In Virginia and U.S., urban heat islands and past redlining practices may be linked, study finds

The rich may get richer and the poor poorer, as the saying goes, but in a world increasingly altered by climate change, the poor may also be getting hotter — especially if they’re people of color.

So finds a study released Monday in Climate journal by Science Museum of Virginia Chief Scientist Jeremy Hoffman, Portland State University Professor of Urban Studies and Planning Vivek Shandas and Virginia Commonwealth University student Nicholas Pendleton.

“It really underscores how decisions made almost 100 years ago are playing out as an acute climate inequity today,” said Hoffman. 

Beginning in the 1930s and until the time of its outlaw in 1968, the U.S. government engaged in a practice known as redlining, under which the federal Home Owners’ Loan Corporation ranked and mapped neighborhoods by how desirable they were for banks to give mortgages to homebuyers. 

Type A and B neighborhoods, which tended to be wealthier and have large proportions of white residents, were considered desirable for investment, while Type C and D neighborhoods, with large populations of black residents, were classified as “declining” or “hazardous” and therefore not considered good places to invest.

Over the years, redlining has been linked to not only lower rates of homeownership and less investment in housing, but also less access to resources like fresh food and health care. The Hoffman and Shandas study draws a new connection to heat exposure, a problem increasingly attracting the attention of policymakers as climate change drives temperatures steadily upward. 

Of those urban areas mapped by HOLC, the researchers found, “in nearly all cases, those neighborhoods located in formerly redlined areas — that remain predominantly lower income and communities of color — are at present hotter than their non-redlined counterparts.”

That pattern holds in the four cities examined in Virginia: Richmond, Norfolk, Roanoke and Lynchburg. 

Of the 108 urban areas examined, Roanoke revealed the ninth-largest difference between average land temperature in areas classified by HOLC as Type A and those classified as Type D. There, researchers found the disparity to be as much as 9.5 degrees Fahrenheit. Smaller but still noticeable differences were found in Norfolk (5.3 degrees), Richmond (4.7 degrees) and Lynchburg (1.8 degrees).

Two key factors drive land temperatures, Hoffman said: tree canopy and impervious surface. Disadvantaged and minority communities tend to have too little of the first, which provide shade, and too much of the second, which absorb and reflect heat. 

Those findings aren’t new. Shandas and Hoffman in 2017, working in conjunction with the National Oceanic and Atmospheric Administration, found that in Richmond, temperature differences between some parts of the city were as much as 16 degrees Fahrenheit. Followup studies were conducted in Baltimore, Washington, D.C., Boston and Philadelphia confirming that temperatures can, and do, vary widely within a city’s limits. 

But now the researchers are proposing a new insight: that these factors are correlated with historic patterns of racial discrimination.

“‘D’-rated areas are now on average 2.6° C warmer than ‘A’-rated areas,” they found. “Areas assigned a ‘hazardous’ HOLC security rating in U.S. cities exhibit quantitatively less coverage by tree canopy and more coverage by impervious surfaces in the present decade.” 

“This is the first time that it’s been tied to a national-scale pattern,” said Hoffman. “It’s not just city-specific. It’s truly systematic in nature.”

Nationwide, the study found the greatest intra-city temperature disparities in southern and western cities, with the smallest differences in Midwestern cities.

Hoffman cautioned that the temperatures used in the analysis were averages derived from satellite data, and that additional studies are needed to accurately capture temperature differences on the ground. NOAA has announced that depending on funding, 20 more cities may be mapped this summer. 

“We don’t yet have the kinds of detailed descriptions of heat that we truly need in order to address these inequitable exposures,” he said.