The biological wealth of our planet has been declining rapidly and the accusing finger is clearly pointing to human activities. The colonisation of tropical Pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds. The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years. 'In-situ' conservation can help endangered or threatened species. Justify the statement. What are the causes of biodiversity loss?

Explanation

In "In-situ" conservation, the threatened organisms are conserved in their natural habitat or ecosystem. Such habitats are legally protected as hotspots, biosphere reserves, national parks, sanctuaries, sacred groves or Ramsar sites. Causes of biodiversity loss are:
(i) Habitat loss or fragmentation: The Amazon rain forest is being cut out and cleared for raising cattle, or conversion to grasslands or cultivating soyabeans. The large habitats are broken up into small fragments due to human activities. Mammals and birds which require large territories are badly affected leading to decline in population. (ii) Over-exploitation: When "need" turns to "greed", it leads to over-exploitation of natural resources. E.g., stellar.s sea cow, passenger pigeon, marine fish population were overexploited. (iii) Alien species invasions: When alien species are introduced deliberately, some of them turn invasive and cause decline in indigenous species e.g., Carrot grass, African catfish (Clarias gariepinus) poses a threat to the indigenous cat fishes.