Carbon Loss from Soil Accelerating Climate Change

In a sort of paradox fashion, research published in the journal Science found that increased levels of carbon dioxide (CO₂) in the atmosphere cause soil microbes to produce more carbon dioxide, accelerating climate change.

These findings challenge scientists' previous notion that increased CO₂ levels accelerate plant growth, which causes more absorption of CO₂ via photosynthesis.

Until now, it was believed that carbon is stored in wood and soil for a long time, stalling climate change for a time. But two Northern Arizona University (NAU) researchers, who led the study, revealed that the extra carbon provides fuel to microorganisms in the soil whose byproducts (such as CO₂) are released into the atmosphere, in fact contributing to climate change.

"Our findings mean that nature is not as efficient in slowing global warming as we previously thought," Kees Jan van Groenigen, research fellow at the Center for Ecosystem Science and Society at NAU, said in a press release.

"By overlooking this effect of increased CO₂ on soil microbes, models used by the Intergovernmental Panel on Climate Change may have overestimated the potential of soil to store carbon and mitigate the greenhouse effect."

To reach their conclusion, and to better understand how soil microbes respond to Earth's changing atmosphere, researchers analyzed results from 53 different experiments in forests, grasslands and agricultural fields around the world. These combined studies measured how excess atmospheric CO₂ affects plant growth, microbial production of carbon dioxide, and the total amount of soil carbon at the end of each experiment.

"We've long thought soils to be a stable, safe place to store carbon, but our results show soil carbon is not as stable as we previously thought," co-author Bruce Hungate added. "We should not be complacent about continued subsidies from nature in slowing climate change."

But the human race does hold some responsibility for the rising CO₂ levels, and can't leave it solely to plant life to restore it to its normal levels. The compound is the primary greenhouse gas emitted through human activities, the Environmental Protection Agency reports, and accounted for about 82 percent of all US greenhouse gas emissions in 2012.