Image via Shutterstock Image via Shutterstock

The city’s once-redlined neighborhoods are nearly 10 degrees warmer than their highest-rated, non-redlined counterparts, a new study shows.

It’s been nearly 90 years since the U.S. government implemented a discriminatory housing policy known as redlining, but the effects are still being felt today. In fact, the impacts of climate change are worse in those neighborhoods, according to new research.

Back in the 1930s, the federal Home Owners’ Loan Corporation (HOLC) began rating and mapping neighborhoods by how desirable or risky they were for banks to provide mortgages to aspiring homeowners. This became known as redlining. Some neighborhoods received “A” grades, meaning they were granted easier access to credit and could receive mortgages, while other neighborhoods—primarily those with a heavy presence of Blacks and immigrants—received “D” ratings, marking them as “hazardous” areas in which to provide mortgages. 

Redlined communities were disinvested in and became rife with poverty as residents struggled to obtain credit or buy homes. While the city’s more “desirable” communities saw public and private funding go toward green spaces and public parks, the limited money that flowed into redlined neighborhoods were directed toward concrete- and asphalt- based industrial plants, highways, or public housing projects. 

The consequences of redlining have previously been documented, but as climate change has become a crisis, the long-term impact on formerly redlined communities has crystallized even further.

A study published this week in the journal Climate, which analyzed data and maps in 108 urban areas, found that 94 percent of formerly redlined neighborhoods experienced higher average daily temperatures compared to non-redlined areas. Disparities vary from city to city, but Philadelphia’s once-redlined areas are 9.4 degrees Fahrenheit warmer than their highest-rated, non-redlined counterparts, the 10th largest difference nationwide. 

“What we think we identify here is a systematic disparity in exposure to extreme heat, potentially brought on by decisions that were made almost 100 years ago,” Jeremy Hoffman, one of the report’s authors and the chief scientist at the Science Museum of Virginia, told COURIER in a phone interview.

The racist roots of redlining are on clear display in HOLC’s maps, which were digitized by the Digital Scholarship Lab at the University of Richmond. 

In its report on an area of North Philadelphia that now includes the Strawberry Mansion neighborhood, HOLC classified the area’s “Negro concentration” as a “detrimental influence.” Similarly, in its report on the Point Breeze neighborhood of South Philadelphia, HOLC included  “Negro encroachment – heavy obsolescence” under the “detrimental influences” section of its report. 

Strawberry Mansion and Point Breeze, both of which received “D” grades from HOLC, are among the Philadelphia neighborhoods currently experiencing higher average daily temperatures, according to the study. In total, nearly two dozen Philadelphia neighborhoods received a “D” grade.

“What we think we identify here is a systematic disparity in exposure to extreme heat, potentially brought on by decisions that were made almost 100 years ago.”

Redlining was prohibited under the 1968 Fair Housing Act, but the law failed to redress past consequences. Many previously redlined neighborhoods remain predominantly home to communities of color with higher rates of poverty than their white counterparts, and the vulnerability of these neighborhoods to extreme heat can be linked directly back to the lack of green spaces and parks. 

Concrete and pavement are impervious surfaces, absorbing heat and releasing it more slowly, while trees cool the air and provide shade. Neighborhoods with a heavy presence of concrete and a lack of trees are thus hotter than their non-urban surroundings, a dynamic known as the urban heat island effect

“Green space has the ability to mitigate climate change as it relates to the urban heat island effect, so a lot of communities of color, particularly in Philadelphia, are hotter and it’s because of a lack of green space,” said Ebony Griffin, staff attorney at The Public Interest Law Center in Philadelphia, in a phone interview with COURIER.

Entire cities experience the urban heat island effect and Philadelphia is particularly susceptible, as tree canopy covers only 20 percent of the land in the city. But this number is even lower in the city’s previously redlined areas, according to research released this month. The study found that in 37 cities around the country, including Philadelphia, previously redlined neighborhoods currently have about half as many trees on average as the highest-rated, predominantly white neighborhoods on HOLC’s maps.

This disparity means formerly redlined communities are more vulnerable to the consequences of extreme heat driven by climate change. From 1999 to 2010, 8,081 heat-related deaths were reported in the United States, according to the Centers for Disease Control and Prevention, and researchers predict the number of heat-related deaths will rise as the planet continues to warm.

Christine Knapp, director of Philadelphia’s Office of Sustainability, told WHYY she’s not surprised by the study’s findings, and the city itself has found that average temperatures between neighborhoods can vary by up to 22 degrees Fahrenheit.

“There’s a history of racist policy in action,” Knapp said. “Not just redlining but other historical race-based policies or actions are definitely one of the major underlying causes of the heat disparity.”

Philadelphia is taking steps to address the issue, setting up cooling centers and working with nonprofits to provide relief this summer, Knapp said. The city also plans to increase its tree coverage to 30 percent, to provide further cooling relief.