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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 Ringold on 9/2/2007 1:59:02 PM , Rating: 2
I see population and deforestation as far more serious threats to producing global warming than industry.

It'd be nice if the environmentalists would update their litany of complaints at least once every couple decades.

Yes, in the 80s it might've looked like runaway population growth would swamp the world.

In the mean time, however, Europe has just not stopping growing but gone in to full retreat. Japan has lost a sizeable portion of its population. The United States grows only due to immigration and will likely join Europe in having below replacement level birth rates. Countries in Eastern Asia show the same pattern.

At the rate India and China are joining the developed world they, too, will stop growing eventually. Then it'll be Africa's turn. The last time I saw the matter discussed the top estimate for human population was a peak around 9 billion, followed by decline.

The era of exponential population growth is over and it's gone forever. While environmentalists cheer, economists now have less than half a century to figure out how to push politicians in the proper directions to avoid fiscal catastrophe, but that's a different issue. It's time to remove population growth from the litany of standard-issue complaints and boogey-men.

RE: Hmm
By Ringold on 9/2/2007 2:01:49 PM , Rating: 2
Oh, and another point about East Asia: I can't recall which country was offering it, but one of them offered a cruise to any married couple as a way to encourage couples to go off and have sex -- hopefully resulting in a child. These aren't exactly rich nations offering these expensive incentives. The times have changed.

RE: Hmm
By masher2 on 9/2/2007 2:06:17 PM , Rating: 2
Sounds like Russia. They've recently been offering larger and larger incentives to increase their birthrate. The birthrate is so low today that population is actually declining.

This is true for many other European nations as well. The only reasons their populations aren't shrinking is immigration from third world nations makes up the losses from their declining birthrate.

RE: Hmm
By Ringold on 9/2/2007 2:52:44 PM , Rating: 2
A few things I quickly came across to illustrate the situation:

Italy, especially, is only being held together by a flood of immigrants.

Japan I just plain remembered wrong; it's population hasn't lost any yet, but is near a peak, projected to drop (rapidly) from the current 128m to 95m by 2050, and 50-70m by 2100.

All of which throws a wrench in to the gears of the current welfare systems that rely on wealth transfers from the young to the old. In the Japanese example, the number of workers in their 20s is current 16m, but within 10 years that'll be a mere 3m -- and 81% decline. Schools and unverisities have all ready been merged and closed, making the impending population decline highly visible on the younger end.

I think it might've been Singapore that I recall hearing that from, but the internet is showing two things:
1) It's age -- it was from around 5-10 years ago, and thus is hard to find now.
2) Words to draw traffic for advertisements -- especially 'cruise vacation'.

At any rate, I'd be much more worried about depopulation rather than overpopulation.

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