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Trees are key to address Boston’s heat islands. But it’s more complicated than just planting new ones.

“I don’t think the question necessarily is, ‘Should we do this?’ The question is, 'How do we do it in a way that’s not just throwing money at the problem?'”

John Tlumacki/Globe Staff
A shriveled up tree in a planter on Harrison Avenue is one of the few trees in Chinatown, one of the city's heat islands. John Tlumacki / The Boston Globe

Boston saw one of its hottest and driest Julys ever this summer. 

The city experienced record-breaking heat on several occasions. Oppressive heat waves prompted officials to declare heat emergencies, urging residents to seek relief from the sweltering temperatures by staying indoors with fans or air conditioning — or by seeking shade, out of the blistering rays of the sun. 

But the cool offered by the shade of trees is not always so easily, or equitably, found in Boston.

Cities already experience hotter temperatures than their rural neighbors. But even within a city, there are neighborhoods that experience more intense heat


Those areas, known as “heat islands,” can be found where there is more concrete, more buildings, more steel — and less trees, grass, or other green space. In what is known as the heat island or urban heat island effect, the built structures — such as buildings and roads — absorb the sun’s heat and re-emit it. That can mean daytime temperatures can be between 1 and 7 degrees higher than spots with more natural landscapes; nightime temperatures can be between 2 and 5 degrees warmer, according to the Environmental Protection Agency.

Communities that have historically seen disinvestment and marginalization are often those experiencing the heat island effect more intensely, according to Rev. Vernon Walker, program director of Communities Responding to Extreme Weather, also known as CREW

“Even at night in those communities, it’s particularly hot because the heat is releasing at night and we know that concrete traps heat,” he told Boston.com. “And as climate change becomes a lot worse and heat waves become more and more frequent, the urban heat island effect, it makes the impact worse of climate change and it amplifies the already oppressive conditions that heat waves cause to a community.” 


Look at a heat map of the area, Walker pointed out, and the difference in temperature in places like Chinatown stands out in stark contrast to the cooling blue in places like Brookline or Franklin Park, where more greenery can be found. 

Unlike neighborhoods that have been subject to redlining and disinvestment, communities that are wealthier tend to have more trees, resulting in cooler temperatures in the summer, David Meshoulam, co-founder and executive director of Speak for the Trees, said. 

That is because trees not only provide shade but also a cooling effect through evapotranspiration

“Really, it’s a public health issue,” Meshoulam said. “If you’re living in a community with 105-degree weather versus 90-degree weather, not only are you going to be dealing with heat stroke and other sorts of health issues, but if you can afford air conditioning, your air conditioning bill is going to be that much more, your electricity bill is going to be that much more. Which is not only an economic issue, but it’s an environmental issue because we’re taxing our grid.”

Ensuring residents understand the public health impacts of heat islands, and the way they amplify already dangerous conditions from heat waves, is one of the missions of CREW. 


That includes spreading awareness and providing support for related issues, since the communities that suffer from heat islands are also those that are more likely to suffer from food insecurity, economic injustice, and racial injustice, Walker said. 

“One of the other things that we do is that we help point out how climate change is intersectional and it’s interconnected to housing justice, racial justice, immigrant justice, and how these injustices are inextricably linked,” he said. “And how we can’t have climate justice without racial justice. Because those communities that are disproportionately affected, coastal communities, urban communities, by the climate crisis are also the same communities that are disproportionately impacted by racial injustice and housing injustice and gentrification, etc.”

The areas that experience the most intense and longest heat in the city are Chinatown, Downtown Boston, the South End, South Boston, and Back Bay, ​​according to the city’s Heat Resilience Plan. But Allston, Brighton, Charlestown, East Boston, as well as parts of Dorchester and Roxbury, also experience hotter and longer heat events compared to the median temperature in the city. 

One of the ways to address heat islands is to increase the tree canopy in those areas by planting and ensuring the survival of new trees. Boston officials say addressing “tree canopy equity” is a measure that is an important part of the city’s plans to address heat islands and the city’s heat resilience in the face of the climate crisis. 


The city is currently putting together its first Urban Forest Plan, which, when it is released this fall, will outline measures and steps for protecting and expanding Boston’s tree canopy.

Ryan Woods, Boston’s Parks and Recreation Commissioner, stressed the importance of trees for cooling and improving air quality in the city. 

“Equitably expanding canopy throughout the city will mean expanding the benefits they provide in areas that are historically marginalized and currently excluded communities that tend to have higher temperatures,” he told Boston.com.

As part of the work on the forest plan, the city has conducted a complete inventory of its street trees.

Woods noted that the team working to develop the forest plan is working closely with the team tasked with addressing heat in the city. But he noted that an equitable canopy — and the work of the Urban Forest Plan — is about more than just the shade that the trees will provide.

“It’s about actively supporting economic justice, doing workforce training with residents,” he said. “It’s so important that residents understand about tree care and the importance of trees and helping to water trees. And it also means holding that space for voice and leadership of communities on how the forest is managed. 

“We may think we know best, but we learn best by having our residents engaged,” he continued. “And that’s how we have a successful canopy — is by having involvement and engagement by the community.”


Speak for the Trees is one of the local organizations working in partnership with the city to both plant trees and provide education around the importance of the urban forest.

Meshoulam said he thinks that this summer in particular people have become much more aware that they are “more on the front line in facing heat than others.”

