In line with the European Green Deal priorities, notably the EU biodiversity strategy for 2030, as well as the EU climate adaptation strategy and the EU's climate mitigation ambition for 2030 and 2050, the successful proposals will support the development of Nature-based Solutions (NBS) contributing to the sustainable management of water resources in a changing climate, with a special attention to reducing the impacts of extreme droughts.

Project results are expected to contribute to all of following expected outcomes:

• Cost-effective ways of implementing NBS at large scale for integrated water management are ready to use for relevant stakeholders and widely replicated;
• Consolidated evidence of the contribution of NBS to sustainable water management and of NBS’ cost and resource efficiency, notably concerning the reduction of impacts of droughts;
• Enhanced implementation of EU policies, notably for water management (Water Framework Directive, as well as the Floods Directive, when relevant), climate adaptation (Article 5 of the European Climate Law, EU strategy for climate change adaptation), the EU biodiversity strategy for 2030 and the EU soil strategy for 2030.

Due to the changing climate, many European regions are already facing more frequent, severe, and longer lasting droughts. Extreme droughts can have cascading effects; e.g., they reduce water levels in rivers and ground water, stunt tree and crop growth, increase pest attacks, favour the occurrence of sand drifts and storms and fuel wildfires. Moreover, impacts of extreme droughts accumulate over time across large areas, and the effect can linger for years. In areas with an intense demand for water supply, the impacts of droughts add up to the stress imposed to water systems by human activities.

In Europe, most of the losses caused by extreme drought (~EUR 9 billion/year) affect agriculture, forestry the energy sector and the public water supply. Extreme droughts in western and central Europe in 2018, 2019 and 2020 caused considerable damage. With global climate change deepening, the impacts will be even more severe in the future, including decreasing quality, occurrence and availability of standing and running water.

By deploying systemic thinking NBS utilise an understanding of the structure and functioning of local ecosystems over time to address a broad range of societal challenges, including having enough water of good quality, both in surface waters and in ground water. They also contribute to restoration of biodiversity and help carbon sequestration in the soil. As such, NBS are highly adaptable to respond to changing local conditions and are often more cost and resource efficient than purely technological approaches in the longer term.

The 2021 EU climate adaptation strategy underlines that NBS represent multipurpose, “no regret” solutions, with environmental, social and economic benefits and help build climate resilience. They can have an essential role in land-use management and infrastructure planning to reduce costs, provide climate-resilient services, and improve compliance with Water Framework Directive (WFD) requirements.

However, evidence on the cost-efficiency of these measures remains dispersed and incomplete, and do not address the whole catchment area in a holistic approach. River basin management plans are still limited in the recognition of NBS capacity to contribute to drought resilience. Furthermore, we are still missing more and longer-term evidence of the combined effects of different designs and combinations of NBS operating in different contexts (urban, peri-urban and rural) and/or at different scales and/or different climatic zones, in what regards the sustainable management of water resources to reduce the impacts of extreme droughts. At the same time, the co-benefit that these NBS may bring to reduce hydrogeological risks such as flood peaking and stabilising hydrographs for both droughts and floods is still to be demonstrated.

The successful proposals should:

• Demonstrate innovative, systemic and locally attuned NBS (as single interventions or as a combination of them), for the management of catchment water resources and the reduction of extreme drought risks, in areas that are heavily impacted by temporary or lasting water scarcity and areas that are being increasingly exposed to this risk with the deepening of climate change.
• Be incorporated into an integrated design concept for land and water management at the appropriate scales (preferably at landscape level, integrating water, soil and ecosystems as a whole), in accordance with WFD objectives, considering longitudinal connectivity of water flows, lateral connectivity with floodplains and adjacent grounds, and connections between surface- and groundwater.
• Plan, co-design and co-deploy solutions in a transdisciplinary multi-stakeholder and participatory context with due consideration and integration of social and cultural aspects and climate change effects.
• Building on the work of Horizon 2020 projects and their taskforces, develop an advanced monitoring programme for the demonstrated solutions and test and further develop as needed the EU Impact Evaluation Framework for NBS to assess the economic, social and ecological benefits of NBS and provide quantitative evidence, including positive and negative synergies, and analysis of trade-offs, for higher performance.
• Identify and assess barriers related to: functional conflicts in land-use; NBS technical, commercial, social and cultural acceptance (e.g., farmers perceptions and values, the role of private landowners); and policy regulatory frameworks (e.g., the role of the common agriculture policy, urban, rural and regional development plans) - and propose ways to overcome them (for example through new business cases and governance approaches).
• Develop methodologies and tools, adapted to end-users (e.g., farmers, forest owners, local authorities, engineers, spatial planners), enabling the replication and up-scaling of NBS.
• To provide a long-term evidence as ambitious as possible, new interventions should be complemented with the analysis of established NBS. In this respect, opportunities to build up from relevant initiatives should be explored (e.g., LIFE, INTERREG, national funded projects, etc).
• Develop protocols and standards for the design, operation and maintenance of NBS, building on existing work, considering:
• The best solutions for different soil characteristics (as these determine the type and impact of droughts) and soil health, relief and geo-morphological conditions, including urban conditions;
• The resilience of NBS, considering present and future climatic conditions and water regimes;
• The ecological performance and resilience of NBS, to deal with both natural and human-induced hazards, such as extreme weather events, desertification, forest fires, plant- and animal diseases (pests), other human activities and socio-political approaches that could have an impact on land-use;
• The long-term maintenance of NBS: also in relation to the adequate management of biomass, synergies with other approaches that affect the management of ecosystems like agroforestry, etc.

Proposals should address all of the above points.

Because of the substantial investments that might be necessary for implementing the NBS, additional or follow-up funding (private or public) should be sought, considering the EU taxonomy, including from relevant regional/national schemes under the Recovery and Resilience Fund, the European Structural and Investment Funds (ESIF), or other relevant funds. Please note, however, that reference to such additional or follow-up funding will not lead automatically to a higher score in the evaluation of the proposal.

This topic requires the effective contribution of SSH disciplines and the involvement of SSH experts, institutions as well as the inclusion of relevant SSH expertise, in order to produce meaningful and significant effects enhancing the societal impact of the related research activities. This means proposals should bring together from the early start multiple types of scientific expertise in both natural sciences (e.g., ecology, climate, pedology) and social sciences and humanities (e.g., economics, geography, sociology) together with a variety of urban and/or rural community representatives, farmers, businesses, civil society organisations and citizens.

Social innovation is recommended when the solution is at the socio-technical interface and requires social change, new social practices, social ownership or market uptake.

Proposals should set out a clear plan on how they will collaborate with other projects selected under this topic and any other relevant topic/call, by participating in joint activities, workshops, as well as common communication and dissemination activities. This includes notably the Horizon 2020 NBS project portfolio, including the European Green Deal Call, and its task forces; Horizon Europe projects Invest4Nature and Naturance and HORIZON-CL6-2022-BIODIV-01-03: Network for nature: multi-stakeholder dialogue platform to promote nature-based solutions. Applicants should plan the necessary budget to cover these activities without the prerequisite to define concrete common actions at this stage.

Proposals should ensure complementarity and foresee synergies with the activities of the Horizon Europe missions "A Soil Deal for Europe”, “Restore our Ocean and Waters by 2030” and “Adaptation to Climate Change”, as well as with the partnerships Biodiversa+ and Water4All.

Proposals should ensure that all evidence, information and project outputs will be accessible through the Oppla portal (the EU repository for NBS). Where relevant, proposals should consider creating links, contributing to and using the information and data of other platforms such as NWRM, Climate-ADAPT, BISE and the European Drought Observatory.