Return on investment for mangrove and reef flood protection

There is a growing need for coastal and marine restoration, but it is not clear how to pay for it given that environmental funding is low, and national budgets are stretched in response to natural hazards. We use risk-industry methods and find that coral reef and mangrove restoration could yield strong Return on Investment (ROI) for flood risk reduction on shorelines across more than 20 Caribbean countries. These results are robust to changes in discount rates and the timing of restoration benefits. Data on restoration costs are sparse, but the Present Value (PV) of restored natural infrastructure shows that ROI would be positive in many locations even if restoration costs are in the hundreds of thousand per hectare for mangroves and millions per km for reefs. Based on these benefits, we identify significant sources of funding for restoring these natural defenses.

Nature as a solution for shoreline protection against coastal risks associated with ongoing sea-level rise

The risks from climate change are ever-growing, especially in more vulnerable and exposed regions such as coastlines. The rise in sea level and increase in the frequency and intensity of climate-induced coastal hazards are threatening the increasing coastal populations. Brazil, with its 8,500 km of coast, is one of the countries most at risk from coastal flooding and erosion. Nature-based solutions have been suggested as climate adaptation strategies with the greatest potential to counteract coastal hazards stemming from sea-level rise and safeguard coastal cities. However, there is still a knowledge gap in the scientific literature on the effectiveness of nature-based solutions, especially at large spatial scales in Central and South America. Here, we assessed the risks from climate-induced hazards of coastal erosion and flooding related to sea-level rise on the Brazilian coast, and the effectiveness of nature-based solutions as climate adaptation strategies. We reveal that nature-based shoreline protection can reduce by 2.5 times the risks to the Brazilian coastline. The loss of existing natural habitats would substantially increase the area and population at risk from these climate-induced hazards. Worrisomely, legal mechanisms to protect these natural habitats are few and being weakened. Only 10% of the coastal natural habitats are within protected areas, and these alone do not ensure coastal protection, as our results indicate that the loss of unprotected natural habitats has about the same risk as the total absence of natural habitats. Our results warn of the severe consequences of the continued loss of natural habitats along the coast. Thus, actions towards the maintenance and protection of coastal habitats are paramount for climate adaptation and to ensure the well-being and livelihoods of coastal populations. Brazil has a central role in demonstrating the benefits of strategies based on nature-based solutions for shoreline protection, favoring their implementation worldwide. We provide both the natural habitat maps and the maps with model results with spatial and numerical information so readers can explore the relations between the natural habitats and coastal risk indexes at a sub-national level and foster their use by local stakeholders.

Carbon Removal Using Coastal Blue Carbon Ecosystems Is Uncertain and Unreliable, With Questionable Climatic Cost-Effectiveness

Mangrove forests, seagrass meadows and tidal saltmarshes are vegetated coastal ecosystems that accumulate and store large quantities of carbon in their sediments. Many recent studies and reviews have favorably identified the potential for such coastal “blue carbon” ecosystems to provide a natural climate solution in two ways: by conservation, reducing the greenhouse gas emissions arising from the loss and degradation of such habitats, and by restoration, to increase carbon dioxide drawdown and its long-term storage. The focus here is on the latter, assessing the feasibility of achieving quantified and secure carbon removal (negative emissions) through the restoration of coastal vegetation. Seven issues that affect the reliability of carbon accounting for this approach are considered: high variability in carbon burial rates; errors in determining carbon burial rates; lateral carbon transport; fluxes of methane and nitrous oxide; carbonate formation and dissolution; vulnerability to future climate change; and vulnerability to non-climatic factors. Information on restoration costs is also reviewed, with the conclusion that costs are highly uncertain, with lower-range estimates unrealistic for wider application. CO2 removal using coastal blue carbon restoration therefore has questionable cost-effectiveness when considered only as a climate mitigation action, either for carbon-offsetting or for inclusion in Nationally Determined Contributions. Many important issues relating to the measurement of carbon fluxes and storage have yet to be resolved, affecting certification and resulting in potential over-crediting. The restoration of coastal blue carbon ecosystems is nevertheless highly advantageous for climate adaptation, coastal protection, food provision and biodiversity conservation. Such action can therefore be societally justified in very many circumstances, based on the multiple benefits that such habitats provide at the local scale.

