Magnitudes, patterns, controls and mitigation potentials of nitrous oxide emissions across peatlands in Europe

European natural peatlands have undergone long-term anthropogenic drainage activities that have severely decreased their functions, such as carbon sequestration. Recent rewetting has been conducted to restore the ecosystem services of peatlands and mitigate the emissions of potent greenhouse gases such as nitrous oxide (N2O). However, the magnitudes and spatial patterns of annual N2O fluxes and their mitigation potentials across European peatlands remain unknown. Here, we synthesized 492 annual N2O flux data points from 77 in situ studies across European peatlands and found that the soil annual N2O fluxes varied extensively from -1.08 to 33.40 kg N2O-N ha-1 yr-1; these results were significantly and interactively (P < 0.05) affected by the peatland status, climatic regime and nutrient supply type. Drainage significantly (P < 0.05) stimulated soil N2O emissions from natural minerotrophic rather than ombrotrophic peatlands, regardless of the climatic regime. Similarly, rewetting significantly (P < 0.05) reduced soil N2O emissions from drained minerotrophic rather than ombrotrophic peatlands, demonstrating that the high N2O emissions were driven by a simultaneous decline in the water table depth and increase in the soil nitrogen (N) availability. Magnitudes of the increases or decreases in N2O emissions due to drainage or rewetting were also significantly influenced by the land-use and drainage history before rewetting and in the years following drainage/rewetting, respectively. The estimated annual mean N2O emission total was found to be 90.42 (95% confidence interval: 64.49-122.57) Gg N2O-N in 2020 from European peatlands. Scenario analysis showed that drained peatlands should be rewetted expeditiously; postponing rewetting would cause larger emissions from continued N2O emissions from drained peatlands. Fully rewetting the drained peatlands used for forestry and peat extraction and partially rewetting those used for agriculture and grassland comprise a strategy for mitigating drained peatland N2O emissions without compromising food security.