Impact of peatland restoration on CO2 and CH4 emissions and microbial communities

Peatlands, known to be important carbon sinks, have been transformed into sources of carbon due to human activities, contributing around 1 GtCO₂ equivalents annually to global emissions. Denmark's Green Deal aims to restore 100,000 hectares of peatlands by 2030 to mitigate these emissions, with studies indicating that rewetting drained peatlands could significantly reduce greenhouse gas emissions. Microbial communities play a central role in peatland carbon cycling, driving the production of CO₂ and CH₄ through decomposition. Moreover, microbial communities are sensitive to changes in moisture conditions, particularly during dry and rewetting cycles. Previous studies show that CO₂ rose during drought but returned to control levels during rewetting, while CH₄ fluxes fell and remained suppressed throughout the rewetting period. Moreover, it has been found that microbial communities differed to a lesser extent between drained and rewetted peatland, than in drained and undrained peatlands, highlighting the importance of restoration.

Our aim in this study was to evaluate peatland restoration effectiveness in carbon sequestration and to improve the understanding of microbial controls on carbon dynamics in these ecosystems. To achieve this, we monitored CO₂ and CH₄ fluxes in restored and unrestored peatlands during spring and summer 2025, alongside assessments of microbial activity and community composition.

Preliminary results indicate that raising the water table in degraded peatlands reduces both CO₂ and CH₄ emissions, suggesting improved carbon storage following restoration. Despite decades of drainage, both sites retained high organic carbon stocks. Bacterial community composition differed more strongly between restored and unrestored sites than between seasons, and topsoil communities showed greater divergence from mid- and subsoil layers. Microbial activity analyses revealed that anoxic conditions limited bacterial growth, whereas fresh litter inputs and elevated temperatures stimulated it.

These findings deepen our understanding of how restoration influences peatland carbon processes and microbial ecology. By identifying conditions that promote carbon storage, this research supports the development of management strategies that enhance peatlands’ capacity to function as effective carbon sinks, contributing to climate change mitigation.