As another wildfire season begins, Unfold heads into the burn zones of last year’s fires in Los Angeles County. 51³Ô¹ÏºÚÁÏ Davis and University of California Agriculture and Natural Resources scientists are learning what the fires left behind — both on the ground and in the air. You’ll hear about one Altadena fire survivor’s efforts to save his oak trees and about a highly toxic carcinogen detected in the air over millions of people. Researchers are building a new kind of fire science, because the fires are changing and science is racing to keep up.
In this episode:
- , associate professor, 51³Ô¹ÏºÚÁÏ Davis Department of Plant Sciences
- , environmental horticulture advisor, 51³Ô¹ÏºÚÁÏ Agriculture and Natural Resources
- , professor, 51³Ô¹ÏºÚÁÏ Davis Department of Civil and Environmental Engineering
Read an in-depth In Focus story on what scientists are learning from the fires in Altadena and the Palisades. You can also find out more at 51³Ô¹ÏºÚÁÏ ANR's .
Transcript
Transcribed Using AI, May Contain Errors
Amy Quinton
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Jeff Henderson
One of the things that made this our home were the trees. This is one that is was is just really the one that we centered everything around.
Caroline Champlin
That's Eaton fire survivor Jeff Henderson, talking about the Oaks in the backyard of what was his Altadena home.
Jeff Henderson
When we first came up, I just prayed for it.
Amy Quinton
The fires that tore through LA destroyed nearly 18,000 structures.
Caroline Champlin
Entire neighborhoods were leveled.
Amy Quinton
But after the flames were put out, people didn't just grieve lost lives or lost homes. They grieved their trees.
Caroline Champlin
Many survived the fires only to be chopped down later during cleanup.
Amy Quinton
Not because anyone was careless, but because it's so hard to know which had a chance at survival and which were just hazards.
Caroline Champlin
The fate of trees wasn't the only big unknown left by the fire.
Amy Quinton
Lots of questions were still hanging in the air, including what might be hiding in the smoke.
Caroline Champlin
In this episode of Unfold, we'll get some answers from the scientists studying the aftermath of LA's fires.
Amy Quinton
Coming to you from 51³Ô¹ÏºÚÁÏ Davis
Caroline Champlin
and from 51³Ô¹ÏºÚÁÏ Agriculture and Natural Resources.
Amy Quinton
This is Unfold. I'm Amy Quinton.
Caroline Champlin
and I'm Caroline Champlin.
Caroline Champlin
Was your house here?
Jeff Henderson
Yeah, yeah, yeah, it was right there where the little porch thing is, that's where it was.
Caroline Champlin
Jeff Henderson had lived on Altadena Drive for more than three decades before his historic home burned down last year.
Jeff Henderson
It was an 1885 house that we'd rebuilt. And you know, it wasn't like we'd been here for five years. You know, it was something that we really loved.
Caroline Champlin
Both of his daughters got married in this backyard, underneath their four towering Oaks. Today, those trees are charred, blackened from trunk to top, and tacked on each of them is a homemade sign,
Jeff Henderson
And it says, Do not cut tree said, if questions, please call owner at my number. And I had signs everywhere I had Don't, don't take the rocks, don't take this, don't take that, because I had no idea who was coming.
Caroline Champlin
Who ended up coming were members of the Army Corps of Engineers tasked with clearing the rubble of people's lots. Throughout LA's burn zones, they determined what vegetation could stay and what had to go.
Jeff Henderson
And unfortunately, some of the opinions in the beginning weren't good, and we've lost a lot of trees
Caroline Champlin
on one of Jeff's oaks, they spray painted three blue dots, what locals call the dots of death, meaning marked for removal. But burnt as they are, those trees are now the only traces of his home. Jeff's wife told him, if the trees go, maybe they should go too.
Jeff Henderson
You know, I just, I just prayed. I said, I said, you know, please give us a shot. Anyway.
Caroline Champlin
Jeff's trees have caught the attention of a team of scientists from 51³Ô¹ÏºÚÁÏ Davis, 51³Ô¹ÏºÚÁÏ ANR, 51³Ô¹ÏºÚÁÏLA and the US Forest Service, because what's happening to these trees gets at a bigger research question: How do trees fare in urban wildfires? Which ones survive and which ones don't?
Chris Shogren
We don't know what trees to replant now, because we don't know how urban trees react to fire, I can't tell you, like this tree is going to do better if a fire happens again or not. We don't have that research yet.
Caroline Champlin
That's Chris Shogren, an environmental horticulture advisor with 51³Ô¹ÏºÚÁÏ ANR. To understand more, he and 51³Ô¹ÏºÚÁÏ Davis plant scientist Alessandro Ossola are getting up close with the scorched trees.
Alessandro Ossola
So one meter diameter oak. Pretty big puppy. Okay.
Caroline Champlin
And determining their health requires specialized tools.
Alessandro Ossola
So what we use is this guy here.
Caroline Champlin
He pulls out what looks like a pink and yellow Nerf gun,
Alessandro Ossola
Which is not a gun.
