Tree structural traits as a key element for ensuring socio-economic equitable access to ecosystem services.

Abstract

Achieving Sustainable Development Goal 11, which focuses on developing safe, resilient, and sustainable human settlements, requires addressing inequities in access to green spaces and urban tree cover to ensure the fair distribution of environmental benefits across socioeconomic groups. The literature consistently demonstrates that tree structural traits are key elements mediating differences in their contribution to urban well-being, as well as potential disservices. In this study, an extension to the Cooling Capacity Index (CCIT) to evaluate the cooling capacity of urban trees primarily in terms of their ability to provide shade is proposed. Bayesian Hierarchical Models were employed to comprehensively analyze disparities in access to multiple ecosystem services and exposure to biogenic volatile organic compounds emitted by urban trees by socioeconomic groups in three municipal districts of Málaga. The estimation relies on the municipal urban tree inventory, i-Tree Eco, and aerial LiDAR data. Spatial distribution patterns are intrinsically dependent on the presence of urban trees. However, certain areas with a high supply of specific ecosystem services exhibit lower availability of others, likely due to differences in tree traits. No inequities in exposure to biogenic volatile organic compounds were found between socioeconomic groups. However, inequities were identified based on income levels, the Gini index, ethnicity, and age groups, varying according to the ecosystem service assessed. These findings are essential for urban planners, providing guidance to address equity issues in future tree-planting strategies while considering that species selection and tree traits play a central role in shaping both access to benefits and exposure to disservices.