Bringing Back the Lost American Chestnut Tree

Bringing Back the Lost American Chestnut Tree

[ ♪INTRO ] Picture a forest full of gigantic trees soaring
30 meters into the sky with five-meter wide trunks. You probably envisioned something like the
giant sequoias and redwoods that grow on the western coast of the United States. But a little over a century ago, the east
coast of America was also home to giant trees. Though somewhat smaller than their western
counterparts, American chestnuts were huge, and they were all over the eastern US at the dawn of the 20th century. Then, within a few decades, they were almost extinct. The culprit: a fungus that strangled the trees from within, brought by accident from Asia. Since their demise, scientists have been trying to figure out if there’s a way to bring the American chestnut back. And thanks to technological advances, they
may finally have a solution — if they can convince the government to let them plant
genetically modified trees. To understand what happened to the American
chestnut, we have to go back in time to the end of the 19th century. Back then, American chestnut trees were known
as the ‘Sequoias of the East’ because they had huge trunks and were tall like the
West Coast giants. And they were all over. In 1900, around a quarter of the hardwood
trees east of the Mississippi were American chestnuts — in some places, they made up
as much as 40% of the forest. But by the 1940s, they were all but gone. The first signs of trouble were seen in the
Bronx Zoo in 1904, when sores called cankers were discovered on a stand of dying trees. Scientists soon realized the disease was widespread,
and by 1912, botanists had managed to identify both the fungus responsible and its point
of origin. The chestnut blight fungus gets under tree
bark by hitching a ride on insects. The fungus then attacks and feeds off of the
trees water-transmitting cambium tissues, essentially choking the tree. The blight fungus probably arrived in New
England in the 1870s, when Japanese chestnut trees became popular ornamental plants. The imports are resistant to the blight, so
it’s likely they carried it to America where the chestnut trees were totally susceptible. And by the 1940s, it’s estimated that nearly
4 billion trees had died. But they didn’t go extinct entirely. A few scattered populations still exist, mostly
trees that people planted outside of their original range. There are also smaller specimens along the
east coast that were isolated enough from their kin to avoid infection. And it turns out that, like the Dread Pirate
Roberts, even the ”dead” trees are only mostly dead. While the blight destroyed their trunks, their
root systems remained. And even decades later, these “living stumps”
occasionally eke out a shoot of new growth. But it’s usually in vain because the blight
is still around. Although doesn’t do much damage to them,
it’s lurking in those oaks that took over after the chestnuts were wiped out. So before any chestnut shoots can reach reproductive
maturity, they catch the blight. But where there’s growth, there’s hope,
so scientists have been trying to figure out a way to bring American chestnuts back to
their former glory. Since the 1980s, forestry specialists and
geneticists have tried all sorts of things make blight-resistant trees. They attempted a technique called backcrossing,
for example, where surviving specimens and their offspring were carefully bred together
to select for natural resistance genes. But, while this method seems to work for European
chestnuts, it hasn’t worked as well with American ones — probably because the European
ones were more resistant to begin with. Researchers have also tried hybridizing American
chestnuts with blight-resistant Chinese chestnuts, but so far, they haven’t been able to get
the resistance traits to reliably pass down from generation to generation. But one method that does seem to work is genetically
modifying the trees. It turns out that wheat rust, a fungal disease
of wheat, has a similar mechanism of infection to chestnut blight. Both use a compound called oxalic acid to
soften up important structural tissues, while also attacking their hosts’ cambium by stimulating
the growth of calcium oxalate crystals, blocking the flow of nutrients. Resistant forms of wheat produce an enzyme
called oxalate oxidase, which breaks down the acid, thereby blocking the dispersal of
the disease and preventing the growth of those crystals. Scientists have introduced this wheat gene
into American chestnuts. And in 2014, they revealed that they’d produced
a 100% resistant tree that passed the trait onto its offspring — success! But… the trees haven’t been planted. Yet. The researchers have conducted some preliminary
studies to show the trees don’t cause any unexpected harm to the organisms that
live in the environments they once inhabited. And then, they requested permission from the
US Department of Agriculture to release the transgenic trees into the wild. But they’re still waiting for the green
light. And that could take a while, if it’s ever granted at all. Aside from the general anxiety that accompanies
the development of any GMO, some ecologists worry that a return of the American chestnut
would disrupt a century-old ecosystem that’s developed without it. On the other hand, if successfully put in
action, this method could also work for restoring other wild tree populations beleaguered by
fungal invasives, like elm trees. I guess only time will tell if the Sequoia
of the East will once again stand tall. Thanks for watching this episode of SciShow! If you liked learning about the efforts to
revive the American chestnut, you might like our episode on how scientists could bring
extinct animals back. And if you like what you see in general, click
that subscribe button to catch every episode! [ ♪OUTRO ]

