CNN  — 

Another wave of wildfire smoke has drifted into the US, dimming blue summer skies and igniting troubling concerns regarding the increasing frequency of fires, and what they have to do with climate change.

More than 100 million people are under air quality alerts from Wisconsin to Vermont and down to North Carolina as smoke from Canadian wildfires continues to waft south, though conditions are expected to improve slowly into the holiday weekend.

Map: Track air quality across the US

Air quality on both sides of the border has been affected as more than 500 active wildfires raging across Canada. Some fires are so out of control officials have no choice but to leave them burning.

Meanwhile, at least 10 countries have deployed their own firefighters to assist Canada with putting out the ones threatening communities whose residents have scrambled to evacuate.

Scientists continue to reiterate warnings the effects of climate change have arrived, emphasizing wildfires and the plumes of toxic smoke generated by them will become more frequent.

As plumes of smoke billow out of Canada’s forests, some may be wondering why many of the fires are being allowed to burn unchecked.

Here’s why:

Some of the fires are in extremely remote areas

While every Canadian province responds to the fires in their regions differently, they all have common guidelines emphasizing the importance of prioritizing which fires to fight and which to leave alone.

Massive fires burning in remote areas – like some of those currently burning in northwestern Quebec – are often too out of control to do anything about.

“If you have limited resources, and you have a lot of fires, what you do is you protect human life and property first,” Robert Gray, a Canadian wildland fire ecologist, told CNN. “You protect people, infrastructure, watersheds, so there’s a prioritization system.”

He added, “If you’ve got these fires that are burning way out in the back forty, and they’re not threatening anything immediately, then you’re going to have to let them do their thing.”

While the thought of massive fires burning through millions of hectares of forestland might sound unfathomable, it isn’t entirely new.

“There’s always been fires Canadian fire managers don’t fight. It’s expensive to do so, ecologically undesirable, and kind of just messing with nature,” said Daniel Perrakis, a fire scientist with the Canadian Forest Service.

“The smoke is a problem but even if we wanted to do something about it, it wouldn’t really be clear how to do so. You’re talking about huge areas where there’s no road access, no communities in some cases.”

Of the 522 fires currently burning, 262 are listed as out of control across Canada, including British Columbia, Alberta, Ontario and Quebec.

Along with remoteness and distance from people, terrain is another factor. Some of the fires are being allowed to burn simply because they are too treacherous for firefighters to even attempt to tackle.

“These fires are so big that you really can’t put people anywhere near them, the winds kick up, they move very fast, they can start out ahead of you and they can trap crews,” Gray said.

There are not enough resources to fight all the fires

Firefighters from at least 10 countries, including the US, Mexico, Costa Rica, Chile, Spain, Australia, New Zealand, South Africa, South Korea, and France, have been deployed to assist with the Canadian wildfires since the first week of June.

Shiraaz Mohamed/AFP/Getty Images
Firefighters from South Africa are among the crews working in Alberta, Canada, to help with ongoing fire suppression efforts.

“Canada doesn’t have a lot of firefighting resources,” Gray said. “Individual provinces have their own contracting crews, but they have brought in thousands of folks from outside the country to help.”

One factor contributing to the lack of resources, evident in the current fight against the out of control fires, is funding, Gray acknowledged.

“They don’t typically appropriate a lot of money upfront for firefighting,” he continued. “But once the fires break out, the governments can certainly find all the money necessary to suppress them.”

“International groups keep saying, you need to shift the focus to upfront mitigation and prevention so you’re spending less money on response and recovery,” he added. “It’s ridiculous. We spend billions of dollars once the fire breaks out, but we don’t invest the money upfront to mitigate the fires from happening in the first place.”

Not enough prevention tactics to decrease the number of fires

More work needs to be done to reduce the opportunity for future wildfires, which may someday end in catastrophic tragedy.

One of the most effective fire prevention tactics is through prescribed burns, which are fires set intentionally as part of a forest management plan to reduce the risk of more serious and damaging blazes.

“We don’t do anywhere near enough prescribed burning in BC,” Gray said. “Right now we’re burning about 10,000 hectares a year. The state of New Jersey burns more than we do here at BC.”

