♪ UMA THURMAN: Life.

The closer you look, the more mysterious it seems.

We can't see the invisible forces at work.

But what if we could?

It's time to look at our home... ..in a whole new way.

Imagine carbon cycling through nature.

It's one of the building blocks of life.

And it's stored in our forests... ..oceans... ..and grasslands on an incredible scale.

But we've released too much of it into the atmosphere, risking our future.

We CAN halt emissions and draw the carbon back down.

And our best ally for that is nature.

Restoring it to abundance is the biggest challenge of our time.

But we CAN do it.

If the future of nature looked brighter, so could the future for us all.

♪ Grasslands are the largest land ecosystems on Earth.

Monitoring and protecting them is essential, as they affect the health of our whole planet.

The steppes of Kazakhstan are part of the most extensive grasslands we have left... ..home to the elusive saiga antelope.

Scientist Albert Salemgareyev is studying these unusual-looking herbivores.

UMA: Albert's study site covers 13 million acres... ..and the only way of tracking these nomadic antelope is with GPS technology.

Most people use darts to tranquilize wild animals before collaring them.

But that's not an option for Albert.

♪ So he and his team have developed a different technique.

(TEAM MEMBER) UMA: For it to succeed, they need to be as fast and agile as the saiga.

(TEAM MEMBER) To avoid dangerous levels of stress, each chase is limited to four minutes per animal.

Time's up.

They'll have to try again.

UMA: Collars are only secured to healthy young adults.

They should provide the most reliable data over the coming years.

Over the next five days, they must fit 20 collars.

It's worth the effort, as saiga are important animals for the health of the ecosystem.

They graze for 20 hours a day, and that stimulates the growth of fresh grass.

If the saiga were to vanish, the consequences would be catastrophic for the grasslands.

♪ (ALBERT) UMA: By 2003, unsustainable hunting and outbreaks of disease caused the saiga population to crash to barely 21,000 animals... ..one of the fastest declines of a mammal species ever recorded.

Much of Albert's work now is focused on saiga protection across their range.

And GPS collars are the only way to be certain where that is.

Saiga traveled great distances to avoid the cold of winter in the north and the heat of summer in the south.

(ALBERT) UMA: But human development can block saiga migrations.

Albert's data helps protect these critical routes.

UMA: With safe passage, saiga are making an incredible recovery.

Numbers have just been declared at an astonishing 2.8 million... ..the highest ever recorded.

♪ There are many different kinds of grassland in the world, but they usually have one thing in common.

Grazers... ..which come in all shapes and sizes.

Their relentless nibbling and trampling stimulates fast growth.

And as the grasses grow, they're doing something amazing.

They absorb carbon from the air... ..which is then transported down into the roots, where some of it is transferred into the soil.

If undisturbed, it can stay there for hundreds of years, locked safely away from the atmosphere... ..where right now, there's too much of it.

And because grasslands cover around 40% of all land, their potential for storing carbon is huge.

But that can only be realized if the ecosystem is healthy.

♪ Countless species bound together in a powerful web of life... ..like here in south-west Uganda, in the rain shadow of the Rwenzori Mountains.

Dr Perpetra Akite is a grassland ecologist.

She's dedicated her life to understanding tropical ecosystems... ..knowledge she passes on to her students.

PERPETRA: The life of a teacher is one interesting life.

When I want to inspire the younger people, I take ecology out of the textbook and take them out into the field like we are here.

And then you will understand ecology.

- Here.

- Oh!

That's an entire grasshopper there.

Amazing.

Yellow legs.

PERPETRA: Grasslands are very rich ecosystems.

The biodiversity within grasslands have always been underestimated.

We have a lot of Uganda kob, which happen to be our...

The Uganda national animals.

Waterbuck, buffaloes.

We have a lot of warthogs.

So there's heavy grazing in grassland ecosystems.

UMA: Grasses cope by regrowing quickly, but in doing so they draw nutrients and minerals from the ground.

These need replenishing, and the best source of fertilizer are the animals themselves.

But getting this dung into the soil requires a helping hand from a creature that likes to emerge at night.

