Wildfire smoke has blanketed Vermont multiple times this summer, clogging the air and making it unhealthy for vulnerable people to be outdoors.
Towns across Vermont have seen several days when the air quality was “unhealthy for sensitive groups” — and Environmental Protection Agency data analyzed by Vermont Public shows an upward trend in recent years.
Is all of this really new? We asked some scientists.
How has air quality in Vermont changed over the years?
Prior to European settlement, wildfires were common across what’s now the northeastern United States and Canada.
Canada’s vast swathes of boreal and taiga forests actually need fire to thrive. Many species of trees there are adapted to fire, and episodic burns help them to reproduce.
“I think it’s important to remind the listener that this part of Canada’s forest, this sort of northern boreal forest, is very much able to burn,” said Dan Thompson, a researcher with the Canadian Forest Service.
Fire is and has always been a natural part of those ecosystems, and that means the northeast has historically seen the occasional smoky day or week from wildfires.
But for many years, it wasn’t the primary source concerning air pollution in the region.
Back in the 1990s, Vermont regularly saw days when it was unhealthy to be outside because of ozone from industrial pollution.
Then the U.S. regulated power plants under the Clean Air Act, and now ozone is seldom an issue.
Now, tiny particles called PM2.5 from wildfire smoke are starting to corrode those gains.
The EPA started collecting data about wildfire smoke in Vermont in 1992.
And in recent years, Vermont has seen more days when the air quality is impaired because of wildfire smoke.
Where is the smoke coming from, and what’s causing the fires?
2023 was a strikingly tough year for poor air quality in Vermont. It was Canada’s worst ever wildfire season on record, if you count the number of hectares of forest that burned.
Then, it was wildfires in northern Quebec that were largely to blame for smoky skies. At one point, Montreal had the worst air quality of any city in the world.
Prolonged drought created conditions that made it easy for those fires to ignite and spread during lightning strikes, but humans also played a role. Logging practices and forest management contributed to greater fire risk and made fires burn with more intensity when they started.
In contrast, this summer, Vermont has mostly seen smoke from fires burning in northern Saskatchewan and Manitoba provinces, hundreds of miles north of Winnipeg.
More from NPR: Wildfire smoke is like smoking 'half a pack a day.' Here's how to protect yourself
“The trees are small, they’re little black spruce trees,” said Dan Thompson, with the Canadian Forest Service. “Think of the vegetation you have on the tops of mountains in Vermont, that sort of low balsam fir-spruce tree forest, where trees are sparse and scraggly.”
Unlike in 2023, these fires are burning at the northern limits of logging, in largely unmanaged forests across what are functionally vast wildernesses, where there is little or no logging taking place because the trees are so small.
Most of the towns are either Indigenous communities or mining settlements and are accessed by ice road in the winter or by air in the summer.
Because there is very little forest management and human activity in these relatively untouched areas, Thompson said this year is a perfect example of how human-caused climate change is changing Canada’s wildfire season.
Are we seeing more smoke in Vermont because of climate change?
The short answer to this question is: yes.
Human-caused climate change is causing northern latitudes to warm faster than most places on earth. The pace of warming accelerates the closer you get to the arctic.
Northern and central Canada have been in a prolonged heat wave and drought. Places just shy of where polar bears live have regularly reached temperatures in the 90s this summer.
Climate scientists can demonstrate that hotter temperatures are driven by climate change — and in forests, this can make an existing drought worse.
Justin Mankin, a climate scientist at Dartmouth College who has served on the United States’ National Drought Task Force, said when the air is very hot and dry, trees function almost like straws — the hot, dry air sucks moisture out of the soil and plants, a bit like kindling or firewood curing in a woodshed.
And like kindling, it means that forest is more primed to burn, and burn with greater intensity, if and when lightning strikes.
“The question is: how much worse is the drought because of the anomalously warm temperatures that we know is indelibly linked to global warming? How much more persistent did it make that drought? How much deeper?” Mankin asked.
Dan Thompson with the Canadian Forest Service said this warming trend is shortening the time between large wildfires in the boreal forest and taiga.
Where forests in central Canada have evolved to burn every 50 years, they now burn every decade or more often. In fact, some of the forests burning this summer burned thoroughly in 2015, he said.
For species like jack pine and balsam fir, this doesn’t leave enough time for their cones to develop and for them to regenerate between fires.
Climate change is also changing the way fires spread. More fires are burning further and hotter for more days at a time, leaving fewer seed trees behind.
How does this all arrive in Vermont? The jet stream carries weather and smoke from central and western Canada to northern New England.
We should expect that more frequent wildfires in the Canadian west and central plains will mean more smoke for New England.
“The most widely experienced impact of climate change [in the Northeast] will be poor air quality from wildfire smoke,” said Dartmouth researcher Justin Mankin.
The United States has no jurisdiction over Canada’s land management, and scientists there say in many cases, there is nothing more they could do to contain these massive, remote fires.
“We have a situation where we’re starting to experience a walkback of those successes because of a pollutant that we cannot regulate,” said Justin Mankin, at Dartmouth. “You can’t shut down a power plant or put a scrubber on it. … The problem here is warming from greenhouse gas emissions writ large. And so the lever to pull on there is mitigation.”
The United States is the second largest producer of emissions globally.
Just how bad is smoke for your health and what can you do to stay safe?
The primary pollutant in wildfire smoke is PM2.5 — tiny microscopic particles that can penetrate deep into lung tissue.
It’s a toxic cocktail — it’s not just wood smoke, but includes volatiles from burning homes and waste, along with all sorts of chemicals.
In Canada, Indigenous communities are disproportionately impacted by wildfire and exposed to risks from smoke.
More from NPR’s Lifekit: How to protect yourself from poor air quality
From a public health perspective, Jill Baumgartner said cities and states in the Northeast would be wise to consider smoke solutions like clean air shelters. And she said, for kids, people who are pregnant and those with chronic health conditions, even episodic smoke exposure may be enough to cause long-term health problems.
Population-wide, health impacts like certain cancers may start to appear more often as more people in our population-dense region are exposed to PM2.5, even at the levels Vermont has seen in recent summers.
In the meantime, wearing a KN95, making your own air filter, staying indoors or decreasing your activity levels when it’s smoky can all help.
“Because wildfire smoke is relatively new to the East Coast, I often hear people saying, ‘Oh, it’s OK, you know, I’m not scared of the smoke, I can just power through,’” Baumgartner said. “And it’s not the time to do that. This isn’t like taking a run in the rain, or something like that. These pollutants are really bad for your health, and breathing in that smoke may even offset the cardiovascular benefit of going for that run.”
More from Vermont Public: A Vermonter’s guide to wildfire smoke and air quality
