Investments in carbon removal, or carbon sequestration, on “natural and working” farmlands have long been part of the U.S. Department of Agriculture and the Environmental Protection Agency's (EPA) climate change strategies. However, just as the USDA Farm Bill is stalled once again, a new study entitled 'The Realistic Potential of Soil Carbon Sequestration in U.S. Croplands for Climate Mitigation' has left many wondering whether or not these efforts are in vain.
According to the research presented in the study by Nazli Uludere Aragon, Yanhua Xie, Daniel Bigelow, Tyler J. Lark, and Alison J. Eagle, "Existing estimates of the climate mitigation potential from cropland carbon sequestration (C-sequestration) are limited because they tend to assume constant rates of soil organic carbon change over all available cropland area, use relatively coarse land delineations, and often fail to adequately consider the agronomic and socioeconomic dimensions of agricultural land use."
In addition, the data shows that their baseline estimate of suitable stable cropland area is 32% of the current U.S. cropland extent. Even when the researchers used a less restrictive definition of stability, a large reduction in area was seen (44% of current U.S. croplands). Compared to the current estimates cited by the USDA and EPA, these new estimates account for less than one-fifth of those previous projections.
As emphasized in the study, "On its own, increasing carbon sequestration via conservation practices on U.S. croplands will be insufficient to achieve agriculture’s climate mitigation goals. [We must impress] the importance of allocating scarce mitigation resources as judiciously and cost-effectively as possible, and to pathways with less uncertainty about expected mitigation."
Other interesting key points of the research include the fact that "cover cropping, though beneficial for soil health, may not be a low-cost pathway for climate mitigation at scale in the U.S." and "This high-cost hurdle needs to be evaluated against the cost-effectiveness of alternatives that compete for the same limited resources for climate mitigation."
If cover crops were implemented across all suitable farmland in the United States, which amounts to roughly 30% of the nation's cropland, it could potentially double the amount of carbon dioxide these lands currently sequester from the atmosphere. However, this increase would only result in a 3% reduction in annual agricultural carbon dioxide emissions in the U.S. This is significantly less than the 10% reduction in greenhouse gas emissions that the USDA has previously estimated could be achieved through cover cropping.
Given this information, we must take a closer look at the allocation of these funds, especially as another Farm Bill is soon to pass. These same investments could be invaluable when handling greenhouse gas emissions and PFAS contamination, for instance. While agriculture is responsible for about 10% of the total annual greenhouse gas emissions in the U.S., transportation and energy related to these industries could serve as far larger sources of emissions where these funds would make a significant dent.
This research is important to analyze even further now, as Oregon recently began its own campaign to encourage more carbon dioxide storage through agricultural efforts. Considering that the legislature allocated $10 million for these practices last year, it may be time to look at their viability, analyze the data, and consider other more effective and cost-conscious ways to take climate action.
