14 May 2010 Last updated at 05:22 ET

Climate change link to lizard extinction

By Victoria Gill Science reporter, BBC News

Lizards are more vulnerable to climate change than previously thought

Climate change could wipe out 20% of the world's lizard species by 2080, according to a global-scale study.

An international team of scientists also found that rising temperatures had already driven 12% of Mexico's lizard populations to extinction.

Based on this discovery, the team was able to make global predictions using an "extinction model".

They conclude, in an article in Science journal, that "lizards have already crossed a threshold for extinctions".

Although the grim prediction for 2080 could change if humans are able to slow global climate warming, the scientists say that a sharp decline in their numbers had already begun and would continue for decades.

The large research team was led by Barry Sinervo from the Department of Ecology and Evolutionary Biology at the University of California in Santa Cruz, US.

He said: "We are actually seeing lowland species moving upward in elevation, slowly driving upland species extinct, and if the upland species can't evolve fast enough then they're going to continue to go extinct."

Lizards, the researchers say, are far more susceptible to climate-warming extinction than previously thought. Many species live right at the edge of their "thermal limits".

Rising temperatures, they explained, leave lizards unable to spend sufficient time foraging for food, as they have to rest and regulate their body temperature.

A group of biologists including Dr Raymond Huey from the University of Washington in Seattle wrote an accompanying article in Science explaining the significance of the research.

Dr Huey and his colleagues said the predictions were "disturbing".

But they pointed out that follow-up surveys were needed to confirm the results.

"Lizard populations rise and fall over time and failure to detect individuals during short surveys may indicate transient rarity rather than extinction," they wrote.

But their article went on to say that the research team had shown that "climate-forced extinctions were not only in the future" but were "happening now".