Project leaders: Prof. Dr. Julia Pongratz (Ludgwigs Maximilians University München), Dr. Wolfgang Obermeier (Ludwig Maximilians University München)

Related to their very high C densities, emissions from global peatland drainage may cumulate to around 80 Pg C, if no further areas are exploited (Leifeld and Menichetti 2018). This corresponds to annual GHG emissions of 1.91 (0.31-3.38) GtCO2-eq, mostly emitted as CO2, that could be reduced or even averted by peatland restoration via rewetting - making it a key yet often underappreciated climate change mitigation option (Leifeld and Menichetti 2018). Despite the clearly beneficial effects of stopping (long-lasting) CO2 emissions from drained peatlands, effects of rewetting drained peatlands on climate are complex and go beyond the often-discussed CO2 fluxes. Biogeophysical effects need to be considered in parallel to changes in GHG fluxes. Land cover conversions and modifications such as those imposed by peatland rewetting alter vegetation and surface properties (albedo, roughness, evaporative efficiency), affecting the exchange of momentum, energy and water and thus local, regional and global climate (Pongratz et al. 2021). Vice versa, climatic changes (particularly, rising air temperatures and an increased frequency and intensity of individual and compound extreme weather events) and local hydrological conditions (particularly, water table height) strongly impact ecosystem functioning and thus, resilience in peatlands as well as the net C balance (e.g. Antala et al. 2022). Further, biodiversity and the provisioning of ecosystem services such as food, fiber and bioenergy production should not be compromised, requiring adapted and multifunctional land use practices (e.g., paludiculture; Wichtmann et al. 2016). C5 will incorporate peatland specific vegetation, hydrological and soil properties via in-situ-based parametrization and a cross-scale hybrid modelling framework into a Dynamic Global Vegetation Model (DGVM, namely JSBACH4). By linking biogeochemical as well as local and nonlocal biogeophysical effects, we will be able to develop a tool for a comprehensive assessment of the contribution of temperate fen rewetting to mitigation of and adaptation to climate change. By conducting simulations using different global climate scenarios, we further address the uncertainties associated with the climate change mitigation potential of peatland rewetting, with a particular focus on the impacts of individual and compound extreme events and legacy effects, as well as adaptation options.