Original subtitles

Almost 200 years ago,

whilst walking these very paths in the English countryside

and observing the banks and meadows near his home,

Charles Darwin developed

his ground-breaking ideas about evolution,

casting a new light on the natural world

and opening our eyes to its true wonder.

Since then, we've explored almost every part of the planet

and seen nature in its astounding variety.

But there's still much to discover.

In this new series of Planet Earth...

..we travel to the most astonishing wild places...

..see mysterious creatures...

..witness spectacular wonders...

..and reveal breathtaking animal dramas.

The natural world continues to surprise us.

But since Darwin's time, it has changed beyond recognition...

..transformed by a powerful force.

Us.

We will see how animals are adapting in extraordinary ways

to survive the new challenges they face.

At this crucial time in our history,

we must now look at the world through a new lens.

This is Planet Earth III.

Tasmania, Shipstern's Bluff...

..where two worlds collide.

These waves have crossed more than 1,000 miles of open ocean...

..building in strength.

It's here that they meet their explosive end.

Coasts are dangerous and dynamic frontiers.

To succeed here, life must adapt to constant change.

South Africa's Robberg Peninsula.

Thousands of Cape fur seals gather here to breed.

This pup was born into a crowded world.

But now, at nearly a year old, he can escape to the water.

He just has to get there.

There is no question as to where this pup belongs.

In the water, he's fast and agile.

And he needs to be.

The rolling surf conceals life-threatening dangers.

A great white shark.

This young pup has had a very lucky escape.

Here on Africa's southern coast,

seals risk their lives every time they set out to eat.

Powerful ocean currents attract huge shoals of fish.

But in recent years,

this stretch has attracted increased numbers of great whites too.

The great whites are shrewd hunters and use whatever cover is available.

This shark won't need to eat for another few days.

But he's not alone.

These usually solitary hunters

are gathering in unprecedented numbers.

A dozen at a time.

The seals are nimble...

..but great whites are patient...

..and have explosive acceleration...

..hitting top speed with just five swipes of their tails.

Cornered...

..the seals keep close to the jagged cliffs.

They are trapped.

But as the great whites move in for the kill...

..the seals do something astonishing.

Together...

..they turn on their enemy.

As more join, the mob grows...

..in both number and confidence.

The tables are turning.

By sheer force of numbers...

..these fur seals drive the world's most notorious predator...

..back out to sea.

Here, animals are adapting to new challenges

in a rapidly changing world.

In the Arctic...

..monumental change is a regular event.

Summer.

Visitors are arriving en masse...

..attracted by the biggest seasonal transformation

on any coast on Earth.

Over 300 billion tonnes of ice are melting...

..releasing nutrient-rich water.

Extraordinary newcomers appear from the depths.

A sea angel.

No bigger than your little finger.

It's eaten little for months.

Its empty stomach glows orange.

And there are other hungry arrivals.

A sea butterfly.

A snail with wings.

Both angel and butterfly are blind.

But each monitors minute changes in the water as they search for a meal.

This angel has a devilish side.

Its mouth parts invert

to form a deadly trap of tentacles...

..from which there is little chance of escape.

With a stomach full of prey, this angel has lost its glow...

..but not its appetite.

It feasts while it can.

Both predator and prey will soon return to the depths...

..before the ice transforms this coast once again.

Namibia...

..where desert lions roam across vast territories.

These desert cats are on a never-ending search for food.

And that has brought these young sisters...

..here.

Africa's infamous Skeleton Coast.

Following years of persecution, Namibia's lions are now protected...

..and their range is expanding again.

These are the first to be seen on these shores for 40 years.

By day, there is little for them here.

But at night, it's a different story.

Sea birds come here to roost

in their thousands.

These hungry sisters have never seen an opportunity like this.

But no cats, certainly no desert cats,

enjoy getting their paws wet.

These roosting cormorants are sitting ducks

for hunters with good night vision.

In theory.

Birds are not a big cat's usual prey,

let alone sea birds.

And these sisters need to get their eye in.

Catching flying prey in the dark is not easy...

..but these lions have acquired the knack.

Coasts can not only provide food...

..they can also be a sanctuary.

This female southern right whale is nearing the end

of a 5,000 mile journey across open ocean.

She's kept a steady course...

..to a special place she has known all her life.

Peninsula Valdes, Argentina.

In these calm, shallow waters...

..her behaviour starts to change.

She rolls and shifts her great body.

Perhaps she's trying to get comfortable.

Other females are close by.

Some have been coming here for five decades...

..seeking the shelter of this bay at a key time in their lives.

This whale is here...

..to give birth.

A new life begins.

The calf is totally dependent on its mother.

She's producing as much as 200 litres of milk a day.

The strength she loses, the calf gains.

And it becomes more and more independent and playful.

In this nursery bay, there are plenty of playmates.

But a mother never lets her calf stray too far...

