1. Introduction
IPCC's projections for the present century foresee an acceleration of sea-level rise, along with an increase in the frequency of storms, heatwaves, flooding episodes, and related climate risks (Abadie et al., Reference Abadie, de Murieta and Galarraga2020). Between 1995 and 2015, 56% of damages caused by weather-related disasters accounted for flooding episodes (United Nations Office for Disaster Risk Reduction, 2019). The intensity and frequency of these episodes is causing important economic losses in Europe (Kumar et al., Reference Kumar, Debele, Sahani, Aragão, Barisani, Basu, Bucchignani, Charizopoulos, Di Sabatino, Domeneghetti, Edo, Finér, Gallotti, Juch, Leo, Loupis, Mickovski, Panga, Pavlova, Zieher, Damia and Jay2020). Estimates indicate that by 2035, 42% of Europe's population will be living in coastal areas, where climate risks are on the rise (Maul & Duedall, Reference Maul, Duedall, Finkl and Makowski2019). In this context, including measures capable to address climate change hazards in urban planning is gaining importance (Pour et al., Reference Pour, Wahab, Shahid, Asaduzzaman and Dewan2020). Urban greening has been long recognised as an optimal strategy to improve living conditions (e.g., enhancing well-being and quality of life for urban residents, decreasing pollution, or providing recreational and aesthetic values, among others). It can contribute for water and climate regulation, while also providing additional ecosystem services highly relevant for human-well-being (e.g., air quality, biodiversity increase, food provision) (Esmail et al., Reference Esmail, Cortinovis, Suleiman, Albert, Geneletti, Mörtberg, Elsevier and Wendy2022). Ecosystem-based adaptation (EbA) measures are presented as cost-effective interventions and solutions supported by nature, to restore natural or modified ecosystems, and address economic, social, and environmental problems related to climate change (Cohen-Shacham et al., Reference Cohen-Shacham, Andrade, Dalton, Dudley, Jones, Kumar, Maginnis, Maynard, Nelson, Renaud, Welling and Walters2019; Commission et al., Reference Commission and for Research2015; Kumar et al., Reference Kumar, Debele, Sahani, Aragão, Barisani, Basu, Bucchignani, Charizopoulos, Di Sabatino, Domeneghetti, Edo, Finér, Gallotti, Juch, Leo, Loupis, Mickovski, Panga, Pavlova, Zieher, Damia and Jay2020).
In recent years, numerous articles have been published addressing the implementation of EbA and proposing frameworks for its evaluation and planning. Albert et al. (Reference Albert, Brillinger, Guerrero, Gottwald, Henze, Schmidt, Ott and Schröter2021), Kumar et al. (Reference Kumar, Debele, Sahani, Aragão, Barisani, Basu, Bucchignani, Charizopoulos, Di Sabatino, Domeneghetti, Edo, Finér, Gallotti, Juch, Leo, Loupis, Mickovski, Panga, Pavlova, Zieher, Damia and Jay2020), Raymond et al. (Reference Raymond, Frantzeskaki, Kabisch, Berry, Breil, Nita, Geneletti and Calfapietra2017) and Sowińska-Świerkosz and García (Reference Sowińska-Świerkosz and García2021) present evaluation frameworks for EbA planning, operationalisation, and implementation stages. Calliari et al. (Reference Calliari, Staccione and Mysiak2019) and Zölch et al. (Reference Zölch, Henze, Keilholz and Pauleit2017) seek to evaluate EbA effectiveness under future climate conditions, while Liquete et al. (Reference Liquete, Udias, Conte, Grizzetti and Masi2016) and Raymond et al. (Reference Raymond, Frantzeskaki, Kabisch, Berry, Breil, Nita, Geneletti and Calfapietra2017) are interested in assessing their co-benefits in urban and peri-urban contexts. Other frameworks proposed are related to the conceptualisation of EbA (Brink et al., Reference Brink, Aalders, Ádám, Feller, Henselek, Hoffmann, Ibe, Matthey-Doret, Meyer, Negrut, Rau, Riewerts, von Schuckmann, Törnros, von Wehrden, Abson and Wamsler2016; Matthews et al., Reference Matthews, Lo and Byrne2015) and the integration of these measures in local adaptation plans and strategies (e.g., Dumitru et al., Reference Dumitru, Frantzeskaki and Collier2020; Geneletti & Zardo, Reference Geneletti and Zardo2016; Raymond, et al., Reference Raymond, Frantzeskaki, Kabisch, Berry, Breil, Nita, Geneletti and Calfapietra2017; Zölch et al., Reference Zölch, Wamsler and Pauleit2018). However, there is a recognised need to understand how assessment frameworks can facilitate the scaling up of EbA interventions at the local level. This involves a better knowledge of their benefits and performance, their recognition in local adaptation plans and governance models, and the availability of sustainable funding resources for their implementation and maintenance. This need is aligned with the European Union (EU) commitment to protect natural capital and value ecosystem services (Raymond, Frantzeskaki, et al., Reference Raymond, Frantzeskaki, Kabisch, Berry, Breil, Nita, Geneletti and Calfapietra2017) as recalled in different strategies (e.g., Biodiversity Strategy to 2030, Green Infrastructure strategies, EU Thematic Strategy on the Urban Environment, European Strategy on Adaptation to Climate Change, European Green Deal, Nature Restoration Law). Within this EU policy framework, green infrastructure has been recognised as a cost-effective alternative to more traditional adaptation approaches, such as grey or hard infrastructure (Davies et al., Reference Davies, Chen, Sanesi, Lafortezza, Martin and Esther2021). This perspective is reinforced by the European Research and Innovation Roadmap for Nature-Based solutions (NBS), which provides an advanced systemic understanding of, and approaches to, NBS development and implementation as a strategic action (El Harrak et al., Reference El Harrak, Lemaitre Biodiversa, Decleer, McDonald, McQuaid, Palomo, Raymond, Wendling, Wilk, Reil, Berry, Naumann, MacIntyre, Bulkeley, Declerck, Delcroix, Donato, Eggermont, Freitas and Wild2023).
