Greenhouse gas and climate effects of global wetland restoration under future warming

Wetland restoration is a promising nature-based climate solution because it enhances carbon sequestration and avoids carbon dioxide (CO2) emissions from drained soils. However, wetlands also emit methane (CH4), which can offset these benefits. The combined impacts of wetland protection and restoration and climate-driven changes on global wetland GHG budgets remain poorly quantified. Here, we estimate CO2 and CH4 fluxes from drained and restored wetlands, and their climate impacts, using historically reconstructed wetland area, outputs from eight CMIP6 Earth System Models and the FaIR reduced-complexity climate model. We compare protection of present-day wetlands with restoration of historically drained wetlands by 2050, under two contrasting warming pathways. By 2100, global wetland CH4 emissions increase by 11%–57% across scenarios, with the largest rise under high warming and restoration. Restoration strengthens carbon sequestration and avoids ongoing emissions from drained soils, improving the net ecosystem carbon balance by 0.4–0.6 Gt C yr−1 , equivalent to a mitigation potential of 1.6–2.3 Gt CO2 yr−1 . Accounting for CH4 warming, restoration reduces net GHG fluxes by up to 0.5 Gt CO2-eq yr−1 relative to protection alone. Carbon gains dominate in the Northern Hemisphere, whereas enhanced CH4 partially offset benefits in tropical and Southern Hemisphere regions. Climate simulations indicate that increased CO2 uptake and avoided drainage emissions offset higher CH4 emissions, producing a small net cooling (−0.03 to −0.007°C). Overall, large-scale wetland restoration provides clear carbon and GHG benefits, though the global temperature impact is modest, highlighting the importance of CO2-CH4 trade-offs.