Science Friday - Fire Risk To Homes Where Cities And Wildlands Meet

Episode Date: January 20, 2025

Since January 7, wildfires have been devastating the Los Angeles area. In the span of 10 days, several different fires, including the Palisades and Eaton fires, have burned more than 40,000 acres and destroyed more than 12,000 structures. At least 25 people have died.The threat of fire is growing, especially in zones known as the wildland-urban interface, or WUI. That’s where unoccupied wildland and human developments meet and mingle. Think of a city sprawling around a forest, for example. In the US, around one in three homes is in this type of high-risk zone.So what’s the science behind urban fires? And how do we protect ourselves in the face of them?Ira Flatow talks with Dr. Kimiko Barrett, senior wildfire researcher and policy analyst at the research group Headwaters Economics in Bozeman, Montana; and Dr. Alexandra Syphard, senior research scientist at the Conservation Biology Institute in San Diego, California.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Flor Lichten. And I'm Ira Flato. Today on the podcast, did you know that around 44 million homes are in a high-risk fire zone? Because urban fires spread far and they spread fast. Millions of little embers are flying through the air. They can crush 10-lane freeways. And whatever they land on, how flammable that is, is whether or not it's going to create a spotfire. Since January 7th, the news has been filled with the fires devastating Los Angeles.

It's been a week since two of the most destructive wildfires in California history erupted in Los Angeles. The flames are just kind of leaping right over us. The multiple blazes combined, singing nearly 40,000 acres in Southern California, decimating communities. The threat of fires is growing in cities around the U.S., especially in a zone, called the Wildland Urban Interface, or as it's known, Wooey. That's where unoccupied wildland and human developments meet and mingle. In the U.S., around one in three homes are in this high-risk zone. So what's the science behind urban fires, and how do we protect ourselves in the face of

them? Here to discuss all these issues are my guests, Dr. Camico Barrett, senior wildfire researcher and policy analyst at the Research Group, Headwater. economics in Bozeman, Montana, Dr. Alexandra Seiford, senior research scientist at the Conservation Biology Institute in San Diego, California. Welcome to Science Friday. Thank you. Thank you. Dr. Barrett, tell me more about the risks of fires and the wooey interface. Why is that so dangerous? So the wooey, which is a terrible acronym for the wildland urban interface, is indeed this location, in this area where homes intermingle and meet the unbuilt wildlands or the vegetation around these

communities. It is indeed the fastest growing land use type in the lower 48 states and accounts for around 44 million households at this time. It is also the most exposed area to wildfires. So we have climate change exacerbating extreme wildfire behavior and then we have ongoing development in wildfire prone lands and the way with which that development is taking place is often done with little thought or foresight for wildfire risk mitigation, meaning how where and under what conditions home to art being placed in high risk locations. Well, Dr. Seifert, does L.A. fit that description very well? Yeah. In fact, I would say Southern California in general has kind of been like the apotheosis

of the wooey. It's always sort of stood out as the classic example of where development meets fire-prone landscapes. And we have been experiencing housing losses to wildfire here in Southern California for decades. And it's something that's not new, but we are also experiencing some unprecedented things, such as the amount of house loss that's been occurring. It's been increasing not only in California, but also across the globe. And is due to a number of factors. that importantly are different in different regions of the state and other parts of the world. Such as? Such as one distinction that I think is critically important that is difficult for people to understand,

especially if they don't live in California, is that Southern California is a non-forested landscape. In other words, it does not have trees. It has shrublands that have been invaded by very flammable grasses. Whereas the forests have experienced a different kind of problem. They typically have very frequent fire, but that fire has been removed from those landscapes. So they have a lot of fuel accumulation, vegetation accumulation, high-density fire that creates different problems.

In Southern California, what's happened is that with Santa Ana winds, that as you've seen in the news, can blow 70 miles an hour, and the vegetation is extraordinarily flammable and does not stop the wildfires here. So why don't we have a burning of this vegetation like we do in other areas in forests to get rid of the fuel? Yeah, the thing that's different is that in forests, we thin from below and we often follow it with prescribed fire. And that creates and mimics the natural conditions of the forest and rediscovered. reduces the likelihood that those fires will become very tall, high flame lengths, as we call them, and reach into the crown and become extraordinarily dangerous to anybody adjacent to those fires.

