Semiarid ecosystems account for large variation in annual greenhouse gas absorption
Placid prairies and austere scrublands may be key ecosystems for explaining mysterious year-to-year swings in the amount of carbon dioxide sucked out of the atmosphere.
The unassuming landscapes are responsible for up to 50 percent of the yearly variation in how much of the greenhouse gas is stashed on land, researchers report in the May 22 Science. Generally, land and oceans each absorb about a quarter to a third of annual CO2 emissions, helping to buffer global warming. But from year to year, land-based “carbon sinks” have seemed inexplicably capricious, amassing large amounts of CO2 one year and little to none the next.
“There’s quite significant variability,” says ecosystem scientist Anders Ahlström of Lund University in Sweden. Previous studies tracking CO2 absorption on land have focused on lush tropical forests, which breathe in the largest share