CAM affords a selective advantage by providing a CO2 concentrating mechanism in submerged conditions (Keeley 1998). Commercial crops are dominated by C3 and C4 species that have been optimized for high yields. Even though some of these crops have wide temperature tolerance ranges, none can survive long durations of drought and extreme heat. Regions with these conditions struggle to maintain agriculture and are frequently deemed unsuitable for crops. Recent field trials in the semi-arid southwestern United States indicate that the obligate CAM species Agave americana and Opuntia ficus-indica yield as much or more biomass than commercial commodity crops with only a fraction of the water requirements (Cushman et al. 2015; Davis et al. 2016). Productivity modeling of Agave spp. and O. ficus-indica demonstrate that these CAM species have great potential for biomass production in semi-arid, marginal lands (Owen and Griffiths 2014). Owen et  al. (2016) found that O. ficus-indica demonstrates better climate resilience on a global basis than Agave tequilana, a commercially produced variety. However, there are over 200 varieties of Agave and several examples that have resilience in extreme climatic conditions. In a field trial comparing Agave fourcroydes (a fiber crop species), A. tequilana (grown for tequila production), and A. americana, it was clear that A. americana had significantly greater cold tolerance than the other two species, surviving prolonged temperatures of −8°C (Davis et al. 2016). Agave americana also has extreme heat tolerance, maintaining optimum photosynthetic rates at daytime temperatures up to 45°C, and is tolerant of temperatures up to 63°C (Nobel and Smith 1983). Other high-yielding species with wide temperature tolerance ranges include Agave salmiana and Agave mapisaga (Table 10.2).

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Table 10.2 Biomass Yields of Agave and Opuntia Reported in Locations with Varying Water Inputs and Associated Water-Use Efficiency (WUE) Biomass Yield (Mg ha−1 y−1) Agave americana  Arizona, USA Agave salmiana  Mazatlan, Mexico  Tacubaya, Mexico Agave mapisaga  Tacubaya, Mexico Opuntia ficus-indica  Nevada, USA  Brazil  Mexico  Spain  Tunisia a b c d e f g

Water Input (mm y−1)

WUE (kg ha−1 mm−1)

530a 300a

17.5 13.3

10b 34b

427b 848b

23.4 40.1

32b

848b

37.8

6.4c 3.1–47.3d 31.7, 47.3e 4.2–9.4f 2.4–10.2g

582c 805–1204d 771, 2352e 206–361f 175–500g

11.0 3.85–49.1 41.1, 20.1 20.4–26.0 13.7–20.4

9.3a 4.0a  

Davis et al. 2016. Davis et al. 2011. Mayer et al. in preparation. Dubeux et al. 2006. Nobel et al. 1992. Sánchez et al. 2012. Monjauze and Le Houérou 1965.

Agave spp. are cultivated as crops in 31 countries that report to the Food and Agriculture Organization of the United Nations and can be managed either as perennial crops by trimming older leaves annually or periodically harvested when the plant reaches an appropriate size. Most Agave crops around the world support fiber production, but some are also used for sweeteners, waxes, beverages, and biofuels. WUE of A. americana grown in Maricopa, Arizona in the United States (Davis et al. 2016) was over ten times that of cotton, grown for fiber and one of the most important crops in the region. Many Agave species also have high concentrations of soluble carbohydrates, and A. americana in particular has low lignin in the cell walls, making it an ideal crop for fermentation to alcohol-based products including fuel (Cushman et al. 2015; Davis et al. 2011, 2015). O. ficus-indica may also be an ideal perennial species for development on lands not suitable for traditional agriculture. Due to high biomass productivity and WUE, Opuntia has been grown in more than 30 countries including its native Mexico and the southwest United States (Nobel et al. 1992). Opuntia is cultivated for the tender pads (nopalitos) and fruit (tunas) used in many traditional meals. The mature pads can also be used as forage for livestock, especially during water-limiting conditions (Guevara et al. 2009). Ongoing work is investigating the potential of Opuntia ficus-indica as a low-input biofuel feedstock (Cushman et al. 2015; Yang et al. 2015). Particular interests revolve around the use of O. ficus-indica as a feedstock for bioethanol or biogas production (Mason et al. 2015; do Nascimento Santos et al. 2016). The field trials performed to date with Opuntia ficus-indica demonstrate its potential as a food, forage, and bioenergy crop for abandoned and marginal lands. Studies in Brazil and Argentina have examined the effects of different nutrient fertilization levels on cladode and fruit productivity (Dubeux et al. 2006; Galizzi et al. 2004). In both cases, fertilization only had a significant impact on productivity at the highest planting densities (∼40,000 plants/ha). Two different planting densities were used in a field trial of O. ficus-indica in Chile and resulted in up to 47 Mg ha−1 yr−1 under well-watered and fertilized conditions (Dubeux et  al. 2006). In Mexico, field-grown O. ficusindica produced an average of 46 Mg ha−1 yr−1 also under well-watered and fertilized conditions

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(Nobel et al. 1992). In southeastern Spain, Geographic Information Systems (GIS) combined with a predictive yield model based upon actual field trial yield data estimated productivity of up to 9.4 Mg ha−1 yr−1 under rain-fed conditions (Sánchez et al. 2012). In Tunisia, productivity up to 10.2 Mg ha−1 yr−1 has been reported also under rain-fed conditions (Monjauze and Le Houérou 1965). Data from year three of a five-year field trial with O. ficus-indica in southern Nevada have produced dry biomass yields similar to those reported previously (Table 10.2). In this instance, plant density was lower than most studies (∼1,300 plants/ha) to accommodate different irrigation rates across the field. A field trial of the more cold-tolerant Opuntia elisiana conducted in Kingsville, Texas reported an above-ground biomass of 17.7 Mg ha−1 y−1 with 662 mm of annual rainfall resulting in WUE of 26.7 kg ha−1 mm−1 (Han and Felker 1997). These productivity estimates vary widely due to the great variation in planting densities in the studies, but an average of 1,700 plants/ ha is a traditional planting density (FAO 1992). The lower limit of absolute minimum annual rainfall for O. ficus-indica is estimated to be in the range of 250–350 mm (FAO 1992; Tuck et al. 2006). The minimal rainfall requirements are arid, similar to desert conditions, but annual precipitation below this amount requires supplemental irrigation to sustain an O. ficus-indica crop. 10.5 CONCLUSION The crops described here serve as examples of alternative agricultural species that can be cultivated on degraded soils in temperate or dry regions, but there are innumerable novel crop species that would be suited to specific local conditions that limit the production of more common commodity crops. The trend of agricultural simplification that has occurred historically can be reversed by promoting diversification of agricultural investments. Adoption of novel cropping systems will require political support, education, and effective communication about potential benefits. REFERENCES AHS. 1997. Plant Heat Zone Map, compiled by Meteorological Evaluation Services Co., Inc., coordinated by H.M. Cathey. American Horticultural Society. Arundale, R. A., F. G. Dohleman, E. A. Heaton, J. M. McGrath, T. B. Voigt, and S. Long. 2013. Yields of Miscanthus x giganteus and Panicum virgatum decline with stand age in the Midwestern USA. GCB Bioenergy 6:1–13. Borland, A. M., H. Griffiths, J. Hartwell, and J. A. C. Smith. 2009. Exploiting the potential of plants with crassulacean acid metabolism for bioenergy production on marginal lands. J Exp Bot 60:2879–96. Campbell, J., D. Lobell, T. Genova, A. Zumkehr, and C. Field. 2013. Seasonal energy storage using bioenergy production from abandoned croplands. Environ Res Lett 8:035012. DOI:10.1088/1748-9326/8/3/035012. Challinor, A. J., J. Watson, D. B. Lobell, S. M. Howden, D. R. Smith, and N. Chhetri. 2014. A meta-analysis of crop yield under climate change and adaptation. Nat Clim Change 4:287–91. Cushman, J., S. Davis, X. Yang, and A. Borland. 2015. Development and use of bioenergy feedstocks for semiarid and arid lands. J Exp Bot 66:4177–93. Davis, S., D. LeBauer, and S. Long. 2014. Light to liquid fuel: Theoretical and realized energy conversion efficiency of plants using crassulacean acid metabolism (CAM) in arid conditions. J Exp Bot 65:3471–8. Davis, S., W. Parton, S. Del Grosso, C. Keough, E. Marx, P. Adler, and E. DeLucia. 2012. Impact of secondgeneration biofuel agriculture on greenhouse gas emissions in the corn-growing regions of the US. Front Ecol Environ 10:69–74. Davis S. C., F. G. Dohleman, and S. P. Long. 2011. The global potential for Agave as a bioenergy feedstock. Global Change Biology Bioenergy 3: 68–78. Davis, S. C., E. R. Kuzmick, N. Niechayev, and D. J. Hunsaker. 2016. Productivity and water-use efficiency of Agave americana in the first field trial as bioenergy feedstock on arid lands. GCB Bioenergy 9:314–25.

