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Wetlands can export particulate organic carbon (POC) through erosion, hydrologic transport, feeding activities, and direct anthropogenic activities including peat extraction and timber harvesting. Once POC is mobilized, its fate depends on the chemistry of the exported carbon and the environment to which it is transported. In some cases, POC can be redistributed and stored in aquatic sediments or even redeposited back onto the wetland (Hopkinson et al., 2018). However, when POC is solubilized or mineralized to CO₂ or CH₄, a large fraction is likely to be returned to the atmosphere (e.g., Brown et al., 2019) and the wetland could change from a net carbon sink to a source (Pawson et al., 2012). A related question concerns the fate of soil carbon in coastal wetlands that are drowned by rising sea levels: Will the soil and its preserved carbon stay intact after the vegetation is lost or will it be eroded and dispersed? This is an area of much uncertainty (e.g., DeLaune & White, 2012; Needelman, Emmer, Emmett‐Mattox, et al., 2018; Pendleton et al., 2012).

Erosion of tidal marshes, peatlands, and other wetlands can represent an important vector for the transport of soil carbon into adjacent aquatic systems. The potential importance of POC exports via erosion can be inferred from metrics like the drainage density (that is, km of channel per km² of wetland) or the extent of wetland edge (Pawson et al., 2012). There is abundant evidence that aboveground plant biomass can reduce erosion by dissipating turbulence and wave energy, even under storm surge conditions (Duarte et al., 2013; Gedan et al., 2011; Möller et al., 2014). Belowground, the network of intact roots and rhizomes helps bind soils, increasing their shear strength and resistance to erosion (Micheli & Kirchner, 2002). Thus, reductions in plant biomass – aboveground or belowground – can make the wetland more susceptible to erosion and losses of particulate organic carbon (Deegan et al., 2012; Shuttleworth et al., 2015; Silliman et al., 2012; Walter et al., 2006). Surface soils in wetlands can be mobilized by rain events (Mwamba & Torres, 2002; Tolhurst et al., 2006). Marsh biota can also facilitate erosion, either directly through activities like bioturbation (S. M. Smith & Green, 2013) or indirectly through grazing that removes the stabilizing influence of wetland vegetation (T. J. Smith & Odum, 1981; Visser et al., 1999).

Particulate organic carbon can be exported as water moves across wetland surface or as the biomass of consumers that feed in the wetland. In tidal wetlands, for example, large accumulations of dead plant material (“wrack”) can be redistributed within a wetland or exported to the estuary, especially during spring tides and large storms (Hackney & Bishop, 1981; Hemminga et al., 1990). Aquatic, terrestrial, and avian consumers are able to forage on the wetland surface, consuming organic matter and removing it when they leave the wetland (Fritz & Whiles, 2018; Gurney et al., 2017; Kitti et al., 2009; Klopatek, 1988; Wantzen et al., 2002), but this likely does not impact long‐term carbon preservation.

Lastly, POC can be lost from wetlands through directed anthropogenic activities. The extraction of peat for fuel and horticultural purposes removes the preserved soil carbon and results in the emission of CO₂ back to the atmosphere through combustion or decomposition (Cleary et al., 2005). Further, peat extraction typically destroys the living vegetation, resulting in the loss of the wetland carbon sink (Waddington et al., 2010). The logging of forested wetlands can be specifically for harvesting timber (Hutchens et al., 2004) or may be incidental to preparing a site for agriculture or aquaculture (Page et al., 2009; Richards & Friess, 2016). Some wetlands are used directly for grazing of livestock or the plants are harvested for off‐site use (Harrison et al., 2017; Morris & Jensen, 1998; D. C. Smith et al., 1989). Whenever significant amounts of primary production are removed, wetland soil carbon pools and long‐term preservation rates can be affected (Morris & Jensen, 1998).