Season-spatial redistribution of rice cultivation as an immediately effective strategy for cutting methane emissions

Paddy rice cultivation is a major source of methane emissions, a greenhouse gas with a relatively short atmospheric lifetime. Reducing methane emissions from rice fields offers significant potential for near-term climate change mitigation. Large rice-producing countries in tropical and subtropical regions, such as China, India, and Vietnam, commonly adopt multiple cropping systems to maximize rice yields. However, according to the IPCC Guidelines for National Greenhouse Gas Inventories (2019), continuous rice cultivation on the same land over consecutive seasons can more than double methane emissions compared to intermittent cropping. The anticipated rapid growth in the rice-consuming population, particularly in Asia, will likely drive further increases in rice demand and production. To mitigate methane emissions from rice cultivation, additional strategies are required beyond existing and emerging agronomic practices such as crop improvement and alternate wetting and drying. Here we propose a season-spatial redistribution of rice cultivation as an immediately effective strategy for reducing rice methane emissions. Using emission factors for various cropping patterns from the IPCC 2019 Guidelines and a temporal-spatial cropland cover database developed by the Taiwan Agricultural Research Institute (TARI), we computed the methane-minimizing season-spatial reallocation for a two-year period (four cropping seasons) in all townships of Yunlin, Taiwan's key rice-growing county, while keeping aggregate harvested area constant. Results indicate that the maximum methane mitigation potential for a single township could reach reductions of 12.63% in the first year, 44.31% in the second year, and 32.80% over the entire two-year period compared to scenarios without such reallocation. This reallocation strategy aligns with existing policies aimed at reducing irrigation water use and promoting self-sufficiency in non-rice staple crops. It can be implemented without incurring additional costs for subsidies or the establishment of new policies. The TARI cropland cover database, which incorporates Sentinel-2 satellite imagery, aerial photographs, and ground truth data analyzed using Geographic Information System (GIS) technologies, provides a detailed season-spatial map of crop cultivation in Taiwan, where two rice cropping seasons are feasible annually. Similar to the Crop Data Layer (CDL) database maintained by the USDA, the TARI database was originally designed for crop production forecasting. However, our study demonstrates its additional utility in informing policies to advance agricultural sustainability. With the increasing accessibility and affordability of digital imaging technologies, the proposed season-spatial reallocation approach could be adopted by other countries with multiple rice-cropping systems, complementing agronomic efforts to cut methane emissions from rice cultivation.