Ribbed mussels (Geukensia demissa) are functionally important salt marsh bivalves along the Atlantic coast of North America that provide ecosystem services such as water filtration, nutrient removal, shoreline stabilization, and sediment accretion. Despite their integral role in ecological and structural marsh processes, it remains unclear whether living shorelines—now widely promoted as a nature-based coastal protection—provide comparable habitat for ribbed mussels as natural fringe marshes. In this study, we compare juvenile ribbed mussel settlement across four living shoreline and natural fringing marsh site pairs in the lower Chesapeake Bay. We deployed artificial substrates for mussel settlement to assess differences across sites and examine relationships with marsh conditions (e.g. cordgrass and mussel density, inundation, connectivity). After a three-month period, juvenile mussel counts were ∼11x lower on substrates deployed in living shorelines than in natural marshes. An additional one-week trial revealed less than half the number of settlers at the living shoreline compared to its natural counterpart. Mussel settlement was most strongly affected by site type (living shoreline versus natural marsh) but did not exhibit any detectable relationships with the other marsh metrics. Our findings suggest that the typical marsh-sill living shoreline design may constrain early recruitment of ribbed mussels through interrupted or absent settlement cues, possibly due to altered hydrodynamics (e.g. presence of the rock sill) and/or substrate conditions. Restoration design that incorporates elements critical for larval delivery, settlement, and survival will enhance mussel recruitment, strengthen positive marsh-mussel feedbacks, and improve the resilience and ecosystem service provision of living shorelines.

Oysters produce critical biogenic habitat in estuaries and have throughout their evolutionary history. Early Holocene coastal environments experienced rapid rates of relative sea level rise, which dramatically shifted the physical footprint of estuaries and intertidal habitat for sessile species. The study objectives were to: 1) describe the distribution and density of fossil oyster shell on the mid-Atlantic continental shelf; 2) identify time since death; 3) construct an age-length-shell weight relationship; and from these 4) simulate population dynamics and habitat production for an early Holocene oyster reef. We conducted dredge surveys on the mid-Atlantic continental shelf and collected 859 fossil oyster shells and shell fragments. Selected shells were radiocarbon dated to 11,072 to 8472 cal yr BP. Using preserved material, we established an age-length-weight relationship to calculate the average shell weight (g) for a given age at death. We simulated early Holocene oyster populations under 300 scenarios, which included three recruitment levels (high, medium, low) and 100 natural mortality levels ranging from similar to 10 to 50% mortality yr(-1) (M = 0.1 to 0.7). Simulated oyster populations were more resilient to relative sea level rise under high recruitment and low natural mortality scenarios. High recruitment and low natural mortality enabled oyster populations to maintain higher mean population size (# m(-2)), mean population biomass (g m(-2)), mean annual carbonate production (g m(-2) yr(-1)) from growth of living oysters, and mean annual gross reef accretion (g m(-2) yr(-1) and mm yr(-1)) from mortality, which was critical for reefs to accrete rapidly to match relative sea level rise.

Nature-based solutions for erosion control that incorporate oyster reefs, alone or in combination with other habitats, are an increasingly popular approach due to their potential to protect shorelines and enhance oyster production. However, the extent to which natural or constructed oyster reefs provide shoreline protection remains unclear. We conducted a global systematic literature review and meta-analysis to summarize and evaluate the potential of oyster reefs in attenuating waves, promoting sediment accretion, and/or reducing shoreline erosion. Factors extracted from studies included shoreline protective measures examined, oyster reef structure type, and oyster reef tidal location. The results of the meta-analysis showed generally positive outcomes across measures, but also considerable uncertainty. Intertidal projects had the most consistent outcomes, but the magnitude of the effects varied by reef type, shoreline protective measure, and tidal location. This review provides a novel synthesis of the protection potential of oyster reefs across multiple shoreline protective measures. Our findings suggest that the success of oyster reefs is highly dependent on site-specific environmental conditions, particularly wave energy and height, as well as design characteristics, such as tidal location and crest height. These findings may serve as a reference for future research and inform the design and implementation of oyster reef structures for shoreline protection.

