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Encyclopedia of the Anthropocene (5 vols.)
 0128096659, 9780128096659

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ENCYCLOPEDIA OF THE ANTHROPOCENE

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ENCYCLOPEDIA OF THE ANTHROPOCENE EDITORS IN CHIEF

DOMINICK A. DELLASALA Geos Institute, Ashland, Oregon, United States

MICHAEL I. GOLDSTEIN Surfbird Consulting, Juneau, Alaska, United States

VOLUME 1

GEOLOGIC HISTORY AND ENERGY SCOTT ELIAS University of Colorado, Boulder, United States Royal Holloway, University of London, Egham, United Kingdom

The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB 225 Wyman Street, Waltham MA 02451 Copyright © 2018 Elsevier Inc. All rights reserved No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers may always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library ISBN 978-0-128-09665-9 For information on all publications visit our website at http://store.elsevier.com Printed and bound in the United States Publisher: Oliver Walter Acquisition Editor: Ruth Ireland Content Project Manager: Sean Simms Associate Content Project Manager: Joanne Williams Designer: Matthew Limbert

ACKNOWLEDGMENTS AND DEDICATIONS The Encyclopedia of the Anthropocene is dedicated to all those fighting for a healthy planet for this and future generations with the intent of creating a world where the planet’s life support systems are sustainable. We dedicate this to the first humans who emerged out of Africa, who eventually used tools to begin transforming their environment that ultimately led to the brilliance of the human cortex that now has the capacity to solve global problems when the willingness to change is fully embraced. We also dedicate this to the next cohort: Iara, Lais, Janelle, Andrew, Jacob, Ella, Ariela, Benjamin, Surin, Bela, and co. Dominick DellaSala Mike Goldstein Scott Elias Bruce Jennings Tom Lacher Pierre Mineau Sanjay Pyare

v

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CONTENTS OF VOLUME 1: GEOLOGIC HISTORY AND ENERGY List of Contributors

xi

Contents of all Volumes

xiii

Editor Biographies

xxv

Introduction

xxix

The Anthropocene: How the Great Acceleration Is Transforming the Planet at Unprecedented Levels

1

DA DellaSala, MI Goldstein, SA Elias, B Jennings, TE Lacher Jr., P Mineau, and S Pyare

Basis for Establishment of Geologic Eras, Periods, and Epochs

9

SA Elias

Finding a “Golden Spike” to Mark the Anthropocene

19

SA Elias

Arguments for a formal Global Boundary Stratotype Section and Point for the Anthropocene

29

J Zalasiewicz and CN Waters

The Geomorphology of the Human Age

35

P Tarolli, G Sofia, and Wenfang CAO

The 1950s as the Beginning of the Anthropocene

45

C Ludwig and W Steffen

Sediments of the Anthropocene

57

A Gałuszka and ZM Migaszewski

Historical Overview of the Natural Gas Industry

63

CJ Castaneda

Concrete: The Most Abundant Novel Rock Type of the Anthropocene

75

CN Waters and J Zalasiewicz

Hydrology in the Anthropocene

87

P Bridgewater, E Guarino, and RM Thompson

Fluxes of Trace Metals on a Global Scale

93

RJ Thorne, JM Pacyna, K Sundseth, and EG Pacyna

Impacts of Anthropocene Fossil Fuel Combustion on Atmospheric Iron Supply to the Ocean

103

AW Schroth

Greatly Increased CO2

115

SA Elias

Anthropogenic Soils as the Marker

129

G Certini and R Scalenghe

Plastics in the Ocean

133

SA Elias

vii

viii

Contents of Volume 1: Geologic History and Energy

Evidence in Polar Ice Records

151

EW Wolff

Humanly Modified Ground

157

M Edgeworth

Plastics and the Anthropocene

163

PL Corcoran, K Jazvac, and A Ballent

The Anthropocene—A Potential Stratigraphic Definition Based on Black Carbon, Char, and Soot Records

171

YM Han, ZS An, and JJ Cao

Magnetic Particulates as Markers of Fossil Fuel Burning

179

MW Hounslow

Spheroidal Carbonaceous Fly Ash Particles in the Anthropocene

189

NL Rose

Isotopic Signatures

197

JR Dean, MJ Leng, and AW Mackay

Geochemical Records in Speleothems

205

IJ Fairchild

Chemical Signals of the Anthropocene

213

A Gałuszka and ZM Migaszewski

The Evidence for Human Agency in the Late Pleistocene Megafaunal Extinctions

219

G Haynes

Editor's Note

227

SA Elias

Increased Acidity of Ocean Waters

233

SA Elias

Loss of Coral Reefs

245

SA Elias

Earth's Sixth Mass Extinction Event

259

T Pievani

Paleoclimatology

265

SA Elias

Rewilding the Pleistocene Fauna

277

SA Elias

Development of Coal-Fired Steam Technology in Britain

285

M Whitmore

Rise of Airline Transportation After WWII

307

M Whitmore

Environmental Effects of Terrestrial Oil Spills

323

A Jernelöv

Rise in Motorized Transportation and Weapons in the World Wars

337

M Whitmore

Sustainable Energy Development; The Role of Geothermal Power

357

B Davidsdottir

Environmental Issues Associated with Energy Technologies and Natural Resource Utilization

381

V Ribé

City Planning and Energy Use H Park and C Andrews

385

Contents of Volume 1: Geologic History and Energy

Energy Use in Food System

ix 397

C Dutilh, H Blonk, and A Linnemann

Introduction to Renewable Energy

405

E Nehrenheim

Wind Farms

407

EL Petersen and PH Madsen

Industrial Energy Use, Status and Trends

421

E Worrell

Environmental Change and Energy

431

IG Simmons

Energy and Natural Resources

441

E Nehrenheim

Combustion to Concentration to Warming: What Do Climate Targets Mean for Emissions? Climate Change and the Global Carbon Cycle

443

AS Denning

Overview Article for the Geologic History Section

453

SA Elias

Climate Change and Energy

457

SA Elias

Metrics for Greenhouse Gas Equivalence

467

IG Enting

Greenhouse Gas Emissions from Energy Systems, Comparison, and Overview

473

C Bauer, K Treyer, T Heck, and S Hirschberg

Water Conflict Case Study – Ethiopia's Grand Renaissance Dam: Turning from Conflict to Cooperation

485

JC Veilleux

Thinning Combined With Biomass Energy Production Impacts Fire-Adapted Forests in Western United States and May Increase Greenhouse Gas Emissions DA DellaSala and M Koopman

491

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LIST OF CONTRIBUTORS FOR VOLUME 1 ZS An Chinese Academy of Sciences, Xi'an, China; Xi'an Jiaotong University, Xi'an, China; Joint Center for Global Change Studies, Beijing, China C Andrews Yonsei University, Seoul, South Korea, and Rutgers University, New Brunswick, NJ, USA A Ballent Algalita Marine Research and Education, Long Beach, CA, United States C Bauer Paul Scherrer Institut, Aargau, Switzerland H Blonk Blonk Consultants, Gouda, The Netherlands P Bridgewater University of Canberra, Canberra, ACT, Australia JJ Cao Chinese Academy of Sciences, Xi'an, China; Xi'an Jiaotong University, Xi'an, China Wenfang CAO University of Padova, Agripolis, Legnaro, Italy CJ Castaneda CSU, Sacramento, CA, USA G Certini Università degli Studi di Firenze, Firenze, Italy PL Corcoran University of Western Ontario, London, ON, Canada B Davidsdottir University of Iceland, Reykjaví k, Iceland JR Dean British Geological Survey, Keyworth, United Kingdom; University of Nottingham, Nottingham, United Kingdom DA DellaSala Geos Institute, Ashland, Oregon, United States

AS Denning Colorado State University, Fort Collins, CO, United States C Dutilh Consultant Sustainable Development, Amsterdam, The Netherlands M Edgeworth University of Leicester, Leicester, United Kingdom SA Elias University of Colorado, Boulder, United States; Royal Holloway, University of London, Egham, United Kingdom IG Enting The University of Melbourne, Marysville, Australia IJ Fairchild University of Birmingham, Birmingham, United Kingdom A Gałuszka Jan Kochanowski University, Kielce, Poland MI Goldstein Surfbird Consulting, Juneau, Alaska, United States E Guarino University of Canberra, Canberra, ACT, Australia YM Han Chinese Academy of Sciences, Xi’an, China; Xi’an Jiaotong University, Xi’an, China; Joint Center for Global Change Studies, Beijing, China JJ Cao, Chinese Academy G Haynes University of Nevada, Reno, NV, United States T Heck Paul Scherrer Institut, Aargau, Switzerland S Hirschberg Paul Scherrer Institut, Aargau, Switzerland MW Hounslow Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster, United Kingdom

xi

xii

List of Contributors for Volume 1

K Jazvac University of Western Ontario, London, ON, Canada

S Pyare University of Alaska, Juneau, AK, United States

B Jennings Vanderbilt University, Nashville, TN, United States

V Ribé Mälardalen University, Västerås, Sweden

A Jernelöv Swedish Institute for Futures Studies, Sweden

NL Rose University College London, London, United Kingdom

M Koopman Geos Institute, Ashland, OR, United States

R Scalenghe Università degli Studi di Palermo, Palermo, Italy

TE Lacher Jr. Texas A&M University, College Station, TX, United States

AW Schroth University of Vermont, Burlington, VT, United States

MJ Leng British Geological Survey, Keyworth, United Kingdom; University of Nottingham, Nottingham, United Kingdom A Linnemann Wageningen University, Wageningen, The Netherlands Cornelia Ludwig Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden AW Mackay UCL, London, United Kingdom PH Madsen Technical University of Denmark, Roskilde, Denmark ZM Migaszewski Jan Kochanowski University, Kielce, Poland P Mineau Pierre Mineau Consulting, Salt Spring Island, BC, Canada; Carleton University, Ottawa, ON, Canada E Nehrenheim Mälardalen University, Västerås, Sweden EG Pacyna NILU–Norwegian Institute for Air Research, Kjeller, Norway JM Pacyna NILU–Norwegian Institute for Air Research, Kjeller, Norway; AGH–University of Science and Technology, Krakow, Poland H Park Yonsei University, Seoul, South Korea, and Rutgers University, New Brunswick, NJ, USA EL Petersen Technical University of Denmark, Roskilde, Denmark T Pievani University of Padua, Padova, Italy

IG Simmons University of Durham, Durham, United Kingdom G Sofia University of Padova, Agripolis, Legnaro, Italy W Steffen Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden K Sundseth NILU–Norwegian Institute for Air Research, Kjeller, Norway P Tarolli University of Padova, Agripolis, Legnaro, Italy RM Thompson University of Canberra, Canberra, ACT, Australia RJ Thorne NILU–Norwegian Institute for Air Research, Kjeller, Norway K Treyer Paul Scherrer Institut, Aargau, Switzerland JC Veilleux Florida International University, Miami, FL, USA CN Waters British Geological Survey, Nottingham, United Kingdom; University of Leicester, Leicester, United Kingdom M Whitmore Imperial War Museum (retired), London, United Kingdom EW Wolff University of Cambridge, Cambridge, United Kingdom E Worrell Utrecht University, Utrecht, The Netherlands J Zalasiewicz University of Leicester, Leicester, United Kingdom

CONTENTS OF ALL VOLUMES List of Contributors

xi

Editor Biographies

xxv

Introduction

xxix

VOLUME 1: GEOLOGIC HISTORY AND ENERGY The Anthropocene: How the Great Acceleration Is Transforming the Planet at Unprecedented Levels

1

DA DellaSala, MI Goldstein, SA Elias, B Jennings, TE Lacher Jr., P Mineau, and S Pyare

Basis for Establishment of Geologic Eras, Periods, and Epochs

9

SA Elias

Finding a “Golden Spike” to Mark the Anthropocene

19

SA Elias

Arguments for a formal Global Boundary Stratotype Section and Point for the Anthropocene

29

J Zalasiewicz and CN Waters

The Geomorphology of the Human Age

35

P Tarolli, G Sofia, and Wenfang CAO

The 1950s as the Beginning of the Anthropocene

45

C Ludwig and W Steffen

Sediments of the Anthropocene

57

A Gałuszka and ZM Migaszewski

Historical Overview of the Natural Gas Industry

63

CJ Castaneda

Concrete: The Most Abundant Novel Rock Type of the Anthropocene

75

CN Waters and J Zalasiewicz

Hydrology in the Anthropocene

87

P Bridgewater, E Guarino, and RM Thompson

Fluxes of Trace Metals on a Global Scale

93

RJ Thorne, JM Pacyna, K Sundseth, and EG Pacyna

Impacts of Anthropocene Fossil Fuel Combustion on Atmospheric Iron Supply to the Ocean

103

AW Schroth

Greatly Increased CO2

115

SA Elias

Anthropogenic Soils as the Marker

129

G Certini and R Scalenghe

Plastics in the Ocean

133

SA Elias

xiii

xiv

Contents of All Volumes

Evidence in Polar Ice Records

151

EW Wolff

Humanly Modified Ground

157

M Edgeworth

Plastics and the Anthropocene

163

PL Corcoran, K Jazvac, and A Ballent

The Anthropocene—A Potential Stratigraphic Definition Based on Black Carbon, Char, and Soot Records

171

YM Han, ZS An, and JJ Cao

Magnetic Particulates as Markers of Fossil Fuel Burning

179

MW Hounslow

Spheroidal Carbonaceous Fly Ash Particles in the Anthropocene

189

NL Rose

Isotopic Signatures

197

JR Dean, MJ Leng, and AW Mackay

Geochemical Records in Speleothems

205

IJ Fairchild

Chemical Signals of the Anthropocene

213

A Gałuszka and ZM Migaszewski

The Evidence for Human Agency in the Late Pleistocene Megafaunal Extinctions

219

G Haynes

Editor's Note

227

SA Elias

Increased Acidity of Ocean Waters

233

SA Elias

Loss of Coral Reefs

245

SA Elias

Earth's Sixth Mass Extinction Event

259

T Pievani

Paleoclimatology

265

SA Elias

Rewilding the Pleistocene Fauna

277

SA Elias

Development of Coal-Fired Steam Technology in Britain

285

M Whitmore

Rise of Airline Transportation After WWII

307

M Whitmore

Environmental Effects of Terrestrial Oil Spills

323

A Jernelöv

Rise in Motorized Transportation and Weapons in the World Wars

337

M Whitmore

Sustainable Energy Development; The Role of Geothermal Power

357

B Davidsdottir

Environmental Issues Associated with Energy Technologies and Natural Resource Utilization

381

V Ribé

City Planning and Energy Use H Park and C Andrews

385

Contents of All Volumes

Energy Use in Food System

xv 397

C Dutilh, H Blonk, and A Linnemann

Introduction to Renewable Energy

405

E Nehrenheim

Wind Farms

407

EL Petersen and PH Madsen

Industrial Energy Use, Status and Trends

421

E Worrell

Environmental Change and Energy

431

IG Simmons

Energy and Natural Resources

441

E Nehrenheim

Combustion to Concentration to Warming: What Do Climate Targets Mean for Emissions? Climate Change and the Global Carbon Cycle

443

AS Denning

Overview Article for the Geologic History Section

453

SA Elias

Climate Change and Energy

457

SA Elias

Metrics for Greenhouse Gas Equivalence

467

IG Enting

Greenhouse Gas Emissions from Energy Systems, Comparison, and Overview

473

C Bauer, K Treyer, T Heck, and S Hirschberg

Water Conflict Case Study – Ethiopia's Grand Renaissance Dam: Turning from Conflict to Cooperation

485

JC Veilleux

Thinning Combined With Biomass Energy Production Impacts Fire-Adapted Forests in Western United States and May Increase Greenhouse Gas Emissions

491

DA DellaSala and M Koopman

VOLUME 2: CLIMATE CHANGE The Anthropocene Climate: Humanity on a Planetary Collision Course

1

DA DellaSala and MI Goldstein

The Carbon Cycle and Global Change: Too Much of a Good Thing

7

DA DellaSala

Glaciers in the Anthropocene: Fighting an Uphill Battle

11

ABG Bush and MP Bishop

Oceans and Global Change: One Blue Planet

17

DA DellaSala

Freshwater and Global Change: Wellspring of Life

21

DA DellaSala

Tropical Rainforests and Climate Change

25

RT Corlett

Primary Forests: Definition, Status and Future Prospects for Global Conservation

31

CF Kormos, B Mackey, DA DellaSala, N Kumpe, T Jaeger, RA Mittermeier, and C Filardi

Evolutionary Responses to Climate Change

43

JS Griffiths and MW Kelly

Evolutionary Responses to Climate Change P Gienapp and J Merilä

51

xvi

Contents of All Volumes

Economics of Reducing Emissions From Deforestation and Forest Degradation: Incentives to Change Forest Use Behavior

61

HJ Albers, KD Lee, and EJZ Robinson

Economics of Sea Level Rise

67

RSJ Tol

Glaciers, Topography, and Climate

71

ABG Bush and MP Bishop

Global Change Impacts on the Biosphere

81

SA Elias

Insects and Climate Change: Variable Responses Will Lead to Climate Winners and Losers

95

SH Black

Cold-Water Fishes and Climate Change in North America

103

JE Williams, DJ Isaak, J Imhof, DA Hendrickson, and JR McMillan

Impacts of Climate Change on Amphibian Biodiversity

113

DP Bickford, R Alford, ML Crump, S Whitfield, N Karraker, and MA Donnelly

Climate Change Effects on Terrestrial Mammals: A Review of Global Impacts of Ecological Niche Decay in Selected Regions of High Mammal Importance

123

F Huettmann

Marine Mammals: At the Intersection of Ice, Climate Change, and Human Interactions

131

M Castellini

Species Responses to Climate Change: Integrating Individual-Based Ecology Into Community and Ecosystem Studies

139

E Bestion and J Cote

Conservation Issues: Polar Seas

149

KE Smith

Mass Changes in Antarctica in Response to Changing Climate

159

A Mémin and F Rémy

Conservation issues: Tundra ecosystems

165

SA Elias

Climate Change Challenges for Africa

177

RW Abrams, JF Abrams, and AL Abrams

Impacts of Climate Change in Central Asia

195

B Mannig, F Pollinger, A Gafurov, S Vorogushyn, and K Unger-Shayesteh

Climate Change in South America

205

MM Vale and APF Pires

Climate Change Effects on European Heat Waves and Human Health

209

C Ramis and A Amengual

Impact of Climate Variability and Change on Tropical Cyclones in the South Pacific

217

SS Chand

Climate Change Impacts on Atolls and Island Nations in the South Pacific

227

JR Campbell

Climate Change May Trigger Broad Shifts in North America's Pacific Coastal Rainforests

233

DA DellaSala, P Brandt, M Koopman, J Leonard, C Meisch, P Herzog, P Alaback, MI Goldstein, S Jovan, A MacKinnon, and H von Wehrden

Ecoregional Planning and Climate Change Adaptation

245

PJ Comer

Strategies for Climate Change Adaptation: A Synthesis RM Gregg, JM Kershner, and LJ Hansen

257

Contents of All Volumes

Whole Community Adaptation to Climate Change

xvii 267

ME Koopman and T Graham

Climate Change Adaptation in Practice: Finding What You Need to Know

277

LJ Hansen

Conservation Issues: Wildlife Connectivity for Climate Change Adaptation

281

PJ Crist

Microrefugia and Climate Change Adaptation: A Practical Guide for Wildland Managers

289

D Olson

Assisted Migration as a Conservation Approach Under Climate Change

301

MH Hällfors, EM Vaara, M Ahteensuu, K Kokko, M Oksanen, and LE Schulman

The Crown of the Continent: A Case Study of Collaborative Climate Adaptation

307

RP Bixler, M Reuling, S Johnson, S Higgins, S Williams, and G Tabor

Supporting Climate-Informed Marine Fisheries Management

317

RM Gregg, A Score, and L Hansen

Taking Action on Climate Change in the Crown of the Continent Ecosystem

327

R Nelson, AA Carlson, E Sexton, IW Dyson, and L Hoang

Robust Conservation Planning for Coast Redwood in a Changing Climate

337

DA DellaSala

Global Change

347

DA DellaSala

Yellowstone to Yukon Conservation Initiative: Robust Conservation and Climate Adaptation in Action

351

JA Hilty, R Nelson, and WL Francis

Indigenous Knowledge and Practice for Climate Change Adaptation

359

DK Bardsley

Human Footprint Affects US Carbon Balance More Than Climate Change

369

D Bachelet, K Ferschweiler, T Sheehan, B Baker, B Sleeter, and Z Zhu

Atmospheric Sciences and Global Change: All I Need is the Air That I Breathe

387

DA DellaSala

Greenhouse Gas Sources and Sinks

391

JM Cloy and KA Smith

Human Activities and Climate Change

401

N Khetrapal

Ocean Acidification and Warming: The economic toll and implications for the social cost of carbon

409

J Talberth and E Niemi

Aerosol, Climate, and Sustainability

419

T Banerjee, M Kumar, and N Singh

Climate Change and Health

429

F Thomas

The Impact of Climate Change on Public Health, Human Rights, and Social Justice

435

BS Levy and JA Patz

Lyme Disease Epidemic Increasing Globally Due to Climate Change and Human Activities

441

DA DellaSala, M Middelveen, KB Liegner, and J Luche-Thayer

Climate Change, Food Security, and Population Health in the Anthropocene

453

CD Butler and RA McFarlane

Impacts of Climate Change on Subsistence-Oriented Communities V Savo, D Lepofsky, and K Lertzman

461

xviii

Contents of All Volumes

Impacts of Global Changes in Cities

467

V Masson

The Social Cost of Carbon

475

EG Niemi

UN Convention on Wetlands (RAMSAR): Implications for Human Health

479

H Skov

Denial Versus Reality of Climate Change

487

KM Jylhä

Denial—The Key Barrier to Solving Climate Change

493

H Washington

Cold Facts, Hot Topics, and Uncertain Futures: Political and Industry Responses to Climate Changes in Greenland

501

C Ren and LR Bjørst

The Law of Climate Change Mitigation: An Overview

505

KF Kuh

Climate Change and Political Instability

511

S Dalby

VOLUME 3: BIODIVERSITY The Status of Biodiversity in the Anthropocene: Trends, Threats, and Actions

1

TE Lacher Jr and NS Roach

6th Mass Extinction

9

R Wagler

Latitudinal Gradients of Biodiversity: Theory and Empirical Patterns

13

MR Willig and SJ Presley

Conservation Biogeography: Monitoring the Status of Earth's Biota

21

SA Elias

Conservation Biogeography of Ecosystem Services

25

J Cimon-Morin, M Darveau, and M Poulin

Wilderness and Intact Ecosystems

31

CF Kormos, SA Casson, RA Mittermeier, and CE Filardi

Anthropocene: Island Biogeography

37

MR Helmus and JE Behm

Biodiversity and Disturbance

45

MR Willig and SJ Presley

Rise of Human Influence on the World's Biota

53

SA Elias

Biodiversity Hotspots

67

RA Mittermeier and AB Rylands

Modern Threats to the Stability of Biological Communities

77

AS Mori

A Decade of the Resource-Based Habitat Paradigm: The Semantics of Habitat Loss

85

RLH Dennis

Indicators of Anthropogenic Change and Biological Risk in Coastal Aquatic Environments

97

EL Thompson

Trends in Global Biodiversity: Soil Biota and Processes EM Bach and DH Wall

125

Contents of All Volumes

Trends in Biodiversity: Insects

xix 131

DL Wagner

Trends in Biodiversity, Plants

145

SF Oldfield

Trends in Biodiversity: Freshwater

151

KO Winemiller

The Future for Reptiles: Advances and Challenges in the Anthropocene

163

LA Fitzgerald, D Walkup, K Chyn, E Buchholtz, N Angeli, and M Parker

Trends in Biodiversity: Vertebrates

175

M Hoffmann, TM Brooks, SHM Butchart, RD Gregory, and L McRae

Conservation Issues: Temperate Rainforests

185

DA DellaSala

Conservation Issues: Oceanic Ecosystems

193

N Neeman, JA Servis, and E Naro-Maciel

Conservation Issues: Temperate Ocean Regions

203

SA Elias

Biogeographical Shifts and Climate Change

217

JG Molinos, ES Poloczanska, JD Olden, JJ Lawler, and MT Burrows

Biodiversity Response to Habitat Loss and Fragmentation

229

R Pardini, E Nichols, and T Püttker

Dams and River Fragmentation

241

DJ Hoeinghaus

Climate Change and Biodiversity: Impacts

249

L Hannah and A Bird

Novelty in Ecosystems

259

AE Lugo, KM Winchell, and TA Carlo

Invasive Species

273

WE Rogers

Genetic Responses to Rapid Change in the Environment During the Anthropocene

281

DA Tallmon and RP Kovach

Measuring Biodiversity

287

JA Veech

Effective Biodiversity Assessment and Monitoring

297

J Schipper and F Rovero

Conserving Biodiversity and Sustaining Ecosystem Services in the Anthropocene: Understanding the Social–Ecological Legacy of Acid Rain in the Adirondack Park (USA)

305

CM Beier

Tools for Monitoring Global Deforestation

313

C Davis and R Petersen

The Convention on Biological Diversity

321

JA McNeely

The Endangered Species Act

327

MW Schwartz

The IUCN Red List: Assessing Extinction Risk in the Anthropocene

333

TE Lacher and C Hilton-Taylor

Key Biodiversity Areas PF Langhammer, SHM Butchart, and TM Brooks

341

xx

Contents of All Volumes

Biosphere Reserves in the Anthropocene

347

S Stoll-Kleemann and T O’Riordan

NGOs and Biodiversity Conservation in the Anthropocene

355

JMC Da Silva and CM Chennault

The Impacts of Conflict on Biodiversity in the Anthropocene

361

LE Ruyle

The Natural and Social History of the Indigenous Lands and Protected Areas Corridor of the Xingu River Basin and Prospects for Protection

369

S Schwartzman, B Zimmerman, AV Boas, KY Ono, MG Fonseca, J Doblas, P Junqueira, A Jerozolimski, M Salazar, R Junqueira, and M Torres

Extinction Risk in the Anthropocene

379

E Polaina and M González-Suárez

Resilience

385

YG Matsinos

Plant Conservation in the Anthropocene: Definitely Not Win–Win But Maybe Not Lose–Lose?

389

S Volis

Conserving Biodiversity by Restoring Ecological Processes

399

LE Ramirez-Yanez, B Miller, and RP Reading

The Growing Importance of Reintroductions and Translocations as Tools for Conservation in an Age of Rapid Climate Change

405

RP Reading, BJ Miller, and LE Ramirez

Management of Nonnative Invasive Species in the Anthropocene

409

SA Bhagwat

Ecosystem Services in Theory and Practice

419

R Costanza

Market-Based Approaches to Biodiversity Conservation: An Overview of Experience in Developed and Developing Countries

423

RE Rice

Biomimicry/Bioprospecting

429

AG Valdecasas and QD Wheeler

Conservation Financing—Looking Forward

435

F Hawkins

Climate Change and Biodiversity: Conservation

441

N Shahbol, L Hannah, and TE Lovejoy

Which Way Forward? Past and New Perspectives on Community-Based Conservation in the Anthropocene

453

L Redmore, A Stronza, A Songhurst, and G McCulloch

Systematic Conservation Planning in the Anthropocene

461

I Lacher

The Future of the Global Commons: A Call for Collective Action

471

N Ishii

VOLUME 4: ETHICS Environmental Ethics

1

JB Callicott

Finding an Ethical Foundation for Economics in the Anthropocene PG Brown, I Mason, and CG Regehr

11

Contents of All Volumes

Ethics for the Anthropocene Epoch

xxi 21

SH Miles and S Craddock

Sustainability and Resilience

29

M Powers

Anthropocentrism in the Anthropocene

39

J Beever

Climate Change Ethics

45

B Williston

Evolving Moral Status

53

JW Walters and LF Greer

Ecomodernism and the Anthropocene

61

M Sagoff

Transhumanism and Posthumanism

67

J McDonald

Beneficence

75

LR Churchill

Global Justice

81

J Wilson

Liberty: The Future of Freedom on a Resilient Planet

87

B Jennings

Replacing the Anthropocene

95

M Smith

Human Rights in the Anthropocene

103

H Shue

Solidarity

111

R ter Meulen

Virtue

119

M Di Paola

Vulnerability

127

F Luna

Aging in the Anthropocene

137

PJ Whitehouse

Suffering in the Anthropocene Era: Contributions of Phenomenology to Understanding the World-Constituting Role of Subjectivity

147

MB Morrissey

Cosmology and Ecology

151

S Mickey

Christianity, Perspectives on the Anthropocene

159

NM de S Cameron

Taoism

163

R Kirkland

Judaism and the Anthropocene

169

M LaGrone

Toward a New Humanism in the Age of Anthropogenic Climate Change: On Sylvia Wynter

175

D Kline and TR Cole

Spiritual Ecology LE Sponsel

181

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Contents of All Volumes

Ecosystems and Human Well-Being

185

I Douglas

Endangered Species and Biodiversity

199

H Rolston III

Biodiversity Conservation

205

C Meine

Common Resource Governance

215

LH Berry

Novel Ecosystems: Adaptive Management and Social Values in the Anthropocene

221

BG Norton

Water Ethics

227

A Wellington

Overshoot

239

H Washington

Rewilding

247

D Johns

Estimating Environmental Health Costs: Monetary Valuation of Greenhouse Gases

257

P Watkiss

Global Governance in the Anthropocene

265

K Bosselmann

Earth Jurisprudence

271

B Mylius

Uneconomic Growth

277

CJ Orr

Society

287

DA DellaSala

International Waters: Conflict, Cooperation, and Transformation

291

AT Wolf

Disaster Ethics

301

LM Lee

Pandemics in the Era of the Anthropocene

307

LP Francis

World Human Population Problems

313

D Pimentel and M Burgess

Population: Growth, Decline, and Control

319

MP Battin

Science, Technology, and Society Studies

331

DR Morrison

Synthetic Biology

339

J Boldt

The Use of Biotechnology for Nonhuman Organisms

343

GE Kaebnick

Human Genetic Engineering: Biotic Justice in the Anthropocene?