♪ PERPETRA: OK, it's now night.

Let's see if there's anyone coming out to do some more building of the mound.

Ah, there are some worker termites coming out.

It's actually lovely.

UMA: There are more termites living beneath this savannah than there are animals above it.

Between them, they consume a third of all herbivore dung.

PERPETRA: The mound is a nest where there's a lot of reproduction.

The more termites we have, the more services we get from them.

UMA: As termites recycle the nutrients back into the soil, they complete the relationship between grass and grazers.

In any ecosystem, there is always this interconnection.

Nothing is living in isolation.

So from the smallest thing to the biggest, they're actually interlinked and their survival is so connected.

(LION ROARS) (PERPETRA) UMA: As night falls in the savannah, many animals take advantage of the cooler air.

Especially hippos, which can eat more than 110 pounds of grass in a single session.

Their constant mowing suppresses trees and bushes, keeping the grasslands open.

♪ But hippo numbers in Queen Elizabeth National Park are down by 90%.

Recent increases in poaching and disease have decimated the population.

When grazer numbers drop, the landscape responds.

Jimmy Kisembo has lived and worked in this park for over 15 years, and is witnessing this decline first-hand.

UMA: With fewer grazers, bushes are taking over... ..and this means there's less grass to eat, unbalancing the savannah even more.

It threatens to destroy this once-pristine habitat.

Jimmy is here to meet fellow conservationist Joseph Arinaitwe from the Uganda Wildlife Authority.

He leads a team of local community members pushing back against the takeover.

There are several invasive plant species that are causing a real problem.

UMA: Kalema Njojo means "defeater of elephants".

These animals are on the rise here due to improved anti-poaching and the recent ban on the elephant ivory trade.

But even the elephants can't touch Kalema Njojo.

It's far too tough and spiky to eat.

(JOSEPH) UMA: Problem plants have taken over an estimated 580 square miles of the park so far, and less than 2% of this has been cut back.

The work can only be done by hand.

Previous efforts with machinery have spread the seeds and made the problem worse.

These bushes threaten to destroy one of Uganda's greatest wildlife strongholds.

For Joseph and his team, it's a war of attrition.

(JIMMY) ♪ UMA: Some of our greatest wildernesses are beyond the reach of most people.

"Tundra" means treeless plain.

At this high latitude, it's too cold for forests to survive.

(CHIRRUPING) A unique biome of grasses, sedges, mosses and lichens thrives here.

TORBEN: We're out here in north-east Greenland.

We are in one of the most remote locations that you can get to.

It's a fascinating place.

We have heath, we have grasslands, we have tundra.

UMA: Professor Torben Christensen leads a team of scientists monitoring this ecosystem.

The valley is only free from snow for three months of the year.

Not long for the team to collect the data that they're after.

It's also the time for tough plants like Arctic willow and polar grasses to do all their growing.

During this summer, there's a lot of biological activity here, and the plants are very fast in utilizing this time where they can do their photosynthesis, their exchange of carbon with the atmosphere.

UMA: An invisible process that Torben and his team are here to assess.

This experiment we're looking at here is a fantastic, very simple technique to measure the exchanges of greenhouse gases between the ecosystem and the atmosphere.

Did you also check the other one over there?

- Yeah.

- Nice.

Perfect.

It's 51.7.

UMA: These instruments can calculate the amount and direction of carbon moving in and out of the ground.

Growing plants absorb it, but it can also be released from the soil by microbes and bacteria.

TORBEN: If there is more drawdown than release, then we start to get accumulation of carbon.

UMA: And that's what the data shows.

That across this vast landscape, the carbon drawdown is huge.

♪ TORBEN: These types of ecosystems, they have been consuming carbon dioxide since the last glacial times.

They are even doing it today.

UMA: The carbon that's taken in by the vegetation is building up in the Arctic soils.

UMA: The tundra is so important to the planet's climate, Torben's team wants to know how it could be affected as the world heats up.

♪ Temperatures in the Arctic are rising up to three times faster than anywhere else on the planet.

It's a major problem for the carbon stored in the earth.

TORBEN: Permafrost is where the soil has been frozen more than two years in a row.

