Article

Living shorelines enhanced the resilience of saltmarshes to Hurricane Matthew (2016)

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Nature‐based solutions, such as living shorelines, have the potential to restore critical ecosystems, enhance coastal sustainability, and increase resilience to natural disasters; however, their efficacy during storm events compared to traditional hardened shorelines is largely untested. This is a major impediment to their implementation and promotion to policy‐makers and homeowners. To address this knowledge gap, we evaluated rock sill living shorelines as compared to natural marshes and hardened shorelines (i.e., bulkheads) in North Carolina, USA for changes in surface elevation, Spartina alterniflora stem density, and structural damage from 2015 to 2017, including before and after Hurricane Matthew (2016). Our results show that living shorelines exhibited better resistance to landward erosion during Hurricane Matthew than bulkheads and natural marshes. Additionally, living shorelines were more resilient than hardened shorelines, as they maintained landward elevation over the two‐year study period without requiring any repair. Finally, rock sill living shorelines were able to enhance S. alterniflora stem densities over time when compared to natural marshes. Our results suggest that living shorelines have the potential to improve coastal resilience while supporting important coastal ecosystems.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... These solutions are based on the principle that certain coastal ecosystems, such as marshes, mangroves, seagrass meadows and biogenic reefs, attenuate hydrodynamic forces (wave, surge and flow) and promote accretion, thus reducing coastal risks (Barbier, 2020 ;Gracia et al., 2018 ;Morris et al., 2019). The main measures deployed so far are the restoration or creation of marshes and mangroves, with or without low rock sill, riprap or fences (Kibler et al., 2019 ;Mitchell et Bilkovic, 2019 ;Polk et al., 2021 ;Smith et al., 2018 ;Van Cuong et al., 2015) and Oyster reefs (Morris et al., 2021) with sometimes the combination of these three habitats (Donnelly et al., 2017). Some projects that integrate different nature-based solutions (NBS) also aim to move infrastructure inland and remove hard protection while restoring ecosystems (Sutton-Grier et al., 2015 ;Toft et al., 2021). ...
... As noted in the review by Smith et al., (2020) on Living Shorelines projects, the application of these solutions is still limited and mainly concentrated in the United States. The evaluation of their effectiveness is still mainly based on modeling (Kumar et al., 2021) and data from monitoring and in situ measurements remain fragmentary (Polk et al., 2021 ;Polk et Eulie, 2018 ;Smith et al., 2018 ;Vuik et al., 2016). Therefore, knowledge of their potential impacts on the coastal zone is still very limited. ...
... Approach have been particularly popular over the past decade (Bilkovic et al., 2017b ;Smith et al., 2020). This approach aims in particular at transplanting shoreline vegetation with or without low rock sills (Currin et al., 2010), in order to reduce coastal erosion (Polk et al., 2021 ;Polk et Eulie, 2018), and increase community resilience to storms (Smith et al., 2018). ...
Thesis
Full-text available
Les caractéristiques des environnements côtiers varient à l’échelle du Québec maritime. Plusieurs types d’ouvrage de protection côtière (OPC) existent pour résoudre une problématique d’érosion ou de submersion dans ces environnements. Les effets des OPC sur le système socioécologique côtier (SSEC) sont complexes en raison des nombreuses rétroactions entre les éléments hydrodynamiques et géomorphologiques qui ont aussi des répercussions sur les aspects écologiques et socio-économiques des communautés côtières. Le choix d’un OPC dépend des caractéristiques socioécologiques propres à un secteur de côte, ainsi que des effets souhaités. Cependant, entre 1980 et 2000, au Québec, les OPC ont été aménagés en situation d’urgence et en réaction aux événements de tempête, sans considération des effets indésirables qu’ils pourraient produire. L’objectif principal de cette thèse doctorale est de développer un outil d’aide à la prise de décision élaboré sur une structuration cohérente de l’information permettant de prendre en considération les données tant géomorphologiques et hydrodynamiques, qu’écologiques et socio-économiques nécessaires à l’identification des meilleures alternatives en termes d’OPC au regard des conditions spécifiques d’un SSEC et des besoins exprimés par les acteurs du territoire (professionnels et gestionnaires). Pour ce faire, plusieurs méthodes ont été utilisées : (1) des consultations des acteurs de la zone côtière; (2) un traçage par système d’information géographique des composantes du SSEC; (3) une revue et méta-analyse de la littérature sur les effets des OPC; (4) le développement d’un algorithme; (5) une application d’une analyse multicritère. La thèse est composée de deux volets : (1) caractérisation des interventions passées et établissement d’une base afin d’orienter les décisions futures; (2) développement d’une approche d’évaluation des OPC. Premièrement, en 2017, 97,6 % des OPC présents dans le Québec maritime étaient des enrochements et des murs de protection. Par le passé, en plus de l’urgence des interventions, les principaux facteurs évoqués par les acteurs consultés pour justifier leur choix d’aménagement de ces OPC étaient un manque de connaissance, de financement et de processus collaboratif. Or, les acteurs consultés en 2017-2018 ont démontré une ouverture pour l’utilisation d’une plus grande diversité d’OPC. Ils ont également soulevé un besoin d’acquisition de connaissances scientifiques sur les effets des différents OPC pour pouvoir prendre de meilleures décisions. Les résultats de la méta-analyse de la littérature internationale sur les effets des OPC sur le milieu côtier démontrent que 52,7 % des 355 sites étudiés sont des côtes basses sablonneuses, que les études portent en majorité sur les recharges de plage (40,9 %), les murs de protection (16,7 %) et les brise-lames (12,5 %) et qu’il y a une absence d’études dans un contexte de climat nordique avec la présence de glaces côtières. Ce qui suggère un déséquilibre dans les connaissances scientifiques se rapportant aux effets produits par les OPC sur des environnements côtiers variés, déséquilibre qui doit être redressé afin d’améliorer le processus décisionnel. Deuxièmement, une approche d’évaluation a été développée pour répondre au besoin d’outils d’aide à la décision soulevé par les acteurs du territoire. Cette approche est basée sur la combinaison d’un algorithme d’identification et d’une analyse multicritère. L’algorithme permet d’évaluer et de hiérarchiser des OPC en fonction de leurs effets sur les différents environnements côtiers, et ce en trois étapes. (i) La caractérisation du SSEC est effectuée au moyen d’indicateurs de suivis géomorphologiques (type de côte, substrat) et hydrodynamiques (marnage, vagues, courants). Des données cartographiques (caractérisation côtière, écosystèmes, activités et usages) et hydrodynamiques (vagues et marnage) servent à définir l’état initial des sites à l’étude. (ii) Tirés d’une revue de littérature, les énoncés d’effets observés associés aux caractéristiques environnementales qui y correspondent (type de côte et de substrat, marnage et vagues) ont été compilés dans une base de données, catégorisés et pondérés selon une échelle qualitative de pondération (-5 à 5). Cette échelle est basée sur la pertinence et sur le caractère positif ou négatif des énoncés. (iii) L’information est traitée par l’algorithme sur la base d’une correspondance entre les caractéristiques environnementales du site d’étude et celles enregistrées dans la base de données. L’évaluation et la hiérarchisation des OPC sont réalisées en colligeant et en classant les effets observés connus, produits par ces OPC dans des contextes environnementaux similaires. (iv) Les résultats de l’algorithme présentent la hiérarchisation des OPC selon une structure d’agrégation à plusieurs niveaux qui peut être utilisée par les gestionnaires, les décideurs et les ingénieurs côtiers pour la planification et la conception de projets d’intervention pour protéger des infrastructures ou des milieux sensibles. L’analyse multicritère est ensuite utilisée pour hiérarchiser les OPC présélectionnés selon les résultats de l’algorithme en trois étapes. (i) Les critères d’évaluation ont été identifiés et pondérés par les acteurs du territoire selon leurs priorités dans le cadre d’une série de cinq ateliers. (ii) Les OPC ont été évalués en regard de chacun des critères et des caractéristiques socioécologiques de quatre secteurs d’études. (iii) Les OPC sont hiérarchisés avec la méthode PROMETHEE. Les résultats de la hiérarchisation montrent que le premier rang est occupé par la végétalisation dans trois des quatre sites et par l’enrochement dans le quatrième site. De manière plus générale, les résultats montrent la pertinence de l’utilisation d’une méthode d’analyse multicritère et de l’implication des acteurs du territoire dans le processus de sélection d’un OPC qui tienne compte des priorités locales et soit adapté aux conditions environnementales. Globalement, cette thèse offre des connaissances permettant d’améliorer le processus décisionnel menant à la sélection d’un OPC. Elle est appuyée sur une approche intégrée et holistique d’identification des OPC adaptés aux conditions spécifiques d’un SSEC, en tenant compte d’une part des effets des OPC sur l’évolution du SSEC et, d’autre part, des besoins exprimés par les acteurs du territoire.
... Living shorelines provide a range of ecological cobenefits and have been implemented with documented instances of success in restoring habitat and ecosystem functions, such as habitat provisioning (compared to hardened structures; Gittman, Peterson, et al., 2016;Scyphers et al., 2011) and shoreline stabilization (Gittman et al., 2014;Polk & Eulie, 2018;Smith et al., 2018). With respect to habitat provisioning, various studies have observed the capacity of living shoreline sites to mimic or enhance biomass and species diversity relative to natural sites (Currin et al., 2008;Gittman, Peterson, et al., 2016). ...
... height, which is critical in fetch-limited environments], sediment supply, space for landward retreat) and design (e.g., height, width, and configuration) of sills is critical (Mitchell & Bilkovic, 2019), as the primary force causing lateral and vertical erosion of salt marsh edges is wind-wave attack (Tonelli et al., 2010). Although recent work has suggested that living shorelines with sills can prevent vertical erosion and shoreline damage from hurricanes (Gittman et al., 2014;Smith et al., 2018), more research is needed investigating the performance of a range of living shoreline sill designs in preventing lateral marsh erosion during highenergy and high-water conditions observed during hurricanes. Thus, the present study quantifies the lateral change in marsh position during a short-term period encompassing Category 1 storm event (Hurricane Florence, 2018) at living shorelines and natural marsh shorelines. ...
... These lateral losses are consistent with North Carolina state average SCR of −0.30 to −3.35 m year −1 , depending on the estuarine location and overall North Carolina is experiencing a state-wide trend of erosion (Eulie et al., 2017;Polk & Eulie, 2018;Riggs, 2001). This study and findings from recent works collectively demonstrate that living shorelines with sills can promote horizontal and vertical building of shore zones (compared to unaltered marshes and bulkheaded shorelines) after a Category 1 storm (Gittman et al., 2014, Smith et al., 2018. Thus, the evidence for living shorelines enhancing resilience of coastal ecosystems, particularly salt marshes, is growing. ...
Article
A growing suite of research has demonstrated that nature‐based shoreline stabilization methods can increase resilience of coastal ecosystems by improving their capacity to return to pre‐disturbance states. Previous work suggests that during hurricanes, living shorelines promote vertical accretion and experience less damage than traditional shoreline stabilization alternatives. Nevertheless, there is limited research looking at the impacts of major storm events on living shorelines and most studies have investigated a small number of sites. This study used in situ real‐time kinematic (RTK)‐GPS surveys to quantify the resilience (via the lateral change in shore position) of 17 living shoreline sites before and after a Category 1 hurricane event (Hurricane Florence, 2018). By doing so, this study seeks to understand the capacity of living shorelines (marsh with seaward breakwater or sill) to provide storm protection as compared to unaltered natural fringing salt marshes. After Hurricane Florence, living shorelines on average experienced significantly less lateral erosion compared to unprotected control segments (shoreline change rates of 0.015 m y‐1 and ‐0.31 m y‐1, respectively). This study also explores how environmental siting variables (i.e. scarp presence, fetch, and bottom sediment) and sill design variables (i.e. sill material, width, and height) influence short‐ and long‐term erosion. Living shorelines were found to reduce erosion of fringing marsh edge among projects with a range of installation ages, structural materials, sill widths, and sill heights, and they were able to provide protection from erosion across a range of fetch, scarp, and bottom sediment conditions. Living shoreline siting and sill design may be suitable for broader environmental conditions than previously known. This study shows that living shorelines can increase resilience, by reducing erosion of fringing salt marshes, and even in some cases promoting lateral building up of shoreline zones during short‐term disturbance events and from their long‐term presence. This article is protected by copyright. All rights reserved.
... A common nature-based infrastructure design used in the United States includes an offshore breakwater or restored oyster reef (made from granite rocks, marl, or bagged/loose oyster shell) in combination with existing or planted marsh grasses landward of the breakwater (hereon referred to as a living shoreline; (United States Army Corps of Engineers, 2016b). Living shorelines can maintain the coastal ecosystem services provided by saltmarshes and oyster reefs, while also providing increased protection from erosion due to wave action, storm events, and boat wakes (Manis et al., 2015;Smith et al., 2018;Chowdhury et al., 2019). Furthermore, living shorelines preserve or enhance natural habitat heterogeneity via the intertidal breakwater that replaces soft bottom where structure was previously limited, and increasing the heterogeneity of marine infrastructure has been shown to enhance biodiversity (Strain et al., 2018). ...
... Our natural marsh sites were the shallowest, followed by living shorelines, and then bulkheads. While revetments and bulkheads tend to be in deeper water, living shorelines are often only possible in areas that have modest shoreline slopes and shallower water and their structure can lead to further shallowing along the shoreline (Smith et al., 2018). This shallower water may make it more difficult for larger fish, who may prey upon smaller fish, to get close to the structure, which could be one mechanism contributing to the nursery value of living shorelines. ...
... structural component (i.e., breakwater). However, it is likely that the breakwater itself is increasing the refuge of the marsh and therefore its nursery value by: 1) providing a physical barrier that limits predator access to the marsh or marsh edge; or, 2) increasing sedimentation and maintaining a shallow water habitat that is difficult for predatory fish to access (Currin et al., 2008b;Smith et al., 2018). While the term "living shoreline" can refer to a variety of different nature-based infrastructure techniques, spanning the spectrum from highly "green" (e.g., marsh plantings alone) to more "gray" (e.g., marsh plantings in conjunction with an engineered breakwater), our study investigated fish use of a relatively "gray" type of living shoreline (Smith et al., 2020). ...
