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in real , and because it facilitates theoretical and methodological developments by recognizing the importance of micro-, meso-, macro-, and cross-scale approaches. The term was coined in 1939 by Arizona State University the German geographer Carl Troll, who was inspired by the spatial patterning of landscapes revealed in aer- ial photographs and the concept developed Spatial heterogeneity is ubiquitous in all ecological sys- in 1935 by the British ecologist Arthur Tansley. Troll tems, underlining the signifi cance of the pattern–process originally defi ned landscape ecology as the study of the relationship and the scale of observation and analysis. relationship between biological communities and their Landscape ecology focuses on the relationship between environment in a landscape mosaic. Today, landscape spatial pattern and ecological processes on multiple scales. ecology is widely recognized as the science of studying On the one hand, it represents a spatially explicit per- and improving the relationship between spatial pattern spective on ecological phenomena. On the other hand, and ecological processes on a multitude of scales and or- it is a highly interdisciplinary fi eld that integrates bio- ganizational levels. Heterogeneity, scale, pattern–process physical and socioeconomic perspectives to understand relationships, , hierarchy, and and improve the ecology and sustainability of landscapes. are among the key concepts in contemporary landscape Landscape ecology is still rapidly evolving, with a diver- ecology. Landscape ecological studies typically involve sity of emerging ideas and a plurality of methods and the use of geospatial data from various sources (e.g., applications. fi eld survey, aerial photography, and ) and of different kinds (e.g., pattern indi- DEFINING LANDSCAPE ECOLOGY ces and spatial statistics). The intellectual thrust of this Landscapes are spatially heterogeneous geographic areas highly interdisciplinary fi eld is to understand the causes, characterized by diverse interacting patches or ecosys- mechanisms, and consequences of spatial heterogeneity tems, ranging from relatively natural terrestrial and in landscapes. aquatic systems such as , , and lakes to Heterogeneity refers to the spatial variation of the human-dominated environments including agricultural composition and confi guration of landscape, which and urban settings (Fig. 1). Landscape is an ecological often manifests itself in the form of patchiness and gra- criterion whose essence is not its absolute spatial scale but dient. In landscape ecology, scale usually refers to grain rather its heterogeneity relevant to a particular research (the fi nest spatial or temporal resolution of a dataset) question. As such, the “landscape” view is equally appli- and/or extent (the total study area or duration). When cable to aquatic systems. This multiple-scale concept of heterogeneity becomes the focus of study, scale matters landscape is more appropriate because it accommodates inevitably because the characterization and understand- the scale multiplicity of patterns and processes occurring ing of heterogeneity are scale dependent. Landscape

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9780520269651_Ch_L.indd 392 11/25/11 7:28 PM FIGURE 1 Landscapes of the real world. The study objects of landscape ecology range from natural, to agricultural, to urban landscapes. Not only may they be dominated by different types (e.g., forests, grasslands, and deserts), but they also may have either a terrestrial or an aquatic matrix (e.g., a lakescape, seascape, or oceanscape). Photographs by J. Wu.

pattern involves both the composition of landscape of a landscape to support and ecosystem elements and their spatial arrangement, and the rela- processes and provide ecosystem services in face of vari- tionship between pattern and process also varies with ous disturbances. scale. Disturbance—a temporally discrete natural or anthropogenic event that directly damages ecosystem EVOLVING PERSPECTIVES structure—is a primary source of spatial heterogeneity Two dominant perspectives in landscape ecology are or pattern. Like pattern and process, disturbance is also commonly compared and contrasted: the European per- scale dependent—meaning that the kind, intensity, and spective and the North American perspective. The Euro- consequences of disturbance will change with scale in pean perspective traditionally has been more humanistic space across a landscape. This scale multiplicity of pat- and holistic in that it emphasizes a society-centered view terns and processes frequently results in the hierarchical that promotes place-based and solution-driven research. structure of landscapes—that is, landscapes are spatially It has focused on landscape mapping, evaluation, conser- nested patches of different size, content, and history. vation, planning, design, and management. In contrast, The goal of landscape ecology is not only to understand the North American approach is more biophysical and the relationship between spatial pattern and ecological analytical in that it has been dominated by a biological processes but also to achieve the sustainability of - ecology–centered view that is driven primarily by scientifi c scapes. Landscape sustainability is the long-term ability questions. It has had a distinct emphasis on the effects

