Original subtitles

[radio static]

[beep]

[indistinct radio chatter]

[David Attenborough] Just 50 years ago,

we finally ventured to the Moon.

For the very first time,

we looked back at our own planet.

Since then, the human population has more than doubled.

This series will celebrate the natural wonders that remain

and reveal what we must preserve

to ensure people and nature thrive.

Dolphins...

panicking.

They're being hunted by false killer whales.

[birds cawing]

Dolphins are faster in short bursts.

But their hunters have stamina.

Just as the killer whales close in,

the dolphins make a sudden turn to evade their predators.

These extraordinary events are taking place far from land,

where few of us ever venture.

This is the ocean beyond the boundary of any country...

largely ungoverned, wild, and lawless.

Nothing symbolizes our relationship with the high seas

better than the blue whale.

Weighing 200 tons and 30 meters long,

these are the largest animals ever to have existed.

Yet much of their lives is still a mystery to us.

Blue whales live far out to sea,

roaming every ocean from the tropics to the poles.

We have only recently discovered

a few special places where they come close to shore.

The Gulf of California,

on Mexico's Pacific coast.

This is a sanctuary for blue whales.

[whale huffing]

Meet the world's biggest newborn...

a baby blue.

Just a month old,

she's already eight meters long and weighs six tons.

Her mother shelters her with a protective fin.

They caress one another, cherishing their close bond.

These are the most intimate images ever captured

of a blue whale mother and her calf.

This female will give birth only once every two or three years,

so each baby blue is extremely precious.

The calf will grow three tons a month.

Once, there were more than 300,000 blue whales,

but last century, they were hunted relentlessly,

and only a few thousand survived.

Blue whales are now protected,

and their numbers are slowly increasing.

Soon, this calf will leave these sheltered waters

to roam the high seas.

We once thought that the high seas were simply too vast for us to damage,

but we now know that her ocean home is under threat as never before.

Out here in the big blue, there remain a few pristine places

to remind us how rich the oceans can still be.

Spinner dolphins.

In the Pacific, off the coast of Costa Rica, Central America,

they are starting to gather in great numbers.

Spinners live in pods,

groups of individuals linked by complex social relationships.

[dolphins clicking]

The dolphins constantly touch and talk with one another,

using a language of clicks and whistles.

[dolphins clicking and chittering]

They are shadowed by yellowfin tuna.

The tuna rely on the dolphins to find food.

Everyone is searching for the same prey...

lantern fish...

the most numerous fish on the planet.

No longer than your finger,

lantern fish spend most of their time hiding in the deep.

So, despite their astounding abundance, we don't fish for them.

They are one of the few fish that still thrives.

As they close in on their prey, the dolphin pod gets bigger and bigger.

This pod could be 10,000 strong.

For every one at the surface, 20 swim below.

[dolphins clicking]

Using echolocation, a type of sonar,

the dolphins detect lantern fish in the depths

and drive them to the surface.

They patrol the underside of the shoal

to stop their prey escaping back to the deep.

[clicking and chittering]

Once the dolphins have had their fill,

there's still plenty more for other predators.

Mobula rays swoop in.

To maximize their catch, the rays attack in formation.

A wall of mouths scooping up their prey.

Because we don't fish for them, lantern fish and their predators thrive.

All these hunters have barely made a dent in the great shoal.

Most life in the open ocean is concentrated in a thin surface layer,

where the power of the sun has its greatest effect.

These sunlit shallows are fertilized in a surprising way.

As the dolphins produce waste, they play a vital role,

recycling nutrients from the deep up to the surface.

[dolphins chittering]

This marine manure

helps to fuel the basis of all life in the open ocean.

Phytoplankton...

microscopic drifting plants.

They combine nutrients in seawater with energy from the sun

to create the very foundation of every food chain out here.

So all animals, from the smallest fish to the largest whale,

ultimately depend on these tiny plants for food.

And in turn, the phytoplankton benefits from the nutrients

produced by these animals.

Crucially, phytoplankton also produce half the oxygen in the air we breathe.

So, no matter where you live,

you can thank these exquisite little plants

for every other breath you take.

In ideal conditions, they can bloom to such an extent

that great swathes of the ocean turn green.

Surprisingly, phytoplankton also play a vital role in cloud formation.

[thunder rumbling]

Moisture evaporating from the ocean

condenses around tiny particles created by the plankton.

These droplets combine to grow into colossal clouds.

They can rise 20 kilometers into the atmosphere.

These oceanic clouds reflect the sun's energy back into space,

helping to protect the Earth from rising temperatures.

