Original subtitles

The living world is connected

by a vast kingdom of life

we are only just beginning to discover.

Fungi.

Sometimes, they reveal themselves above ground as mushrooms.

Mostly, though, they live out of sight

as hidden networks

which have shaped life on land as we know it.

Fungi are the miracle-workers behind

so many of our foods and medicines.

Yet we know so little about them.

They are some of nature's greatest survivors,

enduring through five mass extinctions

in the last billion years.

So how have they adapted to catastrophe and upheaval?

And what might we learn from fungi

to survive our own time of radical change?

When it comes to the study of fungi,

there are few better places

than Kew Gardens, in London...

..home to one of the most diverse collections of plants and fungi

in the world.

British biologist and writer Merlin Sheldrake

has dedicated his life to unravelling the mysteries of fungi.

We're really just at the very beginning of our understanding

of these astonishing organisms.

It's long been known that mushrooms can be delicious

but might also poison you,

cure you or give you visions.

Neither plants nor animals,

fungi actually make up their own kingdom of life.

In fact, scientists now estimate

that for every plant species,

there are as many as ten fungal species.

This building is the Fungarium.

A team of dedicated scientists, called mycologists,

research fungi here,

including Dr Ester Gaya.

Hello. Hi.

Welcome. Thank you. Lovely to meet you.

Right now, we are inside the largest

collection of fungi in the world.

The reference collection is like a library.

Let me show you this one.

It's quite interesting.

The collection holds around a million specimens,

gathered over centuries

by collectors including Charles Darwin.

Each specimen helps illuminate the history of life on our planet.

But much of fungal life happens

on a scale too small for the naked eye to see.

So to really understand them,

we need to enter their world

through the lens of a microscope.

Most fungal life begins with a spore.

From each spore grow tubes,

called hyphae,

five times thinner than a human hair.

Their most urgent task is to find food,

so they start exploring.

As these tubes branch and fuse,

they form a delicate web, called mycelium...

..which can grow into a network with billions of hyphal tips.

Fungi are some of nature's most remarkable chemists.

Whereas animals eat by putting food into their bodies...

..fungi eat by growing into their food.

Digestive chemicals produced by fungi can unlock food sources...

..allowing them to be broken down and absorbed.

Despite having no eyes or nose,

mycelium can still sense the world...

..smelling chemicals,

seeing light,

feeling heat,

even detecting electricity.

Fungi have to be sensitive to what's going on around them.

They have to use that information to make decisions

about what chemicals to produce next, where to grow next.

Fungi show that you don't have to have a brain to solve problems.

This is one of the puzzles of mycelial networks.

Their control and coordination

is somehow everywhere at once

and nowhere in particular.

Mycelium can form elaborate structures

and grow to incredible sizes.

In the wild,

some fungi are known to span

more than ten square kilometres.

They also act as transport networks,

shuttling water and chemicals

on rivers of liquid within their cells.

This makes mushroom growth possible.

A mushroom forms when fungus weaves

hyphae into a tight bundle

and inflates these

with a pulse of water.

With these abilities,

fungi have thrived on every continent.

The Australian island of Tasmania

is home to some of the most ancient rainforests.

The Tarkine is the second-largest

temperate rainforest on Earth,

five times the size of New York City.

These forests have existed for over 65 million years...

..providing a living window to the time of the dinosaurs.

It's the perfect hiding place for fungi,

calling adventurers from around the world

to discover new species

and unravel their secrets.

Old-growth forests are extremely special places.

You don't get to be an old-growth forest

in a very short space of time.

It takes waves of populations of different organisms

rising and falling in each other's wake over centuries,

creating the conditions for the next.

Here in the Tarkine, there's an amazing diversity of fungi

because it's so wet.

Merlin has come halfway around the world to be here

in mushroom season.

At this time of year, there is

a symphony of different colours, shapes and sizes.

Most fungi don't produce mushrooms,

and even the fungi that do

only produce them for a small moment in a year.

Fungi have long enriched and enhanced life on this planet.

But researchers think we've only described about 5% of all

the fungal species on Earth.

I want to better understand how they've survived for so long

and what lessons they might have for humanity

as we wrestle with our most urgent problems.

Merlin's research has helped reveal an essential relationship

between fungi and plants.

Incredibly, over 90% of plants

rely on fungi to survive.

From the earliest moments of their lives,

plants use chemicals to signal to fungi in the soil...

..guiding them towards the roots

and even into them.

A single plant can form relationships

with hundreds of different fungi.

By working with fungi, plants can gain greater access

to nutrients for growth.

In return, fungi receive food, like sugars, that plants produce,

extending their reach far above the forest floor.

Under each footstep, hundreds of kilometres of mycelial networks

weave their way through the soil.

