Episode transcript:
Neil King: The land here is barren, harsh and hostile. There’s no vegetation in sight - the only plants that exist live in the ocean. But that’s all about to change.
This is planet Earth, around 500 million years ago.
A major shift is underway.
At this point in history, plants are preparing to move from water and onto land.
But it’s not going to be easy.
Toby Kiers: What people don't know is that the first land plants, they didn't even have proper root systems.
Without roots, how would they absorb nutrients, feed themselves?
Well, they’re going to need help – from an organism with a special talent for getting at the good stuff locked away in the rocky surface. Fungi.
Toby: Fungi have a sort of a magic power where they can digest their food outside of their bodies. So they actually exude enzymes and chemicals to break down rocks. And as the fungi digested rocks, they started feeding some of these digested nutrients to plants.
Neil: Toby Kiers is a professor of evolutionary biology at the Free University in Amsterdam.
Toby: Plants depended solely on fungi to sort of act as a root system for millions of years. Plant roots are kind of a new evolutionary innovation
Neil: The first land plants team up with fungi and start trading with them in order to survive – a “you scratch my back I’ll scratch yours” kind of arrangement.
Toby: And that was the beginning of this really evolutionary innovation, this one partnership that led to a 90% reduction in atmospheric CO2, as plants started colonizing land and using that CO2 to make sugars and fats that they would then feed to the fungi to get at those rock nutrients…
Neil: This special partnership was crucial for the success of early land plants. They flourished and evolved, triggering a drastic transformation. The planet began to turn green. Ecosystems emerged. The composition of the atmosphere changed – becoming rich in oxygen, while carbon dioxide levels dropped by 90%, creating an environment that would allow animals too to evolve on land.
Toby: Fungi lie at the base of life on earth. Actually, much of what we see today around ecosystems we actually owe to fungi, from wolves to redwoods.
Neil: Without fungi, we wouldn’t be here.
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Neil: All these millions of years later, that special partnership between fungi and plants endures. Today, most plants still depend on fungi in the soil for survival – to feed them nutrients and protect them from disease. And that’s just one class of fungi.
Fungi also give us food like mushrooms, and life-saving medicines… they can digest pollutants, and their ability to lock away carbon underground also offers a solution to climate change.
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Neil: When you hear the word fungus, what comes to mind? Maybe you’re thinking about those semi-circular growths on tree trunks in the forest, or some mold on a piece of fruit, or even a nasty skin infection, like athlete’s foot.
These are all part of the fungus kingdom…
Yeasts, molds, and (perhaps best well known) mushrooms. Mushrooms are the fruits of fungi that you see growing above ground. But most of the time fungi take the form of mycelium – a root-like structure that looks a bit like tiny threads branching out, absorbing nutrients from the environment.
They might seem like plants, because they don’t move around much and often grow in soil, but fungi actually have more in common with animals, because they also have to find food and use enzymes to break it down.
Fungi are often invisible to the human eye. And out of sight, they’re performing an essential role in nature - breaking down organic matter and orchestrating the trade and flow of nutrients in the environment.
Toby: Wood wouldn't rot and release nutrients without fungi. There'd be no soil without fungi. They seem to weave their way into everything and it's almost paradoxical because they're so vast and they underline so many processes that sometimes we don't even notice they're there. It's like not noticing our own breath.
Neil: There are around 150,000 species of fungi that have been formally identified. But estimates suggest there could be more than 2.5 million out there. That means more than 90% of all fungal species are still unknown to science - and that new discoveries are happening all the time.
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Neil: It’s June 2020, and deep inside a cave, about an hour’s drive from Kunming City in southern China, a research team has come to search for fungi.
There’s some old wood on the ground, dead insects, and bat droppings. The team, from the Kunming Institute of Botany, has collected some samples to test back at the lab.
Peter Mortimer: We were quite deep down (in a cave), and I found a small piece of Styrofoam that had blown in or washed in and was sitting in a sump in the bottom of this cave.
Neil: Peter Mortimer is a professor at the Kunming Institute of Botany, focusing on fungi and fungal ecology. He’s originally from South Africa and besides fungi, he’s also passionate about caves.