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9780520269651_Ch_L.indd 393 11/25/11 7:28 PM of spatial pattern on and ecosystem processes stage of diversifi cation to one of consolidation (if not in a heterogeneous area. This research emphasis is prac- unifi cation) of key ideas and approaches. tically motivated by the fact that previously contiguous Both the European and North American perspectives landscapes have rapidly been replaced by a patchwork of are essential to the development of landscape ecology as diverse land uses (landscape fragmentation) and concep- a truly interdisciplinary science. To move landscape ecol- tually linked to the theory of island devel- ogy forward, however, one of the major challenges is to oped in the 1960s and the perspective of develop comprehensive and operational theories to unite that began to take shape in the 1970s. the biophysical and holistic perspectives. Viewing land- However, this dichotomy most defi nitely oversimpli- scapes as complex adaptive systems (CAS) or coupled fi es the reality because such geographic division conceals human–environmental systems provides new opportuni- the diverse and continuously evolving perspectives within ties toward this end. In addition, spatial resilience—which each region. In fact, many ecologists in explores how the spatial confi guration of landscape ele- have recognized the importance of humans in shaping ments affects landscape sustainability—may also serve as landscapes for several decades (especially since the dust a nexus to integrate a number of key concepts, including bowl in the 1930s). Although humans and their activities diversity, heterogeneity, pattern and process, disturbance, have been treated only as one of many factors interact- scale, , and sustainability. ing with spatial heterogeneity, more integrative studies have been emerging rapidly in the past few decades with KEY RESEARCH TOPICS the surging interest in and sustainability Although landscape ecology is an extremely diverse fi eld science in North America. On the other hand, the per- (Fig. 2), a set of key research areas can be identifi ed. These spective of spatial heterogeneity has increasingly been include quantifying landscape pattern and its ecological recognized by landscape ecologists in and the rest effects; the mechanisms of fl ows of , energy, of the world. Thus, the current development of landscape and materials in landscape mosaics; behavioral landscape ecology around the world suggests a transition from a ecology, which focuses on how the behavior of organisms

FIGURE 2 A hierarchical and pluralistic view of landscape ecology (modifi ed from Wu, 2006). “Hierarchical” refers to the multiplicity of organizational levels, spatiotemporal scales, and degrees of cross-disciplinarity in landscape ecological research. “Pluralistic” emphasizes the values of different perspectives and methods in landscape ecology derived from its diverse origins and goals.

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9780520269651_Ch_L.indd 394 11/25/11 7:28 PM interacts with landscape structure; , and fl uxes commonly used in . It also which aims to understand how landscape heterogeneity integrates the pattern-based horizontal methods of land- affects ; causes and consequences of scape ecology with the process-based vertical methods of and land cover change; spatial scaling, which ecosystem ecology and promotes the coupling between deals with translation of information across heterogene- the -centered population perspective and the ous landscapes; and optimization of landscape pattern for fl ux-centered ecosystem perspective. conservation or sustainability. A number of theoretical challenges exist in the study of these key topics. These FUTURE DIRECTIONS challenges hinge on the spatialization of processes of Emphasis on heterogeneity begs questions of the rela- interest—i.e., explicitly describing where processes take tionship between pattern and process. Heterogeneity place and how they relate to each other in space. Math- is about structural and functional patterns that deviate ematically, spatialization introduces heterogeneity, non- from uniform and random arrangements. It is this per- linearity, and delays into models. vasively common nonhomogeneous characteristic that Thus, spatial explicitness is a salient characteristic of makes spatial patterns ecologically important. Thus, landscape ecological studies. and meta- studying pattern without getting to process is superfi cial, communities have been fair game in landscape ecology. and understanding process without reference to pattern is In general, however, a landscape mosaic approach con- incomplete. Emphasis on heterogeneity also makes scale siders more than the network of patches. For example, a critically important issue because heterogeneity, as well in contrast with metapopulations, landscape as the relationship between pattern and process, may vary emphasize not only the dynamics of, and interactions as the scale of observation or analysis is changed. Thus, between, local populations but also the effects of the whenever heterogeneity is emphasized, spatial structures, heterogeneity of the landscape matrix. Thus, landscape underlying processes, and scale inevitably become es- population models explicitly consider the size, shape, sential objects of study. From this perspective, landscape and spatial arrangement of all and nonhabitat ele- ecology is a science of heterogeneity and scale. On the ments. Also, the landscape population approach allows for other hand, with increasing human in the explicit examination of how idiosyncratic features of habi- biosphere, emphasis on broad spatial scales makes inevi- tat patches and the landscape matrix affect the dispersal of to deal with humans and their activities. As a con- organisms or propagules. In general, the theory of island sequence, humanistic and holistic perspectives have been biogeography, theory, and most popula- and will continue to be central in landscape ecological tion viability analysis (PVA) models focus mainly on the research. islands in a homogeneous matrix, whereas the landscape Various effects of the compositional diversity and spa- population approach explicitly considers all landscape ele- tial confi guration of landscape elements have been well ments and their spatial confi guration in relation to popu- documented, and a great number of landscape metrics lation dynamics across a heterogeneous geographic area. (synoptic measures of landscape pattern) and spatial anal- In the study of ecosystem processes in a heterogeneous ysis methods have been developed in the past decades. The area, the landscape mosaic approach is characterized by greatest challenge, however, is to relate the measures of the explicit consideration of the effects of spatial hetero- spatial pattern to the processes and of biodiver- geneity, lateral fl ows, and scale on the pools and fl uxes sity and ecosystem functioning. To address this challenge, of energy and matter within an ecosystem and across a well-designed fi eld-based observational and experimental fragmented landscape. While models of ecosystem proc- studies are indispensable, and remote sensing techniques, esses have been well developed in the past several dec- geographic information systems (GIS), spatial statistics, ades, landscape-scale ecosystem models are still in their and simulation modeling are also necessary. Landscape infancy. The primary difference between these two kinds ecology is leading the way in developing the theory and of models lies in the fact that landscape models explic- methods of scaling that is essential to all natural and social itly account for the locations of pools and rates, and sciences. However, many challenges still remain, includ- in many cases multiple interactive are con- ing establishing scaling relations for a variety of landscape sidered together. The landscape approach to ecosystem patterns and processes as well as integrating ecological and dynamics promotes the use of remote sensing and GIS socioeconomic dimensions in a coherent scaling frame- in dealing with spatial heterogeneity and scaling in ad- work. Massive data collection efforts (e.g., NEON) are dition to more traditional methods of measuring pools expected to provide both opportunities and challenges to

