Further explanation on the potential contribution of soil carbon sequestration on working agricultural lands to climate change mitigation

Editor's note: The following was first published on the World Resources Institute's blog.

The term “regenerative agriculture” is a broad and not-yet-clearly-defined term. It can refer to a range of practices with both climate and non-climate benefits. Our previous blog post focused specifically on the limited potential to mitigate climate change by removing carbon from the atmosphere and storing it in soils.  Our title could have been clearer about this soil carbon focus. One goal of our post was to shift attention away from soil carbon to other ways regenerative practices can achieve climate benefits. For example, in Africa, practices such as agroforestry offer much promise to boost productivity, increase above-ground vegetative carbon and meet rising food demands without clearing natural forests. Similarly, our report, Creating a Sustainable Food Future, identified improved grazing pastures and silvopastoral systems as critical to meeting climate mitigation goals, especially across the tropics.

Implemented in the right way, preserving the huge, existing reservoirs of vegetative and soil carbon in the world’s remaining forests and woody savannas by boosting productivity on existing agricultural land (a land sparing strategy) is the largest, potential climate mitigation prize of regenerative and other agricultural practices. Realizing these benefits requires implementing practices in ways that boost productivity and then linking those gains to governance and finance to protect natural ecosystems. In short, “produce, protect and prosper” are the most important opportunities for agriculture.

By contrast, most claims for the climate mitigation role of regenerative practices focus on their potential to build soil carbon. As our blog post noted, we do not consider this potential to be large.  Among the comments we received was a critical letter from one group of scientists (Paustian et al. 2020) and a supportive letter from another group (Powlson et al. 2020)1. Here we elaborate our thinking:

First, we address the realistic potential to sequester carbon in soils by examining a range of identified practices. Put simply, many practices that sequester soil carbon at the field level involve taking crops out of production. Given growing demand for crops, such practices are unlikely to be scalable because they create a need to expand cropland elsewhere to make up for the foregone production. And this in turn drives conversion of natural ecosystems and release of carbon stored in vegetation and soils.

Second, we address the best-known, large global estimates of potential soil carbon gains. We find that they tend to have limited documentation and analysis of the feasibility of the massive expansion of practices they are relying on to sequester carbon. They also rely largely on practices that decrease crop production or on practices on working lands that more recent science has shown to be ineffective or less effective at sequestering soil carbon, such as no-till farming.

Third, we elaborate on issues related to the use of manure, implications of yield changes and nitrogen limitations.

Finally, we explain our concerns why overestimating potential soil carbon gains could undermine efforts to advance effective climate mitigation in the agriculture sector.