Scientists Uncover the World's Largest Organism and it's Not What You Think | Unveiled

Scientists Uncover the World’s Largest Organism and it’s Not What You Think

When it comes to considering the world’s biggest living things, the blue whale tends to rule our imaginations. And not without reason. Not only is the blue whale the largest mammal alive today, it’s also the largest animal that’s ever lived on Earth, period. But when we expand our definition to include all kinds of other living organisms, a very different picture of Earth’s largest living thing is painted.

This is Unveiled, and today we’re taking a closer look at the natural world to uncover the true “biggest thing that’s out there”.

It turns out that Earth’s biggest organism isn’t a mammal at all, nor does it live in the sea: it’s a fungus. Specifically, it’s a specimen of the Armillaria mushroom family, also known as a “honey mushroom”. And it’s currently growing at an extreme scale in the Malheur National Forest, in Oregon, United States. The particular specimen in question bears the extremely fitting nickname the “Humongous Fungus”, and it’s so big that researchers aren’t even sure quite how to measure it. In terms of weight, estimates range anywhere from 7,000 tons to 30,000 tons, or more. All of it growing underground, overground, inside, and on top of other trees and plants. That’s what makes the Humongous Fungus so tricky to gauge; we can’t just dig it out of the ground, or pull it away from the forest, stick it on some scales and see exactly how big it is. Considering though that a blue whale, on average, weighs about two hundred tons, the fungus has no competition in the size department.

Scientists have been studying fungi structures like this since at least the early 1990s, when the first of really notable size was discovered in Michigan. That specimen was also Armillaria and had grown to a massive size of thirty-seven acres. And these incredible structures really are one big, continuous organism, too… not thousands of small ones. The Michigan specimen has since been dwarfed by the discovery of the Humongous Fungus, however, which covers more than 2,300 acres. It was first investigated back in 1988, but the true scale wasn’t known until much later, after years of careful study.

Armillaria doesn’t only grow in the US. It’s common across North America and Eurasia, too, and in some parts of Europe, it’s considered a delicacy. Be warned, though, because Armillaria mushrooms are also mildly poisonous. When eaten raw, they can trigger stomach cramps and mild illness. And armillaria does look very similar to other VERY poisonous mushroom types, as well… so if you’re foraging for them, you must carefully research and know EXACTLY what you’re doing.

For every Armillaria that is eaten by a human or animal, however, there are hundreds – potentially thousands – of trees and plants getting eaten by it in turn. Yes, this most massive of mushrooms is also deeply parasitic by nature, which is one reason why they’re so closely watched and studied. In short, specimens like the Humongous Fungus are bad news for the trees of Oregon, because they can infect and eventually kill them on a massive scale. The disease caused by Armillaria infection in trees - “Armillaria root rot” - is now a common ailment of the natural world, and it’s vicious. The rot creates a pathogen that lives in soil and gradually infects nearby plants, killing them from the inside out. There’s no cure for it and no real way to get rid of it. If you’re a gardener and notice the rot taking hold in your plants, then, you basically need to destroy all the infected plant life. As with most diseases, prevention is a better option. Although unfortunately, there’s no sure-fire way to guarantee it won’t take hold.

With all of this in mind, Oregon’s Humongous Fungus is definitely here to stay. Prevention is totally meaningless because it’s thought to have existed by now for millennia, around 2,500 years. That means the mushroom started growing about the same time Socrates was alive, and it’s now so vast that there’s nothing we can do about it. It’s gotten a lot more widespread in recent years, too, infecting more and more trees and plant matter to the extent that whole swathes of Malheur National Forest are today totally dead except for the Armillaria specimen.

But this can’t be normal, can it? If giant mushrooms took over huge areas of forest as a matter of course, how could we possibly have any forests left today? Well, one reason is because human action is partly to blame for the spreading Armillaria, specifically. And it links back to forest fire management. In the 1940s, the US Forest Service embarked on a successful campaign to prevent forest fires, creating the famous mascot Smokey Bear to spread the message. This meant that, for a while, people believed that doing everything possible to stop all forest fires was the best way to care for America’s national parks. But more recent research has found that, actually, there were negative knock-on effects – including the rise of fungus.

Though the message to stop any and all wildfires was rooted in a genuine fear of them, thanks to previous fires causing massive loss of life, it’s also the case that wildfires are a vital part of the ecosystem. Decades of putting out as many fires as possible, then, has meant that layers and layers of dead tree and plant material have been allowed to build up on America’s forest floors. In the days before intervention by humans, naturally occurring forest fires would have purged all of this decaying matter, giving the forest a fresh start, time and time again. But now, there’s so much material that hasn’t been routinely purged (because of efforts to halt the fires) that if (and when) a wildfire does happen, it’s today significantly worse than it might have otherwise been. It’s why ecologists, for years, have been calling for controlled burns in some regions… to reinstate what nature was once allowed to do.

So, how does the Armillaria come into it? Well, to some degree, the reason it has been able to grow so significantly is that it has taken over the role of clearing out forest debris. As it does with living matter, the fungus eats into the dead… creating a similar (but also unfortunately different) cycle of life. Because the now uncontained fungal growth can be seen as essentially a symptom of the traditionally mistaken approach to fire management. It's been allowed to feed and spread through a build-up of decaying plant matter, and now it’s the largest organism on Earth and it’s going nowhere.

For now, if there is a fightback that we can mount, it’s through those controlled (or “prescribed”) burns. As we move through the twenty-first century, expert teams are increasingly targeting forest to intentionally raze. These burns don’t happen during the dry and dangerous summer months, but in colder, wetter parts of the year where the weather is much less likely to make the fires worse. The irony is, though, that this isn’t actually a recently developed strategy… but, rather, a forgotten one. Controlled burns similar to today’s were used by Native Americans for centuries, and long before European colonists arrived. And records show that they were actually still done with relative consistency until the early 1900s, at which point the now-known-to-be-disadvantageous fire suppression strategy took hold.

Ultimately, however, it’s not as though Armillaria is the only parasitic mushroom we should be concerned about. Some scientists believe that it might not even be the biggest, with predictions of even larger specimens out there, lurking under and overground and quietly killing off trees, waiting to be crowned the next “largest organism on Earth” – succeeding the Humongous Fungus. As daunting as it is, Armillaria probably isn’t the outright scariest mushroom in the world, either. That title likely goes to the Cordyceps fungi, a variation of which has for years been touted as carrying the potential to someday cause something close to a real-world zombie outbreak. Cordyceps currently infects insects only, mainly ants, and there’s no evidence that it could make the leap to humans. But the way it’s been found to consume and eventually kill all types of bug… is more than a little unsettling.

Oregon’s Humongous Fungus perhaps isn’t quite so fundamentally sinister… and yet, it has still made a quiet and quite merciless journey to today reign absolute. To commandeer a forest. At the top end of estimates, this thing could be many, many times larger than even the biggest blue whale. It looks set to keep on growing, too. And so, no tree is safe… because that’s what the world’s largest organism really is, and the damage it can cause.