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 Outdated and dilapidated infrastructure places coastal communities, in particular, at risk from the increasingly frequent and intense coastal storm events and rising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.
Habitat Type: WTL
Wetlands
Limiting climate warming to <2°C requires increased mitigation efforts, including land stewardship, whose potential in the United States is poorly understood. We quantified the potential of natural climate solutions (NCS)—21 conservation, restoration, and improved land management interventions on natural and agricultural lands—to increase carbon storage and avoid greenhouse gas emissions in the United States. We found a maximum potential of 1.2 (0.9 to 1.6) Pg CO2e year−1, the equivalent of 21% of current net annual emissions of the United States. At current carbon market prices (USD 10 per Mg CO2e), 299 Tg CO2e year−1 could be achieved. NCS would also provide air and water filtration, flood control, soil health, wildlife habitat, and climate resilience benefits.
Constructed wetlands (CW) are effective in treating wastewater, particularly in settings that require low tech-nology and low maintenance as operational constraints. Biomass harvested from CW can be used as a renewableenergy source and treated effluent can provide irrigation for agricultural uses. Biomass yields for four selectedwetland plants in CW, namelyPhragmitesspp.,Typhaspp.,A. donax,andC. papyrus, ranged from an average ofabout 1500g of dry mass per square meter (g/m2) forTyphaspp., up to 6000g/m2forA.donax. The energy yieldfor direct combustion of these plants occupied a narrow range, averaging about 18 megajoules per kilogram ofdry mass (MJ/kg) for all plant types, a comparable amount toAcacia spp. Methane yields varied from about170–360L of methane (normalised to standard conditions) per kilogram of dry mass (LN/kg). 1m2of CWplanted withA. donaxcan produce on average 110MJ through direct combustion or 1660L of methane frombiogas production. In a village of 200 people the biomass from a CW planted withTyphaspp. can reduce cookingfuel needs by 4–55% and therefore save up to 12ha of forest per year. The water footprint of these plants wasmeasured as the percent loss in water in the CW from evapotranspiration (ET). Under a fixed set of assumptionson climate and operation, the water used through ET, the CW could deliver from 64% to 76% of the influentwater for subsequent use. In summary, CW have the potential to offset energy and irrigation needs at scalesranging from small communities to peri-urban areas. Constructed wetlands used to treat wastewater have thepotential to provide a sustainable bioenergy source without placing burdens on water resources or displacingother food or energy crops.
Ecological infrastructure (EI) refers to ecosystems that deliver services to society, functioning as a nature-based equivalent of, or complement to, built infrastructure. EI is critical for socio-economic development, supporting a suite of development imperatives at local, national and international scales. This paper presents the myriad of ways that EI supports sustainable development, using South Africa and the South African National Development Plan as a case study, linking to the Sustainable Development Goals on a global level. We show the need for EI across numerous development and sustainability issues, including food security, water provision, and poverty alleviation. A strategic and multi-sectoral approach to EI investment is essential for allocating scarce public and private resources for achieving economic and social-ecological priorities. Opportunities to unlock investment in EI, both internationally and on the national level, are identified. This includes leveraging private sector investment into landscape management and integrating the costs of managing EI into public sectors that benefit directly from ecosystem services, such as the water sector and infrastructure development. Additionally, investing in EI also aligns well with international development and climate change funds. Investment in EI from a range of innovative sources supports global and national development, while complementing other development investments.
Freshwater ecosystems in many parts of the world have been severely affected by past management practices that have altered the volume, timing and quality of water flows and caused a decline in their ecological health. Some of these systems are also experiencing the negative impacts of climate change. Adaptation to climate change and the continual need to address existing ecological damage poses ongoing challenges for freshwater managers. In this paper we propose and discuss a Catchment Assessment Framework (CAF) that is used to evaluate existing and potential freshwater management actions, such as riparian revegetation and habitat connectivity, for their adaptation potential. The CAF was developed as a tool for prioritizing low risk climate change adaptation options in Australian catchment management. The CAF enables catchment managers and technical experts to assess management actions against seven inter-related criteria to provide a holistic assessment: relevance to the catchment; climate change adaptation potential, including potential for maladaptation and benefit under different climate scenarios; ecosystem service benefits; compatibility with other actions; implementation constraints; socio-economic consequences; and a risk assessment. It was developed and applied by assessing nine management options with stakeholders in three catchments within the Murray-Darling Basin in south-eastern Australia. We found that while management options are undertaken as a response to existing degradation, they can be used as building blocks for a climate change adaptation strategy that considers a range of different but complementary measures to better manage climate-related risk. The CAF enables practitioners to assess the advantages of a range of adaptation options and to subject them to their wider decision making and management planning.
