Much of the earth’s carbon is trapped in soil, and scientists have assumed that potential climate-warming compounds would safely stay there for centuries. But new research from Princeton University shows that carbon molecules can potentially escape the soil much faster than previously thought. The findings suggest a key role for some types of soil bacteria, which can produce enzymes that break down large carbon-based molecules and allow carbon dioxide to escape into the air.

More carbon is stored in soil than in all the planet’s plants and atmosphere combined, and soil absorbs about 20% of human-generated carbon emissions. Yet, factors that affect carbon storage and release from soil have been challenging to study, placing limits on the relevance of soil carbon models for predicting climate change.

In a paper published Jan. 27 in Nature Communications, researchers led by former postdoctoral fellow Judy Q. Yang developed “soil on a chip” experiments to mimic the interactions between soils, carbon compounds and soil bacteria. While bacteria themselves could not reach the nutrients lodged within the synthetic clay’s small pores, bacterial enzymes could break down the nutrients and potentially make smaller sugar molecules available to fuel bacterial metabolism.

“This is a very important phenomenon, because it’s suggesting that the carbon sequestered in the soil can be released [and play a role in] future climate change,” said Yang. “We found out that the enzymes produced by bacteria play an important role, but this has often been ignored by climate modeling studies” that assume clay protects carbon in soils for thousands of years.