Essentials of Landscape Ecology PDF

 OUP CORRECTED PROOF – FINAL, 08/06/19, SPi Essentials of Landscape Ecology OUP CORRECTED PROOF – FINAL, 08/06/19, SPi  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi Essentials of Landscape Ecology Kimberly A. With 1 OUP CORRECTED PROOF – FINAL, 08/06/19, SPi...

 OUP CORRECTED PROOF – FINAL, 08/06/19, SPi Essentials of Landscape Ecology OUP CORRECTED PROOF – FINAL, 08/06/19, SPi  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi Essentials of Landscape Ecology Kimberly A. With 1 OUP CORRECTED PROOF – FINAL, 08/06/19, SPi 1 Great Clarendon Street, Oxford, OX2 6DP, United Kingdom Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide. Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries © Kimberly A. With 2019 The moral rights of the author have been asserted First Edition published in 2019 Impression: 1 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by licence or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this work in any other form and you must impose this same condition on any acquirer Published in the United States of America by Oxford University Press 198 Madison Avenue, New York, NY 10016, United States of America British Library Cataloguing in Publication Data Data available Library of Congress Control Number: 2018962521 ISBN 978–0–19–883838–8 (hbk.) ISBN 978–0–19–883839–5 (pbk.) Printed in Great Britain by Bell & Bain Ltd., Glasgow Links to third party websites are provided by Oxford in good faith and for information only. Oxford disclaims any responsibility for the materials contained in any third party website referenced in this work.  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi Preface Writing a textbook is rather like being enrolled in a of the material. Some students require an introduction multi-year course on the subject, in which the roles of to basic ecological concepts and principles, whereas student and teacher are essentially interchangeable. others are looking for synthesis, critical review, and a Since we are all really students at heart, my approach deeper treatment of the analytical, methodological, or to writing this textbook has been from the standpoint modeling approaches they are hoping to implement in of a student, starting with myself. I know what difficul- their own research. ties I have faced in understanding certain topics and The principal challenge in writing this textbook, as analytical approaches, and after teaching landscape in the classroom, has thus been to develop a curricu- ecology for more than 20 years, I know what difficul- lum that serves the needs of a diverse audience. To that ties many of my students encounter when first exposed end, I have tried to provide a mix of basic concepts, to particular concepts or methods. This textbook is examples, and case studies, as well as a more advanced thus for the student of landscape ecology, whatever treatment of certain topics. The examples and case your academic standing, professional rank, or title. studies were selected to emphasize a range of organ- Welcome to our shared course on landscape ecology. isms, systems, and geographic locations to the extent The scientific domain encompassed by landscape possible, although this was often influenced by the ecology is incredibly vast and wide-ranging. Landscape idiosyncratic nature of scientific research as well as by ecology is built upon contributions from various fields my idiosyncratic research into that literature. I therefore in the natural and social sciences, and in turn contrib- offer advance apologies if I appear to have overlooked utes to both basic and applied problems in each of an important paper or study, perhaps even one of your its constituent fields. No single textbook—including own contributions to the field. I fear this is inevitable, this one—can possibly do it justice. My focus in this given the vastness of the literature, the sheer size of the textbook is thus on the ecology of landscape ecology. task at hand, and the limited space available to address I am an ecologist by training, and besides landscape each topic. ecology, much of my research has been in the areas In terms of the book itself, I thank Sharon Collinge, of behavioral, population, and community ecology. Henri Décamps, Kevin McGarigal, Jean Paul Metzger, In addition, I have long been interested in conservation John Wiens, and Jingle Wu for their suggestions, sup- and the applications of landscape ecology for conser- port, and enthusiasm for the initial book proposal. I am vation biology. Thus, my perspective herein is inevitably also indebted to the following colleagues who took the that of an ecologist, with an eye toward applications time to review and provide comment on various sec- of landscape ecology for conservation and natural tions or chapters of the book (and sometimes, on more resource management. than one): John Briggs, Thomas Crist, Lenore Fahrig, Despite this—or maybe even because of this—it is Olivier François, Janet Franklin, Marie-Josée Fortin, my hope that this book will be of interest to students Doug Goodin, Eric Gustafson, Colleen Hatfield, Nancy and professionals in other areas of landscape ecology, McIntyre, Jean Paul Metzger, Emily Minor, Rick Ostfeld, such as geographers and landscape planners, who Luciana Signorelli, Mark Ungerer, Helene Wagner, might desire an ecological overview to complement Lisette Waits, Jingle Wu, and Patrick Zollner. I would their training or design perspective. Judging from the also like to thank the graduate students who have par- composition of my own landscape ecology course over ticipated in my landscape ecology course at Kansas the years, I envision an audience that is likely to be quite State University, and who provided input on many diverse regardless. In the past, this course has attracted of the initial chapter drafts and offered suggestions students from all over campus and from fields as for improvement, including other examples or topics diverse as ecology, environmental science, entomology, I had overlooked. Special thanks in this regard are geography, agronomy, range sciences, forestry, conser- due to Rachel Pigg, Jay Guarani, Mark Herse, Sean vation biology, fisheries, and wildlife management. Hitchman, Nate Cathcart, Reid Plumb, Emily Williams, The academic background, training, and expectations and E. J. Raynor. of these students are all very different, which demands Of course, this book would never have seen the light a varied and diversified approach in the presentation of day without a publisher. I very much appreciate  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi vi Preface the care and oversight provided by Ian Sherman and McIntyre, for uncovering many of the images con- Bethany Kershaw, senior and assistant commissioning tained within these chapters. The end result is a text- editors, respectively, for biology at Oxford University book that is as attractive as I hope it is informative. Press, and Ioan Marc Jones, senior production editor Last, but certainly not least, I thank my husband, for academic texts at OUP, for managing the book’s Gray Woods, for his unremitting support and encour- transition through to its final production phase. Paul agement throughout the many years it has taken me to Beverley had the unenviable task of copy-editing the complete this project. I dedicate this book to our son, entire text, but the book is better for his efforts. This Johnathan, who I fear no longer remembers a time project started out under the auspices of Sinauer when his mother wasn’t working on this book, becom- Associates (now an imprint of OUP), and I therefore ing a sort of bibliographic sibling. Wise beyond his owe a large debt of gratitude to Andy Sinauer for the years, he had asked me at the start, “How do you know opportunity and for his support (and patience) during what to write?” I don’t recall my answer then, but I this long process; production editors, Kathaleen have one for him now: figuring out what to write is Emerson and Stephanie Bonner, as well as art director easy when one has access to such great material; it’s and production manager, Chris Small, for their guid- figuring out when to stop that is hard. For, as I now ance, design aesthetic, and attention to detail; Jan realize, the book will never truly be finished, but hope- Troutt, for her beautiful artwork; Johannah Walkowicz fully, this is a good and worthwhile start. and Michele Bekta for their efforts behind the scenes in obtaining permissions; copy editor Carol Wigg for Kimberly A. With comments and suggestions on the first set of chapters; Division of Biology and photo researchers, Mark Siddall and David Kansas State University  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi Contents Chapter 1 An Introduction to Landscape Ecology: Foundations and Core Concepts 1 Why Study Landscape Ecology? 2 Birth of a Discipline 4 Regional Perspectives on Landscape Ecology 5 European Perspective 5 North American Perspective 7 Globalization of Landscape Ecology 8 Core Concepts of Landscape Ecology 9 Organization of this Book 11 Chapter Summary Points 12 Discussion Questions 13 Chapter 2 Scaling Issues in Landscape Ecology 14 Why is Scale so Important in Ecology? 