Insights into tree-centric urban cooling: A global meta-analysis of 182 studies across 17 climate zones

Urban trees are pivotal in mitigating urban heat, addressing climate change challenges, and enhancing urban resilience and sustainability. Their cooling effectiveness is governed by a complex interplay of background climate, urban morphology, and tree traits [1]. Our study synthesizes data from 182 studies across 17 global climate zones to quantify the cooling potential of trees in diverse urban settings. Results reveal a non-linear amplification of cooling benefits by up to 12°C with increasing background temperatures, particularly in open urban areas (LCZ 4-6) and hot, arid climates. The use of mixed-species plantings, integrating deciduous and evergreen trees, demonstrates enhanced cooling benefits, particularly in open urban forms. However, challenges such as stomatal closure during extreme heat events and the entrapment of longwave radiation in compact urban environments (LCZ 1-3) highlight the necessity for context-specific planning. The findings emphasize the critical importance of strategically selecting and situating the “right tree” in the “right place,” guided by both current and future climatic conditions. Evidence-based guidelines emphasize the prioritization of climate-appropriate tree species, optimization of ground space for root and canopy growth, and integration of tree planting into urban planning processes. By bridging urban climate science and urban design, we offer actionable insights to support cities in adapting to a warming climate, ultimately enhancing livability and sustainability. 

[1] Li, H., Zhao, Y., Wang, C. et al. Cooling efficacy of trees across cities is determined by background climate, urban morphology, and tree traits. Commun Earth Environ 5, 754 (2024).