Article
Rapid human development in coastal areas is introducing significant amounts of novel habitat and leading to widespread habitat simplification. To predict how species will respond to these changes, it is important to understand how organisms interact with novel habitats versus naturally existing habitats. In this study, we used traditional fish sampling gear (fyke nets and minnow traps) and a Dual-Frequency Identification Sonar (DIDSON) to conduct fish surveys along natural and modified estuarine shorelines in North Carolina, USA. The overall objective of our study was to investigate how fish abundance and other community metrics change as a function of shoreline type (natural marsh, living shoreline, or bulkhead), sampling location (marsh platform or the shallow subtidal area offshore of the structure), and time of day (day or night). Using fyke nets, we caught significantly more fish and recorded higher species richness on the marsh platform at living shorelines versus natural marsh shorelines. However, we found no significant differences in fish abundance in the shallow unvegetated habitats seaward of the different shoreline types, which may have been affected by low sampling efficiency and replication when sampled using minnow traps and the DIDSON. Our findings, in conjunction with similar studies, may reflect a localized shoreline effect where the nursery enhancement observed at living shoreline sites is restricted to the living component of the shoreline (i.e., the marsh). Additionally, the preliminary results from our limited daytime versus nighttime DIDSON sampling show no significant differences in fish detections. This contrasts with many previous studies using traditional fish sampling techniques that report substantially higher fish catches at night. This unexpected finding is worthy of additional research as it may suggest that traditional fish sampling techniques are underestimating fish abundances during the day, perhaps due to visual gear avoidance. Ultimately, a careful consideration of the social and ecological goals of any shoreline stabilization project is needed before choosing a final design; however, maximizing habitat restoration and limiting the use of artificial materials is likely to confer the greatest ecological benefit.
... The proliferation of coastal defense structures is likely as coastal populations grow and hazards intensify (Scyphers et al., 2011;Hinkel et al., 2014); however, common coastal armoring strategies (e.g., seawalls, revetments, groins) can drive habitat loss (Titus, 1998), lower floral and faunal biodiversity (Gittman et al., 2016a), and depress socio-economic resilience by requiring frequent and expensive maintenance (Smith et al., 2017(Smith et al., , 2018. Accordingly, ecosystem-friendly alternatives to traditional coastal defense structures are becoming more prevalent in areas where maintaining a natural shoreline is not possible. ...
... Living shoreline designs are often categorized along a green to gray spectrum, spanning from vegetative plantings for coastal protection on the green end to habitat restoration in conjunction with structural materials on the gray end (Figure 1). Living shorelines are touted for their potential to provide triple-bottom line returns (i.e., ecological, social, and economic benefits) by enhancing coastal habitat function (Currin et al., 2008;Davis et al., 2015;Gittman et al., 2016b) and increasing community resilience to storms (Manis et al., 2015;Smith et al., 2018), while requiring less maintenance and fewer repairs than traditional coastal armoring infrastructure (Smith et al., 2017(Smith et al., , 2018. States within the USA have instituted local-level policies to encourage the installation of living shorelines, and on a national level, the US House of Representatives passed the Living Shorelines Act of 2019 to assist local and state governments and non-profits with living shoreline creation. ...
... Living shoreline designs are often categorized along a green to gray spectrum, spanning from vegetative plantings for coastal protection on the green end to habitat restoration in conjunction with structural materials on the gray end (Figure 1). Living shorelines are touted for their potential to provide triple-bottom line returns (i.e., ecological, social, and economic benefits) by enhancing coastal habitat function (Currin et al., 2008;Davis et al., 2015;Gittman et al., 2016b) and increasing community resilience to storms (Manis et al., 2015;Smith et al., 2018), while requiring less maintenance and fewer repairs than traditional coastal armoring infrastructure (Smith et al., 2017(Smith et al., , 2018. States within the USA have instituted local-level policies to encourage the installation of living shorelines, and on a national level, the US House of Representatives passed the Living Shorelines Act of 2019 to assist local and state governments and non-profits with living shoreline creation. ...
Article
Full-text available
In an era of rapid coastal population expansion and habitat degradation, restoration is becoming an increasingly important strategy for combating coastal habitat loss and maintaining ecosystem services. In particular, techniques that use habitat restoration alone or restoration in combination with built infrastructure to provide coastal protective services are growing in popularity. These novel approaches, often called living shorelines, have the potential to expand the reach and applicability of coastal restoration projects. To understand how living shorelines research has expanded over time, we conducted a scoping review of English-language peer-reviewed articles. We included papers that self-identified as living shorelines research, as well as studies that used other related terminology, to investigate trends in publication rates, geography, site characteristics, and outcomes measured. Using a systematic search protocol, we compiled a database of 46 papers; the earliest study was published in 1981, and the earliest study to use the term living shoreline was published in 2008. Eighty-three percent of studies were conducted in North America, followed by 11% in Asia, and 7% in Europe, but the use of the term living shoreline was almost exclusively restricted to North America. Saltmarshes, oyster reefs, mangroves, and freshwater vegetation were used in living shoreline designs, but 91% of studies also incorporated structural materials like oyster shell and rock. Most living shorelines research was conducted at sites that were <5 years old. The vast majority of studies exclusively reported on ecological outcomes (89%), and of those, ecological processes were measured in 74% of studies. Processes related to coastal protection were measured most frequently (52% of ecological studies), followed by biological interactions, water filtration, nutrient cycling, and carbon sequestration. Altogether, our data suggest that living shorelines research is on the rise, but there is a need for more long-term data, socio-economic research, further consensus on the terminology used to describe different types of projects, and research on the types of living shorelines that are most effective in different environmental contexts. Future long-term and interdisciplinary research will help to elucidate the full effects of living shorelines.
... Shoreline hardening is often implemented with the goal of enhancing resistance to natural hazards (e.g. erosion, storms, floods, tsunamis) and reducing property damage and human casualties; however, shoreline hardening ultimately erodes coastal resilience by undermining the ability of shorelines to adapt and regenerate (Smith et al., 2018). Furthermore, the extensive transformation of naturally sloping coastal habitats into vertical walls fundamentally alters the land-water interface, and has been shown to negatively impact habitat sustainability and the delivery of ecosystem services (Titus, 1998;Peterson et al., 2008;Gittman et al., 2016;Dugan et al., 2018), thus eroding natural capital and increasing future vulnerability to natural hazards (Arkema et al., 2013). ...
... Furthermore, the extensive transformation of naturally sloping coastal habitats into vertical walls fundamentally alters the land-water interface, and has been shown to negatively impact habitat sustainability and the delivery of ecosystem services (Titus, 1998;Peterson et al., 2008;Gittman et al., 2016;Dugan et al., 2018), thus eroding natural capital and increasing future vulnerability to natural hazards (Arkema et al., 2013). While prior research demonstrates frequent and repeated damage to shoreline stabilization structures during hurricane events (Nichols and Marston, 1939;Morton, 1976;Thieler and Young, 1991;Gittman et al., 2014;Smith et al., 2017Smith et al., , 2018, these studies have typically focused on oceanfront shorelines (Nichols and Marston, 1939;Morton, 1976;Thieler and Young, 1991) rather than sheltered estuarine shorelines, or exclusively on damage to the shorelines themselves rather than damage to infrastructure behind the shoreline (Gittman et al., 2014;Smith et al., 2017Smith et al., , 2018. In contrast, more recent studies have shown that natural coastal habitats can buffer storm damage to upland infrastructure (Narayan et al., 2017;Tomiczek et al., 2017). ...
... Furthermore, the extensive transformation of naturally sloping coastal habitats into vertical walls fundamentally alters the land-water interface, and has been shown to negatively impact habitat sustainability and the delivery of ecosystem services (Titus, 1998;Peterson et al., 2008;Gittman et al., 2016;Dugan et al., 2018), thus eroding natural capital and increasing future vulnerability to natural hazards (Arkema et al., 2013). While prior research demonstrates frequent and repeated damage to shoreline stabilization structures during hurricane events (Nichols and Marston, 1939;Morton, 1976;Thieler and Young, 1991;Gittman et al., 2014;Smith et al., 2017Smith et al., , 2018, these studies have typically focused on oceanfront shorelines (Nichols and Marston, 1939;Morton, 1976;Thieler and Young, 1991) rather than sheltered estuarine shorelines, or exclusively on damage to the shorelines themselves rather than damage to infrastructure behind the shoreline (Gittman et al., 2014;Smith et al., 2017Smith et al., , 2018. In contrast, more recent studies have shown that natural coastal habitats can buffer storm damage to upland infrastructure (Narayan et al., 2017;Tomiczek et al., 2017). ...
Article
Hurricanes and tropical storms are among the most frequent and costly natural disasters in the United States, and their impacts are expected to intensify in the future. Understanding the best predictors of hurricane damage in coastal areas is of paramount importance for reducing recovery costs and protecting coastal infrastructure and human lives. This project used surveys of 295 homeowners in coastal North Carolina to evaluate damage to estuarine shorelines and homes caused by Hurricane Matthew in 2016. Specifically, we were interested in the following questions: 1) did homes with hardened shorelines (e.g. bulkheads and riprap revetments) experience more or less damage than homes with natural shorelines during the storm; and, 2) what were the strongest predictors of hurricane damage to shorelines and homes. Overall, we found that past hurricane damage to shorelines was the strongest predictor of shoreline damage during Hurricane Matthew and that flood zone and past hurricane damage to homes were the strongest predictors of home damage. However, homes with bulkheads also sustained more hurricane damage than homes with natural shorelines, perhaps because homes with bulkheads were on average 2 times closer to the shoreline than homes with natural shorelines. Our results show patterns of repeated shoreline and home damage during hurricanes and indicate that environmental context and vulnerability can outweigh individual residents' shoreline management decisions.
... These additional structural features potentially diversify the habitat complexity and may increase the ability of vegetated shorelines to keep pace with sea level rise (Smith et al., 2020;Waltham et al., 2021). Living shorelines tend to resist and recover from hurricanes and storm surges better than shoreline armoring (Gittman et al., 2014;Smith et al., 2018), demonstrating their expected resiliency under future climate regimes. The structural similarity of living shoreline marshes to natural marshes often is assumed to equate to similar ecological functions, such as nursery habitat and foraging opportunities for fish and crustaceans. ...
... Although the community composition abundances at living shorelines and reference marshes are similar, living shoreline marsh construction practices and differing habitat characteristics (rock sill, clean sand fill) can contribute to increased biomass for some marsh-dependent species. Compared to shoreline armoring, living shorelines are often more resilient during extreme storm events and can better protect shoreline properties as seas rise (Gittman et al., 2014;Smith et al., 2018). Living shorelines with rock sills may provide structural benefits similar to biogenic reefs, and have the potential to adapt better than natural marshes as they capture and retain sediment to accrete with sea level rise (Currin et al., 2008;Mitchell and Bilkovic, 2019;Waltham et al., 2021). ...
Article
Full-text available
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.
... When marshes are eroded at the edge, "living shorelines" in the form of oyster reefs, rocks, coir logs, and other materials can be placed at the edge to restore a more gradual vegetated slope and prevent further erosion. Living shorelines can be more resilient to hurricanes than hard edges or natural marshes (Smith et al. 2018). Some living shoreline projects have been installed in New Jersey. ...
... One approach to increase coastal wetland elevation where existing sediment supplies are inadequate is through the repurposing of dredged sediment (Ganju et al. 2017). The addition of sediment can elevate coastal marshes to keep pace with SLR (Morris et al. 2002), reverse losses of salt marsh (Woodhouse et al. 1972), and increase the resiliency of systems that have been degraded by hydrological alterations (Smith et al. 2018). According to Berkowitz et al. (2019), the best way to place dredged sediment on coastal marshes is to add the material in layers up to 30 cm thick to provide "elevation capital" to shallow intertidal areas. ...
Article
Full-text available
Salt marshes are key coastal ecosystems that provide habitats for wildlife, including invertebrates, fishes, and birds. They provide ecosystem services such as protection from storm surges and waves, attenuation of flooding, sequestration of pollutants (e.g., blue carbon), and nutrient removal. They are currently under great threat from sea level rise (SLR). We collected information about trends in the horizontal extent (acreage) of New Jersey salt marshes and recent elevation changes compared with the current local rate of SLR in New Jersey, which is between 5 and 6 mm year ⁻¹ . We found pervasive, although variable, rates of marsh loss that resulted from both anthropogenic disturbance as well as edge erosion and interior ponding expected from SLR. Elevation trends suggest that the current rates of SLR exceed most marsh elevation gains, although some Phragmites-dominated marshes keep pace with SLR. Four potential remedies to address current coastal trends of marsh loss were described in the context of New Jersey’s regulatory and management environment: protection of marsh inland migration pathways, altered management of Phragmites, thin layer sediment placement, and living shoreline installations. Proactive steps are necessary if coastal wetland ecosystems are to be maintained over the next few decades.
... However, there is much still to learn about the longer-term interactions between oyster reefs, sediments, and adjacent salt marshes, particularly with regard to carbon storage in sediments. For example, a marsh fronted by an oyster reef sill or breakwater may show greater accretion or decreased erosion Smith et al. 2018;Chowdhury et al. 2019). Restored or constructed oyster reefs have been shown to reduce erosion of salt marsh edges as well or better than natural oyster reefs, showing that they contribute to shoreline stabilization (Stricklin et al. 2010;Ridge et al. 2017) while others have shown that they may only be effective under certain conditions (La Peyre et al. 2017;de Paiva et al. 2018). ...
... Others have made observations of increases in silt and clay content with the construction of oyster reefs(Meyer and Townsend 2000;Wilber et al. 2012;Kellogg et al. 2013;Chowdhury et al. 2019). Constructed oyster reefs are frequently designed as this project was, breakwater or sill structures specifically engineered to disrupt wave energy, increase sedimentation, and reduce erosion(Currin et al. 2010;Gittman et al. 2016;Smith et al. 2018;Chowdhury et al. 2019).Chowdhury et al. ( ...
... biodiversity enhancement) if this technique is to replace or complement artificial structures. Although hard ecoengineering is less challenging to implement from a coastal defence perspective, there is growing evidence that created or restored habitats using soft engineering can also provide protection that is equivalent to or better than traditional engineered hard structures , Smith et al. 2017a, Smith et al. 2018. As mentioned previously, soft engineering approaches and hard structures may even operate synergistically to enhance coastal protection (Smallegan et al. 2016, Vuik et al. 2016)-as successful hybrid schemes in some cases. ...
... Often, there is stronger support for hard engineering approaches (Gray et al. 2017) that have been more thoroughly tested over time (Sutton-Grier et al. 2015), even when they are unnecessary or less cost effective than soft or hybrid alternatives (Scyphers et al. 2014, Gittman & Scyphers 2017. In contrast, where the asset is less crucial for social and economic health or primarily of local significance, there may be a higher chance for adopting more experimental (and potentially riskier) ecoengineered shoreline approaches that provide protection under most (but not the most severe) storm events, or for which the evidence of efficacy in terms of shoreline protection is limited (but see Gittman et al. 2014, Smith et al. 2018. ...