351

B Gregg

Precautionary Principle: Current Understandings in Law and Society

361

J Hanson

Ecological Risk in the Anthropocene: An Evaluation of Theory, Values, and Social Construct P Kanwar

367

Contents of All Volumes

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VOLUME 5: CONTAMINANTS Contaminants in the Age of the Anthropocene

1

P Mineau

Ozone, SOx and NOx, Particulate Matter, and Urban Air

7

P Salvador

Acid Rain: Causes, Consequences, and Recovery in Terrestrial, Aquatic, and Human Systems

23

GE Likens and TJ Butler

Chlorinated Fluorocarbons and Other Ozone-Destroying Chemicals

33

RJ Salawitch

Contamination of Our Oceans by Plastics

43

L Gutow and M Bergmann

The Rise of CO2 and Ocean Acidification

51

P Williamson and S Widdicombe

The Proliferation of Nanomaterials: Possible Health and Environmental Consequences

61

B Jovanovic

Oil Spills in Coastal Wetlands

67

MW Hester, JM Willis, and MC Baker

Metal Pollution

77

GE Millward and A Turner

Groundwater Pollution: Sources, Mechanisms, and Prevention

87

C Postigo, DE Martinez, S Grondona, and KSB Miglioranza

Organochlorine Pesticides, Rachel Carson, and the Environmental Movement

97

I Newton

Organophosphorous and Carbamate Insecticides: Impacts on Birds

105

P Mineau

Systemic Insecticides and Their Environmental Repercussions

111

F Sánchez-Bayo

Pyrethroid Insecticides—Exposure and Impacts in the Aquatic Environment

119

I Werner and TM Young

The Impact of Pesticides on Our Freshwater Resources

127

S Stehle and R Schulz

Organotins: Sources and Impacts on Health and Environment

133

ACA Sousa, S Tanabe, and MR Pastorinho

Atrazine and Amphibians: A Story of Profits, Controversy, and Animus

141

JR Rohr

Roundup Ready! Glyphosate and the Current Controversy Over the World's Leading Herbicide

149

R Mesnage and MN Antoniou

Rodenticides: The Good, the Bad, and the Ugly

155

RF Shore

The Killing Fields: The Use of Pesticides and Other Contaminants to Poison Wildlife in Africa

161

NL Richards, D Ogada, R Buij, and A Botha

Tetraethyl Lead, Paints, Pipes, and Other Lead Exposure Routes: The Impact on Human Health

169

DC Bellinger

Lead Use in Hunting and Fishing—Consequences to Birdlife, Humans, and the Environment

177

VG Thomas and R Guitart

The Effects of Methylmercury on Wildlife: A Comprehensive Review and Approach for Interpretation D Evers

181

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Contents of All Volumes

Radionuclides: Sources, Speciation, Transfer and Impacts in the Aquatic and Terrestrial Environment

195

L Skipperud and B Salbu

Polychlorinated Biphenyls: Sources, Fate, Effects on Birds and Mammals, and Mechanisms of Action

207

MEB Bohannon and MA Ottinger

Arsenic: Exposure, Toxicology, Use, and Misuse

215

SJS Flora

Fertilizers and Their Contaminants in Soils, Surface and Groundwater

225

M Nasir Khan, M Mobin, ZK Abbas, and SA Alamri

Environmental Epigenetics: The Envirogenomic Interface

241

J Wilkinson

A Cautionary Tale: Diclofenac and Its Profound Impact on Vultures

247

NL Richards, M Gilbert, M Taggart, and V Naidoo

Contamination From the Agricultural Use of Growth Promoters and Medicines

257

ABA Boxall

Human and Veterinary Drugs in the Environment

263

T Rastogi, WMM Mahmoud, and K Kümmerer

E-waste: Environmental and Health Challenges

269

A Pascale, C Bares, and A Laborde

Index

277

BIOGRAPHIES Dominick A. DellaSala is president and chief scientist of the Geos Institute in Ashland, Oregon, and former president of the Society for Conservation Biology, North America. He is an internationally renowned author of over 200 publications on forest ecology, endangered species, conservation biology, and climate change. He has given keynote talks ranging from academic conferences to the United Nations Earth Summit. He has been featured in hundreds of news stories and documentaries, testified in the US congress numerous times, and received conservation leadership and book writing awards. He is on the editorial board of Elsevier’s Earth Systems and Environmental Sciences as global change editor, coeditor of the Encyclopedia of the Anthropocene (Elsevier), and subject editor of several scientific journals. He is motivated by his work to leave a living planet for his daughters and grandkids, and all those that follow.

Michael I. Goldstein is a planner and biologist for the US Forest Service in Juneau, Alaska. Mike has worked on many applied management issues across terrestrial and aquatic systems, addressing pesticides, dispersed recreation, development, timber harvest, and other forms of resource extraction. Mike is on the editorial board of Elsevier’s major reference work “Earth Systems and Environmental Sciences” as the ecology and conservation editor, serves as coeditor-in-chief of this Encyclopedia of the Anthropocene and coeditor of the Anthropocene’s Climate Change volume, and subject editor for several scientific journals. In his spare time, Mike coaches skiing, enjoys fishing and camping in remote places, and teaching his three children.

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Biographies

Scott Elias received both an undergraduate degree and a PhD in environmental biology at the University of Colorado, Boulder. Following postdoctoral fellowships in Canada and Switzerland he returned to the Institute of Arctic and Alpine Research at the University of Colorado, where he pursued research in Quaternary paleoenvironments from 1982 to 2000. In 2000 he took a lectureship in Quaternary science in the Geography Department of Royal Holloway, University of London, where he became professor of Quaternary science in 2007. He has served as editor-in-chief of the first and second editions of the Encyclopedia of Quaternary Science, published by Elsevier. In 2012 he became editor-in-chief of the online Reference Module in Earth Systems and Environmental Sciences. Scott’s research has focused mainly on the reconstruction of Late Pleistocene environments from the Alaska, the Rocky Mountains, and the American Southwest. He retired from Royal Holloway in 2017 and returned to Colorado, where he continues his research in paleoenvironments and his editorial duties. Bruce Jennings is senior fellow at the Center for Humans and Nature, a nonprofit research center, and associate professor in the Department of Health Policy and the Center for Biomedical Ethics and Society at Vanderbilt University. He is also senior advisor and fellow at The Hastings Center, where he served from 1991 through 1999 as executive director. He is the editorin-chief of Bioethics (formerly the Encyclopedia of Bioethics), 4th Edition, 6 vols. (2014), the standard reference work in the field of bioethics. In addition to work in bioethics, he has been active in ethics research and education in the field of public health. He taught ethics at the Yale University School of Public Health from 1996 to 2014, and he served as member and chair of the Ethics Advisory Committee at the Centers for Disease Control and Prevention (CDC) from 2003 to 2009. At the Center for Humans and Nature, he has focused on environmental ethics and policy, with a special emphasis on ecological governance and ecological political economy. He is the editor of the Center’s electronic journal, Minding Nature, and he is author of Ecological Governance: Toward a New Social Contract With the Earth (2016). For 12 years until 2014, he was an elected Trustee in the local government of Hastings-on-Hudson, NY, where he was a leader in sustainability policy and planning. Thomas E. Lacher, Jr., is full professor in wildlife and fisheries sciences at Texas A&M University. He has held positions at the University of Brasilia, Brazil; Western Washington University; Clemson University, where he was the executive director of the research consortium of the Archbold Tropical Research Center, and Texas A&M University, where he was professor and Caesar Kleberg Chair in wildlife ecology in the Department of Wildlife and Fisheries Sciences. From 2002 to 2007 he was at Conservation International, where he was senior vice-president and executive director of the Center for Applied Biodiversity Science. He was also department head in WFSC from 2007 to 2011. Lacher has been working in the Neotropics for 40 years, with field research experience in Dominica, Mexico, Costa Rica, Panama, Colombia, Guyana, Suriname, Peru, and Brazil. He has also served on numerous review panels for NSF and EPA and the Area Advisory Committee for Latin America for the Fulbright Commission. He has been major advisor of 20 MS and 17 PhD students and several postdoctoral fellows. His current research is focused on the assessment of extinction risk in mammals and the analysis and monitoring of large-scale patterns and trends in mammalian

Biographies

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biodiversity. He is a member of the IUCN Climate Change Specialist Group, the IUCN Small Mammal Specialist Group and serves on the IUCN Red List Committee. His research experience spans behavioral ecology, population and community ecology and conservation biology, publishing in journals such as Science, American Naturalist, Ecology, BioScience, Global Ecology and Biogeography, Diversity and Distributions, Conservation Letters and Conservation Biology. Pierre Mineau is senior scientist and founder of Pierre Mineau Consulting, with near 40 years of experience in assessing the environmental risk of pesticides and other contaminants. Pierre received his BSc from McGill University in Montreal, and his MSc and PhD from Queens University in Kingston, Ontario. Most of his working career was with the Canadian Government, culminating as senior research scientist in environmental toxicology within the Science and Technology Branch of Environment Canada (and before that, the Canadian Wildlife Service). For part of that time, he was intimately involved in the pesticide regulatory process in Canada as an advisor to the Federal Department of Agriculture. He continues to hold adjunct professor status at Carleton University in Ottawa. His research encompasses pesticide toxicology, wildlife conservation in agroecosystems, biomarker development, risk assessment, sustainable agriculture and anthropogenic sources of avian mortality. He has been an advisor on pesticide issues and participated in regulatory and legal proceedings in Canada, the United States, the European Union, and other countries. Pierre has authored or coauthored over 200 technical papers, book chapters, and reports, including many seminal analyses of modern pesticide risk assessment, most of them in the peerreviewed literature. He has given a large number of presentations at scientific meetings or to governments, academic institutions, or NGOs. He has had his work featured in several magazines, newspapers, and lay publications (e.g., Wired, The Ecologist, Audubon, Mother Jones, The Globe and Mail, Cottage Life), and been interviewed on radio or television in Canada, the United States, and Argentina. Recently, Pierre has been active in the assessment of neonicotinoid insecticides, a relatively new class of compounds currently being blamed for losses of honeybees and other pollinators as well as widespread contamination of aquatic systems. He was part of an IUCN-sponsored task force of international scientists involved in the review of systemic insecticides and the consequences for agriculture and the environment. With NGOs and commercial partners, he is also currently working on pesticide risk indicator development for certification, research, and regulatory purposes. Sanjay Pyare is an associate professor of geography and environmental science and the coordinator of the Spatial Ecosystem Analysis Lab at the University of Alaska Southeast. His research interests include spatial analysis and remote sensing, ecosystem services, integrated ecosystem modeling, and biogeography. He is leading a multidisciplinary effort to understand ecosystem services in the “icefield to estuary” system of Southeast Alaska. He lives in Juneau, Alaska, with his wife and two children.

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INTRODUCTION: GEOLOGIC HISTORY AND ENERGY This section of the encyclopedia deals with the geologic record and with energy. It may seem strange that an encyclopedia focused on the Anthropocene devotes so much attention to geologic history, but there are two reasons for this. First, in order to put recent and predicted future changes to Earth’s environments in context, it is vital to establish a baseline from which “normal” conditions have departed. We must answer the following questions: Has anything like this ever happened before? When was the last time our planet experienced these conditions? Are the pace and amplitude of environmental changes in the Anthropocene unique in Earth history, or just the most recent example of recurring cycles of changes? As you will see in the articles presented here, there are many unique aspects of the environmental changes we are observing in the modern world, especially in the rate of changes in CO2 concentrations in the atmosphere and the corresponding rapid climb in temperatures. The second reason to bring Geology into a discussion of the Anthropocene concerns the formal classification of the Anthropocene as a formal geologic epoch. A number of articles in this section present arguments for giving the Anthropocene formal geological designation. Articles on energy, especially concerning the development and exploitation of fossil fuels, are also included in this section. This is fitting because the fossil fuels themselves (coal, oil, natural gas) are products of the geologic past—formed millions of years ago and are nonrenewable. Scott Elias

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The Anthropocene: How the Great Acceleration Is Transforming the Planet at Unprecedented Levels DA DellaSala, Geos Institute, Ashland, Oregon, United States MI Goldstein, Surfbird Consulting, Juneau, Alaska, United States SA Elias, University of London, Egham, United Kingdom B Jennings, Vanderbilt University, Nashville, TN, United States TE Lacher Jr., Texas A&M University, College Station, TX, United States P Mineau, Pierre Mineau Consulting, Salt Spring Island, BC, Canada; Carleton University, Ottawa, ON, Canada S Pyare, University of Alaska, Juneau, AK, United States © 2018 Elsevier Inc. All rights reserved.

Humanity’s Planetary Fingerprints We all like to celebrate special occasions in our lives: birthdays, holidays, weddings, winning the lottery, and so on. Given that our genus has survived some 4 million years under conditions much less hospitable than today, we should all be jumping up and down that we made it this far. Our species is now more than 7 billion strong and still growing in number. We are, arguably, living healthier lives (at least longer ones) than our great grandparents did 100 years ago and we have more gadgets to play with than we can imagine. But this has come at an insurmountable price of a degraded planet with consequences often irreversible. Is the Anthropocene a good thing or are we creating an impending planetary doomsday at our own expense? Should we celebrate, run for the hills, or cry in our beer? If you are like us, we read planetary forces like digital indicators on a car’s dashboard—some things are trending up, and a lot—a real lot—are trending down as we have our ecological footprint on the accelerator. Is it time to panic yet? Build a bomb shelter? This reference module is published in the volumes of the encyclopedia representing key aspects of the Anthropocene. It is a compilation of over 250 articles from leading scholars around the world that, like us, are monitoring the dashboard of planet Earth. The reader can access volumes on Geology, Climate Change, Biodiversity, Contaminants, and Ethics. Here, we editors provide an overview of the content to pique your interest.

When Did the Anthropocene Start? Geologists who record major planetary events hotly debate whether the Anthropocene constitutes a distinct geological period worthy of splitting off from the current Holocene. In this overview, we assume that the Anthropocene is a proper way of cataloguing humanity’s enormous impacts on a planetary scale, these being much like the shifting of tectonic plates that marked Earth’s distinct geological periods. Geologists like to mark the beginning of a geological period using Global Boundary Stratotype Sections and Points (commonly referred to as “golden spikes”). These are internationally agreed-upon reference points on stratigraphic sections of rock that define the lower boundaries of stages on a geologic time-scale. Because we humans are living in the period that we now wish to demark, we cannot simply find a stratigraphic magic marker or drive a single golden spike and say—ok—we arrived at the dawn of a new era. Instead, we argue that the Anthropocene is the accumulation of golden spikes overtime with a very recent build-up phase (multiple golden spikes; Fig. 1). Let us begin with the advent of our first known early relatives—“Ardi” (Ardipithecus ramidus) and “Lucy” (Australopithecus afarensis). Until recently, the 3 million-year-old Lucy fossil was thought to be the first human ancestor, but she was displaced by the 4 million-year-old Ardi, both discovered in Ethiopia. Africa, the birthplace of humanity, is why we chose the cover of the Encyclopedia of the Anthropocene. This is where it all “began,” although clearly human evolution is just one branch on a very large tree going back to the primordial ooze that spawned all life. But for now, we will assume that the first golden spike—albeit maybe a small one—was driven millions of years ago in the ancient African cradle from which all humanity regardless of race or color owe our existence. Some 2 million years later, the progeny of Ardi and Lucy got smarter as they began to use tools. Using stones and then primitive axes and cleavers, they manipulated their world and drove another golden spike in the Anthropocene timeline. Tools increasingly improved and we got really good at hunting, driving the next golden spike into the Anthropocene. Some 50,000 to 11,000 years ago, our ancestors became the driving force behind the planet’s 5th great extinction event (Sandom et al., 2014). Just about anything with “giant” in its name was eradicated— giant sloth, giant kangaroo, giant armadillo to name a few of the megafauna extinctions that took place in South America, North America, Australia, and parts of Asia, but curiously enough, not in Africa. As we entered the “Neolithic,” some 11,000 years ago, tool development advanced with the advent of agriculture in the Middle East. Large tracts of forests were cleared, fields plowed, and rivers turned into aqua-ducts to support domestication of a handful of crops and animals that now put food on our tables.

Encyclopedia of the Anthropocene

https://doi.org/10.1016/B978-0-12-809665-9.09957-2

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The Anthropocene: How the Great Acceleration Is Transforming the Planet at Unprecedented Levels

Fig. 1 Accumulation of “golden spikes” over millions of years of planetary degradation useful in demarking the Anthropocene, particularly the post-World War II “Great Acceleration.”

As we follow the advancement of tools, the Industrial Revolution (1750–1900) drove its spike as machinery improved to process goods and services at an accelerated rate, powered by the burning of fossil fuels (coal and oil). These advancements ushered in life’s many comforts: plumbing, warm homes, and more effective medicines. Humanity began to flourish in big numbers as we drove our first major population spike at 1 billion (1804). It took another 123 years (1927) to get to the 2 billionth spike. Then only 33 years to drive the 3 billion (1960) spike, and even less to 4 billion (1974), 5 billion (1987), 6 billion (1999), 7 billion (2011), and, at this rate (even though it is decelerating) we are expected to reach the 8 billion spike by 2024. Additional spikes came with the first atomic bomb (1945), the introduction of plastics, and widespread, mechanized agriculture in the developing world (1950s). These massive changes are further depicted in the volumes of this encyclopedia. While the Anthropocene is really a continuum of golden spikes, it is clear that the “Great Acceleration” ramped up sometime after WW II with explosive population growth, human technological advancement, increased life expectancy, and unsustainable consumption of finite ecosystems. Clearly, we are now the dominant force on the planet. How we got there is no single event, but rather an accumulation of events that have now positioned the Anthropocene to push planetary boundaries beyond the level needed to support us and myriad other species. Where this will end up is anyone’s guess, but if we do not change course soon, the next big golden spike may mark a completely novel and uncertain existence for humanity. What will we become? How far will our technology go? What will our species and our planet look like in 100 years, 1000 years, over the course of the next millennia? Notably, in January 2017, the world’s Doomsday Clock, which is kept by the Bulletin of Atomic Scientists, got 30 s closer to midnight, just 2½ symbolic minutes to global destruction. One of the reasons for the clock ticking closer to midnight, and the closest it’s been since the Cold War of the 1950s is because of America’s declaration to expand its nuclear arsenal with the potential for another arms race.

Geology The evidence from the air, land, and sea is unequivocal: we are living in a time that is remarkably distinct from all previous human history. Human impacts began to reshape the world’s biota toward the end of the last Ice Age, when human hunters played a significant role in the extinction of megafauna on four continents. Shortly thereafter, an even greater biological alteration took place

The Anthropocene: How the Great Acceleration Is Transforming the Planet at Unprecedented Levels

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as people began to settle in villages and take up farming as a means of subsistence. This process started as early as 11,000 years ago in the Fertile Crescent region of the Middle East, and launched the wholesale clearance of natural vegetation for the sake of agriculture and animal husbandry. The temperate regions of the world were the first to come under the plow, and by the middle of the 20th century, this conversion of natural into agricultural landscapes had spread even to the tropical rain forests. The pace and intensity of human-caused environmental impacts on the planet changed dramatically in the 1950s, so this is clearly the most sensible boundary horizon for the beginning of the Anthropocene. Industrial and other technological advancements were growing at a similar pace to the human population. Provision of food and water began to take ever-increasing amounts of land out of natural ecosystems and into agricultural and industrial production. Roads were created to give access to all but the most remote corners of the world. Agricultural chemicals (fertilizers and pesticides) facilitated the “Green Revolution” that helped feed the world’s teaming human population, but at the terrible price of polluting both land and sea. Little or no attention was paid to pollution problems until the 1970s, and even now there is tremendous “push back” on the part of pro-business politicians the world over, seeking to weaken or revoke environmental protection laws. In less than a century, the accumulation of plastics and other waste products is now a definitive marker of the Anthropocene that is pushing the limits of ecosystems (Fig. 1).

Climate Change Delving a little bit further into our changing climate, for over 10,000 years, humanity has prospered in the “sweet-spot” of the Holocene post-glacial climate that allowed agriculture to begin terra-forming much of the planet. Over millennia, the planet has gone through myriad climate changes that have triggered extinction events and caused shifts in distributions of species and ecosystems. Under anthropogenic climate change the “velocity of climate change” is much faster than that which many species can adapt to. Another major difference today is how humanity’s ecological footprint now stands in the way of a species migrating in search of suitable climates and habitats. During the last major climate change event, there were no roads, dams, clearcuts, cities, or other myriad human disturbances blocking species movements. This double whammy of unprecedented land-use working in concert with climate change affects species population size and distribution. In short, rapid climate change is not some “environmental problem” but a planetary alteration affecting all systems— human and ecological. And every continent is impacted, particularly the northern latitudes that feel the extremes of climate change. It is believed that time still exists to reverse direction of this rapid change. The primary discussion today is how to mitigate greenhouse gas emissions by switching to clean, renewable energies and by storing atmospheric carbon in ecosystems. However, even if we stopped all emissions today, greenhouse gasses have long atmospheric “hang-times” and their effects will be felt for decades to centuries. Effective strategies include coupling mitigation with adaptation of species and human communities to avoid some of the inevitable consequences already underway as discussed in the climate change volume.

Biodiversity Biodiversity is a concept that is useful for thinking about life on Earth, as it encompasses the full spectrum of organismal interactions in their environment. One of the most commonly accepted definitions is “the complete range of species and biological communities, as well as the genetic variation within species and ecosystem processes” (Primack, 2014). The definition is logically satisfying but impossible to fully measure and quantify. Therefore, much of the research to measure, monitor, and manage for biodiversity focuses on species, and our attempts to evaluate the status of biodiversity often devolves to assessing trends in species abundance and richness. This oversimplification of the complexity of biodiversity requires caution. However, it does allow us to analyze trends in biodiversity over time. What has happened in the past can provide insights into the trends we might project forward in the Anthropocene. The planet has experienced mass extinction in the past, and dates of approximate occurrence, in millions of years ago (MYA) include the Ordovician-Silurian (440 MYA), the Late Devonian (365 MYA), the Permian-Triassic (250 MYA), the Triassic-Jurassic (210 MYA), and the Cretaceous-Tertiary (65.5 MYA). The Permian extinction was by far the most destructive, eliminating 96% of marine species and 70% of terrestrial species. Eventually there was a recovery of diversity on Earth, but it took over 10 million years to occur. The latter two events opened the way for the explosive radiation of dinosaurs (Triassic-Jurassic), followed by their subsequent near extinction and the emergence of mammals (Cretaceous-Tertiary, also referred to as the K-T extinction). In all cases, there were significant impacts not only on species but also on ecosystems, their associated processes; their recovery measured in millions of years. The Anthropocene has been called the beginning of the sixth mass extinction, with great concern over the loss of key species and cascading impacts on the functioning of entire ecosystems. The Millennium Ecosystem Assessment (2005) presented data that suggest the current extinction rates are 1000 times higher than the fossil extinction rate, and future projections could run 10 times higher than the present rate. Even within developing countries with strong conservation programs the rates are greatly accelerated. Extinction rates of North American freshwater fish, for example, were estimated at 877 times above the background extinction rate (Burkhead, 2012).

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The Anthropocene: How the Great Acceleration Is Transforming the Planet at Unprecedented Levels

Thus, evidence is mounting that we might indeed be at the cusp of greatly accelerated extinction rates; however this time the process will not be caused by asteroid impacts or volcanic activity: it will be driven by the expanding global impacts of humans. The drivers of these extinctions are well known. They include habitat degradation fragmentation, and loss, largely driven by the expansion of agriculture that now covers about 50% of the habitable landmass of the Earth. Vitousek et al. (1986) estimated that over 20 years ago we had already co-opted 40% of global net primary productivity for human use. In addition to crops, we have altered forested ecosystems (not converted into agriculture) by managing forests for wood and fiber. Forests are converted into sterile monocultures, often using exotic species that support only a fraction of their original biodiversity. Other drivers of habitat loss include mining, urbanization, and the complex network of roads that connect the ever-expanding number of population centers or resource exploration and exploitation sites; these roads have greatly fragmented landscapes across the globe (Ibisch et al., 2016). The continued construction of dams fragments freshwater river systems much as roads have sliced up terrestrial habitats, and many of the most damaging dams are being developed in the world’s major tropical river basins (Winemiller et al., 2016). These dams not only threaten species with extinction; they also alter the ecosystem processes of entire drainage systems. Invasive species and invasive pathogens have also taken their toll on native ecosystems. Plants like purple loosestrife (Lythrum salicaria), water hyacinth (Eichornia crassipes), and salt cedar (Tamarix ramosissima) have damaged and degraded wetlands and riparian areas throughout areas of North America. The Nile perch (Lates niloticus) was introduced to Lake Victoria to enhance commercial fisheries, but the species is a voracious predator and quickly decimated the endemic cichlids found in the lake. Some estimates place upward of 200 species now either extinct or near extinction. The expansion of the invasive zebra mussel (Dreissena polymorpha) to the Great Lakes and the Hudson Valley results in annual management and control costs of $500 million/year. The Brown tree snake (Boiga irregularis) invasion of Guam devastated the native bird fauna, and the unwise introduction of European rabbits (Oryctolagus cuniculus) to Australia resulted in control costs of over $500 million/year. Finally, perhaps the most dangerous and pervasive invasive species are plant and animal pathogens. From the Emerald ash borer (Agrilus planipennis) and Dutch elm disease (Ophiostoma novo-ulmi) to chytrid fungus on frogs and white nose syndrome in bats, these introduced pathogens cause devastating ecological and economic impacts. Further, public health officials chase invasive zoonotic diseases across the globe, hoping to contain the likes of SARS, West Nile virus, and the Zika virus before widespread human pandemics occur. As indicated throughout the volumes of this encyclopedia, climate change is the big unknown regarding the future of biodiversity, and is clearly the most problematic child of the Anthropocene with all of its cumulative impacts. As populations grow and per capita consumption or resources increases, our reliance on energy has increased. We have relied for over 100 years on burning things to generate this energy, from firewood to fossil fuels. The processes associated with climate change are described in this Introduction; however there are several points concerning specific impacts on biodiversity that merit mention. Most importantly, we are changing the process of evolution by modifying one of the most important drivers of natural selection: the climate. Climate drives species to alter their timing of reproduction, such as plants flowering earlier or birds nesting sooner. Not all organisms can respond to temperature changes; however, as many use photoperiod as the timing cue, so species within ecological communities often respond in much different ways to a warming climate. Thus, we have started to see the development of novel ecological communities over a relatively short period (Williams et al., 2007), a process that will have unknown consequences to biodiversity and ecosystem functions. In addition, species are moving on the landscape, changing their distributions in response to temperature, seasonality, or precipitation regimes. This compounds issues associated with the novel ecosystems and their processes. We face great uncertainty as a result of our changing climate, and the impacts that this will have on the important ecosystem services we rely on, and which have become a key point in international conservation conventions and agreements, are undefined (Perrings et al., 2010). Climate change affects all aspects of biodiversity and, lest we forget, we are part of this biodiversity.

Contaminants The Anthropocene has seen a massive industrialization of natural chemicals and the proliferation of synthetic chemicals that fundamentally change our everyday lives; whereas manufacturing of these products may aid and assist human populations, the by-products result in undesirable outcomes for our environment. This “chemical era” that is the Anthropocene has paralleled our dependence on petroleum hydrocarbons and the rise in greenhouse gas production. Petroleum has been the source of the necessary feedstock that has allowed the massive production of most synthetic chemicals, including the now omnipresent polymers such as plastics. By the 1950s, oil had replaced coal as the most important fuel for human endeavors as new chemical substances were invented and produced at an unprecedented rate. A June 2015 press release from the American Chemical Society (ACS) announced its 100 millionth chemical abstract service’s (CAS) registration. This is believed to be the best estimate of the number of identified chemical substances worldwide. The ACS has registered a new chemical substance every 2.5 min for the last 50 years. About three quarters of the 100 million have been added in the last decade, so the rate of discovery is growing at an exponential rate. It should come as a no surprise that many of these chemicals come to be environmental contaminants. The very characteristics that made many of these chemicals desirable to their inventers—e.g. the chemical stability of a PCB molecule, a fluorocarbon, or plastic polymer; the biological activity of a pesticide or synthetic drug—has meant that they are often long-lived in the environment and potentially problematic down the road. Even when short lived, they are able to affect far more than the intended customer or recipient; this is now clear from the proliferation of pharmaceuticals and personal care products in our waterways. It is also evident from the above statistics that humankind has been playing catch-up in understanding the consequences of these chemical introductions. Several will trace the birth of the modern environmental movement to the Anthropocene as concerns over

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our “chemical world” were added to what had hitherto been a conservation-oriented environmental movement. At the same time that Rachel Carson was writing her seminal treatise “Silent Spring” to warn humanity of the dangers of persistent and toxic pesticides, the American author Charles Webb in his book (and later a movie of the same name) “The Graduate” was telling the post-World War II (boomer) generation that the future could be summed up in one word: “plastics.” Unfortunately, as new anthropogenic contaminants are born at a frightening rate, old ones are slow to be retired. Contaminants first recognized at the dawn of human civilization—such as lead, arsenic or mercury—continue to run havoc in many areas of the globe as a result of slow and inadequate controls. Corporate, commercial, and financial interests are behind most horror stories of environmental contamination and the concomitant impact on human and wildlife populations. Despite a few notable successes such as reductions in transboundary acid precipitation and the Montreal Protocol for the protection of high altitude ozone, it could be argued that regulatory systems have been totally ineffectual and remain beholden to industrial interests. With the advent of regulatory bodies (such as the Environmental Protection Agency and others around the world) has come a concerted and wellfunded effort on the part of industry to control and dominate the regulatory agenda and forestall regulatory reforms for as long as possible. As stated by the European Environment Agency (2013): Several references and leaked documents have shown that some regulated parties have consciously recruited reputable scientists, media experts and politicians to call on if their products are linked to a possible hazard. Manufacturing doubt, disregarding scientific evidence of risks and claiming overregulation appear to be a deliberate strategy for some industry groups and think tanks to undermine precautionary decision-making.

Industry tactics aimed at discrediting their environmental critics, whether a Rachel Carson or Robert Van Den Bosh for their stand on the indiscriminate use of pesticides; a Yandell Henderson or Clair C. Patterson for exposing the harm of leaded gasoline; or a Tyrone Hayes for linking the herbicide atrazine to amphibian abnormalities, have run a consistent course throughout the Anthropocene. In his thorough analysis of the momentous (and subsequently disastrous for public health) decision of adding tetra-ethyl lead to gasoline, Loeb (1999) argues that the tetra-ethyl lead decision essentially paved the way for a science policy that shunned controls where economic benefits were large and certain in the face of uncertain threats to public health. Despite a brief period of optimism that saw the “precautionary principle” being expounded in the Rio declaration of 1992, the following decades have seen governments under pressure by industrial interests (Sachs, 2011). It is noteworthy that, in their analysis of the dire consequences of ignoring early predictions of risk, the European Environment Agency documented many cases where delays in regulation or legislation had proved incredibly costly and/or damaging: asbestos, PCBs, halocarbons, di-ethyl silbestrol (DES) etc. . . but had difficulty identifying cases where regulatory actions in the face of early warnings had been in error (European Environment Agency, 2001). Only a very few cases were highlighted in their subsequent report (European Environment Agency, 2013) showing that the risk of overregulation should not be an excuse for a failure to act early on perceived threats to health or the environment. The aforementioned tetra-ethyl lead decision also ushered in the mistaken view that industry could and would regulate itself voluntarily. Loeb (1999) believes that the old paradigm of “industry knows best” is alive and well in political circles. Thus, it is not surprising that inadequate, inconsistent, and confused environmental and public health protection defines the Anthropocene.

Ethics Seen as a new epoch in Earth history, the Anthropocene is distinguished by human activities that are shaping the physical and biological systems and processes on a global scale. The ethical significance of the Anthropocene is paradoxical. During the Anthropocene, particularly the last century, the distinctive intelligence, creativity, and social and technological organization of our species have allowed the population to increase and the quality of life to improve over time. Yet the ethical value or goodness of these human gains has come at the ethical cost of many destabilizing and deleterious consequences for other forms of life, ecosystems, and geophysical and geochemical systems. Today it is clear that these destructive consequences are increasing so rapidly that they may come to undermine future human progress and quality of life, the principal ethical rationales upon which they rest. Human artifice, technology, and environmental pollution have pushed human activity up against the boundaries of planetary conditions that have been characteristic of the Holocene epoch. As also discussed in the Geology volume, the Holocene has been quite a hospitable time in the history of the planet—mammalian life has flourished amid its climate and flora, and the human species owes its own flourishing and development to that hospitality. We are on the verge of repaying that gift with ingratitude and betrayal. The ethical challenge of the Anthropocene is to discover how to use human creativity for human betterment in ways that are sustainable, respectful of human dignity and equality, and compatible with the value and resilience of all life. Ethics is the study of right and wrong; good and bad; positive, valuable states of the world and negative, harmful ones. It is an interdisciplinary study today, drawing on writings and modes of research from philosophy, theology, law, the social sciences, and the humanities. Ethics includes the descriptive study of human cultural beliefs and rules concerning right and wrong and the prescriptive and conceptual task of determining which beliefs and rules are philosophically justified (Gert and Gert, 2016). Often referred to as normative ethics, this second form of inquiry investigates the modes of rational thinking and judgment that could be used to determine whether behavior that is taken to be justified in a given society should be considered justified and on what grounds. Normative ethics seeks rational, consistent, impartial, and universal criteria for ethical justification.