Prescribed burns have been an important cultural and environmental tradition in Indigenous communities, who for thousands of years set low-intensity fires to rid the land of wildfire fuel like debris, scrub, undergrowth and certain grasses. Such fuel ignites easily, allowing for more intense flames, which are harder to fight.

The intentional burning practices can increase the forests’ resiliency and decrease the likelihood of future wildfires.

Perrakis echoed Gray’s sentiments: “It would be very useful to have maybe 10 times or 20 times more prescribed burning than what we’re doing presently.”

Since prescribed burns come with liability issues and pose a risk of ending in accidental unmanageable fires if not done correctly and at the right time, this will require more funding from the government and proper training.

“We would be removing the fuel from the fire before there’s even a fire,” Perrakis said. “It wouldn’t be used all across the Canadian countryside, but very strategically around communities and other values and will be in line with the local ecosystem.”

Along with prescribed burns, other tactics, like large scale thinning, need to be ramped up, Gray said.

“We need large scale thinning in these forest types that don’t produce a lot of dimension lumber, so there’s a lot of small trees and we need to come to do something with them,” he added. “We can ship them into the bioeconomy, produce bioenergy markets, engineering, wood products; there’s a lot of things we can do with low value wood, and that’s a lot of what’s out there burning up right now.”

The ecosystem depends on fires, and climate change is making them worse

Fires have always served a vital ecological purpose on Earth, essential for many ecosystems. They restore soil nutrients, helping germinate plants and remove decaying matter. Without fires, overgrown foliage like grasses and shrubs can prime the landscape for worse flare-ups, particularly during extreme drought and heat waves.

Most of Canada is covered by boreal forest, the world’s largest and most intact biome. The ecosystem with trees like spruce, pine, and fir makes up about one-third of all forests on the planet.

But it is a fire dependent ecosystem, meaning the species in the forest have evolved in the presence of fire, and fire “is an essential process for conserving biodiversity,” according to the Nature Conservancy.

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People look out at a hazy Manhattan skyline from the Rockefeller Center viewing deck Friday, June 30, in New York.
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Smoke from wildfires in Canada shrouds the view of the Statue of Liberty on Friday in New York.
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The setting sun is shrouded by smoke from Canadian wildfires in this photo taken from New York's 42nd Street on Thursday, June 29.
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Haze hangs over downtown Pittsburgh and PNC Park as fans take their seats before a Major League Baseball game between the Pittsburgh Pirates and the San Diego Padres on June 29.
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Traffic makes its way across the Chesapeake Bay Bridge in Stevensville, Maryland, on June 29.
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Smoke and haze is seen from the Lincoln Memorial in Washington, DC, on Tuesday, June 27.
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People in Chicago walk along the shoreline of Lake Michigan on June 27.
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A Canadian soldier flies over a wildfire near Mistissini, Quebec, on June 12.
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Wildfires burn in British Columbia in this aerial photo released by the BC Wildfire Service on June 9.
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A jogger wears a face mask in Washington, DC, on June 9.
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A man wears a protective face mask while walking through Times Square in New York on June 8.
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An airplane takes off June 8 from Ronald Reagan Washington National Airport in Arlington, Virginia.
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Traffic heads into Washington, DC, under hazy conditions on June 8.
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Smoke from Canadian wildfires obscures the visibility in Pittsburgh on June 8.
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Buildings in the Philadelphia skyline are shrouded in smoke on June 8.
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A cyclist rides under a blanket of haze that was partially obscuring the US Capitol on June 8.
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A woman in New York City wears a mask during the morning rush hour on June 8. The city saw slight air quality improvements, but levels were still considered "very unhealthy" for residents.
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The One World Trade Center tower is seen in New York, shortly after sunrise on June 8.
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A starting gate is unused at Belmont Park in Elmont, New York, on June 8.
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Transit employee Shanita Hancle, left, hands out masks to commuters at a subway station in New York on June 8.
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The Philadelphia skyline is shrouded in haze on June 8.
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A smoky haze obscures M&T Bank Stadium in Baltimore on June 8.
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Firefighters battle a wildfire in Evansburg, Alberta, on June 8.
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A person on the New York City subway wears a mask as smoky haze blankets a neighborhood on June 7.
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Workers chain up seats at Citizens Bank Park after the Philadelphia Phillies postponed a baseball game because of poor air quality on June 7. The New York Yankees also postponed a game that night.
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Two men stand by the waterfront in Brooklyn, New York, on June 7.
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Smoky haze affects the visibility of the Empire State Building in New York on June 7.
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A man in Piermont, New York, attempts to photograph the sun obscured by smoke on June 7.
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Smoke blankets the Lincoln Memorial Reflecting Pool and the National Mall on June 7.
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A person in Fort Lee, New Jersey, talks on the phone near the George Washington Bridge on June 7.
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Smoke obscures the view from the New York State Thruway, looking north from West Nyack on June 7.
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People wear face masks as they walk in New York's Herald Square on June 7.
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A woman jogs along the Hudson River as a smoky haze hangs over the New York City skyline shortly after sunrise on June 7.
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A couple sits for lunch in Cincinnati on June 6. Smoke from the Canadian wildfires had drifted to the city, causing the air to appear hazy.
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People at Toronto's CN Tower take photos of the smoky city on June 6.
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The sky is discolored during a New York Yankees baseball game on June 6.
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A smoky sky provides a muted backdrop June 6 at Rock Harbor in Massachusetts. Skies over Cape Cod were filled with smoke from the wildfires in Canada.
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People in New York wear masks as they ride bikes on June 6. That morning, the city briefly had the world's worst levels of air pollution.
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The Statue of Liberty is obscured by the air pollution in New York on June 6.
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Wildfire smoke engulfs downtown Ottawa on June 5.
B.C. Wildfire Service via Reuters
Smoke billows upwards from a planned ignition by firefighters who were tackling the Donnie Creek Complex wildfire south of Fort Nelson, British Columbia, on June 3.
Communications Nova Scotia via Reuters
Firefighter Jason Rock sprays hot spots in the Birchtown area while tackling wildfires in Shelburne County, Nova Scotia, on June 3.
NASA
An astronaut aboard the International Space Station took this photo of wildfire smoke near Shelburne, Nova Scotia, on May 29. Human-caused climate change has exacerbated the hot and dry conditions that allow wildfires to ignite and grow.
B.C. Wildfire Service via Reuters
Smoke rises from a wildfire in Fort Nelson on May 27.
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Firefighters stand on a truck while battling a blaze near Fort St. John, British Columbia, on May 14.
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BJ Fuchs, a farmer who has lost some land and had to move his cattle due to the wildfires, stands in Shining Bank, Alberta, on May 11.

