What’s behind the increasing size and severity of California’s wildfires? And if the trajectory continues, what does that mean for people living there? How has this trend already impacted residents? Three co-authors of a recent synthesis on drivers of wildfire in the Golden State share their main findings with us, as well as speculating on some possibilities for future solutions to living alongside increasing fire hazard. Photo credit: USDA
Climate Change Is Escalating California’s Wildfires
Drivers of California’s changing wildfires: a state-of-the-knowledge synthesis
Drivers of California's Changing Wildfires: State Has Potential To Be A Model For Change - International Association of Wildland Fire
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Emile Elias: Welcome to Come Rain or Shine Podcast of the USDA Southwest Climate Hub
Sarah LeRoy: and the USGS Southwest Climate Adaptation Science Center or Southwest CASC. I'm Sarah LeRoy Science Applications and Communications Coordinator for the Southwest CASC.
Emile Elias: And I'm Emile Elias, director of the Southwest Climate Hub. Here we highlight stories to share the most recent advances in climate, science, weather, and climate adaptation and innovative practices to support resilient landscapes and communities.
Sarah LeRoy: We believe that sharing some of the most innovative forward thinking and creative climate science and adaptation will strengthen our collective ability to respond to even the most challenging impacts of climate change in one of the hottest and driest regions of the world.
The contents of this podcast are for informational purposes only, and should not be interpreted as endorsement for any of the products, technologies, or strategies discussed.
In California and across the Southwest, the severity and size of wildfires have increased over the past 40 years. The causes of this increase are widely debated among both professionals and the broader community, and include factors such as climate change, changing ignition sources, and changes in land management. In an effort to contribute to the discussion 19 researchers associated with the Southwest Climate Adaptation Science Center, including myself, recently published articles where they synthesize and assess the drivers of the increasing trend in wildfire size in California. We're joined today by three other authors. Glenn MacDonald holds the chair of California and the American West, and is a distinguished professor in the Department of Geography at University of California Los Angeles.
Tamara Wall is a research professor in atmospheric sciences at the Desert Research Institute in Reno, Nevada, and Carolyn Enquist is with the US Geological Survey and is the acting federal director for the Southwest CASC. Thank you for talking with us today about this effort. So Glen, this effort first started back in 2021 after California saw an especially severe wildfire season in 2020.
So could you give us a bit of background on, on how this whole idea came to be?
Glen MacDonald: Thank you very much for organizing this, and thank you very much for inviting me. How did this all come about? This big paper with 19 different scientists, a herding of cats. 2020 was an extreme fire year in terms of area burned in California, over 4 million acres.
It blew all the historical records right off the charts, so that was right in our minds. At the same time, there was a lot of political debate about how much climate change was responsible for this, how much it was poor management of California's forests according to certain people, how much of it was a historical legacy from the removal of indigenous burning.
And these debates became very heated politically and in the public arena as well as having good scientific debate. So we got together with a meeting of the Southwest Climate Adaptation Science Center, and this was obviously on our minds. We thought, you know, we, we have people who work in forestry, people who work in climate, people who work in long-term trends of environmental change, of just a broad group of people.
Why don't we tackle this and try to look at it from all our different perspectives as dispassionately and unbiased as possible, and try to figure out what's going on with California fire regime and what are the potential drivers? And so it was from the beginning a group effort that arose via consensus.
Sarah LeRoy: Thanks Glen. Carolyn, as acting federal director, could you explain, and Glen touched on this a little bit, how this effort broadened into a Southwest CASC initiative, could you please elaborate on that?
Carolyn Enquist: Yeah, I think really Glen said it very well you know, as a full team with our core staff, with our principal investigators associated with the consortium of universities that work with the CASC.
We recognized this growing urgency and felt that the task was really well positioned, as Glen said to address this in at tractable, you know, collaboration between, you know, PIs, affiliates. And then Glen took the bold step of volunteering to lead with assistance from the core staff. And so it really turned into a really nice collaboration in the end, something that we're really proud of.
