Trees along Boston’s Commonwealth Avenue Mall display fall foliage
Credit: Leslee_atFlickr, CC BY-NC-ND 2.0

Ania Camargo’s Beacon Hill street in Boston was once so beautiful that Logan International Airport hung a photo of it on a welcome banner.

It had all the makings of a postcard: Cobblestone alleys. Red brick row houses. Flickering gas lamps. Tall, broad-leaved linden trees.

Camargo misses the way her street used to look. Although the gas lamps in the historic photo are still standing, many of the trees have grown ill and died in the past several years. “I do not believe a photo of our street as it looks, with sickly trees and baby trees, would be in the airport now.”

Camargo and many others blame natural gas leaks as a driving cause of the trees’ afflictions. The city has thousands of gas leaks in old, cracked pipes and joints under sidewalks and streets.

Photos taken in 2010 and 2021 show changes in trees on Temple Street in Boston
In 2010, Ania Camargo’s tree-lined street was so picturesque a springtime view was used to welcome visitors at Boston’s Logan Airport. By the winter of 2020–2011, 11 of the trees had died, a phenomenon Camargo associated with the natural gas leaks consistently reported and repaired on the street. “There are other factors that also affect trees, like salt and lack of water, but I believe the reason they have been dying so quickly on our street is because of the gas.” Credit: Ania Camargo

Today Massachusetts has some of the most progressive laws in the country regulating gas leaks. They’re largely thanks to a powerful coalition of organizations and researchers called Gas Leaks Allies taking the state’s energy system to task. The movement to plug leaks has gained steam over the past 2 decades and evolved into a campaign to quit natural gas altogether.

Although the campaign has broad ambitions, the movement started with protecting community trees.

The fight in Boston over the future of natural gas is also playing out across the country. Municipalities like San Francisco have banned gas in new buildings, and President Joe Biden singled out gas leaks in an executive order on combating climate change.

The United States and other countries have just decades to drastically slash emissions to avoid the worst consequences of climate change, according to a 2018 report by the Intergovernmental Panel on Climate Change. The United States is the second-largest producer of methane emissions in the world, behind Russia. These emissions primarily come from leaking oil and from gas production and distribution. To get off gas, whole cities must be redone from the inside out.

“It’s like trying to fix the airplane while you’re in flight,” said Nathan G. Phillips, a tree biologist at Boston University and activist who advocates for moving to renewable fuels.

The Whistleblower

The way a tree dies from natural gas poisoning is essentially like drowning: It suffocates, unable to access oxygen. Tree roots need oxygen to convert nutrients into energy in a process called respiration. While leaves use carbon dioxide to photosynthesize and give back oxygen to our atmosphere, roots take the sugars produced by photosynthesis and break them down into energy using oxygen.

“I’ve got pictures of hundreds, thousands of trees, gone.”

But if the roots can’t access oxygen—if natural gas fills up tiny soil pores instead—the tree can’t break down its food. Even mature trees can survive for only so long.

Whereas a person might drown in mere minutes, a tree dies over many months, first losing its leaves, then ceding its twigs and branches, and finally sprouting unusual shoots and leaves directly from its trunk in a final desperate gasp to survive.

Bob Ackley, a member of Gas Leaks Allies, has seen it all. “I’ve got pictures of hundreds, thousands of trees, gone.” He began work with gas companies in 1979 after leaving college for a lucrative summer job scouting gas leaks. That job stretched into a career of surveying gas leaks for utilities up and down the Eastern Seaboard. “I was taught how to find the leaks by looking at the grass, trees, and shrubs.” It was a sure sign of a leak, he said, if trees were losing leaves irregularly, the grass was brown, or other vegetation was dying.

Ackley said the utilities told him to look for dying trees as a clue to gas leaks, but they refused to publicly acknowledge that gas leaks harm trees. He also worried about the human health effects of gas leaks inside people’s homes.