The planetary role of seagrass conservation

Seagrasses are remarkable plants that have adapted to live in a marine environment. They form extensive meadows found globally that bioengineer their local environments and preserve the coastal seascape. With the increasing realization of the planetary emergency that we face, there is growing interest in using seagrasses as a nature-based solution for greenhouse gas mitigation. However, seagrass sensitivity to stressors is acute, and in many places, the risk of loss and degradation persists. If the ecological state of seagrasses remains compromised, then their ability to contribute to nature-based solutions for the climate emergency and biodiversity crisis remains in doubt. We examine the major ecological role that seagrasses play and how rethinking their conservation is critical to understanding their part in fighting our planetary emergency.

Governing for Transformative Change across the Biodiversity-Climate-Society Nexus

Transformative governance is key to addressing the global environmental crisis. We explore how transformative governance of complex biodiversity–climate–society interactions can be achieved, drawing on the first joint report between the Intergovernmental Panel on Climate Change and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services to reflect on the current opportunities, barriers, and challenges for transformative governance. We identify principles for transformative governance under a biodiversity–climate–society nexus frame using four case studies: forest ecosystems, marine ecosystems, urban environments, and the Arctic. The principles are focused on creating conditions to build multifunctional interventions, integration, and innovation across scales; coalitions of support; equitable approaches; and positive social tipping dynamics. We posit that building on such transformative governance principles is not only possible but essential to effectively keep climate change within the desired 1.5 degrees Celsius global mean temperature increase, halt the ongoing accelerated decline of global biodiversity, and promote human well-being.

Protection and restoration of coastal habitats yield multiple benefits for urban residents as sea levels rise

Globally, rising seas threaten massive numbers of people and significant infrastructure. Adaptation strategies increasingly incorporate nature-based solutions. New science can illuminate where these solutions are appropriate in urban environments and what benefits they provide to people. Together with stakeholders in San Mateo County, California, USA, we co-developed nature-based solutions to support adaptation planning. We created six guiding principles to shape planning, summarized vulnerability to sea-level rise and opportunities for nature-based solutions, created three adaptation scenarios, and compared multiple benefits provided by each scenario. Adaptation scenarios that included investments in nature-based solutions deliver up to eight times the benefits of a traditionally engineered baseline as well as additional habitat for key species. The magnitude and distribution of benefits varied at subregional scales along the coastline. Our results demonstrate practical tools and engagement approaches to assessing the multiple benefits of nature-based solutions in an urban estuary that can be replicated in other regions.

Nature-dependent people: Mapping human direct use of nature for basic needs across the tropics

Understanding where people depend the most on natural resources for their basic human needs is crucial for planning conservation and development interventions. For some people, nature is a direct source of food, clean water, and energy through subsistence uses. However, a high direct dependency on nature for basic needs makes people particularly sensitive to changes in climate, land cover, and land tenure. Based on more than 5 million household interviews conducted in 85 tropical countries, we identified where people highly depend on nature for their basic needs. Our results show that 1.2 billion people, or 30% of the population across tropical countries, are highly dependent on nature. In places where people highly depend on nature for their basic needs, nature-based strategies that protect, restore or sustainably manage ecosystems must be carefully designed to promote inclusive human development alongside environmental benefits.

Ecosystem-Based Adaptation to Protect Avian Species in Coastal Communities in the Greater Niagara Region, Canada

Coastal communities are increasingly vulnerable to climate change and its effects may push coastal ecosystems to undergo irreversible changes. This is especially true for shorebirds with the loss of biodiversity and resource-rich habitats to rest, refuel, and breed. To protect these species, it is critical to conduct research related to nature-based Solutions (NbS). Through a scoping review of scientific literature, this paper initially identified 85 articles with various ecosystem-based adaptation (EbA) strategies that could help conserve shorebird populations and promote ecotourism. Of these 85 articles, 28 articles had EbA strategies that were examined, with some like coral reefs and mangroves eliminated as they were inappropriate for this region. The scoping review identified four major EbA strategies for the Greater Niagara Region with living shorelines and beach nourishment being the most suitable, especially when combined. These strategies were then evaluated against the eight core principles of nature-based solutions protecting shorebird as well as human wellbeing. Living shoreline strategy was the only one that met all eight NbS principles. As the coastline of the region greatly varies in substrate and development, further research will be needed to decide which EbA strategies would be appropriate for each specific area to ensure their efficacy.

