In the early 20th century, a blight fungus wiped out most of the 4 billion American chestnut trees on the eastern seaboard. The loss was ecologically devastating. Short Wave host Emily Kwong dives deep into how scientists are trying to resurrect the American chestnut tree — and recent controversy over a plan to plant genetically modified chestnuts in the wild. Want to hear about more efforts to recover endangered or lost species? Let us know by emailing [email protected]!Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy
Chapter 1: What happened to the American chestnut tree?
Hey, shortwavers, Emily Kwong here with an episode from our holiday archives all about chestnut trees. Stick around until the end of the episode for an update on the latest science, too. You're listening to Shortwave from NPR.
Hey, everybody. Maddie Safaya here with shortwave reporter Emily Kwong. Hey, Maddie. Hey, Kwong. You've been delving into the mystery of what happened to one of the most significant trees in the United States, the American chestnut.
Yes. The Kwong family is very into chestnuts. Every Christmas season, we'd buy them roasted on the streets of New York. My dad folds them into his stuffing. And of course, you honestly can't go anywhere this time of year without hearing Nat King Cole sing about them. You know what I'm talking about.
Chapter 2: Why are chestnuts significant in American culture?
I do.
Chestnuts roasting on an open fire. It just sets the mood. Right. You know what time it is. But Maddie, it took years of eating chestnuts, listening to this song to ask myself, why haven't I ever seen a chestnut tree in the United States? Have you ever wondered that? Every day, Kwong. No, really. Have you ever wondered that? No, I haven't.
It's odd because by 1945, when that Christmas song was written, most of the four billion chestnut trees on the eastern seaboard had died. The chestnuts you buy these days, the ones I eat, are all imported from Europe and Asia. And if you ask people from Appalachia, where the chestnut was an important species for the ecosystem and the economy, this tree represented a way of life that was lost.
Rex Mann of Kentucky says his father never got over it.
He never became reconciled to that loss. He was always hopeful that something would happen, you know, that the tree would come back.
Now, Rex is one of the many people working to bring a version of the American chestnut tree back and tapping into the very genetics of the tree to do it.
Today on the show, the death and potential rebirth of the American chestnut tree, how science is trying to give this functionally extinct tree a fresh start and how that has created some controversy. OK, Kwong, the mysterious disappearance of the American chestnut tree. Take it away.
All right. Let's bring it back to Rex Mann. He's retired from the U.S. Forest Service and really knows the trees of southern Appalachia. Last year, he gave a TEDx talk that opened with this memory of sitting around the fire as his father, Howard Mann, told chestnut stories.
He's talking with great passion about what the tree meant to his people. Its huge size, the wonderful wood used for everything, and the never-failing crops of chestnuts that nurtured the mountain people.
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Chapter 3: What caused the decline of the American chestnut tree?
But Rex, he never saw any of this. Because in 1904, a mysterious and deadly fungus was discovered on trees in New York City. It likely came from a nursery stock of Japanese chestnut trees. And this blight began to spread down the coast. So by 1950, a few decades later, most of the four billion chestnut trees were dead or infected with blight fungus. Okay, so what does this fungus look like?
Okay, it's a parasitic fungus with a bright yellow-orange color. It can grow underneath the bark, looking like these orange gashes, or on the top creating these actively fruiting pustules.
Pustules are never good.
Yeah, it's pretty gross and pretty sad because once infected, the trees really don't stand a chance. The blight, it cuts off nutrients and water to the rest of the tree. And for America's forests to change so dramatically just when the Great Depression hit and people really relied on these chestnuts, it was devastating. Rex remembers as a kid walking through the aftermath.
What I saw when I was growing up was what I would call the gray ghosts, the trunks of the chestnuts. They were still standing in the forest.
Important footnote, the blight doesn't actually kill the root system of these trees. American chestnut trees, Jared estimates there are about 400 million now, are basically shrubs sprouting from the roots and they get infected by the blight and are killed back before reaching sexual maturity. It's like the whole species has been condemned to eternal infancy.
Poor little trees never get to grow up.
Exactly. Because the blight lives on, naturalized in the environment, in the leaf litter, on other trees that don't get sick from it. So that's why by 1950, the American chestnut tree was declared functionally extinct. Right.
