Dense + Green Cities: Architecture as Urban Ecosystem 9783035615111, 9783035615319

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DENSE GREEN CITIES

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Thomas Schröpfer

Dense+Green Cities Architecture as Urban Ecosystem

Foreword by Peter G. Rowe Raymond Garbe Professor of Architecture and Urban Design and Harvard University Distinguished Service Professor

Birkhäuser Basel

Contributions by Peter Edwards Christophe Girot Sacha Menz

Researchers Michelle Jiang Yingying (Coordinator) Richard Belcher Peter Christensen Emek Erdolu Srilalitha Gopalakrishnan Mayank Kaushal Thibault Pilsudski Prashanth Raju Ester Suen Yun Ju Jonathan Tan Koon Ngee

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Layout, cover design and typography Waterhouse Cifuentes Design Cover photograph Iwan Baan Copyediting Elizabeth Kugler Editor for the Publisher Andreas Müller Production Heike Strempel

We would like to thank the Singapore-ETH Centre Future Cities Laboratory as well as ETH Zurich and the Singapore University of Technology and Design for their generous support of this publication. Bibliographic information published by the German National Library: The German National Library lists this publication in the Deutsche Nationalbibliografie. Detailed bibliographic data are available on the Internet at http://dnb.dnb.de. Library of Congress Control Number: 2019952517

Paper 135 g/m² Condat matt Perigord Printing Grafisches Centrum Cuno GmbH & Co. KG

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in databases. For any kind of use, permission of the copyright owner must be obtained. This publication is also available as an e-book (ISBN PDF 978-3-0356-1511-1). © 2020 Birkhäuser Verlag GmbH, Basel P.O. Box 44, 4009 Basel, Switzerland Part of Walter de Gruyter GmbH, Berlin/Boston Printed on acid-free paper produced from chlorine-free pulp. TCF ∞ Printed in Germany ISBN 978-3-0356-1531-9 9 8 7 6 5 4 3 2 1 www.birkhauser.com

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Table of Contents

Foreword  8 Peter G. Rowe Raymond Garbe Professor of Architecture and Urban Design and Harvard University Distinguished Service Professor Dense+Green Agendas Dense and Green: An Alternative History of the City  12 Thomas Schröpfer The Collective Power of the Single Building  38 Sacha Menz Green Spaces and Ecosystem Services  52 Peter Edwards Green Buildings and the Ecological Picturesque  66 Christophe Girot Dense+Green Dimensions Learning from Singapore  82 Dense and Green at the Future Cities Laboratory  86 Biodiversity  88 Surface Temperature  98 Construction and Maintenance Costs of Integrated Green Spaces  102 Economic Benefits of Vegetation On and Around Residential Developments  106

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Dense+Green Case Studies Asia

Americas

Solaris  118 Singapore T. R. Hamzah & Yeang/CPG Consultants

Vancouver Convention Centre West  198 Vancouver, British Columbia, Canada LMN Architects/Musson Cattell

One Central Park  124 Sydney, Australia Ateliers Jean Nouvel/PTW Architects

Pérez Art Museum Miami  204 Miami, Florida, USA Herzog & de Meuron/Handel Architects

Punggol Waterway Terraces I  134 Singapore group8asia/AEDAS

Torre Rosewood  212 São Paulo, Brazil Ateliers Jean Nouvel/Triptyque/Königsberger Vannucchi

The Interlace  152 Singapore OMA/Büro Ole Scheeren/RSP Architects Planners & Engineers

The Spiral  220 New York, New York, USA BIG

SkyVille@Dawson  168 Singapore WOHA

Miami Produce Center  228 Miami, Florida, USA BIG/Kimley Horn Associates

Oasia Hotel Downtown  182 Singapore WOHA

11th Street Bridge Park  234 Washington, DC, USA OMA

1000 Trees  194 Shanghai, China Heatherwick Studio/MLA Architects

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Dense+Green Future Europe Bosco Verticale  240 Milan, Italy Stefano Boeri Architetti Google King’s Cross  250 London, UK BIG/Heatherwick Studio Valley  258 Amsterdam, The Netherlands MVRDV 1Hotel Paris and Slo Living  264 Paris, France Kengo Kuma and Associates/Marchi Architects

Future Trajectories  284 Thomas Schröpfer Appendix About the Author and the Contributors  292 Bibliography  295 Acknowledgments  309 Illustration Credits  310 Index of Names  314 Subject Index  321

Mille Arbres  270 Paris, France Sou Fujimoto Architects/Manal Rachdi Oxo Architectes Les Lumières Pleyel  276 Saint-Denis, France Snøhetta/Baumschlager Eberle Architekten/ Chaix & Morel et Associés/Ateliers 2/3/4//Mars Architectes/ Maud Caubet Architectes/Moreau Kusunoki

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Singapore-ETH Centre Future Cities Laboratory at the Campus for Research Excellence and Technological Enterprise (CREATE) Singapore, aerial view.

Foreword

The book Dense+Green Cities: Architecture as Urban Ecosystem, compiled and edited by Thomas Schröpfer, draws on work by a research team comprised from the Singapore-ETH Centre Future Cities Laboratory, ETH Zurich, and Schröpfer’s academic base at the Singapore University of Technology and Design. It takes up with the broad and important question of whether buildings and their architecture can actively and positively contribute to better-functioning urban ecosystems for the good of all concerned. Clearly this is a timely topic, particularly in an era when the fate of humankind’s balance with nature appears to be becoming more and more precarious and threatening. Beyond simply professional responsibility, this is also a matter of envisaging how our cities might be made better, particularly in a manner that is deliberately and increasingly dense and green, as the book’s title suggests. The urban ecosystems under analysis are several-fold, as the 19 cases in the book are comprised of seven in Asia and primarily in Singapore, six in Europe, and six in the Americas. Among them, as it turns out, the tropical eco-zone is the most understudied, especially in comparison to more temperate eco-zones. The main components of the ecosystem under examination are biodiversity, primarily through the proxies of plant and bird life and because of the important ecological services provided, including mitigation of urban heat island effects, improvement of storm-water management, and air pollution abatement. As the book cautions, the loss of biodiversity, even in a region naturally rich in it, is likely to come by way of further population expansion and urbanization, destroying habitat, and of biotic homogenization, that inevitably seems to follow, as well as loss of native species so important to ecosystem propagation. The main thrust of the book’s argument is a good one. If we can green buildings appropriately, then surely we can materially extend the network of other green spaces such as forest preserves, parks, roadway connectors, and the like, into a more expansive and lively urban ecosystem.

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While leaving aside the potential combinatorics of how buildings might fit in to such a scenario more specifically, the book makes a good baseline start on necessary questions, for example: How can greening support biodiversity abundance and connection? Do dense and green buildings actually cool environments? What do property owners likely pay for nearby vegetation? And what are the operating and maintenance costs to integrated green spaces and buildings? Drawing particularly on the strides that have been made in Singapore in its groundbreaking blue and green planning, the documentation and analysis of appropriate green architectural building components covers five types: garden grounds, sky gardens, roof gardens, green walls, and landscaped decks. Appropriate metrics are then used for comparison across 200 ha patches, entailing vegetation surveys, econometric data and models, as well as drawings and close readings of site and related conditions. Overall, the book’s findings are rather to be expected, with few surprises. Ground gardens perform best among alternatives, with green walks doing well within constrained sites and with sky gardens having relatively low vegetation densities. According to albedo effects, shading is useful in reducing surface temperatures, and residents seem to like being near parks. More interestingly, construction and maintenance costs appear to be quite variable but generally affordable. In short, dense and green, as defined and illustrated in the book, has net positive outcomes. This being said, though, the more significant contributions are derived from rationales offered for the empirical findings and the grain of detail offered by the findings themselves. For example, albedo effects are complicated but well-explained and parsed with regard to surface temperature in the book. Actual ranges of costs provide useful guidance to would-be clients, regulators, and designers. Also, much the same can be said for how property owners perceive facets of value in their residences and residential locations. Among the places of interest, in Singapore, for instance, the preference for ‘managed green’ is hardly surprising given the apparent national aversion to something less technically controlled being well-known.

The cases within the book are copious and well-selected, at least within the immediate geographic area and what is dense and green there. Illustration is lavish and well supported with accompanying text. In short, it is a handsome publication and a worthwhile reference document. To be sure, networking is a major way forward for helping and reinforcing ecosystem abundance and performance in urban areas, as noted copiously and earlier by landscape ecologists like Harvard’s Richard Forman. The next step, at least based on this volume, will be to take this networking up seriously, more fully and in an attractive visionary manner. Part of the success will come from being able to be convincing and to sell the network concept, so to speak, to a broader and, at times, more skeptical public. But that will be another book. Peter G. Rowe Raymond Garbe Professor of Architecture and Urban Design and Harvard University Distinguished Service Professor Cambridge, Massachusetts June 2019

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DENSE GREEN AGENDAS

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Dense and Green An Alternative History of the City Thomas Schröpfer

Our planet has been urbanizing for millennia and urbanization has been global and exponential in recent times, these are facts we have to deal with.1 Within the broad and long history of research and publication on intensive urbanization, the focus has tended to be on the themes of density — building typologies, zoning — and infrastructure — transportation, services. Yet although no urbanist or architect would deny the importance of greenery — parks, beltways, vertical green, biodiversity — many continue to treat urban green as an amenity, divorcing it from a more holistic way of understanding, planning, and designing cities and buildings. Urban green is too often thought of as part of the ground level of the city, seen and rendered in the two dimensions of the plan. Currently, a growing number of innovative urban and architectural developments and projects force us to rethink the very dimensionality of urban green: as something that is also vertical and that must, as our cities do, develop vertically as well. The vertical development of green in our cities stands to contribute to the livability and sustainability of our urban environments. The research conducted at the Singapore-ETH Centre Future Cities Laboratory (FCL), ETH Zurich, and the Singapore University of Technology and Design and the resulting contributions and case studies that led to this book demonstrate how the continuing trend towards densification of our cities can inextricably and consistently interact with the active provision of dynamic, and often public, green spaces on elevated levels. In other words, this publication is about architecture as greenery, not about architecture with greenery. The purpose of this introduction is to place the selected projects within a historical context, demonstrating that their specific and topical character is not a unique development of the 21st Century but instead a new articulation of a trend that has been underway for a much longer time. We will revisit some well-known and some lesser-known projects to look at them through a new lens, considering how architecture itself has spawned new thinking about the role of green in the dense vertical city. From Hanging Gardens to Garden Cities The Hanging Gardens of Babylon are widely recognized for their mythical status as one of the Seven Wonders of the Ancient World, among the few of the many no longer extant structures that are deeply embedded in popular imagination. The Hanging Gardens, a terraced mud-brick structure with a series of gardens containing a wide range of trees, shrubs, and vines, were supposedly built for Queen Amytis, the wife

of the Neo-Babylonian King Nebuchadnezzar II, to assuage her longing for the greenery of her far-away homeland.2 Although there is no definitive archaeological proof of their existence, both written accounts of the era and popular imagery of all times have placed the Gardens adjacent to the Tower of Babel, a proto-skyscraper in more than one sense that was testament to both early human ambition as well as hubris.3 If we are to allow that these two structures did exist in direct proximity to one another, then we have here a starting point to contextualize the Gardens as not merely a kingly folly but also an urban intervention, with clear spatial and aesthetic principles and goals. Firstly, the Gardens were set into the architecture along the entirety of the Tower’s perimeter, rendering the greenery itself, rather than the architecture, as the primary feature of the building’s elevations, a feature visible from great distances. Secondly, the diversity of the flora observed in the Gardens represents the King’s interest in a cosmopolitan and vertical model of landscape architecture, one where the world’s plants unite at a location so as to be observed and admired. Thirdly, while the Gardens would most certainly have been accessible to members and guests of the royal courts, their visual impact went much further, impacting the city in its entirety. The fortification of towns and cities hemmed in the open expansion of many cities across Eurasia throughout the medieval period and put a tacit premium on public space. Important structures like the Alhambra in Granada, Spain, the Shalimar Bagh in Srinagar, India, and the Forbidden City in Beijing, China, held within them truly impressive gardens; however, their impact on the general populace was largely lost in the absence of visual and experiential connectedness.4 The rise of humanistic culture, particularly in the Italian Renaissance, articulated the increased importance of the citizen and democratic values and this spurred the slow emergence of a public, as opposed to private, green sphere within the town or city. These spaces went beyond the commons model already in place in England, as they were public open spaces not merely committed to a flexibility of function. They were rather designed as spaces meant for appreciation or, ideally, contemplation.5 This would begin with simple piazzas, often with a central fountain and some planted trees. By the late Renaissance, both interest and faith in science led to the rise of the botanical garden, a place that combined the biodiversity one would have seen at the Hanging Gardens of Babylon with a scientific and largely public mission. The Botanical Gardens of

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Hanging Gardens of Babylon, colored engraving, 19th Century. Alhambra, Granada, Spain, 13th Century, garden. Forbidden City, Beijing, China, 15th Century, Imperial Garden.

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Filippo Toma, Botanical Gardens of Padua, Italy, engraving, 17th Century.

Padua from 1543 are an example of this, as they were open to both students and the public at certain hours of the day.6 The dawn of the Industrial Revolution brought with it an even greater urgency to provide public spaces that could serve as outlets for nature and spaces of recreation for the working masses to ensure their health and, ultimately, their productivity in a capitalist system. Such parks operated to a large degree as pastoral idylls, trying to recall a primordial kinship to nature that most denizens of the city had never really experienced. This new public culture is vividly captured in Georges Seurat’s 1884/6 pointillist masterpiece Un dimanche après-midi à l’Île de la Grande Jatte.7 For most working Parisians, many employed in industry, Sunday was the day to escape the heat of the city and head for the shade of the trees, quietude, and the cool breezes that came off the river. As one might expect in a popular public space, the viewer sees many different people relaxing in a park by the river, a courting couple, children playing. But there are also codes of vice embedded in the image, ready for those who knew where to find them and how to read them: prostitutes, beggars, alcoholics, proving that greenery could not, through “green lungs” alone, cure the ills of the modern metropolis.8 Two quite different designers, on either side of the Atlantic, did grasp how the increasingly dense modern city and the provision of public green space could be formed into a holistic project that superimposed green space onto architecture, both vertically and horizontally, instead of treating it as an amenity or release valve for the working masses. They were Baron Georges-Eugène Haussmann in France and Frederick Law Olmsted in the United States.9 In Paris, Napoleon III commissioned Haussmann to begin a series of enormous public works projects, which entailed the hiring of tens of thousands of workers to upgrade the sanitation, water supply, and traffic circulation of the city. Haussmann’s annexation of eleven communes into the city was step one in a tabula rasa remodeling of the city designed to both further densify and beautify the rapidly growing and increasingly dense city. Over the subsequent two decades, the City of Paris was a construction site that slowly bore out Haussmann’s aesthetic tenets for the new city: similar facades and materials, standard street and sidewalk widths, and the profound modernization of infrastructure such as sewage and transportation.10 Napoleon III also insisted that Haussmann build new public parks and gardens for the recreation and relaxation of Parisians, particularly those

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Georges Seurat, Un dimanche après-midi à l’Île de la Grande Jatte, 1884–1886.

