The change in the number of species occurring in the zone where two habitats are in contact. Since this zone may contain biotic elements from both habitats and some unique to itself it may be rich in species, but because those species are ill-adapted to the immediately adjacent habitat, the rate of local extinction is usually high at edges. Predation, in particular, is greatest at a habitat edge. The effect occurs because the overlap region supports some species from both adjacent ecosystems and some peculiar to itself. Ecologists now regard the edge effect as a sign of ecological deterioration. The fragmentation of habitats causes an increase in edge areas, but a decrease in the internal areas of ecosystems, leading eventually to a loss of species from all affected ecosystems and an increase in edge species, which are usually commonplace.
Subjects: Ecology and Conservation — Plant Sciences and Forestry.