Emile Elias: Excellent. Thanks Carolyn. And because Glenn volunteered to lead, he is the lead author on the article that Sarah mentioned at the beginning of our conversation that was recently published in the International Journal of Wildland Fire. And the article is organized around four specific questions and that first question that that team of authors chose to address is, how has wildfire and land cover changed since 1980?
So Glen, can you describe for us the, the main findings related to that question?
Glen MacDonald: So, what was driving this all, you know, people were debating fire and has fire gotten worse in California? Are there more fires, has it increased, whatever. We thought, well, the first thing we need to do is look at what's actually been happening.
Look at the data before we do any wild conjectures about what you know, what's causing it, what is actually happening. And so we, we took CAL FIRE data and we looked at annual area burned each year. We, from 1980 to 2020, we looked at the number of fires. We tried to gather data about the severity of fires.
Of course we gathered all sorts of climatic data and other data and we also looked at landscape change. And what we found was from that period from 1980 to 2020, there was a statistically significant increase in the annual area burned in California. That doesn't mean that each year there was more than the preceding year, but if we take that entire run of 40 years, there is a a very significant statistical trend of increasing annual area burned.
What's interesting though is there is not a trend like that in the number of fires, the actual number of fires per year. There was a significant trend of decreasing. So what was happening of course, is we were getting some really huge, massive fires, right? Even though the total number of fires was, was actually going down, some of them were just simply beyond control, so we knew we had something going on.
Fire severity, we could only look at some areas. There's only some areas where data was available. There isn't a statewide database of that, but we found in some forests there was a higher propensity for crown fires and greater severity over that time period. So that's what we knew. We, we had some targets. We knew what was happening.
Emile Elias: Excellent. Thanks Glen. So Tamara, one main finding of the article is that the suppression of fire is an important driver of the increasing trend in wildfire size in California. Can you describe this relationship and what you found in your research?
Tamara Wall: Well, it's historically, you know, I, I see the way I see this, you know, it's the, it was the prog, you know, the progressive era at the, the turn of the 20th century.
So we're, you know, we're thinking like 1910, you know, before then, right around in that era. You know, and it, timber was really viewed as a, as a resource, right? And so when things burned, it was considered wasteful in that era. And so the whole point of the progressive era of, you know, forestry, the Yale School of Forestry was really focused on preserving that resource so that it could be utilized, you know, through timber harvesting.
And, you know, the simplest way I think to think about it is that that. That, that that viewpoint won. And what that meant in the long term was that with the exception of the Southeastern United States, fire suppression became the norm. Right? So it was because it was not wasting that resource. So, you know, indigenous burning practices, cultural burning practices there were many, many you know, non-indigenous people that also believe strongly in the practice of prescribed fire, you know, as we will call it now, or just, you know, regular seasonal burning practices.
And all of those were suppressed. Like I said, with the exception of the Southeastern United States. And that suppression, particularly after World War II when fire really became almost a quasi militaristic, you know, enterprise. You know, that was the era we started having smoke jumpers. A lot of that technology came back from World War II and was implemented into the fire management practices and that's really when we had the 10:00 AM the fire should be out the day after it started policy. And that has led to an accumulation of buildup of fuels that we are now seeing the result of that exclusion of fire from fire adapted ecosystems.
Emile Elias: So Carolyn, after highlighting the various drivers of wildfire changes the article describes potential solutions and adaptation strategies that could help to minimize the impacts. Can you describe some of those solutions and adaptation strategies for us?
Carolyn Enquist: Yeah that's a really great question. You know, that's, that's one thing that, you know, at the CASC we're very focused on the solutions part of the problem. And but one thing we should note is that, you know, because of the diversity of vegetation types and different fire regimes that are associated with those vegetation types, we really need what we describe as a multifaceted and locally targeted response.
So this involves fuels management in these different vegetation types addressing human caused ignitions, really starting to think about our building codes and restrictions, thinking about how we integrate urban with ecosystem planning, you know, across not only the wildland urban interface. But you know, the whole expanse of rural to urban, that full gradient that now exists across many of our landscapes.