Chapter
Full-text available
Human population growth and accelerating coastal development have been the drivers for unprecedented construction of artificial structures along shorelines globally. Construction has been recently amplified by societal responses to reduce flood and erosion risks from rising sea levels and more extreme storms resulting from climate change. Such structures, leading to highly modified shorelines, deliver societal benefits, but they also create significant socioeconomic and environmental challenges. The planning, design and deployment of these coastal structures should aim to provide multiple goals through the application of ecoengineering to shoreline development. Such developments should be designed and built with the overarching objective of reducing negative impacts on nature, using hard, soft and hybrid ecological engineering approaches. The design of ecologically sensitive shorelines should be context-dependent and combine engineering, environmental and socioeconomic considerations. The costs and benefits of ecoengineered shoreline design options should be considered across all three of these disciplinary domains when setting objectives, informing plans for their subsequent maintenance and management and ultimately monitoring and evaluating their success. To date, successful ecoengineered shoreline projects have engaged with multiple stakeholders (e.g. architects, engineers, ecologists, coastal/port managers and the general public) during their conception and construction, but few have evaluated engineering, ecological and socioeconomic outcomes in a comprehensive manner. Increasing global awareness of climate change impacts (increased frequency or magnitude of extreme weather events and sea level rise), coupled with future predictions for coastal development (due to population growth leading to urban development and renewal, land reclamation and establishment of renewable energy infrastructure in the sea) will increase the demand for adaptive techniques to protect coastlines. In this review, we present an overview of current ecoengineered shoreline design options, the drivers and constraints that influence implementation and factors to consider when evaluating the success of such ecologically engineered shorelines.
... For example, a marsh toe revetment placed at the eroding edge of a marsh or breakwater oyster reefs seaward of an armored shoreline would be considered nature-based approaches. These approaches can help control erosion and dissipate wave energy (Smith et al. 2018;Gittman et al. 2014;Barbier et al. 2013;Scyphers et al. 2011;Meyer, Townsend, and Thayer 1997), as well as provide a variety of ecosystem services (Bilkovic et al. 2016;Barbier et al. 2008Barbier et al. , 2011. However, they are most effective for shorelines that do not face high wave energy (Currin, Davis, and Malhotra 2017;SAGE 2015). ...
Article
Shoreline hardening is a method of coastal hazard protection that is often implemented by government agencies and individual property owners. As awareness of the potential negative effects of shoreline hardening has increased, natural and nature-based approaches have gained in popularity. Most research related to shoreline protection has focused on understanding the environmental and ecological effects. However, for hybrid, nature-based approaches, in particular, there is limited information available to compare their monetary costs. To fill this gap, this study used information collected from public shoreline protection projects within the New England and Mid-Atlantic areas to estimate the costs of these measures based on the materials used, such as vegetation, sand, and/or stone. This approach allows for a detailed measurement of potential project inputs and provides needed cost information on the types of materials local governments and other stakeholders may use in their shoreline protection approaches. Results suggest that approaches that use natural materials tend to cost less than those that use more traditional, engineered materials, and nature-based approaches tend to cost somewhere in-between. Specifically, projects can be divided into four subgroups based on their average per-unit costs: (A) walls (mean: $5,628, se: $680) or stone at exposed sites (mean: $4,943, se: $725); (B) sand for beach nourishment (mean: $3,094, se: $397) or stone at low exposure sites ($3,014, se: $379); (C) stone and vegetation at low exposure sites (mean: $1,626, se: $217), stone and sand for other purposes at low exposure sites (mean: $1,411, se: $173), or sand for other purposes (mean: $1,384, se: $151); and (D) stone and sand for other purposes at low exposure sites (mean: $1,411, se: $173), sand for other purposes (mean: $1,384, se: $151), vegetation (mean: $1,300, se: $159), or vegetation and sand for other purposes (mean: $1,285, se: $172). Finally, monitoring and maintenance costs are often not accounted for, which may negatively affect the long-term success of shoreline protection efforts. Coupled with information on environmental and ecological effects of these different approaches, this information will allow for more informed decisions on how coastal and inland communities can best adapt to coastal risks.
... However, when the primary objective of the project is to stabilise estuarine shorelines, conditions that are optimal for growth and long-term survival may be overlooked. Failing to consider the hydrodynamic limits required for species establishment can lead to an increase in conventional engineering interventions (Martin et al., 2021;Sharma et al., 2016;Smith et al., 2018;Sreeranga et al., 2021). While artificial material may be incorporated in NbS development, such as when necessitated by the prevalence of extreme events (Vojinovic et al., 2021), the development of NbS establishment thresholds may increase the chance for NbS survivability. ...
Article
Full-text available
Traditional solutions to estuarine flood risk management have typically involved the implementation of static 'hard' shoreline protection structures, often at the expense of the natural landscape and the societal and ecosystem benefits they provide. In a changing climate, there is an increasing need to restore these estuarine ecosystems, and alternative measures in the form of Nature-based Solutions (NbS) are being considered. Guidance that balances ecology and engineering is required for NbS to establish as self-sustaining ecosystems. In this study, a review of NbS guidelines was undertaken, revealing an absence of technical content bridging ecological and engineering values. Instead, most guidelines focus on NbS project implementation, identifying engineering aspects, and providing frameworks for investors and project managers. Integration of technical engineering and ecological outcomes within NbS guidelines is needed. A conceptual approach for integrating eco-engineering aspects for estuarine ecosystems is proposed. This conceptual approach focuses on the critical thresholds and parameter relationships associated with establishment, growth, recovery and mortality, and functionality of estuarine NbS, in efforts to quantify changes in ecological development and flood risk mitigation services. The conceptual approach documents how the suggested relationships between parameters can be adopted by practitioners in the short-term, medium-term, and long-term. The application of this conceptual approach to multi-habitat restoration is explored, including lifecycle timing and ecosystem/design functionality. The findings of this study demonstrate the need for an integrated NbS design guideline that balances ecology and engineering research for the long-term success of estuarine ecosystems.
... Sparks et al. (2013) found that small-scale experimental Juncus roemerianus plots planted at half density were largely more or equally cost-effective for both planting cost and effort when compared to plots planted at full density. Smith et al. (2018) analyzed the resistance of various types of shorelines in North Carolina, United States, to Hurricane Matthew (2016), and found that constructed/planted salt marshes with an offshore rock sill were more resistant to the hurricane's impacts than both traditional hardened shorelines and natural marshes. Given this context, research into wave attenuation as a function of marsh vegetation and, indirectly, marsh restoration, provides valuable insight critical to guiding efforts to optimize funding, effort, and overall cost effectiveness of restoration projects. ...
Article
Full-text available
As coastal communities grow more vulnerable to sea-level rise and increased storminess, communities have turned to nature-based solutions to bolster coastal resilience and protection. Marshes have significant wave attenuation properties and can play an important role in coastal protection for many communities. Many restoration projects seek to maximize this ecosystem service but how much marsh restoration is enough to deliver measurable coastal protection benefits is still unknown. This question is critical to guiding assessments of cost effectiveness and for funding, implementation, and optimizing of marsh restoration for risk reduction projects. This study uses SWAN model simulations to determine empirical relationships between wave attenuation and marsh vegetation. The model runs consider several different common marsh morphologies (including systems with channels, ponds, and fringing mudflats), vegetation placement, and simulated storm intensity. Up to a 95% reduction in wave energy is seen at as low as 50% vegetation cover. Although these empirical relationships between vegetative cover and wave attenuation provide essential insight for marsh restoration, it is also important to factor in lifespan estimates of restored marshes when making overall restoration decisions. The results of this study are important for coastal practitioners and managers seeking performance goals and metrics for marsh restoration, enhancement, and creation.
... Subtidal habitats included hard bottom (Jaap and Hallock, 1990;Ash and Runnels, 2005;Kaufman, 2017;CSA Ocean Sciences, 2019), artificial reefs (Dupont, 2008), tidal flats (Moore et al., 1968;Eisma, 1998), seagrasses (Heck et al., 2003;Sherwood et al., 2017), and oyster reefs (Coen et al., 2007;Ermgassen et al., 2013). Intertidal habitats (or emergent tidal wetlands) included mangroves (Odum and McIvor, 1990), salt marshes (Comeaux et al., 2012;Raabe et al., 2012), salt barrens (Bertness, 1985;Hsieh, 2004), tidal tributaries (Sherwood, 2008;Wessel et al., 2022), and living shorelines (National Oceanic and Atmospheric Administration, 2015;Restore America's Estuaries, 2015;Smith et al., 2018). Supratidal habitats included non-developed uplands (Meyers and Ewel, Frontiers in Ecology and Evolution 03 frontiersin.org ...
Article
Full-text available
Native habitats in Florida face dual pressures at the land-sea interface from urban development and sea-level rise. To address these pressures, restoration practitioners require robust tools that identify reasonable goals given historical land use trends, current status of native habitats, and anticipated future impacts from coastal stressors. A restoration framework for native habitats was created for the Tampa Bay watershed that identifies current opportunities and establishes short-term (2030) targets and long-term (2050) goals. The approach was informed through a three-decade habitat change analysis and over 40 years of habitat restoration projects in the region. Although significant gains in subtidal habitats have been observed, expansion of mangroves into salt marshes and loss of native upland habitats to development highlights the need to target these locations for restoration. The long-term loss of potentially restorable lands to both coastal and upland development further underscores the diminishing restoration opportunities in the watershed. The established targets and goals identified habitats to maintain at their present level (e.g., mangroves) and those that require additional progress (e.g., oyster bars) based on past trends and an expected level of effort given the restoration history of the region. The new approach also accounts for the future effects of sea-level rise, climate change, and watershed development by prioritizing native coastal habitats relative to subtidal or upland areas. Maps were created to identify the restoration opportunities where practitioners could focus efforts to achieve the targets and goals, with methods for repeatable analyses also available using an open source workflow.
... The resilient zone, such as wetlands and green open space, may become of critical importance for generating and maintaining resilience after disturbance and disruption (Smith et al. 2018;2017). In contrast to conventional socialecological management that aims at removing disturbance, resilient management focuses on building the ability of absorbing and recovering from a disturbance. ...
Article
Full-text available
Throughout history, humans living in the coastal area constantly adapt to the natural environment and create a changing environment. The rapid coastal development occurred in the mid-19th century and peaks in the mid-20th century, which was a common process in most industrialized areas. With increasing population growth and urban sprawl, many coastal lowlands are unprecedently vulnerable to climate change impacts such as sea level rise, increasing extreme storm events, and coastal flooding. Under the influence of urban revitalization and conservation, the landward shoreline movement accelerated and coastal land shrank, accompanied by community retreat. This research focuses on the importance of incorporating an understanding of the changing coastal land-ocean interaction into adaptive management strategies by illustrating the relationship of land use change, social-economic development, and climate change. Typical coastal changes in Connecticut were selected: New Haven Harbor reflects a dramatic seaward land accretion under industrial and transportation development, New London downtown waterfront reveals a trend of building retreat under industrial and commercial transformation and coastal hazard, New London Ocean Beach indicates how overdeveloped coastal low-lying community fully retreat after a natural disaster, and Jordan Cove barrier island shows a highly dynamic coastal land change and proactive management strategy. The results reveal that to cope with a constantly changing shoreline and the challenges of climate change, a resilient management process must incorporate a cycle of learning, experimenting, and creating with the goal of developing new solutions that are able to deal with our ever-changing environment.
... Living shorelines incorporate the use of "non-structural" or "soft-structural" control for shoreline stabilization. Vegetating shorelines with marsh grasses can offer comparable levels of protection against shoreline erosion as revetments and bulkheads (Borsje et al., 2017;Smith et al., 2018). These approaches are considered to provide a balance between private shoreline erosion protection and the public benefits derived from natural shoreline features by having little adverse effect and the likely potential for increased ecosystem services . ...
Article
Full-text available
The Shoreline Management Model (SMM) is a novel geospatial approach used to assess conditions along a shoreline, and recommend best management practices for defended and undefended shorelines. The SMM models available spatial data in order to identify areas where the use of living shorelines would be suitable to address shoreline erosion. The model was developed to support and inform decision-making by shoreline managers responsible for management of shoreline resources, shorefront property owners, and tidal habitat restoration actions. Recommended erosion control strategies are based on scientific knowledge of how shorelines respond to natural conditions and anthropogenic measures used to stabilize shorelines. The SMM uses input variables representing current conditions and recommends a strategy that falls into one of three general categories: living shorelines, traditional approaches, and special considerations. Areas of special consideration are areas where the model may not be able to provide an appropriate recommendation due to ecological, geological, or highly developed conditions. These areas are given recommendations that include the instruction to seek expert advice. Data required to run the model include presence of tidal marsh, beach, submerged aquatic vegetation (SAV), riparian land cover, bank height, nearshore bathymetry, fetch, and shoreline erosion control structures. The model has been calibrated and validated along Virginia's Chesapeake Bay shoreline, USA. The model results are largely consistent with field recommendations (i.e., shoreline management recommendations made by scientists based on on-site observations during shoreline evaluation visits). The SMM performed with an overall accuracy of 82.5%. The SMM is exportable; the model code can be adapted to other systems. This geospatial model provides a robust screening tool for local and state governments, coastal and environmental planners and engineers, as well as property owners, when considering best management practices, including living shorelines as an alternative for erosion control.
... Where wave energy, fetch, or bathymetry exceed the thresholds at which marsh plants can survive (Roland and Douglass 2005), additional structural components -like low sills built from oyster shell or rock -may be necessary. These oyster and rock sills can reduce marsh shoreline retreat (Polk and Eulie 2018) and may be more resilient to storm damage (Smith et al. 2018). Further, they frequently support greater densities of native bivalves (Gittman et al. 2016b) than unaugmented marshes or traditional shoreline hardening structures; however, secondary production of sill-associated oysters may not attain the level of oyster reefs (Wong et al. 2011). ...
Article
The detrimental ecological impacts of engineered shoreline protection methods (e.g. seawalls) and the need to protect the coastal zone have prompted calls for greater use of natural and nature‐based infrastructure (NNBI). To balance competing needs of structural stability and ecological functioning, managers require assessments of NNBI designs and materials for differing environmental settings (e.g., among wave‐energy regimes). To examine the effects of setting and oyster‐based NNBI design on the provision of shoreline protection, we constructed reefs from two substrates: a novel, biodegradable material (Oyster Catcher™, OC) and traditional oyster shell bags (SB) on low‐ and high‐energy eroding salt marsh shorelines, designated based on fetch and boat wake exposure. Both reef types buffered marsh elevation change on the high‐energy shoreline relative to unaltered controls, but only SB reefs were able to do so on the low‐energy shoreline. Additionally, both shorelines experienced high ambient rates of retreat and declines in marsh vegetation shoot density. Although constructed reefs did not mitigate marsh retreat on the low‐energy shoreline, novel OC reefs significantly reduced retreat relative to SB reefs and control sites (no reefs) on the high‐energy shoreline. Those SB reefs were severely damaged by storm events, increasing their areal footprints at the expense of vertical relief. Conversely, OC reefs on both shorelines exhibited steady oyster recruitment and growth and hosted higher densities of larger oysters. To successfully provide shoreline stabilization benefits, oyster‐based NNBI must be structurally stable and able to promote sustained oyster recruitment and growth. Our results indicate that deliberate decisions regarding NNBI substrate, siting, and configuration can produce resilient reefs, which reduce rates of erosion and, in some cases, enhance vertical accretion along salt marsh edges. The growth trajectory, structural stability, and co‐benefit provisioning of OC reefs demonstrate the potential of alternative restoration substrates to provide valuable oyster habitat along threatened marsh shorelines.
