American Chestnut Demise and Potential Revival

The Demise and Potential Revival of the American Chestnut

Emma Downey

Emma Downey
Gardening Expert

Updated on 12/4/2022

Before a devastating blight, the American chestnut was a keystone species in eastern forests. Is it possible to bring it back with the help of genetic engineering?

In Central Pennsylvania, there are monuments dedicated to the dead. It is not uncommon to find beams and wide floorboards that are straight-grained and honey red with age inside some of the oldest barns and farmhouses in our country, serving as reminders of one of the deadliest epidemics ever to strike American soil. A fungal blight called Cryphonectria parasitica was responsible for the death of roughly 3.5 billion American chestnut trees in the Appalachian hardwood forest between 1904 and 1940.

Not only did the loss of the tree have profound effects on the ecosystems that cover much of the eastern United States, where it was a keystone species, but it also had profound effects on the Appalachian way of life. In the early 20th century, hundreds of millions of chestnut board feet were milled each year, generating a multibillion-dollar timber industry in today's terms (as measured in value). When the trees and their lucrative nuts and timber were gone, a culture of forest-based subsistence began to erode in the mountains, and at the same time, another business began to flourish.

Chestnut Tree

 

As a result of America's growing energy needs, 11,000 coal mines were working to meet the demand by 1920. Undoubtedly, the Appalachian landscape has been altered twice: first by the death of the chestnut trees, then by a century of coal mining that has stripped and scarred the land, leaving piles of rubble in its wake.

There was almost no metric that could be used to describe how perfect the American chestnut tree was. In addition to its massive size, rapid growth, and rot resistance, it was easy to mill into cabin logs, furniture, fence posts, and railroad ties and make them from them. As soon as it was harvested, it resprouted, and in 20 years, it was ready for the sawyer. 

Below was a forest of diverse, layered limbs that spanned the canopy, filtering sunlight and creating a forest with a diverse range of species. Squirrels, deer, raccoons, and bears feed on sweet, acorn-sized nuts each year.

Cooper's hawks nestled in the tall branches of the trees, and wild turkeys nested in the lower forks of the trees. Several insects thrive in the craggy bark, which is naturally tannic, making it an ideal choice for preserving hides. There was a time when the Cherokee made dough from the crushed nuts, treated heart ailments with the leaves, and dressed wounds with astringents brewed from the sprouts.

As the chestnuts pile

 

As the chestnuts piled up in carpets half a foot thick during the fall, white settler families would collect and sell the chestnuts by the bushel when they piled up. As part of its northern route, a railroad station in West Virginia shipped 155,000 pounds of chestnuts to destinations along its way.

In the eastern hardwood forest, the chestnut trees dominated the landscape from southern Maine to the Florida Panhandle and east to the Mississippi River, occupying a quarter of the trees in the area, stretching from southern Maine to the Florida Panhandle and west to the Mississippi. Generations of people have been rocked in chestnut cradles and buried in chestnut caskets in Appalachia, the heartland of the tree's native range.

However, the dominance would not last for long. As early as 1904, a forester noticed something strange happening to the chestnut trees at the Bronx Zoo in New York.

the chestnut trees at the Bronx Zoo in New York.


It was evident that the trees were growing cankers surrounded by strange spotty, orange-yellow patches on their leaves. To examine the fungus, he called mycologist William A. Murrill to conduct the examination. The disease had spread to the state of New Jersey, Maryland, the District of Columbia, and Virginia by the time Murrill published his findings just over a year later.

In light of my observations in the Bronx this season, I'm inclined to take a rather gloomy view as to the future of the chestnut tree in the immediate future.
Said Murrill in his letter, warning his skeptical colleagues that the blight would kill all chestnut trees.

Several scientists from the US Department of Agriculture would later conclude that the fungus had infected ornamental Japanese chestnuts imported as early as 1876 with the fungus. By the time the blight was discovered at the Bronx Zoo, it was already too late to stop it from spreading.

conclude that the fungus had infected


In addition to SARA FERN FITZSIMMONS, she is part of a small army of biologists, ecologists, foresters, and activists who are passionately dedicated to the cause of reviving this iconic tree. Fitzsimmons, director of the restoration at the nonprofit American Chestnut Foundation (TACF), is waving a golden, jagged-edged leaf at me as she explains that the chestnut genus, Castanea, originated in China. Among three chestnut trees in China, Cryphonectria parasitic blight thrives on dead tree tissue, feeding on damaged cambium under the bark after weather, animals, or insects have wounded the tree. The trees, which evolved along with the blight, grow a burl-like tissue around the wounds, which prevents the fungus from spreading further into the tree's interior.

