Caribbean Small Island Developing States (SIDS) are vulnerable to climate change impacts including sea level rise, invasive species, ocean acidification, changes in rainfall patterns, increased temperatures, and changing hazard regimes including hurricanes, floods and drought. Given high dependencies in Caribbean SIDS on natural resources for livelihoods, a focus on ecosystems and their interaction with people is essential for climate change adaptation. Increasingly, ecosystem-based adaptation (ecosystem-based adaptation) approaches are being highlighted as an approach to address climate change impacts. Specifically, ecosystem-based adaptation encourages the use of local and external knowledge about ecosystems to identify climate change adaptation approaches. This paper critically reviews ecosystem-based adaptation in Caribbean SIDS, focusing on the need to integrate local and external knowledge. An analysis of current ecosystem-based adaptation in the Caribbean is undertaken alongside a review of methodologies used to integrate local and external expertise for ecosystem-based adaptation. Finally key gaps, lessons learnt and suggested ways forward for ecosystem-based adaptation in Caribbean SIDS and potentially further afield are identified.
NbS Target: Food & Water Security
Food and water security
Declining forest health, climate change, and development threaten the sustainability of water supplies in the western United States. While forest restoration may buffer threats to watershed services, funding shortfalls for landscape-scale restoration efforts limit management action. The hydrologic response and reduction in risk to watersheds following forest restoration treatments could create significant nonmarket benefits for downstream water users. Historic experimental watershed studies indicate a significant and positive response from forest thinning by a reallocation of water from evapotranspiration to surface-water yield. In this study, we estimate the willingness to pay (WTP) for improved watershed services for one group of downstream users, irrigators, following forest restoration activities. We find a positive and statistically significant WTP within our sample of $183.50 per household, at an aggregated benefit of more than $400,000 annually for 2181 irrigators. Our benefit estimate provides evidence that downstream irrigators may be willing to invest in landscape-scale forest restoration to maintain watershed services.
Given the unfortunate, frequent occurrence of droughts, practical actions are ever more critical to ensure achieving food security in this region [Africa]. Understanding what has previously worked can provide a guiding vision as we proactively address the current crisis. Food security and human security are inextricably linked, and innovative initiatives are needed to create opportunities to face continental challenges regarding future food security requirements. Sustainable food security strategies must thus, among others, develop new opportunities, increase productivity in agriculture, and assist in the development of domestic markets that can withstand international economic volatility. Investment in EbA is one of the most important keys to job creation opportunities that simultaneously contribute to poverty eradication and to sustainable long-term food security. Such investments will improve the competitiveness of domestic production, increase farmers’ profits, and make food more affordable for the poor. Creative strategies supported by dynamic leadership and management are the only way that Africa will be able to achieve the envisaged food-secure society in which its population does not experience fear of want. With proper planning, transparent resource management, innovative food security policies, and integrative agriculture inputs and outputs, it is not too late to turn the Africa’s food crisis to the benefit of local communities.
Increasing frequency, intensity and duration of severe weather events are posing major challenges to global food security and livelihoods of rural people. Agriculture has evolved through adaptation to local circumstances for thousands of years. Local experience in responding to severe weather conditions, accumulated over generations and centuries, is valuable for developing adaptation options to current climate change. This study aimed to: (i) identify tree species that reduce vulnerability of cropping systems under climate variability; and (ii) develop a method for rapidly assessing vulnerability and exploring strategies of smallholder farmers in rural areas exposed to climate variability. Participatory Rural Appraisal methods in combination with Geographical Information Systems tools and statistical analysis of meteorological data were used to evaluate local vulnerability to climate change and to investigate local adaptation measures in two selected villages in Vietnam, one of the countries most vulnerable to climate change. The low predictability of severe weather events makes food crops, especially grain production, insecure. This study shows that while rice and rain-fed crops suffered over 40 % yield losses in years of extreme drought or flood, tree-based systems and cattle were less affected. 13 tree species performed well under the harsh local climate conditions in home and forest gardens to provide income, food, feed and other environmental benefits. Thus, this research suggests that maintenance and enhancement of locally evolved agroforestry systems, with high resilience and multiple benefits, can contribute to climate change adaptation.