14 Uses (and Misuses) of Scale in Ecology 16 Ecological Scale 16 Relationship between Grain and Extent 16 Effect of Changing Grain and Extent 18 Choosing the ‘Right’ Scale of Study 21 Hierarchy Theory and Landscape Ecology 24 Hierarchical Organization of Biological Systems 27 Structure of a Hierarchical System 28 Landscape Scale or Landscape Level? 29 Implications of Hierarchy Theory for Landscape Ecology 32 Extrapolating Across Scales 33 Extrapolating Within Domains of Scale 34 Extrapolating Across Domains of Scale 34 Uncertainty, Predictability, and Ecological Forecasting 36 Future Directions 39 Chapter Summary Points 40 Discussion Questions 41 Chapter 3 Landscape Heterogeneity and Dynamics 42 Heterogeneity and Disturbance Dynamics as Core Concepts in Landscape Ecology 42 Emergence of Heterogeneity and Dynamical Concepts in Ecology 44 Heterogeneity at Broad Geographic Scales: Biogeography and Life Zones 44 Dynamics of Plant Community Assembly: Climax State or Independent Assembly? 45 Patch Dynamics: A Paradigm Shift in Ecology 47 Toward a Non-Equilibrium View of Ecology 48 Homogeneity: The Frictionless Plane of Ecological Theory 49  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi viii Contents Patch-Based Theory in Ecology 50 Toward a Landscape-Mosaic View of Environmental Heterogeneity 52 How is Heterogeneity Defined? 54 Spatial Heterogeneity 54 Temporal Heterogeneity 55 How are Disturbances Defined? 56 The Disturbance Regime 56 The Intermediate Disturbance Hypothesis 58 Large Infrequent Disturbances 59 Implications of the Disturbance Regime for Landscape Dynamics 61 Formation and Evolution of Landscapes: Geomorphological Processes 63 Formation of Montane Landscapes 63 Formation of River Networks 68 Formation and Diversity of Soils 69 Landscape Dynamics: Abiotic Disturbances 73 Volcanic Eruptions 73 Landsliding 76 Flooding and the Natural Flow Regime 78 Windstorms, Hurricanes, and Storm Surges 85 Drought 89 Fire 94 Landscape Dynamics: Biotic Agents of Landscape Formation and Disturbance 101 Organisms as Geomorphic Agents 102 Organisms as Ecosystem Engineers 102 The Keystone Role of Species 105 Relative Impact of Species on Landscapes 107 Humans as the Primary Driver of Landscape Change 107 Stages of Anthropogenic Landscape Transformation 108 Types of Human Land Use 110 Land-Use Legacy Effects 120 Future Directions 122 Chapter Summary Points 123 Discussion Questions 125 Chapter 4 Landscape Pattern Analysis 127 On the Importance of Landscape Pattern Analysis in Landscape Ecology 127 Sources of Landscape Data 128 Historical Land Surveys 129 Remote Sensing 131 From Landscape Data to Landscape Data Analysis 153 Geographical Information Systems 156 Data Input Subsystem 157 Data Processing and Database Management Subsystem 158 Data Manipulation and Analysis Subsystem 159 Data Output Subsystem 165 Landscape Metrics 165 Measures of Landscape Composition 167 Measures of Landscape Configuration 168 Effects of Pattern and Scale on Landscape Metrics 178 Use and Misuse of Landscape Metrics 184 Spatial Analysis 186 A Primer to Spatial Statistics 186 Spatial Statistics 189  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi Contents ix Future Directions (and Some Caveats) 202 Chapter Summary Points 203 Discussion Questions 205 Chapter 5 Landscape Connectivity 206 What is Landscape Connectivity and Why is it Important? 206 Elements of Landscape Connectivity 208 Structural versus Functional Connectivity 209 Patch Connectivity versus Landscape Connectivity 210 Patch-Based Connectivity Measures 210 Which Patch-Connectivity Measure to Use and When? 212 From Patches to Landscapes 213 Methods for Assessing Landscape Connectivity 214 Neutral Landscape Models 214 Graph-Theoretic Approaches 221 Assessing Connectivity in Heterogeneous Landscapes 227 Assessing Connectivity in River Networks 232 Which Landscape Connectivity Approach to Use and When? 235 Beyond Landscape Connectivity 236 Should Landscape Connectivity be a Dependent or Independent Variable? 236 Future Directions 237 Chapter Summary Points 237 Discussion Questions 238 Chapter 6 Landscape Effects on Individual Movement and Dispersal: Behavioral Landscape Ecology 239 Why are Movement and Dispersal Important from a Landscape Ecological Perspective? 240 Scales of Movement 241 Movement Responses to Hierarchical Patch Structure 242 Allometric Scaling of Movement 245 Movement Responses to Patch Structure 245 Movement out of Patches (Emigration) 246 Movement Between Patches 256 Movement into Patches (Immigration) 260 Analysis of Movement Pathways 264 Tracking Animal Movements 265 Scaling Issues in Tracking Animal Movements 268 Measuring Movement Pathways 269 Models of Animal Movement 272 Mathematical Models of Animal Movement 272 Spatially Explicit Models of Animal Movement 277 Space Use and Home-Range Analysis 280 Methods of Home-Range Estimation 280 Measuring Plant Dispersal 284 Future Directions 286 Chapter Summary Points 287 Discussion Questions 289  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi x Contents Chapter 7 Landscape Effects on Population Distributions and Dynamics 291 Why Should Landscape Ecologists Study Population Distributions and Dynamics? 292 Overview: Effects of Habitat Loss and Fragmentation on Populations 292 Habitat Loss versus Fragmentation 293 Patch Area and Isolation Effects 294 Fragmentation and Edge Effects 294 Species Distribution Patterns 299 Spatial Pattern Analysis of Species Distributions 300 Patch versus Landscape Effects on Species Distributions 302 Species Distribution Models 303 Resource-Selection Functions 303 Ecological Niche Models 306 Climate Envelope Models 308 Summary 309 A Primer to Population Models 310 Basic Population Growth Model 310 Matrix Population Models 310 Source–Sink Population Dynamics 312 How Best to Identify Population Sources and Sinks? 313 Are Habitat Sinks a Drain on Habitat Sources? 314 Metapopulation Dynamics 315 Classical Metapopulation Models 316 Incidence Function Model 318 Source–Sink Metapopulations 319 Metapopulation Viability and Extinction Thresholds 321 Spatially Explicit Population Simulation Models 329 Which Population Model to Use and When? 332 Future Directions 334 Chapter Summary Points 334 Discussion Questions 335 Chapter 8 Landscape Effects on Population Spatial Spread: Range Shifts, Biological Invasions, and Landscape Epidemiology 337 Spatial Spread: The Good, the Bad, and the Ugly 337 Landscape Effects on Species’ Range Shifts 339 Modeling Species Distributions in Response to Climate Change 340 Range Shifts in Fragmented Landscapes 343 Landscape Effects on Invasive Spread 344 Landscape Ecology of Invasive Spread 344 Spatial Models of Invasive Spread 349 Landscape Connectivity and the Potential for Invasive Spread 353 Source–Sink Metapopulation Dynamics and Invasive Spread 355 Species Distribution Models of Invasive Spread 356 Landscape Epidemiology 357 Landscape Ecology of Disease Spread 358 Spatial Models of Disease Spread 362 Metapopulation Models of Disease Spread 364 Landscape Connectivity and the Potential for Disease Spread 366 Disease Risk Mapping 370 Evolutionary Landscape Epidemiology 371  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi Contents xi Future Directions 373 Chapter Summary Points 374 Discussion Questions 375 Chapter 9 Landscape Genetics: Landscape Effects on Gene Flow and Population Genetic Structure 377 What is Landscape Genetics? 378 A Primer to Population Genetics 380 Types of Genetic Markers 380 Estimating Genetic Variation and Divergence 383 Measuring Gene Flow and Population Connectivity 390 From Population Genetics to Landscape Genetics 393 Bayesian Genetic Clustering 393 Multivariate Ordination Techniques 396 Landscape Genetics 398 Landscape Correlates of Population Genetic Structure 399 Functional Connectivity 399 Identification of Movement Corridors and Barriers to Gene Flow 404 Habitat Area versus Fragmentation Effects 409 Source–Sink Population Dynamics 411 Current versus Historical Landscape Effects on Population Genetic Structure 413 Evolutionary Landscape Genetics 415 Beyond Strong Selection: Other Mechanisms of Microgeographic Divergence 416 Toward a Landscape-Genomic Approach to the Study of Adaptive Genetic Variation 421 Adaptive Responses to Future Climate and Landscape Changes 425 Future Directions 429 Chapter Summary Points 431 Discussion Questions 432 Chapter 10 Landscape Effects on Community Structure and Dynamics 434 A Landscape Perspective on the Structure and Dynamics of Communities 435 Measures of Community Structure 436 Species Richness 437 Species Diversity 437 Spatial Partitioning of Diversity 439 Patterns of Species Diversity 446 Latitudinal Gradients in Species Richness 447 Elevational Gradients in Species Richness 451 Species–Area Relationships 455 Island Biogeography and the Habitat Fragmentation Paradigm 467 Effects of Habitat Loss and Fragmentation on Species Diversity 474 Habitat-Amount Hypothesis 475 Interdependence of Habitat Loss and Fragmentation 477 Landscape Effects on Species Interactions 478 Competitive Coexistence 478 Predator–Prey Dynamics 484 Parasite–Host and Host–Parasitoid Dynamics 489 Plant–Pollinator Interactions 495  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi xii Contents Metacommunity Structure and Dynamics 502 Future Directions 505 Chapter Summary Points 507 Discussion Questions 511 Chapter 11 Landscape Effects on Ecosystem Structure and Function 512 Why is a Landscape Ecology of Ecosystems Needed? 