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Better understanding the effects of hurricane waves and storm surges on barrier-island breaching is important for both scientific research and coastal hazard mitigations. In this study, the 2D non-hydrostatic Xbeach model has been applied to investigate interactions of hurricane wave, storm surge, and morphological processes in the case study of St. Joseph Peninsula during Category 5 Hurricane Michael. Model validations show a 2.45% average error and the 0.88 skill score between modeled and observed high water marks and bed elevations, respectively. Analysis of spatial distributions of currents and water levels indicates that a narrow area was overtopped at peak storm surge and wave. The gap was then quickly enlarged as the breaching area by wave-surge actions. By investigating foredune and peak dune along the central axis of breaching area, it shows that the foredune erosion on the ocean-side by wave-surge-current directly lead to the breach of the peak dune area in the barrier island. The Froude number shows a strong correlation with quick erosion of the barrier, indicating wave-surge supercritical flow is one of the major factors causing the barrier breaching. Results of cross sections of bed elevations and instantaneous surge-wave profiles at different storm surge stages reveal the evolution of the barrier-island breach. Results from this study provide valuable references for coastal hazard mitigation and resilience communities. Highlights: Application of non-hydrostatic Xbeach model reveals barrier-island breaching process and wave-surge-barrier interactions. Model validations show a 2.45% average error and the 0.88 skill score for high water marks and bed elevations, respectively. The breach started with a narrow gap overtopped in the peak of storm surge and was then quickly enlarged by wave-surge actions. Wave-surge induced supercritical flow is one of the major factors accelerating the barrier breaching. Foredune erosion by wave-surge-current is another factor that accelerates the breach of the barrier island. [ABSTRACT FROM AUTHOR]

Simple Summary: In human-dominated areas where top predators no longer occur, interactions among medium-sized predators can be complex, especially when considering how they share space and time based on seasonal changes in food and habitat. We studied this using camera traps placed in various habitats from February 2021 to July 2023, at Fort De Soto County Park, a barrier island complex located in west central Florida. Three species of mammals (coyotes, raccoons, and Virginia opossums) were the most frequently photographed. Our analysis showed that during the wet season, these species were most likely to be photographed in similar habitats and times. During the dry season, when perhaps there were fewer food sources, the species shifted when they were active in a manner that created less overlap. Also in the dry season, opossums made more use of mangrove habitats. Understanding the relationships among these species is important because this area supports nesting shorebirds and sea turtles, known prey for these predators. Due to lack of apex predators in human-dominated landscapes, mesopredator relationships are complex and spatiotemporal niche partitioning strategies can vary, especially when seasonal shifts in resource availability occur. Our objective was to understand spatiotemporal niche overlap across seasons among mesopredators inhabiting a barrier island complex. We placed 19 unbaited cameras throughout Fort De Soto County Park, Florida, USA between February 2021 and July 2023. Of six mesopredator species detected, three species had >75 detections during both the wet and dry seasons (coyote, Canis latrans; Virginia opossum, Didelphis virginiana; and raccoon, Procyon lotor). Using general linear mixed models, we determined that during the wet season coyote–raccoon and raccoon–opossum detections were positively associated with each other (p < 0.05). During the dry season, raccoon–opossum detections were positively associated, and opossums were more likely to be detected around mangroves. After calculating coefficients of overlap, we found all three species varied their temporal activity between seasons. During the dry season exclusively, all three mesopredators occupied different temporal niches. The park's isolated but developed nature has potentially led to a destabilized mesopredator community. Understanding seasonal mesopredator dynamics of Fort De Soto is particularly important because this park supports a high number of nesting shorebirds and sea turtles, which are known food sources for mesopredators. [ABSTRACT FROM AUTHOR]

Geological information is required to parameterize hydrogeological properties in groundwater flow models. Our aim was to provide a hydrogeological model for the island of Norderney, Northwest Germany and the surrounding Wadden Sea for this purpose. The model focuses on Holocene, Pleistocene and Pliocene deposits which are the most relevant to groundwater flow in and around the island's freshwater lens. For these geological units, borehole data was available that allowed us to distinguish between sediments acting as aquifers and aquitards. Conceptual units were derived that comprise the most common stratigraphic and petrographic features into discrete entities. The borehole data was supplemented by maps of the pre‐Holocene surface as well as data from an existing stratigraphic model for deeper geological units. The model was developed and created using the open‐source geological modelling software GemPy. The resulting model contains major hydrogeological units that can be assumed continuous over a larger extent of the model area based on the available data. From the deeper geology, a possible range of locations of the aquifer base below Norderney was extracted. By integrating borehole data, existing geological models and geological interpretations available in the literature, this dataset complements the so far mainly cross‐sectional and partial descriptions of the hydrogeology below Norderney. [ABSTRACT FROM AUTHOR]

Background: Sarcoptic mange is a skin disease caused by the contagious ectoparasite Sarcoptes scabiei, capable of suppressing and extirpating wild canid populations. Starting in 2015, we observed a multi-year epizootic of sarcoptic mange affecting a red fox (Vulpes vulpes) population on Fire Island, NY, USA. We explored the ecological factors that contributed to the spread of sarcoptic mange and characterized the epizootic in a landscape where red foxes are geographically constrained. Methods: We tested for the presence of S. scabiei DNA in skin samples collected from deceased red foxes with lesions visibly consistent with sarcoptic mange disease. We deployed 96–100 remote trail camera stations each year to capture red fox occurrences and used generalized linear mixed-effects models to assess the affects of red fox ecology, human and other wildlife activity, and island geography on the frequency of detecting diseased red foxes. We rated the extent of visual lesions in diseased individuals and mapped the severity and variability of the sarcoptic mange disease. Results: Skin samples that we analyzed demonstrated 99.8% similarity to S. scabiei sequences in GenBank. Our top-ranked model (weight = 0.94) showed that diseased red foxes were detected more frequently close to roadways, close to territories of other diseased red foxes, away from human shelters, and in areas with more mammal activity. There was no evidence that detection rates in humans and their dogs or distance to the nearest red fox den explained the detection rates of diseased red foxes. Although detected infrequently, we observed the most severe signs of sarcoptic mange at the periphery of residential villages. The spread of visual signs of the disease was approximately 7.3 ha/week in 2015 and 12.1 ha/week in 2017. Conclusions: We quantified two separate outbreaks of sarcoptic mange disease that occurred > 40 km apart and were separated by a year. Sarcoptic mange revealed an unfettered spread across the red fox population. The transmission of S. scabiei mites in this system was likely driven by red fox behaviors and contact between individuals, in line with previous studies. Sarcoptic mange is likely an important contributor to red fox population dynamics within barrier island systems. [ABSTRACT FROM AUTHOR]

Predation management is an important component of managing species of conservation concern. The piping plover (Charadrius melodus; plover), a disturbance-dependent and conservation-reliant shorebird that nests on sandy beaches and barrier islands on the Atlantic Coast, was listed under the United States Endangered Species Act in 1986, with habitat loss and predation stated as key causes of its decline. We evaluated the relationship between a suite of predators and plover chick survival from 2015-2018. We used a camera grid to establish indices of the abundance of 3 known chick predators: red fox (Vulpes vulpes), raccoon (Procyon lotor), and domestic cat. We used camera detections in a survival model to assess potential relationships between predator species detection and plover chick survival. Plover chick survival was negatively related with red fox detection, but not with detection of the other 2 predators. In addition to the correlation with red fox detections, chick survival was negatively related to high plover nesting density. Our results suggest that red foxes were predators of piping plover chicks during our study, likely augmented by other density-dependent sources of mortality. Targeted predator management could aid in conservation of piping plovers in this system as a short-term solution, but long-term recovery plans must also address habitat limitation. [ABSTRACT FROM AUTHOR]

Drivers of shrub primary production and associated landscape impacts of encroachment are well known in drylands but have not been thoroughly studied in mesic and coastal habitats. The native, nitrogen-fixing shrub, Morella cerifera, has expanded into coastal grassland along the US Atlantic coast due to warming temperatures, but impacts on ecosystem function are not well known. Annual net primary production (ANPP) of Morella cerifera and key environmental drivers were measured long-term (1990 – 2007) across a chronosequence of shrub age on a mid-Atlantic barrier island. Soil and groundwater nutrients were compared with un-encroached grassland soil to evaluate impacts of vegetation on nutrient dynamics. Shrub ANPP declined with age at the same rate among all thickets, but there was variability from year to year. When climate variables were included in models, shrub age, precipitation, and freshwater table depth were consistent predictors of ANPP. Water table depth decreased over time, reducing ANPP. This may be due to rising sea-level, as well as to feedbacks with shrub age and evapotranspiration. Soil N and C increased with shrub age and were higher than adjacent grassland sites; however, there was a significant loss of N and C to groundwater. Our results demonstrate that drivers influencing the encroachment of shrubs in this coastal system (i.e., warming temperature) are not as important in predicting shrub primary production. Rather, interactions between shrub age and hydrological properties impact ANPP, contributing to coastal carbon storage. [ABSTRACT FROM AUTHOR]

