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A new study by paleoecologist Margaret Fraiser at the University of Wisconsin, Milwaukee, offers an interesting new theory behind the cause of the Earth's largest extinction: copious carbon-dioxide

When most people hear the phrase "the earth's largest extinction", they think dinosaurs. 

Margaret Frasier knows better.  As a paleoecologist, she knows that the Earth's largest mass extinction of life occurred at the end of the Permian Period at the end of the Paleozoic Era; 252 million years before the first T-Rex ever walked the earth.  The extinction destroyed the large land amphibians' dominance of the land, and paved the way for dinosaurs to emerge as the dominant land species. 

University of Wisconsin-Milwaukee professor Margaret Frasier is studying this extinction avidly, looking for possible details to further our understandings of what might have caused this landmark event.

Her recent conclusions, published in an Elsevier journal [1] [2] (PDF) and detailed in a recent press release titled "When Bivalves Ruled the World," describe an Earth with run-away carbon dioxide levels.  She concludes that the Permian-Triassic mass-extinction was caused by toxic, oxygen-less oceans created by too much atmospheric carbon dioxide (CO2). 

The Permian-Triassic extinction event wiped out nearly 70 percent of species on land and 95 percent of sea species.

“Estimates of the CO2 in the atmosphere then were between six and 10 times greater than they are today,” Frasier states.  The largest continuous volcanic eruption on Earth – known as the “Siberian Traps” – had been pumping out CO2 for about a million years prior to the Permian-Triassic mass extinction.

Her hypothesis is that high CO2 levels at the close of the Permian Period caused global warming, greatly increasing global temperatures.  With no cold water at the poles, ocean circulation slowed, and the oceans were unable to mix with the little oxygen left in the air.

She cites a variety of evidence of high CO2 and low ocean oxygen levels in this fossil record.  One piece of evidence is darkened rock from underwater fossil strata of the time.  Darkening in ocean rock of this nature indicates a low amount of oxygen at the time of formation.

Frasier also collected evidence to support her theory in the form of bivalve fossils.  The only survivors of the extinction were bivalve mollusks and gastropods -- snails.  Only shallow water, tiny, small-shelled varieties with high metabolisms and a flat shape, which allowed them to spread out while feeding to extract more oxygen, survived.  Deeper water varieties, where there was less oxygen, and larger shelled varieties, which needed more oxygen, became extinct, disappearing from the fossil record.

A final piece of evidence cited is the disappearance of the coral reefs.  Coral reefs die if their environment lacks sufficient oxygen.

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RE: Hmm
By masher2 on 9/1/2007 8:26:04 PM , Rating: 2
> "I didn't link it to modern day global warming"

So your first post to the thread, where you claimed we might be at levels similar to the Permian within the century was a slip of the pen? I saw that as fear-mongering.

If I misunderstood, and you're clearly saying that humans can in no way, shape, or form, trigger another Permian-style event-- then I retract that claim.

Glad to see you're not buying into the hype!

RE: Hmm
By JasonMick on 9/1/2007 9:46:08 PM , Rating: 2
The very first poster compared it to modern levels. I would have been happy to relegate this as a study on what might have happened in the past, without current context, if people had not asked, or began to debate about it.

And I do think humans, between population increases, livestock cultivation, and deforestation to make room for the former, can alter the carbon balance to be on the high side of what it once was in prehistory. Obviously the reaction will be limited by the amount of carbon, we can excrete into the air as CO2, once overpopulation has forced sufficient deforestation to give a net debt of CO2. From there on out it is just a matter of time to reach these levels. Maybe not in our lifetime. But certainly this could be happening in our grandchildren's lifetimes.

You try to distract people by mentioning industrial CO2 emissions, but you never explicitly refuse to refute the dangers of overpopulation and deforestation to the CO2 balance. I think thats because you understand that with time this could become a real threat.

I see a clear difference between trying to discuss a possible major danger to our habitat and "fearmongering" as you put it. I do apologize for putting the lower bound so soon. That was ill-thought out. You probably regret some of the hastier statements you have posted, as well, but I would not label you a "conflictmongering" person because of them. No one is infallible. The important thing, is that the discussion of this problem has merit, and you must as well, since you are sitting here typing verbose arguments against my statements.

RE: Hmm
By masher2 on 9/1/2007 10:30:02 PM , Rating: 2
> " but you never explicitly refuse to refute the dangers of overpopulation and deforestation to the CO2 balance"

Your views are 10 years out of date of modern climatology. Forests are not the large carbon sinks we once thought they were. The ocean itself, river transport, silicate/carbonate weathering, etc...these are the primary global carbon sinks.

There's more and more evidence accumulating that forest planting may actually decrease overall carbon fixation. Here's a link to get you started:

> "But certainly this could be happening in our grandchildren's lifetimes"

By even the most pessimistic of assumptions, we won't reach Permian-level CO2 levels for the next 500 years. The math here is indisputable. No matter what "tipping point" mechanisms one postulates, the carbon still has to come from somewhere. Even with massively disrupted fixation levels, there's still a hard limit on how much CO2 is generated annually.

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