♪♪ ♪♪ -Nature -- the more we learn about it, the more we realize how important it is.

Coral reefs cover less than 1% of the ocean floor, but are home to a quarter of all marine life.

And life in the oceans provides more oxygen than even the rainforests.

Environments like this are precious, something that's taken years of study to fully appreciate.

Back in time, we saw nature quite differently.

-Have you ever dreamed of living an idyllic existence under the waving coconut palms of a remote South Sea island?

Of course you have.

To loaf and sleep and fish and swim lazily, peacefully, and happily on the bounty of a glorious tropical nature.

Yes, life is simple and beautiful on Bikini Atoll -- until today, when there enters into Bikini Lagoon a fantastically incredible thing called the atomic bomb.

[ Explosion ] -In 1946, a nuclear bomb was detonated on the Pacific island of Bikini Atoll.

[ Explosion ] Over the next 12 years, 22 more nuclear tests like this were carried out.

One, named Castle Bravo, was 1,000 times more powerful than Hiroshima.

Three islands and their coral reefs were obliterated.

Nature was not the priority.

Today, we see things differently.

An awakening has begun.

We're at a turning point in history, and moving in a new direction.

How we live with nature now will determine our future.

A new age is upon us -- the age of nature.

♪♪ 50 years after the last nuclear test at Bikini Atoll, a scientific team traveled to this remote location in the Pacific Ocean to see if anything had survived.

-I was invited on an international expedition to Bikini Atoll as the coral expert.

We were, in fact, the first team of scientists to conduct our marine surveys on the reefs.

Heading out to the first dive, I was really full of anticipation.

I didn't know what to expect.

Over the 12 years of nuclear testing, the marine life and the islands of Bikini Atoll were just systematically decimated.

It was just total annihilation.

Having heard about the extent of the nuclear devastation, I thought maybe I would be confronted with a moonscape.

But as I cut through the water descending down to about 20 meters deep, I couldn't believe it.

I was absolutely shocked at what I was seeing.

♪♪ There were corals, there were fish, there were anemones.

There was everything you would expect to see on a normal, healthy reef ecosystem.

If you didn't know about the history, you would think that nothing had ever happened at this location.

♪♪ -Even the wrecks of ships deliberately sunk in the blast were covered in coral.

-It's phenomenal to think that in just 50 years, coral cover can come back to close to as good as you're gonna get on any reef around the world.

♪♪ ♪♪ To think that even the crater itself can be recolonized by corals and other marine life, it just shows you the potential that nature has for recovery if it's left alone.

♪♪ ♪♪ -Across much of our planet, nature is under pressure.

Yet it's essential for our modern way of life.

One of the first places we discovered this was here in Panama.

[ Insects buzzing ] [ Animals calling ] ♪♪ For most of human history, we lived among nature.. ...with great awareness of the plants and animals we depended on... ♪♪ ...something that the Embera-Wounaan still maintain.

♪♪ The forest is their home, but it is also important for the wider world because of one essential thing -- water.

[ Speaking Spanish ] The Embera here live alongside the Chagres River, the principal source of water for the world's greatest trade corridor -- the Panama Canal.

[ Horn blowing ] This 50-mile channel allows cargo ships to take a shortcut between two oceans in just 10 hours, avoiding a month-long journey around South America.

A million containers a week are carried along the canal, accelerating the flow of goods across the world.

-The building of the Panama Canal was the dream of humanity, of mankind.

It just united the world.

[ Horn blows ] -Opened in 1914 after 30 years of construction, this was an incredible feat of engineering, still in operation today.

Each vessel is raised up into the canal and down the other side through a series of colossal locks.

♪♪ -Every ship that goes through the Panama Canal requires about 50 million gallons of fresh water from the Chagres -- every ship.

And there are 40 ships a day, so you multiply that and it's an astronomical quantity of fresh water.

It's the energy, the water of the Chagres that makes possible the Panama Canal.

-Without this river, there would be no Panama Canal.

♪♪ Back in the '70s, the government of the time wanted the land to be more productive, so they encouraged people to create pastures.

The forest began to disappear.

-I started studying anthropology and I was asked to study the peasants of the Panama Canal watershed.

So in 1979, I went to the canal watershed.

And that, to me, was a revelation.

I had no idea of how serious this situation was.

The rate of conversion of forests to pastureland was astronomical.

[ Projector clicking ] That's what it looked like.

The smoke that you can see in the background, they're where a settler's moving in.

You cut here, you burn, and then the fire goes out of control and there's nobody to stop it.

♪♪ What used to be forest, now it's like a desert.