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Place Charles-de-Gaulle, Paris, France, aerial view.

Parc des Buttes-Chaumont, Paris, France. Jardin du Luxemburg, Paris, France, aerial view.

in the new neighborhoods of the expanding city. The Emperor signaled that the parks built in tandem with Haussmann’s renovation of the city be of the English variety: informal, topographically varied, and for strolling, just at a much larger scale. With the assistance of the engineer Jean-Charles Alphand, Haussmann planned four major public parks in the four cardinal directions around the city.11 The massive effort involved the construction of artificial lakes, lawns, flowered areas, waterfalls, channels, and grottoes as well as park chalets and pavilions, perhaps most spectacularly illustrated by the Parc des Buttes-Chaumont.12 The plan was not limited to these four major parks. Haussmann refurbished a number of existing parks, such as the Jardin du Luxembourg, while also creating more than 80 small parks, one in each city neighborhood, intended to replicate the experience of the four cardinal parks en miniature.13 The success of this plan to replicate the English garden model in miniature around the city was measured in the planner’s promise that no Parisian was ever more than a 10 min walk from a park, a measure of livability used widely in the present book for contemporary projects. The English-garden-in-the-city model also served as inspiration across the Atlantic, particularly in the work of Frederick Law Olmsted, who renovated the face of numerous American cities with parks meant to adapt to and augment dense urban agglomerations. Olmsted’s design principles privileged the natural topography, flora, and fauna of a given site while subordinating to them the designed hardscape elements so that they would not compete with their setting, or at most operate as decorative punctuation points.14 This strategy, whether employed in New Orleans or New York City, Spokane or Springfield, became synonymous with the so-called pastoral or picturesque tradition, characterized by small lakes, vast expanses of green, and groves intended to deliver a contemplative, restorative effect.15 Olmsted left the boundaries between zones indistinct, using the “soft” rather than “hard” boundaries afforded by trees and brush. Perhaps this “soft” border type is one reason why urban greenery began to emerge from its two-dimensional confines in the urban plan. Olmsted did not, however, have equally dogmatic principles when it came to a park’s morphology within the North American city. While several of his parks necessitated some land seizure through eminent domain, his approach was more prospective than renovative when compared to that of Haussmann.16 The strict rectilinearity of New York’s Central Park illustrates its

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Calvert Vaux/Frederick Law Olmsted, map of Central Park, New York, New York, USA, 1870. Frederick Law Olmsted, connection of Columbia Road with Franklin Park and Marine Park, Boston, Massachusetts, USA, 1897.

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Following pages: Central Park, New York, New York, USA, aerial view from the northeast.

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Frederick Law Olmsted, Buffalo parks, New York, USA, 1868, map. Ebenezer Howard, Garden City and Rural Belt, 1902, plan.

nature as a planned park on mostly uninhabited land, anticipating further growth around it. This is in sharp distinction to the irregular, practically surgical park systems of cities like Buffalo or Boston, where parks were planned in mostly open zones in the city.17 It was perhaps the latter type that eschewed the simplistic idea of the park as an amenity most effectively. Nevertheless, both approaches were wildly successful and essential, in their inherent value as spaces even more than in their design, in both beautifying and densifying the North American city. Nothing, however, embodies a thoroughly holistic approach to green planning as much as the idea of the so-called “Garden City,” pioneered by the British farmer and humanist Ebenezer Howard. The departure point for Howard’s radical ideas in town planning lay in Edward Bellamy’s utopian novel Looking Backward and Henry George’s Progress and Poverty, both of which outlined conditions for human settlements where man lives in harmony with nature.18 Howard manifested his ideas most vividly in his 1898 book To-morrow: A Peaceful Path to Real Reform, reissued as Garden Cities of To-morrow in 1902.19 In his book, Howard outlined a master plan for a city that could house 32,000 people on 6,000 acres (approx. 2,500 ha), laid out in a concentric pattern that provided a myriad of public parks and open spaces arranged around six radial boulevards originating in the center of the circle. The principle idea of the city is that it would hold, contained within these circles, everything it needed to not only survive, including food production, but also to thrive. The idea was scalable; a cluster of garden cities could also function as satellites of a larger, central city (58,000 people), all linked one to the other by rail and road. Howard’s book was a massive success, read by specialists and everyday people with equal interest. Audiences in both Europe and North America saw in his proposal an antidote to the increasing overcrowding and deterioration of cities, rife with their poverty and poor health. In combining town and country so thoroughly, Howard signaled to assume an ideological position about the ideal humane landscape, positioned at the intersection of rural life and urban life. The “old city” and its “downtown” were, for Howard, destined for failure and consigned to a status of something that may at best be prevented from getting worse, rather than getting better. The Vicissitudes of Green in the 20th Century It would not be long after the impact of Howard’s ideas began to really take hold in Europe and North America that architects

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Ebenezer Howard, Garden City and Rural Belt, 1902, plan.

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Le Corbusier, Plan Voisin, 1922-25, drawings.

were seeking alternative approaches to city and town planning, advocating in particular models of higher-density (read vertical) residential blocks. Foremost among those new models was Le Corbusier’s Plan Voisin, designed between 1922 and 1925.20 The Plan Voisin was a tabula rasa scheme designed for the core of Paris. Almost as if it was an inversion of Howard’s scheme, it comprised high-rise residential blocks occupying a prime location on the right bank of the Seine. These high-rises afforded a density of approx. 3,000 inhabitants per ha, almost nine times higher than that which existed and yet with even more green space. The master plan also comprised two major traffic arteries that were seen as units of what would ultimately be a road network binding France’s four “corners” to its capital.21 The intense rethinking of man’s relationship with nature in the context of the city was not limited to the so-called global north. As European holdings in Africa, Latin America, and Asia successively decolonized in the middle of the 20th Century, the architects of the global north necessarily shifted their objectives from one of civilizing mission to one of foreign expertconsultant. For architects like Jean Prouvé as well as Maxwell Fry and Jane Drew, this meant a shift from designing buildings to designing building schemes and systems which were, perhaps somewhat exaggeratedly, seen as more adaptable and hence more open to the agency of the formerly colonized.22 In the 1950s, as the rate of global decolonization accelerated, it was in the pages of Architectural Review that some of the most evocative debates and designs of new green urbanisms appeared.23 Specifically, these debates coalesced around the “Townscape” series organized by editor Gordon Cullen.24 A considerable thread in the series throughout the 1950s were articles on what would eventually come to be dubbed “world architecture” (i.e. non-Western), with a focus on building in places with distinctly different climates and hence different building needs. The catch-all term “Tropical Architecture,” which could include architecture in Africa, Asia, and the Americas, provided something of a breath of fresh air to a gray and tired post-war Britain.25 A fascinating moment showing the uneasy transition from colonizer-expert to professional-expert is made manifest in the ideas and works published by the architects Maxwell Fry and Jane Drew.26 Fry and Drew published an extensive series of projects and texts in Architectural Record in May 1953 entitled “The African Experiment,” the title already signaling the ways in which the so-called tropics were seen as a background for a

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Fry, Drew and Partners, Mfantsipim School, Cape Coast, Ghana, 1958, exterior view. T. R. Hamzah & Yeang, EDITT Tower, Singapore, 1998, rendering.

broad brushstroke type of proposal for an architecture that could animate both established architectural practice in the West and also buoying fragile new economies with the infrastructure they would “need” to enter the world stage.27 They would eventually publish a refined and expanded book on their research in the so-called tropics in 1964. Simply titled Tropical Architecture in the Humid Zone, it has had a lasting impact on generations of architects in the West working outside of it.28 In the introduction to this book, Fry and Drew walk back some of the colonial undertones of their work in the 1950s, stating “it is necessary at the outset to recognize that we, the authors, are not inhabitants of the tropic zone but have come to it from the temperate zone. We have experienced its climate, lived with its people and dealt with its problems as they have affected our work…”29 Two key elements for Fry and Drew in the larger realm of urban planning and design were passive shading systems and the maximal infusion of greenery, horizontally as well as vertically. With regard to passive systems, Fry and Drew advocated the widespread use of the brise-soleil and thick, textured screen systems, often of concrete, to provide expansive areas of shading. They also saw greenery as equally, if not more effective in providing passive shading at all levels of a building while also improving air quality. Tropical trees and plants were never omitted from the design of boulevards, parks, maidans, plazas, or any other open space. Scholars like Peter Edwards, one of the contributors to this book, continue to prove the pivotal importance of trees to tropical cities to this day.30 Prospective Green in the 21st Century Since the 1970s, many ecologists have turned their interest towards ecological interactions taking place in, and caused by urban environments. The advent of the 21st Century witnessed the rise of ecologically-oriented design in architecture, landscape architecture, and urban design. Landscape architects like James Corner have pioneered new trajectories of design that privilege open spaces of nature, an aesthetic approach that, while perhaps originally somewhat disarming, has become widely admired and sought after in urban renewal projects across the globe.31 Architects, particularly early pioneers like Ken Yeang, have made equally important strides in bringing the aesthetics of ecologically sound design to the vertical dimension of the city.32 And while the two fields of architecture and landscape architecture still work on a more holistic integration to this end,

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James Corner Field Operations/Diller Scofidio + Renfro, The High Line, New York, New York, USA, 2009.

a common, shared language between the two disciplines has emerged that has privileged the concept of ecology. In some cases, the term “city” is now tacitly understood to be an ecology. As a result, the idea that greenery in the urban environment is an amenity is increasingly seen as both reductive and false. The city, as we know it in 2019, is a multi-dimensional ecosystem. Architects and urban designers have also begun to deal with the question of sustainability not merely as a “green” contribution to the zero carbon output agenda but also as an active combatant against the threats of climate change and sea level rise. The exhibition “Rising Currents” at the Museum of Modern Art coalesced a number of these concerns as they related to New York City’s waterfront in 2010. More recently, BIG has taken this precise concern as the basis for a major polemical project called the “Dryline,” a play on the famous New York City “High Line.”33 The “Dryline” comprises an approx. 16-km-long flood defense barrier, conceived in the wake of Hurricane Sandy, which caused severe damage in New York City’s lowest-lying areas in 2012.34 BIG’s novel proposal for this barrier is not a rote piece of infrastructure but rather a seductive waterfront park, one that becomes alternately thick and thin after it is unfurled like a sort of carpet on New York Harbor. The barrier includes many different kinds of protective mechanisms including berms, plantings, and baffles as well as leisure opportunities among the many promenades and bike paths. “We like to think of it as the love-child of Robert Moses and Jane Jacobs,” says Ingels.35 “Our project must have Moses’ scale of ambition, but be able to work at the fine-grain scale of the neighborhoods. It shouldn’t be about the city turning its back on the water, but embracing it and encouraging access. By taking it one conversation at a time, with the principle that everyone can get their fantasy realized, you end up getting there.”36 The barrier originates in the waters off West 57th Street, looping around the tip of Manhattan, and then ending at East 42nd Street. An approx. 3 km portion of the Dryline that runs adjacent to a group of public housing blocks will concentrate on what the architects have described as a “bridging berm.” The berm resembles a serpentine mound that rises to a height of just over 4.5 m, the 100-year flood level that Hurricane Sandy came close to reaching. The berm will serve as the base for several walkways spanning the six-lane highway known as the FDR Drive and connecting it to the existing waterfront park. The long-term objective is to continue the berm around the full

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BIG, Dryline, New York, New York, USA, 2015, renderings.

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16 km, adapting to the existing waterfront infrastructure as it does on the Lower East Side while also providing variegated opportunities for recreation and leisure through different design elements. One alternative to the monolithic barrier, as emblematized by the “Dryline,” is a diffuse and porous strategy known as “sponge city.” Sponge cities can employ any number of strategies but some of the most common and significant include the maintenance and restoration of wetlands in coastal areas, the use of permeable materials in road and sidewalk construction, green roofs that both absorb and store water, and intelligently designed systems for stormwater runoff.37 China has taken the lead in the development of sponge cities. Following a disastrous flood in 2012, flood prevention (and perhaps, tacitly, sea-level rise) became a top priority for the state. The state kick-started a “Sponge City” initiative in 2015 with a plan for 16 model sponge cities, a number that was later increased to 30, including Shanghai. The part of Shanghai serving as its “sponge” site is a district known as Lingang, a district lined with a very large number of trees, gardens, and public squares with plant beds.38 One of the first moves in the design of the district is to eschew the widespread use of concrete, which is widely used in China, due to its nature as a hard and impervious surface that blocks the flow of rain and stormwater. Lingang’s wide streets are constructed using permeable pavement that allows water to drain into the earth below. A number of centralized plots of land are used as rain gardens, which are filled with soil and plants. A manmade lake, Dishui Lake, serves to moderate the flow of water throughout the district. A majority of buildings feature water tanks and green roofs.39 One of the greatest challenges for fashioning a “sponge city” is bringing the course and condition of natural waterways as close as possible to their natural state, something that is often highly problematic in districts and watersheds that are already densely developed.40 Another major challenge is the creation of new green space, for the same reason, and existing parks are often designed in a way that is at odds with the basic principles of sponge city design. Singapore continues to be at the forefront of research and design in this arena. A modern-day Hanging Gardens, Kampung Admiralty by WOHA, awarded World Architecture

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Urban park, Shanghai, China.

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WOHA, Kampung Admiralty, Singapore, 2018, apartment blocks, medical center, and rooftop community park.

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WOHA, Kampung Admiralty, Singapore, 2018, rooftop community park and plaza.

