Scientists Mapped Earth's Vast Fungal Network - And It's Critical For The Climate

0:00Study and play. Come together on a Windows 11 PC. And for a limited time, college students get the best of both worlds. Get the Unreal College deal. Everything you need to study and play with select Windows 11 PCs. Eligible students get a year of Microsoft 365 Premium and a year of Xbox Game Pass Ultimate with a custom color Xbox wireless controller. Learn more at windows.com slash student offer. While supplies last, ends June 30th. Terms at aka.ms slash college PC. You've heard us talk on the podcast about the wood wide web. That's the idea that plants communicate and maybe share resources through a network of underground fungal connections.

0:39That's controversial, but what isn't is that there's an ancient symbiosis between plants and fungi all over the world. Plants provide food to the fungi, and the fungi provide nutrients to the plant. We knew this symbiosis was vital, but we didn't know the extent of this underground fungal network. Now for the first time, scientists have made global maps of the distribution. And the extent and the mass of these fungal networks is frankly insane. If you put all the networks together in a line, it would run between the Earth and the Sun a billion times. And the consequences for our understanding of carbon storage, the movement of water and all nutrients underground are profound.

1:23From New Scientist, this is The World, The Universe and Us. I'm Dr Rowan Hooper. To discuss this first global map of mycorrhizal fungi, I'm delighted to be joined by scientist Toby Kears from the Free University of Amsterdam, Tom Shimizu from the Amalth Research Institute in Amsterdam, and Merlin Sheldrake, author of Entangled Life and also a member of the Free University. Welcome all of you. Thank you so much. Thanks for having us. Let's start with the basics for people who only know about mushrooms. What's the mycorrhizal network? Almost all plants form relationships with fungi that live in and around their roots and which gives them access to the soil.

2:02These fungi are, they grow shape-shifting networks, they're metabolically ingenious and they're able to forage for nutrients in the soil. And they trade these nutrients with plants. So plants in return for these nutrients provide the fungi with carbon compounds like sugars and fats that they've produced in photosynthesis. And there are lots of different ways to be a mycorrhizal fungus, as these fungi are called, myco from root, myco, mycophungus and rhizoroot. And we, in this case, we're studying one type of mycorrhizal fungus called arbuscular mycorrhizal fungi. And what's happening is the fungi are actually penetrating into the root cell and making this beautiful structure called an arbuscular.

2:42And that's the site of nutrient transfer. Now the symbiosis is defined by carbon being taken out of the atmosphere by plants and fed down into these living mycorrhizal networks. But it doesn't come for free. The networks are growing out into the soil foraging for phosphorus and nitrogen and water that they trade back for this carbon. And so that has been known for some time. But what you've done now is just really reveal the extent of it because that's what we didn't have a good grip on, right? Exactly. So this is the first time when we've actually been able to build predictive maps of the density of our muscular mycorrhizal fungi.

3:22And just as the circulatory system moves resources through a body, these microscopic networks of living fungi, they connect the plants to the soil and form this infrastructure of terrestrial life. Okay. And do you want to take us through some of the details, some of the methods of how you did this? Maybe you, Toby or Tom, some of all this robotic imaging you've done. Well, first, let's start with what was already published out there. And this is a big call out to all the scientists across the world who actually went out and put a core into the ground and extracted soil. There were 16 ,000 individual cores that were part of this study.

4:01And these covered the earth. It was about nine of the 14 vegetative biomes. And because each one of these cores was geolocated, it means we have lots of information from data layers and satellites that tell us about that exact place. And that includes elevation and nutrients and water, precipitation. And so we're able to build these machine learning models that took the data from those places where cores were extracted and the fungal hyphae were actually counted and then make predictions in places where cores had never been taken. And that's how you start building these global maps. OK. And tell us a bit about how you've automated this process, because that's what's allowed you really to make this do it at scale, isn't it?

4:52Exactly. So the important part is that that starts to form what we're able to estimate for the density of these fungi across the earth. But to actually understand the mass, the biomass of how much these networks weigh, then we had to start really understanding the bodies of the fungi themselves. And this is where Tom's work was really important. Yeah. So I think the key thing here is that the mass depends not only on the length of these networks, which was something that was in this counting that everybody did all over the world from the field. But what wasn't included in that information is how wide each HIFL tube is.