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Davis S. C., D. Lebauer, R. Ming, S. P. Long. 2015. Toward systems-level analysis of agricultural production from crassulacean acid metabolism (CAM): scaling from cell to commercial production. New Phytologist 208: 66–72. do Nascimento Santos, T., E. D. Dutra, and A. G. do Prado et al. 2016. Potential for biofuels from the biomass of prickly pear cladodes: Challenges for bioethanol and biogas production in dry areas. Biomass Bioenerg 85:215–22. Dubeux, J. J. C. B., M. V. F. Ferreira dos Santos, M. de Andrade Lira, D. Coreiro dos Santos, I. Farias, L. E. Lima, and R. L. C. Ferreira. 2006. Productivity of Opuntia ficus-indica (L.) Miller under different N and P fertilization and plant population in north-east Brazil. J Arid Environ 67:357–72. Emery, I., S. Mueller, Z. Qin, and J. Dunn. 2017. Evaluating the potential of marginal land for cellulosic feedstock production and carbon sequestration in the United States. Environ Sci Technol 51:733–41. Evans, S., L. Kelley, and M. Potts. 2015. The potential impact of second-generation biofuel landscapes on at-risk species in the US. GCB Bioenergy 7:337–48. FAO. 1992. Food and Agriculture Organization of the United Nations. Ecocrop Database. Land and Water Development Division. Opuntia ficus-indica, http://ecocrop.fao.org/ecocrop/srv/en/home. Galizzi, F. A., P. Felker, C. González, and D. Gardiner. 2004. Correlations between soil and cladode nutrient concentrations and fruit yield and quality in cactus pears, Opuntia ficus-indica in a traditional farm setting in Argentina. J Arid Environ 59:115–32. Giovannucci, D., S. Scherr, D. Nierenberg et al. 2012. Food and Agriculture: The future of sustainability. Food and Agriculture Organization of the United Nations. Sustainable Development in the 21st Century (SD21) project. United Nations Department of Economic and Social Affairs, Division of Sustainable Development. Guevara, J. C., P. Suassuna, and P. Felker. 2009. Opuntia forage production systems: Status and prospects for rangeland applications. Rangeland Ecol Manag 62:428–34. Guzman, J. G., and R. Lal. 2014. Miscanthus and switchgrass feedstock potential for bioenergy and carbon sequestration on mine soils. Biofuels 5:313–29. Guzman, J. G., R. Lal, S. Byrd, S. I. Apfelbaum, and R. L. Thompson. 2016. Carbon life cycle assessment for prairie as a crop in reclaimed mine land. Land Degrad Dev 27:1196–204. Han, H., and P. Felker. 1997. Field validation of water-use efficiency of the CAM plant Opuntia ellisiana in south Texas. J Arid Environ 36:133–48. Harrison, T., and M. Berenbaum. 2013. Moth diversity in three biofuel crops and native prairie in Illinois. Insect Sci 20:407–19. Heaton, E., F. Dohleman, and S. Long. 2008. Meeting US biofuel goals with less land: The potential of Miscanthus. Glob Change Biol 14:2000–14. Hudiburg, T. W., S. C. Davis, W. Parton, and E. H. DeLucia. 2015. Bioenergy crop greenhouse gas mitigation potential under a range of management practices. GCB Bioenergy 7:366–74. Keeley, J. 1998. CAM photosynthesis in submerged aquatic plants. Bot Rev 64:121–75. Kirtman, B., S. B. Power, J. A. Adedoyin et al. 2013. Near-term climate change: Projections and predictability. In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, eds. T. F. Stocker, D. Qin, G.-K. Plattner et al., 953–1028. Cambridge, MA: Cambridge University Press. Males, J. 2017. Secrets of succulence. J Exp Bot 68:2121–34. Mao, Y., A. Yannarell, S. Davis, and R. Mackie. 2013. Impact of different bioenergy crops on N-cycling bacterial and archaeal communities in soil. Environ Microbiol 15:928–42. Marra, M., T. Keene, J. Skousen, and T. Griggs. 2013. Switchgrass yield on reclaimed surface mines for bioenergy production. J Environ Qual 42:696–703. Mason, P. M., K. Glover, J. A. C. Smith, K. J. Willis, J. Woods, and I. P. Thompson. 2015. The potential of CAM crops as a globally significant bioenergy resource: Moving from ‘fuel or food’’ to ‘fuel and more food.’ Energ Environ Sci 8:2320–9. Matlaga, D., and A. Davis. 2013. Minimizing invasive potential of Miscanthus x giganteus grown for bioenergy: Identifying demographic thresholds for population growth and spread. J Appl Ecol 50:479–87. Meehan, T. D., B. P. Werling, D. A. Landis, and C. Gratton. 2011. Agricultural landscape simplification and insecticide use in the Midwestern United States. P Natl Acad Sci USA 108:11500–5. Monjauze, A., and H. N. Le Houérou. 1965. Le rôle des Opuntia dans l’économie agricole nord-africaine. Bull Ecole Natl Sup Agron Tunis 8–9:8–164.

DIVERSIFyING AGRIcULTURE wITH NOVEL CROP INTRODUcTIONS

171

Mukhopadhyay, S., R. E. Masto, A. Cerda, and L. C. Ram. 2016. Rhizosphere soil indicators for carbon sequestration in a reclaimed coal mine spoil. CATENA 141:100–8. Nobel P. S., and S. D. Smith. 1983. High and low temperature tolerances and their relationships to distribution of agaves. Plant, Cell and Environment, 6:711–719. Nobel, P. S., E. Garciamoya, and E. Quero. 1992. High annual productivity of certain agaves and cacti under cultivation. Plant Cell Environ 15:329–35. Osmond, C. B. 1978. Crassulacean acid metabolism: A curiosity in context. Ann Rev Plant Physio 29:379–414. Owen, N. A., K. F. Fahy, and H. Griffiths. 2016. Crassulacean acid metabolism (CAM) offers sustainable bioenergy production and resilience to climate change. GCB Bioenergy 8:737–49. Owen, N. A., and H. Griffiths. 2014. Marginal land bioethanol yield potential of four crassulacean acid metabolism candidates (Agave fourcroydes, Agave salmiana, Agave tequilana and Opuntia ficus-indica) in Australia. GCB Bioenergy 6:687–703. Quinn, L., D. Matlaga, J. Stewart, and A. Davis. 2011. Empirical evidence of long-distance dispersal in Miscanthus sinensis and Miscanthus x giganteus. Invas Plant Sci Mana 4:142–50. Robertson, B., P. Doran, L. Loomis, J. Robertson, and D. Schemskes. 2011. Perennial biomass feedstocks enhance avian diversity. GCB Bioenergy 3:235–46. Sánchez, J., F. Sánchez, M. Curt, and J. Fernández. 2012. Assessment of the bioethanol potential of prickly pear (Opuntia ficus-indica (L.) Mill.) biomass obtained from regular crops in the province of Almeria (SE Spain). Israel J Plant Sci 60:301–18. Sartori, F., R. Lal, M. Ebinger, and D. Parrish. 2006. Potential soil carbon sequestration and CO2 offset by dedicated energy crops in the USA. Crit Rev Plant Sci 25:441–72. Skousen, J., C. Brown, T. Griggs, and S. Byrd. 2014. Establishment and growth of switchgrass and other biomass crops on surface mines. J Am Society Min Reclam 3:136–57. Somerville, C., H. Youngs, C. Taylor, S. C. Davis, and S. P. Long. 2010. Feedstocks for lignocellulosic biofuels. Science 329:790–2. Tuck, G., M. J. Glendining, P. Smith, J. I. House, and M. Wattenbach. 2006. The potential distribution of bioenergy crops in Europe under present and future climate. Biomass Bioenerg 30:183–97. USDA. 2012. Plant Hardiness Zone Map, Mapping by the PRISM climate group, Oregon State University and the United States Department of Agriculture- Agricultural Research Service. http://prism.oregonstate. edu. (Accessed: September 8, 2016). USDA. 2017. Census of Agriculture Statistics. United States Department of Agriculture National Agricultural Statistics Service. https://www.nass.usda.gov/. (Accessed: June 8, 2017). US National Climate Assessment. 2014. http://nca2014.globalchange.gov/. (Accessed: November 1, 2016). Vanloocke, A., T. Twine, C. Kucharik, C. Bernacchi. 2016. Assessing the potential to decrease the Gulf of Mexico hypoxic zone with Midwest US perennial cellulosic feedstock production. GCB Bioenergy 9:858–75. Werling, B. P., T. Dickson, R. Isaacs et  al. 2014. Perennial grasslands enhance biodiversity and multiple ecosystem services in bioenergy landscapes. P Natl Acad Sci USA 111:1652–7. Winter, K., and J. Holtum. 2014. Facultative crassulacean acid metabolism (CAM) plants: Powerful tools for unravelling the functional elements of CAM photosynthesis. J Exp Bot 65:3425–41. Yang, L., S. Carl, M. Lu et al. 2015. Biomass characterization of Agave and Opuntia as potential biofuel feedstocks. Biomass Bioenerg 76:43–53.

