Planting trees in urban areas is a relatively cheap and effective way to mitigate the impacts of climate change and help save energy. In Chicago, city officials are planning to plant 75,000 new trees as part of a $188 million climate package passed last month.
But while the concept is straightforward, implementation can be complicated.
Many of the trees will be located in neighborhoods populated by people of color — neighborhoods that because of racist policies and practices have typically suffered from disinvestment of all types, including in green spaces and park services, and which have reduced tree canopies.
A tool developed by the Chicago Department of Public Health and the University of Chicago combines existing tree canopy data with assorted health-related metrics such as air quality and traffic volume to help identify areas in greatest need of additional tree cover.
However, plans to increase tree canopies have also sometimes run into resistance from neighbors who fear that new amenities could spark interest from real estate developers and displace lower-income residents from their homes. The city plans to respond to and overcome this resistance by employing significant community input and a racial equity-focused lens in implementing the tree planting initiative.
This approach is designed to ensure the benefit of the enhanced tree canopy is enjoyed by residents already living in targeted neighborhoods — one aspect of an “all in” approach to increasing resilience in neighborhoods disproportionately impacted by both disinvestment and climate change.
“We expect this historic investment to reap historic outcomes,” said Angela Tovar, chief sustainability officer for the city of Chicago, in a press release. “Taking an equity-centered and data-driven approach, we can identify where trees can have the greatest impact and work directly with residents and community groups in those areas to plant and maintain trees. We are committed to building a safer, stronger, and more just Chicago for all.”
Increasing tree canopies and incorporating green infrastructure not only reduces the adverse effects of urban heat islands, but also presents an excellent opportunity for reversing disinvestment in BIPOC communities, said Trinity Pierce, stewardship coordinator for the Chicago Region Trees Initiative at the Morton Arboretum in Lisle, Illinois.
“So much of this conservation stewardship is making sure that it’s not just about planting trees and moving on to the next site, but it’s also about green infrastructure,” Pierce said. “And now more and more it’s about green jobs. So, it’s helping expose the youth in these communities [and] helping expose folks who might be interested in a career change to these green careers.”
Enhancing tree canopies
Enhancing tree canopies can significantly mitigate the harmful aspects of a heat island by providing direct shade and by indirect cooling through evapotranspiration. However, too often, insufficient consideration is given when planting urban trees, Pierce said.
“Sometimes trees can be an afterthought. … There’s no diversity [in tree species] whatsoever,” she said. “So even just planning for diversity, and that can be local — that can be a community garden in an under-resourced area. That alone is actually a really important big step.
“Diversity is so key as we lose a lot of species to certain pests and diseases, or if a lot of trees were planted at the same time, they’re going to age out at the same time. So, the more trees we can plant properly in the right spot, the better.”
The existing built environment must also be taken into account in the placement of urban trees, Pierce added.
“In an urban environment, it’s not as if everything was bulldozed and we started from scratch,” she said. “We still have gradation changes. Again, water has that memory. There’s still a rich heritage and natural rich heritage there.
“There’s often not a lot of space in the soil. If you think of parkway trees, that’s a pretty small area for a tree that in normal circumstances could get 40, 60 feet tall. But those roots need to be at least as far out as the tips of its branches, if not farther. And we know the roots are going to be in the top 18 inches of soil. We have smaller trees that will stay small.”
Finally, it is also essential to accommodate previously existing geological factors and the application of road salt when considering tree placement, Pierce said.
“What’s their natural habitat? So that means if you’ve got a water issue, what’s going to be pretty happy there? Whereas some other species are actually found in Upland forests, just meaning they want to be away from the water. So, we’re looking at the wetness of the soil,” she said.
“We’re also looking at tolerances in terms of salt. Now there’s actually soil salt. In our built environment, we gleefully apply road salt in winter. Some trees can handle it. Others, that’s going to be a stressor.”
Green infrastructure and future urban development
Along with planting trees, Chicago’s climate action initiatives include $25.75 million for 20 resilient schoolyards at public schools located in the most flood-prone areas of the city and $41 million for retrofitting 500 low-income homes, installing solar arrays at five public libraries and installing community solar on existing roofs at industrial factories. An additional $75 million is targeted toward a package of community-level climate projects designed to remediate contaminated land parcels, provide funding for neighborhood climate resilience projects, decarbonize city fleets and invest in a trail network across the city.
This type of holistic suite of initiatives represents precisely the right approach to dealing with climate change and the built environment, according to Timon McPhearson, director of the Urban Systems Lab at The New School in New York City.
“Our climate has been relatively stable for 10,000 years, and now it’s shaking up like a boiling pot of water on the stove. We can’t design the way we used to. We have to design for uncertainty, and we have to be much more aggressive about it than we have been so far,” McPhearson said.
“So, I think when we think about what a resilient city looks like, we also have to think about it systematically. We have to think about how neighborhoods have resilient, social relationships that can last … and help each other through times of crisis.”