Underestimation of Methane Emissions From the Sudd Wetland: Unraveling the Impact of Wetland Extent Dynamics

Tropical wetlands account for similar to 20% of the global total methane (CH4) emissions, but uncertainties remain in emission estimation due to the inaccurate representation of wetland spatiotemporal variations. Based on the latest satellite observational inundation data, we constructed a model to map the long-term time series of wetland extents over the Sudd floodplain, which has recently been identified as an important source of wetland CH4 emissions. Our analysis reveals an annual, total wetland extent of 5.73 +/- 2.05 x 104 km2 for 2003-2022, with a notable accelerated expansion rate of 1.19 x 104 km2 yr-1 during 2019-2022 driven by anomalous upstream precipitation patterns. We found that current wetland products generally report smaller wetland areas, resulting in a systematic underestimation of wetland CH4 emissions from the Sudd wetland. Our study highlights the pivotal role of comprehensively characterizing the seasonal and interannual dynamics of wetland extent to accurately estimate CH4 emissions from tropical floodplains. Methane (CH4) plays an important role in global warming. About one-fifth of global CH4 emissions come from tropical wetlands, with the Sudd wetland in tropical Africa presenting as a hotspot for CH4 emissions. In this study, we generate a monthly wetland map series based on the latest satellite observation for the Sudd wetland. Our results show that wetland area dynamics present large seasonal and interannual variabilities. However, current widely used wetland products tend to indicate smaller sizes and variations of wetlands, which might lead to the underestimation of wetland CH4 emissions. We point out that refined maps of tropical wetlands can help reduce the uncertainties of CH4 emission estimations. Extended monthly inundation maps across the Sudd wetland for 2003-2022 Rapid growth of the Sudd wetland extent for 2019-2022 driven by upstream precipitation Underestimation of methane emissions from the Sudd wetland due to the inadequate characterization of wetland extent