This might be America's first campus tree inventory

(Press-News.org) Ask anyone what comes to mind when they think of Northern Arizona University and they’ll probably say something about the trees. NAU's Flagstaff mountain campus is home to an estimated 5,000 to 6,000 trees—most of them ponderosa pines.

This precious resource is worth protecting. That’s why, this summer, students, faculty and staff at NAU are working together to take stock of the campus tree collection. Slowly but surely, a team of forestry and environmental scientists will collect information about the health, age and species of every single tree on the mountain campus—whether evergreen or deciduous, short or tall, native or invasive, thriving or rotting—and store the data on the software platform Treekeeper, which will also measure how much carbon each tree is sequestering. It’s possible they’ll be the first team at any American university to complete a full campus tree inventory. 

The project won’t just have important implications for the future care and planting of trees at NAU. It will provide hands-on student research opportunities spanning multiple disciplines for years to come. It will shed light on the trees’ ability to sequester carbon, helping to advance NAU’s ambitious sustainability goals. It will keep future Lumberjacks cool as Flagstaff warms. And it will provide a blueprint for universities and cities across the globe that hope to create more livable, sustainable communities.  

“NAU has been designated an official Tree Campus by the Arbor Day Foundation for 12 years based on the size of our tree canopy and the way we care for it, and it’s a major source of pride,” said Erik Nielsen, the university’s chief sustainability officer. “A campus tree survey gives us a chance to reflect on what we’re doing well, what we can improve upon, how much carbon our trees are sequestering, the value of shade to cool our buildings and so much more. The trees on campus benefit everyone here in a multitude of ways, and that’s why we’re investing time and money into getting to know them better.” 

Ripple effects 

Made possible by a grant from the Arizona Department of Forestry & Fire Management and supplemental funds from the NAU Office of Sustainability, the tree survey project began as an idea raised by the Landscape and Water Action Team, a diverse group of employees from the Office of Sustainability, Facility Services, the Sanghi College of Engineering and the College of Environment, Forestry, and Natural Sciences. 

“Trees can be excellent for stormwater mitigation, which is a big priority for the City of Flagstaff, so one of our goals for this inventory is to determine the current value of our trees for stormwater mitigation and examine how we can prevent flooding more effectively,” said Jim Allen, a professor in the School of Forestry and a member of the Landscape and Water Action Team. “But there are so many other positive ripple effects for sustainability on campus, for tree care and for education.” 

Using funds from the grant, Allen and Nielsen tapped Taylor Joyal, an associate teaching professor at the School of Earth and Sustainability who specializes in hands-on teaching, to lead the inventory project. Joyal got the ball rolling with students in his Spring 2025 capstone course. This summer, three Jacks are building on those students’ initial work: Estella Percarpio, a 2025 environmental sustainability graduate; Sophie Radder, an environmental sustainability major; and Leah Kisto, an environmental science major with an emphasis in climate change. All three agree the project is bringing classroom concepts to life and giving them the hands-on experience they’ll need to pursue careers in fields like conservation, consulting or climate resiliency. 

“I’m looking to do work in climate resiliency, so learning about carbon sequestration and how it can mitigate climate change is really helpful for me,” Percarpio said. “I chose NAU because their sustainability program is a mix of natural sciences and social sciences. You can’t just think about trees on campus through a natural science lens.” 

To illustrate her point, Percarpio pointed out a Siberian elm on the North Quad. Though majestic when it thrives, the imported tree isn’t meant to live in northern Arizona, and it shows. A bacteria nicknamed “slime flux” covers part of the trunk, making it unpleasant to sit beside. Many large branches hang dead 20 feet in the air; whenever they fall, they could pose a danger to passing students. The dead branches also translate to a thinner leaf canopy and very little shade. Those aren’t just environmental problems—they’re also social problems. 

Endless possibilities 

Problematic as they may be, invasive trees like the Siberian elm aren’t all bad: They provide unlimited potential for interdisciplinary student research in the future. 

“There’s a whole swath of environmental and social topics that can build off this inventory and use the NAU campus as a living laboratory,” Joyal said. “Psychology students could use the database to analyze the impact of a healthy tree canopy on student mental health. Students could work with our landscape architect to map out new places to plant trees to improve cooling in classrooms and dorms. The possibilities are endless.” 

Nielsen said Facility Services staff feel the same way. A complete tree map won’t just help landscapers know which specific trees to prune for safety and which trees to leave alone, lest a weed whacker accidentally bite into the bark and expose it to pests. It will also help landscape architects assess which trees are doing more harm than good and which areas on campus could do with a bit more shade. They’ll also be able to assess whether irrigation of turf grass is hurting certain trees while providing little benefit to students. Eventually, some of these small grassy patches could transform into colorful gardens full of drought-tolerant native trees and plants hardy enough to thrive in the harsh seasons of northern Arizona. 

“No one really thinks about university campuses as habitats for wildlife like birds and insects, or as important contributors to mitigating the urban heat island effect in cities, but people can and should,” Nielsen said. 

Because trees and other plants are important to fighting climate change, he believes they’ll play a major role in helping NAU achieve its ambitious goal of achieving carbon neutrality by 2030. 

“To get to carbon neutrality, you don’t just calculate your greenhouse gas emissions and reduce them—you also need to calculate your carbon sinks,” Nielsen said. “Trees absorb carbon and offset emissions. But how much carbon do they absorb, and how much does that offset our campus emissions? Answering that question was a big motivation to back this project.” 

But so, too, was the possibility of helping other communities reach their own sustainability goals. 

“We haven’t heard of any other universities that are doing this—assessing above-ground carbon sequestration and other ecosystem services,” Joyal said. “We could serve as an example of an inventory project for other universities to do, not only for the benefit of campus but also for the benefit of students. When they graduate, they take that practical training into jobs in cities, or jobs in consulting, and they create more climate-resilient societies.” 

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