... Regarding performance metrics, it is significant for supply chains to conduct financial resilience evaluation to facilitate the understanding of risk exposure in supply chains and to evaluate resilience and risk mitigation strategies [61]. Researchers have investigated the measurement of financial resilience by evaluating, for example, density [59], stock level [15], service level, lead time and costs [15]. However, studies on financial resilience measurement criteria remain scarce [17,38,62], as only a few research have discussed financial resilience measurement. ...
Article
Since the financial crisis of 2008, financial resiliency has gradually become a crucial tools employed by supply chains worldwide to resist external risks and shocks. Risks and shocks sometimes creating a turbulent environment can vary in intensity and frequency and may be attributed to a system's internal or external factors. Resilience is defined as the capacity to withstand risks that are more significant, rapid recovery after risks, and reduced degradation by virtue of a certain number of hazards. Financial resiliency focuses on how an organization efficiently deploys the remaining financial resources and invests in maintenance and reconstruction strategies to accelerate the recovery process. This study aims to identify and classify the criteria for measuring supply chain financial resilience using the hybrid Fuzzy Delphi Method (FDM) and intuitive fuzzy DEMATEL technique with interval values (IVIF-DEMATEL). For this purpose, by reviewing the literature, 29 criteria of supply chain financial resiliency were identified, and after screening by FDM, 12 criteria were finalized. In the next step, the desired criteria were classified into two category, and the importance of each was determined.
... Our results reveal key social and environmental influences on cascading shoreline hardening and coastal habitat loss, where a single decision to harden a shoreline results in an increased likelihood that adjacent shorelines will subsequently be hardened. Converting and hardening a natural shoreline can modify the geophysical (Nordstrom, Jackson, Rafferty, Raineault, & Grafals-Soto, 2009;Pope, 1997;Smith, Puckett, Gittman, & Peterson, 2018), ecological (Bilkovic & Roggero, 2008;Gittman, Scyphers, et al., 2016), and socioeconomic (Scyphers, Picou, & Powers, 2015;Smith et al., 2017;Smith & Scyphers, 2019) characteristics of the local ecosystem. Further, converting a hardened shoreline back to its previous state requires considerable, and often costly, human intervention (Nordstrom et al., 2009;. ...
Article
Full-text available
Shoreline hardening is a major driver of biodiversity and habitat loss in coastal ecosystems yet remains a common approach to coastal management globally. Using surveys of waterfront residents in North Carolina, USA, we sought to identify factors influencing individual shore‐protection decisions and ultimately impacting coastal ecosystems, particularly coastal wetlands. We found that neighboring shore condition was the best predictor of respondent shore condition. Respondents with hardened shorelines were more likely to have neighbors with hardened shorelines, and to report that neighbors influenced their shore‐protection choices than respondents with natural shorelines. Further, respondents who expressed climate‐change skepticism and preference for shoreline hardening were opposed to shoreline‐hardening restrictions. Despite preferring hardening, respondents ranked wetlands as highly valuable for storm protection and other ecosystem services, suggesting a disconnect between the ecological knowledge of individuals and social norms of shore‐protection decisions. However, our results also suggest that efforts to increase the installation of living shorelines have the potential to conserve and restore important coastal habitats and support biodiversity along shorelines that may otherwise be degraded by hardening. Further, encouraging waterfront‐property owners who have adopted living shorelines to recommend them to neighbors may be an effective strategy to initiate and reinforce pro‐conservation social norms.
... The anthropogenic view is based on widespread public perception that coastal change is primarily a hazard to property and infrastructure and that both hard and soft structural defenses are required to mitigate coastal hazards (Cooper and Jackson, 2019). There is a growing body of evidence, however, that indicates coastal ecosystems can, and often do, provide coastal protection and resilience to coastal communities (Shepard et al. 2011;Gittman et al. 2014;Narayan et al. 2017;Reguero et al. 2018) and that nature-based solutions, such as living shorelines, enhance the resilience of natural ecosystems and coastal communities (Smith et al. 2016). The ability of natural features to provide resilience is dependent on the health and integrity of the coastal ecosystem both now and in the future. ...
Technical Report
Full-text available
A framework for determining the appropriate type and location of green infrastructure projects designed to improve the resilience of coastal communities and ecosystems through a high-level, landscape-scale screening of possible adaptations using geographical information system (GIS) data.
... Providing coastal resilience while ensuring adequate ecosystem function is crucial due to current loss of natural coastal shoreline communities. Use of living shorelines instead of or in combination with hard structures should provide both coastal resilience and environmental benefits [3]. Living shorelines are defined as a nature-based solution to provide resilience against the adverse effects of sea-level rise [4]. ...
Article
This study investigated the development of a more durable and sustainable cementitious composite sub-strate for oyster reef restoration using recycled oyster shells and low cement content. The effects of concrete mix proportions (w/c ratio, sand content, and cement content) on the physical properties of the hardened concretes were investigated. Increasing the water, sand, cement, and high-range water reducing admixture content improved both the compressive and flexural strength mostly by improving the coating of cementitious materials around the shells. The proposed material for reef restoration is superior in terms of cost, durability, environmental benefits, and carbon footprint.
... In the face of increasing levels of coastal urban growth and sea level rise (Sutton-Grier et al., 2015), there is great potential for living shorelines to both enhance shoreline health and protect people using more natural approaches (Arkema et al., 2013;Toft et al., 2017a). Examples of this include reducing wave heights (Narayan et al., 2016), and maintaining coastal resilience in the face of hurricanes (Smith et al., 2018). To accomplish this, knowledge must be accessible not only to restoration practitioners and scientists, but also to waterfront landowners and government officials (Scyphers et al., 2015). ...
Article
In human-impacted coastal ecosystems, living shorelines are becoming a common restoration technique. However, we lack a comprehensive understanding of the ecological and physical benefits, and how they could inform management needs. To address this, we studied effectiveness of living shorelines at a broad spatial scale within the Washington State boundaries of the Salish Sea, USA, with restored site ages spanning 1–11 years. We surveyed 30 beaches at ten locations, each with three strata of: (1) living shoreline beaches with armor removed, (2) armored control beaches altered by seawalls or riprap, and (3) un-armored reference beaches with natural conditions. We sampled eight physical and biological attributes: beach wrack, wrack invertebrates, sediments, terrestrial insects, riparian vegetation, logs, beach profiles, and stable isotope signatures of talitrid amphipods – generating 27 metrics focusing on upper intertidal and supratidal elevations affected by armoring and targeted by living shoreline actions. These metrics spanned the functions of beach stability, ecological diversity, and food web support for juvenile salmon. Statistical tests showed that 19 of the 27 metrics had significant strata differences, indicating that some beach metrics restore quickly (e.g., wrack accumulation), while others take longer (e.g., log accumulation). Terrestrial-associated metrics were higher at reference beaches, but insect taxa richness and logs with plant growth increased at beaches restored for four or more years (the average age of the living shoreline sites). This implies that certain living shoreline functions increase through time, providing improved food web support. Globally, trajectories of restoration have shown a range of functional improvement with time, and will be important to monitor for nature-based solutions to coastal defense given the increasing rate of shoreline stressors from global change and sea level rise.
... Once pioneer species establish and reach the biomass threshold, bio-geomorphology positive feedbacks would work spontaneously . Similar studies showed that elevation and vegetation was more resilient in "living shoreline" that was protected by low-rising breakwaters during two years, compared to hardened shorelines (Smith et al., 2018) Thus, low levees or detached breakwaters outside the seawall would help to obtain long-term coastal defenses benefits from salt marsh ecosystems with low-cost (Vuik et al., 2019). ...
Article
With the increase in coastal hazards induced by global change, estuarine deltas are urgently required to enhance nature-based coastal defenses. This study sets an example at the Nanhui nearshore salt marshes in the Yangtze Estuary, China, with a one-dimension wave attenuation empirical model and Landscape Resistance Index (LRI). We explored wave attenuation by salt marshes at site and transect scale, and put forward potential approaches to improve coastal defenses. Results showed that 1) the two 10 m-wide stripes of typical vegetation (Spartina alterniflora and Scirpus mariqueter) could attenuate wave height mostly when incident wave height was 0.22 m and 0.20 m, respectively; 2) under the condition of 0.6 m initial wave height, wave attenuation rate among all transects ranged from 32.50% to 98.30% (71.30 ± 16.09% on average); and 3) Land cover-Position-Length weighted LRI was an effective indicator for the relationship between wave attenuation and landscape pattern. Wave attenuation by salt marshes differ in various environments and are species specific. Wave attenuation along transects was also affected by both land cover and spatial configuration. Thus, we proposed some salt marsh restoration strategies, such as preferential restoration of long transects, differentiation of vegetation configuration, and engineering protections like low levees or breakwaters in front of salt marsh edges. These findings could be used to promote ecological functions in the Yangtze Estuary and other coastal marshes in the world.
... Higher vegetation biomass favors sediment trapping and accretion 41,45,48 . Salt marsh grass or mangrove planting, one of the traditional wetland restoration approaches, can reduce tidal current speeds, prevent erosion, trap more sediment, and promote belowground root production to facilitate accretion and sediment retention [49][50][51] . Hydrological restoration like managed realignment (MR) or controlled reduced tide (CRT) can increase tidal inundation compared to prerestoration conditions by breaching artificial barriers and reestablishing tidal exchange between the restoration site and the adjacent estuary or sea, hence promoting more frequent and longer episodes of mineral sediment deposition, enhancing vegetation growth, and accelerating rates of mineral and organic matter accumulation 10,52 . ...
Article
Full-text available
Shorelines and their ecosystems are endangered by sea-level rise. Nature-based coastal protection is becoming a global strategy to enhance coastal resilience through the cost-effective creation, restoration and sustainable use of coastal wetlands. However, the resilience to sea-level rise of coastal wetlands created under Nature-based Solution has been assessed largely on a regional scale. Here we assess, using a meta-analysis, the difference in accretion, elevation, and sediment deposition rates between natural and restored coastal wetlands across the world. Our results show that restored coastal wetlands can trap more sediment and that the effectiveness of these restoration projects is primarily driven by sediment availability, not by wetland elevation, tidal range, local rates of sea-level rise, and significant wave height. Our results suggest that Nature-based Solutions can mitigate coastal wetland vulnerability to sea-level rise, but are effective only in coastal locations where abundant sediment supply is available. Coastal wetlands restored by Nature-based Solutions can trap more sediments than natural ones, and their efficiency is mainly determined by sediment supply, according to a meta-analysis of studies globally.
... Due to environmental, economical, and aesthetic concerns, the sustainability of hard structural armoring using rocks or artificial materials to protect coastal communities and infrastructure from excessive wave energy is beginning to be questioned (e.g., Seitz et al., 2006;Dugan et al., 2008). As a result, natural and nature-based solutions are being widely implemented to mitigate shoreline erosion, provide and conserve habitat, and generate other ecosystem services such as carbon sequestration and support of fish and invertebrate biodiversity (e.g., Davis et al., 2015;Bilkovic et al., 2016;Sharma et al., 2016;Davenport et al., 2018;Morris et al., 2018;O'Donnell, 2018;Polk and Eulie, 2018;Smith et al., 2018). However, the suitability of living shorelines needs to be quantitatively assessed in terms of the interaction of the living shorelines with hydrodynamics. ...
Article
Living shorelines are being widely implemented to mitigate shoreline erosion and provide ecosystem services, but how they interact with waves remains poorly understood. Wave transmission through living shoreline breakwalls is studied using field observations and theoretical approaches. The following hypotheses are tested: (i) living shoreline breakwalls can act as buffers against waves; (ii) wave transmission through these nature-based solutions is modulated by tides; and (iii) wave transmission through living shoreline breakwalls is similar to the behavior observed in waves through porous breakwaters. Observations were collected in intertidal settings where boat wakes and tides are the major flow components. Nearly 1000 boat wakes were identified in the observations using advanced time-frequency data analysis methods. Wave transmission through the breakwalls composed of tree branches was quantified and modulation of this process by tides was investigated. The two tested breakwall designs provided different behaviors of wave transmission. In the first design with an estimated porosity of 0.7 where the tree branches were bundled, transmission rates were found to vary mostly between 9% and 70% and had an average of 53%. Transmission increased with increasing water depth especially at mid-tide and low-tide where the height of the breakwall relative to depth was between 0.5 and 1. In the second design with an estimated porosity of 0.9 where the tree branches were not bundled, transmission rates exceeded 70% in 84% of the cases, sometimes reaching 100% transmission, and had an average of 83% with much less variability with depth compared to the first design. Wave transmission estimates based on theory of porous media were found to be most sensitive to breakwall porosity and the friction coefficient. Best agreement between the observed and theoretical estimates of wave transmission was found using a turbulent friction coefficient of 2.7, the median value of the most common range given in the literature on waves through porous media. The highest discrepancy between observed and theoretical estimates of wave transmission occurs at shallow depths when the breakwall emerged. In these conditions, the theory overestimates transmitted wave energy, most likely due to significant wave breaking and bottom friction in shallow water. The findings support our hypotheses that well-engineered semi-porous living shorelines act as buffers against human-mediated boat traffic and waves, and their related performance in dissipating wave energy and sustaining coastal ecosystems is modulated by depth. The results can be used as guidelines for design of living shorelines for given wave climate and breakwall properties.
... Without any human interaction, shorelines are mainly comprised of biogenic habitats (e.g., saltmarshes, mangroves, oyster and coral reefs) in their natural conditions. These natural coastal habitats secure the provision of essential habitat for marine life, promotion of favourable water quality, and reduction of shoreline erosion and flooding by attenuating waves, stabilizing sediments, and dampening surge [24,26,27]. As such, they are widely valued for their environmental benefits. ...
Article
Full-text available
Rising sea levels are causing more frequent flooding events in coastal areas and generate many issues for coastal communities such as loss of property or damages to infrastructures. To address this issue, this paper reviews measures currently in place and identifies possible control measures that can be implemented to aid preservation of coastlines in the future. Breakwaters present a unique opportunity to proactively address the impact of coastal flooding. However, there is currently a lack of research into combined hard and soft engineering techniques. To address the global need for developing sustainable solutions, three specific breakwater configurations were designed and experimentally compared in the hydraulic laboratory at Coventry University to assess their performance in reducing overtopping and the impact of waves, quantifying the effectiveness of each. The investigation confirmed that stepped configurations work effectively in high amplitudes waves, especially with the presence of a slope angle to aid wave reflection. These results provide a very valuable preliminary investigation into novel sustainable solutions incorporating both artificial and natural based strategies that could be considered by local and national authorities for the planning of future mitigation strategies to defend coastal areas from flooding and erosion.