-When the rains came, the bare soil began to wash away, filling the rivers and lakes with sediment, reducing the amount of water for the canal.

-I came to realize this is gonna be such an accelerated rate of soil erosion and silting of the lakes, there would be no canal.

-Then in 1983, severe drought struck, threatening the canal.

Its closure would mean economic ruin.

-The issue went all the way to the president.

His response was, "Dr. Heckadon, this is a national security issue, and we have to stop it."

-The conversion of forest to pasture was thought to be the root of the problem.

So Dr. Heckadon's team began studying the ecosystem more closely.

-Gradually dawned on me how important a role in the cycle of water trees have.

In the forest, where you have lots of foliage and dried-out leaves and trunks and branches, the soil is softer, and so the water permeates.

And the dry season comes, and all that water stored in the soil begins to be pumped into the creeks, and there's water.

♪♪ -The forest soaks up the rainwater and steadily releases it in what's known as the sponge effect.

♪♪ This keeps rivers flowing through the seasons.

♪♪ It's a fundamental natural process that the Panama Canal depends on.

To protect the water supply, they had to protect the forest.

-If our proposal would not have been taken then, there would've been no Panama Canal today as we know it.

-A national park was created, safeguarding 320,000 acres of watershed forest.

The benefits of these forests are now officially recognized, and their value goes far beyond economics.

-If you do away with your forests, it's not only a matter of the diversity of plants and creature -- it's life itself.

[ Animals calling ] -25% of Panama is now national park.

♪♪ -When you look back, you get this satisfaction.

My goodness, where are we now?

Look how far we've come.

Human development and nature have to go hand-in-hand.

I think each country comes to a point, it has to make decisions.

What is the best not in the short term, but what is the best in the long term for the most people?

-By protecting the forest of the Chagres, Panama has prospered.

And the Embera are able to continue their way of life.

[ Indistinct conversations ] ♪♪ ♪♪ [ Children laughing ] ♪♪ [ Speaking Spanish ] ♪♪ The Panama Canal remains one of the greatest feats of human engineering.

And discovering the role that nature played was an awakening.

All of this is essential to all of this.

Today, more of us live in cities than anywhere else... ...where we can feel far from nature.

But there's a growing awareness that so much of our day-to-day lives depends on it.

[ Steam hisses ] -I think that, in some ways, people are more connected to nature than they realize.

I think that there is a big movement of people really trying to focus on where the things that they buy and the things that they use and things that they throw away come from.

And when you think of the grand scheme of things and everything that goes into just a simple cup of coffee, it can really make you think about your place in the world.

-All of Seattle's drinking water comes from the nearby Cascade Mountains.

It's protected land where natural filters the water for free, providing enough each day for over a million people.

At least 50 major cities are now safeguarding their natural watersheds, showing increasing awareness of the need for nature in our modern world.

♪♪ Midwinter in the Arctic Circle, the skies are lit by the aurora borealis.

♪♪ Here in northern Norway, one of the world's greatest food harvests is about to begin.

Each January, over 400 million Arctic cod migrate from their feeding grounds in the Barents Sea to breed in the warmer, sheltered waters of the Lofoten Islands.

♪♪ At 6:00 a.m., the fishing day starts.

People have worked these shores since the time of the Vikings.

[ Speaking Norwegian ] ♪♪ In its heyday in the 1950s, over 30,000 of these small boats would land more than a million tons of Arctic cod every year, without any restrictions on how much they could catch.

It was assumed that this vast resource could never be exhausted.

-Even many scientists said fishing doesn't matter much, because you cannot deplete the stock by just fishing.

-But nobody really knew how the stocks were doing.

So in the 1960s, Odd Nakken began to investigate.

-I was very interested in how to find out how much fish there is in the ocean.

-By studying cod numbers at sea rather than assessing the annual catch, scientists got a much clearer picture of the impact of fishing.

And the timing was important, as the industry was changing.

By the '70s, trawlers were making huge catches.

And the smaller fleets were still unregulated.

-Everyone tried to harvest as much as he can, of course.

It was very, very wasteful fishing and a lot of the fish were thrown overboard because it was too small for the markets.

And if you fish out the small fish, there will be no big fish some few years later.

♪♪ -Even with such heavy fishing, scientists predicted that cod numbers would grow because of increased spawning.

-In the end of the 1980s, we could see a lot of young ones up in the Barents Sea.

And on that basis, we said that there should be a marvelous, good cod stock at the end of the 1990s.

-But the fish never came.

[ Speaking Norwegian ] ♪♪ The disappearance of the cod was linked to another species of fish.

-The capelin stock broke down, and that's the main food for the big cod.

And what do the big cod do when there is no capelin?

