The Inequality of Urban Tree Cover

By Bill M. Jesdale, Rachel Morello-­Frosch, and Lara Cushing

Berkeley, CA (May 14, 2013) -Berkeley, CA (May 14, 2013) – New research published in the journal Environmental Health Perspectives shows that lower-income neighborhoods were substantially less likely to have trees. Researchers from the University of California at Berkeley looked at 63,436 census block groups from across the country covering 304 metropolitan areas and more than 81 million people.

They identified those blocks most at risk in extreme heat waves thanks to the lack of tree cover or the presence of too much asphalt (or impervious surfaces). Both of these factors have been shown to exacerbate the urban heat island effect, raising surface temperatures, suggesting that people who live in these neighborhoods may be at the highest heat risk as temperatures warm with climate change.

According to the findings, blacks were 52 percent more likely than whites to live in such “heat risk-related land cover” neighborhoods, Asians 32 percent more likely, and Hispanics 21 percent more likely, after adjusting for ecoregion and precipitation, and holding segregation level constant.

Within each racial/ethnic group, heat risk-related land cover conditions increased with increasing degrees of metropolitan area-level segregation. Further adjustment for home ownership and poverty did not substantially alter these results, but adjustment for population density and metropolitan area population attenuated the segregation effects, suggesting a mediating or confounding role.

Researchers conclude that land cover was associated with segregation within each racial/ethnic group, which may be partially explained by the concentration of racial/ethnic minorities into densely populated neighborhoods within larger, more segregated cities. In anticipation of greater frequency and duration of extreme heat events, climate change adaptation strategies, such as planting trees in urban areas, should explicitly incorporate an environmental justice framework that addresses racial/ethnic disparities in heat risk-related land cover.

Related Resources
The Racial/Ethnic Distribution of Heat Risk-Related Land Cover in Relation to Residential Segregation
The Inequality of Urban Tree Cover
Tree canopy’s density indicates wealth of D.C. neighborhoods