Prompt rewetting of drained peatlands reduces climate warming despite methane emissions

Abstract

Peatlands are strategic areas for climate change mitigation because of their matchless carbon stocks^1–4. Drained peatlands release this carbon to the atmosphere as carbon dioxide (CO₂) ^5,6. Peatland rewetting effectively stops these CO₂ emissions^7,8 but also re-establishes the emission of methane (CH₄) ^9,10. Essentially, management must choose between CO₂ emissions from drained or CH₄ emissions from rewetted peatland. This choice must consider the radiative effects as well as the atmospheric lifetimes of both gases, with CO₂ being a weak but persistent and CH₄ a strong but short-lived greenhouse gas¹¹. The resulting climatic effects are, thus, strongly time-dependent. Yet, common metrics like global warming potential (GWP) and its ‘sustained flux’ variants^12,13 fail to account for temporal dynamics and how these relate to expected global warming dynamics.

We used a radiative forcing model to compare forcing dynamics of global scenarios for future peatland management using areal data from the Global Peatland Database¹⁴. Our results show that CH₄ radiative forcing does not undermine the climate change mitigation potential of peatland rewetting. Instead, postponing rewetting increases the long-term warming effect of continued CO₂ emissions. Unlike CO₂ (and N₂O) from drained peatlands that accumulates in the atmosphere, possible CH₄ emission spikes upon rewetting do not add to expected peak warming when rewetting occurs before 2050. Warnings against high CH₄ emissions from rewetted peatlands⁹ are therefore unjustified.