A Washington State University Vancouver professor’s research has revealed the scale of carbon locked in the Earth’s surface soils and potentially found insight into possible means to capture that carbon to fight global climate change.
Marc Kramer, an associate environmental chemistry professor at WSU, and Oliver Chadwick, a soil scientist at the University of California Santa Barbara, spent five years taking and testing soil samples around the world for their latest study, published in the journal Nature Climate Change.
The two analyzed soil data taken from the Americas, New Caledonia, Indonesia and Europe, along with 6-foot deep soil samples from more than 65 sites, through the National Science Foundation’s National Ecological Observatory Network.
Rainfall, they found, takes carbon in the environment and rinses it through soils, where it interacts and bonds with minerals in the soil.
“The way to look at this is a global pathway for how carbon is accumulated in soil,” he said. “What we didn’t know before this paper is … what are the pathways for how carbon accumulates in mineral soil?”
Carbon regularly cycles through the environment, as different reservoirs of the element exchange carbon over time. For instance, photosynthesis, the process in which plants use sunlight to synthesize foods from carbon dioxide and water, cycles about 2.5 billion tons of carbon into the Earth’s soils annually, according to NASA.
Over the long term, the several-hundred-thousand-year cycle has maintained a balance that has kept that carbon out of the atmosphere (think Venus) or entirely in rocks.
Kramer said they found their pathway leads to the retention of about 660 billion tons of carbon in the Earth’s soils. That’s more than twice the carbon added to the atmosphere since the Industrial Revolution.
The research also revealed a strong correlation with a region’s rainfall and the amount of carbon retained in soil. In a dry region, like a desert, the pathway might lead to 3 percent of the total accumulated soil carbon, compared to 70 percent in a wetter forest’s soil.
That was a surprise, he said. As the rainfall amount declines, the amount of carbon in the soil drops fast.
“What we didn’t understand was how strong of a control it had,” he said.
One implication of that relationship is how changes in rainfall due to climate change could “dry out” this pathway for carbon storage, further upsetting the already present imbalance of carbon in the atmosphere and carbon cycle.
This carbon, however, generally lives about 6 feet underground, and because of the nature of how carbon bonds to other molecules, it’s probably not going anywhere.
“But that’s the whole point. It’s a slow pool, and when it gets there, it sicks around,” Kramer said.
They’ve received some interest from geoengineering researchers, those interested in large-scale projects that might combat global climate change, and building off Kramer and Chadwick’s research as a potential pathway for carbon sequestration.
The trick is figuring out how to make that work, which would mean, in part, somehow harnessing and speeding up this natural pathway for soil carbon.
“When it comes to speeding it up, and thinking about that, farmlands across the world are the frontier for innovation,” Kramer said, because most human activity that interacts with the soil and this pathway in the next 100 years will be on agricultural land.
“As to whether we have a silver bullet at this point,” he said, “we don’t.”