Over the past 25 years, scientists have presented us with a captivating, almost Disney-esque tale. Imagine a diverse and vibrant forest, filled with trees of different ages and species, all thriving in the sunlight that powers their cellular functions. But hidden beneath the surface, intertwined within their roots, are thin, hair-like strands of a different kingdom altogether. These branching structures serve not only to expand the reach of each individual tree, but they connect multiple trees together, allowing messages to be communicated in a buzzing, multi-server system akin to the invention that changed the course of human civilization. The Internet. Welcome to the Wood Wide Web. I'm James Stewart and you're watching Astrum Earth. Now buckle up because we're about to recount a scientific tale with more twists, turns and knots than an old oak tree. The discovery of the Wood Wide Web mesmerized the public as much as the Internet itself, resulting in the publication of countless popular science articles, books, documentaries, films, podcasts and more. But is there more to the story? A growing number of scientists certainly seem to think so, and the result has been a bitter academic war that still continues to this day. In this video, join me as we uncover the whole story behind the famed Wood Wide Web, where it all began, its impact on conservation, and the wealth of research it inspired into the secret lives of our wooden friends. Our story begins in the temperate forests of British Columbia in Canada. Suzanne Simard is about to make a discovery that will help her to achieve the near impossible with her PhD thesis, making the cover of Nature. In 1997, her article was published with the title Net Transfer of Carbon between ectomycorrhizal tree species in the field, which is fairly unassuming considering the content of this paper. In essence, Simard was claiming to have observed the transfer of carbon between seedlings of paper birch and Douglas fir in the field, through a shared fungal connection between their root systems. Not just any old fungus can form a connection with trees. This privilege is mostly reserved for mycorrhizal fungi. The term mycorrhizal fungi refers to a broad group of species that have been forming beneficial partnerships with plants for over 450 million years. Their name comes from the Greek mikes meaning fungi and riser meaning root, which is accurate because these fungi form their relationships with the roots of their plant partners, extending the reach of the plants through a fungal network called the mycelium. These networks are so vast, it's estimated that every 1 kilogram of soil can contain up to 200 kilometers of fungal strands, and some individual fungi can extend across 100 square meters. With this impressive reach, the fungus can help its plant friends to absorb more nutrients from the soil in exchange for some of their sugars. This is an example of symbiosis, because both parties get something good out of the relationship. Scientists already knew about this network at the time of Simard's research. All the way back in 1885, the German plant biologist Albert Bernard Frank wrote a paper describing the symbiosis between plant roots and mycorrhizal fungi in Prussian truffle districts. And throughout the 20th century, scientists had documented the transfer of carbon, nitrogen and phosphorus through fungal connections in lab experiments. But what made Simard's discovery so exciting was that she claimed to have seen trees using this network to transfer carbon out in the forest, which was a big deal. In the forest, there are far more variables at play, some of which are near impossible to replicate in a lab study. Anything that you observe in these natural environments is a far more realistic snapshot of what is really going on, so it's often the final piece of evidence needed to prove a theory. This was no different for the theory of a wood-wide web. Scientists knew it existed and had some idea of what it could do, but for many, Simard's research provided definitive evidence that these ideas hold true for real-world habitats. Now, as I'm sure you're wondering, how did she do it? Well, the study looked at paper birch and the Douglas fir trees because they are known to make the same type of fungal connections. Each seedling was given a dose of carbon dioxide gas, which was labelled with different isotopes of carbon, so the team could track where this carbon ended up. On top of this, the Douglas fir was kept in the shade, so that it would make less of its own sugars by photosynthesis. The experiment ran for two growing seasons, and the results were astounding. Simard found that the labelled carbon dioxide had been converted into sugars by photosynthesis in the paper birch, then transferred to the Douglas fir through their fungal link. Some carbon had travelled in the other direction too, but since the Douglas fir was struggling to make sugars in the shade, the paper birch had transferred more carbon to it overall, resulting in a net carbon gain in the Douglas fir. In other words, these trees weren't just going Dutch and spitting their carbon equally, the paper birch was giving extra carbon to the Douglas fir. The team were shocked by this result, and naturally started coming up with some ideas as to why the paper birch was being so generous. This led them to wonder, could it somehow sense that the Douglas fir wasn't making as much carbon on its own? This theory was outrageous. It seemed to tear apart the widely accepted concept of survival of the fittest. Instead of everyone looking out for themselves, we're talking about two different species helping each other via a shared connection with a third, even more, distantly related species. Though they are different, these tree species are competing for the same resources, light, space, water and nutrients. So why don't they just keep everything for themselves? Could it be that they share because their generosity will eventually be returned by another member of the forest? Simard's findings suggested that trees formed far closer in communities than we once thought, and that resources were shared to boost the overall health of the forest, aided by some seriously helpful