Quantifying the fluxes of carbon loss from an undrained tropical peatland ecosystem in Indonesia.

Conservation of undrained tropical peatland ecosystems is critical for climate change mitigation as they store a tremendous amount of soil carbon that is preserved under anoxic water-logged conditions. Unfortunately, there are too few measurements of carbon fluxes from these ecosystems to estimate the climate change mitigation potential from such conservation efforts. Here, we measured carbon dioxide (CO) and methane (CH) fluxes as well as fluvial organic carbon export over the peat swamp forest within an undrained tropical peatland landscape in East Kalimantan, Indonesia. Our measurements throughout one year (Oct 2022-Sep 2023) showed that despite its water-logged condition, peat and water overlying the swamp forest on average emits 11.02 ± 0.49 MgCO ha yr of CO and 0.58 ± 0.04 MgCOe ha yr of CH. Further, the fluvial organic carbon export contributes to additional carbon loss of 1.68 ± 0.06 MgCOe ha yr. Our results help improve the accuracy of carbon accounting from undrained tropical peatlands, where we estimated a total carbon loss of 13.28 ± 0.50 MgCOe ha yr. Nevertheless, the total carbon loss reported from our sites is about half than what is reported from the drained peatland landscapes in the region and resulted in a larger onsite carbon sink potential estimate compared to other undrained peat swamp forests. Together, these findings indicate that conserving the remaining undrained peatland ecosystems in Indonesia from drainage and degradation is a promising natural climate solution strategy that avoids significant carbon emissions.