Abstract
AbstractGlobal assessments predict the impact of sea-level rise on salt marshes with present-day levels of sediment supply from rivers and the coastal ocean. However, these assessments do not consider that variations in marsh extent and the related reconfiguration of intertidal area affect local sediment dynamics, ultimately controlling the fate of the marshes themselves. We conducted a meta-analysis of six bays along the United States East Coast to show that a reduction in the current salt marsh area decreases the sediment availability in estuarine systems through changes in regional-scale hydrodynamics. This positive feedback between marsh disappearance and the ability of coastal bays to retain sediments reduces the trapping capacity of the whole tidal system and jeopardizes the survival of the remaining marshes. We show that on marsh platforms, the sediment deposition per unit area decreases exponentially with marsh loss. Marsh erosion enlarges tidal prism values and enhances the tendency toward ebb dominance, thus decreasing the overall sediment availability of the system. Our findings highlight that marsh deterioration reduces the sediment stock in back-barrier basins and therefore compromises the resilience of salt marshes.
Highlights
Salt marshes provide critical ecosystem services (Costanza et al, 1997)
We extend the results of Donatelli et al (2018b) for Barnegat Bay–Little Egg Harbor estuary to the other five back-barrier bays, and we argue that the effect of marsh loss on the stability of the remaining salt marshes depends on the extent of the eroded marsh area with respect to the basin size
This study shows that marsh resilience to negative stressors might be compromised even by small percentages of marsh lateral erosion, because the relationship between marsh areal extent and marsh sediment trapping capacity is strongly nonlinear
Summary
Salt marshes provide critical ecosystem services (Costanza et al, 1997). In recent years, salt marshes have been the focus of many restoration plans built on the concept of “naturebased solutions” for flood defenses that aim to use vegetated surfaces to protect coastal communities from storms (Temmerman et al, 2013). Projections of salt marsh response to climate change are variable, with initial studies suggesting a 46%–59% reduction of the present-day area by 2100 CE under moderate sea-level rise (Spencer et al, 2016), and more
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