There is a misconception that Chinese chestnuts are immune to the blight; however, there is no such thing as immunity, however, it is possible to wall off the infection very quickly, surround it with callus tissue, and stop it from progressing.
Fitzsimmons says that Japanese chestnuts have about the same resistance to infection as Chinese chestnuts, and "Americans have relatively little resistance." Once Cryphonectria parasitic colonizes a wound on an American saying, it's unstoppable. To expand its reach, it polishes off the already-dead tissue, then secretes oxalic acid, a toxin that kills more and more of the chestnut's cells, feeding the fungus while killing the tree.

In addition to SARA FERN FITZSIMMONS,

 

It is estimated that the blight spreads fifty miles a year, tree by tree, due to the wind carrying it. First, a canker would appear on the bark, causing it to bulge or sink. It was not long before the wound would burst open, spitting out spores from an ocher-colored blotch, the tree's inner layers being exposed as spores flew outward from the injury. First, the mighty upper limbs of the tree died, and then the trunk followed. As early as 1910, coalitions and quarantine lines had been established. It was decided to enlist the Boy Scouts to clean up the forests and cut down the blighted trees. " Burn that tree to the ground; spare not a branch," a Pennsylvania newspaper urged.
It was of no use to me. As a result of the blight, nearly 4 billion American chestnuts had been destroyed across approximately 300,000 square miles by the time it had run its course.

When I was born in 1930, all I remember are dead trees, I found dead stems in the woods here and there, and my father and grandfather said they had been chestnuts, and these were their standing skeletons.
Says Blair Carbaugh, a retired biology professor at Pennsylvania's Lock Haven University and a longtime activist for the recovery of chestnut trees. 

A Century of Coal Mining Stripped The Earth and Left Piles Of Rubble Behind After The Chestnut Trees Died

A Century of Coal Mining Stripped The Earth and Left Piles

 

The American chestnut has one defense mechanism that helps it fight off the blight: even though the part of the aboveground tree dies, the belowground part can sometimes survive. Forests in the Appalachian Mountains and the chestnut roots constantly send new sprouts. They are more similar to shrubs than trees; the live stems are clumped around a dry, dead one, and the leaves are serrated ovals that stand out as golden yellow against the background of the underbrush. Even though most of them are less than an inch in diameter, wild American chestnuts are not challenging to locate if you know what you're looking for. It is estimated that 430 million wild American chestnuts are still growing in their native range. But even these tenacious young trees are destined to perish. The majority only live for another five to ten years before succumbing to the blight.

In the meantime, the coal industry has devastated the Appalachian forest in its way. An average-sized Bucyrus-Erie dragline can move more than one hundred tones of earth in a single scoop. This machine has transformed the mining industry's technology. It was responsible for destroying ecosystems and many underground mining jobs, which had helped the local economy recover after the chestnuts were eradicated.

Bucyrus-Erie

 

The operation of a strip mine, which involves using explosives to break up several hundred feet of ground to expose the coal layers below, requires only a minimal workforce. The dragline scrapes away the topsoil and rocks, then deposits them in the nearby valleys. This reshapes the entire topography of the area, but it also leaves behind large swaths of uninhabitable and polluted land. Even though many state and federal regulations require the cleanup of old mine sites, even the best remediation techniques frequently fall short of restoring the land to anything remotely resembling its natural state.

In the early years, what we were doing was 'recontouring,' which meant filling in the holes.
Carbaugh says.

 It was mandatory for land that was forested before it was mined to be reforested if it had been forested before it was mined.

The trees didn't do well, The topsoil was gone, and the soil fertility was low.  The earth used to be upside-down, and when they did the reclaiming, it was just a matter of rearranging what was 50 feet underground and trying to get something to grow on it.
Carbaugh continues.

As a result of heavy equipment being used to tamp down the ground to stem erosion, fast-growing, non-native grasses have been able to root themselves in the compacted earth, whereas trees did not.

The miners wanted to get out from under this legal obligation.
Carbaugh says. 

Forests of a Century Ago

 

It might be that they could say, 'Look, it's grassland!' and the Bureau of Abandoned Mine Reclamation would let them off the hook if it is green.

French, a restoration ecologist and director of operations for the Kentucky-based nonprofit Green Forests Work, says this twisted approach to restoration led to meadows where forests should have been..

