SCOTT DETROW, HOST:
For millions across the U.S., smoke from wildfires burning in Canada and Northern Minnesota means yet another day living in a thick, toxic haze. President Trump weighed in on the smoke today with a social media post blaming Canada for not maintaining its forests properly. But a big part of the problem is really climate change, which is, of course, not just one country's issue. NPR's Ava Berger joins us to talk about this. Hey, Ava.
AVA BERGER, BYLINE: Hi, Scott.
DETROW: Let's start with these fires I just mentioned. The count's - what? - 900 fires in Canada today. That just seems like such an enormous number. Is that normal?
BERGER: Well, wildfires are typical for this time of year, Scott. So these regions will have fires caused by things like lightning strikes, thunderstorms. But in the province of Ontario, where most of the smoke we're seeing is actually coming from, the number of fires are still increasing, and they're not expected to get under control until maybe the beginning of August.
Ontario now has the most active fires by province. There are nearly 200 burning. And as you mentioned, in Canada, the total is close to 900. Here's how Geoff Coulson puts it. He's a warning preparedness meteorologist. That's a person who studies the weather and public safety. He's with the government agency Environment Canada.
GEOFF COLSON: About a week ago, this was the third busiest season in recent times in terms of amount of area burned.
DETROW: Let's talk about climate change. Scientists know that climate change is a big contributing factor to these fires. Can they quantify or have a sense of just how much of a role it plays?
BERGER: So climate change is a part of this problem, yes, when it comes to the fires. Colleen Reid is an associate professor of geography at the University of Colorado Boulder. She's been studying the impacts of wildfire smoke, and she talked with me about this exact question.
COLLEEN REID: So some of it is due to the fact that, you know, climate change is happening. The world is warming, and what happens when there's higher temperatures is that there's sort of more evaporation of water. And so it dries out fuels so that when there's an ignition source, those fuels are more likely to burn.
BERGER: And she said there's other factors, too. Like, past forest management practices have been to actually suppress fires, and that's led to a buildup of vegetation that we're now seeing burnt. But there was a study out of Stanford in June, and that showed that prescribed fires - starting fires, actually - could cut deadly smoke pollution by 20% in active fire years.
DETROW: OK. How does this year compare to other years?
BERGER: So in terms of the smoke, it's starting to look similar to 2023. If you remember, Scott, that horrible smoke - it was in the same places that we're seeing now. And here's what climate researchers are telling me about that smoke. Because temperatures were so hot in the fire areas, and there was so much dry vegetation, the areas got super, super strong. They got so hot that they generated their own weather, like clouds. And these clouds then functioned like a chimney, a super long chimney shooting smoke into the upper atmosphere and then the jet stream. And then the wind was like a fire hose, and it pushed the smoke into these areas of the U.S.
DETROW: Just how dangerous is the smoke?
BERGER: It's really dangerous. It has a number of health effects on the heart and respiratory system. I want to mention a study last year in the journal Nature that said that as many as 70,000 people could die prematurely from wildfire smoke inhalation by the middle of this century. Currently, the number of deaths from smoke is about 40,000 this year.
DETROW: NPR's Ava Berger, thank you.
BERGER: Thanks, Scott. Transcript provided by NPR, Copyright NPR.
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