Linda Poon is an assistant editor at CityLab covering science and urban technology, including smart cities and climate change. She previously covered global health and development for NPR’s Goats and Soda blog.
Using GIS technology, three environmental organizations are teaming up with residents to plant 1,000 trees in areas that need it most.
Finding shade isn’t always easy in Dallas, Texas. Though home to one of the nation’s largest urban forests—the 6,000-acre Great Trinity Forest—there’s a dearth of trees in the rest of the city. At the same time, the urban heat island effect has made Dallas one of the fastest-warming cities in the United States.
“If we continue to add impervious surfaces and remove trees, we could have an urban heat island that covers almost half the city,” said Matt Grubisich, director of operations and urban forestry at the local Texas Trees Foundation.
That’s why earlier this year, volunteers spread out across the barren sidewalks of Oak Cliff, one of the city’s most vulnerable neighborhoods. With shovels and pick axes in hand, they began digging. The goal is to eventually plant 1,000 trees; so far, some 500 saplings are in the ground as part of a project called Cool and Connected Oak Cliff. Planting trees is a common low-tech solution to battle the heat island, but high temperatures are just one target of this ambitious project. Using sophisticated data and GIS technology, it also aims to harness the many other benefits of trees, from improving public health to taming traffic on the streets.
In 2015, the Texas Trees Foundation laid the groundwork for the project by mapping the tree cover throughout Dallas. They used aerial imagery to capture the overall canopy, and then physically counted the species of trees in a sample of more than 600 plots. On average, they found, Dallas has 29 percent canopy coverage. Some pockets of neighborhoods have less than 10 percent.
A sliver of good news came in the foundation’s 2017 report on urban heat management in the city, which suggested that trees could help curb temperatures by as much as 15 degrees on hot days. Grubisich and his team had collected and analyzed the city’s impervious surfaces, and looked at air temperature readings to identify areas that experience higher than expected temperatures.
For Robert Kent at the Trust for Public Land—which partnered with both the Texas Trees Foundation and the Nature Conservancy on the project—that was plenty of data to work with. He fed them into a visual mapping program, overlaying the numbers with additional data on the socioeconomic and health status of Dallas’s neighborhoods.
“We go beyond just looking at single issues, and actually seeing where are the intersections between challenges posed by climate change within a city,” said Kent, who heads the group’s north Texas division. “So our maps also looked at where are the neighborhoods that suffer from the highest health disparities—we know that urban heat is going to exacerbate cardiovascular conditions and asthma, so let’s find the places that have high prevalences of those diseases.”
When they put together that map, which also included data on the prevalence of diabetes—extreme temperatures deter an active lifestyle—the lower half of Oak Cliff was shaded in an alarming red, indicating high priority for greening intervention.
Trees, though, can do more than mitigate the heat island effect. Kent’s team also put together a map that combines a variety of data: heat, health, equity, flood zones, and pedestrian and biking safety. The groups settled on targeting areas that show high health disparities—particularly among the elderly—as well as public schools that have little to no shade near playgrounds, and places with high foot traffic and pedestrian deaths.
After all, trees provide a good buffer between pedestrians on the sidewalk and vehicles on the road. “It not only provides a physical barrier of separation, but the tree will also be a signal to drivers to slow down,” Kent said. “It also makes the sidewalk a more inviting place to walk.”
While data brought the project to the southern part of Oak Cliff, numbers can only reveal so much about the needs of a community without local input. The project needed the trust of locals in this area of nearly 300,000 people, where almost a third of families live below the poverty line, according to 2016 census data. Across the city, some of the poorest ZIP codes are in areas that are made up of predominantly minority populations.
Historically, the black community here has been neglected, said Holy Cross Catholic Church’s Kebran Alexander, who’s lived in Oak Cliff since the 1980s. “There has been decisions by developers that left Oak Cliff particularly vulnerable over decades to neglect and blight.” Indeed, a recent study out of University of North Texas identified the southern half of the city, where Oak Cliff sits, as the most troubling areas of decline. When Alexander and other volunteers from his church came out to help plant the trees, they came across trash, broken bottles, and leftover concrete from prior constructions.
All that has left seniors, who can’t afford to move to other neighborhoods, vulnerable to the heat island effect. Many of their yards are browning and either lack a tree or have an aging one in need of removal. “So you cut a tree down because you were afraid it was going to fall on your house,” Alexander said, “but then, what happens to your cooling bill? And your grass? [These are] things that add to the quality of your health.”
Also vulnerable are students, whose public schools have little shade to provide relief during recess. Alexander called the playgrounds “literal hotboxes.”
Community leaders like Alexander vetted the good intentions of the project’s plan—to make sure they actually help those who need it most and, in essence, to close the trust gap between residents and the organizers. In one instance, for example, the GIS data pinpointed a residential street running parallel to the busy Illinois Avenue as an area to plant trees, but the thing was, few people walk down that stretch of road. ”The kids actually walk down the busy thoroughfare because they are going to the corner store to get drinks or candy,” said Alexander. “It was those types of granular adjustments from the ground level that we were able to give them some insights.”
Roots of a larger goal
When it comes to tackling climate change, and the human consequences of it, planting 1,000 trees seems almost insignificant—even for Dallas. The Texas Trees Foundation’s report suggests that the city will need to increase its tree canopy by about 5 percent to make a dent in curbing the heat island effect. That can mean roughly 300,000 trees. But Grubisich said it’s a good start to push revitalization efforts in at-risk neighborhoods in a city that’s historically favored new developments, and it could eventually generate more data to drive policy change.
The hope is to take their experience in Oak Cliff and repeat it in other neighborhoods across Dallas. The three groups will monitor the neighborhood’s temperatures and health statistics over the next five years, with the Trust for Public Land updating the GIS maps annually. They’ll also maintain the trees over the next two years, during which they’ll come up with a plan to transition the task over to the community and the local government.
For Laura Huffman, the Nature Conservancy’s state director in Texas, the project is about much more than increasing tree canopy. “Part of what we’re doing in this work is generating the science to connect the dots between trees and vegetation and mental health and well-being, and things like asthma,” she said.
Meanwhile, Alexander is under no illusion that this will solve Oak Cliff’s inequality. But, he said, “I have to remain optimistic because we have to start somewhere.” At the very least, the project has piqued the curiosity of the residents. Dozens have already volunteered to help. Others, meanwhile peeked through their blinds to see what was going on, Alexander recalled of the day he volunteered. Some even stepped outside, asking for a tree in their yard.
For many, Alexander said, this was one of the first times they’d seen anybody invested in their neighborhood. And while they might not see immediate benefits—it takes time for trees to mature—they can at least “see the potential.”