SOME SPEICES HAVE BEEN DISAPPEARING . OTHERS WILL HABEEN WIPED OUT FOR GOOD BY GLOBAL CLIMATE
Mass Lizard Extinctions Looming; Global
Warming Blamed
One in five lizard
species predicted to vanish by 2080.
Published May 13,
2010
Lounging in the shade may sound soothing, but it could
be the death of many lizards if global warmingcontinues at current rates.
As temperatures inch upward, the
reptiles rest more and hunt less. As a result, 20 percent of lizard species
could go extinct by
No matter what we do to fight
global warming, at least 6 percent of lizard species will go extinct by then,
due to the greenhouse gases already in the atmosphere, the study says.
"We've committed ourselves
to 6 percent," said lead study author Barry Sinervo, a herpetologist at
the
And those percentages are
conservative, Sinervo said. For example, the study doesn't account for threats
such as competition between lizard species or the effects of global
warming-caused water shortages.
David Wake, who wasn't involved
in the new study, agreed that the findings are far from exaggerated. "It's
frightening," the
Global Warming to Starve Lizards
to Death?
The study team calculated
extinction risks for more than a thousand lizard species around the globe for
their study, to be published in the journal Sciencetomorrow.
The research was prompted by the
discovery that 50 percent or more of the local populations of certain species
had gone extinct in parts of
The team suspected global warming
was to blame, because the lizard-population crashes had generally occurred in
areas with the warmest springs—when lizards reproduce.
To test their global warming
hypothesis, the researchers created pseudo-lizards out of temperature gauges
and painted pipe. The researchers placed the devices at four sites in
Unlike mammals, lizards and other reptiles are cold-blooded, meaning they can't regulate their body temperatures
and so must seek shade when it gets too hot.
Where the blue spiny lizards are
still living, the spring temperatures were such that the lizards should have
only had to seek shelter from the sun for about four hours a day, the gauges
suggested.
But where the lizard had already
gone locally extinct, the spring temperature was so high it would have dictated
that the lizards spend most of the day hiding from the sun rather than hunting.
That much downtime means the
lizards will "pretty much be starving to death" and not laying eggs,
said Sinervo, whose study was partly funded by the National Geographic
Society's Committee for Research
and Exploration. (The National Geographic Society owns National
Geographic News.)
Lizard Extinctions Predicted
Next the team set out to
determine whether their findings held up at a global scale.
The scientists created a computer
model incorporating temperature data back to 1975, global warming prediction
data from the Intergovernmental Panel on Climate Change, and the maximum
temperatures different lizard species can withstand.
The model calculated the number
of hours each day that a lizard species should be incapacitated due to heat as
well as the hottest temperatures for different parts of the Earth in the past,
present, and future.
The model accurately predicted
specific locations where lizard species are known to have gone locally extinct
in North and South America, Europe, Africa, and
Certain Lizards Especially at
Risk
Global warming will hit lizards
in the Amazon and
"The number of local
extinctions we're seeing [in the Amazon], based on the model, is through the
roof," Sinervo said. "It's
60, 70, 80 percent even in some places."
And because Amazon lizards are
relatively poorly documented, "we don't even know all the different
species that we're going to lose," he added.
Another especially vulnerable
category is lizards that give birth to live young, including the blue spiny
lizard, which Sinervo studied in
Live-birth lizards "had to
evolve slightly lower body temperatures, because if it's too high, the babies
might die or develop developmental abnormalities," Sinervo explained.
Bigger Than Lizards
The new study underscores that
global warming isn't just a lizard problem, saidWarren Porter, a zoologist at the
University of Wisconsin-Madison.
"Many people might consider
changes to lizard populations of small importance," said Porter, who
wasn't involved in the study.
But, he pointed out,
"another major group of cold-blooded animals, the pollinating insects, are
also subject to the same constraints that lizards are."
The loss of pollinators, he
added, would be devastating to the human food supply.
Porter also noted that the team
looked mainly at small lizards. The extinction risks for larger lizards, such
as the Komodo dragon, could be much
higher, he said.
"Larger species of animals
are even more vulnerable to heat stress," Porter said, "because they
have fewer places to find shade and water on a landscape that is drying
out."
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