The impact of disturbed peatlands on river outgassing in Southeast Asia

River outgassing has proven to be an integral part of the carbon cycle. In Southeast Asia, river outgassing quantities are uncertain due to lack of measured data. Here we investigate six rivers in Indonesia and Malaysia, during five expeditions. CO 2 fluxes from Southeast Asian rivers amount to 66.9±15.7 Tg C per year, of which Indonesia releases 53.9±12.4 Tg C per year. Malaysian rivers emit 6.2±1.6 Tg C per year. These moderate values show that Southeast Asia is not the river outgassing hotspot as would be expected from the carbon-enriched peat soils. This is due to the relatively short residence time of dissolved organic carbon (DOC) in the river, as the peatlands, being the primary source of DOC, are located near the coast. Limitation of bacterial production, due to low pH, oxygen depletion or the refractory nature of DOC, potentially also contributes to moderate CO 2 fluxes as this decelerates decomposition. Due to increasing disturbance of peatlands, Southeast Asian rivers are thought to play a major role in the transfer of CO 2 to the atmosphere. Here, the authors present data collected from six Indonesian and Malaysian rivers and show that the region is not an outgassing hotspot as previously assumed.