London, Oct 24 : The five periods in the history of Earth with the
highest levels of mass extinction were all linked to climate change, or
more specifically, a rise in temperature, a recent study of fossil
evidence has shown.

Scientists led by Peter Mayhew from the University of York found
that higher temperatures associated with four of the mass extinctions
were at about the same level forecast by climatologists for the next
100 to 200 years.

Of the five mass extinctions, the most recent was the
Cretaceous-Tertiary, 65 million years ago, when temperatures were about
4C higher than today, while the most devastating one was at the end of
the Permian period, 251 million years ago.

An estimated 95 per cent of marine species and 70 per cent of land
species were killed off. Scientists estimate the temperatures were
about 6C higher than today.

Mayhew said, according to estimates of the effect of global warming
on animals and plants alive today, between 20 and 30 per cent would die
out if temperatures rose by 1.5 to 2.5C.

Climatologists believe such a rise is likely to take place before
the middle of the century, and that rise with temperatures will also
affect extinction rates.

“Our results provide the first clear evidence that global climate
may explain substantial variation in the fossil record in a simple and
consistent manner. If our results hold for current warming - the
magnitude of which is comparable with the long-term fluctuations in
Earth climate – they suggest that extinctions will increase,” said
Mayhew.

Tim Benton, of the University of Leeds, said: “When you look at the
short-term, ten-million-year fluctuations we’ve shown there is quite a
strong correlation between when things warm up and an increase in
extinction rates.”

During each of the mass extinction events in the past 525 million
years, at least half of the animal and plant species were wiped out.

Only the first global mass extinction was linked to lower
temperatures, when vast numbers of marine creatures died as glaciers
formed and sea levels dropped.

The study appears in the journal Proceedings of the Royal Society, reports Times Online. (ANI)