Subtidal nearshore seagrass beds are important components of coastal ecotones. Understanding their association with shoreline morphology and shoreline stabilization interventions is critical to achieving a holistic approach to restoration. We combined geospatial analyses with field-based monitoring to better understand intra-ecotone associations between shorelines and nearshore seagrass beds in a shallow subtropical estuary. Using GIS analyses of aerial imagery, shoreline characterization models, and seagrass coverage models, the relationship between shoreline morphology, erosion, and yearly persistence of seagrass was examined in Mosquito Lagoon, FL between 2011 and 2021. Seagrass beds growing adjacent to stabilized “living shoreline” segments were monitored in the field throughout the 2023 growing season (March–November). GIS analyses indicate that within this microtidal system, seagrass persistence was associated with wider intertidal zones, shallower nearshore depths, and reduced rates of shoreline retreat. These shoreline morphological differences were all relatively small (< 1 m). Increased seagrass density along natural uneroded shorelines relative to three living shoreline designs was observed during field monitoring. Bayesian hierarchical models suggest that in this study, differences in seagrass density appeared attributable to shoreline slope rather than the stabilization treatment itself. Although the individual analyses in this study have relatively high levels of uncertainty, all suggest that seagrass suitability was greater along gradually sloped, slowly eroding shorelines. We recommend measurements of subtidal slope and adjacent SAV be incorporated into living shoreline monitoring protocols, as this represents a potential mechanism by over time, which intertidal deployments can positively impact adjacent subtidal communities.

Abstract Invasive alien species (IAS) are one of the most serious threats to global biodiversity and one of the leading causes of federal protection required for native species under the United States Endangered Species Act (ESA). Our goal was to document how IAS impact threatened and endangered species (T&ES) under the ESA to improve recovery efforts. We reviewed Federal Register listing decisions for 1,545 T&ES listed under the ESA and found that 58% were impacted by IAS. Pacific Island T&ES (97%) face greater threats from IAS compared to Mainland (38%) and Atlantic Island T&ES (22%), but the number of IAS impacting T&ES has increased over time in all 3 geographic areas, except for animals on Atlantic Islands. On Pacific Islands, we found that IAS impacted T&ES most through adverse habitat modification and competition, mainly through invasive plants. Negative interactions caused by IAS on the Mainland were mainly from invasive fish and plants, while on the Atlantic Islands they were caused by invasive mammals and plants. The IAS causing the greatest number of negative interactions included rats (Rattus), wild pigs (Sus), goats (Capra), fish (e.g., Lepomis and Micropterus), and various genera of plants (e.g., Schinus, Rubus, and Psidium). Based on our findings, immediate actions are needed to protect native biodiversity in the U.S. from IAS, especially on Pacific Islands. Such management actions include eradication of IAS, restoration of native habitat, development of robust policies that aim to prevent the further spread and establishment of IAS, and effective decision support tools. These actions will require coordinated leadership to improve recovery of T&ES, especially given the synergistic impacts of international trade and climate change.

Abstract Living shorelines (LSs) increasingly are implemented as a defense against coastal erosion and rising seas; however, their ecological function for wading birds has not been evaluated. Here, we compared heron and shorebird use of LSs (created fringe salt marshes with a wave break fronting the planted marshes) to natural‐fringe marshes (NFMs) in the Chesapeake Bay. We assessed the use between May and August in 2018 and 2019 at 13 tidal marsh pairs, each consisting of one LS and NFM site, with sites within pairs having similar surrounding land use and wave exposure. In each year, we assessed diurnal use with video cameras recording at least four 30‐min segments/day for a total of 677 h of video, and nocturnal/diurnal use with acoustic recording equipment recording 10‐min sound files every 2 h/day for a total of 160 h of recording. We quantified diurnal use by measuring the total time a species spent at a site, and nocturnal/diurnal use by estimating the probability of detection (i.e., presence/absence). We detected four heron and five shorebird species when data were aggregated across pairs and sampling methods. Using Bayesian mixed models, time of use did not differ between LS and NFM sites for great blue herons (Ardea herodias) and yellow‐crowned night‐herons (Nyctanassa violacea). In contrast, time of use was higher for green herons (Butorides virescens) and spotted sandpipers (Actitis macularis) at LS sites but tended to be higher for great egrets (Ardea alba) at NFM sites. The probability of detection did not differ between LS and NFM sites for great blue herons and great egrets (combined as “Ardea spp.” due to difficulty in differentiating calls under noisy conditions), yellow‐crowned night‐herons, and spotted sandpipers. Green herons and killdeer (Charadrius vociferous), however, tended to be detected more frequently at LS sites. Collectively, our research indicates that LSs are functionally equivalent to NFMs for herons and shorebirds. We hypothesize that the low‐profile rock sills of LS provide platforms for resting and preening and offer prey even when vegetated marshes are unavailable to short‐legged species during flooding tides. In addition to their established reduction of coastal erosion, LSs provide habitat for herons and shorebird species.

