Soil leaks up carbon when it warms up but a new research suggests that the soil may release more carbon than previously believed as temperatures increase. This can potentially create a dangerous feedback loop that may aggravate global warming.
Nearly 3 Decades Of Soil Data
While most of the studies on climate change are conducted at atmospheric levels, the findings of a new study are based on 26 years' worth of observations in a Massachusetts hardwood forest, where scientists artificially heated certain sections of the soil and measured the amount of carbon released.
Study researcher Jerry Melillo, from the Marine Biological Laboratory, and colleagues studied three different types of forest plot. In one set of plot, they installed heating cables in the soil and heated them so the soil would be about 10 degrees warmer than the air around it. Heaters were also installed in the second set of plot but these were not turned on and the third set of plot was left untouched.
Carbon From Soil
Analysis revealed that rising temperatures may cause a two-stage cycle characterized by the carbon output increasing for several years and then leveling off, which can be explained by soil microbes adjusting to the warmer condition.
In the study, carbon released from heated soil rose dramatically in the first decade but the effect disappeared. After about seven years, the researchers observed another increase in carbon from the heated plots after readjustment.
"Our results support projections of a long-term, self-reinforcing carbon feedback from mid-latitude forests to the climate system as the world warms," the researchers wrote in their study.
Scientists are concerned that warmer soil may cause a warmer atmosphere that in turn may heat up the ground and perpetuate increase in temperatures.
Planet-Warming Greenhouse Gas
Every year, the world pumps about 10 billion metric tons of this planet-warming gas into the atmosphere mainly through the burning of fossil fuels. The world's soil is believed to contain about 3,500 billion metric tons of carbon.
"If a significant amount of that soil carbon is added to the atmosphere due to microbial activity in warmer soils, that will accelerate the global warming process," Melillo said. "Once this self-reinforcing feedback begins, there is no easy way to turn it off. There is no switch to flip."