Carbon stock recovery and greenhouse gas shifts following wetland restoration: a global meta-analysis

Wetland restoration is widely promoted as a complementary nature-based climate solution, but its net carbon and GHG effects across wetland types and interventions remain poorly quantified at the global scale. We address this gap with a global meta-analysis spanning all major wetland types and restoration strategies. We conducted a global meta-analysis of 617 restored-altered pairs from 149 studies on five continents to assess how restoration influences major carbon stocks and greenhouse gas (GHG) fluxes relative to altered wetlands. Overall, across all wetland types studied, restoration significantly increased aboveground biomass, belowground biomass and soil carbon. Restored wetlands also exhibited significantly lower CO₂ fluxes, consistent with increased primary production and reduced aerobic decomposition following hydrological and vegetation recovery, but also higher CH₄ emissions particularly in peatlands where rewetting enhances anaerobic conditions. By contrast, neither N₂O flux (though close to) nor, particularly dissolved organic carbon concentration showed statistically significant overall changes. These global patterns were robust to sensitivity and leave-one-out analyses but varied strongly among wetland types and restoration approaches. Restored mangroves and peatlands more clearly exhibited significant biomass and soil carbon gains, whereas restored freshwater wetlands and peatlands significantly displayed strong belowground biomass and and decreases in both CO2 fluxes, though the later showed significant CH₄ flux increases. Other wetland types displayed more variable responses to restoration, if any. Hydrological restoration (mainly rewetting) produced the strongest improvements in aboveground biomass, soil carbon and N₂O flux reductions, though it significantly increased CH₄ flux. Vegetation recovery was significantly effective action increasing above- and belowground biomass, soil carbon, and decreasing CO2 fluxes. Data were dominated by studies from Asia, Europe and North America, by far made in the Northern hemisphere, highlighting major geographical gaps in Southern areas. Overall, our synthesis shows that wetland restoration reliably regenerates carbon stocks and reduces CO₂ emissions, supporting its inclusion in climate mitigation portfolios and nature-based solution frameworks. Short-term CH₄ emission increases and ecosystem-specific responses highlight the need for long-term monitoring, context-dependent restoration design and improved global coverage to optimise carbon benefits and inform on climate’s friendly restoration policies and actions.