Scaling-up nature-based solutions. Lessons from the Living Melbourne strategy

Abstract Nature-based solutions (NBS) are heralded as tools to address and tackle a variety of socio-ecological challenges. NBS are increasingly discussed as a response to shocks and stresses such as loss of biodiversity, air pollution, heat waves, flooding, droughts; and issues around residents' health and wellbeing. In recognition of these multiple functions and potential co-benefits, cities are increasingly developing NBS strategies through urban forests, green walls and facades. There has recently been a vibrant debate about extending, linking or merging successful NBS - often framed as 'scaling-up'. Despite the increasing popularity, little is known about the mechanisms and conditions for scaling-up of NBS and how this plays out in practice. How is scaling-up understood and is there an optimal scale for NBS? Previous work has addressed that the misinterpretation of scale can produce suboptimal outcomes for the resilience and sustainability of human-environmental systems. Particularly challenging is the introduction of new and adjusting established institutional arrangements to drive and coordinate socio-ecological change. Using the strategy 'Living Melbourne – Our metropolitan urban forest' as a case study, this paper explores and analyses how NBS and scaling-up are addressed and implemented in a metropolitan-wide greening strategy. The study shows that scaling-up of NBS is complex and needs inter- and transdisciplinary expertise to cope with a range of ecological, institutional and socio-cultural challenges. Intermediaries are needed to provide platforms of ongoing exchange between the heterogenous stakeholders from public and private sectors, academia and society.