Stormwater wetlands (CSWs) have become one of the more popular SCMs, offering a hybrid between larger detention technologies such as wet ponds and newer green infrastructure technologies. A well-functioning stormwater wetland will be a resilient, diverse ecosystem that includes many plant and animal species. This research looks to investigate whether or not wetlands need regular maintenance to sustain their treatment capacity. The research site is located in River Bend, NC. Flow-weighted samples, rainfall, and hydrologic data are being collected at both the inlet and outlet from April 2012 – April 2013, aiming a minimum of 15 storms spaced throughout the year. Monitoring of phosphorus deposition consists of taking soil samples and analyzing for Soil Test Phosphorous. These monitoring results will be compared with the results of a study that was conducted at the same site for a one-year period immediately following construction completion. This will allow researchers to see the effects of no maintenance plan (or activity) and time on wetland performance in removing phosphorus and achieving other wetland performance goals. Vegetation in a CSW is essential for nutrient removal and thermal pollution reduction. However, a portion of the storage volume designed to retain the water quality event is occupied by vegetation, which may result in the CSW being undersized from a hydrologic perspective – especially in unmaintained, mature systems. The fraction of the volume associated with vegetation mass was unknown, and designers have been unsure as to (1) how they should account for volume occupied by vegetation and (2) whether this was a significant design issue. Twelve stormwater wetlands and one hybrid wet pond in North Carolina were sampled to assess their percent vegetative occupancy by volume. A conservative recommended factor of safety is 1.025. Species-specific factors of safety (FOS) were also calculated; at the 30 cm temporary pool elevation, the Iris (Iris spp.) FOS was highest at 1.020 and the mixed vegetation FOS was lowest at 1.005. When designing a wetland, a more specific FOS may be calculated using a weighted average of the FOS for each species in the planting plan. The outcomes of this research allow designers to account for the volume taken up by emergent wetland vegetation; however, the uncertainty in other factors such as discrepancies between designed and as-built bathymetry probably have a greater impact on the design volume loss when compared with vegetation occupancy (<2%). © 2013 American Society of Civil Engineers.
We propose to enhance existing adaptive management efforts with a decision-analytical approach that can guide the initial selection of robust restoration alternative plans and inform the need to adjust these alternatives in the course of action based on continuously acquired monitoring information and changing stakeholder values. We demonstrate an application of enhanced adaptive management for a wetland restoration case study inspired by the Florida Everglades restoration effort. We find that alternatives designed to reconstruct the pre-drainage flow may have a positive ecological impact, but may also have high operational costs and only marginally contribute to meeting other objectives such as reduction of flooding. Enhanced adaptive management allows managers to guide investment in ecosystem modeling and monitoring efforts through scenario and value of information analyses to support optimal restoration strategies in the face of uncertain and changing information.
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.
Ecosystem-based adaptation (EbA) is increasingly being promoted as a cost-effective means of adaptation to climate change. However, in spite of considerable international press, there is still little evidence to substantiate this claim. This study proposes a method through which the cost-effectiveness of ecosystem-based adaptation strategies can be evaluated against alternative adaptation options, and contributes to South African literature on the subject. The potential cost-effectiveness of wetland restoration is assessed as a means of securing the carrying capacity of land for pastoralist communities of the Kamiesberg communal area in South Africa under projected future climate conditions. The conventional alternatives would be to respond to increasingly dry conditions by drilling boreholes and using supplemental feed for livestock. It was assumed that the ecosystem-based adaptation interventions would occur upfront, whereas the alternatives are more likely to be implemented in reaction to droughts over a longer time period. The study found the implementation of conventional alternatives to be more cost-effective than ecosystem-based adaptation as a means to sustaining livestock stocking rates, with ecosystem-based adaptation being twice as costly. However, this is framed from the perspective of those directly affected (the landowners), and does not include the benefits to broader society.
