Peatland restoration can provide climate change mitigation over all time-scales: A UK case-study

Peatlands provide one of the largest terrestrial carbon stocks in the UK. However, a large proportion of peatlands are drained for peat extraction, agriculture and other uses, turning them into a major source of the UKs land use greenhouse gas (GHG) emissions. Successful restoration can ultimately return peatlands into carbon sinks. However, rewetting - the primary step in peatland restoration - can reduce CO2 emissions while increasing CH4 emissions. This may result in little overall climate benefit, or even increased warming for several years post peatland restoration, as CH4 is a short-lived but strong GHG, and may overpower the reduction in CO2. Such consequences are rarely explored in detail, since most studies are based on comparing total CO2-equivalent emissions pre- and post-restoration using the 100-year Global Warming Potential (GWP100), which can fail to reveal the full dynamics. We evaluated the emissions and resultant climate impacts from peatland restoration using data from The Wildlife Trusts, a federation of UK-based conservation charities, as a case-study. The total emissions of each restoration stage were estimated by multiplying peatland areas under restoration with up-to-date UK emission factors (EF), then compared under multiple pulse emission metrics (GWP100, GWP20, GTP100) to indicate the impacts over a range of time-horizons, and GWP* to reveal the varying warming impacts over time. We also used Monte-Carlo Simulation to investigate the uncertainties in total emissions drawing from EF ranges. We found that the restoration so far has provided large emission reductions under all metrics, even considering the uncertainties. Increased CH4 is unlikely to cause extra warming in the extremely near-term (<20 years), and if the peatlands are maintained in their rewetted states, they can contribute to net-cooling in the long term. There is less certainty over the climate benefits of further restoration, from rewetted to "near-natural" states, especially in the shorter term, but we argue that any risks are low, while this continued restoration will provide further ecological benefits and support biodiversity. Our study lends further support for peatland restoration in the UK and other regions with similar habitats, and provides insight into the climate roles of peatlands more broadly.