News Stories

Biggest Extinction Caused by Low Oxygen

Newswise - The biggest mass extinction in Earth history happened 251million years ago and it took millions of years for theEarth to finally repopulate. New research shows that thisextinction event was caused by a sudden sharp decline inatmospheric oxygen?why did this happen and could it happenagain?

250 million years ago, there was a single supercontinent onEarth, which we now called Pangea. Most of the land abovesea level became uninhabitable because low oxygen levelsmade breathing too difficult for most land animals organismsto survive.

Biologist Raymond Huey says an additional reason may be thatgroups of the same species were cut off from each otherbecause there wasn?t enough oxygen in the air for them totravel far enough to find mates.

There is about 21% oxygen in the air today, and there was30% in the early Permian period, shortly before this majorextinction took place. The oxygen level suddenly fell toaround 16% during the extinction event, bottoming out atless than 12%. This situation lasted for the next 10 millionyears.

"Oxygen dropped from its highest level to its lowest levelever in only 20 million years, which is quite rapid, andanimals that once were able to cross mountain passes quiteeasily suddenly had their movements severely restricted,"Huey says. When the oxygen level hit 16 percent, breathingat sea level would have been like trying to breathe on topof a 9,200-foot mountain today.

Not only was atmospheric oxygen content dropping at the endof the Permian, but carbon dioxide levels were rising,leading toglobal warming.

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