The greatest mass extinction pulse was the Permian-Triassic extinction event, and it happened about 250 million years ago, nearly wiping out life on Earth. It was Earth’s most severe extinction even, with 96% of all marine species and 70% of all terrestrial vertebrate species becoming extinct. It is the only known mass extinction that affected insects, 57% of all families and 83% of all genera were extinguished.
The loss of such biodiversity apparently took Earth 10 million years to recover, more than any other extinction pulse. In a recent article in the journal Nature Geoscience, lead scientists Zhong-Qiang Chen from the University of Geosciences in Wuhan and Michael Benton from the University of Bristol analyzed the bounce-back of life.
There were two reasons for the delay of the return biodiversity. The sheer intensity of the extinction and the grim conditions on Earth after the pulse made it harder for species to recover. The Permian-Triassic extinction event was triggered by a number of different factors, including global warming, acid rain, ocean acidification and ocean anoxia. These factors were enough to spur the extinction pulse.
Research shows that the grim conditions continued for five to six million years later, with continued carbon and oxygen crises, warming and other effects. Once the environmental crises ceased to be severe, more complex ecosystems emerged, allowing new groups to take hold.
The new groups, including ancestral crabs and lobsters, as well as the first marine reptiles, re-set evolution, becoming the source of the dominant species on Earth in millions of years to come.
Reference: “The timing and pattern of biotic recovery following the end-Permian mass extinction” by Zhong-Qiang Chen and Michael J. Benton, 27 May 2012, Nature Geoscience.