Latest Research: “Lower-Income Communities of Color Most Vulnerable to Urban Heat Island Effect”

Urban heat islands are places in urbanized areas that experience higher temperatures than less-developed rural areas due to the absorbance of heat by city surfaces, such as buildings and pavement. As climate change increases average temperatures and extreme heat waves across the country, city dwellers are the most vulnerable to heat-related health concerns. This effect is compounded by environmental racism, causing lower-income communities of color to be at greatest risk. A group of researchers set out to investigate this relationship. The study, published in May in Nature Communications, found that during the summer of 2017 in nearly all large urban areas, the average non-white person lived in a census tract with higher heat island intensity.
The Published Study (click to expand)

Hsu, A., Sheriff, G., Chakraborty, T. et al. Disproportionate exposure to urban heat island intensity across major US cities. Nat Commun 12, 2721 (2021).

Research Methods (click to expand)
To measure the spatial distribution of surface heat island (SUHI) intensity, the researchers used the census tract level database of SUHI intensity across the United States. They placed a specific focus on summer months (June-August), where large SUHI intensity is seen alongside increased local warming and extreme heat events in urban areas. To assess potential exposure differences, census tract level demographic information from the 2017 5-year American Community Survey (ACS) was used. Looking at the 175 largest cities, which cover nearly 65% of the total population, the researchers studied the relationship between race, income, age, and mean summer daytime SUHI intensity.

“The average person of color lives in a census tract with higher SUHI intensity than non-Hispanic whites in all but 6 of the 175 largest urbanized areas in the continental United States.” (click to expand)
The findings were clear—race plays a role in SUHI exposure. In urban areas within each climate zone (e.g., arid, snow, temperate, equatorial), Black residents have “the highest average SUHI exposure, for an overall average (±standard deviation) of 3.12 ± 2.67 °C, with Hispanics experiencing the second highest level (2.70 ± 2.64 °C).” Meanwhile, non-Hispanic whites have an overall average of 1.47 ± 2.60 °C, which is the lowest exposure.

Age does not seem to affect these racial and ethnic disparities, as it was found that people of color over the age of 65 or less than 5 are still exposed to higher levels of SUHI than their white counterparts.

“A similar pattern emerges for people living in households below the poverty line relative to those at more than two times the poverty line.” (click to expand)
A trend comparable to that of race and ethnicity can be seen for income as well—people living below the poverty line have the highest exposure in each climate zone (national average 2.70 ± 2.64 °C), whereas people living at above twice the poverty line have the lowest (1.80 ± 2.69 °C).

However, the intersection between poverty and race becomes more complicated. Despite the fact that, on average, only 10% of people of color live below the poverty line, the researchers found that in nearly half the cities, the “average person of color faces a higher summer daytime SUHI intensity than the average person living below poverty.” The racial and ethnic disparities stand on their own and are not explained solely by income level. This remained consistent for age demographics as well.

What does this mean for our children? (click to expand)

This study supports the mounting evidence of disproportionate harm to people of color and those with lower incomes from climate change, including their children.

Globally, children under age five bear 88% of the climate-related disease burden. When it comes to extreme heat, children are less able to regulate their body temperature compared with adults and are thus more vulnerable to extreme heat and its effects such as dehydration, heat exhaustion, and heat stroke. In addition, respiratory illnesses such as asthma are worsened by heat island intensity.

Children in under-resourced communities of color are often also burdened with increased exposure to air, water, and soil pollution, and to aging, hazardous infrastructure from decades of discriminatory housing and zoning policies and disinvestment.

Policy Implications (click to expand)
It is essential that public policy comprehensively addresses the factors perpetuating environmental racism and the burdens of climate change on communities of color:
  • Real measurable progress, not rhetoric, is needed to dismantle racism in our systems and institutions.
  • All levels of government need to reduce or support reduction of exclusionary zoning.
  • State, tribal, local, and territorial governments should develop climate adaptation and resiliency plans that have been driven by and developed with robust community participation, especially from those most impacted. These plans should address the health effects of climate change and the preparedness and adaptation strategies to protect public health.
  • Climate resiliency projects should prioritize impacted communities (e.g., tree planting in under-resourced communities with low urban tree canopy index; more cooling centers in areas with poor public transportation and energy justice concerns; etc.).
  • Vigilance is needed to avoid climate gentrification and other injustices.
  • Children’s physical and mental health should be addressed explicitly, including assessment of the pediatric and prenatal care needs of the community, the schools and child care facilities and other spaces where children spend time, and other key issues relevant to preparedness, adaptation, response, and recovery from climate-related disaster and health impacts.