Simple Summary: This research studied three species of imperiled shorebirds—Piping Plover, Snowy Plover, and Wilson's Plover—that are similar in appearance and share habitats outside the breeding season. Researchers counted the number of these birds on a barrier island in Southwest Florida and examined how tide and wind affected their abundance and foraging behavior. They found that all three species were more likely to be found on the mudflats during lower tides and on the beach during higher tides. All of the feeding observed was on the mudflat, but one of the species, Wilson's Plovers, was never observed feeding during the study. The high densities of these plover species are likely due to the mudflat habitat that provides more food, a beach habitat that provides a relatively safe location to roost, and the location of the barrier island, which is surrounded by other good places to forage and rest. While each species used the barrier island's habitats slightly differently, the high densities of all three species present an opportunity to have a large conservation impact by protecting this dynamic area. Piping Plover (Charadrius melodus), Snowy Plover (Charadrius nivosus), and Wilson's Plover (Charadrius wilsonia) are imperiled species that overlap in both their range and habitat outside the breeding season. The purpose of this research was to document the abundance of these species at a barrier island in Southwest Florida, USA, and to examine the influence of tide and wind on both their abundance and foraging. We walked ~700 m surveys through tidal mudflat and adjacent beach semiweekly at 0730–1030 from 24 September 2021–4 March 2022. During these 38 surveys, Piping Plovers were the most abundant of the three species, and the average number counted was 34 (SD 17.3) compared with 11 (SD 6.3) Snowy Plovers and 14 (SD 14.1) Wilson's Plovers. All of the species were more likely to be found on the mudflats during low tides and the beach during high tides. Our findings suggest the high densities of Piping, Snowy, and Wilson's Plover are due to a mudflat habitat that provides high availability of prey, a beach habitat that provides a relatively safe location to roost, and the context of the barrier island, which is surrounded by other suitable habitats. While each species used the barrier island's habitats slightly differently, the high densities of all three species present an opportunity to have a large conservation impact by protecting this dynamic area. [ABSTRACT FROM AUTHOR]

The expected increase in rates of sea level rise during the 21st century and beyond may cause barrier islands to drown. Barrier drowning occurs due to a sediment imbalance induced by sea level rise, causing inlets to open and expand. It is still unclear how fast barrier islands can drown. To gain insight into the morphodynamics of barrier systems subject to sea level rise, we here present results obtained with a novel barrier island exploratory model, BarrieR Inlet Environment‐Drowning, that considers inlet expansion beyond equilibrium size. We quantify how much of a barrier island chain is drowned by calculating the fraction of its length that is below mean sea level due to sea level rise. Results show that barrier drowning is mostly sensitive to the wave height and the rate of sea level rise. In the model, it takes 100s of years for barrier islands to start drowning in response to high rates of sea level rise (more than 5 mm/yr, for a typical coastal environment). This lag in barrier response is caused by a gradual decrease in the sand volume of the barrier. Higher rates of sea level rise cause earlier and more severe barrier drowning. Modeled barrier systems that face higher waves undergo more frequent inlet closures that lower the rate of drowning, but they also have a deeper shoreface that increases the rate of drowning. In model simulations, the latter process dominates over the former when sea level rise rates exceed 5 mm/yr. Model results fairly agree with available field data. Plain Language Summary: In extreme sea level rise scenarios (like those predicted during the 21st century and beyond) barrier islands may drown. Barrier drowning occurs due to a lack of sediment induced by sea level rise, which causes submergence of (parts of) the barrier chain. It remains difficult to predict when and under which conditions drowning may occur. In this study we investigated the dynamics of drowning barrier islands with an exploratory numerical model. A key finding from our model is that high rates of sea level rise (higher than 5 mm/yr), but also high waves (higher than 1.5 m) result in barrier drowning. However, even under model simulations with high rates of sea level rise, it takes a long time for the sand in the barrier island to erode. Barrier drowning and disappearance therefore might take 100s of years. The model results are consistent with available field data, but more observations are needed to achieve a full model verification. Key Points: Idealized morphological model simulations show that tidal inlets expand until barrier islands disappear under rapid sea level riseModeled barrier drowning lags sea level rise acceleration by 100s of yearsLag in modeled barrier drowning is explained by a decrease in the sand volume of the barrier [ABSTRACT FROM AUTHOR]

The Lower Cretaceous (Barremian) Camarillas Formation in the Galve Sub‐basin of eastern Spain is an exceptionally muddy, synrift, aggradational then retrogradational paralic succession. Deposition within these arid, equatorial paralic systems was strongly controlled by crustal rifting of the Iberia plate linked to the geodynamic evolution of the Atlantic Ocean, the Bay of Biscay and the Tethys Ocean. Although synsedimentary extensional tectonics controlled thickness and facies distributions, the parasequence stacking patterns point to a superimposed high‐order allogenic control on the paralic succession. Field data and drone imagery are combined to document changes in sedimentology and three‐dimensional stratigraphic architecture of these deposits to interpret changes in depositional environments as this basin filled. Three evolutionary stages are identified: (i) tide‐dominated estuary; (ii) mixed‐energy estuary, with a well‐developed wave‐dominated barrier island system; and (iii) barrier island–tidal inlet suite. An exceptional record of back‐barrier‐island depositional interactions is preserved in this high‐subsidence, extensional‐basin setting, including deposition of washover fans, flood‐tidal deltas and ebb‐tidal deltas. Drone‐derived imagery facilitates three‐dimensional architectural characterization of these complex paralic deposits, including multi‐episodic tidal inlets, and correlation of basin scale stratigraphic markers. Spatio‐temporal interactions between climate change, sea‐level variations and rift‐related subsidence generated complex estuarine and barrier island geobodies. The general transgressive trend recorded in the Camarillas Formation correlates well with global eustatic sea‐level rise during the Barremian. [ABSTRACT FROM AUTHOR]

Heffentrager, M.L.; Wasklewicz, T.; Sirianni, H.; Gares, P.; Kernstine, L., and Richter, J., 2023. Reproducibility in coastal physical laboratory experiments: Washover deposits and channel morphology. Journal of Coastal Research, 39(5), 823–835. Charlotte (North Carolina), ISSN 0749-0208. The reproduction of physical laboratory experiments within the field of geomorphology does not occur often, despite the call to reproduce natural landscape experiments as a means of more accurately defining geomorphic changes across a variety of environmental settings. Reproducing published results not only supports prior findings but also builds evidence on geomorphic process across laboratory and natural scales. Overwash, the run-up of ocean water and sediment over a sandy barrier, is both a hazard when it impacts coastal properties and infrastructure and a natural resilience factor as it benefits sustained long-term evolution of the barrier island systems. Here, a coastal physical laboratory experiment that simulates overwash and resulting washover deposits is reproduced. The research objective is to expand the current knowledge of how these deposits form under different laboratory settings. Understanding the influence of the dimensions of a physical laboratory experimental table, sediment variations, and back barrier surfaces can give support to researchers planning future physical coastal laboratory experiments, especially those involving washover deposit formation. The results show that final washover deposit morphologies can be reproduced from similar experimental designs. Variations between the experiments resulted from confining boundaries of experimental tables. The refinement of coastal laboratory experiments, in tandem with fieldwork, enhances the understanding of overwash processes for both scientific research and applied scientific approaches. [ABSTRACT FROM AUTHOR]

Human‐driven land use change can fundamentally alter ecological communities, especially the diversity and abundance of large‐bodied predators. Yet, despite the important roles large‐bodied predators play in structuring communities through feeding, there have been only a few investigations of how the feeding patterns of large‐bodied predators change in human‐dominated landscapes. One group of large‐bodied predators that has been largely overlooked in the context of land use change is the crocodilians. To help fill these gaps, we studied the feeding patterns of juvenile American alligators (Alligator mississippiensis) on neighboring barrier islands on the southeast coast of Georgia, USA. Jekyll Island has multiple golf courses and substantial amounts of human activity, while Sapelo Island does not have any golf courses and a much smaller amount of human activity. We found that juvenile alligator populations on both islands ate the same types of prey but in vastly different quantities. Sapelo Island alligators primarily consumed crustaceans while alligators that lived on Jekyll Island's golf courses ate mostly insects/arachnids. Furthermore, the Jekyll Island alligators exhibited a much more generalist feeding pattern (individuals mostly ate the same types of prey in the same quantities) than the more specialized Sapelo Island alligators (diets were more varied across individuals). The most likely explanation for our results is that alligators living on golf courses have different habitat use patterns and have access to different prey communities relative to alligators in more natural habitats. Thus, land use change can strongly alter the feeding patterns of large‐bodied predators and, as a result, may affect their body condition, exposure to human‐made chemicals, and role within ecological communities. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the long-term changes in the coastal stretch of the Lido barrier island, a 12 km sandy coast bordering the Lagoon of Venice, and to assess the impacts of human interventions in the system. Coastal modifications were examined in a GIS environment through the analysis of aerial photographs covering the period 1955–2019. To achieve our goal, the study area was divided into three cells (i.e., from north to south, A, B, and C), and the rates of shoreline change were calculated over five subsequent periods (i.e., 1955–1978, 1978–1987, 1987–1996, 1996–2006, and 2006–2019). The results mainly showed a positive trend in the long-term (cell A avg. 2.0 m/year; cell C avg. 1.2 m/year) and moderate erosion (cell A and C avg. 0.9 m/year) in the periods 1996–2006 and 2006–2019, probably due to an increase in the frequency of storm surges. However, major effects on beach erosion and progradation were produced by human interventions. In particular, positive impacts were derived from the shore-normal engineering structures intercepting longshore currents, whereas negative effects were from works functional to the realisation of the MoSE system at the Lido and Malamocco inlets, which reduced the amount of available sediment, thus contributing to the worsening conditions of cells A and C. In view of the expected sea-level rise, this area merits higher consideration for correct spatial planning in the framework of integrated coastal zone management. We suggest that a monitoring program of shoreline evolution must be set up to better manage its future development. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Earth Sciences & Environment is the property of Journal of Earth Sciences & Environment and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The advantages derived from the use of Uncrewed Aerial Vehicles (UAVs) are well-established: they are cost-effective and easy to use. There are numerous environmental applications, particularly when monitoring contexts characterized by rapid morphological changes and high rates of sediment transport, such as coastal areas. In this paper, three different case studies of survey and monitoring with high resolution and accuracy obtained through the use of UAVs are presented; these concern transgressive coastal sites. Results allow for the definition and quantification of coastal landforms and processes, including: (i) The anatomy of a parabolic dune and the rate of landward migration that could interfere with a tourist settlement; (ii) The mode and timing of morphological recovery and realignment of a barrier island overwashed by storm surge episodes; and (iii) The potential flood risk of a progradational spit that is a nesting site of a species of migratory breeding birds of conservation concern. The results demonstrate and confirm that, through a good coupling of drone-sensed quality data and accurate topographic control, quantitative estimates that are useful in assessing the impacts of natural processes involving both human and natural assets can be obtained. [ABSTRACT FROM AUTHOR]