... Separate branches indicate statistical differences at P ≤ .05 ecological outcomes than traditional armoring (NRC, 2007), and they may also be more resilient during storm events (Gittman, Popowich, Bruno, & Peterson, 2014;Smith, Puckett, Gittman, & Peterson, 2018). While the delivery of specific services will certainly vary across space and time (Koch et al., 2009), the potential for living shorelines to benefit people and nature is clear (Arkema et al., 2017). ...
Article
Full-text available
Shoreline armoring is a pervasive driver of habitat loss and ecosystem decline along coastlines. Nature‐based strategies for coastal protection, such as “living shorelines,” offer potential alternatives to armoring and are rapidly gaining traction among conservation scientists and practitioners. However, along residential coasts where armoring has often occurred at high rates, transitioning away from armoring has been generally slow. We studied the attitudes, beliefs, and decisions of waterfront homeowners with a goal of identifying effective incentives for living shorelines as a conservation tool for reversing coastal habitat loss. We show that while only 18% of homeowners with armored shorelines would willingly transition to living shorelines during a key window of opportunity, a modest economic incentive could increase the likelihood among 43% of all respondents and up to 61% of recent homeowners. Our study demonstrates potential pathways for navigating social, economic, and environmental influences on landowner decisions for coastal habitat conservation.
... Recognizing this advantage, UASs are incorporated into post-storm monitoring in coastal systems internationally (Turner et al., 2016;Seymour et al., 2019;Casella et al., 2020). Studies conducted on living shorelines to assess their resilience and shoreline protection against storm impacts (e.g., Smith et al., 2018) would benefit from the incorporation of UASs, which would expedite field sampling and reduce unintentional, but inevitable, impacts of direct sampling within the habitat (Figure 1). ...
Article
Full-text available
Assessing, implementing and monitoring ecosystem restoration can be a labor intensive process, often short term (<3 years), and potentially destructive to the habitat. Advances in remote sensing technology are generating rapid, non-destructive methods for siting, executing and monitoring restoration efforts, particularly in fragile marine environments. Unoccupied aircraft systems (UAS), or drones, are a highly flexible method for accessing and remote sensing ecosystems with on-demand capabilities, greater resolution than sensors from satellites and occupied aircraft, and the ability to cover large areas quickly. With the variety of platforms and payloads available, UASs are providing a suite of tools for conservation practitioners to properly plan marine ecosystem restoration projects and evaluate their success. Both conventional and specialized sensors coupled with image processing techniques can be used to gauge impact to and recovery of entire ecological communities. For example, high-resolution, multispectral imaging allows for discernment of population changes across trophic levels, concurrent with the discrimination of species (including rare) across a landscape, and detection of vegetation stress. Structure from Motion photogrammetric processing provides centimeter-scale three-dimensional models of habitat structure to measure ecologically significant aspects like rugosity and assess their change through time. Water quality around a broad impacted area can be remotely monitored via a number of payloads before and after restoration. Additionally, specially designed payloads can be used to manually disperse seeds or materials for restoration applications without disturbing the habitat. UASs have increasing potential to reduce the costs (both time and money) associated with restoration efforts, making site assessment and long-term, broad-scale monitoring more achievable. Here we present a review of the applications of UASs in marine ecosystem restoration with an overview of the special considerations of using this technology in the marine environment.
... The study site is surrounded by living shorelines that transition from mangrove habitat within the estuarine environment to saltmarsh and Juncus romerianus dominated systems and finally freshwater species (Cladium jamaicense, Taxodium distichum, etc.) in its upper reaches. Living shorelines, but mainly saltmarsh and mangrove habitats, have been shown to assist with ecosystem resilience during previous hurricanes and could help protect this ecosystem as well as the other NERR sites from large ecosystem shifts [60,61]. However, the impact of increased storm frequency on these ecosystems is still unknown and could add to future shifts in nutrient cycling and water quality, which requires more long-term monitoring with detailed measurements immediately before, during, and after the storm to determine the outlook for these ecosystems in the future. ...
Article
Full-text available
Hurricanes cause landscape-scale disturbances that affect biogeochemical cycling and water quality in coastal ecosystems. During Hurricane Irma’s passage through northern Florida, water movements driven by wind velocities up to 105 km h−1 caused a salinity peak in an estuary/blackwater river complex. Water quality was monitored across the 15 km site to detect the magnitude and duration of disturbance. Saline water intruded 15 km inland into a freshwater portion of the river that peaked at a salinity of 2 psu. Due to the volume of precipitation from the hurricane, significant runoff of freshwater and dissolved organic matter (DOM) caused a decrease in salinity, dissolved oxygen (DO), and Chlorophyll-a concentrations while increasing turbidity and fluorescent dissolved organic matter (fDOM). The disturbance caused rapid changes observed by in-situ water quality monitors over a 3-week period, but some effects persisted for longer periods as shown by 3-month weekly water sampling. This disturbance caused shifts in DOM loading, altered salinity dynamics, and reshaped landscapes due to wind and wave surge both in upland marsh and downstream estuary. Hurricane disturbance temporarily and abruptly alters the aquatic continuum, and observations of system response can help us understand the mechanisms associated with ecosystem resilience and recovery.
... We found that 6 out of the18 states surveyed approved the Nationwide Permit 54 for living shorelines under the Coastal Zone Management Act and Clean Water Act. The 12 remaining states denied CZMA and/ or CWA certification of NWP 54 for a variety of reasons. ...
Book
Full-text available
America’s coastlines are threatened by increasingly intense storms, rising sea levels, and other climate change impacts, resulting in more frequent flooding and accelerating rates of erosion and land loss. Approaches for shoreline protection traditionally have relied on the construction of hard structures, such as seawalls, bulkheads, and breakwaters. While appropriate in certain settings, coastal armoring can have a number of negative impacts, including loss of coastal habitats, increased erosion of adjacent properties, and high maintenance and post-storm reconstruction costs. In contrast, living shorelines rely on natural and nature-based features, such as marshes, dunes, and oyster reefs, and can often provide the same shoreline protection while providing ecological and community benefits, such as fish and wildlife habitat, improved water quality, and recreational opportunities. Softening Our Shorelines is designed to promote the broader application of living shorelines across the Atlantic and Gulf coasts. National Wildlife Federation partnered with the Coastal States Organization to review the use of living shorelines across these regions and analyze policies and permitting requirements that may provide incentives—or barriers—to the broader use of these ecologically friendly shoreline protection techniques. The report provides a state-by-state summary of policies relevant to living shorelines and offers recommendations and best practices for how federal and state agencies can promote the increased application of living shorelines.
... Some limited work has been conducted in North Carolina that integrates homeowner perceptions with field measures. This was targeted to assess the relationship between perceptions of waterfront homeowners regarding shoreline protection methods to actual measures of their efficacy when impacted by hurricanes [20]. ...
Article
Full-text available
Coastal communities are increasingly vulnerable to changes in climate and weather, as well as sea-level rise and coastal erosion. The impact of these hazards can be very costly, and not just in terms of property damage, but also in lost revenue as many coastal communities are also tourism-based economies. The goal of this study is to investigate the awareness and attitudes of full-time residents and second-home property owners regarding the impact of climate and weather on property ownership and to identify the factors that most influences these attitudes in three coastal counties (Brunswick, Currituck, and Pender) of North Carolina, USA. The majority of previous studies have focused on only full-time residents’ risk perceptions. Given the fact that these coastal communities have a high percentages of second homes, this study fills that research gap by including second-home owners. This study integrates both social (survey data) and physical (geospatial coastal hazards data) aspects of vulnerability into a single assessment to understand the determinants of property owners’ risk perceptions and compare their perceived risks with their physical vulnerability. The study also compared the utility of a global ordinary least square (OLS) model with a local geographically weighted regression (GWR) model to identify explanatory variables in the dataset. The GWR was found to be a slightly better fit for the data with an R2 of 0.248 (compared to 0.206 for the OLS). However, this was still relatively low and indicated that this study likely did not capture all of the factors that influence the perceptions of vulnerability in patterns of property ownership (whether full-time residents or second-home owners). The geospatial variables used to determine coastal vulnerability were found not to significantly impact perceptions related property ownership, but did provide additional insight in explaining spatial patterns of the response variable within each county.
... The change in relative importance of marsh edge erosion over time under conditions of high sea-level rise (Fig. 2) shows that addressing edge erosion through shore protection measures such as bulkheads (Gittman et al., 2015) or living shorelines (Scyphers et al., 2011;Smith et al., 2018) may sustain wetland area in the short-term but is not a long-term solution if the wetlands are vulnerable to inundation loss. Further, protection of shorelines from erosion eliminates or reduces the sediment yield from that erosion, potentially making adjacent wetlands more vulnerable. ...
Article
This study uses modeling results for coastal Louisiana to examine spatial and temporal variation in future wetland loss, and how this variation is influenced by different causes of land loss represented in the modeled processes. Fifty-year model predictions illustrate specific vulnerabilities of the wetlands and the conditions under which they occur, e.g., long-term changes vs. specific events. Environmental scenarios were used to examine model sensitivity to changes in future patterns of precipitation, evapotranspiration, subsidence, and eustatic sea level rise. Based on the model results, the magnitude of wetland loss increases more than three-fold from low to high scenario. The model allows vegetation types to change over time as environmental conditions change. Each type is sensitive to different land-loss causing factors. Across all scenarios, the largest contributor to wetland loss is inundation loss of saline marsh ->40% of loss. Inundation loss of brackish marsh increases from low to high scenarios. Salinity induced loss of fresh wetlands increases from low to high scenario and coastwide contributes <10% of the total wetland loss. Marsh edge erosion is relatively consistent in magnitude across scenarios but its relative contribution decreases from low to high. Model outputs show two contrasting responses to environmental change over a 50-year simulation: a relatively linear response of land area over time, and a non-linear response where a large collapse event is triggered in a single year. Land loss varied dramatically over time within the 50-year simulations with little loss in the first two decades and high rates of loss 25–40 years into the future. Across most of the coast, and for all scenarios, the majority of land loss is caused by excessive inundation. Understanding the threshold conditions for inundation for different species and species mixtures is crucial to predictions of vegetation change, and subsequent wetland loss.
... In their natural condition, shorelines are often comprised of biogenic habitats such as saltmarshes, mangroves, and oyster reefs. These natural coastal habitats are widely valued for their environmental benefits, including the provision of essential habitat for marine life, promotion of favorable water quality, and reduction of shoreline erosion and flooding by attenuating waves, stabilizing sediments, and dampening surge [13,15,16]. Recent reviews of the protective value of wetlands found that vegetated shorelines can significantly reduce wave height and promote shoreline stabilization [17], and can be cost-effective for coastal protection [18]. ...
Article
Full-text available
Coastal communities exist on the front lines of diverse natural hazards and the growing impacts of climate change. While traditional strategies for dealing with coastal hazards have often involved the hardening or armoring of shorelines, more recent research and practice have demonstrated the value and cost-effectiveness of “living shorelines” and other ecosystem-based strategies for coastal protection. To explore potential relationships among geographic exposure (waterfront vs. inland), shoreline condition (armored vs. natural), and hazard concerns, we surveyed 583 waterfront and inland residents in the northern Gulf of Mexico. We found that overall concern for coastal hazards was similar across waterfront and inland residents, as well as among residents with both armored and natural shorelines. However, concern for specific hazards differed across these groups. Waterfront residents were significantly more concerned about major hurricanes and erosion than inland residents. Conversely, inland residents were more concerned with drought and flooding than waterfront residents. Among waterfront residents, specific hazard concerns were similar between residents with natural and armored shorelines with two key exceptions. Residents with armored shorelines reported higher concern for erosion and sea level rise than residents with natural shorelines. Our results suggest that armored shorelines do not necessarily alleviate concerns about coastal hazards. In the context of balancing social and ecological objectives in addressing coastal hazards or adapting to climate change, understanding the perceptions and behaviors of coastal residents is essential for conserving and protecting coastal ecosystems along residential shorelines.
... For 436 example, if the asset to be protected is essential to national or regional infrastructure, such as 437 an airport, hospital or railway, there may be less willingness to accept approaches perceived 438 to carry greater uncertainty with respect to inundation and flood risk. Often, there is stronger 439 support for hard engineering approaches (Gray et al., 2017) that have been more thoroughly By contrast, where the asset is less crucial for social and economic health and/or primarily of 443 local significance, there may be a higher chance for adopting more experimental and 444 potentially riskier eco-engineered shoreline approaches that provide protection under most 445 but not the most severe storm events, or for which the evidence of efficacy in terms of 446 shoreline protection is limited (but see, Gittman et al., 2014, Smith et al., 2018. ...
Article
Full-text available
Human population growth and accelerating coastal development have been the drivers for unprecedented construction of artificial structures along shorelines globally. Construction has been recently amplified by societal responses to reduce flood and erosion risks from rising sea levels and more extreme storms resulting from climate change. Such structures, leading to highly modified shorelines, deliver societal benefits, but they also create significant socioeconomic and environmental challenges. The planning, design and deployment of these coastal structures should aim to provide multiple goals through the application of ecoengineering to shoreline development. Such developments should be designed and built with the overarching objective of reducing negative impacts on nature, using hard, soft and hybrid ecological engineering approaches. The design of ecologically sensitive shorelines should be context-dependent and combine engineering, environmental and socioeconomic considerations. The costs and benefits of ecoengineered shoreline design options should be considered across all three of these disciplinary domains when setting objectives, informing plans for their subsequent maintenance and management and ultimately monitoring and evaluating their success. To date, successful ecoengineered shoreline projects have engaged with multiple stakeholders (e.g. architects, engineers, ecologists, coastal/port managers and the general public) during their conception and construction, but few have evaluated engineering, ecological and socioeconomic outcomes in a comprehensive manner. Increasing global awareness of climate change impacts (increased frequency or magnitude of extreme weather events and sea level rise), coupled with future predictions for coastal development (due to population growth leading to urban development and renewal, land reclamation and establishment of renewable energy infrastructure in the sea) will increase the demand for adaptive techniques to protect coastlines. In this review, we present an overview of current ecoengineered shoreline design options, the drivers and constraints that influence implementation and factors to consider when evaluating the success of such ecologically engineered shorelines
... Hydrodynamic interactions are important controls to shoreline processes and functions, including the transport and retention of sediments and organic matter [13,14], the survival of planted vegetation [15][16][17], long-term vegetation recruitment [18,19], the provision of hydraulic habitat for estuarine species [20], and resilience to extreme events [9,11,21]. In restoring degrading shorelines with native species, restoration practitioners wish to induce physical-biological feedbacks, wherein the structure of placed or planted species reduces current and wave velocities, lessens shear stresses on substrates, and promotes the deposition of sediments and retention of organic matter. ...
