Read the given passage and answer the following questions :
The narrowly utilitarian arguments for conserving biodiversity are obvious; humans derive countless direct economic benefits from nature- food (cereals, pulses, fruits), firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes) and products of medicinal importance. More than 25 percent of the drugs currently sold in the market worldwide are derived from plants and 25,000 species of plants contribute to the traditional medicines used by native peoples around the world. Nobody knows how many more medicinally useful plants there are in tropical rainforests waiting to be explored. With increasing resources put into ‘bioprospecting’ (exploring molecular, genetic and species-level diversity for products of economic importance), nations endowed with rich biodiversity can expect to reap enormous benefits. The broadly utilitarian argument says that biodiversity plays a major role in many ecosystem services that nature provides. The fast-dwindling Amazon forest is estimated to produce, through photosynthesis, 20 per cent of the total oxygen in the earth’s atmosphere. Pollination (without which plants cannot give us fruits or seeds) is another service, ecosystems provide through pollinators layer – bees, bumblebees, birds and bats. There are other intangible benefits – that we derive from nature–the aesthetic pleasures of walking through thick woods, watching spring flowers in full bloom or waking up to a bulbul’s song in the morning. The ethical argument for conserving biodiversity relates to what we owe to millions of plant, animal and microbe species with whom we share this planet. Philosophically or spiritually, we need to realise that every species has an intrinsic value, even if it may not be of current or any economic value to us.
The Amazon rain forest is being cut and cleared for cultivating soya beans and for raising beef cattle. Which major cause of biodiversity loss does this show?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Habitat loss and fragmentation
The present high rate of species extinction is caused mainly by human activities. NCERT groups its causes into four, called ‘The Evil Quartet’: habitat loss and fragmentation, over-exploitation, alien species invasions and co-extinctions. Clearing a forest for farms and cattle removes the home of its species.
Option (1) Habitat loss and fragmentation — Correct. Cutting and clearing the Amazon rain forest for soya beans and beef cattle destroys the habitat of millions of species. Habitat loss and fragmentation is the most important cause of extinction, and tropical rain forests give its most dramatic examples.
Option (2) Over-exploitation — Incorrect. Over-exploitation happens when ‘need’ turns to ‘greed’ and a species itself is harvested too much, as with Steller’s sea cow and the passenger pigeon. In the Amazon the forest is cleared for land; the species are not being harvested.
Option (3) Alien species invasions — Incorrect. Alien species invasions are caused by species brought in from outside, such as the Nile perch in Lake Victoria or Parthenium and Lantana. No new species is introduced in this example.
Option (4) Co-extinctions — Incorrect. Co-extinction is the loss of species that are bound to another species in an obligatory way, such as a host fish and its parasites, when that species dies out. The example describes clearing of a whole forest, not such a linked loss.
NCERT Extract:
Loss of Biodiversity – “… 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. The most dramatic examples of habitat loss come from tropical rain forests. … 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.”