Study:
Heat prolonged ancient extinctions
European
scientists say they've discovered why a "dead zone"
following the worst extinction of all time lasted so long -- it was
simply too hot to survive.
19
October, 2012
Researchers
have studied what happened after a mass extinction around
250 million years ago in the pre-dinosaur era wiped out nearly all
the world's species.
Such
mass extinctions are usually followed by a "dead zone" --
during which new species are not seen -- lasting some tens of
thousands of years, but the event of 250 millions years ago was
followed by a dead zone lasting a puzzling 5 million years, they
said.
A
study led by the University of Leeds with colleagues in Germany and
China shows the cause of this lengthy devastation was a temperature
rise to lethal levels in the tropics: around 120 to 140 degrees
Fahrenheit on land at 104 degrees at the sea surface.
"Global warming has
long been linked to the end-Permian mass extinction, but this study
is the first to show extreme temperatures kept life from re-starting
in Equatorial latitudes for millions of years," said Yadong Sun,
who is completing his doctorate at Leeds.
Water
temperatures near the ocean's surface of 104 degrees would be a
near-lethal value at which marine life dies and photosynthesis stops,
the researchers said.
The
dead zone would have been a strange world, the researchers said, with
no forests, only shrubs and ferns, no fish or marine reptiles in the
tropics, and virtually no land animals because their high metabolic
rate made it impossible to deal with the extreme temperatures.
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