Building blocks for upscaling freshwater ecosystem restoration: Place-based strategies for a transdisciplinary challenge

Freshwater ecosystems are vital for biodiversity and human well-being, but remain amongst the most degraded globally. Nature-based Solutions (NbS) offer a promising pathway to restoration, yet implementation remains fragmented and often limited in scale. This paper synthesises insights from 18 demonstration cases across Europe, carried out under the EU Horizon 2020 MERLIN project, to identify key factors enabling the systemic upscaling of freshwater restoration through NbS. Drawing on practical experiences, five interdependent “building blocks” are proposed: (1) comprehensive status review; (2) narratives of the future; (3) evidence-informed approach; (4) resource management and (5) stakeholder engagement. These dimensions reflect cross-cutting challenges and capacities — such as context-sensitive planning, adaptive learning, financing strategies and inclusive governance. While grounded in diverse local contexts, the framework offers a strategic orientation for scientists, practitioners and policy-makers working to align restoration efforts with the ambitions of the European Green Deal and Nature Restoration Regulation. Rather than prescribing uniform solutions, the paper provides practice-informed guidance for embedding restoration in complex social–ecological systems. Synthesises lessons from 18 diverse freshwater restoration cases across Europe under the MERLIN project; Proposes five strategic building blocks for scaling Nature-based Solutions: system understanding, shared vision, evidence use, resource management and stakeholder engagement; Emphasises the interdependence of ecological, institutional and societal dimensions in upscaling restoration; Demonstrates the value of transdisciplinary collaboration, adaptive planning and embedded implementation; Offers practice-orientated insights aligned with the European Green Deal and Nature Restoration Regulation.