In the course of making Blue Planet II,
we've explored every corner of the underwater world.
We've encountered extraordinary animals,
and discovered new insights into how life is lived beneath the waves.
For years we thought that the oceans were so vast
and the inhabitants so infinitely numerous
that nothing we could do could have an effect upon them.
But now we know that was wrong.
The oceans are under threat now as never before in human history.
In this final episode,
we will meet the pioneers who are striving to turn things around.
People who are helping to save the ocean's most vulnerable inhabitants
and dedicating their lives to protecting the seas.
But is time running out?
Many people believe that our oceans have reached a crisis point.
So just how fragile is our blue planet?
Winter in the Arctic Circle.
Every year, the waters of Norway are the setting
for one of the greatest wildlife spectacles in the ocean.
Over a billion herring pour into these fields.
The Blue Planet II team spent three years
documenting this astonishing event.
Such a wealth of prey attracts predators
in extraordinary numbers.
Orcas
and humpback whales.
But this migration hasn't always been so bountiful.
Leif Notastad is a Norwegian fisheries scientist.
It's been one of the most important fisheries
that we had for centuries along the whole coast of Norway.
But in the late 1960s
the herrings that we see around us here was on the brink of collapse.
50 years ago, fishing was so intensive
that the herring had all but disappeared.
Orcas were seen as rivals
and hundreds of them were killed.
It was only after the Norwegian government imposed severe restrictions
that the herring began to recover.
Today, this is once again an immensely productive fishery,
closely monitored by teams of scientists.
Marine biologist Eve Jourdain
is one of the resident orca experts.
From 1982, orcas got protected in Norway
and we have clearly one of the largest orca population in the world out here.
There are now over a thousand orcas here.
But with so many mouths to feed, including ours,
can the mistakes of the past be avoided?
To answer this vital question,
Eve and her team are using multi sensor camera tags.
With the tags we try to see how the orcas interact with their prey.
How they hunt and all about the underwater behaviour
that we are not able to see from the boat.
A tag has to be attached
to the orca in exactly the right position.
Here it goes. Here it comes.
Oh, that's a good shot.
It is the least invasive method. It is suction cups.
So it is not a scratch on the whale afterwards
which is something we really like.
While studying the orcas,
Eve noticed a worrying change in their behaviour.
They had worked out the easiest way to get a meal.
We have seen that the orcas are waiting
for those fishing boats to drop the net.
It acts like a dinner bell
and then all the orcas of the area gather.
Quite a lot of herring slip from the net
and this is exactly what the orcas are looking for.
But this new tactic is dangerous, as Eve has witnessed.
We were there to monitor the behaviour of the orcas
scavenging around the nets.
And we realised that one large adult male
was actually trapped inside the net.
When the fishermen started to retrieve the net
the orca was obviously starting to panic
and trying to pull as much as he could.
This orca was really fighting for his life.
Stringent rules require fishermen
to get permission before they open their nets.
But that took time.
It was such a long process.
We thought that the whale was going to die of exhaustion.
Thankfully, the fishermen finally got the clearance
to release their net freeing the exhausted orca.
It was a huge relief to see that this orca made it until the end
and finally got back to his family.
With marine mammals and humans competing so directly
accidents are inevitable.
Two days after tagging an orca,
it's released and Eve collects it.
This tag is full of secrets, you know,
because it has been on the whale for several days
and will just reveal exactly what the whales have been doing.
Pictures from the tag reveal the hunting technique in detail.
They dive below the ball offish
and then back flip.
The tail slap stuns the herring.
Eve can even work out how many fish the orcas are taking.
They can kill up to 30 herring with just one tail slap.
And then what is pretty amazing is
all the individuals of the group share the dead herring.
And it's not just the orcas feeding here...
Humpback whales are also drawn to the feast.
They too are being tagged and monitored
giving fishery scientist Leif
a complete picture of how much herring is being eaten.
The whales, they take probably less than 1 %.
The fishermen take less than 10%.
So the balance there is that there is enough for everybody.
Given that we manage to stock in sustainable
and a long term sustainable way.
But it's estimated that almost a third of ocean fisheries
are being over exploited.
The remarkable recovery of the herring here
demonstrates what can happen if a fishery is carefully managed.
Our maltreatment of the seas has many effects.
Some are predictable,
but there are others that are rather more surprising.
Southeast Asia.
The coral reefs here are among the richest on the planet.
Marine biologist Steve Simpson,
is discovering how important sound is
to the animals that live in these bustling coral cities.