Caroline Champlin
It's actually called a resistograph, and he aims it point blank at the tree.
Alessandro Ossola
So this one is essentially pushing this needle into the tree. Essentially, the harder the wood is in that particular location, the more resistance this guy has to do to push the needle in. Gonna squeak. Sometimes, gonna start smoking.
Chris Shogren
It as it's going in, it's getting denser and denser wood, which is what we wanted to see.
Caroline Champlin
Based on the readings, the experts believe these trees have a good shot at recovery.
Jeff Henderson
From day one, it's It's incredible how, how good they look to me. But then again, other people come for the first time and they say, Wow, what do you why did you keep these?
Caroline Champlin
For Jeff, the answer is in the bright green leaves sprouting from the branches. So far, it looks like he made the right call.
Chris Shogren
This could be a nice, happy, healthy tree. It's going to need a little bit of work, but,
Jeff Henderson
But now it's got great character. I'm serious. I'm I do not want to cut it down.
Caroline Champlin
Before the team can draw any conclusions, they'll need a lot more data. That's why they're surveying trees across Altadena and the Palisades.
Chris Shogren
Ultimately there’s a lot we don’t know and it just takes time for those trees to tell us how they’re going to do and how they’re going to recover and so we just have to be out there and listen to them.
Caroline Champlin
The effort got started a year ago when homeowners were still taking in the damage themselves.
Chris Shogren
You're out there, you know, just trying to take a look at trees, and they come up to you, and they're crying and, you know, they almost give you their whole life story of how much time and everything they spent. And so you just kind of get attached to them a little bit.
Caroline Champlin
For Chris, hearing those stories has made his work feel that much more urgent. To understand what's happening with the trees, scientists need to be able to see the big picture.
Alessandro Ossola
Okay, let's see whether I can find a satellite. Five meters accuracy, four meters, three meters, two centimeters.
Caroline Champlin
Alessandro is setting up a LIDAR sensor in the back of his blue Toyota Tacoma truck.
Alessandro Ossola
Okay, anyone familiar with LIDAR? Have you seen a LIDAR unit before?
Caroline Champlin
The device is on a tripod, and he's using it to make a 3d map of the burn zones.
Alessandro Ossola
Now we're going to start a full scan. You're going to be scanned as well. But trust me, it's not dangerous.
Caroline Champlin
The device shoots out lasers which bounce off objects and return to the sensor. As the LIDAR rotates, it captures everything from damaged homes to the condition of individual trees.
Alessandro Ossola
And little by little, it creates a 3-D point cloud of everything in the landscape up to 800 meters away.
Caroline Champlin
By driving hundreds of miles year after year, they'll know exactly which trees were taken out and where to plant new ones. They'll end up with some of the most detailed 3-D maps ever made of urban burn zones.
Amy Quinton
Caroline. I've seen some of the LIDAR system images that Alessandro captured, and I'm really impressed with the detail. Has any of this kind of work been done before?
Caroline Champlin
Yeah, there has been some research on vegetation after urban wildfires in Santa Rosa, Ventura, Paradise and Maui. But this data stands out because it's being collected on the ground, street by street and tree by tree, rather than relying on satellite images.
Amy Quinton
Yeah, you know, it's funny, given the amount of destruction and how much survivors lost in the fires. I guess I'm a little surprised that people still care so much about the trees still there.
Caroline Champlin
Yeah. I mean, it makes sense to me, but I think other people may not realize how green Altadena was as a community, especially if you're not from the area. And I really stood out amongst other neighborhoods in LA as a especially green space. But as Alessandro told me, everyone should care about trees.
Alessandro Ossola
Plants and trees are providing many, many benefits. Shade. They are providing cooling benefits. They are providing benefits in terms of your mental well-being and your general health. So we need to strike a balance between having a landscape that is green enough, but also safe so communities you know, there can be fire resilience for the future.
Caroline Champlin
Alessandro is also running experiments to learn which plants are highly flammable and which ones might help slow a fire.
Amy Quinton
It's all important information to know with a changing climate. And while Alessandro and Chris were studying trees in burn zones. Another 51³Ô¹ÏºÚÁÏ Davis scientist was also at work, Civil and Environmental Engineering Professor Michael Kleeman. He knew something most people may not think about. When fires rip through urban areas, the danger doesn't end when the flames are put out.
Michael Kleeman
16 to 18,000 structures burn, and everything in them, printers, monitors, solar cells, battery operated vehicles, you know, everything in between, wires, plastics, just anything you can imagine. And so I think that there's a huge, you know, potential for toxic materials in the both the smoke and the debris afterwards.
Amy Quinton
Michael studies air quality, so when the Eaton and Palisades fires hit, he saw an opportunity
Caroline Champlin
to monitor potential contaminants in the air,
Amy Quinton
Right. And it just so happened that he was already studying smoke impacts from wildfires, and already had much of the air quality monitoring equipment he would need.
Caroline Champlin
Okay, but most scientists can't just hop in a car, drive six or seven hours to LA and start monitoring air quality. Didn't he need some funding or planning to do that kind of research?