The main objective of this paper is to combine and integrate environmental, economic and social impact assessment procedures in order to support decision-making in the context of flood control policy in the Netherlands. The hydraulic, hydrological, ecological, economic and social effects of alternative flood control policies, such as land use change and floodplain restoration, are evaluated using a combination of advanced quantitative modelling techniques and qualitative expert judgement. The results from the ecological, economic and social impact assessment are evaluated in an integrated way through cost – benefit analysis (CBA) and multi-criteria analysis (MCA). As expected, these methods produce different outcomes. Although traditional flood control policy-building higher and stronger dikes-is a cost-effective option, investment in alternative flood control policy-land use changes and floodplain restoration-can be justified on the basis of both CBA and MCA when including the additional ecological and socio-economic benefits in the long run. The outcome of the MCA appears to be especially sensitive to the inclusion of the qualitative scores for the expected social impacts of land use change and floodplain restoration. An important research question remains how to assess, integrate and trade-off (1) significantly different types of impacts in a methodologically sound way in both cost – benefit and multi-criteria analysis, and (2) significantly different types and quality of available knowledge and information about these impacts.
Hurricanes Katrina and Rita showed the vulnerability of coastal communities and how human activities that caused deterioration of the Mississippi Deltaic Plain (MDP) exacerbated this vulnerability. The MDP formed by dynamic interactions between river and coast at various temporal and spatial scales, and human activity has reduced these interactions at all scales. Restoration efforts aim to re-establish this dynamic interaction, with emphasis on reconnecting the river to the deltaic plain. Science must guide MDP restoration, which will provide insights into delta restoration elsewhere and generally into coasts facing climate change in times of resource scarcity.
For more than a century, coastal wetlands have been recognized for their ability to stabilize shorelines and protect coastal communities. However, this paradigm has recently been called into question by small-scale experimental evidence. Here, we conduct a literature review and a small meta-analysis of wave attenuation data, and we find overwhelming evidence in support of established theory. Our review suggests that mangrove and salt marsh vegetation afford context-dependent protection from erosion, storm surge, and potentially small tsunami waves. In bio-physical models, field tests, and natural experiments, the presence of wetlands reduces wave heights, property damage, and human deaths. Meta-analysis of wave attenuation by vegetated and unvegetated wetland sites highlights the critical role of vegetation in attenuating waves. Although we find coastal wetland vegetation to be an effective shoreline buffer, wetlands cannot protect shorelines in all locations or scenarios; indeed large-scale regional erosion, river meandering, and large tsunami waves and storm surges can overwhelm the attenuation effect of vegetation. However, due to a nonlinear relationship between wave attenuation and wetland size, even small wetlands afford substantial protection from waves. Combining man-made structures with wetlands in ways that mimic nature is likely to increase coastal protection. Oyster domes, for example, can be used in combination with natural wetlands to protect shorelines and restore critical fishery habitat. Finally, coastal wetland vegetation modifies shorelines in ways (e.g. peat accretion) that increase shoreline integrity over long timescales and thus provides a lasting coastal adaptation measure that can protect shorelines against accelerated sea level rise and more frequent storm inundation. We conclude that the shoreline protection paradigm still stands, but that gaps remain in our knowledge about the mechanistic and context-dependent aspects of shoreline protection.
The rehabilitation and restoration of land is a key strategy to recover services -goods and resources- ecosystems offer to the humankind. This paper reviews key examples to understand the superior effect of nature-based solutions to enhance the sustainability of catchment systems by promoting desirable soil and landscape functions. The use of concepts such as connectivity and the theory of system thinking framework allowed to review coastal and river management as a guide to evaluate other strategies to achieve sustainability. In land management, NBSs are not mainstream management. Through a set of case studies: organic farming in Spain; rewilding in Slovenia; land restoration in Iceland, sediment trapping in Ethiopia and wetland construction in Sweden, we show the potential of nature-based solutions (NBSs) as a cost-effective long term solution for hydrological risks and land degradation. NBSs can be divided into two main groups of strategies: soil solutions and landscape solutions. Soil solutions aim to enhance the soil health and soil functions through which local ecosystem services will be maintained or restored. Landscape solutions mainly focus on the concept of connectivity. Making the landscape less connected, facilitating less rainfall to be transformed into runoff and therefore reducing flood risk, increasing soil moisture and reducing droughts and soil erosion we can achieve the sustainability. The enhanced ecosystem services directly feed into the realization of the Sustainable Development Goals of the United Nations.
