Climate Change Mitigation and U.S. Agriculture: Promises, Preemption, and Pathways
Even without specified mechanisms, the Paris agreement could reinforce existing U.S. emission-reduction efforts (offsets, programmatic, and supply-chain). These require accurate data to design and credit actual environmental benefit. Without a strong scientific foundation, investments may be inefficiently allocated, benefits under-estimated, and program credibility eroded. With many models in current agricultural protocols calibrated to narrow, regional data or using IPCC factors, emission reductions are discounted significantly to address uncertainties.
GHG mitigation opportunities in U.S. agriculture face measurement challenges, high variability, and a lack of comprehensive field data for key regions and practices. This is illustrated with a systematic review and meta-analysis of the impact of nutrient management on unintended losses of fertilizer nitrogen (N) as nitrous oxide (N2O). Multi-level (hierarchical) regression models found that, in spite of high variability, N2O emissions increased with N fertilizer rate, July temperature, and soil carbon. Nitrification inhibitors and delaying application of N fertilizer reduced yield-scaled N2O emissions 25% and 45%, respectively. However, poor data coverage limits the broad application of results. Research that targets data gaps and that validates and calibrates biophysical models is key to ensuring that real environmental benefits are achieved, and that agricultural producers receive appropriate credit for actions taken.