And then one of the most important things that we really wanted to point out in this paper is reinvigoration of indigenous traditional burning. That played a huge role previously in a number of ways that were not only ecologically beneficial, beneficial in terms of even safety, but culturally important to indigenous peoples that still manage and still live on within their ancestral homelands.
So that collaboration with tribes, with some of our more westernized approaches we believe is really, really critical. And I think there's a lot of you know, and we, like this is a synthesis. So there are a lot of other authors and thinkers who would agree with that very assessment and that's critical to what we would say doing effective climate adaptation.
Sarah LeRoy: Thanks Carolyn. Glen, the paper mentions a correlation between wildfire and atmospheric vapor pressure deficit, which is a big word. Can you explain what that metric vapor pressure deficit means? Just broadly and then why We used it for the analysis rather than precipitation.
Glen MacDonald: So we looked at different climatic variables that might be influencing fire.
For instance, one might be precipitation, how dry it is, but there is actually no long-term trend in precipitation over the period 1980 to 2020 in California. There is though a very significant long-term trend in temperature, and so we see increasing temperatures over that period, maybe on the order of about half a degree centigrade.
So it's getting warmer and that is gonna produce drier conditions even if precipitation stays the same. Now there's different ways to measure how dry the air is. One would be relative humidity, but one that growers use, and agriculturalists use and foresters use is vapor pressure deficit. That is how much vapor pressure is in the air relative to its saturation vapor pressure, and it's a little bit better measure, quite a bit better measure.
About evapotranspiration and how much water, vegetation, or plants are using, and that's why it's used for, for instance, in greenhouses. So it's used for analysis of crops. Where does it come into play for fires? Well, obviously the drier you can get your vegetation, the more likely it is to ignite and to burn at a high temperature.
What we saw then, just like temperature, we have a long-term increase, statistically significant with vapor pressure deficit, how dry that air is basically measured in a way which is meaningful for how it'll dry out the vegetation. And so we see that happening over the period 1980 to 2020. Other analysis have shown that a very large part of that trend can be explained by increasing greenhouse gases.
Similarly, the trend in higher temperatures, which in and of itself will promote fires, a large proportion of that can be attributed to increasing greenhouse gases. So we have two climatic variables that are changing. We know that both of them can influence fire. We know that vapor pressure deficit is a good measure to look at if you're wondering about how dry your fuel is gonna get.
Drier the fuel more likely to ignite, the hotter the fire, the fire's going to carry easier. And so those are two variables that have come out, not just in our study, but in other studies of the Western United States or of California.
Sarah LeRoy: The paper also mentions the importance of locally targeted management and responses, and Carolyn touched on this earlier.
Can you share some of the most promising things that individuals and communities can do?
Tamara Wall: I, I So, so, so, so what I have done, because I live in a very high risk area outside of Reno, Nevada, or actually, I mean, it's a suburban neighborhood, right? I live in a classic suburban neighborhood, but I'm at the very, very close to public lands.
And so we're in a stage step ecosystem. So we have grass fires predominantly where I live. And so our biggest risk, and I think the risk to most structures is through embers. It's not actually the fire front itself. And what we find over and over again is that homes often burn from the inside out. And so really protecting your home from embers and ember intrusion, I think is the number one thing that an individual can do.
And that often embers come in through vents and so covering up your soffit vents with different products, there's a number of different products out there now, including some very inexpensive screening materials. It does need to be fireproof. So you can't just use standard wire mesh because it will melt.
But there are really good products out there that are really easy to apply now. And if you put those over your vents, then you can still have the breathability in your, you know, your indoor air spaces and your basements and your crawl spaces that you need but then embers won't get in and get into the insulation once embers actually get into the insulation, for example, in your attic.
It's done. It's, it just you, firefighters can come around multiple times to put out attic fires, but once that insulation has been ignited, it's almost impossible to get it out fully.
Sarah LeRoy: Okay, great, thanks. So Carolyn, there, we've talked a lot about wildfire impacts, but there are a lot of ecological benefits of wildfire, especially related to vegetation.
So could you talk a bit about the benefits and what you expect in terms of vegetation in post-fire areas in California?
