Beyond the label: Do coastal nature-based solutions fulfill the scope of European Commission and IUCN definitions? A...

Coastal zones support diverse ecosystem services and host a growing human population, increasing both exposure to hazards and pressure on coastal ecosystems. Traditionally managed through hard engineering approaches, these pressures have increasingly prompted interest in Nature-based Solutions (NbS), promoted as cost-effective, sustainable, resilient, and capable of delivering co-benefits beyond protection. However, it remains unclear to what extent NbS applications in coastal settings align with their conceptual definitions. We conducted a systematic literature review of 119 peer-reviewed manuscripts, assessing compliance with the definitions proposed by the European Commission (EC) and the International Union for Conservation of Nature (IUCN). A two-step approach combined principles-based assessment with coding analysis to evaluate compliance with key definitional elements and their interpretation in practice. Results show that manuscripts align more consistently (66%) with the EC definition than with the IUCN definition (63%). Across both definitions, direct benefits, such as hazard protection, environmental outcomes, and societal contributions, were widely reported (89-98%). In contrast, fundamental principles, including sustainability, resilience, sustainable management, and cost-effectiveness were insufficiently addressed (43.7-65%). Furthermore, many proposed NbS closely resemble long-established measures, suggesting conceptual overlap with approaches such as soft engineering. Our findings reveal a persistent gap between NbS principles and practice in coastal contexts, possibly driven by vague terminology, overlapping concepts, and widespread use of the term. To improve consistency and credibility, we recommend the development of a unified NbS definition supported by locally adapted operational indicators, monitoring frameworks, and clear evaluation guidelines, ensuring NbS can fulfil their intended transformative role in coastal adaptation.