One recent newspaper analysis and a new academic study both agree: tree cover differs between richer and poorer urban neighborhoods.

Last month, the Washington Post conducted its own study of the city’s tree canopy, with some findings that may not surprise anyone who lives in the capital: Lower-income neighborhoods were substantially less likely to have trees, with the city’s densest greenery clustered west of the 16th Street Northwest fault line that divides some of Washington’s wealthiest neighborhoods from the rest of town. Tree density in Washington, in short, provides a kind of proxy for wealth (and if you’ve spent time in Washington, you also know that wealth is a proxy for race).

Lest other cities scoff at Washington’s arbor-inequality, research just published online in the journal Environmental Health Perspectives confirms that a very similar pattern appears all across the country. 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. And 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 neighborhoods, Asians 32 percent more likely, and Hispanics 21 percent more likely (controlling for factors that explain variation in tree growth, like climate and rainfall).

“It’s in the same range of elevated risk that we see for a number of environmental concerns,” says Bill Jesdale, one of the authors, referring to similar findings in the environmental justice literature that show minorities living in communities with greater exposure to traffic, pollution and other environmental hazards. “Often, unfortunately, you see relative risks that are quite a bit higher than that.”

Interesting findings. Trees might seem rather basic, even in cities, until such differences are pointed out.

So, what is behind these differences in tree cover? Are cities planting fewer trees in poorer neighborhoods? Do poorer neighborhoods tend to have fewer parks, fewer tree-lined streets, and more manufacturing and industrial facilities? Do the residents of wealthier neighborhoods make sure that their neighborhoods have more trees? Is this primarily about trees themselves or is this just part of a larger package of fewer amenities in poorer neighborhoods?

Based on these findings, I wonder if we’ll see more people advocate for trees in poorer neighborhoods. Who could be against trees and more greenery, particularly if it is an issue of justice and inequality?