Landscape ecology is the study of the causes and ecological consequences of spatial pattern in landscapes. While there is no specific spatial extent that defines a landscape, most landscape ecologists are interested in large areas ranging from a few square kilometers to entire continents. Within landscapes it is usually possible to define a series of different ecosystem types occurring as patches within the greater landscape. For example, in an agricultural landscape the patches might be different fields, woodlots, hedgerows, buildings, and ponds. The goal of a landscape ecologist is to understand and describe landscape structure; how this structure influences the movement of organisms, material, or energy across the landscape; and how and why landscape structure changes over time.
A landscape’s structure can be quantified by describing characteristics of patches, such as their number, size, shape, position, and composition. Landscape ecologists have defined measures to quantify each of these attributes. For example, a shape index has been defined as the ratio of the patch’s perimeter to the perimeter of a circle the same area as the patch. A circular patch would have the value of 1, and as the patch became more convoluted in shape, its shape index would increase in value.
A landscape’s structure has an important influence on various ecological processes occurring in the landscape. For example, consider two landscapes having equal areas of forest and agricultural land. In one landscape the forest is divided into many small patches, whereas in the other landscape the forested area occurs as one large patch. The more fragmented landscape will provide more habitat to those organisms that thrive at boundaries between two ecosystem types, whereas the less fragmented landscape will be better for those species that require larger areas of undisturbed forest. So, just knowing what percentage of the landscape is forest versus cropland is not sufficient to predict what species may occur; it is also important to know how the patches are distributed across the landscape.
Another example of how landscape structure can be important comes from studies of lakes within a forested landscape. The position of a lake within the landscape can be an important determinant of the lake’s physical, chemical, and biological characteristics. Because water flows downhill, lakes that are lower in the landscape receive more water from streams and groundwater than lakes higher in the flow system, which receive most of their water from precipitation. Lakes higher in the landscape tend to be smaller, more dilute chemically, and have fewer species of fish than lakes lower in the landscape, even though all of the lakes in the landscape experience the same weather and are situated in the same geological substrate .
Nowadays, at least six different conceptions of landscape ecology can be identified: one group tending toward the more disciplinary concept of ecology (subdiscipline of biology; in conceptions 2, 3, and 4) and another group—characterized by the interdisciplinary study of relations between human societies and their environment—inclined toward the integrated view of geography (in conceptions 1, 5, and 6):
Interdisciplinary scientific analysis of subjectively defined landscape units (e.g. Neef School): Landscapes are defined in terms of uniformity in land use. Landscape ecology explores the landscape’s natural potential in terms of functional utility for human societies. To analyse this potential, it is necessary to draw on several natural sciences.
Topological ecology at the landscape scale (e.g. Forman & Godron): ’Landscape’ is defined as a heterogeneous land area composed of a cluster of interacting ecosystems (woods, meadows, marshes, villages, etc.) that is repeated in similar form throughout. It is explicitly stated that landscapes are areas at a kilometres wide ‘‘human scale’’ of perception, modification, etc. Landscape ecology describes and explains the landscapes’ characteristic patterns of ecosystems and investigates the flux of energy, mineral nutrients, and species among their component ecosystems, providing important knowledge for addressing land-use issues.
Organism-centred, multi-scale topological ecology (e.g. John A. Wiens): Explicitly rejecting views expounded by Troll, Zonneveld, Naveh, Forman & Godron, etc., landscape and landscape ecology are defined independently of human perceptions, interests, and modifications of nature. ‘Landscape’ is defined – regardless of scale – as the ’template’ on which spatial patterns influence ecological processes. Not humans, but rather the respective species being studied is the point of reference for what constitutes a landscape.
Topological ecology at the landscape level of biological organisation (e.g. Urban et al.): On the basis of ecological hierarchy theory, it is presupposed that nature is working at multiple scales and has different levels of organisation which are part of a rate-structured, nested hierarchy. Specifically, it is claimed that, above the ecosystem level, a landscape level exists which is generated and identifiable by high interaction intensity between ecosystems, a specific interaction frequency and, typically, a corresponding spatial scale. Landscape ecology is defined as ecology that focuses on the influence exerted by spatial and temporal patterns on the organisation of, and interaction among, functionally integrated multispecies ecosystems.
Analysis of social-ecological systems using the natural and social sciences and humanities (e.g. Leser; Naveh; Zonneveld): Landscape ecology is defined as an interdisciplinary super-science that explores the relationship between human societies and their specific environment, making use of not only various natural sciences, but also social sciences and humanities. This conception is grounded in the assumption that social systems are linked to their specific ambient ecological system in such a way that both systems together form a co-evolutionary, self-organising unity called ‘landscape’. Societies’ cultural, social and economic dimensions are regarded as an integral part of the global ecological hierarchy, and landscapes are claimed to be the manifest systems of the ‘Total Human Ecosystem’ (Naveh) which encompasses both the physical (‘geospheric’) and mental (‘noospheric’) spheres.
Ecology guided by cultural meanings of lifeworldly landscapes (frequently pursued in practice but not defined, but see, e.g., Hard; Trepl): Landscape ecology is defined as ecology that is guided by an external aim, namely, to maintain and developlifeworldlylandscapes. It provides the ecological knowledge necessary to achieve these goals. It investigates how to sustain and develop those populations and ecosystems which (i) are the material ‘vehicles’ of lifeworldly, aesthetic and symbolic landscapes and, at the same time, (ii) meet societies’ functional requirements, including provisioning, regulating, and supporting ecosystem services. Thus landscape ecology is concerned mainly with the populations and ecosystems which have resulted from traditional, regionally specific forms of land use.
This question is the focus of a vast amount of research effort globally, but the following are some notable examples to give the general idea:
Patches: species may prefer a certain kind of habitat, for example mature woodland, or ponds. Individuals of the species of concern may not be able to breed or feed outside of this type of habitat. The habitat thus defines the patch.
Matrix: If one land use dominates the landscape, that landuse forms the matrix, e.g. arable land in eastern England. If the dominant land use is uniformly inhospitable, organisms become isolated in patches of suitable habitat. For example, some characteristic plants of ancient woodland cannot survive in arable fields, and do not have seeds equipped with a mechanism to disperse between isolated woodland fragments.
Corridors: There has been a lot of research and debate about the role of hedgerows as corridors for small woodland mammals and birds. Such species may be able to move between woodland habitat patches along hedgrerows, whereas they might not feel safe enough to cross an arable field.
Barriers: Roads, pipelines or fences might form barriers to movement of shy or less agile animals.
Mosaic: Lesser horseshoe bats are an example of an animal that needs to live in a landscape mosaic. They sleep in old trees in mature woodland, then fly along hedgerows to open, wet places where they hunt for flies.