We're only now just realising by listening underwater
that the fish are making all these sounds.
They use sound to attract a mate.
To try and scare away a predator.
You hear pops and grunts and gurgles and snaps.
There's a whole language underwater
that we're only just starting to get a handle on.
Using an advanced multi directional hydrophone,
Steve is trying to make sense of this extraordinary chorus
by working out who is making which noise.
One fish is especially talkative.
It's perhaps the reef's most famous resident.
The clownfish.
While filming for the series,
we followed this particular family of saddleback clownfish
as they search for a suitable place to lay their eggs.
It's a noisy affair.
For clownfish sound really is everything.
They spend all day talking to each other.
You've got dominance and submission.
You've got all the others calling to each other.
It seems that they also use sound
in protecting themselves from the many predators that hunt around the reef
Including coral trout.
Will this model trout fool the clownfish?
They react almost immediately.
By mimicking a predator,
Steve manages to record their alarm calls without putting them at risk.
You can really hear the deeper pulsing sound of the female
as she tries to scare the coral trout away.
And all the little ones are just popping... Pop, pop, pop.
As if to say, "I'm still okay. I'm still alive."
So they've got this real language of sounds that they're using
just to try and defend the colony against this coral trout.
But that discovery has led to a serious worry.
The fish were really popping away at the predator.
But as soon as the boat came over they looked completely distracted.
With all that noise it completely changed how the fish were behaving.
Unable to make themselves heard above the noise of boats,
the family can't warn each other of danger.
And so they are now vulnerable to attack.
You think about how many boats are driving around.
All of the ships, all of the offshore drilling.
All the noise that we're making in the ocean
you realise just how much we're drowning out
this natural biological noise,
robbing animals of their ability to be able to talk to each other.
All this noise may have serious consequences for many reef fish
because their babies, as soon as they hatch are swept out to sea.
There they feed and grow until strong enough to swim back.
And to find the reef, they use sound.
They listen in. They eavesdrop to the noises that they can hear
and they use that to choose which reef they want to make their home.
But obviously because we're adding all this noise to the ocean
it's a wonder whether they can even hear the reef at all.
Man-made noise is now everywhere in the ocean.
And it has an effect on marine creatures of all kinds.
From tiny fish
to gigantic whales.
But Steve believes there are solutions.
Noise in the ocean is a real problem.
But, it's something that we can control.
We can choose where we make the noise.
We can choose when we make the noise.
We can directly reduce the amount of noise that we make
and we can start doing that today.
We're only now beginning to realise
what an impact our noise is having on the inhabitants of the ocean.
Other forms of pollution are only too familiar.
Since its invention some hundred years ago,
plastic has become an integral part of our daily lives.
But every year, some eight million tons of it
ends up in the ocean.
And there, it could be lethal.
While filming Blue Planet II,
the crews found plastic in every ocean.
Even in the most remote locations.
South Georgia.
900 miles north of Antarctica,
this isolated wilderness is the breeding place
for vast numbers of penguins and elephant seals.
It's also a favourite nesting site
for the largest bird in the sky.
A wandering albatross.
Here we learn of the extraordinary lengths
ancient parents go to give their chicks the best chance of survival.
Each devoted parent travels thousands of miles searching for fish and squid
to feed their hungry chick.
But despite all their efforts,
the albatross colony here is in trouble.
Lucy Quinn is part of the British Antarctic Survey team
studying the birds here for the last 40 years.
Its only through looking at long terms studies
that you get a sense of these creatures.
And the albatrosses here have, over the past 10 years, been in decline.
There are a number of possible reasons.
While foraging at sea,
albatross can get entangled and drowned by fishing gear.
But Lucy is particularly alarmed
by what the parents are bringing back for their chick.
Albatrosses have the ability to cough up
bits of food that they can't digest.
And from that we can tell what they've been eating.
A healthy albatross chick in its diet should really have things like squid.
So we can find the squid beaks that come out of the pellet.
And also things like fish so we can find fish bones as well.
But these chicks are being fed something very different.
We have some plastic that this poor chick has had to bring up.
Plastic bag.
Here we have some food packaging. Looks like rice.
Luckily for this chick, he has managed to get this out of his stomach.
So, fingers crossed he doesn't have any more plastic left in there
before he fledges.
For other chicks, plastic can be fatal.
Unfortunately, there is a plastic toothpick
that have actually gone through the stomach.
Something just as small as that has actually has managed to kill the bird.
It's really sad to see.
Lucy collects and records what plastic she finds around the nests.