Despite the increasing recognition of EbA at the EU level,Footnote 1 its uptake remains significantly lower at local level, where landscape and urban planning are developed (Albert et al., Reference Albert, Brillinger, Guerrero, Gottwald, Henze, Schmidt, Ott and Schröter2021). Discussions on planning and governance of EbA are needed (Kabisch et al., Reference Kabisch, Frantzeskaki and Hansen2022), as climate adaptation should occur at this scale, where adaptation strategies can be targeted and citizens can participate in their design and creation (Picketts et al., Reference Picketts, Déry and Curry2014). When including EbA in policy agendas, governance challenges emerge, such as policy incoherence or misalignment between different local, regional, or national administrations (Davies et al., Reference Davies, Chen, Sanesi, Lafortezza, Martin and Esther2021; Seddon et al., Reference Seddon, Chausson, Berry, Girardin, Smith, Turner, Janet, Yadvinder, Nathalie, Martin, Chris, Nancy and Monica2020). Adapting to governance challenges in EbA (Kabisch et al., Reference Kabisch, Korn, Stadler and Bonn2017), and developing methodological approaches to integrate them into local planning (Tiwari et al., Reference Tiwari, Rodrigues, Lucy and Gharbia2022) is crucial for an effective implementation and upscale of these measures. To integrate EbA in local governance, it is necessary to deepen our understanding of the underlying drivers and processes, such as the ecosystem regenerative potential of EbA and their governance embedding. (Frantzeskaki et al., Reference Frantzeskaki, Kabisch and McPhearson2016). One example is the interrelationship between nature and social systems, particularly the role that urban green initiatives can play in enhancing, among others, biodiversity, recreation opportunities, or climate change mitigation and adaptation. Advancing research in this field can provide systematic guidance to policy makers for the effective implementation of EbA (Wamsler et al., Reference Wamsler, Wickenberg, Hanson, Alkan Olsson, Stålhammar, Björn, Falck, Gerell, Oskarsson, Simonsson, Torffvit and Zelmerlow2020).
While research has focused on analysing the co-benefits of EbA through individual case studies, the broader implications for policy, planning, and governance are often neglected (Frantzeskaki, Reference Frantzeskaki2019). To further advance the implementation of EbA strategies, a better understanding of the related instruments and policy processes operating at the local level is essential. This will increase its potential for replication and scaling up, narrowing the existing knowledge gap between researchers and practitioners. To this end, the main goal of this study is to develop a decision-support framework that identifies and evaluates key operational mechanisms involved in the local-level implementation of EbA initiatives. To this end, the main research goal of this study is to identify and evaluate key operational mechanisms involved in the local implementation of EbA initiatives and to develop a decision-support framework based on these insights. This research addresses the following specific questions: (i) What governance factors may influence the implementation process of EbA in local planning?; (ii) How effectively does the existing policy framework support the implementation and management of EbA?; and (iii) How adequate is the funding model for enabling effective implementation of EbA at the local level? Moreover, this study tests the assessment framework in a coastal urban context, specifically focusing on 10 case studies in Spain (Santander, Barcelona, and Barcelona Metropolitan Area, Vilanova i la Geltrú, Palma, Benidorm) and Portugal (Oeiras and Lisbon). Three of the assessed interventions are derived from the EU-funded SCORE project, while the remaining seven were retrieved from online EBA/NBS repositories. All of them propose solutions to address flooding hazards in coastal areas. By providing insights into the EbA implementation process, the proposed framework aims to enhance the efficacy and sustainability of adaptation efforts.
The remainder of this paper is structured as follows: first, the conceptual discussion of factors influencing the implementation process of EbA (Section 2). It follows the methodological foundations for the proposed framework and the selection of case studies to pilot it (Section 3). Section 4 includes the results of validating the framework in different case study areas, and the discussion of the criteria proposed, to finalise with the conclusions (Section 5).
2. Factors influencing the EbA implementation
Different actors intervene in the design and implementation process of EbA, which takes place in a variety of contexts. Planning appropriate solutions very often occur at local level, and the principles inspiring them (e.g., multifunctionality, equity, efficiency, and sustainability) should be reflected in policies developed at this scale (Leone, Reference Leone2021).
The institutional proximity between local governments and citizens is a great opportunity for innovation, and the identification of societal demands, and challenges which inspire the design of policies. Laying out appropriate governance processes in cities contributes to embrace innovative environmental policies (Frantzeskaki et al., Reference Frantzeskaki, Kabisch and McPhearson2016). Governance refers to formal and informal institutions, rules, mechanisms, and processes, for planning and decision-making (Ostrom, Reference Ostrom2005; Tacconi, Reference Tacconi and Nicholas2011). The lack of proper governance structures hinders a wider implementation of EbA (Zölch et al., Reference Zölch, Wamsler and Pauleit2018). Very often legal frameworks and procedures, and other responsibilities related at this stage are distributed among multiple departments and agencies. This institutional fragmentation is a barrier for an effective implementation (McKenna & Naumann, Reference McKenna, Naumann, Nadja and Korn2017). In contrast, adaptive and flexible governance forms are enablers to reconceptualise green infrastructure for climate change adaptation (Kabisch et al., Reference Kabisch, Frantzeskaki and Hansen2022; Matthews et al., Reference Matthews, Lo and Byrne2015) and successfully implement and uptake these solutions (Cohen-Shacham et al., Reference Cohen-Shacham, Andrade, Dalton, Dudley, Jones, Kumar, Maginnis, Maynard, Nelson, Renaud, Welling and Walters2019; Kapos et al., Reference Kapos, Wicander, Salvaterra, Dawkins and Hicks2019; Nesshöver et al., Reference Nesshöver, Assmuth, Irvine, Rusch, Waylen, Delbaere, Haase, Jones-Walters, Keune, Kovacs, Krauze, Külvik, Rey, van Dijk, Vistad, Wilkinson, Wittmer, Barceló Cullerés and Gan2017; Wamsler et al., Reference Wamsler, Wickenberg, Hanson, Alkan Olsson, Stålhammar, Björn, Falck, Gerell, Oskarsson, Simonsson, Torffvit and Zelmerlow2020).
