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Melissa Harris-Perry: Welcome to The Takeaway. I'm Melissa Harris-Perry.

Song: There's millions and billions and trillions and zillions of interesting things underground.

Melissa: Now, burying your head in the sand usually means you're avoiding something uncomfortable or unpleasant in the world above ground. Today, we're going beneath the earth's surface to understand the magic of fungi. No, not the psychedelic kind of magic or the Alice in Wonderland kind, either.

Caterpillar: One side will make you feel taller.

Alice: One side of what?

Caterpillar: The other side will make grow shorter.

Alice: The other side of what?

Caterpillar: The mushroom, of course.

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Melissa: We're talking about microbial fungi life. Here are a few fungi facts. We have yet to discover all of the millions of fungi species that exist. The one scientists have identified include a singular massive funga that is over three miles long. Fungi that close in the dark. There's even fungi that infect ants and turn them into zombies. Okay, I know that sounds like the stuff of science fiction, but these organisms act as parasites that get all up into those carpenter ants so that they can spread their spores wide and far.

Now, of course, fungi can also be used for good. They can help diagnose the health of trees and forests, and even mitigate climate change through carbon capture. Scientists around the world have been collecting data to better understand the web of fungi species, or otherwise known as the Wood Wide Web that lives beneath the soil. Dr. Colin Averill is a lead scientist at the Crowther lab at ETH Zurich, and co-founder of The Society for the Protection of Underground Networks, and founder of Funga, a fungal biodiversity and climate action corporate benefit organization. You are a co-founder of the Society for the Protection of Underground Networks? Is this about some kind of information-gathering system?

Dr. Colin Averill: No, I wish. We're really focused on mapping, documenting and protecting the network-forming fungi on planet Earth.

Melissa: All right, help us to understand that. When you say underground, this isn't about hip-hop music. This is literally underground. What are the networks going on underground?

Dr. Colin Averill: Most plants on Earth formed this partnership or a symbiosis with fungi on their roots, and we call them mycorrhizal fungi. These fungi are truly fascinating. They can form these vast below-ground fungal networks that connect different plants. Sometimes we refer to them as the plant or the forest microbiome. It's these fungi that are how plants access critically limiting soil resources like water and nutrients. They're really just deeply essential to plant biology.

We're finally coming to discover that there's this vast biodiversity and variety of these fungal organisms and that because of that, there's a real potential to use them to change how ecosystems work and address some of our most pressing problems in agriculture, and in climate and beyond.

Melissa: At the smallest level, or the most direct level, how did we come to discover these underground networks? How long have we known about them?

Dr. Colin Averill: Yes. In the scientific literature, the first descriptions of mycorrhizal fungi come from 1896. Myco means fungus, and rhizal means root, fungus root. This was from people using very early microscopes to look at plant roots and coming to realize they're not really just roots at all, they're fungi. Since then, people all over the world have been studying these organisms for a very long time, but things have radically changed in the past 10 to 15 years. That's because environmental microbiologists have co-opted the tools of DNA sequencing to better understand and see the variety and biodiversity of fungi that live in the soil all over the world.

Melissa: Help me to understand what this looks like. I presume these are things we can actually see with the naked eye. For those of us who maybe haven't paid much attention to what's happening there, how would we know what we were seeing?

Dr. Colin Averill: Often you won't see these things. They are microbial life, but they have this dual life as micro and macro biological organisms. Many of the mushrooms you see in a forest, for example, are actually mycorrhizal mushrooms. They're entirely dependent on those trees for all their carbon resources, a lot of the resources they need to grow and be a thing in biology at all. When they form that mushroom, you might see them, but that's really just the tip of the iceberg. It's really what we call actually a fruit. That's how the fungus reproduces, but most of it lives below ground in invisible microscopic threads that we call hyphae. That's really the true body of the fungus and it lives in the soil.

Melissa: It helps with access to key nutrients. How does it do that?

Dr. Colin Averill: Through so many different ways, and that's because there's tens of thousands, if not more, of species of different mycorrhizal fungi. Some of them are really good at taking up the byproducts of decomposition, which release all these growth-limiting nutrients that other organisms break down in the soil. Some of them actually can do decomposition by themselves and actually break apart all the stuff and soil and get the key juicy nutrients that the plants want out of it. Beyond nutrients, many of these things are essential to how plants tolerate droughts, how they access water, all the resources in the soil, these fungi are essential to how plants access them.

Melissa: Talk to me about your field research, what does it look like?

Dr. Colin Averill: We often draw an analogy to the Human Microbiome Project. Recently, we've discovered that your body is an ecosystem, a microbial one and your stomach are thousands of species of bacteria. By characterizing which bacteria live in hundreds of people's stomachs, medical microbiologists could discover that there are communities of microorganisms that are predictive of your health, whether you're healthy or sick. Furthermore, if you're sick because you have the wrong microbes, we can take the right microbes from a healthy person and treat a lot of human diseases.

My team over the past several years started asking, "What if we take the same approach that they took in medical microbiology, but we applied it to the forest?" What we do is we work with foresters all over the European continent and also all over the world, who have been documenting forest health for decades. Measuring how big the trees are, how fast they grow, how much they capture carbon from the atmosphere. We actually also have them send us a scoop of soil, which we then sequence in my laboratory to characterize which fungi inhabit those forests and start to identify the links between forest health and the forest fungal microbiome.

There are huge effects of which fungi live on forest health, particularly how fast trees grow, and how much carbon they can capture.