5:37And it's that information that we were able to fill in in a highly automated way. So to do that, the big challenge is that biomass, of course, depends not just on length, but on volume. And volume depends. They're mainly like a cylinder. So you have a length of a cylinder and the radius of the cylinder. So estimating that radius was really key. But what we learned from our robotic imaging, which is basically what we've been building up for the last few years within the lab here to complement all the nice work that is done in the field, we now have the ability to image completely every single hyphal tube in these mycelial networks.

6:26And what we found is that there's a huge variation in the width of these tubes. And if you look in the literature, people have tried to relate their length estimates to biomass, but they always have to give a guess about how wide these tubes are. And they do it based on some number of images, but they never have been able to sample completely. So if you take the range of widths that people have used in the literature, there's more than a tenfold range. and because the volume scale is like the square of the width, it's more like two orders of magnitude uncertainty that existed. And with the robots, we were able to really get the full statistics of how these things vary, both within individual species but across a diverse set of species.

7:21That's what I was about to say, is it because of those two things? So they vary within and between species. And Toby, when I visited your lab a couple of years ago, I saw some of these real-time images of the nutrients moving through the network. And it absolutely blew my mind, actually, the speed and the amount of stuff that's being transferred through these. And that's just on a tiny, on one bit. So if you try to scale it up, then you start to grasp an idea of just how much transfer is going on in these things. Exactly. these fungal interactions are really important in regulating the climate.

8:00We know that just the arbuscular mycorrhizal types alone are responsible for drawing about 4 billion tons of carbon every year. So that's roughly 11 % of emissions from fossil fuels. And just this idea that they're able to take that carbon from the plant root and get it very deep into the soil horizon. And especially if that carbon, if it clings on to minerals, it tends to stay down much longer. So we're just learning more and more about how important these fungi are in the carbon cycle. Yeah, I want to get onto what we can do to protect that resource and that ability to lock down carbon in a minute.

8:43But on the activity of the hyphae, Merlin, something I want to ask you about was after I'd seen this activity, I remember this quote from a biologist, Nicholas Money, who said, sensitivity or irritability are not the same things as consciousness, but they are starting points in considering whether filamentous fungi have minds. And, you know, when I saw the network, the movement in the network, you can't help thinking, or I couldn't help thinking about what is going on here in a kind of fungal intelligence. And is that idea being taken more seriously now? I think the idea that intelligence is not limited to humans and higher animals is certainly being taken more seriously.

9:28And I think that's opened up lots of really interesting frontiers and lots of new and exciting questions, which can better help us understand the living world. So these fungi, they are sensing bodies. They're bathed in rich fields of sensory information. They have to integrate these different data streams in their rambling, constantly shape-shifting bodies with no center of operation, no central place to integrate those data streams. And they're responding moment to moment to what's going on around them. And they have to. That's how they do what they do. So there's an astonishing kind of vertigo that I think some of us feel when we're watching these organisms behave in real time because you're watching them solve problems without a brain.

10:15You're watching them navigate a changing world in ways that are so different from the ways that we do it. How can we next start to interrogate that mind or that fungal intelligence of what they're doing? Are there people who are trying to test this? Yes, we're working on this in the lab with this astonishing automated system, which allows us this unprecedented view into these fungi as they behave in real time and allows us to ask questions that were simply not possible to ask before. Amazing. So look, we mentioned what we need to do to protect them. And one of the findings of this new study, Toby, is that about 40 % of these arbuscular mycorrhizal fungi are in grasslands.

11:02And that's some of the ecosystems that are particularly a threat at the moment. So what does that mean? What does that mean we should do to protect these systems? Well, grasslands have just been so underappreciated for so long. And what we found was that about 40 % of the mass of our muscular mycorrhizal networks are found in grasslands. And some of the densest networks on Earth were in really unexpected places, like the flooded wetlands of South Sudan, the Tibetan Plateau, the Everglades in Florida. These are all places that haven't received a lot of attention in terms of conservation. And that's what we're trying to do now.

11:46There's a big push. For example, we're going to be going to COP17, desertification COP in Ulaanbaatar in Mongolia, and start to show these data sets to decision makers to say that these fungi are really critical in preventing desertification. And then we need to sort of flip our bias. We have such an above-ground bias right now, and we really want people to think about conserving underground ecosystems and conserving these fungal communities, because they're going to be so important in restorations of lands globally in the future. Most of us worry about memory lapses as we age. But how do you know when it's something more serious?