Peter: I could see there was a bit of black on the surface of the Styrofoam. And so we thought we would see if that is a mould and what it's doing and turned out to be quite an interesting find…we studied the fungi growing on that Styrofoam and found was a new species to science.
Neil: And that wasn’t all. It turned out this new species of fungi also had the ability to digest the Styrofoam, the plastic it was growing on.
Peter: So coming out of a cave exploration trip, we found not only novel species, but really a species with potential impact for broader industries. So that kind of stands out in my mind as an example of why we should study unexplored habitats.
Neil: Peter has been living in Kunming, Yunnan Province, for more than a decade. In that time, the teams he’s worked with have discovered hundreds of new species. And that’s perhaps not as surprising as you might think, because Yunnan has an incredibly rich biodiversity when it comes to fungi.
Peter: We've described more than 1000 new species now. So it really is just, it's mind blowing how much we are finding here. We really scratching the surface of what we're finding on what is known.
…I'd say arguably it is the most biodiverse place. It's an incredible region to work in.. it you got Alpine mountains above 5000 meters elevation to the north and a few 100 kilometers South, even tropical rainforest, so all these habitats and everywhere in between means there's opportunity and niches for speciation and the development of sort of fungal diversity.
…If you look just at mushrooms, there's about 850 species of edible mushrooms in Yunnan, and globally there's only about 2100. So nearly half of the world's edible mushrooms are just in this one province of China. So an incredible diversity.
Neil: Fungi, and mushrooms, play an important role in China – as key ingredients in Chinese cuisine and traditional medicine. And they’re big for the economy too. China is the world’s biggest mushroom producer.
Peter: It's difficult to describe to someone just how important fungi and mushrooms are to the Chinese. The Chinese are incredibly passionate about fungi and they eat a lot of mushrooms….
…The Chinese produce, harvest and consume about 70% of the world's mushrooms. So it is a huge volume of mushrooms getting eaten.
…But there's other mushrooms. I mean, matsutake can fetch 3 or $4000 a kilo at the start of the season. And areas that produce matsutake get sort of violently protected. And that's their livelihoods. It's their annual income. Villages, towns will be solely dedicated to the trade of mushrooms. You can go to some towns in Yunnan, that's all they do. It's mushroom trade, mushroom restaurants, guest houses aimed at mushroom tourism streets are named after mushrooms. It's really, it's crazy. Mushroom fever is very high. So interesting, interesting place to be.
Neil: Edible mushrooms and truffle are a valuable source of food for us humans. But we also rely on fungi for many other edible products – like yeast to bake bread, or to ferment beer, wine, vodka, and soy sauce.
It’s a fungus – Pennicillium roqueforti, that creates the unique flavour and texture of blue cheeses, such as Roquefort and Stilten. And can you guess what we get from the fungus Penicillium camemberti?
Fungi gave us the antibiotic penicillin, which revolutionized modern medicine. They’ve also been used to develop medication to lower cholesterol, and immunosuppressant drugs used to enable organ transplants. Enzymes produced by fungi are used industrially, fungi have also been employed as pesticides, and in the production of biodiesel.
Peter: Most people don't, or can't conceive the role that fungi play across different industries. You would see it for, maybe for baking and brewing and your yeasts or mushrooms that you eat. With the range of sort of things in your daily life that mushrooms or fungi contribute to I think would blow people away. And the one example I find amazing is there's an enzyme out of certain fungus that's used to make Lego, the building blocks children play with. Like fungi touch on so many different aspects of our lives that we're unaware of…
Neil: A recent study by an international team that included Peter calculated that the contribution fungi make to the global economy amounted to around 54 trillion US dollars – about half of the global gross national product. The researchers stressed that their attempt to give fungi a monetary value was just a starting point, and that more research was needed.
Peter:... And I think one goal for that paper was to really argue that fungi need to be better conserved and be more part of the conversation when it comes to biodiversity conservation, because they do make an enormous contribution to different economies. And often they're ignored or people just aren't aware of the role that they're playing.
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Neil: So it’s clear that fungi are incredibly versatile, and we rely on them in so many ways.
