Question

Explain any two reasons which causes the losses of biodiversity.

Answer 1

The accelerated rates of species extinctions that the world is facing now are largely due to human activities. There are four major causes: (any two)
[i] Habitat loss and fragmentation: This is the most important cause driving animals and plants to extinction. The most dramatic examples of habitat loss come from tropical rain forests. They are being destroyed fast. The Amazon rain forest (it is so huge that it is called the 'lungs of the planet') harbouring probably millions of species is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle. Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species.
[ii] Over-exploitation: Humans have always depended on nature for food and shelter, but when 'need' turns to 'greed', it leads to over-exploitation of natural resources. Many species extinctions in the last $500$ years (Steller's sea cow, passenger pigeon) were due to over exploitation by humans. Presently many marine fish populations around the world are over harvested, endangering the continued existence of some commercially important species.
[iii] Alien species invasions: When alien species are introduced unintentionally or deliberately for whatever purpose, some of them turn invasive, and cause decline or extinction of indigenous species.
[iv] Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct. When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate. Another example is the case of a co evolved plant-pollinator mutualism where extinction of one invariably leads to extinction of the other.