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.