Potential interactions between food production and climate mitigation are explored for two situations in sub-Saharan Africa, where deforestation and land degradation overlap with hunger and poverty. Three agriculture intensification scenarios for supplying nitrogen to increase crop production (mineral fertilizer, herbaceous legume cover crops—green manures—and agroforestry—legume improved tree fallows) are compared to baseline food production, land requirements to meet basic caloric requirements, and greenhouse gas emissions. At low population densities and high land availability, food security and climate mitigation goals are met with all intensification scenarios, resulting in surplus crop area for reforestation. In contrast, for high population density and small farm sizes, attaining food security and reducing greenhouse gas emissions require mineral fertilizers to make land available for reforestation; green manure or improved tree fallows do not provide sufficient increases in yields to permit reforestation. Tree fallows sequester significant carbon on cropland, but green manures result in net carbon dioxide equivalent emissions because of nitrogen additions. Although these results are encouraging, agricultural intensification in sub-Saharan Africa with mineral fertilizers, green manures, or improved tree fallows will remain low without policies that address access, costs, and lack of incentives. Carbon financing for small-holder agriculture could increase the likelihood of success of Reducing Emissions from Deforestation and Forest Degradation in Developing Countries programs and climate change mitigation but also promote food security in the region.
Rajasthan presents evidence for the existence of one of the most advanced examples of ancient mining and accompanied deforestation to be found anywhere in the world. Mining continues to be an important economic activity contributing to 2% of the State Domestic Product and providing at least a 1.76 % share to the regular employment pool in Rajasthan. However, economic benefits of mineral extraction also accompany environmental, economic and social costs. Mine waste dumps and mined out areas viewed simply as the legacies of past may appear overwhelming environmental hazards presenting ugly picture of cultural landscape. However, mine wastes can be transformed into an opportunity for learning, adaptation and productivity enhancement for sustainable livelihoods through ecological restoration. Here we propose a strategy for mine spoil restoration aimed at creating a multifunctional ecosystem in mine waste dumps. We suggest that dredging and sediment removal from traditional tanks and ponds can potentially be used to prepare the substratum over the mine wastes for direct seeding. It will also create enhanced decentralized water storage capacity for wildlife and people. Our strategy combines the concomitant revival of traditional water harvesting systems, ground water recharge, enhanced biomass production and an adaptation to random recurrence of droughts in Rajasthan.
MPAs enhance some of the Ecosystem Services (ES) provided by coral reefs and clear, robust valuations of these impacts may help to improve stakeholder support and better inform decision-makers. Pursuant to this goal, Cost-Benefit Analyses (CBA) of MPAs in 2 different contexts were analysed: a community based MPA with low tourism pressure in Vanuatu, and a government managed MPA with relatively high tourism pressure, in Saint Martin. Assessments were made on six ES: fish biomass, scenic beauty, protection against coastal erosion, bequest and existence values, social capital and CO2 sequestration, which were quantified via different approaches that included experimental fishery, surveys and benefit transfer. Total operating costs for each MPA were collected and the benefit-cost ratio and return on investment based on 25-year discounted projections computed. Sensitivity analyses were conducted on MPA impacts, and discount rates (5%, 7% and 10%). The investment indicators all showed positive results with the impact on the tourism ES being the largest estimated for all MPAs, highlighting the importance of this relationship. The study also demonstrated a relatively high sensitivity of the results to different levels of impacts on ES, which highlights the need for reducing scientific knowledge gaps.
Climate change and associated changes in streamflow may alter riparian habitats substantially in coming decades. Riparian restoration provides opportunities to respond proactively to projected climate change effects, increase riparian ecosystem resilience to climate change, and simultaneously address effects of both climate change and other human disturbances. However, climate change may alter which restoration methods are most effective and which restoration goals can be achieved. Incorporating climate change into riparian restoration planning and design is critical to long-term restoration of desired community composition and ecosystem services. In this review, we discuss and provide examples of how climate change might be incorporated into restoration planning at the key stages of assessing the project context, establishing restoration goals and design criteria, evaluating design alternatives, and monitoring restoration outcomes. Restoration planners have access to numerous tools to predict future climate, streamflow, and riparian ecology at restoration sites. Planners can use those predictions to assess which species or ecosystem services will be most vulnerable under future conditions, and which sites will be most suitable for restoration. To accommodate future climate and streamflow change, planners may need to adjust methods for planting, invasive species control, channel and floodplain reconstruction, and water management. Given the considerable uncertainty in future climate and streamflow projections, riparian ecological responses, and effects on restoration outcomes, planners will need to consider multiple potential future scenarios, implement a variety of restoration methods, design projects with flexibility to adjust to future conditions, and plan to respond adaptively to unexpected change.
