The Soil Won't Save Us

For more than 20 years, Professor Peter Groffman (GC/Brooklyn, Environmental Sciences) has studied the soil at two National Science Foundation funded Long-Term Ecological Research (LTER) sites — one in Baltimore, the other in the White Mountain National Forest in central New Hampshire — to better understand the interactions between ecosystems and the atmosphere.

Recently, he and his research partners came to a conclusion that has significance both for scientists and for environmental policy: over the past two decades, soil — specifically, the bacteria that live in it — is absorbing less methane from the atmosphere.
 
That’s important because soil is one of the ways we depend on nature to ‘fix’ our environmental damage, Groffman said. Methane is one of the main greenhouse gases, which are causing rising global temperatures. For the bacteria in soil, methane is food — but they can’t consume it if they can’t get to it. And they can’t get to it, the researchers concluded, because of a different effect of climate change: higher rainfall.
 
“When methane in the atmosphere diffuses into the soil, then bacteria can eat it,” said Groffman, a member of the Environmental Sciences Initiative at The Graduate Center’s Advanced Science Research Center (ASRC). “But soils are wetter because it’s raining more. When the soil is wet, there’s less diffusion, and less methane consumption.”
 
This effect is not limited to the two long-term ecological research sites that Groffman studied. Xiangyin Ni, a doctoral student from Sichuan Agricultural University who spent a year at the ASRC, reviewed 317 previously published papers, and found that lower methane absorption has been documented around the world in areas that have been experiencing higher rainfall.
 
The researchers detailed their findings in a study published this week in the PNAS (Proceedings of the National Academy of Sciences) journal.
 
Groffman, a biogeochemist, noted the study has both scientific and practical applications. “There are a lot of scientists who are trying to produce budgets for greenhouse gases,” he said. They do this by measuring sources and sinks, or anything that removes a gas from the atmosphere. “Our data suggests that one of the terms in our global budget for methane — soil sink — has been overestimated. And that’s very important to the assessment of global climate change.”
 
Fixing leaks from natural gas pipelines, which release methane into the atmosphere and also cost money, would be one step in the right direction. “Nature solves a lot of our problems for us,” Groffman said. “But its ability and capacity to clean up after us is limited. If we really want to stabilize the concentration of methane in the atmosphere, we’re going to have to work a little harder.”

Photo credit: Credit: © Grecu Mihail Alin