Quantifying How Urban Trees Cool Cities

A new study from researchers from the Chinese Academy of Sciences and the Cary Institute of Urban Ecosystem Studies offers a way to understand the benefits of urban trees at larger scales so they can make more informed decisions about tree planting programs aimed at reducing urban temperatures and improving air quality.

“Overall, the team discovered that the cooling efficiency of urban trees increased at larger scales,” in part thanks to the ability to plant larger groups of trees. “For example, the authors estimate that the city of Baltimore could reduce land surface temperatures by 0.23°C if they increased tree canopy by 1%. To achieve 1.5°C of cooling, they would need to increase tree canopy cover by 6.39%.”

With greater clarity about the relationships between area, tree canopy cover, and cooling effects, the paper makes it possible to predict cooling effects at the whole-city scale, offering a valuable tool for managers to set urban tree canopy goals to reduce extreme heat.

One of the study’s authors points out that while the paper can provide useful data for city-level decision-making, planners should be careful to ensure equity and community buy-in at the neighborhood scale.