Restoration of forestry-drained oligotrophic peatlands can bring climate change mitigation within a few decades

Abstract

Introduction: Climate mitigation by peatland restoration is suggested, but data from restored forestry-drained peatlands (FDP) is sparse. Studies using surrogate emission factors from pristine peatlands have indicated a long-lasting warming effect of restoration of nutrient-poor FDPs, while restoration-specific studies are missing. Objectives: This study aims at estimating the climate mitigation potential of restoration of FDPs based on post-restoration development of vegetation and hydrology. Methods: Dynamic trajectories of green-house gas (GHG) fluxes were calculated with process-based models informed by published studies for hypothetical restoration scenarios and for 12 restored FDPs based on data of Sphagnum moss growth and water-table depth (WTD) trends. The impact of restoration on global climate forcing was modeled against scenarios of continued drainage. Results: Restoration scenarios resulted in initial warming effects, but a hummock-level scenario (deep WTD) shifted to a climate cooling effect already after 15 years of restoration. In contrast, a flark-level scenario (shallow WTD) showed increasing warming effect over 100 years. In the empirical sample, climate cooling effect was predicted in half of cases already after 10 years, and in most cases within 100 years. Restoration resulted in an average reduction of cumulative absolute global forcing by −1.77 (standard deviation 1.74) t CO2-equivalent ha−1 yr−1 over 100 years relative to continued drainage. Alternative drainage scenarios informed by historical peat carbon loss and forest management indicated even higher mitigation potential for restoration. Conclusions: Restoration-specific GHG trajectories predict considerably better mitigation potential than surrogate emission factors for restoration of oligotrophic FDPs.