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In Western ethics, the normative grounding for ethically right conduct has been typically sought by considering four factors, including the: (1) inherent nature of actions (Is it intrinsically wrong to perform certain acts?); (2) consequences of actions (Is the act beneficial or harmful in its effects, and to whom?); (3) motivations or character dispositions of the agent performing actions (Is the action virtuous?); and (4) context within which motivations, acts, and consequences take place (Is the action part of a pattern of life that on the whole permits meaning and flourishing or degradation and waste?). A substantial portion of the Encyclopedia of the Anthropocene has been devoted to articles designed to analyze the ethical and value dimensions of the relationship between humans and nature on a planetary scale. This underscores both the multifaceted meanings that the idea of the Anthropocene has acquired and the fact that a purely scientific and technical treatment of this distinctive epoch would be incomplete (Hamilton et al., 2015). Consider anthropogenic climate change. Scientific knowledge and empirical research are clearly fundamental to that phenomenon and to what will be done concerning it in the future. However, climate change is a problem of such magnitude, complexity, and political difficulty that it has been aptly characterized as a “perfect moral storm” (Gardiner, 2011). It challenges the meaning of our traditional ethical and normative concepts, and our psychological and social capacity to respond to moral principles through effective individual or collective action. In prospect is the difficulty of making the required economic and institutional changes and transitions, many of which involve expending present wealth on mitigation and adaptation efforts that will have future benefit. In this respect, climate change is but one instance of the disturbing message that science is carrying to society about the Anthropocene as a whole. An ethical maxim that is universally acknowledged holds that with great power comes great moral responsibility. For humankind today this entails a collective responsibility, and arguably significant individual responsibility as well, for the ways its planet-shaping power is used. In other words, we need to be able to think about our ethical responsibilities and about matters of right and wrong on a planetary scale, taking into consideration both systems and patterns of activity and specific instances of individual agency and decision. The Anthropocene presents a new situation of planetary tolerances and ethical constraints; that is the truth of this epoch, but it is an exceedingly inconvenient truth. It is difficult to face a responsibility that will, if taken seriously and acted upon, shake up unquestioned habits of social living and transform the scope of economic and political freedom. Those who profess to deny the findings of climate science are in fact distressed and paralyzed by the ethical implications of what science is telling them. For those who do embrace the responsibility to devise new ways of living and new economic and technological regimes, two rather different ethical responses exist. These opposing responses tend to center on the nature of right relationship with nature and on how science and technology ought to be brought to bear to fulfill the ethical responsibility the Anthropocene places on shoulders of our species. One response is to alter our contemporary values and priorities and restrain the motivations, goals, and uses of technology that extract natural resources and produce destructive waste products, such as atmospheric greenhouse gas emissions, that are undermining the living planet. This viewpoint maintains that we should restrain our technological power, and the acquisitive desires that propel it, and instead see ourselves as creaturely good citizens of the biotic community. Technology, which is largely dependent on fossil carbon energy, should be curtailed. Only in this way can the pace and scale of human extractive and polluting economic activity be kept within sustainable bounds, even after a transition to a new energy system based on renewable sources and net-zero utilization systems is made. Another response is to push our previously destructive technological prowess further so as to make it ecologically beneficial. Through further technological innovation humankind can repair and enhance ecosystems so that they will be less susceptible to human stressors and more resilient in future interactions with our rapacious species. On this view, humans should see themselves not as nature’s citizens and trustees, but as nature’s designing architects, fashioning better forms of synthetic life and genetically driving evolution in better ways through anthropogenic selection. Fulfillment of human needs can be done without drawing so heavily on resources offered by natural systems. Ethical responsibility calls upon humanity to seek technological innovation, and the enhancement of the natural with the artificial, not to restrain it. The articles in the section of the encyclopedia devoted to ethics represent the dialogue and debate between these two broad perspectives, each of which draws lessons concerning ethical responsibility from the Anthropocene reality, but prescribe different practical approaches for the near-term future. These articles reflect a spectrum of viewpoints concerning how best to understand the nature of the ethical responsibility concerning the ecological and planetary effects of the use of human power. They also confront the question of how much of a discontinuity in cultural, philosophical, and religious traditions is presented by the new Anthropocene awareness and earth systems science. Will it be possible to revise traditional values and norms, such as liberty and human rights or beneficence and virtue, so that they guide behavior in ways that are appropriate for new conditions for the survival and flourishing of life, including human life? If not, what new kinds of values and moral ideas will be developed to take the place of outmoded and displaced notions? Articles on key concepts such as beneficence, jurisprudence, justice, rights, liberty, obligation, solidarity, and virtue wrestle with this question. Other articles look at new ways of understanding reality that can be helpful for life in the Anthropocene by drawing on major religious traditions, such as Buddhism, Judaism, Christianity, and Taoism, or by drawing on thinking in cosmology and contemporary forms of spirituality. Still others focus on specific experiences that human beings may encounter in the future and ethical ways to respond to them such as, aging, disasters and public health emergencies, pandemics and infectious disease, population control, assessing risk, experiencing vulnerability, and suffering. Finally, several articles address the implications of the Anthropocene perspective for past work in environmental and conservation ethics and bioethics, including adaptive ecosystem management, water management, biodiversity conservation, ecological governance, precaution, and biotechnologies.

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Conclusions The natural world, as it was even 50 years ago, is rapidly vanishing. That is the take-home message of the Anthropocene. We are ostensibly intelligent enough to invent new technologies designed to more efficiently clear forests to make way for cattle ranches, developments, vast tree and palm oil plantations; create more durable plastics that will take thousands of years to decompose; and develop more sophisticated ways of extracting fossil fuels. Predictably, we often always do not have the foresight to comprehend the consequences of our actions, until a nuclear-powered electrical generator plant melts down, or the biota inhabiting the lakes of an entire region die from acid rain, or until iconic animal species (many megafauna) are poised on the knife-edge of extinction. In the face of such catastrophic human impacts on the planet, do official names for an era really matter? Whether historical geologists and stratigraphers accept the Anthropocene as a legitimate geological period is almost irrelevant in the face of this human despoiling of the planet. Imagine a group of geologists attempting to steer a flimsy wooden boat down a river full of rapids and boulders. When the inevitable happens, and a large boulder tears a hole in the bottom of the boat, the geologists could spend the next few minutes debating whether that particular boulder was made of granite, shale, or basalt, but they would be much better off taking action to keep the boat from sinking! Thus, it will not matter to most people whether we affix a geologic period name to the modern era, except that we humans seem to have an inherent need to pigeon-hole the world around us, in order to make sense of it. The word “Anthropocene” should serve as a red flag, warning the human race that we must focus our energies and resources to change the way we do things, before we make the world uninhabitable for our fellow creatures, and, ultimately, for future generations to come.

See also: Basis for Establishment of Geologic Eras, Periods, and Epochs; Finding a “Golden Spike” to Mark the Anthropocene.

References Burkhead NM (2012) Extinction rates in North American freshwater fishes, 1900–2010. BioScience 62: 798–808. European Environment Agency (2001) Late lessons from early warnings: The precautionary principle 1896–2000. Environmental Issue Report 22: 209 pp. www.eea.europa.eu/ publications/environmental_issue_report_2001_22. European Environment Agency (2013) Late lessons from early warnings: Science, precaution, innovation. EEA Report 1: www.eea.europa.eu/publications/late-lessons-2, 760 pp. Gardiner SM (2011) A perfect moral storm: The ethical tragedy of climate change. New York: Oxford University Press. Gert B and Gert J (2016) The definition of morality. In: Zalta EN, et al. (eds.) The Stanford encyclopedia of philosophy. Stanford: Stanford University. https://plato.stanford.edu/archives/ spr2016/entries/morality-definition/. Hamilton C, Bonneuil C, and Gemenne F (eds.) (2015) The anthropocene and the global environmental crisis. New York: Routledge. Ibisch PL, Hoffman MT, Kreft S, Pe’er G, Kai V, Biber-Fredenberger L, DellaSala DA, Vale MM, Hobson PR, and Selva N (2016) A global map of roadless areas and their conservation status. Science 354(6318): 1423–1427. Loeb AP (1999) Paradigms lost: A case study analysis of models of corporate responsibility for the environment. Business and Economic History 28(2): 95–106. Millennium Ecosystem Assessment (2005) Ecosystems and human well being: Synthesis. Washington, DC: Island Press. Perrings C, et al. (2010) Ecosystem services for 2020. Science 330: 323–324. Primack RB (2014) Essentials of conservation biology, 6th edn. Sunderland, MA: Sinauer Associates. Sachs NM (2011) Rescuing the strong precautionary principle from its critics. University of Illinois Law Review 2011: 1285–1338. Sandom C, Faurby S, Sandel B, and Suenning JC (2014) Quarternary megafauna extinctions linked to humans, not climate change. Proceedings of the Royal Society B. https://doi.org/ 10.1098/rspb.2013.3254. Vitousek PM, Erlich PR, Erlich AH, and Mason PA (1986) Human appropriations of the products of photosynthesis. BioScience 36: 368–373. Williams JW, Jackson ST, and Kutzbach JE (2007) Projected distributions of novel and disappearing climates by 2100 AD. Proceedings of the National Academy of Sciences 104: 5738–5742. Winemiller KO, et al. (2016) Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong: Basin-scale planning is needed to minimize impacts in mega-diverse rivers. Science 351: 128–129.

Relevant Websites https://www.journals.elsevier.com/anthropocene/. http://www.smithsonianmag.com/science-nature/what-is-the-anthropocene-and-are-we-in-it-164801414/. http://ngm.nationalgeographic.com/2011/03/age-of-man/kolbert-text. https://dotearth.blogs.nytimes.com/category/anthropocene-2/. http://anthropocene.info/. http://info.craftechind.com/blog/bid/392608/Plastic-Manufacturing-Past-Present-and-Future.

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Basis for Establishment of Geologic Eras, Periods, and Epochs SA Elias, Royal Holloway, University of London, Egham, United Kingdom © 2018 Elsevier Inc. All rights reserved.

Introduction A great deal of debate is currently going on among geologists, concerning the legitimacy of the Anthropocene as a geologic epoch. This topic is discussed at great length in other articles of this section, but it is worth taking a step back from the controversy, and considering the history and current rules of establishment of formal divisions in geologic history of the planet. It is probably fair to say that no one paid much attention to this subject until about 400 years ago. Prior to that, religious belief—not science—governed the way people in Europe thought about geologic history. The development of the scientific disciplines in the late 18th and 19th centuries was a time when people started to try to make sense of the world around them by classifying and categorizing nature. It appears that the human mind can make better sense of the world if it can pigeon-hole the rocks, soils, bodies of water, plants, and animals of the planet. In the biological sciences, the classification breakthrough came with Carl von Linné, the Swedish botanist who developed the system of binomial nomenclature. In this classification system, the first part of the name identifies the genus to which the species belongs and the second part identifies the species within that genus. When Linnaeus (the Latinized version of Linné) published his book, Systema Naturae in 1758, he divided organisms into two kingdoms: the Animal Kingdom and the Plant Kingdom. His classification scheme was based on five levels: kingdom, class, order, genus, and species. He gave scientific names to about 10,000 species of plants and animals, including most of the common species known from Europe at that time. Another vital concept in the biological sciences is the use of type specimens in museums. Type specimens are generally set aside by the person (author) who named the species. These specimens typify the species, and are carefully preserved in museum collections so that future researchers will have access to the established, bona fide representative. Interestingly, geologists adopted this concept when they started designating type localities for the beginning or end of geologic periods and epochs. In one sense, all classification schemes devised by humans to describe the natural world are artificial constructs. They are models of nature—not nature itself. No model is perfect. In other words, we do not and cannot know everything about nature; we can only describe it as best we can, and then be prepared to modify our classification schemes when new data come to light. For instance, some corrections to biological classification schemes based on physical characteristics have had to be made after species’ genomes were worked out in recent decades. In most cases, these corrections to previous classifications have been relatively minor. So even if our classification models are imperfect, they can still be instructive. They help us make sense of the natural world. As such, the classification schemes of 18th and 19th century scientists were a vital step forward for all the natural sciences. What follows is a description of how geologists developed their classification scheme for the rock formations of the planet.

History of Establishing Geologic Eras, Periods, and Epochs At the beginning of the 19th century, science itself was rapidly changing. Up until that time, scholars who performed scientific research were mostly generalists who dabbled in many different fields. They looked upon themselves as natural historians, studying the workings of the natural world, as their whimsy led them. The early 19th century saw the beginnings of specialization in science. As the level of scientific knowledge was rapidly increasing, it was no longer possible for individual scholars to keep abreast of all the new discoveries. People began to devote their time and energy to one or just a few lines of research. This new, focused style of scientific study brought great leaps forward for science as a whole (Elias, 2013). Until the Renaissance, Europeans held to the literal beliefs of the biblical book of Genesis and considered that the Earth had been created in 6 days—intact and complete, with no subsequent changes except those brought about by the flood survived by Noah. As we shall see, the concept that the planet is not immutable, and that the geologic processes observed today have shaped the rock formations exposed around the world, was slow to take shape. The first people who studied the geological relationships between different rock units were miners, since their success was based on their ability to extract valuable minerals from otherwise worthless bedrock formation. In the 1500s and 1600s, the fledgling European interest in natural history included the first systematic studies of relationships between rock types. The observations of mining engineers were key to the establishment of systematic geology. One of the pioneers in this endeavor was the Danish natural historian, Nicolas Steno (Fig. 1). In 1669, he described two basic geologic principles. The first stated that sedimentary rocks are laid down in a horizontal manner, and the second stated that younger rock units were deposited on top of older rock units. Half a century later, an Italian mining engineer, Giovanni Arduino (1714–95), distinguished four orders of strata comprising all of Earth’s history: Primary, Secondary, Tertiary, and Quaternary. Arduino (Fig. 1) distinguished four separate stages or “orders” which he recognized on the basis of very large strata arranged one above the other. These four “orders” were expressed regionally in Italy, as the Atesine Alps, the Alpine foothills, the sub-Alpine hills, and the Po River plain, respectively. This classification scheme did not stand the test of time, but it established an important principle (University of California, Berkeley, 2016).

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Fig. 1 Natural historians who helped establish the principles of geology.

Near the end of the 18th century, a British natural historian, James Hutton (Fig. 1), published a book entitled “Concerning the System of the Earth, its Duration and Stability.” This book contained a better-defined set of geologic principles, based on the following observation: “The solid parts of the present land appear in general, to have been composed of the productions of the sea, and of other materials similar to those now found upon the shores.” Based on this, he concluded the following (Hutton, 1795): 1. That the land on which we rest is not simple and original, but that it is a composition, and had been formed by the operation of second causes. 2. That before the present land was made, there had subsisted a world composed of sea and land, in which were tides and currents, with such operations at the bottom of the sea as now take place. 3. That while the present land was forming at the bottom of the ocean, the former land maintained plants and animals; at least the sea was then inhabited by animals, in a similar manner as it is at present. Hutton thus concluded that the greater part of our land, if not the whole had been produced by operations natural to this globe; but that in order to make this land a permanent body, resisting the operations of the waters, two things had been required: 1st, The consolidation of masses formed by collections of loose or incoherent materials; 2ndly, The elevation of those consolidated masses from the bottom of the sea, the place where they were collected, to the stations in which they now remain above the level of the ocean.

This concept, now known as “Uniformitarianism,” was amplified by British geologist Charles Lyell (Fig. 1) in the early 1800s. This was the idea that natural geologic processes were uniform in frequency and magnitude throughout time. Once this principle became established in the 19th century, natural historians and budding geologists began to classify rock types and attempt to place them in an order. The guiding principle of this classification scheme was that the oldest rocks would have either no signs of fossil life, or the most primitive forms of life (i.e., evidence of one-celled plants or animals). The founder of this concept was English geologist, William Smith (Fig. 1), who was a surveyor and engineer who worked on road and canal projects, and mines. His work gave him ample opportunity for observing rock strata and collecting fossils, and he started arranging his fossil collection according to what we would now call their stratigraphic horizons. In 1799 he devised a table listing the different types of rock strata of southern England, along with their characteristic fossils. He then embarked on the huge project of trying to identify and enter on a colored map the strata of the whole of southern Britain. This single-handed, hand-painted, map was issued in 1815. But the intellectual elite of the Geological Society (founded 1807) hardly gave him credit for this, even though their subsequent map made use of some of his results.

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Fig. 2 The geologic eras and periods showing major biological and environmental characteristics of the periods and the authors and dates of their formal description.

The major subdivisions (eras) of the stratigraphic column (Paleozoic, Mesozoic, and Cenozoic) were proposed by John Phillips in 1840 (Fig. 2). The Paleozoic, or “time of ancient life,” was defined as the first geologic era, characterized by the development of the earliest forms of life visible in the fossil record, including the first fishes, amphibians, reptiles, and land plants. The Mesozoic, or “middle geologic era,” was characterized by the development and extinction of the dinosaurs and the development of the first birds, mammals, and flowering plants. The Cenozoic, or “recent geologic era,” was characterized as the time of the full development of birds, mammals, and flowering plants. The Paleozoic Era is subdivided into six periods: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The entire era spans about 300 million years and saw the development of life from marine invertebrates in the earliest stages (Cambrian) through to the development of bony fish, amphibians, and the first large reptiles on land (Permian). The Mesozoic Era is divided into three periods, all characterized by the rise and increasing dominance of dinosaurs on land, but the first flowering plants and mammals also arose toward the end of the era. The Cenozoic Era is divided into the Tertiary and Quaternary Periods— the only remnants of Arduino’s classification scheme. The Cenozoic is characterized by the dominance of mammals and angiosperms on land. One might have thought that the designation of geologic eras would have led to the creation of subdivisions (periods) within the eras, but actually it was the other way around. As shown in Fig. 2, most of the geologic periods were named in the 1820s and 1830s, a decade or more before Phillips proposed the geologic eras. It is also useful to note that the scientists who proposed geologic eras and periods had no idea of the age of the deposits they were describing—only their stratigraphic position in relation to one another (i.e., the Cambrian comes before the Ordovician, the Triassic comes before the Jurassic, etc.). It was not until the early 20th century

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Fig. 3 Geological epochs of the Tertiary Period showing major biological and environmental characteristics of the epochs.

that any absolute dates could be ascribed to the various eras and periods. This was made possible by the discovery of radioactive elements, and their rates of decay, including the work of Arthur Holmes. During the 19th century, geologists generally rejected the church’s view as expounded by Archbishop Ussher (1650) that the Earth was about 6000 years old, and most held that the planet formed many millions of years ago, but the actual age of the Earth was the subject of considerable debate until radiometric dating became available. Another point worth noting is that the theory of evolution propounded by Charles Darwin (1859) came well after most of the geologic periods were defined on the basis of the fossil record. The geologists knew that whole groups of organisms had been replaced by other groups in the different intervals of the deep past, but they had little or no idea of the biological mechanism by which these changes took place. Within geologic periods, there are finer subdivisions called epochs. The creation of these finer divisions was necessary because many important geological, environmental, and biological changes took place within the tens of millions of years associated with geologic periods. The younger the period, the more scientists have been able to reconstruct about their environmental and biological history. For instance, the Tertiary Period spans about 62 million years of Earth history, during which many dramatic changes took place on this planet (Fig. 3). The Paleocene Epoch spanned the interval from roughly 65 to 55 million years ago

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(Hooker, 2005). The asteroid collision that caused a mass extinction at the end of the Cretaceous period devastated life on Earth, and it took several million years for new forms to evolve and diversify. New groups of marsupial and placental mammals flourished in the middle Paleocene, but there was another extinction event at the end of the epoch. The Eocene Epoch, the longest of the Tertiary Period, saw some very warm climatic conditions, tied with the expansion of tropical forests to the middle latitudes. In contrast, the Oligocene Epoch included large-scale cooling, accompanied by the extinction of both marine invertebrates and terrestrial mammal groups. This was followed by the Miocene, which is marked by an interval of global warming at the beginning, accompanied toward the middle and end of the epoch by the expansion of grasslands for the first time in geologic history. The presence of grasslands fostered the evolution of grazers, including the hoofed mammals, or ungulates. There are two major groups of ungulates: the odd-toed ungulates such as horses and rhinoceroses, and the even-toed ungulates such as cattle, pigs, giraffes, camels, deer, and hippopotamus. The last Tertiary epoch was the Pliocene, which spans the interval from about 5 million to about 2.6 million years ago. The Pliocene saw the gradual decline of global temperatures that led to the subsequent onset of glaciations that characterize the Pleistocene Epoch of the Quaternary Period. The Pleistocene sequence of glacial and interglacial oscillations ended about 11,700 years ago. The current interglacial warm interval is known as the Holocene epoch.

Links With Mass Extinctions The delineation of many geologic periods and epochs has been based on mass extinction events. During Earth’s history, there have been five major mass extinction events, including those demarking the boundaries between the Ordovician and Silurian periods, the extinction at the end of the Devonian Period (three-quarters of known species died out), the mass extinction at the end of the Permian Period (96% of known species became extinct), the extinction that marks the Triassic–Jurassic boundary (eliminated many of the primitive dinosaur groups), and the end-Cretaceous extinction (end of the dinosaurs, and also many groups of marine invertebrates). These enormous extinctions are thought to have been brought about by a wide variety of causes, including large-scale environmental change (global warming or cooling), periods of extreme volcanism, and asteroid impacts. Whatever their cause, these extinction events are clearly marked in the geologic record because the fossil assemblages that typified each geologic period disappeared, and were replaced by whole new suites of species in fossil assemblages preserved rocks deposited a few million years later. The only prehistoric large-scale extinction that has occurred within modern human history has been the extinction of megafaunal mammals toward the end of the last glaciation. Megafauna are defined as animals with an adult weight of at least 44 kg. This extinction event is covered in an article by Haynes (2017). One of the aspects that convinces many scientists of the validity of the Anthropocene Epoch is that we are now experiencing what has been called the Sixth Mass Extinction. According to a recent appraisal of the situation by Ceballos et al. (2015), modern extinction rates are extremely high, vastly exceeding the background rates of extinction.

Establishment of Geologic Boundaries Through the last 150 years, there has been considerable debate about the exact timing of the boundaries of geologic eras, periods, and epochs. More refined radiometric dating techniques have helped to settle some of these thorny issues, but the question of which geologic site best exemplifies these boundaries has remained contentious. In recent decades, the geological community has settled upon a procedure meant to resolve these debates, once and for all. This has been the designation of global stratotype sections and points (GSSPs). A point of some confusion for people who are not stratigraphic geologists is that the two systems of classifying units of Earth history use different names for these units. Geochronologic units are basically units of time, including eons, eras, periods, epochs, and ages (Fig. 4A). Chronostratigraphic units are essentially time-rock units, including eonothem, erathems, systems, series, and

Fig. 4 Comparison of geochronologic units (A) with chronostratigraphic units (B).

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stages (Fig. 4B). Geochronology expresses the timing or age of events (depositional, diagenetic, biotic, climatic, tectonic, and magmatic) in Earth’s history. Geochronology can also qualify rock bodies, stratified or unstratified, with respect to the time interval(s) in which they formed. Chronostratigraphy is an important branch of stratigraphy because the age correlations derived are crucial to drawing accurate cross sections of the spatial organization of rocks and to preparing accurate paleogeographic reconstructions. Chronostratigraphy includes all methods for establishing the relative time relationships of stratigraphic successions regionally and worldwide (e.g., biostratigraphy, magnetostratigraphy, chemostratigraphy, cyclostratigraphy, and sequence stratigraphy). It is also used for formally naming bodies. Both hierarchies continue to be used, as recommended by a formal vote of the International Commission on Stratigraphy in 2010. The geological context helps determine the appropriate usage of the component units. To further clarify, chronostratigraphic units are geological materials. In the chronostratigraphic context, fossils of Tyrannosaurus rex are found in the Upper Cretaceous series (i.e., the bedrock units from the Upper Cretaceous). In contrast, geochronological units are periods of time. In geochronologic context, T. rex lived during the Late Cretaceous Epoch. The following discussion of stratigraphic subdivisions uses the chronostratigraphic terminology.

Global Stratotype Sections and Points In recent decades, good progress is being made with definition of GSSPs that establish the lower boundary of all geological stages, using discrete fossil and physical events that correlate well in the rock record (Gradstein and Ogg, 2005). Each set of GSSPs defined a division of geologic time. More than 25 years ago, the first “golden spike” established the boundary between the Devonian and Silurian. The type locality was a site in the Czech Republic. As with all golden spike localities (Fig. 5), a bronze plaque marks the

Fig. 5 GSSP golden spike localities, showing the bronze plaque at each site. (A) GSSP site in the Ediacara Hills in the Flinders Range of South Australia. The bronze plaque marks the golden spike marking the end of the Precambrian Era (photo from Wikipedia); (B) GSSP site in Guadalupe Mountains National Park, Texas, marking the beginning of the Wordian age, a subdivision of the Guadalupian Epoch in the Permian Period that spans the interval from 268.8 to 265.1 million years ago (photo by the National Park Service, United States); (C) GSSP site near Pueblo, Colorado, marking the beginning of the Turonian age, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.9  0.8 and 89.8  1 Ma (million years ago) (photo by Brad Sageman, Northwestern University); (D) GSSP site in Guadalupe Mountains National Park, Texas, marking the beginning of the Capitanian age, immediately above the Wordian age (photo by the National Park Service, United States).

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exact position of the Silurian–Devonian boundary at the site. The GSSP concept has gained wide acceptance among geologists because the boundary of a stage can now be defined with multiple criteria that are synchronous throughout the world. These criteria include geomagnetic reversals, global changes in a stable isotope values, and the first appearance of one or more prominent and widespread fossil taxa. At present, 69 GSSPs have been defined (International Commission on Stratigraphy, 2016). A few examples serve to demonstrate the variety of criteria used to set these boundaries. The golden spike for the Holocene has been established from an ice sample taken from 1492.45 m depth in the NGRIP2 borehole, located at 75.1000 N 42.3200 W in Greenland, marking the point 11,700 years ago when the Younger Dryas cooling gave way to the Holocene warming. This GSSP was ratified by the International Commission on Stratigraphy in 2008. The golden spike setting the boundary between the Tertiary and Quaternary at 2,580,000 years ago is located at a site in Sicily. It is set on the basis of two criteria: a magnetic reversal boundary (the base of the Matuyama polarity) and the extinction of two marine algal species. Further back in time, the golden spike separating the Cretaceous from the Paleocene (hence, separating the Mesozoic from the Cenozoic) is marked at a site called El Kef in Tunisia. At this site there is a layer rich in the mainly extra-terrestrial element, iridium. This iridium almost certainly was deposited when an asteroid collided with Earth at the Yucatan Peninsula, Mexico. As yet there has been no GSSP to demarcate the Cretaceous–Jurassic boundary, although there are three candidate sites being debated. The golden spike marking the Triassic–Jurassic boundary is at a site in the Austrian Alps, where a group of ammonites (primitive cephalopods) make their first appearance at the base of the oldest Jurassic strata. Moving deeper in geologic time, nearly all the GSSPs are defined on the basis of first or last appearance of various types of marine fossils, such as ammonites, brachiopods, trilobites, conodonts, and graptolites (Fig. 6). The exception to this formula is the Precambrian Era. Although the Precambrian contains more than 85% of Earth history, its fossil record is poor. The majority of Precambrian fossils are stromatolites. Because of their great age, these fossils are often heavily altered (metamorphosed) or so deeply buried that they are extremely difficult to find. Primitive marine fossil cells have been discovered at a few sites, such as the 2.0 billion year-old Gunflint Formation in Canada. The earliest life forms were prokaryotes (eubacteria or archaea) that evolved in the seas, as early as 3.8 billion years ago. So the subdivisions of the Precambrian are all defined by radiometric dating, not by fossil types.

Is the Anthropocene Different? The articles in this section by Zalasiewicz and by Maslin, and a previous publication by Zalasiewicz et al. (2013), argue for the formal designation of the Anthropocene as a formal geological epoch, following the Holocene, while the article by Finney presents the arguments against this formal designation. Many of my colleagues in Quaternary science are against the formal designation of the Anthropocene, yet all of them agree that humans have been changing the planet in significant ways in recent times. Perhaps their opposition to the formal designation of the Anthropocene comes from a deep-seated adherence to the classification model discussed earlier. The Anthropocene does not fit the classical model, which has always applied to past events—never to current ones. Everyone accepts that the Holocene is a bona fide epoch that is separated from the Pleistocene on the basis of a large-scale climatic change that signified the end of the latter. Interestingly, the current global warming is on a likely trajectory to become an even more dramatic climate change than the one designated at the end of the Pleistocene, but it has not yet reached this level of change, so many geologists are loath to place the Anthropocene in the same kind of classification scheme as previous epochs. Likewise, we are on a trajectory to bring about a sixth mass extinction event because of anthropogenic change to the planet, including not only climate change but also massive reductions in the size and quality of natural habitats. As discussed earlier, many of the geological periods and epochs have been defined on the basis of mass extinctions, but because the current extinction event has not reached its zenith, many geologists do not consider it as suitable evidence for a new epoch. As discussed earlier, all classification schemes are artificial: they are human constructs designed to help us make sense of the world around us. In that sense, it scarcely matters what we call the current time period. Emissions of atmospheric CO2 will not change, simply because we have decided to name our era something different, nor will species extinction rates be any different— except for one thing. By giving the current time period a name that clearly indicates the source of the planet’s woes, human domination, we may find it easier to convince people of the need to take action to lessen the extent of human impacts on the planet. The need to pigeon-hole the natural world in order to make sense of it comes into play, here. If we get used to thinking of the times we live in as distinct from all previous times in human history, because of the very high level of human impact on the modern world, then perhaps everyone, from ordinary citizens of countries to their national leaders and international organizations, will be convinced of the need to change what we are doing. Linnaeus gave our species the name Homo sapiens, which is Latin for “wise man.” Are we wise enough to take the immediate actions needed to limit the damage of our species on the planet’s natural systems, or will we carry on exploiting Earth’s resources and polluting the environment to the point of no return? Should that day arrive, historians will probably look back on the debate over formal designation of the Anthropocene as an exercise in rearranging the deck chairs on the sinking Titanic.

See also: The Anthropocene: How the Great Acceleration Is Transforming the Planet at Unprecedented Levels.

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Fig. 6 Fossil specimens representing invertebrate groups typically used to define geologic units. (A) Peltoceratoides, an ammonite (Virtual Fossil Museum website); (B) Spiriferina rostrata, a brachiopod (Wikimedia); (C) Lochriea sp., a conodont (D&D Fossils website); (D) reconstruction of entire conodont (Evolution Institute); (E) Didymograptus murchisoni, a graptolite (Wikimedia); (F) reconstruction of entire graptolites (Dreamstime.com); (G) Walliserops trifurcatus, a trilobite (image from i.imgur.com).

