He cools down by squirting himself with a spray bottle, using the power of evaporative cooling to stay fresh. It’s the same basic process that trees deploy to cool their surroundings. By transporting water through their roots and releasing water vapor into the air through their leaves, trees cool the space around them — including our paved cities.
Scientists have documented that tree-created water vapor and shade moderate the so-called urban heat island effect, reducing daytime temperatures an average 3 degrees compared to un-forested urban areas.
At night, temperatures rise when concrete and asphalt surfaces release the heat they accumulated during the day, compounding the cycle.
Extreme heat events affect all of us, but have a greater impact on vulnerable populations, such as older adults, young children and people in poor health. And because of the inequitable distribution of city trees, low income urban areas are hotter than higher income areas.
Climate change will make trees in cities even more critical. In 1990, people in Salt Lake City experienced about seven days above 100 degrees. In 2050, people in Salt Lake City are projected to encounter 41 days over 100 degrees.
But there is hope for these heat islands. For example, in Highland, Utah, just south of Salt Lake City, urban planners created its town center with heat island reduction elements, which includes trees, reflective roofing and green landscaping.
The benefits of these actions go beyond just reducing heat islands. They support an improved quality of life in our growing cities: reduced noise, habitat for wildlife and the peaceful beauty of trees around us.
