Which of the following are causes of biodiversity losses?(A) Habitat…

The correct answer is Option (3) → (A), (B), (C) and (D)

The fast loss of species today is caused mainly by human activities. NCERT names four major causes, called ‘The Evil Quartet’, and all four are listed here.

(A) Habitat loss and fragmentation — A cause. It is the most important cause of extinction. Tropical rain forests once covered more than 14 per cent of the earth’s land and now cover no more than 6 per cent. When a large habitat is broken into small pieces, animals that need large territories, and birds that migrate, decline.

(B) Alien species invasions — A cause. Some species brought in from outside turn invasive and wipe out local species. The Nile perch in Lake Victoria killed off more than 200 species of cichlid fish; carrot grass (Parthenium), Lantana and water hyacinth are invasive weeds.

(C) Over-exploitation — A cause. When ‘need’ turns to ‘greed’, natural resources are used faster than they can recover. Steller’s sea cow and the passenger pigeon were lost this way, and many marine fish are now over-harvested.

(D) Co-extinctions — A cause. When one species dies out, species tied to it in an obligatory way also die out, such as a host fish and its parasites, or a plant and its pollinator.

NCERT Extract:
Loss of Biodiversity – “… Causes of biodiversity losses: The accelerated rates of species extinctions that the world is facing now are largely due to human activities. There are four major causes (‘The Evil Quartet’ is the sobriquet used to describe them).
(i) Habitat loss and fragmentation: This is the most important cause driving animals and plants to extinction.”
Loss of Biodiversity – “(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 overexploitation by humans.”
Loss of Biodiversity – “(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.”
Loss of Biodiversity – “(iv) Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligatory way also become extinct.”