Modern plant breeding tends to focus on maximizing yield, with one of the most ubiquitous implementations being shorter-duration crop varieties. It is indisputable that these breeding efforts have resulted in greater yields in ideal circumstances; however, many farmed locations across Africa suffer from one or more conditions that limit the efficacy of modern short-duration hybrids. In view of global change and increased necessity for intensification, perennial grains and long-duration varieties offer a nature-based solution for improving farm productivity and smallholder livelihoods in suboptimal agricultural areas. Specific conditions where perennial grains should be considered include locations where biophysical and social constraints reduce agricultural system efficiency, and where conditions are optimal for crop growth. Using a time-series of remotely-sensed data, we locate the marginal agricultural lands of Africa, identifying suboptimal temperature and precipitation conditions for the dominant crop, i.e., maize, as well as optimal climate conditions for two perennial grains, pigeonpea and sorghum. We propose that perennial grains offer a lower impact, sustainable nature-based solution to this subset of climatic drivers of marginality. Using spatial analytic methods and satellite-derived climate information, we demonstrate the scalability of perennial pigeonpea and sorghum across Africa. As a nature-based solution, we argue that perennial grains offer smallholder farmers of marginal lands a sustainable solution for enhancing resilience and minimizing risk in confronting global change, while mitigating social and edaphic drivers of low and variable production.
Conflict over water allocations and the need to adapt to climate change in Australia’s Murray-Darling Basin has resulted in decision makers choosing engineering interventions to use water more efficiently for wetlands conservation. We review a range of policy and infrastructure adaptation measures implemented in the Basin by governments. The water supply and demand “environmental works and measures” adopted in the Coorong and Lower Lakes region, as well as along the River Murray, are assessed and compared with the opportunity costs for ecosystem-based adaptation. The results suggest that risks of disruption to ecological processes, desiccation of wetland areas and institutional failure with infrastructure-led adaptation measures are little appreciated. Further, ecosystem-based measures to maintain a more diverse range of ecological processes that would spread risk and conserve a more diverse range of biota have not been identified or adopted by governments. We conclude that as a primary adaptation to climate change environmental works and measures may represent overly-narrow or mal-adaptation that can reduce the resilience of wetland ecosystems.
Autonomous adaptation in the water sector is assessed to derive lessons for more successful climate change adaptation from six empirical, consistently designed river management case studies based on projects of WWF. They show that when adaptation measures are considered in the context of common problems in water management, many practical ways of building resilience to climate change through mainstream programs are evident. The cases are mainly from developing countries—India, China, Mexico, Brazil, the lower Danube basin and Tanzania—where efforts to reduce environmental degradation and enhance livelihoods have directly helped to reduce vulnerability to natural hazards and climate change. The key lessons include: the benefits of concurrent measures for improving livelihoods and reducing physical vulnerability; the need to enhance and fund local institutions to mainstream adaptation programmes; and the value in implementing ‘no and low regrets’ measures despite uncertainties.