Long‐term and seasonal geomorphological changes at Padre Island, Texas are identified and linked with potential external drivers. Aerial and satellite images from 1950 to 2018, monthly images from 2019 to 2020, and a 2018 LiDAR data set are used to assess long‐term and seasonal geomorphological changes within a 50 km2 area of Padre Island near Port Mansfield, Texas. Trends in landcover are evaluated by mapping and comparing the relative areal coverage of each facies. Vegetated dunes, absent initially, emerged in the fore‐island and expanded into the back‐barrier to cover 14% of the study area. The active vegetation‐free back‐barrier dune field steadily decreased in areal extent from 12% to 6% as vegetation spread. Nebkha dune coverage fluctuated between 4% and 7%. Expansive microbial mats colonized the wind tidal and deflation flats surrounding the vegetated dunes and back‐barrier dune field giving rise to a remarkably different landscape over the 50‐year period studied. An assessment of external forcing factors identifies increased rates of relative sea level rise and decreased sediment influx as the most likely primary factors driving the geomorphological changes. These changes have induced a widespread shift toward stabilization of island sediments by vegetation and microbial mats, which in turn has starved the back‐barrier of sediments resulting in low rates of accretion and increased flooding. These findings highlight the sensitivity of the back‐barrier and, in particular, the dune facies to changes in sea level and sediment supply, and show that microbial mats are effective at stabilizing island sediments and may be harbingers to barrier island response to rising sea level. As shown in this study, long‐term monitoring of geomorphic facies changes and topography can detect important shifts in the island state that can be used to inform decision making for these sensitive coastal landscapes. [ABSTRACT FROM AUTHOR]

Barrier islands are especially vulnerable to hurricanes and other large storms, owing to their mobile composition, low elevations, and detachment from the mainland. Conceptual models of barrier‐island evolution emphasize ocean‐side processes that drive landward migration through overwash, inlet migration, and aeolian transport. In contrast, we found that the impact of Hurricane Dorian (2019) on North Core Banks, a 36‐km barrier island on the Outer Banks of North Carolina, was primarily driven by inundation of the island from Pamlico Sound, as evidenced by storm‐surge model results and observations of high‐water marks and wrack lines. Analysis of photogrammetry products from aerial imagery collected before and after the storm indicate the loss of about 18% of the subaerial volume of the island through the formation of over 80 erosional washout channels extending from the marsh and washover platform, through gaps in the foredunes, to the shoreline. The washout channels were largely co‐located with washover fans deposited by earlier events. Net seaward export of sediment resulted in the formation of deltaic bars offshore of the channels, which became part of the post‐storm berm recovery by onshore bar migration and partial filling of the washouts with washover deposits within 2 months. This event represents a volumetric setback in the overwash/rollover behavior required for barrier transgression, but the new ponds and lowland habitats may provide beneficial habit for endangered species and will likely persist for years. Plain Language Summary: As sea level rises, barrier islands tend to migrate toward land, helped by storms that move sand from the ocean to the back side. In rarer events, such as Hurricane Dorian (2019), storms can transport sand from the back side to the ocean. Using overlapping photos collected from a plane, we created 3‐D elevation maps and stitched‐together photo mosaics of North Core Banks, North Carolina, immediately before and after Hurricane Dorian, and then once a month for 3 months afterward, to document the erosion and recovery of the beach and barrier island. We found major changes. During the storm, abnormally high water levels in Pamlico and Core Sounds flooded the island and created distinct channels as water drained from the sound side into the Atlantic Ocean. This process, called outwash, moved 18% of the island sand into the ocean over the course of a few hours. The maps also showed the initial stages of a recovery process, as beach sand was moved by ocean waves and plugged the channels, creating new, and semi‐permanent, habitats within the barrier island. Events such as Hurricane Dorian may slow the typical migration process of barrier islands and change the landscape for years to come. Key Points: Wind‐driven surge from Pamlico Sound inundated the barrier island of North Core Banks during Hurricane DorianSeaward‐directed flow (outwash) through gaps in the dunes eroded about 18% of the island volume, mostly from antecedent washover depositsThis event represents a setback for barrier transgression but has created beneficial habitat for endangered species [ABSTRACT FROM AUTHOR]

Vegetation shifts can directly alter habitat dynamics and indirectly impact habitat stability relative to disturbance response. Barrier island dune habitats exhibit spatiotemporally dynamic topography that is affected by vegetation. However, vegetation distribution data can be rare and vegetation persistence is largely unknown such that species turnover over in communities can occur unnoticed. This is true despite concerns and documented cases of woody encroachment related to climate change in these ecogeomorphic habitats where physical stability to resist storm erosion varies with vegetation distribution and density. In 1956 and 1957, the vegetation of Island Beach State Park, NJ, was mapped as a permanent record for subsequent ecological study. In June 2020, we remapped the vegetation of 5.4 of 17 km north to south, seaward of the thicket community boundary. We maintained the same classification system as the historic record, physically mapping vegetation patches via GPS. We quantified changes in thicket, heather, and grass community distribution between the two time periods. Habitat persistence and conversion varied in the 63 years. Heath communities saw 80%–97% habitat loss in conversion to woody thicket. Conversely, thicket community distribution drastically increased, replacing heath where it was previously prevalent. This represents the first known documented instances of woody encroachment for Morella pensylvanica. When they did not expand, thicket communities receded landward or underwent turnover to an invasive species. Woody species of interest for dune stabilization occupied areas of similar habitat characteristics. Dune vegetation distribution persistence from 1957 to 2020 was relatively consistent and stable with the exception of heath habitat conversion. Barrier island stability is directly related to vegetation stability such that understanding where community shifts might occur over time can aid in managing and modeling efforts surrounding these dynamic ecogeomorphic habitats. [ABSTRACT FROM AUTHOR]

The coastal zone, a highly dynamic and complex environment, has important ecological and jurisdictional implications for governments and coastal managers. Based on the CORINE Land Cover classification system, this paper examined the effects of land use and land cover change (LULC) on the coastlines' dynamics along the ~24 km barrier island of Nador lagoon on the Mediterranean coast of Morocco during a period of 62years (1954-2016). The study utilized high-resolution orthoimages in the geographic information system (GIS) environment to characterize coastline evolution and LULC changes. The evolution of the coastline was assessed using a GIS tool, in particular the Digital Shoreline Analysis System (DSAS). The net rates of coastline change were calculated by using statistical methods: the End Point Rate (EPR) and the Linear Regression Rate (LRR). Results concerning the LULC changes showed that agricultural area and beach/dune classes decreased over the entire study period (62 years) by 11.14% and 28.45%, respectively. Urban fabric, shrub, forest, and saltmarsh/peat bog classes increased during the 62 years of evaluation by 2.69%, 19.92%, 16.77%, and 0.19%, respectively. Results regarding coastal analysis indicated that the accretion and erosion processes along the barrier island of the Nador lagoon (~24km) were observed at 45% (10.6 km) and 55% (12.8 km) of the coastline, respectively. The beaches of Oulad Zehra and Oulad Aissa were characterized by erosion (-0.58m/yr to -0.57m/yr respectively), while accretion was observed on the beaches of Boukana and Kariat Arkmane at rates of +2.15m/yr and +0.82m/yr, respectively. This study highlighted that natural and anthropogenic processes have a strong influence on the erosion/accretion trends identified along the barrier island of Nador lagoon. The changes in LULC have affected the barrier island of the lagoon in two different forms: (1) a significant spatial conversion due to dune reforestation and (2) a fundamental spatial modification that affects the sea-lagoon connection (inlet) and the construction of new hard engineering structures. [ABSTRACT FROM AUTHOR]

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Wind influence on tidal inlet hydrodynamics is examined using 40 days of wind, water level, and current observations collected in Spring 2019 at Oregon Inlet, NC, a large (1 km wide, 1–13 m deep) meso‐tidal inlet with complex delta systems. Wind velocities through the inlet (ranging 0–18 m/s) are modulated at subtidal timescales and are well correlated (R = 0.87) to a subtidal component of the water level slope through the inlet. The subtidal wind and water level slope are also well correlated to the subtidal current along the principal flow axis in the main inlet channel (R = 0.92 and 0.96, respectively). In combination with findings from previous studies, these findings suggest that regional winds induce the subtidal water level slope through the inlet by causing opposing setup/setdown to either side of the inlet. A force balance at the inlet demonstrates that the wind‐induced pressure gradient forces the subtidal currents, with wave forcing and local wind shear acting as lower‐order influences. The magnitude of the subtidal current is substantial, exceeding that of the tidal currents 45% of the time. Cumulatively, these findings indicate that regional winds exert a first‐order control on the currents at Oregon Inlet and cause irregular hydrodynamic patterns not well described by the traditional inlet classification scheme. Regional geographic characteristics may contribute to the high level of wind influence at Oregon Inlet, but similar processes are likely to be important to net flow dynamics at other inlets with large, shallow inland water bodies. Plain Language Summary: Tidal inlets are constricted coastal channels maintained by the flow and are particularly common along barrier island systems where they have important implications for the flux of sediments along the coast. The traditional tidal inlet classification system is based on the relative strength of tides and waves; however, mounting evidence suggests winds may also be an important control of inlet dynamics. This works uses observations of winds, currents, and changes in water levels at Oregon Inlet, NC, to examine the role of local and regional winds in altering tidal inlet currents. Results suggest that regional winds induce a water level gradient through the inlet that varies over time periods longer than tides (>12 hr), and that this gradient then forces a current through the inlet over the same timescales. The magnitude of the wind induced current exceeds that of the tidal current 45% of the time and far exceeds contributions from waves, implying that winds may play an underappreciated role in tidal inlet dynamics. Improving our understanding of wind control on tidal inlets has important implications for dredging efforts common to tidal inlets, for numerical models simulating island chain evolution, and to the navigation of vessels that use charts to determine times of safe transit based on expected water levels and currents. Key Points: Observational data suggest regional winds induce a water level gradient through Oregon Inlet that varies over subtidal time scalesSubtidal water level gradients induced by regional winds account for 92% of the variance of along‐inlet subtidal currentsSubtidal currents through the inlet are of the same order as the tidally driven currents and exceed the tidal currents 45% of the time [ABSTRACT FROM AUTHOR]