Coastal wetlands mitigate storm flooding and associated costs in estuaries

As storm-driven coastal flooding increases under climate change, wetlands such as saltmarshes are held as a nature-based solution. Yet evidence supporting wetlands’ storm protection role in estuaries—where both waves and upstream surge drive coastal flooding—remains scarce. Here we address this gap using numerical hydrodynamic models within eight contextually diverse estuaries, simulating storms of varying intensity and coupling flood predictions to damage valuation. Saltmarshes reduced flooding across all studied estuaries and particularly for the largest—100 year—storms, for which they mitigated average flood extents by 35% and damages by 37% ($8.4 M). Across all storm scenarios, wetlands delivered mean annual damage savings of $2.7 M per estuary, exceeding annualised values of better studied wetland services such as carbon storage. Spatial decomposition of processes revealed flood mitigation arose from both localised wave attenuation and estuary-scale surge attenuation, with the latter process dominating: mean flood reductions were 17% in the sheltered top third of estuaries, compared to 8% near wave-exposed estuary mouths. Saltmarshes therefore play a generalised role in mitigating storm flooding and associated costs in estuaries via multi-scale processes. Ecosystem service modelling must integrate processes operating across scales or risk grossly underestimating the value of nature-based solutions to the growing threat of storm-driven coastal flooding.

The blue carbon wealth of nations

Carbon sequestration and storage in mangroves, salt marshes and seagrass meadows is an essential coastal ‘blue carbon’ ecosystem service for climate change mitigation. Here we offer a comprehensive, global and spatially explicit economic assessment of carbon sequestration and storage in three coastal ecosystem types at the global and national levels. We propose a new approach based on the country-specific social cost of carbon that allows us to calculate each country’s contribution to, and redistribution of, global blue carbon wealth. Globally, coastal ecosystems contribute a mean ± s.e.m. of US$190.67 ± 30 bn yr−1 to blue carbon wealth. The three countries generating the largest positive net blue wealth contribution for other countries are Australia, Indonesia and Cuba, with Australia alone generating a positive net benefit of US$22.8 ± 3.8 bn yr−1 for the rest of the world through coastal ecosystem carbon sequestration and storage in its territory.

Coral Reef Restorations Can Be Optimized to Reduce Coastal Flooding Hazards

Coral reefs are effective natural coastal flood barriers that protect adjacent communities. Coral degradation compromises the coastal protection value of reefs while also reducing their other ecosystem services, making them a target for restoration. Here we provide a physics-based evaluation of how coral restoration can reduce coastal flooding for various types of reefs. Wave-driven flooding reduction is greatest for broader, shallower restorations on the upper fore reef and between the middle of the reef flat and the shoreline than for deeper locations on the fore reef or at the reef crest. These results indicate that to increase the coastal hazard risk reduction potential of reef restoration, more physically robust species of coral need to be outplanted to shallower, more energetic locations than more fragile, faster-growing species primarily being grown in coral nurseries. The optimization and quantification of coral reef restoration efforts to reduce coastal flooding may open hazard risk reduction funding for conservation purposes.

Protecting People and Property While Restoring Coastal Wetland Habitats

Flood mitigation and protection of coastal infrastructure are key elements of coastal management decisions. Similarly, regulating and provisioning roles of coastal habitats have increasingly prompted policy makers to consider the value of ecosystem goods and services in these same decisions, broadly defined as “the benefits people obtain from ecosystems.” We applied these principles to a study at three earthen levees used for flood protection. By restricting tidal flows, the levees degraded upstream wetlands, either by reducing salinity, creating standing water, and/or by supporting monocultures of invasive variety Phragmites australis. The wetlands, located at Greenwich, NJ, on Delaware Bay, were evaluated for restoration in this study. If unrestricted tidal flow were reestablished with mobile gates or similar devices, up to 226 ha of tidal salt marsh would be potentially restored to Spartina spp. dominance. Using existing literature and a value transfer approach, the estimated total economic value (TEV) of goods and services provided annually by these 226 ha of restored wetlands ranged from $2,058,182 to $2,390,854 y−1. The associated annual engineering cost for including a mobile gate system to fully restore tidal flows to the upstream degraded wetlands was about $1,925,614 y−1 resulting in a benefit-cost ratio range of 0.98–1.14 over 50 years (assuming no wetland benefits realized during the first 4 years). Thus, inclusion of a cost-effective mobile gate system in any engineering design to improve long-term flood resilience in the region would produce dual benefits of protecting people and property from major storms, while preserving and enhancing ecosystem values.

