Across the globe, nature-based solutions (NbS) are pursued to address interrelated environmental, social, and economic challenges. They often span multiple policy domains at once, thus encompassing diverse actors and stakeholders interacting within polycentric and cross-sectoral governance structures. As this can create challenging trade-offs and substantial complexity for researchers and practitioners, a comprehensive understanding of governance structures, outcomes, and factors for effectiveness is crucial. However, assessments of NbS effectiveness frequently remain limited to biophysical outcomes with insufficient recognition of social effects, as well as the interconnectedness and diversity of outcomes within complex socio-ecological systems. We argue that the Institutional Analysis and Development (IAD) and Network of Action Situations (NAS) frameworks are particularly suited for navigating this complexity inherent to nature-based solutions. Moreover, they provide means for the integrated analysis of outcomes and the factors behind effectiveness.
To explore the extent to which the frameworks were hitherto applied to our questions of interest and what conceptual deficits remain, our study presents a systematic literature review of IAD and NAS applications to NbS contexts. By investigating how different publications adapt the IAD or NAS approach and apply their theories, we provide insights for the further methodological advancement of perspectives on NbS contexts. This includes considerations of biophysical, community and multi-level, multi-sector institutional factors, and NbS effectiveness. We aim to contribute to the broader discourse around NbS by establishing a comprehensive understanding of their governance and conceptual and knowledge gaps and discuss the implications for future research needs as well as for practitioners. These findings provide a foundation for subsequent empirical case studies of NbS.
