Incorporating stakeholders' preferences into a multi-criteria framework for planning large-scale Nature-Based Solutions

Worldwide replicability of alternative water recovery technologies to close water loops in decentralised populations

Decentralised systems to recover alternative sources of water (wastewater, rainwater, and seawater) can reduce water scarcity in rural areas by closing water loops while improving the local economy. However, their implementation commonly faces difficulties owing to social, legislative, technical, and economic barriers that must be assessed in local contexts. In this study, the implementation of six decentralised solutions (DCS) that were previously tested to recover water and other products was evaluated at 26 replication sites worldwide. Small, isolated locations were considered for site selection. They generally have scarce water resources and/or inappropriate water sanitation systems, and a high dependency on external regions. A quantitative feasibility assessment methodology (QFAM) developed in a previous study was used to evaluate the potential implementation of the DCS by quantifying relevant data regarding social, legislative, technical, and economic factors collected from the sites. From the results obtained in the overall assessment, the sites could be divided into two main groups: European sites that showed many similarities, especially in terms of common legal frameworks ruled by EU directives, and non-European sites that showed higher variations in local specificities. Most EU replicability sites showed high feasibility scores; however, for non-European sites, the results were distributed between high and medium feasibility scores. High scores were significantly influenced by high social and legislative feasibility assessments obtained at most sites. However, a general lack of understanding of the specificities of decentralised systems in local authorities and administrations was detected, which can be a significant barrier. Technical and economic assessments sometimes showed medium or low scores owing to certain limitations in the production of some circular products and the lack of financial instruments at some sites to reduce the initial investment for the implementation of DCS.

Assessing the IUCN global standard as a framework for nature-based solutions in river flood management applications

Nature-based Solutions (NbS) are actions that harness nature to help address major societal challenges. The assessment frameworks for NbS proposed in the literature differ in scope and intended use. In 2020, the International Union for Conservation of Nature (IUCN) introduced their Global Standard for NbS as a framework that can be used by anyone working on different types of NbS. Since research on the applicability of the IUCN Standard remains limited, the aim of this paper is to analyse whether the IUCN Standard may be used as an overarching assessment framework for NbS in river flood management applications and to identify the main differences in content with other NbS-frameworks. This was achieved through a comparison with 29 assessment frameworks for NbS, that are applicable to physical interventions for riverine flood risk reduction. The comparisons showed that the IUCN Standard has the largest breadth in scope of application and may therefore be used as an overarching framework. In addition, we identified a distinction between frameworks for the assessment of project processes (process-oriented) and project results (results-oriented), where the IUCN Standard can be characterized as process-oriented. This implies that the IUCN Standard may be used to assess the processes (e.g. stakeholder engagement and adaptive management) of planned, ongoing or completed NbS projects for a wide variety of environmental contexts and societal challenges. This will help persuade policy makers to consider NbS as one of the solutions in flood management issues, next to or in combination with e.g. engineering solutions or changing land use. We also identified that, while the IUCN Standard is straightforward to use and incorporates stakeholder input, the environmental context specificity as well as guidance depth on resources for assessment can be improved.

Riparian Landscape Change: A Spatial Approach for Quantifying Change and Development of a River Network Restoration Model

Natural river landscapes can be biodiversity hotspots but are one of the most human altered ecosystems with habitats significantly damaged around the world, and a third of fish populations threatened with extinction. While riparian ecosystems have been negatively altered by anthropogenic activities, effective planning and restoration strategies can reverse negative impacts by improving habitat quality. However, restoring rivers requires appropriate data on current riparian health while also considering priorities for different stakeholders. To address this, a Geographic Information System (GIS) was used to create a new and transferable restoration priority model based on a section of the river Linth in Switzerland as a case study. The restoration priority model is founded on connectivity, river condition, national priority species and species hotspots. Landscape change of the riparian zone was analyzed using aerial imagery and landscape metrics. Almost a quarter of rivers within the study area were considered high or very high restoration priority, with many aquatic species set to benefit from restoration. From 1946 to 2019, the riparian landscape became highly fragmented due to significant growth in impervious surfaces and a concomitant loss of agricultural land. The GIS model provides a tool by which environmental agencies can manage natural features over large scales, while also planning priorities and targeting conservation strategies to the areas of greatest need.