When designing and implementing the EbA intervention, challenges such as overlapping competences, and shared management may arise, complicating the coordination with government agencies operating at different (vertical cooperation) or same levels (horizontal cooperation) (Droste et al., Reference Droste, Schröter-Schlaack, Hansjürgens, Zimmermann, Kabisch, Korn, Stadler and Bonn2017; Matthews et al., Reference Matthews, Lo and Byrne2015). Therefore, intragovernmental and intergovernmental cooperation is needed to harmonise policies and processes (Kapos et al., Reference Kapos, Wicander, Salvaterra, Dawkins and Hicks2019; Leone, Reference Leone2021). The decision process might be inspired by a power-relation, where the investment decision might be influenced by individual interests, such as land ownership (Seddon et al., Reference Seddon, Chausson, Berry, Girardin, Smith, Turner, Janet, Yadvinder, Nathalie, Martin, Chris, Nancy and Monica2020). While not having the necessary political support turns into a barrier (Mell et al., Reference Mell, Clement and O'sullivan2022), a co-creation process involving local citizens and stakeholder collaboration (Albert et al., Reference Albert, Brillinger, Guerrero, Gottwald, Henze, Schmidt, Ott and Schröter2021; Brink et al., Reference Brink, Aalders, Ádám, Feller, Henselek, Hoffmann, Ibe, Matthey-Doret, Meyer, Negrut, Rau, Riewerts, von Schuckmann, Törnros, von Wehrden, Abson and Wamsler2016; Wamsler et al., Reference Wamsler, Wickenberg, Hanson, Alkan Olsson, Stålhammar, Björn, Falck, Gerell, Oskarsson, Simonsson, Torffvit and Zelmerlow2020) facilitates public acceptance of the intervention (Anderson & Renaud, Reference Anderson and Renaud2021; Sowińska-Świerkosz & García, Reference Sowińska-Świerkosz and García2021) and increases the legitimacy of the process (Nesshöver et al., Reference Nesshöver, Assmuth, Irvine, Rusch, Waylen, Delbaere, Haase, Jones-Walters, Keune, Kovacs, Krauze, Külvik, Rey, van Dijk, Vistad, Wilkinson, Wittmer, Barceló Cullerés and Gan2017). Involving local actors in planning and implementation integrates their knowledge, customizing measures to the local context and thereby enabling the process (Niki et al., Reference Niki, Borgström, G, E, E, Nadja and Korn2017).
The support of high community levels (governors, and other executive representatives) and greater involvement of stakeholders are key to integrate EbA and related concepts (e.g., regulation, provision, and cultural-based ecosystem services) in urban planning (Zölch et al., Reference Zölch, Wamsler and Pauleit2018). It also makes it possible to consider the valuation and accounting of multiple co-benefits in the decision-making process (Anderson & Renaud, Reference Anderson and Renaud2021; Kabisch et al., Reference Kabisch, Frantzeskaki and Hansen2022; Mell et al., Reference Mell, Clement and O'sullivan2022; Toxopeus & Polzin, Reference Toxopeus, Polzin, Dewil, Evans, Tansel and Zhang2021). The lack of know-how is identified as a frequent barrier in ecosystem management practices (Brink et al., Reference Brink, Aalders, Ádám, Feller, Henselek, Hoffmann, Ibe, Matthey-Doret, Meyer, Negrut, Rau, Riewerts, von Schuckmann, Törnros, von Wehrden, Abson and Wamsler2016). To convey the necessary knowledge and evidence, scientists are to be involved in the process. More evidence on the effectiveness of the measures across spatial and temporal scales contribute to decrease the uncertainty surrounding their performance (Krauze & Wagner, Reference Krauze and Wagner2019). Sufficient knowledge on EbA (Davies et al., Reference Davies, Chen, Sanesi, Lafortezza, Martin and Esther2021; Kapos et al., Reference Kapos, Wicander, Salvaterra, Dawkins and Hicks2019; Mell et al., Reference Mell, Clement and O'sullivan2022; Schneider et al., Reference Schneider, Walz, Albert and Lipp2021; Zölch et al., Reference Zölch, Wamsler and Pauleit2018) and existence of monitoring framework to guide the implementation process and follow-up their performance (Cohen-Shacham et al., Reference Cohen-Shacham, Andrade, Dalton, Dudley, Jones, Kumar, Maginnis, Maynard, Nelson, Renaud, Welling and Walters2019; Geneletti & Zardo, Reference Geneletti and Zardo2016; Nesshöver et al., Reference Nesshöver, Assmuth, Irvine, Rusch, Waylen, Delbaere, Haase, Jones-Walters, Keune, Kovacs, Krauze, Külvik, Rey, van Dijk, Vistad, Wilkinson, Wittmer, Barceló Cullerés and Gan2017) are fundamental requirements for an adequate management of these interventions.
Moreover, it is important to understand, map, and balance the synergies and trade-offs associated with EbA implementation (Dumitru et al., Reference Dumitru, Frantzeskaki and Collier2020). While these interventions are often associated with significant benefits, it is equally important to consider whether they might have adverse societal impacts (e.g., green washing, land speculation leading to green gentrification) (Anguelovski & Corbera, Reference Anguelovski and Corbera2023). Besides knowledge creation, dissemination through suitable channels is also recognised as a significant facilitator (Sarabi et al., Reference Sarabi, Han, Romme, de Vries, Wendling, Peter, Laura, Teresa and Anna2019). Sharing experiences and lessons learnt through knowledge repositories (i.e., Oppla, Urban Nature Atlas) is a way to disseminate and increase the knowledge of existing experiences with potential to be replicated elsewhere.