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13:25apply. Need a hiring hero? This is a job for Indeed Sponsored Jobs. One of the reasons grasslands are under threat is not just because of climate change, but also because of land use demands and the demand for extra agricultural land. And one of the other things that jumped out at me from your study is that you found that these large agricultural cropped lands are associated with about half the amount of fungal network density than the average that you found. So what's that telling us about what agriculture is doing to this really important symbiosis? Well we have to be careful about these data sets.

14:04What we found was that on average these croplands had about 50 % decrease in network density but we weren't able to pinpoint specific agricultural practices that led to that decrease. We know from past work that mycorrhizal networks can be suppressed by things like fungicide. By definition, fungicide kills fungi. Similarly, high input fertilizers, chemical fertilizers, if you're dousing the soil with these nutrients, then the plants stop feeding carbon to mycorrhizal networks. We also know that breeding has changed the way that crops interact with their mycorrhizal partners, often supporting them less if they're really highly bred.

14:48So we do know that there are specific agricultural practices that can decrease network density, but that doesn't mean that all agriculture is bad. And that's a really important point. There are agricultural practices that can really stimulate mycorrhizal density, really healthy ecosystems that even grow larger and healthy under crop rotations. So, again, it's looking at this across all of the earth and really trying to understand what is happening during this land conversion and how can we bring those healthy mycorrhizal networks back. Yeah, I mean, I thought you were quite circumspect in the paper about that, about not assigning blame to, you know, not all agricultural practice.

15:32But, you know, we know that industrial farming does have these impact on symbiosis. It causes dysbiosis, breakdown of symbiosis. And it's funny because I read in, I was rereading Silent Spring. And even in that, Rachel Carson says she warns of this back then. She doesn't use the word symbiosis, but she says a curious but beneficial relation between fungi and the roots of higher plants is seriously disrupted. So she was warning of this breakdown of the thing that you're mapping, you know, 65 years ago. So, you know, it's taken a long time, but thank God we're there now, starting to really map this out and show it and get people's attention on this.

16:17Exactly. We were really shocked by that number. At the same time, we're really trying to concentrate on all these places where there still are really dense mycorrhizal networks and really understand the reasons why they get so dense. I think that's another thing that is still unknown, is trying to understand, define what is a healthy underground ecosystem and what drives that health. This is something that we're working on with researchers around the world. Merlin, fungi have been ignored in conservation or certainly neglected. And your work and Toby's and Tom's or this new paper, it's going to help change that.

16:57What can people do? Is there anything people can do? Like we can change our eating habits if we want to, say, reduce the pressure of farming meat, for example, or we can ride a bike if we want to cut down on fossil fuels, that sort of thing. What about for increasing awareness of the importance of fungi? It depends who you are and how you live and what you're interested in. but on the whole taking interest in soils taking interest in what happens below our feet whether that is changing the way that you plant your window boxes whether that is changing the way that you farm or manage an orchard maybe it changes the way you walk through a park yeah it's a little hard to to to come up with um a simple action that everyone can do but on the whole sending our attention down to the soil i think has the potential to change a lot of the decisions we make from the food that we choose to eat to the um the places we choose to spend time and and just how we orient you know just sticking your hands in the soil that's um an amazing practice yeah and smelling it tasting it yeah tasting it um well because soil that's also been super neglected.

18:14I mean, weirdly, farmers have always known its importance, but they've also maybe abused what's going on in the soil. Because tell us about the amount of carbon that's stored, because it's an incredible amount, isn't it? It is. Well, we know that 75 % of all terrestrial carbon is stored in soil systems. So this is sort of a massive percentage of terrestrial carbon, And soils are incredibly important for this. Mycorrhizal fungi and their role in climate is really a new topic in the sense of being able to quantify the role. And there's still so many unknown questions. For example, we know a lot of carbon goes down through these pipes.

18:5313 billion tons of CO2 every year are processed by plants and fed to mycorrhizal networks. But how long does the carbon stay down there? And what is it attaching to? In what form is it most able to stay underground? We know, for example, that the networks themselves, even when they die, they form this beautiful scaffold called necromass that holds soils together. And even if you lose that skeleton, you're going to have more soil erosion. You're going to have more loss. One of the big open questions right now is trying to understand the deep soil layers for carbon storage. So we have a project where we're actually trying to take cores under a meter down to understand what fungal communities are deeper in the soil profiles, because there is some suggestion that they're different down there, that they respire less, that they're slower growing.