Amy Quinton
Well, ideally, but he says there was no time
Michael Kleeman
you know you have to respond in the moment. I mean, the fire doesn't wait for you to write your NSF grant and like, make it pretty. The fire demands that you get out there in time to be relevant, because if you miss it, you're not relevant.
Amy Quinton
So he drove down with all his monitoring equipment strapped to the back of a truck, and what he found in the air over LA surprised everyone. All right, should I just get in?
Amy Quinton
I climb into a white electric pickup truck. But this is no ordinary electric truck. It's a mobile air quality lab.
Michael Kleeman
Wildfires are really dynamic, and so it's hard to predict where the pollution is going to be. And so with an electric vehicle platform like this, we can drive to wherever the smoke is, or the dust is, or whatever is happening that's that's generating the air pollution that we're worried about.
Amy Quinton
Michael drove this truck straight into the burn zones in Altadena and the Palisades, five trips over nine months from shortly after the fire through the long, dusty cleanup phase. In the back seat, machines buzz.
Michael Kleeman
So we've got monitors on board that are measuring airborne particles and oxides of nitrogen are the two active things that are running right now.
Amy Quinton
He's also measuring black carbon and volatile organic compounds. On the back of the truck, air is constantly being pulled into multiple instruments. One device, called a cascade impactor, separates particles by size.
Michael Kleeman
So we're sweeping through the ultra fine particle size range, looking for particles smaller than 100 nanometers.
Amy Quinton
The smaller the pollution particle, the more potential danger to your body.
Michael Kleeman
And there's a huge difference in how your body responds to particles of different sizes. We have evolved sort of filtering out dust, larger particles, and so we can get rid of the big stuff, but the really, really tiny, small stuff we're not very evolved to handle. And so that stuff, when you inhale, it will go through your cell membranes. It'll circulate in your blood. It will go into all your major organs. It will be in your brain, your liver and everything in between.
Amy Quinton
And it was among those smallest particles where he found something alarming.
Michael Kleeman
That's where we saw the action. It was those very, very tiny particles where we found hexavalent chromium.
Amy Quinton
Hexavalent chromium. A toxic substance. A known carcinogen. What's worse, it was a particle so small it's never even been studied.
Michael Kleeman
We just flat out don't know what a 56 nanometer or smaller hexavalent chromium particle does to you. No one has ever measured the health effects of that.
Amy Quinton
Michael then looked at atmospheric models to track how those tiny particles moved.
Michael Kleeman
And when we put in what we observed in the cleanup zones into those models and predict where the wind would carry it and who was exposed? We can see concentrations that are elevated all through the Western central part of Los Angeles.
Amy Quinton
More than 3 million people in 100 different zip codes in LA were likely exposed. Maybe more. Michael says the source of the hexavalent chromium isn't entirely clear, electronics, artificial turf, and possibly even the chemicals used to fight the fires.
Michael Kleeman
Even the flame retardant that they dropped from the aircraft, can potentially have the chrome in it, and we're working to try to understand all those things, but we're not ready at this point to know definitively where it might have come from.
Amy Quinton
Flame retardant was designed for wildland fires, back when those fires stayed in the wild, that line is disappearing. Michael says, the way we fight urban fires may have to evolve. The fires also left behind debris, hundreds of 1000s of truckloads of it. Clean up. Crews did everything they could to prevent dust, wetting down the rubble and covering truck beds.
Michael Kleeman
But even when you're moving that much material, even a few percent slippage, you know, you're going to potentially have issues. And again, we certainly measured something in the air when we were out there, so we believe that there was some, you know, debris, dust, that that was getting out there and potentially could expose people.
Amy Quinton
Michael says that's important to keep in mind when the next urban fire hits, but it's complicated, even knowing the risk, some survivors may feel compelled to go back to their home to see if they can find any belongings.
Michael Kleeman
It's very much hard. I think people have fire proof safes. People have valuables, family heirlooms that they you know, they don't want to lose, and so I understand the desire to go back there, but you just have to be aware that all that ashy material is toxic. You know, the last thing you want to do is survive the fire and then die in the aftermath.
Amy Quinton
On later visits to the burn areas, Michael says the hexavalent chromium started changing into a less toxic form. Within six months, virtually all of it was gone. For Michael, the work is about understanding what's left behind, not just for this fire, but for the next one, because the fires are changing and what's in the air is changing with them.
Caroline Champlin
You can learn more about all this fire research at our website, ucdavis.edu/unfold.
Amy Quinton
You can also read an in depth story at 51³Ô¹ÏºÚÁÏ ANRs green blog. Unfold's website will also have links to photos and videos. I'm Amy Quinton
Caroline Champlin
and I'm Caroline Champlin. Thanks for listening.
Andy Fell
Unfold is a production of 51³Ô¹ÏºÚÁÏ Davis. Original Music for Unfold comes from Damien Verrett and Curtis Jerome Haynes. Additional music comes from Blue Dot Sessions.