Collaborative governance arrangements: what makes nature-based solutions endure?

'Nature-based Solutions' (NbSs) are considered key actions to address urban regeneration and foster greener cities. Such actions are based on collaborative governance arrangements, where public administration, private companies, research and citizens cooperate to test and manage innovative solutions. Reflecting a quadruple helix logic, these arrangements display different actors leading responsibility for maintenance while cultivating collaborative relations. Hence, collaborative governance arrangements can assume the shape of public-led, private-led, research-led or community-led types, addressing specific maintenance challenges. Yet, the conditions that allow different types of collaborative governance arrangements to make NbSs endure are still poorly investigated. Through an in-depth analysis of the proGIreg Urban Living Laboratory in Turin (Italy), this paper analyses different types of collaborative governance arrangements, exploring which challenges, risks and potentials characterise them. Particularly, the paper investigates conditions that make NbSs endure over time. The results outline how legitimacy, institutional leadership and administrative commitment, networking capacities, integration of resources, competencies, co-responsibility, knowledge transfer and empowerment play a pivotal role in making NbSs endure. Overall, this article contributes to contemporary research and practices on urban experimentation, NbSs and maintenance.