Urban tree canopy has greater cooling effects in socially vulnerable communities in the US

Cities are home to around half of the global population but face intensified and unevenly distributed heat stresses. Trees are utilized to adapt to urban heat; however, most tree planting is prioritized by either biophysical or social metrics, rather than an integration of the two. It therefore remains unclear how to maximize ecological and social benefits of tree planting in the context of environmental justice. Here, we analyze social vulnerability to heat and the cooling capacity of trees across 38 of the largest cities in the United States. We find that socially vulnerable people tend to live in hotter neighborhoods with less tree canopy. Furthermore, tree planting in such neighborhoods can achieve greater cooling benefits per unit increase in canopy. Increasing tree cover in these neighborhoods will meet the greatest need for cooling and achieve greater cooling capacity, creating social and ecological co-benefits. Adaptation measures must address both the distributional injustices of urban heat and procedural justice in planning and managing nature-based cooling approaches.