Festival Building of the Year 2018, is the city state’s first integrated public development that brings together a mix of public facilities and services under one roof. The scheme builds upon a layered “club sandwich approach,” as the architects call it. A vertical village is formed through the design of a community plaza on a lower level, a medical center on a central level, and a community park with apartments for seniors on the upper level. These three distinct levels juxtapose the various building uses so as to foster a diversity of cross-programming. The community plaza, in particular, is a fully public area conceived as a community living room. It is an intimately scaled, elevated green space where the community can come together to undertake any number of activities. Meanwhile, in Shanghai, Heatherwick Studio’s 1000 Trees is making new paradigms of its own. Conceived as a piece of topography, 1000 Trees is designed not to resemble a stand-alone piece of architecture but a pair of “tree-covered mountains.”41 Once completed, 1000 Trees will serve as a mixed-use development comprising over 400 terraces designed to encourage more outdoor interaction among its users and link the sites, and 1000 living trees scattered over the entire structure will sprout from the structural supports. According to the studio, these supports “are the defining feature of the design, emerging from the building to support plants and trees.” Like many of the projects discussed in this book, 1000 Trees will act as part of larger urban green and blue systems; in this case the projects is an extension of a neighboring park in the vertical dimension and it relates to an adjacent canal. Thomas Heatherwick, the principal of Studio Heatherwick, said, “we got interested in the park, as it felt like it could be the glue that somehow connected those elements together.” The result is a lyrical embodiment of the verticalization of urban greenery. About the Book The Sponge City and Kampung Admiralty are just some of the more recent innovations in a longer story of innovation in the ecologically minded renovation of our increasingly dense cities. The research presented in this book builds on that published in Dense+Green: Innovative Building Types for Sustainable Urban Architecture earlier but shifts the emphasis to the urban scale.42 It analyzes innovative examples that were selected from a total of 400 surveyed dense and green projects to shed light on how contemporary planners and designers around the world are meeting the issues of sustainability and densification by fashioning urban and architectural projects

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Heatherwick Studio, 1000 Trees, Shanghai, China, 2019, views along and from Suzhou River.

that reject the idea that the role of urban green is limited to a two-dimensional amenity or a mere “greenwashing” of building developments. The selected projects rather point to an emergent understanding of the building and the city as ecological systems, an understanding which immediately raises important questions about their interaction. Here we witness the ways in that “green” developments can contribute to the ecology of their immediate surroundings and the city at large. And we witness the means by which, across Asia, the Americas, and Europe, ecologically designed buildings and cities, with their green and blue networks, can produce more livable and sustainable urban environments. The subsequent contributions to Part 1 by Sacha Menz, Peter Edwards, and Christophe Girot discuss important aspects related to the topic of this book. Part 2 describes Singapore’s leading role in the development of dense and green cities in Southeast Asia and provides an overview of the Dense and Green research at FCL, followed by important findings on biodiversity, surface temperature, construction and maintenance costs, and economic benefits. Part 3 presents the case studies and Part 4 explores future trajectories of Dense and Green.

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Following pages: WOHA, Kampung Admiralty, Singapore, 2018, rooftop community park with playground.

1. There is much scholarly literature on the rise of the city. See, for example: Nadine Moeller, The Archaeology of Urbanism in Ancient Egypt: From the Predynastic Period to the End of the Middle Kingdom (Cambridge: Cambridge University Press, 2016). 2. See Stephanie Dalley, The Mystery of the Hanging Garden of Babylon: An Elusive World Wonder Traced 1st Edition (Oxford: Oxford University Press, 2015). 3. Paul-Alain Beaulieu, A History of Babylon, 2200 BC – AD 75 (Hoboken, NJ: Wiley Blackwell, 2018). 4. On the Alhambra see: D. Fairchild Ruggles, Gardens, Landscape, and Vision in the Palaces of Islamic Spain (College Station, PA: Penn State University Press, 2003). On the Forbidden City see Guo Daiheng, China’s Lost Imperial Garden: The World’s Most Exquisite Garden Rediscovered (Shanghai: Shanghai Press, 2016). 5. See, for example: John Dixon Hunt, The Venetian City Garden: Place, Typology, and Perception (Basel: Birkhäuser, 2005). 6. See Alessandro Minelli, The Botanical Garden of Padua 1545 – 1995 (Venice: Marsilio Editori, 1995). 7. See Matthew Gandy, “The Paris Sewers and the Rationalization of Urban Space,” in Transactions of the Institute of British Geographers 24:1 (1999), 23 – 44. 8. The idea of a major park being the “green lungs” of a city is most commonly attributed to Frederick Law Olmsted. See William D. Solecki and Cynthia Rosenzweig, “A Metropolitan New York Biosphere Reserve?,” in Rutherford H. Platt (ed.), The Humane Metropolis: People and Nature in the 21st-Century City (Amherst and Boston: University of Massachusetts Press, 2006), 103. 9. On Haussmann, see David H. Pinkney, Napoleon III and the Rebuilding of Paris (Princeton, NJ: Princeton University Press, 1958). On Olmsted, see Witold Rybczynski, A Clearing in the Distance: Frederick Law Olmsted and America in the 19th Century (New York: Scribner, 2000). 10. See Colin Jones, “Theodor Vacquer and the Archaeology of Modernity in Haussmann’s Paris,” in Transactions of the Royal Historical Society 17 (2007), 157–83. 11. See Patrice de Moncan, Les jardins du Baron Haussmann (Paris: Les Éditions du Mécène, 2012). 12. See Ann Komara, “Concrete and the Engineered Picturesque at the Parc des Buttes Chaumont (Paris, 1867),” Journal of Architectural Education 58:1 (September 2004): 5–12. 13. De Moncan, Les jardins du Baron Haussmann. 14. The National Association for Olmsted Parks list the following central tenets to Olmsted’s designs: “1. A Genius of Place: The design should take advantage of unique characteristics of the site, even its disadvantages. The design should be developed and refined with intimate knowledge of the site. 2. Unified Composition: All elements of the landscape design should be made subordinate to an overarching design purpose. The design should avoid decorative treatment of plantings and structures so that the landscape experience will ring organic and true. 3. Orchestration of Movement: The composition should subtly direct movement through the landscape. There should be separation of ways, as in parks and parkways, for efficiency and amenity of movement, and to avoid collision or the apprehension of collision, between different kinds of traffic. 4. Orchestration of Use: The composition should artfully insert a variety of uses into logical precincts, ensuring the best possible site for each use and preventing competition between uses. 5. Sustainable Design and Environmental Conservation: The design should allow for long-term maintenance and ensure the realization and perpetuation of the design intent. Plant materials should thrive, be non-invasive, and require little maintenance. The design should conserve the natural features of the site to the greatest extent possible and provide for the continued ecological health of the area. 6. A Comprehensive Approach: The composition should be comprehensive and seek to have a healthful influence beyond its boundaries. In the same way, the design must acknowledge and take into consideration what surrounds it. It should create complementary effects. When possible, public grounds should be connected by greenways and boulevards so as to extend and maximize park spaces.” Accessed January 31, 2019, http://www.olmsted.org/the-olmsted-legacy/ olmsted-theory-and-design-principles/design-principles 15. See John Dixon Hunt, Gardens and the Picturesque: Studies in the History of Landscape Architecture (Cambridge, MA: The MIT Press, 1994). 16. Olmsted displaced a settlement of mostly African American landowners to be able to create Central Park. See Hope Killcoyne and Mary Lee Majno, The Lost Village of Central Park (New York City: Silver Moon Press, 1999). 17. On Olmsted’s interventions in specific cities, see Francis R. Kowsky and Andy Olenick, The Best Planned City in the World: Olmsted, Vaux, and the Buffalo Park System, 2nd ed. (Amherst and Boston: University of Massachusetts Press, 2018); Cynthia Zaitzevsky, Frederick Law Olmsted and the Boston Park System (Cambridge, MA: Harvard University/Belknap Press, 1982); Jennifer Ott, Olmsted in Seattle: Creating a Park System for a Modern City (Seattle: HistoryLink, 2019).

18. Edward Bellamy, Looking Backward 2000-187 (New York: Houghton Mifflin, 1889); Henry George, Progress and Poverty: An Inquiry Into the Cause of Industrial Depressions and of Increase of Want with Increase of Wealth: The Remedy (New York: D. Appleton and Company, 1881). 19. The former was reissued by Cambridge University: Ebenezer Howard, To-Morrow: A Peaceful Path to Real Reform (Cambridge: Cambridge University Press, 2010). The latter is Sir Ebenezer Howard, Garden Cities of To-Morrow (London: 1902). 20. Robert Fishman, Urban Utopias in the Twentieth Century: Ebenezer Howard, Frank Lloyd Wright, Le Corbusier (Cambridge, MA: The MIT Press, 1982). 21. See also Thordis Arrhenius, “Restoration in the Machine Age: Themes of Conservation in Le Corbusier’s ‘Plan Voisin’,” AA Files 38 (Spring 1999): 10-22. 22. See this outlined in Ayala Levin, “Basic Design and the Semiotics of Citizenship: Julian Beinart’s Educational Experiments and Research on Wall Decoration in Early 1960s Nigeria and South Africa,” ABE Journal 9–10 (December 2016), accessed January 31, 2019, http://journals.openedition.org/abe/3180 . 23. See Clément Orillard, “Tracing Urban Design’s ‘Townscape’ Origins: Some Relationships Between a British Editorial Policy and an American Academic Field in the 1950s,” Urban History 36:2 (August 2009): 284–302. 24. Mira Engler, Cut and Paste Urban Landscape: The Work of Gordon Cullen (Abingdon: Routledge, 2015). 25. See Chang Jiat-Hwee, A Genealogy of Tropical Architecture: Colonial Networks, Nature, and Technoscience (Abingdon: Routledge, 2016). 26. On Fry and Drew’s career see: Iain Jackson and Jessica Holland, The Architecture of Edwin Maxwell Fry and Jane Drew: Twentieth Century Architecture, Pioneer Modernism, and the Tropics (Abingdon: Routledge, 2016). 27. The publications of 1953 are detailed in Jackson and Holland, The Architecture of Edwin Maxwell Fry and Jane Drew: Twentieth Century Architecture, Pioneer Modernism, and the Tropics. 28. Maxwell Fry and Jane Drew, Tropical Architecture in the Humid Zone (London: Batsford, 1956). Other works include Maxwell Fry and Jane Drew, Village Housing in the Tropics with Special Reference to West Africa (Abingdon: Routledge, 2013); Maxwell Fry and Jane Drew, Architecture and the Environment (Crow’s Nest, Australia: Allen & Unwin, 1976). 29. Fry and Drew, Tropical Architecture, 17. 30. See, for example, Song Xiao Ping, Daniel Richards, Peter Edwards, and Tan Puay Yok, “Benefits of Trees in Tropical Cities,” Science 235:6344 (2017): 1241. 31. See, for example, James Corner and Alison Bick Hirsch, The Landscape Imagination: Collected Essays of James Corner, 1990-2010 (Princeton, NJ: Princeton Architectural Press, 2014). 32. See Sara Harr, EcoArchitecture: The Work of Ken Yeang (Hoboken: Wiley, 2011). 33. See Oliver Wainwright, “Bjarke Ingels on the New York Dryline: ‘We think of it as the love-child of Robert Moses and Jane Jacobs’,” The Guardian, 9 March 2015, accessed January 31, 2019, https://www.theguardian.com/cities/2015/mar/09/ bjarke-ingels-new-york-dryline-park-flood-hurricane-sandy. 34. John Abraham, “New Study Links Global Warming to Hurricane Sandy and Other Extreme Weather Events,” The Guardian, 22 June 2015, accessed 31 January 2019, https://www.theguardian.com/environment/climate-consensus-97-per-cent/2015/jun/22/ new-study-links-global-warming-to-hurricane-sandy-and-other-extreme-weather-events 35. Wainwright, “Bjarke Ingels.” 36. Ibid. 37. See a comprehensive outline of the concept of the “Sponge City” in Sophie Barbaux, Sponge City: Water Resource Management (Mulgrave, Australia: Images, 2016). 38. Helen Roxburgh, “China’s ‘Sponge Cities’ are Turning Streets Green to Combat Flooding,” The Guardian, 27 December 2017, accessed January 31, 2019, https://www.theguardian.com/world/2017/dec/28/ chinas-sponge-cities-are-turning-streets-green-to-combat-flooding. 39. Ibid. 40. Ibid. 41. Georgie Sinclair, “Transforming Shanghai’s skyline with 1000 trees,” in “Let it Grow,” accessed March 19, 2019, https://letitgrow.org/city-culture/ transforming-shanghais-skyline-1000-trees/. 42. Thomas Schröpfer, Dense+Green: Innovative Building Types for Sustainable Urban Architecture (Basel: Birkhäuser, 2016).

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The Collective Power of the Single Building How Small-Scale Can Influence Large-Scale in Urban Planning in the Future Sacha Menz

“Perhaps the best definition for the inhabitants of an early city is that they are a permanently captive farm population.” – Lewis Mumford, The City in History (1961)1 People have been meeting up in public spaces since time immemorial — praying, talking, bargaining, eating, arguing, and making music together. Living in communities and wanting to exchange views and experiences physically and on the spot are characteristic traits that are primordially human and will never be replaced by virtual platforms. Touch, sounds, smells and glances produce stimuli that cannot be transmitted across electronic networks, which can neither replace nor conjure up our physical and mental presence. A single glance may often say more than a thousand printed words. The greater the density of our surroundings and the scarcer the public space available, the more we tend to appreciate how important it is to genuinely experience the reality of spaces right up close. These are the conditions in which contacts are made from person to person and in which stimuli and impulses are transmitted. When we look back at the way in which the railways developed during the age of industrialization, it appears that this new form of transport gave rise to a network of links between the commercial centres and had an accelerating effect on the cities and their growth. Railway stations — large-scale public receptacles built to house the railway infrastructure — often formed the interface between existing urban structures and new urban areas that developed during industrialization in the 19th Century. Planning new structures allowed for the creation of a very wide and diverse range of different usages. In accordance with traditional models, buildings that served the driving forces behind the economy such as education, manufacturing, and trade were again intermingled with buildings for residential and religious purposes. The ground floors, providing a kind of connecting medium, became established as vital levels of urban life. The next level of public space was established by streets, squares, markets, parks, and gardens. By definition, these are all publicly accessible places that even today still function in accordance with agreed social rules, promoting social, cultural, and economic exchange among people. In the early 20th Century, Ebenezer Howard advocated the Garden City as a model in reaction to the growing separation of town and country. Howard cited the town as symbol of society, of mutual help and friendly cooperation, of broad relationships, and of science and art which contrasted the country as symbol of God’s love and

care of men.2 In its structural pattern, the Garden City is arranged circularly around a core city, with residential areas alternating with green spaces, intended as an open criticism of the terrible living conditions then predominant in English cities and as a response to disproportionately high rental costs. In contrast to established 19th-Century conceptions of the city, life in the Garden City focused on residential usage. Many years later, the Congrès Internationaux d’Architecture Moderne (CIAM) developed a fundamentally new principle for urban planning. In the Athens Charter that he presented at the Fourth CIAM Congress in 1933, Le Corbusier produced a radical manifesto advocating a revolutionary way of thinking about and planning cities. In essence, the Congress concluded with the idea of a functional form of urban planning that regards itself as mediating in an interplay between individual functional areas within the continuum of the city. This modernist view of urban planning passed into European culture during the postwar period and influenced planning work in many cities. The disentangling and separation of functional areas still provide the framework for many assumptions and tools used in urban planning today. Fortunately, modern cities have proven to be more adaptable than what was originally put down on paper, and in the end they are also to some extent resistant to passing trends in planning. Not only the built masses of the city itself, but also its inhabitants dispose of a degree of robustness that should not be underestimated. It is people who shape buildings, and they do not all follow the latest fashions. It is all about appropriation: city-dwellers are showing that they are able to appropriate areas and spaces to themselves and pour the widest possible variety of functions into them. The result is a natural, refreshing diversity. “Not only is the city an object which is perceived (and perhaps enjoyed) by millions of people of widely diverse class and character, but it is the product of many builders who are constantly modifying the structure for reasons of their own … No wonder, then, that the art of shaping cities for sensuous enjoyment is an art quite separate from architecture or music or literature.” – Kevin Lynch, The Image of the City (1960)3 This statement by Kevin Lynch initially suggests hope, but the appearance is deceptive. Today, as there are more people living in cities than in the countryside and the imbalance is likely to become even more extreme in the future, established political and social planning processes are often unable to keep up with

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Herzog & de Meuron, Caixa Forum, Madrid, Spain, 2008, view from the southeast.

