Priority knowledge needs for implementing nature-based solutions in the Mediterranean islands

Despite the increasing recognition of the critical role that nature-based solutions (NBS) play in urban resilience, decision-makers in many cities across the Global South continue to prioritize grey infrastructure and engineered solutions. This prevailing approach may offer short-term economic advantages but ultimately falls short in ensuring the long-term sustainability and resilience of communities facing the challenges of a changing climate. This article aims to identify the main enabling factors that foster the application and implementation of NBS in cities, through a detailed analysis of urban NBS case studies. For this reason, the research focused on grey literature, providing insights into real-world implementation and identified 52 case studies through a thorough review of web databases and relevant publications on NBS case studies, supplemented by a web-based questionnaire distributed to identify additional cases. A qualitative methodology was employed to analyse the data collected for each case, covering various phases of each project, including planning, delivery, and stewardship. The findings indicate that enabling the implementation of urban NBS in the Global South requires attention to four key dimensions: good governance, financial feasibility and economic sustainability, social acceptance, and environmental sustainability. Additionally, the results highlight the importance of cross-cutting pathways emerging from these dimensions, such as adopting an integrated, context-specific, and data-driven approach in planning and implementation, enabling mechanisms for participatory approaches and multi-stakeholder engagement, planning for the delivery of multiple benefits by NBS, and prioritizing NBS in urban land acquisition and management policies.

<p>A research project called "Nature based solutions for water management in the peri-urban: linking ecological, social and economic dimensions (NATWIP)" started in 2019 and has the overall goal of: contributing to closing the water cycle gap by exploring the potential that nature-based solutions (NBS) offer to address water management challenges in landscape areas that have been neglected because they lie in the transition zones between the urban and the rural. Since NBS have most commonly been applied in urban areas, it is interesting to broaden the focus to assess the application of NBS on the outskirts of urban areas or the urban fringe as such areas are often affected by expansion processes of the city. Furthermore, these areas have historically played important roles in development and sustenance of urban centres, provision of water-related ecosystem services, particularly water supply, wastewater management and flood control.</p><p>Key NATWIP activities include the establishment of a methodological framework to analyse the social, economic and ecological sustainability dimensions of NBS and subsequently to apply the framework at case study sites in Norway, Sweden, Brazil, India, South Africa and Spain. These case study sites present very diverse water management problems as well as NBS. As more emphasis is placed on the use of NBS in the Nordic countries it is important to identify successful mechanisms for their implementation and monitoring. The case study site in Norway, Skien, represents a highly relevant urban challenge to balance water quality and the increases of water quantity as a result of climate change. This site focuses on the opening of a buried river using blue-green infrastructure as a catalyst for city development. In Sweden rain water harvesting in Gotland has been used in order to address water shortages caused by drought as well as water excess.</p><p>The other case studies sites present interesting examples where the framework is used to explore potential management practices that Nordic countries could learn from. In Spain, the Barcelona Metropolitan backbone is home to green-blue infrastructure and a variety of NBS that aim to improve environmental quality and water cycle management. The Brazilian case study focuses on the most advanced Payment for Environmental Service initiative in Latin America. Through this project, fees collected from water users pay farmers to conserve and restore riparian forests on their lands. In India rainwater harvesting is used to combat water scarcity and compromised water quality in new peri-urban areas. Two case studies in South Africa show how NBS can address the problems of water scarcity in combination with increasingly variable rainfall, frequent drought and floods as well as growing water demand.</p><p>Results from the first assessment of these case study sites will be presented to highlight similarities, differences, challenges, as well as potential synergies for learning from the different case study site contexts.</p>

