Watershed scale changes in natural habitats with a focus on habitat fragmentation measurement and metrics

State of Knowledge The loss of habitat is a leading cause of the loss of biodiversity that we are seeing in what is being called the ‘sixth great extinction.’ Landscape ecology is the study of the spatial pattern of landscapes. Although the term has been used since the early 1900’s, it has only become a field of study in its own right with the technological advancement of remote sensing through aerial photography and satellite imagery. Spatial pattern and ecological processes are related and although there are many different types of spatial patterns, ecologists have focused much of their attention first on habitat abundance, second at the subsequent fragmentation of remaining habitat. This is because the spatial distribution of patches influences many ecological process, for example animal behavior (Hargis et al. 1998). To quantify the effect of increasing fragmentation (i.e. patchiness) on a given landscape requires metrics, and hundreds have been devised by statisticians, mathematicians and ecologists from the relatively simple, like edge density which is the total length of patch edge per unit area within a landscape, to the complex and lesser understood, for example contagion, the extent to which pixels are aggregated. Several software programs have been developed to help scientists calculate these do this. The most widely used amongst landscape ecologists is FRAGSTATS. FRAGSTATS is distributed for free over the Internet, and describes each of the metrics it calculates in detail in its User Guidelines, which is also available for free via the Internet.