All language subtitles for 4) A Perfect Planet-Oceans

A Perfect Planet.

All life in the oceans depends
on the continuous movement of water.

There are not five separate oceans
on Earth...

..but just one...

..whose parts are linked by
powerful, unceasing currents.

Every drop of seawater on Earth
rides these currents,

taking a thousand years
to complete a single circuit.

And where there are currents...

..there is life.

Off the coast of South Africa,

dolphins are on the hunt.

They have found a cold-water current

and are now travelling along it
looking for food.

Gannets follow them.

They know that doing so
is the fastest way to a meal.

A shoal of mackerel...

..just what the dolphins
have been looking for.

They encircle the fish,
driving them into a bait ball,

and then trap them against
the surface

to prevent them from escaping
to deeper water.

Now, the fish are within range
of the dive-bombing gannets,

who hit the water at 50mph.

A sudden gathering of thousands
of predators brought together

by the flow of currents.

Last to the feast are sharks.

In these vast, open waters,

finding food would be all but
impossible without currents...

..the highways of the seas
that bring this life together.

When the bait ball
has been dispersed,

all that is left are scales
drifting downwards.

They are part of a slow,
never-ending blizzard

of organic waste that eventually
settles on the sea floor.

But it doesn't stay here forever.

The currents sweep it back up
into the sunlit surface waters...

..where it nourishes
clouds of phytoplankton...

..simple microscopic plants
that are the pastures of the seas.

There are thousands
of different kinds,

and together they produce half of
all the oxygen in the atmosphere...

..more than all our forests
and jungles combined.

And, by absorbing carbon,

they are our greatest ally
in combating climate change.

Plankton are the foundation
of almost all life in the ocean,

for, in those places where
the currents bring nutrients

to the surface, they multiply
in astonishing numbers...

..turning the ocean green.

The currents travelling through our
oceans bring life to seas

that would otherwise
be marine deserts.

The Galapagos Islands lie
in the path of one of them,

the deep-flowing Cromwell Current

that runs for 6,000 miles
across the Pacific.

As it approaches Fernandina Island,

it rises and delivers nutrients
into its shallows.

And it also brings life
to this otherwise barren island.

Iguanas.

There are thousands of them.

And yet there's nothing on the
island for these vegetarians to eat.

Or...

..almost nothing.

Cormorants bring seaweed ashore
with which to make their nests.

But what is building material
for a cormorant

is food for an iguana.

Both these species evolved here,

but that doesn't necessarily
make them good neighbours.

No matter.

He knows where there's
more elsewhere.

He's a marine iguana...

..the only lizard in the world

that gets its food from the sea.

The seaweed on which
he totally relies

only grows in abundance here

because of the nutrients
brought by the Cromwell Current.

Once in the water, he has just
30 minutes to find food.

Any longer than that,

and his muscles will seize up
and he'll drown...

..for, like most reptiles,
he can't handle the cold.

Chilly water isn't a problem
for a warm-blooded cormorant.

She can swim in it all day,

but can only hold her breath
for a few minutes.

He, on the other hand,

completes his whole half-hour trip

on one single breath.

His flat face and sharp teeth

make him an efficient
seaweed-cropping machine,

but with the clock ticking,
he must eat fast.

The cormorant, having caught
its fish...

..goes back to the surface.

One last mouthful,

and it's also time for the iguana
to head for home.

But to stop his muscles from seizing
up in the cold water,

he must get back quickly.

So he could do without
the attentions

of an inquisitive sea lion.

Dry land is now just 30 metres away,

but the biggest hurdle
is still to come.

The surging water now fights
against him.

He's out, but he's stayed
in the cold so long

that he's lost his strength.

And he's made it.

Few reptiles on the planet have
to work harder for a meal

than he does.

And, tomorrow, he'll have to
do it all over again...

..unless next time...

..he can outwit his neighbour.

Over 100,000 marine iguanas
live on Fernandina...