Seven lessons for planning nature-based solutions in cities

<p>Nature-based Solutions (NbS), inspired or supported by nature, aim to address societal challenges in a fast-changing environment via an integrated and sustainable approach. Effective implementation of such intervention certainly requires compliance with specific societal configurations in different geographies. Here two cases of NbS to hydrological disaster risks are used to demonstrate the relevance of social barriers and opportunities for the full function of NbS.</p><p>Firstly, we introduce a novel large-scale NbS designed for reducing water scarcity in the Bolivian city of Santa Cruz de la Sierra. In this case, strategic reforestation was planned to bring rainfall to a downwind city taking advantage of atmospheric moisture pathways. In the process of co-designing reforestation sites, experiences from failed reforestation projects have improved the site selection originally based solely on the scientific evidence of the moisture pathways. Social barriers to implementation include underground economic activities and pressures for local food production. The latter factor also implies a trade-off between the fulfilments of different sustainable development goals.</p><p>Secondly, a case of landscape-scale NbS that aims to mitigate flood risk from typhoons in Taiwan will be discussed. It consists of a flood diversion framework that directs excess runoff to local farmlands following Typhoon storms. The concept of payment for ecosystem services has been employed to increase the willingness of farmers and landowners to participate in this framework. Institution of compensation for agricultural loss established from previous meteorological disasters has paved the way for implementation. A combination of subsidies and agricultural loss compensation has offered an opportunity for the new intervention to take place in the rice-cropping landscape, while the effect of this ongoing framework will be further documented.</p><p>These two cases show that the inertia from existing policy/institutional schemes and the lessons from past unsuccessful experiences provide an opportunity to identify and overcome social barriers to the implementation of innovative NbS.</p>

The concept of nature-based solutions (NbS) has been endorsed by multiple international organizations as one of the priority approaches to address climate-related challenges. These solutions are versatile, and can simultaneously address challenges such as climate impacts, public health, inequality, and the biodiversity crisis, being uniquely suited for urban adaptation. NbS are particularly relevant in the developing world, where strategies should be as self-reliant as possible, reducing the need for technological processes that require expensive and complex maintenance. NbS can also promote political, societal, cultural, and ultimately, systems change. The purpose of this paper is to present a literature review on the use of NbS for urban adaptation, identifying the main opportunities, challenges, and, most specifically, knowledge gaps, which can be addressed in subsequent research. The present paper identifies four types of knowledge gaps that are particularly relevant for the use of NbS for urban adaptation: future climate uncertainty, lack of site-specific technical design criteria, governance strategies, and effectiveness assessment evaluation. To overcome local governments’ limitations, specific implementation strategies and structures should be considered, centered on knowledge transfer within a transdisciplinary and participatory framework. These should be developed in partnership with urban planning entities, seeking to consolidate these approaches in policies that support social resilience and institutional capacity. Therefore, urban adaptation should be initiated with pilot projects to simultaneously address the urgency for implementation, while allowing urban planning practices the time to adjust, building capacity at the local level, and filling knowledge gaps through the assessment of effectiveness. The climate-resilience of urban tree species adequate to the future climate was identified as a relevant knowledge gap for the implementation of NbS.

Multidimensional assessment of a Nature-based Solution for decentralized greywater treatment in Costa Rica

Floods are a reoccurring global phenomenon. Practical implementation of flood risk management relies heavily on grey infrastructure with a lesser focus on nature-based solutions (NBS). With the rising awareness about ecosystem services, natural flood management measures are getting more attention from scientists and policymakers. Lithuanian authorities in the national flood risk management plan provide four NBS for flood management: afforestation, wetlands restorations, agri-environmental measures, and water retention in urban areas (e.g., ponds). However, implementation of the NBS requires more land than grey infrastructure. In the case of Lithuania, in some instances, the NBS require a change of the land use or impacts upon the private land. Therefore, it can be influenced by the legal regulations related to land use planning and protection of private property rights. The problems may occur in case of the insufficient, incomplete, incoherent, or contradictory legal framework. The analysis revealed that the Law on the Land, the Law on the Special Land Use Conditions, and the Law on the Territorial Planning are insufficiently coordinated, which may influence implementation of the NBS on the private property. The afforestation is foreseen only for the public land. However, those lands are mainly used for the agriculture, and in this case possibilities to change the land use are restricted. A similar problem may occur if the area for the afforestation lays within the protected area. The Law on the Protected Areas allows land use changes only in exceptional circumstances; the flood mitigation is not one of them. The incoherence or incompleteness of law, which can hamper implementation of NBS, can occur not only in Lithuania. Therefore, the study can be a starting point for further investigations and solutions in this regard.

