Barrier island migration dominates ecogeomorphic feedbacks and drives salt marsh loss along the Virginia Atlantic Coast, USA

Deaton, Charles; Hein, Christopher J.; Kirwan, Matthew L.

doi:10.1130/g38459.1

Cited by 58 publications

(59 citation statements)

References 33 publications

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“…Increased variance in rates of marsh–upland conversion identified here is consistent with a shift in the system toward increasing rates of landward barrier island migration, a change that has been recognized in other recent work (Deaton et al, ). At the same time, the expansion of woody vegetation is creating new ecological scenarios (e.g., monotypic thickets that dominate the landscape) that have not been present historically.…”

Section: Discussionsupporting

confidence: 89%

“…Understanding connectivity of sediment via the transport of sediment across multiple habitat types on barrier islands is essential in improving future predictions of coastal response to climate change, especially given the various drivers that can alter the system. Recently, it was demonstrated that connection between the upland and backbarrier environment plays as an important in the maintenance of barrier island–marsh systems (Walters et al, ), and is an innovative framework for assessing barrier system stability over the past 150 years (Deaton et al, ) and sediment mobility during storms (Houser, Hapke, & Hamilton, ). Here, we fill a knowledge gap by extending the framework of coupled ecosystems identified in previous work by considering how upland vegetation affects the conversion of backbarrier marsh into barrier island upland along the VBI.…”

Section: Introductionmentioning

confidence: 99%

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Connectivity in coastal systems: Barrier island vegetation influences upland migration in a changing climate

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Nettleton

et al. 2019

Global Change Biology

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Due to their position at the land–sea interface, barrier islands are vulnerable to both oceanic and atmospheric climate change‐related drivers. In response to relative sea‐level rise, barrier islands tend to migrate landward via overwash processes which deposit sediment onto the backbarrier marsh, thus maintaining elevation above sea level. In this paper, we assess the importance of interior upland vegetation and sediment transport (from upland to marsh) on the movement of the marsh–upland boundary in a transgressive barrier system along the mid‐Atlantic Coast. We hypothesize that recent woody expansion is altering the rate of marsh to upland conversion. Using Landsat imagery over a 32 year time period (1984–2016), we quantify transitions between land cover (bare, grassland, woody vegetation, and marsh) and the marsh–upland boundary. We find that the Virginia Barrier Islands have both gains and losses in backbarrier marsh and upland, with 19% net loss from the system during the timeframe of the study and increased variance in marsh to upland conversion. This is consistent with recent work indicating a shift toward increasing rates of landward barrier island migration. Despite a net loss of upland area, macroclimatic winter warming resulted in 41% increase in woody vegetation in protected, low‐elevation areas, introducing new ecological scenarios that increase resistance to sediment movement from upland to marsh. Our analysis demonstrates how the interplay between elevation and interior island vegetative cover influences landward migration of the boundary between upland and marsh (a previously underappreciated indicator that an island is migrating), and thus, the importance of including ecological processes in the island interior into coastal modeling of barrier island migration and sediment movement across the barrier landscape.

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Connectivity in coastal systems: Barrier island vegetation influences upland migration in a changing climate

Zinnert

Via

Nettleton

et al. 2019

Global Change Biology

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“…Deaton et al () show that under some circumstances the sediment input and basin geometry do not allow a back‐barrier marsh to prograde as quickly as the associated barrier island is migrating, ultimately resulting in loss of the back‐barrier marsh due to burial of the marsh by the island. However, given the interdependencies between barrier islands and back‐barrier marshes, increased resilience for back‐barrier marshes, even if only temporary, has important implications for barrier islands.…”

Section: Discussionmentioning

confidence: 99%

Effects of Marsh Edge Erosion in Coupled Barrier Island‐Marsh Systems and Geometric Constraints on Marsh Evolution

et al. 2018

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Previous results show that overwash provides an important sediment source to back‐barrier marshes, sustaining a narrow marsh state under conditions in which marsh drowning would otherwise occur. We expand the coupled barrier island‐marsh evolution model GEOMBEST+ to explore the effects of wind waves on back‐barrier marshes. We find that the addition of marsh edge erosion leads to wider, more resilient marshes and that horizontal erosion of the marsh edge is a more efficient sediment source than vertical erosion of the marsh surface as it drowns. Where marshes and bays are vertically keeping up with sea level, and the net rate of sediment imported to (or exported from) the basin is known, the rate of marsh edge erosion or progradation can be predicted knowing only the present basin geometry, sea level rise rate, and the net rate of sediment input (without considering the erosion or progradation mechanisms). If the rate of sediment input/export is known, this relationship applies whether sediment exchange with the open ocean is negligible (as in basins dominated by riverine sediment input) or is significant (including the loss of sediment remobilized by waves in the bay). Analysis of these results reveals that geometry and stratigraphy can exert a first‐order control on back‐barrier marsh evolution and on the marsh‐barrier island system as a whole and provides new insights into the resilience of back‐barrier marshes and on the interconnectedness of the barrier‐marsh system.

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“…In this study, we quantify dispersal in a spatially disconnected system, where long-distance events contribute to woody encroachment. As islands become reduced in size, inter-island distance is increasing , Deaton et al 2017.…”

Section: Introductionmentioning

confidence: 99%

Interaction of seed dispersal and environmental filtering affects woody encroachment patterns in coastal grassland

et al. 2019

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Encroachment of woody plants into grasslands has occurred worldwide and includes coastal ecosystems. This conversion process is mediated by seed dispersal patterns, environmental filtering, and biotic interactions. As spatiotemporally heterogeneous, harsh environments, barrier islands present a unique set of challenges for dispersal and establishment. Environmental conditions act as filters on dispersed seeds, thereby influencing encroachment and distribution patterns. Seldom have patterns of propagule dispersal been considered in the context of woody encroachment. We quantified dispersal and post‐dispersal processes of an encroaching woody population of Morella cerifera relative to directional rate of encroachment and observed distribution patterns on an Atlantic coastal barrier island with strong environmental filtering. We analyzed historic foredune elevation as a proxy for reduced interior environmental stress. The dispersal kernel was leptokurtic, a common characteristic of expanding populations, but rate of encroachment has slowed since 2005. Expansion pattern was related to foredune elevation, which limits encroachment below a threshold elevation. This difference between dispersal kernel behavior and encroachment rate is due to limited availability of suitable habitat for Morella and temporal variability in chlorides during the time of germination. Our results demonstrate that processes mediating seeds and seedling success must be accounted for to better understand establishment patterns of encroaching woody plants.

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Barrier island migration dominates ecogeomorphic feedbacks and drives salt marsh loss along the Virginia Atlantic Coast, USA

Abstract: *-note that Table DR1 only contains data sources used to map marsh and open water areas. We direct the reader to Himmelstoss et al. (2010) for a list of the sources used in that study to compile the shoreline dataset (of which we used the "Delmarva south" portion in this study).

Cited by 58 publications

References 33 publications

Connectivity in coastal systems: Barrier island vegetation influences upland migration in a changing climate

Connectivity in coastal systems: Barrier island vegetation influences upland migration in a changing climate

Effects of Marsh Edge Erosion in Coupled Barrier Island‐Marsh Systems and Geometric Constraints on Marsh Evolution

Interaction of seed dispersal and environmental filtering affects woody encroachment patterns in coastal grassland

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