Beyond the luxury effect: individual and structural drivers lead to 'urban forest inequity' in public street trees in Melbourne, Australia

Urban trees are increasingly being used to help cities adapt to climate change, improve health and wellbeing, and promote biodiversity. Yet these benefits are distributed unequally, mirroring the uneven distribution of the urban forest in many cities. Contrasting theories have been proposed to explain these observed patterns that focus either on the economic wherewithal of individuals (the 'luxury effect'), or the outcome of structural factors such as municipal decision-making processes. Here, we explore patterns across 10 municipal authorities in greater Melbourne, Australia to compare the relative importance of these competing mechanisms. We show that both individual and structural processes are both major determinants of the density and diversity of trees in this large Australian city. Interestingly, education level was strongly related to tree density, while household income was negatively related to tree density and diversity in some municipalities. The luxury effect was not able to adequately explain the patterns observed in Melbourne. This finding has important implications for the planning and management of urban forests and the equitable distribution of the benefits they provide, in the context of the rapid expansion of urban populations across the globe. To counteract inequity, local municipalities must acknowledge and deliberately overcome internal biases that favour the provision of street trees to more advantaged sections of the community.