..and each owes its existence
to the Cromwell Current

that brings nutrients
to these shores.

But there is another,
much bigger, current

which carries water from the Pacific
into the Indian Ocean.

On this great journey, it travels
through the islands of Indonesia,

bringing together life
from both oceans.

A third of all the world's
reef fish live here.

Some call it the Coral Triangle,

the most diverse marine region
on Earth.

The variety here is dazzling,
not just of coral,

but of animals of all kinds.

Few are stranger than
the flamboyant cuttlefish.

This is a male,
just five centimetres long.

Swimming against the current
isn't easy when you're small,

so, instead, he prefers to walk...

..very, very slowly.

He's a master of camouflage.

But, right now,
he wants to be noticed.

He's looking for a mate.

His potential partner
is a giant, by comparison,

four times his size.

When it comes to courtship,

being flamboyant isn't enough.

To win her over, he must dazzle.

His aim is to deposit
a packet of sperm

inside her mouth.

Close...

..but no cigar.

He'll have to turn up the dazzle.

Take two.

Bingo!

His job is done.

Now she must find somewhere
to lay their eggs.

An old shell will do nicely

if she can slip past
the present occupant.

She fastens her eggs to
the underside of the shell,

where they'll be safe
from predators.

The current that brings so much life
to the Coral Triangle

now washes the eggs with clean,
oxygenated water.

After just three weeks,
they start to hatch.

Smaller than a human fingernail,

the hatchlings are now carried
by the current

to other parts of the reef.

And, in just a few months,

this young male will be ready
to find a female of his own.

By a stroke of cosmic good fortune,

the Earth has a satellite...

..the moon, which orbits our planet
every 27 days.

Its gravitational pull drags
our oceans across the planet...

..and so gives us the tides.

Unlike currents that stir
the open ocean,

the tides have their greatest impact
on the coasts,

flushing them with nutrients
from both sea and land.

And nowhere are they more violent
and dramatic than here...

..Norway's Saltstraumen strait.

Every six hours,

nearly half a billion tonnes
of water

are forced through a channel
just 150 metres wide.

Its very narrowness accelerates
the water...

..making this the strongest
tidal pull in the world.

Most animals caught here
would be swept away.

But not these tidal specialists.

Eiders are one of the few ducks

that depend totally on the ocean
for their survival.

And they're the only kind
strong enough

to live permanently
in these racing waters.

But there is food here,
and in great quantity,

for any that can gather it...

..mussels.

They filter out particles of food
brought to them by the tide.

And eider ducks love mussels.

The challenge is reaching them.

Eiders seem to be the only creatures

that can hold their own
in the fast-flowing water...

..so they have the mussels
all to themselves.

They swallow them whole,
shell and all.

Each eider duck eats
hundreds of mussels a day...

..a year-round feast
that no others can reach.

The tides here owe their power

to the unique geography
of the coastline.

But, elsewhere in our oceans,

the lay of the land influences tides
in a very different way.

Here in the Bahamas,

wide, shallow sandbanks
mean the tide moves gently

over the sea floor...

..turning what would be
a sandy desert

into a rich underwater habitat.

This is the home of garden eels
and razorfish.

And fresh food arrives for them
from deeper waters twice a day.

Life seems unhurried and gentle...

..but there is trouble in paradise.

These bottlenose dolphins
eat razorfish,

and they're not so easily fooled
by vanishing tricks.

They scan the sand
with echolocating clicks

to discover exactly
where the razorfish are hiding.

But knowing where they are
is not the same as catching them.

The more the dolphins dig,

the deeper the razorfish burrow.

But it's clearly not deep enough.

Blowing jets of water into the sand

exposes even the most
hard-to-reach razorfish.

Before long, the dolphins
have had enough and they move on.

It looks as if they have picked
the sand clean...

..but here, at least,

there really are
plenty more fish in the sea.

Closer to the land, the same tides
bring nourishment

to one of the most threatened
of coastal habitats...

..mangrove forests.

Part land...

..part sea.