Article
Full-text available
Hydrodynamic differences among shorelines with no vegetation, reference vegetation (mature mangrove), and vegetation planted on restored shoreline (marsh grass and young mangrove) were compared based on field observations 6.5 years after living shoreline restoration. Mean current velocities and waves were more strongly attenuated in vegetation (from channel to shoreline: 80–98% velocity decrease and 35–36% wave height reduction) than in bare shoreline (36–72% velocity decrease, 7% wave height reduction, ANOVA: p < 0.001). Normalized turbulent kinetic energy dissipation rates were significantly higher in reference vegetation (0.16 ± 0.03 m−1) than in restored (0.08 ± 0.02 m−1) or bare shoreline (0.02 ± 0.01 m−1, p < 0.001). Significant differences in the current attenuation and turbulence dissipation rates for the reference and planted vegetation are attributed to the observed differences in vegetation array and morphology. Although the hydrodynamic analyses did not suggest limitations to recruitment, mangrove seedlings were not observed in restored vegetation, while four recruited seedlings/m were counted in the reference vegetation. The lack of recruitment in the restored shoreline may suggest a lag in morphological habitat suitability (slope, sediment texture, organic matter content) after restoration. Although hydrodynamics suggest that the restored site should be functionally similar to a reference condition, thresholds in habitat suitability may emerge over longer timescales.
... In addition to efforts to enhance nekton production, intertidal oyster restoration is increasingly being employed to protect eroding salt marsh shorelines (e.g. living shorelines), with case studies demonstrating reduced marsh shoreline erosion postreef restoration (Piazza et al. 2005;Currin et al. 2010;Smith et al. 2018). Eroding marsh shorelines are characteristically affected by exposure to wind-generated sheer stress, which depends on the unobstructed distance over which the wind can blow (i.e. ...
Article
Restoration is increasingly implemented as a strategy to mitigate global declines in biogenic habitats, such as salt marshes and oyster reefs. Restoration efforts could be improved if we knew how site characteristics at landscape scales affect the ecological success of these foundation species. In this study, we determined how salt marsh shoreline geomorphologies (e.g., with variable hydrodynamic energy, fetch, erosion rates, and slopes) affect the success of restored intertidal oyster reefs, as well as how fauna utilize restored reefs and forage along marsh habitats. We constructed oyster reefs along three marsh shoreline geomorphologies in May 2012: 1) “creek” (small‐fetch, gradual‐sloped shoreline), “ramp” (large‐fetch, gradual‐sloped shoreline), and “scarp” (large‐fetch, steep‐sloped shoreline). Following recruitment, oyster spat density was greatest on ramp reefs; however, two years later, the highest adult oyster densities were found on creek reefs. Total nekton and blue crab catch rates in trawl nets were highest in the creek, while piscivore catch rates in gill nets were highest along the scarp shoreline. We found no difference in predation on snails in the salt marsh behind constructed reef and non‐constructed reference sites, but there were more snails consumed in the creek shoreline, which corresponded with the distribution of their major predator – blue crabs. We conclude that oyster reef construction was most successful for oysters in small‐fetch, gradual‐sloped, creek environments. However, nekton abundance did not always follow the same trends as oyster density, which could suggest constructed reefs may offer similar habitat‐related functions (prey availability and refuge) already present along existing salt marsh borders. This article is protected by copyright. All rights reserved.
Article
Full-text available
The North Atlantic Basin (NAB) has seen an increase in the frequency and intensity of tropical cyclones since the 1980s, with record-breaking seasons in 2017 and 2020. However, little is known about how coastal ecosystems, particularly mangroves in the Gulf of Mexico and the Caribbean, respond to these new "climate normals" at regional and subregional scales. Wind speed, rainfall, pre-cyclone forest height, and hydro-geomorphology are known to influence mangrove damage and recovery following cyclones in the NAB. However, previous studies have focused on local-scale responses and individual cyclonic events. Here, we analyze 25 years (1996-2020) of mangrove vulnerability (damage after a cyclone) and 24 years (1996-2019) of short-term resilience (recovery after damage) for the NAB and subregions, using multi-annual, remote sensing-derived databases. We used machine learning to characterize the influence of 22 potential variables on mangrove responses, including human development and long-term climate trends. Our results document variability in the rates and drivers of mangrove vulnerability and resilience, highlighting hotspots of cyclone impacts, mangrove damage, and loss of resilience. Cyclone characteristics mainly drove vulnerability at the regional level. In contrast, resilience was driven by site-specific conditions, including long-term climate trends, pre-cyclone forest structure, soil organic carbon stock, and coastal development (i.e., proximity to human infrastructure). Coastal development influenced both vulnerability and resilience at the subregional level. Further, we highlight that loss of resilience occurs mostly in areas experiencing long-term drought across the NAB. The impacts of increasing cyclone activity on mangroves and their coastal protection service must be framed in the context of compound climate change effects and continued coastal development. Our work offers descriptive and spatial information to support the restoration and adaptive management of NAB mangroves, which need adequate health, structure, and density to protect coasts and serve as Nature-based Solutions against climate change and extreme weather events.
Article
Decision-making in a coastal socio-ecological system involves managing a site-specific complexity arising not only from the interaction between hydrodynamic and morphological conditions, but also from the interactions between human structures and ecological systems, as well as the conflicting needs and interests of local actors. In addition, the projections of climate change impacts on coastal systems have a degree of uncertainty, which increases the general unpredictability of coastal dynamic behaviour, and adds a layer of complexity to the decision-making process. Decision-making in a coastal socio-ecological system involves managing a site-specific complexity arising from the interaction between hydrodynamic and morphological conditions, and resulting in uncertain patterns. In addition, projections show that sea level will rise in the near future, thus increasing the uncertainty of coastal dynamic behaviour, and adding a layer of complexity to the decision-making process. Scientific knowledge can help reduce some of the inherent uncertainties, and is essential when it comes to making sound decisions on the choice of appropriate coastal defence measures (CDMs) that are adapted to specific coastal environments and improve the resilience of coastal communities. This paper is based on a meta-analysis of 355 CDMs case studies drawn from 301 publications. From these published case studies, the objectives were to analyze the geographical and physical contexts in which CDMs monitoring was carried out and, based on the findings, to recommend areas of improvement necessary to help make sound decisions in any type of coastal environment. The meta-analysis showed that study sites are not evenly distributed around the world. Most originate from Europe (n=106), the USA (n=151) and Australia (n=30), while few studies have been carried out in Africa and Asia where dense population resides in high-risk zones. Also noticeable is the absence of sites in high latitude climates where ice plays a major role in the erosion process. Five basic variables (coastal type, sediment type, wave characteristics, tidal range, and currents or sediment transport characteristics) are used in publications to characterize study sites according to their physical components. However, only 13 of the 355 sites included a complete characterization using the 5 variables, of which coastal and sediment types are the most frequently identified (77.2% and 72.7% respectively). In general, CDMs are studied in the context of unconsolidated low shore (59.4%) and in sandy environments (74.6%). Information on tidal range, wave climate, and currents, or sediment transport characteristics, is much scarcer. Since 1990, 3 of the 10 CDMs identified in the studies have received more attention than the others; these are beach nourishments, seawalls and breakwaters, with respective cumulative study sites of 164, 67 and 50. The geomorphological effects of CDMs are the most studied (55.1%), followed by ecological (31.2%), hydrodynamic (9.1%), and social (4.6%). Overall, this meta-analysis helped identify knowledge gaps regarding geographical and physical contexts in which CDMs monitoring was held. It also gave an indication of the kind of improvement necessary for global-scale adaptation planning, and for a better decision-making process to reduce coastal risks in the most vulnerable coastal communities. Finally, the analysis shows that 4.4% of the studies on defence measures include monitoring of their effects on the coastal zone. A conceptual scheme is proposed for the evaluation of adaptation solutions based on the global monitoring of coastal zones to measure coastal change trajectories in the context of climate change.
Article
Full-text available
Increasing anthropogenic pressure on the sea and alteration of coastscapes challenge the functioning of marine ecosystems and long-term reliance on blue economies, especially for developing southern economies. The structural hardening of shores can result in ecological disruptions, with cascading effects on the wellbeing and livelihoods of marginalised groups who depend on marine resources. Mitigation, adaptation and rehabilitation options for coastal developments should include innovative, socially responsible solutions to be used to modify shorelines and ensure long-term functionality of metropolitan coastal ecosystems. Nature-based innovations are being developed to improve surrogacy for natural marine ecosystems. The co-creation of nature-based structures, entailing partnerships between scientists and a local rural community is currently being considered in South Africa and we present this regional case study as a transdisciplinary framework for research in nature-based, ecological engineering of coastal systems. Novel transdisciplinary approaches include ecomusicological interventions, where traditional cultural expressions (TCEs) create opportunities for transgressive pedagogy. This step aims to ensure that the knowledge gathered through nature-based scientific research remains a part of community developed Indigenous knowledge systems. The merging of innovative, eco-creative approaches and TCEs has the potential to sustainably and ethically improve the functioning and diversity of coastal urban habitats. This review tackles the potential of transdisciplinary settings to transform urban coastlines using “low-tech” engineering and Indigenous eco-creative innovations to pedagogy, to benefit the people and biological communities as well as reduce social and gender inequalities.
Preprint
Full-text available
The North Atlantic Basin (NAB) is seeing a significant increase in the frequency and intensity of tropical cyclones since the 1980s, with record-breaking seasons such as 2017 and 2020. However, little is known about how coastal ecosystems, particularly mangroves in the Gulf of Mexico and the Caribbean, are responding to these new climate normals at regional and subregional scales. Wind speed, rainfall, pre-cyclone forest structure, and hydro-geomorphology are known to influence mangrove damage and recovery following cyclones in the NAB. However, these studies have focused on site-specific responses and individual cyclonic events. Here, we analyze 25 years (1996-2020) of mangrove vulnerability (damage after a cyclone) and short-term resilience (recovery after damage) for the entire NAB and its subregions, using multi-annual, remote sensing-derived databases. We applied machine learning to characterize the influence of 22 potential drivers that include previously researched variables and new ones such as human development and long-term climate trends. The characteristics of the cyclones mainly drive vulnerability at the regional level, while resilience is largely driven by site-specific conditions. These include long-term climate conditions, such as air temperature and drought trends, pre-cyclone habitat conditions, such as canopy cover and height and soil organic carbon stock, and human interventions on the land. Rates and drivers of mangrove vulnerability and resilience vary across subregions in the NAB, and hotspots for restoration and conservation actions are highlighted within subregions. The impacts of increasing cyclone activity need to be framed in the context of climate change compound effects and heavy human influences in the region. There is an urgent need to value the restoration and conservation of mangroves as fundamental Nature-based Solutions against cyclone impacts in the NAB.
Article
Full-text available
Motivation The scientific community devotes considerable attention to defining and implementing approaches for preventing and managing disasters. The article presents an innovative disaster management approach that considers societal, economic, and environmental issues and expectations, in order to stimulate actors' collaboration at different scales (local, national, etc.). Purpose The article proposes an innovative approach to disaster management that integrates the characteristics of recent approaches—resilience‐based, sustainability‐based, and responsible research and innovation (RRI)‐based. Methods and approach The article present a detailed overview of the evolution of disaster management approaches, evaluating their different characteristics to identify the most effective approach, as well as an analysis of the pillars characterizing the resilience, sustainability, and RRI concepts and the different phases of each approach. Findings The article suggests practices to reduce/mitigate the impacts of disasters, classified according to their different actors and components. Policy implications First, the implementation of the approach has to be aligned with adequate policies or funding. It also requires the involvement of many different actors and a range of public‐sector agencies at different levels of government.
Article
Marshes play a key role in global nitrogen cycling at the land–water margin. Invasive species are generally considered detrimental as they alter ecosystems they invade, but recent studies have shown some established invasive species can enhance certain ecosystem functions. The European haplotype of Phragmites australis is an aggressive and widespread invasive plant species in North America. We hypothesized that P. australis may play an important role in marsh nitrogen cycling by promoting higher rates of sediment denitrification compared with native marsh species. Seasonal measurements of sediment dissolved gas (N2 and O2) fluxes at three sites within the Albemarle-Pamlico Region of North Carolina compared sediments from invasive P. australis, native Spartina alterniflora, and/or Juncus roemarianus, and unvegetated sediments. In a marine tidal site, annual net denitrification in sediments associated with upland P. australis was highest compared to lower elevation marsh species or unvegetated sediments under ambient (139 μmol N2-N m−2 h−1) and nitrate enriched (219 μmol N2-N m−2 h−1) conditions. N2 fluxes were lower in sediments from two brackish marshes and did not differ between associated species, unvegetated sediments, or between high or low organic matter sites. Treatments with elevated nitrate showed enhanced net denitrification in most sediments at the marine site, suggesting the capacity to remove additional nitrate delivered episodically. Additionally, N2 fluxes measured before and after Hurricane Florence showed an increase in denitrification in P. australis sediments after the hurricane. Ecosystem value for this nitrogen removal service in the marine tidal site was estimated at US$ 266–426 *ha−1*yr−1. These results demonstrate an important role for invasive P. australis in coastal nitrogen cycling in marine environments and provide landscape context for potential biogeochemical impacts of this invasion.
Article
This study clarifies the role of sense of place, social capital, and psychological resilience as valuable resources that can build psychological wellbeing (PWB) in long-term disaster recovery. Existing studies on disaster recovery often examine these intangible resources in isolation, without recognizing their inter-dependencies. Based on 25 in-depth interviews with residents, following the Canterbury earthquake sequence, we identify themes and visualize them through a post-disaster wheel of wellbeing (PDWWB) to highlight the need for greater recognition of PWB in the provision of tangible resources in disaster recovery. The results show that both individual (psychological resilience) and community resources (social capital) as well as an individual's sense of place provide different levers to activate in rebuilding residents' PWB (hedonic and eudaimonic aspects). For example, social capital can enhance psychological resilience and PWB while sense of place can contribute positively to social capital, psychological resilience and PWB. Thus, re-establishing sense of place and supporting social ties and networks can improve both psychological resilience and PWB post-disaster.
The need for sustainable and resilient long-term strategies for coastal restoration and development projects is largely due to pressures brought by changing climate conditions and growing human populations along coastal boundaries. As anthropogenic impacts along our coasts increase, the demand for sustainable, nature-based solutions (NbS) will grow commensurately. Trusted approaches are needed for successful implementation of NbS, especially in regions hardest hit by environmental changes. Nearshore strategies for new construction and protection of existing coastal infrastructure are shifting rapidly from hardened approaches to more ecologically aligned techniques that work with natural forces and enhance natural habitat. This paper highlights the benefits of living shorelines composed of ecotypic native plants, wave attenuation structures for coastal protection, and managed retreat to restore coastal environments while supporting and maintaining natural habitats. We review several NbS and present two case studies to illustrate the value of incorporating nature-based approaches to vulnerable coastal environments and highlight the importance of maximizing synergies and understanding tradeoffs in their use long-term. This article is protected by copyright. All rights reserved.
