Landscape Pattern Metrics

Abstract

AbstractReal landscapes contain complex spatial patterns in the distribution of resources that vary over time; quantifying these patterns and their dynamics is the purview of landscape pattern analysis. Landscape pattern analysis involves quantifying the spatial heterogeneity of point patterns, linear networks, continuous surface patterns, and categorical patch mosaics, and sometimes custom hybridizations of these basic models, although the focus in landscape ecology and of this article has been on patch mosaics. In this context, landscape metrics are algorithms that quantify specific spatial characteristics of patches, classes of patches, or entire landscape mosaics, or of the patch mosaic in the neighborhood of each focal cell. These metrics fall into two categories: those that quantify the composition of the map without reference to spatial attributes (i.e., the variety and abundance of patch types), and those that quantify the spatial configuration of the map (i.e., the spatial character and arrangement, position, or orientation of patches within the class or landscape). Metrics are further categorized as structural metrics that measure physical structure of the mosaic without explicit reference to a particular phenomenon, or functional metrics that require additional parameterization and measure the structure of the mosaic as it relates to a specific organism or ecological process. Not surprisingly, landscape metrics are highly sensitive to landscape definition with respect to the thematic content and resolution, spatial grain and extent, and the landscape boundary. The current use and interpretation of landscape metrics is constrained by the lack of a proper theoretical understanding of metric behavior across a wide range of landscape structure gradients, the lack of a proper spatial and/or temporal reference framework for ecologically interpreting the computed value of each metric, and the challenges of choosing a parsimonious suite of metrics for a particular application given the plethora of existing metrics. Ultimately, the definition of the landscape, the establishment of a meaningful reference framework, and the choice of metrics should be based on some hypothesis about the observed landscape pattern and what processes or constraints might be responsible for that pattern. Fortunately, programs like FRAGSTATS make the calculation of landscape metrics practical and accessible to all landscape ecologists.