Destruction of wildlife habitats by increasing pressure for land by fast-growing human populations, pollution and over-exploitation. Whole species or populations of plants and animals have disappeared causing a loss of genetic resource that is not only regrettable from an aesthetic or philosophical point of view but also threatens man's food supply. Habitat loss takes several forms: outright loss of areas used by wild species; degradation, for example, from vegetation removal and erosion, which deprive native species of food, shelter, and breeding areas; and fragmentation, when native species are squeezed onto small patches of undisturbed land surrounded by areas cleared for agriculture and other purposes.