Methane emissions from canals draining tropical peatlands: Constraining temporal variability and emissions pathways

Abstract

Drainage canals are potential hotspots of methane (CH ₄ ) emissions from degraded peatlands in Southeast Asia. Estimates of CH ₄ emissions from these canals remain scarce, and both the temporal variability and pathways of CH ₄ emissions are uncertain. Here, we present a year‐round study of CH ₄ emissions from canals draining peatlands in Southeast Asia. We quantified diffusive and ebullitive fluxes and tracked canal CH ₄ dynamics by measuring δ ¹³ C‐CH ₄ . Diffusion was the primary pathway of CH ₄ fluxes throughout the year, accounting for > 80% of net CH ₄ emissions. Periods of low rainfall limited CH ₄ oxidation and enhanced diffusive CH ₄ emissions, particularly in canals blocked to rewet the adjacent peat soils. By synthesizing data from past studies, we find an apparent decrease in canal CH ₄ emissions with time following peatland drainage. Our results highlight the importance of considering seasonal to decadal variation in efforts to include drainage canals in the global CH ₄ budget.