Use of local greenhouse gas inventories to prioritise opportunities for climate action planning and voluntary mitigation by agricultural stakeholders in California

To meet the mitigation targets set by California's Global Warming Solutions Act there is a need for locally adapted greenhouse gas (GHG) inventory methods and policy principles that help rural communities prioritize opportunities for agricultural GHG mitigation. Here, inventory methods prescribed by the Intergovernmental Panel on Climate Change and local activity data on agricultural land uses and inputs were used to conduct an inventory of agricultural emissions for a rural county in California for 1990 and 2008. Total emissions from agriculture in Yolo County were found to decline by 10.4% during this period, due to a reduction in irrigated cropland acreage, a shift towards crops which require less N, and a reduction in N rate for some crops. Average emissions per hectare of urban land were >70 times more than our estimate for irrigated cropland. This suggests that policies which protect farmland and encourage ‘smart growth’ may help curb future emissions. Opportunities also exist to reduce emissions through voluntary, incentive-based, and market-driven initiatives which promote the adoption of innovative agricultural practices. To be effective, local policy makers must work closely with agricultural stakeholders to anticipate and adapt to the practical tradeoffs and co-benefits of new climate policies.