Mangroves are the only trees

capable of surviving in salt water

and are specially adapted to it
coming and going twice every day.

As sea water floods in,
fish come with it.

Here in the flooded forests,

they can find both food and shelter.

Stingrays ride on the incoming tide.

Other commuters follow.

Young lemon sharks,
still far from full-grown,

are looking for food.

When the tide is at its highest,

even adult lemon sharks

can get into the mangroves.

A three-metre female
moves cautiously into the shallows.

She can't stay here for long,

but, then, she hasn't come here
to hunt.

She's come to give birth...

..returning to the very place
where she was born.

She has nourished the pups
inside her body

with a placenta, as we do.

The mangroves provide
an ideal nursery for them,

and placing them here gives them
an excellent start,

but that is the end of her
parental care.

She has to return to deeper water
before the tide goes out.

Her young must now fend
for themselves.

The pups instinctively take refuge
among the roots of the mangroves.

They're so small, they can swim deep

into this tangled labyrinth.

With the tide fast receding,

even they need to find a place

where they won't be left
high and dry.

A place like this...

..a permanent pool in the heart
of the mangrove forest.

Only the smallest sharks
can get here,

and only at the highest tides.

The pups will spend
the next two years here

perfecting the skills that make them
one of the ocean's top hunters.

And it seems...

..that there's a lot to learn.

Got one!

All life at the coasts has to move
to the daily rhythm of the tides,

but tides are not the same
throughout the year.

Every month, when our planet, the
moon and the sun are all aligned,

the increased gravitational pull

produces particularly high tides.

And this triggers
a truly extraordinary event

on one particular reef
in the central Pacific.

Thousands of resident surgeonfish

begin to assemble
on these high tides.

And they are being followed by one
of the largest fish in the sea...

..manta rays.

The rays spend their year
moving between coral islands.

But it's only now, when the tide
is at its highest

and the surgeonfish have gathered,
that they appear

on this particular reef.

Their timing is so perfect

that they rarely have to wait
more than an hour

for the event to begin.

At the precise moment
when the tide is at its highest,

the surgeonfish begin to spawn.

They release billions of eggs
and sperm into the water.

Breeding in this way
gives their fertilised eggs

the best chance of being
carried on the tide

away from predators
that haunt the reef.

All except one.

The mantas move in.

They gorge on the eggs,

filtering them out
using specially adapted gills.

If the mantas had arrived
just an hour later,

there would have been nothing here
for them to eat.

No-one knows how the mantas
are so perfectly in tune

with the rhythm of the tides.

But they appear without fail
whenever the surgeonfish spawn.

Most of the eggs, however,

are carried out into the open ocean

before the mantas
are able to eat them all.

The rhythms of coastal life are
influenced by another ocean force.

Winds blowing over the sea
so batter the surface

that it begins to rise and fall.

These swells may travel far

and reach the shores
of even the most sheltered bays.

As they approach shallower water,

they turn into waves.

A shoal of hardyheads,

close to the beach
of Australia's Lizard Island.

The clearness of these glassy waters
shows that they lack nutrients.

But the gentle waves
expose food hidden in the sand,

and that's what the hardyheads
are looking for.

But... they must beware.

Packs of trevally are on the hunt.

The hardyheads stick together.

There's safety in numbers.

But they're vulnerable, nonetheless.

They're so small, they can swim
in the shallowest waters...

..even in the body
of the waves themselves,

out of the reach of their enemies.

But trevally aren't their
only concern.

Blacktip reef sharks.

They are bigger and more powerful
than trevally...

..but not as fast or as agile.

The hardyheads are well aware
of them,

but, so long as they stay
just out of reach,

they have little to fear.

But now the sharks
and the trevally join forces.

Together, they enter the shallows,

each looking for a chance to attack.

The trevally make the first move...

..and the hardyheads take refuge
again in the waves.

And this is what the sharks
have been waiting for.

Surging forwards, they chase
the hardyheads out of the water...

