From Drainage to Rewetting—Soil Transformations in European Agricultural Peatlands: A Review

European peatlands have been extensively drained for agriculture, resulting in substantial carbon losses and widespread soil degradation. Peatland restoration is therefore a global priority, with rewetting recognised as a key strategy for mitigating greenhouse gas emissions and climate change. This review synthesizes current knowledge on soil transformations following the rewetting of agriculturally drained peatlands in Europe. We describe major degradation processes induced by drainage, including land subsidence, organic matter oxidation, and microbial community shifts from anaerobic to aerobic conditions. We then examine key rewetting approaches—ditch blocking, controlled flooding, and paludiculture—and their intended restoration outcomes. Rewetting fundamentally alters soil physical, chemical, and biological properties by raising and stabilizing water tables, restoring anoxic conditions, and modifying nutrient cycling and microbial processes. Findings indicate long-term stabilization of organic carbon in peat soils under anaerobic conditions, but also reveal trade-offs between reduced CO2 emissions and increased CH4 and N2O fluxes. Vegetation–soil interactions strongly influence recovery trajectories, and paludiculture offers potential to align agricultural land use with climate mitigation objectives. Finally, we evaluate current research methodologies and identify major knowledge gaps, including limited long-term data and insufficient integration of hydrological, chemical, and biological processes. We highlight priorities for future research to support evidence-based rewetting strategies that deliver climate benefits while maintaining ecological and economic sustainability in European peatlands.