fungi, of course. And on the cover page of Nature, with the catchy slogan, Wood Wide Web. This discovery caused quite the stir, and the idea that trees had beaten us to the punch with their own internet with wooden servers and fungal routers really caught on. There were articles on the hidden language of trees, manuals on deciphering tree feelings, documentaries, TED Talks and Bizarrely, even a name drop for Simard in the hit show, Ted Lasso. If you look at the use of the phrase, Wood Wide Web, in publications between 1997 and 2022, you can see an exponential increase in popularity from the early 2000s. The Wood Wide Web had even spun its silk over Hollywood, with Amy Adams set to star as Simard in the feature film adaption of her research career. The world, it seemed, had gone tree crazy. But Simard took things one step further, publishing a book titled Finding the Mother Tree in 2021. The book is essentially a memoir, telling the story of Simard's professional and personal life against the backdrop of the Canadian forest. Besides her 1997 research, Simard discusses her discovery that fungal networks can allow for warning signals to be communicated between trees, kin recognise, and preferential treatment applied to closer relatives. She even suggests that the fungal network in forests works like a human brain, with the fungal strands as neurons and chemical signals as neurotransmitters. This concept transforms the forest into an ecosystem where no tree stands alone, and familiar bonds can get you through hard times. With a picture like that, who wouldn't have the urge to run to the nearest forest and hug a mother tree? It certainly was a beautiful idea, that organisms from totally different kingdoms, plantae and fungi, could come together in symbiosis to promote communication across the entire forest. It had the potential to revolutionise the way we thought about conservation going forward. More emphasis could be placed on maintaining mother trees in the forest. But perhaps even more revolutionary was the idea that trees were more like us than we thought. They too could speak, could provide for their kids, give preferential treatment to their friends and maintain a social life. Amid these global shifts in perspective, it seems like the golden opportunity to seek similarities between us and the plants. In fact, these scientists were giving us the green light to do so. The world had certainly fallen in love with the woods wide web, but like a tree being felled, it was all about to come crashing down. Justine Kast, Jason Hooccymer and Melanie Jones. These scientists shared something vital in common. They had all worked with Suzanne Simard at some point in their careers. Melanie Jones even co-authored the famous 1997 paper that started our story off. Despite sharing Simard's belief in the woods wide web for years, these three tree experts had begun to get an uneasy feeling about where it was all heading, both in academic circles and the wider media. So they did what any good scientist would do and asked the difficult questions, forcing themselves to look objectively, even if that meant casting doubts on their own research. In a later interview, Kast explained that they didn't initially set out to debunk any of Simard's claims about the woods wide web. Re-reading the literature had forced them to face an uncomfortable truth about the fungal networks they had once put so much faith in. Unnerved by what they found, the authors voiced their concerns in an article published in 2023 to greater claim by the rest of the science community. This article garnered almost as much attention as the 1997 study that had inspired it and brought the dream of the woods wide web as we knew it to an abrupt end. But what did the authors take so much issue with? In their paper, Kast and her colleagues reviewed all research surrounding what they call common mycelial networks, which is just a more technical term for woods wide web, where mycorrhizal fungi connect the roots of the same of different plant species underground. We'll call it the network from now on to make things simpler. They identify three common claims that have been made about these networks and sorts to review each claim in turn to see if the evidence agreed. The first one, namely that the networks are widespread in forests, was fairly simple to explore. Many mycorrhizal fungi can and do form associations with lots of different host species, which would suggest that networks are common in forests. However, there is a problem, because we can't really observe these networks in situ, that is in the forest itself, as you would damage and fragment it before you could tell whether it was one continuous connection or not. Each fungal strand is only about the width of a human hair after all. There has been research mapping the presence of mycorrhizal fungi using techniques like machine learning, but to actually know whether these fungi link together in one big, continuous network across a forest. Well, scientists would need to analyse the DNA of the fungi and the plant roots they attach to everywhere in the woods, well at least in as many different locations as possible to see if they match up. It's a long, expensive and slow process and had only been done by five studies for two tree species at the time the authors were writing. The point is that even though these networks do form, we can't be sure that the links are continuous enough through time and space to make them a viable tool for communication. For all we know, the links might only last a few days, or could be too fragile to connect trees from opposite ends of the forest. The second claim was that seedlings can use the network to share resources, like the carbon we saw earlier, in order to help them grow, and not just within the same species. This one hit especially close to home for the authors, because they had all worked with Suzanne Simard on this and her 1997 study was the first to properly test it out in the field. But what Cast and her colleagues started to question years later was that this behaviour doesn't seem to lie within the fungi's self-interest at all. Think about it, if you were a fungus connecting the roots of two tree species, why