Summer days are for shady strolls down a tree-lined street and picnics under a canopy of leaves. But how many trees — and how much shade — a person can find in their neighborhood might depend on how rich it is.
Not everyone has equal access to trees and the endless benefits they provide, especially when trying to escape the summer’s sweltering heat, according to a map created by a conservation nonprofit.
A recent analysis by American Forests highlights Denver’s shady divide: neighborhoods of color and areas with higher poverty rates have fewer trees than those that are predominantly white and more affluent.
The interactive map highlights the tree canopy in neighborhoods across the city using geospatial and census data to show which parts of the city are less protected by tree cover and more exposed to increasing and unhealthy heat levels.
“You have the communities that have the most stacked against them getting the least benefit from green spaces in urban areas. It’s really important to try to increase equity in terms of access to parks and trees and green spaces,” said Colleen Reid, an assistant geography professor at University of Colorado who specializes in climate change and human health, but was not involved in the analysis.
How do the trees in your community stack up?
Find out your neighborhood’s tree equity score through
this map by American Forests
For those living in less affluent neighborhoods, where the lack of shade and an abundance of heat-absorbing asphalt can cause temperatures to soar, temperatures can be as much as 10 degrees higher than in surrounding neighborhoods.
As daytime temperatures rise and climate change brings record-breaking heat year after year, Colorado’s fabled 300 days of sunshine are no longer a boon for those less-shady areas.
Denver just wrapped up its 16th warmest July since 1872, when records first started being collected, according to the National Weather Service’s Boulder office. Studies suggest temperatures will continue their upward trend.
Experts say branches, leaves and needles casting shade over a city’s sidewalks and green spaces can play a large role in reducing the health impacts of the rising temperatures.
When there is no shade, heat waves can lead to serious illness, Reid said, explaining that trees and vegetation can absorb moisture and release it to cool down the environment. That release of moisture has the potential to reduce peak summer temperatures by 2 to 9 degrees, according to the Environmental Protection Agency.
“You have the highest rates of all kinds of chronic diseases in low-income communities and communities of color because of the many challenges facing those communities,” Reid said.
Sparse tree cover disproportionately affects communities of color and translates into higher rates of respiratory illness, including asthma among children, hospitalizations and deaths, said Ian Leahy, vice president of urban forestry for the nonprofit American Forests.
Urban trees can help reduce ground-level ozone levels — and in turn improve air quality by reducing air temperature and absorbing pollutants, according to a study by the U.S. Forest Service.
“The fewer trees you have, generally speaking, the more hospitalizations you have from respiratory illness, the more acute respiratory illness you have, the more deaths you have,” Leahy said. “It is really a life-saving infrastructure when it is well maintained and properly distributed.”
For example, in Sun Valley, where 88% of those who live in the neighborhood identify as people of color, only 3% of the area is shaded by trees, according to the map by American Forests. Its average temperature during the summer, which was measured using surveys and remote sensing data, is 94 degrees.
That’s four degrees higher than in Capitol Hill, where the tree canopy ranges between 10% and 17%. Only 15% of residents identify as people of color in that neighborhood, according to the nonprofit, which completed its analysis prior to the release of the latest census data.
About 2% of the North Park Hill neighborhood is shaded by trees and the average temperature hovers at 95 degrees. But travel slightly to the south into the wealthier South Park Hill neighborhood and the tree canopy jumps to 30% and the temperature drops 7 degrees, according to the map.
Extreme heat can lead to heat exhaustion or heat stroke, which happens when the body isn’t able to properly cool itself. Usually the body cools itself by sweating, but when temperatures rise to extreme levels, sometimes that isn’t enough to avoid damage to the brain and vital organs.
Trees provide critical infrastructure for helping cool the city and its residents, Leahy said.
“What’s happening as cities heat up, our bodies are not cooling down at night when you don’t have air conditioning,” he said. “So basically, it becomes a public health issue on that front, even at night when you’re out of the hot summer sun.”
Historically, trees were planted in more affluent neighborhoods where white people lived. Fewer green spaces were planned for neighborhoods where people of color and the poor lived because racist lending policies, known as redlining, characterized them as too high risk to warrant investment. Leahy pointed to studies that show that neighborhoods shaped by racist housing practices decades ago, have higher temperatures today.
Correcting the problem is harder in urban areas and even more so in places like Denver, which were not forested when they were settled.
“The landscape there is not naturally forested, so any urban forest there is human made,” Leahy said. “They’ve done an incredible job.”
The nonprofit scored Denver’s overall tree equity at 88 out of 100.
Efforts by organizations like The Park People are helping to reduce the urban heat island effect by providing low-cost trees for planting on private and public lands. The organization’s program, Denver Digs Trees, has donated more than 60,000 trees over the past 35 years, according to its website.
Mayor Michael Hancock has also pledged to adopt long-term strategies to ensure more city residents are within a 10-minute walk to a park or green space.
Even so, there’s more work to be done, Leahy said.
“Urban forestry is notoriously underfunded so it is really: How do we focus the resources that we do have in the areas with the highest impact and really trying to build on that layer of moderation and moderating those surface temperatures in the city and really treating the tree canopy as an infrastructure that can protect lives and reduce hospitalizations.”
And the power of shade branches beyond heat-related illnesses, Reid said.
“There is a lot of evidence of mental health benefits of just being able to see some vegetation where you live, as you walk down the street, as you look out of the window of your home,” Reid said. “If you have less of that in your community, that can be a detriment to the ability to cope with stressors and mental health generally.”
Ninety percent of Denver residents live within a 10-minute walk of a park, compared with the national average of 55%, according to the Trust for Public Land.
But in its tree equity assessment released earlier this year, the organization gave Denver a park equity score of 68 out of 100 for its green spaces, finding that neighborhoods of color have 18% less park space than white neighborhoods. Low-income neighborhoods have 26% less park space than high-income neighborhoods.
The demand for geospatial data showing trees’ impact in communities is growing, said Vikalpa Jetly, CEO of EarthDefine, the company that provided data for American Forests’ analysis.
“There are so many ecological impacts and environmental impacts of trees and cities and planners are realizing more and more their value. So to measure and try to improve tree canopy, you need really good baseline data,” Jetly said.
By using the geospatial data, city planners can see where parts of their community may impact the greatest from adding more trees, Jetly said.
He said he thinks the latest heat waves in the Pacific Northwest, where triple-digit temperatures killed hundreds of vulnerable people, highlighted the immediate threat from the rising temperatures and the potential role trees can play in reducing heat.
“There’s a whole bunch of services that trees provide,” Jetly said, “and slowly, I think there’s been a greater appreciation that, ‘Hey, these are not just an aesthetically nice thing to have, but there is real economic value in these trees.’”