Mainstreaming urban nature: Uncovering structural conditions for urban nature-based solutions

Nature-based solutions (NBS), such as green roofs, community gardens or bioswales, present a promising approach to urban sustainability, primarily because of their capacity to address environmental, social, and economic sustainability challenges simultaneously. Yet despite high expectations, mainstreaming urban NBS remains challenging. Challenges in mainstreaming NBS may arise from path dependencies in urban development. Structural conditions in urban infrastructure regimes - such as policy and funding frameworks, social networks or existing physical infrastructures - shape and stabilize the development and use of urban infrastructures. In doing so, they can hinder the development of divergent, innovative approaches to urban infrastructure development such as NBS. In this thesis I provide theoretical and empirical insights into the structural mechanisms that hinder or enable NBS mainstreaming. First, the research provides more clarity about the NBS concept in relation to sustainable urban development. In addition, I use two perspectives on embedding sustainable innovation in broader social structures, a socio-spatial and a sociotechnical perspective, and apply these in a quantitative database analysis and in qualitative case studies. The research shows the nuances, interactions, interdependencies and hierarchies in how structural conditions influence the mainstreaming of NBS, as well as the context-specific characteristics of these conditions. Recognizing these system dynamics can prevent overly simplistic and one-size-fits-all attempts at NBS mainstreaming. A conceptualization of urban infrastructure regimes as heterogeneous - multi-domain and multi-dimensional - structures supports an improved and more context-sensitive understanding of the persistence of barriers to NBS mainstreaming and opportunities to accelerate urban sustainability.