100 thoughts on “Bringing Back the Lost American Chestnut Tree

  • I've met some older people who were alive in the final days of the massive chestnuts and they've told me about how massive they were and how some of them were so big itd be a struggle to get five men to reach around them.

  • We need this man I love American chest nut so hard of wood to get u have u scored ur own seeds well I do and then plant them i grow then and use branched as what I need

  • "GMOs are bad and unnatural!" Meanwhile, viruses have naturally been moving genes between hosts for millions of years…

  • Just last month I was lucky to see for myself a fully grown American Chestnut tree! It was a surreal experience.

  • I fail to see how adding diversity to the eco system can harm it, at least in THIS case, since it's returning a native plant to the ecosystem that it belongs in…
    And I fail to see how the forests would have trouble adapting (re-adapting) to the presence of chestnuts. We're talking decades before we see major impact, true, but we'd see signs of trouble long before the first decade, would we not?
    Frankly I despise the term GMO these days because of all the hate surrounding it. Every time someone whines to me about GMO anything I get quite tetchy and remind them that MOST of the animals we've domesticated, and ALL of the plants/crops, are nearly unrecognizable from their ancient forms because of exactly the thing they're whining about. Selective breeding is genetic modification, just slower than current techniques. And most of the crops that have been altered have been changed to improve things for us humans – a fact that gets left behind in the general fear mongering. It's the sort of ignorance that infuriates me daily.

  • I'm pretty sure my cousin has an american chestnut in her backyard. Anyway, I'll gladly grow one here in my backyard.

  • At a time when tree planting may be the best hope of stemming climate change, preventing the planting of a large hardwood with a history in the region seems foolish.

  • I'm curious as to what the effects on animals who eat the chestnut will be. There's also the birds that eat the bugs that eat the chestnuts.

  • GMOs and proper Gun control, the two things that aren't excepted in America, sorry, Murica. (Finland sounds nice this time of year.)

  • there is nothing wrong with GMO's, just speeding up adaptation a bit, plant those fungus-resistant chestnuts already.

  • I'd heard about the chestnut blight before but I had no idea they used to be such big trees. I'd love to see them come back even if they have to keep it out of the wild

  • I don't remember the chestnut tree die off but I do remember the elm tree die off. It was so sad to see street after street in our community lose their majestic trees that provided such beauty, shade, and bird and squirrel homes. The streets seem empty and bare afterward even though many replanted with maples and oak trees, it just wasn't the same.

  • I cant believe that ecologists are worried about a 100 year ecosystem that came about only because one that was millions of years old was disrupted due to an invasive fungi. Ridiculous!
    Let's see, should we restore an ecosystem that existed for millions of years? Or just let this 100 year old one take over now? Hmmm. They shouldn't even be asking that question as far as I am concerned!

  • Not to mention how we lost a banana species to fungi… and the remaining bananas might become extinct as well for the same reason

  • There is an exhibit about the American chestnut on The blue ridge parkway west of Asheville North Carolina at the visitor center. There are a few trees left in the area.

  • A shame a lot of people here don't seem to understand every plant we eat is already a GMO.. that's kinda what humans do to things, modify them until they're useful.

    Remember, corn was the size of wheat before Humans domesticated it and bred corn to produce larger cobs.