The conceptual quantitative assessment framework for Nature-based Solutions (NbS)

Subject. We investigate the potential for integration of ecosystem approaches to "nature-based solutions" and circular economy aimed at sustainable development. Objectives. The focus is on implementation of principles of circular economy and "natural solutions" as important elements of the sustainable development plan. Methods. We employ analytical and logical methods, theoretical and practical issues of sustainable development in the context of concepts of circular and natural economy. Results. We address the evolution of the circular economy concept, emphasize that it cannot support sustainability, if social processes are ignored. The paper explores the intersection points of the circular and green economy. It shows that ecosystem approaches result in environmental, social, and economic benefits. The potential of achieving sustainability through the synergy of "nature-based solutions" and circular business models is demonstrated on the case of reusing urban wastewater. Conclusions. The circular economy cannot be considered as a stage in the "green economy" development. It is important to use them together, when sustainable development strategies are designed. "Natural solutions" provide opportunities for interdisciplinary studies on development and implementation of nature-based solutions, their versatility creates a potential for trade-offs. Cities have a potential to implement sustainable development concepts through the synergy of "natural solutions" and circular business models. Integrated use of the potential of complementary concepts is required.

The Caribbean islands are among the 25 most-vulnerable nations in terms of disasters per-capita or land area, and climate change is only expected to intensify these vulnerabilities. The loss caused by climate events drags the ability of the Caribbean countries to invest in infrastructure and social programs, contributing to slower productivity growth, poorer health outcomes, and lower standards of living. Within this context, building resiliency should become a priority for the Caribbean countries. The series “Building a more resilient and low-carbon Caribbean”, focuses on improving the resiliency, sustainability and decarbonization of the construction industry in the Caribbean. The results show that increasing building resiliency is economically viable for the high-risk islands of the Caribbean, generating long term savings and increasing the infrastructure preparedness to the impacts of CC. The first three reports of the series analyze the economic losses caused by climate related events, the benefits of improving building resiliency to reduce those economic losses and the benefits of subsidized financing for resilient buildings in the Caribbean. The results show that increasing building resiliency is economically viable for the high-risk islands of the Caribbean, generating long term savings and increasing the infrastructure preparedness to the impacts of CC. This report Report 4: Infrastructure Resilience in the Caribbean through Nature Based Solutions - extends the previous analysis to examine the potential role for nature-based solutions (NBSs) in the region. The report first defines NBSs in the context of the Caribbean construction industry. It then considers specific NBS options that could be viable in the region. Next, the report reviews the status of NBS related projects in the Caribbean, including efforts supported by the IDB. This analysis also identifies several barriers to the development of NBSs in the region. Finally, the report suggests measures that can be taken to address these barriers and increase the use of NBSs in the Caribbean.

In recent years, the changing weather patterns caused by climate change have already impacted the population, but in 2022, these weather extremes surpassed the ones of previous years. Severe droughts across Europe posed significant challenges, primarily through water scarcity and caused severe (security of supply and economic) damages to different societal sectors. Drier summers and warmer, snow-less winters significantly change the water cycle and thus the amount of naturally retained rainwater on site. A long-term, sustainable solution is the widespread implementation of nature-based solutions.The Lake Velence watershed in Hungary has been showing signs of drying up for years. To implement nature-based solutions, the catchment's natural features, the stakeholders' general requirements, the economic opportunities, and possible benefits must be incorporated. Small- and large-scale agricultural activities face a growing deficit in irrigation water, while the surrounding settlements of Lake Velence can collect a significant amount rainwater. The research focuses on the potential amount of rainwater that can be collected in the selected hilly settlements, it’s uses, and its ability to generate additional income. We evaluated the costs and benefits of implementing or non-implementing nature-based solutions based on the extent of rainwater usage. Using basic calculations of the area's present and possible future cultivation/agricultural activities, we examined the impacts of blue-green infrastructures on local GDP through a lost profit versus available surplus income comparison.

Financing climate adaptation in Flemish cities: Unpacking financial strategies and policy dynamics for nature-based solutions

