♪ 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.

♪ ♪ YADVINDER MALHI: To me personally, forests are special because you're surrounded by giant beings, these trees.

A forest is much more than the individual bodies, objects that you can see, the trees or the soil or the animals.

There's a huge world of interaction and communication beyond our immediate experience.

And through science, we begin to get glimpses of that world.

UMA: Professor Yadvinder Malhi from Oxford University, has been studying this forest for over 20 years.

YADVINDER: It's a profoundly central part of my being, I think, being out, realizing that you're just one being in a community of species and entities and different forms of consciousness all around you.

UMA: Research at Wytham Woods began in the 1920s.

It's one of the first places where scientists came up with the concept of an ecosystem.

YADVINDER: So here, we've got this caterpillar consuming the leaves of this tree, and it's what makes up a forest ecosystem - not the individual tree or the individual caterpillar, but this interaction between the two.

This caterpillar may end up being consumed by a blue tit, taking the food to feed its young chicks.

And the leaf is also probably creating chemical signals to attract birds to tell them that this caterpillar is here.

This is just one small example of thousands of such interactions between species occurring above the forest, in the canopy, and below in the ground as well.

UMA: These connections keep the forest healthy.

All living trees are adorned with leaves.

Beneath every single one are thousands of tiny holes - stomata.

♪ They draw in carbon dioxide from the air, which the trees turn into food to help them grow.

And nowhere is carbon drawdown more powerful than in the great tropical forests of our planet.

Fed by constant rain and sunshine, the trees grow rapidly here.

It's been like this for millions of years.

Dense forests are the hardest to study, the animals often impossible to see.

So the few places where we can learn about how the forest works are invaluable.

Kibale National Park lies on the eastern edge of the Congo rainforest ecosystem.

Here, our closest relatives are under observation.

(CHIMPS HOOT AND HOLLER) Margaret Kobusingye is the field manager of the Kibale Chimp Project.

She leads a team of researchers who keep up with the chimps from dawn until dusk.

Every detail of their lives is recorded.

Who's grooming who.

What they eat.

And where they go.

(HIGH-PITCHED HOOTING) A fig tree in fruit brings them all together.

Chimps are fast eaters, consuming up to ten figs a minute.

And they can eat for up to eight hours at a time.

By feasting on these fruits, they provide an invaluable service for the trees, helping to spread their seeds across the forest.

♪ Animals like chimps are critical to the health of the forest.

Yet across the whole of Africa, less than 250,000 remain.

Here in Kibale, protection is making a difference.

We cannot have the trees without the animals.

And so we need them to be around.

The Congo rainforest is home to some of the largest trees on the planet.

And when it comes to carbon, the bigger the tree, the better.

Giants here can tower over 200ft tall.

But to reach their full potential, they need help from another creature.

(TRUMPETING) Forest elephants are nature's gardeners.

Smaller than their savanna cousins, they still eat an incredible 400 pounds of vegetation per day... ..mostly the shrub layer that's easy to reach... ..which gives larger trees more space to grow.

There are over 10,000 animal species in the Congo rainforest.

They're all part of a complex web of life that keeps the ecosystem working.

♪ The Congo rainforest covers more than 1 million square miles.

It is so large, it influences the climate across the entire region.

♪ The rainforest causes humid air to rise into the atmosphere... ..forming rivers of cloud that transport billions of tons of water north... ..where it hits the Ethiopian highlands as rain... ..feeding rivers which sustain some of the driest regions in Africa.

The influence of a forest extends far beyond its borders.

And every forest on Earth has its own unique character.

In the north are the boreal forests... ♪ ..dominated by evergreens that take time to grow.

It's quieter here.

Not so many animals and only a few tough species of tree.

Scots pines can live for 500 years.

They're not the fastest at drawing carbon down, but they are good at storing it.

To study this, David Coomes and Aland Chan from Cambridge University are using some unusual technology.

♪ DAVID: We can map the trees and work out how much carbon is in them.

We've been working with this lidar data set.

We've popped it into one of the bits of software that game developers use, and then we just see it from a person's perspective.

♪ UMA: This helps map the forest.

And lidar can show precisely how much carbon is locked up within it.

♪ In this restoration area, David and Aland can assess the drawdown benefits of regrowing a forest.