There was a feeling of planting trees in a gravel parking lot when you went to plant trees.
French says. 

It is estimated that a million acres or more of the Appalachian forest were denuded by the coal companies and then converted, in the name of reclamation, into pastures with low or nonexistent biodiversity by the coal companies.

During the early 2000s, a coalition of environmental groups, mining companies, and government agencies launched the Appalachian Regional Reforestation Initiative, which works with Green Forests Work and other local restoration organizations to encourage reforestation along the Appalachian Mountains.

We use a bulldozer to rip up the compacted ground, allowing rainwater to penetrate the soil, It is like tilling your garden but on a larger scale. We use a combination of volunteers and paid contractors to plant native trees - pine, oak, tulip poplar, locust, and chestnut - along with native shrubs.
French says.

This method successfully reclaims over a quarter of a million acres of land. However, while the poplars will produce flowers and the oaks will reach for the sun, the chestnuts' days are numbered from the moment they are planted. Oaks will stretch for the light.

This method successfully reclaims


I am  picking my way Through Bramble While, attempting to keep up with Fitzsimmons as she navigates a stand of young trees while identifying species in a clipped, low alto. This woman in her forties, with a head full of dark curls and a hearty laugh, seems to have the ability to make the thorny bushes part their ways willingly for her.

An hour's drive to the north of Harrisburg, Pennsylvania, lies Coal Township, home to the hillside we are currently standing on. Even though Fitzsimmons has assured me that the trees on the property we are surveying once grew in neat rows, there is nothing fantastic about them at this point. A tall fence and white plastic tubes wrapped around the bases of the trees are the only things that suggest this area is not entirely wild. 

While Fitzsimmons is bending over to pull on a tube, he pushes dirt and bits of coal with a shiny black surface out of the way. Fitzsimmons and a group of other volunteers from TACF planted hundreds of chestnut trees in this location in 2014. They drove tubes into the ground to shield the young trees as they emerged from the soil. One of the people who helped plant was a volunteer for the first time named Liz Schwartz. She recalled saying a quick prayer every time she tucked a nut into the hardscrabble.

Chestnut


Incredibly, six years later, the chestnut trees appear to be thriving, with the largest possibly reaching a height of 25 feet. There are yellow poplar, black locust, aspen, sumac, and fire cherry trees growing in the space between them. These trees are volunteers whose seeds were carried in by the wind or were dropped by birds or small mammals.

It has been fascinating to watch these sites develop, at this stage, the growth is as thick as dog hair, and you're fighting through brambles. In 10 years, we will have canopy closure.
Fitzsimmons says.  

Low, barbed bushes will die from lack of sunlight. The trees will mature, and the shrubbery will spread. Eventually, “the land turns into a forest.”

This is one of 40 trees planted on former coal mining sites throughout the coal region of Pennsylvania. It has turned out to be quite an unusual nursery for TACF's breeding program, which has spent more than three decades trying to create trees resistant to blight in reclaimed mines. Chestnuts seem to thrive in torn-up, thin, acidic soil. There is a very close overlap between the maps of the historic chestnut range and the coalfields if you superimpose them.

In my experience, I find that the chestnuts significantly grow pretty well in rocks, it's a drainage issue—they don't like it when they have wet feet.
Fitzsimmons says. 

 Due to the open landscape, saplings don't have to compete for sunlight. There is an acidic ground that gives chestnut trees the low-pH soil that they prefer to grow in. Since the topsoil was carried along with the coal, there is no Phytophthora, a mold that lives in dirt and causes root rot, which has plagued chestnut test plantings worldwide.

Coalfields and Historic Chestnut Range Maps Almost Precisely Overlap

Coalfields and Historic Chestnut Range Maps Almost Precisely

 

It is likely that most of these trees will succumb to Cryphonectria parasitica at some point. Meanwhile, the plantings offer an opportunity to observe how the trees produced by the breeding program grow and whether they are resistant to blight if any if they are.

The mine lands aren't doing anything at the moment, I think it's an excellent opportunity to experiment with them and make them productive. You won't make things worse.
Fitzsimmons says.

Fitzsimmons inspects chestnut sprouts in plastic pots in a plastic-walled shade house at Penn State University. Some of them appear in good condition, with large, saw-toothed leaves, and others struggle with orange spores creeping up their tiny trunks as they struggle to survive. Several mixed chestnut trees have been produced this year, trees that are the result of a cross between American, Japanese, and Chinese chestnuts. Fitzsimmons and her colleagues punctured their bark a few months ago, introduced Cryphonectria parasitic spores, and let the fungus do its magic on the trees.

