Following 2015’s designation as the International Year of Soils by the UN Food and Agriculture Organization, soil carbon sequestration is experiencing something of a renaissance among policy and scientific circles. Farmers are also getting involved, most recently through the Climate Leaders program of the National Farmers Union. Now the challenge is to translate all this momentum to action, starting with how we approach and develop climate-smart projects.
In April 2015, USDA released the Building Blocks of Climate Smart Agriculture and Forestry to focus on 10 action areas for voluntary and incentive-based conservation, the first being soil health. Taken together, the USDA’s 10 Building Blocks are expected to reduce greenhouse gas emissions by 120 million metric tons of carbon dioxide equivalent (CO2e) annually by 2025—more than 5 times the compliance credits issued to date through the California Air Resources Board cap-and-trade program. Then, during the Paris climate negotiations in December, a broad international partnership launched the 4 per Thousand Initiative to encourage better stewardship of soil carbon stocks for meeting long-term climate stabilization goals; an initiative aimed to improve food security around the world. Though the 0.4 percent per year increase in soil carbon sequestration they call for is aspirational, the result at a global scale would be another 4.4 billion metric tons CO2e removed annually from the atmosphere (or nearly two-thirds of all U.S. emissions).
These initiatives have since been bolstered by several timely studies, from an exploration of what it would take to meet the 4 per Thousand goals at a national scale, to a global review of the latest soil carbon research and mitigation potentials. The former, written by Adam Chambers and colleagues of USDA’s Natural Resources Conservation Service, calculates that a $3 to $5 billion investment in U.S. cropland and grassland soils over the next decade could increase sequestration by 250 million metric tons CO2e per year. The figure below reveals a significant gap between recent USDA efforts and this potential, which the authors estimate would require 10 million cropland acres and 20 million grassland acres (on average) to enroll each year. By 2025, then, a concerted effort by US farmers and ranchers could yield carbon benefits similar to the EPA Clean Power Plan, at roughly half its modeled annual cost in the same year. The latter study, by Keith Paustian and colleagues of Colorado State University, puts the global mitigation potential of a broader range of soil management practices, including biochar and restoring degraded lands, at 8 billion metric tons CO2e per year (or one-fourth of global energy-related emissions).