On July 5, Mothers Out Front Newton hosted a Heat Island Safari outside Newton City Hall and the Newton Free Library. Three teams of volunteers used infrared thermometers to measure how much the sun heats up asphalt, cement, brick, gravel, wood chips, mulch and grass compared to those same surfaces in shady, tree-covered areas.
They found that the tree-shaded areas were from 10 to almost 40 degrees cooler even though the temperature on that afternoon was only around 83 F and somewhat overcast. The differences between sunny and shaded surfaces would have been greater on a hotter sunnier day.
Unlike shade umbrellas that only block the sun’s rays, trees block the sun and also actively cool the air by transpiration, the process of water evaporating from the leaves. The shade from a tree also covers a wider area than an umbrella, creating safer outdoor spaces by mitigating “heat islands” created by asphalt, concrete pavement, poured-in-place rubber and other heat absorbing surfaces.
Especially as heat waves become more frequent and intense, it is important to consider the protection of trees as well as how they work with grass and other landscaping choices to reduce ambient temperatures. Our shade trees are more than just beautiful landscape features, they are our shared green infrastructure that make neighborhoods more livable.
