Greenhouse gas emissions from global agriculture
Food systems currently contribute about one-third of total anthropogenic greenhouse gas (GHG) emissions, and these emissions are expected to rise as demand for agricultural products increases. Thus, improving the GHG emissions efficiency of agriculture – tons of CO2equivalent emissions per hectare or kilocalorie of production – will be critical to support a resilient future global system. Here, we model and evaluate global 2000-era GHG emissions, including those from N fertilizer application, rice cultivation, and peatland draining. We then predict potential emissions from future crop production increases achieved through intensification and extensification.
We find that N fertilizer application, rice cultivation, and peatland draining each have similar total CO2 equivalent emissions. Yet, these emissions were highly heterogeneous across crops types, crop management practices, and regions. Rice agriculture, although it occupied only 12% of global cropland harvested area, produced substantially more CO2-equivalent emissions than any other crop. Similarly, just a few countries, including Indonesia, India, and China, contributed the vast majority of total emissions. Of the top emitting crops, oil palm stood out with a very high efficiency on a caloric basis because of its extremely high caloric yields. Bananas had one of the lowest efficiencies on an area basis, because of relatively high N fertilizer application rates. Wheat and maize were associated with the bulk of N2O emissions because these well-fertilized crops are quite extensive. Our results suggest that while intensification tends to generate more GHG efficient production than cropland expansion, doubling caloric production will require some degree of crop expansion. We conclude by discussing potential region- and crop-specific agricultural development pathways that may boost the GHG emissions efficiency of agriculture, and acknowledge that efficiency is just one dimension of food system resilience.