Climate mitigation potential of forestry-drained peatland restoration in Finland

Restoration-specific trajectories of greenhouse-gas fluxes are needed to estimate potential climate mitigation by restoration, as reflected against scenarios of alternative land-use. I explored the case of restoration of forestry-drained peatlands (FDP) in Finland. Dynamic trajectories of GHG-fluxes were calculated informed by published studies for restoration scenarios and the trajectory models were applied for 12 restored FDPs with data of new moss layer growth and water-table depth (WTD). The impact of restoration on global climate forcing was modelled against different alternative scenarios of continued drainage. Restoration resulted in initial warming in all scenarios, but a hummock-level scenario (deep WTD) shifted to a climate cooling effect already after 15 years. In the 12-sites sample, climate cooling was predicted in half of cases after 10 years, and in most cases within 100 years. Restoration resulted in an average reduction of cumulative absolute global forcing between -2.02and -6.29 t CO2-equivalent ha-1 yr-1 over 100 years, depending on choice of alternative continued drainage scenarios. The results indicate that climate mitigation by restoration can be improved by optimizing establishment of new Sphagnum moss layer, resulting in temporarily high CO2 sequestration and likely dampening of CH4 emissions. An initial period with warming impact can be expected after restoration, but development of the Sphagnum moss layer is suggested already to indicate the onset of climate cooling impact. Realistic dynamic scenarios specific to restoration and drainage are crucial, but more studies are needed to unravel detailed process-specific input and monitoring to verify the realized impacts.