As the climate warms, heat waves are predicted to increase in both frequency and intensity. But that heat, and the threats to public health that come with it, will not be distributed evenly.

In cities like Portland, some areas are referred to as “heat islands,” areas where development has exacerbated the effects of high temperatures. Now, a new study from Portland State University is showing, for the first time, that areas prone to excessive heat are disproportionately populated by low-income communities and people of color due to racist housing policies that stretch back more than a century.

Nearly every city included in the study saw higher temperatures in neighborhoods that were historically subject to discriminatory housing policies, with poorer areas seeing averages temperatures about five degrees higher than their wealthier counterparts. And, of the 108 urban areas analyzed, Portland came in with the worst temperature discrepancy between rich and poor, a difference of almost 13 degrees.

“The patterns of the lowest temperatures in specific neighborhoods of a city do not occur because of circumstance or coincidence,” said Vivek Shandas, urban studies and planning professor at PSU and co-author of the study. “They are a result of decades of intentional investment in parks, green spaces, trees, transportation and housing policies that provided ‘cooling services,’ which also coincide with being wealthier and whiter across the country.”

The study, one of the first to link historic housing policies to threats from climate change, shows what researchers have been saying for years: As extreme weather events like heat waves become more common, poor communities will face disproportionate risks.

Decades of racism in housing policy

As far back as the early 20th century, housing policies in Portland were explicitly racist. Exclusionary covenants, legal clauses written into property deeds, prohibited people of certain races, specifically African Americans and people of Asian descent, from purchasing homes. In 1919, the Portland Realty Board adopted a rule declaring it unethical to sell a home in a white neighborhood to an African American or Chinese person. The rules stayed in place until 1956.

In 1924, Portland voters approved the city’s first zoning policies. More than a dozen upscale neighborhoods — including familiar names like Irvington, Eastmoreland and Laurelhurst — were zoned for single-family homes. The policy, pushed by homeowners under the guise of protecting their property values, kept apartment buildings and multi-family homes, housing options more attainable for low-income residents, in less-desirable areas.

After the passage of the National Housing Act in 1934, the federal government asked the Home Owners’ Loan Corporation to create “residential security maps” for cities across the country, including Portland. These maps were intended to rate neighborhoods, with “A” areas being the most desirable and “D” being least desirable, for investment security purposes, but their effects were much more pernicious. Areas rated “D” were surrounded with red lines on the maps, and residents who lived there, often low-income minorities, were frequently denied mortgage loans and insurance. In the mid-20th century, Portland’s African American communities — Albina, Alberta and other parts of Northeast and inner Southeast Portland — were all redlined.

On an individual level, the practice prevented residents from accessing home loans, denying them the opportunity to build intergenerational wealth by owning property. On a citywide level, redlining, along with zoning restrictions, maintained segregation and made redlined neighborhoods ripe for development of multi-unit buildings and industrial use.

By the 1950s, many of these neighborhoods were gutted by so-called “urban renewal,” as construction of Interstate 5, Emanuel Legacy Hospital and the Veterans Memorial Coliseum saw the forced displacement of entire communities in Northeast Portland.

Freeways sliced neighborhoods in half. Warehouses sprung up next to apartment buildings and parking lots. Residential lots were built to the edges, leaving little room for yards or trees. Redlined areas saw more concrete and asphalt but fewer green spaces and parks than their wealthier counterparts.

Then the climate began to change.

Urban heat islands

Shandas began studying areas of excessive heat, known as urban heat islands, more than a decade ago. In 2018, he published his first analysis of Portland temperatures, collecting more than 300,000 data points across the city.

He found Portland was home to a number of heat islands, among them: the 82nd Avenue corridor between Interstate 84 and Southeast Foster Road, the inner Southeast industrial area, and the inner Northeast along the I-5 corridor.

A map from Vivek Shandas' 2018 analysis shows temperature disparities in Portland.

