When the emerald ash borer swarmed through Chicagoland, the pest took with it 13 million ash trees, decimating that part of the urban forest. The Morton Arboretum declared it a catastrophic loss. Those ash trees accounted for 20 percent of all the street trees in the city proper, let alone the extended suburbs.
But even though it was a terrible blow to the tree population in Chicago, it wasn’t the worst that could have happened—32 percent of all the street trees are maple, so if a pest comes through that attacks maple trees, it’ll be even worse.
The Morton Arboretum, a 1,700-acre living tree museum in Lisle, about 30 minutes from downtown, is working to make sure nothing like that happens, both in Chicago and in the world at large. The facility has assembled a team of scientists dedicated to saving and conserving trees throughout the world.
Dr. Nicole Cavender, the Arboretum’s vice president of science and conservation, focuses on the local level, helming the Chicago Region Trees Initiative (CRTI). This project is the country’s largest initiative to maintain and preserve the health of Chicago’s urban forest—which “is any tree that’s located where people live,” said Lydia Scott, CRTI’s director, who handles the majority of the on-the-ground work for the initiative.
“Even the forest preserves are identified as part of the urban forest because they’ve been substantially impacted and segmented due to urban development. The urban forest encompasses trees anywhere development has taken place. It can even be just one tree in someone’s backyard.”
Aside from invasive pests like the ash borer, Scott and the CRTI are facing a number of challenges affecting the tree population in Chicago. Lack of tree diversity is a major one. With such large percentages of the urban forest being one specific type of tree, any kind of illness or pest coming through will have devastating effects—and not just to the trees, but also to local homes.
Scott notes that the 13 million lost ash trees sucked up 13 billion gallons of water per year, saving basements and streets from flooding after major rain events. Now that water has nowhere to go, and our environment is worse off.
“When we drive by our trees, we don’t think of them as standing there like straws in a glass, where they’re holding all of this water and carbon and pollution to help make our quality of life much better than if they weren’t there,” she said.
The CRTI team works at the community level to encourage residents to plant more diverse tree species—and to plant them properly. Scott says the majority of Chicago’s trees don’t have enough room to grow and as a result, rarely get larger than six inches in diameter and die a lot faster than they would with proper planting. But the biggest challenge is a lack of understanding about trees in the general community.
“People don’t realize the value that trees are to them,” she said. “I often hear, ‘I cut down that 100-year-old oak tree on my front yard, but that’s okay because I’m going to plant ten smaller trees on my property.’ It’s not the same thing at all.”
In response, CRTI has developed two wildly popular initiatives: Urban Forestry Basic Training and the Community Tree Network. They’re both training and mentoring programs designed to help educate the community about trees, proper planting, and maintaining the health of the urban forest.
Outside of Chicago, Audrey Denvir is taking the Arboretum’s work saving trees to a more global level. She’s the manager of the Global Tree Conservation Project in Mexico and Central America, striving to save trees from extinction adjacent to the United States in order to mitigate eco-damage we’d face as a result of their loss.
Denvir focuses on conserving oaks, specifically ones in Mexico that are unable to reproduce and are nearing extinction. She likens her project to a retirement home—except all the residents are trees (endangered Quercus brandegeei oaks) and are more than 100 years old with no descendants.
“It’s kind of this dinosaur species that’s having trouble regenerating on its own and if we don’t intervene, it will go extinct,” she said. “All the old trees will eventually die off.”
The project has already seen some major successes. Denvir and her team now know the reason the trees won’t reproduce: climate change and a native ecosystem that’s becoming hotter and dryer every year.
They’ve also formed a group called the Oaks of the Americas Conservation Network, where experts from the Americas come together and share knowledge across international borders. The network’s knowledge base is indispensable for creating conservation projects tailored to each specific oak species—and there are more than 200 in Mexico alone, many of which are rare or endangered.
Denvir says that although she mainly works on trees in Mexico, her research is easily translated to the local Chicago landscape.
“When we’re thinking about planting trees in an urban setting, we really need to consider the biology of the species itself and how it’s going to grow,” she said. “It’s important to remember that trees globally affect our world just as much as they do locally. Conserving trees in Mexico affects us in Chicago because it’s helping conserve the biodiversity of the earth and mitigating climate change on a global level.”
If you’d like to get involved in these programs or others happening on the grounds, the Arboretum offers a full slate of educational programs and workshops—including the Woodland Stewardship Program, a certification course that trains participants to do some of the same integral conservation work the scientists are doing in their own backyards.
Even though these scientists are working around the world to save our trees, Scott encourages city residents to do their part to help by starting in their own front yard.
“A single tree in and of itself can be a tremendous respite for somebody,” she said. “Just to be able to stand underneath that tree when you’re waiting for the bus to come or have your lunch, it’s really a luxury that not everybody has. We need to be cognizant of that. Nature needs to be everywhere we live.”