# Landscape ecology

 Topics:

## Introduction

Landscape ecology is a subdiscipline of ecology that focuses on the spatial patterns of ecological processes. Whereas ecological disciplines often consider processes that create patterns in biota, landscape ecology represents an unique field because it looks at the effect of spatial pattern on ecological processes. The main themes of landscape ecology are heterogeneity, scale, and temporal/spatial relations. Some have called landscape ecology the true environmental interdisciplinary science that can bridge the disciplines of biology, geography, and social sciences in order to tackle the problems of environmental degradation.

## History

The German biogeographer Troll coined the phrase "landscape ecology" in 1939 and defined landscape as “‘the total spatial and visual entity’ of human living space, integrating the geosphere with the biosphere and its noospheric [of knowledge] man-made artifacts.” Throughout the following decades, the field of landscape ecology developed in Europe by employing the concepts of regional geography and botanical science (e.g. classification, nomenclature, and a focus on built environments). Thus, this European school of landscape ecology expended its effort toward understanding the human aspect of landscape.

The American school developed much later than, and quite distinctly from, the European one. While Europeans focused on “smaller scale dimensions,” American scientists paid more attention to the coarse grained landscapes. Ecologists, geographers, and resource scientists examining interactions among landscapes formed the basis of the North American school. While ecologists and biogeographers began to look at the human aspect of ecosystem studies during the 1960s and 1970s (e.g. Egler's work on the total human ecosystem, Dansereau's on human ecology in 1966), the emphasis of the work remained on quantification of structure and function of populations, communities, and ecosystems.

The 1983 Allerton Park Workshop served as the organizational moment for this fledgling science in America. It focused on areas that unite landscape and ecology: spatial pattern and ecological process; spatial and temporal scales; the effect of heterogeneity on fluxes and disturbance; changing patterns; and a framework for natural resource management. As Rissert noted, the definition of landscape ecology crafted at the workshop focused on the variety of components occurring through space: "Landscape ecology considers the development and dynamics of spatial heterogeneity, spatial and temporal interactions and exchange across heterogeneous landscapes, influences of spatial heterogeneity on biotic and abiotic processes, and management of spatial heterogeneity."

Despite the energy at the conference, the discipline experienced lethargy during the 1980s. Many scientists considered the theory of landscape ecology to be an extension of island biogeography, assuming that observed ecosystem processes simply could be enlarged to the broader scale of landscape. This lack of understanding of scale, coupled with lack of communication and collaboration, hampered progress in research. In addition, an assumption that generating maps would reveal the problems and the answers in spatial pattern research led to some complacency. Some scientists held the belief that humans should be incorporated into the study of ecological patterns and processes, but no systematic study of this element developed. Finally, a lack of quantification hampered progress, which in turn hindered acceptance of this new discipline by other scientists.

These challenges aside, the theory and application of landscape ecology have coalesced since the 1990s. Today island biogeography does not play a predominant role in landscape ecology theory. With increased knowledge and experience, the definition of landscape ecology formulated at Allerton Park would be simplified today, yet the questions that framed the workshop still remain pertinent.

## The Domain of Landscape Ecology

The Allerton Park definition makes clear that heterogeneity, or distinct spatial patterns, comprise the core research question in landscape ecology. The main themes comprising landscape ecology include:

• the spatial pattern or structure of landscapes, ranging from wilderness to cities
• the relationship between pattern and process in landscapes, including the ecological implications of pattern for populations, communities, and ecosystems
• the effect of scale on landscape
• the processes involved in pattern formation, such as the physical (abiotic) environment, demographic responses to this, and disturbance regimes
• the relationship of human activity to landscape pattern, process and change (e.g. applications in land-use planning)

Landscape ecology occurs at a variety of scales, so that a “landscape” may encompass a region composed of multiple ecosystems, or it may constitute the home range of an insect that extends a few meters across. Rather than a particular size, landscape is defined by the spatial pattern (heterogeneity) and the processes occurring on it that are under consideration. Thus, resolution, grain, and extent are important concepts in landscape ecology. This also means that levels of organization, as distinct from scale, is an essential concept, which derives from the kinds of interactions under consideration in a particular research endeavor. With the determination of these aspects of a study, the pattern can be assessed, which is usually described as a mosaic of patches.

## Research directions: Space—the final frontier

As the field develops and strengthens (the International Association of Landscape Ecology had ~1700 members in over 42 countries in 2005), it faces particular challenges. Landscape ecology research needs to tackle multiple scale studies of fundamental concepts, including spatial and temporal scale relationships; connections between population and ecosystem processes; organisms' relationships to spatial pattern; and comparisons of natural and managed systems. The discipline seeks to increase experimental research—certainly, the large scale of landscapes makes experimentation and replication difficult. The research challenges remain, and many landscape ecologists call for an increase in experimentation, rigor, and quantification. Theory and formal propositions need to be developed and tested through experimental methods. On a more practical level, methods for managing and communicating data to scientists, decision makers, and the public are always needed. As Dean Urban of Duke University has noted, space is the final frontier in ecology.

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