Impacts of Rice Cropping System Changes on Paddy Methane Emissions in Southern China

Rice paddies are one of the main sources of anthropogenic terrestrial CH4. In recent decades, the substitution of single-cropping rice (SCR) for double-crop rice (DCR) has become more common in southern China. However, the concomitant impacts on CH4 emissions have not been quantified. We incorporated high-resolution rice cropping system maps into the CH4MOD model to calculate changes in CH4 emissions in southern China due to DCR conversion to SCR over the period 1990 to 2015. We find that a total planting area of 253.64 x10(4) ha was converted from DCR to SCR. This conversion resulted in a 451.94 Gg reduction in CH4 emissions, accounting for 8.4% of CH4 emissions from paddies in China in 2015. The largest reduction was in the Middle-Lower Yangtze plain with high labor pressures. As urbanization continues, we project that the total CH4 emissions have the potential to decrease by between 17.1% and 9.2% under DCR conversion to SCR in southern China in the extreme and most likely scenarios, respectively. As farmers voluntarily move to SCR in response to labor scarcity, making full use of the land-use change trend of DCR to SCR may be an opportunity to reduce agricultural methane emissions, which is important for achieving Sustainable Development Goals (SDGs) and should be given more attention.