Paris - Mass extinctions that wiped out up to 90 percent of Earth's flora and fauna were driven in large part by shifting ocean levels, according to a study published in Nature.

Understanding what made many of the planet's living organism rapidly die out at least five times over the last half billion years remains one of the great challenges in paleontology and biology.

Some theories point an accusing figure at the cooling effect of massive dust shrouds thrown into the atmosphere by volcanoes and asteroids crashing into Earth, or the warming caused by rising levels of carbon dioxide.

Other scientists highlight the role of disease and competition among species for limited resources.

But the new study suggests that it was the ebb and flow of sea levels and sediment over geologic time, rather than cataclysmic events, that doomed tens of thousands of species to extinction.

"The expansions and contractions of those environments have pretty profound effects on life on Earth," said Shanan Peters, a geologist at the University of Wisconsin-Madison and sole author of the study.

Since the beginning of life on Earth, some 3,5 billion years ago, there have been more than 20 mass extinction events, many involving single-cell organisms, say scientists.

And during the last 540 million years that have been five well-documented periods of mass die offs, mainly of marine plants and animals.

With the exception of a colossal asteroid impact some 65 million years ago that left a 180-kilometre wide crater in Mexico, the cause for the other mass extinctions is sharply contested.

Even that one coincided with an abrupt retraction of oceans then covering much of North America and Europe that could have played a major role in the disappearance of dinosaurs, Peters said.

"I looked at rates of extinction in the fossil record over the last 500 million years," Peters said.

"And then I compared them to the environmental changes - mostly explained by shifts in sea level - that are encoded in the sedimentary rocks."

What Peters found was a very strong match, showing that the sometimes dramatic rise and fall of oceans levels correlated more consistently with mass extinctions that any other factor.

Sea levels rose more than 80 meters at the end of the last major glacial period some 15,000 years ago, he said.

Climate and the movement of tectonic plates are the key factors that influence the degree to which the continents would flood.

"Most people think of sea level changes in terms of depth of meters or feet. I am looking at a different measure - the environmental consequences of sea level change, the impact on habitats," he explained.
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A 80m rise in sea level would flood out 3/4s of the earth there wouldnt be any place to run to. Be a good idea to invest in some high place real estate owls.

I have always said that she (our planet) is a living organism, just like other organisms, and we are responsible for her care. Instead of caring for her, we have become parasites, and like fleas on a dogs back.

All the beautiful habitat is being taken up by industry. There are wars, violence, hunger, famine, drought etc, etc. We shouldn't be surprised that she is so ill, as we are the germs who made her that way. I am sorry to say that, but to see so much beauty being destroyed for the sake of lucrative money for the big bugs, I do feel like I am a parasite, because I am forced to buy into what they are selling to survive,although what they produce is of no benefit to our planet.

i have a question, anyone know the answer, if sea levels rise, will Panama by Costa Rico be submerged? and if it does would that alter the gulf stream, so instead of the gulf stream coming from the gulf of Mexico across the Atlantic to northern Europe it will just go straight over where Panama once was and so cut off the gulf stream to Europe?

I doubt 80m over panama would be sufficient to alter the gulf stream, after all the gulf stream is at a very very deep level in the ocean.

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