Not only do the oceans produce half the oxygen we breathe,

they also drive the weather and climate,

transporting life-giving fresh water around the world.

[thunder rumbling]

The high seas are the life-support system of our planet.

They have such power simply because they're so vast.

The oceans cover two-thirds of the globe, and that's just the surface.

They're also immensely deep.

We can only journey to this unexplored space

in special submarines that can withstand the crushing pressure.

The average depth of the oceans is nearly four kilometers,

and the deepest point more than ten.

The deep makes up 95 percent of all the space available for life.

This alien world is home to weird and mysterious creatures.

Few are stranger than this one.

For years, we only knew they existed from the occasional one washed ashore.

They have hardly ever been seen alive.

An oarfish.

Ten meters long.

Hanging vertically

and using rhythmic waves along their dorsal fin,

oarfish commute easily between the surface and the depths.

Below 200 meters, there's not enough light for plants to grow,

so deep-sea animals depend on food sinking down from the surface...

marine snow.

A crown jellyfish drifts with tentacles outstretched

to ensnare pray.

They live in every ocean, to depths of seven kilometers.

The deep is so vast that these could be the most abundant of all jellyfish.

We used to think the deep supported little life,

but scientists now believe

there are ten times more animals living here than previously thought.

So, there must be many yet to be discovered.

This deep-water crustacean, Cystisoma, is as clear as glass.

It hides in plain sight.

In this twilight zone,

invisibility can be the difference between finding a meal and being one.

Its huge eyes strain to see in the gloom.

No light penetrates below a thousand meters.

In this darkness, animals create their own light...

bioluminescence.

A glowing lure entices victims into this dragonfish's terrifying teeth.

On most expeditions down here, we are surprised by something new.

A deep-sea anglerfish.

Her extraordinary array of sensors

will detect even the faintest movement by prey tempted to her lure.

Here, in the deep midwater, predators play a patient game.

Eventually, we reach the bottom,

nearly a thousand meters down.

The deep-sea plains cover more than half the Earth's surface,

and yet we know more about the surface of the Moon.

Chimaera, an ancient relative of the shark,

up to two meters long.

Few species of this size can make a living on the barren seafloor.

Moving slowly to conserve energy,

they use special electrical sensors around their mouths

to search for scarce prey buried in the sediment.

Rocky outcrops rising from the seafloor can be oases in this desert.

This ragged-tooth shark has come here for good reason.

Five hundred meters down off the coast of Florida,

a rare hot spot of life.

Lophelia, deep-sea coral reefs.

We used to think that corals

were only found in the warm, sunny shallows.

But, astonishingly, deep-sea reefs cover a greater area of the seafloor

than their shallow-water relatives.

These underwater forests

provide shelter and food for a rich community of marine life.

They're also vital nurseries for many deep-sea creatures.

The corals are made up of many anemone-like individuals,

polyps that live in colonies connected by a hard skeleton.

The polyps have stinging cells in their tentacles

to snare passing prey, their only source of food.

But they don't always get to keep their catch.

A bristle worm has set up home within the coral.

It checks the polyps for a freshly caught morsel...

and steals it from the coral.

But this theft is actually a protection racket.

Urchins attack and eat the corals.

Time for payback.

The urchin may have protective spines, but the worm has a shocking weapon,

and goes on the attack.

The urchin has been seen off,

and the worm has saved its home.

Like most deep-sea animals,

these corals grow extremely slowly.

Some reefs may be 40,000 years old.

Despite being so far beneath the surface, these corals are still within our reach.

Deep-sea fishing nets dragged across the seafloor

reduce the fragile reefs to rubble.

Half of all deep-sea corals have already been destroyed.

It will take centuries for these communities to recover.

Beyond the boundary of any one country,

the high seas are wild and barely protected.

Wildest of all, the Southern Ocean,

home of the albatross.

Albatross live solitary lives far out to sea.

They can travel hundreds of kilometers a day,

often for weeks at a time, searching for food.

A dead sea lion is a rare opportunity.

Giant petrels are the first to arrive.

They use their powerful beaks to rip the carcass open.

Known as sea vultures,

they are the top scavenger in Antarctic waters.

[cawing]

Black-browed albatross have an extraordinary sense of smell

and can follow a scent from 20 kilometers away.

The black-browed must grab mouthfuls when they can.

They are bullied by the more aggressive giant petrels.

Wilson's petrels are too small to compete

and pick off scraps from the edge of the frenzy.

These delicate little petrels are the most numerous of all seabirds

because they're found in every ocean.

[cawing and squawking]

It's only when these normally solitary birds

gather like this

that we can appreciate the wealth of life supported by the high seas.