ALAND: We have this sort of...

If you look at the mountains behind us, that will be around 800m in elevation.

So naturally, the forest would extend all the way back up to 650m to 700m in elevation, and the goal is to try to get the trees and forest to extend back up there through natural regeneration.

UMA: As it grows, each sapling has the potential to draw down half a ton of carbon dioxide.

And what makes the boreal forest even more unique is where that carbon ends up.

DAVID: So as well as understanding what these amazing, ancient trees are doing, we're also interested in what's happening below ground.

And in these boreal systems, the soil is mostly made up of organic materials like this - leaf litter, pine cones, but also roots and some incredibly important fungi sitting in there as well.

Together, they form a layer which is incredibly slow to decompose.

This organic matter accounts for over half of all the carbon stored in the boreal forest.

The rest is held in the trees.

It's the largest carbon store on terrestrial Earth.

♪ Looking after it in the face of climate change is essential.

♪ VALERIE: So the boreal forest, first of all, is a forest of cold.

The vegetation grows quite slowly.

It stores twice as much carbon per hectare as any other terrestrial ecosystem, including the tropical forests.

I'm a member of the Innu community of Mashteuiatsh.

But I'm also the executive director of the Indigenous Leadership Initiative.

Because of my connection as an Innu woman, I've always known that I would be doing work to protect and work with nature.

The boreal is very much home to the iconic species of caribou, and it's such a fundamental part of Canadian identity.

I mean, it's on our quarter.

It is what has allowed my people to survive in this landscape for over 10,000 years.

Because the caribou are so sensitive, when they're present, it's a good indication that other species who are a little bit less sensitive will also be present in that area.

They're kind of like canaries in the coal mine or a way of really giving us an alarm about what's coming in these ecosystems.

And so we're definitely looking, as foresters and as people who manage these areas, to find caribou, because it's a good way of telling that the whole system is healthy.

UMA: Caribou need old-growth forests.

In this cold environment, the lichens they eat take up to 50 years to grow.

But even the slowest ecosystems need a boost now and then to get the nutrients moving.

VALERIE: Boreal is an ecosystem of fire.

The soils in the boreal are quite poor.

And because that organic matter decomposes so slowly, over time, that soil can break down and become less and less productive over time.

Well, what brings back that productivity, in part, is fires, because what it does is it breaks down that organic matter and all the nitrogen that is in that matter gets released into the soil.

Natural fires are usually started by lightning.

(THUNDER CRACKING) UMA: Big burns used to happen once a century, giving time for the slow-growing forest to recover.

VALERIE: Fires are becoming more intense, larger and more persistent than the norm.

Canada has had a long forest management history, so we know what is the natural cycle of fires.

And so every once in a while, there's a big fire.

Then there's a lot of little fires.

But what's happening is we're not getting a lot of little fires anymore.

We're just getting big fires.

UMA: More frequent storms and hot, dry weather are causing infernos that are actually damaging soils, impacting the old-growth forest, caribou and also local residents.

I've got a lung disease that was probably exacerbated by the fires last year.

Two weeks after the fire started, did I notice that I was having shortness of breath.

Peter Durocher lives in Ile-a-la-Cross, in Saskatchewan.

PETER: I feel like I'm grounded when I'm right here.

I don't feel grounded in my house.

Here, I'm grounded.

(BIRD CALLS) It's beautiful.

Forest is healing.

UMA: Peter belongs to the Metis Indigenous community.

The boreal forest has been their home for generations.

PETER: Indigenous people need forest.

I feed my family off the forest and the water, whether it's the rabbit, or the deer, or the moose.

UMA: But under the pressure of climate change, life in the forest is getting harder.

This fire was only about four hectares the first time it was seen.

Four hectares.

And it ended up burning close to a million hectares.

That's a crazy number, eh?

UMA: The initial fire seemed too small and too far from habitation to be a priority for the province.

There was no response to the community's calls for help.

By the time action was taken, the fire was bigger than Chicago.

In all my life, all my 62 years of living on this earth, I never seen a fire behave like that.

Fire was burning at 2:00 or 3:00 in the morning, as hot as it was burning at 2:00 or 3:00 in the afternoon.

By the time May 29th came around, the fire was uncontrollable.

