Biogenic carbon fluxes from global agricultural production and consumption

Quantification of biogenic carbon fluxes from agricultural lands is needed to generate comprehensive bottom-up estimates of net carbon exchange for global and regional carbon monitoring. We estimated global agricultural carbon fluxes associated with annual crop net primary production (NPP), harvested biomass, and consumption of biomass by humans and livestock. These estimates were combined for a single estimate of net carbon exchange and spatially distributed to 0.05 degrees resolution using Moderate Resolution Imaging Spectroradiometer satellite land cover data. Global crop NPP in 2011 was estimated at 5.25 +/- 0.46 Pg Cyr(-1), of which 2.05 +/- 0.05 Pg Cyr(-1) was harvested and 0.54 Pg Cyr(-1) was collected from crop residues for livestock fodder. Total livestock feed intake in 2011 was 2.42 +/- 0.21 Pg Cyr(-1), of which 2.31 +/- 0.21 Pg Cyr(-1) was emitted as CO2, 0.07 +/- 0.01 Pg Cyr(-1) was emitted as CH4, and 0.04 PgCyr(-1) was contained within milk and egg production. Livestock grazed an estimated 1.27 Pg Cyr(-1) in 2011, which constituted 52.4% of total feed intake. Global human food intake was 0.57 +/- 0.03 Pg Cyr(-1) in 2011, the majority of which was respired as CO2. Completed global cropland carbon budgets accounted for the ultimate use of approximately 80% of harvested biomass. The spatial distribution of these fluxes may be used for global carbon monitoring, estimation of regional uncertainty, and for use as input to Earth system models.