Salt marshes provide valued services to coastal communities including nutrient cycling, erosion control, habitat provision for crustaceans and fish (including juvenile and forage fish), and energy transfer from the detrital based food web to the greater estuarine system. Living shorelines are erosion control structures that recreate natural shorelines, such as fringing marshes, while providing other beneficial ecosystem services. Living shorelines are expected to provide fish and crustacean (nekton) habitat, but few comprehensive studies have evaluated nekton habitat use across a range of living shoreline settings and ages. We sampled the intertidal marsh and subtidal shallow water nekton community at 13 paired living shoreline and reference marsh sites, with living shorelines ranging in age from 2 to 16 years from construction. We compared nekton diversity, nekton community abundance, nekton community biomass, forage abundance, and juvenile abundance at reference marshes and living shorelines. Our results indicate that living shorelines are providing suitable marsh habitat for nekton communities, including juveniles and forage base species. The difference in living shoreline construction (rock sill, soil composition) did not appear to diminish habitat quality in the marsh or in nearshore waters, and rock sills may provide enhanced structural shoreline habitat. Living shorelines have the potential to combat marsh habitat loss and provide resilient nekton nursery habitat.

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

Accelerating sea level rise in Virginia, United States, will significantly increase the flooding threat to low-lying roads, residences, and critical infrastructure as well as raise the water table, allowing saltwater intrusion into well water and threatening the function of septic fields. Although most of the adaptation work in Virginia has focused on urban economic centers, the majority of the coastline is rural and faces different threats and opportunities to address them compared to urban areas due to their reduced economic assets and their reliance on private infrastructure. In this case study, we assess the potential for geospatially quantifying impact to septic systems and adjacent water ways due to sea level rise. The case study found that the data necessary to reliably quantify these impacts on a state-wide scale are lacking and collection of that information needs to be prioritized given the potential for extensive sea level impacts.

ABSTRACTClimate change and coastal development pressures have intensified the need for shoreline protection. Nature-first approaches that use natural habitats, particularly marshes, are being promoted globally as ecologically-beneficial alternatives to grey infrastructure. The ability of these novel shorelines to provide nursery habitat to blue crab, an ecologically and economically important species along the Atlantic and Gulf coasts of the United States, has not been quantified.We quantified the abundance and size distribution of juvenile blue crabs from a chronosequence of living shorelines (created fringing marshes) spanning 2 to 16 years in age (since construction) and compared with paired natural fringing marshes in the southern Chesapeake Bay.Both created and natural fringing marshes are being used by blue crabs as primary nursery habitats. While there were interannual differences in abundance, young blue crabs (≤ 2.5 cm carapace width) were observed in similar densities and sizes at living shoreline and natural marshes. There was no relationship between the age of the living shoreline and blue crab density, indicating that even the youngest living shorelines (2 years) were providing primary nursery habitat. Young blue crabs were more abundant in more isolated marshes and those that were inundated for longer periods of time each tidal cycle, which may be evidence for habitat-limitation.Synthesis and applications:We provide evidence that juvenile blue crabs are comparably using natural and created fringing salt marshes as primary nursery habitat. Although the relative importance of salt marshes as young crab nursery habitat is not fully understood and likely varies by system, the value of marshes within a suite of available structural nursery habitats may increase under a changing climate. The potential for living shorelines to serve as nursery habitat for an economically important species may provide additional incentives to implement these climate adaptation strategies.