19:47And so if you can get the carbon down there, it tends to stay longer. So again, big global surveys trying to understand what's down there. Even in this data set that we are working with to publish this paper, I think about only 2 % of the data came from 15 centimetres or below. So all the data sets are really concentrated on that top layer. And that's one of our big uncertainties right now in these models is really trying to understand what happens in the deeper layers. Yeah, because roots go much deeper than that. And so there's going to be a whole lot more going on there. When you were talking about what happens when it dies, It made me think of one of the criticisms of the Wood Wide Web, and this is a bit different to your work, but has been the durability of the networks.

20:32And I wondered if your work sheds any light on how long these last. It's still a very open question. And carbon scientists around the world are working hard to answer the question about durability. And it really actually, this data set is important because we had even a hard time understanding HIFL turnover, meaning how many times per year does the body regrow and die? And the numbers are very wide, very, very wide variation in what scientists are finding for that HIFL turnover, both in the lab and in soil systems. But that can change the entire magnitude of how much carbon is going down below ground.

21:10So we're trying to take uncertainty incredibly seriously because this is important. I mean, if fungi are playing this major role, we really have to understand what are the open questions. And so another big open question is trying to understand ecosystems where samples just haven't been taken before. One of the most important parts of this paper is that we show in figure one a map of the density of these arbuscular microhousal networks across the Earth. but panel two right below that is a map of uncertainty and what that tells us is there are parts of the world with really high uncertainty and we need to go to those places work with local scientists and understand those fungal communities because these are places where the model had to extrapolate even more and and those places suggest those places tell us that we really need to have a much much higher coverage across the earth and what about how how this all might change as as the planet warms up, right?

22:10I mean, that's another big, or is it a big unknown? It's a big unknown. And we're doing some work with Tom and Merlin to look at the role of heat in the flows of nutrients in these mycorrhizal networks. Yeah, I mean, it's pretty dramatic what we see with pretty mild changes in temperature already in the lab. You know, the way they grow even, you can see by eye, The shapes of the networks are already different. And yeah, when it gets to the flows inside, yeah, there's very big differences. So we're only starting to characterize these differences. But this is another reason why sort of scaling up the automation has become really important because it just allows us to test so many more combinations of different environmental conditions that we care about and that are important right now.

23:04And what about, you know, we know that plant distribution is changing a lot with global warming, global heating. Do we see the same shifting in the distribution of fungi? I think this is a call for more data in terms of temporal patterns of fungal change. We're just starting to be able to get the first species range maps of mycorrhizal fungi. And those are going to be key because we have to understand, are those range maps shrinking or expanding? There are places where, of course, they're getting into colder habitats. They're moving north. In other cases, the species distribution is shrinking.

23:43It's very different than studying the distribution of animals. You need different kinds of techniques. You have to ask different kinds of questions. And so even when we publish this paper and we're using data sets that we've harmonized from all over the world, it's still just one snapshot where a single core was taken. And so if there's anything that this field needs to really, really lean into, it's just getting better temporal data about these changes. And you started Spun, the Society for the Protection of Underground Networks, to work on all these questions. We'll put a link on this in the show notes so people can go to Spun and see what you're doing.

24:21But tell us a bit about that. What's exciting about Spun is that we're working with scientists all over the world to start mapping the biodiversity patterns to mycorrhizal fungi, the threat patterns, carbon drawdown patterns, and really get these data sets into the hands of decision makers. I think academics get frustrated because a lot of time the data are very siloed and just stay in academia. And many scientists are interested in being able to turn their data into impact. And so through Spun, we're actually able to work together and get these hands and get these data into the hands of decision makers and sort of challenge conservation agendas and challenge climate agendas so they start considering fungal communities.

25:05Great to talk to you guys. Thank you for joining us. There's so much more to learn about the real importance of this. So, you know, let's keep an eye on it and please come back soon and tell us about it. Toby Kears, Merlin Sheldrake, Tom Shimizu. Thanks so much. And for everyone else, thanks for listening and do follow wherever you get your podcasts. Bye for now. Thank you.

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