CHapTer  11

Agroecology Education to Sustain Resilient Food Production Charles A. Francis, Tor Arvid Breland, Geir Lieblein, and Anna Marie Nicolaysen CONTENTS 11.1 Introduction: Participatory Learning and Climate Change................................................ 173 11.2 A Case for Open-Ended Case Studies................................................................................. 175 11.3 Core Agroecology Competences......................................................................................... 176 11.4 Observation......................................................................................................................... 178 11.5 Participation........................................................................................................................ 179 11.6 Dialogue.............................................................................................................................. 180 11.7 Reflection............................................................................................................................. 180 11.8 Visioning............................................................................................................................. 181 11.9 Combining Key Competences............................................................................................. 182 11.10 Conclusions and Outlook.................................................................................................... 182 11.11 Summary............................................................................................................................. 183 References....................................................................................................................................... 184 11.1  INTRODUCTION: PARTICIPATORY LEARNING AND CLIMATE CHANGE Global climate change is manifested in severity of short-term weather events as well as long-term modifications of spatial and temporal differences in temperature, rainfall, and wind. In spite of continuing popular debate, anthropogenic climate change is a reality accepted by serious analysts in meteorology (Blanc and Riley 2017). Whether change is partly due to long-term cycles or primarily caused by human activities such as massive burning of fossil fuels and land use changes leading to increased greenhouse gas (GHG) concentrations in the atmosphere is a moot issue. The large majority of scientific studies describe the change as real and attributed to human activities (Oreskes 2018). Our current challenge is to seek rational ways to mitigate and cope with the impacts of current build-up of carbon dioxide and other GHGs in order to maintain a livable environment for humans, crops, and other species that sustain us (Altieri and Nicholls 2017). Education in agroecology is our focus, defined as the ecology of food systems (Francis et al. 2003). Other chapters in this book present many examples of specific mechanisms of adaptation of plants and cropping systems to climate change, and the need to design for resilience comes through clearly as we consider the components of systems and how they may be manipulated by management. They include discussion of physiological and morphological mechanisms that contribute to resilience to climate change and how crops and their genetic diversity and plasticity may contribute to future 173

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adaptation. Specific examples of how crops in temperate and tropical regions will adapt include their potentials in unique systems such as agroforestry, permaculture, and perennial polycultures. Success in these alternative systems will provide possible solutions to the complex and global challenge of climate change. Our ability to achieve crop adaptation to evolving climatic conditions will to a large extent influence the success of the human experiment for long-term survival. What can agroecology educators contribute to a process of human adaptation to learn to deal with greater complexity and increasing pace of change, and contribute to needed crop adaptation? We need to move beyond the simplistic categorizing of agroecology “as a science, a movement, and a practice” (Wezel et al. 2009) and move the conversation in education to a higher order to deal with complexity of issues such as climate change. Recent meetings, symposia, and publications on climate change, adaptation in agriculture, and resilience have provided valuable ideas (e.g., Agricultural Adaptation to Climate Change, Bryant et al. 2016). In April 2012, FAO and OECD hosted a workshop on “Building Resilience for Adaptation to Climate Change in the Agricultural Sector” (FAO/OECD 2012) and emphasized the importance of economic, biophysical, social, and institutional dimensions of the challenge, noting that these are specific for different agroecological zones. The NCCARF in Australia (George et al. 2016) puts focus on the importance of post-graduate education in general and other agencies specifically with key roles for informing the public about climate change based on solid science and indicates a need for more sophisticated weather and climate models to aid in the prediction of change. There is growing interest in practical education about climate change. In a review of 50 recent articles on education in climate change, Monroe et al. (2017) concluded that it was important to make lessons personally meaningful to students and to use active teaching methods. Examples were working directly with scientists and designing projects in schools or the community. Li and Monroe (2017) explored the quantitative measures of hope among high school students for finding solutions to climate change. In working with farmer audiences, educators are urged to address people’s beliefs, their capacity to affect change, how they sort out multiple and conflicting sources of information, and prior experience with extreme weather events (Chatrchyan et al. 2017). A recent Massive Open Online Course (MOOC) on “National Adaptation Plans: Building Climate Resilience in Agriculture” organized by UNDP, FAO, and UNITAR and presented in November-December of 2017 included lessons, videos, and case studies (UNDP/FAO/UNITAR 2017). The goal was to provide guidelines for countries to develop their own national plans for mitigation and adaptation to change, concluding with a section on communication and evaluation. It is important to build on this foundation, address the complexity of dealing with climate change in a thoughtful and well-informed way, and design educational programs to reach the next generation of agroecologists and decision-makers and enable them to take effective action. Can we adapt our learning methods to meet large and emerging challenges never faced before by educators? Farming systems must also be designed in the context of a growing reality of increasingly scarce land, water, and other production resources. Advances in technology will help to achieve mitigation of some resource challenges. However, there is a generic need for more focus on systems thinking and competence for action when addressing long-term and “wicked” problems such as anthropogenic climate change. We explore in this chapter how education in agroecology through participatory, actionbased, and action-oriented learning in open-ended cases (Francis et  al. 2009) can provide a foundation for study of location-specific farming system mitigation and adaptation to local weather unpredictability and global climate change. Recognizing that there are no simple and widespread solutions is an essential first step in seeking long-term answers to complex challenges in farming system design. Future systems will be unique to local soil and climate conditions, and they will of necessity be both temporally and spatially biodiverse. Their design and implementation will be tempered by local resource endowment as well as politics, economics, culture, and human goals in each location. Agroecology education, as exemplified by our transdisciplinary course in

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Norway (https://www.nmbu.no/course/PAE302), emphasizes multi-perspective approaches in a framework of systems thinking and action-orientation in the pursuit of ecologically, economically, and socially sustainable solutions. It also provides a valuable platform to practice learning the competences needed to meet this challenge. Our goal is to seek innovative educational approaches that are robust and flexible and that prepare students to apply what they learn to problems today as well as those not yet even anticipated (Scharmer and Kaufer 2013). An educational process in Norway has been designed and operationalized that develops five key competences for agroecology students to prepare them well for working in a complex and uncertain future (Francis et al. 2016). These include skills in unbiased and multi-perspective observation, capacities for participation with stakeholders in the learning process, methods for effective dialogue that allow all voices and viewpoints to be heard and considered, skills in comprehensive and in-depth reflection on what has been observed and discussed, and abilities and tools for thoughtful and farreaching visioning that promote long-term thinking and capacity to look over the horizon to facilitate desirable change. In our learning strategy, visioning is not about anticipating what is likely to take place, but rather creating a series of potential scenarios that provide guidance and potential traction for local actions that can help people meet their goals. Similar methods to adapt this strategy to other disciplinary research seem to us essential to build effective teams that can construct a technical foundation for sustainability of future systems. Transdisciplinary teams can build on talents developed in a number of disciplines and seek important complementarities among them. Often these help to reveal emergent properties of systems that are unexpected results not easily detected from understanding only components. Such properties may be especially valuable to help us understand the myriad complexities of unanticipated and seemingly intractable issues (Book and Phillips 2013). This intellectual activity builds on the excitement of interactions among people from different fields of science, an area we might call the “ecotone between disciplines.” Complex issues are not easily understood and analyzed using conventional methods and thinking found in any single discipline in agriculture or in ecology. In designing agroecology education, we have intentionally focused on evaluation of whole systems, on taking into account the value of ideas coming from practitioners in the field, and on developing the skills described above in order to become facilitators of informed action for improved sustainability. This process of education can foster adaptation of unique methods of knowledge building and comprehensive understanding of applications that are not strongly encouraged in our current departments and discipline structures. Many universities, state and national research institutes, and commercial research and development organizations are focused on short-term solutions with patentable results and products. Our orientation in agroecology as defined and practiced in Norway addresses the ecology of food systems (Francis et al. 2003), consistent with the definition as the science or field of knowledge about farming and food systems, including how to improve each system. This can provide a logical conceptual umbrella over our complex and too often poorly defined search for long-term yet location-specific answers to seemingly intractable questions. In this chapter we provide examples from our own educational experience of the past two decades that have prepared us as instructors to better catalyze the learning experience and help our students seek understanding of systems, how to unravel their complexities, and then how to facilitate needed changes. On a higher order, we help them learn about their own learning styles. 11.2  A CASE FOR OPEN-ENDED CASE STUDIES The open-ended case approach has been proposed for dealing with contemporary challenges that are complex, multi-dimensional, and “wicked” in the sense that solutions are incommensurate in meeting the varied goals of multiple stakeholders (Ostrom 1990). These are challenges that have not yet been resolved, making their pursuit somewhat uncomfortable for those students who are