Photo of a crumbling cast iron pipe used to transport natural gas
Natural gas can leak from crumbling cast-iron pipes under the city’s streets. Cast-iron and steel pipes and joints are more than 50 years old in some places in Boston, and their sealants are cracking. Credit: Audrey Schulman

Spurred by growing concerns about leaks and the fact that working as a contractor was getting “laborious,” Ackley left the gas industry in 2006. Ever since, he’s been trying to get the word out.

He’s reached out to legal groups, mayors, city councils, and environmental organizations in Massachusetts and across the country to warn them of the dangers of leaking gas. Eventually, Ackley founded Gas Safety USA, a Southborough, Mass.–based company with a mission to protect trees and human health from leaking gas.

Gas companies in the area have repeatedly emphasized that they are doing the best they can to protect human lives and property.

Spokesperson Christine Milligan of National Grid, one of the two major gas companies operating in Boston, said, “while safety is our biggest priority, we do also work to minimize the impacts of our system on the environment, and we include environmental considerations in our main replacement planning and in our repair programs.”

National Grid declined to comment on whether the company was responsible for the loss of street trees, and the other primary gas company operating in Boston, Eversource, did not respond to a request for comment on this story.

An Alliance

A rectangular black instrument labeled “Gas-Sentry™” connected to a spiral cord leading out of frame nestles at the trunk of a tree. On the box, a window displays “38.0” in glowing red.
Bob Ackley (just out of frame) probes the root zone of an oak tree in Jamaica Plain in Boston. He has been known to roam grocery stores and cross property lines with a cavity ring-down spectroscopy backpack to measure gas concentrations and anomalies. Credit: Bob Ackley

One November day in 2010, Phillips was out for a walk with his son in his Newton neighborhood. The pair happened upon Ackley, who was probing the soil around trees along the street to test for methane.

The men struck up a conversation, and Phillips realized that looking at leaks was an important research and policy question that happened to cross over deeply into his work.

Gas leaks are a threat to the state’s climate goals, after all: Natural gas is composed almost entirely of methane, a greenhouse gas 84 times more effective at warming Earth’s surface than carbon dioxide. Despite this, it has been touted as a bridge to renewables.

Phillips asked Ackley whether he’d be interested in working together, using a technology similar to the cavity ring-down spectroscopy instrument on top of Phillips’s university building. Phillips and his colleagues used the instrument to survey carbon dioxide and other gases—including methane—24 hours a day, and he thought it could be a perfect, high-precision device for finding gas leaks. If leaks were as ubiquitous as Ackley claimed they were, then use of natural gas in Boston might not be as efficient as people had thought.

Researchers found a whopping 3,356 leaks across Boston.

A year after they met, the pair took a newly designed roving gas spectrometer and drove more than a thousand kilometers of Boston’s streets in Ackley’s Pontiac, measuring methane as they went. They found a whopping 3,356 leaks across the city. Most were small, but one methane reading reached 14 times higher than background levels.

While most gas leaks aren’t dangerous, they can be costly: Customers pay for lost natural gas through their rates. Scientist Kathryn McKain estimated that a little less than 3% of natural gas delivered to eastern Massachusetts leaks into the atmosphere, equivalent to about $90 million per year (using 2012 and 2013 gas prices).

Ackley and Phillips published their work in the journal Environmental Pollution, and it had an immediate impact. The next year, the Massachusetts state legislature passed a law requiring utilities to disclose a list of their leaks each year for all to see.

A map of Boston showing spikes in methane concentrations
It’s common to smell natural gas when walking the streets of Boston. This map of methane concentrations shows why: Leaks are everywhere. Nathan G. Phillips and Bob Ackley collected the data by car in 2011. Credit: Kaiguang Zhao; Map data: Google Earth, SIO, NOAA, U.S. Navy, NGA, GEBCO © 2012 Cnes/Spot Image; Image © 2012 TerraMetrics

Their work continued in the years following, gaining national media coverage and catching the attention of local climate groups and activists, including Camargo, who volunteered with the climate advocacy group Mothers Out Front. The success of Phillips and Ackley’s work “galvanized us to be more focused on what we were going to be working on and really to get into gas leaks,” she said.