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9780520269651_Ch_L.indd 395 11/25/11 7:28 PM landscape ecology to develop and test models and theories Forman, R. T. T., and M. Godron. 1986. Landscape ecology. New York: using detailed data spanning from local to regional scales. John Wiley & Sons. Naveh, Z., and A. S. Lieberman. 1994. Landscape ecology: theory and ap- Mathematical theory and modeling are critically impor- plication. New York: Springer. tant for the development of a science of spatial scale. Pickett, S. T. A., and M . L. Cadenasso. 1995. Landscape ecology: spatial Overall, landscape ecology is expected to provide not heterogeneity in ecological systems. Science 269: 331–334. Turner, M. G. 2005. Landscape ecology: what is the state of the science? only the scientifi c understanding of the structure and Annual Review of Ecology and Systematics 36: 319–344. functioning of various landscapes but also the pragmatic Turner, M. G., and R. H. Gardner. 1991. Quantitative methods in land- guidelines and tools with which resilience and sustainabil- scape ecology: the analysis and interpretation of landscape heterogeneity. New York: Springer–Verlag. ity can be created and maintained for the ever-changing Turner, M. G., R. H. Gardner, and R. V. O’Neill. 2001. Landscape ecology landscapes (Fig. 2). The rapid developments and advances in theory and practice: pattern and process. New York: Springer. in landscape ecology are best refl ected in the pages of the Wiens, J., and M. Moss, eds. 2005. Issues and perspectives in landscape fl agship journal of the fi eld, Landscape Ecology (http:// ecology. Cambridge: Cambridge University Press. Wu, J., and R. Hobbs, eds. 2007. Key topics in landscape ecology. www.springeronline.com/journal/10980/). Cambridge: Cambridge University Press. Wu, J., and O. L. Loucks. 1995. From balance-of-nature to hierarchi- SEE ALSO THE FOLLOWING ARTICLES cal patch dynamics: A paradigm shift in ecology. Quarterly Review of 70 :439–466. Adaptive Landscapes / Geographic Information Systems / Metacommunities / Metapopulations / Population Viability Analysis / / Urban Ecology

FURTHER READING LANDSCAPES ADAPTIVE Forman, R. T. T. 1995. Land Mosaics: The ecology of landscapes and regions. Cambridge: Cambridge University Press. SEE ADAPTIVE LANDSCAPES

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