Here, it's been frozen for thousands of years.

It covers 14 million square kilometers in the northern hemisphere.

UMA: When the earth is frozen, the breakdown of organic matter like dead grasses slows right down, so the carbon release is minimal.

But rising temperatures are threatening this ice-bound store.

We have known this area for 28 years, and this collapse that happens right under our feet was quite unexpected.

♪ What's happening here is fascinating, but also a bit frightening.

The foundation was made out of ice.

That ice has now melted... ..and this has caused a complete collapse.

UMA: With the soil defrosted and exposed to the air, carbon is escaping back into the atmosphere.

TORBEN: A piece like this is a little piece of 1,700 billion metric tons of carbon that is stored in the Arctic at large.

UMA: This type of permafrost collapse is happening all around the top of the planet.

TORBEN: The concern is that with the warming that we are causing, we are starting a feedback mechanism where the warming leads to increased releases of carbon to the atmosphere... ..and that in turn leads to further warming.

That's a bad trajectory for mankind.

UMA: To win this fight, we need to drastically reduce fossil-fuel emissions and support nature in drawing the excess carbon back down to Earth.

♪ One group of scientists believe there is an ally that's critical to changing the fortunes of the planet... ..right below our feet.

TOBY: The Netherlands famously allows you to do high-risk research.

We are allowed to try all kinds of new techniques to unlock the secrets of the underground.

UMA: Dr Toby Kiers works as part of a team of scientists in an organization called SPUN - the Society for the Protection of Underground Networks.

This is beautiful.

You have to see this.

This is good.

This is what we have here, is a plant root growing in the lab that is colonized by a symbiotic fungal network that encases the root system.

Mycorrhizal fungi are a class of soil fungi that trade resources with plant roots.

It's a partnership where the plant is feeding carbon into the fungal network in exchange for phosphorus and nitrogen and all the nutrients that the fungi collect.

♪ The fungal network penetrates into the root system itself and forms these beautiful structures.

The partnership between fungi and plants is one of the oldest on Earth, and it underlies basically all terrestrial ecosystems.

To be able to see inside the fungi themselves and to see the nutrient flows, we have to use a much more powerful microscope.

♪ UMA: Toby takes living fungal networks to be imaged at a physics laboratory on the other side of town.

TOBY: Tom works with really powerful microscopes that can see things that we simply could not see in my lab.

TOM: We can see the traffic patterns inside.

A lot of the things that are moving are carbon.

It starts to bring us towards an understanding of how carbon can be drawn down into the soil and kept there.

TOBY: So now I'm just going to switch to the fluorescence.

- Whoa!

- Whoa!

That was so cool.

It's so full of carbon.

- TOM: And it's all flowing.

- It's all flowing.

TOBY: Right now what we're looking at is carbon moving through the living fungal network.

It wasn't until we could start labeling the carbon with fluorescence that the game really started to change, because now we were able to pinpoint exactly the carbon inside the network.

This year, for the first time, we harmonized all the datasets that had ever been published where people actually measured how much carbon was going from root systems into mycorrhizal fungi.

It's a big number.

Our estimates are about 13 billion tons of CO2 per year are processed by plants and then fed to mycorrhizal networks below ground.

That's equivalent to about a third of all emissions from fossil fuels.

These mycorrhizal fungi, they are an ally in our fight against climate change.

UMA: But the clock is ticking to find and safeguard these amazing networks.

We're not protecting these fungal systems.

And I think one of the big problems is that there are no maps of the fungi themselves.

We don't know where the Amazon of the underground is.

UMA: Part of SPUN's goal is to identify where these places are.

- Let's see what we got.

- Have a core.

We go to those spots, and we actually work with local scientists and collect soils to understand what fungal communities are there.

♪ Just to give you a bit of perspective, we have sampled about 0.01% of terrestrial earth.

So that means 99.9% of terrestrial earth has not been sampled for these fungi.

So we have a big job ahead of us.

UMA: Grasslands are huge.

As well as capturing carbon, they help produce our food.

Our staples of wheat, barley, oats, and rice are all cultivated grass species.

