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The Temperature of Disinvestment: Examining Urban Heat Islands and Historically Redlined Communities

Hot pavement. Blistering heat with no shade. Buildings that work as large-scale convection ovens. 

The urban heat island effect – as it has been coined by climate scientists – is more than just uncomfortable. For many communities, it can be deadly. Extreme heat is the number one weather-related killer in America, and it disproportionately affects historically redlined communities

Urban heat islands exist in urban spaces that have replaced natural heat “sinks” or absorbers, such as trees and vegetation, with pavement, buildings and other structures that retain heat. It is a growing issue as urbanization increases and global temperatures rise from human-induced climate change. But this worldwide phenomenon is less urgent for wealthier, Whiter communities with the resources to mitigate its impact. 

Historically redlined communities are not so lucky. These neighborhoods, which were cut off from lending and investment for decades starting in the 1930s, are today still majority-minority and low- and moderate-income (LMI) communities. A recent NCRC study found that 8.25 million people live in neighborhoods today that were identified by the federal government 80 years ago as “hazardous” and redlined, per 2020 Census data, with more than three-quarters of these Americans identifying as belonging to a minority group. 

“The disproportionate impact of urban heat coupled with fewer resources creates a situation in which minorities and poor people bear a very real burden on their health, especially during heat waves, despite the fact that they have benefited economically the least from the activities that have raised global temperatures,” said Bruce Mitchell, a senior research analyst at NCRC. 

Historically disinvested communities have significantly less green space such as trees and parks and more paved space compared to wealthier, Whiter communities, with the results being that formerly redlined communities are today five to 12 degrees hotter on average during the summer months compared to historically non-redlined communities. White communities where redlining policies encouraged lending have roughly twice as much tree cover as Black neighborhoods that were starved of investment, according to one analysis of 37 metropolitan areas.

In addition to a lack of green space, historically redlined communities often lack access to air conditioning or the money to afford running it. Black households in four cities – Chicago, Detroit, Minneapolis and Pittsburgh – were less than half as likely to have central A/C as White households, one study found.

Solutions are available, advocates say. According to a recent Brookings study, state and local governments are well positioned to lead the green infrastructure movement. 

“There are many measures which can reduce the local impact of urban heat islands, like increasing greenspace through parks and planting street trees, reducing the storage of heat in buildings by promoting reflective “cool” and/or green roofs, improving the energy efficiency of homes and reducing the energy use for air conditioning of homes,” Mitchell said.

Some legislation is already taking up these solutions, such as California state law AB 259, which aims to require that all dwelling units have air conditioning

“AB 2597 is a promising solution so long as additional measures are in place,” said Sona Mohnot, the associate director of climate resilience for the Greenlining Institute in California, an NCRC member organization

Mohnot outlined these additional measures as:

  1. Tenant protections to make sure that the cost of installing AC systems does not get passed down to tenants.
  2. Financial assistance if energy bills increase as a result of cooling. 
  3. Installation of efficient HVAC systems such as heat pumps, which could reduce operational energy costs and reduce strains on the grid. 

While these direct investments in improving heat resistance in people’s homes are vital, they are not enough. Cities must also build public spaces to mitigate heat-related health issues, advocates who spoke to NCRC said.

The importance of offering cooling services in holistic community resilience centers or hubs is another potential tool to tackle urban heat islands,” said Nicole Wong, the climate resilience program manager at the Greenlining Institute. Resilience hubs have been much more effective than traditional cooling centers, Wong said, pointing to the resilience hub at the Boyle Heights Art Conservatory just south of downtown Los Angeles. Not only does the resiliency hub offer cooling and heating facilities, but it also provides access to community resources, such as vaccines.

There are some other relatively simple solutions to help address the urban heat island effect, such as planting more trees in areas where there is little green space. Trees not only provide shade – they also help to absorb heat.

MillionTreesNYC is a city-wide, public-private program that achieved their goal of planting and caring for one million new trees in the city. The city of New York planted 70% of the trees, with private organizations planting the other 30%. The MillionTrees program aimed to not only reduce urban heat, but to also improve air quality, habitat preservation and improve rainwater capture. In addition, Washington, DC, has introduced a RiverSmart Homes shade-tree planting effort and in Chicago a tree canopy program called “Our Roots Chicago” was announced in April.

“These initiatives can be combined with measures to decrease the area taken up by concrete and asphalt impervious surfaces and to increase the reflectance of sunlight, preventing its absorption by roofs,” Mitchell said. Program designers also note that tree planting can have added health benefits such as reducing asthma and other respiratory illnesses. These efforts could even help lower crime rates, as seen in one study of canopy cover in Baltimore.

Trees provide a low-cost, comprehensive approach to combating the urban heat island effect. Green roofs and increased vegetation can have similar benefits at relatively low costs to cities.

It is very easy and direct to see the difference in the heat profile of individual buildings when cool roofs are implemented. These have an immediate, localized effect that can be seen on satellite imagery,” Mitchell said. There is, however, reason to fear that green spaces will increase gentrification in historically redlined communities. Any policy to include green space should work to address the threat of gentrification. 

Efforts to assess and repair the lasting harm of redlining must expand beyond simple dollars-and-cents lending analysis. Policymakers must also consider how the economic isolation of redlining furthers the impact of climate change, including the urban heat island effect and its role in shaping – and continuing – environmental and financial racism. 

Marlee Bird is a Communications, Marketing, and Development Intern at NCRC. She is currently pursuing her Master of Public Administration at American University in Washington, D.C.

Photo courtesy of rawpixel.



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Redlining and Neighborhood Health

Before the pandemic devastated minority communities, banks and government officials starved them of capital.

Lower-income and minority neighborhoods that were intentionally cut off from lending and investment decades ago today suffer not only from reduced wealth and greater poverty, but from lower life expectancy and higher prevalence of chronic diseases that are risk factors for poor outcomes from COVID-19, a new study shows.

The new study, from the National Community Reinvestment Coalition (NCRC) with researchers from the University of Wisconsin–Milwaukee Joseph J. Zilber School of Public Health and the University of Richmond’s Digital Scholarship Lab, compared 1930’s maps of government-sanctioned lending discrimination zones with current census and public health data.

Table of Content

  • Executive Summary
  • Introduction
  • Redlining, the HOLC Maps and Segregation
  • Segregation, Public Health and COVID-19
  • Methods
  • Results
  • Discussion
  • Conclusion and Policy Recommendations
  • Citations
  • Appendix

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