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accustomed to clarity and the desire to “find the right answer” to any question posed in class or as an assignment. We have chosen to call these open-ended cases to illustrate unresolved situations where solutions and perhaps even problems are not yet fully known (Francis et al. 2009). The approach, as we apply this to learning, stands in stark contrast to case studies in law schools or business colleges where instructors explore precedent by assigning cases that have already been resolved, and students must be clever enough to figure out what the teachers already know. Other authors have used the terms action research (Lieblein et al. 2012), action learning (Lieblein et al. 2012), real-life cases (Cliff and Nesbitt 2005), problem-based learning (Margetson 1993), and service learning (Jordan et al. 2005). What has distinguished our approach is that new and complicated situations are uncovered by students during their interviews with farmers and food system stakeholders in an agroecology course. One of their learning objectives is to determine the most important goals of these cooperators, so together they can envision an improved future situation and begin to understand the complexity of achieving it. The process for this learning activity has been developed using case studies in the field with both farmers and food system decision-makers. Student teams gather observations and impressions during transect walks across the farm and through the community. Through interviews, the groups learn and record stakeholder goals, then assemble, digest, and present the information from their field observations and interviews, and then analyze and evaluate the present situation, keeping in mind key goals of people within the system. They often use visioning sessions with the farmer or with people in the community who are concerned about their future food system. This leads to identifying a number of feasible interconnected actions for clients to pursue their visions and thus achieve their goals. Developing future scenarios in cooperation with clients builds ownership by all the participants, encourages clients to choose their own path from among the alternatives or some combination of them, and thus creates an environment where ideas will be co-created by students and those most concerned with the transformation and its outcomes. The open-ended case also increases the relevance of learning because it deals with challenges not yet resolved, and students and clients can all feel they are a part of the solution. From their visioning activities students can give direction to their scenarios and create ownership among their cooperators in the field. The stakes are raised even more when communities offer to pay some of the students’ expenses for lodging and meals during their field research. Students feel an obligation to do their best because of this confidence shown in their projects by leaders in the communities. Food system decision-makers in each community also show more respect and are more willing to make time for student interviews and tours when they know that some of their own funds are invested in the students and the project outcomes. We consider these exemplary field project learning activities important because they represent a valuable type of student research that will lead to responsible action (Lieblein and Francis 2007). The open-ended case has been a key component of learning activities in the Agroecology MSc comprehensive semester at the Norwegian University of Life Sciences (https://www.nmbu.no/courses/PAE302). 11.3  CORE AGROECOLOGY COMPETENCES Traditional university introductory courses in most disciplines begin with definitions and theory, with history and introduction of key players from the past, and lectures on why a particular discipline is important. Many students are intent on learning as a source of skills and tools, eventually gaining the credibility of an academic degree that can help them apply for employment or further study. Traditionally, the teachers lecture and the students listen, with feedback on exams that reflect what students have memorized. Relatively complacent students are willing to learn whatever is taught, with some confidence that the instructors will be wise enough to select the references and topics

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that are most important. Such a conventional learning environment is comfortable to both teachers and students, as everyone has been conditioned by prior classical formal educational experiences to accept this as the norm. The narrow goals of learning information within a specific discipline are clear, and often the answers are not ambiguous nor clouded by the complexity of current and future realities. Yet all too often no one stops to consider whether this type of teaching actually leads to learning the skills for problem-solving and creative thinking that are needed in our present complex societies, especially as related to farming and food systems. We wonder if these traditional students will be prepared to address such complex challenges as designing future systems that will exhibit resilience in the face of climate change. Are they ready to solve other higher-order issues, such as sustaining food systems with limited land and water resources, dealing with uncertainty in food economics and power politics, or addressing alternatives to current inequities in distribution of benefits that result in continuing hunger that plagues a large portion of the global human community? Over the past two decades we have learned that motivated students who are intent on making a difference in the world by addressing complexity are insisting on more practical and relevant education. We have also found that putting focus on learning the key competences of observation, participation, dialogue, reflection, and visioning will help students prepare for a future where there is no syllabus, and it is up to them to work with clients and set directions for change. We insist that research must follow the scientific working method that includes transparency, clarity, logic, and rigor to provide repeatability and credibility. Now and in the immediate future we observe that many people are skeptical of science, and there are ever more “fake news” reports and “alternative facts” that may be comfortable and fit people’s individual bias or economic goals but have no real basis. Education and objectivity are clearly needed to guide the quest for a sustainable future. The learning process can achieve more relevance when it follows a strategy of “dialogue-based education” (Lieblein and Francis 2013) and “participatory learning” (Francis 2014). The five competences are illustrated in Figure 11.1 (inspired by Lieblein et al. 2012), showing how they can connect activities during the learning process and create a unique “dialogue space” in

Figure 11.1 Observation, participation, dialogue, reflection, and visioning competences developed in agroecology courses and degree programs, including multiple interactions in a “learning-action web” of educational activities. (Inspired by Lieblein et al. 2012. J Agr Ed Ext 18:27–40.)

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the middle where ideas and shared meaning are built among those in the university community and stakeholders in the field. In the following sections we explore each of these competences and what we have observed while students are learning and practicing to achieve them. 11.4 OBSERVATION Observation is often confined to the visual arena, with focus on what we can see in a field, on a farm, from a particular “viewscape”, or across a landscape. Learning to understand complexity of farm life compels us to engage students in a captivating type of experience that involves all the senses: vision, smell, taste, feel, and hearing. Our students experience transect walks across fields and farms to observe and sense the total context of where these fit into the larger landscape, as well as the details that they can sense when walking through a new place (Francis et al. 2012a). Farm transect walks taken by students in Norway often expose them to a new type of farming, different crops, integration of animals, and a biodiverse surrounding landscape that is unique compared to what they have experienced before. They smell the aroma of livestock, of rain-soaked forests, and of compost newly applied to fields. They hear the sounds of unfamiliar birds and of human activities on the farm, taste berries along paths in the woods, and get stung by nettles. Social dimensions include meeting other people during the walk, including farmers who are not surprised nor angered with strangers “trespassing” on their land. This experience is digested and related to prior personal experiences, and at times students create innovative metaphors that help them relate in new ways to the unique experiential knowledge gained from a transect walk (Francis et al. 2012b). Several years ago, one Swedish student observed a perennial weed in a pasture and exclaimed, “I feel like that weed, with my roots deep in the soil of my homeland.” Another saw swallows gliding around the fields and barns, and said, “If I had the capability to fly I could see this farm and its details in another way.” Of course today with drone technology we have that “extended human capability.” These walks are experiences students tell us they remember weeks later, as they traverse an unfamiliar landscape in a new place and build a rich context for their open-ended farm case. The instructions we provide before students embark on their “open-ended” observations encourage them to suspend judgement about what they see and to avoid premature and narrow interpretations of the experience. One interesting twist is to require students to walk both farm and community transects with another person in the class, but to accomplish the journey with at least twenty meters between them and to avoid all conversation. During the return they are encouraged to share observations and add value to the exercise. We hope that students can use these skills to later engage their farm and community project environments with a desire and capacity to understand as much of the total situation as possible before designing scenarios for the future. Similar to the farm project, later in the semester students are assigned the task of developing a community case study to uncover goals and work with local residents to explore alternative scenarios for the future. A preliminary transect walk is used for students to traverse a community new to them and observe the details of the built landscape and activities of people interacting there. This transect walk activity has been reported by students to be a unique component in the first semester of an intensive, full-time course in agroecology: farming and food systems. It is also an experience that provides a basis for discussion in student team groups and with stakeholders about historical changes in the landscape and community and observed impacts of climate change and system resilience to these phenomena. Although we do not observe “climate change in action” during a transect walk, which essentially provides a snapshot of one point in time, it is possible to observe some effects of change just as one examines the tree rings of a stump to determine age and past climate from different widths of the rings. We can also see foundations of abandoned barns or houses, clear cutting of small timber tracts, and landforms as a result of glaciation and thus learn about changes that occurred in the past.