He said it is clear, based on the inventory done by the city, that there is a “massive opportunity” to plant trees in Boston.

“That’s not a surprise,” he said. “There are trees that have died; there’s empty tree wells in certain neighborhoods. There’s potential to remove concrete and plant trees. I don’t think the question necessarily is, ‘Should we do this?’ The question is, How do we do it in a way that’s not just throwing money at the problem?’”

Answering that question runs up against a structural problem, he said, since a lot of trees are going in the ground, but they are not surviving.

According to Meshoulam, about 30 to 40 percent of the street trees planted in Boston don’t survive past their seventh year, with most of the mortality occurring in the first two years.

“The question is how do you develop a system that allows these trees to not only survive but thrive?,” he said. 

A group enjoys lunchtime under the shade of a tree in the Boston Common to escape the heat in July. – David L. Ryan/The Boston Globe

Both Meshoulam and Woods stressed that engaging city residents for the care and stewardship of Boston’s trees is going to be essential to ensuring that the urban forest flourishes. 


And that’s not just because only an estimated 40 percent of the city’s trees are on public land, compared with 60 percent on private property.

The city’s street trees are supposed to be watered by contractors during their first two years in the ground, but even then, they can always use more water, Meshoulam said. 

After their third year, the trees are largely left on their own. 

“We think there’s a way to build community partnerships and get residents involved in actually helping water those trees in years three through seven where the trees need time to get established in their new home,” Meshoulam said.

It’s an effort that Speak for the Trees is piloting with its Teen Urban Tree Corps program, which is in its fourth year. Participating in the program, Boston teens learn about the importance of trees and their inequitable distribution in the city. They also spend time caring for about 4,000 trees in Dorchester’s Fields Corner, watering and mulching them. 

Meshoulam said the program also demonstrates to teens that there are career opportunities — and a real need — in the field of forestry. 

“These are good paying jobs, these are local jobs, these are jobs for people who love to work with their hands, who love to be outside, who love to engage with communities, can really make a difference,” he said. “It’s a career; it’s not just a job.”


The hope is that the model of engagement and education offered by the Teen Urban Tree Corps can be expanded to other neighborhoods and communities. 

“We want to expand that to … working with community groups to get people excited about this, to get people to request trees, but then agree to water them more regularly,” Meshoulam said. “The climate we’re seeing this summer will probably repeat itself in future summers as well, so we really need to think, how are we going to ensure that these trees that we plant or that have been planted get the attention they deserve? And I think that needs to come not only from the city but also from residents.”

It can’t just be about planting a tree and walking away, he said. 

With its lack of trees and heat radiating off the surrounding buildings, Chinatown is one of the hotter neighborhoods in Boston. – John Tlumacki / The Boston Globe, File

By engaging with local community groups and hosting workshops, Meshoulam said Speak for the Trees aims to not just provide information about caring for trees and the important role they play in the city for heat resiliency, but to also better understand how people relate to the urban forest. 

“Trees are complicated objects,” he said. “Some people love them, and some people don’t want to rake the leaves in the fall. For some immigrant groups, trees are a source of, back in their home country, of food and sustenance that here in the city, we don’t really have that. … So they are complicated historical objects, and trying to understand how different communities engage with and think about trees is one of our goals.”


Such engagement is important to encouraging residents to plant trees or care for those already on their private property. 

“It’s about really shifting about how people think about and relate to trees in their daily lives and in our community,” he said. 

Woods said the city is looking to lean into and grow the enthusiasm and support for trees in Boston, since resident engagement is so important for tree care and planting, particularly given that 60 percent of the urban forest is on private property. 

There’s only so much space available on city sidewalks — with utilities, hydrants, mailboxes, and stop signs among other limitations — to grow trees. Boston really needs to continue looking at private property as the place to continue growing the city’s canopy, he said. 

“It sounds a little corny or cliche, but to grow a city forest, it takes a city,” Woods said. “It takes everyone working together regardless of where these trees live, they need to be cared for so they continue growing and expanding their canopy.”

With Boston and most of the state experiencing a critical drought, the role of private property owners and residents in caring for the city’s trees becomes even more important, Woods said. 

“It’s so crucial to understand, especially in these times of drought, that the heat on these trees, the stress that they’re taking on, adding 20 gallons of water a week makes a huge difference and it’s not at a big cost to the residents,” Woods said. “So that tree that’s in front of your home or in your yard that’s giving you that shade and that respite on hot days and taking in stormwater, that needs the love and care of these residents.”


At this point, he said he believes the biggest obstacle to ensuring residents are part of the stewardship of the city’s urban forest is just the process of getting the message out and making the formal ask of the community. That includes making sure people understand the needs of the trees, that there is minimal cost involved in watering once a week during drought conditions, and that anyone can report pruning needs to 311.

The city forest is as much a verb as it is a noun, he said.

“It’s very cliche that there’s that old proverb that the best time to plant a tree was 20 years ago, and the second best time is today,” Woods said. “The importance of the role that trees play in our everyday lives and the need for us to engage with them, to help provide the resources for them, is very important. And that’s something we’re trying to get out there and find ways the city can partner with the residents so that we really do have a healthy, equitable canopy across our city.”

The leaves on a city tree stressed by drought turn brown in Boston. – Michael Dwyer / AP


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