Local tree experts say cure for negative health effects of Philly ‘heat islands’ is made in the shade

PHILADELPHIA (KYW Newsradio) — Scientific evidence now shows that high summertime temperatures in Philadelphia have been exacerbated by a nationwide issue: urban heat islands.

A heat island is an area specifically within an urban setting that traps heat, according to Ayanna Mitchell, trees field specialist for the Pennsylvania Horticultural Society .

“An area that has a larger surface temperature than shaded tree areas,” she explained, “characteristically asphalted and concreted areas that are in direct baking sunlight that soak up heat.”

Mitchell says the areas don’t just trap heat, they also release it after the sun sets, which means areas around them can experience temperatures of 10 to 20 degrees Fahrenheit higher than shaded areas.

She adds heat islands have detrimental effects on people who live within them, including increased heart rate, cardiovascular stress and dehydration. Psychological effects can include anxiety, anger, frustration and shortness of temper.

Data from the U.S. Census Bureau shows 52% of Philadelphians live in heat islands. According to Mitchell, these areas are overwhelmingly industrialized areas with little to no tree cover or green spaces. And they disproportionately affect communities of color and communities of people with low incomes, she says.

Mitchell says PHS has several programs aimed at combating the phenomenon, aided by a $12 million federal grant from the Inflation Reduction Act. Those programs include planting trees and creating green spaces in places such as vacant lots, and forming connections with facilities that offer tree-planting supplies such as mulch.

“We are working with homeowners and residents to make sure we are planting the right tree in the right place,” she said.