Samuli Launiainen, Anssi Ahtikoski, Janne Rinne, Paavo Ojanen, Hannu Hökkä

Rewetting of drained peatland forests restores ecosystem functions and improves peatland ecological status. It is also considered to mitigate climate change, yet some studies challenge this view Recently, Laine et al. (2024, Restoration Ecology, 32(7), p.e14213) considered feasible restoration outcomes of boreal forestry drained peatlands and proposed that rewetting nutrient-rich peatland forests can yield immediate climate benefits. They, however, focused only on the change of soil greenhouse gas balance following rewetting. Here, we extend their analysis by including tree stand carbon sink-source dynamics, direct radiative forcing by albedo change, and broaden the system boundaries to include wood product carbon storage. We show that restoring nutrient-rich drained boreal peatland forests contributes to climate warming in short- and medium term (<200 yr), except in specific cases when tree stand carbon storage is preserved. Rewetting nutrient poor boreal peatland forests yield to persistent warming impact. Results show that ecological benefits of rewetting drained boreal forest peatlands have a climate cost, and rewetting is unlikely to mitigate climate change in the timescale commensurate with that of, e.g., EU climate goals.