Integrating climate adaptation and biodiversity conservation in the global ocean

The impacts of climate change and the socioecological challenges they present are ubiquitous and increasingly severe. Practical efforts to operationalize climate-responsive design and management in the global network of marine protected areas (MPAs) are required to ensure long-term effectiveness for safeguarding marine biodiversity and ecosystem services. Here, we review progress in integrating climate change adaptation into MPA design and management and provide eight recommendations to expedite this process. Climate-smart management objectives should become the default for all protected areas, and made into an explicit international policy target. Furthermore, incentives to use more dynamic management tools would increase the climate change responsiveness of the MPA network as a whole. Given ongoing negotiations on international conservation targets, now is the ideal time to proactively reform management of the global seascape for the dynamic climate-biodiversity reality.

Time equals money? Valuing ecosystem-based adaptation in a developing country context

To guide investments in ecosystem-based adaptation (EbA) in developing countries, numerous stated preference valuation studies have been implemented to assess the value of ecosystem services. These studies increasingly use time payments as an alternative to money. There is limited knowledge, however, about how to convert time to money and how the type of payment affects willingness to pay (WTP). In this study, the results of choice experiments using time and money payments are compared in the context of EbA measures in Vietnam. Six, of which five individual-specific, conversion rates are applied. WTP estimates are found to be higher for time payments. Moreover, the type of payment vehicle as well as the conversion rate has substantial effect on mean WTP and WTP distributions. We discuss implications of these results for the conversion of time to money and the use of resulting WTP estimates in cost benefit analyses in developing countries.

Nurturing ecosystem-based adaptations in South Africa’s Garden Route: a common pool resource governance perspective

Increasing human demands for ecosystem services due to climate change, population growth, poverty, lack of employment, tourism, and concomitant coastal property development threatens adaptive capacity in South Africa’s coastlines. Adaptation strategies frequently propose ecosystem-based adaptation (EBA) as a model for transformative change. However, several studies point to difficulties implementing EBA across the world. The aim of this paper is to assess to what extent social-ecological systems approaches and common pool resource (CPR) governance theories could inform EBA. Data obtained from interviews and surveys with policy makers and residents in South Africa’s Garden Route District were interpreted using the robustness framework (RF) and the design principles (DPs), two common tools for analyzing CPR governance. We found that the Garden Route coast is threatened by negative interactions between hard public and private infrastructures and ecological infrastructures (the cornerstone of EBA) which are driven by weak local government bodies and asymmetrical power relations. By coding the data for elements/interactions within the RF and then identifying and mapping the DPs onto the RF, we also revealed ways to leverage transformative EBA in the Garden Route. Our analyses suggest that the interactions between human-made and ecological infrastructures, as well as power relation, should be at the core of any development debate. Trade-offs should aim for maximum congruence between sustainability and equity in ecosystem services provisioning. This paper provides some considerations for researchers and decision makers to leverage transformative EBA that could potentially apply to areas experiencing similar challenges.

Evaluating wider benefits of natural flood management strategies: An ecosystem-based adaptation perspective

Climate change is projected to alter river flows and the magnitude/frequency characteristics of floods and droughts. Ecosystem-based adaptation highlights the interdependence of human and natural systems, and the potential to buffer the impacts of climate change by maintaining functioning ecosystems that continue to provide multiple societal benefits. Natural flood management (NFM), emphasising the restoration of innate hydrological pathways, provides important regulating services in relation to both runoff rates and water quality and is heralded as a potentially important climate change adaptation strategy. This paper draws together 25 NFM schemes, providing a meta-analysis of hydrological performance along with a wider consideration of their net (dis) benefits. Increasing woodland coverage, whilst positively linked to peak flow reduction (more pronounced for low magnitude events), biodiversity and carbon storage, can adversely impact other provisioning service-especially food production. Similarly, reversing historical land drainage operations appears to have mixed impacts on flood alleviation, carbon sequestration and water quality depending on landscape setting and local catchment characteristics. Wetlands and floodplain restoration strategies typically have fewer disbenefits and provide improvements for regulating and supporting services. It is concluded that future NFM proposals should be framed as ecosystem-based assessments, with trade-offs considered on a case-by-case basis.

