Agricultural Soil Carbon and Carbon Markets for Mitigating Climate Change

The management of agricultural soil carbon is an important tool in battling the climate crisis. By adopting healthy soil practices that keep carbon in soil and sequester carbon for the long term, farmers can contribute to climate change mitigation and adaptation (IPCC 2019; Bossio et al. 2020). Such practices can boost resilience to increasingly extreme droughts and floods, reduce air and water pollution, and help farmers and their communities to thrive (Stillerman and DeLonge 2019).

Carbon management is valuable, and policies that support farmers to build soil health are needed. Crucially, such policies must be based on science, and they must be beneficial on a range of scales, from farm to global. At the same time, policies are needed to address numerous other food and farm-system challenges, including repairing longstanding inequities and discrimination in the way US agricultural policy distributes resources. All this gives the federal government an essential role to play in ensuring equitable opportunities and outcomes in efforts to manage carbon, especially for small, midsize, and diversified farms, Black and Indigenous farmers, and other farmers of color (UCS and HEAL 2020).

Currently, momentum is growing to pay farmers for adopting practices that sequester carbon in soil (Bloch 2020; Growing Climate Solutions Act 2021), and farmers can be compensated in many possible ways for doing this. For example, government payments can help farmers cover the costs associated with implementing beneficial practices, which several US Department of Agriculture (USDA) programs already do, albeit on a relatively small scale. Scaled-up investments in programs such as the Conservation Stewardship Program (CSP) and the Conservation Reserve Program (CRP) could enable US agriculture to contribute to net emissions reductions while making farmland more resilient and providing other environmental benefits.

Also under development are various market-based approaches to spur agricultural soil carbon sequestration. Publicly or privately funded programs could pay farmers to sequester carbon in agricultural soils and offer “credits” for the emissions they offset. And governments or other entities could establish markets for buying and selling permits or credits to reduce heat-trapping emissions within the agricultural sector or across industries. While such market-based approaches are gaining traction among federal policymakers and stakeholders, the discussion often glosses over important requirements for successfully and equitably meeting climate mitigation goals: for example, the need to accurately estimate and value long-term soil-carbon sequestration, the need to ensure total greenhouse gas reductions, and the need to ensure equitable outcomes. Designing market-based approaches that meet those requirements will be challenging and require careful attention.

Critically, achieving national climate goals by any means requires deep absolute cuts in heat-trapping emissions from the power and transportation sectors. Rather than substitute for those cuts, soil-carbon sequestration should be pursued in addition to reducing emissions toward the goal of net zero emissions no later than 2050. Also, although scientists have shown the value and potential for soil-carbon sequestration, they caution that it is challenging to measure, monitor, and verify accurately at the required scales (Paustian et al. 2019). Further, soil-carbon sequestration is subject to reversal and other changes in response to such factors as land management and climate conditions (Harden et al. 2018). And changes to farming practices that sequester soil carbon may unintentionally increase other sources of farm-related emissions, introducing additional uncertainties (Li, Frolking, and Butterbach-Bahl 2005).

These issues pose challenges for determining appropriate payments and ensuring that they contribute to meeting targets for mitigating climate change. In addition, programs focused exclusively on soil carbon may fail to account for other benefits that ecologically based agriculture can provide to society, such as improving water and air quality and promoting biodiversity. At the same time, there is a risk that credit-based approaches could have the perverse effect of exacerbating or enabling dangerous levels of air and water pollution in communities near emission sources (Hernandez-Cortes and Meng 2020). Thus, market-based proposals to mitigate climate change through agricultural soil carbon management as defined here run the risk of being ineffective (Green 2021), inequitable, volatile, and dangerous.

Given the potential benefits and challenges, the Union of Concerned Scientists (UCS) supports initiatives to promote increased soil-carbon sequestration in agricultural soils as a key part of an overall climate change mitigation and adaptation effort.

However, we oppose the use of market-based approaches that rely on agricultural soil-carbon sequestration to offset emissions produced by other industries, particularly to meet mandatory obligations to reduce emissions.

In general, programs that pay farmers to manage soil carbon or adopt practices to sequester it must incorporate rigorous safeguards, ensuring both that we achieve the desired outcomes to mitigate climate change and that we distribute resources and benefits equitably. UCS proposes encouraging the management of agricultural soil carbon through expanding programs based on whole-farm approaches that promote soil health and other benefits (House Select Committee on the Climate Crisis 2020).

Further, we recommend the distribution of federal incentives through existing and familiar USDA authorities, such as CSP and CRP. Conservation programs like these would be effective avenues for scaling up the ability of agriculture to manage and sequester soil carbon and reduce heat-trapping emissions, while yielding additional environmental benefits. At the same time, we recommend strengthening these existing programs to more equitably and more powerfully support science-based and regionally tailored healthy-soil practices implemented through whole-farm systems.

Acknowledgments

This report was made possible through the support of the Grantham Foundation for the Protection of the Environment, the W.K. Kellogg Foundation, and UCS members. The Union of Concerned Scientists bears sole responsibility for the report’s contents.

References

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