Kochi: Scientists are sure the world is moving towards what has been called a “sixth mass extinction”. Species are going extinct at a rate that exceeds what you would expect to see naturally, as a result of a major perturbation to the system. This perturbation is caused by humans. A new study published on Wednesday in the Science magazine confirms this. In the world’s oceans, threats of extinction aren’t apportioned among all species equally, but the larger ones, in terms of body size and mass, are uniquely imperiled right now. The disproportionate threat to larger marine organisms reflects the “unique human propensity to cull the largest members of a population,” the authors wrote.
“What to us was surprising was that we did not see a similar kind of pattern in any of the previous mass extinction events that we studied," geoscientist Jonathan Payne of Stanford University, the study's lead author, said. "So that indicated that there really is no good ecological analogue ... this pattern has not happened before in the half billion years of the animal fossil record."
A statistical analysis of a 2,497 different marine animal groups at one taxonomic level higher than the level of species - called "genera" was conducted by the researchers. "Human hunting has been extensive for many thousands of years on land, whereas it's been extensive for a couple of hundred years in the oceans," says Payne.
Humans have driven to extinction many land-based large animal species in what was dubbed the Late Quaternary extinction event as the most recent ice age came to a close. "The preferential removal of the largest animals from the modern oceans, unprecedented in the history of animal life, may disrupt ecosystems for millions of years even at levels of taxonomic loss far below those of previous mass extinctions," the authors wrote.