Melissa: Talk to me about the carbon capture part. What do these fungi have to do with climate change?

Dr. Colin Averill: One of the biggest drivers of climate change is excess carbon dioxide gas we put into the atmosphere, which warms the planet. However, about 30% of all CO2 that we've ever emitted actually didn't end up in the atmosphere because we stimulated plant growth. Plants can absorb CO2 as part of growing, that's what photosynthesis does. They turn it into things like wood, and it builds carbon in soils. That's how ecosystems like a forest, for instance, can act as carbon sinks and actually remove carbon dioxide from the atmosphere.

How well they can do that often depends on how well they can access other growth-limiting nutrients. If they had more nutrients, perhaps they could grow faster, capture more carbon. Through our research, looking across hundreds of forests, we found that which fungi live on the roots of the trees in a given forest is linked to threefold variation in tree growth and carbon capture. If you had two pine forests sitting side by side, experiencing the same rainfall and climate, growing in the same soils, but one had the "right fungi," it could potentially grow up three times as fast as an adjacent forest with the wrong set of fungi.

Melissa: Is this something that is widely part of our current approach to climate change mitigation?

Dr. Colin Averill: No, it's really, really not. We're really just starting to discover this, but that is what's so exciting about it. We have spent a century optimizing forestry for tree genetics and for how we prep sites and how we manage forestry plantations. We have not thought for a moment about how do we optimize the microbial biodiversity in ways that both enhance outcomes in the forest, but also allow for a greater variety of fungi to live in those places. What we're doing now is trying to understand, can we essentially in a lot of these forest landscapes, rewild soils, bring back fungal biodiversity, and in the process, make these trees grow faster and be part of the climate solution.

Melissa: How would you do that? What's the language you used? Rewild these spaces?

Dr. Colin Averill: Yes. A lot of especially in forestry, which is essentially an agricultural practice, through multiple forest rotations where you will grow trees and then we clear cut them and we grow trees, and we clear cut them. We've really massively altered which fungi live below ground. There's still fungi there. They just don't happen to be the ones that are linked to the trees growing very quickly or capturing a lot of carbon. One thing we're exploring now is just like in medical microbiology where we do things like fecal transplants to reestablish the right healthy gut microbiome of a person, can we take soils that harbor high-performing and healthy fungal communities and actually bring them back into these managed forestry landscapes? Can we rewild the soils with native fungi, and by doing so, accelerate how fast they grow and their ability to act as carbon sinks?

Melissa: Tell me, where on our planet are these underground networks most common or abundant, or is this something happening on all of our continents?

Dr. Colin Averill: Nearly every ecosystem you go to, these network-forming mycorrhizal fungi are present. They're present in your lawn, they're present in a forest, they're present in a desert. What we're learning, though, by putting together many, many observations, and this is work The Society for the Protection of Underground Networks does in collaboration with the Crowther Lab and a team in Prague called Global Fungi. We've been trying to understand, where are the highest levels of biodiversity of these fungi on the planet?

What is the Amazon rainforest, a below-ground network-forming fungi? What we're finding is it's really counterintuitive and remarkably different from where we see hotspots of plant and animal life. We think of the tropics as really the most diverse places on the planet for plants, in particular. When we look at these fungi, it's actually completely opposite. Some of them are most biodiverse in the boreal latitudes, so high Canada, Russia, sub-Arctic forests. Others seem to be really biodiverse in the last really intact grasslands on the planet, so the eastern part of Mongolia, those highlands, those harbor really biodiverse networks of fungi.

Melissa: What would it mean to take a fungi-first approach to fighting climate change?

Dr. Colin Averill: A fungi-first approach to fighting climate change is recognizing that these fungi can facilitate so many services we ask of our ecosystems. When we think about we want more nutritious crops and food production, we want trees that grow faster and capture more carbon, doing these things can be done with a lot of these mycorrhizal fungi, but it needs to be done in a way that actually acknowledges that we can't just put the same fungus everywhere. There's no "silver bullet" fungus. We need personalized medicine, but for the forest, or for an ecosystem.

Different fungi are native to different places and locally adapted to different situations. How do we start building biodiversity back into these managed landscapes, like our food and forced agricultural ecosystems, in a way that allows them to act as reservoirs of this below-ground fungal biodiversity and also allows them to essentially act as better and stronger carbon sinks?

Melissa: Is this work that really has to be done with and by scientists, or are there things that ordinary folks who have a little bit of yard can do to help support these underground networks of life?

Dr. Colin Averill: Yes, absolutely. Actually, it's a lot of the things we'd want to do to support biodiversity in our urban systems, anyway. We want to work and we want to see places work with native plant species, species that are actually from and of the place where you live. Those allow, in turn, those plants to support native and endemic communities of fungi. We know things like fertilizers can really shift and disrupt these fungal networks especially, and so finding ways to manage your lawn or manage whatever ecosystems you actually support on your home or in and around your home, finding ways to grow those without fertilizers.

Think things compost before you think of a Miracle-Gro, for example. Finally, avoid tilling. These things are fungal networks. They create these elaborate structures in the soil and we till and disrupt soil, or essentially just shredding them. You want to keep the ground covered. You want to avoid disturbing it when you can because when you do that you allow these networks to flourish.

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Melissa: Colin Averill is lead scientist at the Crowther Lab at ETH Zurich, and co-founder of The Society for the Protection of Underground Networks. Colin, thanks again so much for being here today.

Dr. Colin Averill: Thank you so much for your time.

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