UMA: In 2023, the hot, dry spring caused fires to burn so intensely, they destroyed over 70,000 square miles of boreal forest and sent a veil of smoke to New York City and far beyond.

Hundreds of wildfires continue to burn across Canada, many of them out of control.

An ominous orange haze envelops the Statue of Liberty.

Wildfire smoke from Canada has billowed across the border.

As firefighters try to contain the fires, officials in many US cities warn air quality is at code red.

100 million Americans are under air quality alerts.

The potential health threat posed by wildfire smoke spanning as far south as Georgia and Texas.

Normally, where it burnt here would have slowed down, but because the fire was so hot, look how high it burned.

Look at my hands.

I mean, this is just from one tree.

You know?

This is only from one tree.

One little...one little tree that's probably only 15 years old.

Now, if you look at a fire of our size here that has 10 million trees, you know, how much carbon is actually being released?

If this tree released that much carbon, what happens if a million trees burn like that?

What happens if a billion trees burn like that one year?

There's a problem out there, just nobody's listening to us.

♪ UMA: Keeping the infernos in check is essential if we want the boreal forest to help balance the Earth's climate.

PETER: The generations that are coming up behind me, what are they going to see?

Change is going to happen.

The biggest worry I have is how fast the change is coming.

I love my grandkids, all of them, and the forest is up there.

And I want my granddaughter to experience it.

I call her an old soul because she feels what I feel.

And how do you say rabbit in Cree?

- Wapos.

- Wapos, yeah.

- See right there?

Look.

- Yeah.

Yeah, wapos.

We went hunting moose, and she came with me, and we were sitting there, and she says, uh, "Listen."

I said, "What?"

I said, "You hear a moose?"

"No."

She said, "You can hear the forest," you know, which is the wind, right?

So... And I thought it was just a blessing, a blessing for her to feel that, to understand that.

♪ UMA: Indigenous people take care of more than a quarter of all the land on Earth.

But they need support.

In Canada, the government has pledged $800 million to fund that stewardship.

It's a start, but there's an urgency for us to recognize the value of forests.

♪ To understand what forests do for our global climate... ..we have to take a more mathematical approach.

Forests are the cathedrals of nature.

They are where most of the biodiversity lives.

And so it shouldn't be a surprise that forests are central to the carbon story of this planet.

And we're all trying to understand the climate system and help society fight against climate change.

Now, part of that fight is understanding precisely how carbon moves across the planet, in and out of our ecosystems.

UMA: Building on years of scientific data, the Climate Center has created detailed maps that show us where the carbon flows in and out of our forests.

♪ They show that it's not just the tropical and boreal forests that are significant in the global carbon story.

One of the world's largest managed forests is found along the Appalachian Mountains on the eastern side of North America.

♪ GIULIO: Temperate forests can be extraordinary sinks.

If managed well, they can draw down carbon at rates that are comparable to the other forests of the planet.

♪ And because we live with and next to them, we have an extraordinary opportunity to really manage them better.

UMA: The Appalachians are 2,000 miles long, and they're home to 26 million people who live amongst the deciduous forest.

♪ Each farmstead has a different story.

SUSAN: My grandfather purchased this property in 1943, and we've held it since then.

UMA: Susan Benedict is the third generation manager of her family's land.

Today, it's filled with over 2,000 acres of mixed hardwood forest.

But this hasn't always been the case.

In the early 1900s, great swaths of it were harvested.

♪ SUSAN: There was so much environmental damage done with all of that clear-cutting, the streams were all clogged with mud.

I'm sure that species that need trees weren't here then.

UMA: Since that initial felling, trees have been planted and cut several times.

Often just a single species was used for easy timber.

But this left the trees vulnerable to pests and disease.

SUSAN: The year my father died, in 2006, we had a three-year outbreak of gypsy moth, coupled with a drought, and our consulting forester estimated that our losses of timber was in excess of $1 million.

And there's no insurance for that.

That's just an economic loss that we can't make up.

UMA: To hold their place in this working landscape, forests have to be economically viable.

And that means healthy... ..which is where nature comes in.

Even in those woodlands managed for timber, animals like black bears, which spread seeds far and wide, can really enhance forest biodiversity.

They're a keystone species along the entire Appalachian range.

But biologist Katie Martin has noticed what looks like a worrying decline.

