Landscape Connectivity

Landscape connectivity is essential for maintaining ecological flows across landscapes. Processes as diverse as dispersal; gene flow; the flow of water, materials and nutrients; the spread of invasive species, diseases, or pests; or the spread of disturbances like fire, are all potentially influenced by the connectivity of different land covers and land uses. Landscape connectivity can be defined structurally as well as functionally. Landscape connectivity may therefore be treated as either an independent variable, in terms of studying how landscape connectivity influences ecological flows, or as a dependent variable in which landscape connectivity emerges as a consequence of how species or ecological flows interact with landscape structure. This chapter thus explores the different scales and ways in which connectivity can be measured and studied, providing a bridge between the previous chapter on landscape pattern analysis and the chapters that follow on the effects of landscape pattern on ecological processes.

Landscape Heterogeneity and Dynamics

Heterogeneity is a defining characteristic of landscapes and therefore central to the study of landscape ecology. Landscape ecology investigates what factors give rise to heterogeneity, how that heterogeneity is maintained or altered by natural and anthropogenic disturbances, and how heterogeneity ultimately influences ecological processes and flows across the landscape. Because heterogeneity is expressed across a wide range of spatial scales, the landscape perspective can be applied to address these sorts of questions at any level of ecological organization, and in aquatic and marine systems as well as terrestrial ones. Disturbances—both natural and anthropogenic—are a ubiquitous feature of any landscape, contributing to its structure and dynamics. Although the focus in landscape ecology is typically on spatial heterogeneity, disturbance dynamics produce changes in landscape structure over time as well as in space. Heterogeneity and disturbance dynamics are thus inextricably linked and are therefore covered together in this chapter.

Scaling Issues in Landscape Ecology

Spatial patterns are ubiquitous in nature, and ecological systems exhibit patchiness (heterogeneity) across a range of spatial and temporal scales. Landscape ecology is explicitly concerned with understanding how scale affects the measurement of heterogeneity and the scale(s) at which spatial pattern is important for ecological phenomena. Patterns and processes measured at fine spatial scales and over short time periods are unlikely to behave similarly at broader scales and extended time periods. An understanding of pattern-process linkages, a major research focus in landscape ecology, thus requires an understanding of how patterns change with scale, spatially and temporally. The development of methods for extrapolating information across scales is necessary for predicting how landscapes will change over time as well as for ecological forecasting. This chapter explores how scaling issues affect ecological investigations, discusses problems in identifying the correct scale for research, and outlines when and how ecological data can be extrapolated.

Landscape Effects on Ecosystem Structure and Function

Landscape ecosystem ecology is concerned with the study of how landscape structure affects ecosystem structure and function, and how landscape heterogeneity in turn is generated or sustained by the redistribution of nutrients or organisms within and among ecosystems. This chapter begins with an overview of how landscape context influences ecosystem processes, including the effects of land management and land-cover change on nutrient dynamics and productivity. Next, the chapter considers the linkages among systems (metaecosystems) and how spatial subsidies are important for understanding ecosystem function in a landscape context. The chapter then explores under what conditions landscape function becomes disrupted, possibly precipitating irreversible system state changes, before concluding with a clarion call for landscape sustainability; that is, landscape management that preserves the productivity, multifunctionality, and ecological resilience of landscapes in the face of future societal demands, intensifying land use, and rapid climate change.

Landscape Effects on Community Structure and Dynamics

Ecological communities consist of species that interact to varying degrees within the same geographical area, and so by definition exist within a landscape context. This chapter begins by reviewing the measures and different scales at which species diversity can be assayed, including the use of spatial partitioning to evaluate multiscale patterns of diversity. The chapter then reviews correlates of species diversity, including explanations for latitudinal and elevational diversity gradients, before considering how habitat loss and fragmentation are expected to influence species diversity. The chapter tackles the debate surrounding the relative importance of habitat amount versus fragmentation in predicting species’ responses to landscape change, and highlights the importance of studying these effects at a landscape rather than patch scale. The chapter concludes with a discussion of landscape effects on different types of species interactions, and how interactions among species in different communities can give rise to metacommunity structure and dynamics.

Landscape Genetics

Landscape genetics explores how the microevolutionary processes of gene flow, genetic drift, and natural selection interact with environmental heterogeneity to shape population genetic structure. This chapter begins with a review of the various types of genetic data used in population and landscape genetics and discusses how these data are used to estimate genetic variation (heterozygosity) and gene flow among populations. From there, the chapter considers how population genetic structure can be assayed, which then segues into an analysis of the landscape correlates of population genetic structure, the identification of movement corridors and barriers to gene flow, and the relative effects of current versus historical landscape factors on population genetic structure. The chapter concludes with an overview of evolutionary landscape genetics, by considering the adaptive potential of populations in response to future landscape and climatic changes.

Landscape Effects on Population Distributions and Dynamics

The distribution and dynamics of populations reflect the interplay between dispersal and demography with landscape structure. Understanding how landscape structure affects populations is essential to effective habitat management and species conservation, especially within landscapes undergoing habitat loss and fragmentation as a result of human land-use activities. This chapter thus begins with an overview of the effects of habitat loss and fragmentation on populations, followed by a discussion of species distribution modeling. Then, because population assessment figures so prominently in evaluating a species’ extinction risk to landscape change, the chapter considers the different classes of population models used to estimate population growth rates and population viability, including the use of metapopulation and spatially explicit simulation models.

Landscape Effects on Individual Movement and Dispersal

Movement is a fundamental process that enables individuals to find food or mates, locate suitable habitat, and colonize new areas. The effect of environmental heterogeneity on individual movement behavior is the finest scale at which organisms respond to landscape structure, and can be used to define different species’ perceptions of landscape structure. This chapter discusses different types and scales of movement, how patch structure is expected to influence movement, and various methods for tracking and analyzing animal movement. Because animal movements are typically bounded in space, the estimation of space utilization and home-range size is also considered in this chapter. The chapter concludes with a discussion of various approaches to measuring plant dispersal, which is likewise important for evaluating how movement (via propagules) translates into the redistribution or spread of populations across the landscape.

Landscape Pattern Analysis

The analysis of landscapes and other spatial patterns is a major focus of landscape ecology, being essential to the study of how landscape patterns affect ecological processes. Landscape pattern analysis has become a sine qua non for environmental monitoring, natural resource management, landscape planning, sustainable development, and species conservation. The intensification of human land use is a major global-change issue, requiring an in-depth analysis of how landscapes are being transformed over time, as well as how anthropogenic disturbances compare to the natural disturbance regime. This chapter covers the types and availability of landscape data, such as from historical land surveys and remote sensing; how spatial data are processed and manipulated within a Geographical Information System (GIS); and finally, how to analyze landscape structure using landscape metrics and spatial statistics, including a discussion of best practices.

An Introduction to Landscape Ecology

Landscape ecology provides the scientific basis for the study and management of landscapes, as well as the ecological systems they contain. More generally, landscape ecology investigates the reciprocal interactions between spatial patterns (environmental heterogeneity) and ecological processes across a wide range of scales. This introductory chapter discusses the rise of landscape ecology as a discipline, its regional perspectives, core concepts, and research themes, and provides an overview of the textbook itself. Among its core concepts, landscape ecology asserts that heterogeneity is a defining characteristic of landscapes; that landscapes can be defined and studied at any scale; and that landscapes occur within aquatic and marine systems, as well as terrestrial ones. As such, landscape ecology can benefit the study and management of any ecological system, from populations to ecosystems, through its explicit consideration of how heterogeneity, scale, spatial context, and disturbance dynamics influence critical ecological processes.