512 Ecosystem Processes in a Landscape Context 514 Topographic and Land-Management Effects on Nutrient Availability and Ecosystem Productivity 516 Effects of Land-Cover Change on Nutrient Dynamics 521 The Metaecosystem: Interacting Ecosystems in a Landscape Context 524 Spatial Subsidies 525 Mobile-Link Species 527 Source–Sink Metaecosystem Dynamics 529 From Ecosystem Function to Landscape Function 530 Landscape Function and ‘Dysfunctional’ Landscapes 530 Assessing and Monitoring Landscape Function 532 Managing for Landscape Multifunctionality and Sustainability 539 Future Directions 541 Chapter Summary Points 542 Discussion Questions 545 Glossary 547 References 573 Index 623  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi 1 An Introduction to Landscape Ecology Foundations and Core Concepts At first glance, this image (Figure 1.1) evokes a pastoral landscape, with cultivated fields of row crops and perhaps some lavender growing in the distance. Fields are neatly arrayed and delineated, some apparently fallow or newly plowed, others bearing regular furrows or bisected by roadways and irrigation canals. The land- scape bears the strong imprint of human land use, with all of its lines and orderli- ness. Upon closer inspection, however, we come to realize that this is not an actual photograph, but an abstraction, a quilted landscape created using colored swatches of silk crepe. Nevertheless, the quilt does depict an actual landscape— the ‘fields of salt’ in a region of the San Francisco Bay Area where natural wetlands have been converted to salt ponds for industrial use. As with our earlier impression of an agricultural landscape, this image similarly calls to mind the dramatic effects humans can have on landscapes through the alteration of their structure and function. A quilt is thus an apt metaphor for the landscape: as patchworks of Figure 1.1 Fields of Salt, art quilt. © Linda Gass 2007. Essentials of Landscape Ecology. Kimberly A. With, Oxford University Press (2019). © Kimberly A. With 2019. DOI: 10.1093/oso/9780198838388.001.0001  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi 2 Essentials of Landscape Ecology different land covers and land uses, landscapes are to tackle the complex ecological and societal conse- similarly shaped by humans and, like quilts, they are quences of human land use. sometimes in need of restoration and conservation. The human modification of landscapes is hardly a recent phenomenon, however. Landscapes bear the imprint of past human land uses that in some cases Why Study Landscape Ecology? date back centuries or even millennia. We humans We are living in a transformative era. Since the start of have a long history of altering the landscapes around the Industrial Revolution, humans have issued in a us, whether it be for quarrying stone, felling forests, new geological period—the Anthropocene—a ‘geology plowing grasslands, draining wetlands, or damming of mankind’ (Crutzen 2002). There are few places on and diverting rivers. For example, the indigenous people Earth that have not been touched, either directly or of the Mississippian culture, which flourished more indirectly, by humans (Vitousek et al. 1997; Figure 1.2). than a thousand years ago throughout the river valleys A burgeoning global population has increased both of the midwestern and southeastern United States, our need for land and the mass consumption of transformed these floodplain landscapes through the resources provided by that land. Modern technologies creation of huge earthen mounds. One cannot help but have made it more efficient and economical for us to marvel at the industry of the people who created these exploit the land and its resources, while global trans- earthen pyramids, the largest of which stands 30 meters portation networks and the globalization of economies tall and covers 6 hectares, solely by packing mud and have increased not only the interconnections among clay by hand. The largest Mississippian site is Cahokia, diverse regions of the globe, but also the extent of our located just east of modern-day Saint Louis, Missouri impact on those regions. With landscapes worldwide (Figure 1.3). During its heyday (around 1100), Cahokia being transformed at a rate and scale that rivals even was one of the world’s great cities, with a population the largest of natural forces, it should come as no sur- exceeding that of many European cities of the time, prise that a new and comprehensive science is needed including London. The inhabitants of Cahokia were Pristine Minimal impact Low impact Moderate impact 0 2,000 4,000 6,000 8,000 High impact Very high impact km Indeterminate Figure 1.2 Anthropic landscapes. Humans have a pervasive influence on landscapes. Worldwide, few areas have not been affected—either directly or indirectly—by our activities. This global anthropic landscape map was generated from the overlay of a global human population density map with a global land-quality map to illustrate the distribution of anthropic tension zones where humans are having the greatest impact, particularly on soil resources. Source: USDA-NRCS (2000).  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi An Introduction to Landscape Ecology 3 (A) (B) Figure 1.3 Cahokia. Cahokia was a cultural mecca in its day (1050–1250), a bustling urban center at the heart of what was then one of the largest cities in the world. (A) Aerial view of Cahokia today, with Monks Mound in the distance. (B) Artist’s rendition of what the Central Plaza with Monks Mound might have looked like during Cahokia’s heyday (~1100). Source: (A) © National Geographic Creative/Alamy Stock Photo. (B) Courtesy of Cahokia Mounds State Historic Site, painting by L. K. Townsend. early landscape architects, having carefully designed and The effect of human land use on landscapes—past, engineered these mounds, which evidently required present, and future—is a major focus of landscape a great deal of technical expertise (Dalan et al. 2003). ecology. As humans alter the landscape, they also The largest mounds were likely built for ceremonial invariably alter its ecology, including the ecological and religious purposes, and may have been topped flows and myriad ecological interactions that occur by large buildings where the elites or rulers lived within the landscape. All landscapes are heterogeneous (Figure 1.3B). Although the stonemasonry involved in in that they are made up of a variety of landforms, eco- the construction of the better-known pyramids of ancient systems, vegetation communities (habitat types), and Egypt and Mesoamerica is also a marvel of engineering, land uses, reflecting the different processes—physical, these earthen mounds, which persist today as small biological, and anthropogenic—that have shaped hills dotting the landscape (Figure 1.3A), are a testa- them. In turn, the structure of the landscape—its com- ment to the ability of even pre-industrial humans to position and configuration of habitat types or land physically shape the landscape. uses—influences the biological and physical processes  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi 4 Essentials of Landscape Ecology that give the landscape its form. The flows of materials, The largest of the IALE regional chapters is the nutrients, and organisms across the landscape are all United States chapter (US-IALE).1 Its inaugural meet- important for the maintenance of critical ecological ing was held in January 1986 in Athens, Georgia (USA), functions that contribute to the structure and diversity just a few years after the establishment of the inter- (i.e. heterogeneity) of the landscape in the first place. national governing body, reflecting an early interest in Landscape ecology, then, is the study of the reciprocal the field by a number of American ecologists. Indeed, effects of pattern on process: how landscape patterns several American ecologists had been among the influence ecological processes, and how those ecological attendees at the landscape ecology symposia in Europe. processes in turn modify landscape patterns (Risser In April 1983, 25 ecologists and geographers were et al. 1984; Turner 1989; Pickett & Cadenasso 1995; invited to a three-day workshop in Allerton Park, Turner et al. 2001). From this standpoint, humans are Illinois (USA) to discuss opportunities for developing but one of the many forces that shape landscapes, landscape ecology in North America (Risser et al. 1984; albeit an important one. Risser 1995). The Allerton Park workshop represents a In this