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Earth's Biggest Doomsday Event: Death By CO2

By Sarah Simpson

22 November, 2011
Discovery News

Earth's biggest mass extinction rolled over the planet like hell on wheels.

For the first time, paleontologists have pinned down exactly when and how fast the granddaddy of all mass extinctions took place, and their findings leave the finger of blame pointing squarely at a colossal and long-lived injection of carbon dioxide into the atmosphere. Sound familiar?

That ancient carbon dioxide came not from cars and factories, of course, but from massive volcanic eruptions, brush fires, and possibly even the combustion of coal seams ignited by hot lava.

The greenhouse gas increase, in turn, raised global temperatures and turned the oceans acidic and oxygen-deprived, among other trying consequences. Needless to say, life did not fare well. An oft-quoted estimate suggests that 90 percent of all marine life went extinct.

The new study, published this week in Science, puts that stark statistic into a fresh, rigorous perspective: At the peak of the crisis, right around 252.28 million years ago, and for at least 20,000 years, the planet was losing 3 percent of species every millennium.

“If we had continued losing at that rate for another 20,000 years, we wouldn’t be here to talk about it,” paleontologist Charles Henderson of the University of Calgary in Alberta, Canada, told Discovery News.

Henderson is among an international team of scientists, led by Shu-zhong Shen of the Nanjing Institute of Geology and Palaeontology in China, who compiled an intensive calibration of this most extreme of all biological crises, known to scientists as the end-Permian extinction, which occurred millions of years before the cosmic collisions that may have paved the way for dinosaurs.

Asteroid Fingered for Dino Era Boom—Not Just Bust

For years the standard summary for the end-Permian extinction has been that 90 percent of life on earth was wiped out. But that number was just a statistical extrapolation. No study had ever considered more than a handful of samples at a time, Henderson explains.

This new study took into account the changes and disappearances of a total of 1,485 species, including shellfish, eel-like creatures called conodonts (see conondont teeth in the photo below) and various animals living on land. The team also took advantage of great improvements of dating techniques to determine absolute ages of the fossils.

A major conclusion of the study is that terrestrial and marine extinctions happened at the same time, a conclusion that has been controversial until recently.

The Annihilation Was Not Just in the Seas

Curiously, though, this new-and-improved analysis of the end-Permian extinction does not corroborate the oft-quoted 90 percent. “If you look at our species richness curve, it’s really only about a 60 percent extinction,” Henderson says.

No need to rewrite headlines, though. The end-Permian extinction is still the worse the planet has ever experienced—so far.

Copyright © 2011 Discovery Communications, LLC




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