..beaching themselves in a daring
bid to hoover up their prey.

The hardyheads that escape
the sharks

swim back out to deeper water...

..but into the mouths
of the trevally.

Now the receding waves
help to pull the sharks back

into deeper water.

In the chaos, the sea birds
get their chance.

It's a feeding frenzy...

..in only ten centimetres of water.

The power of waves
is dramatically evident

when they crash onto our shores.

But the biggest of all start far
away from land, out at sea.

Great storms blowing over
the surface of the ocean

raise towering walls of water.

Such giant swells can travel
for thousands of miles.

As they approach land,

the shallowing sea floor begins
to drag on their undersides,

and they topple forward...

..and break.

This stirring of the ocean
produces great riches.

The Falkland Islands are surrounded

by some of the stormiest
waters on Earth...

..ideal hunting grounds
for rockhopper penguins.

It's the breeding season

and, for the last two weeks,

the males have been incubating
the eggs by themselves.

They're confined to the nest
with nothing to eat,

while the females are out at sea
collecting food.

All across the colony,
eggs are starting to hatch.

This male now has two youngsters
to care for.

But he has no food to give them,
and he can't leave them unprotected.

He can do nothing but wait.

The females, after weeks
fishing in the stormy seas,

are now heading for home
with food in their crops.

There's just one problem.

The colony sits at the top
of huge cliffs.

The waves that make feeding
so good here

have now become major obstacles.

Timing is vital.

Go too early...

..and they could be smashed
against the rocks.

Too late...

..and they will be carried
back out to sea.

Hooked claws now help
to get purchase

on the slippery rocks.

But they're not out of trouble yet.

Success depends on both judgment...

..and luck.

Time and again,
the waves drag her back in.

She has to persevere.

The lives of her chicks
depend on her safe return.

Finally...

..she's made it.

They're not called rockhoppers
for nothing.

With one more jump, she's home.

And just in time.

Her chicks are desperately hungry.

This is their first proper meal.

The oceans have sustained life
on our planet for millions of years.

But, today, there's growing evidence
that this is changing.

As our climate warms,

polar ice sheets are melting
at an alarming rate.

In the Arctic alone,
14,000 tonnes of fresh water

are emptying into the sea
every second.

This is slowing the flow of currents
around the globe.

And, if the atmosphere
continues to warm,

ocean circulation could eventually
stop altogether.

Our seas would then stagnate,

threatening the life within them.

And there are places
in the oceans today

where this is already
beginning to happen.

The Gulf of Thailand.

Eden's whales have lived here
for generations.

But the world around them
is changing.

Today, agricultural pollution
flowing from the land...

..is beginning to suffocate
this sea.

Many fish now stay closer
to the surface,

where the waters still contain
enough oxygen to survive.

Eden's whales depend on these fish.

They swallow huge
quantities of water

before filtering out their prey.

It takes a lot of energy
to drive their 15-tonne bulk

through the water.

And, with so few fish,

the rewards from feeding like this
are barely worth it.

So, to survive here,

the whales have developed
a new hunting technique...

..one that requires almost
no effort.

They simply open their mouths...

..and wait.

The panicked fish jump right in.

Swimming alongside,

another whale scares even more
into the open jaws.

With this ingenious new technique,

Eden's whales have found a way
to survive the pressures

they now face.

All across the planet,
animals are having to adapt

to a changing world.

But the speed of these changes
will be too fast for many.

If we could only halt our
unrestrained plunder of the ocean,

its habitats and species
would recover.

And, at a time when our
overexploited lands

are already failing us,

this has never been more important
for humanity.

The volcanic island of Fernandina
in the Galapagos

is home to two incredible lizards...

..the land iguana
and the marine iguana.

There are two parts to their story

that cameraman, Richard Wollocombe,
has wanted to film

since he first came to
these islands 25 years ago,

and, on A Perfect Planet,
he got his chance.

Driven by powerful currents,

the cold Pacific Ocean
slams into Fernandina's shores.