..and will always offer a welcome embrace.

The family keeps in constant contact with whispered calls.

New research has revealed

that in shallow coastal waters, their calls not only fade quickly,

but are also concealed by the sound of waves breaking on the shore...

..so they won't attract the attention of predators.

Not so long ago, these whales faced a graver threat.

They were hunted to near extinction.

But 40 years ago, commercial whaling was banned.

Today, their population is 12,000 strong...

..and this bay now attracts one of the largest gatherings

of these whales anywhere on Earth.

There are over a million miles of coastline around the world.

Together, they constitute the most varied habitat on the planet.

Here on Canada's west coast,

some of the most powerful of all ocean currents

deliver a constant supply of nutrients

to the shores of countless islands.

And those that live here take full advantage.

This is the aptly-named wandering garter snake.

He may seem out of place...

..but he's here to eat.

The water here is more than ten degrees colder than the air.

But that doesn't deter this intrepid hunter from taking the plunge.

Under the water, there is an abundance of food...

..if he can catch it.

Snakes are cold-blooded,

so he can't stay in these chilly waters for long.

Back in the sunshine, he warms his head,

perhaps sharpening his senses.

And then, with a gulp of air...

..he continues his hunt.

It's thought that garter snakes

can use their forked tongue underwater as they do in air,

smelling in stereo...

..detecting prey wherever it hides.

He's got something.

A small fish.

Now, he has to land it.

Success.

For those animals able to cross the divide between land and sea,

there are surprising rewards.

Raja Ampat in Indonesia.

Here, there's a greater variety of animals

than on any other coast on Earth.

The corals are protected by mangroves.

Salt tolerant trees that prop themselves on curving aerial roots.

These fish have learned how to catch prey from high in the trees.

Archerfish use jets of water like arrows.

This pinpoint accuracy...

..requires some complex calculations.

The hunter first estimates the range of its target...

..then loads with a precise amount of water.

Aiming, they allow for the refraction and distortion

created by the water's moving surface.

And then...

..release...

..an arrow of water.

They can hit prey up to two metres above them.

But they're not born with this skill.

They have to learn it.

And they do that by studying others.

This youngster is watching a master at work.

It's time for the apprentice to have a go.

First, he must select a target.

This seems rather ambitious.

Missed.

Others watch to learn from his mistakes.

Or...

..to steal his prize.

Enough is enough.

There is one way to beat the thieves.

The archer himself...

..becomes the arrow.

Mangroves are unusually stable coastal environments,

where an archerfish can focus on beating the competition.

But on the exposed coast of Mexico's Yucatan,

life is precarious.

Concentrated by the tropical sunshine,

the brine in these shallow lagoons cannot be tolerated by most animals.

And yet, these Caribbean flamingos

have flown hundreds of miles to gather here.

These hypersaline waters keep many predators at bay...

..so it's here they choose to nest.

There are more than 10,000 pairs here.

It's the largest breeding colony in North America.

Nest mounds keep chicks clear of the brine

while they are still at their most vulnerable.

But this generation faces a problem.

The storms that come each season are arriving earlier every year.

And the colony lies directly in their path.

Rising winds create a storm surge

that overwhelms the most exposed nests.

And then...

..it rains.

The adults do what they can, bailing out their nests.

But they can only do so much.

The storm passes, but leaves devastation in its wake.

Most nests are submerged.

The chicks are soaked and cold...

..and will soon perish...

..unless they can get out of the water.

The adults are unable to help.

A chick must save itself.

Some years, no chicks survive in this colony.

Our coasts are vulnerable places.

Increasingly so, as rising global temperatures create bigger storms.

The biggest are hurricanes.

They form over warm tropical water, building in strength at sea.

But their full force is unleashed on our coasts...

..where 40% of the world's human population have made their homes.

In this changing world...

..coasts are on the front line.

Raine Island.

One of the planet's most important breeding sites

for one particularly precious species.

The green turtle.

On a few special nights each year,

as many as 20,000 females come ashore here.

Their instinct to nest is strong...

..and many haul themselves far inland in search of nesting space.

In a single night, they may lay as many as two million eggs.

Dawn.

This exhausted female has nested,

but now she faces a long return journey

through the dunes to the sea.

As the sun rises...

..she's at risk of being baked alive.

Every inch she travels is gruelling.

And the ebbing tide has exposed a rocky reef.

It has already claimed many lives.

Other females overcome by heat and exhaustion.

Her temperature is rising.

She has to keep going.

As many as 2,000 female turtles may die here each year.

But the coast is always changing.

And the turning tide

may yet save her.

Half of all the green turtles in the Pacific come here to nest,

as they have done for at least 1,000 years.

But for how much longer?

If sea levels rise as predicted, within the next 30 years,

Raine Island will disappear beneath the waves.

Coasts are dynamic, dangerous frontiers...

