Hydrological Threshold for Optimizing Wetland Climate Mitigation

Abstract Wetland carbon cycling reflects an intrinsic balance between CO 2 sequestration and anaerobic methane production, though hydrological drivers remain insufficiently quantified. Here, we synthesize eddy covariance data from 43 natural wetlands spanning diverse climates and hydrological regimes to quantify greenhouse gas (GHG) responses to water table depth (WTD). Both net ecosystem productivity and methane fluxes exhibit consistent unimodal relationships with WTD, peaking at 50 and 60 cm above the surface, respectively. While robust in temperate wetlands, uneven data distribution limits confirming this exact unimodal pattern in tropical and boreal systems. Accounting for GHG temperature sensitivity, 500 years radiative forcing simulations reveal that near surface water tables maximize long term cooling and sustain mitigation efficacy under future warming, whereas deeper or persistently flooded conditions diminish net climate benefits. These findings provide a generalized benchmark for optimizing wetland restoration to advance nature‐based climate solutions.