(CNN) — Another flurry of wildfire smoke has drifted into the United States, darkening blue summer skies and raising concerns about the increasing frequency of fires and their link to climate change.

More than 100 million people are on air quality alert from Wisconsin to Vermont to North Carolina as smoke from Canadian wildfires drifts south, although conditions are expected to slowly improve over the holiday weekend. .

Air quality on both sides of the border has been affected by more than 500 active wildfires that raged across Canada. Some fires are so out of control that authorities have no choice but to let them burn.

Meanwhile, at least 10 countries they sent their own firefighters to help Canada put out fires threatening communities whose residents have rushed to evacuate.

Scientists continue to reiterate warnings that the effects of climate change have arrived, pointing out that wildfires and the plumes of toxic smoke they generate will become more frequent.

As smoke billows from Canada’s forests, some may wonder why so many fires are allowed to rage out of control.

That is why:

Some of the fires are occurring in extremely remote areas

While every Canadian province responds to fires differently, they all have common guidelines that emphasize the importance of prioritizing which fires to fight and which to let burn.

Massive fires burning in remote areas — like some 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 are doing is protecting human life and property first,” Robert Gray, a Canadian wildfire ecologist, told CNN. “You are protecting people, infrastructure, watersheds, so there is a prioritization system.”

He added: “If you have these fires burning in remote areas and they’re not immediately threatening anything, then you’re going to have to let them do their thing.”

Although the idea of ​​massive fires ravaging millions of hectares of forest may seem incomprehensible, it is not entirely new.

“There have always been fires that Canadian officials don’t fight. It’s expensive to do, environmentally undesirable, and you’d just be playing with nature,” said Daniel Perrakis, a fire specialist with the Canadian Forest Service.

“Smoke is a problem, but even if we wanted to do something about it, it wouldn’t be very clear how to do it. You’re talking about large areas where there is no road access; no communities in certain cases.”

Of the 539 fires currently burning, 270 are out of control across Canada, including those in British Columbia, Alberta, Ontario and Quebec.

Besides remoteness and distance from people, terrain is another factor. Some of the fires are allowed to burn simply because they are in terrain that is too dangerous for firefighters to even attempt to tackle.

“These fires are so big you can’t really get people near them, the winds pick up, they move really fast, they can start in front of you and trap equipment,” Gray said.

There are not enough resources to fight all the fires

Firefighters from at least 10 countries, including the United States, Mexico, Costa Rica, Chile, Spain, Australia, New Zealand, South Africa, South Korea and the France, have been deployed to Canada to help fight forest fires since the first week of June.

“Canada doesn’t have a lot of resources to fight the fires,” Gray said. “Each province has its own recruiting teams, but they’ve brought in thousands of people from outside the country to help out.”

One of the factors contributing to the apparent lack of resources in the current wildfire fight is funding, Gray acknowledged.

“They don’t usually allocate a lot of money to firefighting,” he continued. “But once the fires have started, governments can certainly find all the money they need to put them out.”

“International groups keep saying there is a need to focus on mitigation and prevention up front so that less money is spent on response and recovery,” he added. . “It’s ridiculous. We spend billions of dollars once a fire starts, but we don’t invest the money upfront to mitigate the fires.”

There are not enough prevention tactics to reduce the number of fires

More work is needed to reduce future wildfires, which could one day end in catastrophic tragedy.

One of the most effective fire prevention tactics is to use prescribed burns, that is, fires intentionally set as part of a forest management plan to reduce the risk of larger fires. and more damaging.

“We don’t do enough prescribed burns in British Columbia,” Gray said. “Right now we’re burning about 10,000 acres a year. The state of New Jersey is burning more than we are here in BC.”

Controlled burns have been an important cultural and environmental tradition in Indigenous communities, who for thousands of years have lit low-intensity fires to clear the land of wildfire fuels such as debris, brush, brush and some herbs. Such fuel ignites easily, allowing for more intense flames that are harder to fight.

Intentional burning practices can increase forest resilience and reduce the likelihood of future wildfires.

Perrakis echoed Gray’s sentiments: “It would be very helpful to have maybe 10 or 20 times more controlled burns than we have now.”

Since controlled burns lead to liability issues and pose the risk of accidental fires if not done correctly and at the right time, this will require more government funding and proper training.

“We would get the fuel out of the fire before there was even a fire,” Perrakis said. “It wouldn’t be used across the Canadian countryside, but very strategically around communities and other values ​​and would be in line with the local ecosystem.”

Along with controlled burns, other tactics, such as large-scale land clearing, need to be stepped up, Gray said.

“We need large-scale logging in these types of forests that don’t produce a lot of big timber, so there are a lot of small trees and we have to come and do something with them,” he said. added. “We can send them into the bioeconomy, produce markets for bioenergy, engineering, wood products – we can do a lot with low-value wood, and that’s a lot of what’s burning 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 to many ecosystems. They restore soil nutrients, help plants germinate, and remove decaying matter. Without fire, overgrown foliage such as grass and shrubs can prepare the landscape for more severe outbreaks, especially during extreme droughts and heat waves.

Most of Canada is covered in boreal forest, the largest and most intact biome in the world. The ecosystem with trees like fir and pine accounts for about a third of all forests on the planet.

But it’s a fire-dependent ecosystem, which means species in the forest have evolved in the presence of fire, and fire “is an essential process for the conservation of biodiversity,” according to the Nature Conservancy.

“We have records from the 1700s and 1800s of days with yellow skies, black skies and smoky skies,” he adds. “It’s the natural cycle of the boreal forest. There really isn’t much that Canadian fire agencies can do, even if they wanted to.

While wildfires in the system have always existed and are usually caused by natural elements like lightning, climate change is making them more frequent, increasingly unmanageable and much harder to prevent.

A year ago, after enduring a record temperature of 121 degrees Fahrenheit (49 degrees Celsius), the village of Lytton in British Columbia was engulfed in a wildfire, drawing attention to the effects of climate change.

Heat-trapping emissions have led to hotter, drier conditions, and wildfires are now lasting longer and getting hotter in places where they have historically occurred; meanwhile, fires ignite and also spread to unexpected places.

“We know that time is the most important ingredient in fire behavior, and time and weather are intertwined,” Perrakis said.

Another problem is the increase in forest fires caused by climate change which, at the same time, makes climate change worse.

Boreal forests are carbon-dense, releasing 10 to 20 times more planet-warming carbon pollution per unit area burned by wildfires than other ecosystems, according to a 2022 study published in the journal Science Advances. Over the years, researchers say, it’s become a vicious feedback loop of climate change. Emissions from wildfires contribute to rising global temperatures, which in turn fuels even more wildfires.

“Things are changing because of climate change, and it takes everyone a bit by surprise, even though we’ve been talking about it for decades,” Perrakis said. “It takes a big season like this for everyone to really realize what climate change looks like. It’s pretty undeniable.”

As Canadians near the fires evacuate their homes while firefighters attempt to save their properties and communities, other larger fires are burning freely with no way to control them, and people across the United States will continue to breathe harmful smoke.

Everything points to the question: When will this end?

“People should probably get used to it, because it’s not something that just came out of nowhere,” Perrakis said. “Climate change is undeniable, and now is the time to think about the future, 10 to 20 years from now, and what to do about it.”