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Kevin Lynch, The Image of the City, 1960, image of Boston, Massachusetts.

the dynamic force of the urban centers’ rampant growth. In the face of an urgent need to create space, and also due to shortages of finance, central aspects of urban development such as the production and implementation of master plans are often left to private or institutional investors. The established competence and independent authority of those responsible for planning in the cities are often ignored and ultimately undermined. Public responsibilities of the democratically elected representatives who are involved in urban development shift into private hands. The rapid influx of new city-dwellers fundamentally challenges efforts to achieve a quality of life suited to the circumstances. Both the built and natural environments are coming under pressure. Never before have so many areas of public usage been privatized in cities throughout the world — in areas such as education, health care, living for the elderly, trade, culture, infrastructure facilities, etc. Public market halls are a good example, as they have given way to department stores and malls in which the customer is subordinated to the applicable house rules — often making the spontaneous occurrence of unexpected events impossible and refusing entry to unwelcome guests. Particularly in the booming big cities — in Asia, for example — privatized areas are increasingly pushing out publicly usable and freely available spaces. For reasons of financial shortages and increased efficiency, cities are passing the responsibility for creating and managing public space to private investors. The latter are enticed with higher usage bonuses for their development projects, and they compensate for the obligations agreed with the authorities by raising the rental income and sales returns. In the short term, this is usually good business for both sides, but in the long term it is a pact with uncertainty. Seen over the long term, private investors are never as robust as municipal communities and they tend to adapt their structures to economic facts very quickly, so that they are the first to put an end to unprofitable expenses and services. Even as the substance of the city is robust and city-dwellers are ultimately capable of resisting the superficial attractions of the market, the preconditions for this need to be established and fortified — meaning in particular allowing the public authorities to welcome novelty and ensuring that investors are willing to take part in experiments. This is the only way in which innovative forms of new residential and living spaces can be developed. How can we describe and assess the quality of experiments and their sustainability in this field? In the city rankings published by The Economist or Monocle — both internationally respected and widely available print media — various different criteria are used

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to measure quality of life. Factors such as distance to hospitals and recreational facilities, unemployment rates, availability and routing of public transport, trends in rental prices, and even dog-friendliness, are taken into account as factors influencing urban well-being. Usually derived from questionnaires, such data tend to produce an abstract and overly technical picture of contemporary lifestyles. People’s characteristics and idiosyncrasies are difficult to assess. If Google constantly measures the movement speed of mobile phones in order to identify the locations of traffic jams, we know nothing about what the drivers are thinking, why they are in their cars in the first place, or where they are heading. Why do people become ill, how do communities arise, what is it that creates job satisfaction, how are educational services actually used, and what effects do all these factors have on the job market? These and other characteristics that are difficult to measure have a very substantial influence on the quality of life in cities. Despite its tremendous popularity, the SoHo neighborhood in Manhattan would not meet all of the criteria listed in the Livability Index of the AARP Foundation, a private foundation in the United States for the improvement of living standards. The index itemizes, for example, housing costs and availability, neighborhood, safety and access to jobs, access to public facilities, transportation, road safety and accessibility, environment, quality of air and water, health, number of smokers, distance to hospital services and their quality, engagement, Internet access, voting rate, number of social institutions and opportunities, equality of opportunity, average age, and high-school graduation rates. SoHo, as an example, shows a low rate of housing affordability, with a select and privileged class able to afford to live in this neighborhood. This drastic social limitation calls into question all of the other factors taken into account in the calculation. Despite this, SoHo is an extremely popular area in New York City, particularly among tourists. SoHo creates what many people experience as a pleasant atmosphere. In comparison with downtown Manhattan, it has a small-scale, clearly arranged appearance comprising urban green, it promotes interpersonal relationships, and provides many communal and publicly usable spaces. It is spatially comprehensible for people and its clear arrangement conveys a sense of physical protection. It is a district you can get your hands on. There is a sense of neighborliness that gives the deep-rooted community in the district a sense of being at home. SoHo attracts people — but living there does not

offer the same open equality of opportunity that was present in the age of the great immigration. In this sense, Richard Sennett, in his book The Conscience of the Eye,4 is correct to describe New York City as being dead: the Big Apple has long since closed the open arms that it held out to every class of society. It was the colorful mixture of immigrants that made it great. Ellis Island, the central arrival point and distributing hub for the immense stream of immigrants, no longer has a purpose. The culture of difference — the elemental force behind urban coexistence — now survives only in limited form. One essential aspect that will bring us closer to the issue of quality of life and livability are the ways in which individual groups of buildings, or even individual buildings, are able to exert a positive influence on neighborhoods and improve the quality of life of their residents. This situation has prompted us to investigate the nature of ‘Collective Form.’ Collective Form represents groups of buildings and quasi-buildings — the segment of our cities. Collective form is, however, not a collection of unrelated, separate buildings, but of buildings that have reasons to be together. “Cities, towns, and villages throughout the world do not lack in rich collections of collective form. Most of them have, however, simply evolved: they have not been designed. This gives some reason why today so many professionals, both architects and planners, often fail to make meaningful collective forms — meaningful to give the forms forceful raison d’être in our society.” – Fumihiko Maki, Investigations in Collective Form (1964)5 Important small-scale components of the city, either individual buildings or groups of buildings, have a greater influence on their surroundings than is commonly thought. This is the hypothesis that is being investigated in the Dense and Green research at the Singapore-ETH Centre Future Cities Laboratory, where new building typologies are being studied in relation to their social, cultural, climatic, and eco-stabilizing capabilities. The city state is one of the most popular places in Asia to live and work in, and it is aiming to become a megacity based on essential Asian values such as harmony, respect, and hard work. This was how the city was described in the National Geographic magazine, November 2017 issue. Singapore has notable examples of building types that stand out from the mass of the city’s other structures and devote themselves to coexistence, to a sense of community, comfort, and biodiversity without losing sight of economic considerations.

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Greene Street, SoHo Cast Iron Historic District, New York, New York, USA, 2019, view from the northeast.

WOHA, Oasia Hotel Downtown, Singapore, 2016, section.

For example, there are buildings that have vertically arranged green plantings and feature community spaces for recreation within an extremely densified urban environment. The incorporation of green areas within and around high-rise buildings occurs in buildings with a wide range of usages. Sky terraces and sky bridges, a step beyond the traditional roof gardens, as well as vertical green elements are used here for cooling and providing shade. Other combinations of this type of green approaches to architecture are found in cities around the world, including Milan, Sydney, and Miami. Departing from established types of buildings, they propose a serious vision and novel models for the vertical expansion of the city. The cross-sections of these buildings make the idea clearer: the urban ecosystem, with its public and private green spaces, has been shifted to the vertical plane and reinvented for this new dimension. The ways in which public, communal, green-planted spaces can be integrated by this approach is likely to be a challenge in the development of future architectural typologies. A single green-planted building that is accessible to a district’s inhabitants has the potential of creating better social links within a limited space and footprint while at the same time representing a successful economic model. The growth of Asia’s cities is advancing tirelessly, and statisticians have predicted growth of a further 20% over the next 10 years. An extremely worrying prediction! Will that mean the end for good quality of life in the cities, or will public activities that were previously so popular then only take place on the vertical plane? Seen from the point of view of evolutionary history, humans are beings that live close to the earth. But human beings are also adaptable, and the approaching explosive growth of the world’s population, together with the rural exodus and subsequent development of large cities, have shifted many human activities from the horizontal to the vertical plane. Living and working at dizzy heights have already become part of everyday life, above all in Asia. At the 1959 CIAM congress held in Otterlo, Ernesto Rogers triggered a debate on basic principles when he presented the Torre Velasca, which he had designed together with his colleagues Gianluigi Banfi, Lodovico Barbiano di Belgiojoso and Enrico Peressutti (BBPR). The tower-like, multifunctional building in Milan reflects working and residential usages that are differentiated in terms of cross-section and elevation. But Rogers did not succeed in explaining to his colleagues the way in which the building’s expression represents a construct formed of interlocking conditions and an image of its constituting

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Street markets in Asia and Italy, 2018.

influences; and so he failed to persuade them of the need for urban planning at this small scale. Through its combination of functions and also in its structural quality (based on the principle of structural honesty), the Torre Velasca represents a logical way of densifying the city. And yet it was Peter Smithson’s severe criticism of its formalism and historicizing attitude that won out at the Congress. This discussion occurred at a time when the focus was perhaps more on large-scale overall contexts, and this might explain the conference’s dismay over the presentation of an individual object. Peter Smithson then presented his London Roads Study and contradicted Rogers. The Smithsons, Louis Kahn, and Aldo van Eyck — the intellectual heavyweights at the Congress — vehemently defended the view that one should concentrate on the greater reality of the large scale. This attitude, and their vote in favour of a statement opposing object-like qualities and rejecting any processing of traditions, were from then on demonstrated in new practices of architectural design — and wrongly so, since Rogers’s tower already anticipated the concerns of densified and combined living and working, and with its slender substructure provided scope for valuable public space from which the surrounding district could benefit. There are many who believe that the construction of our cities is essentially complete. Europe and North America have almost given up looking at things on a genuinely large scale. At the other end of the spectrum, entire cities have been springing up in Asia within an extremely short time. But in the process of their development, the small-scale concerns of the individual and in the scale of districts are often overlooked. Mainly financed by private investors, these projects provide residential and working spaces in order to satisfy the demand by merely following the market. Gated communities, for example, are popular, but the way in which they are closed off to the outside world means they do not in the end make any genuine contribution to public life. The ways in which an individual building can influence its immediate surroundings are still underestimated even today. How much public and communal space do buildings contain? Do they offer space for recreation within the district? Do they promote the development of the flora and fauna, do they radiate less heat into their surroundings so that they reduce the “heat island effect,” do they regulate their water balance inside a separate and independent system? These and other factors that influence the environment can lead to improved living conditions in the cities. If we look at the large scale once again, it becomes evident that cities can and must make shared and public green spaces available, implement them and ultimately also manage them.

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Safdie Architects, Jewel Changi Airport, Singapore, 2019, interior.

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CPG Consultants/RMJM Hillier, Khoo Teck Puat Hospital, 2010, courtyard with sky bridges, view from the west.

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Fumihiko Maki, Investigations in Collective Form, 1964, Japanese lineal village. Gruppo BBPR, Torre Velasca, Milan, Italy, 1958, view from the east.

But all this on its own is still not enough to satisfy the larger aspiration to allow greater urban density in the future. As the example of the Torre Velasca and its mixture of functions shows, it will become necessary to integrate all of these concerns into individual buildings: implement them architecturally in order to supplement districts with high-quality usable space. More creativity, courage, and social commitment are needed in the development of new architectural typologies. This will enable property developers to reposition themselves, no matter whether they are private companies or institutional or public bodies, and allow them to take responsibility for the community and contribute to improving the quality of life. Just as Ernesto Rogers was able to deduce the whole from individual elements, we will in the future increasingly experience the way in which buildings on a small scale can influence our living conditions. The examples presented in this book have the potential to become persuasive models for the ways in which cities can be made more enjoyable to live in and more environmentally compatible, with smaller interventions. High density does not necessarily mean any loss of green areas or community-used spaces; the apparent opposites can in fact complement one another. Ebenezer Howard conceived of the Garden City and implemented several examples of it; and Singapore today is gradually trying to develop itself into a “City in a Garden.” Here the idea of rethinking cities is in accordance with political goals and is being established as a guideline through the strong influence of the city planning authorities and implemented ”from the top down.” Conversely, ”from the bottom up” development, from small scale to large scale or from a single building to the level of the district, requires commitment on the part of each individual. The demand to create networked and active forms of urban existence emerges from large numbers of small, compartmentalized structures. In his book Building and Dwelling: Ethics for the City, Richard Sennett distinguishes between “two different things — one a physical place, the other a mentality compiled from perceptions, behaviours and beliefs. The French language first came to sort out this distinction by using two different words: ville and cité.”6 The ville is laid out and planned on a large scale, it is built of stone and mass. The cité embodies the Latin civitas, in contrast to urbs. Instead of buildings made of stone, it is interpersonal concerns, touch, sounds, smells, glances, etc., that come to the surface and constitute what makes life in the city worth living in the first place. This recognition has less to do with the size of one’s own dwelling than with the quality of the spaces that we are able to use in common as city dwellers.

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group8asia/AEDAS, Punggol Waterway Terraces I, Singapore, 2015, view from the northeast.

One important question remains: is there any hope to gain control over urban planning in the future and make the cities worth living in again? What will the cities of the future look like? Resourceefficient, emission-free, green, and at the same time spatially densified — that is the provisional answer at the moment. In the search for civitas within the urbs, several of the projects presented in this volume are already making a contribution to public life while at the same time incorporating community spirit. They stand as individual architectural works that have been conceived and implemented through tremendous commitment and were not developed solely on the basis of profit calculations. 1. Lewis Mumford, The City in History: Its Origins, Its Transformations, and Its Prospects (New York: Harcourt, Brace & World, 1961), 47. 2. Ebenezer Howard, Garden Cities of To-Morrow (London: Swan Sonnenschein, 1902), 17–18. 3. Kevin Lynch, The Image of the City (Cambridge, MA: MIT Press, 1960), 2. 4. Richard Sennett, The Conscience of the Eye: The Design and Social Life of Cities (New York: Knopf, 1990); German translation: Civitas: die Grossstadt und die Kultur des Unterschieds, trans. Reinhard Kaiser (Frankfurt am Main: Fischer, 1991). 5. Fumihiko Maki, Investigations in Collective Form (St. Louis, Missouri: Washington University School of Architecture, 1964), 5. 6. Richard Sennett, Building and Dwelling: Ethics for the City (New York: Farrar, Straus and Giroux, 2018), 1.

