Evolution of Tidal Marsh Distribution under Accelerating Sea Level Rise

Mitchell, Molly; Herman, Julie; Hershner, Carl

doi:10.1007/s13157-020-01387-1

Cited by 20 publications

(16 citation statements)

References 38 publications

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“…Our study relies on tidal marsh-forest boundaries determined independently from these metrics (Molino et al 2021), allowing us to capture small-scale variability from both tidal range and salinity, despite a large study area. Our median threshold elevation (0.54 m) determined across the entire Chesapeake Bay from aerial imagery is largely in agreement with the threshold elevation determined from mean HAT in Virginia (0.61 m) (Mitchell et al 2020). However, we find that threshold elevations vary more than fivefold across our study region, from 0.20 m NAVD88 in low-salinity watersheds to 1.05 m NAVD88 in exposed, high-salinity watersheds (Fig.…”

Section: Quantifying Elevation Thresholdssupporting

confidence: 84%

“…Predictions of coastal ecosystem migration typically depend on establishing threshold elevations, beyond which inundation drives state change (Enwright et al 2016;Borchert et al 2018;Mitchell et al 2020). A single threshold elevation is often determined for large areas (e.g., county, estuary) despite potential spatial variation in the processes that control threshold elevation.…”

Section: Quantifying Elevation Thresholdsmentioning

confidence: 99%

“…higher threshold elevations (Boon et al 1977). Alternatively, previous modeling and remote sensing studies of marsh vulnerability typically assume that the upper elevation limit of marsh corresponds to astronomical tidal datums alone (e.g., highest astronomical tide [HAT]) (Thorne et al 2018;Mitchell et al 2020;Holmquist et al 2021). However, we demonstrate that salinity is also a driver of threshold elevation (Fig.…”

Section: Quantifying Elevation Thresholdsmentioning

confidence: 99%

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Variability in marsh migration potential determined by topographic rather than anthropogenic constraints in the Chesapeake Bay region

Molino¹,

Carr

Ganju

et al. 2022

Limnol Oceanogr Letters

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Sea level rise (SLR) and saltwater intrusion are driving inland shifts in coastal ecosystems. Here, we make high‐resolution (1 m) predictions of land conversion under future SLR scenarios in 81 watersheds surrounding Chesapeake Bay, United States, a hotspot for accelerated SLR and saltwater intrusion. We find that 1050–3748 km2 of marsh could be created by 2100, largely at the expense of forested wetlands. Predicted marsh migration exceeds total current tidal marsh area and is ~ 4× greater than historical observations. Anthropogenic land use in marsh migration areas is concentrated within a few watersheds and minimally impacts calculated metrics of marsh resilience. Despite regional marsh area maintenance, local ecosystem service replacement within vulnerable watersheds remains uncertain. However, our work suggests that topography rather than land use drives spatial variability in wetland vulnerability regionally, and that rural land conversion is needed to compensate for extensive areal losses on heavily developed coasts globally.

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Section: Quantifying Elevation Thresholdssupporting

confidence: 84%

Section: Quantifying Elevation Thresholdsmentioning

confidence: 99%

Section: Quantifying Elevation Thresholdsmentioning

confidence: 99%

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Variability in marsh migration potential determined by topographic rather than anthropogenic constraints in the Chesapeake Bay region

Molino¹,

Carr

Ganju

et al. 2022

Limnol Oceanogr Letters

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“…From a physical standpoint, marshes in microtidal (≤1-m tide range) settings with both a limited sediment supply and limited opportunities for inland migration are expected to experience the greatest proportional losses (Kirwan et al, 2010;Mitchell et al, 2017). Losses are likely to be exacerbated where these conditions overlap with extensive watershed development (Mitchell, Herman & Hershner, 2020).…”

Section: Introductionmentioning

confidence: 99%

Living shorelines achieve functional equivalence to natural fringe marshes across multiple ecological metrics

