Carbon and nitrogen losses from degraded wetlands and methane emissions from flooded wetlands are both important sources of greenhouse gas emissions. However, the net-exchange dependence on hydrothermal conditions and wetland integrity remains unclear. Using a global-scale in situ database on net greenhouse gas exchanges, we show diverse hydrology-influenced emission patterns in CO₂, CH₄ and N₂O. We find that total CO₂-equivalent emissions from wetlands are kept to a minimum when the water table is near the surface. By contrast, greenhouse gas exchange rates peak in flooded and drained conditions. By extrapolating the current trajectory of degradation, we estimate that between 2021 and 2100, wetlands could result in greenhouse gas emissions equivalent to around 408 gigatons of CO₂. However, rewetting wetlands could reduce these emissions such that the radiative forcing caused by CH₄ and N₂O is fully compensated by CO₂ uptake. As wetland greenhouse gas budgets are highly sensitive to changes in wetland area, the resulting impact on climate from wetlands will depend on the balance between future degradation and restoration.

Zou, J., Ziegler, A.D., Chen, D. et al. Rewetting global wetlands effectively reduces major greenhouse gas emissions. Nat. Geosci. 15, 627–632 (2022). https://doi.org/10.1038/s41561-022-00989-0