Understanding street tree inequities: The interrelation of urban layout and socio-economics

Trees play a crucial role in urban ecosystems, such as enhancing air quality, mitigating climate change impacts, and promoting community well-being. However, their distribution within cities often reflects socio-spatial disparities, disproportionately benefiting some neighbourhoods over others. This study examines the distribution of trees, particularly street trees, in Pōneke Wellington, Aotearoa New Zealand and investigates whether urban layout and socio-economic indicators explain the observed disparities in street tree distribution and planting potential. Using spatial analysis of a comprehensive city-wide tree dataset, we explore spatial patterns of (street) tree distribution and employ spatial error models to explore the influence of urban layout and socio-economic indicators on street tree distribution. Our findings reveal significant spatial disparities in tree coverage across the urban area. Notably, only a small fraction of trees (7 %) are located on roadside reserves, despite substantial non-treed roadside areas suitable for additional planting (17 %). The spatial error model indicates that factors such as building set-backs, parcel irregularity, and road complexity significantly influence street tree distribution and planting potential, while socio-economic indicators alone provide limited explanatory power. These results highlight the critical role of urban design in shaping urban greening justice within cities, while also illustrating the complex interrelations between urban layout and socio-economic factors in shaping tree distribution. The study suggests that targeted street tree planting and informed urban planning have potential to address observed disparities in (street) tree distribution.