Barrier islands predominate the Atlantic and Gulf coastlines of the USA, where population and infrastructure growth exceed national trends. Forward‐looking models of barrier island dynamics often include feedbacks with real estate markets and management practices aimed at mitigating damage to buildings from natural hazards. However, such models thus far do not account for networks of infrastructure, such as roads, and how the functioning of infrastructure networks might influence management strategies. Understanding infrastructure networks on barrier islands is an essential step toward improved insight into the future dynamics of human‐altered barriers. Here, we examine thresholds in the functioning of 72 US Atlantic and Gulf Coast barrier islands. We use digital elevation models to assign an elevation to each intersection in each road network. From each road network we sequentially remove intersections, starting from the lowest elevation. We use the maxima of the second giant connected component to identify a specific intersection—and corresponding elevation—at which functioning of the network fails, and we match the elevation of each critical intersection to local annual exceedance probabilities for extreme high‐water levels. We find a range of failure thresholds for barrier island road network functioning, and also find that no single metric—absolute elevation, annual exceedance probability, or a quantitative metric of robustness—sufficiently ranks the susceptibility of barrier road networks to failure. Future work can incorporate thresholds for road network into forward‐looking models of barrier island dynamics that include hazard‐mitigation practices for protecting infrastructure. Plain Language Summary: Barrier islands are popular places to live and visit. To navigate barrier islands, people depend on extensive road networks. But barrier islands are especially exposed to impacts from hazards like storms, flooding, and sea‐level rise. We use tools from network science to investigate how barrier island road networks might be disrupted by coastal hazards such as flooding (and other related hazards like road damage from flood water, and debris/sand accumulation). To do this we find the elevation of each intersection in each road network on 72 US Atlantic and Gulf barrier islands, and then track what happens to the network as we remove intersections, one at a time, starting with those at the lowest elevations. This process reveals the specific intersection at which a given network fails. We then link the elevation of that intersection to the likelihood of flooding from extreme high‐water levels, which enables us to estimate whether a network might fail often or only rarely. Knowing which intersection in a barrier island road network plays this critical role could improve model forecasts of how barrier environments may evolve in the future, and inform coastal management and planning strategies for adaptation to changing coastal hazards. Key Points: Living on barrier islands depends on functioning road networks, which are highly exposed to coastal hazard impactsRoad networks of US barrier islands have a range of network failure thresholds derived from elevation and annual exceedance probabilityThresholds in road network functioning can be incorporated into forward‐looking models of barrier dynamics [ABSTRACT FROM AUTHOR]

Forecasting biogeomorphological conditions for barrier islands is critical for informing sea‐level rise (SLR) planning, including management of coastal development and ecosystems. We combined five probabilistic models to predict SLR‐driven changes and their implications on Fire Island, New York, by 2050. We predicted barrier island biogeomorphological conditions, dynamic landcover response, piping plover (Charadrius melodus) habitat availability, and probability of storm overwash under three scenarios of shoreline change (SLC) and compared results to observed 2014/2015 conditions. Scenarios assumed increasing rates of mean SLC from 0 to 4.71 m erosion per year. We observed uncertainty in several morphological predictions (e.g., beach width, dune height), suggesting decreasing confidence that Fire Island will evolve in response to SLR as it has in the past. Where most likely conditions could be determined, models predicted that Fire Island would become flatter, narrower, and more overwash‐prone with increasing rates of SLC. Beach ecosystems were predicted to respond dynamically to SLR and migrate with the shoreline, while marshes lost the most area of any landcover type compared to 2014/2015 conditions. Such morphological changes may lead to increased flooding or breaching with coastal storms. However—although modest declines in piping plover habitat were observed with SLC—the dynamic response of beaches, flatter topography, and increased likelihood of overwash suggest storms could promote suitable conditions for nesting piping plovers above what our geomorphology models predict. Therefore, Fire Island may offer a conservation opportunity for coastal species that rely on early successional beach environments if natural overwash processes are encouraged. Plain Language Summary: Predicting a barrier island's future characteristics is important for planning, particularly given that these areas contain habitats used by threatened and endangered species and are popular sites for housing and recreation. In this study, we combined five models to predict barrier island characteristics like elevation, beach width, and dune height under three rates of shoreline erosion at Fire Island, New York. Models were also used to predict how likely parts of the island were to be permanently flooded by sea‐level rise or to experience overwash with storms, where waves move sand deeper into the island. We found that Fire Island would likely become narrower and flatter while experiencing more overwash with storms as rates of shoreline erosion increase. These changes may lead to more flooding in housing communities and businesses on the island. However, models also predicted that beach habitats used by shorebirds like the piping plover would not flood permanently. Instead, they would move as the shoreline changes position as long as human structures like buildings or seawalls do not block sand movement. This migration of beaches and sand is important, as it also allows a barrier island to evolve and survive with rising sea levels. Key Points: With increasing shoreline erosion and landward retreat, Fire Island was predicted to become flatter, narrower, and more overwash‐proneBeaches are expected to be least impacted and to replace other landcover types as they migrate with the shorelineHabitats used by piping plovers are expected to persist as long as development and stabilization structures do not limit beach migration [ABSTRACT FROM AUTHOR]

Physical processes driving barrier island change during storms are important to understand to mitigate coastal hazards and to evaluate conceptual models for barrier evolution. Spatial variations in barrier island topography, landcover characteristics, and nearshore and back‐barrier hydrodynamics can yield complex morphological change that requires models of increasing resolution and physical complexity to predict. Using the Coupled Ocean‐Atmosphere‐Wave‐Sediment Transport (COAWST) modeling system, we investigated two barrier island breaches that occurred on Fire Island, NY during Hurricane Sandy (2012) and at Matanzas, FL during Hurricane Matthew (2016). The model employed a recently implemented infragravity (IG) wave driver to represent the important effects of IG waves on nearshore water levels and sediment transport. The model simulated breaching and other changes with good skill at both locations, resolving differences in the processes and evolution. The breach simulated at Fire Island was 250 m west of the observed breach, whereas the breach simulated at Matanzas was within 100 m of the observed breach. Implementation of the vegetation module of COAWST to allow three‐dimensional drag over dune vegetation at Fire Island improved model skill by decreasing flows across the back‐barrier, as opposed to varying bottom roughness that did not positively alter model response. Analysis of breach processes at Matanzas indicated that both far‐field and local hydrodynamics influenced breach creation and evolution, including remotely generated waves and surge, but also surge propagation through back‐barrier waterways. This work underscores the importance of resolving the complexity of nearshore and back‐barrier systems when predicting barrier island change during extreme events. Plain Language Summary: Barrier islands are particularly vulnerable to coastal erosion and flooding during extreme storms, such as hurricanes, because they are narrow and low‐lying. Breaching across a barrier, when the ocean becomes connected to a back‐barrier waterway, can result in damage to coastal communities requiring extensive repair efforts, and changes to ocean navigation or water dynamics that sometimes persist for many years. Barrier breaching can be driven by both ocean and back‐barrier waterway processes. However, the conceptual framework describing coastal change during an extreme storm often only considers ocean processes. In this work, we hindcast barrier breaching using a physics‐based numerical model that was recently extended to include infragravity (IG) waves. IG waves are long waves with periods of 25 s to 5 min, which contribute substantially to extreme water levels during hurricanes. The model was able to predict breach formation with good skill, though the modeled breaches did not occur in the exact locations where breaches were observed. Through analyses of modeled water levels, waves, and sand movement, this work demonstrates the importance of resolving the co‐evolution of the beach, the ocean, and the back‐barrier. Key Points: The Coupled Ocean‐Atmosphere‐Wave‐Sediment Transport model was adapted to include infragravity wave dynamics and applied to investigate barrier breaching during two hurricanesDifferent breaching mechanisms driven by remote to local forcing led to barrier breaches modeled with good skillOcean‐side processes were as important as back‐barrier processes when breaching occurred from back‐barrier inundation, and vice‐versa [ABSTRACT FROM AUTHOR]

Barrier islands are dynamic environments that experience gradual change from waves, tides, and currents, and rapid change from extreme storms. These islands are expected to change drastically over the coming century due to accelerated sea-level rise and changes in frequency and intensity of storm events. The dynamic nature of barrier islands coupled with the importance of these environments make it critical for natural resource managers to understand how habitats on barrier islands are changing or may change over time to determine when and where management actions may be needed. In this study, we applied a habitat change assessment framework, which included exploring areal coverage and distribution changes and change component analysis. Change component analysis, which breaks differences into net gain/loss and allocation difference (i.e., habitat oscillation), has not previously been used to study barrier island habitat evolution. Here, we demonstrate the approach using habitat predictions from a geomorphic modeling effort on Dauphin Island, Alabama (USA). We explored differences of habitat predictions for potential island configurations with and without a beach and dune restoration action under future conditions related to sea level and storminess. We found a potential linkage between landward migration of barrier islands and exchange, an output of change component analysis. The hypothesis may be tested to explore whether this linkage applies over space and time and whether the approach is applicable to monitoring landward migration of coastal wetlands. Collectively, our results highlight the utility of change component analysis for monitoring and quantifying barrier island habitat change and migration. [ABSTRACT FROM AUTHOR]

