–-To get the maximum benefit of this cooling service, the study found that tree canopy cover must exceed 40 percent.
Carly D. Ziter, Eric J. Pedersen, Christopher J. Kucharik, Monica G. Turner. Scale-dependent interactions between tree canopy cover and impervious surfaces reduce daytime urban heat during summer. Proceedings of the National Academy of Sciences, 2019; 201817561 DOI: 10.1073/pnas.1817561116
….Impervious surfaces — like roads, sidewalks and buildings — absorb heat from the sun during the day and slowly release that heat at night. Trees, on the other hand, not only shade those surfaces from the sun’s rays, they also transpire, or release water into the air through their leaves, a process that cools things down.
To get the maximum benefit of this cooling service, the study found that tree canopy cover must exceed 40 percent. In other words, an aerial picture of a single city block would need to be nearly half-way covered by a leafy green network of branches and leaves….