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Planting Trees To Reduce Urban Heat? Works Better In Dry Climates, Study Finds

Sep 4, 2019
Originally published on September 4, 2019 11:26 pm

As the climate warms, cities are thinking about how to mitigate urban temperature increases. But cities in wet climates like South Louisiana may have a tougher time cooling off than those in drier climates, according to a new study published Wednesday in the scientific journal Nature.

Due to a variety of factors known as the "urban heat island effect," cities typically get a little hotter than suburbs and rural areas. Those factors include things like background climate, building height, population size and the amount of greenspace.

Conventional wisdom has been that planting trees can help lower temperatures, but according to the new study, that strategy has its limits in soggy South Louisiana.

"The conventional wisdom is right, it’s just not always as effective as you want it to be," study co-author Elie Bou-Zeid said. Bou-Zeid is a professor of civil and environmental engineering at Princeton University.

The paper found that adding trees to the urban landscape always helps reduce the heat island effect, but makes a much bigger difference in drier climates than it does in more tropical ones like South Louisiana.

“If you are a tropical city,” Bou-Zeid said, “you will get a benefit from adding more parks and trees in the city. But that benefit is not going to be as significant as [it would be in], let’s say, Phoenix.”

Bou-Zeid said the study suggests cities in wetter climates will have to find other ways to cool off -- like painting surfaces white to reflect more sunlight.

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