..and they are changing faster than ever before in human history.

Life is remarkably resilient...

..and adapts to new challenges.

But there is a limit on how fast it can do so.

As far as I know,

I was one of the first people to film on Raine Island, back in 1957.

After a fortnight of travelling north,

we at last sighted Raine Island.

From the sea, it looked no more than a low sandbank covered in scrub.

But as we rowed ashore,

we were deafened by the cries of thousands of sea birds

which hung above the island like a black cloud.

I was 31 and it was here that I first met a green turtle.

The turtles come up to lay at night,

and after a night spent laying maybe over 100 eggs,

she's very weary and very anxious to get back to the sea.

Nearly 70 years later,

the Planet Earth III team are welcomed by people

whose connection to the island goes back very much further than mine.

Welcome to Raine!

The Wuthathi and Meriam people

have been coming here for several thousand years.

Raine Island's a beautiful and special place.

Like, there's nowhere else on the planet

where you come and see this much turtles.

It's a wonder to see.

Since I was there, it's been discovered that Raine Island

attracts more nesting green turtles than anywhere else on the planet.

There's so many, isn't there?

As soon as you're up, you're like, "Oh, there are a lot."

And the crew soon meet some other residents too.

This is behind the behind the scenes!

See you, mate!

The team are here to record

the mother turtles' perilous journeys back to the sea.

Oh, God.

Trapped turtles can often free themselves

with the help of the rising tide.

Nearly. Just a bit more to the right there. Yeah, there.

But in this case, Keron makes the decision to intervene.

Ready? One, two, three.

Yeah, any time we're here we'll walk the beach.

Any turtles that have no chance of making it back to the ocean,

if we can save them, we save them, because every turtle is precious.

At the time of my first visit,

little was known to outsiders about Raine Island.

But for the last few decades,

scientists have been working with the Wuthathi and Meriam people

to understand more about this special place.

Scientists have been coming to Raine Island since about the mid '70s

and over that time they've been monitoring

the nesting population here.

This work involves long hours...

98.7.

..and a certain degree of patience.

Oh!

We're going to be wearing half of Raine Island by the end of tonight!

Helping the year's first hatchlings is a little easier.

So we'll take these ones down to the water's edge

and so hopefully we'll see these turtles back here,

laying eggs in 30 years' time.

With the help of this dedicated team,

Raine Island's turtles might seem to have a good future.

But research is revealing a hidden threat.

The direct effects of climate change.

Do you want to hold this against the flat part of the data-logger?

A developing turtle's sex

is determined by the temperature of its nest.

Higher temperatures produce female hatchlings.

The temperature of the sand on Raine Island is now at a record high.

So 99% of the turtles that hatch here are female.

More alarmingly, we now know this has been case

for at least the last 20 years.

You do the maths.

All females, no males. What's going to happen?

There's going to be a population crash

and there'll be no more turtle.

Work is under way to find solutions.

But that's not their only problem.

Not only are temperatures rising, sea levels are too.

Increasingly, high tides on Raine

are flooding many of the nests from below...

..drowning the developing turtles before they hatch.

It's really upsetting.

You'll dig down to check to see success,

and you get down to the nests

and you're just pulling up dead eggs.

To try to stop this happening, they have devised a heavy-duty solution.

These machines have been shipped hundreds of miles

from the Australian mainland to re-shape the beach.

They have already shifted sand

that would fill 16 Olympic-sized swimming pools

and doubled the number of safe nesting sites.

The hope is that this will ensure that over five million more eggs

will hatch in the next decade.

But from then on, the future of Raine Island looks very uncertain.

At this stage, we think that we have to about 2050

until we start seeing massive impacts of sea level rise.

It's crazy to think that, you know, the work that we do here,

someone might not be doing this in 30 years' time

cos there's no island to do it on.

What sort of world is it going to be for my children and their children?

Is there going to be anything for...

..for them? Or is it...

..all in vain?

We'll always be here fighting for Raine Island, for the turtles.

But we can't do it alone and we need government and big business

to wake up and see what they're doing to the planet and get real.

This little fellow is newly hatched from an egg

which had been laid a month or so earlier

and he too is very anxious to get down to the sea.

Having at last successfully reached the water,

he's still got a great number of hazards to face before he grows up.

Little did I know then

what hazards that little turtle would have to face

or the extraordinary lengths to which people would go

to protect it and its island.

In the 66 years since my visit, Raine Island has remained

the most important green turtle nesting site on the planet.

The question is, can it last another lifetime?

Next time...

..an extraordinary journey through the ocean.

The last unexplored frontier on our planet...

..where life has evolved...

..in the most surprising ways.

Habitat Explorer brings animals and their habitats to life.

Explore this free interactive and make origami animals.

Go to bbc.co.uk/planetearth3

and follow the links to the Open University.

Or to order a free printed version,

visit the website or call the numbers on the screen.