would you only ever find resources between the two trees, rather than taking some for yourself? And how is the fungus supposed to know the difference between carbon it can use for itself, and carbon to be sent for Paper Birch's friend, the Douglas Fur? The authors reviewed 26 studies that claim to prove resource transfer through the network, and found that for all of them, the results could be explained without involving the network at all. For many, the resources could just have easily been transferred through the soil with no need for fungal connections, and that includes the 1997 study. Similarly, the authors note that no study has actually provided proof that this transferred carbon, if it exists, actually benefits the performance of the tree receiving it. How could it? If you were a tree with a system to generate food and find resources on your own, why would you depend on help from an unrelated neighbour tree, one that could easily die, become disconnected, or simply stop cooperating? It doesn't seem like a very good strategy evolution wise. Well the authors weren't finished there. The final claim was that mature trees were more likely to communicate and share with their own offspring through the network, which largely covers the whole mother tree idea. And this one may be shocking, because the authors actually found no published peer reviewed evidence from forests at all to support this claim. In fact, a master's thesis from Simard's own lab actually found the opposite. As Douglas Furs placed in a shared fungal network, were less likely to survive if they were close to their older genetic relatives in the field. Even more uncomfortable is that Simard made a narrative choice to write in her book that the grad student had found support for her theory, even though she has since denied that she was deliberately misleading her readers. To top off their review, Cast and her colleagues looked to see whether there had been any bias in the literature surrounding the network. They identified 18 studies that had been influential in this field, and looked at how they were used in subsequent research. There can be a tendency for more positive or more interesting results to be cited more than those that are neutral or disagree with the hypothesis, even if methodically the research was correct. It's called positive citation bias and can lead to misconceptions being spread. And sadly, that is exactly what the authors found in this case. There were nearly 1700 papers citing the 18 original studies. Around 25% of them were misinterpreting these studies as support for claims about network structure, and 50% of them for claims about network function. To give just one example of this bias, several of the 18 papers have reported evidence that networks could form. But many papers published later had cited these studies as evidence that networks were present in forests. In research, wording is everything, and evidence suggesting that networks can form is not the same as evidence that they do form in complex real-world habitats. But you can see how that kind of positive bias is a bit of a runaway train, and if even published researchers are doing it, then it's bound to happen in the mainstream media too. As you may expect, Simard wasn't too pleased when the Wood-Wide Web began to unravel at her feet, calling casts review paper an injustice to the whole world. She labelled all the critics as reductionist scientists, and has since published response articles pushing back on some of their arguments. Now although we're often quick to take sides during a drama, it's important to note that there are no heroes and villains in this story. Some scientists may disagree with Simard's stance, but others don't. And if nothing else, Simard has done good work for the forest too. Her 2015 Mother Tree Project is a research initiative aimed to protect the biodiversity of British Columbia woodlands, drawing on indigenous knowledge and changing forestry practices in North America to be more sustainable. These are admirable goals, goals which we can agree are probably good for conservation regardless of whether the person advocating for them believes in the Wood-Wide Web or not. Like many scientific arguments, the situation has become messy, with researchers picking at details and scrabbling to express where they stand on the matter. Unfortunately by the time the smoke clears on this debate, the public may have lost interest in the result, and scientists will definitely struggle to garner the same kind of enthusiasm that once buzzed around the Wood-Wide Web. But as Kars says, our job as scientists is to present the truth, as close as we can get to it. Errors, misinterpretation and even over-excitement are all traps that scientists and the media reporting their findings can fall into. We are all human after all. So we need to always be open to reflect objectively and update our presentation of truth as we gain new insights. And one thing scientists can all agree on, these revelations about the Wood-Wide Web should never be used to discount trees altogether or neglect their conservation. Now with all that disillusionment behind us, it's time to move on to something more concrete because we may be unsure about the extent of plant communication, but there is no doubt among scientists that plants do communicate. Moving from sink to source, plant leaves can be the trigger for vital messages. Volatile organic compounds or VOCs encompass a large group of molecules that tend to have a low molecular mass so they can evaporate easily and travel through the soil or air. For several decades now, scientists have suspected that they play a role in tree communication, particularly when trees are exposed to stress. Because trees can't just run away from predators, they may have adapted to make use of VOCs as a warning signal in the event of an attack, giving them more time to prepare. A 2013 study cut the leaves of willow trees to mimic the damage caused by nibbling creatures. This caused them to release VOCs and as a result, neighbouring trees were there more likely to be munched on instead. The same was found in another study, this time on alder trees. They saw the same effect, but, funnily