So the big, strong trees, they were basically gone.
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Chapter 4: What is the American Chestnut Foundation doing?
So there's a lot more genes involved. And as you do more crossing to American chestnut, you get trees that are less blight tolerant.
So traditional breeding has its limits. The more you make these trees American chestnut-y, the less able they are, it appears, to combat the blight. Which brings us to prong number two, attacking the blight itself by infecting it with a virus. That's probably fine. I'm not worried about that at all. But it makes sense, right, to go directly to the source? Counter-strike? No?
Sure.
What happened? Well, this strategy has been effective in Europe, saving their trees from blight. But the problem in the U.S. is you'd have to go around and individually infect each spot of fungus on the tree, and that is just... Not realistic. So much work.
But we can't go out to the forest and treat 400 million trees with this virus every year. So it's too labor-intensive for large-scale restoration, but it works for our breeding efforts.
So what about prong number three? What's that? Prong number three, it's the most interesting but also the most controversial for some folks because it involves transgenic organisms. So think about corn or cotton. Got it. Okay. We've added new genes to those agricultural crops to protect them from insects or allow them to tolerate certain weed killers. Yeah, sure. We got some GMOs out there. Yeah.
And members of the New York chapter wondered, could we do something like that for the American chestnut tree? Researchers at the State University of New York, their College of Environmental Science and Forestry, tackled that question. They chose a gene naturally found in wheat and a lot of other grass plants and inserted it into American chestnut trees.
They planted that first transgenic tree outside the lab in 2006 and And their hope is that such a tree will be planted in the wild someday.
And how does this gene affect the American chestnut tree?
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Chapter 5: How can science help revive the American chestnut tree?
OK, so this gene is responsible for creating an enzyme which has the ability to combat oxalic acid. And oxalic acid is what's ultimately attacking trees that have been infected with the blight fungus, killing their cells. So this gene is essentially protecting the tree from being totally consumed by the fungus. Right.
So these trees have been genetically modified at this point.
That's right. They're not wild American chestnut trees, but a GMO version. Researchers at SUNY call these samples darling American chestnut trees. And before they can be planted in the wild, they have to pass federal regulatory approval. The USDA, the EPA, the FDA, they all have to sign off.
And what are these regulatory agencies looking for?
Basically, they'll want to know how these transgenic chestnuts are impacting the environment around them. The soil, nearby fungi, other plants. They'll want to know about tree growth rates and pollen flow. There are a lot of variables to consider, a lot of testing to be done on trees that are still pretty young. And that's made some people very nervous.
Right. Some people are worried about genetically engineered trees and other things being released into the wild. Right.
Yes. For those concerned about GMOs, this tree is raising eyebrows. In March, two members of the foundation's Massachusetts Rhode Island chapter stepped down over this. A group of activists released a white paper saying this would be a, quote, massive and irreversible experiment. They're fearful this could change the ecosystem in ways we just can't predict.
And Jared gets where these critics are coming from.
It messes with people's idea of what is natural or what is nature. And we're doing an interventionist approach to a problem that humans caused in terms of bringing in introduced pathogens that the native species are naive to and they're susceptible to.
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Chapter 6: What role does Dolly Parton play in this story?
Since this episode first published five years ago, a lot has happened. In December 2023, the American Chestnut Foundation withdrew its support for SUNY's darling transgenic chestnut project. I got in touch with Jared Westbrook again to explain why. And he said the foundation found issues with the transgenic trees in the long term, including diminished blight resistance and slow growth.
So I reached out to SUNY for comment. Andrew Newhouse, who directs the chestnut restoration project there, told me over email that the college has made improvements to their programs since these concerns came to light. And he defended the viability of darling trees against blight in the long term. He wrote, As for the American Chestnut Foundation...
Jared says, this is over email too, that their main strategy at the moment is an advanced version of prong one, where the foundation uses genomics to select the very best hybrid trees, crossbreed them, and ultimately create a line of progeny with blight resistance woven into their DNA at birth. That's all for me, Emily Kwong. Thanks for listening to Shortwave, the science podcast from NPR.