Reducing Hydro-Meteorological Risk by Nature-Based Solutions: What Do We Know about People’s Perceptions?

Nature-based solutions (NBS) have recently received attention due to their potential ability to sustainably reduce hydro-meteorological risks, providing co-benefits for both ecosystems and affected people. Therefore, pioneering research has dedicated efforts to optimize the design of NBS, to evaluate their wider co-benefits and to understand promoting and/or hampering governance conditions for the uptake of NBS. In this article, we aim to complement this research by conducting a comprehensive literature review of factors shaping people’s perceptions of NBS as a means to reduce hydro-meteorological risks. Based on 102 studies, we identified six topics shaping the current discussion in this field of research: (1) valuation of the co-benefits (including those related to ecosystems and society); (2) evaluation of risk reduction efficacy; (3) stakeholder participation; (4) socio-economic and location-specific conditions; (5) environmental attitude, and (6) uncertainty. Our analysis reveals that concerned empirical insights are diverse and even contradictory, they vary in the depth of the insights generated and are often not comparable for a lack of a sound theoretical-methodological grounding. We, therefore, propose a conceptual model outlining avenues for future research by indicating potential inter-linkages between constructs underlying perceptions of NBS to hydro-meteorological risks

Engaging coastal community members about natural and nature-based solutions to assess their ecosystem function

Hazards in coastal ecosystems, such as flooding and land loss, demand natural and nature-based solutions from local communities due to the protective and non-protective services they provide when compared with traditionally engineered approaches. In this context, natural solutions are those that consider conserving existing habitats whereas nature-based solutions are those created by humans. These solutions support important coastal ecosystem functions, such as nutrient uptake, fisheries habitat, soil carbon storage, and surge attenuation. Our main research questions were: (1) Based on community engagement, what are the possible natural and nature-based solutions to address coastal hazards in Breton Sound Estuary, Louisiana? and (2) How do these community co-designed nature-based solutions support various ecosystem functions? To help answer these questions, we leveraged the competency group methodology to incorporate the local needs and traditional ecological knowledge of community stakeholders into collaborative ecosystem modelling. In total, fifteen members regularly met five times over an eight-month period to design nature-based solutions to address coastal hazards. Two nature-based solutions, created marshes and restored ridges, were identified most frequently by the competency group (>75% occurrence) in a final survey. Associated ecosystem functions of the identified solutions were assessed with simulation models to determine future ecosystem functions of nutrient uptake, fisheries habitat, soil carbon storage, and surge attenuation after 20 years. By adding created marshes to an ecosystem, our model results indicate slight increases in nutrient uptake, likely increases to fisheries habitat and soil carbon storage capacity, as well as storm surge attenuation in some areas following ridge restoration. Quantifying these ecosystem functions with management actions has been limited and is needed to assess how natural and nature-based solutions impact local communities and resource users. This novel approach to modeling ecosystem-based solutions through a collaborative modeling process with researchers and residents can be applied elsewhere to assess the viability of natural and nature-based solutions.

Nature-Based Solutions in Coastal Research – A New Challenge for Coastal Engineers?

Nature-based solutions attract more and more interest due to increasing maintenance costs of grey infrastructure, increasing design conditions and growing environmental awareness. Integrating ecosystems in coastal engineering practice not only scores with societal and ecological benefits, such as biodiversity and cultural services, but also provides coastal protection services by attenuating waves and stabilizing sediments. Although nature-based solutions can already be found along many coasts around the globe, coastal engineers are still posed to challenges when evaluating, designing, implementing or maintaining nature-based solutions as guidance and in-depth investigations on efficiency, vulnerabilities and natural dynamics are often lacking. Current challenges for science and practice relate to the general requirements of nature-based solutions, the determination of fundamental data and insecurities and knowledge gaps. To overcome these challenges, close collaboration of engineers and ecologists is necessary.

