If you want to do something about global warming, look under your feet. Managed well, soil's ability to trap carbon dioxide is potentially much greater than previously estimated, according to researchers who say the resource could "significantly" offset increasing global emissions.
The scientists also call for a reversal of federal cutbacks to related research programs to learn more about this valuable resource.
The work, published in two overlapping papers Oct. 5 in the Annual Review of Ecology, Evolution, and Systematics, and Global Change Biology, emphasizes the need for more research into how soil—if managed well—could mitigate a rapidly changing climate.
Stanford University researchers led both research teams, which include scientists from more than a dozen institutions, including the University of Michigan.
"Dirt is not exciting to most people," said Stanford's Rob Jackson, lead author of the Annual Review paper and co-author of the Global Change Biology paper. "But it is a no-risk climate solution with big co-benefits. Fostering soil health protects food security and builds resilience to droughts, floods and urbanization."
The Global Change Biology paper resulted from an International Soil Carbon Network Workshop. U-M ecologist and biogeochemist Luke Nave worked with collaborators at the Northern Institute of Applied Climate Science in Houghton, Mich., to establish the network and served as its coordinator from 2010 until this year. The network now includes more than 650 researchers from more than 30 countries.
"Collectively, we have long known that conserving soil organic matter is vital to sustaining the soil-based ecosystem services that support life as we know it," said Nave, an assistant research scientist at the U-M Biological Station and in the Department of Ecology and Evolutionary Biology, and a co-author of the Global Change Biology paper.
"Increasingly, though, the sequestration of soil carbon—which is the principal constituent of soil organic matter—is considered a promising way to mitigate atmospheric carbon pollution and climate change. In recent years, our science has reached a point that we can actually put numbers on the soil carbon impacts of management or policy decisions by creatively synthesizing and applying existing datasets."
Organic matter in soil, such as decomposing plant and animal residues, stores more carbon than do plants and the atmosphere combined. Unfortunately, the carbon in soil has been widely lost or degraded through land use changes and unsustainable forest and agricultural practices, fires, nitrogen deposition and other human activities.
The greatest near-term threat comes from thawing permafrost in Earth's northern reaches, which could release massive amounts of carbon into the atmosphere.
Despite these risks, there is also great promise, according to Jackson and Jennifer Harden, a visiting scholar at Stanford's School of Earth, Energy & Environmental Sciences and lead author of the Global Change Biology paper.
Improving how the land is managed could increase soil's carbon storage enough to offset future carbon emissions from thawing permafrost, the researchers find. Among the possible approaches: reduced tillage, year-round livestock forage and compost application. Planting more perennial crops, instead of annuals, could store more carbon and reduce erosion by allowing roots to reach deeper into the ground.