Article
Stabilization of eroding estuarine shorelines using living shoreline techniques, including native vegetation and nearshore structural components, has the potential to combat erosion while increasing shoreline ecotone function. However, there are few detailed field studies and little quantitative data available to assess hydrodynamic changes that occur immediately following living shoreline implementation. To address this gap, detailed hydrodynamic observations were made along eroding and stable reference shorelines over a 16-month period spanning living shoreline stabilization, which included the landfall of a major hurricane (Irma) 9 weeks after stabilization. In the months following stabilization, planted vegetation was sparse and shoreline hydrodynamics were governed by water level relative to breakwater structures. When water levels were at or below breakwater crest elevation, current velocities were initially reduced by 62% and wave heights by up to 83%; however, at higher water levels, shoreline velocities at the stabilized site vastly exceeded those observed at a nearby bare control site. Sixteen months after stabilization, flow-vegetation interactions had become a dominant control over shoreline hydrodynamics, and current attenuation was similar to that observed in nearby mature mangrove vegetation. Additionally, turbulence dissipation rates at the stabilized site (2.2∙10⁻⁵ m²/s³) and vegetated reference site (1.1∙10⁻⁵ m²/s³) were an order of magnitude greater during boat wake events compared to the bare shoreline site (1.6∙10⁻⁶ m²/s³,p < 0.001). This first experimental assessment of hydrodynamic effects related to living shoreline stabilization indicates that more than one year may be required before planted vegetation meaningfully influences shoreline hydrodynamics.
Article
As communities face increased flooding from relative sea level rise and attempt to preserve their marshes, they face a number of policy challenges including limited public awareness of the extent of the risk, limited authorities, and limited funds. This paper highlights these legal and policy challenges and discusses some tools to address them.
Preprint
Full-text available
Habitat restoration efforts should integrate past trends, current status, expected climate change and coastal development impacts, remaining realistic opportunities, and resource management community capabilities. Integrating these concepts, a new target setting approach is being implemented in the Tampa Bay region with broad transferability potential. Past changes, as determined through a three-decade habitat change analysis and over forty years of habitat restoration experience in the region, has informed the new approach. It is also primarily focused on what is possible today and the projected needs for the future, rather than focusing on or attempting to replicate past ecological conditions. Likewise, this new paradigm accounts for persistent local and global stressors - especially watershed development, sea level rise, and climate change. As such, newly established numeric targets are "place-based," meaning that they attempt to maximize the remaining restoration and conservation "opportunity areas" within the watershed. Lastly, the approach is comprehensive in that targets for the range of critical habitats, from subtidal to uplands, are now defined. This approach represents a general framework for addressing competing interests in planning for habitat restoration that could be applied in other coastal settings where sustainable urbanization practices are desired to co-exist with natural environments.
Article
Full-text available
Much of the United States’ critical infrastructure is either aging or requires significant repair, leaving U.S. communities and the economy vulnerable. Outdated and dilapidated infrastructure places coastal communities, in particular, at risk from the increasingly frequent and intense coastal storm events and rising sea levels. Therefore, investments in coastal infrastructure are urgently needed to ensure community safety and prosperity; however, these investments should not jeopardize the ecosystems and natural resources that underlie economic wealth and human well-being. Over the past 50 years, efforts have been made to integrate built infrastructure with natural landscape features, often termed “green” infrastructure, in order to sustain and restore valuable ecosystem functions and services. For example, significant advances have been made in implementing green infrastructure approaches for stormwater management, wastewater treatment, and drinking water conservation and delivery. However, the implementation of natural and nature-based infrastructure (NNBI) aimed at flood prevention and coastal erosion protection is lagging. There is an opportunity now, as the U.S. government reacts to the recent, unprecedented flooding and hurricane damage and considers greater infrastructure investments, to incorporate NNBI into coastal infrastructure projects. Doing so will increase resilience and provide critical services to local communities in a cost-effective manner and thereby help to sustain a growing economy.
Article
Full-text available
Human population growth and sea-level rise are increasing the demand for protection of coastal property against shoreline erosion. Living shorelines are designed to provide shoreline protection and are constructed or reinforced using natural elements. While living shorelines are gaining popularity with homeowners, their ability to provide ecological services (e.g., habitat provision and trophic transfer) is not well understood, and information is needed to improve coastal and resource management decision-making. We examined benthic community responses to living shorelines in two case-study subestuaries of Chesapeake Bay using a before-after control-impact study design. At Windy Hill, a bulkhead was removed and replaced by three tombolos, sand fill, and native marsh vegetation. At Lynnhaven, 25 m of eroding marsh shoreline was stabilized with coir logs, sand fill, and native marsh vegetation. Communities of large (> 3 mm) infauna adjacent to living shorelines at both locations tended to increase in biomass by the end of the study period. Community compositions changed significantly following living shoreline construction at Windy Hill, reflecting a trend toward higher density and biomass of large bivalves at living shorelines compared to pre-construction. Increasing trends in density and biomass of clams and simultaneously decreasing density and decreasing trends in biomass of polychaetes suggest a transition toward stable infaunal communities at living shorelines over time, though longer-term studies are warranted.
Article
Full-text available
Tidal marshes and the ecosystem services they provide may be at risk from sea-level rise (SLR). Tidal marsh resilience to SLR can vary due to differences in local rates of SLR, geomorphology, sediment availability and other factors. Understanding differences in resilience is critical to inform coastal management and policy, but comparing resilience across marshes is hindered by a lack of simple, effective analysis tools. Quantitative, multi-metric indices are widely employed to inform management of benthic aquatic ecosystems, but not coastal wetlands. Here, we develop and apply tidal marsh resilience to sea-level rise (MARS) indices incorporating ten metrics that contribute to overall marsh resilience to SLR. We applied MARS indices to tidal marshes at 16 National Estuarine Research Reserves across the conterminous U.S. This assessment revealed moderate resilience overall, although nearly all marshes had some indication of risk. Pacific marshes were generally more resilient to SLR than Atlantic ones, with the least resilient marshes found in southern New England. We provide a calculation tool to facilitate application of the MARS indices to additional marshes. MARS index scores can inform the choice of the most appropriate coastal management strategy for a marsh: moderate scores call for actions to enhance resilience while low scores suggest investment may be better directed to adaptation strategies such as creating opportunities for marsh migration rather than attempting to save existing marshes. The MARS indices thus provide a powerful new approach to evaluate tidal marsh resilience and to inform development of adaptation strategies in the face of SLR.
Article
Full-text available
Protecting coastal communities has become increasingly important as their populations grow, resulting in increased demand for engineered shore protection and hardening of over 50% of many urban shorelines. Shoreline hardening is recognized to reduce ecosystem services that coastal populations rely on, but the amount of hardened coastline continues to grow in many ecologically important coastal regions. Therefore, to inform future management decisions, we conducted a meta-analysis of studies comparing the ecosystem services of biodiversity (richness or diversity) and habitat provisioning (organism abundance) along shorelines with versus without engineered-shore structures. Seawalls supported 23% lower biodiversity and 45% fewer organisms than natural shorelines. In contrast, biodiversity and abundance supported by riprap or breakwater shorelines were not different from natural shorelines; however, effect sizes were highly heterogeneous across organism groups and studies. As coastal development increases, the type and location of shoreline hardening could greatly affect the habitat value and functioning of nearshore ecosystems.
Article
Full-text available
Living shorelines are a type of estuarine shoreline erosion control that incorporates native vegetation and preserves native habitats. Because they provide the ecosystem services associated with natural coastal wetlands while also increasing shoreline resilience, living shorelines are part of the natural and hybrid infrastructure approach to coastal resiliency. Marshes created as living shorelines are typically narrow (< 30 m) fringing marshes with sandy substrates that are well flushed by tides. These characteristics distinguish living shorelines from the larger meadow marshes in which most of the current knowledge about created marshes was developed. The value of living shorelines for providing both erosion control and habitat for estuarine organisms has been documented but their capacity for carbon sequestration has not. We measured carbon sequestration rates in living shorelines and sandy transplanted Spartina alterniflora marshes in the Newport River Estuary, North Carolina. The marshes sampled here range in age from 12 to 38 years and represent a continuum of soil development. Carbon sequestration rates ranged from 58 to 283 g C m-2 yr-1 and decreased with marsh age. The pattern of lower sequestration rates in older marshes is hypothesized to be the result of a relative enrichment of labile organic matter in younger sites and illustrates the importance of choosing mature marshes for determination of long-term carbon sequestration potential. The data presented here are within the range of published carbon sequestration rates for S. alterniflora marshes and suggest that wide-scale use of the living shoreline approach to shoreline management may come with a substantial carbon benefit.
Article
Full-text available
During the past century, human modification of environmental systems has greatly accelerated tidal salt marsh deterioration and shoreline retreat in many coastal regions worldwide. As a result, more than 50% of the original tidal salt marsh habitat in the U.S. has been lost. Numerous human activities have contributed directly or indirectly to wetland loss and alteration at local, regional, and global scales. Human impacts at the local scale include those that directly modify or destroy salt marsh habitat such as dredging, spoil dumping, grid ditching, canal cutting, leveeing, and salt hay farming. Indirect impacts, which can be even more significant, typically are those that interfere with normal tidal flooding of the marsh surface, alter wetlands drainage, and reduce mineral sediment inputs and marsh vertical accretion rates. These impacts usually develop over a greater period of time. At the regional scale, subsidence caused by subsurface withdrawal of groundwater, oil, and gas has submerged and eliminated hundreds of square kilometers of salt marsh habitat in the Chesapeake Bay, San Francisco Bay, and Gulf of Mexico. At the global scale, atmospheric warming due to increased burden of anthropogenic greenhouse gases and tropospheric sulfate aerosols appears to be strongly coupled to glacial melting, thermal expansion of ocean waters, and eustatic sea-level rise. Changes in coastal water levels ascribable to eustatic sea-level rise pose a long-term threat to the stability and viability of these critically important coastal systems.
Article
Full-text available
Coastal ecosystems provide numerous services, such as nutrient cycling, climate change amelioration, and habitat provision for commercially valuable organisms. Ecosystem functions and processes are modified by human activities locally and globally, with degradation of coastal ecosystems by development and climate change occurring at unprecedented rates. The demand for coastal defense strategies against storms and sea-level rise has increased with human population growth and development along coastlines worldwide, even while that population growth has reduced natural buffering of shorelines. Shoreline hardening, a common coastal defense strategy that includes the use of seawalls and bulkheads (vertical walls constructed of concrete, wood, vinyl, or steel), is resulting in a "coastal squeeze" on estuarine habitats. In contrast to hardening, living shorelines, which range from vegetation plantings to a combination of hard structures and plantings, can be deployed to restore or enhance multiple ecosystem services normally delivered by naturally vegetated shores. Although hundreds of living shoreline projects have been implemented in the U.S. alone, few studies have evaluated their effectiveness in sustaining or enhancing ecosystem services relative to naturally vegetated shorelines and hardened shorelines. We quantified the effectiveness of (1) sills with landward marsh (a type of living shoreline that combines marsh plantings with an offshore low-profile breakwater), (2) natural salt marsh shorelines (control marshes), and (3) unvegetated bulkheaded shores in providing habitat for fish and crustaceans (nekton). Sills supported higher abundances and species diversity of fishes than unvegetated habitat adjacent to bulkheads and even control marshes. Sills also supported higher cover of filter-feeding bivalves (a food resource and refuge habitat for nekton) than bulkheads or control marshes. These ecosystem-service enhancements were detected on shores with sills three or more years after construction, but not before. Sills provide added structure and may provide better refuges from predation and greater opportunity to use available food resources for nekton than unvegetated bulkheaded shores or control marshes. Our study shows that unlike shoreline hardening, living shorelines can enhance some ecosystem services provided by marshes, such as provision of nursery habitat. Read More: http://www.esajournals.org/doi/abs/10.1890/14-0716.1
Article
Full-text available
There is substantial evidence that natural infrastructure (i.e., healthy ecosystems) and combinations of natural and built infrastructure (“hybrid” approaches) enhance coastal resilience by providing important storm and coastal flooding protection, while also providing other benefits. There is growing interest in the U.S., as well as around the world, to use natural infrastructure to help coastal communities become more resilient to extreme events and reduce the risk of coastal flooding. Here we highlight strengths and weaknesses of the coastal protection benefits provided by built infrastructure, natural ecosystems, and the innovative opportunities to combine the two into hybrid approaches for coastal protection. We also examine some case studies where hybrid approaches are being implemented to improve coastal resilience as well as some of the policy challenges that can make implementation of these approaches more difficult. The case studies we examine are largely in the U.S. but also include a couple of international examples as well. Based on this analysis, we conclude that coastal communities and other decision makers need better information in order to incorporate ecosystem protection and restoration into coastal resilience planning efforts. As additional projects are developed, it is important to capitalize on every opportunity to learn more about the cost of natural and hybrid infrastructure projects, the value of the storm and erosion protection benefits provided, and the full suite of co-benefits provided by healthy coastal ecosystems. We highlight top priorities for research, investment in, and application of natural and hybrid approaches. These data are critical to facilitate adoption of these approaches in planning and decision-making at all levels to enhance the resilience of our coasts. Full text available open access: http://www.sciencedirect.com/science/article/pii/S1462901115000799
Article
Full-text available
Extreme weather, sea-level rise and degraded coastal ecosystems are placing people and property at greater risk of damage from coastal hazards. The likelihood and magnitude of losses may be reduced by intact reefs and coastal vegetation, especially when those habitats fringe vulnerable communities and infrastructure. Using five sea-level-rise scenarios, we calculate a hazard index for every 1 km2 of the United States coastline. We use this index to identify the most vulnerable people and property as indicated by being in the upper quartile of hazard for the nation's coastline. The number of people, poor families, elderly and total value of residential property that are most exposed to hazards can be reduced by half if existing coastal habitats remain fully intact. Coastal habitats defend the greatest number of people and total property value in Florida, New York and California. Our analyses deliver the first national map of risk reduction owing to natural habitats and indicates where conservation and restoration of reefs and vegetation have the greatest potential to protect coastal communities.
Article
Full-text available
Recent improvements in mapping of global population distribution makes it possible to estimate the number and distribution of people near coasts with greater accuracy than previously possible, and hence consider the potential exposure of these populations to coastal hazards. In this paper, we combine the updated Gridded Population of the World (GPW2) population distribution estimate for 1990 and lighted settlement imagery with a global digital elevation model (DEM) and a high resolution vector coastline. This produces bivariate distributions of population, lighted settlements and land area as functions of elevation and coastal proximity. The near-coastal population within 100 km of a shoreline and 100 m of sea level was estimated as 1.2 × 109 people with average densities nearly 3 times higher than the global average density. Within the near coastal-zone, the average population density diminishes more rapidly with elevation than with distance, while the opposite is true of lighted settlements. Lighted settlements are concentrated within 5 km of coastlines worldwide, whereas average population densities are higher at elevations below 20 m throughout the 100 km width of the near-coastal zone. Presently most of the near-coastal population live in relatively densely-populated rural areas and small to medium cities, rather than in large cities. A range of improvements are required to define a better baseline and scenarios for policy analysis. Improving the resolution of the underlying population data is a priority.
