Managing the Global Wetland Methane‐Climate Feedback: A Review of Potential Options

ABSTRACT Methane emissions by global wetlands are anticipated to increase due to climate warming. The increase in methane represents a sizable emissions source (32–68 Tg CH4 year−1 greater in 2099 than 2010, for RCP2.6–4.5) that threatens long‐term climate stability and poses a significant positive feedback that magnifies climate warming. However, management of this feedback, which is ultimately driven by human‐caused warming and thus “indirectly” anthropogenic, has been largely unexplored. Here, we review the known range of options for direct management of rising wetland methane emissions, outline contexts for their application, and explore a global scale thought experiment to gauge their potential impact. Among potential management options for methane emissions from wetlands, substrate amendments, particularly sulfate, are the most well studied, although the majority have only been tested in laboratory settings and without considering potential environmental externalities. Using published models, we find that the bulk (64%–80%) of additional wetland methane will arise from hotspots making up only about 8% of global wetland extent, primarily occurring in the tropics and subtropics. If applied to these hotspots, sulfate might suppress 10%–21% of the total additional wetland methane emissions, but this treatment comes with considerable negative consequences for the environment. This thought experiment leverages results from experimental simulations of sulfate from acid rain, as there is essentially no research on the use of sulfate for intentional suppression of additional wetland methane emissions. Given the magnitude of the potential climate forcing feedback of methane from wetlands, it is critical to explore management options and their impacts to ensure that decisions made to directly manage—or not manage—this process be made with the best available science. Methane emissions from wetlands are rising due to climate change and contribute to a feedback loop that further amplifies global warming. Management of these additional emissions from wetlands has not been widely explored, despite this representing a large fraction of “indirectly” human‐caused emissions. Here, we review studies of methane management in wetlands and model the hypothetical use of sulfate in hotspots of the wetland methane feedback (noting uncertainties and externalities). Overall, there needs to be more research on mitigation options of these indirect emissions or more rapid reduction