They eat other small fishes.

So the cannibalism in the cod stock increased tremendously in those years.

-The cod were eating their own young.

This, combined with overfishing, caused the population to crash by 75%.

They had to stop fishing before there was nothing left.

That's exactly what happened on the other side of the Atlantic.

The impact on people's lives in Newfoundland, Canada, was devastating.

-In St. John's tonight, angry fishermen vented their rage.

They charged the room where John Crosbie was holding a news conference, but security would not let them in.

Mr. Crosbie says he has no choice but to close the fishery if the industry is to be saved.

-I have decided that effective at midnight tonight, there will be a moratorium on harvesting of Northern cod until the spring of 1994.

-Everyone expected the minister to close the Northern cod fishery... -But it was too late.

Pressure from international fleets in the trawling of the spawning grounds reduced the largest cod fishery in the world to almost nothing.

40,000 people lost their jobs in the biggest layoff in Canadian history.

♪♪ The situation in Norway was hanging in the balance.

-People that grow up in nature will see that if I take everything in one year, I will have nothing next year to eat.

-Severe quotas were introduced, and many fishermen went out of business.

No one knew if things would ever get back to normal.

-We were very lucky with nature.

We got a fantastic survival of the small fish.

For our cod stock, it took very short time.

So a few years later, we could start fishing again.

♪♪ ♪♪ [ Speaking Norwegian ] ♪♪ -Today, fish stocks are monitored rigorously.

And the information the scientists collect helps set the fishing quotas to ensure enough cod survive to spawn in the future.

This is also important for the ecosystem because a single cod releases as many as 9 million eggs.

Only one or two will become adults -- the rest, the foundation for an incredible web of life.

♪♪ ♪♪ All fishing here is now sustainable.

And Norway provides half the world's cod... ♪♪ ...working within nature's limits.

♪♪ In Newfoundland, some fishing villages remain abandoned and traditions are likely to be lost.

♪♪ 30 years since the moratorium, the Northern cod stocks still haven't recovered.

♪♪ Marine ecosystems are complex.

Perhaps in time, nature will repair itself.

But we can't predict how and when.

In Gorongosa National Park in Mozambique, a team of scientists are searching for Africa's top predator.

It's the best indicator of a healthy environment.

-They love tall grass.

This is where they hang out, and this is what makes them really good ambush killers.

It's like trying to find a needle in a haystack.

The signal is very strong now.

-Even with a tracking device, it's not easy to hunt them down.

-I think okay here, Doctor.

-Stop.

Be really quiet.

Don't make eye contact.

Do you have a clear shot from here?

-Yes.

-[ Whispering ] Quiet, quiet.

Nice.

-It went low, ah?

-Yeah, it went low.

-Alright.

-Okay, let's start the timer.

-The tranquilizer is low-risk to the lioness, but they still must work fast.

-This is a critical time.

We need to keep her within range and make sure she's safe while we sedate her.

You see her?

-Yeah.

12:00, Doctor.

-She's sleeping, ah?

-The team has just 20 minutes to change the collar and collect vital statistics.

-[ Clapping hands ] -She's out, ah?

-[ Clapping hands ] -Can we get her into the shade?

-Yeah.

-[ Grunts ] -The condition of these apex predators reflects the health of the entire ecosystem.

-While lion numbers are plummeting across the continent, this is one place where we actually are seeing a recovery take place.

And the way we study that is with the use of satellite collars.

This population of lions is indigenous to Gorongosa.

There's no one quite like them.

So they're a very unique group of lions, and they've survived a number of things.

But today, they're making a strong recovery.

-It's remarkable that lion numbers here are on the rise, given the difficult history of Gorongosa National Park.

Gorongosa was once known as the jewel of Mozambique because of its range of habitats and rich biodiversity.

In the 1960s, this 1,500-square-mile reserve was described by visitors as the place where Noah left his ark.

The amount of wildlife was extraordinary -- 14,000 buffalo, over 2,000 elephants, and the highest density of lions in Africa.

[ Gunshots ] Then, in 1977, everything changed.

-Civil war was very bad in Gorongosa National Park.

Almost 90% of mammals, animals were killed.

Opposition army used to come to the park and hunt animals.

They've killed first these big animals like elephants because of elephant tusk in order to sell the ivory, in order that they can buy firearms and ammunitions.

It was a disaster.

After war, everybody was down in terms of hope because they did not manage to recover the animal population in the park.

-With no wardens in the park and people desperate for food, the poaching continued.

The situation seemed hopeless.

[ Engine starting ] In 2003, philanthropist Greg Carr was looking for a new project when he was invited to Gorongosa.

