NPR’s Adrian Florido speaks with ecologist Justin Stewart about mapping the complex network of fungi connecting the Earth’s plants.
ADRIAN FLORIDO, HOST:
I want to tell you about a massive underground network of fungi, specifically vast fungus networks that form relationships with the roots of plants. They’re called mycorrhizal networks. The Society for the Protection of Underground Networks, SPUN, is the group that studies them, and it’s just released the first-ever map of the global mycorrhizal network. To talk about what this map tells us, we’ve reached one of the scientists who published it, ecologist Justin Stewart. Mr. Stewart, welcome.
JUSTIN STEWART: Thank you very much. I’m excited to be here.
FLORIDO: Can you just help us picture what this mycorrhizal fungus network is? What does it look like? Is this an underground, like, network of mushrooms?
STEWART: So these are very ancient. They’ve shaped life on land for around 450 million years, and they form symbiotic networks with plants. So think of them as small filaments in soil. You have this network that doesn’t make a fruiting body. There’s no mushroom, but it’s a vast network of mycelial threads in soils.
FLORIDO: And what does it look like?
STEWART: Well, I mean, this is one of the most difficult things about mycorrhizal fungi, is they look so foreign to anything that we see above ground. They form meter-long threads of mycelium. So if you imagine something like a rail network or a road network, we often talk about mycorrhizal fungi as infrastructure in Earth’s soils.
FLORIDO: And so, you know, what do these fungal networks do?
STEWART: These fungal networks complete a very important resource transfer that’s important for planetary health. Plants make carbon through photosynthesis and because these fungi form such intimate associations with the roots of plants, they have direct access to that carbon, and they funnel it deep into Earth’s soils. These plants are being fed by these fungal networks. In exchange for carbon, they are being fed nutrients like nitrogen and phosphorus. So last year, some of the people that are on this study that we just published estimated that around 11% of current CO2 emissions are being funneled to these fungal networks each year. But at the same time, you have nutrients that are being funneled to nourish plants above ground.
FLORIDO: If I were to scoop up, you know, a handful of soil, how much of this network would I be holding in my hands?
STEWART: The length of networks in a single teaspoon of soil is astounding. In certain soils, you can have up to 10 or even 100 meters of mycelial networks in soil.
FLORIDO: Wow. And so globally, this is a massive underground network of fungus.
STEWART: This was the perfect moment to try to estimate globally how much mycorrhizal network there is on Earth. We had just enough data where scientists have collected very carefully cores of soil, brought it back to the lab. I mean (ph), this in enough locations around the Earth, we were able to rely on satellite data and create through AI predictive models of the global density and length of these networks. If you add up the total length, it’s about 110 quadrillion kilometers, which if you round a little bit, it’s about 1 billion times the distance of the Earth to the sun. And this is all in our soils.
FLORIDO: You’ve published this pretty remarkable map of what this underground network looks like, and specifically where – how it’s distributed across the Earth. And there are places like the Florida Everglades where this network of underground fungus is very dense. And then there’s places like the Sahara Desert where there’s almost none of it. I’m wondering, like, why did you want to map this network out?
STEWART: You can’t protect what you don’t know. Once you know where there’s a high density of networks or potential threats to networks, you’re able to then start working on restoration and conservation practices. So our goal was to have something that we could hand to decision-makers to include fungal networks in things like climate agendas and carbon models.
FLORIDO: When you look at this map that you’ve just published, what do you see?
STEWART: I see this map as a sense of wonderment. These fungi form complex associations with plants, enact very complex trade decisions, all while not having a single place in their body where information is being processed. By seeing that there’s a 110 quadrillion kilometers of this on Earth’s soils, it’s also giving a sense of scale about other ways of living that humans can also learn from. And so I’m very excited about the conversations that will be coming out of that.
FLORIDO: Well, I’ve been speaking with ecologist Justin Stewart from the Society for the Protection of Underground Networks, SPUN. Mr. Stewart, thanks so much.
STEWART: Thank you very much for having me.
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