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11.5 PARTICIPATION Participation within the team and interactions with stakeholders on the farm and in the community build life skills in communication that will be vital for our students in the future. For several years we have included in the curriculum early in the semester an opportunity for each team to spend a full day dedicated to working with farmers on priority tasks. These have included cleaning barns, weeding vegetables, preparing produce for market, picking stones from fields, stacking firewood, milking cows and goats, and once looking for goats that may have been killed by a wolf. Students report that their interactions with the farmer as well as among their team members are invaluable to building an understanding of what a typical day’s work on the farm could be like and that they gathered information impossible to obtain only from a transect walk or an interview. It is the first such experience and a totally new challenge for some students not acquainted with this type of work. One of the most valuable aspects is working alongside a farmer, hearing about the decisions and priorities that are set each day, and how the myriad tasks needed to keep a farm running are accomplished by the owner, manager, family, interns, and others who are part of each operation. Most students report on the complexity of farms, especially our project farms that include both livestock and crops, and how dependent farmers are on the weather. Farmers often invite our students to join the family and others on the farm for a noon meal, where there is an excellent opportunity to learn more about the people and the multitude of tasks that must be finished each day. Although we were somewhat concerned that students might be assigned to “busy work” by farmers who are already fully occupied, this has not been an issue. We show a cartoon in class that depicts two men working with picks to split some huge stone boulders. One has a bubble of his thoughts, “I am cutting stones,” while the other is thinking, “I am building a cathedral.” Four years ago students who spent a day stacking wood on a small dairy and vegetable farm came in tired in the evening and shared their discussion. “We learned to stack the wood in the first ten minutes, and during the work the rest of the day we were discussing the sustainability of this renewable resource over specific time periods. Why use firewood in place of propane to heat the house and the milking barn? Where are the airborne contaminants from burning wood going and what are their effects on people and livestock? What is the life-cycle analysis of comparing various sources of fuel for heating? And what have we learned from conversations within the team, with the farmer, and with other workers during a lengthy noon meal?” It has turned out to be a valuable experience for our students, as they have learned that enterprise and system planning, designing a marketing plan, and choosing among various long-term farming strategies may be exciting, but there is also plenty of drudgery and hard work involved in farming. These are experiences that cannot be duplicated in the classroom and may be crucial to becoming good facilitators of sustainable transitions, for example, to farming and food systems adapted to and mitigating climate change. In addition to acquiring generic competences needed to deal with change for improved sustainability, interactions with farmers during the working sessions also provide opportunity to inquire more specifically about local observations of climate change and its impacts on food systems at present and in the recent past. Often farmers’ responses reflect a reductionist view of system components. Many express dismay at the general warming, how pastures are ready for cattle to be sent out from the barns earlier each spring, and how there seems to be less snowfall in their areas of Norway in recent years. These are all clues to accumulate and provide insight about how to discuss climate change, what additional questions to ask and terms to use, and what practices or systems farmers have in mind to build greater resilience into their operations for the future. In the interpretation and integration of new information and observations, we urge students not to fall into narrow “reductionist traps” that would attribute change to one or a few causes. Open minds are needed to put each new fact or idea into a holistic systems view of the farm and the community. Such information and perspective can help students design questions in later interviews and inform the group discussion and reflection about potential scenarios for the future.

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11.6 DIALOGUE To successfully interact with a range of people with different goals, world views, and opinions, it is essential to appreciate and develop empathy and respect for others and to understand which types of questions are appropriate and which are sensitive (Francis and Salomonsson 2012; Østergaard et al. 2013; Salomonsson et al. 2005). These may include financial status of enterprises and the whole farm, and personal family involvements and interactions that may be vital to achieving goals but too personal to disclose to outsiders. In the agroecology course at NMBU, we emphasize communication skills, including the tools that are useful in conducting interviews with farmers and others in community food systems. These are practiced in the second week of the course while staying on a biodynamic dairy farm located two hours from the university. Student teams spend parts of two days performing work tasks on nearby farms and interviewing farmers and others involved in the operation. After walking a farm transect and working to gain experiential knowledge, student teams conduct in-depth interviews to explore the goals, resources, potentials, and challenges that are important in helping or hindering the farmer in reaching long-term goals. Some of the methods for conducting this strategy for “just-in-time education” have been reported (Salomonsson et al. 2005), including the students’ motivation and need for specific information at the appropriate time in a learning program. We discuss the importance of listening skills, giving full attention to the person being interviewed. It is important to avoid the trap of distraction, when an interviewer is preparing for the next question or hoping to intervene with important knowledge rather than putting all their energy into gaining insight from the farmer. These same skills are useful in the community food system project, where student teams interview people in school cafeterias, managers of government canteens, food wholesalers and retailers, key local officials, and others involved with the food system. Beyond asking farmers the simple questions about enterprises, sizes of fields, and marketing strategies, student teams need to explore long-term goals of the farmer and family, their methods for designing enterprises and systems to achieve resilience and sustainability, and how they assess their own human, farm, and economic resources needed to realistically achieve those goals. With this type of information, the student teams can integrate new insights into prior knowledge to help the farmer develop strategies to meet goals for the farm, or community members to plan for meeting their goals for the local food system. Mind mapping has been used by teams to help synthesize their information and see what is missing (Breland et al. 2012). The same dialogue skills and tools are valuable in the internal student team interactions, as people with different life experiences and prior levels of involvement in farming or food systems share information and meaning. We have gained an appreciation for the complexities of dialogue over two decades of teaching as a team, and recognize that this is not a trivial perspective to introduce in the educator community (Lieblein and Francis 2013). 11.7 REFLECTION In our experience, reflection is one of the most underrated and least-appreciated capacities for enriching student learning (Lieblein et al. 2012). There is no doubt that people continuously reflect on experiences, and we commonly admonish each other to “learn from our mistakes.” Students may leave a lecture or return from a field trip and discuss how boring a particular experience has been, or how much they learned from working on the farm or seeing firsthand how an organic dairy operation functions. Yet reflection is rarely a structured or guided activity. We believe strongly that this capacity should be learned, practiced, and included in the activities of the agroecology courses and degree curricula, just as the others we previously discussed.

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Reflection can be an individual process where people write in journals or think about how a recent experience has “opened their eyes” in an “aha moment.” Reflection can also be a group process where people who have shared a common experience such as a transect walk or an interview with a farmer come together to share their interpretations and, in the process, add value to the original activity. Importantly, we have observed that in a class of 25 students each one has a slightly different experience in a field interview, as they hear a farmer answering questions and observe body language, filter each part of the encounter through their own unique prior education lens, and recall interactions with farmers in different cultures. Such details can be shared in a group reflection session. Group team discussions are one more method of interpreting what has been experienced, linking this to relevant theory, relating it to personal development, and preparing for extrapolations to similar situations and challenges. Reflecting on observations, participation, and dialogue can help each of us as well as the collective learning community relate to what is happening on the farm and food system as viewed through our unique and individual lenses, and is essential to the process of assimilating observations and information from interviews into holistic ideas on systems and to eventual integration into ideas that emerge from team visioning. This is especially important in dealing with complex issues such as climate change. 11.8 VISIONING Among the strengths in agroecology education is potential for learning to deal with whole systems and looking beyond immediate challenges to understand current and long-term goals of farmers, food system professionals, and other stakeholders, and then envisioning a more desirable future state. The next step is finding informed, desirable, and achievable strategies that could be followed to reach those goals and visions. The activity could be called action planning, developing a capacity to create a vision of how to imagine and set a course to achieve a desirable future situation. This is an underrated and even denigrated competence that is particularly needed when dealing with complex goals and situations. In our agroecology education its value is appreciated, and it is being learned and practiced through thoughtfully designed educational activities (Lieblein et al. 2011). In order to be effective, such strategies include creative ways to look over the horizon and anticipate the environmental conditions, resource constraints, and potential socio-economic and political realities that will dominate in the future. Students attempt to identify hindering and supporting forces that will affect the farmer’s or the community’s ability to achieve their goals. Envisioning future scenarios builds on integrating ideas and information gained while building the competences of observation, dialogue, and reflection. Yet they go beyond narrow thinking based on observing current trends and fine tuning them to marginally improve the present situation and predict what is more or less likely to happen. Understanding the forces that will slow down or enhance the process introduces a sense of realism into the exercise. Envisioning future scenarios that can truly help stakeholders achieve their goals often requires student teams to suspend reality and dream of the possible, unconstrained by current rationality. Rather than dwell in the present and focus on negative consequences of not dealing with current challenges such as climate or other change, it is more uplifting and valuable to create a vision and generate enthusiasm about what we all think the future should be. When practiced well the process should involve farmers and other stakeholders in order to build broad ownership of the results. Beyond having future visioning sessions on campus in the agroecology class where students study and critique the process, the teams need to take their draft scenarios back to farmers and food system people in the project sites. They have conducted visioning sessions with these stakeholders to sort out which scenarios seem most appropriate and achievable. They also attempt to determine the potential impacts of each and report the results in their final farm project and community project documents.

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During this process the teams are well aware of climate change as one of the hindering or supporting forces, depending on location, that will shape the future of production as well as the entire food system, and bring their clients along in accomplishing an evaluation of their scenarios. It is essential to focus on resilience of systems rather than short-term gains, and on the feasibility of alternative paths toward achieving the goals (Lieblein et al. 2011). Among other emergent properties of students observing first and then visioning with clients are new opportunities for farmers and community food system people to see their own activities and systems through the eyes of concerned outsiders, and some stakeholders have informed us that they will use visioning in the future in their own organizations. 11.9  COMBINING KEY COMPETENCES Today our food system challenges are far larger, more complicated, and widely pervasive than those we recognize in small geographic areas and national cultures. Competences for understanding current systems and envisioning innovative alternatives provide a foundation for dealing with broad and “wicked” problems. Climate change is one of a number of critical issues that recognizes no political boundaries, along with others such as impacts of synthesized chemicals on ourselves and on the environment, distribution of benefits in agriculture, global epidemics of obesity together with over one billion undernourished, globalization of corporations and markets, and control of production resources and wealth in a few hands. To deal with widespread challenges, new educational strategies are needed that include thinking both globally and locally, and designing cooperative efforts with stakeholders that can lead to effective local change. Based on our experience in mentoring student teams, we have observed that the agroecology class activities help students bring together methods from basic and applied research and use these to apply their energies for better understanding local farming and food systems. The integration of principles, perspectives, and practices and their applications can inform understanding and potential improvement of systems to meet the goals of multiple stakeholders. We have observed that students who learn about, practice, and then apply the five competences in their class project work and thesis research become well prepared to deal with complexity. They can bring together multiple sources of information, incorporate both science and practical knowledge learned from farmers, and use these to explore complex questions in the field. They demonstrate an integrative capacity to apply the skills to new and unique situations, moving beyond the methods of any single discipline to blend the methods of biophysical science with those of socioeconomic investigation in their thinking and their research. These are the types of capacities and competences needed to deal with issues related to climate change in agriculture. 11.10  CONCLUSIONS AND OUTLOOK Education that prepares graduates to deal with seemingly intractable problems such as system resilience in the face of climate change must go beyond the artificial boundaries of individual disciplines and specializations. Students learn the challenges faced by diverse stakeholders in farming and food systems and understand their incommensurable goals that may appear unique to each player in the system. Short-term production and profits, meeting local food needs while maintaining exports, using renewable resources efficiently while preserving non-renewable resources for the future, maintaining a quality environment for survival of humans and other species are among the challenges not easily addressed in compartmentalized approaches to research and development. Agroecology provides a platform to guide the needed education. There are broad goals to which everyone should subscribe: producing adequate food for a growing human population, creating a level of equity in distribution of food so that everyone can achieve their

