Nature-Based Solutions and Public Participation: Unpacking Tensions in Sustainable City Development in Northern Europe

Securing the acceptance of nature-based solutions (NbS) in urban greening is central for addressing current social, environmental, and climate-related challenges. To achieve this, participatory planning processes are increasingly encouraged in NbS projects. However, challenges often arise, as NbS and public participation are not always seamlessly compatible. Based on a cross-case, qualitative content analysis of project organizers' experiences in seven urban NbS planning projects in Northern Europe, we unpack three social tensions that can limit the role of participatory NbS: (1) tensions between the openness or "closedness" of environmental and participatory objectives; (2) tensions between the increasing time demands for participatory NbS processes and limitations for largely project-based NbS delivery; and (3) tensions between the roles of expert and lay knowledge. We illustrate these tensions through our cases, showing the challenges that they create for project organizers, both in terms of implementing NbS projects, as well as the risks that they have for broader NbS and participatory goals. We use the experiences and learnings from our cases to suggest paths that can help planners balance these tensions and potentially lead to more inclusive and transformative NbS planning models.