Cambridge's Urban Forest: Exploring and collecting data on a valuable city asset

Cambridge's Urban Forest: Exploring and collecting data on a valuable city asset

A partnership between Earthwatch, Cambridge, and the community to further research on urban forests and guide the urban forestry program.

  • Posted on: 9 July 2014
  • By: cuenk

There are more than 20,000 publicly owned trees in Cambridge that are interwoven into the city’s urban fabric. Most line the streets or fill the city parks and open spaces. Earthwatch, an international environmental nonprofit, has been collaborating with Cambridge’s City Arborist for the past three years to study the city’s urban forest with the help of volunteers. Led by trained scientists, volunteers have the opportunity to take on the role of a “citizen scientist” and collect data that tracks the health and growth of individual trees in the city. During the expeditions organized by Earthwatch, these citizen scientists learn how to identify tree species, measure trees, and record tree and environment conditions.

Volunteers who participated in the June 7th expedition came from all parts of Boston and Cambridge. Dr. Vanessa Boukili, lead scientist on the “Exploring Boston’s Urban Forest” expedition began the day with a comprehensive introduction to the program and urban forests. Boukili outlined the benefits of urban forests in a time when more than half of the world’s population lives in cities that produce over 80% of carbon emissions. According to Boukili, trees play a role in strengthening the urban ecosystem through carbon sequestration, flood prevention, and pollution reduction. Studies have also shown that urban forests provide aesthetic benefits which can lead to an increase in property values. From cooling cities to filtering pollutants, trees do more than provide shade to urban residents. However, trees face a number of environmental stress factors in their urban environments including poor soil and air quality. Urban forests also depend on “burdened city budgets” for maintenance, which includes watering, pruning, pest treatment, and the removal of diseased, hazardous, and dead trees. According to Boukili, limited budgets also affect data collection efforts. Earthwatch’s partnership with the city has provided Cambridge with the opportunity to build upon a database that will inform research on urban forests and guide the city’s urban forestry planting plans.

The goals of the expedition include: teaching and actively participating in science, encouraging local action, and engaging people from the community. Through their participation, volunteers learn “how trees grow and survive in an urban environment.” The data that they collect is used by Earthwatch scientists and the City of Cambridge for monitoring tree health and guiding new tree planting efforts. Larger research questions include: “How do we maintain and manage healthy urban forest? How do we manage the urban forest to provide maximum ecosystem benefits?” David Lefcourt, the City Arborist said that the program helps Earthwatch’s research and keeps Cambridge’s data inventory updated. Volunteers get to see Cambridge and trees “in a different light” and produce data that strengthens the city’s forestry program by identifying “things that work, things that don’t work, [and] areas for change.” Lefcourt addressed a concern raised by an Earthwatch volunteer who asked Boukili if the city would use their data to target old, large trees or trees causing sidewalk damage. Lefcourt said that his department considers all options to preserve healthy trees and that they “don’t remove trees because they create sidewalk issues.” In the long-term, Lefcourt envisions maintaining the Cambridge’s urban forest, continuing to build upon it and keep increasing tree diversity so that residents and businesses of Cambridge can “enjoy [it] for years to come.”

The Earthwatch program will play a significant role in making that long-term vision come to fruition. Already, the data collected through previous expeditions have passed quality measures and yielded a few important findings. In 2012, a quality test was conducted by Earthwatch scientists, in which data collected by an expert was compared to data collected by the volunteers, finding that “overall, volunteer measurements are good and very useful.” According to Boukili, research results from Cambridge’s urban environment in 2012 indicated that several species of trees grow more slowly when they are surrounded by a “higher proportion of impermeable surfaces (i.e. asphalt and concrete)”, but honey locust trees (Gleditsia triacanthos) actually grow faster in these situations. They also have preliminary findings that trees planted in the fall have slower growth rates than those planted in the spring. For the 2014 fieldwork, Earthwatch intends to measure the growth of trees planted in 2013, continue tracking growth of young trees, and start tracking the growth of older trees.

Armed with a diameter tape measurer, datasheets, and a binder full pictures and descriptions to identify tree species, 24 “citizen scientists” measured and logged 464 trees in one day. Field tasks included identifying species, measuring trunk diameter, assessing tree condition, and recording sidewalk damage. Volunteers covered an area of 1.1 square miles, with some volunteers measuring data in their own backyard and others exploring new parts of the city. Jeanette Eisenberg of Boston said, “It was a really great opportunity and experience to notice [the trees] for the first time...” It was Karen Levin’s first expedition and her group measured trees in Central Square. The experience “made [her] notice it’s really an urban forest.” According to Kara Lovell, a Boston high school teacher, her team could see the potential of coordinating an expedition for high school students because the work is “purposeful” and made them feel that “you can collect data that might be useful.” Boukili believes that the program is “good for science and good for citizens.” She hopes that volunteers will “tell friends and neighbors about what they learned” and continue to “think about trees as they walk around the city.” '

Through volunteers can see the data they and others collected, follow results of the program, and continue contributing to the program.
Interested volunteers can sign up for an upcoming expedition for free with the promo code TREES.
Dates include: July 19, July 31, August 2, August 8, September 6, and October 11.

Check the Earthwatch’s website for more information:


Hi Karen, this was a fascinating story, and today when I saw some of these volunteers out in front of my house I thought I'd find out some more about it if possible. I posted a short item about it:, and I put in a link to your piece, because there's so much good information in here.