Ditch emissions partially offset global reductions in methane emissions from peatland drainage

Abstract

Peatlands are globally important carbon sinks but are frequently drained. Drainage activities reduce overall methane emissions; however they are often accompanied by the construction of ditches, which are potential methane emission hotspots. Yet, the offsets of methane emissions from creating ditches in peatlands under different climate zones and land-use types remain unclear. Here we conducted a global meta-analysis by compiling annual methane emissions from paired near-pristine peatlands and terrestrial portion of drained peatlands and ditches to address this issue. Results showed that ditches occupy approximately 3.8 (95% confidence interval: 3.1~4.4)% of all drained peatlands. Ditches emit 695 (511~898) kg ha−1 yr−1 methane overall, with the highest emissions observed in (sub)tropics. Globally, ditch emissions offset approximately 12 (10~14)% for reductions in methane emissions from peatland drainage. Our findings demonstrate the importance of including ditch methane emissions to quantify emission factors for regional to global peatlands affected by drainage. Peatland ditches are methane emissions hotspots that offset around 12% of the emissions reductions that result from drainage, according to a global meta-analysis of peatland studies.