introductory chapter, we place the emer- pivotal moment, not just for landscape ecology in gence of landscape ecology as a relatively new scien- North America, but for the discipline as a whole. The tific discipline within its historical context by discussing workshop is widely credited with establishing a new the contributions from its elemental disciplines to its paradigm for landscape ecology, one that continues to development, as well as the different schools of thought guide it today—a focus on the reciprocal effects of that have subsequently shaped its science and practice. landscape pattern and ecological process (Wiens 2008; Next, we highlight the core principles and major Wu 2013). research themes in landscape ecology, which will be addressed more fully throughout the remainder of this textbook. We conclude with an overview of the book At the outset, the idea of landscape ecology sounded appeal- itself to help guide our study of landscape ecology. ing.... Urgency and a sense of responsibility for the quality of landscapes motivated us... and we realized that the integra- tion of ecology and human activities was not only necessary Birth of a Discipline but could bring new insights to the study of landscapes. In comparison to many other established fields in the Forman & Godron (1986) natural and social sciences, or even to other areas of ecology, landscape ecology is a relatively new science. If we mark the birth of a scientific discipline by the At around this same time, the publication of two sem- establishment of a professional society and/or a schol- inal textbooks (one by Zev Naveh and Arthur Lieberman arly journal dedicated to its study, then landscape ecol- , and the second by Richard Forman and Michel ogy emerged only about 35 years ago. Since it is rare to Godron ) further helped to elevate and establish witness the birth of a discipline, a brief overview of its landscape ecology as a new discipline. The discipline’s development is warranted, especially since this pro- flagship journal, Landscape Ecology, published its first vides insight into the different perspectives on the issue in 1987, with American ecologist Frank Golley at study and practice of landscape ecology today. its helm (Golley 1987). The journal has since developed The International Association for Landscape Ecology into one of the top-ranking journals in the fields of (IALE) was officially founded in October 1982 at an geography and ecology (Wu 2007a). Not surprisingly, international symposium held in the spa town of these early scholars and leading figures in landscape Pieštʼany, in what is now western Slovakia. Its con- ecology were all participants in the initial European ception, however, occurred some 18 months earlier, in symposia, the Allerton Park workshop, or both. April 1981, at the first international congress for land- The mid-1980s thus represented a watershed period scape ecology at Veldhoven in the Netherlands (Antrop for landscape ecology. The rise of landscape ecology 2007). The formation of IALE thus represented the cul- at that time can be attributed to a number of factors mination of a long gestation among European ecolo- related to theoretical and conceptual developments in gists and geographers, who as far back as the late 1960s ecology, technological advances, and increasing concern and early 1970s had perceived the need for a broader, over human impacts on the environment. In the field multidisciplinary science concerned with the manage- of ecology, several developments had particular rele- ment, planning, and design of landscapes (Naveh 2007; vance for landscape ecology: (1) island biogeography Wu 2007a). The IALE now consists of more than two and metapopulation theory provided a new paradigm dozen regional chapters from all over the world, repre- 1 The United States regional chapter voted in April 2019 to become senting individual countries as well as collectives of IALE-North America, so as to better reflect its multi-national nations (e.g. Africa-IALE and IALE-Europe). constituency.  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi An Introduction to Landscape Ecology 5 for studying the effects of habitat patchiness on eco- to study elevational vegetation gradients. As one of the logical systems; (2) there was a growing recognition of first landscape ecologists, Troll deftly blended the spa- the importance of spatial scaling in the design and tial approach of the geographer with the functional interpretation of ecological research; and (3) there was approach of the ecologist, a combination that has come a shift from viewing ecological systems as closed (iso- to epitomize landscape ecology today (Turner et al. lated) and driven toward an equilibrium state to view- 2001). ing them instead as open (connected) and dynamic systems. In addition, technological advances in remote sensing, geographic information systems (GIS), and Regional Perspectives on computer processing were making it possible to Landscape Ecology collect, store, analyze, and display unprecedented Early contributions by European geographers and ecolo- amounts of geospatial data over vast spatial extents, gists to the nascent field of landscape ecology helped allowing for the first time a true study of landscapes at define—as well as gave name to—a new discipline. The broad spatial scales. Finally, the growing concern over European perspective pervades the science and practice human modification of the environment, especially of landscape ecology in many parts of the world today, in the heavily industrialized nations where landscape although the subsequent establishment of landscape ecology originated, was a motivating force in the ecology in North America followed a very different tra- development of the discipline in the mid-1980s. The jectory during its development. In this section, we con- cumulative effects of human land use were clearly sider how these different regional perspectives have responsible for the loss and fragmentation of habitats contributed to the development of landscape ecology. that in turn were contributing to a global extinction cri- sis (e.g. Wilcove et al. 1998). Indeed, it is no coincidence that conservation biology also emerged as a scientific European Perspective discipline during the 1980s (Soulé 1985). European landscape ecology has a long tradition that Although landscape ecology may not have emerged has greatly influenced its subsequent development as a scientific discipline until the 1980s, its antecedents and character. Europeans recognized early on that can be traced back decades and even centuries. Well society was placing increasing demands on landscapes before there was a journal or a society of landscape and that the environmental problems created by those ecology, there were societies and journals devoted to demands were far too complex to be solved individu- human ecology, land-use planning, and design (i.e. land- ally by existing disciplines, but instead required a new scape architecture). Journals such as Landscape Planning multidisciplinary perspective to address them (Antrop and Urban Ecology (which have since been merged into et al. 2009). From its earliest beginnings, then, European a single journal, Landscape and Urban Planning) were landscape ecology has been marked by a strong holis- first published in the mid-1970s, more than a decade tic and human-centered perspective (Wu & Hobbs 2007; before Landscape Ecology. Journals and professional Figure 1.4A). organizations concerned with the management of eco- nomically important landscapes such as forests and rangelands date from the first half of the 20th century. In densely populated Europe, the main concern is on cultural Ecologists and geographers can trace their academic landscapes and the natural and cultural heritage related to roots back even farther, to the many professional soci- these. Most traditional landscapes lose rapidly their ecological eties and their journals that appeared in the late 19th and heritage values, which are considered as “natural and and early 20th centuries. Indeed, a German geographer, cultural capital.” There is a growing need to plan future land- Carl Troll, is widely credited with coining the term scapes in an increasingly urbanized society and polarised ‘landscape ecology’ (landschaftsökologie) in 1939 (Troll environment in the perspective of sustainable development 1939). Over the ensuing decades, Troll continued to and participatory planning. Antrop et al. (2009) refine his view of landscape ecology, which he defined as ‘the study of the main complex causal relationships between the life communities and their environment’ The concept of holism, as applied to the landscape, that ‘are expressed regionally in a definite distribution implies that its functioning cannot be understood sim- pattern (landscape mosaic, landscape pattern)’ (Troll ply by studying some aspect of it in isolation. The 1971). Troll’s training in geography, coupled with his Dutch landscape ecologist Isaak Zonneveld, for example, early interest in botany, contributed to