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The legacy of the discriminatory federal housing policy known as redlining continues to deprive some urban neighborhoods of investment. Now, a new study maps how that former policy exacerbates the impacts of climate change.

Starting in the 1920s, federal housing policy redlined neighborhoods, grading some “A” — worthy of bank mortgages and insurance policies. Others, including large swaths of Philadelphia, were rated “D” – or “hazardous.”

As a result, the bulk of capital flowing into redlined areas was for industrial, manufacturing, or high-rise public housing projects. So while decades of bank mortgages encouraged suburban developments with yards, trees and parks, inner city neighborhoods got more concrete and asphalt.

The new study maps these effects, making a link between historic redlining and areas that are most vulnerable to suffering from extreme heat caused by a warming climate. Heat-related illnesses lead to more deaths than any other natural disaster or weather event in the last decade.

Published this week in the journal Climate, “The Effects of Historical Housing Policies on Resident Exposure to Intra-Urban Heat: A Study of 108 US Urban Areas,” shows that in 94% of the 108 cities examined, once-redlined neighborhoods experience increased average daily temperatures compared to non-redlined areas. In Philadelphia, the disparity is almost 10 degrees Fahrenheit.

“Today, as climate change becomes far more acute of an issue for us to tackle, that policy is playing out as those communities living in formerly redlined areas are exposed to much more extreme heat,” said Vivek Shandas, a Portland State University urban studies professor and co-author of the report.

The study took redlined areas mapped by the New Deal-era Home Owners Loan Corp. and mapped them on top of current satellite data recording surface temperatures.

“It’s a relatively simple integration of existing data sets that revealed incredible results,” Shandas said.

“Not just redlining but other historical race-based policies or actions are definitely one of the major underlying causes of the heat disparity.”

In many cases, redlined areas still house poorer residents or people of color. The lack of trees and investments in amenities like parks helped create a situation in which today people of color and poor people in those areas could suffer more from increased heat.

“Environmental justice is not something that just happened yesterday,” Shandas said. “It’s actually a long-standing thing that was presented and developed and created decades ago that we’re now dealing with, especially with climate change.”

Philadelphia as an example

Not all of the redlined areas in Philadelphia continue to see disinvestment or instances of high heat. For example, Fairmount was a redlined neighborhood but now has more trees and white roofs relative to other areas. Some of the hottest areas now include Cobbs Creek, Point Breeze, Strawberry Mansion, and Hunting Park.

The city’s director of sustainability, Christine Knapp, said she’s not surprised by the results of the study. It’s something the city recognized while planning to combat high heat in the Hunting Park section. By creating heat maps, city officials 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.”

Knapp said that the city is expected to have more days over 100 degrees and that some areas of the city will be more affected than others if steps aren’t taken.

The city has moved to set up cooling centers, and Knapp said the nonprofit Esperanza has a grant to establish a “heat relief network” for the neighborhood this summer.

Philadelphia’s tree canopy ranges across only 20% of its landmass. In highly industrial Hunting Park, trees cover less than half that range. The city now has a goal to increase tree coverage overall to 30%.

Shandas said his next plan is to dig in and find out how urban-planning processes continue to encourage disparities.

Knapp said that there are currently no land-use policies addressing heat, but that the mayor recently announced plans to create a citywide climate adaptation plan.

“That’s the main way in which we want to start having some of those conversations about policies around land use and fully understanding all the implications,” Knapp said. “Because as we know with redlining as an example, one land use policy decision can have ramifications for many decades to come.”

This story is produced in partnership with StateImpact Pennsylvania, a collaboration among The Allegheny Front, WPSU, WITF and WHYY to cover the commonwealth's energy economy.


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