Took 10 Million Years for Life on Earth to ‘Re-set’ After Mass Extinction

More than 250 million years ago, most life on Earth was wiped out by a catastrophic event called the Permian–Triassic extinction. New research suggests it took our planet 10 million years to recover from what is now known as “The Great Dying.”

The Great Dying took place millions of years earlier than the Cretaceous-Tertiary extinction, which killed off the dinosaurs 65 million years ago. It was also much more devastating, destroying 90 percent of all plants and animals.

Scientists theorize a “perfect storm” of conditions – global-warming, acid rain, ocean acidification and ocean anoxia (loss of oxygen) – followed by a catastrophic event such as increased volcanism, contributed to Earth’s most dramatic and devastating biological crisis.

For some time now, they’ve debated how quickly life on Earth bounced back from this mass extinction. A new article in Nature Geoscience puts that number at 10 million years.

So why did it take our planet so long to recover from this devastating loss of life? Why didn’t life just “bounce back?”

The sheer intensity of this crisis, coupled with the bleak conditions which remained on Earth after that first devastating surge of extinction, are the reasons for the delay, according to the report authors.

These bleak conditions continued, in bursts, for some five-to-six million years after the initial calamity, triggering repeated environmental crises.

“Life seemed to be getting back to normal when another crisis hit and set it back again,” said Michael Benton, one of the report authors who is a professor at England’s University of Bristol. “The carbon crises were repeated many times and then, finally, conditions became normal again after five million years or so.”

While certain groups of marine and land animals recovered quickly to a certain point, they suffered continual setbacks with each of these bursts of dire conditions following the initial crisis because, according to the researchers, their permanent ecosystems were not firmly established.

But after the waves of environmental devastation began to wane, not only did life return to Earth, but much more complex ecosystems were formed, allowing for much more sophisticated life forms which eventually led to human life.

“We often see mass extinctions as entirely negative but in this most devastating case, life did recover, after many millions of years, and new groups emerged,” Benton said. “The event had re-set evolution. However, the causes of the killing – global warming, acid rain, ocean acidification – sound eerily familiar to us today. Perhaps we can learn something from these ancient events.”

Source
Voice of America


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