Earthwatch Program Sheds Light on Trees in Cambridge

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Newly published results demonstrate the power of citizens and scientists working together on urban resiliency

Earthwatch volunteer measures a tree in Cambridge, which served as a "living laboratory" for this effort to quantify the value of green infrastructure and compare growth rates to model predictions.

We know we’ve got work to do to ensure that our urban ecosystems are resilient in the face of climate change. There’s no better way to do that than to involve citizens directly in the research itself.

More than 500 “citizen scientist” volunteers – from school teachers to students, corporate employees, retirees, and more – measured and monitored nearly 9,000 trees that comprise Cambridge’s urban canopy, far surpassing what city officials could have done on their own.

Between 2012 and 2015, David Lefcourt, the Arborist for the City of Cambridge, worked alongside the research director, Vanessa Boukili, Ph.D., and volunteers from the Earthwatch Institute, a Boston-based nonprofit that teams citizens with scientists, on a unique urban forest program that essentially turned Cambridge into a “living laboratory” for researchers. They recently published some of the results in the scientific journal Urban Forestry & Urban Greening.

Boukili, lead author of the publication, is now the urban forestry and landscape planner for the City of Somerville. “Accurately assessing the value of green spaces within urban environments is a hot topic,” Boukili said. City planners generally rely on various computer models to predict how quickly trees will grow, for example.

“While tree models offer solid, broad-stroke estimates of growth for city-wide estimates,” Boukili said, “our study shows they may fall short if you’re trying to accurately assess their value for specific communities.”

It can be really helpful to back up what the models predict with data gathered on the ground, she said, which is the gap the Earthwatch program filled.

Boukili also used the program results to author an Urban Forest Management Plan for Cambridge (, which Lefcourt said will soon be incorporated into an even more comprehensive master plan.

Some of the results were unexpected, said Lefcourt. For example, some of the trees in Cambridge grow much more slowly than predicted by current computer models, but they also survive longer.

“The models tell me the trees we plant ought to last eight to 12 years in an urban environment, but the Earthwatch data suggest it’s more like 25 to 30 years,” he said.

Moving forward Lefcourt will also consider planting trees in the spring season only, as opposed to spring and fall because the Earthwatch data indicate the younger trees fare much better in the spring.

Each tree he plants in Cambridge currently costs about $1,000, which includes both the initial planting and the maintenance for two years.

“It was a blast to work with the volunteers who lent a hand on such a powerful program,” Boukili said, “and we were thrilled with the quality of the data we collected. It really showcases the power of citizen science.”

Earthwatch took the successes from the Boston program to launch a large program in Los Angeles ( and plans to continue to scale the effort in other cities.

Besides their aesthetic value, urban trees can take the edge off city life, cleanse the air, conserve water from runoff, provide shade and cooling, and much more. Several studies demonstrate the human health value of healthy urban landscapes, which are under threat from climate change. Climate change tops Lefcourt’s worry list, he says, noting that Cambridge’s trees leafed out much more slowly this year because of last year’s drought and the irregular spring weather.

“We know we’ve got work to do to ensure that our urban ecosystems are resilient in the face of climate change,” said Scott Kania, Earthwatch CEO. “There’s no better way to do that than to involve citizens directly in the research itself so they become true ambassadors of our shared environment.”

The Earthwatch work was funded by the Goldring Family Foundation, the Borun Family Foundation, and EY.

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Kristen Kusek
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