We come in every week. We call, and that is how we measure the variable resistance. In terms of survival, we could get about 40 to 50 percent  this year.
She says

1989 marked the beginning of the breeding program on a research farm in Meadowview, Virginia. The researchers at TACF came up with the theory that it would be possible, throughout several generations, to breed a chestnut tree that retained all of the qualities of its native ancestors but also had a trace amount of Chinese genes in its DNA to protect it from the blight.

The amercian massacusetts

Half American and Half Chinese

Their process, known as backcross breeding, started with the creation of chestnut trees that were half American and half Chinese. This generation, referred to as F1, was backcrossed with an American, resulting in generation B1 F1. The backcross was performed twice, which produced B2 F1 and then B3 F1, respectively. The tree from the fourth generation was then bred twice with other backcrosses, resulting in generation B3 F2 and finally generation B3 F3, a tree that is essentially 15/16ths American chestnut.

Even after six generations, the trees being studied in Fitzsimmons's lab at Penn State are not guaranteed to be resistant to the disease. Some don't seem to have any resistance at all, and others put up a fight to prevent the blight from spreading further. On the other hand, even B3 F3s only have a survival rate of about 20 percent throughout their lifetime.

In the early days of the backcrossing program, Fitzsimmons says,

There was a misconception that resistance was an elementary inherited trait controlled by two or three genes. In that case, it would have worked. Despite that, we now know that chestnut blight resistance is more complicated than that.
 

Sunny College of Environmental Science and Forestry professor William Powell, contracted by the state's chapter of TACF to assist in solving the chestnut puzzle, had a eureka moment in the 1990s.

american cestnut

 

Several years ago, Powell had been exploring ways in which You can introduce blight resistance directly into the American chestnut genome. He posited that if resistance is genetically complicated, a more straightforward solution would be to add a defense mechanism from somewhere else to make it more effective. It has been found that wheat and other cereals produce an enzyme called OxO, which protects the plants

From disease caused by oxalic acid by having an enzyme called oxalate oxidase.
 Powell explains. 

The chestnut blight

Revolves around this acid, and it suddenly cannot get into healthy tissue if you can get rid of it.
 

In the beginning, Powell had embryos from an American chestnut tree near Binghamton, New York, that hadn't ultimately succumbed to the blight. To produce the OxO enzyme, he inserted a gene that would make the enzyme and grew seedlings that looked like tiny palm trees on islands of agar in Petri dishes. It was achieved by inserting a single OxO gene into different parts of the genome, allowing him to test whether the transgenic trees would produce the enzyme that fights off the blight. There were varying levels of success regarding the placement of genes.

We had to do a lot of weeding out.
 Powell says.

In 1995, the first chestnuts were grown

 

In 1995, the first chestnuts were grown in a petri dish, and since then, the process has been consistent but slow. One particular iteration, in particular, was particularly promising. It was called the Darling line (after Herb Darling, a conservationist who had supported Powell's work from its earliest days) and named after Herb Darling. Linda McGuigan, a coworker of Powell's, inserted the OxO gene into Darling 58 on July 12, 2012, and the tree produced has a good chance of being the one that could potentially save the species.

Regarding its genetic makeup, Darling 58 is an entirely American chestnut variety. However, it possesses an additional gene that confers a bonus quality: opposition to Cryphonectria parasitica.
This is where everything begins to turn into a mess. In 1996, the American agrochemical company Monsanto introduced the Roundup Ready soybean, a transgenic plant modified with a bacterium strain that rendered it immune to glyphosate the active ingredient in Monsanto's Roundup herbicide. 

This was followed by the introduction of several other Roundup Ready crops. At the same time, Powell was cracking chestnuts to fish out diminutive embryos. In the years that have followed, transgenic plants have been met with public opposition in the United States and abroad. Additionally, some environmental groups, such as the Sierra Club, have been vocal in opposing the cultivation of genetically modified crops.

genome of Darling 58 has been modified

 

However, all of these transgenics have been done for commercial purposes. In the interest of restoring its original state, the genome of Darling 58 has been modified. The fact that there are no plans to establish timber plantations or turn a profit should make it less objectionable to some people, but it still might be. There are some who oppose this idea: In response to the announcement that TACF would support Darling 58, two board members of the organization's chapters in Massachusetts and Rhode Island resigned in protest.