But the way we farm them is harming soil biodiversity.

Digging and tilling can break up fungal networks and release the carbon they hold.

Globally, a third of all soils are degraded, and getting worse... ..not only contributing to climate change, but threatening global food security.

♪ Many farmers recognize this and want to boost underground biodiversity... ..returning soil to health.

This unproductive field has been set aside to let nature help it heal.

And student Robbie Sidhu is monitoring its recovery in an unusual way.

I think it's really important to develop new ways of looking at how we can help save our planet as the climate crisis moves forwards, try new approaches that we haven't looked at before.

(VIBRATING AND CLICKING) The first time I listened to soil was in my own garden, and I plugged the microphones in and wasn't prepared for the amount of noise that I heard and the variation of the noise that I heard.

(RUMBLING AND PINGING) UMA: Robbie is trying to make sense of this subterranean chorus.

ROBBIE: There's a lot of cracks and pops and rustling going on.

It's soothing to listen to, in a weird way.

UMA: Bioacoustics is a promising way to observe soil biodiversity without disturbing it.

ROBBIE: We're thinking of this fieldwork as kind of an orchestra that we're listening to, and now we're going back into the laboratory and trying to identify what all the instruments are.

(RUSTLING AND TWANGING) It's quite surprising to hear the rustling from the root systems... ..and the percussiveness of the insects.

(RAPID CLICKING) UMA: These methods are in their early stages, but the difference between healthy and unhealthy soil is obvious.

(RUSTLING AND CREAKING) ROBBIE: As things become more restored, you get a lot more noise from an improved ecosystem.

It's really exciting to be at the edge of something that could garner quite important results going forwards.

A lot of the methods of monitoring soil at the moment are quite invasive, quite expensive, quite time-consuming, whereas monitoring the acoustic aspects of soil is quite easy.

UMA: This tool is a simple way to understand if our efforts to restore nature are working.

All of the animals and the biology that lives in the soil is what captures that carbon the most.

And if we can encourage that biology to flourish, then we're doing our job in terms of capturing carbon, and listening to the soil is an important way that we can do that.

It's only been a few years, but already when we compare this field that's being regenerated to those around it that are still in constant use, we can hear a difference.

And it's getting louder.

(CRACKLING) UMA: If protected, all of the world's grasslands can help us fight climate change.

Like those found in the prairies of North America.

But less than a fifth of these ecosystems remain... ..and over a million acres are lost to crops every year.

♪ But there are those who believe that wild prairies can coexist with our human needs.

We're going to go see if we can find bull bison, these kind of...

I'd say solitary, but I think there's a group of, like, three of them up here.

It's pretty typical this time of year, outside of the rut, that they're on their own for the most part.

UMA: Here in Montana, there's a large area of prairie that looks wild... ..but it's really just a shadow of its former self.

The biggest difference between the prairies today and the prairies let's say 150 or 200 years ago is the absence of big herds of large mammals, predators and migratory birds.

Large indigenous grazers, things like bison, have been replaced by domestic species, cattle for the most part.

♪ (CHEEPING) UMA: For wild animals to return, they need substantial areas of land.

The best available science says that a fully functioning prairie ecosystem needs to be about 3.2 million acres.

That's 5,000 square miles.

UMA: And that's just how much land a project called American Prairie intends to rewild.

DANIEL: That's Yellowstone National Park, Glacier National Park, and then eventually, we hope to create this kind of comparable large protected area for wildlife right in the middle of the state here.

UMA: Much of the land has been owned by ranching families for generations, and many have made their feelings clear about rewilding.

There is a fear that native animals, especially predators, will have an impact on their livelihoods.

DANIEL: We know our neighbors are always going to be ranchers no matter what this looks like.

So how do you extend the effects of a wildlife refuge by increasing wildlife tolerance on the other side of the fence?

UMA: Success is only guaranteed if everyone works together.

Brother and sister Grant and Glenna Finkbeiner help run the family's livestock operation in central Montana.

GLENNA: Well, we ranch.

We got a lot of different enterprises, though.

GRANT: We're fifth-generation ranchers now, pretty much in this area since the late 1800s.