Local adaptation responses to coastal hazards in small island communities: insights from 4 Pacific nations

Coastal hazards pose a serious and increasing threat to the wellbeing of coastal communities. Adaptation responses to these hazards ideally need to be embedded in the local adaptation context. However, there is little understanding of factors that shape local adaptation choices, especially in rural and remote island settings. In this paper, we compile data on adaptation responses to coastal hazards and key factors that shape adaptation across 43 towns and villages in four Pacific island nations. Local communities cite erosion as a critical coastal hazard, even more often than coastal flooding and sea level rise. We find that communities prefer protective adaptation responses that use local knowledge and resources eand protect coastal ecosystems. Our findings reveal differences in preferred versus implemented adaptation responses.Ecosystem-based adaptation is the most commonly implemented response to coastal hazards. Seawalls and other hard structures are widely preferred and perceived as effective adaptation responses but are often not implemented due to a lack of social, institutional and technical capacity. Retreat is a highly unpopular adaptation response, and difficult to implement, as coastal communities in this study indicate a strong place attachment and are deeply embedded in their social and natural environment. Our results suggest that the selection of adaptation responses might involve important trade-offs between multiple, potentially conflicting, local priorities, such as the preference for seawalls and the need to protect coastal ecosystems. Findings emphasize the importance of considering the local context when making adaptation choices and show that even when responding to the same hazard, adaptation responses can vary significantly depending on local priorities and capacities.

Does mangrove plantation reduce coastal erosion? Assessment from the west coast of India

Mangroves are believed to stabilize the coastlines by controlling erosion and facilitating sediment deposition. Coastal managers often plant mangroves to counter coastal erosion. The state of Gujarat in West India has planted thousands of hectares of mangroves over the years, and control of coastal erosion has been one of the prime reasons of plantation. This study performed a statistical assessment of the effect of the planted mangroves on the coastline changes in the state from 1990 to 2013. The study utilized geographic information system and remote sensing data to demarcate the areas under erosion and accretion during this period, and then compared these changes with the change in mangrove cover using statistical models. This cross-sectional analysis was conducted at the level of a tehsil, an administrative unit below a district. The results show that mangrove plantation did not decrease erosion, not even after normalizing the coastline changes by the length of the coastline and using controls for physical and anthropogenic features of the tehsils. Tehsils with increased mangrove cover witnessed both increased erosion and accretion, although the latter was much higher. The geophysical features of the area appeared to be the main determinants of coastline changes in Gujarat.

Marine reserves can mitigate and promote adaptation to climate change

Strong decreases in greenhouse gas emissions are required to meet the reduction trajectory resolved within the 2015 Paris Agreement. However, even these decreases will not avert serious stress and damage to life on Earth, and additional steps are needed to boost the resilience of ecosystems, safeguard their wildlife, and protect their capacity to supply vital goods and services. We discuss how well-managed marine reserves may help marine ecosystems and people adapt to five prominent impacts of climate change: acidification, sea-level rise, intensification of storms, shifts in species distribution, and decreased productivity and oxygen availability, as well as their cumulative effects. We explore the role of managed ecosystems in mitigating climate change by promoting carbon sequestration and storage and by buffering against uncertainty in management, environmental fluctuations, directional change, and extreme events. We highlight both strengths and limitations and conclude that marine reserves are a viable low-tech, cost-effective adaptation strategy that would yield multiple cobenefits from local to global scales, improving the outlook for the environment and people into the future

Implementation of Nature-Based Solutions for Hydro-Meteorological Risk Reduction in Small Mediterranean Catchments: The Case of Portofino Natural Regional Park, Italy

Nature-based solutions (NBS) are usually defined as complementary or alternative solutions to “grey infrastructures” (traditionally made with cement) aimed at conserving and regenerating the functionality of natural and semi-natural ecosystems. The research to date shows a considerable potential of NBS to address the current challenges related to climate change and geo-hydrological risks. Despite significant interest in NBS by researchers and practitioners, knowledge concerning their practical implementation, monitoring, and evaluation is still lacking. This is particularly true for large-scale NBS. The present paper discusses how such solutions can be implemented in the context of hydro-meteorological risk reduction in small Mediterranean catchments with a strong tourist vocation. The work presented here is situated within the RECONECT Project (Regenerating ECOsystems with Nature-based solutions for hydro-meteorological risk rEduCTion), which aims to contribute to a European reference framework on NBS by demonstrating, upscaling, and replicating large-scale NBS in rural and natural areas. The Italian case study of RECONECT is the Portofino Natural Regional Park, which represents a unique natural landscape element with high ecologic, social, and economic (touristic) value, which is threatened by a range of geo-hydrological hazards, such as flash floods, hyper-concentrated floods, shallow landslides, rockfalls, and storm surges. This paper also presents details of NBS interventions in two pilot catchments (San Fruttuoso and Paraggi) visited by thousands of tourists throughout the year. It addresses some of the key aspects related to monitoring meteorological and hydrological processes, as well as remote sensing activities (i.e., LiDAR surveys), which are necessary for the identification of critical-instability areas along waterways and the reconstruction of dry stone walls. Lastly, a discussion of relevant mitigation and adaptation strategies that are potentially replicable at national and international levels is also provided.