The idea of ‘nature-based solutions’ (NBS) is now being used to reframe policy debates on biodiversity conservation, climate change adaptation and mitigation strategies, and the sustainable use of natural resources, among other issues. While interesting and potentially useful for those debates, it is a concept that still needs to be clearly defined; its use is not confined to discussions about ecosystem services and natural capital. For example, it is also used to describe such things as soft engineering approaches designed to enhance resilience and reduce risk to people in large settlements (e.g. Marton-Lefevre, 2012; van Wessenbeeck, 2014), and to work in the field of biomimicry and industrial design2 (e.g. Neves and Francke, 2012) – learning from nature, rather than finding strategies based on nature that would contribute to its conservation. However, by emphasising the utilitarian aspect of natural capital and ecosystem services, the idea of ‘nature-based solutions’ is clearly eye-catching and relevant to current debates about the links between people and nature. It is therefore wise to ask what new insights it brings. Is it intended to re-package the demand for sustainable development and nature conservation in a way that concepts of biodiversity and ecosystem services do not? Does it represent an approach to policy and management distinctly different from those already being applied? It is not altogether clear that it does. For example, the idea of NBS can be seen to encompass existing concepts such as ‘nature-based interventions’, ‘ecosystem-based solutions’, and particularly ‘ecosystem-based adaptation’ (see for example Rizvi et al, 2015; Andrade et al., 2011). A report from the Horizon 2020 Expert Group on NBS suggests that the concept “builds on and supports other closely related concepts, such as the ecosystem approach, ecosystem services, ecosystem-based adaptation/mitigation, and green and blue infrastructure” (EC, 2015). From another perspective, however, the use of the term ‘NBS’ might prompt positive changes in how some of these existing concepts are framed. It could refocus attention on sustainable development and encouraging consideration of biodiversity and ecosystems within solutions to wider societal challenges including climate change adaptation, food security, water crises etc.
Ecosystems provide important services that can help people adapt to climate variability and change. Recognizing this role of ecosystems, several international and nongovernmental organizations have promoted an ecosystem-based approach to adaptation. We review the scientific literature related to EbA (ecosystem-based adaptation) with forests and trees, and highlight five cases in which forests and trees can support adaptation: (1) forests and trees providing goods to local communities facing climatic threats; (2) trees in agricultural fields regulating water, soil, and microclimate for more resilient production; (3) forested watersheds regulating water and protecting soils for reduced climate impacts; (4) forests protecting coastal areas from climate-related threats; and (5) urban forests and trees regulating temperature and water for resilient cities. The literature provides evidence that ecosystem-based adaptation with forests and trees can reduce social vulnerability to climate hazards; however, uncertainties and knowledge gaps remain, particularly for regulating services in watersheds and coastal areas. Few studies have been undertake non ecosystem-based adaptation specifically, but the abundant literature on ecosystem services can be used to fill knowledge gaps. Many studies assess the multiple benefits of ecosystems for human adaptation or well-being, but also recognize trade-offs between ecosystem services. Better understanding is needed of the efficiency, costs, and benefits, and trade-offs of ecosystem-based adaptation with forests and trees. Pilot projects under implementation could serve as learning sites and existing information could be systematized and revisited with a climate change adaptation lens.
Considering extreme events of climate change and declining availability of appropriate quality water and/or highly productive soil resources for agriculture in dryland regions, the need to produce more food, forage and fibre will necessitate the effective utilization of marginal-quality water and soil resources. Recent research and practices have demonstrated that effective utilization of these natural resources in dry areas can improve agricultural productivity per unit area and per unit water applied. This paper focuses on the following three case studies as examples: (1) low productivity soils affected by high levels of magnesium in soil solution and on the cation exchange complex; (2) degraded sandy soils under rainfed conditions characterized by low water-holding capacity, organic matter and clay content and (3) abandoned irrigated soils with elevated levels of salts inhibiting growth of income generating crops. The results of these studies demonstrate that application of calcium supplying phosphogypsum to high-magnesium soils, addition of clays to light textured degraded soils and phytoremediation of abandoned salt-affected soils significantly improved productivity of these soils. Furthermore, under most circumstances, these interventions were economically viable, revealing that the efficient use of marginal-quality water and soil resources has the potential to improve livelihoods amid growing populations in dry areas while reversing the natural resource degradation trend. However, considerably more investment and policy level interventions are needed to tackle soil degradation/remediation issues across both irrigated and dryland agricultural environments if the major challenge of producing enough food, forage and fibre is to be met.