Abstract Coastal communities increasingly invest in natural and nature‐based features (e.g., living shorelines) as a strategy to protect shorelines and enhance coastal resilience. Tidal marshes are a common component of these strategies because of their capacity to reduce wave energy and storm surge impacts. Performance metrics of restoration success for living shorelines tend to focus on how the physical structure of the created marsh enhances shoreline protection via proper elevation and marsh plant presence. These metrics do not fully evaluate the level of marsh ecosystem development. In particular, the presence of key marsh bivalve species can indicate the capability of the marsh to provide non‐protective services of value, such as water quality improvement and habitat provision. We observed an unexpected low to no abundance of the filter‐feeding ribbed mussel, Geukensia demissa, in living shoreline marshes throughout Chesapeake Bay. In salt marsh ecosystems along the Atlantic Coast of the United States, ribbed mussels improve water quality, enhance nutrient removal, stabilize the marsh, and facilitate long‐term sustainability of the habitat. Through comparative field surveys and experiments within a chronosequence of 13 living shorelines spanning 2–16 years since construction, we examined three factors we hypothesized may influence recruitment of ribbed mussels to living shoreline marshes: (1) larval access to suitable marsh habitat, (2) sediment quality of low marsh (i.e., potential mussel habitat), and (3) availability of high‐quality refuge habitat. Our findings suggest that at most sites larval mussels are able to access and settle on living shoreline created marshes behind rock sill structures, but that most recruits are likely not surviving. Sediment organic matter (OM) and plant density were correlated with mussel abundance, and sediment OM increased with marsh age, suggesting that living shoreline design (e.g., sand fill, planting grids) and lags in ecosystem development (sediment properties) are reducing the survival of the young recruits. We offer potential modifications to living shoreline design and implementation practices that may facilitate self‐sustaining ribbed mussel populations in these restored habitats.

Living shoreline marshes are coastal wetlands constructed as alternatives to “hardened shorelines” (e.g., bulkheads, riprap) to mitigate erosion and to allow for landward migration of intertidal habitat as sea level rises. Living shorelines are designed to mimic natural fringing marshes and over time should be sinks for carbon and other nutrients. We collected soil cores and aboveground plant material from 13 pairs of natural fringing marshes and living shoreline marshes of different ages and degree of isolation from more extensive marsh shorescapes to compare nutrient pools and accrual. Although the nutrient content of plants was similar within and between marsh types, soil nutrients were variable from both living shorelines aged 2–16 years and long-established natural marshes. Most—but not all—living shoreline marshes had lower soil organic content, higher bulk density, and lower soil % carbon, nitrogen and phosphorus than their natural marsh pair. Variation in soil nutrients from living shorelines was not strongly correlated with either marsh age or degree of isolation in the estuarine shorescape. Assuming constant accrual within individual marshes, we estimated soil nutrient levels in living shorelines would approach those observed in their paired, natural fringing marshes over timescales from less than 10 years to many decades. Living shoreline marshes are on trajectories to match natural marsh function with respect to carbon and nutrient storage in estuarine systems.

Salt marshes and their inhabitants are being displaced by climate change and human development along the coastline. One inhabitant, the ribbed mussel (Geukensia demissa), forms a mutualistic relationship with smooth cordgrass, Sporobolus alterniflorus, along the US Atlantic Coast. Ribbed mussels stabilize the marsh, remove particulate matter from the water column, and promote denitrification, thereby improving local water quality. To quantify the potential effects of SLR on ribbed mussel abundance and resulting impacts on water quality functions, we compared the current and projected future (2050) spatial distributions of ribbed mussels in Chesapeake Bay assuming an intermediate SLR for the region. We found that ribbed mussel abundance was reduced by more than half due to a combination of drowning marshes, coastal squeeze, and a shift from higher to lower quality habitat. Mussel losses were greatest along the mainstem of the Chesapeake Bay, with modest gains in the headwaters. Our results highlight the importance of permeable land cover (including living shorelines) in the future tidal extent to promote marsh transgression for future mussel populations. The projected mussel abundance reductions will result in a > 50% reduction in mussel-mediated filtration and nitrogen processing, ultimately reducing the resilience of marshes in the system.

