“New Rules for Life” – A New Way to Understand Boston’s Trees with Kathryn Atherton
This post is part of our #BUandBoston series, highlighting the work and research of BU students, faculty, and staff throughout the City of Boston and the Greater Boston region. Interested in having your Boston-related work featured? Tag us on Instagram or Twitter (@BUonCities) using the #BUandBoston or send us an email at ioc@bu.edu.
Kathryn Atherton, a Bioinformatics PhD candidate in the BU URBAN Program and an IOC Early Stage Urban Research Award recipient, is working to solve this puzzle by studying how urbanization affects the tree-associated microbiome (the bacteria and fungi that live on and with trees). Kathryn’s research on trees highlights a theory for “the new rules of life,” which suggests that urbanization pressures city trees to innovate and develop new ways to survive.
Kathryn’s fieldwork spans city trees across nine different Boston neighborhoods, as well as trees in forests along an urban-to-rural gradient going into western Massachusetts. Through her ongoing sampling and testing, she has identified certain urban characteristics that may explain why city trees are changing where they receive their nutrients. “In cities, we have so much nitrogen pollution and nitrogen deposition in the air, and city trees are boxed into the sidewalks. The nutrients can’t permeate the sidewalk, so there isn’t enough nutrient availability below ground. This causes the trees to look above ground to survive, which is very interesting.” This phenomenon is what Kathryn and her advisor call the “new rules of life.”
While urban trees search higher upwards for their nutrients, they are interestingly rooting deeper below. Not only does the boxing of trees into sidewalks halt the flow of nutrients, but it also blocks urban trees from rooting far and wide. Kathryn explains that in around 70-80 percent of urban forest trees, their roots spread widely across only the top couple of inches of soil since that is where nutrients and water are most saturated. Urban trees, on the other hand, do not have the same ability to stretch their roots across only the first few inches of soil. As these city trees root deeper and deeper underground to compensate, this constitutes another potential new rule for life.
Trees in cities are not only crucial for the air and climate, but they also serve as integral parts of people’s homes and communities. Kathryn explains: “When you think about doing fieldwork as an ecologist, a lot of my colleagues and friends go out to a forest in the middle of nowhere. I’m taking samples from the trees outside people’s front doors, and people come up to me asking, ‘What are you doing to my tree?’” For Kathryn, working in an urban environment means collecting data from the soil and learning about the trees from the people who enjoy them. “It was a really cool way to learn from the community, learn about their thoughts on the trees I was sampling, and to get the oral history of those trees,” she continues.
Maintaining the health and well-being of Boston’s trees, which are highly valued by residents, requires strong city policies. To address this, Mayor Wu launched Boston’s first Urban Forestry Plan in 2022 to build a more climate-resilient urban forest. Kathryn is particularly excited about the plan’s focus on soil management, a crucial aspect that is often overlooked. She elaborates, “Below-ground tree care can be kind of invisible to us – we can’t see what’s going on and whether the tree has enough access to nutrients, water, or physical space. We can’t see whether the roots are thriving or dying, and a lot of times, we are only measuring the above-ground conditions.”
Beyond enacting policy at the local level, Kathryn advocates that people become more involved with community partners supporting urban forestry. Speak for the Trees is an organization in Boston that has a tree giveaway program that offers the opportunity to adopt an existing tree in the city. For renters in tree-rich areas, adopting a tree through this organization offers a direct way to help care for Boston’s local trees. Kathryn explains, “The Speak for the Trees organization will send you guidelines on how often and how much water you should give this tree to ensure it’s going to survive through a drought condition. They also give you information on how to spot whether the tree is diseased or suffering, so you can flag that to the city so they can take more drastic measures than just watering.” Through organizations like Speak for the Trees, community members have the opportunity to support the trees that support them.
The need for research is at the crux of any political or social action for protecting urban trees. Kathryn emphasizes how bridging the gap between academia and public knowledge is crucial. Referring to researchers, she says, “As you’re getting your results, share them.” Making research more transparent and understandable to governmental officials, commercial actors, and everyday people helps inform everyone of the steps to protect our urban forestry. “That continuous conversation about what they need, what you need, and what you are finding together can give you even better ideas on how to make your work as effective as possible. Not just in academia, but in the real world.”