  • I think it is great that scientists figured out how to make this species "better". It is good practice for doing more useful things with genetics. Humanity does not have a monopoly on extinction. Life has been evolving and going extinct for far longer than humans have been here. I think that unless there is ongoing ecological harm, for example the lack of wolves in the yellowstone area causing deer populations to be unsustainable, we should not be reintroducing extinct or critically endangered species to the environment. Too many times we overcorrect a problem and spend decades trying to get it right.

  • LOL. Will NEVER happen. Feds will blindly plow ahead and approve GMOs when the politicians are going to make ass-loads of cash. Sadly there are no riches to be made for them by recovering from ecological disasters.

  • Theres no need in the sierra of dgo in mx theres a hole area filled with these type of trees….its sad to now that i know what they are couse people from said area use them to make fence post due to how big they are…massive

  • If you can't use hand gestures properly, don't use them at all. It just makes you look (more) like a f*cking idiot. Go get a real job, youtube isn't for you.

  • By the way , the open-pollinated cross selection with Chinese Chestnut and multi-generational back-crossing with other American Chestnut trees (work by the American Chestnut Foundation, Dr. Fred Hebard) is yielding promising results. See August 1, 2019 article:

  • Not that I'm a scientist or anything, but I would want to see some data taken over time before allowing them to be planted wild, and even then I would want them planted in open areas (not established forests) and watched for some years. We are talking about plants that live for centuries and have huge impacts on their environment. A few years of study and carefully selected propagation are not too much.

  • Just say no to gmo! Its a bad solution to an environmental correction problem, better find the bacterial strains which eat the fungus to kill the fungus.

  • I grew up on Chestnut Street. We had a huge, glorius elm tree that my mother was forced to cut down because of elm tree blight. I remember that beautiful elm tree. Sad.

  • We do need more carbon sinks in the world and trees are really good at that. If you can bring back a native species with a modified genome that allows it to once again flourish in its native environment while helping to combat global warming I'm all for it.

  • Uh, I actually had one of these trees in my yard as a kid and thought it was the coolest because I had never see any tree taller or wider. It even survived being struck by lighting twice and loosing half of its branches as a result. But then the fungus struck and we had to cut it down for safety reasons . . . I was so sad to see it go.

  • I have a beech tree. It must be 300 years old the trunk is massive. It has a root that's formed a bowl. And there is water that runs down a crack in the bark and keeps water in that root bowl. Weird.

  • To not RE-INTRODUCE a native species for such a ridiculous reason as the idea of GMO is pretty idotic. If thats your way of thinking then just stop eating All the produce that you think are "natural"….. They are all heavily hybridized for a whole list of reasons, same as GMO. Diversity is the secret of good horticulture….. and…. pretty much life in general !

  • Finally, someone shined a spotlight on the plight of the chestnut tree. About a decade ago, I had the privilege of refurbishing an historic home that was furnished with copious chestnut trim and had doors made of this gorgeous hardwood. I could not believe that this wood – very similar in grain to walnuts, only a blonde version of such – went extinct! I had no idea how large these trees grew in size. No wonder lumber companies were so eager to chop these these trees down. I feel, after all this exhaustive work to restore this species, they deserve a chance to be regrown in the U.S. Perhaps our governement can issue permits to concerned citizens to 1 – purchase these seedlings for $1000 a piece, 2 – the new owners must fill out annual reports stating how well these are growing and impacting wildlife around them, and c – take these funds and reinvest in more GMO-modified chestnut strains to perpertuate this vast regrowth process nationwide.

  • I grew up in the 60s in lower Michigan. Everywhere in the rural areas in almost any direction you chose to look, incredibly tall, dead American elm trees, most always without any bark, towered above the remaining forests. I have never seen a living, healthy American Elm. This video gives me hope, but I probably won't live to see the return of some of the greatest trees of the Americas.

  • I suggest keeping very tall trees away from populated areas as well as major roads. When they fall due to very strong gusts of wind (which has happened) there has been property damage and deaths. Taller trees in forests and trees that tend not to grow tall, in residential areas. Increasing the amount of tree foliage, is one of the things we can do to combat the buildup of carbon dioxide in the air.