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References Ceballos G, Ehrlich PR, Barnosky AD, García A, Pringle RM, et al. (2015) Accelerated modern human-induced species losses: Entering the sixth mass extinction. Science Advances 1: 5 pp. Elias SA (2013) Introduction: History of Quaternary science. In: Elias SA and Mock CJ (eds.) Encyclopedia of Quaternary Science, Second Edition, pp. 1–8. Amsterdam: Elsevier. Gradstein FM and Ogg JG (2005) Time scale. In: Selley RC, Cocks RM, and Plimer IR (eds.) Encyclopedia of geology, pp. 503–520. Amsterdam: Elsevier. Haynes G (2017) The evidence for human agency in the Late Pleistocene megafaunal extinctions. Encyclopedia of the Anthropocene, in press. Hooker JJ (2005) Tertiary to present: Paleocene. In: Selley RC, Cocks RM, and Plimer IR (eds.) Encyclopedia of geology, pp. 459–465. Amsterdam: Elsevier. International Commission on Stratigraphy (2016) GSSP table—All periods. http://www.stratigraphy.org/gssp/. University of California, Berkeley (2016) The geologic time scale in historical perspective. http://www.ucmp.berkeley.edu/exhibit/histgeoscale.html. Zalasiewicz J, Cita MB, Hilgen F, Pratt BR, Strasser A, et al. (2013) Chronostratigraphy and geochronology: A proposed realignment. GSA Today 23: 4–8.

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Finding a “Golden Spike” to Mark the Anthropocene SA Elias, Royal Holloway, University of London, Egham Hill, United Kingdom © 2018 Elsevier Inc. All rights reserved.

Introduction A great deal of debate is currently going on among geologists, concerning the legitimacy of the Anthropocene as a geologic epoch. In recent decades, good progress is being made with definition of Global Stratotype Sections and Points (GSSPs) that establish the lower boundary of all geological stages, using discrete fossil and physical events that correlate well in the rock record (Gradstein and Ogg, 2005). Each set of GSSPs defines a division of geologic time. More than 25 years ago, the first “golden spike” established the boundary between the Devonian and Silurian. The type locality was a site in the Czech Republic. The GSSP concept has gained wide acceptance among geologists because the boundary of a stage can now be defined with multiple criteria that are synchronous throughout the world. These criteria include geomagnetic reversals, global changes in a stable isotope values, and the first appearance of one or more prominent and widespread fossil taxa. The Anthropocene only fits one of these criteria. Since the 1950s, there have been marked, world-wide changes in stable (and radioactive) isotope values, clearly signaling dramatic change in the Earth system. But because this is a very recent phenomenon, it has not been marked in the geologic record by the appearance of the fossil remains of newly evolved creatures. Nor have any magnetic reversals taken place to mark the boundary between the Holocene and the Anthropocene. Does the lack of these GSSP elements negate the establishment of the Anthropocene as a distinct geologic epoch? The aim of this article is to examine this issue, in light of the available lines of evidence.

The GSSP Criteria The International Commission on Stratigraphy provides a number of criteria for the establishment of a global chronostratigraphic standard (Remane et al., 1996). These include the following: (1) A GSSP has to define the lower boundary of a geologic stage; (2) The lower boundary has to be defined using a primary marker but there should also be secondary markers (such as fossils, chemical, or geophysical markers); (3) The horizon in which the marker appears should be able to be radiometrically dated; (4) The marker must be regionally and globally cosynchronous and be independent of facies (bodies of sediment recognizable as distinct from adjacent sediments); (5) Sedimentation must be continuous; (6) The sequence should be unaffected by tectonic and sedimentary movements, and metamorphism; (7) The sequence has to be accessible to research, free to access; be located where it can be visited quickly; be kept in good condition (ideally a national reserve), extensive enough to allow repeated sampling and open to researchers of all nationalities. Let us address these criteria one by one, as concerning the Anthropocene. First, we only know of the beginning of the Anthropocene, although the exact start date is still being debated. One of the unique aspects of the Anthropocene, of course, is that it is ongoing. No one can predict when its end may come. Second, there are a number of markers for the lower boundary of the Anthropocene, as discussed in the following sections. There are no unique fossil markers, as these can only apply to previous geologic epochs—not to the present one. This is an aspect of designating the Anthropocene as a formal epoch that forces geologists to “think outside the box.” The Anthropocene straddles the boundary between geology and modern biology, chemistry, and physics. As such, it crosses important scientific boundaries. All other GSSP golden spikes are firmly embedded in the past. The modern aspects of the Anthropocene take the proposed epoch out of the hands of historical geologists and stratigraphers. Perhaps, it should not be surprising that this group of geologists—the ones who have developed the GSSPs for all the ancient geologic eras—are divided when it comes to designating a modern epoch as part of their otherwise ancient scheme. Third, radiometric dating is, of course, essential to the establishment of the chronologies of ancient geologic intervals. Without a chronologic framework, the designation of former geologic periods is purely a descriptive exercise. As discussed by Elias (in press) in a related article regarding the basis for establishment of geologic eras, the laws of superposition (older rocks and fossil beds lie below younger beds) allowed quite a reliable sequence of geologic periods to be fleshed out in the 19th century, long before the invention of radiometric dating. The dating methods developed in the 20th century allowed geologists to place the alreadydescribed sequences into an absolute chronological context. Fourth, a number of the Anthropocene markers discussed later are either regionally or globally synchronous, and they are independent of facies, that is, they occur in lots of kinds of depositional environments (lake sediments, terrestrial sediments, ocean sediments, and polar ice cores).

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Fifth, continuous sedimentation is another feature that rely only applies to ancient GSSPs. In other words, if there are gaps in sedimentary records before or after the geologic event that distinguishes a certain geologic period, then stratigraphers are unable to tell whether these gaps hide the timing of the true beginning or end of an era. Quite obviously, this does not apply to current events. We do not have to investigate the geologic record to find out when the Anthropocene started, because it began in recent memory of humans and has been documented by the historic record of various branches of science. All other geologic epochs were prehistoric. Sixth, because the Anthropocene started recently, its record in the sediments has not been disturbed by tectonism or metamorphism, both of which phenomena occur on time scales of hundreds of thousands to millions of years. Likewise, access to sediments (terrestrial, freshwater, oceanic sediments, and polar ice records) is the most widespread and extensive of any geologic epoch. This recitation of facts, comparing the criteria for GSSPs of the geologic past with the known characteristics of the Anthropocene, may seem overly pedantic, but these are the criteria used by stratigraphers and historical geologists to set the golden spike boundaries. The criteria establish a philosophical boundary that has been hard for many geologists to cross. Many of my colleagues in quaternary science are against the formal designation of the Anthropocene, yet they all agree that humans have been changing the planet in significant ways in recent times. Perhaps their opposition to the formal designation of the Anthropocene comes from a deep-seated adherence to the classification model discussed earlier. The Anthropocene does not fit the classical model, which has always applied to past events—never to current ones. Everyone accepts that the Holocene is a bona fide epoch that is separated from the Pleistocene on the basis of a large-scale climatic change that signified the end of the latter. Interestingly, the current global warming is on a likely trajectory to become an even more dramatic climate change than the one designated as the end of the Pleistocene, but it has not yet reached this level of change, so many geologists are loath to place the Anthropocene in the same kind of classification scheme as previous epochs. Likewise, we are on a trajectory to bring about a sixth mass extinction event because of anthropogenic change to the planet, including not only climate change, but also massive reductions in the size and quality of natural habitats. As discussed in the article (Elias, in press), on the basis for establishment of geologic eras, periods, and epochs, many of the geological periods and epochs have been defined on the basis of mass extinctions, but because the current extinction event has not reached its zenith, many geologists do not consider it as suitable evidence for a new epoch.

Lines of Evidence The Geology section of this encyclopedia includes more than 20 articles presenting different lines of evidence supporting the establishment of the Anthropocene epoch. It is beyond the scope of this article to review all of these lines of evidence. What follows is a brief summary of just some of them. The Anthropocene “signal” is strong, and does not need a great deal of amplification.

Chemical Contaminants As discussed by Gałuszka and Migaszewski (in press), the chemical signal for the Anthropocene begins with the addition of chemical pollutants into the environment in the 1950s. Among these are a variety of inorganic pollutants that are exerting high levels of impact on geochemical cycles. Increased anthropogenic fluxes have been recorded for the major nutrient elements carbon, nitrogen, and phosphorus (C, N, and P), as well as trace metals silver, chromium, copper, nickel, lead, and zinc (Ag, Cr, Cu, Ni, Pb, and Zn). Artificial long-lived radioisotopes introduced to the environment during atmospheric nuclear weapons testing are also markers of the beginning of the Anthropocene, including two isotopes of plutonium: 239Pu and 240Pu. The presence of 239Pu and 240 Pu in sediments has been marked since 1952 and will be detectable for at least 100,000 years for 239Pu and 30,000 years for 240Pu (Waters et al., 2016). The onset of the Anthropocene, if set in the 1950s, is thus extremely well marked by the presence of these manmade plutonium isotopes. The use of nitrogen in chemical fertilizers since the 1950s has been so great that the nitrogen cycle has been altered more than any other basic element cycle (Fig. 1). Human production of reactive nitrogen is currently estimated to be about 1.7 billion metric tons per year (Galloway et al., 2003), and the global use of nitrogen fertilizers is increasing by about 15 million metric tons (MMT) per year. The global production of aluminum has likewise boomed since the 1950s. Since the invention of electrolytic Hall–Heroult process in the 1890s, the production of this metal has steadily increased, reaching half a billion tons in 2010. About 98% of this production dates from 1950 onward. The use of leaded gasoline until the 1970s and 1980s caused global lead pollution at record levels. Even after leaded gasoline was banned in most countries, the amount of lead in the environment remains more than 100 times the background level in Europe and North America (Marx et al., 2016). Persistent organic pollutants (POPs) are organic chemical compounds that are toxic, accumulate in animal tissues, and are resistant to degradation for decades to perhaps centuries. Some of these compounds have been accidentally released into the environment as pollutants (polycyclic aromatic hydrocarbons (PAHs), dioxins); others have been intentionally introduced into the environment as pesticides (organochlorine compounds) or as coolants for electrical equipment and other uses (polychlorinated biphenyls, PCBs; Fig. 2). PAHs are a byproduct of the incomplete combustion of fossil fuels. In North America and Europe, the maximum concentrations of PAHs have been found in sediments from the 1950s—another indicator of the start of the Anthropocene. Since that time, the development of improved technologies to remove these pollutants from fossil fuel combustion in engines and in industry, and the enforcement of clean-air laws in many countries, has brought PAH levels down considerably in Europe and North America. Because

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Fig. 1 Map of the United States, showing runoff of nitrogen from the cities and agricultural lands in the Mississippi River drainage. Most of the nitrogen from farms comes from chemical fertilizer, from ranches in the western states cattle feedlots, and from cities waste water. Note that nitrogen concentrates in the Mississippi River delta region, where it causes marine algal blooms. From NOAA.

Fig. 2 PCB contamination is high in the Housatonic River and New Bedford Harbor, Massachusetts. PCBs were banned in the United States in 1979 amid evidence that these chemicals have unintended impacts on human and environmental health. From U.S. Fish and Wildlife Service.

of the carcinogenic properties of PAHs, PAH pollution remains a serious health problem in the developing world, especially noted in China because of the large number of coal-fired electrical generating plants, petroleum combustion, and plastic manufacturing (Zhang et al., 2012).

Humanly Modified Ground Humanly modified ground consists of settlement debris (Fig. 3), dumped waste, landfill, reclaimed land, cut features, earthworks, cultivation soils, and other kinds of ground significantly modified by humans (Edgeworth, in press). Geomorphologists who have studied this phenomenon surmise that the annual volume of human-induced flows of materials is at least three times greater than the amount of sediment eroded, moved, and deposited by the world’s rivers. But there is a major difference between these anthropogenic and natural processes. Rivers transport sediment loads in a downward direction, whereas humans and their machines frequently raise material up against the force of gravity, constituting an anthropogenic form of geological uplift. Of course people have been extensively modifying landscapes using simpler technology for thousands of years. Possibly the earliest documented land surface transformation by humans was about 10,000 years ago, when agriculture was invented in the Fertile Crescent region (Lev-Yadun et al., 2000). The rise in human population, which was about 1 billion at the start of the Industrial Revolution and reached exponential growth levels after World War II, caused increasing amounts of land to be converted to agriculture, industrial estates, and cities. It is estimated that humanly modified ground in some form covers about half the ice-free terrestrial surfaces of the Earth, with this area expanding rapidly since the 1950s. Human-made surfaces, such as concrete and tarmac, now cover large parts of the surfaces of urban and suburban areas, cladding the ground like a kind of armor. Concrete is the signature building material of the Anthropocene, being used for every kind of building from skyscrapers to parking lots and road tunnels (Waters and Zalasiewicz, in press). The largest concrete structure built thus far is the Three Gorges dam on the Yangtze River in China. The size of the dam is equivalent to a 50-storey building, 1.6 miles long. Its construction used 16 million cubic meters of concrete (Fig. 4). More concrete is now used than all other building materials put together. Annual production was recently estimated at 3.8 billion cubic meters, or 8.78 billion metric tons. With the world population of humans at 7.3 billion, that works out at 1.2 tons of concrete produced per person per year.

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Fig. 3 Cross-section of the ground beneath London’s Liverpool Street Station, showing the sequence of human occupation layers from Roman times onward. From the London Crossrail Project.

Fig. 4 The Three Gorges Dam, Yangtze River, China. This is the largest concrete structure in the world. Photo courtesy of Le Grand Portage.

Isotopic Signatures As discussed by Dean et al. (in press), isotopic signatures in many kinds of sedimentary records document the history of human pollution of the environment. In some cases, such as lead and sulfur, isotopic records detail pollution histories going back millennia. Lead was one of the first metals to be mined by humans. Different lead ores in different parts of the world can be traced from their lead isotope ratios. For example, lead isotopes have shown that between 150 BC and AD 50, the majority of the lead particles deposited on Greenland ice came from Roman lead mines (Fig. 5) in southern Spain. Today, lead isotopes show that a large proportion of the lead pollution in Greenland ice is coming from China. Sulfur isotopes can be used to track pollution because natural (e.g., volcanic eruptions and forest fires) and anthropogenic (e.g., burning of coal in power stations) sources of sulfur often have different isotope ratios. Anthropogenic sulfur emissions are often low in d34S compared with natural sources. Since the 1950s, there was a particular need to understand the sources and changes in sulfur

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Fig. 5 Roman lead ingot found at Heyshaw Bank, Yorkshire, in 1731. The inscription translates to “Emperor Caesar Domitianus Augustus Consul VIII. Caesar Domitianus Augustus VIII” was Roman Consul from late AD 81 to early AD 82. Photo courtesy of the British Museum.

Fig. 6 (A) Coal-fired electrical power plant. One of the by-products of coal combustion of coal is fly-ash. (B) Fly-ash from the burning of coal. (A) From NOAA.

emissions from power stations as acid rain began to pollute fresh waters and damage ecosystems in Europe and North America. Acid rain is caused by a chemical reaction that occurs when sulfur dioxide, nitrogen oxides, and other compounds are released into the air. These substances react with water, oxygen, and other chemicals to form acidic pollution. Carbon and nitrogen isotopes show substantial change since the Industrial Revolution, and especially since the 1950s, related to increased fossil fuel consumption and fertilizer production. There have also been substantial changes to the global carbon cycle because of human activities. Since the 19th century, there has been a substantial decline in atmospheric d13CO2 along with the increase in atmospheric CO2 concentrations, with the trend to lower values accelerating after 1950. The decline in d13CO2 and d14CO2 is known as the Suess effect. It is presumed linked to the burning of fossil fuels with low d13C and d14CO2. Boron isotopes record ocean acidification related to CO2 emissions. Ocean pH, measured directly from seawater samples, can be used to assess acidification trends. Ancient ocean pH can be reconstructed from boron isotopes extracted from calcium-carbonate shells of marine organisms, such as foraminifera and corals that incorporate the borate ion from seawater as they grow. Ocean sediment records show that there has been an increase in ocean acidity since the Industrial Revolution, as CO2 levels have risen. In fact the isotopic record suggests that this change in ocean pH may be the fastest rate of ocean chemistry change in the last 50 million years.

Spherical Carbonaceous Particles Rose (in press) discusses the presence of spherical carbonaceous particles (SCPs) as another Anthropocene marker. SCPs are a component of fly-ash (Fig. 6) and are formed solely from the high temperature combustion of fossil fuels such as coal and oil. The scale of fly-ash particle emissions to the atmosphere is enormous, even from a modern, efficient industrial power station. About 119 MMT of fly-ash are produced annually by the 460 coal-fired power plants in the United States. A 2000-megawatt coal-fired power station, operating for 24 h, consumes over 20,000 metric tons of coal a day. In 2010, 480 MMT of fly-ash was produced in China—10 times the amount produced in all the EU countries. In 2016, Chinese fly-ash emissions are projected to exceed 580 MMT (Wei et al., 2015).

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Fly-ash particles may be transported many thousands of kilometers in air streams prior to deposition. The particles have been found in the most remote regions of the Earth, including ice deposits in Greenland and Antarctica. The SCP record in sediments begins from 1850 to 1900 in most European countries and North America. Significant increases in SCP deposition began in the 1950s. This dramatic rise is linked with the major expansion of coal-fired electrical generation at power stations as a result of a dramatic increase in demand for electricity from commerce, industry, and domestic users. Also, the 1950s saw the greatly increased availability of cheap fuel-oil, leading to the development of the first large-scale oil-fired power stations. As a result, fossil fuel consumption increased rapidly as did power plant emissions to the atmosphere and consequently the distribution and deposition of fly-ash to the Earth’s surface.

Hydrologic Evidence Bridgewater et al. (in press) review the hydrologic evidence for the start of the Anthropocene. Exponential growth in the human population since the 1950s has given rise to large increases in demand for freshwater. Global freshwater resources are finite and vulnerable in many parts of the world. Water resource management provides services and benefits to people, but it also feeds back into the rapidly changing hydrological situation of the Anthropocene. In any situation involving increasing demand of the limited, finite resource, inequalities of resource distribution arise between rich and poor countries. Vörösmarty et al. (2010) state that nearly 80% of the world’s population is exposed to high levels of threat to water security. As the standard of living rises in developing countries, so does their use of fresh water. But this demand is not, as might be expected, just about drinking water. By 2050, global water demand is projected to increase by 55%, mainly due to growing demands from manufacturing, thermal electricity generation, and domestic use. But this increase in global demand flies in the face of water resources that are both finite and diminishing. Not surprisingly, increased economic productivity of human societies comes at a cost to the environment. From an ecological perspective, increasing consumption of freshwater by humans is damaging ecosystem services and biodiversity. Wetlands provide critical habitat for thousands of species of wildlife, and act as giant filter systems to clean the water passing through them, but people have been draining wetlands and rechanneling the water flowing through them for many centuries. According to a global survey by Zedler and Kercher (2005), the remaining areas of global wetland are about half what they were originally. However, an international treaty (the 1971 Ramsar Convention) has helped 144 nations protect the most significant remaining wetlands. The world’s remaining wetlands probably occupy 15 m high) were built over the last 70 years at a rate of >2 day1 and more than half of these have been in China (Syvitski and Kettner, 2011). Concrete is an important component of many large dams, being a suitable material for rapid construction of large containing walls that are mostly stable when exposed to huge volumes of reservoir water. The Three Gorges Dam on the Yangtze River in China (Fig. 5A) is considered the world’s heaviest concrete structure, built from 28 million cubic meters (66 million tons) of concrete. Cement and concrete are increasingly being introduced into the subsurface as either a fill of excavations, notably boreholes, or to line and protect excavations such as tunnels (Fig. 5B), replacing the use of bricks. Modern towns and cities are associated with a complexly engineered substructure of foundations, many of which extend to depths of 20 m in areas of office spaces, museums, underground car parks, warehousing, and so on. This subsurface zone of human interaction includes complex networks of public utility water supply and sewage extraction tunnels, and metro systems, which may incorporate concrete as a significant component. As buildings get ever taller, the foundations of concrete get deeper. For example, the Burj Khalifa in Dubai has foundations to >50 m depth and some 330,000 m3 of concrete was used to construct the tower. Concrete is not widely present in the oceans. On some continental shelves, concrete has been used as part of the hydrocarbon extraction industry. Some 1.3 million cubic meters of concrete has contributed to 20 platforms in the United Kingdom and Norwegian sectors since 1971 and there has been development of concrete oil storage tanks (Mehta and Monteiro, 2006).

Abundance The annual production of Portland cement is estimated at 4.1 billion tons in 2015 (Fig. 6). Initial global figures for cement production of 62.4 million tons in 1926 showed a steady rise until the start of World War II in 1939 and by the end of the war in 1945 global production had fallen by 47% to only 49.5 million tons. Rebuilding after the war contributed to a marked increase in

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Fig. 6 Global production of cement over the last century, derived from United States Geological Survey global cement production statistics which commence in 1926. Approximate global production of concrete is derived by assuming most cement goes into concrete and that 15% of average concrete mass is cement. Both annual and cumulative production amounts are shown (left and right, respectively). Note that the mid-20th century “Great Acceleration” is clearly seen, with increased and ongoing acceleration this century. Reproduced from Gherardi F, Audigane P, and Gaucher EC (2012) Predicting long-term geochemical alteration of wellbore cement in a generic geological CO2 confinement site: Tackling a difficult reactive transport modeling challenge. Journal of Hydrology 420–421: 340–359. http://minerals.usgs.gov/minerals/pubs/commodity/cement/.

cement production, which had increased by an order of magnitude by 1967. Production figures increased year-on-year, except for small and short reductions in output in 1975, 1989, 1992, 1998, and 2015. Approximate global production of concrete (Fig. 6) is derived by assuming most cement goes into concrete and that 15% of average concrete mass is cement (Table 1). This results in an estimated annual production of concrete in 2015 of 27.3 billion tons, at an average of approximately 1.6 m3 per person on the planet, assuming a density of 2375 kg m3 (Table 1). This is more than double the 11 billion tons per year in the mid-2000s (Mehta and Monteiro, 2006) and nine times the magnitude of 3 billion tons produced in the early 1960s and equates with 4 tons per person on the planet per year. Marked inflections in concrete production are seen around 1950, but also around about 1990 (Fig. 6). This may be a conservative estimate. The United States and United Kingdom provide figures for output of cement and aggregates, which are used in concrete manufacture, but also in tarmac and crushed rock fill. This allows an estimate of a multiplication factor of aggregate over cement that evolves with time and is estimated in 2010 to result in an estimate of 90 billion tons (Ford et al., 2012). Whatever multiplier is used to estimate the relationship between cement and concrete, there is no denying in recent decades concrete has been produced in extraordinary quantities. The cumulative total amount produced worldwide is of the order of 500 billion tons (Fig. 6), which is equivalent to about a kilo for every square meter of the Earth, both land, and sea (Waters et al., 2016). Of that, well over 90% has been made since the mid-20th century, and over 50% in the last couple of decades—and its production is still accelerating. Concrete, mortar/cement, and breeze-block material are a significant component of construction and demolition wastes (from 20% to 80%), which in total are estimated to be 900 million tons in the United Kingdom, United States, and Japan alone. It has been estimated that a billion tons of construction and demolition wastes are disposed of annually in road-bases and landfill (Mehta and Monteiro, 2006). Recycling rates vary from country to country, with almost complete recovery in Japan and the Netherlands. Concrete can be broken down into aggregate, especially for road works, but also as an aggregate in new concrete, with up to 30% recycled concrete being acceptable for structural uses. But in many countries, it is sent to landfill or allowed to contribute to the foundations of subsequent building developments.

Future Preservation Potential in the Geologic Record The continued existence of Roman concrete buildings shows the extent to which concrete has the potential to persist above-ground as a coherent lithology for thousands of years. Increasingly, concrete buildings are redeveloped, resulting in concrete debris (masonry) being a common component of artificial deposits within urban areas. The concrete is seen as an inert waste that acts as a suitable foundation for subsequent development. Consequently, thick accumulations may develop with time, as does the likelihood that these deposits will persist over geological time scales. But in such a terrestrial environment, the processes of mechanical attrition or physical and chemical weathering would ultimately lead to the degradation of concrete. Highly porous concrete allows ready penetration of water, resulting in increased rates of both physical and chemical deterioration.

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Fig. 7 (A) Extensive flaking as a consequence of oxidation of rebars, commonly referred to as “concrete cancer”; (B) exudation of water-soluble salts at two distinct joins of concrete panels in a road bridge; (C) development of stalactites along a fracture present in a concrete road bridge constructed in 1997. Photograph © C.N. Waters.

Physical weathering can result from surface wear in response to abrasion (e.g., by vehicular traffic), erosion (through abrasion by particles in a fluid medium, e.g., wind, rivers), or cavitation (e.g., seawalls affected by wave activity). The rate of attrition is reduced in concretes containing abrasion-resistant aggregates. Cracking and ultimately physical disintegration of concrete can also result from excessive structural loading, or seismic disturbance (Fig. 3B). Marked temperature fluctuations (particularly extreme cold or heat) can have a deleterious effect on concrete, with porous concrete particularly prone to freeze–thaw activity in areas of extreme cold. The chemical weathering of concrete may occur in the presence of water, especially sulfate- or chloride-rich groundwaters. The resulting degradation can be evident as expansion and cracking of concrete or the progressive decrease in the strength and loss of mass. Extensive flaking or spalling, commonly referred to as “concrete cancer,” can result from salt crystallization and volumetric expansion through mineral hydration. Alkali–silica reactions in concrete, particularly associated with aggregates that are reactive, are associated with a loss of strength and exudation of viscous fluids, notably in dams and sea walls exposed to humid environments (Mehta and Monteiro, 2006). Iron-based metals present as rebars or mesh within the concrete can corrode and greatly expand in the presence of oxygen and chloride ions is a further common cause of concrete cancer (Fig. 7A). Concrete is an alkaline medium, with phases typically at equilibrium pH value ranges from 12.5 to 13.5 (Mehta and Monteiro, 2006) that is very prone to attack by water ranging in pH from acidic through to even mildly alkaline, and is exacerbated by “acid rain.” Weathered concrete, concrete masonry units (cinder blocks), and masonry commonly develop a white efflorescence coating of natural minerals such as calcite (CaCO3), gypsum (CaSO42H2O), and halite (NaCl) (Hazen et al., in press), reflecting dissolution and transportation of water-soluble salts to subsequently recrystallize at the structure’s surface (Fig. 7B). Calcium hydroxide (portlandite) is highly soluble in pure water, causing leaching of lime which may react with atmospheric CO2 to produce such calcite efflorescence as a crust or stalactites (Fig. 7C). The presence of the tricalcium aluminate monosulfate hydrate in portland cement concrete makes it vulnerable to sulfate attack (Mehta and Monteiro, 2006), notably in areas of pollution associated with combustion of fossil fuels. Sulfate attack results from high-sulfate groundwaters sourced from industrial effluents or decaying organic matter. The sulfate ions may be sourced internally through cement with high sulfate content and through the decomposition and subsequent recrystallization of ettringite (the so-called delayed ettringite formation) (Mehta and Monteiro, 2006). Many of these causes of concrete deterioration may be exacerbated within marine conditions. Over centuries, the primary mineralogy of the concrete will modify to secondary minerals, in the presence of acidic groundwaters. Many of these secondary minerals are also commonly naturally occurring, for example, calcite and Ca-phillipsite, the latter ultimately changing to silica and dawsonite (Gherardi et al., 2012; Fig. 4). This mineral transformation results in an initial rapid fall in porosity, but which subsequently increases (Fig. 4), with the potential of degradation of the concrete in response to these phase changes. This suggests that these anthropogenic minerals might not have potential for long duration, although novel geochemical or isotopic fingerprints, such as in natural speleothems, may still be observable long into the future. An engineered barrier using a cementitious/concrete backfill would eventually react with groundwater and advect to produce an “alkaline-disturbed zone” around the repository.

Discussion: The Use of Concrete as a Stratigraphic Signal of the Anthropocene Concrete is certainly widespread; it represents the most abundant anthropogenic sedimentary rock on the planet and increasing in abundance by about 27 billion tons per year. This is nearly twice the river sediment flux reaching the oceans (Syvitski and Kettner, 2011). But is it a suitable marker for the start and body of the Anthropocene Epoch, if taken to commence in the mid-20th century (Waters et al., 2016)? To mark the start of the Anthropocene, it would be ideal to have a signal that is absent or rare prior to the onset

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of the unit/below the base of the unit, but to be abundant and globally distributed at or soon after the start/above the base of the unit. Although concrete has been around for several thousand years as a building material, it has only been since the 20th century that it has become common and certainly a ubiquitous component of the modern technosphere. Earlier concrete, notably used by the Romans, is geochemically and mineralogically distinct from modern concrete and was produced in much smaller quantities. Greater than 90% of concrete has been produced since the proposed mid-20th century start of the Anthropocene. But that does mean that a significant amount of modern concrete predates the proposed Anthropocene. So, in order to identify a fragment of concrete in a deposit that lacks historical context and from this recognize unequivocally that the deposit is of Anthropocene age, it would be necessary to carry out mineralogical and geochemical assessments, which could include recognizing modern additives distinctive of late 20th century technologies, for example, organic polymer fibers and plasticizers, silica fume, fly ash, and presence of microscopic air bubbles and nanotubes and nanospherules of silica, iron, graphene, and titanium oxide. The CaCO3 component of cement and concrete contains carbon from CO2, absorbed directly from the atmosphere at the time of construction (Heinemeier et al., 1997). This provides the ability to carry out accelerator mass spectrometry 14C (radiocarbon) dating, which records the age of hardening of the material (Heinemeier et al., 1997). A significant problem, described earlier, is the modeled gradual recrystallization of the concrete, with the formation of new minerals, such as calcite (Fig. 4), potentially hundreds of years after the primary age of concrete production. This would give an artificially young age for the concrete. In order to select unrecrystallized carbonate it may be possible to use stable carbon and oxygen isotopes. Typically, the lighter isotopes 12C and 16O are enriched in the precipitated carbonates compared with the atmospheric CO2 and the source limestones from which the cement formed (Kosednar-Legenstein et al., 2008). Alteration of the carbonate matrix, through recrystallization in the presence of porewater and atmospheric O2 and CO2, will change the isotopic composition. d13C values in the matrix may become heavier for atmospheric CO2 or lighter for biogenic CO2 (Kosednar-Legenstein et al., 2008). Where the porewaters are mostly of meteoric origin, the d18O in the matrix value should get heavier compared with the ideal isotopic behavior of the calcite matrix (Kosednar-Legenstein et al., 2008). The isotopic compositions may also be a means of indicating variations in the limestone source areas. Pre-Anthropocene manufacture of concrete is likely to use cement sourced from the nearest supply of limestone bedrock. But over recent decades, bulk transport of cement means that source limestones may have markedly different stable isotopic compositions compared with local supplies, and may change regularly as supply sources change based upon market variation in costs. Concrete is predominantly an anthropogenic rock-type limited to the terrestrial (surface and subsurface) environment, with comparatively little present within the oceans. This limits the function of concrete as a potential marker for the Anthropocene as it is less widely distributed than other signals that have been transported by rivers (e.g., microplastics) and especially aerially (fly ash, greenhouse gases, radiogenic fallout). The impact of concrete manufacture as a marker for the Anthropocene may be observed in its effect upon atmospheric pollution, which is rapidly expressed and distributed globally. The 4 billion tons of cement produced annually accounts for about 5% (Damtoft et al., 2008) to 7% (Mehta and Monteiro, 2006) of all human-generated CO2 emissions through the burning of fuel needed to heat the kilns to 1500 C and through release of CO2 from the baked limestone. Approximately 840–1150 kg of CO2 is released for every ton of cement produced, but practically no other greenhouse gases are generated (Damtoft et al., 2008). This is a significant contributor to an important marker for the Anthropocene, the rapid increase in atmospheric CO2 concentrations and marked shift of stable carbon isotopes to more negative values (a depleted d13C signal) that occurred about 1965 (Waters et al., 2016). There is no doubt that concrete production and its widespread distribution within the terrestrial environments that we humans occupy is a prominent marker for the Anthropocene. Production figures provide encouragement to suggest that the rapid upturn in concrete manufacture at about the time of the mid-20th century “Great Acceleration” provides a strong candidate as a marker for the Anthropocene. However, it is likely that there will be a decadal scale diachroneity in the appearance of abundant concrete within sedimentary successions. This is in part a product of the timing of economic development not being globally observed at the same time immediately after World War II. But also there will be an inherent time-lag between concrete production and its recycling as a waste material accumulating in anthropogenic deposits or reworked by river or wave erosion. These are likely to be limiting factors in concrete’s suitability as a primary signal for this proposed new epoch.

