MADDIE SOFIA, BYLINE: You're listening to SHORT WAVE from NPR.
GEOFF BRUMFIEL, HOST:
Hello, SHORT WAVE. This is Geoff Brumfiel, your host today. And I'm here with our climate correspondent Lauren Sommer. Hi, Lauren.
LAUREN SOMMER, BYLINE: Hey.
BRUMFIEL: And today, we're headed to the mountains of California, where you'll find some of the largest living things on the planet, giant sequoias. These massive trees have come under threat in the latest round of wildfires. Lauren, how are they holding up?
SOFIA: I have to say I've seen a lot of tough stuff as a climate reporter, and I really wasn't ready for this. I went to Sequoia National Forest, a pretty remote part of it in the Sierra Nevada.
ALEXIS BERNAL: That is what we would call a real giant sequoia monarch.
SOMMER: Alexis Bernal was standing next to that monarch, which is the name given to the largest sequoias. She's a research assistant at UC Berkeley.
BERNAL: It's massive. Jenny, what was the diameter on this tree.
SOMMER: So it was 40 feet around at the trunk...
BRUMFIEL: Wow.
SOMMER: ...Two hundred feet tall. So that's easily more than a thousand years old. And some sequoias live more than 3,000 years.
BRUMFIEL: I mean, that timeframe is just so hard to wrap your mind around. Those trees were growing 3,000 years ago.
SOMMER: Right. But this particular tree isn't getting any older. The trunk is pitch black. It looks like charcoal. And the burn marks stretch all the way to the top.
BERNAL: But it's 100% dead. There's no living foliage on it at all. Within just 100 meters of us, I can see one, two, three, four, five, six, you know, seven, eight, you know, giant sequoia monarchs. And they're all dead.
SOMMER: These trees and up to 10.000 other old-growth sequoias were killed in a big fire last year called the Castle Fire.
BRUMFIEL: I mean, that just sounds like a huge loss.
SOMMER: Yeah. And that's up to 14% of the entire population of giant sequoias. So it's unprecedented, Bernal says.
BERNAL: It's hard to see these trees that I've lived hundreds to potentially thousands of years just die because it's just not a normal thing for them.
SOMMER: Giant sequoias can normally handle fire. They're adapted to it. But the way humans are changing both the climate and the forest itself, the wildfires are getting more extreme. Still, this isn't just a depressing story because scientists are trying to move quickly to protect the sequoias that remain.
SOMMER: So today on the show, the future of the largest trees on Earth and how these giants are forcing us to confront how quickly the planet is changing. You're listening to SHORT WAVE, the daily science podcast from NPR.
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BRUMFIEL: So, Lauren, wildfires have been bad in the U.S. again this summer. And earlier this month, a wildfire was threatening a grove of giant sequoias in Sequoia National Park. I remember seeing pictures of a sequoia tree wrapped in what looked like kind of aluminum foil to protect it.
SOMMER: Yeah, that was probably the General Sherman tree. It's the largest tree on the planet. And the foil around the base is kind of a last-ditch effort to protect it. But the thing is it's weird that these sequoia trees would need that at all. They are built for fire. Their bark is a foot thick. They tower over the rest of the forest, and they don't have any low branches that might catch on fire from other trees.
BRUMFIEL: Wow, that's actually really interesting. I didn't realize that. So, I mean, if they are naturally fireproof, what's changed now? Why are so many dying recently?
SOMMER: Well, the fires have changed. I mean, the Sierra Nevada has always had regular fires but mostly these low-grade fires that kind of had this effect of clearing out the brush from time to time. They were started either by lightning strikes. Or they were set by Native American tribes. And that's known as cultural burning. The tribes use it to kind of cultivate the land for game or plants or for materials that they used. But things changed dramatically when they were forced from their lands. You know, burning stopped, and then came the era of fire suppression.
SOMMER: Right. And by fire suppression, you're talking about, like, Smokey Bear saying, only you can prevent forest fires - things like that.
SOMMER: Yeah, yeah. Like, I remember those ads. You know, and it was the mission of firefighting agencies to extinguish all fires. Without fires, the Forest got a lot denser. The trees are closer together. The undergrowth has built up, and that's what's helping fuel these really extreme fires, the kind that sequoias, it turns out, just can't survive. That's what was striking to Scott Stephens. He's a UC Berkeley fire scientist who was out with the field crew that day. They were there to catalog the mortality but also to study the forest density around the sequoias.
SCOTT STEPHENS: You know, they've been here 1,500 years. You know, and each tree maybe survived 60, 70, 80 fires. You know, that's incredible. And then one fire comes in 2020. And all of a sudden, they're gone. That is a travesty.
BRUMFIEL: So if you're losing so many of these sequoias at once, I mean what is going to happen? Does Sequoia National Park, like, have to get renamed? Or are there enough of these trees making it through?
SOMMER: Yeah, well, that was the other thing they were there to inventory. They were really looking for signs of hope.