his unique was a proponent of the land-unit concept (Zonneveld understanding of interactions between geomorphology 1989). The land-unit concept was first proposed by the and vegetation patterns, particularly in the mountainous Australian land surveyor and mapper Clifford Stuart regions of the world, where he used aerial photographs Christian, who advocated for a systems approach to  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi 6 Essentials of Landscape Ecology (A) European perspective mapping, planning, design, and management of land- Functional scapes for human land use (e.g. Zonneveld 1972; Human Naveh & Lieberman 1984; Schreiber 1990). (holistic) geography ecology In many respects, the European view of landscapes, and thus of landscape ecology, is a reflection of the political and economic integration of Europe itself. With the integration of the European Communities in Landscape 1967 and the subsequent formation of the European ecology Union in 1993, the rapidly changing face of the European landscape is now being shaped largely by Planning & common policies, such as the Common Agricultural Land-use Political Resource Policy. Although the EU does not have a common Sociology landscape policy science economics architecture landscape policy, there has been some progress at the political level in recognizing the broad value of land- (B) North American perspective scapes beyond the economic or resource benefits they provide. In 1995, the EU’s European Environmental European Ecology Spatial Agency published its Dobříš Assessment, a report on landscape (patch pattern ecology dynamics) analysis the state of the European environment, which includes a chapter devoted to landscapes and their importance to the future of the European environment (Stanners & Bourdeau 1995). Most notably, the chapter emphasizes Landscape the importance of preserving the unique character and ecology diversity of landscapes as part of the natural and cul- tural heritage of Europe. The Dobříš Assessment is thus credited with helping to draw the attention of Resource policymakers to the various pressures that are leading GIS Modeling management to a decline in the diversity, distinctiveness, and value Figure 1.4 Regional perspectives on landscape ecology. of landscapes throughout Europe (Antrop et al. 2009). The development of landscape ecology in the 1980s followed The Dobříš Assessment was influential in the Council different trajectories in (A) Europe and (B) North America. of Europe’s development of the European Landscape Source: After Wiens 1997. Convention, which went into force in 2004. The conven- tion is an international treaty for the comprehensive the study of landscapes as ‘hierarchical wholes.’ In his protection, management, and planning of landscapes view, a landscape is a system of interacting land units, throughout Europe, including all natural, rural, and defined as ‘parts of the land surface... having a similar urban landscapes as well as inland waters and coastal genesis and [that] can be described similarly in terms marine areas, regardless of their condition (it includes of the major inherent features of consequence to land ‘everyday, outstanding and degraded landscapes’). use—namely, topography, soils, vegetation and cli- mate’ (Christian 1958, p. 76). We’ll return to this idea of The landscape has an important public interest role in the landscapes as hierarchical systems in Chapter 2. For cultural, ecological, environmental and social fields, and con- now, it is worth noting that the land-unit approach was stitutes a resource favourable to economic activity and whose ultimately an effort to develop a more systematic way of defining, mapping, and integrating multiple attributes protection, management and planning can contribute to job of landscapes (e.g. landforms, soils, vegetation, or land creation; uses) that had traditionally been studied individually... The landscape contributes to the formation of local by different types of scientists. Beyond providing a cultures and... is a basic component of the European natural more holistic approach to the study of landscapes and cultural heritage, contributing to human well-being and as integrated wholes, however, the land-unit approach consolidation of the European identity; was also presented as a more efficient and cost-effec-... The landscape is an important part of the quality of life tive land survey method and mapping tool that could for people everywhere; aid in ‘the evaluation of the suitability of landscape... The landscape is a key element of individual and social for any kind of land use’ (Zonneveld 1989, p. 68). This well-being and... its protection, management and planning approach thus epitomizes the practical and human- entail rights and responsibilities for everyone. centered applications of European landscape ecology, Preamble to the European Landscape Convention whose primary aim has been to facilitate the evaluation,  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi An Introduction to Landscape Ecology 7 Remarkably, the establishment of the European Land- backgrounds and research interests of this small gath- scape Convention was principally motivated not by ering of ecologists and geographers. This is immedi- economic concerns over the provisioning services pro- ately apparent from the definition of landscape ecology vided by landscapes (although they are seen as one of given in the report of that workshop, as the study of its benefits), but rather by a concern for societal well- ‘the relationship between spatial pattern and ecological being and the quality of life for European citizens; that processes [that] is not restricted to a particular scale’ is, by the public good. Landscapes are perceived to (Risser et al. 1984, p. 255). In contrast to the European have strong cultural as well as natural values and, as perspective, this definition is clearly more ecological such, become part of a country’s identity and cultural and explicitly spatial; it also allows for the possibility heritage. Because the landscape plays such an important that landscapes—and thus landscape ecology—need role in the well-being of individuals and society not be concerned solely with broad spatial scales, an at large, the Convention argues, all Europeans are issue we’ll return to later. adversely affected by a deterioration in the quality of At the Allerton Park workshop, participants were their surroundings. The public should thus have some asked to consider how landscape ecology might con- say, as participating stakeholders, in how landscapes tribute to four major areas of inquiry (Risser et al. 1984): are managed, rather than leaving these sorts of decisions solely to those with specialized or economic interests. 1. How heterogeneity influences the flux of organ- By agreeing to the terms of the European Landscape isms, materials, and energy across the landscape. Convention, participating nations have acknowledged 2. The formative processes, both past and present, their collective duty to make provision for the protec- that give rise to landscape patterns. tion, management, and planning of landscapes to ful- 3. How heterogeneity affects the spread of fill these sociocultural values, especially at the local or disturbances, such as fire, across the landscape. regional level. As of February 2019, the convention had 4. How natural resource management might be been ratified by 39 of the 47 member states in the enhanced by adopting a landscape ecological Council of Europe. approach. In response to these developments, IALE-Europe was formed in 2009 as a new supranational chapter of Thus, the workshop put forward many of the now- the International Association for Landscape Ecology recognizable themes of landscape ecology—the import- (Antrop et al. 2009). IALE-Europe aims to promote col- ance of heterogeneity, scale, and disturbance dynamics laboration among members of Europe’s diverse aca- for understanding the reciprocal effects of spatial pat- demic community of landscape ecologists and to make tern and ecological process (Wu 2013). In retrospect, this their collective expertise available to institutional and is not surprising, given that many of the participants societal stakeholders as well as the policymakers had also been active in the International Biological involved in decisions about landscape management Program (1964–1974), whose ambitions included the and planning at the European level. development of complete systems models to predict the effects of anthropogenic and environmental change on North American Perspective entire ecosystems (e.g. on total productivity), in addition The emergence of landscape ecology in North America to the more general application of ecosystem science to was clearly influenced by its success in Europe, which natural resource management (Boffey 1976). Thus, many had excited the interest of a number of ecologists in of the Allerton Park participants were already, to quote both the United States and Canada (Figure 1.4B). As one of them, ‘primed... for thinking about landscapes