Fate of methane in canals draining tropical peatlands

Abstract Tropical wetlands and freshwaters are major contributors to the growing atmospheric methane (CH 4 ) burden. Extensive peatland drainage has lowered CH 4 emissions from peat soils in Southeast Asia, but the canals draining these peatlands may be hotspots of CH 4 emissions. Alternatively, CH 4 oxidation (consumption) by methanotrophic microorganisms may attenuate emissions. Here, we used laboratory experiments and a synoptic survey of the isotopic composition of CH 4 in 34 canals across West Kalimantan, Indonesia to quantify the proportion of CH 4 that is consumed and therefore not emitted to the atmosphere. We find that CH 4 oxidation mitigates 76.4 ± 12.0% of potential canal emissions, reducing emissions by ~70 mg CH 4 m −2 d −1 . Methane consumption also significantly impacts the stable isotopic fingerprint of canal CH 4 emissions. As canals drain over 65% of peatlands in Southeast Asia, our results suggest that CH 4 oxidation significantly influences landscape-scale CH 4 emissions from these ecosystems.