Coastal wetlands have two dimensions of vulnerability to sea-level rise (SLR), a vertical one, in cases where SLR outpaces their capacity to vertically accrete, and a lateral one, in cases where they are restricted from migrating inland by topography and land use. We conducted a meta-analysis of accretion rate, contemporaneous SLR, and other covariate data and used model intercomparison techniques to generate a vertical resilience index, a function of local SLR, tidal range, and tidal elevation category for the tidal wetlands of the contiguous United States. We standardized our analysis by using only 137Cs based estimates of sediment accretion. We paired the vertical resilience index with a lateral resilience index made up of elevation, water level, and land cover maps, then projected them both into the future using localized SLR scenarios. At the regional scale, the vertical resilience index predicts changes from marsh aggradation to submergence for the coastal US mid-Atlantic, Southeast, and portions of the Northeast by 2100. At the sub-regional scale, there is a geographic tradeoff between vertical and lateral resilience with more northerly wetlands vulnerable to the lack of suitable proportional area to migrate into, and more southerly wetlands vulnerable to accretion deficit. We estimate between 43% to 48% of existing contiguous US wetland area, almost entirely located in watersheds along the Gulf of Mexico and mid-Atlantic coasts, is doubly vulnerable, subject to both vertical and lateral limitations. These vertical and lateral resilience indices could help direct future research, planning and mitigation efforts at a national scale, as well as supplement more processed informed approaches by local planners and practitioners.
This data release contains tables for: 1. the full meta-analysis including all dating types, 2. gauge-level derived flow-weighted average suspended sediment concentration data used in the analysis, 3. detailed information on a subset of radiocesium dated cores used in linear modeling, 4. a table of derived relative sea-level rise and modeled vertical resilience indices for tide gauges, and 5. intermediate watershed level summaries of vertical and lateral resilience ratios.
RCN: Building a Collaborative Network for Coastal Wetland Carbon Cycle Synthesis