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potential, and preserving a livable environment and quality of life. As summarized in the Brundtland Report (WCED 1987), we need to use resources to meet the needs of our current human population while not reducing opportunities for future generations to make their own choices. More than twenty years of experience using an agroecology approach in education in MSc and PhD courses confirm that the methods work, in different countries and cultures, and in diverse agroecoregions and economic systems. Success in the program is demonstrated by a continuous flow of motivated students to the Agroecology: Farming and Food Systems MSc degree program at NMBU in Norway (https://www.nmbu.no/en/studies/study-options/master/master_of_science_in_ agroecology). We observe strong interest from other universities that have emerging agroecology programs, where we have mentored instructors and helped design curricula in Sweden, Uganda, Ethiopia, India, and Sri Lanka. These programs demonstrate the effectiveness of an agroecology program that uses the open-ended case method to build key competences in graduate education. New capabilities learned and practiced in agroecology courses help students internalize and apply a process to study and solve seemingly impossible challenges in farming and food systems, especially through close participation with stakeholders in the field. The competences of observation, participation, dialogue, reflection, and visioning appear to transcend culture and language, and to have applicability in a range of educational settings. Based on our experiences in Norway, as well as in universities in Africa and Asia, we conclude that the holistic approach using open-ended cases is a viable and robust educational strategy that is beneficial for building key competences in students, as well as promoting a close working relationship with stakeholders. Such involvement with end users of new strategies for resilience in farming is a key step in eventual adoption of innovative methods for resource-efficient food production. The exploration of local food opportunities, of potentials for increasing organic and biodynamic food in the local diet, of ways to promote and grow local economies, and of alternatives that can be generated by cooperation among all players in the system is key to understanding systems and developing a shared agenda for the future. The cooperation of stakeholders with students creates synergies in thinking and potential actions that will lead to a more sustainable and resilient future. Climate change is an important reality, and our educational approach prepares students to work toward resilience under climate unpredictability and other uncertainties of economics, politics, and cultural change. We strongly endorse this strategy for learning in other universities, colleges, and educational venues. 11.11 SUMMARY Learning the competences to deal with adapting food production systems to the complexities of climate change requires appreciation of whole systems research and education. We use open-ended cases where students work directly with stakeholders on the farm and in the community to determine the goals of these clients, to listen and assimilate and understand their challenges, and to work together to envision and design alternative scenarios that will help clients meet their goals. In an open-ended case, no one really knows the solutions, but students, teachers, and stakeholders work together to discover and evaluate a priori the potential outcomes of implementing each of the scenarios. Key competences that students learn and practice are observation, participation, dialogue, reflection, and visioning, and this is accomplished on campus in classes and on the Internet, and in the field working with clients who become co-learners. These competences are developed during the implementation of team projects on the farm and in community food systems, as students integrate multiple sources of information and opinions that will help inform future strategies to achieve stakeholder goals. We have found that students respond with enthusiasm to real-world challenges and the chance to apply what they learn in the context of farms and communities in Norway. The participatory model for learning agroecology has been extended by our teaching team to emerging education programs at

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University of Calcutta and Kerala University [India], Mekelle University [Ethiopia], Uganda Martyrs University, and three universities in Sri Lanka. Positive student evaluations, enthusiastic participation by stakeholders, and recognition of the teaching team by university and national organizations provide indicators of the success and impacts of this educational program, and future goals are to extend the learning strategies to other disciplines and universities. REFERENCES Altieri, M. A., and C. I. Nicholls. 2017. The adaptation and mitigation potential of traditional agriculture in a changing climate. Climatic Change 140:33–45. Blanc, E., and J. Riley. 2017. Approaches to assessing climate change impacts on agriculture: An overview of the debate. Rev Environ Econ Policy 11:247–57. Book, L., and D. P. Phillips. 2013. Creativity and Entrepreneurship: Changing Currents in Education and Public Life. Cheltenham, UK: Edward Elgar Publisher. Breland, T. A., G. Lieblein, S. Morse, and C. Francis. 2012. Mind mapping to explore farming and food systems interactions. Teaching Tips. NACTA J 56:90–1. Bryant, C. R., M. A. Sarr, and K. Delusca. 2016. Agricultural Adaptation to Climate Change. New York, NY: Springer. Chatrchyan, A. M., R. C. Erlebacher, N. T. Chaopricha, J. Chan, D. Tobin, and S. B. Allred. 2017. United States agricultural stakeholder views and decision on climate change. WIREs Climate Change 8:e469. https:// doi.org/10.1002/wcc.469. Cliff, W. H., and L. M. Nesbitt. 2005. An open or shut case? Contrasting approaches to case study design. J College Sci Teach 34:14–7. FAO/OECD. 2012. Building Resilience for Adaptation to Climate Change in the Agricultural Sector. Rome, Italy: Food and Agriculture Organization. Available at: www.oecd.org/tad/sustainable-agriculture/49552063. pdf. (Accessed: April 4, 2018). Francis, C. 2014. Participatory learning experiences: What these mean to me as an agroecology instructor. Teaching Tips. NACTA J 58:81–4. Francis, C., J. King, G. Lieblein, T. A. Breland, L. Salomonsson, N. Sriskandarajah, P. Porter, and M. Wiedenhoeft. 2009. Open-ended cases in agroecology: Farming and food systems in the Nordic Region and the U.S. Midwest. J Agr Educ Ext 15:385–400. Francis, C., G. Lieblein, S. Gliessman, T. A. Breland, N. Creamer, R. Harwood, L. Salomonsson et al. 2003. Agroecology: The ecology of food systems. J Sustain Agr 22:99–118. Francis, C., S. Morse, T. A. Breland, and G. Lieblein. 2012a. Transect walks across farms and landscapes. Teaching Tips. NACTA J 56:92–3. Francis, C., E. Østergaard, A. M. Nicolaysen, G. Lieblein, T. A. Breland, and S. Morse. 2016. Learning through involvement and reflection in agroecology. In Agroecology: A Transdisciplinary, Participatory and Action-oriented Approach, ed. V. E. Mendez, C. M. Bacon, R. Cohen, and S. R. Gliessman, 73–98. Boca Raton. FL: CRC Press. Francis, C., and L. Salomonsson. 2012. Farmer interview role play exercise. Teaching Tips. NACTA J 56:87–8. Francis, C., L. Salomonsson, G. Lieblein, T. A. Breland, and S. Morse. 2012b. Metaphors in agroecology education: One personal method of learning. Teaching Tips. NACTA J 56:82–3. George, D. A., P. L. Tan, and J. F. Clewett. 2016. Identifying Needs and Enhancing Learning about Climate Change Adaptation for Water Professionals at the Post-graduate Level. New York, NY: Taylor & Francis Publisher. Jordan, N. R., D. A. Andow, and K. L. Mercer. 2005. New concepts in agroecology: A service-learning course. J Nat Res Life Sci Ed 34:83–9. Li, C. J., and M. C. Monroe. 2017. Exploring the essential psychological factors in fostering hope concerning climate change. Environ Educ Res. DOI: 10.1080/13504622.2017.1367916. Lieblein, G., T. A. Breland, C. Francis, and E. Østergaard. 2012. Agroecology education: Action-oriented learning and research. J Agr Ed Ext 18:27–40. Lieblein, G., T. A. Breland, S. Morse, and C. Francis. 2011. Visioning future scenarios. Teaching Tips. NACTA J 55:109–10.

