Forests fight climate change, but trees shouldn't get all the credit. According to a new study, tiny salamanders also help sequester carbon before it can waft into the sky and trap heat from the sun.
How? Salamanders are the most abundant vertebrates in North American forests, where they eat insects that would otherwise release carbon dioxide and methane by chewing up leaf litter on the forest floor. (About 48 percent of leaf litter is carbon, the study's authors note.) Those leaf eaters aren't doing anything wrong, of course, but since humans now overstuff the atmosphere with nearly 40 billion tons of CO2 per year, anything that naturally offsets our excess can suddenly seem heroic.
In hopes of learning how these mysterious amphibians regulate invertebrates on the forest floor — and how that affects soil formation and carbon storage — the researchers conducted one of the most in-depth studies yet into the secret lives of salamanders, published in the journal Ecosphere.
"These organisms haven't been investigated very thoroughly in terms of what their role is, which is one of the reasons I wanted to do this," study co-author and U.S. Forest Service herpetologist Hartwell Welsh tells the Environmental Monitor.
On paper, lots of salamanders would mean fewer ants, beetles and other leaf shredders on the forest floor, thus letting more carbon slowly "humify" into soil rather than escaping into the air. To test that theory, the researchers set up a dozen 16-square-foot enclosures in a northwestern California forest, each of which held an equal amount of leaf litter. They weighed the leaf litter and sampled the invertebrates in each enclosure, then added an ensatina salamander to half of them. The invertebrates were resampled every month, and the leaf litter was reweighed after four months.
After repeating this experiment over two rainy seasons, the researchers found an average of 13 percent more leaf litter in enclosures with salamanders than in those without them. The salamanders had suppressed a variety of leaf-shredding invertebrates, including beetle and fly larvae as well as adult ants, beetles and springtails. Based on these results, the researchers conclude a single salamander can sequester about 178 pounds of carbon per acre during a rainy season.
A fire salamander navigates the forest floor in the French commune of Buais. (Photo: William Warby/Flickr)
And given the ubiquity of woodland salamanders around the world, that could be enough carbon sequestration to affect global climate change. Salamanders aren't the only animals eating these leaf shredders, but they do fill a unique ecological niche — partly due to the fact that many salamanders don't have lungs. Breathing through their skin requires less energy than lung breathing, freeing up salamanders to exploit tiny prey that wouldn't provide enough calories for birds or mammals.
It's not clear how widely these findings apply, since humification doesn't happen uniformly in all climate types. But it is clear that salamanders can help forests hang on to carbon, making them a potentially important bulwark against climate change. Unfortunately, however, they may also be a victim of it.
Another recent study, published in the journal Global Change Biology, reports "rapid reductions in body size" among 15 salamander species over the past 55 years, a common biological response to climate change. Woodland salamanders have apparently shrunk in size by 8 percent in recent decades, which is "one of the largest and fastest rates of change ever recorded in any animal," says study co-author and University of Maryland biologist Karen Lips. "We don't know exactly how or why it's happening, but our data show it is clearly correlated with climate change."
That's on top of broader population declines among amphibians, Welsh points out, caused by an array of threats including habitat loss, pollution and a globe-trotting fungal infection. And given the ability of salamanders and other amphibians to keep carbon out of the air, stopping such declines is all the more important — especially in carbon-hungry habitats like old-growth forests.
"[Forests] are the biggest carbon sequestering machines on the planet, and we're still cutting them down," Welsh says. "From the perspective of salamanders, that's a serious impact on the population. But it's an even greater impact on the ability of this planet to naturally sequester carbon."
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