Ribbed mussels (Geukensia demissa) are a highly abundant bivalve filter feeder throughout the salt marshes of the U.S. Atlantic Coast. These mussels form a mutualistic relationship with smooth cordgrass Spartina alterniflora wherein the grass provides habitat and shade to the mussels, and the mussels stabilize the sediment and fertilize the grass. Salt marshes are, however, rapidly changing and eroding as humans modify the coast, and the rate of sea level rise is accelerating. In order to understand how ribbed mussels may respond to their changing habitat, we collected mussel density and distribution data from 30 marshes covering the range of geomorphic settings found in lower Chesapeake Bay. We used a combination of in situ and GIS-derived spatial variables to develop spatially applied models of ribbed mussel density and physical condition. Of the estimated 1.06 billion ribbed mussels in Virginia, we found that mussels were most abundant along the front edge of marshes in wide creeks, rivers, or bays with dense Spartina and minimal proximal forest, set in agriculturally dominated areas. In contrast, mussel condition was highest in fringing marshes located in narrow tidal creeks. Ribbed mussels responded to factors at a variety of scales, ranging from extremely local (0.5 m) to larger shorescapes (>= 300 m). The methods that we used to create models linking both aquatic and terrestrial variables to explain the variation in ribbed mussel populations along the shoreline provide a valuable tool for identifying baselines and assessing potential for change across estuary-level spatial scales not only for ribbed mussels in the Chesapeake Bay, but also for other sessile, intertidal species in other systems.

Connectivity at the aquatic-terrestrial ecotone is essential for maintaining the delicate balances between biotic and abiotic factors. However, humans have been modifying and disrupting this connectivity through activities such as land-use changes, shoreline development, and resource extraction for centuries. In order to assess how these modifications are affecting connectivity, we conducted two studies within the Chesapeake Bay. The first study focused on identifying socio-economic and landscape factors that affect the rates and distribution of shoreline development along Virginia’s coastline while the second study examined how the spatial distribution of diamondback terrapins (Malaclemys terrapin) responded to human alterations to the aquatic-terrestrial ecotone of the lower Chesapeake Bay. For the shoreline development study, we mapped out changes in two forms of shoreline development (docks and shoreline armoring) from 2002 to 2009 within 83 sites placed along Virginia’s coastline. Overall, we documented 1093 new docks and 53.75 km of new shoreline armoring within our study sites. For a fine-scale spatial assessment of shoreline development distribution, we also conducted occupancy surveys for both docks and shoreline armoring in 1250 sites using aerial imagery from 2009, of which, 25.9% of sites had docks, and 15.1% of sites had shoreline armoring. Model results revealed that both rates and distribution were positively affected by human development and negatively affected by large areas of marsh. To examine the spatial distribution of diamondback terrapins, we conducted repeated occupancy surveys at 165 sites in 2012 and 2013. We modeled potential relationships between occupancy and local and spatial factors related to human modifications to the terrestrial-aquatic ecotone. Tidal saltmarsh was the most important positive predictor of diamondback terrapin occurrence, while agriculture, crab pots, armored shoreline, and low urban were important negative predictors. We also identified thresholds for the major predictive factors which indicated that diamondback terrapins have a low sensitivity to anthropogenic alterations. Overall, our results indicate that humans have extensively developed the shoreline and are continuing to do so at high rates, and that those modifications are having detectable effects on diamondback terrapin distribution over large spatial scales. The ability to predict shoreline development growth and how it will affect connectivity throughout the Chesapeake Bay provides important information to resource managers about restoration and conservation targets

Abstract Salt marsh ecosystems have declined globally and are increasingly threatened by erosion, sea level rise, and urban development. These highly productive, physically demanding ecosystems are populated by core species groups that often have strong trophic interactions with implications for ecosystem function and service provision. Positive interactions occur between ribbed mussels (Geukensia demissa) and cordgrass (Spartina alterniflora). Mussels transfer particulate nitrogen from the water column to the marsh sediments, which stimulates cordgrass growth, and cordgrass provides predator and/or heat stress refuge for mussels. Here, we test mussel facilitation of two functions in salt marshes that relate to N removal: microbial denitrification and water filtration. Microcosm experiments revealed that the highest rates of N2 production and nitrification occurred when mussels were present with marsh vegetation, suggesting that mussels enhanced coupling of the nitrification–denitrification. Surveys spanning the York River Estuary, Chesapeake Bay, showed that the highest densities of mussels occurred in the first meter for all marsh types with mainstem fringing (1207 ± 265 mussels/m2) being the most densely populated. The mussel population was estimated to be ~197 million animals with a water filtration potential of 90–135 million L/hr. Erosion simulation models demonstrated that suitable marsh habitat for ribbed mussels along the York River Estuary would be reduced by 11.8% after 50 years. This reduction in mussel habitat resulted in a projected 15% reduction in ribbed mussel abundance and filtration capacity. Denitrification potential was reduced in conjunction with projected marsh loss (35,536 m2) by 205 g N/hr, a 16% reduction. Because of the predominant occurrence of ribbed mussels at the marsh seaward edge and because the highest proportional loss will occur for fringing marshes (20%), shoreline management practices that restore or create fringing marsh may help offset these projected losses.