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Lieblein, G., and C. Francis. 2007. Towards responsible action through agroecological education. Italian J Agron/Riv Agron 2:79–86. Lieblein, G., and C. Francis. 2013. Faculty prerequisites for dialogue-based education. Teaching Tips. NACTA J 57:72–4. Margetson, D. 1993. Understanding problem-based learning. Educ Philos Theory 25(4):40–57. Monroe, M. C., R. R. Plate, A. Oxarart, A. Bowers, and W. A. Chaves. 2017. Identifying effective climate change education strategies: A systematic review of the research. Environ Educ Res 1–22. https://doi. org/10.1080/1360842 Oreskes, N. 2018. The scientific consensus on climate change: How do we know we’re not wrong? In Climate Modeling: Philosophical and Conceptual Issues, ed. E. A. Lloyd, and E. Winsberg, 31–64. New York, NY: Palgrave Macmillan. Østergaard, E., C. Francis, and G. Lieblein. 2013. Practicing and preparing for stakeholder interviews. Teaching Tips. NACTA 57:97–9. Ostrom, E. 1990. Governing the Commons: The Evolution of Institutions for Collective Action. New York, NY: Cambridge University Press. Salomonsson, L., C.A. Francis, G. Lieblein, and B. Furugren. 2005. Just in time education. Teaching Tips. NACTA J 49:5–13. Scharmer, C.O., and K. Kaufer. 2013. Leading from the Emerging Future: From Ego-system to Eco-system Economies. San Francisco, CA: Berrett-Koehler Publisher. UNDP/FAO/UNITAR. 2017. National adaptation plans: Building climate resilience in agriculture. NAPMOOC. Available at: https://napmooc.uncclearn.org. (accessed: April 4, 2018). WCED. 1987. Our common future. World Commission on Environment and Development, United Nations. Oxford, UK: Oxford Univ. Press. Wezel, A., S. Bellon, T. Dore, C. Francis, D. Vallod, and C. David. 2009. Agroecology as a science, a movement or a practice. Agron Sustain Dev 29:503–16.

Index A ABA-independent signalling pathways, 40 Abaxial stomatal density, 45 Abiotic stresses, integrated approach, 73 Abscisic acid (ABA) accumulation, 150 Absorptive capacity, 96 Acclimatization mechanisms, 22 Action learning, 176 Action research, 176 Adaptation and mitigation measures, 94–97 Adaptive capacity, 96 Adaxial stomatal density, 45 Aerenchyma, 47 Agavaceae, 46 Agricultural extension services, 8 Agricultural suitability, 166 Agriculture, 109 Agroecological systems, 3 Agroecosystems for resilience and sustainability, 119–123 Agroecosystems diversity, 113 Agroecosystems, 95, 122–125 Aha moment, 181 Amino acids, 39 Anthropogenic climate change, 2 Antinutrients, 151–153 APX, see Ascorbate peroxidase (APX) Aquaculture, 95 Arabidopsis roots’ epidermal cells, 41 Arabidopsis thaliana stomata, 60 Arabidopsis vacuolar Na+/H+ antiporter, 42 AsA/DHA ratio, 64 Ascorbate peroxidase (APX), 40 AtNHX1, 42 Autophagy, 38 Avoidance and tolerance, strategies, 147

B Barley (Hordeum vulgare), 40 Barley HVA1 gene, 76 Betaine aldehyde dehydrogenase (BADH), 40 Brassica juncea, 60 Bromeliaceae, 46 Brown spot, 62 Building blocks for climate smart agriculture, 9 Bulliform cells, 46

C C3 crop photosynthesis, 75 C3 crops, 93 C4 crops, 94 C4 cycle basic enzymatic reaction, 75

C4 plants, 3 C4-PEPC maize, 76 Cactaceae, 46 Caffeine, 63 CAM, see Crassulacean acid metabolism (CAM) Carbon dioxide (CO2), 2, 149–150 Carbon fertilization effect, 93 Carbon fixation engineering of plants, 73–75 Carbon sequestration, 77 Carbon to nitrogen ratio (C/N), 22 Care for people, 111 Care for the earth, 111 Cassava mosaic virus, 89 CAT, see Catalase (CAT) Catalase (CAT), 40 Catastrophe design, 115 Catch and store energy, 114 CDL, see Cropland data layer (CDL) Cell dehydration, 38 Cell division, 37 CGIAR, see Consultative group on international agricultural research (CGIAR) Choline monooxygenase (CMO), 40 Choline oxidase (codA), 41 Choline oxidation, 40 Clean water act, 9 Climate change (CC), 20–21 Climate change and agroecosystems, 107–119 Climate change and crop production, 1–12 adaptation and crop production agroecosystems, 6–10 policy mechanisms and programs, 8–9 resilience in agroecosystems, 9–10 technology and development, 7–8 background, 2 direct and indirect effects, 2 on agricultural economies, 4–5 socioeconomic impacts, 5–6 driving causes, 2–6 future directions and research priorities, 10–11 Climate change and crop quality, 27 Climate change and physiological responses in photosynthesis, 26–27 Climate change challenges agricultural yields, 7 Climate change mitigation through agroforestry systems, 107–108 Climate change mitigation through perennial polyculture systems, 116–119 Climate change mitigation through permaculture, 108–112 Climate change related challenges and opportunities for adaptation, 138–140 Climate changes and crop productivity, 93–94 Climate information, 140 Climate smart agricultural production strategies, 140 Climate variability, 85–87 Closed stomata, 43 187

188

Cloud formation, 22 Clustered regularly interspaced short palindromic repeats (CRISPR), 8 CMIP5/Cordex, 85 CMO, see Choline monooxygenase (CMO) CO2 effects, 22–23 Combining key competences, 182 Common agriculture policy of Europe, 121 Compatible solutes, 38 Concentration pathway (RCP4.5), 87 Connective tissue, 47–48 Consultative group on international agricultural research (CGIAR), 10 Cool season crops, 150 Coping strategies, 95 Core agroecology competences, 176–178 COST, see European Cooperation in Science & Technology (COST) Cotton (Gossypium hirsutum), 40 CPR, see Crop-pasture rotation (CPR) Crassulacean acid metabolism (CAM), 27, 76, 149, 167 Cretaceous age, 134 CRISPR, see Clustered regularly interspaced short palindromic repeats (CRISPR) Crop and varietal impacts, 89–91 Crop insurance, 8 Crop production systems, 85 Cropland data layer (CDL), 165 Crop-pasture rotation (CPR), 95 Cropped land area across zones, dynamics of, 134–136 Crops and income diversification, 96 Cultivar diversity, 96 Cuticular transpiration under water stress, 43–44 Cyclin-dependent kinase (CDK) activity, 37

D De novo synthesis of compatible solutes, 38–41 Decline in crop production, 90–91 Deep rooting, 148 Description of case study, 132–133 Dialogue, 180 space, 177 Dialogue-based education, 177 Disease-soil-plant cycle, 88 Diversified crops on abandoned lands, 165–166 Downy mildew, 62 Drought effects, 24–25 Drought stress, 144 Drought-susceptibility index, 24 Drummond’s rockcress (Boechera stricta), 26

E ECOLISE, 121 Economic viability, 122 El Niño Southern Oscillation (ENSO), 7 Energy and resources conservation, 114

INDEX

ENSO, see El Niño Southern Oscillation (ENSO) Epigenetics, 78 Epigenetics/phenotypic plasticity/Responses to climate change, 77–78 Erysiphe cichoracearum, 60 Ethylene (ET), 152 European Cooperation in Science & Technology (COST), 115 Extension disaster education network (EDEN), 9 Extensive leaf rolling, 46 Extreme weather alerts, 7

F FACE, see Free-Air Carbon dioxide Enrichment (FACE) Fair share, 111 Farm Service Agency (FSA) programs, 7 Farming system, 85 Fertilization effect, 149 Floral pathway expression, 25 Flowering of crops, 25 Food and Agriculture Organization (FAO), 145 Food insecurity, 5 Food security, 5 Forests and food forests in permaculture, 114 Free-Air Carbon dioxide Enrichment (FACE), 22 Future climate change and crop quality, 94

G Galegoid clade, 144 GB biosynthetic pathways, 41 GCMs, see Global circulation models (GCMs) GDC, see Glycine decarboxylase complex (GDC) GDD, see Growing degree day (GDD) Gene expression, 25 Generalized impacts of climate change, 85–91 Genetic biodiversity, 72–73 Genetically modified (GM) crops, 8 Genomic level, advances, 25 GHG, see Greenhouse gas (GHG) GHG mitigation, 10 Global circulation models (GCMs), 85 Global climate change, 2 Global dynamic prediction models, 7 Global pulse production, 144 Global warming, 24, 87 Glutamate, 39 Glutamic-γ-semialdehyde (GSA), 39 Glycine decarboxylase complex (GDC), 75 Glycine N-methylation, 40 Glycinebetaine, 40–41 Glycolate catabolism, 75 Grain legumes and sustainable agriculture, 144–146 Grain legumes, 150 Grapevine, 152 Greenhouse gas (GHG), 2 Growing degree day (GDD), 7 GSH/GSSG ratio, 64

INDEX

H HARDY gene, 76 Hormones, 151–153 Hyaloperonospora brassicae, 60

I Inorganic ions, 41–42 Instantaneous transpiration efficiency (ITE), 22 Insurance, 8 Integrated water resource management (IWRM), 11 Intergovernmental Panel on Climate Change (IPCC), 9, 108 IPCC, see Intergovernmental Panel on Climate Change (IPCC) IPCC (2014), 146 ITE, see Instantaneous transpiration efficiency (ITE) IWRM, see Integrated water resource management (IWRM)