♪♪ ♪♪ Restoring this landscape was an enormous task.

But a closer look revealed that the foundations were still there.

-[ Laughs ] Wow!

You look under this fallen tree here and there's termites, there's ants.

Everything bigger depends on these little things.

So a slightly larger insect will eat these tiny insects and then a bird will eat the bigger insect and so on and so forth.

There were small populations of all the wildlife that had been here -- maybe only 5%, maybe only 1%, but they were here.

The medium-sized grazers, like an impala, they were here in small numbers.

And that said to me it would be possible to restore this.

But because we were missing 14,000 buffalo, the grass was crazy high and the system was out of whack.

So we did need to bring back what they call the bulk grazers -- buffalo, zebra, wildebeest, the larger animals.

-Working with conservationists across southern Africa, they began a program to reintroduce the animals.

♪♪ ♪♪ This included 200 buffalo and 180 wildebeest.

-You got to start there 'cause it's what's called a grazing succession, meaning simply, the big guys like buffalo come through, they eat the big, tall grass, the coarse stuff that smaller antelope can't eat.

Then the smaller impala and the bushbuck and the reedbuck come through, and they munch on the smaller stuff.

-They also released a handful of other key animals, such as hippos and elephants.

[ Elephant trumpets ] -When animals were released, that was a very special occasion.

People start realizing that the old Gorongosa is coming.

♪♪ -Just 15 years later, the importance of these large animals is clear.

Ecologist Dominique Gonçalves has been studying the biggest of them all, and its impact on the forest.

-So, elephants really like Vichellia, or we call it here fever tree forest.

So, what happens, basically, is that they come here and they knock down the trees to eat.

It's really clear evidence of big, large herbivores kind of help maintain the place the way it should be.

For example, knocking down these trees not just maintain the ecosystem, the system the way it is, which is a mix of grasslands and forests and the way that it does not take over the grassland, but also, it's very important for the other organisms -- smaller antelopes and herbivores that would go and eat, for example, the roots of the trees and other things.

♪♪ ♪♪ ♪♪ This male elephant is just eating the shrub.

He's just enjoying some nice green leaves now from the shrub.

So, elephants can eat a lot.

And here in this park, we have more than 650 elephants, so imagine all of them eating and knocking down trees, shaking trees, eating the fruits just like he did.

Now he takes the seeds, see?

He shook that tree, he's eating the fruit.

It's all about taking the seeds from here.

And then he moves around throughout the landscape, which means it's just replanting the trees.

And that's why the trees also depend on the animals in this forest.

♪♪ -Today, the park is working well, and people have been a big part of that success.

-[ Singing in native language ] -Villages are helping to replant native forest, which creates shade for their coffee plantations.

♪♪ Agroforestry improves land and livelihoods, one of the many initiatives that benefits 200,000 people.

♪♪ A team of rangers patrol the park, keeping wildlife safe by removing any traps and snares.

-The park rangers here are all hired from the local community, and that's really key.

So, if the local community is empowered as the rangers, it's really the local people protecting their own heritage.

They're protecting their own national park.

-People are at the center of conservation.

If you don't help people, then conservation will not success.

-We ultimately removed 27,000 traps and snares from Gorongosa Park.

So, just as important as going to some other country and finding animals was just removing the traps here that were killing them and maiming them, and let nature rebound all by itself.

-The rate of the recovery is extraordinary.

A recent aerial census revealed the number of large animals had risen tenfold in just a decade, to 100,000.

♪♪ ♪♪ Carnivores are returning.

There are now 150 lions and counting.

Not one was reintroduced.

♪♪ ♪♪ -And this teaches that when given time, protection, and space, nature can come back very strongly.

It bounced back.

♪♪ ♪♪ ♪♪ -Now that we're finding ways to help nature, we can see the potential to restore the Earth.

♪♪ Much of central China once looked like this.

♪♪ But there are places where 8,000 years of human activity had stripped the land bare.

♪♪ The story of the Loess Plateau is little short of a miracle.

John Liu has followed it for over 25 years.

-Coming out to the Loess Plateau has completely changed my perspective on life.

There's no difference between the interests of human beings and the interests of nature.

-In 1994, John was sent to cover the biggest story of his career.

-I'd been a journalist in China for about 15 years, and then the World Bank asked me to go out to the Loess Plateau.

Well, the Loess Plateau is 640,000 square kilometers, approximately the size of France.

But it's also the cradle of Chinese civilization because all the cultures were growing up around the Yellow River because it's very, very fertile.

The soil type is loess, and it's a wind-borne sediment.

It's very minerally rich.