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Following pages: Safdie Architects, Jewel Changi Airport, Singapore, 2019, interior.

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Green Spaces and Ecosystem Services

Peter Edwards

The green spaces that add variety to today’s cities are the legacy of past decisions and circumstances. While some green spaces, notably public parks, playing fields, and gardens, were deliberately planned, many are the by-products of other decisions, such as constructing a roadside embankment or roundabout, or a cemetery. Yet others owe their existence to chance or local circumstance, such as quarries that have been abandoned or wetlands that could not easily be developed for other purposes. Whatever their origins, these urban ecosystems — and the biodiversity they support — are increasingly valued for their role in improving the urban environment and making cities more livable. But as we come to appreciate the importance of green spaces for urban life, we also realize that their continued existence is threatened by economic pressures. We see that the combination of chance and circumstance that produced the present mosaic of green spaces will not be sufficient to ensure that it persists. Like other essential infrastructure, urban ecosystems must be planned, designed, and maintained. Green Spaces and Biodiversity in Cities The idea of greening cities is not new. In Roman times, the Emperor Nero set his palace, the Domus Aurea, in a vast landscaped garden that included groves of trees, pastures with flocks, vineyards, and even an artificial lake. Many wealthy Romans followed his example and surrounded their villas with elaborate gardens or horti. It was not until the 19th Century, however, that the importance of open spaces for human well-being was generally recognized. In Britain, concern over the poor health of people living in overcrowded industrial towns led to the public park movement, which arose in the 1830s. By the end of the 19th Century, the importance of public open spaces had become widely appreciated, and parks even became symbols of civic pride, providing inhabitants and visitors alike with attractive surroundings where they could enjoy their leisure time.1 The interest in urban biodiversity is more recent. The oldest organization dedicated to recording and protecting the wildlife of a city is the London Natural History Society (LNHS), founded in 1858. As its website proudly proclaims, there are some fantastic places for wildlife in the London area. “More than 40% of London is green space or open water. As many as 2,000 species of flowering plant have been found in the LNHS area. The tidal Thames supports 120 species of fish. Over 60 species of bird nest in central London. LNHS members have recorded 47 species of butterfly, 1,173 moths and more than 270 kinds of spider around London. London’s wetland areas support nationally

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Clichy-Batignolles Eco-district, Paris, France, green and blue spaces.

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Botanic Gardens, Singapore, board walk.

Wild otters in Kallang Basin, Singapore.

important populations of many water birds. London has 38 Sites of Special Scientific Interest (SSSIs), two National Nature Reserves and 76 Local Nature Reserves.”2 Another city justly proud of its wildlife is Singapore, which is home to a remarkable variety of plants and animals, many of which can be still be found in their natural habitats. Singaporean naturalists have recorded more than 390 species of birds and at least 2,100 native vascular plants, of which more than 1,500 species still occur in Singapore. The city contains over 300 parks and four nature reserves, including a 163 ha fragment of the rainforest that formerly covered the island.3 As these examples show, there is no reason why even a large, densely populated city cannot support a high biological diversity. But what are the origins of these species? Every city has its own history and circumstances, which determine how much green space it has within its boundaries, and how many species it supports. One source of species is deliberate introduction — what we might call the planned biodiversity; this includes the many plants grown in parks and gardens, as street trees, and increasingly also on buildings. Indeed, the number of introduced species sometimes exceeds that which would occur in an equivalent area of natural habitat. A second important origin is relicts of the ecosystems that existed before the city was constructed. Some cities contain patches of land that for various reasons have never been developed: perhaps they were too steep or wet, or were areas of religious significance such as sacred groves, or enjoyed some special legal protection. Whatever the reason, these patches of “natural habitat” can be extremely important for the overall biodiversity. The few fragments of original rainforest in Singapore, for example, contain over 450 tree species, most of which occur nowhere else in the city. Similarly, London has large areas that were either common land or royal hunting forests. A third souce of urban biodiversity is the species that have spread into cities and found there the habitat conditions they need. Many of these occur in unplanned green spaces such as roadside verges and waste ground, or on built structures such as walls and derelict buildings, or in canals and drains. The red fox has become an urban species in many European cities, while tropical cities such as Singapore have thriving populations of animals such as the palm civet and python, and even of endangered species such as the smooth-coated otter.

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PLANT Architects, Toronto City Hall, Ontario, Canada, 2010, green roof (building design by Viljo Revell, 1965).

Benefits from Urban Ecosystems Only recently have urban ecosystems and the biodiversity they support become a focus of intensive research. The results of this research are important for understanding the value of green areas and how they can be better managed. A conclusion emerging from this work is that urban ecosystems are not just “nice to have,” but deliver important benefits for the quality of the urban environment and for the health and psychological well-being of residents. In attempting to understand these benefits, two concepts – biophilia and ecosystem services – have proved especially influential. “Ecosystem services” refers to the benefits that people obtain from functioning ecosystems, including green areas within cities.4 These benefits are very diverse, but usually classified into four main types: provisioning, regulating, socio-cultural, and supporting ecosystem services. The first of these, provisioning ecosystem services, refers to the production of harvestable goods such as food, building materials, and fuel. The second is regulating ecosystem services, which helps maintain environmental conditions within safe or comfortable limits. Vegetation can have a big effect upon the urban microclimate and contribute to mitigating urban heat islands. Similarly, temporarily retaining rainwater, vegetation, and unsealed land can help prevent floods following heavy rain. A third type is socio-cultural ecosystem services, meaning those services important for human psychological well-being and culture. Trees and gardens increase the amenity value and attractiveness of the urban landscape, while nearly all green spaces offer recreational potential. As places where people meet, rest, and play, public green spaces foster social and cultural integration, especially among children and young adults. The final category, supporting services, underlies the provision of the other three, and contributes to the overall resilience of urban systems. Key supporting services include pollination, which helps maintain plant populations and produce food, and biodiversity, which can increase the resilience of an ecosystem in providing services. The second concept, biophilia, emphasizes the importance of biodiversity for human thriving. First formulated by the German philosopher Erich Fromm in the 1960s,5 the biophilia hypothesis proposes that humans possess an innate tendency to seek connections with nature and other forms of life. This hypothesis has been the subject of many studies, with most of them supporting the idea that interacting with nature can be beneficial

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Renzo Piano Building Workshop, California Academy of Sciences, San Francisco, California, USA, 2008, green roof.

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James Corner Field Operations/Diller Scofidio + Renfro, The High Line, New York, New York, USA, 2009.

for health and well-being. Given that most people now live in cities, some of which are very large, efforts are increasing to ensure that urban dwellers are not excluded from these benefits. Biophilic design is an architectural approach aimed at promoting people’s contact with nature; its advocates see such design as a means to reduce stress, enhance creativity and clarity of thought, improve human well-being, and expedite healing. Partly for this reason, many architects now include features such as green roofs, roof gardens, sky terraces and green facades as an integral part of their building designs. Urban Ecosystems under Pressure When we think about the benefits of urban ecosystems, we need to consider not only the formal parks and gardens, but also smaller, informal areas such as derelict land, roadside verges, railway corridors, and urban streams. This means we must extend the concept of urban green spaces to include all habitat patches that support wildlife, however small or temporary they may be. Which raises some interesting questions. How much green space is there altogether? How is it distributed across the city? What benefits do different types of green space provide? These may seem to be simple questions, but they can be surprisingly difficult to answer. Here are some important conclusions about urban green spaces based upon the rather few studies that have been conducted. First, most urban green spaces are small. In one recent study, the green spaces in nine large Chinese cities were found to be highly fragmented, consisting of few large areas such as parks and many more small patches with an area of less than 0.1 ha.6 If only the larger patches were considered, which is usual when green spaces are assessed using a low-resolution satellite image, then the total area of green spaces was greatly underestimated (averaging around 20% of the urban area rather than the true value of 34%). One lesson from this study is that, by concentrating on the larger areas, we overlook the important contribution of small patches to urban ecosystem services. Second, the proportion of green space declines towards the center of cities. Because of high land prices, there is enormous pressure to utilize land in the urban core as fully as possible: houses with gardens are replaced by blocks of flats or offices, rivers are put into pipes, open corridors are appropriated for roads, and even railways are put underground. Except where there are legal or planning restrictions upon development, urban centers usually end up being almost devoid of green spaces or biodiversity.

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Rail Corridor, Singapore. The Rail Corridor is a former railway line that stretches 24 km north to south. Now a “green corridor,” it will be transformed into a community space that links many parts of the City over the coming years. Tree-lined road, Singapore.

Third, the pressure to develop the urban core increases as cities grow. This is because land prices increase disproportionately with population,7 so that the available land is used ever more intensively. Large cities are therefore less likely to enjoy the benefits provided by green spaces, especially in the dense urban core, making them prone to problems such as poor air quality and urban warming. Given this negative relationship between urban density and environmental quality, novel approaches are urgently needed to restore ecosystem services, for example through the use of sky-rise greenery. Strategies to Protect Urban Ecosystems Given the economic pressures to develop land, it is unrealistic to expect the green areas we have inherited to persist into the future unless cities develop clear strategies to protect and enhance them. Many cities around the world are doing just that, for example by setting targets for green areas and putting a value upon ecosystem services. Indeed, it is encouraging that cities have even begun to compete for the accolade of being the greenest and most ecological city. Set targets for green space and biodiversity. This is perhaps the single most important step towards enhancing biodiversity and improving ecosystem services. London recently announced its plan to become the “first National Park City,” rich in wildlife and with 50% of its area green by 2050. As the mayor of London said recently, “We are working to make our city’s parks, green spaces and waterways great places for people and spaces where wildlife can thrive.”  Singapore also has ambitious goals to create more green and blue spaces near people’s homes. By 2030, it plans that over 90% of citizens should live within a 10 min walk of a park, and the park connector network should be doubled to 400 km. In the same period, the total area of public green space is planned to be increased to over 4,000 ha, and 180 km of new green corridors (known in Singapore as Nature Ways) will be created. Creating new green areas is undoubtedly good for wildlife, but it is not possible to set firm targets for biodiversity. Nonetheless, it is possible to monitor the factors that favor biodiversity and set goals accordingly. Singapore has developed the Singapore Index on Cities’ Biodiversity (SI), which it uses as a quantitative tool to monitor progress in conservation.8 The index uses 23 indicators that measure native biodiversity, ecosystem services provided by biodiversity, and governance and management of biodiversity.

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The method has proved very valuable in setting priorities for planning and conservation not only in Singapore but also in many other cities around the world. Assess the value of ecosystem services. Setting aside land in a city as green spaces entails costs. It entails opportunity costs, since using the land as a green space means not using it for other purposes such as housing, which might be very profitable. It entails management costs for operations such as mowing grass, pruning trees, and raking up leaf litter. And it entails indirect costs, such as those caused when tree roots damage pavements and buildings, damage and injury from falling trees, and blockage of drains by leaf litter. All these are real costs, and it is scarcely surprising that creating green areas and planting trees is often politically controversial, being seen by some as a luxury that the city cannot afford. Given these costs, the political argument for creating green areas is greatly strengthened if the benefits can be measured and presented in financial terms. In the past few years there have been several studies aimed at assessing the diverse economic benefits of street trees and urban ecosystems. Among sources of value that can be readily measured, one of the most important in cities is amenity benefits, which can be assessed through the effects of green spaces and trees upon property prices in the neighborhood (known as the “hedonic pricing method”). Other benefits relate to the regulatory functions of ecosystems, such as cooling, which can be assessed in terms of electricity saved, and reducing the risk of flooding, which can be assessed in terms of the cost of structures that would otherwise be needed to manage stormwater. Finally, the “contingent valuation method” allows researchers to assess other non-market benefits by asking people how much they would be prepared to pay for green spaces or urban ecosystems. The methods for assessing the value of ecosystem services are far from perfect, but progress is being made in capturing social and cultural values that are less easily assessed. Even with their present limitations, however, these methods provide striking evidence of the value of urban ecosystems. A recent review of the costs and benefits of urban trees found that the economic benefits usually outweighed the costs, even when only one or a few sources of benefit were considered.9 In that survey, the benefits with the highest valuations, and those most likely to outweigh costs, were “aesthetic and amenity,” shading, and water regulation.

Planning for Ecosystem Services: Some Principles The proportion of green areas in a city offers a simple metric for urban environmental quality, and many cities use it. But not all green areas are equally valuable; an intensively managed lawn, for example, probably delivers much less in ecosystem services than a patch of woodland. The type of ecosystem, the level of biodiversity, and the spatial arrangement of green patches are all important in determining the benefits we obtain from green areas. To get the most value out of urban greening, planners need some guiding principles about how to design and care for them. Here are some suggestions: Take a system approach. In a natural ecosystem, the individual trees and patches are linked spatially through many processes. Birds and butterflies migrate, water flows, wind blows, seeds disperse, and so on. This means that a landscape is a system of systems: hydrological systems, nutrient cycles, the breeding systems of all the species, etc. All too often, these systems are drastically altered through urbanization, and we should be much more aware of them as we design urban landscapes. A good example of taking a systems approach is Singapore’s Active, Beautiful, Clean Waters (ABC Waters) program,10 which is based upon a detailed understanding of how water flows through an urban catchment. The ABC program incorporates a variety of measures for retaining water at the source, thereby ensuring that less water is lost in storm runoff and reducing the need for large storm drains. Plan for multifunctional land use. Urban landscapes must fulfill many functions, especially in the most land-scarce cities.11 In particular, all green areas should contribute to regulating environmental conditions, even if they are primarily intended for some other purpose, such as cultural amenity or recreation. A nice example of a multifunctional landscape is Bishan Park in Singapore, a recently restored segment of the Kallang River, which is not only much used for recreation and escape, but also forms part of the water catchment, contributes to cooling and flood mitigation, and is a haven for wildlife. For the planner, multifunctionality means asking a simple question about every green area: “what benefits can it provide?” While this may seem rather obvious, especially for larger urban green spaces such as parks and playing fields, the same question needs to be asked also about smaller patches of green space such as roadside verges and roundabout islands. Even areas set

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Ramboll Studio Dreiseitl, Bishan-Ang Mo Kio Park, Singapore, 2012, green and blue spaces, aerial view from the southwest.