J Jozini municipality, 133

L

189

Multiple lines of evidence, 146–147 Mustard (Brassica spp.), 41 Myriad policies, 8

N Na+ vacuolar sequestration, 41 Na+/H+ antiporters, 41 NAD+-dependent enzyme, 40 NASS, see National Agricultural Statistics Service (NASS) National Agricultural Statistics Service (NASS), 165 National Meteorological or Hydrometeorological Service, 7 Natural Resources Conservation Service (NRCS), 7 Natural scavengers, 39 Natural systems agriculture (NSA), 117 Necrotrophic pathogens, 62 Nicotine, 63 Nitrous oxide (N2O), 2 No waste production, 113 Non-stomatal transpiration (cuticular transpiration), 43 Northern Australia climate, 91 NRCS, see Natural Resources Conservation Service (NRCS) NSA, see Natural systems agriculture (NSA) NUE, see Nutrient use efficiency (NUE) Nutrient use efficiency (NUE), 22 Nutrients management engineering of plants, 77

Land Institute, 117–118 Land use change over time, 136–137 LDPs, see Long-day plants (LDPs) Leaf anatomical changes, 44–47 Leaf gas exchange, 37 Leaf pubescence, 45 Leaf succulence, 44–45 Leaf surface cuticular wax, 47 Legumes, 144 Local food systems, 116 Local plant genetics, 122–125 Long-day plants (LDPs), 144

O

M

P5C dehydrogenase (P5CDH), 39 P5CDH, see P5C dehydrogenase (P5CDH) PAL, see Phenylalanine ammonialyase (PAL) Paleocene and eocene epochs, 89 Paris agreement, 121 Participation, 179 Participatory learning, 177 Pastoral production system, 92 Pathogen-/microbe-associated molecular patterns (PAMPs/MAMPs), 60 PCIs, see Private conservation initiatives (PCIs) PDH, see Proline dehydrogenase (PDH) PEPC, see Phosphoenolpyruvate carboxylase (PEPC) PEPC/PCK-transgenic rice, 75 Perennial bunchgrass (Poa secunda), 78 Perennial crops, 164–165 Perennial polycultures, 118 Permaculture climate change solutions, 118–119 Permaculture, 111 design, 114

Maize (Zea mays), 40 Maize production in tropical Mexico, 92 Maize streak virus, 89 Major constraints imposed by osmotic stress, 37–38 Maximum temperatures, 3 Meristem activity, 37 Mesophyll and epidermis thickness of leaves, 46 Methane (NH4), 2 Methylxanthine, 27 Microclimates design, 114 Mild osmotic stress, 37 Millettioids/phaseoloid and galegoid clades, 145 Minimum temperatures, 3 Mitigation activities in agriculture and forestry, 109 Mitigation options, 95 Modern agroecology, 25 Morphological and anatomical mechanisms, 44–48 Multi-peril crop insurance (MPCI), 8

Observation, 178 Open-ended case studies, 175–176 Optimum water, 43 Opuntia, 168 Organic carbon sequestration, 88 Organic osmolytes, 38; see also Compatible solutes Ornithine, 39 Osmitic adjustment, 38–39

P

190

Permanent agriculture, 111 Pessimistic pathway (RCP8.5), 87 Pests and diseases, 88–89 Phaseoloid clade, 144 Phenolic compounds, 23 Phenolic content, 27 Phenology, 153 Phenotype plasticity, 26 Phenylalanine ammonialyase (PAL), 63 Phloem, 47 Phosphoenolpyruvate (PEP) carboxylase, 167 Phosphoenolpyruvate carboxylase (PEPC), 75 Photorespiration, 75 Phytic acid (PA), 152 Phytohormones, 61 Plant heat tolerance, 166 Plant strategies to tackle water stress, 147–153 Plant water budget, 148 Plant water use efficiency, 43 Plants response to climate change, 22 Plasticity, 78 Policy-makers, 23 Polyols, 39 Positive or negative implications of agroforestry practices, 108 Potato (Solanum tuberosum), 41 Potential adaptation strategies, 140 Potential production of perennial crops, 165 Potential yield, 4 Powdery mildew, 62 POX, see Proline oxidase (POX) Prairie states forestry project, 7 Primer on plant-water relation, 147 Private conservation initiatives (PCIs), 7 Problem-based learning, 176 Proline, 39–40 accumulation in plants, 40 exogenous application of, 40 foliar application of, 40 Proline dehydrogenase (PDH), 39 Proline oxidase (POX), 39 PYL-like receptor genes, 152 Δ′-pyrroline-5-carboxylate (P5C), 39 Pytohormone-mediated defenses, 61–62

Q Quaternary amines, 39

R Radiation balance of the Earth, 2 Raffinose families of oligosaccharides (RFOs), 152 Rain-fed agriculture, 92 Rainwater catchment, 112 Reactive oxygen species (ROS) production, 39, 64, 149, 151 Recommended management practices (RMP), 108 Redox homeostasis, 64 Redox-mediated resistance, 64 Reflection, 180–181 Relocation breaks, 5

INDEX

Renewable energy resources, 122–125 Residual transpiration, 43 Resilience, 9, 120–121 Resilience/sustainability/climate change, 106–107 Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), 74 Rice (Oryza sativa), 41 Rice farming, 95 Rising seawaters, 95 RLD, see Root length density (RLD) RMP, see Recommended management practices (RMP) Rolling cells, 46 Root aerenchyma, 47 Root and stem anatomical change, 47–48 Root architecture, 147–149 Root length density (RLD), 148 Root phenes, 148 ROS, see Reactive oxygen species (ROS) RuBisCO, see Ribulose-1,5-bisphosphate carboxylase/ oxygenase (RuBisCO) RuBisCO pathway, saturation, 27

S SA/JA cross talk, 62 Salicylic acid (SA), 152 Salinity low concentration, 45 Salinity stress, 37 Sclerenchyma, 47 SDPs, see Short-day plants (SDPs) Secondary metabolism, influence, 63–64 Shelterbelt project, 7 Shifting environmental conditions impact, 4 Short-day plants (SDPs), 145 Slow Food, 115 Slow food organization, 121 Smallholder farmers, livelihood stability of, 5 Social dimensions, 178 Social processes/food/economic localization, 115–116 Socioeconomic impacts of climate change, 4 SOCRATES, see Soil organic carbon resources and transformations in ecosystems (SOCRATES) SOCRATES model, 77 SOD, see Superoxide dismutase (SOD) Soil carbon decomposition, 88 Soil compaction, 88 Soil erosion and depletion, 88 Soil organic carbon resources and transformations in ecosystems (SOCRATES), 77 Soil protection and rebuilding, 112–113 Soil storage of water, 112 Soil variation across altitudinal zones, 133–134 Soil water status, 150 Soils impacts, 87–88 Solar radiation, 22 Sophisticated solutions, 95 Sorghum (Sorghum bicolor), 40 Southern Oscillation (ENSO) episode, 136 Spinach (Spinacia oleracea), 40 Stomata role, 60–61

INDEX

Stomatal apertures, 150 Stomatal density and size, 45–46 Stomatal opening, 42 Stomatal transpiration under water stress, 43 Stress escape, strategy, 153–154 Stress tolerance, 151–153 Sugar beet (Beta vulgaris), 40 Sugars, 39 Sunflower, 118 Sunken stomata, 46 Superoxide dismutase (SOD), 40 Sustainability, 121–123 Switchgrass, 164

T TCA cycle, 63 Temperature effects, 23–24 Three-tier rice production system, 95 TMV, see Tobacco mosaic virus (TMV) Tobacco (Nicotiana tabacum), 39, 41 Tobacco mosaic virus (TMV), 63 Tomato (Solanum lycopersicum), 41 Traditional farming, 85 Transformative capacity, 96 Transgenic plants, 40 Transpiration and regulation, 149–151 Transpiration ratio, 43 Transpirational control, 42–44 Transpirational water loss, 45 Tropical agriculture systems, 85 Tropical crop production systems, 93–94 Tropical crops and production systems, vulnerabilities of, 91–94 Tropical horticultural soils, 87

191

U UAVs, see Unmanned aerial vehicles (UAVs) United States Department of Agriculture (USDA), 7 Unmanned aerial vehicles (UAVs), 7 Urban permaculture agroecosystems, 115 USDA Forest Service, 7 USDA, see United States Department of Agriculture (USDA) Use and value renewable resources and services, 114

V Vacuolar pyrophosphatase TVP1, 42 Vascular bundles, 47 Vernalization, 153 Vietnam’s Mekong Delta, 92 Visioning, 181–182

W Water harvesting techniques (WHT), 96 Water management design, 112 Water management in agroecosystems under permaculture, 112 Water use efficiency (WUE), 22, 43, 75–77 Wheat (Triticum aestivum), 40, 118 Wheat Na+/H+ antiporter TNHX1, 42 WHT, see Water harvesting techniques (WHT) WUE, see Water use efficiency (WUE)

X Xylem, 47