in mentioned previously, the landscape ecology move- terms of flows and fluxes, energy and materials, and ment in North America can be traced to the workshop management implications’ (Wiens 2008, p. 127). held in 1983 at Allerton Park, a former estate now over- Given the ecological and systems modeling back- seen by the University of Illinois at Urbana-Champaign grounds of many of the Allerton Park participants, near Monticello, Illinois. Most of the 25 invited partici- it was perhaps inevitable that landscape ecology in pants were from the United States, although individual North America would take on a more quantitative and attendees from Canada and France were also present spatial modeling character than that of its European (Wiens 2008). This small group, most of whom were congener (Figure 1.4). The Allerton Park workshop systems ecologists, formed the nucleus of what became occurred at a time when microcomputers and GIS were a new movement in landscape ecology (Wu 2013). both in their infancy, but already several participants The specific developmental pathway that landscape were keen to exploit the opportunities these new ecology took in North America might thus be attrib- technologies afforded landscape ecology, especially for uted to a strong founder effect (Wiens 1997), as it devi- analyzing broad-scale patterns of landscape change ated from its European roots as a result of the particular (Iverson 2007). The need to quantify and compare the  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi 8 Essentials of Landscape Ecology spatial attributes of landscapes spurred the develop- many European landscape ecologists who study the ment of new landscape metrics (O’Neill et al. 1988a) as relationship between landscape pattern and ecological well as spatial modeling approaches to permit the process. Thus, to quote Wu & Hobbs (2007, p. 277): statistical comparison of landscape data with known distributions (i.e. neutral landscape models; Gardner It is evident that the European and North American approaches to landscape ecology have differed et al. 1987). Patch-based ecological theory, such as the historically. On the one hand, the European approach theory of island biogeography, metapopulation theory, is characterized by a holistic and society-centered view and patch dynamics theory, provided a quantitative of landscapes... On the other hand, the North and predictive framework that helped inform initial American approach is dominated by an analytical and landscape ecological research into how patch structure biological ecology-centered view of landscapes...This could influence the structure and dynamics of ecological dichotomy, of course, is an oversimplification of the systems (MacArthur and Wilson 1967; Levins 1970; reality because neither of the two approaches is Pickett & White 1985). internally homogeneous in perspectives and because The early focus on natural resource management is both have been changing as an inevitable consequence also quite telling. Whereas Europeans were principally of increasing communications and collaborations concerned with the management of cultural land- among landscape ecologists worldwide. scapes, North Americans were more focused on natural or managed landscapes, of which vast tracts still These two traditional landscape perspectives have been remain. Many of these lands are owned and managed variously adopted—and adapted—in other areas of by the federal government. For example, the federal the world, such as Australia, Latin America, and China. government owns more than a quarter of the land in Australian landscape ecologist Richard Hobbs has the United States (28%), amounting to about 2.6 mil- characterized the Australian approach as taking ‘a lion km2 (Gorte et al. 2012). For comparison, this is an pragmatic middle road which combines both aspects’ area roughly two-thirds the size of the entire European (Hobbs & Wu 2007, p. 7). Landscape ecology in Latin Union. Most federal lands are located in the western America, whose emergence led to the formation of half of the United States, where 42% of the land area is three IALE chapters (Argentina and Brazil in 2005, federally owned, and in Alaska, where 62% of the land and Chile in 2016) likewise appears to have embraced area is federally owned. Federal lands are held in the both perspectives. For example, the first bulletin for public trust, and most (96%) are managed for a variety the IALE-Chile chapter (published May 2018) defines of competing purposes (timber, grazing, mining, recre- landscape ecology as ‘an interdisciplinary science that ation, wildlife, conservation) by four different govern- studies the spatial variation of landscapes [across] a ment agencies: Forest Service, National Park Service, wide range of scales,’ but also emphasizes the chap- Bureau of Land Management, and Fish and Wildlife ter’s commitment to applying landscape ecology to the Service. The US National Forest System, for example, sustainable use of natural resources and ‘to work and encompasses 780,000 km2, which is about the size of collaborate on public policies on management issues the total land area of Germany, UK, Slovakia, Denmark, related to landscape ecology, such as territorial plan- and the Netherlands combined. In Canada, forest covers ning, ecosystem services and the effects of global change’ about 4 million km2 (equivalent to the size of the (https://www.iale-chile.cl/). The development of EU), and 93% of this forested land is publicly owned landscape ecology in China was similarly influenced (crown land) and managed under the purview of either by the North American perspective at the outset, but the provincial (77%) or federal (16%) crown (Annual now appears to be embracing the more holistic Report, The State of Canada’s Forests 2011). Little won- European perspective that places greater emphasis on der then that forest and natural resource management landscape planning, design, and environmental man- should play such a major role in the subsequent devel- agement (Fu & Lu 2006, pp. 239–240): opment and application of landscape ecology in North China is a developing country with [a] large human America (Boutin & Hebert 2002; Liu & Taylor 2002; population and diversified environmental conditions. Bissonette & Storch 2003; Perera et al. 2007). The drive for socioeconomic development is very strong, and at the same time environmental quality, Globalization of Landscape Ecology resource usability and ecological security are also Although interesting from a historical standpoint, these important concerns for the sake of regional sustainable different regional perspectives should not be taken too development. Therefore, it is crucial to harmonize the literally, at least in terms of how landscape ecology is relationships between human population growth, currently practiced. There are many North American regional economic development and environmental landscape ecologists who are concerned with land-use conservation. Consequently, future landscape ecological planning and management issues, just as there are research in China should take the responsibility of  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi An Introduction to Landscape Ecology 9 Social Sciences Archaeology Sociology Political science Economics Psychology History Law (policy) Architecture and design Human geography Human ecology Economic geography Resource management Regional/urban planning Conservation biology Transportation Sustainable planning development Landscape Ecology Geography Ecology/Evolution Physical geography Movement ecology Regional geography Zoogeomorphology Population ecology Cartography Paleobiology Population genetics GIS science Biogeography Invasion ecology Remote sensing Ecological modeling Disease ecology Geostatistics (spatially explicit) Community ecology Systems ecology Spatial ecology Figure 1.5 Domain of landscape ecology. Landscape ecology is a multidisciplinary science that occurs at the intersection of fields in ecology/evolution, geography, and the social sciences. exploring the complex interactions between human traditional boundaries between science and practice activities and landscape dynamics under a holistic by promoting the integration of interdisciplinary landscape framework, in which humans are treated as research with stakeholder concerns about the environ- landscape ingredients equivalent to other biotic and mental and societal consequences of human land use abiotic components of the landscapes... Many aspects, (Wu 2006). including ecological, economic and cultural, should be integrated. The holistic approach is effective in studying the multifunctionality of Chinese landscapes. Core Concepts of Landscape Ecology Today, the apparent difference in perspectives on land- From the start, landscape ecologists have emphasized scape ecology is perhaps less a ‘European versus the structure and function of landscapes and how North American’ distinction than an ‘applied science landscapes change over time (Forman & Godron 1986). versus basic science’ dichotomy found in many fields Three attributes are characteristic of all landscapes and in the ecological, biological, and physical sciences. provide the basis for quantifying and comparing them: Although this dichotomy is a false one in any science, 1. Landscape structure pertains to the diversity and it is especially so in landscape ecology. The relation- spatial arrangement of landscape elements (e.g. ship between science and practice is reciprocal (Wiens habitat patches). 