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Learning Forest, Botanic Gardens, Singapore.

aside for later development should not be overlooked but utilized to provide ecosystem services and recreation. Strengthen connectivity. Given that any landscape involves many interconnected systems that operate over different spatial scales, it is obviously important to strengthen ecological linkages whenever possible. The idea of ecological corridors is now well accepted, and many cities have developed greenways and blueways to connect the urban centers with the surrounding countryside. These corridors are not only a great resource for recreation, but also help wildlife spread and establish within the city. However, green corridors need not be confined to the open spaces between buildings; they can also connect buildings with the landscape, and even be made features of individual

buildings. As other contributions in this book illustrate, examples of this approach can be found in many cities around the world, including the famous Bosco Verticale in Milan and the hanging vertical gardens of One Central Park in Sydney. In Singapore, vertical greenery, sky terraces, roof gardens, and green roofs are now officially recognized as important types of urban greenery, along with the more traditional parks and green corridors. Given these new trends, it seems fair to assume that the urban landscape of the future will be one in which the green covers on buildings merge – perhaps imperceptibly – with the surrounding vegetation. Connecting the urban landscape in this way offers enormous possibilities to improve walkability, promote biodiversity, and provide ecosystem services.

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Ramboll Studio Dreiseitl, Bishan-Ang Mo Kio Park, Singapore, 2012, green and blue spaces.

Following pages: Rain Tree, Singapore.

The smaller subpopulations are often unstable, and sometimes die out because of disturbance, disease, or some other reason. When this happens, the patch may be recolonized, but only if there is another subpopulation nearby. This metapopulation concept is very helpful in thinking about urban biodiversity; we need to ensure that there are patches of relatively undisturbed habitat where there are stable populations of species that can colonize more disturbed areas. Why Green Spaces and Ecosystem Services Matter In closing, it is worth emphasizing once again why urban green spaces, and the ecosystem services they provide, have become so important. We have entered an urban era in which well over half the world’s population now lives in cities. The magnitude of many cities far exceeds any that existed in the past, with some urban areas extending over hundreds, and even thousands, of square kilometers. These cities consume vast amounts of water and energy, and are sinks for huge quantities of materials, including essential nutrients for life. Some megapolitan areas have become so large that they alter the regional climate, being generally hotter than their surroundings and subject to more intense bursts of rainfall.

Provide undisturbed areas for wildlife. To persist in an urban environment, many species of wildlife require patches of habitat free from human disturbance. This is true of many birds, especially during the nesting season, and also of some mammals. In practice, most cities provide such inaccessible areas unintentionally: examples include the fenced land surrounding transformer substations or highway embankments. Provided that such areas are not over-managed—for example, by excessive mowing or shrub clearance - they can contribute greatly to urban biodiversity. But there is another reason why “no-go areas“ can contribute to urban biodiversity, which is related to the ecological concept of the metapopulation. This concept describes how the individuals of a species in a landscape usually occur as scattered subpopulations in places where the habitat is suitable.

In all these ways, cities are increasingly out of balance with their environment. For a sustainable future, cities will have to become more “ecological,” in the sense that they regulate their environment, including temperature, flooding, and air quality, collect and recycle their water, and provide residents with open spaces for recreation and solitude. To a large extent, these goals can be achieved by strengthening the ecosystem services provided by green areas. These green areas represent the city’s natural capital, and it is essential that we care for it appropriately. 1. Harriet Jordan, “Public Parks, 1885-1914,” Garden History, 22, 1 (1994): 85–113. 2. http://lnhs.org.uk. 3. https://www.nparks.gov.sg/biodiversity/wildlife-in-singapore. 4. E. Gómez-Baggethun et al., “Urban ecosystem services, chapter 12, in T. Elmqvist et al. (eds.), Urbanization, Biodiversity and Ecosystem Services: Challenges and Opportunities: A Global Assessment (Dordrecht Heidelberg New York London: Springer, 2013). 5. Erich Fromm, The Anatomy of Human Destructiveness (New York: Henry Holt and Company, 1992). 6. Zhou et al., “The rapid but ‘invisible’ changes in urban greenspace: A comparative study of nine Chinese cities,” Science of The Total Environment, 62 (2018): 1572–1584. 7. L. M. A. Bettencourt, “The origins of scaling in cities,” Science 340 (2013):1438–1441. 8. https://www.nparks.gov.sg/biodiversity/urban-biodiversity/the-singapore-index-oncities-biodiversity. 9. X. P. Song et al., “The economic benefits and costs of trees in urban forest stewardship: A systematic review,” Urban Forestry & Urban Greening 29 (2018): 162–170. 10. https://www.pub.gov.sg/abcwaters/about. 11. S. Taylor Lovell and J. R. Taylor, “Supplying urban ecosystem services through multifunctional green infrastructure in the United States,” Landscape Ecology 28 (2013): 1447-1463.

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Green Buildings and the Ecological Picturesque

Christophe Girot

The fashion of greening buildings has grown in architecture over the past decades; now seems like the right moment to look at this short history and question some of the outcomes. Some trends can be identified, differentiated, and compared over this relatively short time period. Green like many other living things has specific material, temporal, and climatic requirements; it is important to consider physical conditions pertaining to a specific location, in light of the actual performance, endurance, or development of a plant on a roof or against a tall facade. Before entering in any sort of typological consideration on green buildings, one should first understand two basic laws of physics that are being exerted on living materials, the one being temperature and the other being wind and rain. Both the roots and foliage placed upon a building are typically exposed to extremes that are not commonly found on the ground. Roots, for instance, cannot withstand variations at very high or very low temperatures, a recurrent problem that limits the geographic range of a given plant and its capacity for exposure off ground. Wind tends to desiccate foliage and often prevents plants from growing normally, which in turn prevents full development because young and tender foliage tends to break and dry up. The two fundamental indicators of temperature and wind appear recurrently as a common thread throughout this short study. Like the warp and weft in a weaving, roots tend to adapt horizontally, whereas foliage tends to operate vertically, which contributes to the structural and compositional logic of the whole building. The vertical surface of most plants placed on buildings tends to cascade downwards or climb upwards, while the horizontal organization of the roots adds considerable weight and eats up vital space on a facade. These two fundamental axes of green on a building determine to a large extent the physics, rate of exchange (CO2, O2, and H2O), and exposure of the building to the outside. Depending on the orientation and height of the structure, the microclimatic forces at play on a building are considerable as they interact and change in effect. A cooling effect can indeed be achieved on tall towers with the help of Venturi effects, but these same effects can also rapidly dry up the vegetation so much so that this is liable to jeopardize the green concept. Through a selection of four European examples that have been more or less successful, we will try to evaluate the gradual progress that has been achieved in the design of vertical green in temperate climate zones over the past decades. The goal is to sort out the wheat from the chaff in a discourse on greening buildings that has at times left the bounds of horticultural reality behind.

Case 1: “La Tour Verte” in Noisiel, France, Christian de Portzamparc, 1971–1974 When Christian de Portzamparc was awarded the Pritzker Architecture Prize in 1994, 20 years had already elapsed since his first built “Tour Verte” (Green Tower) project was completed in Noisiel in the far-off suburban reaches of Paris. The 37-m-high tower was meant to shroud a concrete water tank in dense vegetation, supported by a “Babylonian” Constructivistlooking metal cage clad in wood lattice.1 By using the water tank’s structure made of concrete posts to wrap the steel frame around a narrow spiraling service path, some ivy and other vines placed in planter boxes with irrigation along the spiral were meant to climb to the top and cover the entire structure.2 Almost 50 years later, the structure remains for the most part bare of any kind of vegetation, despite several attempts at patching it with green planters from the inside. What happened, and why did the plants not behave properly? The reasons are multiple and can be explained by a combination of ambient conditions defined by wind and temperature. The example is interesting precisely because of the fact that plants never acclimated to this highly exposed structure on the windswept Plateau de Brie. It serves almost as a textbook example of important things to consider before venturing into vertical greening. The fact that the metal structure was open to all winds meant that there was almost no thermal respite to be found anywhere on its surface for the plants. The wind swept not only from without, but also around and from within. Plants that are not protected at least on one side by a wall or container tend to desiccate rapidly in the wind, and this is precisely what happened in Noisiel.3 The other premise was that ivy and other climbers would grow from the ground up and cover the entire structure. The height of the structure, despite its moderate 37 m, offered a true challenge for climbing ivy. Ivy is one of few native climbers in Europe and it seldom reaches such heights in nature except under the tall shade of forest trees. Ivy typically grows on solid walls made of wood, concrete, or stone, and even in normal forest conditions seldom does it attain a height of 30 m or more. In the case of the Green Tower, the ivy that grew remained close to the ground, where it was firmly rooted and more protected by surrounding vegetation. It never climbed the structure because its rootlets could not find the required nutrients or humidity to feed upon, as they were incessantly exposed to extremes of heat and cold borne by the wind.

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Christian de Portzamparc, La Tour Verte, Noisiel, France, 1974, view from the east.

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Christian de Portzamparc, La Tour Verte, Noisiel, France, 1974, elevation and plan, section.

Christian de Portzamparc, La Tour Verte, Noisiel, France, 1974, view from the south and facade detail.

The idea then was to add containers with ivy that would hang from the inside of the structure high above the ground in the hope that growth would finally succeed in covering the structure.4 But the conditions on the wood-lattice-clad structure had not changed, and moreover the roots in those containers were exposed to repeated thermal shock year-round as it was either too hot or too cold most of the time. So the plants dwarfed their growth in reaction to ambient conditions and remained almost at a standstill in their containers. The young de Portzamparc, bearing this beautiful image of a perfectly composed decagonal “Tour Verte,” was right to choose ivy because of its sound ecological basis. Ivy flowers in autumn deliver a rich source of nectar for bees, the berries ripen the following summer and provide also ample food for birds. The dense overlapping foliage of the vine offers shelter and nesting possibilities to many sorts of insects, animals, and birds. Evergreen ivy is dynamic and becomes metamorphic: when it grows vertically on a tree it switches to an arborescent mode, the leaves change shape, the stems becomes a solid trunk, and the plant begins to bloom. An open concrete and metal structure, although entirely clad with wood lattice, simply could not succeed in taming temperate ivy to grow on its sides. The young architect was unable to find a plant that would actually match his green cage concept drawn with the golden section.5 Unmitigated exposure to the three Ws (water, wind, and weather) made sure that nothing would ever grow properly there. Despite efforts to add some patchy spots of green here and there, few plants actually succeeded in establishing themselves permanently on the “Tour Verte,” which has remained green, to this day, only by name. Case 2: “Cathedrale de la Résurection” in Évry, France, Mario Botta, 1992–1996 When Mario Botta designed the “Cathedrale de la Résurection” (Cathedral of the Resurrection), he had the vision of a cylindrical brick building crowned with a ring of deciduous trees bearing a strong symbol of Christ.6 This was to be the first and only cathedral built in France in the 20th Century and was in that sense highly emblematic of its time. The cylindrical brick building of 38 m in diameter was to be built at the heart of the new satellite town of Évry, located 35 km south of Paris. A beveled roof topped the structure, reaching 34 m in height to the northwest and tapering down to 17 m on the southeast.7 The roof was rimmed with a golden ceramic crown and planted with a ring of 24 majestic silver Linden trees. The native tree species that

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Mario Botta, Cathedrale de la Résurection, Évry, France, 1996, section perspective.

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Mario Botta, Cathedrale de la Résurection, Évry, France, 1996, view from the southeast.

was chosen corresponded to some of the oldest forest stands of Europe, where they can reach the age of 1,000 years or more. The Linden tree was an important feature of pagan rituals in Europe since times immemorial. According to the architect, the 24 trees were meant to symbolize Christian life, harmony, and resurrection, as well as the 24 hours of the day, and the 12 apostles together with the 12 tribes of Israel.8 Because the Linden tree held such sacred place in early Celtic, Germanic, and Slavic tribes, it was able to serve as a universal symbol of faith. The Linden was meant to give a sense of life, community, and belonging to the cathedral. Many villages across Europe still have a Linden planted at their heart for people to gather and dwell in its shade. Linden wood as well was considered sacred and was frequently used for altar pieces and religious statues. At the same time, the Linden tree fills an important ecological niche for bees and other insects when it blossoms in the spring. It serves also as habitat for a large variety of birds and insects. It has been cultivated and trimmed in pollard form since Roman times, which will also be the fate of the trees on the roof as they grow older and have to be contained. The most remarkable point about this project is that all trees have managed to survive 25 years of ambient exposure on the roof through summer heat waves and winter cold spells rather well. The reason for this is that each tree was planted in roughly 30 m³ of soil in a continual stepped ring trench that circles the roof. This is about six times the normal quantity of soil required to plant a street tree in a pit. The soil and trench added considerable weight to the roof, but this was integrated in the structural calculations and costs from the beginning. Each tree was fastened with cables and irrigated regularly with water and nutrients to ensure healthy root growth. Yet despite these vital precautionary measures, there still remain noticeable differences in the sizes and development of the trees depending on where they are actually located on the roof. Those showing the most promising development are located mostly towards the base of the roof facing south and protected from the wind, whereas those showing slower development tend to be located towards the top of the roof facing north that is more exposed to temperature extremes. All things considered, and because of the intensive care and attention given to each individual tree, these differences remain minimal and may be expected to gradually equalize when all trees are trimmed and maintained in their mature form.

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Andrée Putman and Patrick Blanc, Hotel Pershing Green Wall, Paris, France, 2001.

Patrick Blanc, Green Wall, Musée du Quai Branly, Paris, France, 2004, view from the northeast and northwest.

