Tropical Wetland Methane Emissions and Trends (2004–2023) Inferred from Landsat-Based Inundated Vegetation Data

The role of tropical wetlands in the recent rise of atmospheric methane remains unclear. Most models find no significant emission trends, partly because wetlands are defined by surface water extent without distinguishing high-emitting inundated vegetation from weakly emitting open water. Here we use 30-m Landsat observations to identify tropical inundated vegetation and combine them with chamber- and flux-tower-derived emission intensities to construct a Wetland Methane Emission Inventory at 0.1° × 0.1° spatial and quarterly temporal resolution for 2004–2023. The quarterly periods are defined as December–February, March–May, June–August, and September–November. We find that tropical wetland methane emissions increased by 16.3 ± 5.1 Tg a^–1 over this period, driven by Africa (11.3 ± 3.5 Tg a^–1) and Asia (5.0 ± 1.6 Tg a^–1), with no net increase from South America. Tropical wetlands account for 21% of the long-term global methane emission increase over 2004–2023 but do not contribute significantly to the 2020–2022 surge. Increases in wetland methane emissions correlate strongly with the expansion of vegetated wetlands.