Actors mainstreaming nature-based solutions in cities: A case study of Melbourne's change agents and pathways for urban sustainability transformations

Nature-based solutions (NBS) are implemented across multiple cities worldwide and feature as promising solutions in local and global agendas. As solutions that can deal with interlinked urban challenges, NBS are being taken up by cities in different geographies and are considered to be mainstreaming. The process, referred to as mainstreaming, and how this can be achieved needs to be better understood, which is identified as a research gap. In this paper, we examine the roles that actors can undertake that contribute to the mainstreaming of NBS in cities. The aim is to understand the roles that urban actors, especially those within local governments, assume in the process of NBS mainstreaming to mobilise and implement novel and innovative strategic solutions for cities. This topic is explored in a case study of the metropolitan Melbourne region in Australia, where urban forest strategies are gaining traction in local governments for addressing urban resilience concerns. We present how the roles different actors assume contribute to the (re)shaping, building, and/or transformation of institutions to attain climate and ecologically resilient cities. The main contribution of this paper is a pathways framework that illustrates how sustainability norms can move through the mainstreaming process, facilitated by the roles that actors undertake – to champion, advocate, and realise transformative discourses and actions within urban politics and urban practices. Our key findings are framed as success factors of mainstreaming agencies and pathways underpinning transformation, which are: commitment longevity, innovative capacity, collaborative mindset, and on-ground delivery.