In this project, the architect’s green concept came across successfully – at the expense of adding more than 750 m³ of soil substrate on the roof, which translates into more than 1,000 t of extra weight when wet. The question of the mass and quantity of soil is a recurrent theme in green buildings, because it concerns directly the structural costs of a project. All things considered, the Cathedral of the Resurrection can be considered as one of the better examples, albeit expensive, of a hanging tree garden today, as its Babylonian proportions are somewhat reminiscent of Antiquity. The accent was placed on a unity of planting form to obtain a strong Christian symbol through the use of identical Lindens that were probably hybridized or cloned to maintain an identical structure. This formal choice, which belongs to the past century, may appear too dogmatic nowadays, when the need for ecology and a greater diversity of species is being proclaimed. Case 3: The Green Wall, “Hotel Pershing Hall” in Paris, France, Andrée Putman & Patrick Blanc, 2001 When architect and designer Andrée Putman invited botanist Patrick Blanc to create a vegetative wall in the inner courtyard of the Pershing Hall Hotel that she was restoring, little did she know that she was launching him on an extraordinary odyssey of architectural greening. Patrick Blanc had already experimented with green walls as art forms since the mid-1980s, but had never ventured into full architectural scale until that point. The green courtyard wall of the hotel was composed essentially of exotic tropical and subtropical groundcover, vines, and epiphytes, which created an extraordinary quilt of lush vegetation in colorful textured patches all the way to the top.9 The trick was to suspend the vegetation in thin felt pouches hung directly on a steel frame fixed to the wall and to feed them hydroponically. Each individual plant received nutritious liquid, fed regularly by capillarity via small plastic tubes. Patrick Blanc used a hydroponic technique that was already widespread in greenhouse horticulture. He traveled to riverbanks, cliffs, and waterfalls to select plants that thrived there year-round on the basis of a liquid solution, without any sort of substrate or soil.10 The ensuing plant selection, comprised of small ligneous and herbaceous species, made the Green Wall installation light and compatible with most conventional architectural structures. The Green Wall planted with ferns, fuchsia, heuchera, hosta, irises, tricyrtis, and willows became an instant wonder of horticultural high-tech. The impact of the Pershing Hall Hotel project on the fashion world was immediate and seduced many

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Stefano Boeri Architetti, Bosco Verticale, Milan, Italy, 2015, view from the south.

architects. The project was followed shortly thereafter by a series of projects initiated by Jean Nouvel with his Quai Branly Museum in Paris in 2004, and Herzog & de Meuron with the Caixa Forum in Madrid in 2007, to mention a few. Both these projects, done together with the team of Patrick Blanc, exhibited artfully vertical horticultural techniques that were robust enough to withstand all seasons under temperate climes.11 The key to the success was the complete absence of soil or substrate in the felt pouches; the planting system consisted essentially of a highly efficient drip irrigation system, requiring regular maintenance, to ensure each plant was feed a nutrient solution in continual hydroponic transfusion. Some projects, like the green wall on Rue d’Aboukir in Paris, used the opportunity to recycle greywater and rainwater produced by the building into the irrigation fluid. The lush vegetation, composed essentially of small ligneous and herbaceous perennials like Berberis, Spirea, Stachyurus, Cotoneaster, Begonias, Balsamina, Orchids, Bromeliads, and Aracea, to mention but a few, grows and reaches maturity on the facade rapidly. The picture-perfect result simulated a vertical biotope without adding much stress to the structure. The complete absence of large ligneous plants and particularly of trees is an important point of comparison to other greening approaches. The small ornamental plants provide only limited ecological services in terms of CO2 retention, but the green wall acts as a good protective membrane for cooling, capable also of trapping fine particles. A drawback is the cost of the permanent hydroponic irrigation system in terms of maintenance and the fact that some of the perennial plants are relatively short-lived and need to be replaced. The Quai Branly Museum green wall, for instance, is being entirely replaced at the time of writing, restructured and replanted only 15 years after it was first delivered. Another advantage linked to this green wall technique is that the plants with their support system become an integral part of the building’s skin and contribute to some kind of climatic insulation. The intrinsic thickness and opacity of the suspended green wall tends to serve the architecture, while competing with window surfaces on the facade. This makes it quite difficult to apply the technique to normal housing or office conditions. The latest ultra-modern twin tower project in Sydney, “One Central Park,” designed in 2013 by Jean Nouvel with PTW Architects and Patrick Blanc as green wall expert, demonstrates that it is possible to design high-end mixed-use residential buildings

reaching over 100 m in height using this green wall technique. In this instance, the vertical plantation beds are spread out in patches over 1,000 m² of facade. Patrick Blanc claims that more than 250 different plant species were integrated in this project where hydroponic nature meets high-tech architecture.12 This method of facade greening has caught on worldwide now. It is a high-maintenance technique akin to that used in greenhouses to produce flowers and crops. Although the ecological performance of these projects can be questioned, there is reason to hope that future projects will develop more appropriate plant selections that are more in keeping with the local environment. There prevails, however, a strong limitation in matters of plant dynamics that is inherent to the system. As each plant is fixed in place in a predetermined pattern, the system remains permanently bound to its original form. Plant dynamics per se on the green wall are, therefore, quite limited, but this critical point may evolve and be improved. The exuberant floral style of the green wall and the thermal comfort and architectural luxury associated with it undoubtedly means that the method is here to develop, diversify, and stay. The green wall toilets by the landscape architect Kim Wilkie, recently inaugurated at Longwood Gardens near Philadelphia, make a case in point. 17 individual pods, equipped with skylights and planted with almost 50,000 ferns, function well aesthetically while serving our basic bodily functions. It is still not quite clear, though, beyond the green awareness that it stirs in the user, how such a picturesque latrine truly contributes to the environment. Case 4: “Il Bosco Verticale” at Porta Nuova in Milan, Italy, Stefano Boeri, 2014 When Stefano Boeri completed his “Bosco Verticale” (Vertical Forest), his idea was somewhat reminiscent of an old Corbusian dream, where two towers respectively 76 m and 110 m high would host 750 trees and 4,500 shrubs to recreate the equivalent of 2 ha of forest cover on the ground.13 In light of the previous example of the Cathedral of the Resurrection, can one reasonably elevate and maintain that many trees upon a concrete frame so far off the forest floor? In addition to the soil problem, critical questions linked to water, wind, and exposure in this city needed also to be addressed and solved. The solution came from the development of deep concrete planters placed on every side and at each level of the towers, providing ample room for soil substrate and good anchoring and watering possibilities for each tree.14

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Stefano Boeri Architetti, Bosco Verticale, Milan, Italy, 2015, elevation, rendering.

Stefano Boeri Architetti, Bosco Verticale, Milan, Italy, 2015, construction.

The deep planters were the answer to most of the problems in this project, and together with the selected trees they became part of the architect’s branding signature. This choice of construction translated into more steel and a thicker concrete slab on each floor, at an extra cost of about 5% for the built structure.15 Substantial maintenance costs and year-round care were needed to ensure the provision of water, nutrients, pruning, and plant replacement in the first five years of the project. 90 plant species, comprised of a mix of shrubs and trees, were carefully selected to meet the harsh climatic requirements of the tower. According to the architect, the trees meant to produce oxygen and capture CO2 in their ligneous fibers were carefully chosen by experts, taking the microclimatic constraints of the tower into account. A selection of native and ornamental trees species was carefully established, either as flowering, deciduous, or evergreen, ranging from olive trees and Mediterranean evergreen oaks to hazelnuts, ashes, beeches, as well as flowering cherry, plum, and apple trees from China and Japan that flower spectacularly in spring. The final outcome is a compelling collection of plants and trees growing as large bonsais in an artificial cliff-like concrete setting.16 The maximum height of a tree is set at 9 m, which corresponds to three stories in the tower. Whether the word “bosco” (forest) is the appropriate term in this context remains debatable. The result on each floor appears more like a manicured Japanese garden, and the external aspect of both towers reminds one more of a composite grove or “bosquet” than a forest per se. The success of this project, however, has been immediate, and even the surrounding neighborhood has experienced a significant increase in the greening of the existing building stock. The “Bosco Verticale” promoted an exclusive lifestyle in Milan that was entirely new, through the creation of luxurious apartments with ample garden terraces surrounded by trees on two sides, as promoted by the developer Hines. The project received worldwide acclaim, including the prestigious International Highrise Award in 2014. It seems as though the vertical tree planting model in architecture has caught on, and Stefano Boeri is now planning several other such “Bosco Verticale” around the globe all the way to China. One which is in an early project phase and not approved at the time of writing is located at Chavannes-Près-Renens near Lausanne. It should measure 117 m and may become the tallest building in western Switzerland. It will be covered by no less than 80 trees.

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Ateliers Jean Nouvel/PTW Architects, One Central Park, Sydney, Australia, 2014, view from the north, heliostat.

Could it be that the trees, with all the ecological symbolism that they bear, can help make tall buildings more acceptable to the general public? There are still strong ecological limitations with this model of building and planting. It will, therefore, be interesting to see how the prototype developed by Stefano Boeri will be able to adapt, evolve, and perform under different climes. Despite the extraordinary efforts deployed to make the twin towers in Milan seem “forested,” there remain some patchy problems at the top of both buildings, where Venturi wind effects accelerate the desiccation of plants and puts the vegetation under duress. The fact that mature trees 9 m tall were transplanted directly onto the structure adds to the stress of climatic exposure. Planting smaller, younger trees would have significantly increased their rate of establishment and survival, but the marketing image of a completely forested tower from the beginning was more important to the developer. Problems in thermodynamics may vary significantly depending on the latitude, the ambient humidity, and the actual height and breadth of a building. Nonetheless, the Vertical Forest has become a pioneer of green architecture, in that it has opened up an array of new possibilities that can be tested, improved, and developed in the future. It may eventually become possible to lower structural costs through the establishment of better height-to-output equations, ingenious prefabrication processes, and innovative maintenance procedures. Some of the costs may also be reduced and born directly by the inhabitants, assuming they acquire proper training as urban foresters in their own right. But the main ecological question remains whether the extra cost of steel, concrete and CO2 emissions will ever be compensated by the output of the trees. It will, therefore, be interesting to analyze further the exact data of the “Bosco Verticale” towers in Milan concerning improvements in thermal comfort, the reduction of energy consumption, and the production of oxygen as claimed by the architect. The question of biodiversity will also need to be addressed more critically, because the vegetation that has been chosen to withstand the harsh climatic conditions of the towers differs fundamentally from that of the Po Plain down below, which is one of the flattest places on earth. This choice of vegetation may in turn affect the diversity and fauna that will actually inhabit the Vertical Forest. Let us hope that, for the first time in history and with many more towers to come, architecture will finally become a significant game changer in matters of urban ecology and biodiversity.

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The four cases of vertical greening that have been examined illustrate some of the trends to be found today in dense and green cities located under temperate climes. (We have left Scandinavian sod roofs out of the picture, despite the fact that they correspond probably to some of the oldest forms of green architecture in Europe, because of the sheer weight problems that they would pose in high-rise structures.) The trends that we have examined continue to evolve rapidly both in terms of method, efficiency, plant content, and ecology. Even early prototypes, like the Green Tower by de Portzamparc, have served as a lesson for more recent developments in steel frame buildings turned green. This applies particularly to recent buildings like the Oasia Hotel Downtown by WOHA architects in Singapore, built under tropical latitudes with high atmospheric humidity, where constant temperature and wind remain stable. The vegetation in that case grows as an external membrane that breathes and transpires, reducing the building’s exposure to direct light and reflectiveness. The thin translucent layer of leaves placed on the outer steel frame protects the building from excessive exposure to solar radiation. Another example in Singapore is the new PARKROYAL on Pickering, also by WOHA architects, that uses a planting technique closer to that which inspired the “Bosco Verticale.” The concrete building uses ample planters and irrigation to provide lush vegetation throughout the inner and outer floors, while the use of tall trees remains quite limited.

1. Jean-Pierre Le Dantec, Christian de Portzamparc (Paris: Editions du Regard, 1995), 29-33. 2. Michel Jacques and Armelle Lavalou, Christian de Portzamparc (Bordeaux and Basel: Arc en Rêve Centre d’Architecture and Birkhäuser, 1996), 14-17. 3. Patrick Le Merdy, “A la recherche du végétal urbain,” Urbanisme 209 (1984): 77-81. 4. Christian de Portzamparc, “Château d’Eau à Marne la Vallée,” in Christian de Portzamparc (Milan, Paris: Electa Moniteur, 1984), 50-54. 5. Christian de Portzamparc, Les dessins et les jours, L’architecture commence avec un dessin (Paris: Somogy éditions d’art, 2016), 85-91. 6. Jean-François Pousse, “Pour la Ville, Cathédrale d’Evry,” Techniques et Architecture “Architectures Sacrées” 405 (1993): 34-37. 7. Mario Botta, The Complete Works, Volume 3, 1900-1997 (Basel: Birkhäuser, 1998), 126-145. 8. Mario Botta, Architetture del Sacro (Bologna: Editrice Compositori, 2005), 66-80. 9. Anna Lambertini and Jacques Leenhardt, Vertical Gardens (London: Thames and Hudson, 2007), 94-103. 10. Maria Kmiec, “Green Wall Technology,” Technical Transactions Architecture 10-A (2014): 47-60. 11. Patrick Blanc, The Vertical Garden from Nature to the City (New York: W. W. Norton & Company, 2011), 86-91. 12. Karl Ludwig, Compendium of Landscape Architecture and Open Space Design (Berlin: Braun Publishing, 2018), 128-129. 13. Melanie Müller-Boscaro, “A Vertical Forest in Milan,” Topos “Plants and Design”83 (2013): 43-47. 14. Caterina Testa, “Vertical Forest Residential Complex,” The Plan Magazine 10 (2015): 81-87. 15. Elena Giacomello and Massimo Valagussa, Vertical Greenery: Evaluating the High-Rise Vegetation of the Bosco Verticale, Milan (Chicago: Council on Tall Buildings and Urban Habitat, 2015). 16. Ibid.

There are a lot of green “showcases” being built out there, without much consideration for their actual performance. We need to know more about the effective function and purpose of architectural vegetation to better understand the range of ecological services that it could provide. At present, we are still delving for the most part in an aesthetically pleasing form of green, akin to what I would call the “ecological picturesque,” a sort of greening that makes the user feel closer to nature and its needs. The day when ecological forests will effectively grow on buildings, however, is still quite far away. The same could be said of the hydroponic green walls that now decorate banks, museums, and shopping malls worldwide. They are ravishingly pretty and striking, but what are actually the ecological benefits that they account for in a rapidly depleted environment? Is this green fashion just a matter of taste and image that will pass, or does it offer a substantial answer to our quest for a more balanced urban environment? The lessons to be learned from the considerations put forward here will be vital for contemporary architecture to contribute more significantly and critically towards ecology and sustainability.

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DENSE GREEN DIMENSIONS

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WOHA, School of the Arts, Singapore, 2010, view from the south, facade with greenery.

Learning from Singapore

A number of fortuitous and strategic conditions have made Singapore a leader in dense and green buildings for the tropics. Projects like WOHA’s School of the Arts (completed in 2010) and PARKROYAL on Pickering (completed in 2013) have led the way in design with visionary leadership. Asia in general and Singapore in particular have great potential for the further exploration of dense and green as well as livability principles. The breathtaking scale of many of the new developments in Singapore captures the attention of politicians and developers and the imagination of its citizens. As a small island state with limited land and natural resources and a current population of approx. 5.6 million, Singapore’s developmental approach has been guided by green agendas even before the term became a buzzword. The late Lee Kuan Yew, Prime Minister of Singapore from 1959 to 1990, wanted to transform the City into a ‘Garden City’ already in the 1960s. It was a revolutionary concept at that time because no one else talked about ‘going green’ or climate change.1 Since then, Singapore has recognized the importance and benefits of a green environment. Even as the city state embarked rapidly on industrialization and urbanization programs to provide jobs and housing for its people, the natural environment was high on the Government’s agenda. Since the 1960s, the city state’s vision has evolved from ‘Garden City’ to ‘City in a Garden’.2 This concept is seen to strengthen its brand as a distinctive, livable city. The new vision also embodies ideas of conserving and nurturing biodiversity in the urban context, an area where Singapore has contributed scientifically through, for example, the Singapore Index on Cities’ Biodiversity.3 As its population continues to grow and with limited land available, developing a compact city with extensive greenery and highly livable environments will continue to be an important strategy. Singapore currently pursues three key strategies to realize its ‘City in a Garden’ vision: using pervasive greenery from the ground to the facade and rooftops of buildings, infusing biodiversity into urban landscapes, and fostering community involvement as active participation. Ownership and pride among the community are seen as factors that will sustain the ‘City in a Garden’ vision.4 Since the early 2000s, Singapore has pursued a number of research studies and small demonstrations that explore the integration of greenery in buildings. These projects led to a number of policies and initiatives such as GFA Exemption for

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WOHA, PARKROYAL on Pickering, Singapore, 2013, view from the northeast, sky gardens. Following pages: WOHA, School of the Arts, Singapore, 2010, aerial view from the south.

