Lizards May Face Mass Extinction

Lizard species worldwide may already have declined past the point of no return. The reason? Rising temperatures.

By 2080, researchers estimate, as much as 40 percent of lizard species worldwide could be extinct. The problem is that temperatures in many regions where lizards live have changed too rapidly for the animals to keep pace.

Barry Sinervo from the Department of Ecology and Evolutionary Biology at the University of California in Santa Cruz, along with colleagues from across the globe reached that conclusion by taking current data on Mexican lizards and running it against extinction modeling and projected risks worldwide.

They also estimate that 4 percent of local species have already gone extinct worldwide. That number could jump to 20 percent by 2080, they say, if carbon dioxide levels aren't lowered to reduce warming.

Their work will appear in Thursday's edition of the journal Science.

The team looked at 48 species of Sceloporus lizards at 200 sites around Mexico. The sites were first sampled from 1975 to 1995. By 2009, researchers couldn't find lizards at 12 percent of those sites.

Lizards that bear live young are especially at risk of extinction, the researchers point out, compared to those that lay eggs.

"Live-bearers have evolved lower body temperatures that heighten extinction risk," Sinervo said in a statement. "We are literally watching these species disappear before our eyes."

Although current evidence shows climate change is affecting the habitat ranges of many species, little research has been done on extinctions at either local or global scales. There's still a lot of uncertainty about how much climate change will affect species, researchers say.

They advocate changing the way scientists make those predictions, saying forecasts should be global in scale, taking into account macro and micro climate variables as well as evolutionary rates.

Many Mexican lizard species live in high altitude "islands," where climate change is happening the fastest. The lizards can't adjust fast enough to survive. The scientists said they don't think the animals are likely to save themselves just by shifting into a new zone, either.

"How quickly can Earth's lizards adapt to the rising global temperatures? That's the important question," Sinervo said in a press release. "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."

Photo by Ignacio De la Riva. Map courtesy of Barry Sinervo.