Climate change is good news, at least for Swedish sand lizards

In a study published Wednesday, researchers suggests that a northern lizard species has greater reproductive success because of climate change.

After analyzing more than 350 female Swedish sand lizards over 15 years, a group of researchers has published a study in the Biomed Central Evolutionary Biology journal Wednesday suggesting climate change could increase local population levels.

“Shifts in the timing of lifecycle events in response to climate change are widespread,” but not all shifts in species' population fitness are positive, Gabriella Ljungstrom from the University of Gothenburg, Sweden and lead author of the study explains in a press release.  

Over 90 percent of all animals are ectotherms, also referred to as "cold-blooded," meaning they rely on the outside climate to regulate their own heat instead of producing it internally. Because ectotherms are heavily influenced by environmental temperatures, implications from climate change will likely be pronounced.

In a study published in December in the journal Nature Climate Change, a group of researchers found that physiological rates of ectotherms, such as heart rate and metabolism, have increased in the last 20 years along with increasing global temperatures, often to the individual's disadvantage.  

But the result of warming temperatures for the Swedish sand lizard are good.

The researchers concluded that higher temperatures are causing the female lizards to lay their eggs earlier, and this new reproductive timeline is causing higher offspring survival rates. It is safe to say that Swedish sand lizards “respond adaptively to fairly rapid annual changes,” at least in the short term.

So “for this high-latitude population, our results contrast global projections of extinction risk for lizards as a result of climate change,” says Ms. Ljungstrom.

It’s important to note that Ms. Ljungstrom and her colleagues don’t think all ectotherms will have the same positive response to climate change.

Instead, “there is a latitudinal cline in predicted impacts of climate change on ectotherms, by which tropical ectotherms appear to be the losers,” the paper explains. The performance of ectotherms living in tropical habitats is expected to decrease with increasing temperature as they already live in an optimal climate.

But for ectotherms living at high latitudes, such as European sand lizards, climate change could bring individuals currently living at suboptimal temperatures closer to their ideal internal temperature, enhancing reproductive fitness.

And Ljungstrom says this differentiation is really the important take-away.

“This highlights the importance of taking spatial differences into account when predicting future effects of climate change on species and populations,” says Ljungstrom. 

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