The rise in heatwaves in the U.S. is not just dangerous to human health. It’s also driving more wildfires across the West. And it’s not just because it’s drying out forests and creating more kindling.
John Abatzoglou is a professor in the School of Engineering at the University of California, Merced, and he and his colleagues are out with new research that proves the link. The Show spoke with him more about it.
Full conversation
JOHN ABATZOGLOU: We had this intuition that when there are heatwaves, we’d see an uptick in fire activity, but we really wanted to quantify just how important heatwaves are across the West and how they varied across the West. And we came up with this number that across the West, about 42% of the burned area happens either during or immediately following heatwaves. That’s a pretty, you know, that’s a pretty large portion of the overall fire activity that we see in the West.
LAUREN GILGER: Wow, yeah, definitely is. OK, so let’s talk about the why here, because this is where some of the nuance, I think, comes in. Because like we said, there’s an intuitive nature to this that, you know, heatwaves will dry things out, and then basically you have more kindling out there. But it sounds like other factors are at play as well.
JOHN ABATZOGLOU: That’s right, yeah. So, I think that that’s right. The main ... thing I think that we thought going into this is that certainly heatwaves dry vegetation out, making everything that much more flammable, and that’s a key component. But the other things I think that we uncovered here were were also useful, right?
One thing you definitely need for fire is ignitions. And one thing we see across a huge portion of the West is that during heatwaves, we see an increase in the number of lightning-caused fires. So, when you combine sort of dry fuels and lightning, that is not a great combination when it comes to fire activity.
We also see during heatwaves, it’s — they’re chronic in nature. It’s not just one day. It’s day after day after day after day. And so, you get sort of this sequence of hot, hot conditions day after day that continues to drive fuels out, and that really sets the stage for, you know, continued growth of a fire.
And then maybe also the other thing is during heatwaves, it just doesn’t cool down at night. And typically, on fires, you know, at night, the fire behavior will start to calm down a little bit. Fires will lay down, and that will give fire suppression an opportunity to make some ground on a fire. But when we have elevated temperatures at night, fires can burn through the night, and so we we effectively have much longer burn hours for these fires.
LAUREN GILGER: Longer burn periods can lead to much more destruction, I’m sure. Tell us, John, how you went about studying this, right? There’s not been a lot of research done on this front, right?
JOHN ABATZOGLOU: There’s been certainly work looking at the role of weather and climate on fire, you know, not so much when it comes to heatwaves per se. But the approach here was to take, you know, about 20, 25 years of data on fire activity, on weather, ignitions, etc. And then to analyze this across different sections of the western United States. And one thing we we thought is we might see some differences between how heatwaves enable and drive fire in the deserts versus our forests. But the reality is it sort of it sort of contributes to increased fire activity pretty universally across the West —
LAUREN GILGER: Everywhere, right. So, I was going to ask that because obviously we’re in a desert region here in in Phoenix, but, you know, we have many forests throughout the state where we do see many more forest fires these days. Sounds like it’s like an equal opportunity phenomenon here?
JOHN ABATZOGLOU: Yeah, as long as there’s fuels. And that’s the thing, is in some of your in some of your desert systems, fuel can become a limiting factor. In the forests, the way that they’ve been managed, not so much. There’s plenty of fuel. And so there, there’s much more opportunity for heatwaves. But the same factors, drying fuels out, long burn periods, lightning ignitions, all those things are conducive to fire activity.
LAUREN GILGER: So, let’s talk, John, about how it is that you’d want this research to be used. The first thing that comes to mind for me is that — and this is one of many things I think right now that is sort of changing the way that we, not just here in the desert where it’s always been hot, but across the country, how we think about heat, right? Like, it’s not just a nuisance that it’s hot outside. They are a driver of wildfire activity. There could be, you know, so many more implications down the line. Did it change the way you think about heat?
JOHN ABATZOGLOU: Yeah, maybe. That’s a — I mean, I think I think we started this research a couple years ago. And this summer, just looking across much of the U.S. and Canada and Europe, we’re seeing stories of heatwaves and fire. And it’s impacting a lot of different facets of life and the economy in summer. And and certainly there are places like like Phoenix that are very accustomed to heat. Certainly that’s a little different than other places.
But fire is certainly a factor that influences people, you know, well beyond where a fire burns, right? Smoke can transcend country boundaries, for example. So, it is something that we are paying attention to more. There actually are not — when it comes to sort of weather warnings, there’s certainly weather warnings for heat issued by the National Weather Service that advise people to take it easy when we have heatwaves, alter their alter their behavior outdoors. We don’t necessarily have that for fires, at least codified in terms of heatwaves.
And one thing that this research may do along with other factors is increase the awareness of ... people such that when there are heatwaves, there’s a higher potential for fire. Be ready, don’t ignite things, right? Sort of the the behavioral activities, but also from the fire management perspective, to be sure that there’s resources that can be allocated in the event that ignitions break out during a heatwave.
LAUREN GILGER: Yeah. So, I mean, as we’re kind of getting at here, like there are many more heatwaves happening, it seems, across the country as climate change is leading to increased temperatures just about everywhere. Should we also expect more wildfires? Like if these two are going to go together, it sounds like we could think about planning, as you’re talking about there, a little differently.
JOHN ABATZOGLOU: Yeah, I think we we definitely have seen a significant uptick in fire activity over the past 50 years. More fires happen when it’s hot and dry. We are expecting more of that going forward, as long as there’s fuel available, vegetation, etc. So, we should plan for more fire. And realistically, we need to really sort of change our mindset in that we’ve done a really good job at avoiding fire for a long time. Fire is supposed to be on these landscapes, and the warming and drying climate is making it much more likely. So, we need to actually prepare for when a fire is coming so that we’re more resilient and can withstand it.
LAUREN GILGER: Yeah. OK, we’ll leave it there. John Abatzoglou, professor in the School of Engineering at UC Merced, he worked on this study. John, thanks for coming on The Show. Appreciate you shedding some light on this.
JOHN ABATZOGLOU: Great, thanks for having me.
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