Biodiversity and conservation class 12 Part 3

Causes of biodiversity losses :-

There are four major cause of biodiversity loss. There are also known as ‘the evil quarter’.

Destructions of habitat is the primary cause of extinction of species.
Tropical rain forests covering more than 14 per cent of the earth’s land surface, these rain forests now cover no more than 6 per cent.
The Amazon rain forest called as the’ lungs of the planet’ harboring probably millions of species is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising beef cattle.
Breaking of large areas into small fragments cause biodiversity loss due to human settlements, building of roads, digging of canals, etc.,
The population of animals requiring large territories and some animals with migratory habitats declines.

Many species extinctions in the last 500 years were due to overexploitation by humans.
For example-Steller’s sea cow, passenger pigeon.

Some alien (exotic) species when introduced unintentionally or deliberately become invasive and cause harmful impact, resulting in extinction of the indigenous species.
Nile perch, a large predator fish when introduced in lake Victoria (east Africa) caused the extinction of an ecologically unique species of cichlid fish in the lake.
Invasive weed species like parthenium (carrot grass), lantana and eicchornia (water hyacinth) caused environmental damage and posed threat to our native species.
Introduction of African catfish (clarias gariepinus) for aquaculture purposes is posing a threat to the indigenous catfishes of indian rivers.

When a species becomes extinct, the plant and animal species associated with it in an obligatory manner, also become extict.
For ex:- When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate. In plant –

pollinator mutualism extinction of one invariably leads to the extinction of the other.