But because it's so powdery, if you remove the vegetation and you expose it to the wind and to the rain, you get a completely different result.

Essentially, when it rained, without any vegetation, all of that water would run off and it would take the topsoil.

And so that's what makes the Yellow River the Yellow River.

And so, over thousands of years, it became the most eroded place on Earth.

The Loess Plateau was contributing 1.6 billion tons of silt into the river every year.

-This made it prone to flash floods.

Over the last 150 years, it has claimed 7 million lives, earning it the name China's Sorrow.

-We had images of the place without any vegetation.

This is the scale of it.

The scale was just astonishing.

You couldn't believe that this was happening.

I mean, the whole place was denuded of vegetation.

There was just nothing there.

We saw that the sheep and goats were just denuding everything.

I mean, if anything stuck its head up, it was food.

The area was in ecologic collapse, and the reason was human activity.

[ Bleating ] -The loess soil is so fine, it would take to the wind, causing severe respiratory symptoms, and send dust storms as far as Beijing.

-You know, the situation was so grim -- the repeated cycle of flooding then followed by drought and followed by famine.

[ Speaking Chinese ] ♪♪ The Chinese government said we have to do something here.

And when I went out there and I saw a place that looked like the moon, I was just fascinated.

So enormous, and really nobody knew anything about it.

You know, when you look in an area which is that massively degraded, it's not your first thought that, "Well, that's fine.

We can just fix that."

-In the 1980s, around 85 million people were living in the Loess Plateau, putting enormous pressure on the land.

-When the experts came through and started to analyze what was going on, they said, well, in order to change it, we have to basically change the behaviors of all the people.

-[ Speaking Chinese ] -Essentially, all their behaviors were banned.

So they were unable to cut trees, they were unable to farm on the slopes, and then free-ranging of goats and sheep was made illegal.

-The people had to be part of the solution.

[ Speaking Chinese ] -So what they did was they paid the people to redevelop the landscape.

-In 1994, work began in earnest on one of the biggest land rehabilitation projects ever attempted.

The hills were terraced to slow the flow of water, allowing it to soak into the soil.

-The scale of this was just unbelievable when you when you went out there and you saw that they were using just hand tools or simple machinery and that they were doing this over vast areas.

And of course, revegetation was a big part of it.

The top had to be trees and had to be totally vegetated, totally reforested.

♪♪ ♪♪ -John has documented the results ever since.

♪♪ -I put my tripod here and looked out at these areas back in 1995.

♪♪ Well, this is a change.

This is amazing.

If you can take a place that has been destroyed over thousands of years and bring it back to life, this is pretty astonishing.

Took a long time to degrade, but actually, the restoration is going much faster.

Now you can see, in 25 years, it's completely different.

And this is done by ordinary people.

This is huge.

This is the way forward.

-In just a generation, the land has returned to health.

The fertile soil is now stable, and the water is retained in the earth and the plants.

-Now we feel the relative humidity, we see the mist in the air, and so that's very important for increased productivity.

♪♪ -More plants mean more insects... ...attracting more birds, which spread new seeds, increasing the plant life further in a natural cycle of recovery.

-When we see a stream which is flowing clear as this is, then it's an indicator of ecological health.

Without all this vegetation, without organic soil, you'd be taking the sediments in here and it would be cloudy.

Amphibians are a really good indicator of ecologic health.

-And healthy nature benefits everyone.

The people who still live in these communities now have a much better quality of life.

♪♪ [ Speaking Chinese ] -Humans are part of nature.

And we need to change the intention of human civilization to restoring ecological function on a planetary scale.

If we do this, we're ensuring the quality of life for future generations.

[ Speaking Chinese ] I'm happy to see that they're in another space.

The grandchildren are all college-educated.

That's pretty impressive.

There's been massive improvement not only in the ecology, but in socioeconomic circumstances.

Materialism has suggested that wealth is coming from things, but in fact, wealth is coming from ecological function.

-The benefits of this restoration are felt all across China.

[ Birds crying ] The sediment in the Yellow River has been reduced by 80%.

It's the healthiest it's been for centuries.

-The lessons of the Loess Plateau, you can see that it's possible to rehabilitate large-scale damaged ecosystems.

But we can also see a next step, the next level of understanding.

We're looking at a new age -- the age of nature.

-Our world faces many challenges, but we have learned so much.

We're aware that our actions have impact.

We can see nature's ability to recover... ...and the good that comes with restoring our Earth.

This is the awakening of a new era.

♪♪ -To order "The Age of Nature" on DVD, visit shopPBS or call 1-800-PLAY-PBS.

This program is also available on Amazon Prime Video.

♪♪ ♪♪