Evaluating Carbon Dynamics and Carbon Credits of Peatland Restoration in Switzerland

However, due to slow biogeochemical processes, the carbon accumulation in peatlands typically occurs at a low rate. In addition, peatlands that have been degraded or drained from land-use conversion become net carbon sources, as is the case with 82 % of the peatlands in Switzerland.

Restoring drained peatlands is therefore widely recognised as a nature-based solution for carbon removal. With the development of carbon market, carbon credits from rewetting peatlands are often issued based on generalised estimates on avoided emissions. However, information on long-term greenhouse gas (GHG) exchanges in restored peatlands remains scarce, with limited spatiotemporal coverage and inconsistent outcomes likely stemming from varying climate conditions, initial states, vegetation types, and restoration approaches. Consequently, there is an urgent need to account for site-specific carbon dynamics and improve the methodologies for assessing the GHG balance when evaluating carbon credit schemes for peatland restoration.

In this study, we use simulations of the well-established Terrestrial Biosphere Model, LPX-Bern, to investigate peatland carbon dynamics in Switzerland. Combined with empirical estimates based on field measurements, the modelled peatland carbon storage from the preindustrial period to the present day is analysed under natural processes, land use, and different restoration scenarios to assess the peatland restoration potentials. The results are compared with a carbon credit scheme using max.moor, a conservative estimate on avoided emissions following rewetting according to a generalised carbon density (56 kg C m^-2) for a peatland in Niremont, Switzerland.

We demonstrate that, over a 50-year timeframe, the dynamically simulated peatland carbon storage indicates a substantial overestimation, up to 43 %, of avoided emissions by the max.moor approach for the Niremont site. This highlights the necessity of incorporating approaches with increased accuracy on estimating peatland restoration impacts on carbon dynamics and GHG exchanges. Moreover, future climate change is expected to exacerbate the uncertainties associated with these estimates. This work thus contributes to advancing the understanding of peatland restoration impacts on GHG exchanges and feedback to climate change.