Vegetation dynamics and methane emissions: insights from East African wetlands

Abstract Previous studies have shown that methane emissions from East Africa are globally significant, yet their environmental controls remain poorly constrained. In this study, we use satellite observations of enhanced vegetation index (EVI), land surface temperature (LST), and rainfall to interpret methane emission estimates inferred from Greenhouse gases Observing SATellite (GOSAT) observations over 2010–2020, with a focus on the anomalous emission pulse during 2018–2020. We identify a pronounced seasonal contrast in the relationships between methane emissions and environmental variables. During the long rains, methane emissions are strongly correlated with contemporaneous EVI, LST, and rainfall across both the regional and basin scales. In contrast, during the short rains, cumulative EVI explains more variability in methane emissions ( r = 0.74) than seasonal EVI ( r = 0.35), indicating the importance of lagged ecosystem processes such as vegetation senescence and organic matter decomposition. We interpret this delayed emission peak as likely reflecting the combined influence of vegetation-driven carbon inputs and catchment-scale hydrological transport, whereby biomass production and water redistribution during the long rains contribute to enhanced methane emissions in the subsequent season. Periods of anomalously high EVI (2018–2020) coincide with elevated methane emissions, particularly over the Juba, Tana, Nile, and Rift basins. While these relationships are empirical, our results suggest that vegetation dynamics provide a stronger large-scale empirical indicator of methane variability than rainfall alone, and highlight the importance of accounting for lagged biogeochemical processes when interpreting wetland methane emissions.