Lizards - the next canary in the global warming coal mine

Lizards.  My first love. I know, but it’s true. And not just any lizards, but Sceloporus lizards.  I mean look at this guy.

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Think his camouflaged ways make him too drab?  Flip him over and take a look at his underside.  Spectacular, really.

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I’ve spent a lot of time in the southwestern US and even in Costa Rica, taking a close look at these lizards.  Their spiny scales and large jaws make them well suited for easy capture with a long stick and a piece of string shaped as a noose.  Don’t worry, it doesn’t harm them – just leaves them dangling as you bring them in for better look.  In my case, I was measuring them and weighing them for some basic population data.  But what I loved most was the peaceful time I spent in the beautiful southwest desert “fishing” for these lizards.

A new study out in today’s issue of Science indicates that those fishing days may soon be over.  Scientists who have been studying Sceloporus lizards in Mexico for the last 40 years have found that 12% of 200 populations are now locally extinct.  A hot climate might not be the most obvious explanation given that lizards require heat to attain physiological activity, are not susceptible to water loss and thermo-regulate in a number of ways including retreating to cool refuges, like hiding under a rock.  Taking a closer look, however, the scientists found that the window of time between temperatures that are too cold for lizards and those that are too hot is shrinking – leaving little time for the lizards to actively search for food. 

Interestingly, it’s not the most extreme summer temperatures that are a problem.  The shortening of their optimum activity window is affecting them most in the spring – when pregnant females have increased energy needs.  If there’s not enough time in the day for them to forage for food, they are unable to reproduce – and without reproduction, the population goes extinct.

Applying their findings to a global model, the researchers predict 40% of lizard populations and 20% of lizard species will go extinct by 2080.

I know that not everyone loves lizards the way that I do – and some may not even be moved by these findings.  But like all creatures, lizards play an important role in the larger interconnected web of life by, for example, feeding on insects and providing a food source for birds.  

More than anything, this study provides one more example of how climate change is already affecting our world in ways that we may not be anticipating and the subsequent effects are likely to be equally drastic and unpredictable.  We are perhaps limited in our ability to envision all of the changes that may come.

After all, can you imagine a desert without lizards? I know I can’t. And I really don’t ever want to.

We need comprehensive clean energy and climate legislation now. 

Photo credits: by Flickr users kibuyu (top) and Ken-ichi (bottom), both under Creative Commons licensing.