Species flee warming faster than previously thought
27 August BBC
Animals and plants are shifting their natural home ranges towards the
cooler poles three times faster than scientists previously thought.
In the largest study of its kind to date, researchers looked at the
effects of temperature on over 2,000 species. They report in the journal
Science that species experiencing the greatest warming have moved
furthest.
The results helped to "cement" the link between climate change and
shifts in species' global ranges, said the team.
Scientists have consistently told us that as the climate warms we
should expect animals to head polewards in search of cooler
temperatures. Animals like the British comma butterfly, for example, has
moved 220km northward from central England to southern Scotland in the
last two decades.
An uphill struggle There is also evidence that more species seem to
be moving up mountains than down, explained conservation biologist Chris
Thomas from the University of York, UK, who led the study.
But studies had stopped short of showing that rising temperatures are
responsible for these shifts in range, he added.
Now he and his team have made this link.
Analysing the range shifts of more than 2,000 species - ranging from
butterflies to birds, algae to mammals - across Europe, North and South
America and Malaysia over the last four decades, they show that
organisms that experience the greatest change in temperatures move the
fastest.
The team found that on average organisms are shifting their home
ranges at a rate of 17km per decade away from the equator; three times
the speed previously thought. Organisms also moved uphill by about 1m a
year.
"Seeing that species are able to keep up with the warming is a very
positive finding," said biologist Terry Root from Stanford University in
California, US.
She added that it seemed that species were able to seek out cooler
habitats as long as there was not an obstacle in their way, like a
highway.
Out of range But what about the animals that already live at the
poles, or at the top of mountains?
"They die," said Dr Thomas. Take the polar bear, it does most of its
hunting off the ice, and that ice is melting - this July was the lowest
ever recorded Arctic ice cover - it has nowhere to go.
However, the loss of this one bear species, although eminently
emblematic, seems insignificant when compared to the number of species
that are threatened at the top of tropical mountains.
On Mount Kinabalu in Borneo, Dr Thomas' graduate student, I-Ching
Chen, has been following the movement of Geometrid moths uphill as
temperatures increase. Their natural ranges have shifted by 59m in 42
years.
These moths "don't have options; they are being forced up, and at
some point they will run out of land," reflected Dr Thomas.
The British scientist said that it was really too early to start
generalising about the characteristics of the species that had shifted
their distribution to stay within their optimal temperature range.
"But we know that the species which have expanded the most and
fastest are the species that are not particularly fussy about where they
live," he told BBC News.
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