Plane trees were originally planted in cities because of their resistance to pollution, disease, compacted soils and the harsh environment. Now researchers have discovered they have another quality: keeping people cool in heatwaves.
Swiss scientists found that plane trees do not, as previously believed, close their leaf pores and “shut down” when the temperature reaches 30C to 35C. Instead, the hotter it gets, the more water the trees pump up from underground. As this water evaporates from their leaves, the more the surroundings are cooled.
Plane trees are a hybrid between oriental plane and American sycamore and are particularly associated with London, where they were grown in the 17th century. However, they are magnificent trees and popular in many urban settings where they thrive in tough conditions.
With London and other urban areas increasingly enduring temperatures above 30C, the plane tree should continue to be a good choice for those hoping to reduce the worst effects of climate breakdown.
However, the researchers believe planes may not be the only trees that have this cooling quality when the weather gets hotter. They are planning to measure the rising sap in other species to give an indication of the best trees to plant in urban settings to alleviate the worst effects of heatwaves.
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