In most situations, existing regulations have not been specifically designed to address EbA implementation (Davis McKenna & Naumann, Reference McKenna, Naumann, Nadja and Korn2017). Geneletti and Zardo (Reference Geneletti and Zardo2016) identify the failure to explicitly refer to EbA in plans and regulations as a disabler for their implementation. Increasing the inclusion of EbA in adaptation plans and strategies, underpinned by ecosystem protection principles, may facilitate to encompass all environmental components and upscale these interventions. Avoiding conflicting regulations, i.e., between building permits and environmental plans which might hinder EbA implementation (Seddon et al., Reference Seddon, Chausson, Berry, Girardin, Smith, Turner, Janet, Yadvinder, Nathalie, Martin, Chris, Nancy and Monica2020). The existence of transnational treaties (Baravikova, Reference Baravikova2020), as the EU strategies mentioned above, favours a wider inclusion of environmental regulations in national, regional, and local legislation, towards a green transition in cities.
Advancing EbA requires securing sufficient economic and financial resources sourced from diverse institutions, including but not limited to EU funds, national programs, local budget, private funds. Toxopeus and Polzin (Reference Toxopeus, Polzin, Dewil, Evans, Tansel and Zhang2021) highlight the lack of coordination between private and public bodies as a key barrier for EbA financing. To overcome this challenge, innovative funding mechanisms might be explored, such as the establishment of partnerships to secure resources from different public and private institutions (Seddon et al., Reference Seddon, Chausson, Berry, Girardin, Smith, Turner, Janet, Yadvinder, Nathalie, Martin, Chris, Nancy and Monica2020). This could be the case of Public–Private Partnerships (PPP), which combine public sector regulations with the operational flexibility of the private sector (van Ham & Klimmek, Reference van Ham, Klimmek, Nadja and Korn2017). Fiscal incentives, such as the reduction of municipal fees or ecological fiscal transfers can be suitable options to enable the successful implementation and uptake of EbA (Albert et al., Reference Albert, Brillinger, Guerrero, Gottwald, Henze, Schmidt, Ott and Schröter2021; Kumar et al., Reference Kumar, Debele, Sahani, Aragão, Barisani, Basu, Bucchignani, Charizopoulos, Di Sabatino, Domeneghetti, Edo, Finér, Gallotti, Juch, Leo, Loupis, Mickovski, Panga, Pavlova, Zieher, Damia and Jay2020). Moreover, the structural composition of the local budget plays a central role in shaping the integration of EbA into policy objectives. Ensuring a stable, and ideally growing, budget allocation may guarantee an effective embeddedness of these measures in local planning, overcoming the short-term allocation of financial resources to measures which co-benefits emerge in the long term (Niki et al., Reference Niki, Borgström, G, E, E, Nadja and Korn2017).
3. Materials and methods
Building upon the review of barriers and enablers for EbA implementation identified in Section 2, it is proposed an assessment framework intended to support the decision process accompanying the EbA implementation process. There are three core categories which enfold the proposed criteria: (i) governance system; (ii) policy framework; (iii) funding model. To explore the governance system for EbA implementation at local level, the criteria considered include cooperation, management, decision process, and trade-offs and synergies. The criteria for assessing the adequacy of existing policy framework to implement and manage EbA include the existence of adaptation plans or strategies, fiscal incentives, and regulations, as well as global or bilateral treaties or agreements. Sustainable funding is necessary to drive the implementation of EbA. Identifying the source of funding, understanding the local budget structure, and the existence of fiscal incentives and partnerships as alternative financial support options are the criteria considered in this area Figure 1. Table 1 ¡Error! No se encuentra el origen de la referencia. provides further details of the categories and criteria considered.
Figure 1. Summary of the methodological process.
Table 1. Categories, criteria, and description of the assessment framework
To test the assessment framework, there were selected several EbA experiences across the Iberian Peninsula. Case studies were limited to (i) EbA interventions suitable for flood mitigation; and (ii) located in coastal cities (as described in Eurostat (Reference Eurostat2024)). This study started by analysing various EbA implementation experiences, derived from the case study regions included in the EU SCORE project: a wetland restoration project in the beach of ‘Platja Llarga’ in Vilanova i la Geltrú (Province of Barcelona, Spain); a riparian reforestation in various intermittent rivers in Benidorm (Province of Alicante, Spain); and the green corridor of ‘Eixo Verde e Azul’ (Green-Blue Axis) in Oeiras (Metropolitan Area of Lisbon, Portugal). These initiatives were thoroughly analysed through the review of grey literature (adaptation plans, urban planning, etc.) and in-depth interviews with relevant practitioners (see Supplementary Material).
Additionally, seven case studies were included in the assessment after reviewing online EbA catalogues, such as the Urban Nature AtlasFootnote 2, OPPLAFootnote 3, GeoIKPFootnote 4, and the Climate Adapt databaseFootnote 5. These case studies were selected to further test the framework based on the criteria mentioned above. The EbA experiences included urban farming in the ‘Hort del Cànem’, the green corridor of ‘Passeig Sant Joan’, and the introduction of Sustainable Urban Drainage System (SUDS) in the park of Joan Reventós (Barcelona, Spain); a dunes restoration initiative in the Barcelona Metropolitan Area; the Monsanto Green Corridor (Lisbon, Portugal); wetland restoration in the park ‘Las Llamas’ (Santander, Spain); and the renaturation of Palma beach (Palma, Spain). The assessment was based on the review of grey literature, and direct contact with relevant stakeholders involved in the implementation process of selected interventions, as well as online interviews whenever stakeholders were available.
Based on the information retrieved from the literature review and the interviews, it was assessed whether the criteria and sub-criteria included in the framework were met in the selected case studies. This exercise helps to validate the impact of the selected criteria throughout an EbA implementation process.
4. Results and discussion
Several basic elements are necessary for setting the course for climate change adaptation and the successful implementation of EbA interventions. These include the governance system, as referred, among others, to political support, operational knowledge and scientific expertise, and the involvement of key stakeholders. The adequacy of the policy framework, with non-conflicting regulations, and the availability of sustainable funding are some of the elements discussed next, based on the results of testing the decision-support framework in 10 case studies. Table 2 summarizes the information retrieved from interviews and review of the grey literature of the 10 selected case studies. It indicates which of the selected criteria were met during the EbA implementation process, and which were not.
Table 2. EbA measures assessed with the decision-support framework
Source:
a Information obtained from grey literature review
b information obtained from grey literature review and interviews.
