Permian Extinction Linked To Planetary Warming, Oxygen Depletion

[hatrack]

"The world nearly suffocated about 250 million years ago, according to a new study of oxygen levels drawn from sediments laid down around the time of the biggest mass extinction in Earth's history. Not only did plummeting oxygen levels over a 20 million-year span directly contribute to an event called the "Great Dying," but the changes also made most dry land above sea level uninhabitable for many animals and plants for millions of years.

"Oxygen dropped from its highest level to its lowest level ever (during the time Earth has supported life) in only 20 million years, which is quite rapid, and animals that once were able to cross mountain passes easily suddenly had their movements severely restricted," said Raymond Huey, a University of Washington biology professor and co-author of the report. It was published yesterday in the journal Science.

Scientists calculate that 90 percent of all marine life and three-quarters of all land plants and animals became extinct during the episode of low oxygen, greenhouse conditions and lowered sea levels at the boundary of the Permian and Triassic geological periods. Huey and co-author Peter Ward, a paleontologist at the university who specializes in extinction events, say that global warming, triggered by massive volcanic activity and a lower sea level, was the biggest contributor to the Great Dying. Ward and other researchers, in another report published by Science in January, reported that fossil evidence collected in South Africa showed that the die-off was gradual over about 10 million years, then accelerated for 5 million more years. Oxygen levels -- and ecological diversity -- didn't fully recover for 100 million more years.

EDIT

Sediment analysis from early in the period shows oxygen saturation of the air at sea level was about 30 percent. By the end of the Permian period, the air was only about 16 percent oxygen, falling to a low of 12 percent -- the ratio now found atop some of the world's highest mountains -- about 10 million years into the Triassic. It seems that thinner air not only starved many animals and plants into extinction, it forced survivors into low-lying niches where they could breathe more easily. And those survivors not only could live with less oxygen, but also adapted to live in new terrain."

EDIT

http://seattlepi.nwsource.com/national/220394_greatdying16.html

[fasttense]

1. I've heard this theory before but in association with the smaller sized

Mammals of modern times. Very interesting to have found some actual proof for the oxygen theory. You know, some other aspects of evolution start to fit into place once you consider this.