A wandering albatross is last to arrive.

It dwarfs the other birds and uses its great size

and three-meter wingspan to dominate.

Even the giant petrels back off.

The wanderer finally gets its share.

In recent years, albatross and other seabirds

have been in decline.

Their need to travel great distances exposes them

to the dangers of a poorly regulated and overexploited ocean.

It's a problem for all hunters of the high seas.

These giants cross entire oceans in their search for food.

They can grow over three meters long and weigh half a ton.

Bluefin tuna.

They're streamlined to perfection and built for speed.

They hunt in great packs, hundreds strong.

The target: a school of anchovies.

They gently corral the anchovies into a tight ball at the surface,

careful not to cause panic.

And then they attack.

This is a highly coordinated hunt.

The tuna take turns,

striking from the same direction to keep the anchovies on the run.

After a mouthful, each bluefin peels off to take its place at the rear.

Wave after wave continues the assault.

With their power and devastating pace,

bluefin tuna are one of the ocean's most impressive hunters.

They are also the most prized fish in the sea.

So valuable that a single bluefin can sell in Japan

for over a million dollars.

So, perhaps it's inevitable

that they have been fished almost to extinction.

Bluefin tuna are not the only ones in peril.

Decades of unsustainable fishing

have left many fish stocks in serious decline.

A third have collapsed altogether.

Plastic pollution is a grave issue for our oceans,

but industrial overfishing is far more dangerous.

If we continue to harvest the seas in this way,

it's not just fisheries that will collapse.

The whole ocean system could follow.

One hundred million sharks are killed every year,

just to make shark fin soup.

Ninety percent of all large ocean hunters have disappeared.

Without them at the top of the food chain, the whole community of marine life

is declining and changing beyond recognition.

Squid are increasingly replacing fish.

We have severely depleted both their predators and competitors,

so squid are taking over,

an indication of a serious imbalance in the oceans.

Squid breed quickly and have lots of fast-growing young,

so they can rapidly exploit the gaps left by the fish that we have harvested.

They lay their eggs in cases on the seafloor.

The young develop even faster in these warm, shallow waters.

With such drastic changes in the marine menu,

predators are having to adapt.

Sea lions prefer to eat more energy-rich prey,

like anchovies and sardines,

but with these in short supply,

they're forced to rely more on a diet of squid.

We, too, will be forced to change the seafood we eat

if we continue to fish as we do.

But if we harvest the oceans in a sustainable way,

they can be marvelously productive

and will provide us with an abundance of food.

There are already signs that the ocean has the power

to recover astonishingly quickly.

Humpback whales.

They live in every ocean,

traveling the high seas, from their polar feeding grounds

to the tropics, where they breed.

[whale song]

Yet whales have not always enjoyed such freedom.

Once, there were more than a hundred thousand humpbacks

in the oceans,

but last century, they were hunted to near extinction.

Just a few thousand survived the onslaught.

A huge public outcry

finally led to a ban on commercial whaling in 1986.

Since then, the number of humpback whales has been steadily increasing.

They're returning to their ancestral feeding grounds,

like these off the coast of South Africa.

[whale song]

They are gathering to take advantage of a seasonal abundance of krill,

tiny shrimp-like crustaceans.

The whales take in great mouthfuls of water,

trapping the krill on sieves of hairy bristles

that line their jaws.

Each whale can eat over a ton a day.

With food so plentiful, fur seals come to claim their share.

[whale song]

These extraordinary scenes were unimaginable just a few years ago.

They form super-groups, hundreds strong.

This is the greatest gathering of whales seen for a century.

Whales recycle nutrients that enrich surface waters,

which fuel the growth of phytoplankton,

and they, in turn, feed krill in a perfect self-sustaining cycle.

We now know that a healthy community of great hunters,

whales, dolphins, tuna, and sharks,

is essential for a fully-functioning ocean.

And a functioning ocean is vital to the health of our planet

and humanity.

In a remarkable recovery,

humpback whales have almost returned to their original numbers.

But during that time,

we have done more harm to the oceans than ever before in human history.

Only with global cooperation

will our oceans recover and thrive once again.

We saved the whales by international agreement.

Now, it is time to save our oceans.

Please visit ourplanet.com to discover what we need to do now

to protect the high seas.

♪ I can hear the whole world Singing together ♪

♪ I can hear the whole world Say it's now or never ♪

♪ 'Cause it's not too late If we change our ways ♪

♪ And connect the dots to our problems ♪

♪ I can hear the whole world Say we're in this together ♪

♪ We're in this together ♪

[vocalizing]

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