Waves and water level setup during storms can create overwashing flows across barrier islands. Overwashing flows can cause erosion, barrier breaching, and inlet formation, but their sediments can also be deposited and form washover fans. These widely different outcomes remain difficult to predict. Here we suggest that a breach develops when the sediment volume transported by overwashing flows exceeds the barrier subaerial volume. We form a simple analytical theory that estimates overwashing flows from storm characteristics, barrier morphology, and dune vegetation, and which can be used to assess washover deposition and breaching likelihood. Our theory suggests that barrier width and storm surge height are two important controls on barrier breaching. We test our theory with the hydrodynamic and morphodynamic model Delft3D as well as with field observations of 21 washover fans and 6 breaches that formed during Hurricane Sandy. There is reasonable correspondence for natural but not for developed barrier coasts, where traditional sediment transport equations do not readily apply. Our analytical formulations for breach formation and overwash deposition can be used to improve long‐term barrier island models. Plain Language Summary: Storms can have big impacts on coastlines. Beaches and dunes can be eroded, their sands can be blown inland, coverings houses and streets. Sometimes, there is so much erosion that new channels have formed that breach the island and make a new connection between the ocean and the lagoon. Here, we develop and test a new theory to predict these outcomes ahead of time. We find that high storm surges along narrow dunes are most vulnerable to breaching. Key Points: New analytical theory compares overwashing flow against barrier volume to predict breaching and washover depositionWe test our theory against Delft3D simulations and Hurricane Sandy observations: vegetation and island elevation help to prevent breachingDeveloped barrier islands do not follow predicted trends, suggesting alternative controls on overwashing and breaching [ABSTRACT FROM AUTHOR]

The burial of "blue carbon" in coastal marsh soils is partially offset by marsh‐atmosphere methane (CH4) fluxes, but this offset may be greater if other pathways of CH4 export exist. Here we report that salt marshes also export dissolved CH4 via submarine groundwater discharge (SGD). The volumetric fluxes of salt marsh groundwater into adjacent tidal creeks were calculated from mass balances of the conservative tracer 226Ra at four study sites in coastal Georgia, USA. Over the 2‐year study period, volumetric groundwater fluxes across all sites ranged between 1,700 and 105,000 m3 day−1. Dissolved CH4 fluxes of 27–1,200 μmol CH4 m−2 day−1 were calculated by multiplying the volumetric groundwater flux by the groundwater CH4 concentration and normalizing to the intertidal salt marsh area estimated from satellite images. On a mass basis, the cross‐site range in CH4 fluxes was 1.3–5.5 g CH4 m−2 year−1 with a cross‐site mean of 2.8 g CH4 m−2 year−1. This is equivalent to 125 (56–245) g CO2 m−2 year−1 assuming that CH4 is 45 times more potent than CO2 as a greenhouse gas over a 100‐year time frame. This sustained‐flux global warming potential is similar to the 138 (1.1–260) g CO2 m−2 year−1 average calculated across other studies of the direct marsh soil to atmosphere CH4 flux. Therefore, SGD drives an effective doubling of salt marsh CH4 export that offsets a combined total of ~30% of the global cooling potential derived from soil carbon sequestration. Plain Language Summary: Salt marshes are wetland ecosystems found along the coast. Scientists and policymakers are interested in salt marshes because they accumulate carbon in their soil over long time scales. This carbon would otherwise enter the atmosphere as carbon dioxide, exacerbating global climate change. However, microorganisms living in the soil break down some of this buried carbon and produce other greenhouse gases, such as methane, that contribute more to warming than carbon dioxide. Scientists have measured how much methane escapes from the soil to the atmosphere. Carbon burial more than offsets this methane export, meaning that salt marshes have a small net cooling effect on Earth's climate. In this study, we incorporate a previously unaccounted pathway for methane export from salt marshes into their radiative budget. Methane in marsh soil and surrounding sediments can be dissolved in groundwater that discharges from the pore spaces between soil and sediment particles. This groundwater flows slowly toward the marsh edge until it discharges into nearby surface waters, carrying dissolved methane with it. We estimate that this methane export from groundwater approximately doubles total methane emissions from salt marshes. This is still not enough methane export to counteract all of the climate cooling benefit of carbon burial in salt marsh soils. However, it is important for policymakers to include both pathways of methane export when calculating the climate cooling benefit of carbon burial in salt marsh soils or its economic value. Key Points: Submarine groundwater discharge drives methane export from salt marshes to adjacent coastal surface watersGroundwater‐derived methane export is similar in magnitude to the direct flux of methane from salt marsh soil to the atmosphereThis effective doubling of salt marsh methane export offsets ~30% of their carbon sequestration potential [ABSTRACT FROM AUTHOR]

Beck, T.M.; Wang, P.; Li, H., and Wu, W., 2020. Sediment bypassing pathways between tidal inlets and adjacent beaches. Journal of Coastal Research, 36(5), 897–914. Coconut Creek (Florida), ISSN 0749-0208. This study investigated the sediment transport pathways in three sandy barrier, tidal inlet systems through sediment tracking within a numerical model that simulates hydrodynamics and morphodynamics. The three tidal inlet systems, Coos Bay, Oregon, Shark River Inlet, New Jersey, and John's Pass, Florida, represented high-, medium-, and low-wave energy regimes for U.S. inlets (Pacific, Atlantic, and Gulf of Mexico Coasts, respectively). Three methods employed to define sediment pathways from the results of a numerical morphology model were evaluated: (1) morphodynamic interpretation, (2) mean transport vectors across the modeled inlet, and (3) sediment tracer migration. The sediment tracing methodology employed in this study allowed for an evaluation of the sediment transport pathways between the various morphologic features of a tidal inlet, as well as their respective processes that drive the exchange of sediments. Characterizing and correlating the dominant and subdominant, or seasonal, sediment pathways between tidal inlet morphologic features (sediment reservoirs) can improve long-term models of an inlet sediment system. Divergences in pathways to subfeature shoals of a complex tidal inlet shoal, such as the updrift and downdrift shoals of an ebb-tidal delta, can be resolved through tracking sediment migration. The results of this study illustrate the value of including sediment-tracking techniques in simulating sediment bypassing and the potential of this application to inform coastal engineering and design modifications to the sediment reservoirs of tidal inlet systems. [ABSTRACT FROM AUTHOR]

Knowledge of roost selection by northern yellow bats (Lasiurus intermedius) is limited to a small number of known roost locations. Yet knowledge of basic life history is fundamental to understanding past response to anthropogenic change and to predict how species will respond to future environmental change. Therefore, we examined male northern yellow bat roost selection on 2 Georgia, USA, barrier islands with different disturbance histories. Sapelo Island has a history of extensive disturbance and is dominated by pine (Pinus spp.) forests; Little Saint Simons Island has a limited disturbance history with maritime oak (Quercus spp.) forest as the dominant cover type. From March–July 2012 and 2013, we radio‐tracked 35 adult male northern yellow bats to diurnal roosts and modeled roost characteristics at the plot and landscape scales. We located 387 roosts, of which 95% were in Spanish moss (Tillandsia usneoides) hanging in hardwood trees. On both islands, bats selected roost trees with larger diameters than surrounding trees and selected roost locations with greater open flight space (i.e., low midstory clutter) underneath. Roosts were located farther from open areas on Sapelo and closer to fresh water on Little Saint Simons compared to random locations. Lower availability of hardwood forest on Sapelo may have resulted in small‐scale roost site selection (i.e., plot level) despite potential increased costs of commuting to water and open areas for foraging. In contrast, greater availability of hardwood forest on Little Saint Simons likely allowed selection of roosts closer to fresh water, which provides foraging and drinking opportunities. Our results indicate that mature hardwood trees in areas with low midstory clutter are important in male northern yellow bat roost selection, but landscape‐level features have varying influences on roost selection, likely as a result of differences in disturbance history. Therefore, management will differ depending on the landscape context. Further research is needed to examine roost selection by females, which may have different habitat requirements. © 2020 The Wildlife Society. Mature hardwood trees in areas with low midstory clutter are important in male northern yellow bat roost selection at the plot level, but landscape‐level features have varying influences on roost selection. Management to provide suitable roosting habitat for male northern yellow bats should be tailored to specific landscape conditions. [ABSTRACT FROM AUTHOR]

Quantifying demographic parameters of freshwater turtle populations at the local scale is necessary in order to understand their natural history and assess their status. To examine whether maritime forest populations display different demographic traits compared to other populations, we studied the freshwater turtle assemblage at Nags Head Woods Ecological Preserve (NHWEP), located on a barrier island of North Carolina. We determined specific demographic traits such as abundance, sex ratio, size distribution, somatic growth, annual survival, and population growth rate of Snapping Turtles (Chelydra serpentina), Yellow-bellied Sliders (Trachemys scripta), Chicken Turtles (Deirochelys reticularia), and Northern Red-bellied Cooters (Pseudemys rubriventris). We determined that most demographic traits of freshwater turtle populations at NHWEP are structured similarly to other populations studied. We found that the population growth rates for three out of the four species analyzed are increasing, indicating expanding populations (with the exception of T. scripta). The annual survivorship rate for D. reticularia was similar to that of many semiaquatic turtles, contradicting previous studies for this species that have reported low annual survival because of reduced longevity. Analyzing multiple demographic traits of different freshwater turtle species within a maritime forest assemblage on a barrier island provides an important baseline on freshwater turtle demographics in unique habitats that are subject to intense environmental stochasticity. [ABSTRACT FROM AUTHOR]

