Trees are crucial for the temperature and future of our cities

Recent study shows that trees play a big role in keeping cities cool.

Skyscrapers and tree. © Philippe Le Jeanvre/Getty

According to a study published in Proceedings of the National Academy of Sciences, the right amount of tree cover can lower daytime temperatures in city landscapes by more than 5°C.

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“We knew that cities are warmer than the surrounding countryside, but we found that temperatures vary just as much within cities,” says Monica Turner, co-author of the study and a professor from University of Wisconsin-Madison. “Keeping temperatures more comfortable on hot summer days can make a big difference for those of us who live and work there.”

With climate change increasing summer temperatures, it imposes potential health and economic costs on people in cities.

Trees may be the secret weapon city planners need to keep the places we live liveable.

Our man-made structures, like roads, buildings and pavements, absorb the sun’s heat during the day, but trees can provide shade from the sun and also transpire, releasing water and cooling things down.

To get the maximum benefit of this cooling service, the study found that tree canopy cover must exceed 40 per cent.

“Tree canopy cover can actually do more than offset the effects of impervious surfaces,” says Carly Ziter, lead author of the study. “During the day, an equivalent amount of canopy cover can cool the air down more than pavement will warm it up.”

For her research, Carly Ziter biked around Madison with a small weather station strapped to the back of her bike. © Carly Ziter
For her research, Carly Ziter biked around Madison with a small weather station strapped to the back of her bike. © Carly Ziter

The results point to the importance of urban landscaping to make our neighbourhoods more liveable in the future.

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Read the paper in Proceedings of the National Academy of Sciences of the United States of America.