KATIE: Bears are a pretty good indicator of healthy forest.

Forest and the wildlife are truly linked.

They all work together in a working ecosystem.

For the forest to function as it should, we need the wildlife.

And vice versa, the wildlife need the forest.

If one is out of balance, the whole thing can fall apart.

Virginia bear populations have been a huge success story, but unfortunately, in recent years, we have noticed a change in our bears and something that's on the landscape that's making us pretty nervous about what's happening with our bear population.

♪ UMA: The bears are unwell... ..and many are dying.

Katie is trying to find out why.

KATIE: We've actually got these little field kits we've developed where you can do a skin scrape really easily on the bear while you've got it down, look at it underneath the scope.

UMA: This bear is suffering from a severe outbreak of mange, a painful skin condition caused by mites.

It's something bears normally survive, but recently it's been getting more dangerous.

KATIE: And unfortunately, here in Virginia, we see a lot of really severe cases that do end up leading to the death of the bear.

So it's really sad and heartbreaking to see.

It is certainly a wide variety of factors that we think are probably impacting the bears and maybe causing these impacts from mange.

The mites are likely able to live longer out on the landscape if we have warmer winters because they're just, you know, not succumbing from cold temperatures in a den site or out on the forest floor.

Potentially, that's helping the bears that are picking up mites more frequently, because the mites can live longer.

UMA: A mite population unchecked by winter may be impacting less resilient bears.

As we've seen winters get a little bit warmer over the past few years, this obviously, when it's 70 degrees in January, a bear is a hot animal, they're going to get up and start wandering about.

There's still not food available in the forest at that time of year.

So unfortunately, that means likely getting into more urban or residential areas where garbage can be available to them.

All of these things that are not natural foods for a bear end up becoming maybe a primary source of their diet.

UMA: Junk food could be weakening the bears' immunity, and in the south, they're waking early because of rising temperatures.

♪ To help this whole area become more resilient to climate change, an ambitious project is needed.

I'm Marc Anderson.

I direct The Nature Conservancy's Center for Resilient Conservation Science.

My generation's spent so much time convincing our peers that climate change was real and serious, that we didn't realise the effect we were having on our own kids, who were losing hope and not seeing a future.

But there is a future, and now we have to focus on solutions.

And a big part of that solution is healthy, functioning, thriving nature.

♪ UMA: The Appalachians are one of the largest remaining areas of temperate forest in the world.

Running north to south, they are also a major corridor for wildlife.

We call it a climate highway, where most of nature will be moving northward or upward to adjust to a warming temperature.

UMA: It's predicted that, every decade, plants and animals will move 11 miles north and 36ft higher.

Mark's project aims to ensure that they have the space to do so.

MARK: So the key to creating a resilient landscape for the future is understanding where we need to work.

That's what I've been working on for the last 15 years.

And we've produced a map of the results of that which we're now sharing publicly.

The green areas on this map are the lands most resilient to climate change, and the blue areas connect those places together into a connected, resilient landscape.

UMA: To create effective wildlife corridors, landowners in the Appalachians will have to help out.

MARK: One of the reasons we've created this tool and released it is because we need people as part of the solution.

So we need to involve them in the science and involve them in the conservation.

- That would be interesting.

- Yeah.

Susan has recently enrolled in the Family Forest Carbon Program, a new market for sustainable forestry.

BRITTNEY: So, Susan, how's the program working out for you?

SUSAN: We really have benefited from it.

This area here is part of our mature forest that's enrolled in the program.

UMA: Through the project, carbon offsets can be sold and experts help people manage their forests better.

SUSAN: Right now, I think our our biggest project is to train the next generation in how to steward this property.

That's why we involve the grandchildren.

This is the forest for them that we're planting now.

They're the ones that will be able to enjoy it and benefit from it.

Riley is our expert tree planter.

She does a good job.

I love coming up here.

It is my favourite place in the world.

Being up here makes me think of the future and what I can have and what I want to have.

I'm gonna own this place one day.

And I just think that it's really cool that I have to learn all this stuff from my family.

I think that climate change is one of the biggest problems in our world.

And my family is trying to help by, like, keeping this forest healthy.

And personally, I feel like we're doing a good job.