Acknowledgments CNW publishes with the permission of the Director, British Geological Survey, Natural Environment Research Council.

References Damtoft JS, Lukasik J, Herfort D, Sorrentino D, and Gartner EM (2008) Sustainable development and climate change initiatives. Cement and Concrete Research 38: 115–127. Ford JR, Waters CN, Price SJ, and Cooper AH (2012) GC53C-1303 assembling the Anthropocene: the global significance of anthropogenic sediment flux through the creation of artificial ground. San Francisco: AGU. Francis P, Flagg R, and Crisp G (2016) Nine thousand miles of concrete: a review of Second World War temporary airfields in England. In: Historic England. p. 37. Gherardi F, Audigane P, and Gaucher EC (2012) Predicting long-term geochemical alteration of wellbore cement in a generic geological CO2 confinement site: tackling a difficult reactive transport modeling challenge. Journal of Hydrology 420–421: 340–359.

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Hazen RM, Grew ES, Origlieri MJ, and Downs RT (in press) On the mineralogy of the “Anthropocene Epoch”. American Mineralogist. Heinemeier J, Jungner H, Lindroos A, et al. (1997) AMS 14C dating of lime mortar. Nuclear Instruments and Methods in Physics Research B 123: 487–495. Jackson MD, Moon J, Gotti E, et al. (2013) Material and elastic properties of Al-tobermorite in ancient Roman seawater concrete. Journal of the American Ceramic Society 96: 2598–2606. Jackson MD, Landis EN, Brune PF, et al. (2014) Mechanical resilience and cementitious processes in Imperial Roman architectural mortar. Proceedings of the National Academy of Sciences of the United States of America 111(52): 18484–18489. Kosednar-Legenstein B, Dietzel M, Leis A, and Stingl K (2008) Stable carbon and oxygen isotope investigation in historical lime mortar and plaster—results from field and experimental study. Applied Geochemistry 23: 2425–2437. Mehta PK and Monteiro PJM (2006) Concrete: microtructure, properties, and materials. In: 3rd edn. New York: McGraw-Hill. Sanchez F and Sobolev K (2010) Nanotechnology in concrete—a review. Construction and Building Materials 24: 2060–2071. Scrivener KL and Kirkpatrick RJ (2008) Innovation in use and research on cementitious material. Cement and Concrete Research 38: 128–136. Syvitski JPM and Kettner A (2011) Sediment flux and the Anthropocene. Philosophical Transactions of the Royal Society 369(1938): 957–975. Waters CN, Zalasiewicz J, Summerhayes C, et al. (2016) The Anthropocene is functionally and stratigraphically distinct from the Holocene. Science 351(6269): 137. Zalasiewicz J, Williams M, Waters CN, et al. (2016, online) Scale and diversity of the physical technosphere: a geological perspective. The Anthropocene Review. https://doi.org/10. 1177/2053019616677743.

Relevant Websites http://www.burjkhalifa.ae/en/the-tower/construction.aspx—Burj Khalifa: Building a global icon. http://www.cement.ca/images/stories/recyclingconcrete_summary_csi.pdf—The Cement Sustainability Initiative. http://www.cement.org/cement-concrete-basics/products/concrete-pavement, http://www.cement.org/concrete-basics/paving/concrete-paving-types/highways—The Portland Cement Association. http://www.concretenetwork.com/concrete-history/—Concrete Network. http://www.concretethinker.com/Papers.aspx?DocId¼337—Concrete Thinker, The Portland Cement Association. http://e360.yale.edu/—Yale Environment 360: ‘In post-Tsunami Japan, a push to rebuild coast in concrete’. http://en.people.cn/200101/02/eng20010102_59432.html—People’s Daily Online. www.festungguernsey.supanet.com/about_us.htm—Festung Guernsey. https://www.geopolymer.org/archaeology/roman-cement/high-performance-roman-cement-and-concrete-high-durable-buildings/—Geopolymer Institute. http://iti.northwestern.edu/cement/—The Science of Concrete Monograph. http://minerals.usgs.gov/minerals/pubs/commodity/cement/, http://pubs.usgs.gov/fs/2006/3127/2006-3127.pdf—United States Geological Survey. https://todayinsci.com/A/Aspdin_Joseph/AspdinJoseph-Cement.htm—Today in science history.

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Hydrology in the Anthropocene P Bridgewater, E Guarino, and RM Thompson, University of Canberra, Canberra, ACT, Australia © 2018 Elsevier Inc. All rights reserved.

Introduction The hydrologic (water) cycle is a natural process, which has become increasingly transformed by direct and indirect drivers. These drivers all derive from human activity, and this activity is increasing in the Anthropocene, in turn changing hydrologic processes through positive feedback. For the purposes of this article, we refer to hydrology as the science that encompasses the flows of water through rivers, lakes, and wetlands, including the important role of groundwater. The cycle for water from cloud to earth and cloud again may be short or it may take millions of years. Hydrology in the Anthropocene will be controlled by links to other environmental processes and be affected by feedbacks from those processes. The water cycle is a primary regulator of ecosystem productivity, ecosystem goods and services, and other aspects of biodiversity. In this article, we use biodiversity in the sense of the Convention on Biological Diversity (CBD)—genes, species, and ecosystems and their hierarchical links. Understanding links between water and nutrient cycles is essential to understand impacts on freshwater biodiversity. This understanding is also crucial to ensuring freshwater provisioning ecosystem services for people. Global freshwater resources are known to be finite and often vulnerable, and the way these resources are managed to provide services and benefits to people (and increasingly the rest of biodiversity) feeds back into the rapidly changing hydrologic situation of the Anthropocene. Vörösmarty et al. (2010) point out that “nearly 80% of the world’s population is exposed to high levels of threat to water security. Massive investment in water technology enables rich nations to offset high stressor levels without remedying their underlying causes, whereas less wealthy nations remain vulnerable.” The 2015 UN World Water Development Report continued with that theme, emphasizing that water resources and the range of services they provide to people and ecosystems reduce poverty, stimulate economic growth, and promote environmental sustainability. From a human perspective, secure water supply is vital for food, energy, and health, as well as being necessary for sustainable growth. The UN World Water Development Report (2015) noted that global water demand is influenced by “population growth, urbanization, food and energy security policies, and macro-economic processes such as trade globalization, changing diets and increasing consumption. By 2050, global water demand is projected to increase by 55%, mainly due to growing demands from manufacturing, thermal electricity generation and domestic use.” But this global demand faces a reality check; water resources really are finite and diminishing.

Drivers of Hydrologic Change in the Anthropocene Hydrologic change derives from a range of drivers that cause stresses and change in hydrologic systems and the water cycle generally. Direct stressors on hydrologic systems include widespread land-cover change, urbanization, industrialization, and significant engineering interventions. Engineered changes to hydrologic systems include reservoirs, hydrodams, irrigation, and interbasin transfers that maximize human access to water. Benefits of water provision to economic productivity often result in impairment of ecosystem services and change to biodiversity. These direct stressors are synergized by a range of indirect stressors, including human population growth, with concomitant demands for drinking water, food, and energy. Global warming and other influences of climate change, as specific aspects of the Anthropocene, have resulted in major changes to the global hydrologic cycle over the last century, shown by increasing salinity at the sea surface in areas dominated by evaporation and decreasing surface salinity in areas dominated by precipitation. In many regions of the world, climate change has resulted and continues to result in changes in frequency, intensity, and timing of precipitation. Changes in precipitation, in combination with “fertilization effects” from increased atmospheric CO2, may dramatically alter the surface water yields from catchments (Ukkola and Prentice, 2013). Rivers are increasingly modified in terms of flow and form, and those modifications are not only both evidence of the Anthropocene but also global threats to water security (Poff and Matthews, 2013). Artificial impoundments are a feature of the majority of the large rivers of the world and have effects on magnitude and timing of flow, rates of groundwater recharge, local water balances, and microclimates. Significant downstream effects on sediment provision and water availability often extend across national borders and can be a substantial factor in regional tensions. Rockström et al. (2009) discuss a wider range of environmental parameters causing change in the Anthropocene, including biodiversity loss and global freshwater use. They use the term “planetary boundaries” and note we may soon be approaching the boundary for global freshwater use beyond which we enter uncharted territory. Alongside climate change, they cite rates of biodiversity loss and interference with the nitrogen cycle as possibly already having transgressed their boundaries. But the loss of biodiversity should be seen as part of an overall set of global biodiversity changes and linked closely to changing climate, nitrification, and reduction in available freshwater. The planetary boundaries concept is further complicated when including sociocultural factors, and hydrology is also heavily influenced by sociocultural factors.

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As part of the changes in the Anthropocene, an increase of natural hazards related to stressed hydrologic systems, including extreme flood and drought, is already evident and forecast to increase. This was anticipated in 2005 by the parties to the Ramsar Convention on Wetlands who agreed a resolution that “underlined the devastating impacts of natural disasters on the delivery of ecosystem benefits/services and thus on the maintenance of the ecological character of Wetlands of International Importance and other wetlands in affected countries.” The resolution noted that peatlands, in both temperate and tropical zones, are especially vulnerable to the risk of fires in times of drought. Such fires can impact the provision of water supply to urban and rural populations and disrupt a range of functions in adjacent ecosystems. Debate on this resolution took place only a year after the Indian Ocean tsunami of 2004, which created unprecedented damage to coastal systems and habitations. This damage was accelerated by removal or replacement of hydrologic systems, especially natural coastal features such as mangrove ecosystems and lagoons.

Ecohydrology as a Response to the Anthropocene Hydrology originated as physical science, with an applied side leading to hydroengineering. In the 1990s, UNESCO, through its International Hydrology and Man and Biosphere programs, developed and promulgated the concept of ecohydrology to help set the physical science in a socioecological context. Ecohydrology helps determine the structure, function, and evolution of freshwater ecosystems. We include as freshwater ecosystems rivers, lakes, reservoirs, rice paddies, swamps, peatlands, and subterranean ecosystems driven by groundwater flows. Restoring ecohydrologic relationships aims to improve ecosystem function and service delivery through increasing the carrying capacity of ecosystems. Instead of “protecting” ecosystems, conserving, restoring, recognizing, and managing historical and novel ecosystems in order to increase their service delivery in terms of water resources and resilience to global change are the aims of ecohydrology. Ecohydrology can be defined as trying to understand, explain, and use links between ecology and hydrology. It integrates landscape hydrology with freshwater biology. Ecohydrology, as a blending of hydrology and ecology, will help in managing many critical problems dealing with the water-related aspects of sustainable development in the Anthropocene. There are four key points that underscore the nature of ecohydrology. These are the following:

• • • •

Integrating water and biodiversity science at management-relevant scales Understanding ecological change and the role of people in managing change Understanding the role of ecological services Using ecosystem properties as indicators of change

Zalewski (2013) attempts to give clarity to the concept of ecohydrology by proposing an approach termed WBSR—to indicate the key elements, W for water, B for biodiversity, S for (ecosystem) services, and R for resilience. He also articulates three key principles, namely, a hydrologic principle, an ecological principle, and an ecological engineering principle. The hydrologic principle implies quantification of hydrologic processes at the basin scale and links to quantification of ecosystem function. The ecological principle implies the need for understanding of water–biodiversity interactions, inextricably linked to cycles and flows of nutrients and energy. It is also important to understand ecosystem structure and state of modification, including the increasingly important role of novel ecosystems in the Anthropocene. The ecological engineering principle deals with deliberate alteration or construction of ecosystems to help manage disturbed water regimes. The World Water Vision statement prepared in 2000 for the World Water Council focuses more on an ecosystem service approach to ecohydrology and identifies two kinds of water, blue and green. The term green water refers to rainfed agricultural, pastoral, or uncleared land ecosystems. It refers to water transpired from plants and soil water available to plants and other organisms. Green water not only supports the Earth’s vegetation but also influences groundwater recharge and stream base flow. A key distinction exists between green water, used in situ by plants, and blue water, the portion of rainfall that directly enters streams and recharges groundwater. In the context of the Anthropocene, it is also useful to understand the concept of gray and black waters. Gray water is wastewater from human habitations or light industry without fecal contamination. Gray water contains fewer potential pathogens than wastewater from toilets or other sources that may have potential pathogen contamination. That water has been termed blackwater and requires treatment in some form before being released back to the environment. Gray water, however, can be used without further treatment for toilet flushing or irrigation of landscaping or crops, which in turn helps treat and degrade any potential pollutants in the water. Collectively, these terms categorize global water resources into a set of functional units that are amenable to different forms of management. To be fully effective in the Anthropocene, however, a third dimension needs to be included in the ecohydrology paradigm, culture. Water and water availability have profound influences on culture and social stability. Across the world, modern societies continue to shape their cultures around water as a necessity or for recreation. These often cultural aspects reinforce both the biodiversity (ecological) and water (hydrologic) parts of ecohydrology (Bridgewater and Arico, 2016). It is clear in the Anthropocene that water and environmental management cannot be achieved solely by hydroengineering approaches. While hydrologists and hydroengineers play a role in ensuring sufficient water, resources are available to societies to ensure economic development; at the same time, ecologists are focused on conservation and restoration of biodiversity and ecosystems, often based on the results of such engineering intervention. At the same time, landscape modification is resulting in changes to the hydrologic cycle, increasing the likelihood of water deficits, floods, and salinization.

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Hydrology and Freshwater Biodiversity Habitats associated with 65% of continental rivers are classified as moderately to highly threatened (Vörösmarty et al., 2010). This emphasizes the necessity of limiting threats at their source in order to assure global water security for both people and freshwater biodiversity. Freshwater biodiversity faces a growing set of challenges, not least the fact that already highly dynamic freshwater ecosystems are threatened by greater fluctuations, especially under global change, and increasing human demands for water. Freshwater ecosystems have a high level of connectivity, which means fragmentation and pollution can have profound effects, while invasive species and wildlife diseases are easily transported across watersheds (Vörösmarty et al., 2010). In addition to these direct threats, climate change represents a growing challenge to the integrity and function of freshwater systems (Dudgeon et al., 2006). All this lends urgency to the study of species richness and community patterning, demonstrating the relative risk from the loss or extinction of species in freshwater ecosystems and the consequences of those extinctions on ecosystem function. Globally, important areas for freshwater species richness include the Amazon basin, the southeastern United States, West Africa across to the Rift Valley lakes, the Ganges and Mekong basins, and large parts of Southeast Asia. Countries with highest species richness include Brazil, the United States, Colombia, and China. Threatened species are most numerous in South and Southeast Asia, Central America, parts of eastern Australia, and African Rift Valley. This, in part, reflects these regions’ high concentrations of human population and water use. Freshwater ecosystems with high levels of species richness are at risk from multiple interacting stresses that are primarily concentrated in areas of intense agriculture, industry, or domestic activity. Further stresses on freshwater ecosystems are being brought by water extraction, the introduction of exotic species, and the alteration of flow through channelization and the construction of dams and reservoirs. Added to these are the overexploitation of water resources and increasing levels of organic and inorganic pollution (Vörösmarty et al., 2010). Freshwater species across a range of vertebrate and invertebrate groups are under a greater level of threat than species found in terrestrial ecosystems (Dudgeon et al., 2006). These patterns of threat are compounded by high rates of habitat loss and degradation, pollution, and overexploitation and are particularly problematic in species inhabiting flowing waters. A “sleeper issue” is the emergence and rapid spread of fungal pathogens, which attack plants through the root system. Initially identified as the causal agent of stripe canker of cinnamon trees (Cinnamomum burmannii) in Sumatra, a range of Phytophthora species, especially Phytophthora cinnamomi, have been found to cause plant disease on all continents except Antarctica. The impacts of Phytophthora dieback on native vegetation can be severe and may include considerable decrease in flora species richness, reduction in ecosystem primary productivity and biomass, major disruption to plant community structure, and degradation of habitat for flora and fauna (Wilson et al., 2012). The importance of hydrology to this problem is that zoospores of P. cinnamomi may be carried in water flowing across and more usually below the surface of the landscape, resulting in the rapid downslope spread of disease. The infection process is dependent on high soil moisture and warm soil temperatures. Climate is thus a key factor controlling the life cycle of P. cinnamomi. This lethal epidemic of Phytophthora “dieback” (the process of an area becoming infested with P. cinnamomi) has been identified as a “key threatening process” in the Australian environment. While P. cinnamomi is particularly pernicious, there are also several other species of Phytophthora that use groundwater as a means of inducing and rapidly spreading infection.

Hydrologic Management Options in the Anthropocene A more holistic approach to freshwater ecosystems for sustainable development maintains a mix between anthropogenic and ecological infrastructure that can ensure maximum delivery of ecosystem services. Ecological infrastructure can be divided into green and blue infrastructure, with green being vegetated land and blue with flowing or persistent surface water as part of the infrastructure. Blue infrastructure has obvious links to hydrology, especially ecohydrology. This holistic focus on infrastructure is best seen through the lens of the CBD/ecosystem approach or by applying the concept of ecosystem-based management (EBM). The widely accepted CBD definition of EBM is human centric: “the use of biodiversity and ecosystem services (. . .) to help people adapt to the adverse effects of climate change” “. . . that may include sustainable management, conservation, and restoration of ecosystems, as part of an overall adaptation strategy that takes into account the multiple social, economic, and cultural cobenefits for local communities.” Conservation of ecosystem structure and functioning, in order to maintain ecosystem services, should be a priority target of the ecosystem approach. That approach has 12 principles—five of which are especially appropriate to hydrology in the Anthropocene:

• • • • •

Ecosystems must be managed within the limits of their functioning. The ecosystem approach should be undertaken at the appropriate spatial and temporal scales. Recognizing the varying temporal scales and lag effects that characterize ecosystem processes and objectives for ecosystem management should be set for the long term. Management must recognize that change is inevitable. Recognizing potential gains from management, there is usually a need to understand and manage the ecosystem in an economic context.

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A problem with “economic context” is that models are normally used to explore that context, and most economic models undervalue ecosystem services provided by water-driven ecosystems, leading to unsustainable use of water resources and ecosystem degradation (e.g., Loomis et al., 2000). This is in addition to pollution from untreated residential and industrial wastewater (gray and black water). Water pollution also includes increasingly significant agricultural runoff that further weakens the ability of ecosystems to deliver hydrologic services. The Ramsar Convention on Wetlands resolution on impacts of natural disasters on the delivery of ecosystem benefits/services from wetlands noted that wetlands (which included rivers, reservoirs, and lakes) were vulnerable to natural disasters through such disasters affecting their natural hydrologic regimes. The convention saw restoration of affected wetlands as important, in order to ensure that they can continue to deliver their full range of ecosystem services for people and for the rest of the biological diversity. Parties to the convention noted the need for assistance with ensuring the implementation of ecologically sustainable management and redevelopment approaches and enhanced integrated coastal zone management throughout the region, in order to assist with the mitigation of impacts of any future tsunami and storm damage, including the establishment or maintenance of coastal greenbelts of mangroves and other appropriate species. In all those discussions, the role of monitoring long-term ecological impacts of disasters on wetlands was seen as critical. Ecological engineering deals with deliberate alteration or construction of ecosystems to help manage disturbed water regimes. As Mitsch and Jorgensen (2004) show, ecological engineering is strongly rooted in the tenets of ecosystem restoration. Ecosystem engineering has a range of tools and options for managing ecosystems, restoring ecosystems, and creating new, synthetic (novel) ecosystems. These tools are complementary to the already used hydrotechnical solutions and should be used toward enhancement of ecosystem carrying capacity for WBSR (Zalewski, 2013). The use of the ecosystem properties is compliant with the rules defined for ecological engineering (Mitsch and Jorgensen, 2004), with the following three assumptions in mind: 1. Biota is regulated by hydrology and vice versa. 2. Various types of biological and hydrologic interactions should be integrated at a basin scale with other conservation and restoration measures to achieve synergy among them. 3. Harmonization of ecohydrologic measures with necessary hydrotechnical infrastructure (dams, irrigation systems, sewage treatment plants, and so on) should provide a system-based solution in a catchment. The practice of ecological engineering has developed a range of artificial wetland systems (mainly using species of Phragmites and Typha as emergent plants) to process gray water, but under controlled conditions such wetlands can also treat fresh blackwater, that is, blackwater that is still oxygenated. Such wetlands, with the right set of species, are capable of removing heavy metals, organic pollutants, and sequestering pathogenic bacteria and viruses. The East Kolkata Wetland of international importance, a wetland system listed under the Convention on Wetlands (Ramsar, Iran, 1971), is the recipient of considerable volumes of Kolkata blackwater. The wetland treats the blackwater through natural processes as effectively as a mechanical sewage treatment plant. Waters that leave the wetland flowing to the sea are clean and pathogen-free. Such solutions (termed nature-based solutions) are likely to become more widely used and better known in the Anthropocene. In the European Union (EU), freshwater resource management is governed by the Water Framework Directive (WFD), which has integrated water resources management (IWRM) at its heart. The use of IWRM for management of existing resources, based on the knowledge of the water and nutrient cycles, is critical in the Anthropocene. IWRM was defined by the Global Water Partnership as “a process which promotes the coordinated development and management of water, land and related resources in order to maximize economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems.” Ecohydrology also reflects the IWRM concept but uses novel approaches to achieve sustainability. The first principle of ecohydrology, the hydrologic principle, implies quantification of hydrologic processes at the basin scale and uses the entire hydrologic cycle as a template for quantification of ecological processes. Reduction of nutrient loads (stimuli of eutrophication and toxic algal blooms in reservoirs, lakes, and coastal zones) from a catchment is one of the key challenges in implementing the EU WFD. In Poland, over 60% of the phosphorus and almost 70% of the nitrogen load to the Baltic Sea originate from diffuse (nonpoint) source pollution. Also in Europe, agricultural land covers up to 70% of the landscape. Creation of land–water ecotones has proved to be an effective tool for reducing the impacts of nutrients originating from a landscape on freshwater ecosystems. However, very often, shoreline zones are too narrow for these ecotones to work effectively.

Disease and Pollution Particular changes that have immediate and important aspects for people include disease incubation and spread and chemical pollution. According to a 2015 UNEP report, more than 300 million people in Asia, Africa, and Latin America are at risk of lifethreatening diseases like cholera and typhoid because of the increasing pollution of water in rivers, lakes, and even groundwater. The report noted that between 1990 and 2010, pollution caused by viruses, bacteria and other microorganisms, and nitrogen and phosphorous from fertilizer, as well as persistent organic pollutants such as fuel oil, increased in more than half of rivers across the three continents. In addition to pollutants, salinity levels in freshwaters increased in nearly a third of the rivers studied.

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Pollution from pharmaceutical and cosmetic products is another emerging issue for freshwaters, globally. These products have become essential and widely used in our society, primarily for medical reasons. Specifically, there are a range of compounds and substances (e.g., microbeads in cosmetics and endocrine-disrupting chemicals), which pose significant threats to the Earth’s hydrologic systems and associated ecosystems. Active pharmaceutical ingredients are designed to affect various processes in the human body. In order to reach and interact with the right organ in the body, they are designed to be stable, which also means they can remain and be potentially active in the environment for a long time. Their use is likely to increase due to a growing, aging population. The ability to interact with biological processes also means that these drugs can affect other species as well (e.g., Richmond et al., 2016). Due to the risk of promotion of antibiotic resistance, antibiotic pollution is of especial global concern, as are the hormonemimicking compounds known as endocrine disrupters. In sufficient concentrations, this range of compounds will impact the recipient waterbody, although many tools to reduce their environmental impact are already available but less widely used than is desirable. Combining efforts along the pharmaceutical life cycle—production, procurement, consumption, and wastewater treatment—is vital for a sustainable development that does not have impacts on hydrologic processes.

The Waterscape of the Anthropocene The trends emerging as the Anthropocene progresses paint a challenging picture for hydrology, especially waterways. Growing global populations will place increasing demands on freshwaters, which occupy the critical “food–water–energy” nexus between food production (irrigation), potable water use, and energy production (hydroelectricity). These pressures will be compounded by the effects of both point and nonpoint pollution and emerging issues with contamination of groundwater resources and salinization of freshwaters. Changes in patterns of rainfall will reinvigorate the demands for impoundments for water storage and flood control. Globally, floodplain systems will become increasingly disconnected from their river systems as the demand for agricultural land increases and increased occupancy leads to the development of flood-protection works. An emerging feature of the Anthropocene is the damming and management of the world’s largest rivers. While in developed nations there has been some amelioration of the effects of dams on rivers, including complete removal, on a global scale, the construction of large dams is far outstripping these remediation efforts. In the absence of clear alternatives in energy production and with continued social concern around nuclear power, it seems likely that hydroelectric development will continue to expand, particularly in the developing world. The impacts of these developments have been described earlier and will become more profound as the Anthropocene progresses. In particular, the loss of large-bodied fish from the lower reaches of rivers and widespread disruption of river-supported coastal marine fisheries have already been documented; these problems will continue to intensify (Poff and Schmidt, 2016). Despite increased understanding of the importance of connectivity between rivers and floodplains, as the Anthropocene proceeds, we will increasingly see the “death of the floodplain” and declines in the societies, biodiversity, and agricultural productivity that they have previously supported. A combination of increasing demands for water upstream, reduced seasonality of flows due to impoundments, and increasing habitation will greatly reduce the frequency of inundation of floodplain ecosystems, bringing about the degradation and loss of some of these iconic systems. Urban systems have the potential to be much more efficient in water use, and a significant driver of this is likely to be increased variability in rainfall, leading to concerns over water potability. There is already a global shift toward the use of water recycling and desalinization technologies, although these often have major energy costs. The evolution of “water-sensitive cities” with highly managed hydrologic cycles has been proposed (Wong and Brown, 2009), yet this may be countered by an increased need for flood control, generated by a higher frequency of extreme rainfall events. In the developing world, the immediate concerns are likely to be supplies of potable water, waste disposal, and flood control, in that order. Ensuring a rapid transition to more effective management of the urban hydrologic cycle requires technology transfer and changes in governance that will be very challenging (Wong and Brown, 2009). In the Anthropocene, large rivers will become highly managed ecosystems, with greatly reduced patterns of flow variability, posing major challenges around downstream water quality. The best management objective in this scenario may be to maintain a “healthy working river,” that is, a system that is highly modified and managed but is able to support biodiversity and ecosystem services that society is willing to invest in conserving. Key to this will be the ability to be more efficient in water use in producing food and allowing water savings to be allocated to environmental flows (Poff and Zimmerman, 2010). The way in which energy technologies develop may seem to be an unlikely key to the challenges of hydrologic management in the Anthropocene, but it is critical if current patterns in hydroelectric developments for energy continue. Finally, clean and inexpensive energy is a critical factor in promoting technological solutions to the increasing global shortage of potable water.

References Bridgewater P and Arico S (2016) Turbocharging the ecohydrology paradigm for the Anthropocene. Ecohydrology & Hydrobiology 16: 74–82. Dudgeon D, Arthington AH, Gessner MO, et al. (2006) Freshwater biodiversity: importance, threats, status and conservation challenges. Biological Reviews 81: 163–182. Loomis J, Kent P, Strange L, Fausch K, and Covich A (2000) Measuring the total economic value of restoring ecosystem services in an impaired river basin: results from a contingent valuation survey. Ecological Economics 33: 103–117.

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Mitsch WJ and Jorgensen SE (2004) Ecological engineering and ecosystem restoration. New York: Wiley. Poff NL and Matthews JH (2013) Environmental flows in the Anthropocene: past progress and future prospects. Current Opinion in Environmental Sustainability 5: 667–675. Poff NL and Schmidt JC (2016) How dams can go with the flow. Science 353(6304): 1099–1100. Poff NL and Zimmerman JK (2010) Ecological responses to altered flow regimes: a literature review to inform the science and management of environmental flows. Freshwater Biology 55: 194–205. Richmond EK, Rosi-Marshall EJ, Lee SS, Thompson RM, and Grace MR (2016) Antidepressants in stream ecosystems: influence of selective serotonin reuptake inhibitors (SSRIs) on algal production and insect emergence. Freshwater Science 35: 845–855. Rockström J, Steffen W, Noone K, et al. (2009) A safe operating space for humanity. Nature 461: 472–475. Ukkola AM and Prentice IC (2013) A worldwide analysis of trends in water-balance evapotranspiration. Hydrology and Earth System Sciences 17: 4177–4187. Vörösmarty CJ, McIntyre PB, Gessner MO, et al. (2010) Global threats to human water security and river biodiversity. Nature 467(7315): 555–561. Wilson BA, Zdunic K, Kinloch J, and Behn G (2012) Use of remote sensing to map occurrence and spread of Phytophthora cinnamomi in Banksia woodlands on the Gnangara Groundwater System, Western Australia. Australian Journal of Botany 60: 495–505. Wong THF and Brown RR (2009) The water sensitive city: principles for practice. Water Science and Technology 60: 673–682. Zalewski M (2013) Ecohydrology: process-oriented thinking towards sustainable river basins. Ecohydrology and Hydrobiology 13: 97–103.

Fluxes of Trace Metals on a Global Scale RJ Thorne, NILU–Norwegian Institute for Air Research, Kjeller, Norway JM Pacyna, NILU–Norwegian Institute for Air Research, Kjeller, Norway; AGH–University of Science and Technology, Krakow, Poland K Sundseth and EG Pacyna, NILU–Norwegian Institute for Air Research, Kjeller, Norway © 2018 Elsevier Inc. All rights reserved.

Abbreviations AMAP EMEP FGD GHG GMOS IPCC LRTAP REE UNEP

Arctic Monitoring and Assessment Programme European Monitoring and Evaluation Programme Flue gas desulfurization Greenhouse Gas Global Mercury Observation System Intergovernmental Panel on Climate Change Long-range transboundary air pollution Rare Earth element United Nations Environment Programme

Overview Biogeochemical Trace Metal Cycling Over the last decades, many studies have assessed the emission, fate, behavior, and effects of trace metals in the environment. These are usually present in very low background concentrations (parts per million or less), and often have important physiological functions. As with other elements, trace metals undergo natural biogeochemical cycles that are initiated when magma within the Earth rises to the surface to form rock, or through other geological sources such as volcanic and geothermal gaseous emissions. As the term “biogeochemical” indicates, biological, geological, and chemical factors are involved in the cycling. Mobilization from rocks can occur by various natural processes, whereupon chemical processes such as oxidation, reduction, complexation, and other reactions may occur. The concentration and type of trace metal in the environment varies greatly since these factors are dependent on the source type, and transport pathways, which are region or locally specific. Subsequent to emission, trace metals are transported and cycle within and between biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) components of the Earth. Transport between abiotic components may occur through movements of soil/sediments and water, or on wind currents. Uptake and metabolism of trace metals such as bioavailable mercury (Hg) and cadmium (Cd), by organisms may lead to bioaccumulation in the environment. The extent of uptake into living organisms is governed to a large extent by the type of metal species, since metals adsorbed or complexed are generally not available for biological uptake. Bioavailability may be increased by oxidation and reduction, as well as other types of reaction such as methylation. Many trace metals have important and well-established biological roles in the human body, the most well-known being the role of iron (Fe) in efficient transport of oxygen. Other roles for Fe and other essential trace elements such as zinc (Zn), copper (Cu), and selenium (Se) include uses in enzymes, gene expression, regulation of biological processes, and the immune system, to give a few examples. Ultimately, trace metals are deposited during cycling and buried again, mostly in sediments, whereupon subsidence completes the cycle. While most natural trace metal cycling is a crucial factor enabling life on Earth, in recent years anthropogenic activity has dramatically changed biogeochemical cycling on local, regional, and global scales. Since trace metals are found almost universally in industrial raw materials such as coal and ores, they may be released in high quantities when utilized, especially in high-temperature processes. Deposition in areas directly surrounding an industrial emission source may reach high levels that exceed permissible environmental values, but trace metals may also be transported long distances and deposited, with resulting effects on a much wider scale. This has led to concentrations of many trace metals even at remote locations being higher than expected from natural occurrence, such as the Arctic where few anthropogenic emission sources exist. The situation is exacerbated due to demands from a growing human population, which requires increasingly large amounts of energy, industrial commodities and food. The concentration increase of a trace metal in the environment can be expressed by an enrichment factor, to normalize concentration with respect to a reference element. Our understanding of perturbations of natural biogeochemical cycles of trace metals is currently somewhat limited. Fig. 1 demonstrates a typical modern biogeochemical cycle. Although similar in nature to a natural biogeochemical cycle, anthropogenic activity has greatly increased emissions and depositions (as well as the quantity transferred between compartments), and introduced additional metal stocks from mining. For some trace metals, continued increase in mass movement from stocks within the Earth to

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Fig. 1 Example biogeochemical trace metal cycling between abiotic components of the Earth. Major pathways are simplified for clarity.

stocks in-use has repercussions for the future of environmental emissions, despite reductions in atmospheric emissions. For the first assessments of Earth’s global biogeochemical cycles of trace metals including Pb, Cu, Zn, silver (Ag), chromium (Cr), and nickel (Ni), see Rauch and Pacyna (2009).

