A tree grows in a sidewalk.
Philadelphia A tree grows in a city sidewalk. © Jaci Downs

Stories in Pennsylvania

Urban Heat Islands

The Nature Conservancy helps cities beat the heat in Pennsylvania.

An aerial view of row house rooftops in an urban area
Urban Neighborhood Many neighborhoods in Philadelphia boast row houses and scattered trees. © Creative Commons/Ed

A well-established, healthy urban tree canopy cools air temperature, reduces energy consumption, removes pollution from the air and stores carbon. Their root systems filter rainwater before it flows into local waterways. Studies also show that trees and green space helps to reduce crime, improve safety, increase property values and even lower blood pressure.

It’s the new normal. Excessive heat warnings and unhealthy air quality alerts, especially for children and senior citizens, have become part of summer in the city. 

You can see for yourself in South Philadelphia where brick row homes, stacked next to each other in a concrete checkerboard that goes on for miles, experience a summer heat index that often hits triple digits. At night, there’s no respite from the heat. It just doesn’t cool down.

The Nature Conservancy's primary strategy to reducing heat islands revolves around putting nature to work, in many cases, by planting more trees

TNC's Director of Urban Conservation in Pennsylvania

That’s how it happens. Today, more than 80 percent of Americans live in cities where, on average, temperatures are notably higher than in surrounding suburban and rural communities. Within these urban areas, concentrations of pavement—streets, rooftops, parking lots and other surfaces—absorb and retain more heat than the parks, yards and other natural ground cover they have replaced. 

The numbers tell the story. Warmer temperatures emerging from urban heat islands result in higher energy costs, increased air pollution and more heat-related illnesses. Climate change is likely to exacerbate the situation with increasingly frequent and severe record-breaking heat waves.

“Tackling heat islands represents some of The Nature Conservancy’s most cutting-edge approaches to conserving nature,” says Julie Ulrich, TNC’s director of urban conservation in Pennsylvania. “It is an issue that not only jeopardizes the natural environment; it also directly threatens human health and economic prosperity.”

In fact, issues related to urban heat islands jeopardize more people in the United States each year than hurricanes, floods, tornadoes and lightening combined. This is a reason why, in 2016, the nation’s mayors adopted unanimously, the Reducing Urban Heat and Protecting Human Health with Green Space resolution, which recognizes the connection between environmental, human and economic health.

While an emerging issue in Pennsylvania, TNC is working with the City of Philadelphia to make strides in reversing this trend in the following ways:

  • Working with the U.S. Forest Service and college students to collect data on Philadelphia’s tree canopy to establish protocols for using citizen science to monitor urban forest health.
  • Providing technical assistance on an eastern hemlock conservation plan for Wissahickon Valley Park in order to protect this urban forest from infestation by the hemlock woolly adelgid.
  • Partnering with the Philadelphia Orchard Project to establish tree cover and pollinator gardens in schoolyards and other asphalt-covered areas throughout the city.
  • Establishing nine schoolyard gardens through TNC’s Nature Works Everywhere program.

According Ulrich, progress made on these and other efforts to reduce the heat island effect in Philadelphia can be exported to other urban areas in Pennsylvania, such as Pittsburgh, where the city’s Department of Public Works is working with local non-profits and state agencies to create a forested city.

“TNC’s primary strategy to reducing heat islands revolves around putting nature to work, in many cases, by planting more trees,” adds Ulrich. “We look forward to doing more of this in Pennsylvania as we engage with partners around the state to determine our role in this important issue. We look forward to making a positive impact in any way that we can.”

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