Climate Change Is Causing Some Serious Salamander Shrinkage

It's one of the fastest physical changes scientists have ever seen.

Image: Nicholas Caruso

The changing climate is shrinking salamanders in Appalachia as the amphibians are forced to burn more energy in order to survive. According to a new report published in Global Change Biology salamanders caught in the Appalachian Mountains since 1980 are, on average, 8 percent smaller than museum specimens caught before then.

Its the confirmation of something that has long been posited: Higher temperatures cause creatures to expend more energy, and if you’re expending more energy, you’re going to be smaller. University of Maryland professor Karen Lips says that the speed at which the salamanders have shrunk is “one of the largest and fastest rates of change ever recorded in any animal.”

A 2011 paper published in Nature Climate Change by David Bickford of the National University of Singapore is often cited as one of the first warning signs that this was even possible. In that paper, Bickford wrote that the “observed and expected patterns of decreased body size are widespread across different taxa, and are likely to be reported from an increasingly wide array of taxa over the coming century.” He cited at least 38 mammals, birds, frogs, fish, and plants that had shrank due to climate change. Another 9 species showed some growth because of the phenomenon.

“It’s like a general law of chemistry and biology,” Lips said. 

As one biologist explained to me last year, when there’s less energy going into an ecosystem, there’s less energy that can be spent. If temperatures are higher, the cold-blooded salamanders are forced to spend more energy in order to maintain a similar lifestyle. As a result, they are smaller.

The implications for all of this aren’t exactly known—it’s possible that as the climate changes, certain species, such as salamanders, get smaller, and everything goes on more or less as normal. But Lips says that’s probably not the case. She’s an expert on chytridiomycosis, a fungal disease she helped identify in Panama that has since spread throughout the world and has devastated amphibian populations along the way. While researching these salamanders, she expected to find that they had been infected by the fungus, because their population has been dwindling. Instead, she found nothing.

“We couldn’t find the disease anywhere in these animals but noticed they were definitely not as abundant as they used to be, so we thought, ‘What could actually cause this?’” she said. “Other than disease, climate was the only thing I could think of.”

To test the theory, Lips thought of Bickford’s paper, and decided to compare salamanders in the field with museum specimens. From there, she found that ones in the wild are smaller than their historical counterparts.

To confirm whether the shrinkage is definitively due to temperature increases, Lips is designing a set of experiments to raise salamanders in different lab environments. From there, she’ll be able to test whether they show any sort of ill effects from being smaller and whether there’s anything to suggest that smaller amphibians will do worse in a wild environment. 

She theorizes that it puts them at a disadvantage.

“I think with amphibians and reptiles, bigger is almost always better. There’s fewer things that can eat you, you can produce more offspring, life is better overall,” she said. “But it’s not totally obvious how bad this is.”

Better to shrink than to die off: "They’re changing pretty quick. They’re certainly trying to keep up, so that's a good thing for them," she said.

That was the crux of Bickford’s paper, as well. Anytime you screw with nature, there’s going to be unintended consequences, both for that species and, potentially, for humans. 

“Although there will be adaptive responses that natural selection will favor, ecosystem services and global ecological processes will most likely be altered, but not in the ways that will benefit human livelihoods. Reduction in nutrients, food availability, and water will probably have negative implications and are inter-related with climate change and shrinking organisms,” he wrote. “We need to understand how and why organisms are shrinking, how feasible it is to mitigate or adapt to such climate change effects, and what it means for biodiversity and humanity if we are unable to change this pattern.”