GW researchers found access to urban parks is unequal within major U.S. cities, leading to higher risks of heat exposure, respiratory illness and other health disparities for residents in a study published late last month.
Greta Martin, one of the authors of the study and a postdoctoral associate at the Milken Institute School of Public Health, conducted the study analyzing park conditions across the 24 most populous urban areas in the United States, including D.C., using spatial and environmental data to assess differences in park size, temperature, pollution exposure and air quality, publishing her findings in the Environmental Research Letters journal in late April. She said the study revealed that environmental inequalities can exist even in communities with access to parks as lower-income areas often only have access to parks with fewer environmental and public health benefits — like higher temperatures and greater pollution exposure — than wealthier neighborhoods.
“We should care about who has that privilege and who’s being deprived of those spaces that allow for these activities that are really important to humans,” she said.
Martin said the study found parks in higher-income neighborhoods were generally larger, greener and cooler than those in lower-income communities, reflecting broader patterns of environmental inequality within U.S. cities. The study also found park access and environmental quality varied sharply across metropolitan areas, with park space — the share of land dedicated to parks — ranging from less than 1 percent of land area in Indianapolis, Indiana, to 37.5 percent in the Seattle-Tacoma region in Washington.
Researchers defined park quality through environmental conditions such as park size, vegetation and tree cover, temperature levels and exposure to air pollution. The study found environmental disparities varied substantially within cities, with some metropolitan areas showing much larger gaps in park quality than others. In the Washington-Arlington-Alexandria metropolitan area, the study found relatively small differences in park size between neighborhoods compared to several other major U.S. cities.
She said unequal access to quality green space can have significant public health consequences, like higher rates of chronic illness, heat-related health risks and poorer mental health outcomes, because parks often provide opportunities for exercise, social interaction and stress reduction.
“To be able to just see green spaces is calming and a reducer of stress,” she said. “And also just having access to that means that you can do things like go on a run or meet up with friends in the park and all these activities that are really beneficial to your physical and mental health.”
The study used data from ParkServe, a nationwide database developed by the Trust for Public Land — a nonprofit organization that works to create, protect and map access to parks and green spaces across the United States — that maps publicly accessible parks across the United States.
“We use that to look at whether there are disparities in the environmental conditions of parks by neighborhood privilege across the biggest cities in the U.S.,” she said.
Martin said historical redlining and discriminatory housing policies had a lasting effect on environmental conditions in many neighborhoods by concentrating investment, green space and environmental resources in wealthier and white communities while limiting access in lower-income neighborhoods and communities of color.
“At the time of redlining, the areas that were given better grades were already described as being greener and having more trees and more nature, and by restricting who got to live in those areas, those patterns clearly still exist today,” she said.
Researchers noted in the study that while disparities in park conditions were still present across the D.C. area, the gap in park size by neighborhood privilege was less pronounced than in cities with the most extreme inequalities in the analysis. But D.C. still followed the broader national pattern in which neighborhood socioeconomic conditions were strongly linked to environmental quality in nearby parks, according to the study.
Jason Farr, an assistant teaching professor at Georgetown University’s Earth Commons Institute, said park development can also cause tensions around gentrification, with efforts to improve green space sometimes increasing property values and leading to displacement in surrounding neighborhoods.
He pointed to D.C.’s 11th Street Bridge Park project in Southeast D.C. as an example of a long-running effort to balance new park investment with anti-displacement strategies as planners have worked alongside community groups to try to ensure that nearby residents are not pushed out as the area becomes more desirable. He said the project stands out because planners began considering affordable housing and displacement concerns before the park was completed rather than responding only after property values increased.
“We’re not going to come in there just to make a beautiful park,” he said. “We’re coming in there to think about what are the actual burdens that this community faces, what would the park access actually bring them and how can you do it in ways that don’t lead to gentrification.”
Farr also said the issue of park access becomes even more urgent in the context of climate change, especially in cities like D.C., where heat and infrastructure differences like tree canopy coverage and pavement density can significantly affect neighborhood conditions by increasing temperatures and worsening residents’ exposure to extreme heat.
Climate change in D.C. has intensified in recent years an urban “heat island” effect, where neighborhoods with fewer trees and more pavement experience significantly higher temperatures than greener, wealthier areas. Washington Post climate reporters confirmed last year D.C.’s tree canopy is increasingly strained by rising temperatures, drought and development pressure, even as it remains one of the more tree-covered major U.S. cities overall.
Farr said green space plays a key role in climate adaptation by reducing heat, providing shade and helping mitigate environmental risks like flooding.
“We should be thinking a lot about how do we not double down on the injustices of climate change by continuing to build and rebuild cities in ways that inflict damage upon those communities,” he said.
Jon Christensen, a professor in the Institute of the Environment and Sustainability at University of California Los Angeles, said decades of research have shown unequal access to parks is closely tied to broader public health disparities, particularly in lower-income communities and communities of color.
“There are strong correlations between the lack of nearby parks and nature and some really important and concerning health problems like cardiovascular disease, obesity, diabetes, low birth weights,” he said.
Christensen said differences in tree cover and shade have become increasingly important as cities face rising temperatures and more intense heat waves linked to climate change. He pointed to previous research in Los Angeles County showing that increasing vegetation and tree coverage in neighborhoods significantly improves long-term public health outcomes.
“If you brought those areas that lack vegetation and trees up to the average for the county, you would add almost a million years of life expectancy to the population in those neighborhoods,” he said. “So it’s really a matter of life and death.”
