In 1904, the forester for the Bronx Zoo noticed something unusual. Some of the zoo’s trees were sick. They looked wilted and scorched, with ugly cankers growing out of them. Hermann Merkel called in a mycologist, a fungus expert. By the time William A. Murrill figured out the cause two years later, the disease had spread as far south as Virginia.
And that is how the great chestnut blight began. Within just a few decades, most American chestnuts were gone, whole forests wiped out by something we couldn’t see (at least not without a microscope).
Today, we don’t fully appreciate what happened with the chestnut. That’s because we’re living in the arboreal equivalent of a post-apocalyptic horror, with no real memory of what came before. For us, the forests we see around us are normal, yet they’re not normal. They are what remained after their most dominant species was rendered functionally extinct.
This past Friday was Arbor Day, a day we set aside to think about trees (and maybe plant a few more). We also still are in a global pandemic. If we combine those two thoughts, Venn diagram-style, we wind up thinking about tree pandemics. Perhaps the greatest of those was the chestnut blight that swept through Virginia in the early 1900s and completely changed the look — and the culture — of Appalachia.
Chestnuts were the climax species of the Appalachian forest — the biggest and most dominant tree. The Sierra Club, in a recent article about chestnuts, calls it “the perfect tree”:
“Massive, fast-growing, and rot-resistant, it was easy to mill into cabin logs, furniture, fence posts, and railroad ties. After being harvested, it resprouted; in 20 years, it was ready for the sawyer again. Wide limbs spanned the canopy, filtering sunlight and creating a diverse, layered forest below.
“Sweet, acorn-size nuts fed squirrels, deer, raccoons and bears. Cooper’s hawks nested in the high branches, wild turkeys in the lower forks. Insects thrived in the craggy bark, which was naturally tannic and a good choice for preserving hides.
“Cherokee people made dough from the crushed nuts, treated heart troubles with the leaves, and dressed wounds with astringent brewed from the sprouts. And in the fall, when the chestnuts piled up in carpets half a foot thick, white settler families collected and sold them by the bushel.”
By some measures, the chestnut accounted for 1 of every 4 trees in the forest and, because it fed so much livestock, a key part of the rural economy. “In Appalachia,” the Sierra Club writes, “the heart of the tree’s native range, generations of people were rocked in chestnut cradles and buried in chestnut caskets.”
And then, just like that, they were gone. Biological forensic work traces the chestnut’s demise to 1876. That’s when we think the blight arrived, a stowaway on some trees imported from Japan. That’s why governments today are so rigorous about inspections. By the time the first infected trees were found in the Bronx Zoo that day in 1904, the website Forest Floor Narrative says “it was probably already too late.” The blight was carried by the wind, sometimes spreading 50 miles a year.
Within a few years, there were frantic efforts to quarantine the blight. “Boy Scouts were enlisted to scour forests and cut down blighted trees,” the Sierra Club writes. “It was no use. By the time the blight had run its course, nearly 4 billion American chestnuts across some 300,000 square miles were gone.”
By 1940, the forests of Appalachia were full of dead trees. The New York Times writes: “The chestnut blight arguably ended Appalachian subsistence farming as a common practice, forcing upon a region’s worth of people a stark choice: Go into the coal mines, or move away.”
Now here’s where things get curious. Notice we said earlier that chestnuts were “functionally extinct.” That’s an important distinction because they’re not truly extinct. Chestnut stumps, persistent things, continue to put up shoots. They just don’t live very long before the blight gets them. There also are some isolated chestnuts that somehow have survived — the world’s largest remaining stand is said to be on 60 acres in West Salem, Wis., but the blight has arrived there, as well. The world can be a cruel place.
Human ignorance helped kill off the chestnut; human ingenuity now is trying to bring it back.
Since 1983, the American Chestnut Foundation has been trying to breed a new type of chestnut. The Chinese chestnut is resistant to the blight — asymptomatic carriers, in modern parlance. The idea is to cross the two until there’s a tree that’s 15/16th American chestnut, but with just enough Chinese genes to be blight-resistant.
The foundation has a breeding farm in Washington County but breeding and cross-breeding trees is a long, slow process. The Sierra Club writes that, at one lab at Penn State that’s been taking part in chestnut breeding, the results are mixed: “Six generations down the line, resistance still isn’t guaranteed. Some appear to have no resistance at all. Others put up a fight, attempting to wall off the blight.” The ultimate survival rate only is about 20%.
Now, some scientists at SUNY College of Environmental Science and Forestry in Syracuse, N.Y., are experimenting with another method: They’ve inserted a wheat gene into one particular line of chestnuts, named Darling 58 after New York chestnut advocate Herb Darling. That gene produces a blight-resistant enzyme. The Sierra Club writes: “Genetically speaking, Darling 58 is an entirely American chestnut with one extra gene that gives it a bonus characteristic: resistance to Cryphonectria parasitica.”
There’s only is one catch: This is genetic modification and to say it’s controversial is an understatement. This past year, those scientists filed an application with the U.S. Department of Agriculture to deregulate this genetically modified chestnut — which would allow it to be planted anywhere. There’s no decision yet. Environmental groups are torn: Some see this as a low-risk way to bring back a species; others are dead-set against letting genetic-modified plants loose anywhere. Frankentrees, some call them.
American chestnuts once lived for upward of 200 years. Even if the government says it’s OK to start planting genetically modified chestnuts this year, those trees would be just one-quarter grown by 2076 — the 200th anniversary of the blight’s arrival. They would not yet be halfway grown by 2104 — the 200th anniversary of the blight’s discovery. Trees slowly grow but quickly can die. There probably is a lesson there somewhere.
— Adapted from The Roanoke Times