Humble dirt could pack an unexpected climate punch, according to a new study published Wednesday in the journal Nature. An experiment that heated soil underneath a tropical rainforest to mimic temperatures expected in the coming decades found that hotter soils released 55 percent more planet-warming carbon dioxide than did nearby unwarmed areas. If the results apply throughout the tropics, much of the carbon stored underground could be released as the planet heats up.
“The loss rate is huge,” said Andrew Nottingham, an ecologist at the University of Edinburgh, who led the study. “It’s a bad news story.” The thin skin of soil that covers much of our planet’s land stores vast amounts of carbon — more, in total, than in all plants and the atmosphere combined. That carbon feeds hordes of bacteria and fungi, which build some of it into more microbes while respiring the rest into the atmosphere as carbon dioxide. Many of these microbes grow more active at warmer temperatures, increasing their digestion and respiration rates.