Harmful Impacts From Trace Metals in the Environment Environmental and human health impacts depend on the degree of alteration of a trace metals’ biogeochemical cycle caused by anthropogenic activity, although significant health effects are usually only caused by high perturbations at a local scale. Effects depend on the specific bioavailability, concentrations, and toxicity of each trace metal in various environmental compartments, and the extent of transfer to human food chains. Human exposure to higher than background trace metal concentrations may result in serious impacts to health. Humans are mostly exposed through consumption of contaminated food and water or inhalation of air, but may also be exposed through handto-mouth pathways. Many biological and physicochemical parameters influence the trace metal environmental bioavailability, while other factors such as the dose, route of exposure, chemical species, the mixture of stressors with similar end-points, and current health of exposed individuals, influence the resulting toxicity. In biological systems, some trace metals have been reported to affect cellular organelles and other components, including deoxyribonucleic acid (DNA) and nuclear proteins. Resulting human health effects primarily include carcinogenesis and genotoxicity, but may also cause effects to other organ systems. For a review, see, for example, Wu et al. (2016) and Duruibe et al. (2007). Other indirect harmful consequences from trace metal accumulation in the environment may result from loss of soil functions, such as those associated with environmental quality, crop productivity, and biota toxicity (see He et al., 2005; Tang et al., 2016), as well as economic impacts. External costs associated with measureable damage to the environment and human health may be direct or indirect, and relate to costs of treatment itself or effects on job attainment, education, and performance. One example is societal damages caused by loss of intelligence quotient from human exposure to methylated Hg (see Sundseth et al., 2010). Of the trace metals, mercury (Hg), lead (Pb), cadmium (Cd), and arsenic (As) are traditionally considered a primary concern due to extensive perturbations to their biogeochemical cycles and documented effects on human health. However, others with significantly altered biogeochemical cycles and human health risks are also a concern. Table 1 shows data on the scale of perturbations of biogeochemical cycles, exposure pathways, and the related possible health impacts, for a selection of major trace metals, as quantified by Pacyna et al. (2016a). In recent years, emissions to the atmosphere and aquatic and terrestrial ecosystems from anthropogenic sources have outweighed metal emissions from natural sources, changing natural biogeochemical cycles.

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Table 1

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Information on perturbations of geochemical cycles, exposure pathways, and health concerns for selected trace metals Scale of perturbation

Metal

Global (>1000 km)

Metals of primary concern Mercury (Hg) þ Lead (Pb) þ Arsenic (As)  Cadmium (Cd)  Metals of secondary concern Zinc (Zn)  Copper (Cu)  Selenium (Se) þ Antimony (Sb)  Tin (Sn) þ Chromium (Cr)  Manganese (Mn)  Nickel (Ni)  Vanadium (V)  Molybdenum (Mo) 

Regional (1000 > 100 km)

Local (1 mm) include soil and other material largely from the Earth’s surface. Transport varies for different metals, see, for example, Wai et al. (2016), Schroeder and Munthe (1998), and Niisoe et al. (2010) for further discussion. Since trace metals such as Hg, Pb, and Ni are volatile, they may vaporize during high-temperature production processes and condense on fine particles in a flue. Thus, enrichment of these metals often occurs predominantly in the smaller size fractions of atmospheric particles that are easily carried by prevailing winds and are prone to transport. Transport in the atmosphere is dependent on the type of emission (gas or particle), physical and chemical characteristics including the nature of the substrate, and meteorological parameters such as wind (direction, speed) and precipitation. Trace metals have a characteristic atmospheric residence time; for metals such as Hg, long-range atmospheric transport is well documented but is dependent on the redox state. The three predominant Hg species are thought to exhibit different transport characteristics dependent on the residence time, and only Hg0 has a long residence time and is capable of aerial transport over tens of thousands of kilometers. Two major natural processes have been recognized as participating in the removal of trace metals from the atmosphere: dry and wet deposition. Deposition resulting from precipitation (wet deposition) is an efficient but episodic cleansing mechanism of the atmosphere for both dissolved gases and particles, whereas dry deposition of particles is a continuous process dependent on the properties of a surface and the depositing species. Dry deposition processes are linked to turbulent vertical transport and interactions with natural surfaces, and are dependent on parameters including micrometeorology, particle parameters, other atmospheric constituents, and the particulars of the site. The relative importance of wet and dry deposition is dependent not only on the efficiency of the two mechanisms, but also on the local frequency and extent of precipitation. In addition, efficiencies depend on the individual concentrations of the different metal species available, due to variation in solubility among metal ions. Since local precipitation rates are highly location and temporally dependent, it is difficult to obtain simultaneous wet and dry deposition measurements, and there is much discussion over their relative and combined contribution toward total deposition (see Pan and Wang, 2015; Lynam et al., 2015). It is also important to consider the biogeochemical cycle at differing scales. Atmospheric dry deposition, for example, is one of the major pathways for the transport of chemical species from the continents to coastal and open marine ecosystems. Due to long-range transport, deposition of trace metals from anthropogenic sources to relatively unpolluted regions can occur. One region that acts as a major recipient for transboundary long-range trace metals pollution is the Arctic. The prevailing air movement over the Arctic is from Europe and Asia to North America, and models show that Europe and Asia contribute the majority of the air pollution in the Arctic. Thus, although the Arctic is a relatively nondisturbed habitat, the biogeochemical cycles of trace metals in the region have been altered. Threats to the terrestrial environment, lake and sediments, fresh water and marine ecosystem, marine birds and mammals, and human health in the Arctic have been assessed by AMAP, with most concern caused by Hg, Cd, and Pb.

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Once deposited, trace metals transfer between air, soil, and water, for example, via sediments in water currents. Some elements, such as Hg, can be reemitted in air–surface exchanges, which may involve air–water, air–soil, or air–vegetation exchange. This is dependent on oxidation form; the Hg(II) species is relatively immobile unless chemical, photolytic, or biological reduction to elemental form or methylation occurs. Numerical models of atmospheric transport and deposition are essential to interpret measurement data and establish abatement strategies. Since there is also some indication that some recently deposited trace metals may be more bioavailable than “legacy” trace metals, it is also important to quantify spatial and temporal trends in ecosystem contamination. The first comprehensive atmospheric model for long-range transport of a trace metal was the modified European Monitoring and Evaluation Programme (EMEP) model, which was used to simulate long-range transport of Hg from the European continent to Scandinavia. Updated EMEP models for Cd, Pb, and Hg are now available, and many other models are also used (e.g., Cohen et al., 2016). Better understanding of redox behavior, sorption processes, speciation, and cycling are required to improve models.

Future Trends in Trace Metal Emission and Deposition Future trace metal emission levels are dependent upon many variables, including the direction of policy (global and regional), development of the global economy, development of mitigation options for reducing emissions, and factors relating to climate change. The major uncertainty with anthropogenic emission estimates is largely due to rapid economic development in developing economies, particularly in South and South East Asia. Extensive modeling of future emissions of trace metals has not yet been widely performed, but some examples are available. Most scenarios developed predict a decrease in the concentrations of the major trace metal emissions in future. Hg has been the most widely studied in this context, with emission scenarios to air developed for the year 2020 using a base year of 2005 as part of the UNEP research toward the Minamata convention (Pacyna et al., 2010). These have been periodically updated, for example, on the basis of results obtained during the EU Global Mercury Observation System (GMOS) project (Pacyna et al., 2016b). Three different scenarios were developed: a current policy (CP) scenario assuming continuation of government policies and measures adopted in the year 2010, a new policies (NP) scenario assuming that policy commitments and plans announced by countries worldwide since the year 2010 to reduce GHG and other emissions (including the Minamata convention) are fully implemented, and a maximum feasible reduction (MFR) scenario assuming highest feasible/available reduction efficiencies in each sector. Results predict that Hg emissions in year 2035 will be reduced by up to 85% for the best-case scenario (Fig. 3). Two global chemical transport models were used to predict Hg pollution levels of the various scenarios (GLEMOS and ECHMERIT). Both models showed similar spatial patterns of Hg concentrations with a pronounced gradient in the Southern and Northern Hemisphere and elevated concentrations in major industrial regions. Changes in deposition in a given region depend not only on local emission dynamics but also on emission changes in other global regions. Projections of future changes in Hg deposition on a global scale were also simulated by Pacyna et al. (2016b) using GLEMOS and EHMERIT models for the three emission scenarios. Under the CP scenario for 2035, a considerable decrease of Hg deposition of 20%–30% was predicted for Europe and North America, and a strong deposition increase of up to 50% in South and East Asia. For the NP scenario, a moderate decrease in Hg deposition was predicted globally, except for South Asia, where a 10%–15% increase in deposition was predicted. For the MFR scenario, a decrease of Hg deposition of 35%–50% was predicted for the Northern Hemisphere, and a decrease of 30%–35% in the Southern Hemisphere. Results did not take into account possible responses of global biogeochemical reservoirs to changes in anthropogenic emissions, and effects from climate change such as changes to vegetative cover and atmospheric oxidants, increased forest fires, and enhanced air–water exchange. In addition, changes to the environment through climate change (increasing air temperature, changes in the seasonal variability of droughts/rainfall, and sea level rise) may affect trace metal fluxes in the environment. However, these effects are complex, and so suffer from high levels of uncertainty. An increase to groundwater and lake temperature increases the solubility of many trace metals, but reduced groundwater flow associated with droughts may reduce leaching to surface waters. Wet deposition fluxes may increase for regions predicted to experience higher precipitation, and changes to speciation and an increase of trace metal vaporization from land/water to the atmosphere may occur with higher temperatures. See, for example, Mollema and Antonellini (2016) and Zhang et al. (2016) for some associated studies.

Summary Trace metals are ubiquitous in the environment, and many are essential at background concentrations for environmental and human health. However, harmful effects to humans and the environment result when concentrations are enriched beyond background concentrations. Emissions may be natural or anthropogenic in origin, with research showing that anthropogenic emissions now dominate. The largest anthropogenic emissions derive from high-temperature processes in the energy and industrial sectors, for example, stationary fossil fuel combustion. After entering the atmosphere on fine particles or in gaseous form, trace metals may be transported over long distances within the atmosphere on air masses, and deposited to aquatic and terrestrial ecosystems through wet or dry deposition

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Fig. 3 Spatial distribution of mercury (Hg) emissions in 2035 according to the current policy (CP) scenario, the new policy (NP) scenario, and the maximum feasible reduction (MFR) scenario. (Taken from Pacyna, E. G., Pacyna, J. M., Sundseth, K., Munthe, J., Kindbom, K., Wilson, S., Steenhuisen, F., and Maxson, P. (2010). Global emission of mercury to the atmosphere from anthropogenic sources in 2005 and projections to 2020. Atmospheric Environment, 44, 2487–2499.

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processes. Transport also occurs between other environmental compartments, such as in sediments carried on water currents. Humans are exposed primarily through consumption of contaminated food and water or inhalation of air. Resulting impacts to the environment and human health depend on various factors, with key parameters including those that affect biogeochemical metal cycling. This primarily includes the type and quantity emitted, and associated transport pathways to the biotic component of the Earth. Up-to-date emission inventories, future emission scenarios, and transport models are required for assessments of current and future exposure to be made, which can be used by both modelers and policy makers. Few in-depth global scenarios of future emissions have been created, but for some major trace metal contaminants a decrease in emissions is expected (at least to some regions), primarily due to several global initiatives such as the phasing out of Pb additives to gasoline and the establishment of the Minamata convention to reduce Hg emissions. Trace metal emissions may also be reduced as a co-benefit of progress toward other international commitments, such as fuel switching and increasing use of renewables for reducing emission of GHGs. Motivated by policy, emission reductions may be obtained through technological and nontechnological measures. Despite the great progress achieved in the last decades, much work is still to be done. Information is somewhat lacking on chemical and physical forms of trace metal emissions, important for toxicity determination, as well as information on natural emissions/reemissions from water, land, and other sources. More legislative action is also required for trace metals with altered biogeochemical cycles other than Hg and Pb, and newly emerging metal contaminants including the REEs. REEs are used extensively in industry despite only limited knowledge existing regarding their toxicity and environmental impacts. The significant body of ongoing research in this field makes it likely that progress can continue, and environmental and human exposure to concentrations of trace metals at harmful high levels can be further reduced.

References AMAP (2010) Updating historical global inventories of anthropogenic mercury emissions to air. AMAP Technical Report No. 3 (2010). Oslo, Norway: Arctic Monitoring and Assessment Programme (AMAP). Cohen MD, Draxler RR, Artz RS, Blanchard P, Sexauer Gustin M, Han Y-J, Holsen TM, Jaffe DA, Kelley P, Lei H, Loughner CP, Luke WT, Lyman SN, Niemi D, Pacyna JP, Pilote M, Poissant L, Ratte D, Ren X, Steenhuisen F, Steffen A, Tordon R, and Wilson SJ (2016) Modelling the global atmospheric transport and deposition of mercury to the Great Lakes. Elementa: Science of the Anthropocene 4: 000118. Dias GM and Edwards GC (2003) Differentiating natural and anthropogenic sources of metals to the environment. Human and Ecological Risk Assessment 9: 699–721. Duruibe JO, Ogwuegbu MOC, and Egwurugwu JN (2007) Heavy metal pollution and human biotoxic effects. International Journal of Physical Sciences 2: 112–118. Garrett RG (2000) Natural sources of metals to the environment. Human and Ecological Risk Assessment 6: 945–963. Giripunje MD, Fulke AB, and Meshram PU (2015) Remediation techniques for heavy-metals contamination in Lakes: A mini-review. Clean-Soil Air Water 43: 1350–1354. He ZLL, Yang XE, and Stoffella PJ (2005) Trace elements in agroecosystems and impacts on the environment. Journal of Trace Elements in Medicine and Biology 19: 125–140. Li XF, Chen ZB, Chen ZQ, and Zhang YH (2013) A human health risk assessment of rare earth elements in soil and vegetables from a mining area in Fujian Province, Southeast China. Chemosphere 93: 1240–1246. Lynam MM, Dvonch JT, Hall NL, Morishita M, and Barres JA (2015) Trace elements and major ions in atmospheric wet and dry deposition across central Illinois, USA. Air Quality, Atmosphere and Health 8: 135–147. Mollema PN and Antonellini M (2016) Water and (bio)chemical cycling in gravel pit lakes: A review and outlook. Earth-Science Reviews 159: 247–270. Niisoe T, Nakamura E, Harada K, Ishikawa H, Hitomi T, Watanabe T, Wang Z, and Koizumi A (2010) A global transport model of lead in the atmosphere. Atmospheric Environment 44: 1806–1814. Pacyna EG, Pacyna JM, Sundseth K, Munthe J, Kindbom K, Wilson S, Steenhuisen F, and Maxson P (2010) Global emission of mercury to the atmosphere from anthropogenic sources in 2005 and projections to 2020. Atmospheric Environment 44: 2487–2499. Pacyna JM, Sundseth K, and Pacyna EG (2016a) Sources and fluxes of harmful metals. In: Pacyna JM (ed.) Environmental determinants of human health. New York: Springer. Pacyna JM, Travnikov O, De Simone F, Hedgecock IM, Sundseth K, Pacyna EG, Steenhuisen F, Pirrone N, Munthe J, and Kindbom K (2016b) Current and future levels of mercury atmospheric pollution on a global scale. Atmospheric Chemistry and Physics 16: 12495–12511. Pagano G, Guida M, Tommasi F, and Oral R (2015) Health effects and toxicity mechanisms of rare earth elements-Knowledge gaps and research prospects. Ecotoxicology and Environmental Safety 115: 40–48. Pan YP and Wang YS (2015) Atmospheric wet and dry deposition of trace elements at 10 sites in Northern China. Atmospheric Chemistry and Physics 15: 951–972. Pirrone N, Cinnirella S, Feng X, Finkelman RB, Friedli HR, Leaner J, Mason R, Mukherjee AB, Stracher GB, Streets DG, and Telmer K (2010) Global mercury emissions to the atmosphere from anthropogenic and natural sources. Atmospheric Chemistry and Physics 10: 5951–5964. Rauch JN and Pacyna JM (2009) Earth’s global Ag, Al, Cr, Cu, Fe, Ni, Pb, and Zn cycles. Global Biogeochemical Cycles 23: GB2001. Schroeder WH and Munthe J (1998) Atmospheric mercury—An overview. Atmospheric Environment 32: 809–822. Singh A and Prasad SM (2015) Remediation of heavy metal contaminated ecosystem: An overview on technology advancement. International Journal of Environmental Science and Technology 12: 353–366. Sundseth K, Pacyna JM, Pacyna EG, Munthe J, Belhaj M, and Astrom S (2010) Economic benefits from decreased mercury emissions: Projections for 2020. Journal of Cleaner Production 18: 386–394. Tang X, Li Q, Wu M, Lin L, and Scholz M (2016) Review of remediation practices regarding cadmium-enriched farmland soil with particular reference to China. Journal of Environmental Management 181: 646–662. Wai KM, Wu SL, Li XL, Jaffe DA, and Perry KD (2016) Global atmospheric transport and source-receptor relationships for arsenic. Environmental Science & Technology 50: 3714–3720. Wu XY, Cobbina SJ, Mao GH, Xu H, Zhang Z, and Yang LQ (2016) A review of toxicity and mechanisms of individual and mixtures of heavy metals in the environment. Environmental Science and Pollution Research 23: 8244–8259. Zhang H, Holmes CD, and Wu S (2016) Impacts of changes in climate, land use and land cover on atmospheric mercury. Atmospheric Environment 141: 230–244.

Impacts of Anthropocene Fossil Fuel Combustion on Atmospheric Iron Supply to the Ocean AW Schroth, University of Vermont, Burlington, VT, United States © 2018 Elsevier Inc. All rights reserved.

Introduction Iron (Fe) is thought to be a limiting nutrient of phytoplankton biomass in roughly one third of the world’s oceans due to the multiple roles that it plays in algal photosynthesis and nutrient assimilation. Iron-limited waters are often characterized by excess macronutrients (high nutrient low chlorophyll, HNLC), particularly nitrate, as seen in Fig. 1. A common geographical feature associated with many Fe-limited waters is that they tend to be well offshore of continental shelf and river plume supplies of terrestrial-derived Fe (Fig. 1). While relatively enriched in N and P, these waters often bear subnanomolar (1300 blue whales. Buoyant plastics float on the ocean surface for years. Physical abrasion and exposure to sunlight eventually break larger pieces into smaller ones (Fig. 3). Floating hard surfaces, such as plastic debris, attract planktonic organisms, from bacteria to phytoplankton and zooplankton that attach themselves to these platforms. This is called “biofouling,” and it can eventually weigh down the plastic debris sufficiently to make it sink. However, on the annual to decadal time scale, much of the ocean’s floating plastic debris is transported by winds and currents and ends up in high-concentration ocean gyres. There are five of these massive collections of debris trapped in gyres around the world (Fig. 4), the most notable being the one in the North Pacific. The North Pacific Ocean contributed importantly to the global plastic load (between 33% and 35%), mainly owing to the size of this gyre (Cózar et al., 2014). The North Pacific Gyre, also called “The Great Pacific Garbage Patch,” covers an area as large as France and Spain together (Hammer et al., 2012). This vast ocean region is covered with plastic debris (Fig. 5).

Plastic on the Ocean Floor About half of the plastic litter that enters the ocean sinks to the bottom because it is not buoyant. Eventually, the buoyant pieces sink, as well, though this process may take many years. In either case, once plastic debris reaches the ocean floor, it poses environmental hazards. There is also potential danger to marine ecosystems from the accumulation of plastic debris on the sea floor. The quantity of plastic debris generally increases with proximity to coastal regions with large human populations. For instance, Kanehiro et al. (1995) found that plastics made up 80%–85% of the seabed debris in Tokyo Bay. On the other hand, ocean debris is increasing dominated by plastic as one travels further from shore. This is because plastic is so durable, and so much of it floats for a very long time. The accumulation of plastic debris on the ocean floor inhibits gas exchange between the overlying waters and the pore waters of the sediments. This can result in either too little oxygen or a total lack of oxygen in sea floor sediments. This, in turn, interferes with

Fig. 3 Flow chart showing the fate of plastic debris in the ocean, and some of the associated effects on marine life.

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Fig. 4 Concentrations of plastic debris in surface waters of the global ocean. Colored circles indicate mass concentrations (legend on top left). The map shows average concentrations in 442 sites (1127 surface net tows). Gray areas indicate the accumulation zones predicted by a global surface circulation model. Dark and light gray represent inner and outer accumulation zones, respectively; white areas are predicted as nonaccumulation zone. After Cózar, A., Eschevarria, F., González-Gordillo, J. I., Irigoien, X., Úbeda, B., et al. (2014). Plastic debris in the open ocean. Proceedings of the National Academy of Sciences (USA) 111, 10239–10244.

Fig. 5 Plastic debris floating in the North Pacific gyre. Source: theweek.com http://theweek.com/articles/541440/surprising-economics-great-pacificgarbage-patch

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Table 4

Plastic debris on the seabed

Location

Quantity of debris on sea floor

North Sea Mediterranean Sea at 2500 m depth, off France and Corsica Sicily-Tunisia channel Adriatic Sea Dutch coast from 2000 to 2006 Greek area of eastern Mediterranean Tokyo Bay Norton Sound, Alaska

110 pieces of debris per km2; 48% plastic 300 million pieces; 19 items per hectare; 77% plastic 4 items per hectare; 75% plastic 3.78 items per hectare; 70% plastic 500 tons of debris 89–240 items per km2; 55%–83% plastic 2.7–5.0 items per hectare; 41% plastic 2.5 items per hectare; 49% plastic

Source: Hammer, J., Kraak, M. H. and Parsons, J. R. (2012). Plastics in the marine environment: The dark side of a modern gift. In: Whitacre, D. M. (ed.), Reviews of Environmental Contamination and Toxicology 220, pp. 1–44; Barnes, D. K., Galgani, F., Thompson, R. C. and Barlaz, M. (2009). Accumulation and fragmentation of plastic debris in global environments. Philosophical Transactions of the Royal Society, Series B 364, 1985–1998.

normal benthic ecosystem functioning and can alter the composition of biological communities that inhabit the sea floor. Benthic biota are likewise subjected to entanglement and ingestion hazards. As shown in Table 4, the quantity of plastic debris on the ocean floor varies greatly from region to region. Some of the most highly contaminated sea floor areas are in the Mediterranean, where large population centers and intense fishing combine to put large amounts of plastic litter into the sea. This principle also holds true for the North Sea. A survey of the Dutch coast over the period of 2000–06 found 500 tons of debris.

Plastic Washed up on Beaches Floating debris of all kinds frequently washes up on the shore. Beach litter in the 21st century is, not surprisingly, dominated by plastics. Carson et al. (2011) performed a study of plastic litter on Kamilo beach, Hawaii. They examined the physical properties of beaches contaminated with plastic fragments. They took sediment cores from the beach and compared the contents to cores taken from a nearby beach. Compared to the nearby beach, Kamilo sediments contained more plastics (up to 30% by weight), were coarser-grained, and were more permeable. They found that 85% of the fragments were polyethylene, and that 95% of the plastic debris was concentrated in the top 15 cm of the cores. Quantities of plastic debris items on beaches are highly variable over the course of a year and per location, but numbers of >40,000 plastic items (mostly plastic pellets) per square meter are not uncommon (Hammer et al., 2012) (Fig. 6). Plastic pellets (nurdles) are found in quite considerable amounts on beaches around the world. On New Zealand beaches, counts of over 100,000 nurdles were found per meter of coast, with the greatest concentration near large industrial centers (Derraik, 2002). How do beaches choked with plastic debris compare to unpolluted beaches? One of the differences concerns the thermal characteristics. Carson et al. (2011) found that the beach sediments with plastic warmed more slowly and reached lower maximum temperatures. So the upper layer of plastic-choked beach sediments is markedly cooler. This thermal difference can have biological consequences. For instance, sex-determination of sea turtle eggs is temperature-dependent. A paper by Davis and Murphy (2015) discusses the results of two studies of debris on beaches. One study evaluated the abundance of anthropogenic debris on 37 sandy beaches bordering the Salish Sea (Puget Sound region) in Washington State, while the other characterized plastic debris in surface waters from Puget Sound along the Inside Passage to Skagway, Alaska. Both studies concluded that expanded polystyrene foam was the dominant pollutant (Table 5). Plastic was found in surface waters the full length of the Inside Passage but was concentrated near harbors. At the wrack line (the zone of dried seaweed on the beach), an average square meter of the sandy beaches in the Puget Sound region had 61 pieces of anthropogenic debris. The total load of debris for the 1 m wide band investigated was estimated by the authors to be 72 million pieces, weighing 5.8 metric tons. They also concluded that most of this beach debris is generated within the region. In a different kind of study, plastic and other kinds of debris were categorized and counted, based on 25 years of data collected by International Coastal Clean Up volunteers. These volunteers devoted one day per year to cleaning up their local beach, at sites around the world. The data (Table 6) were then compiled by the Ocean Conservancy (2016), revealing some interesting patterns. Food wrappers and containers were the most abundant type of plastic beach litter, followed closely by caps, lids, cups, plates, eating utensils, drinking straws, and plastic bags. Discarded rope, fishing line, and fishing nets were also abundant, as were balloons and children’s toys.

Effects of Plastic Debris on Ocean Life Plastic debris adversely effects marine life in many ways. The two most important of these are ingestion of plastic by marine animals of all kinds, and entanglement of marine animals in various kinds of plastic debris, including fishing nets, fishing line, and plastic

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Fig. 6 Plastic pellets (nurdles) washed up on a beach. Photo courtesy of Journey to the Plastic Ocean. https://journeytotheplasticocean.wordpress.com/tag/ nurdles/

Table 5

Average count of anthropogenic debris per m2 in beach samples

Debris type

Number of pieces per square meter

Percent of all debris

Plastic foam Other plastic fragments Glass Plastic film (packaging and carrier bags) Plastic fibers/filaments Plastic pellets (nurdles) Cigarettes

42.6 6.99 6.6 1.86 1.04 0.73 0.57

69.4 11.39 10.75 3.05 1.69 1.19 0.93

Data from Davis, W. and Murphy, A. G. (2015). Plastic in surface waters of the Inside Passage and beaches of the Salish Sea in Washington State. Marine Pollution Bulletin 97, 169–62177.

packaging materials. Ingestion of plastics is becoming increasingly lethal as the quantity of plastic litter increases in the world’s oceans. Sea birds, sea turtles, marine mammals, fish, mollusks, and zooplankton mistake plastic in their environment for food. As the plastic is indigestible, plastic pieces eventually fill up the digestive tract of these animals, causing them to starve to death.

Ingestion and Entanglement by Marine Mammals As shown in Table 7, marine mammals, including whales, seals, and sea lions, are affected by both entanglement and ingestion of plastic in the world’s oceans. About one-third of whale species are known to have been entangled in plastic marine debris—mostly

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Plastics in the Ocean Table 6 Plastic debris items collected by International Coastal Clean Up volunteers, one day per year, for the past 25 years, and top five plastic items collected in 2015 Type of item

Total number collected 1985–2010

Total number collected 2015

Food wrappers and containers Caps, lids Cups, plates, utensils Plastic beverage bottles Plastic bags Drinking straws, stirrers Rope Cigarette lighters Toys Fishing line Balloons Fishing nets Bleach and cleaner bottles 6-pack holders Oil and lube bottles Bait containers, packaging Syringes

14,766,533 13,585,425 10,112,038 9,549,156 7,825,319 6,263,453 3,251,948 1,468,366 1,459,601 1,340,114 1,248,892 1,050,825 967,491 957,975 912,419 382,811 349,251

888,589 1,212,925 1,024,470 828,056 439,571

Data from Ocean Conservancy (2016). Coastal clean up data for 2015. http://www.oceanconservancy.org/our-work/marine-debris/2016data-release/2016-data-release-1.pdf

Table 7

Number and percentage of marine species that have documented entanglement and ingestion records

Animal group

Total number of species, worldwide

Number and percent of species with entanglement records

Number and percent of species with ingestion records

Sea turtles Sea birds Whales Seals and sea lions Marine fish Crustaceans

7 312 125 33

6 (86%) 51 (16%) 38 (30%) 19 (58%)

6 (86%) 111 (36%) 28 (22%) 2 (6%)

– –

34 8

33 0

Data from Laist, D. W. (1997). Impacts of marine debris: entanglement of marine life in marine debris including a comprehensive list of species with entanglement and ingestion records. In: Coe, J. M. & Rogers, D. B. (eds.) Marine debris: Sources, impacts, and solutions, pp. 99–139. New York: Springer Series on Environmental Management.

in fishing nets. When this happens, whales become exhausted in the attempt to free themselves, and often drown. Thus, the percentage of whales species affected by entanglement may be considerably larger, as the remains of drowned whales in the open ocean eventually sink to the bottom, undetected by human observers. Marine mammals also die from ingestion of plastic debris (Table 8). Much of this seems accidental, such as the swallowing of fishing nets and plastic fibers. In the case of baleen whales, it appears that their filter feeding habit causes them to swallow microplastic particles. Phthalates (DEHP and MEHP) have been found in blubber samples from baleen whales. This indicates that the whales ingested microplastics that were contaminated with persistent organic pollutants. These are bioaccumulators in fatty tissues, possibly leading to death. Fishing fleets, especially gill-netters, do considerable damage to marine wildlife other than the fish they catch. Julian and Beeson (1998) reported the results of a study of the impacts of the California gill-net fishery on marine mammals, birds, and sea turtles in the 1990s. This study found that over 1200 marine mammals were entangled in the nets and died. Most of these were California sea lions (Zalophus californicus) (899 deaths). Harbor seals (Phoca vitulina) suffered the second most deaths (257).

Ingestion and Entanglement by Sea Turtles A study by Laist (1997) found that six out of the seven species of sea turtles are affected by ingestion of plastic debris, and also by entanglement in plastic debris. Sea turtles ingest plastic bags, fishing line, and other plastics. They likely are confusing plastic bags for one of their favorite prey items: jellyfish.