More than one tree can connect to a single fungus,

forming shared networks,

sometimes called "the wood-wide web".

Through these networks,

resources can move between plants of different species

throughout the forest.

Older trees with the most connections act as central hubs,

allowing younger plants to take root and thrive.

Fungi can teach us about the symbiotic way of life,

about how all life is lived in relationships

with other organisms.

In this sense, life is collaboration...

..and collaboration is always a blend

of cooperation and competition.

Fungi are one of the circulatory systems of the planet.

If you were to stretch out all of the mycelium on Earth,

it would span half of the width of the Milky Way galaxy.

But perhaps the most overlooked superpower of fungi

is their ability to recycle life through decomposition.

Fungi are some of the only organisms

capable of breaking down

the complex chemistry of wood.

After penetrating the wood,

fungi deploy a range of digestive chemicals...

..breaking down plant matter

and releasing the nutrients back into the soil

to be taken up by future generations

of forest life.

You think about the life of the tree as a living tree, standing up,

but then you think about the life of the tree

after the tree has fallen, creating the conditions for other life.

Without fungi, dead wood and other plant matter would pile up and up.

Other fungi specialise in recycling animal life...

..including this fascinating species.

The ghoul fungus is living in the shadow

of the body that was once there.

Fungi can decompose

but they can also grow mushrooms,

the next stage in the food web.

When these mushrooms are eaten, they provide the nutrients

that other organisms can then use to grow...

..connecting all life in the forest...

..from the smallest

to the largest.

So it helps us to think about how the matter

that composes our own bodies will continue its journey

after we die.

Forests exist thanks to the transformational powers of fungi.

But fungi also offer world-changing opportunities for humanity.

In the Yunnan province of China,

new discoveries are showing how fungi

might help address some of our biggest environmental challenges.

These forests are home to over 6,000 species of mushroom,

making Yunnan one of the most diverse fungal ecosystems

on the planet.

Some of the oldest-known fossils of fungi have been found here,

as well as the earliest evidence of mushroom farming,

over 2,000 years ago.

Today, the people of Yunnan forage and farm over 800 edible mushrooms.

Other species have been used in traditional medicine for millennia,

with health benefits modern medicine is only now beginning to explore.

With such diversity, it makes sense that Yunnan is at the forefront

of fungal research,

led by biologists like Peter Mortimer

and his team from the Kunming Institute of Botany.

Yunnan is a wonderland for fungi.

It's really muddy, it's rainy, there's leeches everywhere,

the mosquitoes are biting you,

but it is so much fun looking for fungi,

these hardships don't really matter.

To date, we've been part of

describing more than 1,000 new species of fungi.

Recently, Peter and his team made a discovery

that might help us deal with plastic waste.

There's about 400 million tonnes of plastic produced annually.

Much of it enters natural ecosystems,

and chemicals inside the plastics are leaching out

into soil systems and water bodies.

So, plastic is long-lived,

it's absolutely everywhere,

and it really is disastrous.

We were collecting fungi in the forest

and we came across a piece of plastic,

and it was full of fungus.

So we seal it up and we bring it back to the laboratory.

Lo and behold, we got a whole range of fungi.

Four of those are new species to science.

And even better, it turns out those four species are able

to break down plastic.

So, under this microscope in the petri dish, we can see

how the mycelium from the fungi

is penetrating this plastic sheet,

breaking it apart,

and then actively digesting it.

It just shows how rapidly fungi adapt

in a change to the environment.

Plastic has only come into existence in the last, say, 100 years,

yet fungi have the chemical arsenal

to digest a range of plastics.

If we can just find that one species that can be very efficient

at breaking down the plastic, we can start doing it at scales

where real-world problems start getting addressed.

Other fungi studied here have produced therapeutics used

in organ transplants, as well as treatments

for cancer and epilepsy.

The most famous fungal medicine, penicillin, has saved

billions of lives by fighting bacterial infections.

Under the microscope,

you can see penicillin holding back bacterial growth.

All of this lies within the fungi around us.

Until we find and discover those fungi,

we're never going to know what that potential benefit could have been.

But breaking down pollutants and healing people

aren't the only benefits that fungi offer us.

In the United States,

a revolutionary industry is emerging...

..driven by the idea that not only can fungi break things down,

they can also build them up.

One company at the forefront is Ecovative Design

in upstate New York, led by CEO Eben Bayer.

We want to use mycelium materials to solve problems

that are really important.

So, for us right now, that's around animal agriculture

and single-use plastics, which are two of, like, the biggest

material-related pressures on the ecosystem.

Researchers here have discovered

how to grow materials using mycelium...

..replacing plastic products with alternatives

which are fully recyclable.