Legend: 1 indicates that the criterion is fulfilled; −1 indicates the criterion is not fulfilled; o indicates that no evidence was found to validate the accomplishment of the criteria.
1 Sustainable Urban Drainage Systems
Building on results reported, aspects such as political support, operational knowledge on EbA, and synergies with future projects are present in nearly all the case studies. In contrast, none of the case studies met the criteria for fiscal incentives, while vertical cooperation was only met in one.
As for the measures that were only assessed for a single study area, there was a clear prevalence of criteria being fulfilled (score = 1) (Table 2). ‘Political support’, ‘Operational knowledge on EbA’, ‘Source of funding’, and ‘Regulations’ received consistent scores of one across nearly all measures. These could be considered critical success factors when implementing EbA interventions. In contrast, certain criteria may suggest systemic challenges, scoring −1 or 0 in mostly all the measures assessed. These are ‘Vertical cooperation’, ‘Treaties/Agreements’, ‘Fiscal incentives’, and ‘Trade-off or disservice’.
When assessing the measures individually, more accurate information was available in those cases where it was possible to interview practitioners. This applies in Dune restoration and Beach renaturation, which show the most consistent evaluations across all criteria, with very few scores −1 or 0. Both interventions show to have broad institutional backing, to be supported by scientific knowledge and operational experience, and exhibit solid policy frameworks and cooperation mechanisms. In the case of Dunes restoration, only ‘Scientific knowledge’ and ‘Treaties/Agreements’ are not fulfilled. Beach renaturation lacks negative scores, though evidence was not found in the case of ‘Trade-off or disservice’ and ‘Partnerships’. In the assessment of SUDS in a park, where no interviewed was conducted, several pieces of information are missing, especially in relation to the policy framework and sustainable funding evaluation.
Wetland restoration was assessed in two study areas, while Green corridors in three. The frequency of evaluation of these two EbA across the proposed range of criteria are represented in the figure below (Figure 2). Each cell shows how many times the score (−1, 0, or 1) was assigned to a criterion for each measure. Cells with darker shade show a higher frequency.
Figure 2. Green corridors and wetland restoration. Frequencies per criteria.
As for the mostly repeated criteria across the areas assessed, we found that “Co-creation” was met in all sites assessed (1). ‘Scientific knowledge’, ‘Political support’, and ‘Synergies’ with other projects and initiatives were considered in both Wetland restoration and Green corridors, suggesting being a widely valued criteria in both contexts. ‘Institutional cooperation’ was either not fulfilled or with insufficient evidence, indicating broader necessary efforts in institutional cooperation.
There was a divergent assessment in both ‘Monitoring framework’ and ‘Operational knowledge on EbA’ with scores ranging from −1 to 1. This could be explained either due to context-specific performance or differing stakeholder views. ‘Trade-off or disservice’ received moderate frequencies at all scores.
Further analysis and discussion of the results are provided in the following subsections.
4.1. Influence of the governance system on the implementation of EbA
EbA implementation involves multiple steps and actors, crossing jurisdictional boundaries. The corresponding decision-making processes might range from urban-drainage systems managed at the local level, watershed restoration managed regionally, to wetland restitution involving national authorities. Government cooperation occurs both horizontally (within the same institution and/or same governance level) and vertically (among institutions at different scales). This cooperation is necessary to implement any intervention (Kapos et al., Reference Kapos, Wicander, Salvaterra, Dawkins and Hicks2019; Leone, Reference Leone2021) as competences might be distributed across different governing bodies and/or different departments involved in the decision and implementation process.
The natural setting of each area shapes not only the types of measures implemented but also their governance complexity. For instance, riverine restoration projects (Benidorm) involve different actors and jurisdictional scales than coastal dune rehabilitation (Barcelona Metropolitan Area), or urban green infrastructure (Oeiras). City council departments usually serve as primary planners for climate change adaptation, setting up a wide range of interventions that affect the well-being of the inhabitants. Based on the assessed examples, horizontal cooperation within the same institution has proven effective in small and medium-sized city councils, as demonstrated by the case studies of Palma, Benidorm, Vilanova i la Geltrú, and Oeiras. However, bureaucracy and protocols increase with the size of the institution, hindering the decision-making process and lengthening the implementation process as it was observed in all case studies from the city of Barcelona.
EbA projects very often involve natural restoration efforts that extend beyond municipal boundaries. Therefore, cooperation among neighbouring municipalities is essential, as these projects cannot be confined to a single municipality. This is the case of the green corridor “Eixo Verde e Azul” in Oeiras, where the neighbouring municipalities of Sintra, Amadora, and Oeiras have agreed to cooperate on restoring and naturalising the Jamor River. The main objectives of this initiative were to reduce flooding, enhance recreational opportunities, ensure accessibility, and establish green connectivity along the 16-km length of the river.
In terms of vertical cooperation, the responsibility for restoring a natural area can be shared between local (e.g., land ownership, security) and regional administrations (e.g., maintenance competence, regulations). These competences are often transferred to the local or metropolitan level, as they might be better able to apply for the necessary funding (Santander, Benidorm, Vilanova i la Geltrú, Barcelona Metropolitan Area). Nevertheless, the high bureaucracy involved in obtaining the necessary permits from supra-municipal departments delays and hinders the process (Vilanova i la Geltrú, Santander, Barcelona Metropolitan Area, Oeiras). Standardizing and simplifying the application process will contribute to the uptake of EbA. Both vertical and horizontal cooperation are important for strengthening the governance system and ensuring the effective implementation of EbA.
The implementation of any measure is preceded by a decision-making process whose factors will influence the outcome. These include, among others, co-creation, scientific knowledge, and political support. Engaging influential individuals is key to boost local social networks and increasing the legitimacy of the proposed measures (Kabisch et al., Reference Kabisch, Frantzeskaki and Hansen2022; Sowińska-Świerkosz & García, Reference Sowińska-Świerkosz and García2021). Evidence from the assessed interventions indicates that involving citizens in the process enhances acceptance and deepens understanding of the benefits and adaptation implications of the proposed measures (Santander, Barcelona Metropolitan Area). In some situations, the implementation of EbA responds to citizens' demand (Barcelona – Hort del Cànem, Vilanova i la Geltrú). Bottom-up approaches enable the uptake of EbA by encouraging decision-makers to prioritise co-creation, leading to more widely accepted interventions. Projects that fostered co-creation and included scientific bodies and local actors in the design and implementation process (Vilanova i la Geltrú, Palma, Lisbon), strengthened multi-actor collaboration, and appear to be a key differentiator, even within the same geographical context (Oeiras, Barcelona–Passeig de Sant Joan).