Assessment of nature-based solutions for water resource management in agricultural environments: a stakeholders' perspective in Southern Italy

This paper explores the potential implementation of Nature-Based Solutions (NBSs) in agriculture, specifically focusing on soil and water management in Southern Italy, particularly in the Apulia and Basilicata regions. Through a tailored questionnaire, it investigates farmers' perceptions of the utility of NBSs, addressing key issues in the region and evaluating their role in addressing soil and water management challenges. Findings reveal primary challenges such as drought, floods, and water pollution, with soil erosion being a major concern. Several NBSs, including wetlands and bioswales, demonstrate consistent utility and performance, while disparities exist for agroforestry and strip cropping. The study underscores a significant gap in the economic valuation of NBSs, emphasizing the need for comprehensive assessments that incorporate livability improvements, water quality enhancement, and socio-cultural benefits. Additionally, an analysis of NBS implementation across Italian agriculture reveals limited case studies, suggesting the need for strategic expansions to meet Sustainable Development Goals. This research offers critical insights into the effectiveness and challenges of NBSs in agricultural soil and water management, advocating for enhanced stakeholder engagement and the development of multidimensional evaluation frameworks to support sustainable practices.

A dam or a polder? Stakeholders' dispute over the "right" flood-protection measure in the Czech Republic

This study focuses on the Skalička Waterwork (SWW), a largely debated and media-covered water-related/flood-protection project in the Czech Republic. Relying primarily on stakeholder interviews, we traced back and reconstructed the project's development, including its key tipping points reflecting the changing societal preferences for particular measures, yet also the involvement of individual actors/stakeholders, and their differing views. The case eventually crystallized into the "dam versus polder" dispute; concerned by the repercussions for the local landscape, a joint initiative of NGOs, local activists, and politicians not only opposed the dam variant proposed by the state river basin administration but also succeeded in pushing through the alternative scheme of side dry polder. While in many ways specific (e.g. not entailing local resistance), the case exemplifies recent shifts (and respective struggles) within flood risk management, including the increasing importance attributed to complex, catchment-wide perspectives, joint local and scientific knowledge, participatory decision-making processes, or implementation of nature-based and hybrid solutions.

Identifying the optimal type and locations of natural water retention measures using spatial modeling and cost-benefit analysis

Water management has shifted from solely technical and engineering approaches towards nature-based solutions (NBS), like natural water retention measures (NWRM), offering benefits beyond hydrology, such as improved well-being and biodiversity conservation. Determining the best type and location of these measures is challenging due to diverse options with varying benefits and effects depending on measure type and location characteristics. While most studies regarding the optimal allocation and implementation of NBS focus on the urban environment, this study presents a methodology for decision-makers focusing on inter-urban regions with limited data on NWRM implementation. Through hydrological modeling and cost-benefit analysis (CBA), we identify Pareto optimal NWRM sites and types, considering water quantity and quality alongside economic, environmental, and social objectives. We defined optimal locations that seek the most significant reduction of runoff, sediment, and pollutants, whilst optimal NWRM types are defined to seek the most cost-effective measures based on hydrological, ecological, and social criteria. Using the Open Non-point Source Pollution and Erosion Comparison Tool (OpenNSPECT), we simulated increased infiltration in different inter-urban areas and identified the optimal placement. The criteria for selecting suitable NWRM types for the identified areas are derived from the EU Directorate General for the Environment (DG-ENV) NWRM database. The results show different effective areas for reducing runoff, sediment, and pollutants. While one NWRM (natural bank stabilization) was identified as most beneficial for reducing sediment, several measures were selected for runoff reduction. Interestingly, measures with high potential for pollutant reduction seem to offer limited social and biodiversity benefits, suggesting conflicting objectives and highlighting the importance of accounting for multiple criteria. By employing simplified models and qualitative benefit assessments, this paper presents a practical decision-making approach to facilitate NWRM implementation in data-scarce areas.

Optimization of the integrated green-gray-blue system to deal with urban flood under multi-objective decision-making

The integrated green-gray-blue (IGGB) system is considered to be a new way of stormwater management, and a comprehensive evaluation of the green-gray-blue infrastructure layout mode under different return periods is the key to the implementation decision-making of stormwater management. In this study, a blue-green synergism evaluation model is established to optimize the layout of blue-green infrastructure. An evaluation framework combining the evaluation indicator system and the hydrology model is established. Stormwater storage, peak flow reduction, and life cycle cost are selected as evaluation indicators. On this basis, seven optimal scenarios, including green, blue, gray, green-blue, green-gray, blue-gray, and green-gray-blue, are established. The Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method is used to analyze these seven scenarios under different return periods. The results indicate that (1) when the drainage infrastructures are arranged in combination, the peak flow reduction is significantly improved compared to that of a single drainage. (2) TOPSIS results show that green-gray and blue-gray perform better when the cost weight is 0-0.35, and green-gray-blue performs best when the cost weight is 0.35-1. (3) The integrated green-gray-blue system has obvious synergistic effects. This study can provide support for planning department workers for the urban stormwater management strategy.