The marine iguanas must brave
these waters every day.

Their journey through the big surf
is what Richard and the team

are here to film...

..but from underwater.

It looks fairly benign
from the surface here,

but, underneath,
it's really shallow,

and there's all these really sharp
rocks with lots of jagged edges.

So if we were taken by the wave,

it would cut us up really badly,
I think.

Whose idea was this?

Ha-ha, ha-ha.

I'm a glutton for punishment,
did you know?

The waves are certainly punishing.

With these dangerous conditions,

extra protection is clearly needed
for Richard and dive buddy Rafael.

So what better than surf helmets?

It isn't long before Richard
realises what he's up against.

The relentless churning
of the water makes it difficult

to stay the right way up...

..let alone film the iguanas.

In between the waves,
the iguanas briefly appear.

But Richard barely has time
to line up a shot...

..before the iguana disappears
behind another wave.

In the violent surge,

the iguanas have learned
to hang on to the rocks...

..a trick Richard is quick to copy
to avoid being swept away.

That, however, only leaves
one hand to film with.

But, with adrenaline
carrying him through,

Richard is able to get the perfect
shots of iguanas in the surf.

And to achieve that totally
unscathed is a great relief.

I don't need to go to the gym
for months after that!

Well done, mate. Good job.

On the shore, land iguanas have
to battle a very different force.

Each year, they migrate up to the
top of Fernandina's active volcano,

a journey of ten days
across razor-sharp lava

before descending into its heart
to lay their eggs

in the ashy floor.

It's this behaviour Richard
and the team plan to film,

and the scale of the expedition
is one that's rarely been attempted

in the Galapagos.

To reach the top takes the crew
ten gruelling hours.

When they finally arrive on the rim,

the experience doesn't disappoint.

I can't believe it.

It's absolutely awe-inspiring.

I just can't believe the iguanas
actually manage

to navigate down these slopes
into the bowl of this volcano.

More people have been into space
than to the bottom

of Fernandina's crater.

But that is exactly where Richard
and the team must go

if they are to film
the nesting iguanas.

From their campsite
at the edge of the volcano,

it's an extremely dangerous journey
down to the crater floor,

and assistant producer Toby wants
to be clear with everyone

what is at stake.

There's only one passable
route down,

and, as the team enter the lip
of the volcano,

the sound of rock fall
is all around.

Regular earthquakes make
the crater walls very unstable.

Just keeps getting better.

Not far away, some iguanas
are making their own descent,

disturbing the loose surface
as they go.

If a creature only a sixth
the size of a person

can start a deadly avalanche
of razor-sharp rocks,

what can a whole film crew do?

It's clear the crew are going
to have to be extremely cautious.

On the steepest slopes,
the equipment needs to be

lowered with ropes.

With rocks falling all around,
the longer they're on the slopes,

the greater the risk of an accident.

But, when one misstep
can start an avalanche,

hurrying is impossible.

Finally, the prize of
the crater floor is in sight.

Look, just below there is
where the iguanas are nesting.

We're very close to it now,
about an hour's walk.

All that lies between them
is a stretch of loose lava

that has cascaded down the slopes
after the last eruption.

We're actually in the crater now,

surrounded by these vertical walls.

I just can't believe that
we really made it down here.

Sometimes I doubted that, you know,
we would actually make it.

And there they were, iguanas,
using the warm volcanic ash

to incubate their eggs.

For Richard, after 25 years
living in the Galapagos,

filming this unique behaviour
is a lifelong dream come true.

My, God, what an incredible place
this is!

It's such a vivid feeling
to be constantly challenged

by the forces of nature like that.

But they have to do this every year
in order to survive.

I'll never forget,
for as long as I live.

What an adventure!
What an adventure!

Next time...

..a new force...

..humans.

Now so dominant...

..we're disrupting
the forces of nature...

..and the vital habitats
life needs to survive.

This is the most important story...

..of our time.

Whose future? Our future.

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