  • It appears that this is about planting new fungus-resistant trees. Is there anything that can be done for those roots that are still alive from the original population?

  • Morons in charge of science. In WHAT universe is reintroducing a PLANT into it's former ecosystem "dangerous"? No, introducing a INVASIVE specie is dangerous and you idiots already DID that soooooo explain to me the utter stupidity in assuming that putting something BACK is ecologically detrimental, and show me the precedence where it failed and created MORE issues before. There is none.

  • That’s stupid to say it’s gonna mess up the ecosystem that’s developed without the chesnut when we are still importing invasive plants now but we can’t bring back a native one ?

  • Hmm, I suppose we shouldn't clean up Chernobyl or Fukushima either because the local bacteria have already gotten used to the radiation and we don't want to disrupt the new ecosystem.

  • WE HAVE OPTIONS! Go Native Tree Farm has pure seed grown American Chestnuts for sale. I helped my dad plant the parent trees 20 years ago. They're now 50ft tall and produce seeds for us to germinate and sell. Yeah they have a 50% failure rate. But sure beats the .10% we had as little as 10 years ago. I for one think we should try the blight resistant ones before we play mad scientist.

  • A law should be passed requiring that all living things be genetically modified, just to upset those people who hold particular beliefs regardless of evidence, who try to cherry pick facts to support their argument, and dismiss facts that don't. They are the real blight. Okay, I'm done ranting.

  • I am whole-heartedly for fixing things with gene modification, but I do believe transgenic organisms need to be approved on a case-by-case basis.

  • Okay I have no issue with chestnuts being genetically modified but why not find or create a virus that kills the fungas or create a pesticide to protect the tree so we can keep the chestnuts as orginal as possible

  • We humans screwed up when we brought the blight over, now we want to fix the damage we did back then.
    Wonder if in 100 years people will say, if we only knew this or that before we released the GMO versions we would have done X first, because we are smarter now. I'm not saying that there is anything wrong with them at all. I just wonder when we will be as smart as the force that put them here in the beginning, so that we won't cause more unintended circumstances.

  • The next step would probably be to crossbreed the GE trees, with the traditionally backcrossed trees, as well as surviving rootstocks, to introduce more genetic diversity and hopefully provide another layer of protection against the blight.

  • err century ecosystem does not an ecosystem really make. It depends on who owns the GMO chestnut tree. If the tree is a public product release to the commons then I'd be behind it. At the same time, GMO partly has a bad name by there own companies doing for a reason.

  • Are we not going to mention the Tim Hortons Onondaga Farms successful effort to selectively breed resistant trees in Southern Ontario?

  • You know, when we imagine green house gases, and the cause, we think of cars, and heating our homes. Yeah, that's true, but there is a ghost industry the produce just as much green house gases. It's the agriculture industry. All food we eat is heavily dependent on oil industry. Not only do they burn fossil fuels, agriculture depends on pesticides, a herbicide to maintain the crop, and live stock. Long, long ago, it was thought that if plants could be modified so didn't need oil industry provide fertilizers, and herbicides, and if they didn't have to be planted every year, billions of tons of green house gases wouldn't be dump in to atmosphere. The goal was to modify plant so they woundn't need the oil industry to support them, we could stop billions of tons of green house gases from destroying the Earth. This scaried the oil industry, and they started this Aniti GMO crazy all the f-ing morons worried about. I seen this thing were they modified Elm tree so they wouldn't die from Dutch Elm disease. They had some planted, and the GMO nuts got a court order, and had them all cut down. That wasn't bad enough, but these GMO scum bags broke in, and killed all the disease proof Elms in the lab. Now, no one wants to do the research, so trying to stop the destruction of our planet is going on full force.

  • One of my professors actually grows American Chestnuts and it’s honestly amazing. He takes good care of his trees.

  • Wasn't the loss of the American Chestnut devastating to wildlife? It's an important source of winter protein for foraging animals. I say bring it back.

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