“We have records as far back as the 1700s and 1800s of yellow sky and black sky and smoky sky days.” he added. “It’s the natural cycle of the boreal forest. There really isn’t much Canadian fire management agencies can do, even if they wanted to.”

While natural fires in the system have always been present and are usually caused by natural elements like lightning, climate change is making them more frequent, increasingly unmanageable, and a lot more difficult to prevent.

One year ago, after enduring a record-breaking temperature of 121 degrees, the British Columbia village of Lytton was leveled by a wildfire, drawing stark attention to the effects of climate change.

Heat-trapping emissions have led to hotter and drier conditions, and wildfires now burn longer and are becoming hotter in places where they have always occurred; meanwhile, fires are also igniting and spreading in unexpected places.

“We know that the weather is the most important ingredient of fire behavior, and climate and weather are linked,” Perrakis said.

Another issue is the increase in the wildfires are caused by climate change, and are simultaneously making climate change worse.

Boreal forests are carbon dense, releasing 10 to 20 times more planet-heating carbon pollution for each unit of area burned by wildfires than other ecosystems, according to a 2022 study published in the journal Science Advances. Over the years, researchers say it has become a vicious climate change feedback loop. The emissions from wildfires contributes to increasing global temperatures, which in turn fuel even more wildfires.

“Things are changing due to climate change, and that’s catching everyone somewhat by surprise, even though we’ve been talking about it for decades,” Perrakis said. “It takes a big season like this one for everyone to really wake up to what climate change looks like. It’s pretty undeniable.”

As Canadians near the fires evacuate while firefighters try to save their homes and communities, other, bigger fires burn freely with no way to control them, and people in the US will continue breathing in unhealthy smoke.

It all begs the question: When will it end?

“People should probably get used to it, because it’s not something that has come out of nowhere,” Perrakis said. “Climate change is undeniable, and now it’s time to think about the future, 10 or 20 years down the line, and what needs to be done.”