Researchers have long recognized that the spatial distribution of animals relates to habitat requirements. In birds, despite recent advances in tracking techniques, knowledge of habitat needs remains incomplete for most species. Using radio telemetry, we quantified the relative space use of 37 Wood Thrush (Hylocichla mustelina) males, captured over 2 years (2013, 2014) on their breeding grounds in coastal Virginia. Following tracking, we collected data on prey availability (n = 370 plots) and habitat structure (n = 222 plots) within bird home ranges, and modeled bird utilization distribution with both sets of variables using mixed models. Our objectives were to (a) determine the relative importance of habitat structure and prey availability for bird use, (b) identify specific resources that related to bird utilization distribution, (c) test the hypothesis that soil moisture explained prey availability, and (d) evaluate models by determining whether model-identified conditions agreed with data at sites where Wood Thrushes were absent over the preceding 5 years. Of prey variables, high-use areas within bird home ranges were linked to higher biomass of spiders and worm-like invertebrates, which were strongly correlated with soil moisture. Of habitat structure variables, bird use related negatively to red oak (Quercus spp.) count and pine (Pinus spp.) basal area, and positively to forest canopy height, snag basal area, and number and species richness of trees, among others. Evaluation of 12 covariates in our best model revealed that 5 were significant, with conditions at bird absence sites congruent with our models. Goodness-of-fit tests revealed poor fit of the prey-only model, whereas the habitat-only model explained nearly 8 times the variation in bird use. The model utilizing both prey and structure covariates yielded only marginal improvement over the habitat-only model. Consequently, management objectives aimed at habitat improvement for the declining Wood Thrush should particularly consider habitat structure resources.

AimEstuaries world-wide have been modified or fragmented due to human stressors in their terrestrial and aquatic components. Estuary fragmentation often results in reductions in species richness, diversity and connectivity. Effects of human modification on estuaries have been well studied, but less is known about how land use alters connectivity of the terrestrial-aquatic ecotone. We studied the relationship between terrestrial-aquatic connectivity and the distribution of an estuarine turtle, diamondback terrapin (Malaclemys terrapin).LocationChesapeake Bay, Virginia, USA.MethodsWe conducted diamondback terrapin surveys at 165 sites from late spring to mid-summer in 2012 and 2013. We evaluated associations between terrapin occurrence, land use, salt marsh, shoreline armouring and crabbing intensity in concentric-circular neighbourhoods ranging from 0.27 to 2km to cover daily and annual terrapin movements. We used occupancy modelling and model averaging to identify key terrestrial and aquatic variables explaining heterogeneity in terrapin occupancy. We evaluated the final model with an independent data set and identified occurrence thresholds for key variables.ResultsDiamondback terrapin occupy areas with 10% of marsh within a 750-m neighbourhood, 17% armoured shoreline within a 1-km neighbourhood, 20% of agriculture within a 500-m neighbourhood, 33% low-density housing within a 270-m neighbourhood and 9 active crab pots within a 270-m neighbourhood. Our model performed well when evaluated with an independent data set.Main conclusionsWe are the first to identify thresholds and quantify negative associations between the distribution of diamondback terrapin and alterations to terrestrial-aquatic connectivity from land development, shoreline armouring, and fishing activity. Because diamondback terrapin responses are reflective of changes in coastal habitats, especially marshes, terrapin occurrence can be used to direct wetlands conservation and restoration efforts.