These are items that were regurgitated just from last season.
And that's gonna be a vast underestimation
because that's just ones that we happen to find.
There'll be many more that we never see being brought back.
To find out where all this rubbish is coming from,
Lucy and her team have attached GPS trackers to adult birds.
It's showing where they're going to find food for themselves
and to find food to bring back for their chicks.
It really shows us that they could be picking up plastic
from thousands of miles away.
Plastics coming from either being dumped at sea
or also from people's homes.
Plastic gets into the rivers and then the rivers flow into the sea.
So this isn't just a problem around these remote parts.
This is happening worldwide.
And it's our rubbish that's going into the oceans.
It's our problem that we need to solve.
In some parts of the ocean,
it's estimated that there are now over one million pieces of plastic
for every square mile.
And we're only beginning to discover
Just how seriously that affects marine life.
On the east coast of the United States,
researchers are investigating the mysterious deaths of young dolphins.
The team is led by Dr Leslie Hart.
It looks to be a young animal.
Maybe a little bit over a year.
So we're gonna try to find out more information on why this dolphin died.
Looking at young dolphins...
The very young dolphins, it's always heart-breaking.
Leslie takes tissue samples.
Their chemical analysis could provide crucial evidence.
We are often shocked by the high levels of toxins
that we detect in these animals.
These young calves are dying for a number of reasons.
But we suspect man-made toxins are playing a large role.
And plastic could be part of the problem.
Once in the ocean,
plastic breaks down into tiny fragments.
Micro plastics.
Along with all the industrial chemicals that have drained into the ocean
these form a potentially toxic soup.
The really small organisms
can mistake these tiny, tiny plastics as food.
Then the larger organisms eat the plankton.
Then the larger fish eat the smaller fish,
and so on and so forth.
Dolphins are at the top of this food chain
and it's now thought that pollutants may be building up in their tissues
to such a degree that a mother's contaminated milk could kill her calf
Industrial pollution and the discarding of plastic waste
must be tackled for the sake of all life in the ocean.
Around the world, people are now devoting their lives
to saving some of the most threatened sea creatures.
As here in the Caribbean.
Every year on just a few islands,
a remarkable event takes place.
As the sun sets,
giant reptiles begin to emerge.
This magnificent creature preparing...
Preparing to lay her eggs
is the largest of all turtles.
A leatherback.
They can grow up to half a ton in weight.
And they have an ancestry that goes back a hundred million years
to the age of the dinosaur.
But in recent times their numbers have fallen catastrophically.
Here, however, in the Caribbean there is hope.
Leatherback turtles leave the sea
in order to lay their eggs in the dry sand.
But out of water, these huge creatures are easy targets for hunters.
In a small fishing village in Trinidad,
Len Peters has experienced this first hand.
I grew up in a household where the presence of turtle meat was normal.
The fridge was always full of it.
Everybody... Everybody harvested turtles, including my parents.
It's only when I became exposed to things
that were being published about leatherbacks
who were on the verge of extinction.
And nobody cares.
That piqued my interest.
Len took the leatherback's future into his own hands.
He began patrolling the beach at night to protect the turtles.
A brave thing to do.
We were met with tremendous resistance.
People would pelt us at night.
I have had persons insult me.
I've had persons curse me.
I've had persons physically try to wrestle me with a machete.
So it was really a hostile time back then.
If Len was going to save these turtles
he needed to win over the whole community.
We had to find a way to get the villagers to benefit
from the presence of these animals.
He began to encourage tourists to visit the beach
and trained some villagers to be their guides.
To help secure the turtle's future,
he took the message to the next generation.
Now what's... What's the largest size a leatherback can grow to?
Uh, Shanie.
- 2,000 pounds. - That's correct.
Leatherbacks can grow to 2,000 pounds.
Well, that's a big turtle.
Len's hard work paid off
And now, attitudes have changed.
It took us a while to reach out to the villagers.
But gradually we got them involved as well.
We got some of the poachers who would be hunting the animals to
be part of the conservation programme.
As well as protecting the adult turtles,
the team also collect any eggs that might be flooded at high tide.
If the eggs are laid too close to the sea,
we relocate the eggs and rebury them.
Thanks to the efforts of this community,
these turtles have had an extraordinary change in fortune.
This is now thought to be one of the densest
leatherback nesting beaches in the world.
When we started at the height of the nesting season,
the numbers will be 30-40 turtles a night.
Now, it's over 500.
So, we have seen an increase from 40 turtles
to 500 turtles a night in just around 20 years.