Seagrass provides a wide range of economically and ecologically valuable ecosystem services, with shoreline erosion control often listed as a key service, but can also alter the sediment dynamics and waves within back‐barrier bays. Here we incorporate seagrass dynamics into an existing barrier‐marsh exploratory model, GEOMBEST++, to examine the coupled interactions of the back‐barrier bay with both adjacent (marsh) and nonadjacent (barrier island) subsystems. While seagrass reduces marsh edge erosion rates and increases progradation rates in many of our 288 model simulations, seagrass surprisingly increases marsh edge erosion rates when sediment export from the back‐barrier basin is negligible because the ability of seagrass to reduce the volume of marsh sediment eroded matters little for back‐barrier basins in which all sediment is conserved. Our model simulations also suggest that adding seagrass to the bay subsystem leads to increased deposition in the bay, reduced sediment available to the marsh, and enhanced marsh edge erosion until the bay reaches a new, shallower equilibrium depth. In contrast, removing seagrass liberates previously sequestered sediment that is then delivered to the marsh, leading to enhanced marsh progradation. Lastly, we find that seagrass reduces barrier island migration rates in the absence of back‐barrier marsh by filling accommodation space in the bay. These model observations suggest that seagrass meadows operate as dynamic sources and sinks of sediment that can influence the evolution of coupled marsh and barrier island landforms in unanticipated ways. Plain Language Summary: Seagrass often grows in coastal bays sheltered behind barrier islands and salt marshes. While seagrass provides essential habitat for marine organisms, it also makes waves in the bay smaller and helps hold sediment in place. We use a barrier‐marsh‐bay computer model (GEOMBEST++Seagrass) to investigate how seagrass impacts the evolution of neighboring marsh and barrier island landforms. In our model simulations, we find that the presence of seagrass in the bay generally reduces the loss of marsh but under certain conditions may actually increase marsh loss. Additionally, we find that when seagrass is added to the bay, the marsh responds temporarily by eroding more rapidly because sediment that would otherwise be added to the marsh is instead held within the bay by seagrass. When seagrass is removed, in contrast, sediment that was once held within the bay by seagrass is free to deposit on the marsh, causing the marsh to expand. Lastly, we find that when no marsh exists, the presence of seagrass slows the landward migration of the barrier island. Our results suggest that it is important to consider the effects of seagrass on adjacent landforms in order to better understand or predict the evolution of the entire barrier‐marsh‐bay landscape. Key Points: Seagrass is generally beneficial for adjacent marsh but may enhance marsh erosion when sediment export from the back‐barrier is negligibleExpanding (contracting) seagrass meadows operate as dynamic sinks (sources) of sediment that impact adjacent marsh and barrier evolutionSeagrass reduces barrier island migration rates in the absence of back‐barrier marsh by filling accommodation space in the bay [ABSTRACT FROM AUTHOR]

Barrier islands are important landforms in many coastal systems around the globe. Studies of modern barrier island systems are mostly limited to those of siliciclastic realms, where the islands are recognized as mobile features that form on transgressive coastlines and migrate landward as sea‐level rises. Barrier islands of the 'Great Pearl Bank' along the United Arab Emirates coast are the best‐known carbonate examples. These Holocene islands, however, are interpreted to be anchored by older deposits and immobile. The mid‐Holocene to late‐Holocene depositional system at Al Ruwais, northern Qatar, provides an example of a mobile carbonate barrier island system, perhaps more similar to siliciclastic equivalents. Sedimentological and petrographic analyses, as well as 14C‐dating of shells and biogenic remains from vibracored sediments and surface deposits, show that after 7000 years ago a barrier system with a narrow back‐barrier lagoon formed along what is now an exposed coastal zone, while, contemporaneously, a laterally‐extensive coral reef was forming immediately offshore. After 1400 years ago the barrier system was forced to step ca 3 km seaward in response to a sea‐level fall of less than 2 m, where it re‐established itself directly on the mid‐Holocene reef. Since that time, the barrier has retreated landward as much as 1000 m to its current position, exposing previously‐deposited back‐barrier lagoonal sediment at the open‐coast shoreline. In modern neritic warm‐water carbonate settings mobile barrier island systems are rare. Their construction and migration may be inhibited by reef formation, early cementation, and the relative inefficiency of sourcing beach sediments from open carbonate shelves. Carbonate barrier island systems likely formed more commonly during geological periods when ramps and unrimmed shelves predominated and in calcite seas, when meteoric cementation was minimized as a result of initial calcitic allochem mineralogy. As with their siliciclastic analogues, however, recognition of the influence of these transient landforms in the rock record is challenging. [ABSTRACT FROM AUTHOR]

Barrier island response to sea‐level rise depends on their ability to transgress and move sediment onto and behind the barrier, either through flood‐tidal delta deposition or via overwash. Our understanding of these processes over decadal or longer timescales, however, is limited. Here we use a recently developed barrier island model (BRIE) to better understand the interplay between tidal dynamics, overwash fluxes, and sea‐level rise on barrier coasts and barrier island stratigraphy. Model results suggest that in microtidal environments with large alongshore sediment transport fluxes, tidal inlets are ephemeral and migrate rapidly. These conditions lead to effective deposition of flood‐tidal deltas and allow inlets to constitute most of the landward sediment flux. Whether barrier islands can survive sea‐level rise depends on the combined landward sediment flux from overwash and flood‐tidal delta deposition, likely making barrier islands with artificially stabilized inlets (via jetty construction or maintenance dredging) more vulnerable to sea‐level rise. Key Points: Flood‐tidal deltas built by ephemeral and rapidly migrating tidal inlets contribute significantly to barrier landward movement in response to sea‐level riseAdditional landward sediment flux from tidal inlets can help barrier islands keep pace with sea‐level riseBarrier stratigraphy is not always a good indicator of formative landward sediment fluxes [ABSTRACT FROM AUTHOR]

Low‐lying, wave‐dominated, sandy coastlines can exhibit high rates of shoreline change that may impact coastal infrastructure, habitation, recreation, and economy. Efforts to understand and quantify controls on shoreline change typically examine factors such as sea‐level rise; anthropogenic modifications; geologic substrate, nearshore bathymetry, and regional geography; and sediment grain size. The role of shoreline planform curvature, however, tends to be overlooked. Theoretical and numerical model considerations indicate that incident offshore waves interacting with even subtle shoreline curvature can drive gradients in net alongshore sediment flux that can cause significant erosion or accretion. However, these predictions or assumptions have not often been tested against observations, especially over large spatial and temporal scales. Here, we examined the correlation between shoreline curvature and shoreline change rates for spatially extended segments of the U.S. Atlantic and Gulf Coasts (~1,700 km total). Where shoreline stabilization (nourishment or hard structures) does not dominate the shoreline change signal, we find a significant negative correlation between shoreline curvature and shoreline change rates (i.e., convex‐seaward curvature [promontories] is associated with shoreline erosion, and concave‐seaward curvature [embayments] with accretion) at spatial scales of 1–5 km alongshore and timescales of decades to centuries. This indicates that shoreline changes observed in these reaches can be explained in part by gradients in alongshore sediment flux acting to smooth spatial variations in shoreline curvature. Our results suggest that shoreline curvature should be included as a key variable in modeling and risk assessment of coastal change on wave‐dominated, sandy coastlines. Key Points: Shoreline change on sandy, wave‐dominated barrier islands is partially explained by shoreline smoothing from alongshore transport gradientsWhere shoreline stabilization is not prevalent, shoreline curvature can explain a significant amount of the shoreline change signalCorrelation strength varies regionally with wave climate in ways that are consistent with theoretical and model predictions [ABSTRACT FROM AUTHOR]

Coastal resilience is threatened as storm‐induced disturbances become more frequent and intense with anticipated changes in regional climate. After severe storms, rapid recovery of vegetation, especially that of dune‐stabilizing plants, is a fundamental property of coastal resilience. Herbivores may affect resilience by foraging and trampling in disturbed areas. Consequently, assessing the impacts of herbivores on recovering vegetation is important for coastal land management.We combined imagery classification, wildlife monitoring, and trend analysis to investigate effects of white‐tailed deer on recovery rates of vegetation four years poststorm in nine overwashed areas. We estimated local deer density with trail cameras, how it relates to an index of primary productivity, and assessed the relationship between deer density and rates of vegetation recovery in overwash fans.Prestorm vegetation cover consisted of shrubs and sporadic patches of beach grass. Poststorm cover was dominated by beach grass. At current rates, vegetation coverage will return to prestorm conditions within the decade, though community transition from grasses to shrubs will take much longer and will vary by site with dune formation.The effect of deer on rates of vegetation recovery was negative, but not statistically significant nor biologically compelling. Although effects of deer trampling on beach grass are evident in classified imagery, deer foraging on beach grass had little effect on its rate of spread throughout overwash fans.While the rate of spread of the primary dune‐building grass was not deleteriously affected by deer, locally high deer densities will likely affect the future establishment and development of herbs and shrubs, which are generally more palatable to deer than beach grass. [ABSTRACT FROM AUTHOR]