But in Southern California, the problem here is that we have had so much fire, so much uncharacteristically highly frequent fire. And when the winds are blowing in Southern California, the vegetation does not readily stop the fires. And in fact, when the vegetation converts from sort of higher fuel moisture, Chaparral vegetation, which does produce high intensity fires, but when it turns into grassland, this is just kindling for fire propagation under severe winds. And what I mean by that is that most of the fire spread and these Santa Ana wind conditions is actually going through the air instead of the vegetation.

Little millions of little embers are flying through the air. They can crush 10 lane freeways. And whatever they land on, how flammable that is, is whether or not it's going to create a spotfire and then keep the fire moving that much farther and that much faster. And so a lot of times the typical vegetation management that's so effective and critical in forests just doesn't have the same effect in Southern California at a landscape scale. Instead, it's really more important when it's around individual houses and when it provides a safe place for firefighters to get in and do the good work that they do. Camille, what happens when the embers are traveling? I mean, what effects, what factors affect if a house burns or not?

I just really loved Dr. Seiford's explanation here because indeed, embers account for a vast majority of home loss during a wildfire. statistics are on the range of around 90% of home loss is a result of, as Dr. Seiford said, these tiny balls of flame. And so when we think through these embers flying so far ahead of that wildfire front, these balls of flame and billions and billions of them under a high wind event, if they land on a flammable surface area, they can grow into that spot fires, Dr. Seiford noted. So it's bark mulch around a home, for example, or it's what is on top of a deck. It's the deck itself. some situations, it's what's underneath that deck. If you have pine needles, if you have vegetation

in your gutters, if the roof itself is made of wood, all of these factors collectively greatly influence that vulnerability to ignition from embers. And then once the home itself starts to burn, you're dealing then with radiant heat as another form of exposure. And the home itself becomes a source of fuel. And that's very, very important when we think through these configurations that lead to disasters. After the break, how do we make our community safer in the face of fires? People shouldn't get discouraged and say, well, I can't get a new roof, so I'm not going to do anything. It's better to at least do something than to do nothing at all.

Stick around. All right. So now that we know what the factors are and how these fires work, how do we plan for them, Alexandra? I mean, what can we do to build a less risky fire zone? Yeah, great question. I think the short answer is that we need to consider multiple strategies at one time because it's not going to take just one action to make Los Angeles as well as other cities more fire resilient. You could first start with invariably the structures are going to go back where they were before. And Gavin Newsom has facilitated that with his executive order. So what we hope, first of all, is that they are built Up to the codes. The buildings built after 2008 in California have been built to a fire code that has significantly reduced the risk of homes burning that are newer. Of course, it's important to also mention that no house is fireproof. And while these measures all substantially reduced risk, they do not eliminate it. I don't want to create false sense of safety, but it starts with building back in a fire safe way. It starts with education about defensible space and where it's

most important, which is usually the first zero to five feet around the house. It involves having adequate ingress and egress so people can safely get in and out during a wildfire event. And ultimately, I think city planning should start thinking about where certain land uses are placed relative to one another. And ultimately, you know, every house in the wild and urban interface right now is a function of decisions that people made 10, 20, 30, 40 years ago. And so we have the opportunity now. We can't get rid of the existing development. We have the opportunity now to say, where do we want to put our new houses in the future? Is there any way to retrofit your home or retrofit your building? Yes, we do know that mitigation strategies to the home itself can go to great lengths to reduce ignition exposure.

Some of the most effective mitigation strategies are also the most affordable in the sense of removing the flammable surface area in and around the home. So it is looking at that decking, what's on top of it, what's on top of your roof, what type of mulch do you have? What's your vegetation around the home itself? And then when you go on the larger scale, some of these bigger retrofits like a roof replacement, for example, that is going to be a cost. And that is something that homeowners will have to thoughtfully budget into their account or seek and get subsidy support if available through local fire districts in California. They do have funds available. It's surely not to the degree that is going to meet the scale of retrofitting needs, nor is it available at the federal level

the way it needs to be. We know that socially vulnerable populations are disproportionately impacted by wildfire. Socially vulnerable populations experience fire more often than affluent populations. And also, the recovery is nearly impossible for somebody who doesn't have insurance or have the resources to deal with that. And so one strategy might be to identify those places that are most at risk for fire and where the people really need the help the most. But also, as Kimmy was mentioning, there are some things that are really not that expensive.

