Exceptional methane emissions from an African papyrus wetland

Abstract Tropical wetlands are major natural methane sources 1-3 , yet long-term ecosystem-scale measurements remain extremely scarce across Africa 4,5 , limiting their attribution and representation in methane budgets and models 4-8 . Here we present the highest persistent methane emissions ever recorded from a wetland. We combine a 25-month eddy-covariance record spanning nearly three years at the permanently flooded Mpologoma papyrus wetland in Uganda with chamber measurements, microbial profiling and satellite-derived phenology. Mpologoma emitted 720.5 ± 378.7 mg CH₄ m⁻² d⁻¹, surpassing all published natural-wetland eddy-covariance records in sustained mean flux and seasonal peak. Its mean flux was more than twice the next-highest value, and its seasonal peak nearly three times higher. Our results reveal a different process hierarchy: phenology-controlled methane variability; hydrology modulated this control; microbial communities underpinned methane production and oxidation; and soil/water fluxes constitute the dominant methane-emission pathway to the atmosphere. This process-level understanding provides the missing link between methane signals detected by satellites and atmospheric inversions 2,9-15 , the ecosystems producing them 4,16-18 , and the mechanisms Earth-system models must represent 11,19-21 . Applying Mpologoma’s flux to four million hectares of East African papyrus wetlands yields 10.5 Tg CH₄ yr⁻¹—nearly 7% of global wetland emissions— revealing that a single wetland type could reshape the global methane budget.