Forest-dependent indigenous communities rely on natural resources for their livelihoods, but those are currently under threat due to many factors, including the adverse impact of climate change. The present study looks into climate change-related perception and adaptation strategies of three forest-dependent indigenous communities, namely, Khasia, Tripura and Garo in the Lawachara National Park of Northeastern Bangladesh. Household surveys, focus group discussions, key informant interviews, and observation methods were used to unveil the climatic events, impacts and related adaptations. The events include the change in temperature and rainfall patterns, landslide, soil erosion and flash flood, heavy cold and fog, and natural calamities. Moreover, livelihood problems emanating from these events are the drying up of streams and wells, irregular rainfall, increased dieback and mortality of seedlings, pests, diseases, and the attack of crops by wild animals. Likewise, the reduction of soil moisture content, growing season and crop productivity, landslides, damage of roads and culverts, and increased human diseases are common. This study recognized 29 adaptation strategies and divided them into six management categories, drawing on their local knowledge of the natural resources and other technologies. The study reveals that, although adaptation strategies through land use and land cover changes are not enough to sustain their livelihoods, the tactics help them to reduce the risk of, and increase food security and community resilience against, climate change.
Ecosystem-based approaches to adaptation (EbA) involve the use of biodiversity and ecosystem services to help people adapt to the adverse effects of climate change. This research looks at two components of effective EbA: ecosystem resilience and the maintenance of ecosystem services. It assesses EbA effectiveness in terms of how such approaches support community adaptive capacity and resilience at two sites in Bangladesh: Chanda Beel wetland and Balukhali Village in the Chittagong Hill Tracts. Research findings suggest that more attention should be paid to EbA as an important climate-change response. Results show that the many diverse natural resources available and utilized at each site have increased the number of different subsistence and livelihood options available in the community and hence local adaptive capacity, especially for poorer households. Major structural shifts in ecosystem functioning observed at each site to date can be attributed primarily to non-climate-change-related factors, although climate-change-related factors increasingly threaten to dramatically alter ecosystems, especially in Chanda Beel. Such shifts have important consequences for adaptive capacity and have led to a number of trade-offs. The lack of effective institutions, good governance and enabling policy at both sites has limited potential resilience gains from sound ecosystem management.
Small island developing states (SIDS) are among the countries in the world that are most vulnerable to climate change and required to adapt to its impacts. Yet, there is little information in the academic literature about how SIDS are adapting to climate change, across multiple countries and geographic regions. This paper helps to fill this gap. Using a sample of 16 countries across the Atlantic, Indian Ocean and South China Sea, Caribbean and Pacific regions, this study has two main aims, to identify (1) national-level adaptation trends across climate, climate-induced and non-climate-induced vulnerabilities, sectors and actors, as reported in National Communications (NCs) to the United Nations Framework Convention on Climate Change (UNFCCC), and (2) typologies of national-level adaptation actions in SIDS. It identifies, codes and assesses 977 adaptation actions. These actions were reported as addressing 47 climate and climate-induced vulnerabilities and 50 non-climate-induced vulnerabilities and were undertaken in 37 sectors by 34 actors. The paper proposes five typologies of adaptation actions for SIDS, based on actions reported by SIDS. It specifically explores the implications of its findings for global adaptation strategies. As this work establishes a baseline of adaptation action in SIDS, it can assist national governments to gauge their adaptation progress, identify gaps in their adaptation effort and, thereafter, develop appropriate strategies for filling the gaps. It can also assist donors, whether bilateral or multilateral, to make more ‘climate-smart’ investment decisions by being able to identify the adaptation needs that are not being met in SIDS.
We investigated the coping strategies of rural communities in three countries in Africa to climate hazards. Forest ecosystems deliver food and shelter during extreme events (droughts and floods) and are thus key assets for increasing the resilience of poor communities. In some villages, forests and their NTFP serve as supplementary income during periods of climate stress at the community-level. These coping strategies can form a basis for dealing with future climate changes and can contribute to the development of planned adaptation strategies for anticipated changes. We identified factors that promote or prevent the use of sustainable coping strategies related to forest ecosystems.
Legume tree-based farming systems sit at a crucial nexus of agroecological sustainability. Their capacity to support microbial N2 fixation can increase soil nitrogen (N) availability and therefore improve soil fertility, crop yields, and support long-term stewardship of natural resources. However, increasing N availability oftentimes catalyzes the release of N into the surrounding environment, in particular nitrous oxide (N2O) — a potent greenhouse gas. We summarize current knowledge on the agroecological footprint of legume-based agroforestry and provide a first appraisal of whether the technology represents a pathway toward sustainable development or an environmental hazard.