2005). The two perspectives are in fact complementary, and both are ultimately necessary to the science and 2. Landscape function refers to the interaction among practice of landscape ecology (Hobbs & Wu 2007). these spatial elements (e.g. the flow of energy, Landscape ecology is a vibrant, cross-disciplinary sci- nutrients, species, or genes among habitat patches). ence that not only integrates research across the natural 3. Landscape change refers to how landscape and social sciences (Figure 1.5), but also transcends the structure and function vary over time.  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi 10 Essentials of Landscape Ecology Research in landscape ecology is motivated by sev- scale-dependent acknowledges that patchiness (i.e. het- eral guiding principles or core concepts (Wiens 1997, erogeneity) may exist simultaneously across a range of 2005) that are variously related to these three land- scales. Multiscale patch structure may reflect the differ- scape characteristics. ent scales at which various processes or disturbances that shape the landscape operate. Such a view also Landscapes are heterogeneous. By definition, landscapes broadens the definition of ‘landscape,’ and thus the are mosaics of different landforms, ecosystems, habitat domain of landscape ecology. From this viewpoint, any types, or land uses (Forman & Godron 1986; Forman type of spatial distribution at any scale could constitute 1995b). While landscapes are often viewed as comprising a landscape. This perspective is important, for it recog- discrete elements (e.g. habitat patches, corridors, roads, nizes that landscape ecology is not simply ‘regional water bodies), heterogeneity can also vary continu- ecology’ or ‘broad-scale ecology,’ but a research para- ously over the landscape, as it does along an ecocline digm for investigating the effect of spatial pattern on or ecological gradient. Different formative processes ecological processes at any scale. We will discuss this give rise to different landscape structures, a topic that perspective more fully in Chapters 2 and 3. we will explore further in Chapter 3. One consequence of heterogeneity, however, is that elements of the land- Landscapes are dynamic. As the biochemist and science scape mosaic—the collection of land covers and land- fiction writer Isaac Asimov once famously observed, use types—are likely to vary in quality or suitability ‘the only constant is change.’ All ecological systems are for different species. This will be a recurring theme dynamic, and landscapes are no exception. Distur- in the later chapters of this book, where we deal with bances across a wide range of scales, from those occur- the ecological consequences of landscape structure. ring over minutes within a few square centimeters to those operating over tens of millennia across thou- Landscapes are diverse in form and function. We can sands of square kilometers, have all contributed to the characterize landscapes based on a diverse array of landscapes we see around us today. Landscapes are features related to their geomorphology (e.g. moun- thus better viewed as ‘shifting mosaics’ than as static tainscapes), primary land cover or land use (e.g. forest systems in some sort of equilibrium (Wu & Loucks landscape), a specific ecological or biological function 1995). Understanding how anthropogenic landscape (e.g. landscape of fear; Laundré et al. 2001; sound- change compares to the natural disturbance regime, scapes, Pijanowski et al. 2011), the amenities or com- and whether it fits within the range of historical variation modities they provide (e.g. agricultural landscape), or for a particular landscape, is important for evaluating in relation to human occupation and values (urban the potential impacts of human activities on the struc- landscape; cultural landscape). Landscapes need not ture and function of landscapes. We will discuss this be landlocked, however. If heterogeneity is a defining topic more fully in Chapter 3. Furthermore, the rate at characteristic of landscapes, then marine and freshwater which landscapes change may be just as important systems would similarly qualify, for they also exhibit as—if not more important than—the resulting structural heterogeneity in the distribution of substrates, habi- changes (e.g. in the amount or configuration of habitat) tats, resources, and environmental conditions. Thus, for certain ecological responses or landscape functions. we can define riverine landscapes (Wiens 2002) and For example, species may exhibit a lagged response marine landscapes or ‘seascapes’ (Pittman et al. 2011). to rapid habitat loss or fragmentation, such that an These are all ‘landscapes’ in that they comprise spa- assessment of a population’s responses to landscape tially heterogeneous areas, whose study might there- change might underestimate its actual risk of extinc- fore benefit from a landscape ecological perspective. tion (Schrott et al. 2005). We will consider the effects of landscape dynamics on a variety of ecological responses Landscapes are scale-dependent. Although landscapes throughout this book. have traditionally been viewed on human terms, as areas of broad spatial extent, there has been a persistent Spatial context is important. Given that landscapes are movement within landscape ecology to define a land- heterogeneous, we can expect that ecological dynam- scape simply as a spatially heterogeneous area (Turner ics will vary spatially. For example, if habitats vary in 1989) that is scaled relative to the process or organism their suitability for a particular species, then population of interest (Wiens & Milne 1989). Two species that occur growth rates of that species will likewise vary among within the same habitat, such as grasshoppers and habitat types. High-quality habitats should support bison (Bison bison) on the tallgrass prairies of North viable populations, whereas low-quality habitats can- America, are likely to have very different perceptions of not (Pulliam 1988). Our understanding of the popula- the landscape in terms of the distribution and availabil- tion dynamics within patches thus requires information ity of their preferred forage, given the different scales at on habitat quality (in other words, population dynam- which they each operate. The idea that landscapes are ics are habitat-dependent). However, habitat quality  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi An Introduction to Landscape Ecology 11 may also be spatially dependent, such that two sites structural sense (e.g. via habitat corridors). Connectivity within the same habitat might vary in quality depend- can be considered an emergent property of landscapes; ing on their specific location (i.e. their spatial context). it emerges as a consequence of the interaction between For example, reproductive success for forest-breeding ecological flows and the landscape pattern (Taylor et al. songbirds might be higher for individuals that nest in 1993; With et al. 1997). It could thus be argued that much the center of a habitat patch than at its margins (where of landscape ecology is ultimately concerned with the nest predation rates tend to be higher), or in a forest measurement and study of connectivity. Connectivity patch surrounded by second-growth forest than in one is important for understanding the propagation of surrounded by agricultural fields (where again, nest disturbances across the landscape; the movement and predation rates are expected to be higher), or in a land- redistribution of organisms, materials, and nutrients; scape that is still predominantly forested than in one the resulting structure and dynamics of populations; that has very little forest cover remaining (where nest gene flow and population genetic structure; the spread predation rates are uniformly greater; Donovan et al. of invasive species and diseases; community patterns 1997). Thus, spatial context may well be important for and dynamics; and ecosystem structure and function understanding what goes on within individual patches (Chapters 6–11). Thus, connectivity will be a pervasive (or landscapes), and will definitely be important for theme throughout this book, and an entire chapter understanding what goes on between patches. (Chapter 5) is devoted to this important concept. Ecological flows are important. Because spatial context Landscapes are multifunctional. Humans are the princi- is important, we should anticipate that the nature of pal driver of landscape change worldwide, as land- the patch boundary and the intervening matrix—the scapes are increasingly being transformed and used for mosaic of land-cover or land-use types that occurs a variety of ecological, societal, and economic functions between habitat patches—can influence the magnitude (Ojima et al. 1994b; Vitousek et al. 1997; Figure 1.2). of ecological flows among patches. Patch boundaries Landscapes are thus multifunctional in that they pro- may be porous to the movement of certain organisms vide humanity with an array of goods and services. but impermeable to others, depending on how differ- Therefore, landscape management requires a means of ent organisms perceive and respond to the structure identifying and resolving the conflicts that inevitably of the habitat edge, which occurs at the juxtaposition arise in response to competing interests and valuation of different vegetation communities. The transition systems (Mander et al. 2007). Sustainability is a key between vegetation types may be abrupt, creating what concept in landscape ecology (Wu 2006) and is the is known as a ‘hard edge,’ especially if organisms are basis for sound ecosystem and natural resource man- unwilling or unable to cross that boundary, or may be agement (Liu & Taylor 2002; Bissonette & Storch 2003). a more gradual transition from one habitat type to the Recall that landscape ecology arose in response to the next, creating a ‘soft edge.’ Flows may also occur perceived need to manage resources more holistically between ecosystems, such as across the land-water and at a broader landscape scale. Although we will interface. Agricultural or stormwater runoff from the consider the management implications of landscape surrounding landscape is a familiar source of non- ecology throughout this book, the final chapter point-source pollution in marine and freshwater sys- (Chapter 11) examines in greater detail how principles tems. However, these flows do not occur in just one derived from landscape ecology can be used to meet direction, from land to water, but may also occur in the the environmental and societal challenges that stem opposite direction, from water to land, as in the case of from human land use (i.e. landscape sustainability). marine subsidies along coastal areas or desert islands (Polis & Hurd 1996). Asymmetrical flows across patch or system boundaries can have profound effects on the Organization of this Book dynamics within, as well as between, patches or sys- The demands of time and your personal interests will tems on the landscape. This will be a recurring theme necessarily dictate how you use this text. Because many in many of the later chapters of this book, where we diverse fields contribute to landscape ecology, readers consider the effects of asymmetrical flows (individual of this book are also likely to be quite diverse. Thus, movement and dispersal, gene flow, and nutrient flows; although the book’s organization represents a natural Chapters 6, 9, and 11) on various ecological processes. ordering of topics (at least from the author’s perspec- Connectivity is important. The notion that organisms, tive), your individual interests and needs will obviously materials, or nutrients flow to varying degrees among dictate which topics are emphasized, and in what order. patches or systems on the landscape implies that some The first five chapters cover not only the discipline areas of the landscape are connected, at least function- of landscape ecology (introduced in this chapter), but ally, even if they are not obviously connected in a also its major research themes, including issues of spatial  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi 12 Essentials of Landscape Ecology and temporal scale (Chapter 2), landscape heterogeneity of the basic concepts should focus on the introductory and dynamics (Chapter 3), landscape pattern analysis sections of the chapter and the chapter summary points (Chapter 4), and landscape connectivity (Chapter 5). at its end. More advanced students and research scien- These chapters provide many of the core concepts that tists are likely to benefit most from the more in-depth will be emphasized repeatedly throughout the remain- coverage of methodologies, analyses, and modeling der of the book. Chapter 5, on landscape connectivity, considerations featured in most chapters. However, could be considered a bridge chapter, given that it spans this book is not an instruction manual. Although issues the domains encompassed by landscape pattern analysis involved in the collection, analysis, and modeling of in the chapter that precedes it and ecological responses spatial data are discussed, the primary objective is to to landscape pattern in the chapters that follow. give you the necessary information with which to Chapters 6–11 consider the ecological consequences evaluate these concerns from the standpoint of your of spatial pattern for a wide range of processes and own interests, research, or management needs. The phenomena involving individual movement and dis- intent is to provide an overview of available tools and persal (Chapter 6), population distributions and dynam- methods, along with some general guidance as to their ics (Chapter 7), population spatial spread (Chapter 8), use, and then direct interested readers to additional gene flow and population genetic structure (Chapter 9), resources where they can obtain more detailed infor- community structure and dynamics (Chapter 10), and mation on the topic. ecosystem structure and function (Chapter 11). Although Finally, as a pedagogical tool, this book has been readers should feel free to focus on chapters that are of organized around the way in which these topics are particular interest, the chapters have been developed presented in my own course on landscape ecology. It is and arranged in a hierarchical fashion, such that hoped that the discussion questions at the end of each material in later chapters builds on concepts and chapter will challenge the reader to think more deeply approaches presented in earlier chapters. or broadly about the topics presented within the chap- Each chapter provides a mix of basic concepts, ter. These questions can also help facilitate discussion examples, and case studies along with more advanced within a classroom or seminar setting. Some of these topics related to the theoretical foundation, quantita- questions can be used for class assignments or as essay tive methods, or modeling applications relevant to a questions on examinations, and thus might prove particular area of research. The beginning student, especially useful in that regard for instructors—and practitioner, or casual reader wishing for an overview students—of landscape ecology. Chapter Summary Points 1. Landscape ecology studies the reciprocal effects of concern over human impacts on the environment, spatial pattern (heterogeneity) and ecological especially in the heavily industrialized nations processes. It emphasizes the structure, function, where landscape ecology first originated; and change in landscapes over time. (ii) technological advances in remote sensing, 2. The ways in which human land-use activities geographic information systems, and computer modify landscape structure and function are a processing, which made the collection, analysis, major research focus in landscape ecology, which and modeling of geospatial data over broad provides a scientific basis for understanding and regional areas not only feasible, but efficient; and managing landscapes as well as the goods and (iii) conceptual and theoretical developments services they provide. within the field of ecology, especially patch-based theory, a growing recognition of the importance 3. Landscape ecology is a relatively new scientific of spatial scale for the design and interpretation discipline, having become established some 35 of ecological research, and a shift away from years ago in Europe before spreading to North equilibrium theories to dynamic views of America, Australia, and elsewhere. Its historical ecological systems such as landscapes. roots can be traced back much earlier, however. The German geographer Carl Troll first coined the 5. Different regional perspectives influenced the term ‘landscape ecology’ (landschaftsökologie) in early development of landscape ecology as a 1939 in reference to his study of the interaction science. In Europe, the focus was more on between geomorphology and vegetation patterns land-use planning and the management of along elevational gradients. cultural landscapes; the focus was thus squarely human-centered. In North America, the 4. The rise of landscape ecology in the mid-1980s development of the discipline was more heavily may be attributed to three factors: (i) an increasing  OUP CORRECTED PROOF – FINAL, 08/06/19, SPi An Introduction to Landscape Ecology 13 influenced by ecological theory and spatial wide range of scales, and thus landscape ecology modeling applications, and thus the focus was is not restricted simply to the study of broad more on the study and management of ecological spatial extents; (iv) landscapes are dynamic, such landscapes. Landscape ecology has benefitted