Academic and scientific organisations share their expertise to inform decision-makers with the latest scientific developments (Davies et al., Reference Davies, Chen, Sanesi, Lafortezza, Martin and Esther2021; Kapos et al., Reference Kapos, Wicander, Salvaterra, Dawkins and Hicks2019; Nesshöver et al., Reference Nesshöver, Assmuth, Irvine, Rusch, Waylen, Delbaere, Haase, Jones-Walters, Keune, Kovacs, Krauze, Külvik, Rey, van Dijk, Vistad, Wilkinson, Wittmer, Barceló Cullerés and Gan2017). Providing this support to city council planners, technicians and other local stakeholders – who often lack research capacity – is essential for gaining knowledge on topics such as climate change projections, hazard risk modelling, and the socioeconomic impact of potential adaptation measures and strategies. Based on our assessment, whenever there are climate and environmental reports to support the need for intervention, successful implementation results were found, as demonstrated in the case studies of Oeiras, Lisbon, Palma, Barcelona–SUDS, and Vilanova i la Geltrú. Both in Oeiras and Lisbon, researchers from local universities assisted the technical reports informing on flooding hazards of the areas under intervention and the convenience of transforming the landscape into a permeable green area. A similar situation occurred in Barcelona and Vilanova i la Geltrú. Addressing scientific challenges related to climate uncertainty, biodiversity dynamics in response to main threats, and the design of future scenarios requires a comprehensive assessment. This can be achieved through effective monitoring frameworks and the development of robust governance strategies (Hossaert & Le Roux, Reference Hossaert and Le Roux2023).
When political support for the proposed intervention exists, it reflects a strong commitment to adaptation, initiated and sustained by city officials with local leadership and influence (Zölch et al., Reference Zölch, Wamsler and Pauleit2018). On the contrary, the lack of political support can be a barrier to EbA implementation, alongside the absence of financial resources and conflicting regulations (Duffaut et al., Reference Duffaut, Frascaria-Lacoste and Versini2022). In all but one of the case studies with information available, the decision was political. In two situations, it was initially led by the community (Barcelona–Hort del Cànem; Vilanova i la Geltrú) before being embraced by local institutions. Political support is thus revealed as an enabler for EbA implementation, showing strong support in all situations under study.
Successful management of interventions is highly related to the existence of a monitoring framework (Cohen-Shacham et al., Reference Cohen-Shacham, Andrade, Dalton, Dudley, Jones, Kumar, Maginnis, Maynard, Nelson, Renaud, Welling and Walters2019; Geneletti & Zardo, Reference Geneletti and Zardo2016; Nesshöver et al., Reference Nesshöver, Assmuth, Irvine, Rusch, Waylen, Delbaere, Haase, Jones-Walters, Keune, Kovacs, Krauze, Külvik, Rey, van Dijk, Vistad, Wilkinson, Wittmer, Barceló Cullerés and Gan2017), operational knowledge related to the multiple co-benefits EbA measures provide (Anderson & Renaud, Reference Anderson and Renaud2021; Kabisch et al., Reference Kabisch, Frantzeskaki and Hansen2022; Mell et al., Reference Mell, Clement and O'sullivan2022) and know-how related to the rules, operations and relationships with external actors involved in the adaptation efforts. Lisbon, Palma, and Barcelona Metropolitan Area track the performance of the assessed EbA measures, while know-how on EbA is present in all cases interviewed, overcoming a frequent barrier in ecosystem management practices (Brink et al., Reference Brink, Aalders, Ádám, Feller, Henselek, Hoffmann, Ibe, Matthey-Doret, Meyer, Negrut, Rau, Riewerts, von Schuckmann, Törnros, von Wehrden, Abson and Wamsler2016). In-house technical knowledge on adaptation and the additional benefits of these measures drives EbA implementation as an alternative to other engineered-based infrastructures.
Two assessed interventions (Las Llamas–Santander; Parc Joan Reventós–Barcelona) were pioneering in inspiring future SUDS interventions across Spain. Other projects inspired the development of further urban green corridors (Sant Joan–Barcelona), promoted dunes restoration interventions along the Metropolitan Area of Barcelona shoreline, as well as river restoration with additional recreational purposes (Oeiras). As recalled by Dumitru et al. (Reference Dumitru, Frantzeskaki and Collier2020), balancing and mapping the synergies and trade-offs of EbA projects contribute to their uptake. Trade-offs are not necessarily negative, especially when the restoration of natural capital is enhanced. In some cases, urban development may result in allocating less space for housing and other uses, allowing to increase biodiversity and recreational areas (Santander) or to restore a wetland (Vilanova i la Geltrú). Moreover, decisions may lead to the reduction of beach area designated for recreational activities, favouring dunes restoration and coastal erosion mitigation (Barcelona Metropolitan Area).
4.2. Influence of the policy framework in the implementation of EbA
Failing to explicitly mention EbA in plans and strategies can hinder their implementation (Geneletti & Zardo, Reference Geneletti and Zardo2016). Integrating EbA interventions into climate change plans (Lisbon, Oeiras, Barcelona Metropolitan Area, Benidorm, Vilanova i la Geltrú) as well as other strategies promoting biodiversity, enhances green infrastructure in urban areas (Palma; green corridor – Barcelona). These documents ensure that spatial planning is adequate for the proper implementation and management of EbA (Sowińska-Świerkosz & García, Reference Sowińska-Świerkosz and García2021), thereby reducing the vulnerability of human and natural systems to climate change. Based on the research conducted, the existence of climate change plans and strategies enable the implementation of these measures, increasing urban climate resilience.
