SCOTT DETROW, HOST:
In 2006, Kathleen Knight was walking through a forest in northwest Ohio. She’s a researched ecologist with the U.S. Forest Service. All around her were big, beautiful ash trees, tall trunks with lush green canopies. These trees were thriving. Just three years later, when Kathleen revisited the same forest, she was met with a completely different scene, hundreds of dead ash trees as far as the eye could see.
KATHLEEN KNIGHT: And that was kind of our moment of shock, saying, wow, they’re all dead.
DETROW: All because of a small invasive bug, the emerald ash borer. Interlochen Public Radio’s Points North podcast tells stories all about the Great Lakes region. In this excerpt, host and producer Dan Wanschura tells the story of researchers who are trying to save North America’s ash trees from extinction.
DAN WANSCHURA, BYLINE: There are billions of ash trees all over North America. Ash trees filter groundwater. They give habitat to all sorts of plants, animals and insects. Indigenous people depend on ash to make baskets. Ash is used for things like baseball bats and handles for tools.
KNIGHT: And to see it disappear so quickly and change so quickly, it’s – it is – it’s heartbreaking.
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WANSCHURA: But Kathleen and her colleagues have a job to do. They gather a bunch of data from these dead ash trees. They measure their trunks, look for emerald ash borer exit holes, and then they pack up their gear and head back to their cars.
KNIGHT: And as we’re walking across the bridge, I think it was one of our interns who spotted the tree, was, like, hey, is that an ash? And we all stop and look at this tree, and we’re, like, that’s an ash. It’s definitely an ash. It’s healthy. It’s full of green leaves. It looks great. It was really this moment of confusion. How is this tree possibly existing after what we’ve seen all day long here? We knew it was big. We knew it was big to find a surviving tree.
WANSCHURA: Now they had to figure out why it survived because that answer might save an entire species from extinction. The emerald ash borer – or EAB, for short – was first found in North America just outside Detroit, Michigan. It was more than 20 years ago in 2002.
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UNIDENTIFIED REPORTER: This is a story of death and destruction. It’s about an invasion.
WANSCHURA: That’s a clip from a Detroit public television program.
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UNIDENTIFIED REPORTER: It’s the story of a desperate fight against a little emerald green bug from Asia that’s killing millions of shade-giving ash trees like these. As you’ll see at the end of this program, these trees are doomed.
WANSCHURA: The little beetle arrived on wood-packing material in cargo ships or airplanes from China. The bugs have wings and can fly short distances, but people are the main way they get around.
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UNIDENTIFIED NARRATOR: Do you know what’s in your firewood? Stop the spread of emerald ash borer. Don’t move firewood.
WANSCHURA: Now EAB is found in 36 states and five Canadian provinces.
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WANSCHURA: Kathleen has seen the effects of that here in central Ohio. She’s got a tan Forest Service baseball hat on and a backpack with a water bottle and a can of bug spray sticking out of it. She spots an ash tree and walks up to it.
KNIGHT: So this is a – one of our larger ones. It died, too, and you can actually see the canopy of the dead tree. That’s up there.
WANSCHURA: The real damage done by the emerald ash borer is done by its larvae. Kathleen pulls back a little bit of the bark.
KNIGHT: Oh, you can already see a few up here. So as the emerald ash borers create these tunnels, if you get enough emerald ash borers, they basically cut off that circulatory system and girdle the tree. And it can’t get water and nutrients transported up to the canopy, and that kills the tree fairly quickly.
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WANSCHURA: As EAB devastated ash trees in North America, researchers scrambled to find a solution. Early on, they tried cutting down large swaths of trees to create a sort of firebreak to stop the spread. Then they tried insecticides. Those can work to save a small number of trees or maybe one in your yard but not a whole forest. Later, the focus shifted to tiny wasps from Asia, which kill emerald ash borer eggs and larvae. They help but don’t completely get rid of EAB. Overall, the outlook for ash trees in North America was still really dire…
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WANSCHURA: …Which brings us back to that moment when Kathleen finds that lone surviving ash tree. She looks at it and wonders if she’s staring at another possible solution. But for her to figure out how this tree survived, Kathleen has to find more of them. So in 2010, she puts together this team, and they go on a mission to see if they can find more of these surviving ash trees, and they do.
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WANSCHURA: One of the people Kathleen is most excited to tell is Jennifer Koch, a geneticist with the U.S. Forest Service. Jennifer has been working with ash trees for so long, she’s now allergic to them.
JENNIFER KOCH: It’s like poison ivy to me.
WANSCHURA: Jennifer is based out of a research station in central Ohio. When she hears about these surviving ash trees that Kathleen found, she’s pretty skeptical.
KOCH: Because of the data that was being reported, we didn’t believe – we were buying into the, yeah, nothing is going to survive. There’s no resistance, because so many other scientists were saying that, until we saw Kathleen’s field data and the pictures that she took of the healthy trees that she found.
WANSCHURA: That’s when Jennifer starts thinking, they might actually be onto something here. The emerald ash borer is really good at finding mature ash. It’s not like the bugs are just missing certain trees. So Jennifer and her team come up with a hypothesis, and that is, some ash trees in North America have a genetic resistance to the emerald ash borer, basically, the ability to fight off EAB. But Jennifer says that’s just the hypothesis. They need more data.
KOCH: We’re scientists, so we’re skeptical.
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WANSCHURA: They come up with a term for these trees that’s cautious, but hopeful, lingering ash.
KOCH: It’s kind of like, you know, that last person that leaves the party. They just linger. And you’re just, like, well, what are you doing here still?
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WANSCHURA: Kathleen Knight keeps looking for even more of these lingering ash trees. She finds them in parts of Ohio and Michigan and takes branches from these trees back to Jennifer Koch’s lab. There, Jennifer clones them and runs tests to see if there’s genetic resistance. And she discovers something amazing. These trees not only have resistance to the emerald ash borer, they actually kill EAB larvae. Scientists really didn’t see that coming.
KOCH: The mantra at the time was no co-evolution, no resistance, meaning that since this insect was from a whole another continent and our trees didn’t grow up exposed to them – that they didn’t evolve any sort of mechanisms to defend themselves.
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WANSCHURA: But in order to prove their hypothesis, Jennifer still has to find out if the genetic resistance is passed down from parent to offspring.
KOCH: Because that is the key piece of information you have to have to know that breeding is actually going to work.
WANSCHURA: So Jennifer and her team clone a bunch of different lingering ash. They crossbreed them in the lab and then wait for them to produce their own seedlings. Not only do they get seedlings that are resistant to this bug, they get seedlings that are more resistant than their parents.
KOCH: So now we’re really starting to get excited. I shouldn’t say starting to get excited, but now we’re convinced. We’re close enough to being convinced.
WANSCHURA: And that means their hypothesis is right. Resistance to the emerald ash borer is genetic in some ash trees in North America.
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WANSCHURA: Then comes the big task, actually saving the trees. Jennifer needs to create an entire orchard of resistant ash to prove her lab results out in the field. Her team will harvest the seeds from the most resistant trees and grow them into seedlings. Eventually, those seedlings will be planted in forests across the region. Jennifer says that could happen in the next decade. This entire process can be replicated, helping spread resistant ash all across the continent.
DETROW: That – you can hear more of Points North from Interlochen Public Radio wherever you get your podcasts.
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