Shade from trees can make a dramatic difference in combating urban heat, especially amid blistering heat waves like the one gripping the western U.S. this week. A new analysis quantifies just now unequal tree cover is in the U.S.: Neighborhoods with a majority of people of color have, on average, 33% less tree canopy than majority-white communities, according to data from the Tree Equity Score map, a project of the conservation nonprofit American Forests. The poorest neighborhoods, where 90% of residents live in poverty, have 41% less coverage than the wealthiest ones.

The new findings add to mounting research on the unequal distribution of trees. As Jad Daley, president and CEO of American Forests, told CityLab last August, any map of tree cover in a U.S. city likely reflects its racial and socioeconomic divide.

But while the portrait of tree inequality is bleak, the map is meant to be a tool for advocates and local officials. The score reflects how many trees are needed in each tract based on factors like the region’s climate and population density, as well as six equity measures: income level, employment rate, race, age distribution, health outcomes and the severity of the urban heat island effect. 

Additional analysis using data from the U.S. Bureau of Economic Analysis and the U.S. Forest Service also helped quantify the potential economic, environmental and public health benefits of the effort, which can be key to getting buy-in from the communities they’re trying to help. 

Nationally, some 522 million new trees are needed for every city to reach a score of 100, according to the analysis. That could lead to the creation of more than 3.8 million jobs, curb air pollution by 56,613 tons of particulates each year, and remove 9.3 million tons of carbon from the atmosphere — equivalent to 92 million cars, the analysis estimates. It could also generate roughly $5 billion in annual ecosystem service benefits, like air quality improvement and stormwater drainage.

Among major cities, Los Angeles, San Diego and Houston have some of the highest need, and would have to plant 5.1 million, 4 million and 2.4 million, respectively, to achieve tree equity. But the report argues they’re also the ones with the most to gain, because planting all those trees would mean proportional benefits in job creation and pollution reduction.

The map could be particularly helpful to cities with fewer resources and smaller budgets to conduct their own tree canopy survey. “What's exciting to me is that, yes, we’re bringing [this tool] to the Milwaukees and the Philadelphias and the Los Angeleses, but we’re also bringing it to those smaller cities,” says Chris David, the group’s vice president of GIS and data science. “If we can make it just a little bit easier for them, I think it can have a major impact.”

David and his team are also working on creating more detailed analyses for many states and cities. The first such tool was completed for Rhode Island, and includes information like flood risk, and whether a parcel of land is publicly or privately owned. “We identify what’s possible on an individual parcel, if the space potentially could have tree canopy cover, and then we provide the tool to set targeted goals for a series of neighborhoods,” David says.

Some of the data come from public records, but building out the tool requires strong partnerships with government agencies, local foresters and community members. 

“Tree inequity has consequences, and extreme heat and reduction in air and water quality, as well as the lack of ecosystem benefits means reduced health and general well-being,” he says. “That’s what we’re trying to change.”