Modeling place-based nature-based solutions to promote urban carbon neutrality

Nature-based solutions (NbS) are recognized as widely available and cost-effective mechanisms for sequestering carbon and offsetting carbon emissions. Realistic NbS implementations for carbon neutrality need to be effective at the global level and also appropriate for the socio-economic and physical conditions prevailing at the local level. This paper presents a framework that can help stakeholders identify demands, locations, and types of NbS interventions that could maximize NbS benefits at the local scale. Key processes in the framework include (1) interpolating carbon emissions data at larger spatial scales to high-resolution cells, using land use and socio-economic data; (2) assessing NbS effects on carbon reduction and their location-related suitability, through qualitative literature review, and (3) spatially allocating and coupling multiple NbS interventions to land use cells. The system was tested in Stockholm, Sweden. The findings show that the urban center should be allocated with combinations of improving access to green spaces and streetscapes, while the rural and suburban areas should prioritize preserving and utilizing natural areas. Our proposed method framework can help planners better select target locations for intended risk/hazard-mitigating interventions.

Nature-based solutions to global environmental challenges

Nature-based solutions (NBS) supply many ecosystem services key to wellbeing. There is evidence that several ecosystems that serve as NBS (e.g., forests) are being threatened by land use and climate change. Urban expansion and agriculture intensification is imposing an extensive degradation in several ecosystems, increasing human vulnerability to climate change-related events. Therefore, it is key to rethink how to develop strategies that minimize these effects. Halt ecosystem degradation and establishing NBS in areas of high human pressure (e.g., urban and agriculture) is essential to reduce environmental impacts. Numerous NBS can be helpful in agriculture (e.g., retention of crop residues/mulching) to reduce erosion or diffuse pollution or in urban areas (e.g., urban green spaces) to mitigate urban heat island effects or floods. Although these measures are important, it is crucial to raise awareness among the stakeholders, assess case by case and minimize the tradeoffs associated with the NBS application (e.g., area needed). Overall, NBS are vital in addressing present and future global environmental challenges.

Socio-economic or environmental benefits from pondscapes? Deriving stakeholder preferences using analytic hierarchy process and compositional data analysis

Ponds occupy a large share of standing water worldwide and play an important role in providing various ecosystem services. There are concerted efforts of the European Union either to create new ponds, or to restore and preserve existing ponds as nature-based solutions to provide benefits to ecosystem and human well-being. As part of the EU PONDERFUL project, selected pondscapes (i.e. landscapes of ponds) in eight different countries - hereafter "demo-sites", are studied to comprehensively understand their characteristics and their efficiency to provide ecosystem services. In addition, the needs and knowledge of stakeholders who own, work, research, or benefit from the pondscapes are also important, because of their capabilities to create, manage and develop the pondscapes. Therefore, we established connection with stakeholders to study their preferences and visions on the pondscapes. Using the analytic hierarchy process, this study shows that in general stakeholders in the European and Turkish demo-sites prefer environmental benefits to economic benefits, while stakeholders in the Uruguayan demo-sites rank the economic benefits higher. More specifically, in the European and Turkish demo-sites, the biodiversity benefits, i.e. life-cycle maintenance, habitat and gene pool protection, receive the highest ranking among all groups. On the other hand, stakeholders at the Uruguayan demo-sites rank provisioning benefits as the most important, because many ponds in Uruguayan demo-sites are being used for agricultural purposes. Understanding those preferences helps policy makers to address the needs of stakeholders more correctly, when considering any action or policy for the pondscapes.

A nature-based solution selection framework: Criteria and processes for addressing hydro-meteorological hazards at open-air laboratories across Europe

Nature-based solutions (NbS) can be beneficial to help human communities build resilience to climate change by managing and mitigating related hydro-meteorological hazards (HMHs). Substantial research has been carried out in the past on the detection and assessment of HMHs and their derived risks. Yet, knowledge on the performance and functioning of NbS to address these hazards is severely lacking. The latter is exacerbated by the lack of practical and viable approaches that would help identify and select NbS for specific problems. The EU-funded OPERANDUM project established seven Open-Air Laboratories (OALs) across Europe to co-develop, test, and generate an evidence base from innovative NbS deployed to address HMHs such as flooding, droughts, landslides, erosion, and eutrophication. Herein, we detail the original approaches that each OAL followed in the process of identifying and selecting NbS for specific hazards with the aim of proposing a novel, generic framework for selecting NbS. We found that the process of selecting NBS was overall complex and context-specific in all the OALs, and it comprised 26 steps distributed across three stages: (i) Problem recognition, (ii) NbS identification, and (iii) NbS selection. We also identified over 20 selection criteria which, in most cases, were shared across OALs and were chiefly related to sustainability aspects. All the identified NbS were related to the regulation of the water cycle, and they were mostly chosen according to three main factors: (i) hazard type, (ii) hazard scale, and (iii) OAL size. We noticed that OALs exposed to landslides and erosion selected NbS capable to manage water budgets within the soil compartment at the local or landscape scale, while OALs exposed to floods, droughts, and eutrophication selected approaches to managing water transport and storage at the catchment scale. We successfully portrayed a synthesis of the stages and steps followed in the OALs' NbS selection process in a framework. The framework, which reflects the experiences of the stakeholders involved, is inclusive and integrated, and it can serve as a basis to inform NbS selection processes whilst facilitating the organisation of diverse stakeholders working towards finding solutions to natural hazards. We animate the future development of the proposed framework by integrating financial viability steps. We also encourage studies looking into the implementation of the proposed framework through quantitative approaches integrating multi-criteria analyses.