enough, trees further from the damaged ones showed weaker resistance to herbivores, suggesting that if a signal was involved, there was a limit to how far it could travel through the forest. So we've discussed some of the evidence for VOCs being used in communication. But how did scientists piece this together into a theory of what was really going on? These studies were suggesting that when a tree is attacked by a herbivore and damaged in some way, its neighbours could pick up on this and prepare themselves for an attack. This is possible, as trees have a host of chemicals they can use in herbivore defence, like bitter tasting tannins or toxic alkaloids, which have been shown to be effective tools in fending off pests. And scientists could be pretty sure that it was VOCs that were inducing these responses, since any efforts to block airborne signals by putting the tree branches in airtight bags meant that neighbouring trees took more damage from the herbivores. But hang on, because there's a danger here of entering into the same minefield as the wood-wide web drama. This behaviour seems too selfless to work with the principle of survival of the fittest. Why would a tree bother to send a warning signal to its neighbours whilst it was being attacked by herbivores? Wouldn't it be better for that tree if its neighbours did get damaged, since that might leave more light and other resources for itself? But consider this, what if the damaged tree wasn't intentionally sending out a warning to help its neighbours? But the neighbours had evolved to make use of a warning that the damaged tree was releasing anyway. Scientists call this eavesdropping, and it explains these results in a way that agrees with why the accepted principles of natural selection. Any individual plant produces many VOCs when it's attacked by herbivores, to signal to itself, coordinating a response between distant branches or leaves. It is this signal, meant for communication within each individual plant that other plants can pick up on and use to prime their own responses. So trees have adapted to eavesdrop on their fellow trees in the forest, but perhaps more impressive is their ability to call for help during an attack. From the most unlikely allies. Turpenes are a specific group within the VOCs, and are responsible for that nice tree smell you get when you walk into a forest. These molecules are also used in tree communication, in response to herbivores, environmental stress, and changes to the soil microbiome. In 2011, an experiment looked into how the European field elm responds to attacks from the elm leaf beetle, with the help of turpenes. See, the elm leaf beetle likes to lay its eggs on the leaves of the tree, ready for the larvae to feast on them when they hatch. But the elm has some tricks up its sleeve to combat this. They release turpenes, which seem to attract another insect. The eufelid wasp to eat the eggs. Like insect bodyguards, they can protect the elm from damage and get a nice egg feast as a reward. The 2011 study was designed to prove whether it was the turpenes that were signalling for wasp backup. So the authors allowed the beetles to do their thing and lay eggs on the elm, whilst treating half of the trees with chemicals that stopped them from being able to make turpenes. They then collected all the odours produced by the trees during this ordeal, and presented them to the wasps to see what they'd do. As the team suspected, the wasps spent significantly more time in the test field when the tree odours included turpenes than when turpen production had been cut off. With these results, the authors concluded that it is the turpenes that attract the wasps, and that the trees are far more skilled at fending off beetle attacks than we make it So as it turns out, trees have some amazing ways of interacting with the world around them. Like any living thing on earth, trees can sense changes to their surroundings, and have employed sweets of molecules that help them to respond, whether it's seeking out food, preventing attacks, or calling out for help. So yeah, trees are amazing, but just maybe not in the way we thought. And if nothing else, the pushback on the Wood Wide Web should motivate us to understand trees better as there are still so many fascinating answers to be found. I'll be honest, I originally expected to tell a more traditional story of the Wood Wide Web, exploring a forest of trees that are all for one and one for all, assisting each other with their intricate network of fungal friends. But thanks to this new research, that is definitely not how the story unfolded. But I hope you'll agree that this is still a tale worth telling. Though they strive to be, scientists are not always right. Ideas can and should be questioned, details revised, and corrections made as their research unfolds. Ideas is built on debate and continuous pursuit of knowledge and truth, no matter how long it takes to find what that truth is. Sadly, the Wood Wide Web may be one of those cases where our heads would turn before the real truth came out. I hope this video can go some of the way towards setting the record straight, and show that the world of popular science isn't always as infallible as it may seem. And who knows, maybe next week the world will be captivated by a new narrative with an equally catchy name. But by then, hopefully we'll have learned from the Wood Wide Web, and we can start looking more closely at the results and where they come from before we start signing book deals and making calls to Hollywood. So let's stay curious, look a little closer, and keep giving the trees the attention they've always deserved. There is so much they can do, and they are a huge part of what makes our planet such a wonderful, thriving place to call home. Fortunately for us though, the World Wide Web is very real, but does face similar issues to the Wood Wide Web, especially when it comes to people trying to steal your resources without you necessarily wanting them to. Here's a quick message from today's sponsor, CyberGhost VPN. And I'm sure if you spend a lot of time online, you've heard of VPNs by now, but what do they actually do? 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