The first step is we get agricultural by-products -

things like wood chips.

That's where we add the mycelial cells.

Over the next few days, they go crazy,

they grow all around the wood chips.

When you're done growing it,

you always end up with a product that's completely compatible

with the planet.

You get this thing that looks like Styrofoam,

but you can actually compost in your garden.

You can literally just throw this anywhere in the environment.

And it would actually serve as a nutrient for planet Earth,

not a pollutant.

Mycelium materials have been used to grow everything

from packaging to surfboards.

They can even replace fabrics, like leather.

Researchers like senior scientist Molly Boutin are working

towards even more surprising materials.

We really take our inspiration from nature.

So when we go out into the woods and collect samples...

If you look at fungi out in the wild,

they might be different colours...

..they form different structures.

The diversity of fungi is very important because it means

that there are such a wide variety of materials that we can make.

When you collect these different samples and bring them back

to the lab, you will see that they grow in different ways.

As you do research, you're seeing things and you're learning things

that no-one's ever seen before.

Mycelial materials touch so many different industries,

like, 1,001 things you can do.

Medical applications is definitely a passion of mine.

Growing things like organs with mycelium sounds way far out,

but my long-term dream would be able to actually grow organs, or at least

the scaffolding for organs, using mycelium.

If materials can be reimagined in such a radical way,

what other opportunities might the fungal kingdom hold for humanity?

Back in the Tarkine,

fungi are shaping their environment in ways that have

long been hidden from view.

A single mushroom can produce 30,000 microscopic spores each second.

As water evaporates from the underside of the mushroom,

small wind currents lift the spores into the air.

Fungal spores are the largest source

of airborne living particles on Earth, equal to the weight

of half a million blue whales each year.

As the spores rise,

they attract water vapour...

THUNDER RUMBLES

..eventually forming raindrops by the billions.

THUNDER CRASHES

At least 16,000 species of mushroom

release spores this way,

helping to stimulate rainfall

in forests all around the world.

It's a win for fungi.

Not only do they succeed in spreading far and wide,

they also nurture the moist environments necessary

for fungal life.

THUNDER RUMBLES

MERLIN: The forest feels different at night.

It feels like it's inhabited in a different way.

The whole forest is the outgrowth of fungal relationships.

Everywhere you look, there are stories unfolding around fungi.

Long-nosed potoroos here in the Tarkine

have adapted to eat over 60 species of fungi.

Potoroos rely on smell to find the fungi that they need to survive.

Underground fungi produce powerful odours that can

travel through layers of damp soil out into the air.

By producing aromas to attract animals, fungi which live

out of sight can make themselves known,

ensuring their spores are spread.

Some fungi have figured out another way to attract attention at night.

This is the ghost fungus.

It's one of around 90 species of mushroom

known to glow in the dark.

Bioluminescence is another example

of the chemical wizardry of fungi.

Oxygen reacts with chemicals made by the mushroom, producing light.

It's really exciting to see these bioluminescent fungi glowing,

and when your eyes adjust to the dark, they become

more striking and vivid.

Some species glow to attract insects,

helping the fungi by spreading their spores.

Why other species glow

remains a mystery.

Mushrooms have been illuminating these forests for millions of years.

But that light may soon be fading.

Fungi may be some of nature's greatest survivors,

but never before have they faced a threat like us.

Forests like the Tarkine,

where fungi are most diverse,

are being cleared at the rate of one football field every two minutes.

Of the old-growth forest that once existed around the world,

only one fifth remains.

Some trees in the Tarkine can live for over 2,000 years.

Ripping out these ancient trees disrupts the wood-wide web.

Deforestation interrupts other crucial benefits

fungi provide the world.

Each year, mycelium draws down more than five billion tonnes

of carbon from the atmosphere, which would otherwise

drive climate change.

When I'm in these burnt, clear-cut areas,

I'm reminded of the Library of Alexandria,

which burned down, and much of the knowledge and the wisdom

of the ancient world was lost.

Imagine that, but on a much greater scale.

We're burning the library,

a library of different ways to rise to the challenge of living.

What aspects of this library might be crucial for

the planet's ecosystems and for humans in the future?

We risk losing entire branches

of the fungal tree of life to extinction.

But if fungi have taught us anything,

it's that those who can adapt, survive.

In a world rapidly changing,

it makes sense to study the most resilient players.

Merlin and other scientists are working together to

map the Earth's fungal networks -

a vital step in better understanding

the behaviour of fungi,

and a critical tool in protecting their ecosystems.

Every sample collected builds on the knowledge already gathered

by scientists and traditional cultures -

knowledge we pass on to generations yet to come.

With millions of fungi still to discover...

..it's a journey we're just beginning.