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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 8:21:15 PM , Rating: 2
> "That statement does not make sense. Increasing ocean circulation would increase ocean O2."

Its not my theory, so don't ask me to support it. But it's supported by quite a few climatologists. Here's a link:

> "would actually cause a large decrease in atmospheric O2 over time, as plants could not keep up with animal demand."

Come Jason, do the math. CO2 levels are in the range of 300ppm. O2 levels are in the range of 210,000 ppm-- a thousand times higher. Historically, atmospheric oxygen has never varied substantially, not even when CO2 levels were 20X higher than current levels. There's just too darn oxygen in the air to be affected. The idea that any increase in CO2 levels could ever lower O2 enough to harm mankind is just plain silly.

> "I see population and deforestation as far more serious threats to producing global warming than industry."

Then you'll be pleased to know that the US actually has a higher level of forestation today than it did in the year 1900. Today, more of the US is covered in trees than was 100 years ago.

RE: Hmm
By JasonMick on 9/1/2007 9:32:53 PM , Rating: 2
Then you'll be pleased to know that the US actually has a higher level of forestation today than it did in the year 1900. Today, more of the US is covered in trees than was 100 years ago.

I am thrilled by that! I am happy to see those lazy environmentalist finally accomplished something!

However, the biggest forests, the Amazon, Congo, and Malaysian rainforest are being slashed and burned. While some will tell you that rainforests produce O2/consume CO2, this is only true respectively. Rainforests are a large, balanced systems. They do not have a net production of O2. However, if you replace these large areas with endless large cow plantations and towns, you are replacing a system in balance, with a CO2 producing system with virtually no CO2 fixing component. True they could plant crops, but the soil would fail after a few years, which is why they move on to slashing more forest. Meanwhile the human population remains behind.

Historically, atmospheric oxygen has never varied substantially

Has a single species ever systematically gone about clearing the earth of large portions of its largest biomass contributors, on a global scale?? I think we are dealing with a situation that has no historical precedent when it comes to man and its relationship with nature. Maybe there is not enough carbon to affect the O2 levels. The reaction would either be limited by carbon or o2, and I am guessing carbon would limit it. Still, over time, the CO2 levels would increase to levels not seen since the Silurian.

Ah, but I grow weary of this debate, as we could go back and forth on points like this all day, you know.

RE: Hmm
By masher2 on 9/1/2007 10:09:02 PM , Rating: 2
> "I am happy to see those lazy environmentalist finally accomplished something!"

Environmentalists had nothing to do with it. Increased forestation in the US is due to reclamation of previously cultivated farmland which, in turn, is due to the massive increases in agricultural output per acre since 1900.

In other words, we have more forests in the US today because we use fertilizers, pesticides, farm machinery, pesticides, and high-yield crops. We grow far more food on far less land. An achievement made possible only through use of fossil fuels.

> "Maybe there is not enough carbon to affect the O2 levels."

You're right, there isn't. O2 isn't CO2. There's far too much oxygen in the atmosphere to ever worry about reduced levels. Your previous point was incorrect, plain and simple.

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