Climate Change: The Role of the U.S. Agriculture Sector

Publication Date: March 2007

Publisher: Library of Congress. Congressional Research Service

Author(s):

Research Area: Environment

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Abstract:

The agriculture sector is a source of greenhouse gas (GHG) emissions, which many scientists agree are contributing to observed climate change. Agriculture is also a "sink" for sequestering carbon, which might offset GHG emissions by capturing and storing carbon in agricultural soils. The two key types of GHG emissions associated with agricultural activities are methane (CH4) and nitrous oxide (N2O). Agricultural sources of CH4 emissions mostly occur as part of the natural digestive process of animals and manure management at livestock operations; sources of N2O emissions are associated with soil management and fertilizer use on croplands. This report describes these emissions on a carbon-equivalent basis to illustrate agriculture's contribution to total national GHG emissions and to contrast emissions against estimates of sequestered carbon.

Emissions from agricultural activities account for about 6% of all GHG emissions in the United States. Carbon captured and stored in U.S. agricultural soils partially offsets these emissions, sequestering about one-tenth of the emissions generated by the agriculture sector, but less than 1% of all U.S. emissions annually. Emissions and sinks discussed in this report are those associated with agricultural production only. Emissions associated with on-farm energy use or with food processing or distribution, and carbon uptake on forested lands or open areas that might be affiliated with the farming sector, are outside the scope of this report.

Most land management and farm conservation practices can help reduce GHG emissions and/or sequester carbon, including land retirement, conservation tillage, soil management, and manure and livestock feed management, among other practices. Many of these practices are encouraged under most existing voluntary federal and state agricultural programs that provide cost-sharing and technical assistance to farmers. However, uncertainties are associated with implementing these types of practices depending on site-specific conditions, the type of practice, how well it is implemented, the length of time practice is undertaken, and available funding, among other factors. Despite these considerations, the potential to reduce emissions and sequester carbon on agricultural lands is reportedly much greater than current rates.

The debate in Congress over whether and how to address possible future climate change is intensifying. Historically, legislative initiatives have not specifically focused on emissions reductions in the agriculture sector. Instead, emissions reductions and carbon uptake are incidental benefits of existing voluntary conservation programs that provide financial and technical assistance to implement certain farm management practices, predominantly for other production or environmental purposes. The pending 2007 farm bill could expand the scope of these types of initiatives to more broadly encompass the agriculture sector in overall efforts to address climate change. Policies and incentives that might further encourage farmers to adopt such practices include expanding cost-sharing and technical assistance under existing conservation programs, low-cost loans, grants, incentive payments, and tax credits.