The world is warming too quickly for lizards to adapt, and 20 per cent of species could be extinct by 2080, a new study shows.
In Australia, lizards living in the central desert areas and alpine districts are most at risk if current climate change trends continue.
Even if greenhouse gas emissions are reduced, a 6 per cent decline in the world's lizard populations by 2050 is almost unavoidable, an international team of scientists has concluded.
David Chapple, of Monash University, said the cold-blooded reptiles basked in the sun to warm up, but had to seek shade when they get too hot.
"If it is too warm for too long, and they spend too long under the shelter, they can't be out their looking for mates and finding food."
The researchers, led by Barry Sinervo of the University of California, surveyed 48 species of lizards at 200 sites in Mexico and found that 12 per cent of local populations had become extinct since 1975.
They then built devices to mimic the body temperature of lizards lying in the sun and placed some at at sites where the reptiles had survived and others at places where they had disappeared.
Professor Sinervo said the results clearly showed that lizards at the extinction sites would have had very little time to forage. "They would barely have been able to emerge to bask before having to retreat."
His team then developed a model of extinction risk due to temperature rises for different species and found this accurately predicted places where local die-offs had occurred on five continents, including Australia.
"We thought we'd see evolution occurring in response to climate change, but instead we're seeing extinctions. Beyond a certain point, the lizards can't adapt," said Professor Sinervo, whose team's results are published in the journal Science.
He said they were confident global warming was the culprit, rather than habitat loss. "These sites are not disturbed in any way, and most of them are in national parks or other protected areas."
Dr Chapple, a member of the team, said the model matched population changes in the Great Desert skink and Slater's skink, which are both becoming extinct at sites around Uluru-Kata Tjuta National Park.
He said the study also found that lizards which have live offspring, which is common among Australian alpine species, have almost double the risk of extinction.
Lizards are important food for birds and snakes and they eat insects.