Methane oxidation minimizes emissions and offsets to carbon burial in mangroves

Maximizing carbon sequestration in mangroves is part of the global effort to combat the climate crisis. However, methane (CH 4 ) emissions can partially offset carbon sequestration in mangroves. Previous estimates have suggested that CH 4 emissions offset organic carbon burial by 20% in mangroves with substantial freshwater inputs and/or in highly impacted mangroves. Here we resolve the magnitude and drivers of the mangrove CH 4 offset using multiple isotopic tracers across a latitudinal gradient. CH 4 emission offsets were smaller in high-salinity (~7%) than in freshwater-influenced (~27%) mangroves. Carbon sequestration was disproportionally high compared with CH 4 emissions in understudied tropical areas. Low CH 4 emissions were explained by minor freshwater inputs minimizing CH 4 production in saline, high-sulfate conditions and intense CH 4 oxidation in porewaters and surface waters. CH 4 oxidation in mangrove surface waters reduced potential aquatic CH 4 emissions by 10–33%. Overall, carbon sequestration through mangrove preservation and restoration is less affected by CH 4 emissions than previously thought.