Carolyn Enquist: Yeah, so you know, lest we forget again, I mean as Tamara did just mention, we've got fire adapted ecosystems in California. There's over 20 different major vegetation types in California.
And again, they experience different fire regimes and these are what we're finding are being altered. But that being said, a lot of them require fire to regenerate said vegetation. So there's a, a number of pine species that require fire to open up their cones, for example. And so these systems need to have regular intervals of fire to reproduce and persevere.
So when you have an altered fire regime, you know, you're really kind of setting yourself up, not only for increased fuels, but you know, the inability for some forests to re, you know, regenerate. So, you know, it's something to keep in mind that there is good fire as well as bad fire. And, you know, ultimately it's trying to strike that balance because again, we're facing such extreme circumstances, you know, particularly as a function of the aridity that Glen pointed out, and then the fuel buildup from the suppression activities over the past century that Tamara described.
Emile Elias: Thanks Carolyn. Thanks for bringing up good fire and bad fire. I like that framing. And Tamara, thanks for talking about the embers.
That was a very practical down, down to earth piece. And we have another question for you. The author team decided to publish an article, a sort of companion article in Wildfire Magazine. And so can you talk with us about why you chose that journal? What the motivation for that article was?
Tamara Wall: Sure.
So this piece, you know, came out in the International Journal of Wildland Fire. So Wildfire Magazine is actually the sister magazine. They're both under the auspices of the International Association of Wildland Fire. So those two journals, you know, or that magazine and that journal were really amenable to us.
Publishing in both to reach the broadest audience possible. You know, when we wrote this it was because we were really frustrated by, I don't know, the, there was so much information out there and people were just kind of cherry picking what they wanted. And so we really wanted to yard up everything that we thought was relevant and synthesize it and make that available, not just to researchers and, and to, you know, aca, you know, academic people and people who are, you know, will really use all of that peer reviewed literature. But there's also a huge number of fire managers and fire practitioners out there who are equally interested in this topic, but often don't know even where to start to go to dig in deeper.
So we felt it was really important to write this companion piece in Wildfire Magazine that would get out to that fire practitioner article so that those people who wanted to dig deeper would, would know where to go look for that information. So the two pieces actually align quite nicely with each other.
You can go through the Wildfire Magazine piece and easily, I think, transfer that of where to look in the larger peer reviewed piece. And we also covered the cost of the publication in the International Journal of Wildland Fire, so it was open access so anybody can access it.
Emile Elias: Excellent. Thanks Tamara.
Really appreciate that you made the information accessible to a broader audience. Partially because this topic is so important to so many people, scientists, of course, but, but the managers and even more recently, people that are trying to buy new homes in California. So Glen, State Farm, the biggest insurer in California, announced earlier this year that it would no longer insure new homes citing both wildfires and rebuilding costs.
And so do you have any thoughts about this or advice for new homeowners in California?
Glen MacDonald: Yeah, the impact of California's wildfire challenges on housing. And in the insurance industry to getting insurance for your, your housing has become increasingly, increasingly important. And so the withdrawal of some insurance companies from the state for insuring new homes, new policies, rather, on one sense, it's troubling.
If you're trying to get a house and you have to then turn to the state for the insurance, it's high cost and it doesn't provide the kind of coverage that you might want. On the other hand, this is the private sector, the private enterprise system applying the pressure of the marketplace. And there will be responses to that in terms of, for instance, the building materials you'll use, your defensible space where we put in communities. And so this could in some ways, and it is, it can be a tragedy for people who are trying to get in the housing market and suddenly get hit with these huge insurance costs. And of course, if you want a mortgage, you're gonna have to insure your home here.
That can be very problematic, tragic, I understand it. Let's hope though it pushes us to a more fire resistant, fire resilient, sustainable building practices. And in terms of our planning, that's what we can hope. How this is gonna unfold, I'm not a hundred percent sure in, in the near term.
Emile Elias: Excellent.
Thanks Glen. And Carolyn, I understand you have personal experience with this, with your home in Big Bear Lake.
