Wednesday, October 24, 2007

Climate threat to biodiversity

Earth viewed from space
The last mass extinction wiped out one-fifth of life on Earth
Global temperatures predicted for the coming centuries
could trigger a mass extinction, UK scientists have warned.
The temperatures are within the range of greenhouse phases early in the Earth's history when up to 95% of plants and animals died out, they say.

Experts examined the link between climate and diversity over 520 million years, almost the entire fossil record. They found that global diversity is high during cool (icehouse) periods and low during warm (greenhouse) phases.

"Our results provide the first clear evidence that global climate may explain substantial variation in the fossil record in a simple and consistent manner," said Dr Peter Mayhew, one of the paper's co-authors.

"If our results hold for current warming, the magnitude of which is comparable with the long-term fluctuations in the Earth's climate, they suggest that extinctions will increase." The study by researchers from the Universites of York and Leeds, published in Proceedings of the Royal Society B, compared data sets on marine and land diversity against estimates of sea surface temperatures for the same period.

They found that four out of the five mass extinction events on Earth are associated with greenhouse phases (warmer, wetter conditions) rather than icehouse phases (cold, dry conditions). These include Earth's worst mass extinction 251 million years ago when some 95% of all species were lost. "We could - at worst - be experiencing that in the next century - only a few human generations down the line," Dr Mayhew told BBC News. "We need to know why temperatures and extinctions are linked in this way."

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