From geckos and iguanas to Gila monsters and Komodo dragons they are among the most common reptiles on Earth – found on every continent except Antarctica.
But a study of lizard populations worldwide has found an alarming link between extinctions and climate change.
If current trends continue 20 per cent of all species could disappear by 2080, according to the findings published in Science.
The researchers developed a model of risk using lizard numbers and rising temperatures which accurately predicted specific locations in North and South America, Europe, Africa, and Australia where local populations have already become extinct.
The drop in the lizard population could cause an explosion in the numbers of insect they normally feed on as well as devastating creatures higher up the food chain which rely on them for food.
Evolutionary biologist Professor Barry Sinervo said: “Our research shows the ongoing extinctions of lizards are directly due to climate warming from 1975 to the present.”
He added: “We did a lot of work on the ground to validate the model and show the extinctions are the result of climate change.
“None of these are due to habitat loss. These sites are not disturbed in any way and most of them are in national parks or other protected areas.”
He said as local populations continue to disappear species extinctions will follow.
“Most of these species currently registering local extinctions will be completely extinct by 2080, unless we change and limit the carbon dioxide production that is driving global warming,” said Prof Sinervo.
The disappearance of lizards is likely to have repercussions up and down the food chain as they are important prey for many birds, snakes, and other animals and they are important predators of insects.
Prof Sinervo, of California University, said: “We could see other species collapse on the upper end of the food chain – and a release on insect populations.”
Biologists have also documented dramatic declines and extinctions of amphibian populations around the world leading to estimates that one-third of species are at risk of extinction.
But Prof Sinervo said these are attributed mostly to the spread of a deadly fungal disease – with a possible indirect link to environmental factors such as global warming.
He began studying extinctions after he and colleague Dr Donald Miles, of Ohio University, noticed a disturbing trend in recent years after he went looking for populations other researchers had studied in the 1980s and 90s – only to find many had disappeared.
In Mexico his team re-surveyed 48 species of spiny lizards at 200 sites where they had been studied between 1975 and 1995 and discovered 12 per cent had disappeared.
To investigate the link with temperature they visited a site on the Yucatan Peninsula where the blue spiny lizard was declining.
After building a device to mimic the body temperature of a lizard basking in the sun and record the temperatures on a microchip they set them in sun-exposed sites for four months in locations with and without surviving populations of blue spiny lizards.
Prof Sinervo said: “The results were clear. These lizards need to bask in the sun to warm up but if it gets too hot they have to retreat into the shade and then they can’t hunt for food.
“At the extinct sites in the Yucatan, we found that the hours per day they could be out foraging had collapsed. They would barely have been able to emerge to bask before having to retreat.”
Prof Sinervo used these findings to develop a model of extinction risk based on maximum air temperatures, the physiologically active body temperature of each species and the hours in which a lizard’s activity would be restricted by temperature.
The researchers found climate change is occurring too rapidly for lizards to compensate with physiological adaptations to higher body temperatures.
Prof Sinervo said: “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.
“We’re predicting 40 per cent of local populations will go extinct – and that will translate into roughly 20 per cent of species going extinct by 2080. If we begin reducing CO2 output now, we might be able to hold that to 6% of all species.
“Several species in Mexico face an eminent risk of extinction. But there are many other areas in which biodiversity is more poorly known and we probably have already lost species to climate warming in these areas.”
“There are critical hot spots such as in Mexico and the equatorial tropics around the world. In Mexico, the number of species lost by 2080 could be as high as 60%.
“The reason has to do with the rate of climate change in these areas and also because there are a lot of lizard species on isolated mountain ranges.
“These species will likely be going extinct at a rapid rate because they are adapted to cool environments and have a low body temperature. As climate warming really kicks in many of these areas of biodiversity will be devastated.
“We point out in our paper that all of the tropical areas are experiencing very high rates of local extinction.
“However, even in Europe the common lizard is going extinct at the southern margin of its range where 30% of the populations are now extinct.
“This is because it has evolved a relatively low body temperature and it has been getting hotter in southern Europe.
“In our article we also point out that lowland species have likely driven a number of higher elevation species extinct in Mexico.
“Thus, as widespread species expand because cool habitat is getting warmer, they will accelerate the decline of high elevation endemic species.
“This is a very severe effect in addition to the thermal extinctions per se – in other words it is now just too hot for the cool adapted species.
“I have a son who like me loves lizards – and dinosaurs. What an incredibly sad fate to have such splendid biodiversity lost because of our own inability to limit CO2 emissions. I personally am doing everything I can to lower my CO2 footprint.”
Many of the extinctions projected for 2080 could be avoided if global efforts to reduce emissions are successful, but the scenario for 2050 is probably inevitable, said Prof Sinervo.
He said: “The extinctions are happening really fast. I’m watching new populations go extinct every year.”
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