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Table 8

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Plastic debris found in the digestive tracts of stranded marine mammals

Marine mammal species

Plastic found in stomach

Blainville’s beaked whale (Mesoplodon densirostris) off Brazilian coast Franciscana dolphins (Pontoporia blainvillei) off coast of Argentina Mediterranean fin whale (Balaenoptera physalus) off coast of France Sperm whale (Physeter macrocephalus)

Bundle of blue plastic threads

Fur seals (Arctocephalus spp) in sub-Antarctic waters Harbor seals (Phoca vitulina) off Dutch coast

Packaging, plastic bands, fishing line, ropes, nets Phthalates (DEHP and MEHP) found in blubber samples indicate ingestion of chemically contaminated microplastics in baleen (filter feeding) whales 134 different types of floating fishing nets in two animals (California coast); many types of plastic debris from agriculture (Andalusian coast of Spain) Plastic pellets (nurdles) Plastic sheets, rope fibers, other plastic fragments

Entanglement in fishing nets is a very serious problem for sea turtles (Fig. 7). More than 250,000 sea turtles are accidentally captured, injured, or killed by U.S. fishermen every year (Sea Turtle Conservancy, 2016). Many of these injuries and deaths take place while turtles are migrating through fishing areas. The turtles, attracted to the bait, get caught on the hooks used to catch fish. Loggerheads (Caretta caretta) and other species of sea turtles are killed by international fisheries throughout their respective ranges. Many immature loggerheads spend their early years in the Eastern Atlantic where they are captured by the thousands, especially by Spanish boats. Marine biologists estimate that international longline fleets hook or entangle 150,000–200,000 loggerheads and 30,000–60,000 leatherback turtles (Dermochelys coriacea) in the Atlantic each year, with significant mortality.

Ingestion and Entanglement by Birds Sea birds comprise a large group, with 312 species, worldwide. About one-third of these species are known to be affected by ingestion of plastic debris, and one-sixth of them have records of death by entanglement (Laist, 1997). In their study concerning the impacts of gill-net fishing off the California coast in the 1990s, Julian and Beeson (1998) recorded the deaths of 1025 entangled seabirds, including the Common murre (Uria aalge) (880 birds), Pacific loon (Gavia pacifica), Common loom (Gavia immer), Western grebe (Aechomprohus occidentalis), Double-breasted cormorant (Phalocrocorax auritus), and Brandt’s cormorant (Phalocrocorax penicillatu). Sea bird entanglement does not just occur in the open ocean. Some seabirds collect marine debris for nesting material, which may lead to entanglement. Votier et al. (2011) investigated the use of plastics as nesting material by northern gannets (Morus bassanus) and found that the gannet nests contained an average of 469.91 g of plastic. Most of this nesting material was synthetic rope, which appears to be used preferentially. On average 63 birds in the colony were entangled each year, totaling 525 individuals over 8 years. The majority of these were nestlings (Fig. 8). Unfortunately, many species of sea birds use synthetic fibers as nesting material. A study done in the North Pacific (Blight and Burger, 1997) found plastic particles in the stomachs of 8 of the 11 seabird species caught as bycatch. Like sea turtles, sea birds often mistake floating plastic for food items. A Dutch study of plastics in stomachs of northern fulmars (Fulmarus glacialis) from the North Sea examined the stomach contents of these birds from 2003 to 2007 (van Franeker et al., 2011). They found that 95% of the 1295 fulmars studied had plastic in their stomachs. The average bird had 35 pieces of plastic in its stomach, weighing 0.31 g, which is more than triple the weight of plastic they can survive. Lethal levels of plastic were found in 58% of the birds. The sources of plastic debris found in North Sea fulmars have changed through time. In the 1980s, Dutch studies found mainly industrial plastics in sea bird stomachs. Since then there has been a shift toward consumer plastics, with shipping and fisheries as the main sources. Adult Laysan and black-footed albatross have also been found to consume floating plastic objects on the open ocean. A study by Gray et al. (2012) found that these two species not only consumed substantial quantities of plastic as adults, but that they were also feeding plastic debris to their chicks (Fig. 9). One of the important contributors to the plastic found in the adult albatrosses was fishing line. Pieces of fishing line, enmeshed in floating masses of fish eggs, were consumed as the birds ate the eggs. A recent study by Savoca et al. (2016) suggests a likely reason why these and other open-ocean sea birds in the same family (albatrosses, petrels and shearwaters, storm petrels, and diving petrels) may be attracted to floating plastic debris in the open ocean. Their study shows that the slow breakdown of floating plastic debris in seawater produces dimethyl sulfide (DMS). Specifically, three different types of plastic (HDPE, LDPE, and PP) were shown to emit the odor of DMS. These sea birds rely greatly on their sense of smell to find food, and the smell of DMS is one of the characteristic odors of their natural food. These birds are zooplankton feeders, and zooplankton frequently accumulates in large numbers to feed on floating masses of marine algae. The algae release DMS. Laboratory studies discussed by Savoca et al. (2016) indicate that these birds can detect DMS particles in the air at concentrations of one part per billion (1  1012).

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Fig. 7 Diver attempting to free a sea turtle entangled in a fishing net. Photo courtesy of NOAA.

Fig. 8 Plastic used as nesting material by northern gannets. The amount of plastic varies greatly among nests from a few small fragments to very large nests with layers of material presumably formed over many years. Death by entanglement occurs mainly in nestlings. Photo from Votier, S. C., Archibald, K., Morgan. G. and Morgan, L. (2011). The use of plastic debris as nesting material by a colonial seabird and associated entanglement mortality. Marine Pollution Bulletin 62, 168–172.

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Fig. 9 Plastic debris found in dead albatross chick, North Pacific Gyre region. Photo courtesy of bluebird-lectric.net.http://www.bluebird-lectric.net/oceanography/ Great_North_Pacific_Gyre_Garbage_Patch.htm

Ingestion by Other Marine Organisms Predators that feed on zooplankton represent an important trophic guild in the ocean. Most of these are small fish that accidentally ingest plastic while feeding. Studies of these small predators show that between 1% and 29% of individuals have plastic fragments in their stomachs. The stomachs of small fish living at intermediate depths of the ocean were also found to contain plastic. Up to one-third of these fish had plastic in their stomachs. The most frequent plastic size ingested by fish in all these studies was between 0.5 and 5 mm, and the same size range of plastic commonly found in predators of zooplanktivorous fish (Cózar et al., 2014). As discussed earlier, microplastics have become ubiquitous in the world’s oceans, where they eventually sink to the sea floor. Once there, they are ingested by a variety of invertebrate animals. Wright et al. (2013) surveyed this problem and found a host of invertebrates from different orders that have been shown to consume microplastic fragments. These include grazing microzooplankton, such as the marine ciliate Strombidium sulcatum, and the benthic deposit feeders such as the polychaete worm, Arenicola marina and the sea cucumber, Holothuria floridana. Larger benthic scavengers also ingest plastic, such as the Norway lobster (Nephrops norvegicus). Larval stages of echinoderms, copepods, and arrow worms (Chaetognatha) have also been found to ingest plastics, as have benthic suspension feeders, such as the mussel (Mytilus edulis). Thus it is apparent that plastic particle ingestion is affecting every kind of marine animal life, from zooplankton to whales, and from the sea surface to the bottom of the ocean.

Chemical Contamination From Plastic Debris As discussed earlier, persistent organic pollutants (POPs), such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), dioxins, and DDT, have been shown to preferentially sorb to plastics when they encounter them in the ocean. These toxic chemicals accumulate, especially in the fatty tissues of animals, where they present serious health hazards. Little is known of animal responses to POPs ingested with plastic particles. As Andrady (2011) has said, Bioavailability and the efficiency of transfer of the ingested POPs across trophic levels are not known and the potential damage posed by these to the marine ecosystem has yet to be quantified and modelled. Given the increasing levels of plastic pollution of the oceans it is important to better understand the impact of microplastics in the ocean food web.

Invasive Species’ Use of Floating Plastic Debris One final aspect of plastic debris in the oceans to be discussed here is the “hitch-hiking” of invasive marine species on floating plastic debris. As discussed earlier, plastic debris floats across the world’s oceans and is caught up in ocean currents that transport them thousands of kilometers from their point of origin. Webb et al. (2013) have discussed the role of plastic debris in providing increased opportunity for invasive species to migrate to new environments. The authors discuss many reports of barnacles, bryozoans, polychaetes, dinoflagellates, algae, and molluscs found to adhere to plastic debris in the ocean. Terrestrial animals are also capable of riding marine debris to new areas. Ants have been reported to ride debris from the Brazilian mainland to San Sebastian Island, several kilometers away, and there are even examples of animals as large as iguanas riding flotsam to new islands in the Caribbean.

Remediation Humans are responsible for all the plastic in the oceans (and elsewhere). Our chemists were smart enough to invent polymers. Are we smart enough to deal with the environmental problems they have created? As this review has shown, plastics started to be

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dumped into the world’s oceans in significant amounts in the 1960s and 1970s. By the 1980s, people were becoming aware of some of the environmental problems associated with plastic debris in the oceans, and their impacts on marine biota. In 1997, Charles Moore discovered the Great Pacific Garbage Patch, while sailing from Hawaii to California after competing in a yachting race. Crossing the North Pacific Subtropical Gyre, Moore and his crew noticed millions of pieces of plastic surrounding his ship. In the 21st century, the problems have become much better known, and various groups of scientists and environmental organizations have been developing strategies to remediate the problems caused by plastic ocean litter.

Removal of Debris From Oceans There are several problems involved with the removal of plastic debris from the world’s oceans (Fig. 10). The scope of the problem is overwhelming, as sea water covers 70% of the planet, and there is now no region that remains free of plastic debris. It would seem to make sense, perhaps, to concentrate efforts on removing plastic from the gyre regions in which it has become concentrated. Here is what NOAA spokesperson Dianna Parker had to say about this idea (NOAA, 2016): The words ‘garbage patch’ accurately describes what it is, because these are patches of ocean that contain our garbage. But they’re not areas where you can easily go through and skim trash off the surface. First of all, because they are tiny micro plastics that aren’t easily removable from the ocean. But also just because of the size of this area. We did some quick calculations that if you tried to clean up less than one percent of the North Pacific Ocean it would take 67 ships one year to clean up that portion.

This sums up the dilemma—the problem is far too big. We have been dumping millions of metric tons of plastic rubbish into the seas for the last 40 years. The world’s oceans comprise 362 million square kilo meters of surface. Plastic debris is floating throughout

Fig. 10 Divers attempt to hoist a mass of abandoned fishing nets to the surface. Photo courtesy of NOAA.

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every sea and ocean. All that can be done at this point is to clean up the world’s beaches, severely limit the dumping of additional plastic into the oceans, and find ways of making plastic more biodegradable. We will deal with these responses, one by one.

Beach Clean Up Hammer et al. (2012) point out that the clean-up of existing marine debris often falls to local authorities, nongovernmental organizations, and volunteers. Clean-up costs can be very high, and great efforts are required to motivate a sufficient number of people to assist in clean-up efforts. For example, the Korean government recently removed derelict fishing gear from the deep seabed of the East Sea by bottom trawling with heavy hooks and ropes. A total of 470 tons of marine debris was removed from the seabed over 2 years. Most of this debris was derelict fishing gear. The total cost of this 2-year project was $2.3 million US dollars. The Ocean Conservancy (2016) has achieved great success in garnering financial support from large corporations and recruiting volunteers to clean beaches in countries around the world. In 2015 they enlisted the assistance of 800,000 volunteers, who collected almost 14 million pieces of litter from the beaches of 93 countries, representing every continent except Antarctica.

Improved Recycling In an ideal world, all plastic products would be recycled and therefore reused. Some countries are better at recycling than others, but no nation will ever be able to recycle 100% of their waste plastic. The European Commission’s recently adopted Circular Economy package includes the development of a program to increase plastic packaging recycling to 55%, a binding target to reduce landfill to 10% of all waste by 2030, and a total ban on landfilling of all separately collected waste. With the exception of Iceland, all of the Nordic countries operate container deposit schemes. Such schemes have also been deployed in the United States, where the overall recycling rate is 34%, while states with container deposit laws have an average rate of 70%. The state of Michigan charges the highest container deposit in the nation (10 cents per bottle), and this state achieved the highest recycling rate (95%) in 2013. In 2015, a European Union directive came into force that required member states to reduce the use of plastic carrier bags. France outlawed single-use plastic bags in January 2016. Since the British government forced large retailers to charge five pence for plastic carrier bags in 2015, the use of these bags has dropped by upward of 75%. These are encouraging signs of progress.

Development of New Biodegradable Plastics One alternative is to develop biodegradable plastics. Biodegradability allows plastic to break down into harmless, but essentially low-value elements such as water and CO2. Compostable packaging could be a valuable mechanism for returning nutrients to the soil (Ellen MacArthur Foundation, 2016). Chemical companies in America and Europe are working to develop biodegradable plastics, as well as a low-cost, low-temperature method of breaking down PET.

Banning of Microbeads There are hundreds of thousands of tons of microbeads floating in the ocean, and it is not feasible to clean up these nearly microscopic particles that are spread thousands of square kilometers of sea surface. Instead, we have to turn off the tap and prevent this waste from entering the ocean (Lavender Law and van Sebille, 2016). Public support for banning microbeads is growing and has prompted action from governments, multinational companies, NGOs, and policymakers. The U.S. government banned the manufacture and sale of microbeads in 2015. The British government plans to ban microbeads in 2017, and the Canadian government plans to do the same in 2018. As of 2016, the European Union was studying the microbead problem. These agreements and legislation are vitally important first steps, but they will not remove all sources of microbeads from the aquatic environment because of the wording of these documents. Microbeads used in products such as deodorants, lotions, nail polish, and cleaners that are not considered “personal care” or “rinse-off products” (Rochman et al., 2015), and so microbeads are not thus far banned in these products.

Tight Controls of Losses From Landfill Sites As discussed earlier, many of the world’s poorer countries that have ocean coasts are doing a poor job of keeping plastic debris within municipal waste facilities. A study by sponsored by the World Economic Forum (2016) reports that 72% of plastic packaging is not recovered at all, including 40% that is landfilled, and 32% that escapes the collection system. The latter is either not collected at all or is collected but then illegally dumped or mismanaged. Either these countries (Table 2) need to find the means to boost recycling of plastic waste and properly dispose of landfilled waste, or international organizations will have to lend a hand, financially.

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Conclusions Unfortunately, one of the hallmarks of the Anthropocene has been the dumping of millions of tons of plastic waste into the oceans. The problem has been escalating since the 1960s, and in recent years it has become clear that no part of the world’s oceans, no matter how remote, is free from plastic debris. According to a recent study for the World Bank by the Ellen MacArthur Foundation (2016), the weight of all the plastic debris in the oceans will equal the combined weight of all marine fish by the year 2050. Plastic ingestion and entanglement is killing millions of marine organism per year, ranging from the macroscopic birds, sea turtles, and marine mammals to microscopic zooplankton that confuses microplastic beads for food items. Whole marine ecosystems are being affected by these problems. As if these were not doing enough harm, the plastic debris itself (especially nurdles and microbeads) are poisoning marine life with persistent organic pollutants. These toxic chemicals bioaccumulate in the fatty tissues of the animals that consume them. The removal of plastic debris from the oceans is far too great a task for us to manage. The debris is simply too widely disbursed and too abundant. Individual efforts are being made to clear channels and near-shore environments of such deadly debris as old fishing nets and lines. The world’s oceanic beaches receive millions of tons of plastic debris per year, and volunteer groups organized by the Ocean Conservancy and others have made great strides in cleaning beaches. But the most important steps in ridding the oceans of plastic are to clamp down on the plastic debris that reaches the oceans. Ocean-going ships are now banned from dumping such debris overboard. If the international deep-sea fishing industry would comply with this ban, the world’s oceans would be significantly cleaner. Many nations have already banned the manufacture and sale of products containing microbeads, while other countries are joining this international movement. Plastic manufacturers are recognizing the need to keep tighter control of the plastic pellets (nurdles) they produce in their billions each year so that these do not end up in the ocean. The recycling of plastic packaging and bans or limits on the use of plastic carrier bags are also having a positive impact in reducing plastic waste in the oceans. If the developing countries with marine coasts can prevent plastic debris from escaping municipal landfills, this will also make a significant contribution to alleviating the problem. The development of biodegradable plastics would also be a major step forward in the process. There are no easy, cheap solutions to the problem of marine plastic pollution. It took decades of neglect to build to its current regrettable condition. It will certainly take decades of dedicated effort on land and sea to clean it up.

See also: Plastics and the Anthropocene; Contamination of Our Oceans by Plastics.

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Evidence in Polar Ice Records EW Wolff, University of Cambridge, Cambridge, United Kingdom © 2018 Elsevier Inc. All rights reserved.

The Anthropocene Human activity has clearly altered many aspects of the Earth system. For example, land use changes have changed the nature of the Earth’s surface in many parts of the world, in themselves changing the ecosystem structure of much of Earth. The acidity of the ocean has increased. The temperature of the atmosphere and the heat content of the ocean are increasing. The composition of the atmosphere—notably the aerosol (particulate) and trace gas composition—has changed. Taken together, these and other changes imply that one species (Homo sapiens) is altering major parts of the Earth system. This has led to the suggestion that we are entering or have entered a new era, coined the Anthropocene (Crutzen, 2002). Whether this should be treated as a formal geological entity or, for the moment, only as an informal usage, is a matter of debate (e.g., Wolff, 2013a). The purpose of this article is to describe the aspects of human activity that are recorded in polar ice cores, and the extent to which they are unusual in the context of previous millennia. I also discuss the occurrence in ice cores of many of the features that have been proposed to provide a formal definition of the start of the Anthropocene.

The Ice Core Record The archive of information held in ice cores relies on the fact that snow is laid down sequentially, snowfall by snowfall and year by year. In the absence of melting, this sequence is preserved along with impurities held in the snow, as it is buried, and eventually turns to ice. These conditions (no melting) hold over most of the Greenland and Antarctic ice sheets, and in a few high-altitude nonpolar glaciers. The latter are generally harder to interpret, although they add vital regional information, and this article will mainly concentrate on polar ice. The ice can be considered to hold information in three different ways (see, e.g., Wolff, 2012). Firstly, the isotopic content of the water molecules themselves contains information about the temperature over the ice core site at the time when the snow fell. This forms the template on which many other ice core records are hung. A second source of information is the aerosol [and sometimes “sticky” (i.e., attaching to ice surfaces) gaseous] material that is collected by falling snow and at the snow surface. In this component we find, for example, terrestrial dust, sea salt from the ocean surface and from sea ice, and many materials that arise partly from pollution, such as sulfate and lead. The concentrations of these chemical components can be measured on the melted ice using techniques such as ion chromatography, fluorescence spectrometry, and inductively coupled plasma mass spectrometry. Finally, ice cores trap bubbles of air that contain a record of the composition of stable gases in the atmosphere: N2, O2, Ar, CO2, CH4, and other molecules. This part of the record arises in a slightly different way: snowflakes turn to what is called “firn”—a mixture of ice crystals and air that densifies with depth. Eventually, at depths typically between 60 and 100 m, the porous firn compresses to an impermeable ice matrix in which small bubbles of air are trapped. The gases in these bubbles can be extracted by crushing or subliming the ice so that the air composition can be analyzed in the same way as for flasks of modern air. Obtaining the ice generally involves drilling out cylinders of ice sequentially. The longest ice cores obtained penetrate to over 3,000 m, reaching the bed of the ice sheet, and the oldest ice core drilled so far (at Dome C, Antarctica) reaches 800,000 years old. In Greenland, the oldest ice recovered and dated is 128,000 years. One factor in deciding where to drill is the snow accumulation rate, which affects the resolution and age, which often have to be traded against each other. Sites with high snowfall rate (some cores drilled at the famous site at Law Dome have an accumulation rate of about 1 m water equivalent per year) easily resolve annual layers in the components trapped with the snow. The record in air bubbles is always less well resolved, because air diffuses in the firn, and bubbles close over a finite depth range, with the result that even at the sites with highest snow accumulation, a single depth horizon contains air with ages covering just over a decade. At sites with very low snow accumulation, such as Dome C in central East Antarctica (2.5 cm water equivalent per year), annual layers cannot be resolved, and the air at a given depth has a distribution of ages covering centuries. Thus, for well-resolved records of recent decades, sites with a high snowfall rate must be used; but sites with a low snowfall rate are good for providing records covering a long period of time.

Signals of Anthropogenic Change Ice cores record a wide range of anthropogenic signals. A distinction has to be drawn between those that are signs of a global change, such as the long-lived (and, therefore, well mixed) greenhouse gases, and those that are signs of regional change, such as many aerosol species with a relatively short atmospheric lifetime. I will start with the long-lived gases that have global climate significance.

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Trace Gases Ice cores are the primary evidence about past changes in trace gases, including those identified as greenhouse gases. Although it is possible to infer CO2 concentrations indirectly for periods from which ice core data are unavailable (for instance, from boron isotope measurements in marine sediments), only ice cores provide direct measurements, and of all three major long-lived greenhouse gases—carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). The pattern of all three gases over the last 800,000 years, represented by ice cores, has been of low values in cold glacial stages and higher concentrations in warm interglacial periods. In each case, the values reached in the last century exceed any value recorded in the previous 800,000 years.

CO2 Between 800,000 years ago and AD 1800 (Fig. 1), the concentration of CO2 recorded in ice (using a compilation of several cores) always fell within the range 174–299 ppm (parts per million) (data summarized in Bereiter et al. (2015)). The low resolution of some parts of the record means that higher values could have occurred for short periods, but the long lifetime of CO2 concentration excursions in the atmosphere means that substantial breaches of this range could not have occurred. The earliest occurrence of concentrations exceeding 299 ppm was in the first decade of the 20th century, although they had been on a steady upward trend (Fig. 2) for several decades before that (MacFarling Meure et al., 2006), after some centuries in which they had been about 280 ppm. Concentrations in Antarctica are now around 400 ppm, that is, 40% above their mean for centuries before the recent rise. The accompanying change in carbon isotopic content of the CO2 (d13C) is also highly unusual: the range of d13C in the last 25,000 years (Schmitt et al., 2012) had been 6.3 to 6.8%, but values have been falling (Rubino et al., 2016a) in parallel with the increase in CO2 concentration, and are now below 8%. The increase in concentration is clearly due to fossil fuel and cement industry emissions, with a contribution from changes in land use. There is some discussion in the literature about the beginning of sustained influence of human activity on the CO2 concentration. As discussed above, concentrations rose above their multi-century average in the early 19th century and above the envelope of the previous 800,000 years in the early 20th century. However, it has been argued in a series of papers (Ruddiman et al., 2016) that humans raised CO2 concentrations above their “natural” trajectory in the early Holocene period, about 8000 years ago, through farming and land clearance activities. It has been proposed that the usual pattern is that CO2 concentrations fall slowly during interglacials, and that the slow rise (about 20 ppm from 8000 to 200 years ago) was anomalous. If this were the case, it would be quite significant because the difference in concentration suggested to have been due to human influence might have been enough to avoid the triggering of a glacial period. The arguments about this early anthropogenic influence remain controversial, and are based on two pillars. The first of these is the plausibility of the required emissions being caused by the much smaller human population of that time. The second concerns the feasibility of estimating the expected trends in CO2 during warm interglacials, based on previous interglacials and the temporal pattern of Earth’s orbital characteristics. A final issue needs to be discussed with respect to CO2 and the Anthropocene. A prominent dip in CO2 concentration (by up to 10 ppm) is seen, centred at 1610 AD in the Law Dome record. It was suggested (Lewis and Maslin, 2015) that this dip was the result of the arrival of Europeans in the Americas, and might represent a suitable marker for the start of the geological Anthropocene. The

Fig. 1 Greenhouse gases over the last 800,000 years. The blue lines are Antarctic ice core data from Dome C for methane (Loulergue et al., 2008), and from Dome C and Vostok for CO2 (Lüthi et al., 2008); red lines are from Law Dome (Antarctica) (MacFarling Meure et al., 2006); green data are recent atmospheric data. Figure reprinted from open access article (Wolff, 2013a).

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Fig. 2 Some ice core measures of human influence in the last three centuries. For the CO2 and CH4 panels, the blue dots are ice core data from Law Dome (Antarctica) (MacFarling Meure et al., 2006); the red lines are monthly atmospheric data from Cape Grim Observatory (Australia, courtesy of CSIRO Marine and Atmospheric Research and Australian Bureau of Meteorology); the black horizontal line is the highest value measured in ice cores covering the previous 800,000 years. Beta radioactivity is from a snow pit in Coats Land, Antarctica (Wolff et al., 1999). Black carbon in snow from D4 (Greenland) (McConnell et al., 2007).

excursion in CO2 concentration is hard to discern in ice cores with less resolution than Law Dome. Evidence has recently been presented that the dip was caused by Little Ice Age cooling (Rubino et al., 2016b), and is not, therefore, an anthropogenic signal.

Methane Similar to CO2, the concentration of methane started to increase (Fig. 2) during the early 19th century (MacFarling Meure et al., 2006). Until then, its value during the previous 800,000 years always fell between 340 and 800 ppb (parts per billion, Fig. 2) (Loulergue et al., 2008). In 2015, its concentration at high southern latitudes had reached almost 1800 ppb, more than double any preindustrial value. The increased concentrations result from emissions from a range of human activities, including agricultural activity such as farming of rice, cattle ranching, landfill emissions, and leakage from the fossil fuel industry. Although atmospheric methane concentrations are two orders of magnitude less than those of CO2, they are important because methane is, with commonly used metrics, about 30 times more potent as a greenhouse gas. Just as with CO2, there is a debate about whether a slower increase in methane over the 6000 years before the 19th century is also due to human activity (in particular early Asian rice farming) (Ruddiman et al., 2016). The increase contrasts with a decrease in the preceding millennia and during many other interglacials. However, modeling studies suggest that the increase might also be explained at least in part by natural variability (Singarayer et al., 2011). Although there is little doubt that emissions from agriculture had some effect before the 19th century, the extent of the early anthropogenic influence on methane remains under discussion.

N2O and other trace gases The nitrous oxide record of the last 800,000 years is incomplete, but no values higher than 303 ppb are recorded (Schilt et al., 2010) before the industrial era. Although N2O concentrations started to increase in the 19th century (MacFarling Meure et al., 2006), presumably because of agricultural practices, it is only in the second half of the 20th century that the previous maximum was exceeded. Values in 2015 were approaching 330 ppb. The atmosphere now contains many other trace gases whose main origin is anthropogenic—for example, halogenated gases such as chlorofluorocarbons (CFCs) and hydrofluorocarbons and SF6. Because many of these compounds only started to be emitted in the last few decades, they would not yet have a very useful profile in the air bubbles in ice cores, and few measurements have been

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made. In the future, it should be possible to use ice cores to document not only the increase but the subsequent decrease of some of these gases due to regulatory action, for example, those implicated in depleting stratospheric ozone. The course of their increase can currently be charted from measurements in firn air (Butler et al., 1999): the air in the diffusive column above the depth at which the air bubbles become closed off. In this firn air section, large air samples can be collected and data with depth can be deconvolved to provide temporal profiles covering recent decades.

Summary of trace gases Ice cores show that the concentrations of the most important long-lived greenhouse gases have increased to unprecedented levels during the 20th century, with trends that started in the 19th century. Such levels have not been seen in at least the previous 800,000 years. These increases have already had a significant effect on global climate, and they have altered the pH of the ocean (IPCC, 2013). There remains controversy about whether anthropogenic emissions were also responsible for much slower (and less unprecedented) rises in concentration of CO2 and CH4 over the previous several thousand years. Ice cores are capable of recording increases in a range of anthropogenic gases, some of which have no natural sources.

Aerosol (Particulate) Compounds Radioactive material The dawn of the nuclear age, represented by the first nuclear bomb tests in the atmosphere in 1945, has been suggested as a possible marker for the start of the Anthropocene. Nuclear tests place many radioactive isotopes that were previously not present, or present at low concentrations, into the atmosphere. Those derived from explosions that reached the stratosphere are widely spread and should appear in different sedimentary archives, making them a potentially suitable marker. Both bulk beta radioactivity and tritium have been extensively measured in ice cores, and indeed used as an age marker to help date ice. At their peak, concentrations of b-radioactivity and tritium were 100 times their background levels, and the concentration increase is easily detected in Greenland, Antarctic, and low-latitude ice cores. A first significant jump in b-radioactivity is seen in 1954, with a further jump in the 1960s, followed by a slow reduction as material was removed from the atmosphere and as the radioactivity decayed (Fig. 2). The onset of the nuclear age is, therefore, easily documented in ice, although the relatively short halflife of the components involved in producing b-radioactivity (90Sr and 137Cs, 30 years) and of tritium (12 years) makes them unsuitable as a long-term “golden spike.” Isotopes with longer half-lives, such as 239Pu (half-life 24,000 years), can also be detected in polar ice. Profiles through recent decades from a range of Greenland and Antarctic cores have recently been published (Arienzo et al., 2016), clearly showing the sharp increase in the 1950s and subsequent reduction in concentration. This signal will show up for many millennia as a sharp spike in concentration of this isotope.

Sulfur and nitrogen compounds In many parts of the world, human activity has taken over as the main quantitative contributor to the sulfur and nitrogen cycle. For nitrate and sulfate, combustion is the main contributor, while for ammonium, agricultural emissions are crucial. The sulfate concentration in Greenland ice rose to about four times its preindustrial value in 1980, with particular increases in the periods 1900–1920 and 1940–1980 (Fischer et al., 1998). Concentrations did not reach those achieved in the last glacial maximum, or during brief excursions due to the impact of volcanic eruptions, but the sustained high concentration was nonetheless unprecedented in the Holocene (last 11,000 years). Concentrations have decreased again since 1980, as emission controls in some countries have taken effect. Sulfate aerosol is of climatic importance as the aerosol itself has a radiative effect, and acts as a cloud condensation nucleus. However, the lifetime of aerosol in the atmosphere is short (weeks), so the spatial footprint of emissions is quite small. It is possible to see a sulfate increase in high-altitude lower latitude ice cores, representing, for example, European emissions for alpine cores, and Chinese and Indian emissions in the Himalayas. However, there are large natural sources (e.g., marine biogenic) and there is not yet any discernible increase above background for sulfate in Antarctica. The concentration of nitrate in Greenland ice rose by about a factor of 2 in the 20th century, mainly between 1950 and 1980, and reached a level that was probably somewhat higher than achieved in the previous 100,000 years (summarized in Wolff (2013b)). However, no significant increase is yet seen in Antarctic ice and snow.

Other aerosol compounds Many other compounds of (partial) anthropogenic origin can be and have been analyzed in polar ice cores, though they all share the issue that the signals are regional rather than global. This regional issue means that the anthropogenic trend is not contemporaneous at different sites, although taken together the data from different cores can define an anthropogenic footprint and influence. The cycles of a range of heavy metals are dominated by human activity. Particular attention has been paid to lead (Pb). A Greenland ice core study showed that smelting and mining activity in the Greek and Roman eras already elevated the lead concentration in Greenland ice above its Holocene natural background (Hong et al., 1994) over 2000 years ago. Further increases in the 18th century and later were vastly enhanced by the emissions of lead from leaded gasoline (petrol) from the 1950s. At its maximum, in the 1960s, the concentration of lead in Greenland was enhanced 200 times above the background (Boutron et al., 1991); the banning of lead from fuel has caused a significant decrease in the last three decades. Despite this very strong hemispheric

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contamination, the highest concentrations only just exceeded those seen in the last glacial maximum, which were due to the much greater concentration of natural terrestrial dust. The concentration of lead in Antarctic snow also increased by a factor of about 5 above its natural level during the late 20th century (Wolff and Suttie, 1994). Many other metals also show enhancements in ice cores from both polar regions. Although most studies have focussed on inorganic chemical analysis, it is clear that there are many anthropogenic organic compounds (persistent organic pollutants) that could be measured at unprecedented concentration in samples of polar snow and ice from recent decades. Analytical issues mean that few have been systematically investigated, however, particularly in the Antarctic. One material of considerable climatic interest is black carbon, which can have an important radiative impact, both in the atmosphere and in snow. Black carbon shows an increase in Greenland snow (Fig. 2) starting about 1850, reaching a maximum (about seven times background) in 1910 (McConnell et al., 2007). A subsequent decrease in concentration (especially since 1950) still leaves concentrations above background levels, and continues to contribute a significant radiative forcing which could be enhancing Greenland snow melt.