Identifying global hotspots where coastal wetland conservation can contribute to nature-based mitigation of coastal flood risks

Low-lying coastal zones are increasingly exposed to flood risks due to global change including sea level rise, increasing storm intensity and growing coastal population densities. Local to regional-scale studies have demonstrated that conservation or restoration of coastal wetland ecosystems, such as salt marshes and mangroves, provides nature-based risk mitigation, as these wetlands have the natural capacity to mitigate the impacts of storm surges and related flood risks. Yet, it is unknown how important this nature-based mitigation of coastal flood risks is on a global scale. Here we present the results of a global-scale GIS model assessing the global distribution of inland surface areas and population numbers exposed to storm surges that would first propagate through tidal wetlands before they reach the inhabited land, and hence that would receive storm surge mitigation by the mangrove forests and salt marshes. Further our model quantifies the distance travelled by a storm surge through the tidal wetlands as a measure of the magnitude of storm surge mitigation. Results show that on a worldwide scale, about 30% of the flood-exposed low-lying coastal plain benefits from nature-based storm surge mitigation by tidal wetlands, with the largest areas located in deltas (e.g. Pearl River, Yangtze, Mekong) and estuaries (e.g. Elbe). Areas protected by large wetlands, where a storm surge would first propagate through >5 km of tidal wetlands before it reaches vulnerable land and people, are located in river deltas such as of the Guayas (Ecuador), Mississippi (USA) and Ganges-Brahmaputra (India and Bangladesh). About 35% of the global flood-exposed coastal population receives nature-based storm surge mitigation. The majority of that population (80%) is located in five countries, i.e. China, Vietnam, the Netherlands, India and Germany. Areas more exposed to extreme storm surges (Eastern America, Caribbean Sea, Eastern Asia) include hotspot areas where storm surges are travelling through wider tidal wetlands generating higher risk mitigation, as for example in the Mississippi delta, Chesapeake bay, Ganges-Brahmaputra delta or Yangtze delta. Our global assessment aims to increase general awareness on the capacity of nature-based coastal flood risk mitigation, and to stimulate further local scale analyses in support of its wider application around the world.

Multi-dimensional well-being associated with economic dependence on ecosystem services in deltaic social-ecological systems of Bangladesh

While the benefits humans gain from ecosystem functions and processes are critical in natural resource-dependent societies with persistent poverty, ecosystem services as a pathway out of poverty remain an elusive goal, contingent on the ecosystem and mediated by social processes. Here, we investigate three emerging dimensions of the ecosystem service-poverty relationship: economic contribution of provisioning ecosystem services to the household livelihood mix, social-ecological systems producing different bundles of ecosystem services and material wealth versus reported life satisfaction. We analyse these relationships in Bangladesh, using data from a bespoke 1586-household survey, stratified by seven social-ecological systems in the delta coastal region. We create poverty lines to ensure comparability with traditional poverty measures that overlook environmental factors and subjective measurements of well-being. We find that any contribution of ecosystem service-based income to the livelihood mix decreases the likelihood of the incidence of poverty, and of individuals reporting dissatisfaction. We find no relationship between the incidence of material poverty and the specific social-ecological systems, from agriculture to fishery-dominated systems. However, the probability of the household head being dissatisfied was significantly associated with social-ecological system. Individuals living in areas dominated by export-oriented shrimp aquaculture reported lower levels of life satisfaction as an element of their perceived well-being. These results highlight the need for social policy on poverty that accounts for the diversity of outcomes across social-ecological systems, including subjective as well as material dimensions of well-being. National poverty reduction that degrades ecosystem services can have negative implications for the subjective wellbeing of local populations.