Challenges and Opportunities for Monitoring and Modeling Wetland Management as a Nature-based Climate Solution.

In recent years, wetland management has garnered considerable interest as a possible nature-based climate solution (NCS). Yet some of the very same features of wetlands that generate interest in their management as an NCS make it difficult to measure and model the climate impacts of such actions, including: (1) large, deep stores of soil carbon, (2) dynamic hydrology near the soil surface, (3) large lateral fluxes of carbon, (4) large non-CO2 greenhouse gas (GHG) emissions. This talk will provide specific examples of each of these challenges from recent research. Wetland soil carbon represents a large potential emission when disturbed, which is poorly characterized by current regional to global spatial data products and earth system models. These rarely account for soil carbon beyond 1 m depth or soil accretion rates of centimeters per decade. Potential emissions are also poorly characterized by flux measurements, which rarely occur in areas actively transitioning from wetlands into another land use. The dynamic hydrology of wetlands represents a potential mechanism in their management as an NCS, but also makes their spatial extent difficult to characterize via remote sensing, especially where/when groundwater tables are near the soil surface, but no surface water is present. Large fluxes of allochthonous carbon into wetlands may result in upland management increasing emissions of wetlands downslope, while large exports of carbon from wetlands into adjacent water bodies are missed by flux measurements with a "vertical bias" such as eddy-covariance and chamber-based approaches. Fluxes of non-CO2 GHGs such as methane and nitrous oxide are potentially very productive NCS targets for wetland management. However, the sensitivity of non-CO2 GHG emission rates to small variations in environmental drivers such as salinity and water level, as well as biological aspects of the wetland community, makes predicting their response to many management actions extremely difficult. Despite these many challenges, current research in wetland carbon cycle science is revealing ways to overcome such challenges and, if properly integrated into large-scale monitoring and modeling efforts, give a full accounting of wetland management as an NCS opportunity.