Benefits humans rely on from the ocean – marine ecosystem services – are increasingly vulnerable under future climate. This paper reviews how three valued services have, and will continue to, shift under climate change: (1) capture fisheries, (2) food from aquaculture, and (3) protection from coastal hazards such as storms and sea-level rise. Climate adaptation planning is just beginning for fisheries, aquaculture production, and risk mitigation for coastal erosion and inundation. A few examples are highlighted, showing the promise of considering multiple ecosystem services in developing approaches to adapt to sea-level rise, ocean acidification, and rising sea temperatures. Ecosystem-based adaptation in fisheries and along coastlines and changes in aquaculture practices can improve resilience of species and habitats to future environmental challenges. Opportunities to use market incentives – such as compensation for services or nutrient trading schemes – are relatively untested in marine systems. Relocation of communities in response to rising sea levels illustrates the urgent need to manage human activities and investments in ecosystems to provide a sustainable flow of benefits in the face of future climate change.
Massive deforestation induced by unplanned urbanization in the hilly watersheds of Brahmaputra basin, India, has led to ecological imbalance and is gradually transforming this basin into a multi-hazard zone. Removal of green cover is also becoming a matter of global concern, as it can accelerate the adverse impacts of climate change. People coming in search of work generally reside in the hills, as they cannot afford the high cost of land in plains. This has led to deforestation of the hilly area and has resulted in increased surface erosion from the upper catchments. Though sediment and water yield from these degraded watersheds could have been minimized by implementing ecologically sustainable management practices (EMPs), such as grass land, forest land and detention pond, poor economic conditions of the people stands in the way of field implementation. On the other hand, major industries, which can be held responsible for emission of greenhouse gases, can be asked to finance greenery development in these hilly watersheds through implementation of selected EMPs to earn carbon credit for them. To convert this concept into reality, the EMP combination must be selected in such a way that it restricts sediment and water yield from the watershed within the permissible limit and maximizes its carbon sequestration capacity at minimum possible cost. Such optimal planning is a prerequisite for preparing an acceptable logical agreement between Government and private companies. Keeping this in mind, an optimization model was developed and applied to a micro watershed of Guwahati to explore its applicability in actual field. The model developed in this study provides most logical carbon credit negotiation, subject to the availability of reliable value of CO2 sequestration for different EMPs.
The welfare of people in the tropics and sub-tropics strongly depends on goods and services that savanna ecosystems supply, such as food and livestock production, fuel wood, and climate regulation. Flows of these services are strongly influenced by climate, land use and their interactions. Savannas cover c. 20% of the Earth’s land surface and changes in the structure and dynamics of savanna vegetation may strongly influence local people’s living conditions, as well as the climate system and global biogeochemical cycles. In this study, we use a dynamic vegetation model, the aDGVM, to explore interactive effects of climate and land use on the vegetation structure and distribution of West African savannas under current and anticipated future environmental conditions. We parameterized the model for West African savannas and extended it by including sub-models to simulate fire management, grazing, and wood cutting. The model projects that under future climate without human land use impacts, large savanna areas would shift toward more wood dominated vegetation due to CO2 fertilization effects, increased water use efficiency and decreased fire activity. However, land use activities could maintain desired vegetation states that ensure fluxes of important ecosystem services, even under anticipated future conditions. Ecosystem management can mitigate climate change impacts on vegetation and delay or avoid undesired vegetation shifts. The results highlight the effects of land use on the future distribution and dynamics of savannas. The identification of management strategies is essential to maintain important ecosystem services under future conditions in savannas worldwide
The failure of conventional approaches to achieve equitable and sustainable water management has prompted a new way of perceiving and acting with water. This is creating a ‘new water paradigm’ that emphasizes broader stakeholder involvement; integration of sectors, issues and disciplines; attention to the human dimensions of management; and wider recognition of the economic, ecological and cultural values of water. This article reviews three approaches arising within the new water paradigm: integrated water resources management; ecosystem-based approaches; and adaptive management. The article concludes that the strengths of each approach address different moral and ecological challenges. Combining these strengths, while minimizing tensions, may contribute to more effective water management in the Anthropocene.
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 macroinvertebrate 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 m22 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.
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.