Climate and socio-economic drivers of urban tree abundance, richness and composition in Australian cities

Urban trees provide multiple ecosystem services to city dwellers across the globe. However, their distribution differs greatly across and within cities, often reflecting contrasting environmental, socioeconomic, cultural and political characteristics, acting as an indicator of environmental inequality. We analyzed how the abundance, diversity and species composition of street trees in 51 Australian urban areas were related to socio-economic indices, such as income, education, age and immigration status. The effect of climatic conditions, including mean temperature of the warmest quarter (°C; Tmean), and aridity on urban tree distributions was also evaluated. Our results revealed that tree abundance was positively correlated with population density and negatively correlated with the proportion of residents born overseas; tree species richness was also negatively related with Aridity. Tree abundance varied across climatic gradients, with lower abundance observed in areas with high Tmean. Species composition was strongly related to both socio-economic and climatic variables. Our findings highlight important relationships between the abundance, richness and species composition of urban trees and socio-economic and climatic characteristics of urban areas across Australia. This study provides data-driven insights that can inform more equitable and climate-sensitive urban forestry planning and management.