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Tropical wildlife 'will struggle'
06/05/2008 13:41 - (SA)
Washington - Polar bears may have it
relatively easy. It's the tropical creatures that could really
struggle if the climate warms even a few degrees in places that
are already hot, scientists reported on Monday.
That doesn't mean polar bears and other wildlife in the
polar regions won't feel the impact of climate change. They
probably will, because that is where the warming is expected to
be most extreme, as much as 10 degrees C by the
end of this century.
But there are far fewer species living in the Arctic and
Antarctic and in the temperate zones than in the tropics, said
Curtis Deutsch of the University of California at Los Angeles.
Many of these tropical creatures are living at the edge of
their temperature tolerance already. Even the slight tropical
warming predicted by 2100 - 3 degrees C - could push them to the brink, Deutsch said.
In research published in Proceedings of the National
Academy of Sciences, Deutsch and his co-authors investigated
what could happen to cold-blooded animals in the tropics over
the next 100 years if the predictions of greenhouse warming
hold true.
They chose cold-blooded creatures - mostly insects but
also frogs, lizards and turtles - because warm-blooded animals
have other ways of regulating their body temperatures, such as
growing a thick coat of fur to guard against cold and shedding
when it gets warm.
Tropical population crash
Cold-blooded organisms can either seek shade when it's hot
or sun themselves when it's cool, but otherwise they are
limited, Deutsch said.
"If nothing else happens, if they were just subjected to
warming temperatures and everything else in their environment
stayed the same, we would predict that their populations would
crash more quickly," he said, meaning that many would die and
their reproductive rates would plummet.
These animals do have other options besides a species
crash, he said: they can migrate uphill or toward the poles to
seek cooler climates, or they can evolve, and those with the
best tolerance for heat would survive.
If they migrate or mutate, this could have an important
impacts on humans living outside the tropics, Deutsch said,
since insects particularly play key roles in pollinating
agricultural crops and breaking down organic matter into
essential nutrients for other creatures.
"The direct effects of climate change on the organisms we
studied appear to depend a lot more on the organisms'
flexibility than on the amount of warming predicted for where
they live," said co-author Joshua Tewksbury of the University
of Washington.
"The tropical species in our data were mostly thermal
specialists, meaning that their current climate is nearly ideal
and any temperature increases will spell trouble for them,"
Tewksbury said in a statement.
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