Isdell

Bilkovic

Guthrie

et al. 2021

PeerJ

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Nature-based shoreline protection provides a welcome class of adaptations to promote ecological resilience in the face of climate change. Along coastlines, living shorelines are among the preferred adaptation strategies to both reduce erosion and provide ecological functions. As an alternative to shoreline armoring, living shorelines are viewed favorably among coastal managers and some private property owners, but they have yet to undergo a thorough examination of how their levels of ecosystem functions compare to their closest natural counterpart: fringing marshes. Here, we provide a synthesis of results from a multi-year, large-spatial-scale study in which we compared numerous ecological metrics (including habitat provision for fish, invertebrates, diamondback terrapin, and birds, nutrient and carbon storage, and plant productivity) measured in thirteen pairs of living shorelines and natural fringing marshes throughout coastal Virginia, USA. Living shorelines were composed of marshes created by bank grading, placement of sand fill for proper elevations, and planting of S. alterniflora and S. patens, as well as placement of a stone sill seaward and parallel to the marsh to serve as a wave break. Overall, we found that living shorelines were functionally equivalent to natural marshes in nearly all measured aspects, except for a lag in soil composition due to construction of living shoreline marshes with clean, low-organic sands. These data support the prioritization of living shorelines as a coastal adaptation strategy.

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“…With sea‐level rise, the influx of more water increases wetland hydroperiod, and wetlands that cannot accrete sediment to match rapidly rising waters may drown (Kirwan and Megonigal 2013, Weston 2014). Alternately, wetlands may migrate farther upstream or into adjacent undeveloped uplands if the elevation is gradual, but those opportunities may be limited adjacent to forests (Field et al 2016) and along incised coastal plain river systems (Torio and Chmura 2013, Mitchell et al 2020). The encroaching tidal water also brings additional salt, which is a stress to many of the plant species living in low‐salinity tidal marshes (Spalding and Hester 2007, Neubauer 2013).…”

Section: Introductionmentioning

confidence: 99%

Changes in plant communities of low‐salinity tidal marshes in response to sea‐level rise

Humphreys

Gorsky

Bilkovic³

et al. 2021

Ecosphere

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As sea-level rises, low-salinity tidal marshes experience greater flooding with more saline water. In the Chesapeake Bay estuary, we compared the 1980 and 2014 tidal marsh inventories (TMIs) of plant communities from James City County, Virginia, USA, with respect to the spatial distribution of two species-the invasive reed Phragmites australis and native salt marsh grass Spartina alterniflora-plus overall species richness. Since the 1980 TMI, the total area of low-salinity tidal marshes in which P. australis occurred increased from 0.46 km 2 to 6.30 km 2 in 2014. Between TMIs, however, the total area of lowsalinity marshes occupied by S. alterniflora increased by only 0.02 km 2 . Species richness in low-salinity tidal marshes decreased from 41 to 25 between TMIs. To assess seedling emergence under increased flooding and salinity, we completed two seed bank germination experiments using soil samples collected from six low-salinity marshes containing established P. australis stands. In the first experiment, more seedlings emerged in the two low-salinity (0 vs. 5 ppt) treatments after seven weeks, irrespective of flooding (water 3.75 cm below vs. at soil surface), but no P. australis or S. alterniflora germinated. For the second experiment, we added seeds of P. australis and S. alterniflora to soils exposed to the same flooding and salinity treatments to test the impact of these plant competitors on seedling emergence. No difference in number of seedlings was detected among treatments, but the number of species and their relative abundance was significantly affected by flooding (ANOSIM, R = 0.138, P < 0.001). The presence of P. australis and S. alterniflora seedlings appeared to shift the physical factor more influential on seedling emergence from salinity to flooding. For both seed bank experiments, more seedlings but not more species emerged from soils collected from marshes where P. australis coverage was <50%. High diversity plant communities of low-salinity tidal marshes along the upper reaches of this estuary are gradually being replaced by those dominated by P. australis and S. alterniflora-a trend expected to continue here and in other riverine estuaries of the Atlantic and Gulf Coasts.

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Evolution of Tidal Marsh Distribution under Accelerating Sea Level Rise

Cited by 20 publications

References 38 publications

Variability in marsh migration potential determined by topographic rather than anthropogenic constraints in the Chesapeake Bay region

Variability in marsh migration potential determined by topographic rather than anthropogenic constraints in the Chesapeake Bay region

Living shorelines achieve functional equivalence to natural fringe marshes across multiple ecological metrics

Changes in plant communities of low‐salinity tidal marshes in response to sea‐level rise

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