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Q&A: Hyper-Segregated Cities at Greater Risk of Heat Island Effect

Ngoc Nguyen, Special to The Informer from New America Media | 7/17/2013, 3 p.m.

The Western United States baked in the heat last week, with record-setting temperatures seen in Las Vegas, NV and Death Valley, Calif., as well as in California’s Central Valley, Oregon, Washington, and Utah, among other states. In some places, the deadly heat combined with extreme drought conditions and dry thunderstorms to fuel wildfires, including the massive Yarnell Hill fire in Ariz. A new study published this week in Environmental Health Perspectives makes a link between heat waves and public health. NAM’s Ngoc Nguyen spoke with study co-author Dr. Rachel Morello-Frosch, a professor in the School of Public Health at UC Berkeley about who is most vulnerable to the phenomenon known as the “heat island effect.”

New America Media: What is heat island effect?

Dr. Rachel Morello-Frosch: Places that have a lot of impervious surface, like a lot of asphalt, cement and very little tree canopy — all these conditions can increase the mean temperature in your neighborhood by quite a bit and can cause a temperature difference of up to 10-15 degrees. It’s particularly noticeable in a heat wave.

NAM: What did you try to find out in the study?

RMF: What this study did was look at over 300 metropolitan areas across the United States and Puerto Rico to look at potential racial disparities at the neighborhood level for heat island risk. We looked at disparities in tree cover. Trees provide shade and mediate the effects of heat waves in cities. [Finally], we mapped the distribution of heat island risk across racial and ethnic groups and also by degree of racial residential segregation — meaning we wanted to see if there were differences in heat island risk depending on if they lived in highly segregated cities versus less segregated cities.

NAM: What did you find?

RMF: After accounting for the fact that there are definite differences across cities in the ecology of trees and differences in … rainfall, we found that African-Americans, Asian and Latinos are much more likely than non-Hispanic Whites to live in neighborhoods with a lot of heat island risks. Blacks across the country were 50 percent more likely than whites to live in high heat island risk neighborhoods. We also saw within each racial [and] ethnic group that health island risk increased with increasing levels of segregation. In other words, in cities characterized by high levels of segregation, people tended to have higher levels of health island risk compared to their less segregated counterparts.

NAM: What accounts for greater health island risk in hyper-segregated cities?

RMF: What we are seeing in the physical environment — the planting of trees and infrastructure that tries to decrease heat island risk in cities — these kinds of investments, you tend to see less of in places with high levels of racial inequality. The physical environment in cities is a reflection of the social environment, and it tends to disadvantage people of color particularly.

It’s possible in cities with higher levels of segregation there is less investment to protect people from health island risk, such as tree-planting campaigns, greening of space and neighborhood, reduction in impervious surfaces that really absorb heat, whiter roofs, those kinds of things, certain levels of public investment.