Our assessment highlights certain governance mechanisms and policy processes that could contribute to joint adaptation and economic planning and in achieving multiple objectives. These include leadership, institutional mechanisms, science–policy nexus, decision-making structures, stakeholder involvement, and technological innovation. These readiness factors as well as knowledge gaps on future risks provide lessons for other SIDS in their climate change and integrated coastal management initiatives.
The Elephant Marsh, a wetland in Southern Malawi, is important for fishing, agriculture, hunting and the collection of natural resources for the livelihoods of local communities. However, there has been increasing pressure driven by a changing climate, population growth, rural poverty and agricultural conversion, all of which threaten the future of the wetland. Currently, Malawi does not have either a national wetland policy or a climate change policy and wetland issues are only marginally present in the National Parks and Wildlife Policy of 2000 and National Fisheries and Aquaculture Policy of 2001. As a result, the country lacks a framework that could be strong enough to achieve balanced and sustainable wetland management for multiple resource users. The objective of this study was to establish the development potentials of Elephant Marsh from an ecosystem-based (‘working-with-nature’) perspective. It was revealed that there are development potentials in fisheries, recession agriculture, biomass for energy, conservation and tourism. This paper emphasizes that as these opportunities are developed, there will be the need to strengthen management institutions at local and national levels, and the coordination between the two.
This study proposes a novel approach for establishing adaptive environmental-flow prescriptions for rivers, channels, and floodways with substantial flow augmentation and a limited decision space using the highly altered Atchafalaya River Basin (ARB) in Louisiana as an example. Development of the ARB into the primary floodway of the Mississippi River and Tributaries Project has contributed to hydrologic changes basin-wide that have altered the river-floodplain interface threatening important ecosystems, notably the expansive baldcypress-water tupelo swamp forests. Current restoration efforts only address the spatial distribution of water in local areas of the basin; however, the timing, frequency, magnitude, and duration of ecologically-important high and low flows are determined at the basin-wide scale by the daily implementation of a federal flow mandate that limits available water management options. We used current hydrologic conditions and established flow-ecology relationships from the literature to develop an environmental flow prescription for the ARB that provides basin-wide flow targets to complement ongoing restoration efforts. Hydrologic analysis of current flows and the flow-ecology requirements for these wetland forests revealed an overlap in the range of flow variability under the current water management model, suggesting environmental flows can be complementary with the desired hydraulic and geomorphic characteristics of the floodway. The result is a first step towards an adaptive flow regime that strives to balance important flow-ecology relationships within a decision space limited by a federal flow mandate. We found high potential for success in managing water for nature while accommodating other management needs for the river.
Sea-level rise, potential changes in the intensity and frequency of storms, and consequent shoreline erosion and flooding will have increasing impacts on the economy and culture of coastal regions. A growing body of evidence suggests that coastal ecosystems—natural infrastructure—can play an important role in reducing the vulnerability of people and property to these impacts. To effectively inform climate adaptation planning, experts often struggle to develop relevant local and regional information at a scale that is appropriate for decision-making. In addition, institutional capacity and resource constraints often limit planners’ ability to incorporate innovative, scientifically based approaches into planning. In this paper, we detail our collaborative process in two coastal California counties to account for the role of natural infrastructure in climate adaptation planning. We used an interdisciplinary team of scientists, economists, engineers, and law and policy experts and planners, and an iterative engagement process to (1) identify natural infrastructure that is geographically relevant to local jurisdictional planning units, (2) refine data and models to reflect regional processes, and (3) develop metrics likely to resonate within the local decision contexts. Using an open source decision-support tool, we demonstrated that protecting existing natural infrastructure—including coastal dunes and wetlands—could reduce the vulnerability of water resource-related structures, coastal populations, and farmland most exposed to coastal flooding and erosion. This information formed part of the rationale for priority climate adaptation projects the county governments are now pursuing. Our collaborative and iterative approach, as well as replicable use of an open source decision-support tool, facilitated inclusion of relevant natural infrastructure information into regional climate adaptation planning processes and products. This approach can be applied in diverse coastal climate adaptation planning contexts to locate and characterize the degree to which specific natural habitats can reduce vulnerability to sea-level rise and storms.
