Delineation of Tidal Wetlands Boundaries in Lower Chesapeake Bay and Its Tributaries

Boon, John D.; Boule, Mark E.; Silberhorn, Gene

doi:10.21220/v50160

Cited by 3 publications

(4 citation statements)

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“…Consistent with this conceptual framework, we find that threshold elevations increase with salinity (Figure 3b), and that salinity is a key driver of threshold elevation in the multiple linear regression model (Table 1). Within the Atlantic coastal lagoon watersheds, which have the highest salinities in our study region (Figure 2b), exposure to highly saline waters from salt spray during storms measurably deviated the elevation of the coastal treeline from that expected by tidal range alone (Boon et al, 1977). In low salinity and low slope environments, representative of watersheds interspersed throughout our study region (Figures 2a and 2b), shading from plants has been shown to reduce evapotranspiration and facilitate forest regeneration, extending the lower limit of terrestrial forest, irrespective of increases in sea level rise and tidal inundation (Poulter et al, 2009;Veldkornet et al, 2015).…”

Section: Tablementioning

confidence: 84%

“…These ecosystems are arranged in patterns largely set by elevation relative to position within the tidal frame (Brinson et al, 1995;Oertel, 1985). However, the elevation of transition from marsh to coastal forest, or threshold elevation, deviates from what is expected based on tidal datums due to complex interactions between other physical and biotic variables (Boon et al, 1977). Climate change adds a global-scale driver of threshold elevation as accelerating rates of global sea level rise (SLR) shift the marsh-forest boundary landward, but it remains unclear how local variables will interact to mediate the degree of change (Poulter et al, 2009;Robichaud & Begin, 1997).Untangling the interactions between global drivers and local factors is central to understanding the process of upland conversion to marsh.…”

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confidence: 99%

“…Most seedlings and saplings are unable to tolerate even brief inundation by saline water, preventing forest regeneration years before mature trees die (Brinson et al, 1995;Williams et al, 1999). Salt spray during storms can further limit trees to elevations higher than those regularly inundated from tides (Boon et al, 1977;Robichaud & Begin, 1997). Saturated soils and salt-stress increase forest vulnerability to disturbance events, such as storms, which are responsible for large-scale forest dieback events (Ury et al, 2021).…”

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confidence: 99%

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Biophysical Drivers of Coastal Treeline Elevation

Molino,

Carr,

Ganju

et al. 2023

JGR Biogeosciences

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Sea level rise is leading to the rapid migration of marshes into coastal forests and other terrestrial ecosystems. Although complex biophysical interactions likely govern these ecosystem transitions, projections of sea level driven land conversion commonly rely on a simplified “threshold elevation” that represents the elevation of the marsh‐upland boundary based on tidal datums alone. To determine the influence of biophysical drivers on threshold elevations, and their implication for land conversion, we examined almost 100,000 high‐resolution marsh‐forest boundary elevation points, determined independently from tidal datums, alongside hydrologic, ecologic, and geomorphic data in the Chesapeake Bay, the largest estuary in the U.S. located along the mid‐Atlantic coast. We find five‐fold variations in threshold elevation across the entire estuary, driven not only by tidal range, but also salinity and slope. However, more than half of the variability is unexplained by these variables, which we attribute largely to uncaptured local factors including groundwater discharge, microtopography, and anthropogenic impacts. In the Chesapeake Bay, observed threshold elevations deviate from predicted elevations used to determine sea level driven land conversion by as much as the amount of projected regional sea level rise by 2050. These results suggest that local drivers strongly mediate coastal ecosystem transitions, and that predictions based on elevation and tidal datums alone may misrepresent future land conversion.

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Section: Tablementioning

confidence: 84%

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confidence: 99%

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confidence: 99%

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Biophysical Drivers of Coastal Treeline Elevation

Molino,

Carr,

Ganju

et al. 2023

JGR Biogeosciences

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“…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).…”

Section: Quantifying Elevation Thresholdsmentioning

confidence: 99%

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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