Greenhouse gas emissions intensity of global croplands

Abstract

Stabilizing greenhouse gas (GHG) emissions from croplands as agricultural demand grows is a critical component of climate change mitigation. Emissions intensity metrics - including carbon dioxide equivalent emissions per kilocalorie produced ('production intensity') - can highlight regions, management practices, and crops as potential foci for mitigation. Yet the spatial and crop-wise distribution of emissions intensity has been uncertain. Here, we develop global crop-specific circa 2000 estimates of GHG emissions and GHG intensity in high spatial detail, reporting the effects of rice paddy management, peatland draining, and nitrogen (N) fertilizer on CH 4, CO 2 and N 2 O emissions. Global mean production intensity is 0.16 Mg CO 2 e M kcal'1, yet certain cropping practices contribute disproportionately to emissions. Peatland drainage (3.7 Mg CO 2 e M kcal'1) - concentrated in Europe and Indonesia - accounts for 32% of these cropland emissions despite peatlands producing just 1.1% of total crop kilocalories. Methane emissions from rice (0.58 Mg CO 2 e M kcal -1), a crucial food staple supplying 15% of total crop kilocalories, contribute 48% of cropland emissions, with outsized production intensity in Vietnam. In contrast, N 2 O emissions from N fertilizer application (0.033 Mg CO 2 e M kcal'1) generate only 20% of cropland emissions. We find that current total GHG emissions are largely unrelated to production intensity across crops and countries. Climate mitigation policies should therefore be directed to locations where crops have both high emissions and high intensities.