STEPHENS: Two tiny sequoias here growing from the regeneration from the fire. Pretty rare.
SOMMER: Scott spotted two tiny sprouts in the ground, you know, these little specks of green in the ash. They're only two inches tall. It just seems, like, impossibly tiny compared to what they might become. Sequoias need fire to reproduce because it's the trigger for them to release their seeds. Their cones open up from this blast of heat, and then there's a shower of seeds that hits the forest floor. But the whole day I was there, we only saw a dozen seedlings. And normally, researchers would expect to see hundreds or even thousands.
BRUMFIEL: Huh. I mean, why are there so few?
SOMMER: Yeah, researchers are trying to figure that out. You know, maybe the fire was just too hot for the seeds. But there's also a drought right now, so the seedlings are having to survive another hot, dry summer. And even in a normal year, most sequoia seedlings don't make it through the first year.
STEPHENS: Unless we see some regeneration at some of these sites, my goodness, you're not going to see sequoia here.
BRUMFIEL: Wow. I mean, what's really striking is how abrupt this change can happen. Like, a whole ecosystem can transform from just one event, just one big fire.
SOMMER: Yeah. And I think that's what was kind of hitting the scientists I spoke to, as well. You know, we think of climate change as this kind of gradual warming. And it's what helped set the stage for this. I spoke to Nate Stephenson, who's studied sequoias for decades as a scientist with the U.S. Geological Survey. He says it really showed when a drought hit California in 2012. The old-growth sequoias - they weathered it OK. But the conifers and other trees didn't.
NATE STEPHENSON: The extra warmth that came with the drought pushed it into a whole new terrain. And that's what really helped kill a lot of trees. And they become fuel for fires.
BRUMFIEL: Right. So it wasn't that the drought hit the sequoias particularly hard. It was the trees around them that died, and then those trees fueled the fires that ended up killing the sequoias, right?
SOMMER: Yeah. And until recently, Nate had never seen a group of all old-growth sequoias just die. It was unheard of. And then he saw the damage assessment from the Castle Fire.
STEPHENSON: That's when I couldn't help it. I don't cry often, but I cried when I saw the photos 'cause I love these trees. I mean, they've been part of my life for most of my life.
BRUMFIEL: Yeah. I mean, it sounds like such a huge tragedy. Is anyone talking about going in and planting seedlings if they're not seeing them come back naturally in some places?
SOMMER: Yeah, they are. I mean, but it's very early in those discussions because climate change is throwing another wrench in here. These trees live thousands of years. So what's the climate going to be like then?
BRUMFIEL: Oh, I see. Like, the spot they have might be good habitat for sequoia right now. But if things get hotter, that's going to change.
SOMMER: Yeah, like, maybe in the future, the best sequoia habitat might be higher up in the mountains, where it's a little cooler. I've been talking to Christy Brigham about that. She's the head of resource management and science for Sequoia & Kings Canyon National Parks. She says planting new trees is the backup plan right now because it takes so long to replace these old-growth trees. Christy says what's more urgent than replanting is to identify the sequoia groves that are at highest risk for fire. She says in some Groves, the park has already reduced the overgrown vegetation by using controlled burns. That's been done in the grove with the General Sherman tree, actually. But she thinks about 40% of the groves still need some help.
BRUMFIEL: But I guess if one fire can take out such a huge swath of the sequoia population, I wonder whether the work can be done fast enough to protect the trees that are left.
SOMMER: Yeah. I mean, that's the key question. Christy says it's not easy to do these controlled burns. They need more funding. They need personnel. There are other constraints. Like, when it's really dry and hot, it's not safe to do the burns in some cases. But she's really pushing to get this done quickly.
CHRISTY BRIGHAM: It is not too late. We can do better. And - sorry. And people love these trees, so I just hope that we can take that love and translate it into immediate action to protect the groves and long-term action to limit climate change and its impacts.
BRUMFIEL: There's a lot of grief here, but there's also a lot of passion for these trees.
SOMMER: Yeah. I mean, even if you're not kind of, like, into these trees, it's hard to see something that's 2,000 years old die. They really are unique. And I think Christy is hoping that people are paying attention to what they're showing us. She says that's why sequoias are iconic. They're making us think about these things.
BRIGHAM: That is one of the gifts of giant sequoias - is that they force us to think in deep time. It forces us to confront the challenge of climate change.
BRUMFIEL: Deep time - I mean, these are time frames we as humans are just not used to operating on. And climate change is just making it that much harder to think about. But it is worth thinking about. And, Lauren, I really appreciate you and appreciate you bringing this story to us today.
SOMMER: I was very glad to.
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BRUMFIEL: This episode was produced by Rebecca Ramirez, edited by Gisele Grayson and fact-checked by Indi Khera. I'm Geoff Brumfiel, and this is SHORT WAVE, the daily science podcast from NPR.
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