In this study we assess multiple benefits (environmental, social and economic) provided by a multi-purpose green infrastructure (a series of constructed wetlands surrounded by a park) in a peri-urban area, and compare it with the alternative grey infrastructure and with the previous situation (a poplar plantation). We apply a multi-criteria analysis as a basis for integrated valuation. We address specific policy needs (strategic objectives) for the local territorial planning in the implementation of the EU Water Framework Directive. The analysis is used retrospectively (ex post evaluation) but our results could also be used prospectively to appraise new proposals of constructed wetlands under similar circumstances. The results reflect that the green infrastructure performs equal or even better than the grey infrastructure alternative for water purification and flood protection, it has a similar cost, and it provides additional benefits (like wildlife support and recreation). The most preferred alternative is the green infrastructure, followed by the grey infrastructure and the poplar plantation. This study demonstrates (a) the effectiveness of investments on nature-based solutions, (b) the potential of green infrastructures for delivering a broad range of ecosystem services, and (c) the utility of integrating different value systems and stakeholders’ viewpoints to support environmental decision-making.
Wetlands have many important functions. To a wide range of wildlife species, they offer critically important habitats. They also act to mitigate flooding, regulate micro and macro climate changes, degrade pollutants and control erosion etc. Wetland benefits are these functions, which provide direct, indirect, and non-use values to humans. In this study, field soil data are used to calculate the flood mitigation benefits of wetland soils within the Momoge National Nature Reserve, Jilin Province, the People’s Republic of China. Calculations are based upon environmental economic assessment methods and GIS techniques. The estimated flood mitigation capacity of wetland soils within the Momoge Reserve was 7.15 × 104 m3/hm2/yr. This translated into an economic benefit of 5700 $/hm2/yr due to flood mitigation. Spatial differences in the flood mitigation ability of soils were observed across the Momoge wetlands. Benefits associated with flood mitigation were highest within the middle reaches of the Momoge wetlands and least in the East. This quantitative analysis of flood mitigation benefit, with its investigation of wetland soils, will be a useful reference both for the assessment of wetland values in the local region and also for the greater understanding wetland function and value assessment methods.
Climate change is occurring and not being mitigated, motivating adaptation but adaptation strategies can have biophysical, economic, technological, and social limits. We review publicly available documents to assess how successful current and proposed adaptation strategies may be for the Australian Alps, including likely limits and potential collaborations and conflicts among stakeholders. Conservation managers, the tourism industry, and local communities have implemented or are proposing a range of adaptation strategies in the region. Some stakeholder strategies complement each other (e.g. invasive species control, fire management), while others are potential sources of conflict (water and electricity for snowmaking, year-round tourism). Economic costs and biophysical constraints are the most important limits to these adaptation strategies. These types of limits and conflicts between different stakeholders on adaptation strategies are likely to occur in other regions and demonstrate that adaptation may only provide partial and short term solutions to the challenges of climate change.
