Disturbance of any type in an ecosystem tend to reduce its biodiversity. The pressure of human demand and pollution of environment damages the biotic components of natural systems. Thus, major causes of threats to biodiversity as are follows:
The primary cause of loss of biodiversity is the habitat. The primary cause of loss of biodiversity is the habitat destruction which from the expansion of human population and human activities. Habitats which protect wildlife are being converted to human settlements harbours, dams, reservoirs, croplands, grazing grounds and plantation.
Habitat loss is the primary threat to majority of vertebrates. Huge amounts of habitat are lost each year as the world’s forests are cut down.
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2. Habitat Fragmentation :
Habitats are now being divided into pieces of roads, fields, towns, canals, power lines etc. Habitat fragmentation is the process where a large area of habitat is reduced in area and divided into more fragments.
3. Habitat Degradation Pollution :
The major cause of habitat degradation is environmental pollution. Deforestation and environmental pollution have resultant in the degradation of important habitats. Migratory animals are particularly vulnerable to destruction of habitats. Some of the dams are blocking spawning migration of fishes by circumdating the habitats and by altering the physical environment.
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4. Introduction of Exotic Species :
The introduction of exotic deliberately has affected many species by imposing new factors in competition for food and spare predation habitat destruction and degradation, transmission of diseases and parasites. The native species of fish of fresh water and of islands are especially affected by the introduction of new species.
5. Over Exploitation :
Over exploitation is a serious threat to wildlife. Over fishing is seriously depleting the marine living resources and significantly affecting the fresh water. Many species of fish and mollusks whales, sea, cow and sea turtles are facing total extinction as they are caught by mechanical devices for the sea food industry. Even if a species is not completely eliminated by over exploitation the population size may become so low that the species is unable to recover.