There are still purists who advocate for either backcrossing or transgenics within the chestnut-restoration community; those who support backcrossing believe that transgenics are risky, while those who advocate for transgenics believe that backcrossing is pointless. However, after it became clear that the backcross breeding program had some flaws, the two separate initiatives started cooperating.

"The American Chestnut Foundation believes we should use all methods to accomplish this," Fitzsimmons says.

You won't be able to solve such a big problem with just one solution.

She has been cross-pollinating the Darling 58s with the advanced backcross trees since the first Darling 58s matured.

At present, transgenics are subjected to a strict set of guidelines, The pollinated individuals are placed in bags, and then a steel mesh bag is placed over them to ensure that squirrels or other critters do not get to the nuts. Under the USDA's permitting guidelines, there is no chance, zero risk, that that gene will enter the wild and become independent of your control. It's impossible if these guidelines are followed for it to escape.
She says.

However, Powell and Fitzsimmons agree

 

However, Powell and Fitzsimmons agree that the next step toward restoration is releasing the animals back into the wild. Early in 2020, Powell and his team handed in a petition to the USDA nearly 300 pages long, requesting that the agency deregulate Darling 58 and make it so that anyone can legally plant it. If the proposal is carried out, it will be the first time a genetically modified organism is permitted to be released into the wild.

The USDA initiated a period for public commenting after evaluating the application in the previous year. Although more than sixty percent of respondents favored deregulatory policies, many were opponents.

The Campaign to Stop GE Trees issued a warning, stating, "Introducing genetically modified [American chestnuts] into wild forests entails many risks, and regulatory agencies are ill-equipped to assess GE forest trees intended for deliberate dissemination." [Citation needed] Carbaugh has a different perspective on the situation and thinks that intention is important in genetic engineering.

The thought of modifying a plant to make it resistant to Roundup distresses me, however, I am very excited about what is happening with the chestnut.
He says.

For its part, the Sierra Club has advised caution, but it sees Darling 58 as having a low environmental risk because it would be closely monitored, which makes it a soft risk for the environment. A comment made by the Club on the USDA application noted that while genetic engineering "carries some uncertainties," it is quite possible that, with proper precautions, genetic engineering can produce an organism that "provides a significant environmental benefit."

If Darling 58 is released and its seeds are planted

 

If Darling 58 is released and its seeds are planted by members of the public, restoration groups, and anyone else who wants them, their locations will be entered into a TACF database. When everything goes according to plan, they will reproduce and pollinate both wild shoots and trees that have been backcrossed. As a result, genetic diversity and resistance will result: Of Darling 58's offspring,

Half will give you the resistance, and half will preserve the wild type, In 100 years, a transgenic tree will still produce wild ones.
 Powell says.

According to Fitzsimmons, this is the only way to give the American chestnut a fighting chance as he sees it.

Some people think Darling 58 is a silver bullet or the OxO gene is an immunity gene, but this is not true.
She says the path to actual resistance depends on the variable Chinese-derived resistance of backcrosses and the OxO gene expression of transgenics to achieve solid resistance. "Combining these methods gives you a much more robust and resilient population with more than one method of fighting the fungus."

chestnut tree

Cultivating the Tree

We will be able to cultivate trees that can survive the blight, but they will need help to thrive on the scale of a forest - which is why the abandoned mines of Pennsylvania have become so important. A healthy chestnut tree produces many seeds, but those seeds do not readily germinate on their own since humans often eat them. It will be the same for the Darling 58 offspring as well.

At the end of a hundred years, it might travel a mile, although it will spread, it is not a weed.
 Powell says. 

If you were to transform the coalfields into thriving and mature chestnut forests, the trees would take care of the rest, seeding themselves into the surrounding forestlands. From these degraded landscapes, a new forest would sluggishly expand outward in all directions. Imagine the fall season in a wooded area with a gentle slope, trees with broad, craggy trunks climbing the hill, and the long, golden leaves of the trees drifting down to become entangled in the rhododendron branches and evergreen needles below. 

American Chestnut Imagine the fall season in a wooded area

 

In both the forest that once was and the forest that could be, salamanders are skittering through vernal pools and black bears dragging their feet on the loamy ground after stuffing their faces with sweet American chestnut.

This is what we call a century project, if we are going to get it to look even somewhat like it did before the blight, it will take centuries. It is for the future, and it is planting a tree you will never be able to sit under its shade.
Powell says.

Faith requires an optimism unique to those who envision a forest amid a strip mine.