And people shouldn't get discouraged and say, well, I can't get a new roof, so I'm not going to do anything. It's better to at least do something than to do nothing at all. Let me go to Kimmy. I understand that the city of Austin, Texas, used its experience with a huge wildfire in 2011 to think and rebuild better. Is Austin, does it give us any hints about what to do? It certainly can be an example of the process with which they have very thoughtfully and deliberately thought about living with increasing wildfire risk, knowing that their city and their communities within that city were going to be exposed to increasing risk down the road.

And so what elected officials did there in partnership with the city of Austin, including the fire districts, of course, but not just stopping their local arborists, architects, the construction industry itself, they went through a very methodical process of going through a wildland urban interface code adoption. But in Austin, they went through a learning process in that they tried to adopt it first in 2018 and it failed because it did not have the full buy-in from all the partners and stakeholders on the ground. So the city of Austin fire department went back to the table. They brought in the right partners. They brought in the government, the building industry. They very thoughtfully went through the building materials that were being

requested. And in doing so, they bought in. They approved the building material list. They did actually in turn advocate for the Wooi Code adoption. And it was unanimously adopted in 2020. That is the city of Austin. It's a fastest growing metropolitan area in the country. They do have a lot of resources and a lot of capital to help them support this type of building code adoption. And, Louis code adoption, but that isn't to say that communities elsewhere facing similar increasing risk can't replicate that type of process and also adopt these codes and regulations that do work and do reduce risk in the future to wildfire. What about with climate change, though? Many coastal areas have made new rules saying, hey, you can't build here? It might be underwater soon. I mean, can you make

similar rules for fires? You know, I think it's a very valid question. It's complex. in the sense that these risks are manifesting at a very local scale. Embercast accounts for a huge distance spread of how that risk is buffered into a community. So is there truly any place that is safe from a wildfire here in the West? All of these questions really compound and confound that crisis of what does safe development look like in the future. There is the argument to be made that if you cannot mitigate from all of these sources, of potential exposure from a wildfire should you allow development to occur in the first place.

And I think that's really a community question to ask and is going to guide how and where and under what conditions development occurs, knowing that wildfires are inevitable and knowing that these risks are going to increase. That is a reality we must live with. What gives you hope that all these factions can band together and fix this problem, Kimmy? So I would actually lean on a great wildfire. historian. I know that Alexandra knows him as well, Steve Pine, and what he remarks is that you look at the Western settlement, European settlement in the late 19th century through the 20th century, and we routinely built our cities and our urban areas, and they continually burned down over and over

again. We had the Chicago and the Pestago fire of 1871. Later, we had the San Francisco fire of 1906. You know, it's worth noting 1,200 people died in the Pesstico and Chicago fire. And after these devastating events, and again, particularly the 1906 San Francisco fire, we as a society decided to fundamentally do things very, very differently in the sense of structural interior fires. We stopped using wooden sawdust. We started putting in evacuation protocols and exit doors and exit strategies and interior fire hydrants and stopped using wooden boardwalks. And we don't have that sense of interior structural fire to the same degree that we did in the past.

And so Steve Pine always remarks, you know, in that sense, we have solved this problem before from an interior structural perspective. We can do so again if we apply those lessons learned outward looking at the wildlands. You know, I'm reminded of a study from a few years ago about how the communities that are more resilient to climate change tend to be the ones where neighbors know each other, right? I mean, doesn't community play a role in how we live with fires, Alexandra? This is a great point because one of the things that we've been talking about among we aspire scientists lately is the importance of doing these actions at a community scale where people all get together and they maintain their yards and they retrofit their houses. And the idea is that on one hand, if you have everybody who's done everything right and one person who's done it wrong, that person is actually, their safety is increased by virtue of the fact that they, all their neighbors have done something good, but it's the flip side as well. If you're one person and you've made your house very fire resilient, but none of your neighbors have, you're also at a higher risk. So there is something about looking into whether we can as communities together,

work together to become more fire safe and resilient. Well, our hearts go out to everybody who's affected in the Los Angeles area, and we hope it's more than prayers that will help them recover. Thank you both for taking time to be with us today. Thank you. Thank you very much. You're welcome. Dr. Camico Barrett, senior wildfire researcher and policy analyst at Headwaters Economics. That's in Bozeman, Montana, and Dr. Alexandria Seiford, senior research scientist at the Conservation Biology Institute in San Diego, California.

That's all the time we have for today. Lots of folks help make this show happen, including Kathleen Davis. John Dancosky Jordan Smudjick Diana Plasker I'm Ira Flato Thanks for listening