In 2015, Camargo formed Gas Leaks Allies, a coalition of more than 25 organizations and researchers with a mission to slash methane emissions from the state’s natural gas distribution system. The group included mostly local organizations—arborists, climate activists, and social justice groups—as well as national partners like the Sierra Club and Clean Water Action.

Three Strikes

In the years that followed, the collaboration between scientists and activists in the state deepened, much of it at the hands of, or partnered with, members of Gas Leaks Allies. Three big breakthroughs have since changed the region’s understanding of gas leaks—and spurred those involved to take even more drastic action.

First, Ackley worked with Phillips and his graduate student Margaret Hendrick to hunt down environmentally damaging leaks. They found that the city could cut its methane emissions from leaks in half by just plugging the worst offenders. The results were published in Environmental Pollution in 2016 and quickly made their way to members of the state legislature.

Because of the research, the Massachusetts legislature passed a law in 2016 ordering gas companies to develop a new classification system to fix environmentally harmful leaks more quickly than before. In 2019, the Massachusetts Department of Public Utilities adopted the new classification, and the changes may slash the state’s emissions by approximately 4% in as little as 3 years, said Audrey Schulman, a climate activist with the Boston nonprofit the Home Energy Efficiency Team (HEET) and member of the Gas Leaks Allies. This reduction is roughly equivalent to stopping emissions from half of the state’s stores and businesses.

The argument “is straight out of the tobacco playbook.”

Second, a first-of-its-kind study in Chelsea, Mass., challenged an argument from supporters of natural gas—namely, that gas leaks don’t commonly harm trees. After the survey by Ackley and Phillips exposed thousands of leaks in the city in 2013, for instance, Tom Kiley, head of the Northeast Gas Association, said that while methane can damage vegetation, it isn’t a regular occurrence. “There certainly are a lot of potential causes to the damage to trees and vegetation. That can include insect infestation, vehicular damage, disease, storm damage, drought, salt,” he said.

Milligan of National Grid said something similar when responding to questions for this article: “We know there can be a variety of factors—such as restricted root growth, disease, predatory insects, age, exposure to road salt, motor vehicle hits, and other environmental factors—that can cause damage to trees.”

The gas company’s argument “is straight out of the tobacco playbook,” Phillips said. He acknowledged that street trees experience stress from many sources, like salt from roads, drought, and construction. “None of those in any way somehow diminishes the importance of gas leaks in damaging trees. And I think it’s really, really important to stress that point.”

To put the issue to rest, the Chelsea community organizing group GreenRoots asked Ackley and Boston University scientist Madeleine Scammell to survey Chelsea’s trees. Led by Scammell, the team looked at 180 trees in Chelsea and found that dead or dying trees were 30 times more likely to have gas leaks nearby. These trees had elevated and unhealthy levels of methane in their soil. The study showed that gas leaks are statistically associated with dying trees.

The third and last breakthrough came from work by a geographer at Salem State University who has found that gas leaks cluster in neighborhoods with more people of color, more renters, and those with lower English proficiency. Chelsea, for instance, is one of few Massachusetts cities with a majority Latino population and is a fenceline community that bears the brunt of industry activities. Fenceline communities are those situated near industrial plants and other industrial activities and are exposed directly to pollution, noise, and other adverse effects.

Marcos Luna compared census data with a public map of leaks and found that gas leaks are an unequal burden statewide. Whiter, home-owning neighborhoods have fewer leaks, and their leaks are fixed faster than those of others.

A chart showing the risk of living near a gas leak for different populations
This dot graph compares the relative risks of exposure to unrepaired leaks by different groups in 2019. Black and African American people have a relative risk of 1.8 (for all leaks), which means their exposure to unrepaired gas leaks was 1.8 times (80%) higher than that of the general population. By contrast, white people have a relative risk of 0.8, meaning their exposure was 20% lower than that of the general population. HH=household, HU=housing unit HS=high school. Click image for larger version. Credit: Marcos Luna

Taken together, local action by scientists and community organizers spurred legislation, revealed the relationship between gas leaks and tree death, and exposed the unequal burden of gas leaks on people of color and immigrants. But the next fight was already underway—one to dismantle the state’s gas system altogether.