UMA: Family tree farms like this one can be part of a connected and resilient landscape, enabling wildlife to move around and settle in newly restored areas.

♪ SUSAN: Recently, we're very excited because beavers have come back to our stream and our pond, and we feel like that is a real ecological success for us, that they've chosen to be here, and we're very happy to have them with us.

♪ UMA: Our forests are holding on in the face of climate change... ..but they're under extreme pressure.

Keeping them strong and resilient is key to their future... ..and ours, too.

There are nearly 400 billion trees in the Amazon rainforest.

That's three times more than the stars in the Milky Way.

But if the world continues to burn fossil fuels, this entire ecosystem is at risk of failure.

How this might happen is what an experiment in the heart of the forest is trying to find out.

I usually scared of heights, but then, you know, the first time I flew on this was so amazing.

♪ UMA: Here in Brazil, Dr Carlos Alberto Quesada runs a project called AmazonFACE.

It stands for Free-Air Carbon Enrichment.

♪ The idea is to try to mimic these conditions, particularly with the CO2, the best we can, so we look how the forest will behave and try to understand what's going to happen to the Amazon in the future, and then we can get prepared.

UMA: It took ten years to get the funding to build these structures deep in the forest.

16 towers 100ft tall, encircling 90 adult trees.

Carbon dioxide is pumped in, simulating the elevated levels that scientists are expecting in the near future.

♪ BETO: We really need to get this right, you know, to understand, OK, how this will work.

This will influence your life, my life, everybody's life.

So we really need to study everything we can inside of those rings.

So please don't step off the path.

OK?

How the trees respond will help predict the fate of the forest.

Here, we measure the soil respiration.

And here is the root productivity.

This machine measures the CO2 concentration.

UMA: As well as increased carbon dioxide in the atmosphere, climate change is predicted to make the area seven degrees hotter, with only half the rainfall.

If this happens, conditions couldn't support a rainforest at all.

The tests will help to indicate how soon this scenario might become reality.

Without this giant forest absorbing carbon dioxide, the effects on the world's climate will be catastrophic.

This great forest pump can't be allowed to switch off.

♪ Protecting the Amazon should be a high priority.

But as well as suffering climate change, it's under constant human pressure.

♪ Over a million acres are destroyed every year in Brazil alone.

The country has pledged to cease deforestation by 2030.

But so much has already been lost.

The only hope for restoration is with the communities who know it best.

Like the Xingu people of Mato Grosso.

When people have to help nature, it requires an intimate knowledge of the ecosystem.

Some of the seeds the women gather will be used by the Xingu Seed Network, an organization funding forest restoration.

Working for this network is Milene Alves de Oliveira Lima.

Since joining the Seed Network ten years ago, Milene's life has transformed from a young girl in a poor neighborhood to a mother embarking on a master's degree.

She's now using her academic training to find out if any of these seeds will survive in the fast-warming climate.

Seeds that can still germinate in heat wave temperatures are now essential for successful reforestation.

Some species will be lost, but there is hope.

The tests show that the larger, harder seeds can survive extreme heat waves.

This helps Milene choose the perfect cocktail, mixed together in a process called Muvuka.

The mixing mimics the chaos of nature, and it's nearly four times more effective than traditional tree planting.

Many of the farms here are agricultural wastelands.

Regulation requires them to restore forests to a fifth of their land... ..and some farmers have responded with promising results.

Valmir Schneider has been on his reforestation journey for many years.

The seeds of over 40 species of native trees were planted here.

These pockets of trees will draw down carbon as they grow, but if they're isolated by miles of farmland, the biodiversity that makes them sustainable will never return.

♪ These small patches must become so much more.

Whatever challenges we face, we are stronger when we work together.

(SINGING) Nurturing a connection with our forests is the first step to looking after them.

SUSAN: You have to think forward to the next generations and take joy in the hope of the future.

UMA: Resilient forests are the best carbon drawdown tool we have.

♪ Imagine a world where forests can thrive and flourish hand in hand with humanity.

♪ While we still have forests, we still have hope.

♪ There still remains huge opportunities to really protect what's left.

♪ Not only for our own benefit, but that of the rest of the world.

♪ Well, we need nature to adapt to a changing climate because we need a living, breathing world.

♪ UMA: With forests in our future, that future will be brighter.

♪ ♪ ♪