Deliberating options for nature-based river development: Insights from a participatory multi-criteria evaluation

To address societal challenges in river landscapes, various options are conceivable that differ in the degree of adopting nature-based solutions (NBS) and the respective impacts on people and nature. Multi-criteria evaluation (MCE) can aid participatory deliberations about the performance and significance of such options. However, little experience and evidence exist from the application of participatory MCE in planning NBS in river landscapes. This study aims to expand the understanding of individual and collaborative judgments of agency representatives about river development options with varying levels of NBS interventions. A process tracing approach with a rigorous participatory MCE for four alternatives to develop an exemplary river in Germany is adopted, as well as weighted linear aggregation, descriptive statistics, principal component analysis, and decision tree modelling for data analysis. The results reveal a wide agreement among participants on the positive impacts of NBS on biodiversity and water quality. Participants also tended to judge those ecological dimensions as more important than non-ecological ones. The rankings of alternatives differed when elicited individually but seemed to converge during the deliberation process. Overall, the results indicate a relative preference of participants for medium NBS interventions, but also shed light on potential implementation hurdles. The study closes by proposing key questions to consider for MCE of NBS.

A Framework to Evaluate the SDG Contribution of Fluvial Nature-Based Solutions

Nature-based solutions (NBSs) are measures reflecting the ‘cooperation with nature’ approach: mitigating fluvial flood risk while being cost-effective, resource-efficient, and providing numerous environmental, social, and economic benefits. Since 2015, the United Nations (UN) 2030 Agenda has provided UN member states with goals, targets, and indicators to facilitate an integrated approach focusing on economic, environmental, and social improvements simultaneously. The aim of this study is to evaluate the contribution of fluvial NBSs to the UN 2030 Agenda, using all its components: Sustainable Development Goals (SDGs), targets, and indicators. We propose a four-step framework with inputs from the UN 2030 Agenda, scientific literature, and case studies. The framework provides a set of fluvial flooding indicators that are linked to SDG indicators of the UN 2030 Agenda. Finally, the fluvial flooding indicators are tested by applying them to a case study, the Eddleston Water Project, aiming to examine its contribution to the UN 2030 Agenda. This reveals that the Eddleston Water Project contributes to 9 SDGs and 33 SDG targets from environmental, economic, societal, policy, and technical perspectives. Our framework aims to enhance the systematic considerations of the SDG indicators, adjust their notion to the system of interest, and thereby enhance the link between the sustainability performance of NBSs and the UN 2030 Agenda.

Hydromorphological and socio-cultural assessment of urban rivers to promote nature-based solutions in Jarabacoa, Dominican Republic

In Latin America and the Caribbean, river restoration projects are increasing, but many lack strategic planning and monitoring. We tested the applicability of a rapid visual social-ecological stream assessment method for restoration planning, complemented by a citizen survey on perceptions and uses of blue and green infrastructure. We applied the method at three urban streams in Jarabacoa (Dominican Republic) to identify and prioritize preferred areas for nature-based solutions. The method provides spatially explicit information for strategic river restoration planning, and its efficiency makes it suitable for use in data-poor contexts. It identifies well-preserved, moderately altered, and critically impaired areas regarding their hydromorphological and socio-cultural conditions, as well as demands on green and blue infrastructure. The transferability of the method can be improved by defining reference states for assessing the hydromorphology of tropical rivers, refining socio-cultural parameters to better address river services and widespread urban challenges, and balancing trade-offs between ecological and social restoration goals.

Planning and governing nature-based solutions in river landscapes: Concepts, cases, and insights

Nature-based solutions (NBS), understood as actions that use ecosystem processes to address societal needs, can play important roles to future-proof river landscape development for people and nature. However, knowledge gaps exist how NBS can be planned and implemented at landscape scales. This Special Issue brings together insights and experiences from studies of assessing, planning, and implementing NBS in river landscapes in Europe and beyond. It addresses three research fields: (i) NBS effects, looking at the effectiveness of NBS to achieve ecological, social, and/or economic outcomes, (ii) NBS planning, focusing on approaches for planning and designing NBS, and (iii) NBS governance, relating to governance and business models for implementation. The twelve contributions deliver evidence on how NBS outperform conventional, rather technical solutions, provide guidance and tools to operationalize the NBS concept into practice, and showcase successful governance models of NBS in different contexts. The editorial ends with an outlook on further research needs.