Plans provide clear guidance and reduce bureaucratic obstacles, leading to harmonious top-down regulations that avoid conflicts, for instance, between urban planning and environmental regulations, which might hinder EbA implementation (Seddon et al., Reference Seddon, Chausson, Berry, Girardin, Smith, Turner, Janet, Yadvinder, Nathalie, Martin, Chris, Nancy and Monica2020). Evidence of these benefits have been observed in the cases assessed (Barcelona Metropolitan Area, Barcelona, Palma, Oeiras, Vilanova i la Geltrú, and Benidorm) resulting in positive long-term additional benefits (Niki et al., Reference Niki, Borgström, G, E, E, Nadja and Korn2017), such as carbon capture, biodiversity improvement, or increase of recreational opportunities, among others.
Including green infrastructures into regulations helps shifting traditional approaches, which often rely on grey engineering solutions. This change reflects the growing interest among practitioners and policy makers in adaptation. Embedding EbA interventions into existing policies demonstrates institutional recognition of their importance in addressing climate change. It highlights the role these interventions play in adapting urban areas and rises awareness on the ecosystem services and additional benefits they provide. This is the case of the interventions undertaken in Barcelona Metropolitan Area, Palma, Barcelona (Urban Farming), Oeiras, Vilanova i la Geltrú, and Benidorm, where all the applying norms and regulations were aligned and did not interfere with each other, making it easier to ask for the necessary intervention permits.
Some examples of local regulations alignment are the Open spaces and Sustainable drainage regulations with the beach renaturation in Palma. Actions proposed do not interfere with the aims and principles included in both regulations, such as the promotion of leisure activities in open spaces or the inclusion of permeable pavements and similar interventions to reduce impervious surface in floodable prone areas. In Vilanova i la Geltrú, the wetland restoration project was supported by the Special Plan, which was aligned with the urbanism city council department's recognition of the site as a green area.
The transition to greener cities is driven by international treaties, guiding the inclusion of environmental principles in downscale regulations (Baravikova, Reference Baravikova2020). European Directives or strategies, such as the Green Deal or the Biodiversity Strategy to 2030 contribute to align and set the priorities at local scale. These international agreements shape adaptation interventions, such as the United Nations Sustainable Development Goals (SDG) (Palma, Benidorm) or support key objectives of the EU2020 strategy (Oeiras), facilitating their effective implementation at the local level.
The green corridor (Eixo Verde e Azul) in Oeiras was framed within the Biodiversity Strategy to 2030, which inspired the design of the specific interventions to implement in the area. Similarly, this initiative was also aligned with the objective of the EU2020 strategy of reducing greenhouse emissions. Former initiatives, such as the white paper ‘Adapting to climate change: towards an European framework for action', which inspired the EU2020 strategy, also led to interventions like the green corridor in Lisbon. This document advocated for a significantly increase in activities related to climate change adaptation, and was incorporated into the Portuguese National Strategy for Adaptation Climate Disturbances (2010). In the case of Palma and Benidorm, the interventions proposed are aligned with the following SDGs: ‘Clean water and sanitation', ‘Sustainable cities and communities', and ‘Climate Action’. Additionally, Palma's beach renaturation project is aligned with the SDG of ‘Life below water goal’.
4.3. Influence of the funding model in the implementation of EbA
Limited funding opportunities for EbA implementation are widely recognised as a barrier to scaling up these measures (Sarabi et al., Reference Sarabi, Han, Romme, de Vries, Wendling, Peter, Laura, Teresa and Anna2019). International programmes and institutions, such as Horizon Europe from the European Commission, or the European Regional Development Fund, have been designed to finance research and development cooperation to strengthen economic, social, and territorial cohesion. Very often EbA implementation requires huge financial efforts which are not possible to undertake under limited local budgets. Access to EU funds managed locally has opened opportunities to increase the number of adaptation projects (Barcelona Metropolitan Area, Palma, Oeiras, Vilanova i la Geltrú). Local resources also play a central role in the co-funding of these initiatives, ensuring their long-term sustainability (Lisbon, Oeiras, Vilanova i la Geltrú, Benidorm). Self-managed initiatives are rare but can offer a viable option when organised groups of committed citizens work towards transforming cities into greener and more liveable spaces. This was the case of the urban farming project in Barcelona, where in the early stages of the project residents organised themselves to transform an abandoned plot into an urban farming initiative. In addition to their personal dedication, crow funding initiatives contributed to fund gardening tools and related materials necessary to set up the orchard.
The composition of a local budget reflects the policy objectives, while its size is related to the dimension of the municipality. The allocation of resources for EbA interventions demonstrates a clear interest by institutions to integrate EbA into local planning. During this research, it was not possible to access and analyse the local budget structures of the municipalities under study. However, evidence from the interviews suggests growing efforts by local institutions to adapt to climate change by increasing the budget of environmental related departments (Barcelona Metropolitan Area, Palma, Benidorm, Oeiras). All case studies reported that the amount invested in these interventions varies with resource availability. When high budgets are available, there is a clear intention to increase the number of these interventions through its co-funding with local and external sources, such as EU funds. Practitioners confirmed that maintenance costs decrease once the intervention is well established (Barcelona Metropolitan Area, Oeiras, Vilanova i la Geltrú). Nevertheless, significant maintenance or even partial restoration investments will be required after extreme events such as severe storms and flooding.
