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Data Analysis of Urban Trees Forecasts Climate Change Impact

Researchers from the Portland, Ore., metro area are collecting data on trees in urban environments to help predict the effects of climate change and resident health, particularly on underserved communities.

Dr. Hannah Prather from Reed College collecting early morning twig samples of Douglas fir branches to assess plant water status across trees in the Portland metro area.
Orion Coleman
MetroLab Network has partnered with Government Technology to bring its readers a segment called the MetroLab Innovation of the Month Series, which highlights impactful tech, data and innovation projects underway between cities and universities. If you’d like to learn more or contact the project leads, please contact MetroLab at for more information.

In this month’s installment of the Innovation of the Month series, we highlight Smart Trees, a project that is studying the health of urban trees as indicators of, and solutions to, climate change and resident health. MetroLab’s Ben Levine and Josh Schacht spoke with the leaders of the project: Jonathan Fink, director of the Digital City Testbed Center at Portland State University (PSU); Jason Maxfield, a biology adjunct researcher at PSU; Todd Rosenstiel, dean of the PSU College of Liberal Arts and Sciences; Aaron Ramirez, assistant professor of Biology and Environmental Sciences at Reed College; Vivek Shandas, professor of Urban Studies and Planning at PSU; and Hannah Prather, a post-doctoral researcher in biology at Reed College.

Ben Levine: Can you describe the origin of this project and who has been involved in it?

Jonathan Fink: "Smart Trees" grew out of the collective interest of researchers from across metro Portland, including Portland State University, Reed College, WSU-Vancouver and The Nature Conservancy, to position our city as a hub for research about urban trees, with an emphasis on equity, digital technology and climate change. In 2019, PSU's Digital City Testbed Center provided funding to explore ways that technology could improve the monitoring of urban tree health, complementing support the researchers obtained from federal research grants and philanthropic contributions.

Josh Schacht: What information are you collecting about urban trees and how do you collect it?

Jason Maxfield: Cities are a great place to study trees. Urban heat and pollution create natural experiments in tree stress, and emerging technology provides new ways to monitor tree health. We do fieldwork, including climbing tall trees, to measure things like water movement in branches and chlorophyll content in leaves. We also collect hyperlocal environmental data, both with our own instruments and by mining existing data streams of satellite imagery and environmental sensor networks. This gives us a robust study system to explore how both trees and people are impacted by climate change.

Dr. Hannah Prather, a postdoctoral researcher at Reed College, climbs a 30-meter Douglas-fir tree at Powell Butte to collect water potential data for the Smart Trees Project. This data will potentially provide insight into the effects of urban heat islands on the hydraulic health of trees in the Portland area.
Levine: How does the health of urban trees in our communities impact us on a day-to-day basis? How about on a long-term basis?

Todd Rosenstiel: Urban trees provide numerous benefits day to day, including most prominently cooling and cleaning the air, reducing noise, and increasing groundwater recharge. They can enhance real estate value, provide aesthetic value and encourage people to walk more. At the same time, stressed trees can become hazardous, dropping limbs and branches in windstorms and ice storms, and becoming more susceptible to burning during urban wildfires. These impacts are important on a day-to-day basis and also in the long term, as climate change increases temperatures, wildfire risk and severe weather events.

The many benefits of trees underscores the significance of the unequal distribution of trees in cities based on past and current planning practices and investments.

Schacht: Have any of the results you’ve found in the last year been particularly surprising?

Aaron Ramirez: Our work has shown that redlining and related urban planning policies that continued through the 1970s have led to significantly fewer trees in underserved neighborhoods, which in turn has contributed to those areas having hotter summertime temperatures and fewer tree-related amenities, with associated adverse health impacts.

Our monitoring of individual "Discovery Trees," 30-meter-tall trees to which we have attached various measurement devices, has shown great variations in temperature, humidity and air quality from the ground to the crown. We've documented how, because of the urban heat island effect, our cities can act as a crystal ball as regards climate change, allowing us to see its potential impacts on our natural environment and human health a decade or more in the future.

Levine: What are some of the most pressing changes U.S. cities can make to improve the state of their urban tree population?

Vivek Shandas: With climate change, the cooling role of urban tree canopies is becoming increasingly important, just as city temperatures, more erratic rainfall patterns and the spread of insect pests are all increasing. Additionally, older and larger trees provide more benefits than newer, smaller trees, and are harder to replace. Cities should better monitor tree health to get earlier warnings of potential catastrophic canopy collapse. Heat-stressed trees are also more prone to catching fire, putting more and more urban residents at risk. Cities should also prepare for and plant different tree species that are more tolerant of the changing climatic conditions. Maintenance of existing trees is also important — cities should inventory existing park and street trees (as Portland recently did) to aid in those measures; likewise, private homeowners need to be better trained in how to monitor and take care of trees on their property.

Schacht: What are the next steps for your team?

Hannah Prather: In the past year, we have been busy developing research protocols for monitoring urban canopies and their environmental and social impacts. We've been making baseline measurements of tree physiology throughout metro Portland by installing instruments from the bottoms to the tops of trees (the Discovery Trees), collecting and analyzing remote sensing data and establishing partnerships with local community groups and nonprofits. We are now planning to expand our attention beyond Portland, first to the Pacific Northwest, and then across North America, through collaborations with the University of British Columbia (UBC) in Vancouver, B.C., and with the national City Parks Alliance (CPA), respectively.

Fink: UBC has an active urban tree team that is partnering with Canadian cellphone provider Rogers Communications to explore how 5G technology can be used to help monitor urban tree health and public use of green space. We'd like to extend some of that team’s methods to Portland and replicate some of our methods in Vancouver. This Vancouver-Portland cooperation will position us to track the impacts of climate change on urban trees throughout the "Cascadia" region.

With CPA, we're exploring using a novel digital engagement platform called Hello Lamp Post to let people ask questions of or share observations with trees about their experience in parks, an approach we call “Hello Trees.” Analysis of the resulting dialogs may help park managers quantitatively demonstrate the psychological and physical benefits people derive from spending time in nature. Our hope is that this information can help city leaders and parks departments better understand the range of value that urban trees provide to city residents.
Ben Levine serves as executive director of MetroLab Network.
Josh Schacht is the director of technology and strategy at MetroLab Network. He works to support MetroLab members and the civic research community as a whole in promoting evidence-based policy and local community engagement. Prior to his role at MetroLab, Josh was a solutions architect on the Master Data Management team at Katerra, working to leverage sustainable building materials to create efficient and affordable housing.<br/><br/>