Spatial and temporal dynamics of methane emissions from agricultural sources in China

Agricultural activities contribute significantly to the global methane budget. Agricultural sources of methane are influenced by land-use change, including changes in agricultural area, livestock keeping and agricultural management practices. A spatially explicit inventory of methane emissions from agriculture is made for China taking the interconnections between the different agricultural sources irate account. The influence of land-use change on methane emissions is studied by linking a dynamic land-use change model with emission calculations. The land-use change model calculates changes in rice area and livestock numbers for a base-line scenario. Emissions are calculated for 1991 based on land-use statistics and for 2010 based on simulated changes in land-use patterns. Emissions from enteric fermentation and manure management are based on emission factors, while emissions from rice paddies involve the calculation of total organic carbon added to rice paddy soils and assume that a constant fraction is emitted as methane. Spatial patterns of emissions are presented for the different sources. For the land-use scenario considered it is expected that total methane emissions from agricultural sources in China increase by 11% while the relative contribution of rice fields to the emission decreases. Emissions from manure management are expected to become more important. These results indicate that agencies should anticipate changes in source strengths as a consequence of land-use changes when proposing mitigation strategies and future national greenhouse gas budgets.