Fate of methane in canals draining tropical peatlands

Tropical wetlands and freshwaters are major contributors to the growing atmospheric methane (CH₄) burden. Extensive peatland drainage has lowered CH₄ emissions from peat soils in Southeast Asia, but the canals draining these peatlands may be hotspots of CH₄ emissions. Alternatively, CH₄ oxidation (consumption) by methanotrophic microorganisms may attenuate emissions. Here, we used laboratory experiments and a synoptic survey of the isotopic composition of CH₄ in 34 canals across West Kalimantan, Indonesia to quantify the proportion of CH₄ that is consumed and therefore not emitted to the atmosphere. We find that CH₄ oxidation mitigates 76.4 ± 12.0% of potential canal emissions, reducing emissions by ~70 mg CH₄ m^-2 d^-1. Methane consumption also significantly impacts the stable isotopic fingerprint of canal CH₄ emissions. As canals drain over 65% of peatlands in Southeast Asia, our results suggest that CH₄ oxidation significantly influences landscape-scale CH₄ emissions from these ecosystems.