We document a case of exceptionally large natural breaching of a sandy spit (Sacalin spit, Danube Delta) using multiannual to seasonal surveys of topography and bathymetry on successive cross‐barrier and shoreface profiles, LiDAR data, satellite imagery, and wind and wave data. The large breach, which quickly reached 3.4 km in May 2014, is attributed to morphological preconditioning of the narrow (50–150 m) barrier, which was susceptible to breaching even during moderate storm conditions. The event switched the barrier's decadal evolution from low cross‐shore transport to high cross‐shore transport over the barrier, which is an order of magnitude larger than during the non‐breach period. Upper shoreface erosion, as indicated by the extensive erosion down to −4 m, indicates that this zone is a significant source for the rebuilding of the barrier. Barrier recovery and widening trigger a negative feedback which limits the back‐barrier sediment transfer. As a result, back‐barrier deposition decreases whilst the barrier aggradation through overwash becomes more frequent. The Big Breach (TBB) closed naturally in three years. The very high deposition rate of sediment in the breach is a testimony of the high sediment volumes supplied by the longshore transport and the high sediment released through shoreface retreat, and resulted in widening the barrier to a maximum of 1 km. Since the newly‐formed barrier shoreline retreated 500 m, this reveals that barrier breaching is an important mechanism which significantly accelerates the landward migration of the barrier system and is a proof of the highly non‐linear morphodynamics involved in the barrier island translation. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Schulz, J.L. and Leberg, P.L., 2019. Factors affecting prey availability and habitat use of nonbreeding piping plovers (Charadrius melodus) in coastal Louisiana. Journal of Coastal Research, 35(4), 861–871. Coconut Creek (Florida), ISSN 0749-0208. The Gulf of Mexico is home to a large proportion of the wintering population of the threatened piping plover (Charadrius melodus), but little is known about the bird's ecology in this region. In Louisiana, the majority of nonbreeding piping plovers are found on the state's rapidly eroding barrier islands. Between August 2013 and May 2014, surveys were conducted to assess the abundance and habitat use of piping plovers, as well as to characterize their invertebrate prey base, on Whiskey and Trinity islands. Seventy-eight percent of piping plovers observed were foraging, 18% roosting, and 4% engaged in other ambulatory activities. Intertidal habitat, such as foreshore beach and tidal flats, was used by 87% of foraging and 96% of roosting piping plovers. Though available, backshore beach, interior sand flats, and dunes were rarely used. The invertebrate community was dominated by haustoriid amphipods (87.5% of individuals collected), followed by bivalves (9.3%) and polychaetes (2.7%). Seasonal patterns and between-island differences were observed in all three invertebrate taxa, but these effects differed between beach habitat and the gulfside and bayside of prominent sand spits. Moisture had a positive effect on amphipod abundance and polychaete presence. There was no association between invertebrate and plover abundance, and prey abundance did not differ between sample sites where piping plovers were observed foraging and random sites. The low abundances of birds and prey, coupled with high variation among samples, are challenges for establishing baseline datasets to evaluate the consequences of coastal restoration activities. [ABSTRACT FROM AUTHOR]

Preserved beach and foredune ridges may serve as proxies for coastal change, reflecting alterations in sea level, wave energy, or past sediment fluxes. In particular, time‐varying shoreface sediment budgets have been inferred from the relative size of foredune ridges through application of radiocarbon and optically stimulated luminescence dating to these systems over the last decades. However, geochronological control requires extensive field investigation and analysis. Purely field‐based studies might also overlook relationships between the mechanics of sediment delivery to the shoreface and foredune ridges, missing insights about sensitivity to changes in sediment budget. We therefore propose a simple geomorphic model of beach/foredune‐ridge and swale morphology to quantify the magnitude of changes in cross‐shore sediment budget, employing field measurements of ridge volume, ridge spacing, elevation, and shoreline progradation. Model behaviors are constrained by the partitioning of sediment fluxes to the shoreface and foredune ridge and can be used to reproduce several cross‐shore patterns observed in nature. These include regularly spaced ridges ("washboards"), large singular ridges, and wide swales with poorly developed ridges. We evaluate our model against well‐preserved ridge and swale systems at two sites along the Virginia Eastern Shore (USA): Fishing Point, for which historical records provide a detailed history of shoreline progradation and ridge growth, and Parramore Island, for which a relatively more complex morphology developed over a poorly constrained period of prehistoric growth. Our results suggest this new model could be used to infer the sensitivity of field sites across the globe to variations in sediment delivery. Plain Language Summary: Understanding past change in the sediment budgets of coastal systems is expensive and time consuming, often missing crucial insights about sensitivity to future changes. In this study, we developed a model to reconstruct sediment delivery through time, using relationships describing the size and distribution of beach ridges relative to rate of shoreline advance. We tested our model against a field site with a detailed history of coastal evolution, later applying it to a location which largely developed in a prehistoric setting. Our results show that we can use field and remote measurements of beach ridges to model past rates of sediment delivery, providing insights into how future changes may affect the behavior of coastal systems. Key Points: We develop a model to quantify the magnitude of changes in past sediment delivery to prograding coasts based on beach‐ridge morphologyWe validate the model against a field site with a history of beach and ridge growth and then apply it to a prehistorically developed siteThe model is most applicable to investigations of coastal evolution with limited geochronologic control [ABSTRACT FROM AUTHOR]

Dune spits of the island of Sylt (North Sea) persisted through millennia by mobile dunes transferring sand from exposed to sheltered shores. However, 150 years of systematic planting on washovers, blowouts and migrant dunes have almost completely stopped this sand conveyor belt. Spits lost sand until sand replenishments to the exposed side compensated for losses during the last three decades. Based on maps since 1878, aerial images from the 1930s onward as well as botanical ground surveys, we document a long-term shift from loose grass cover to dense heather dominated vegetation. Bare sand areas almost vanished and high shrubs proliferated. Only three dunes continue migrating with about 3 m a-1 since 1936. Mainly artificial dune stabilizations and introduced plants have facilitated succession to an almost complete plant cover. Thus, revitalization of aeolian dynamics would be desirable, and pilot projects may acquire the appropriate knowledge. For a 1.7 × 2.5-km corridor across the island spit, we therefor discuss two suggested experiments: (1) intensify sand nourishments to the eroding beach and stop stabilization measures to allow excess sand blown inland and washovers entering deflation plains, and (2) examine the potential of tunnels for roads to let mobile dunes passing over. Such experiments may not only contribute to dune biodiversity but also to long-ranging adaptations of crowded barrier islands to accelerating sea level rise. [ABSTRACT FROM AUTHOR]

Barrier islands are dynamic ecosystems that change gradually from coastal processes, including currents and tides, and rapidly from episodic events, such as storms. These islands provide many important ecosystem services, including storm protection and erosion control to the mainland, habitat for fish and wildlife, and tourism. Habitat maps, developed by scientists, provide a critical tool for monitoring changes to these dynamic ecosystems. Barrier island monitoring often requires custom habitat maps due to several factors, including island size and the classification of unique geomorphology-based habitats, such as beach, dune, and barrier flats. In this study, we reviewed barrier-island-specific habitat mapping efforts and highlighted common habitat class types, source data, and mapping approaches. We also developed a framework for mapping geomorphology-based barrier island habitats using a rule-based, geographic object-based image analysis approach, which included the use of field data, tide data, high-resolution orthophotography, and lidar data. This framework integrates several barrier island mapping advancements with regard to the use of landscape position information for automated dune extraction and the use of Monte Carlo analyses for the treatment of elevation uncertainty for elevation-dependent habitats. Specifically, we used the uncertainty analyses to refine automated dune delineation based on elevation relative to extreme storm water levels and to increase the accuracy of intertidal and supratidal/upland habitat delineation. We found that dune extraction results were enhanced when elevation relative to storm water levels and visual interpretation were also applied. This framework could also be applied to beach–dune systems found along a mainland. [ABSTRACT FROM AUTHOR]

The upper beach, between the astronomical high tide and the dune-toe, supports habitat and recreation along many beaches, making predictions of upper beach change valuable to coastal managers and the public. We developed and tested a Bayesian network (BN) to predict the cross-shore position of an upper beach elevation contour (ZlD) following 1 month to 1-year intervals at Fire Island, New York. We combine hydrodynamic data with series of island-wide topographic data and spatially limited cross-shore profiles. First, we predicted beach configuration of ZlD positions at high spatial resolution (50 m) over intervals spanning 2005-2014. Compared to untrained model predictions, in which all six outcomes are equally likely (prior likelihood = 0.16), our prediction metrics (skill = 0.52; log likelihood ratio = 0.14; accuracy = 0.56) indicate the BN confidently predicts upper beach dynamics. Next, the BN forecasted three intervals of beach recovery following Hurricane Sandy. Results suggest the pre-Sandy training data is sufficiently robust to require only periodic updates to beach slope observations to maintain confidence for forecasts. Finally, we varied input data, using observations collected at a range of temporal (1-12 months) and spatial (50 m to > 1 km) resolutions to evaluate model skill. This experiment shows that data collection techniques with different spatial and temporal frequencies can be used to inform a single modeling framework and can provide insight to BN training requirements. Overall, results indicate that BNs and inputs can be developed for broad coastal change assessment or tailored to a set of predictive requirements, making this methodology applicable to a variety of coastal prediction scenarios. [ABSTRACT FROM AUTHOR]

Gulf Islands National Seashore in Florida, USA, hosts breeding populations of migratory beach‐nesting birds, along with other avian species. It consists of 2 barrier islands with a public paved road that runs through the center. For the past decade, bird carcasses were observed opportunistically along the roadway, and this mortality sparked interest among wildlife managers about population‐level effects on species of conservation concern. Accurately estimating wildlife mortality from carcass counts requires correcting negative bias due to imperfect detection and scavenging between surveys. We had only 1 observer available to perform road surveys, leading to a carcass detection rate of 1.0 after discovery, and a persistence rate that was only estimable after discovery. We therefore employed a robust design version of a time‐of‐detection model to estimate detection and persistence rates. We used a post hoc derivation of the superpopulation size for carcasses, which is an estimate of the total number of carcasses that were ever present on the road for any period of time. Each primary survey consisted of 2 passes on the road within 4 hours. Probability of detection for 2 passes was near 100%. We counted 77 avian carcasses between 22 May and 4 July 2013 and estimated that this represented 106.8 ± 21.3 (SE) birds killed on the road during that time period. Opportunistic surveying by park service staff detected between 0% and 100% of carcasses we estimated to be present, depending on the date. Standardized surveys are needed going forward to estimate annual variation in carcass numbers and to determine effectiveness of mortality mitigation. Moreover, further research can use these estimates to understand the contribution of road mortality to population trends. © 2018 The Wildlife Society. We implemented a robust design framework of a time‐of‐detection model for a single observer to estimate the number of birds killed by vehicle collisions on park roadways at Gulf Islands National Seashore, Florida, USA. Our results indicate that raw counts substantially underestimate avian carcasses, and management action is needed to mitigate the effects of road mortalities on protected beach‐nesting bird species in the park. [ABSTRACT FROM AUTHOR]

