The concept of 'nature-based solutions' applied to urban coastal risks: A bibliometric and content analysis review

Nature-based solutions (NBS) are increasingly proposed as a response to the growing vulnerability of coastal areas to the risks of coastal erosion and flooding. These solutions rely on the functioning of ecosystems to mitigate the effects of coastal hazards. However, the ability of ecosystems to act as buffer zones is being compromised due to increasing urbanization in coastal areas. The implementation of NBS in urbanized coastal areas is becoming a major challenge for our societies, as coastal cities densely concentrate populations and valuable assets. This study has two main objectives: (1) to provide a structured overview of current NBS research and (2) to explore whether and how NBS are utilized in urban coastal risk management. A critical review of the literature serves as a foundation for understanding how NBS is conceptualized, identifies the factors contributing to the ambiguity of the term, and proposes five key elements for defining NBS. A systematic review of 3384 publications from Scopus shows that coastal issues represent a secondary focus in NBS research (14%). Coastal NBS studies primarily address coastal erosion and flooding exacerbated by sea level rise through natural coastal ecosystems. While urban issues related to climate change are at the heart of NBS research, the urban dimension has very little connection with coastal NBS. This article highlights the need for a multifaceted response to manage coastal risks in coastal cities, combining hard and soft engineering (hybrid solutions), inshore and offshore NBS, coastal and stormwater NBS, and regulating urbanization in flood-prone areas. The application of NBS in coastal risk management calls for incorporating natural coastline dynamics into land-use planning and rethinking our fixed modes of coastal occupation. This article provides keys to understanding the concept of NBS to facilitate its integration into coastal risk management plans.