Sixth Extinction
ஆறாவது பேரழிவு
Evolution took billions of years to build the biosphere. Human activity is dismantling it in a geological blink. Do not confuse 'background extinction' with the current anthropogenic crisis.
The idea
The current extinction rate is 100 to 1,000 times faster than pre-human levels. This is the Sixth Extinction. Ecologists project that 50% of all extant species face total extinction within the next 100 years. This is driven entirely by anthropogenic habitat loss, overexploitation, and climate change.
Why it matters
This exists as a consequence of anthropogenic environmental degradation, habitat destruction, and over-exploitation of natural resources.
NEET lens
NEET focuses on the '100 to 1,000 times' statistic and the '50% in 100 years' projection. Memorize these figures exactly. Do not mistake 'Sixth Extinction' for natural evolutionary turnover; it is strictly anthropogenic.
Clinical significance
Biodiversity loss triggers the collapse of ecosystem services, including the loss of medicinal plant species essential for pharmacology. When keystone species vanish, the trophic structure destabilizes, leading to the proliferation of zoonotic pathogens. Ecosystem failure is the precursor to human health crises.
Introduction
The current species extinctions, driven by human activities, are called the 'Sixth Extinction'. It is different from the previous five because it is occurring at a much faster rate.
Core concept
The fossil record shows that there have been five episodes of mass extinction of species since the origin and diversification of life on Earth. The 'Sixth Extinction' presently in progress is estimated to be 100 to 1,000 times faster than in the pre-human times, and our activities are responsible for the faster rates. Ecologists warn that if the present trends continue, nearly half of all the species on Earth might be wiped out within the next 100 years. The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years. Some examples of recent extinctions: dodo (Mauritius), quagga (Africa), thylacine (Australia), Steller's sea cow (Russia) and three subspecies (Bali, Javan, Caspian) of tiger. The last twenty years alone have witnessed the disappearance of 27 species. More than 15,500 species world-wide are facing the threat of extinction: 12 per cent of all bird species, 23 per cent of all mammal species, 32 per cent of all amphibian species and 31 per cent of all gymnosperm species.
Go deeper
Loss of biodiversity in a region may lead to decline in plant production, lowered resistance to environmental perturbations such as drought and increased variability in certain ecosystem processes such as plant productivity, water use, and pest and disease cycles.
From Class 10
Many species are disappearing right now, much faster than in the past, mainly because of human activities.