Warming soils may belch much more carbon

As the planet warms, carbon stashed in Earth’s soils could escape into the atmosphere far faster than previously thought. In the worst-case scenario for climate change, carbon dioxide emissions from soil-dwelling microbes could increase by 34 to 37 percent by 2100 , researchers report online March 9 in
Science. Previous studies predicted a more modest 9 to 12 percent rise if no efforts are taken to curb climate change. Those extra emissions could further intensify global warming.
Much of that extra CO will originate from soils at depths overlooked by previous measurements, says study coauthor Margaret Torn, a biogeochemist at Lawrence Berkeley National Laboratory in California. “We ignore the deep at our peril,” she says.
Soils cover about two-thirds of Earth’s ice-free land area and store nearly 3 trillion metric tons of organic carbon — more than three times the amount of carbon in the atmosphere. Dead organisms such as plants contribute to this carbon stockpile, and carbon-munching microbes belch some of that carbon into the atmosphere as CO . Rising temperatures will spur the microbes to speed up their plant consumption, scientists warn, releasing more CO into the air. And the data back up that fear.
Scientists have mimicked future warming by heating the top 5 to 20 centimeters of experimental soil plots and measuring the resulting CO emissions. Those studies missed deeper soils, though, known to contain more than half of all soil carbon. Warming such deep soils is technically challenging and scientists had generally assumed that any emission increases from so far down were insignificant, says study coauthor Caitlin Hicks Pries, an ecosystem