Abstract
Urbanization has intensified human heat-stress risk. Although vegetation transpiration (Ec) can partly mitigate the urban heat island, the associated rise in local humidity may also exacerbate heat stress. How rapid urbanization and its associated three-dimensional (3D) urban form regulate vegetation’s coupled “cooling–humidifying” effect remains poorly understood. To address this gap, we analyzed 251 rapidly developing cities in China, classified them into four background-climate types based on temperature and specific humidity, constructed a 3D urban form index, and assessed the impacts of Ec on wet-bulb temperature (Tw) and how these impacts vary across different urban forms. Results show that as the background climate becomes hotter and more humid, Ec is increasingly likely to have a warming effect on Tw. In humid heat cities, the number of cities in which Ec exhibits a warming effect on Tw increases, and 63.8% of this upward trend is attributable to urbanization. Under high-rise compact forms, Ec raises Tw primarily by significantly enhancing humidity, while the cooling pathway is not significant. For the same Ec increase, the population-weighted Tw exposure intensity is 23 times that of low-rise dispersed forms (p < 0.05). These findings underscore the need to account for 3D form when evaluating vegetation cooling in humid heat regions and to mitigate health risks through coordinated optimization of urban form and vegetation configuration.
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Subjects
- Climate sciences
- Ecology
- Environmental sciences
Acknowledgements
The authors would like to thank all the authors for their hard work in this research. This study was financially supported by the National Natural Science Foundation of China (42530115, 42471469, 42561067).
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Zhang, Y., Yang, K., Zhu, Y. et al. Urban high-rise compact form amplifies humid heat risk from vegetation transpiration.
npj Urban Sustain (2026). https://doi.org/10.1038/s42949-026-00459-1
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DOI: https://doi.org/10.1038/s42949-026-00459-1
Source: Ecology - nature.com