Carolyn Enquist: Yes. I found out the hard way. I merely thought that when I bought a home in this fire prone area of the San Bernardino National Forest, Just to the northwest, or sorry, the northeast of the LA Basin.
You know, I just used my typical homeowners, which I'd been with for so long, no problem. And it was a shock and I panicked when they said no. And so I had to go through the traditional sort of, you know, hiring an insurance broker. Who could then look around and then thankfully the state of California had the Fair Plan available, and so I had to purchase that plan in conjunction with kind of a low end.
You know, I don't even know much about my insurance company to tell you the truth, but just the fact that they insured me, I was like, I had to grab it. So you do feel vulnerable when you don't have those assurances that you might have otherwise had in other places. And for example, now my home state of Colorado is looking to do a very similar thing that California has done as well.
So it's, it's starting to become a trend and we'll see, like Glen said, where this leads us.
Emile Elias: Yeah, thanks for sharing your personal story. It's happening a lot of other places, Florida, other states are going through similar climate related insurance changes. So we like to ask all of the experts that we get to, to speak with on this podcast about hope and specifically what gives them hope.
So I'll go ahead and start with Tamara and ask you, despite all of all of the research that you've done and, and your perspective, what gives you hope?
Tamara Wall: I think it's the adaptability of humans and my hope is really in fire adapted communities and we stop trying to have, you know, we, we've tried to you know, kind of suppress our way out of this problem, you know, with through wildfire suppression.
And I think we're finally at a tipping point, not just with wildfire, but with many other climate hazards as well, of really trying to figure out how do we adapt our communities in a way that mitigates the hazard and overall makes these communities more resilient. I think as Glen pointed out, you know, we have the pressure of a market-based system now, and there are so many great construction approaches and new materials, and all of these could be integrated into not just making individual homes more fire resilient and fire adapted, but actually entire community so that our infrastructure is protected so that our schools are protected. So that if fire moves through a community, the damage is such that it is recoverable relatively easily and people can come back and they have not just their homes to come back to, but they have roads and water and sewer and their schools and their municipal buildings available to them.
And so, But there's also a lot of rigidity in how we build buildings and construction approaches. And I think getting us over that hump is kind of the place where we're at right now. But I see there's so much out there and I think we're just, we're just, California is gonna be a leader in this and I think other states will follow.
Emile Elias: Oh, thanks Tamara. I'm gonna hold on to your vision of fire adapted communities. I think that was brilliant. So Glenn, the same question to you. What gives you hope?
Glen MacDonald: What gives, what gives me hope looking forward? You know, you would think that this should be all doom and gloom. You know, we've got, climate change is an overriding factor on this.
It is gonna continue to exacerbate the fire challenges through the 21st century. So how could there be any hope? But what does give me hope is more on the ground. First of all, I think we've gotten past the point where people in the state or in Western United States, think that the Forest Service or CAL FIRE or something can put out these fires by 10:00 AM the next morning.
People are sensitized to the fact that this is not something that we can throw more dollars at in terms of simply fighting the fires once they start. And we've seen that in the public arena, and we see that in politics. The state has really embarked on investing money in terms of forest management and fuel management.
They're feeling their way, but they understand and people understand that simply fighting fires is not gonna work. So that gives me hope that people are understanding the situation better at a, at a public level and a policymaker level. And then I think the science is just getting so much better. You know, we're really understanding a lot more about the nitty gritty about fires themselves.
They're fantastic scientists working on that. The climatology, landscape scale analysis and hopefully more and more about how the vegetation itself is gonna respond, how ecosystems will respond. And so I think there's tremendous progress that has been made, and that was one of the things working on this paper, hundreds and hundreds of citations of exciting work in many different areas where people were dedicated to getting at that and seeing that science and seeing how much we've learned over the last couple of decades. I think that was also really exciting and that gives me hope.
Emile Elias: Excellent. Thanks. Yeah, our increase in knowledge on the individual and the policy and the scientific levels really that is hopeful. Carolyn, the same question to you. What gives you hope?
Carolyn Enquist: Yeah, I love the answers that Glen and Tamara gave.
