The diet of worms: Soil dwellers emerge as climate change heroes in study

Worms and other small soil-dwelling animals act as a buffer against climate change, according to a new Yale-led study published Tuesday.

The animals do so by feeding on microbes that release carbon dioxide from decaying organic matter, according to the report, “Biotic Interactions Mediate Soil Microbial Feedbacks to Climate Change,” published Tuesday in The Proceedings of the National Academy of Sciences.

The microbes ingest organic material to gain energy in a process that releases carbon dioxide waste into the atmosphere.

Researchers behind the study found that soil animals, including insects and worms, graze on the microbes. This means the more animals in the soil eating microbes, the less carbon dioxide is emitted in the decomposition process.

Global warming accelerates decomposition and leads to greater emissions, said Thomas Crowther, a postdoctoral fellow at Yale and the lead author of the study. Elevated temperatures stimulate growth and enzyme production, which aids the decomposition process. That in turn leads to a feedback cycle in which human-caused warming exacerbates microbial-caused warming, he said.

“Effectively, the microbes that live in the soil are responsible for producing 10 times more carbon emissions than even humans have produced,” he said. “That's the biggest flux of carbon into the atmosphere that there is on Earth.”

Crowther said an increase in microbial carbon dioxide production will likely be responsible for a rise of 2 to 3 degrees Celsius in global temperatures over the next 100 years.

As temperatures warm, “the limitations on fungal growth are alleviated, stimulating total enzyme activity and decomposition rates,” the report said. In this scenario, according to the study, grazing soil animals emerge as one of the largest controls on that growth.

“The failure to incorporate animals and their interactions with microbial communities into global decomposition models has been highlighted as a critical limitation in our understanding of carbon cycling under current and future climate scenarios,” the report said. 

While Earth’s climate change woes may not be solved simply by dropping worms onto soil, Crowther said the study suggested that improving soil conditions can make a significant difference in combating global warming.

“It’s never really been considered as an approach to mitigate climate change before, because we didn’t know how complex the interactions were,” he said.

“Now that we know, adding soil animals may be the kind of thing that could be a viable option, but a more realistic approach is to leave the ecosystem alone or cultivate natural biodiversity,” he added. “Natural regeneration is the best way.”