A new species of the Sympistis badistriga species-group, Sympistis eleaner Adams, sp. n. is described from Sapelo Island, a back-barrier island in coastal Georgia, United States of America. Adults and genitalia of S. eleaner are illustrated, in addition to adults of similar species in the Sympistis badistriga species-group. The composition of this species-group is discussed. [ABSTRACT FROM AUTHOR]

Barrier islands are found around the world and are important environmentally and economically. With accelerated sea level rise and relentless storms, their evolution is complex but important to understand, especially from a coastal planning and managing perspective. In this study, shoreline change estimates from aerial photography (1949, 1974, 2006), sedimentological and stratigraphic investigation, and analysis of geomorphic character were used to evaluate the hurricane response and decadal evolution of Ocracoke Island, NC. Between 1949 and 2006, the majority (> 65% of transects) of the entire island eroded at an average rate of − 0.54 m/year. Cross-island width decreased by as much as 40% (180 m) over the period. Hurricane Isabel (2003) represented up to 23% of the long-term net change in some regions of the island. The rate of narrowing of Ocracoke Island appears to have increased in the last half century and is due to a combination of natural and anthropogenic factors. Isabel overwashed a total of 9% of the island based on aerial photographic analysis with an average deposit thickness of 0.24 m based on trench investigation. Assessment with the Storm Impact Scale showed a direct relationship between overwash and the pre-existing dune conditions, which had been affected by long-term erosion. Sedimentological signatures interpreted from cores show up to four distinct stacked overwash deposits, potentially dating back as far as 1944. This multi-pronged analysis shows the complexity of barrier island evolution and highlights the necessity to examine and model a system response in four dimensions (i.e., spatially and with time). [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

The results from an investigation of the coupled Mustang Island-Corpus Christi Bay complex, Gulf of Mexico, shows that the island was eliminated as an effective salinity barrier between 8.86 and 8.17 ka. This event is recorded by a 5-fold increase in dinoflagellate cysts within Corpus Christi Bay. During this time, the bay-head delta shifted 15 km landward and oyster reefs within the bay died off. Our age model indicates that this event most likely resulted from the most rapid period of eustatic rise of the Holocene, which peaked at 8.18-8.31 ka. This event is attributed to late-stage ice sheet disintegration, particularly in North America, by the rapid draining of Lake Agassiz-Ojibway. Local glacial-isostatic factors resulted in a sea-level rise of only 0.2-0.56 m in the western Gulf of Mexico, which was less than needed to submerge the barrier. Rather, it was the marked nature of this sea-level rise that led to the virtual destruction of Mustang Island as an effective salinity barrier. These results provide an analog for predicting coastal morphodynamic response to accelerated sea-level rise and emphasize the need for better understanding of barrier response to sea-level rise and developing improved numerical models for predicting future changes to coastal barrier shorelines. [ABSTRACT FROM AUTHOR]

Storm-driven sediment fluxes onto and behind barrier islands help coastal barrier systems keep pace with sea level rise (SLR). Understanding what controls cross-shore sediment flux magnitudes is critical for making accurate forecasts of barrier response to increased SLR rates. Here, using an existing morphodynamic model for barrier island evolution, observations are used to constrain model parameters and explore potential variability in future barrier behavior. Using modeled drowning outcomes as a proxy for vulnerability to SLR, 0%, 28%, and 100% of the barrier is vulnerable to SLR rates of 4, 7, and 10 mm/yr, respectively. When only overwash fluxes are increased in the model, drowning vulnerability increases for the same rates of SLR, suggesting that future increases in storminess may increase island vulnerability particularly where sediment resources are limited. Developed sites are more vulnerable to SLR, indicating that anthropogenic changes to overwash fluxes and estuary depths could profoundly affect future barrier response to SLR. [ABSTRACT FROM AUTHOR]

Thresholds for belowground decomposition rates based on nearness to groundwater were identified on a Virginia barrier island. Negative exponential decay rates (k = 0.310-0.915 yr.) varied according to average distance to the freshwater free surface, with lowest decay occurring in low elevations (marsh and deeper soils of a wooded swale), and highest decay occurring at mid to high elevations (surface soils in wooded swales and all dune sites). The majority of decay rate variances were explained by mean annual depth to the freshwater free surface (r = 0.78). Locations with mean annual groundwater depths greater than 0.95 m were substantially less affected by fluctuations in groundwater levels (r = 0.09) than where groundwater was near the soil surface (r = 0.83). Two vegetation-based decay thresholds were identified at mean annual groundwater depths of −0.041 m and 0.538 m, separating belowground decay into three groups (low, moderate, and high decay). These groups tended to correspond to the three interior barrier island plant communities (marsh, wooded swale, and dune), but with overlap. The groundwater free surface provides a useful metric that can be used in geospatial models to predict process rates and vegetation patterns in the dynamic barrier island landscape. [ABSTRACT FROM AUTHOR]

Backbarrier saltmarshes are considered carbon sinks; however, barrier island transgression and the associated processes of erosion and overwash are typically not included in coastal carbon budgets. Here, we present a carbon-budget model for transgressive barrier islands that includes a dynamic carbon-storage term, driven by backbarrier-marsh width, and a carbon-export term, driven by ocean and backbarrier shoreline erosion. To examine the impacts of storms, human disturbances and the backbarrier setting of a transgressive barrier island on carbon budgets and reservoirs, the model was applied to sites at Core Banks and Onslow Beach, NC, USA. Results show that shoreline erosion and burial of backbarrier marsh from washover deposition and dredge-spoil disposal temporarily transitioned each site into a net exporter (source) of carbon. The magnitude of the carbon reservoir was linked to the backbarrier setting of an island. Carbon reservoirs of study sites separated from the mainland by only backbarrier marsh (no lagoon) decreased for over a decade because carbon storage could not keep pace with erosion. With progressive narrowing of the backbarrier marsh, these barriers will begin to function more persistently as carbon sources until the reservoir is depleted at the point where the barrier welds with the mainland. Undeveloped barrier islands with wide lagoons are carbon sources briefly during erosive periods; however, at century time scales are net carbon importers (sinks) because new marsh habitat can form during barrier rollover. Human development on backbarrier saltmarsh serves to reduce the carbon storage capacity and can hasten the transition of an island from a sink to a source. [ABSTRACT FROM AUTHOR]

Shrubs have become more dense and expanded beyond their range all over the world for a variety of reasons including increased temperatures, overgrazing, and alteration of historical fire regime. Native shrubs have been encroaching on Virginia barrier island grasslands for over half a century for unknown reasons. Species composition, soil nutrients, leaf area index (LAI), and ground and air temperature were recorded across the shrub to grass transition and at free-standing shrubs in a coastal grassland in order to determine the effect of shrub encroachment on plant community and microclimate. Species richness was significantly lower inside shrub thickets. Soil water content, organic matter, nitrogen (N), carbon (C), and LAI were higher in shrub thickets and free-standing shrubs compared to grasslands. Summer and fall maximum temperatures were lower and more moderate where shrubs were present. Fall and winter minimum temperatures were highest inside shrub thickets. Native shrubs impact microclimate and species composition immediately upon encroachment. These shrubs lower overall species composition, increase soil nutrients and moisture, moderate summer temperature, and increase winter temperature, which has consequences on a larger scale. As barrier islands are critical for protecting marsh and mainland habitats, understanding this mechanism for shrub expansion is important to predict future encroachment of shrubs and displacement of grassland habitat. [ABSTRACT FROM AUTHOR]

Coastal freshwater aquifers are highly vulnerable to climate change and other anthropogenic environmental impacts. Therefore, managing coastal freshwater for future use requires critical planning. This is especially true for small barrier islands where, in most cases, groundwater could be the only freshwater resource. In this study, the combined effects of climate change, land-use changes, and increased groundwater pumping on freshwater resources of a barrier island were studied. A case study was completed using the field data available for Dauphin Island, a small barrier island located in Alabama, U.S., and by using the simulation data generated from multiple water-resource-management models. Soil and Water Assessment Tool (SWAT) simulations provided recharge estimates under various future land use/land cover and climate-change scenarios. Downscaled global circulation model provided precipitation and temperature patterns for the period 2011–2030. The recharge estimates from SWAT were then used as input in a numerical groundwater model to evaluate saltwater-intrusion effects and forecast the changes in freshwater storage within the island aquifer system. Various groundwater-management scenarios were simulated using the MODFLOW-family computer code SEAWAT to assess the sensitivity of the groundwater system to increased pumping rates and decreased recharge due to climate change and/or future developments. SEAWAT was used to predict the lateral saltwater-intrusion effects and its impacts on groundwater quality and freshwater volume. The simulation results show that the saltwater wedge would advance laterally under all future climate-change scenarios. These results indicate that the shallow unconfined aquifer might not be able to sustain any significant future population growth, especially under adverse climate-change conditions. Analysis of changes in the volume of freshwater lens provided a broader understanding of the coupled effects of climatic and anthropogenic changes on freshwater storage and this information can be used to better manage Dauphin Island’s unconfined groundwater system. [ABSTRACT FROM AUTHOR]