The need for economic and financial resources sourced from diverse institutions involves exploring innovative mechanisms (Seddon et al., Reference Seddon, Chausson, Berry, Girardin, Smith, Turner, Janet, Yadvinder, Nathalie, Martin, Chris, Nancy and Monica2020). To promote the adoption of EbA, fiscal incentives – such as the reduction of municipal fees or ecological fiscal transfers – can be made conditional upon their implementation and the achievement of specific performance indicators (Albert et al., Reference Albert, Brillinger, Guerrero, Gottwald, Henze, Schmidt, Ott and Schröter2021; Kumar et al., Reference Kumar, Debele, Sahani, Aragão, Barisani, Basu, Bucchignani, Charizopoulos, Di Sabatino, Domeneghetti, Edo, Finér, Gallotti, Juch, Leo, Loupis, Mickovski, Panga, Pavlova, Zieher, Damia and Jay2020; Seddon et al., Reference Seddon, Chausson, Berry, Girardin, Smith, Turner, Janet, Yadvinder, Nathalie, Martin, Chris, Nancy and Monica2020). Ecological fiscal transfers can serve as an alternative funding source for EbA interventions, particularly when the financial resources are managed locally. Different situations have been identified in the assessed case studies. Although none of them currently implement these innovative mechanisms, the interviewed Spanish practitioners in Vilanova i la Geltrú, Palma, Benidorm, and Oeiras showed a high interest in exploring these options. However, based on the interviews conducted for the Portuguese case studies, these mechanisms are not viable options for the Portuguese municipalities, as most taxes are collected at the national level. Promoting local tax management and fiscal transfers to municipal scale can be a great opportunity for EbA upscale.
Cooperation between private and public bodies offer a great opportunity to fund and upscale EbA interventions (Toxopeus & Polzin, Reference Toxopeus, Polzin, Dewil, Evans, Tansel and Zhang2021; van Ham & Klimmek, Reference van Ham, Klimmek, Nadja and Korn2017). One example documented in the case studies is the urban farming project in Barcelona, where hotel promoters were asked to finance the redevelopment of the surrounding area, including the urban farming settlement. Nonetheless, this and similar experiences reported in Benidorm and Palma, may fail to invest in other areas of the city where EbA implementation is needed to restore natural values disrupted by urbanisation. There is potential to further explore PPP to upscale of EbA interventions, as they constitute an additional source to fund initiatives that the municipalities might not be able to support on its own.
NGOs can play an important role in the promotion of EbA. They may support advocacy, promote dialogue on adaptation, support monitoring programmes, and facilitate knowledge exchange, while also providing an alternative source of funding. The collaboration between these institutions and the municipalities is showcased in various case studies. For instance, the involvement of NGOs in monitoring bird communities in Las Llamas Park (Santander), revegetating the restored wetland in Platja Llarga (Vilanova i la Geltrú), and conducting outreach activities in Oeiras. Moreover, the case studies of Barcelona Metropolitan Area and Vilanova i la Geltrú highlighted the involvement of private sector entities in the cleaning and maintenance activities of EbA interventions as part of its corporate social responsibility strategy.
5. Conclusions
Although EbA, along with NbS, is increasingly recognised at the EU level, their implementation in urban contexts is still limited. This research focuses on EbA implementation processes in coastal urban areas and develops a decision-support framework to facilitate local-level adoption in these contexts. The framework assesses the enabling conditions that influence the implementation of EbA, focusing on governance systems, policy frameworks, and funding models. While the empirical findings provide valuable insights into specific coastal urban case studies of Spain and Portugal, the broader contribution of this research lies in the framework capacity to assist local decision makers and practitioners through the implementation of EbA measures and strategies across diverse contexts.
The results of this research suggest that local scale is the optimal level to operate EbA interventions, as there is better knowledge of the adaptation needs and institutions are closer to citizens, allowing for effective co-creative processes. However, local-level implementation remains limited to governance challenges, policy misalignments, funding, and financial limitations.
Misalignments between different administrative levels, and bureaucracy hinder the implementation process of EbA. To overcome these challenges, it is important to adopt interdisciplinary approaches and enhance capacity building and policy support. Adaptive and flexible governance structures are necessary to ensure the integration of EbA in local planning and their sustainability. Vertical and horizontal cooperation amongst institutions would contribute to improve the necessary cooperation and communication, protocols and plans to articulate the processes and avoid conflicting regulations.
Increasing our understanding of the potential benefits and drawbacks of EbA, as well as the creation of systematic guidance for policymakers, are central for successful implementation experiences. For long-term performance and EbA uptake, monitoring frameworks and knowledge dissemination will help to reduce uncertainties and promote EbA replication. The formulation of this framework responds to a growing demand within the global scientific and policy communities for integrative tools that can bridge the knowledge gap between EbA planning and practice. Its structure – grounded in institutional, technical, and socio-political dimensions – allows researchers, practitioners, and decision-makers to identify enablers and barriers to implementation in consistent and replicable manner.
This study emphasises the importance of addressing governance and financial challenges, to scale up EbA interventions, and contribute to adaptation and urban resilience. Embedding EbA in local and regional adaptation plans and strategies is central to address environmental challenges more effectively. Securing diverse and sustainable funding sources is key for an effective EbA implementation. Innovative funding mechanisms, such as fiscal incentives and PPP, together with stable or growing budget allocations, can further support the overcoming financial barriers and long-term benefits.
This framework has been developed under coastal urban contexts mainly affected by flooding episodes, but it was designed to be adaptable. Future research in this field could consider the application of this framework across geographies, governance levels, and scales of intervention, making it a valuable instrument for cross-case comparisons, long-term monitoring, and policy learning. This assessment will help to have a better evaluation of EbA and support evidence-based planning.
This research offers a methodological contribution with the potential to inform future comparative studies and research within the field of climate adaptation. It lays the foundation for building cumulative knowledge on enabling conditions for EbA, encouraging both critical reflection and harmonisation in assessment approaches across the scientific community.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/sus.2025.10023.
Acknowledgements
The authors would like to thank the Environmental Department of Vilanova i la Geltrú City Council, Horts de la Llacuna Association, City Council of Benidorm, Environmental Management of Metropolitan Beaches Department of Barcelona Metropolitan Areas, Environmental Management Department and Territorial Intelligence Office of Oeiras Municipality, and Palma City Council for their availability to undertake in-depth interviews and their support in providing documents to further assess the selected case studies.
Author contributions
Conceptualization, M.R-S., A.F.M., and L.C-R.; methodology M.R-S. and L.C-R.; formal analysis, M.R-S; writing – original draft preparation, M.R-S.; writing – review and editing, M.R-S., L.C-R., and A.F.M.
Funding statement
This research was supported by the EU SCORE project under grant agreement No. 101,003,534 of the European Union's Horizon 2020 Research and Innovation Programme.
Competing interests
The authors declare that they have no known financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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