Precious new hatchlings are also given a helping hand.
Any that emerge during the day are collected
to be released safely back to the sea, away from hungry birds.
This little leatherback will have to face a thousand hazards
before it returns as an adult to this beach where it hatched.
And those dangers will be greatly increased
because of damage that we have done to the ocean.
Good luck, little leatherback.
Protecting breeding sites on beaches
may improve the fortune of some marine animals,
but safeguarding them while they roam the high seas is much more difficult.
Out here, there is little protection.
Every night, thousands of miles of fishing lines laden with hooks are set.
There's enough, it's said, to wrap twice around the world.
Nets large enough to engulf cathedrals
trap hundreds of tons offish at a time.
Long distance travellers such as sharks are particularly at risk.
It's estimated that tens of millions are killed every year,
including the biggest fish in the sea, the whale shark.
Shark biologist Jonathan Green is concerned
that time is running out for these extraordinary creatures.
We know that they're being fished possibly at a massive rate.
They may be taken by the thousands, possibly tens of thousands a year.
If that is indeed true,
we don't know how long they can withstand that kind of fishing pressure.
To save them, Jonathan is trying to solve
the mystery of where they give birth.
And, for the first time, he has a clue as to where this might be.
Pregnant whale sharks are thought to be travelling from across the Pacific Ocean
to Darwin Island in the Galapagos.
Jonathan is going to try and attach
a multi-sensor camera tag to a pregnant female.
Okay. We're good to go.
These sharks only stay in the area for a few days.
This may be his only chance.
Jonathan has to attach the tag before the shark dives to dangerous depths.
The tag will remain on the giant's fin for two days
before it's automatically released.
Once retrieved, it reveals some unusual behaviour.
Oh, beautiful, beautiful.
There's a silky rubbing at the in front. Next to her right.
The silky sharks are brushing up against her rough skin,
perhaps to scrape off parasites.
These predatory sharks make the surface waters very unsafe places
for young fish of any kind.
There is a surprise in store.
The tag's depth sensor reveals that she dived
to a depth of 600 metres.
But down there, it's too dark for the camera.
The only way Jonathan can prove if they're giving birth
is to go down and look.
Out of the gloom, a shape materialises.
Another massive whale shark.
Oh, look at her. She's having a look at us. She's looking right at us.
She is huge.
And look at the belly. Absolutely massive.
That's a large pregnant female.
She's turning around. She's turning around.
Goes to show we can follow them. We can follow them in the submarine.
She leads them down into the darkness.
Rover control. Passing 100 metres, descending.
Heading down. I think she's accelerated slightly.
She's too fast.
And with the strong current running against them, the sub can't keep up.
But, for the first time, Jonathan can see for himself
exactly where she's headed.
What specifically Darwin could provide
is a safe refuge for those new-born pups where predators can't access.
Perfect conditions for the formative years
of these ocean-travelling giants.
That was unbelievable.
Dream of a lifetime.
His discovery that pregnant whale sharks
are visiting this very deep patch of the sea floor
is strong evidence that this is indeed where the giants produce their young.
If I can actually prove that they are giving birth in this area,
then we'll have the information necessary
to go to governments and actually say,
"You must preserve those routes that they're migrating through."
And then, and only then, can we really truly afford protection
for this beautiful ocean traveller.
Today, less than one percent
of our international waters are protected.
And the creation of marine reserves is vital
if we're to safeguard the future of many ocean creatures.
It will require international cooperation.
But here, too, there is hope.
We can turn things around.
We've done so once before.
For centuries, the sea-going nations of the world
hunted the great whales until they were close to extinction.
And then, in 1986, those nations got together
and agreed to put a stop to commercial whaling.
Today, although a few nations continue to hunt whales,
some of the great whales are making a recovery.
In the tropical seas surrounding Sri Lanka,
there are stories of vast gatherings of whales.
When the civil war ended in 2009,
locals here were able once again to fish these waters.
There were soon reports of assemblies of sperm whales,
the likes of which had not been seen for centuries.
Marine guide Daya was determined to get to the truth
behind these fishermen's tales.
The fishermen told me that there are lots of whales
a little bit north from here.
They didn't actually tell me a number,
but in big numbers, not one or twos.
Er, many.
It took him three years,
but eventually, he found evidence to support these rumours.
We saw about 15 sperm whales go past us.
Then, another four came past us.
After about 40 then passed me, I started counting.
Still, they kept coming, so I lost count.
I estimated that we saw about 300 sperm whales.
