Essay On Habitat Fragmentation

The effect of forest fragmentation is a growing concern among ecologists and forestry managers. Habitat fragmentation is often defined as a process during which “a large expanse of habitat is transformed into a number of smaller patches of smaller total area, isolated from each other by a matrix of habitats unlike the original” (Wilcove et al., 1986). The exact definition of fragmentation differs among studies and commentators, but such features as size of biggest fragment, total amount of perimeter, mean size of fragment, number of fragments, and average distance between fragments have been seen as aspects of fragmentation. The definition of habitat fragmentation above implies four effects of the process of fragmentation on habitat patterns: (a) reduction in habitat amount, (b) increase in number of habitat patches, (c) decrease in size of habitat patches, and (d) increase in isolation of patches. These four effects form the basis of most quantitative measures of habitat fragmentation (Fahrig, 2003). Because fragmentation is generally accompanied by habitat loss, parsing the effects of the two processes is a difficult matter (Wilcove et al., 1986). Many people use the term “fragmentation” loosely, to refer to both processes together. Habitat fragmentation is generally thought to have a large negative effect on biodiversity and is therefore widely viewed as an aspect of habitat degradation (Haila, 2002). This conclusion is, however, generally valid only for conceptualizations of fragmentation that are inseparable from habitat loss. Empirical studies to date suggest that habitat loss has large, consistently negative effects on biodiversity. Habitat fragmentation per se has much weaker effects on biodiversity that are at least as li...

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... interpreted as an intensification of the effects of habitat loss at low habitat levels. One aspect of the fragmentation issue, and the one that has been most widely bruited and treated in models, is the extent to which landscape configuration permits movement. The matter of connectivity in general and corridors in particular is thus part of the fragmentation issue.

The bottom line is that complex landscapes beget complex interactions and it will require some clever manipulative experiments to untangle the often confounding effects of boundary quantity, boundary quality, matrix habitat, patch area and patch isolation on different species. This separation is crucial for conservation purposes, seeing as fragmentation and habitat loss are among the most important causes of species decline worldwide (Haila et al., 1994; Murcia, 1995; Didham et al., 1996; Didham, 1997).