How Plants Influence Resilience of Salt Marsh and Mangrove Wetlands to Sea-Level Rise
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REVIEW PAPER
How Plants Influence Resilience of Salt Marsh and Mangrove Wetlands to Sea-Level Rise Donald R. Cahoon 1
&
Karen L. McKee 2 & James T. Morris 3
Received: 20 May 2020 / Revised: 28 August 2020 / Accepted: 9 September 2020 # This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2020
Abstract This review evaluates the importance of plants and associated biological processes in determining the vulnerability of coastal wetlands to sea-level rise. Coastal wetlands occur across a broad sedimentary continuum from minerogenic to biogenic, providing an opportunity to examine the relative importance of biological processes in wetland resilience to sea-level rise. We explore how plants influence sediment accretion, elevation capital (vertical position in the tidal frame), and compaction or erosion of deposited material. We focus on salt marsh and mangrove wetlands, which occupy a similar physiographic niche and display similar physical and biological controls on resilience to sea-level rise. In both habitats, plants stabilize emergent mudflats and help sustain the wetland position in the tidal frame relative to ocean height through both surface and subsurface process controls on soil elevation. Plants influence soil elevations by modifying (1) mineral sediment deposition and retention, (2) organic matter contributions to soil volume, and (3) resistance to compaction and erosion. Recognition of the importance of plants in coastal wetland resilience to sea-level rise is key to accurate predictions about the future fate of salt marshes and mangrove forests and for development of effective management and restoration plans. Keywords Accretion . Elevation capital . Erosion . Resilience . Sedimentation . Wetland loss
Introduction Sea-level rise, a known consequence of global warming, will modify shorelines worldwide and cause major changes in coastal ecosystems and the human communities reliant on them (IPCC 2014). Because of their low-lying position at the landsea interface, coastal wetlands are particularly vulnerable to submergence and lateral erosion caused by rising sea level, as well as sea-level extremes and wave activity during storm surges (Nicholls 2004; Lovelock et al. 2015; Roman 2017; Leonardi et al. 2018). To persist in a particular location, these ecosystems must maintain sufficient elevation capital (vertical position in the tidal frame, see Fig. 1) by accreting at a rate equal to the Communicated by Kenneth L. Heck * Donald R. Cahoon [email protected] 1
U.S. Geological Survey, Patuxent Wildlife Research Center, Laurel, MD 20708, USA
2
U.S. Geological Survey, Wetland and Aquatic Research Center, 700 Cajundome Boulevard, Lafayette, LA 70506, USA
3
Belle Baruch Institute for Marine & Coastal Sciences, University of South Carolina, Columbia, SC 29208, USA
relative rise in sea level (Cahoon et al. 2019). Coastal wetlands must also resist lateral erosion at the seaward edge, especially if landward migration is blocked by natural or arti
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