Shandas’ more recent analysis was simply a matter of taking two maps, of heat islands and of areas that were subject to discriminatory housing practices, and laying them on top of each other. The results were clear.

“We found that those urban neighborhoods that were denied municipal services and support for home ownership during the mid-20th century now contain the hottest areas in almost every one of the 108 cities we studied,” Shandas said. “Our concern is that this systemic pattern suggests a woefully negligent planning system that hyper-privileged richer and whiter communities. As climate change brings hotter, more frequent and longer heat waves, the same historically underserved neighborhoods — often where lower-income households and communities of color still live — will, as a result, face the greatest impact.”

A map from Vivek Shandas 2020 analysis shows temperature disparities in Portland, overlaid with areas that were subject to redlining, marked by red crosshatch.

A few extra degrees might not sound like much, but extreme heat-related illnesses kill more than 600 people every year across the country, according to the U.S. Centers for Disease Control. Researchers predict that, as the global climate warms, extreme heat events will increase in both frequency and intensity.

Jeremy Hoffman, chief scientist at the Science Museum of Virginia and co-author of the study, said the impacts on residents of these concentrated heat islands are wide-ranging.

“They are not only experiencing hotter heat waves with their associated health risks but also potentially suffering from higher energy bills, limited access to green spaces that alleviate stress and limited economic mobility at the same time,” Hoffman said. “Our study is just the first step in identifying a roadmap toward equitable climate resilience by addressing these systemic patterns in our cities.”

A green path forward

If Portland is going to find its way to a cooler future, the path to get there will need to be lined with trees. Curtailing carbon emissions is an essential part of mitigating the impacts of climate change, but the amount of carbon dioxide already in the atmosphere will make some amount of warming inevitable, Shandas said, and adapting to those warmer temperatures will be important, too.

Increasing foliage and green space is the best way to combat the pernicious heat islands, at least in the short term, Shandas said. Trees absorb more heat from the sun and create shade. Plants pull moisture from the ground, which in turn evaporates into the air, providing a cooling effect.

Portland is looking to make changes to increase greenery in some of the neighborhoods that saw the worst of the discriminatory housing policies, officials said.

In December, city councilors voted to adopt changes to city code that would require new development to allocate areas for greenery and put limitations on the size of parking lots. The city council is currently debating a plan that would allow apartments and multiplexes in neighborhoods previously zoned only for single-family homes.

“Portland is really trying to connect the dots when it comes to institutional racism and some of the outcomes and address these issues moving forward,” said Bill Cunningham of the Portland Bureau of Planning and Sustainability. “Urban heat islands are a legacy of those past planning decisions.”

Community groups have been active, too. Plans to widen I-5 in the Rose Quarter have been met with strident opposition from environmental and neighborhood groups. Some have criticized the freeway widening itself, others said plans to cap the freeway must be more extensive and allow for buildings atop them. The group Albina Vision Trust has called for a wholesale neighborhood revival and an expansion of green space in inner North and Northeast Portland.

Friends of Trees, a nonprofit that has operated in Oregon and Washington for the past 30 years, has used Shandas’ heat maps to target areas needing more trees. The group has planted more than 800,000 in three decades, said interim Executive Director Whitney Dorer, and Friends’ contract with the city requires 70 percent of those plantings go into Portland’s low-income communities.

For years, researchers have warned that as the climate warms, extreme weather events like heat waves will become more common and poor communities will face bigger threats from these events than their wealthier peers. Shandas’ findings are what those threats look like on the ground.

“By recognizing and centering the historical blunders of the planning profession over the past century, such as the exclusionary housing policies of ‘redlining,’ we stand a better chance for reducing the public health and infrastructure impacts from a warming planet,” Shandas said. “This is the first step. It's going to take a lot more work on development to undo what we’ve done in the past.”

-- Kale Williams

kwilliams@oregonian.com

503-294-4048

@sfkale

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