Biodiversity and Conservation - Notes | Class 12 | Part 2: Loss of Biodiversity
Loss of Biodiversity
Loss of Biodiversity
IUCN Red List (2004) reports that 784 species (338 vertebrates, 359 invertebrates, and 87 plants) have gone extinct in the last 500 years. Examples include Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Stellar’s Sea Cow (Russia), and three subspecies of tiger (Bali, Javan, Caspian).
27 species have disappeared in the last 20 years.
More than 15,500 species are currently facing the threat of extinction.
12% of birds, 23% of mammals, 32% of amphibians, and 31% of gymnosperm species face the threat of extinction.
The current extinction rate is 100–1000 times faster than in pre-human times. If this trend continues, nearly 50% of species might be extinct within the next 100 years.
Impacts of Loss of Biodiversity
Decline in plant production.
Environmental perturbations such as drought.
Increased variability in ecosystem processes such as plant productivity, water use, and pest and disease cycles.
Causes of Biodiversity Losses (‘The Evil Quartet')
Habitat Loss and Fragmentation: The most important cause.
Tropical rainforests have reduced from 14% to 6% of Earth’s surface.
Thousands of hectares of rainforests are lost within hours.
The Amazon rainforest is being cut for cultivating soybeans or converting to grasslands for cattle.
Fragmentation severely affects animals requiring large territories and migratory animals.
Over-exploitation: Species like Stellar’s Sea Cow and Passenger Pigeon went extinct due to over-exploitation.
Alien Species Invasions: Alien species cause decline or extinction of indigenous species.
Nile Perch introduced in Lake Victoria (East Africa) caused the extinction of over 200 species of cichlid fish.
Invasive weeds like Parthenium (carrot grass), Lantana, and Eichhornia (water hyacinth) have damaged native species.
Illegal introduction of the African Catfish (Clarias gariepinus) for aquaculture threatens indigenous catfishes in rivers.
Co-extinction: When a species becomes extinct, associated species also go extinct.
Extinction of parasites when their host goes extinct.
In co-evolved plant-pollinator mutualism, extinction of one causes extinction of the other.