We still have large herds of elk.

You know, it's not crazy to see a thousand head elk coming out of the trees.

GLENNA: Predators as well.

Had a lion come through and it killed 20 ewes.

Considering that year the ewes were averaging in the market $230 apiece... ..it adds up pretty quick, the economic loss.

GRANT: Many ranchers around here still kill a lot of predators.

If they saw a wolf, they'd shoot it immediately.

I feel as though getting rid of all the predators kind of upsets the ecological balance.

UMA: To improve carnivore numbers, American Prairie has a plan to incentivise ranchers to see them in a different way.

GRANT: These cameras are owned by the American Prairie, and they use them to see and manage how much wildlife is in an area.

UMA: Camera traps are set... ..and every picture taken of a contentious species earns the landowner money.

It helps compensate for any financial impact the wildlife might cause.

Over 60 sites have been photographed so far... ..capturing over 30,000 images... ..including the rarest predators.

Ventures like this improve relations with nature... ..which is doing better as the project grows.

But persecution has driven some species to extinction in Montana.

With a little help, even those lost can be returned.

DANIEL: The reason we're working where we are is because the habitat is intact enough that what you can do is just add animals back into it.

UMA: The Fort Belknap Indian Reservation is home to the Aaniiih and Nakoda people.

Over 650,000 acres of intact prairie and the site of an incredible reintroduction program.

DANIEL: Why Fort Belknap?

Because it's an Indian reservation, it is a sovereign nation, so they are able to make essentially unilateral decisions about how much or how little wildlife will be in their lands without the need to get approval from the state wildlife agency or the federal wildlife agency.

UMA: Scientists are joining students from the reservation's college to reintroduce a small but vital predator back into the ecosystem.

Thank you guys for being here.

Tonight we are going to release two foxes that have been brought up from Colorado.

UMA: Student Ethan Werk is part of the swift fox reintroduction team.

ETHAN: The work is tough, it's hard, but being able to see the foxes on the landscape is rewarding in itself.

They eat small rodents and prairie dogs and insects, so they're kind of like a pest control.

DANA: Swift foxes are so fascinating.

They're very, very small, about the size of a house cat.

And what's so special about them is that you can only find them in these large tracts of intact shortgrass prairie ecosystems.

So the foxes that we have in the pen here with us today, they've been fitted with a GPS collar and were placed into an acclimation pen for five days.

And now we will release them to find a new home on Fort Belknap.

♪ DANIEL: There it is.

ETHAN: There he goes.

(LAUGHS) (THEY LAUGH) Oh!

Godspeed, little buddy.

ETHAN: Look the other way.

You're free now.

I'm gonna call this fox North cos he has no sense of direction.

His first steps into his new home.

He's hunting.

We're gonna watch him catch one.

He got it!

He missed.

That was BLEEP cool.

I hope that guy caught that on camera.

These animals, they have a place here, too, just like anybody else.

Their land was taken, most of their habitat was taken, so having a place to go is crucial for them.

And being able on the reservation here to provide that is pretty great.

UMA: And it's not only the native animals that benefit from this project.

Thriving prairies can help us to draw down and store staggering amounts of carbon.

DANIEL: I think we're so close.

It seems so very doable to be able to rewild this place and bring it back so all of us can enjoy that wild North America that came so close to being lost forever.

I think I will see this place in a wild state before I retire, let alone before I die.

This is not something that takes 100 years.

You could do this in 40 years and have this place be wild again.

UMA: We know how to protect and rebuild the ecosystems we rely on.

♪ And the work has begun in grasslands right across the world... ..saving species, keeping soil healthy and locking carbon beneath the ground.

TOBY: This is all about urgency.

It's even hard to sit here and talk about it and not be in the field sampling and restoring ecosystems that have been degraded.

UMA: It won't be easy, but the payoffs are huge.

There are wild possibilities just ahead of us.

Building a future for nature benefits us all.

PERPETRA: There is a future, and everyone will be involved.

Definitely.

UMA: With nature on our side, we CAN overcome even the greatest challenge.

♪ ♪ ♪