The development of ecological networks could enhance the ability of species to disperse across fragmented landscapes and could mitigate against the negative impacts of climate change. The development of such networks will require widespread ecological restoration at the landscape scale, which is likely to be costly. However, little information is available regarding the cost-effectiveness of restoration approaches. 2. We address this knowledge gap by examining the potential impact of landscape-scale habitat restoration on the value of multiple ecosystem services across the catchment of the River Frome in Dorset, England. This was achieved by mapping the market value of four ecosystem services (carbon storage, crops, livestock and timber) under three different restoration scenarios, estimating restoration costs, and calculating net benefits. 3. The non-market value of additional services (cultural, aesthetic and recreational value) was elicited from local stakeholders using an online survey tool. Flood risk was assessed using a scoring approach. Spatial Multi-Criteria Analysis (MCA) was conducted, incorporating both market and non-market values, to evaluate the relative benefits of restoration scenarios. These were compared with impacts of restoration on biodiversity value. 4. Multi-Criteria Analysis results consistently ranked restoration scenarios above a non-restoration comparator, reflecting the increased provision of multiple ecosystem services. Restoration scenarios also provided benefits to biodiversity, in terms of increased species richness and habitat connectivity. However, restoration costs consistently exceeded the market value of ecosystem services. 5. Synthesis and applications. Establishment of ecological networks through ecological restoration is unlikely to deliver net economic benefits in landscapes dominated by agricultural land use. This reflects the high costs of ecological restoration in such landscapes. The cost-effectiveness of ecological networks will depend on how the benefits provided to people are valued, and on how the value of non-market benefits are weighted against the costs of reduced agricultural and timber production. Future plans for ecological restoration should incorporate local stakeholder values, to ensure that benefits to people are maximised.
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.
This paper considers an emerging group of coastal management approaches which offer the potential to reduce coastal flood and erosion risks whilst also providing nature conservation, aesthetic and amenity benefits. These solutions mimic the characteristics of natural features, but are enhanced or created by man to provide specific services such as wave energy dissipation and erosion reduction. Such approaches can include beaches, dunes, saltmarshes, mangroves, sea grasses, coral and oyster reefs. The paper describes a number of innovative projects and the lessons learned in their development and implementation. These lessons include the planning, design and construction of projects, their development following implementation, the engagement of local communities and the cost effectiveness of solutions.
Globally, shoreline protection approaches are evolving towards the incorporation of natural and nature-based features (living shorelines henceforth) as a preferred alternative to shoreline armoring. Emerging research suggests that living shorelines may be a viable approach to conserving coastal habitats (marshes, beaches, shallows, seagrasses) along eroding shorelines. Living shorelines typically involve the use of coastal habitats, such as wetlands, that have a natural capacity to stabilize the shore, restore or conserve habitat, and maintain coastal processes. They provide stability while still being dynamic components of the ecosystem, but due to their dynamic nature, careful designs and some maintenance will be required if habitat conservation is a goal. Living shorelines may represent a singular opportunity for habitat conservation in urban and developing estuaries because of their value to society as a shoreline protection approach and resilience to sea level rise. However, enhanced public acceptance and coordination among regulatory and advisory authorities will be essential to expand their use. To fully understand their significance as habitat conservation strategies, systematic and standardized monitoring at both regional and national scales is vital to evaluate the evolution, persistence, and maximum achievable functionality (e.g., ecosystem service provision) of living shoreline habitats.
Whether or not exacerbated by climate change, flood risks are becoming more frequent in the capital city of Nouakchott in Mauritania. Flooding in Nouakchott is due to a combination of both natural factors and human activities. The extreme fragility of the barrier beach that protects the city from the sea, the accelerated exploitation and inadequate infrastructure built along the coast have made this barrier beach highly vulnerable to wave action, exposing the city to a high risk of flooding. Flooding is further exacerbated by rising groundwater levels in several neighborhoods of the city. Cartographic analysis of flood risk indicated that socio-economic impacts associated with floods could be high. In the case of sea water intrusion, up to 30 % of the city could be potentially submerged. This would directly affect nearly 300,000 people and entail high risks of casualties. Associated economic losses due to flooding could be as high as USD 7 billion (Senhoury, Ame´nagements portuaires et urbanisation accelere´e des coˆtes basses sableuses d’Afrique de l’Ouest dans un contexte de pejoration climatique, cas du littoral de Nouakchott (Mauritanie). Thesis state, University of Dakar, April 29, 2014, 157 pp, 2014). The following measures based on nature-based approaches are recommended to tackle flood risks in Nouakchott: • Restore and consolidate the barrier beach through reforestation of degraded areas; • Put in place an appropriate drainage system for rain and marine waters and a sewage sanitation system; • Optimize a solution to safeguard the harbor of Nouakchott; and • Transform wetlands created by the permanent flooding of low-lying areas in the city into urban protected areas.