It took 10m years to come out of mass extinction

It took about 10 million years for the earth to recover from the greatest mass extinction which has nearly wiped out life some 250 million years ago, a new study has suggested.

Scientists have long been debating on how life recovered, whether quickly or slowly, from this cataclysm that allowed only 10 per cent of plants and animals to survive. Now, an international team from the China University of Geosciences in Wuhan and the University of Bristol found new evidence that suggested the recovery from the crisis lasted some 10 million years.

According to the team, which detailed its finding in the journal Nature Geoscience, there were apparently two reasons for the delay, the intensity of the crisis and continuing grim conditions on the earth after the first wave of extinction.

The end-Permian crisis, by far the most dramatic biological crisis to affect life on the earth, was triggered by a number of physical environmental shocks — global warming, acid rain, ocean acidification and ocean anoxia. These were enough to kill off 90 per cent of living things on land and in the sea, the researchers said.

“It is hard to imagine how so much of life could have been killed, but there is no doubt from some of the fantastic rock sections in China and elsewhere round the world that this was the biggest crisis ever faced by life,” said Zhong-Qiang Chen from the China University of Geosciences.

Current research shows that the grim conditions continued in bursts for some five to six million years after the initial crisis, with repeated carbon and oxygen crises, warming and other ill effects.

Some groups of animals in  sea and land did recover quickly and began to rebuild their ecosystems, but they suffered further setbacks, the researchers said. Life had not really recovered in these early phases because permanent ecosystems were not established, they added.