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Future changes to the carbon stock dynamics of wetlands will be driven by changes to either the plant productivity that serves as carbon inputs to these ecosystems, or by the rates of carbon loss through decomposition and combustion. The first of these is likely to be most strongly driven by CO₂ fertilization, which has increased global primary productivity substantially over the historical period (Campbell et al., 2017). The second of these is strongly driven by changes to wetland hydrology and associated anoxia, which in turn may be heavily influenced by changes in temperature, particularly in permafrost‐affected soils, and by anthropogenic disturbance, particularly in tropical peatlands.

The dynamics of wetland carbon stocks are not well captured in existing global models, and thus not well integrated into assessments of climate feedbacks arising from these ecosystems. Approaches to improving the representation of wetland carbon dynamics in these models have focused on developing sub‐grid representation of hydrology dynamics, and coupling of these to carbon cycle models, as in Kleinen et al. (2012). The high degree of fine‐scale heterogeneity in wetland carbon stocks, and the difficulty in representing these at global scales, has limited the applicability of such approaches. However, many land surface models are resolving hillslope to valley hydrological gradients, which will better enable them to represent wetland processes and the dynamics of wetland carbon within the Earth system (Fan et al., 2019).

In permafrost‐affected ecosystems, where flooding and anoxia are driven mainly by an impermeable permafrost layer, coupling of the hydrology and climate is more direct; results of such models suggest that with warming and loss of near‐surface permafrost, increased drainage may rapidly lead to loss of anoxia and increase in resulting soil decomposition rates, though such losses may trade off with reductions in CH₄ emissions, also due to the loss of anoxia (Lawrence et al., 2015). Interactions between warming trends and abrupt permafrost thaw, fire, hydrologic shifts, and resulting ecosystem changes in response to these drivers suggest additional high latitude carbon losses beyond these simple one‐dimensional vertical soil column permafrost thaw models (Turetsky et al., 2020).

In tropical peatlands, the dominant driver to carbon losses are agricultural drainage of peat forests, and increases to fire and enhance respiration that result from drainage, which are projected to generate enormous losses of carbon over the 21^st century (Warren et al., 2015). Adoption of management practices on anthropogenically disturbed peatlands to encourage anoxic conditions may strongly mitigate future carbon losses from peatlands, and such practices would be only partially offset by increases in CH₄ accompanying restoration (Gunther et al., 2020). Further feedbacks to tropical peatland carbon stocks may arise from climate change even in undisturbed peatlands, which are likely to have particularly high sensitivity to changes in precipitation and thus seasonal losses of near‐surface anoxia (Cobb et al., 2017). Linking all of these processes into mechanistic models that can be used to project interacting effects of climate, CO₂, and land use on wetland carbon stocks remains a major challenge for developing more accurate simulation models.