This study presents insights from the EU Biodiversa+ NatureScape project (2025–2028). The project offers a new perspective for understanding nature-based solutions (NBS) in cities by focusing on the post-implementation phase, in which environmental justice in urban planning is put to the test.In recent years, cities have increasingly pursued NBS in urban development projects such as community gardens, green roofs, and temporary green spaces to support biodiversity while simultaneously improving human well-being. Despite growing recognition of NBS in urban planning, their potential for cities' socio-ecological transformation remains constrained by overlooked post-implementation challenges. While the planning and implementation of NBS already receive considerable attention, critical dimensions of environmental justice – distributive equity, accessibility, and procedural justice for continuous public participation and stakeholder engagement – become apparent only in the post-implementation phase. This phase is characterized by dynamic interactions between social and ecological components, shaping whether NBS are consolidated and sustained in ways that contribute in the long term to transformative effects and environmental justice, or whether they instead undermine these aims.NatureScape addresses this critical transition and its challenges in urban planning. Through transformation laboratories (T-Labs) in seven cities (Oslo, Dublin, Riga, Milan, Lisbon, Lublin, and St. Gallen), the research team explores two central questions: (1) What enablers and barriers in urban planning shape the post-implementation stewardship of urban NBS? (2) What governance mechanisms, strategies, and measures lead to the successful integration of urban NBS into urban planning to unfold their transformative potential for biodiversity-positive transitions and environmental justice?Initial findings from the T-Labs reveal crucial barriers. The post-implementation phase is often reduced to technical maintenance. Insufficient incorporation of NBS into urban planning is associated with fragmented institutions and responsibilities, weak strategic and instrumental anchoring, financial insecurity, and the erosion of institutional and political support.The project identifies interconnected governance mechanisms that could successfully integrate NBS into urban planning: adaptive planning processes, institutional anchoring that fosters shared ownership among stakeholders, co-management approaches with formal agreements, public planning frameworks, and institutional structures that support integrated action. Together, these mechanisms highlight stewardship as a pivotal principle for achieving just and biodiversity-positive urban futures.

Mainstreaming Nature-based Solutions (NbS) is vital to translating the EU Water Resilience Strategy (2025) into meaningful action. Yet, bridging the gap between policy design and practical implementation requires not only technical and financial alignment, but also broad social acceptance and participatory governance.The NbS Fresco©, supported by the Horizon Europe project NBRACER (n°101112836), emerges as an innovative tool designed to foster this social dimension by raising awareness and engagement around NbS. Inspired by the successful Climate Fresk, the NbS Fresco© builds on proven approaches that use visual storytelling and collaborative learning to make complex scientific knowledge accessible and emotionally resonant. Research shows that traditional environmental communication often fails to engage the public effectively because scientific concepts are presented as isolated facts with limited context. Storytelling helps connect logic with emotion, enhances trust, improves information retention, and motivates action.The NbS Fresco©’s scope currently focuses on three landscapes (urban, rural, and coastal/marine) and the set of 22 NbS covered in the first version of this serious game addresses a variety of water resilience-related solutions. Through a visual, interactive, and collective narrative experience, the Fresco transforms the complex, interdisciplinary science of NbS into an engaging format that empowers participants to understand the systems behind them, recognize their benefits, and build hope and connection to nature. While not a practical training on NbS implementation, the Fresco’s strength lies in fostering social acceptance and stakeholder buy-in, both critical factors for mainstreaming NbS in integrated water management.Citizen engagement approaches exemplified by the Fresco contribute to integrated governance by democratizing knowledge, encouraging shared learning, and supporting adaptive management through increased awareness. This participatory dimension is essential to aligning societal values with the EU’s water resilience goals and advancing NbS as viable, complementary alternatives to grey infrastructure.This presentation will introduce and discuss the NbS Fresco©’s potential as a scalable, agile tool to close the implementation gap by building collective intelligence and fostering inclusive dialogue. It underscores the importance of innovative engagement methods in complementing scientific evidence and policy frameworks to accelerate NbS adoption, thereby enhancing water resilience and socio-ecological sustainability across Europe.

Increasing urbanization and climate change challenges are leading to relevant environmental, economic and social pressures on European cities. These include increasing flood hazards and the urban heat island (UHI) effect. Nature-Based Solutions (NBS) are increasingly recognized within strategies to provide multiple ecosystem services to mitigate existing risks and pressures, as well as to make cities more resilient and livable. Although being increasingly addressed within the literature, NBS implementation on the ground still faces many technical and financial barriers. This paper aims to test the potential of selected NBS in mitigating the effects of identified climate change risks, i.e., the UHI effect and urban floods, in the Turin urban area (north-western Italy). Four different intervention NBS-based scenarios are developed. The supply of ecosystem services by NBS in each scenario is assessed using InVEST models and the effectiveness of NBS investments is analyzed by calculating and comparing the associated costs and benefits. Different results in terms of effectiveness and economic viability are observed for each scenario and each NBS. Flood risk mitigation oriented NBS seem to have the most impact, in particular forested green areas and retention ponds. The results are relevant to suggest policy mix strategies to embed NBS in city planning.