Fire Risk To Homes Where Cities And Wildlands Meet

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Since January 7, the news has been filled with the fires devastating Los Angeles.

SPEAKER 1: It’s been a week since two of the most destructive wildfires in California history erupted in Los Angeles.

SPEAKER 2: The flames were just kind of leaping right over us.

SPEAKER 3: The multiple blazes combined singeing nearly 40,000 acres in Southern California, decimating communities.

IRA FLATOW: The threat of fires is growing in cities around the US, especially in a zone called the wildland urban interface, or as it’s known, WUI. That’s where unoccupied wildland and human developments meet and mingle. In the US, 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. Kimiko Barrett, senior wildfire researcher and policy analyst at the research group Headwaters Economics in Bozeman, Montana. Dr. Alexandra Syphard, senior research scientist at the Conservation Biology Institute in San Diego, California. Welcome to Science Friday.

KIMIKO BARRETT: Thank you.

ALEXANDRA SYPHARD: Thank you.

IRA FLATOW: Dr. Barrett, tell me more about the risks of fires in the WUI interface. Why is that so dangerous?

KIMIKO BARRETT: So the WUI, which is a terrible acronym for the wildland urban interface, is indeed this location, this area where homes intermingle and meet the unbuilt wild lands 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 homes are being placed in high risk locations.

IRA FLATOW: Well, Dr. Syphard, does LA fit that description very well?

ALEXANDRA SYPHARD: Yeah. In fact, I would say Southern California in general has kind of been like the apotheosis of the WUI. 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.

IRA FLATOW: Such as?

ALEXANDRA SYPHARD: 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.

IRA FLATOW: 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?

ALEXANDRA SYPHARD: 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 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 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 in these Santa Ana wind conditions is actually going through the air instead of the vegetation. Millions of little embers are flying through the air. They can cross 10 lane freeways.

And whatever they land on, how flammable that is whether or not it’s going to create a spot fire 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.

IRA FLATOW: Kimiko, what happens when the embers are traveling? I mean, what factors affect if a house burns or not?

KIMIKO BARRETT: I just really loved Dr. Syphard’s explanation here, because indeed, embers account for a vast majority of home loss during a wildfire. Statistics are on the range for around 90% of home loss is a result of, as Dr. Syphard 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 high wind event, if they land on a flammable surface area, they can grow into that spot fire, as Dr. Syphard 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, in 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 conflagrations that lead to disasters.

IRA FLATOW: 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?

ALEXANDRA SYPHARD: 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 reduce 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, every house in the wildland 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, but we have the opportunity now to say, where do we want to put our new houses in the future?

IRA FLATOW: Is there any way to retrofit your home or retrofit your building?

KIMIKO BARRETT: 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 of 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.

ALEXANDRA SYPHARD: 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 Kimiko 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.

IRA FLATOW: Let me go to Kimiko. I understand that the city of Austin, Texas, used its experience with a huge wildfire in 2011 to think and rebuild better. Is it Austin? Does it give us any hints about what to do?

KIMIKO BARRETT: 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 there, 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 association, 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 WUI code adoption, and it was unanimously adopted in 2020. That is the city of Austin.

It’s the 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 WUI 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.

IRA FLATOW: 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?

KIMIKO BARRETT: I think it’s a very valid question. It’s complicated in the sense that these risks are manifesting at a very local scale. Ember cast 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.

IRA FLATOW: What gives you hope that all these factions can band together and fix this problem, Kimiko?

KIMIKO BARRETT: So I would actually lean on a great wildlife historian– I know that Alexandra knows him as well– Steve Pyne, 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 burnt down, over and over again.

We had the Chicago and the Peshtigo Fire of 1871. Later, we had the San Francisco Fire of 1906. It’s worth noting, 1,200 people died in the Peshtigo 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 wood and 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 Pyne always remarks, 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.

IRA FLATOW: 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. I mean, doesn’t community play a role in how we live with fires, Alexandra?

ALEXANDRA SYPHARD: This is a great point, because one of the things that we’ve been talking about among– we, us fire 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 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.

IRA FLATOW: 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. Thank you both for taking time to be with us today.

ALEXANDRA SYPHARD: Thank you.

KIMIKO BARRETT: Thank you very much.

IRA FLATOW: You’re welcome. Dr. Kimiko Barrett, senior wildfire researcher and policy analyst at Headwaters Economics. That’s in Bozeman, Montana. And Dr. Alexandra Syphard, senior research scientist at the Conservation Biology Institute in San Diego, California.

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