The Way of the Arborist

Ever the biologist, Phillips thinks getting off of gas is like cutting down a tree.

When arborists fell a tree, they start by trimming the uppermost branches. Little by little, they remove each branch down the tree’s trunk. Finally, they cut the bare trunk to the ground.

Phillips said it’s important to prune natural gas in the same way, starting with the thinnest branches—transitioning to electric or geothermal heating, then moving to bigger and bigger branches until the original natural gas system is gone. The leaks will go with it.

In one geothermal model Boston is considering, gas companies don’t have to go out of business.

Gas Leaks Allies is now hard at work discussing what should be planted in place of natural gas. Several pilot projects for geothermal energy are underway.

Although the most well-known use of geothermal is in Iceland, geothermal infrastructure doesn’t require being near a volcano. Passive geothermal technology, for example, merely uses the heat of the Earth to create a heat exchange with the surface. In Europe, many cities heat and cool their buildings with this form of geothermal heat.

In one geothermal model that Boston is considering, homes and businesses along a street would share a circulation loop operated by the local gas utility. Water would travel up and down 150-meter-deep boreholes spaced every 6 meters along the street. The water would flow into customers’ homes and into their heat pumps before progressing on to their neighbors.

Gas companies don’t have to go out of business with this model, said HEET’s Schulman.

In this geothermal loop, pipes carry water up and down boreholes to exchange heat. The ground a few feet below Boston stays near 50℉ year-round, so the water pumped through the boreholes moves the ambient temperature up to the buildings, where heat pumps can use it to heat or cool buildings.
In this geothermal loop, pipes carry water up and down boreholes to exchange heat. The ground a few feet below Boston stays near 50°F year-round, so the water pumped through the boreholes moves the ambient temperature up to the buildings, where heat pumps can use it to heat or cool buildings. Credit: HEET

Utilities could capitalize on the knowledge and infrastructure they already have to transition to geothermal. They could use the same pipes, keep the same customers, and use the right of way on the street.

In a feasibility study, HEET found that the proposed geothermal system would work for all but the most densely populated parts of Boston, where they’d need to dig more boreholes. The study calculates that customers would pay less on geothermal than on gas.

The idea may be put to the test soon: In Massachusetts, two separate pilot programs are in various stages of development, and another is awaiting approval. New York and Connecticut are also piloting shared geothermal loops. (These are distinct from universities running their own geothermal systems, which several schools in the United States already do.)

Photograph of a tree and leaves
Credit: Bob Ackley

The passage of sweeping climate legislation in March of this year will make it easier for companies to pilot projects and provides $12 million for workforce retraining. “Everything about this new law [Senate Bill 9—An Act Creating a Next-Generation Roadmap for Massachusetts Climate Policy] makes the first pilots and scaling up from the pilots easier,” Schulman said.

Roseann Bongiovanni, executive director of GreenRoots, supports the efforts to get off of gas. But she said that the neighborhood Chelsea has more immediate concerns, like developing its own source of energy. By doing this, she said, the community can disconnect from the larger grid and still power up if there were a catastrophic event.

With more legislation in the pipeline, notably the Future of Heat bill introduced by state senator Cynthia Stone Creem (D) and state representative Lori Ehrlich (D), the work of Gas Leaks Allies continues. In 5 years, “we’d like to see people transitioning to electric appliances with well-insulated homes,” Camargo said.

She has similar hopes for her street.

Her house is already all-electric, and ideally, in the next decade, the houses along her block will switch away from gas too. The beautiful historic lamps have been converted to electric power, and the trees grow strong and healthy.

Above all, Camargo sees the future of her street summed up in three words.

“Absolutely no leaks.”

Author Information

Jenessa Duncombe (@jrdscience), Staff Writer


Duncombe, J. (2021), The surprising root of the Massachusetts fight against natural gas, Eos, 102, Published on 21 May 2021.

Text © 2021. AGU. CC BY-NC-ND 3.0
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