Methane Emissions in Asian Wetlands During 2010–2020: Insights From an Online-Coupled Microbial Functional-Group-Based Model

Abstract

Wetland ecosystems are the dominant natural source of atmospheric methane (CH4) in the global methane cycle, yet significant uncertainties remain. Along with the warming climate system, CH4 emissions from these ecosystems are projected to increase, presenting challenges for accurate CH4 budget accounting and climate mitigation efforts. This study assessed CH4 emissions and controlling factors in wetlands across East, South, and Southeast Asia (EA, SA, and SEA) for 2010–2020, using a regional Earth system model coupled online with a microbial functional-group-based CH4 model (RegESM-Microbe). The results from the RegESM-Microbe model were evaluated against 11 offline wetland models from the Global Carbon Project and revealed consistent hotspots for wetland CH4 emissions, including the Yangtze River floodplain, the Ganges and Brahmaputra River basins, and the Mekong River basin. The annual total wetland CH4 emissions in Asia estimated (34.69 ± 2.55 Tg CH4 yr−1) by the RegESM-Microbe model was close to the bottom-up wetland model ensemble (36.66 ± 1.19 Tg CH4 yr−1). The time series of emissions showed a decreasing trend before 2014. Meanwhile, the weakening of anaerobic CH4 oxidation between 2014 and 2020 contributed to increased CH4 flow in the three transport sub-processes, driving the enhanced CH4 emissions. Most wetlands in the region exhibited an upward trend in CH4 emission, with precipitation and radiation as the primary driver, followed by rising atmospheric CO2. Our study highlighted the critical role of climate change-induced wetland CH4 emissions in shaping long-term greenhouse gas mitigation strategies.