The Future of the Ice Core Record While ice cores are an attractive medium for recording the temporal pattern of various human influences, it should be borne in mind that some parts of the glaciological record are themselves at risk from the effects of anthropogenic warming. Many nonpolar glaciers are shrinking, and the records they might contain are becoming increasingly vulnerable to melting and percolation of water (which can scramble their records). For this reason, a project “Protecting Ice Memory” has been initiated (see http://fondation.univgrenoble-alpes.fr/menu-principal/actions/preservation-des-patrimoines/ice-memory-in-english/) to preserve such records by storing ice sequences in an ice cave in Antarctica, so that they would be available in the future when new analyses are devised. The Greenland ice sheet is considered vulnerable to irreversible retreat beyond a certain degree of global mean temperature rise, recently estimated to lie between 2 and 4 C (IPCC, 2013, p. 1140). While loss of ice would take centuries or longer, such a sustained warming is within the range of future projections, so the permanence of the ice core archive must be in some doubt. Antarctica (or at least East Antarctica) is generally considered to be able to withstand much larger climate changes, beyond those that are usually projected.

Conclusion: Ice Cores and the Anthropocene Ice cores document increases in a range of atmospheric constituents. In some cases, these show a clear anthropogenic influence but do not exceed levels seen to occur naturally during the period covered by ice cores. Anthropogenic influence for lead is clear as long as 2000 years ago, although there was a strong acceleration in anthropogenic footprint (qualitatively and quantitatively) in the mid19th century and again about 1950. The possibility that human activity had a significant influence on CO2 and CH4 some thousands of years ago remains a matter of debate among scientists. For those materials that do reach unprecedented (in the last 800,000 years) levels, the date at which this occurs varies from the early 20th century (CO2) to the 1950s (radioactive material from nuclear bomb tests) and later. The ice core and firn record documents both bad news (increases in atmospheric contamination) and good news—reduced concentrations due to regulatory action and reduced emissions (e.g., lead in gasoline, sulfate in the Arctic, CFCs). The most obvious signs in ice of a global scale influence of human activity come from two sources. The large increases in greenhouse gas concentrations reflect the increasing influence of humanity on the climate. The increases in many radionuclides document the start of the human ability, not yet used, to transform the planet through nuclear war. Both of these would be significant proof of a human era, the Anthropocene. Long into the future, and as long as the great ice sheets survive, ice cores will document what form this human influence eventually took.

References Arienzo MM, McConnell JR, Chellman N, et al. (2016) A method for continuous (PU)-P-239 determinations in Arctic and Antarctic ice cores. Environmental Science & Technology 50(13): 7066–7073. Bereiter B, Eggleston S, Schmitt J, et al. (2015) Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present. Geophysical Research Letters 42(2): 542–549. Boutron CF, Görlach U, Candelone J-P, Bolshov MA, and Delmas RJ (1991) Decrease in anthropogenic lead, cadmium and zinc in Greenland snows since the late 1960s. Nature 353: 153–156. Butler JH, Battle M, Bender ML, et al. (1999) A record of atmospheric halocarbons during the twentieth century from polar firn air. Nature 399: 749–755. Crutzen PJ (2002) Geology of mankind. Nature 415(6867): 23. Fischer H, Wagenbach D, and Kipfstuhl J (1998) Sulfate and nitrate firn concentrations on the Greenland ice sheet. 2. Temporal anthropogenic deposition changes. Journal of Geophysical Research 103(D17): 21935–21942. Hong S, Candelone JP, and Boutron CF (1994) Greenland ice history of the pollution of the atmosphere of the northern hemisphere for lead during the last three millenia. Analusis 22(7): M38–M40. IPCC (2013) Climate change 2013: The physical science basis. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change. Cambridge and New York: Cambridge University Press.

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Lewis SL and Maslin MA (2015) Defining the anthropocene, Nature 519(7542): 171–180. Loulergue L, Schilt A, Spahni R, et al. (2008) Orbital and millennial-scale features of atmospheric CH4 over the last 800,000 years. Nature 453: 383–386. Lüthi D, Le Floch M, Stocker TF, et al. (2008) High-resolution carbon dioxide concentration record 650,000-800,000 years before present. Nature 453: 379–382. MacFarling Meure C, Etheridge D, Trudinger C, et al. (2006) Law Dome CO2, CH4 and N2O ice core records extended to 2000 years BP. Geophysical Research Letters 33(14): L14810. McConnell JR, Edwards R, Kok GL, et al. (2007) 20th-century industrial black carbon emissions altered arctic climate forcing. Science 317(5843): 1381–1384. Rubino M, D’Onofrio A, Seki O, and Bendle JA (2016a) Ice-core records of biomass burning. The Anthropocene Review 3(2): 140–162. Rubino M, Etheridge DM, Trudinger CM, et al. (2016b) Low atmospheric CO2 levels during the Little Ice Age due to cooling-induced terrestrial uptake. Nature Geoscience 9(9): 691–694. Ruddiman WF, Fuller DQ, Kutzbach JE, et al. (2016) Late holocene climate: Natural or anthropogenic? Reviews of Geophysics 54(1): 93–118. Schilt A, Baumgartner M, Blunier T, et al. (2010) Glacial-interglacial and millennial-scale variations in the atmospheric nitrous oxide concentration during the last 800,000 years. Quaternary Science Reviews 29(1–2): 182–192. Schmitt J, Schneider R, Elsig J, et al. (2012) Carbon isotope constraints on the deglacial CO2 rise from ice cores. Science 336(6082): 711–714. Singarayer JS, Valdes PJ, Friedlingstein P, Nelson S, and Beerling DJ (2011) Late-Holocene methane rise caused by orbitally-controllled increase in tropical sources. Nature 470: 82–85. Wolff EW (2012) Chemical signals of past climate and environment from polar ice cores and firn air. Chemical Society Reviews 41(19): 6247–6258. Wolff EW (2013a) Ice sheets and the anthropocene. In: Waters C, Zalasiewicz J, Williams M, Ellis MA, and Snelling A (eds.) A stratigraphical basis for the anthropocene. London: Geological Society of London. Wolff EW (2013b) Ice sheets and nitrogen. Philosophical Transactions of the Royal Society B 368. https://doi.org/10.1098/rstb.2013.0127. Wolff EW and Suttie ED (1994) Antarctic snow record of southern hemisphere lead pollution. Geophysical Research Letters 21(9): 781–784. Wolff EW, Suttie ED, and Peel DA (1999) Antarctic snow record of cadmium, copper, and zinc content during the twentieth century. Atmospheric Environment 33(10): 1535–1541.

Humanly Modified Ground M Edgeworth, University of Leicester, Leicester, United Kingdom © 2018 Elsevier Inc. All rights reserved.

Glossary Archaeosphere The totality of humanly modified ground considered as a global entity. Artifacts Objects made by humans, bearing traces of manufacture and use. Diachronous Of more than one time, varying in date of formation. Novel materials Manufactured materials (such as ceramics, concrete, glass, and plastics) that are unprecedented in earlier geologic strata. Stratigraphy The study of rock and soil strata and their patterns of layering in the ground. Technofossils Artifacts considered as potential trace fossils of humans. Tells Settlement mounds formed from the accumulation of occupation debris.

Introduction Humanly modified ground is known by various names including artificial ground, man-made ground, made ground, and anthropogenic ground. It is classified differently, depending on the discipline, so that what geologists call artificial ground, for example, might be identified by soil scientists as anthrosols and technosols, by architects and civil engineers as made ground, and by archaeologists as archaeological strata. Each discipline brings its own methods and perspectives to bear upon it, perceiving it through the prism of its specific conceptual frameworks. But as the ground beneath our feet, humanly modified ground cannot be “claimed” by any one specialism, since it is wider than all of them. It is a transdisciplinary phenomenon manifesting, in one form or another, as matter relevant to a range of scientific, humanistic, artistic, and practical fields—not least to the study of the Anthropocene.

Early Study The story of the discovery of humanly modified ground starts in cities. Cities are built on platforms of their own debris, rising up over time so gradually that city dwellers hardly notice its vast presence. The first to take stock of this phenomenon were civil engineers working on large urban infrastructure projects in the mid-19th century. One of these was Eduard Suess, the well-known Austrian geologist. As a civil engineer who brought a supply of fresh water to Vienna from the Alps, he was actively involved in the physical transformation of the city from a medieval stronghold to modern urban center. In the 1850s, ancient ramparts surrounding the historic core were removed and replaced by boulevards and parks of the Ringstrasse, a process that involved cutting great cliff faces through urban strata. It was during these groundworks that Suess observed the platform of accumulated occupation debris upon which Vienna was built, which he called the Schuttdecke or “rubble blanket.” This layer of humanly modified ground varied greatly in thickness but was up to 10 m deep in places. Within it were abundant inclusions of artifacts, novel materials unprecedented in earlier geologic layers (such as ceramics, glass, concrete, and metal alloys), and domesticated animal bones, dating mostly from Roman to postmedieval times. Suess recorded and mapped the rubble blanket as a geologic layer in his famous book on the ground of Vienna (Suess, 1862). Meanwhile, other European cities were undergoing transformations on a similar scale. In London, Joseph Bazalgette was engaged in the construction of a modern sewer system and associated river embankments. During the works, he systematically recorded the thickness of what he called “made ground.” It contained, among other things, large quantities of human bones from numerous burial grounds cut through by the trenches. In the center of London, the layer was 5–8 m thick. The paradox is that in uncovering and recording the existence of humanly modified ground, 19th-century engineers were simultaneously transforming it—and on a massive scale. In cutting through the existing formations, they were extending these even deeper into the ground. In raising the level of the ground through the building of river embankments and other earthworks, they were adding yet more humanly modified material to ancient accumulations of it. Their works left substantial traces, which inevitably became integral parts of newly configured and transformed versions of humanly modified ground. In the 1920s, geologist Robert Sherlock noted that made ground tends to be much thicker in older parts of London, decreasing in thickness the further one goes away from the historic core. He observed local thickenings of it where older towns and villages had been absorbed into the expanding metropolis, thereby hinting at processes of coalescence of previously separate formations. Such findings apply to the development of historic towns and cities throughout the world. However, Sherlock was concerned with all types of humanly modified ground, not just accumulations of urban occupation debris. He realized that humans were agents of

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denudation and agents of deposition, comparable to wind or water in their erosive power. Mines and quarries, railway cuttings, canals, and so on are all examples of human denudation. But whereas natural forces of erosion tend to wear away softer material and surfaces first, the human activities of mining and tunneling often remove hard rock from deeper strata to leave the surface relatively undisturbed (Sherlock, 1922). Sherlock’s great insight was to make the connection between processes of denudation and deposition, and his approach was to study both together as part of the overall impact of humans on the Earth’s surface. Examine any area of humanly modified ground that is raised up, and there is probably a roughly equivalent hole or set of holes cut into the Earth’s surface, from where the material was originally obtained. The same applies the other way round. Wherever there is a created void in the ground surface, there is likely to be some accumulation of material elsewhere. The correspondence is not exact, but as a general rule of thumb, it is extremely useful to bear in mind. We might think in terms of flows of material, human-induced, from one geologic context to another.

Flows of Materials Take for example Grant Park in Chicago. Covering over 300 ac, the park is laid out on reclaimed land. The process of reclamation probably started in 1851, when a railroad was built on a causeway in Lake Michigan. It ran parallel to the shore, creating a lagoon between it and Chicago itself. In 1871, the Great Fire of Chicago devastated the city, and much of the rubble was dumped in the lagoon, with the causeway acting as a revetment wall for the landfill. But the process did not stop there. In the early 20th century, the Chicago Tunnel Company built a network of tunnels for a subsurface freight railway below the city streets, and the spoil from tunnel excavations was dumped in the lake, extending the reclaimed land far beyond the original causeway. In subsequent decades, the underground railway helped to move millions of tonnes of spoil from construction sites, ashes and cinders from the burning of coal, and general city waste to a lakeside disposal station, where a large derrick dumped it out in the lake. Spoil from construction of the Chicago subway in the late 1930s provided further landfill material. The essential point about raised ground being connected with holes, voids, and cuts—and vice versa—could be illustrated with examples from every country in the world. Cities like San Francisco, Mumbai, and Mexico City—to name just a few—are built in part on substantial landfill deposits. An important research question to ask is where did that material come from? The answer is different in each case but always illuminating. In London, one of the largest engineered structures is the Thames Embankment, constructed by teams of navvies led by Joseph Bazalgette. Millions of tonnes of earth fill were required, and this was mostly obtained by dredging gravel from the bed of the river. A deepening of the river and its estuary was inextricably connected with the building up of the banks in the city. At the same time in London, engineers constructing the world’s first metro system had the opposite problem—how to dispose of millions of tonnes of spoil. Here, the question might be asked, where did this material go? Some of it was used to make railway embankments on overland stretches of line. Some was used to fill in quarries or mines or gravel pits where mineral extraction had taken place. Much was taken by barge downriver to be dumped on the shores of the Thames Estuary, to reclaim land for agriculture. Some of it was even used to make the terraces of Chelsea’s football ground. More recently, during the construction of Crossrail tunnels, over 5 million tonnes of earth were dumped at Wallasea Island in Essex to create a bird sanctuary and wildlife reserve. Any future geologist studying the stratigraphic signature of metros would have to consider not only the tunnels but also the numerous places of deposition of spoil throughout the country. To complicate matters further, material was imported into metro tunnels and exported out from them, in a kind of geologic exchange. Hundreds of millions of bricks were used in the construction of early metro tunnel linings, for example. Some of these came from the very clay that had been excavated from the tunnels themselves, but most were manufactured from material quarried from clay pits in and around London. These clay pits, then, are also part of the overall stratigraphic signature of early metros. Some of those pits were subsequently filled with spoil from further tunneling activity. Large clay pits of south Bedfordshire, the United Kingdom, were dug by giant dragline excavators from the early to late 20th century, cutting deep down into Jurassic clays. The pits are situated in a rural location, but there are at least two senses in which they might be regarded as giant trace fossils of the city. First, the clay extracted was used to make bricks for the construction of houses in London suburbs. Secondly, some were subsequently used as containers for landfill, much of it consisting of household rubbish generated from the same suburban housing. The compacted landfill is up to 70 m deep. That is not necessarily the end of the story. The landfill deposits may themselves be mined for their mineral content at some point in the future. In Berlin, immense amounts of rubble were created by wartime bombing, and there were no convenient holes in the ground nearby to dump it. The solution was to spread it over available open areas and to use the raised ground for parks or airports or alternatively to heap it up into great mounds, forming artificial hills. The greatest of these is the Teufelsberg or “Devil’s Mountain.” At 80 m high, it is the highest point in the city. The rubble hill is mainly made up of concrete, bricks, window glass, slates, tiles, and mortar—the constituent materials of which were mostly excavated from the ground, though it would be practically impossible to locate the original quarries, most of which have since been filled in. It is now known that the annual volume of human-induced flows of materials is at least three times greater than the amount of sediment eroded, moved, and deposited by the world’s rivers. But whereas rivers tend to carry their sediment loads in a downward direction, humans and their machines can raise material up against the force of gravity, constituting a form of geologic uplift. Geologists studying humanly modified ground along the east coast of Japan found it behaves differently from nonmodified geologic strata when placed under stress by extreme events such as earthquakes and tsunamis. It is subject to liquefaction and fluidization or liable to shear off along its lower bounding surface. Geopollution can be caused by contaminated substances

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migrating along pathways within it (Nirei et al., 2012). On the other hand, human modification of ground can have stabilizing effects or may limit geopollution. For example, in the aftermath of damage to the nuclear plant at Fukushima, scientists injected synthetic materials into the ground and created a barrier of frozen soil in efforts to prevent leaks of radioactive water into the sea.

The Archaeosphere It might be thought from the aforementioned examples that humanly modified ground is only a recent phenomenon. But while the advent of steam-powered and petrol-fueled engines accelerated the rate of landscape modification, land has been extensively modified by people using simpler technology for thousands of years. Humanly modified ground includes these more ancient strata and more recent deposits. All are part of a single, growing entity, which has also been called the “archaeosphere.” (Edgeworth, 2014) This term is useful when considering humanly modified ground on a global scale, as a thin layer interposed between the unmodified geosphere and the atmosphere, intermeshed with the biosphere and the hydrosphere, and forming the material residue part of the technosphere (Haff, 2014). This archaeosphere layer may be shallow and patchy, like a well-worn carpet, but it occupies a crucial interface zone. It is in active interchange with the atmosphere, for example, in the absorption or release of carbon dioxide by plants and microbes in cultivation soils depending on farming regimes (large amounts of CO2 are released from soils through intensive plowing). It sustains some forms of life and smothers others. Many habitats have been destroyed, but others have been created by it. The structures of the human world—fields, gardens, farms, villages, cities, skyscrapers, airports, shanty towns, roads, and railway networks—are supported by it. Multiple small-scale local modifications of land, such as terracing of hills and valleys, when viewed over large areas and long periods of time, amount to landscape transformations on a vast scale. Terraces formed by building low walls act as dams for flows of sediment moving downhill, with gravity and flowing water being harnessed to do most of the work in moving material. Sediment trapped behind the walls is used to form the terraces of level fields. Huge tracts of land have been terraformed in this way. Agricultural production throughout much of Asia and other parts of the world is based on this long-established and still evolving material infrastructure. The growth of humanly modified ground in urban settings, noted by Suess and others, is prefigured by accumulation of occupation debris in “tells” or ancient settlement mounds. In the earliest protourban centers in the valleys of the Tigris and Euphrates, mud bricks fired in the sun were used to build houses. When these decayed, the material from which they were made formed part of the ground on which subsequent houses were built, raising the height of the settlement mound. Surrounding the mounds are the stratigraphic traces of quarries and hollows from which clay for the mud bricks was taken. Some of these were used as dumps and infilled with settlement rubbish—the world’s first landfills. The Teufelsberg in Berlin, discussed earlier, was not the first dump of wartime rubble. When Carthage was destroyed by the Romans in 146 BCE, for instance, demolition rubble was spread over a wide area and can still be found as a substantial destruction layer in the ground beneath the later Roman city. There is no difference in principle between these ancient deposits and the recent or contemporary ones, though the latter may have been created by machine and contain plastic and ceramic artifacts. In many places, they can be found together in the same stratigraphic sequences, with later layers and features overlaying or cutting through earlier ones. The archaeosphere did not stop forming at some point in the past. Its features got bigger and its accumulated layers accelerated in their rate of formation. Isolated deposits coalesced into larger conglomerations, which were themselves expanding. Cities continued to rise up on their platforms of occupation debris, burying rivers and streams in the process. There was also an extension of humanly modified ground downward, as mines and metros and deep tunnel sewers and other subterranean tunnel systems were built deeper into the ground. Such processes are ongoing. The archaeosphere and its humanly modified ground are still forming. “Archaeo” means old, but there is no contradiction in applying the term to an entity which contains recent and contemporary, as well as ancient, things. The appropriateness of the term derives from the fact that extensive modern human modifications of the ground leave stratigraphic traces, which will form the archaeology of tomorrow. Significantly, the archaeosphere has a lower bounding surface, which can be located in the ground. It varies from being clear-cut to very diffuse. Archaeologists sometimes informally refer to it as “the surface of the natural.” Geologists in Japan call it the Jinji unconformity, which when loosely translated means the conjunction of human and natural. Its key characteristic is that it is a diachronic boundary, changing in date of formation from one part of its surface to another (Edgeworth et al., 2015). One part of it might date to the 21st century, while an adjacent part might date to the Neolithic or the Iron Age. At present, it has a time variability of about 10,000 years. It is presently regarded as unsuitable to mark the start of the Anthropocene because it does not provide a sufficiently high degree of resolution in terms of its date of formation. However, if looking from a greater distance away—say, 100 million years in the future—the boundary might be perceived as a high-precision stratigraphic marker.

Geologic and Archaeological Approaches Despite early work on humanly modified ground by geologists such as Suess and Sherlock, it was only from the 1980s that geologists started to systematically record it as a geologic layer, now more usually referred to as “artificial ground” (Price et al., 2011; Ford et al., 2010). The category is taken to comprise made ground (where material has been deposited on the natural ground

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surface), worked ground (where the ground has been cut away), infilled ground (where cut away and filled in with material), landscaped ground (where greatly reshaped), and disturbed ground (where disturbance is too ill-defined to classify as any of the aforementioned text). There is some scope for greater detail. Thus, the category of infilled land can be subdivided into types of fill, for example. This classification system works well for large-scale mappings of landscapes where the required level of detail is low. But for more fine-grained description, it would be necessary to switch to archaeological methods of identification and recording. What is the difference between artificial ground and archaeological stratigraphy? The material entity in question is essentially the same no matter what it is called. But there are disciplinary differences in perception and method. Thus, geologists generally map artificial ground as a single entity relative to other strata, with only basic subdivisions noted within it, while archaeologists record it in much more detail as a complex set of deposits made up of multiple layers, cuts, features, lenses, and so on. There are many advantages in taking a multidisciplinary approach to the study of humanly modified ground. It is useful to shift between scales of analysis—to zoom in from the bigger picture to the detail and zoom back out again. To get an overall grasp of scale of human impact on the stratigraphy of the Earth, the more general geologic characterizations may be most appropriate. To pinpoint the first appearances, developments, and spreads of novel materials (such as ceramics, metals, concrete, or plastics) or specific types of artifact (such as iPhones) in the stratigraphic record, the more detailed focus and method of archaeology becomes relevant. Humanly modified ground is a multiscalar phenomenon. The closer it is examined, the more information it can reveal, but it is also crucial to step back to study it as a global-scale entity. It is estimated that humanly modified ground in some form covers about half the ice-free terrestrial surfaces of the Earth, with this area expanding rapidly as the population of humans (and their domesticated animals) increases. However, mapping of surface extent needs to be supplemented by data on the crucial third dimension of depth. To capture its growth and transformation in the fourth dimension of time, furthermore, it would also be necessary to map it at periodic intervals. The so-called rubble blanket of Vienna, for example, now covers an area several times larger than it was when Suess mapped it in the 1850s. Its time-transgressive character should be recorded. “Humanly modified ground” is used here as a broad term, which can be easily transferred across disciplines. It is important to be critical of terms still in common usage such as “man-made ground.” Needless to say, all humans of whatever gender or age are responsible for the formation of this material entity, and the name should reflect this. Similarly, the term “artificial ground” might be taken to imply that it is wholly human-made. Yet, even the most humanly shaped ground is subject to a range of biological and geologic forces—activity of soil microbes, tunneling of ants or termites, burrowing of earthworms and small mammals, delving of plant roots, groundwater percolating through, and so on—which may play significant roles in its formation and transformation. In his early encounter with the Schuttdecke, Eduard Suess perceived it mainly as a single entity. But he was also aware of its internal differentiation and presciently remarked that within it could be found the whole poignant history of Vienna. The implication was that if one learned to read the configuration of physical traces and placement of objects it contains, that history could be unraveled. In the 150 years since Suess made those observations in Vienna, archaeologists have honed geologic principles of stratigraphy to the specific character of humanly modified ground. There are aspects of humanly modified ground that are unprecedented in earlier geologic strata. One difference is the prevalence of large numbers of cuts and recuts, some of which are intentionally placed and embody elements of intentional design. Another difference is the presence of architectural formations such as wall foundations within strata. Geologic principles alone are not sufficient to explain such configurations of evidence. However, by treating cuts and other interfaces as stratigraphic entities, it becomes possible to disentangle sequences of layers, structures, cut features, and their fills. Of particular relevance is the Harris matrix (Harris, 1989, 2014), which, though originally designed to deal with microsequences of strata on complex urban archaeological sites, can be scaled up to cope with much larger human-made features, such as metro tunnel systems or giant quarries filled with landfill.

Other Unique Aspects Unlike ancient deposits used to define the beginnings and ends of previous geologic time periods, humanly modified ground is still in the process of formation. The cutting and deposition of it can be observed in real time. Another remarkable aspect is that even the scientists who study it are agents in those formation processes. This is expressed in the material stratigraphy itself. Within the configurations of strata are the cuts and fills of archaeological trenches and geologic boreholes. Any subsequent investigation by means of excavation or drilling will inevitably leave further traces. The layer is likewise unusual in being found not only on Earth but also, in incipient form, on Earth’s moon and on other planets in the solar system, where humans or their remotely operated robotic vehicles have left traces (Gorman, 2014). Perhaps the main distinguishing characteristic of humanly modified ground is the abundance of artifacts and novel material inclusions. Artifacts are trace fossils of humans, sometimes called “technofossils” for that reason. But these are very different from fossils of biological organisms, which when alive were subject to forces of natural selection. Artifacts, in contrast, are subject to cultural and technological processes of development but only indirectly influenced by forces of natural selection. A similar observation can be made in relation to the remains of domesticated animals and plants often found in the same assemblages as artifacts and novel materials. Unlike organisms that lived in all previous geologic periods, domesticated species have been subject to human selection alongside forces of natural selection. This subtle difference marks something quite new in the history of the Earth.

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For a stark illustration of the difference in stratigraphic terms, consider the clay quarries filled with landfill mentioned earlier. Because the quarries were cut down deep into Jurassic clays, the lower boundary or cut is formed of material containing the fossilized remains of ammonites, belemnites, Gryphaea, marine crocodiles, plesiosaurs, and other creatures that lived in warm, shallow seas over 145 million years ago. Above the boundary and in close proximity are disposable diapers, electric wires, tin cans, glass bottles, broken plates, rubber gloves, bricks, bathroom tiles, toilet seats, window frames, car tires, school exercise books, and computer motherboards, among a plethora of other items. The most common bones to be found are those of factory-reared chickens and other domesticated animals, sometimes still in packaging. It might be objected here that some artifacts, such as hand axes, are found in earlier geologic strata. This is true, but these are made out of natural materials like stone. Humanly modified ground, however, contains materials completely unprecedented in earlier strata. Pottery, glass, brick, tile, metal alloys, and plastics are examples of such novel materials. Then, there are the “anthropic rocks” (Cathcart, 2011) such as concrete and tarmac, which now cover large parts of the surfaces of urban and suburban areas, cladding the ground like a kind of armor. Concrete in particular forms a common building material for every kind of building from skyscrapers to car parks to metro tunnels and is a major component of construction and demolition rubble going into landfill and urban strata. More concrete is now used than all other building materials put together. Annual production was recently estimated at 5 billion cubic yards or 8.78 billion metric tonnes. With the world population of humans at 7.3 billion, that works out at 1.2 tonnes of concrete produced per person per year. It is interesting to follow the thought experiment of Zalasiewicz (2008) in asking the question, how might an outcrop of the “human event stratum,” containing the fossilized traces of such objects and materials, appear to a hypothetical geologist in a 100 million years times?

References Cathcart RB (2011) Anthropic rock: A brief history. History of Geo- and Space Sciences 2: 57–74. Edgeworth M (2014) The relationship between archaeological stratigraphy and artificial ground and its significance to the Anthropocene. In: Waters CN, Zalasiewicz J, and Williams M, et al. (eds.) A stratigraphical basis for the Anthropocene, pp. 91–108. London: Geological Society. Edgeworth M, Richter DB, Waters C, Haff P, Neal C, and Price SJ (2015) Diachronous beginnings of the Anthropocene: The lower bounding surface of anthropogenic deposits. The Anthropocene Review 2(1): 33–58. Ford, J. R., Kessler, H., Cooper, A. H., Price, S. J. and Humpage, A. J. (2010). An enhanced classification of artificial ground (British Geological Survey), Open Report, OR/10/036. Gorman AC (2014) The Anthropocene in the solar system. Journal of Contemporary Archaeology 1(1): 87–91. Haff PK (2014) Technology as a geological phenomenon: Implications for human well-being. In: Waters CN, Zalasiewicz J, and Williams M, et al. (eds.) A stratigraphical basis for the Anthropocene, pp. 301–309. London: Geological Society. Harris E (1989) Principles of archaeological stratigraphy, 2nd edn. London & New York, NY: Academic Press. Harris EC (2014) Archaeological stratigraphy: A paradigm for the Anthropocene. Journal of Contemporary Archaeology 1(1): 105–109. Nirei H, Furuno K, Osamu K, Marker B, and Satk~unas J (2012) Classification of manmade strata for assessment of geopollution. Episodes 35: 333–336. Price S, Ford J, Cooper A, and Neal C (2011) Humans as major geological and geomorphological agents in the Anthropocene: The significance of artificial ground in Great Britain. Philosophical Transactions of the Royal Society of London 13: 1938. Sherlock R (1922) Man as a geological agent: An account of his action on inanimate nature. London: H.F. & G.: Witherby. Suess E (1862) Der Boden der Stadt Wien. Vienna: W. Braumüller. Zalasiewicz J (2008) The earth after us. Oxford: Oxford University Press.

Multimedia Components 99percentinvisible. Making up ground. Episode 228. Podcast, web article and video links. Published online: 13th September 2016. http://99percentinvisible.org/episode/making-upground/. Lecture on ‘Beyond the Surface of Anthropocene landscapes’ by Matt Edgeworth, presented at DieAngewandteWien (University of Applied Arts, Vienna) 2015. https://www.youtube. com/watch?v¼NqM3V6nnHk4.

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Plastics and the Anthropocene PL Corcoran and K Jazvac, University of Western Ontario, London, ON, Canada A Ballent, Algalita Marine Research and Education, Long Beach, CA, United States © 2018 Elsevier Inc. All rights reserved.

Introduction Plastics are materials that are composed of polymers, which are repeating chains of molecules that can be processed and shaped. Conventional plastics are produced from organic substances, such as crude oil and natural gas, through distillation, polymerization, and processing. Plastics can be characterized as thermoplastics, which can be melted, molded, and resolidified repeatedly, and thermosets, which upon formation, form irreversible chemical bonds between polymers. Most plastics used in consumer goods are thermoplastics, and can therefore be recycled, although they also represent the largest source of plastics pollution in the environment. Petroleum-based plastic products have become ubiquitous in the modern urban lifestyle as cost-effective alternatives for materials such as metal, glass, paper, ceramic, and natural fibers. Industrial production of commercial plastic has increased exponentially since the 1960s, with global production levels reaching 311 million tonnes per year in 2014 (PlasticsEurope, 2015). It is anticipated that an additional 33 billion tonnes of plastic will be added to the planet by 2050 if there is no change in current consumption rates (Rochman et al., 2013). The consequence of increased plastics production is greater input into the environment. Jambeck et al. (2015) estimated that 4.8–12.7 million metric tonnes of mismanaged plastic waste entered the world’s oceans in 2010. The global plastics contamination of Earth’s ecosystems has resulted from the immense scale of the plastic industry, poor product design that does not consider the postconsumer stage, low-recycling rates, and the lack of policies supporting a circular plastics economy (Neufeld et al., 2016). Plastic products in the natural environment undergo photo-, thermooxidative, and hydrolytic degradation, which, combined with mechanical weathering, promotes embrittlement by reducing the molecular weight of the polymer (Andrady, 2011). The result of embrittlement is the creation of microplastics, plastic particles that are