Take mycorrhizal fungi – this is the fungi that forms partnerships with plant roots in the soil. We heard about them at the top of the show. Well, 90% of plants depend on this fungi to survive… from crops… to garden shrubs.. to trees in rainforests.
This network - sometimes cleverly called the Wood Wide Web – is also used by trees to share resources with each other. And they’ve been shown to use it to receive advance warnings of threats, for example if they need to boost defenses because a neighboring tree is under attack from pests.
And Toby says these fungi, building networks underground, can also be powerful allies in the fight against climate change – because mycorrhizal fungi act as a kind of vacuum to draw carbon into soil systems, keeping it out of the atmosphere.
Toby: Fungi are really important in climate change. And this is where we say fungi are more than just organisms, right? They're creating this underground infrastructure that helps store soils, actually store this massive amount of carbon.
Neil: Toby co-authored a recent study published in the journal Current Biology that found the world’s plants transfer around 13 billion tons of carbon to soil fungi each year – that’s more than a third of current annual CO2 emissions from fossil fuels. It’s enough to cancel out the annual carbon emissions from China - the world’s biggest emitter.
Toby: And this carbon, this drawdown is actually a major contributor to the structure and health of soils. I mean soils in general, we know they store about 75% of all terrestrial carbon. And fungi, they're like the gateway of that carbon to the soil and they play a major role in making that carbon drawdown happen.
… So just as trees are built of carbon, fungi- these fungal mycorrhizal, fungal networks - are built of carbon. The second thing they do is so cool, is they make sort of specific compounds and these are compounds that… make this soil stronger, they make aggregates which are sort of chunky bits of soil that act as a stable carbon reservoir, so it reduces erosion and maintains soil structure, it makes the soil sticky.
Neil: Underground fungi also hold soils together, preventing erosion, and they increase the volume of water soil can retain, which is important during drought or flooding – and for reducing stress trees might face in times of climate change.
But this underground fungi is at risk.
Toby: Mycorrhizal fungi are threatened by agricultural expansion, by deforestation, by urbanization...
I mean, if you're putting concrete over underground ecosystems, you're going to really destroy the biodiversity that's there.
…It's worrying. I mean the data, the data are there. Scientists have been sort of trying to sound the alarm on the threats to underground ecosystems for decades.
Neil: More than 90% of the earth’s topsoil could be degraded by 2050, according to the UN. It says one soccer pitch of earth erodes every five seconds. Logging can decrease the abundance of mycorrhizal fungi by as much as 95%. And intensive farming practices and use of chemicals like fungicides can also disrupt fungal networks.
Toby: This is what we're worried about is: what is going to happen to above ground biodiversity and stability, these ecosystems, if we lose the foundation of the soil, if we lose these mycorrhizal networks. You know we call mycorrhizal networks the coral reefs of the soil because they support so much biodiversity and life and it's hard to know what's going to happen.
Neil: Toby is also the executive director of an organization called SPUN, which stands for the Society for the Protection of Underground Networks. The group is currently working to map fungal networks around the world and advocate for their protection.
Toby: Sometimes it really feels like a race against time. I mean, it's about 99.9% of the Earth's surface that still needs to be sampled, but some of this biodiversity is disappearing, and so the urgency is quite real.
…The good news is that there's hope. I mean, these organisms... they're very resilient, they've been around for millions of hundreds of millions of years.
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Neil: The world of fungi is varied and complex. And while these organisms underpin life on earth, fungi can also cause us harm.
Fungi are behind common maladies like athletes foot and ringworm. But they can also cause life-threatening infections, such as pneumonia. And the number of fungal infections has been growing.
Of the 150,000 known species of fungi, only a few hundred are pathogenic to humans. They’re microscopic and are usually only dangerous for people with compromised immunity.
David Denning, a professor of infectious diseases in global health at the University of Manchester in the UK, says around 3.8 million people die globally every year as a result of fungal infections. That’s more than malaria.
But many of these cases go undetected.
David Denning: One of the reasons why we think there are many more deaths than there have been before is because the diagnosis has just been missed completely. The second problem is that they usually, not always, but usually complicate other diseases. So if you have leukaemia, or you've had a transplant, and then you get a fungal infection and you die, it's attributed to the leukaemia or to the transplant, not to the fungus.
