Legislators, farm groups, and corporations are increasingly turning to agriculture as a climate solution. Research documenting the capacity of healthy soils and plant communities to remove excess carbon dioxide from the atmosphere has led to rapidly growing support for paying agricultural producers to sequester carbon and reduce greenhouse gas (GHG) emissions through soil health and conservation practices. An alliance of the American Farm Bureau Federation, National Farmers Union, National Association of State Departments of Agriculture, Environmental Defense Fund, The Nature Conservancy, and others collaborated to publish the Food and Agriculture Climate Alliance (FACA) report including over 40 policy recommendations. Meanwhile, dozens of major corporations from Smithfield to Walmart have set ambitious net GHG reduction goals to help keep global warming below 2°C.
Many of these initiatives focus on carbon markets, offsets, and tax credits – essentially, agreements through which GHG emitters pay other entities to compensate for their emissions by sequestering carbon. The recently introduced bipartisan Growing Climate Solutions Act would authorize USDA to help farmers and forest landowners participate in private carbon markets by creating a self-certifying registration process for technical assistance providers and carbon market verifiers. Despite the lack of accreditation and conflict of interest provisions that are normally considered essential government practices for such programs, the bill has gained support from multiple sectors including FACA and some farmers and conservationists.
However, danger lurks in this rush toward agricultural carbon markets. Leaders in the field know that the science is not yet in place for accurate and cost-effective measurement and quantification of soil carbon sequestration. For example, a recent Agri-Pulse article quotes John Mesko of the Soil Health Partnership stating that “we can't measure everything fast enough … to quantify in real terms what's going on,” and Kris Johnson of The Nature Conservancy explaining that “If you have to … dig a meter soil core to quantify the change in carbon [in every field], that's really expensive.”
In an effort to avoid these costs, proponents of carbon markets intend to use “simulation modeling” to assign carbon credits for cover crops, no-till, and other practices estimated to convert X tons of carbon dioxide (CO2) into soil organic carbon (SOC) per acre. However, both the amount and the duration of SOC sequestration depend on so many variables, including soil type and condition, climate, and farming practices, that accurate verification for carbon crediting is virtually impossible. Furthermore, long-term monitoring would be needed to assure that management changes and associated SOC accrual are permanent.
Research progress in understanding soil carbon dynamics and the development of advanced field sensing technologies may lead to accurate, low-cost methods to track net SOC changes and provide a basis for real-time agricultural carbon crediting in the foreseeable future. Yet, these advances could leave carbon market farmers vulnerable to adverse events beyond their control. Extreme weather that accelerates soil erosion or causes cover crop failure, intense heat that oxidizes SOC, or herbicide-resistant weeds that necessitate tillage can cause a net loss of SOC, leaving the farmer to foot the bill.
Furthermore, research shows that we cannot substantially offset GHG emissions simply by adding cover crops and no-till to annual crop rotations. The major gains will come through advanced rotational grazing management; conversion of highly erodible or marginal cropland to perennial production systems, including permanent pasture, silvopasture, agroforestry, orchards with permanent ground cover, and perennial grain crops; and restoration of native forest, prairie and wetlands.
For annual cropping systems, integrated strategies such as organic and conservation agriculture will sequester more carbon than merely eliminating tillage or adding a cover crop to a simple rotation such as corn-soy. Diversified rotations that include cover crops, minimize fallow periods, reduce tillage, use organic soil amendments, eliminate or minimize use of synthetic agrochemicals, and reintegrate livestock and crop production, where practical, can yield lasting increases in cropland SOC and soil health.
Yet, in today’s agri-food economic system, farmers cannot undertake such transformative changes on their own. To address the mounting climate crisis, we, as a society of eaters, must support farmers and ranchers by paying them for the very real ecosystem services they provide. How can we do this?
Government policy must promote and support resource-conserving crop rotation, cover cropping, management-intensive rotational grazing, agroforestry and other soil health practices for the full gamut of their benefits and not just SOC sequestration. These practices prevent soil erosion, improve water infiltration and storage, protect water resources from nutrients, sediment, and pathogens, and – most importantly – improve resilience to weather extremes, thereby stabilizing yields, farm income, and food security.
Farmer surveys by USDA’s Sustainable Agriculture Research and Education (SARE) program show that cover cropping builds soil health, reduces fertilizer, irrigation, and weed management costs, stabilizes grain yields, and can improve net returns. Yet less than 10% of US acreage is cover cropped, while fertilizer nitrogen (N) use rates continue to rise, indicating a missed opportunity to derive N from legume covers and decrease agriculture’s dependence on fossil-fuel based products.
Farmers hesitate to plant cover crops because of perceived risks. For example, in the recent Agri-Pulse article, California farmer Cannon Michael suggested that cover cropping “doesn’t work as well in the Central Valley, where the cover crops can compete for valuable soil moisture.” Yet, field trials in central California show that winter cover crops greatly improve the soil’s capacity to absorb winter rainfalls without ponding or runoff, retrieve over 100 lb N per acre that would otherwise be lost to leaching, and reduce fertilizer and irrigation water needs during summer vegetable production. In addition, SARE-funded studies show that, when used as one component of an integrated soil health strategy, cover crops can significantly improve farmers’ bottom line.
Clearly, farmers need technical and financial assistance to adopt cover cropping and other valuable soil health practices. In this age of climate crisis, addressing this need through research, extension, and conservation programming must become a top priority in agricultural policy. Payments to farmers for cover cropping and integrated soil health management must reflect all the ecosystem services provided – soil conservation, moisture and nutrient efficiency, protection of drinking water and critical watershed ecologies, and agricultural resilience, as well as SOC sequestration. The Conservation Stewardship Program and other USDA conservation programs exist to support farmers and ranchers to maintain and enhance conservation outcomes on their land. These programs can and should be amended to better reward the many benefits of cover cropping, rotational grazing, and other soil health practices, and to add climate mitigation and resilience to the traditional list of resource concerns addressed.
While we are highly encouraged that industry is getting on board with climate mitigation and resilience goals for agriculture, we are also concerned that the current emphasis on carbon markets could lead to false hopes and missed opportunities to take a more holistic and realistic approach to addressing the climate crisis through soil and agroecosystem health. First and foremost, we believe that existing public conservation and research programs should be improved and expanded to equip farmers and ranchers with the tools and resources they need to be part of the climate solution and to build resilience into their operations.
Mark Schonbeck, Virginia Biological Farming Association, and Research Associate, Organic Farming Research Foundation
Cristel Zoebisch, Climate Policy Associate, National Sustainable Agriculture Coalition and Organic Farming Research Foundation
For more news, go to www.agri-pulse.com.