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Much of the research on wetland carbon dynamics focuses on conversion to agriculture, settlements, or preservation of wetland functions, such as through conservation easements. Development of wetlands for agricultural production of upland crops tends to reduce soil carbon stocks, particularly in drained peatlands, and although methane emissions may be reduced, the overall effect is an increase in GHG activity (Buschmann et al., 2020; Lajtha et al., 2018). Nitrogen pollution can stimulate nitrous oxide emissions and is a common impairment caused by agricultural production on or around wetlands, which may be created or natural, drained, or flooded (Kritee et al., 2018). Assessments of agriculture‐related carbon losses from different soil types show that the losses from drained organic soils far outweigh carbon losses from other soil types. Carbon losses are close to zero in well managed agricultural production systems (Hristov et al., 2018).

Federal policies such as the Clean Water Act, Food Security Act, and their amendments (such as the 1989 “no net loss” wetland policy and habitat restoration efforts) stimulate wetland restoration and wetland creation. These policies also stimulate research into the effects of these conversions (Kolka et al., 2018). Restoration has mixed results in terms of its effectiveness in reducing or enhancing methane emissions and overall GHG emissions (Hemes et al., 2018). More research is needed into the most appropriate restoration methods and post‐restoration management methods for different wetland ecosystems. A meta‐analysis showed that restoring biodiversity and ecosystem services (including climate regulation and biogeochemical cycling) is variable in terms of providing desired benefit, but indicated that some key benefits provided from restored wetlands are lower than those of natural, non‐disturbed wetlands, with climate regulation services 30% lower in restored than natural wetlands (Meli et al., 2014).

In comparison with research on inland wetlands, efforts to inventory GHG emissions from tidal wetlands are relatively new, and comprehensive programs to reduce emissions are not yet developed. In recent years, a growing body of research has supported the rapidly increasing interest in the potential for GHG management in tidal wetlands (research includes Chmura et al., 2003; McLeod et al., 2011; Pendleton et al., 2012; Windham‐Myers et al., 2018; and Najjar et al., 2018). Carbon accumulation rates are particularly high in tidal wetlands and soil carbon is controlled to a significant degree by sea‐level rise (Windham‐Myers et al., 2018; McLeod et al., 2011). Under saline conditions, methanogenesis and methane emissions are suppressed by abundant sulfate from seawater (Poffenbarger et al., 2011); tidal wetlands have a long history of intensive management, resulting in substantial loss and degradation (Pendleton et al., 2012; Roman & Burdick, 2012), and thus there is significant opportunity for GHG management through restoration (Kroeger et al., 2017).

Agriculture and other land use changes are common examples of disturbances to wetland ecosystems. Tidal wetlands are also strongly affected by sea‐level rise and changes in land elevation due to subsidence and glacial rebound. Globally, tidal wetlands are lost at a rate of 0.5–3% per year (Pendelton et al., 2012). Although tidal wetlands have historically survived rising sea levels by accumulating inorganic and organic sediments, this process is threatened by the potential future rate of sea‐level rise and reduced sediment transport (sometimes due to coastal development), which has a range of ecosystem effects including changes to nutrient availability and vegetative growth (Kirwan and Megonigal, 2013). At present, ~27% of CONUS tidal wetlands have some level of impoundment and freshening due to tidal restriction, which can drive enhanced methane and carbon dioxide emission (Kroeger et al., 2017).