… rapid diagnosis is really the core need across the world, and that's a combination of the doctor considering the diagnosis and the tests being readily available and the results turned around within 24-48 hours
Neil: The World Health Organization has sounded the alarm about the issue. In 2022, for the first time, it released a list of fungi considered to pose the most danger to humans. Among those of most concern was Aspergillus fumigatus – a mold found in soil and decaying leaves, capable of producing life-threatening infections in people with weakened immune systems.
Another one on the WHO’s list, a yeast pathogen called Candida auris, was first identified in 2008 and has since spread around the world.
Such fungi can also be difficult to treat, because they’ve become increasingly resistant to the antifungal drugs. That’s mainly due to the use of fungicides to spray crops.
And there’s also the possibility that climate change is making the situation worse, allowing some pathogens to adapt to higher temperatures and spread to people. Here’s David again:
David: So there are many different influences of climate change on fungal disease. So there are few fungi and probably Candida auris which has gone across the world as a multi resistant blood borne infection, was driven by warmer climates in seawater.
We’re not absolutely sure about that, but it was never seen before 2008 and now it’s a global pathogen. So we think that’s possibly one reason.
Another issue is the extreme weather that we’re getting, which is causing a lot of damage to housing and flooding and other things. So people are getting exposed to many more fungi in damp, moldy houses as a result of direct climate damage.
And that’s a problem not so much for the systemic infections which kill you in a week or two, but more chronic indolent infections related to what is often called black mold.
And then the other thing is the issues around travel and migrations. So as the world gets hotter, some places in the world become uninhabitable or they run out of water. And so we’re seeing already and we will see many, many more mass migrations of people and they will take fungal disease with them and a good example of that, although they’re not migrating out of India at the moment, this is more people just travelling. There’s a multi resistant skin fungus called trichophyte causing ringworm and it's resistant to the typical’topical treatments that you'd use the creams and things like that and it started in India about 10 years ago and it’s a new fungus and it’s now been found in many, many countries around the world, quite a lot of cases in the US which were missed for many years for example.
Neil: Humans aren’t the only ones affected by these harmful fungi. Thousands of fungus species can cause disease in plants.
The fungal disease rice blast destroys up to 35% of the world’s rice crop each year. Fungi has also decimated populations of bats and frogs. So the consequences for food security and biodiversity can be serious.
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Neil: So where does that leave us? As dangerous as they can be for some, fungi also present huge opportunities.
We’ve learned that modern medicine relies on fungi… they keep trees healthy and can even help us sequester heat-trapping CO2 …
Some fungi have the ability to break down pollutants such as crude oil in the environment, for example after an oil spill - a process known as mycoremediation. Fungi have also been shown to digest plastic – as we heard from Peter in Kunming earlier in the show.
But he thinks there’s still a lot of untapped potential.
Peter: the mainstream adoption of mycelium based packaging, replacing Styrofoam and plastic packaging with mycelium materials, that is definitely the biggest point of impact we can make with current technology. A company like Ecovative which pioneered it, and IKEA recently gave a commitment to transition and to include mycelium based packaging for all their products. That's a step in the direction we need to be going and I think this is an easy win that's available to us now. We need to look at the economics of it, scaling of such industries to be competitive and viable against such well-established industries in plastics and Styrofoam, but the technology is there and I think the shift will happen.
Neil: Mycelium-based materials can also be used to replace energy-intensive building materials in the construction sector, or unsustainable materials in the fashion industry.
Peter: Then there's I mean there's huge potential to revolutionise textiles and fashion, the electronics industry even. So I think we will see a whole change in revolution in a number of industries. We have the technology, the economics needs to follow.
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Neil: There’s one thing I want to leave you with. Consider all that fungi can do – from feeding plants over millions of years, to making medicines, to providing an economically-valuable food source, to digesting plastic waste – and then consider that less than 10% of fungi species have been discovered so far.
That means there is likely an abundance of fungi still out there – with unknown potential. And that’s what we also stand to lose if we fail to protect this complex and incredible versatile life form.
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