I share their are thoughts there. I would say the additional piece that I would add is just this real growing interest and willingness to work together across governments, across sectors, across communities, states, and even internationally to really, you know, take this problem seriously.
Recognizing, you know, not one entity can fix it. It really is, and I say this really more broadly in the context of climate change and exacerbating, you know, these, these various hazards. So it's gonna be through all hands on deck that we actually move the needle on facing climate change. And I think this also applies to really working with indigenous peoples and communities through authentic partnerships and proactive policies to bring these traditional methods back to the fold and support those in any way we can. So the, and just that growing recognition and willingness to do just that gives me a lot of hope.
Emile Elias: Excellent. Thanks Carolyn. I always appreciate how you bring in the indigenous perspective to almost every conversation. It's very much appreciated by me and I know a lot of your colleagues as well, so thank you for that and being a consistent voice there. So the last question that we have is, if our listeners remember one thing from this podcast, one thing from our conversation today what would you like it to be?
And we'll go ahead and we'll start with Glen first on this question.
Glen MacDonald: So what is one thing that I would like people to take away from this podcast? Oh my gosh, that's really difficult. It's this, look. Wildfire certainly is a challenge. It's certainly a challenge to our developed areas, to people of California.
Wildfire is also a natural part of our ecosystem, and we've gone kind of crazy over, let's say, 4 million acres burning in 2020, but in the pre-European period, there are some studies which suggest that might have been the normal acreage which was burned, that we can persist through this. Our ecosystems can get through this, we can get through this, but we have to understand.
We're not gonna dodge this bullet. Climate change is gonna make it worse. And we're gonna have communities which are endangered. And as Carolyn said, if we work together, if we rediscover indigenous knowledge, we can get through this, the state will get through this, and California can be an example of how to do it.
Because we are not the only jurisdiction in this country or in the world that is facing similar challenges.
Emile Elias: Thanks Glen. Carolyn, same question to you. What's one thing you would like people to remember?
Carolyn Enquist: Well, Glen just said that so well I'll just repeat something maybe I said already. And it's that, you know, fire is something that we shouldn't just fear, but it should be respected.
As many of our indigenous partners often point out, there's good fire, there's bad fire. We have to recognize this is something we have to live with. And so again, using our ingenuity, new innovations in terms of, you know, through partnerships and technologies, I think we can do it. And I think that's, that's a big message this paper is trying to, you know, push forward is that we can do this. We just have to work together and draw upon some of these great innovations and have the political will to move this issue forward.
Emile Elias: Excellent. Thanks Tamara. You have the last word. What's one thing you'd like people to remember?
Tamara Wall: We spend billions of dollars every year up on fire suppression.
I mean just the federal agencies, just DOI agencies alone. Plus the Forest Service, I think average close to $3 billion a year on fire suppression across like a rolling five year average. And that doesn't even count what states or other agencies spend. And so we still spend so much on fire suppression and still like that is just the you know, the, it, it sucks all the oxygen out of the room.
And I think we really need to pull back from that and really think about how do we actually create fire adaptive communities. I really, and, and also resilient landscapes, like in combination. So it's not just a suppression response, but it's more, it's better balanced with that creation of fire adapted communities.
Not just individual homes and individual structures, but you know, as I said earlier, entire communities, the infrastructure, the roads, the sewer and also then create those resilient landscapes that pulls in that indigenous and cultural and lived experience knowledge on how to help support our landscapes become more resilient under climate change.
Tamara Wall, Carolyn Enquist, Glen MacDonald, thank you so much for the excellent work that you've done and provided us with and for talking with us today.
Carolyn Enquist: Thank you.
Glen MacDonald: Thank you very much.
Tamara Wall: Thank you.
Emile Elias: Thanks for listening to Come Rain or Shine podcast of the USDA Southwest Climate Hub
Sarah LeRoy: and the USGS Southwest CASC. If you liked this podcast, don't forget to rate or review it and subscribe for more great episodes. A special thanks to our production crew, Skye Aney and Reanna Burnett. If you want more information, have any questions for the speakers or would like to offer feedback, please reach out to us via our websites.