Article
Full-text available
Narrow fringing salt marshes dominated by Spartina alterniflora occur naturally along estuarine shorelines and provide many of the same ecological functions as more extensive marshes. These fringing salt marshes are sometimes incorporated into shoreline stabilization efforts. We obtained data on elevation, salinity, sediment characteristics, vegetation and fish utilization at three study sites containing both natural fringing marshes and nearby restored marshes located landward of a stone sill constructed for shoreline stabilization. During the study, sediment accretion rates in the restored marshes were approximately 1.5- to 2-fold greater than those recorded in the natural marshes. Natural fringing marsh sediments were predominantly sandy with a mean organic matter content ranging between 1.5 and 6.0%. Average S. alterniflora stem density in natural marshes ranged between 130 and 222 stems m−2, while mean maximum stem height exceeded 64 cm. After 3 years, one of the three restored marshes (NCMM) achieved S. alterniflora stem densities equivalent to that of the natural fringing marshes, while percentage cover and maximum stem heights were significantly greater in the natural than in the restored marshes at all sites. There was no significant difference in the mean number of fish, crabs or shrimp captured with fyke nets between the natural and restored marshes, and only the abundance of Palaemonetes vulgaris (grass shrimp) was significantly greater in the natural marshes than in the restored ones. Mean numbers of fish caught per 5 m of marsh front were similar to those reported in the literature from marshes adjacent to tidal creeks and channels, and ranged between 509 and 634 fish net−1. Most of the field data and some of the sample analyses were obtained by volunteers as they contributed 223 h of the total 300 h spent collecting data from three sites in one season. The use of fyke nets required twice as many man-hours as any other single task. Vegetation and sediment parameters were sensitive indicators of marsh restoration success, and volunteers were capable of contributing a significant portion of the labor needed to collect these parameters.
Article
Full-text available
Background: Salt marshes lie between many human communities and the coast and have been presumed to protect these communities from coastal hazards by providing important ecosystem services. However, previous characterizations of these ecosystem services have typically been based on a small number of historical studies, and the consistency and extent to which marshes provide these services has not been investigated. Here, we review the current evidence for the specific processes of wave attenuation, shoreline stabilization and floodwater attenuation to determine if and under what conditions salt marshes offer these coastal protection services. Methodology/principal findings: We conducted a thorough search and synthesis of the literature with reference to these processes. Seventy-five publications met our selection criteria, and we conducted meta-analyses for publications with sufficient data available for quantitative analysis. We found that combined across all studies (n = 7), salt marsh vegetation had a significant positive effect on wave attenuation as measured by reductions in wave height per unit distance across marsh vegetation. Salt marsh vegetation also had a significant positive effect on shoreline stabilization as measured by accretion, lateral erosion reduction, and marsh surface elevation change (n = 30). Salt marsh characteristics that were positively correlated to both wave attenuation and shoreline stabilization were vegetation density, biomass production, and marsh size. Although we could not find studies quantitatively evaluating floodwater attenuation within salt marshes, there are several studies noting the negative effects of wetland alteration on water quantity regulation within coastal areas. Conclusions/significance: Our results show that salt marshes have value for coastal hazard mitigation and climate change adaptation. Because we do not yet fully understand the magnitude of this value, we propose that decision makers employ natural systems to maximize the benefits and ecosystem services provided by salt marshes and exercise caution when making decisions that erode these services.
Article
Full-text available
Shorelines at the interface of marine, estuarine and terrestrial biomes are among the most degraded and threatened habitats in the coastal zone because of their sensitivity to sea level rise, storms and increased human utilization. Previous efforts to protect shorelines have largely involved constructing bulkheads and seawalls which can detrimentally affect nearshore habitats. Recently, efforts have shifted towards "living shoreline" approaches that include biogenic breakwater reefs. Our study experimentally tested the efficacy of breakwater reefs constructed of oyster shell for protecting eroding coastal shorelines and their effect on nearshore fish and shellfish communities. Along two different stretches of eroding shoreline, we created replicated pairs of subtidal breakwater reefs and established unaltered reference areas as controls. At both sites we measured shoreline and bathymetric change and quantified oyster recruitment, fish and mobile macro-invertebrate abundances. Breakwater reef treatments mitigated shoreline retreat by more than 40% at one site, but overall vegetation retreat and erosion rates were high across all treatments and at both sites. Oyster settlement and subsequent survival were observed at both sites, with mean adult densities reaching more than eighty oysters m(-2) at one site. We found the corridor between intertidal marsh and oyster reef breakwaters supported higher abundances and different communities of fishes than control plots without oyster reef habitat. Among the fishes and mobile invertebrates that appeared to be strongly enhanced were several economically-important species. Blue crabs (Callinectes sapidus) were the most clearly enhanced (+297%) by the presence of breakwater reefs, while red drum (Sciaenops ocellatus) (+108%), spotted seatrout (Cynoscion nebulosus) (+88%) and flounder (Paralichthys sp.) (+79%) also benefited. Although the vertical relief of the breakwater reefs was reduced over the course of our study and this compromised the shoreline protection capacity, the observed habitat value demonstrates ecological justification for future, more robust shoreline protection projects.
Article
Full-text available
Complexity theory predicts that local feedback processes may strongly affect the organization of ecosystems on larger spatial scales. Whether complexity leads to increased resilience and stability or to increased vulnerability and criticality remains one of the dominant questions in ecology. We present a combined theoretical and empirical study of complex dynamics in mineralogenic salt marsh ecosystems that emerge from a positive feedback between clay accumulation and plant growth. Positive feedback induces self-organizing within the ecosystem, which buffers for the strong physical gradient that characterizes the marine-terrestrial boundary, and improves plant growth along the gradient. However, as a consequence of these self-organizing properties, salt marshes approach a critical state as the edge of the salt marsh and the adjacent intertidal flat becomes increasingly steep and vulnerable to wave attack. Disturbance caused, for instance, by a storm may induce a cascade of vegetation collapse and severe erosion on the cliff edge, leading to salt marsh destruction. Our study shows that on short timescales, self-organization improves the functioning of salt marsh ecosystems. On long timescales, however, self-organization may lead to destruction of salt marsh vegetation.
Article
Full-text available
Estuarine and coastal transformation is as old as civilization yet has dramatically accelerated over the past 150 to 300 years. Reconstructed time lines, causes, and consequences of change in 12 once diverse and productive estuaries and coastal seas worldwide show similar patterns: Human impacts have depleted >90% of formerly important species, destroyed >65% of seagrass and wetland habitat, degraded water quality, and accelerated species invasions. Twentieth-century conservation efforts achieved partial recovery of upper trophic levels but have so far failed to restore former ecosystem structure and function. Our results provide detailed historical baselines and quantitative targets for ecosystem-based management and marine conservation.
Article
Full-text available
Human-dominated marine ecosystems are experiencing accelerating loss of populations and species, with largely unknown consequences. We analyzed local experiments, long-term regional time series, and global fisheries data to test how biodiversity loss affects marine ecosystem services across temporal and spatial scales. Overall, rates of resource collapse increased and recovery potential, stability, and water quality decreased exponentially with declining diversity. Restoration of biodiversity, in contrast, increased productivity fourfold and decreased variability by 21%, on average. We conclude that marine biodiversity loss is increasingly impairing the ocean's capacity to provide food, maintain water quality, and recover from perturbations. Yet available data suggest that at this point, these trends are still reversible.
Article
Growing coastal populations, rising sea levels, and likely increases in the frequency of major storm events will intensify coastal vulnerability in coming decades. Decisions regarding how and when to fortify estuarine shorelines against coastal hazards, such as erosion, flooding, and attendant property damages, rest largely in the hands of waterfront-property owners. Traditionally, hard engineered structures (e.g. bulkheads, revetments, seawalls) have been used to protect coastal properties, based on the assumption that these structures are durable and effective at preventing erosion. This study evaluates the validity of these assumptions by merging results from 689 surveys of waterfront-property owners in NC with empirical shoreline damage data collected along estuarine shorelines after Hurricanes Irene (2011) and Arthur (2014). The data show: 1) homeowners perceive bulkheads to be the most durable and effective at preventing erosion, but also the most costly; 2) compared to residents with revetments and natural shorelines, property owners with bulkheads reported double the price to repair hurricane damage to their property and four times the cost for annual shoreline maintenance; 3) 93% of evident post-hurricane shoreline damage was attributable to bulkheads or bulkhead hybrids and a higher proportion of surveyed homeowners with bulkheads reported having property damage from hurricanes; and, 4) shoreline hardening increased by 3.5% from 2011 to 2016 along 39 km of the Outer Banks. These results suggest that bulkheads are not meeting waterfront property-owner expectations despite continued use, and that nature-based coastal protection schemes may be able to more effectively align with homeowner needs.
Article
Coastal ecosystems provide numerous services, such as nutrient cycling, climate change amelioration, and habitat provision for commercially valuable organisms. Ecosystem functions and processes are modified by human activities locally and globally, with degradation of coastal ecosystems by development and climate change occurring at unprecedented rates. The demand for coastal defense strategies against storms and sea-level rise has increased with human population growth and development along coastlines worldwide, even while that population growth has reduced natural buffering of shorelines. Shoreline hardening, a common coastal defense strategy that includes the use of seawalls and bulkheads (vertical walls constructed of concrete, wood, vinyl, or steel), is resulting in a “coastal squeeze” on estuarine habitats. In contrast to hardening, living shorelines, which range from vegetation plantings to a combination of hard structures and plantings, can be deployed to restore or enhance multiple ecosystem services normally delivered by naturally vegetated shores. Although hundreds of living shoreline projects have been implemented in the United States alone, few studies have evaluated their effectiveness in sustaining or enhancing ecosystem services relative to naturally vegetated shorelines and hardened shorelines. We quantified the effectiveness of (1) sills with landward marsh (a type of living shoreline that combines marsh plantings with an offshore low-profile breakwater), (2) natural salt marsh shorelines (control marshes), and (3) unvegetated bulkheaded shores in providing habitat for fish and crustaceans (nekton). Sills supported higher abundances and species diversity of fishes than unvegetated habitat adjacent to bulkheads, and even control marshes. Sills also supported higher cover of filter-feeding bivalves (a food resource and refuge habitat for nekton) than bulkheads or control marshes. These ecosystem-service enhancements were detected on shores with sills three or more years after construction, but not before. Sills provide added structure and may provide better refuges from predation and greater opportunity to use available food resources for nekton than unvegetated bulkheaded shores or control marshes. Our study shows that unlike shoreline hardening, living shorelines can enhance some ecosystem services provided by marshes, such as provision of nursery habitat.
Article
Significance In recent years, there has been a flurry of restoration projects aimed at mitigating the impact of coastal storms using salt marshes and vegetated surfaces (called “living shorelines”). Based on a large dataset of salt marsh erosion and wave measurements collected all around the world, we find that erosion rates of marsh boundaries and incident wave energy collapse into a unique linear relationship. Our result clearly shows that long-term salt marsh deterioration is dictated by average wave conditions, and it is, therefore, predictable. Violent storms and hurricanes contribute less than 1% to long-term salt marsh erosion rates. This result is of high value for coastal restoration projects and the use of living shorelines to mitigate storms effect.
Article
Pre- and post-storm aerial videotape surveys were made along 51 km of the barrier island coast of South Carolina from Garden City to Folly Beach. Before Hugo the shoreline from the beach landward to, and including the first row of development, was classified as dune field (45%), bulldozed dune ridge (25%), revetment (14%), bulkhead (12%), vegetated washover terrace (3%), and beach only (1%). After the storm, 80% of the shoreline was classified as washover sheet, and 5% as washover fan. The only areas that were not overwashed were sections of very high dune field (13%) and large bulldozed dune ridge (2%). Our most important observations can be summarized as follows. 1) Provided the dune field was not submerged, the minimum width of dune field required to survive Hurricane Hugo, was 30 m. 2) Two types of dunes survived the storm: those high enough to prevent being overwashed and wide enough to prevent being completely eroded. 3) All bulkheads and revetments were overtopped, and wave activity was carried inland to the first and succeeding rows of development. 4) Fifty percent of all buildings completely destroyed or removed from their foundations were fronted by a combination of dry beaches less than 3 m wide and dune fields less than 15 m wide. -from Authors
Chapter
Rapidly growing populations and expanding development are intensifying pressures on coastal ecosystems. Sea-level rise and other predicted effects of climate change are expected to exert even greater pressures on coastal ecosystems, exacerbating erosion, degrading habitat, and accelerating shoreline retreat. Historically, society’s responses to threats from erosion and shoreline retreat have relied on armoring and other engineered coastal defenses. Despite widespread use on all types of shorelines, information about the ecological impacts of shoreline armoring is quite limited. Here we summarize existing knowledge on the effects of armoring structures on the biodiversity, productivity, structure, and function of coastal ecosystems.
Article
Acting on the perception that they perform better for longer, most property owners in the United States choose hard engineered structures, such as bulkheads or riprap revetments, to protect estuarine shorelines from erosion. Less intrusive alternatives, specifically marsh plantings with and without sills, have the potential to better sustain marsh habitat and support its ecosystem services, yet their shoreline protection capabilities during storms have not been evaluated. In this study, the performances of alternative shoreline protection approaches during Hurricane Irene (Category 1 storm) were compared by 1) classifying resultant damage to shorelines with different types of shoreline protection in three NC coastal regions after Irene; and 2) quantifying shoreline erosion at marshes with and without sills in one NC region by using repeated measurements of marsh surface elevation and marsh vegetation stem density before and after Irene. In the central Outer Banks, NC, where the strongest sustained winds blew across the longest fetch; Irene damaged 76% of bulkheads surveyed, while no damage to other shoreline protection options was detected. Across marsh sites within 25 km of its landfall, Hurricane Irene had no effect on marsh surface elevations behind sills or along marsh shorelines without sills. Although Irene temporarily reduced marsh vegetation density at sites with and without sills, vegetation recovered to pre-hurricane levels within a year. Storm responses suggest that marshes with and without sills are more durable and may protect shorelines from erosion better than the bulkheads in a Category 1 storm. This study is the first to provide data on the shoreline protection capabilities of marshes with and without sills relative to bulkheads during a substantial storm event, and to articulate a research framework to assist in the development of comprehensive policies for climate change adaptation and sustainable management of estuarine shorelines and resources in U.S. and globally.
Article
The 2014 Working Group II report of the Intergovernmental Panel on Climate Change (IPCC) warns that lowlying coastal areas are increasingly exposed to risks from sea-level rise, flooding, and extreme storm events ( 1 ). Low-lying coasts of developing countries in particular face two types of vulnerability: (i) a lack of capacity to respond quickly and effectively to natural disasters and (ii) declining protection for people and property as coastal habitats disappear. A science-based global strategy for protecting coastal populations should address both sources of vulnerability, through investments in short-run emergency response and long-term coastal adaptation.