Communal Sky Terraces, GFA Exemption for Communal Planter Boxes, Skyrise Greenery Incentive Scheme, Landscape for Urban Spaces and High-Rises (LUSH), as well as the Landscape Excellence Assessment Framework (LEAF). These have been instrumental for the subsequent experimentation with dense and green buildings. Many property developments in Singapore employ marketing phrases such as “near a park,” “rooftop greenery,” or ”vertical greenery.” The quantifiable benefit of such features is land value appreciation. At the same time, dense and green buildings can also be seen as having a potential alleviating effect on land use competition as they are able to layer horizontal city functions vertically, thereby optimizing land use in Singapore. Also, Singapore increasingly recognizes the unquantifiable benefits of living within or near natural areas with rich biodiversity that can result in improved physical and mental health and mitigate some of the negative effects associated with high-density urban environments.5 Further, pockets of green spaces can also function as part of a larger urban ecosystem. For example, dense and green buildings can perform as high-quality habitats for flora and fauna. The combination of buildings with green spaces such as green corridors, parks, nature areas, and nature reserves can form an interconnected matrix that becomes part of a larger ecosystem. Dense and green buildings can mitigate the negative effects of high-density areas and improve urban environments by synthesizing the architectural, environmental, social, and economic aspects of living. Singapore offers a wealth of case studies for dense and green buildings research. The information at hand and knowledge gleaned from these can enable similar ideas to be applied to other cities. This helps to improve urban environments there as well, steering the Dense and Green agenda from its current status to an integrated and tacit element of planning and design in that density and livability are not seen as contradictory but rather as mutually dependent and synergistic.

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Singapore-ETH Centre Future Cities Laboratory, Campus for Research Excellence and Technological Enterprise (CREATE) Singapore, interior. “Dense and Green: Architecture as Urban Ecosystem” exhibition, Palazzo Mora, Venice Biennale, Italy, 2018.

Dense and Green at the Future Cities Laboratory

Dense and Green is an ongoing research project that was launched at the Singapore-ETH Centre Future Cities Laboratory (FCL) in 2015.6 FCL was established by ETH Zurich and the National Research Foundation Singapore in collaboration with key academic partners including the Singapore University of Technology and Design in 2010 to study sustainable future cities through science, by design, and in place. Its High-Density Mixed-Use scenario develops new integrated planning paradigms, research methodologies, and implementation processes to support higher population densities, higher standards of environmental sustainability, and enhanced livability.7 In this context, Dense and Green explores innovative building projects and developments in high-density urban contexts through case studies and a systematic study of their urban planning and design, architectural, environmental, social, and economic aspects with a focus on Singapore.8 The following paragraphs provide a brief overview of the research approach and the methods applied to the project as a whole and the case studies featured in this book. Urban Scale Each case study explores the particular project background and context based on document reviews and interviews with its various stakeholders. It analyzes the project on the urban scale in terms of density and greenery, landscape space provisions, as well as its contributions to larger urban ecosystems such as green and blue networks. The typical urban analysis covering an area of 200 ha around the projects allows for the capturing of at least one ecosystem in the urban context and therefore a meaningful quantification of the project’s greenery contributions. This analysis further provides the basis for a comparison with other case studies. Each case study includes a detailed review of relevant master plans and development guidelines. The density analysis is comprised of various project mappings, 3D-modeling, and quantifications of land based on drone videography, Google Earth Pro satellite images, ArcGIS/QGIS data, and Open Street Maps (OSM) vector components. Capturing roads, other building plots and footprints, open and elevated landscape spaces around the project allows for a cross-case comparison of urban morphologies.

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Architecture The case studies capture relevant building regulations and analyze the spatial organization of the projects in terms of massing, layout, as well as greenery and community provisions. The analysis is based on information provided by various stakeholders, including building owners, clients, architects, landscape architects, and contractors, as well as on-site documentation. The spatial information is captured in isometric drawings that are also the basis for the analytical mappings of research data such as biodiversity and space use. Each case study includes geographic and climatic information, building area calculations, green plot ratios, and greenery typology quantifications. Biodiversity The case studies provide a thorough and detailed analysis of plant and animal biodiversity in the developments and their urban surroundings. The vegetation of all landscaped areas is surveyed as a basis for the study of plant biodiversity. Plants are identified as species and mapped onto the isometric drawings. Plant species identifications are cross-referenced with landscape plans provided by contractors, Flora Fauna Web, and plant identification reference books. The vertical and horizontal vegetation structure of each landscaped area in the projects is assessed and recorded also qualitatively to capture its spatial complexity and potential for biodiversity. Animal biodiversity is investigated through bird point count surveys for patches of 250 to 1,000 m2. The applied statistical model correlates the abundance of birds found in different green elements around the projects at each survey patch. To capture species diversity, researchers walk transects within each project to provide a general backdrop of what types of animals, aside from birds, are found in its different parts. Methodologies of studying the animal biodiversity connections with the larger ecosystems include the scientific modeling of how animals move in the surrounding urban environments.

categorized digital images in order to determine the mean temperatures for shaded and un-shaded surface types in each pair. To allow for comparisons between case studies, the research applies a linear Mixed-Effects Model based on mean temperatures of shaded and un-shaded surfaces in all analyzed images.9 This allows for predictions regarding typical surface temperatures in the projects, with the mean surface temperature as the response variable and the surface type, shading condition, air temperature, relative humidity, wind speed, and solar radiation as explanatory variables. Space Use The case studies investigate the relationship of greenery provisions, space use, and pedestrian movement in the developments through onsite observations with a focus on public and shared spaces. Data including space users’ age and gender, the start and end time of their use, activity types, as well as context information such as weather conditions is collected. The data is visualized through space use ‘heat maps’ that are mapped onto isometric drawings. The collected data is subsequently analyzed to establish relationships between space types and uses, as well as time of use and user age groups. Additional methodologies include on-site interviews with residents and visitors of the case studies that enquire about preferences and perceptions in terms of green spaces in the respective projects. Cost The case studies analyze construction and maintenance costs affiliated with the provision of green spaces. These are derived, for example, from government agency plant classification data and information provided by various project stakeholders. In addition, the case studies feature detailed cost analyses for integrated landscape design components.

Surface Temperature For studying the effects of greenery on the surface temperatures in outdoor spaces, the research identifies areas highly frequented by residents and visitors. Surface temperatures of surface types in these areas are documented through thermal images. The images are also superimposed with correspondingly

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Biodiversity

Population growth in cities is expanding by 3.3% per year in the tropics and 2% per year in other eco-zones.10 This expansion is likely to result in a loss of biodiversity, as cities often replace natural landscapes with artificial ones. Numerous studies showing that fauna species richness per unit area of natural landscape such as forests has declined with the loss of natural landscape areas.11 Urbanization causes biotic homogenization: the process of biodiversity becomes more similar within a city and between cities, of both plants and animals.12 In plants, this is driven by active planting of replacement of native fauna with the same species that are planted at multiple cities throughout the globe. This leads to a loss of native animal species that have special species or habitat requirements, while generalist species, especially those that benefit from human activity, survive.13 These are often introduced species, which then compound this effect by outcompeting the remaining native species for resources, including those with less specific requirements.14 Native species not only provide color and character to urban environments; they are also providers of important ecological services. For example, native birds are pollination agents, seed dispersers, nutrient recyclers, and scavengers.15 As such, they support vegetation that provides other regulating and provisioning ecosystem services, for example stormwater management and urban heat island-effect mitigation. Birds also act as bioindicators of ecosystem health.16 Having more native plants and animals in the city can support global biodiversity conservation by reversing the extinction of ecological experiences, which cause distinct ecoregions with specific and rare or threatened species to be perceived as “natural” with invasive species.17 Urban vegetation that is more similar to native forests and that is providing a higher vertical complexity and structure for native species can also support biodiversity. An actual higher leaf area can scale with certain ecosystem service benefits, such as air quality improvement. In recent years, the benefits of urban biodiversity have increasingly been recognized and led to urban development that aims for increased abundance and richness of species — primarily on, but not limited to, the ground level.18 Larger core patches, such as big urban parks, are built and semi-natural forest are retained. They are linked by continuous green connectors such as naturalized rivers, pedestrian walkways and designed habitat corridors, or discrete stepping stones such as small forests and neighborhood parks.

On elevated levels, urban designers, architects, and landscape architects increasingly experiment with the integration of green spaces, producing innovative building types, often for high-density urban environments. These include extensive roof terraces, sky bridges, vertical parks, roof gardens, and other components. Combinations of all of these, often applied to mixes of residential, civic, and commercial programs, conjoin at times to produce ‘vertical cities’ in which the built section becomes part of larger urban ecosystems. Density and sustainability in these developments are not seen as contradictory but rather as mutually dependent and synergistic.19 As the number of such dense and green buildings increases, it is important to consider how they can best support biodiversity abundance and connectivity. While research on ground level vegetation at the urban scale is well established, little research has been done regarding whether green elements, for example in the form of green walls and roof gardens, on and around buildings can impact animal and plant species richness; or whether they can support native and introduced fauna.20 As for existing studies, research in Singapore found an increase in bird and butterfly biodiversity around flowering plants at elevated green spaces.21 In Hong Kong, an increase in bird species richness was found on green roofs as foliage cover increased.22 In temperate locations, research has compared diversity or abundance of bird species on buildings featuring green elements against buildings devoid of them. One study found a positive impact of elevated green spaces such as sky gardens, ground gardens, and green walls, while another one did not.23 To date, only limited research has been done on green spaces in buildings using ecological metrics of vegetation.24 The Dense and Green research aims to fill some of the current gaps in knowledge by exploring how incorporating green spaces in buildings on and above the ground level in the form of ground gardens, sky gardens, roof gardens, and green walls impacts plant and animal biodiversity in urban environments. It also compares the vegetation structure and species composition of these different green spaces, using ecological metrics to identify areas of high and low performance.

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Plants

The Interlace

Roof gardens, which essentially have the same conditions as ground gardens but are elevated, require substantial structural loading capacity to support the same weight of substrate and

Skyville@Dawson

Ground gardens provided the highest species richness in all case studies. The number of their species steadily increased with the total leaf area, showing that landscape architects and designers generally tended to plant a variety of species in these locations. This may be due to an increased soil depth, allowing for the planting of multiple canopy layers that support higher plant species richness.

SOLARIS

In those case studies where the building footprint did not extend to the plot boundary, ground gardens provided by far the highest vegetation density, measured in terms of total leaf area, of any green space type; examples include The Interlace, Punggol Waterway Terraces I, and Skyville@Dawson. Where a building footprint did reach the plot boundary, green walls were the dominant typology; examples include Oasia Hotel Downtown, Solaris, Bosco Verticale, and One Central Park.

Punggol Waterway Terraces I

Density Richness and Structural Complexity

Oasia Downtown

Total leaf area (ha)

Vegetation surveys analyzed each patch to the species level. This information was cross-referenced with the ecological characteristics of each species according to locally available databases, resulting in a suite of ecological metrics for each species patch. Each green space type was subsequently compared to other types within a given case study to draw conclusions as to what extent ecologically important factors of vegetation were considered in the design.

12 11 10 9 8 7 6 5 4 3 2 1 0

Khoo Teck Puat Hospital

In the case studies featured in this book, an area was classified as a green space based on the fact that it contains vegetation and constitutes a single, intentionally designed space. These identified green spaces provided unique observational units. They were categorized as five types: ground garden (garden on bare soil), landscape deck (garden on the first floor of a development), sky garden (midlevel spaces with vegetation), roof garden (uncovered rooftops with vegetation), or green wall (building facade with vegetation). For each case study, multiple patches with an area of approx. 200 m2 for each of the five green space types were identified. This allowed for the characterization of their biodiversity in terms of plants and animals as well as for a fair comparison by a number of ecological metrics.

Total leaf area across different space types and case studies in Singapore

Case study

Ground garden

Landscape deck

Sky garden

Roof garden

Greenwall

plants. This often makes them a costly option and explains why the total leaf area on roof gardens in the case studies was generally lower than in ground gardens.25 However, in some of the case studies, such as The Interlace, roof gardens feature a vegetation density comparable to its ground gardens. In these buildings, the species richness per space was also comparable to that of the ground gardens. Landscape decks were typically designed primarily for social uses and they generally provide fewer plant species than, for example, the ground gardens. As vegetation density increases in sky gardens, the richness of species generally does not increase at the same rate as on roof gardens, ground gardens, and landscape decks, due to the smaller palette of species available for this green space type. Plants in sky gardens need to be able to survive in natural light conditions that are typically less favorable than in other green space types. Sky gardens were also found to have the second lowest vegetation density of all green space types. This is due to their locations on midlevel floors, often adjacent to circulation areas with high human traffic, for example, at the Oasia Hotel Downtown and at Skyville@ Dawson, where they are located in close proximity to the entrances of both the hotel and the residential units.

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The species richness across green walls was generally found to be lower than across other green space types and it increased at the lowest rate with vegetation density. For example, in the Oasia Hotel Downtown and One Central Park, most facades consist of climbing plants directly exposed to wind and solar radiation, which means that their selection needed to be limited to few hardy species. Furthermore, there is a low soil area on which to plant the individual species, which further limits the range of plants that could be used. However, in the case of Solaris, the continuous green ramp that wraps around the facade provides a higher species richness than the building’s roof gardens. This may be due to its unique design that uses deep soil able to support the weight of small trees with understory layers. Native Plants With very few exceptions, the native plant species total leaf area was less than 50% across all roof garden areas, for every vegetation type and in all case studies. This is not ideal, as native plants can help to augment and support local habitats.26 When green walls, for example at Oasia Hotel Downtown, showed a very low percentage of native species (