Sperm whales were once killed in vast numbers
and it's thought that if the slaughter had continued,
the species would be in danger of extermination.
But now, here at least, they are being seen in huge numbers.
I believe they come here to feed, mate, and raise their young.
So, this must be a holiday spot for them, you know.
At the moment, I don't know of any other place in the world
that, er, sperm whales gather like this.
Although some whale populations are still in decline,
scenes like this prove that when sea-going nations come together,
they can achieve astonishing results.
But today, the oceans face threats on a truly global scale.
The Great Barrier Reef
The largest coral reef system in the world.
Here, we filmed stories which reveal Just how smart fish can be.
This ingenious tuskfish, for example,
used a favourite coral anvil to smash open shellfish.
This astonishing behaviour has been closely studied
by local scientist Alex Vail.
We're calling Percy "Percy the Persistent"
because he took, like, an hour to open the first shell.
He must have hit it well over 50 times,
but he just kept on going and finally got it open.
Alex grew up on the Great Barrier Reef
on one of its more remote islands, Lizard.
He knows the reef intimately.
But, in 2016, while he was filming for Blue Planet II,
Alex witnessed a catastrophe.
When we started filming, everything was pretty much fine.
All of the corals were basically healthy.
But in the last few weeks, everything changed.
I have never seen anything like this before.
A combination of a warming ocean
and an unpredictable weather event called El Niño
raised sea temperatures to record levels.
And this had a disastrous effect on the corals.
The heat causes reef-building corals to lose their nourishing algae,
exposing their white skeletons.
When temperatures remain high, bleached corals die off
The bleaching this year has been the worst in history
for the Great Barrier Reef.
About 90 percent of the branching corals
on the reef out here at Lizard Island are dead.
It also has disastrous consequences
for the other creatures that live here.
Percy swimming around out there.
The really sad thing is that his castle's starting to bleach.
If we lose our coral, there's a chance we're going to lose our tuskfish.
It's incredibly sad to see areas that you've dived on
since you were a little kid just turn to rubble.
I cried in my mask, when I saw,
you know, some of the devastation from this bleaching.
In the last three years,
over two-thirds of the world's coral reefs
are thought to have suffered from rises in ocean temperatures.
This is not the only challenge they face.
Research is revealing how the fundamental
chemistry of the ocean is changing.
Professor Chris Langdon shows me what this might mean
for the future of our seas by pouring dilute acid over shells.
And how much more acidic is this than the present ocean?
This is more concentrated than the pH of the ocean
but it accelerates the process so we can see something visually.
So, what's happening is, these shells, they're made out of calcium carbonate,
and the acid is dissolving them.
And coral reefs are made out of the same material as these shells here.
But surely this is not happening in the ocean now. Right now?
What we're seeing here is more dramatic than what's happening in the ocean.
But the shells and the reefs are really truly dissolving.
Coral reefs could be gone by the end of this century.
And the cause of this? Carbon dioxide.
Dissolved in the sea water, it forms carbonic acid.
The more carbon dioxide in the atmosphere,
the more acidic the ocean becomes.
Evidence points to the burning of fossil fuels
as the primary cause for these increasing levels of carbon dioxide.
And this is man-made beyond question.
Beyond question.
But Chris believes all is not lost.
All we have to do, and I say all, is reduce our CO2 emissions.
We can switch to renewable fuels, wind and solar,
instead of natural fossil fuels.
And so, none of this has to
- develop to the worst case. - And that could fix it?
Yeah, absolutely. So, this future does not have to play out. It's up to us.
As the climate changes, the seas warm.
Our oceans are being seriously affected.
And this is nowhere more apparent than at the poles.
Antarctica.
For the Blue Planet II team, this was their most ambitious expedition.
For the first time in history, a manned submersible
will try to dive to a depth of 1,000 metres
and reach the Antarctic seabed.
A true journey into the unknown.
(RADIO CHATTER
Control rover. Passing 40 metres. Over.
Leading the team on this historic dive
is deep sea scientist John Copley.
We get our first glimpse of this landscape.
And the carpet of life around us is astounding.
It's beautiful.
Diving in a submersible gives John an entirely new understanding
of how this rich ecosystem works.
But it also offers him a unique opportunity
to investigate how the ocean here is changing.
While we're observing the marine life down there,
the subs are also recording what the environment is like,
so we're getting measurements of temperature, of salinity.
It's hopefully gonna enable us to understand the changes
that are happening in this vital part of our planet.
To get a fuller picture, John also lowers
a deep sea temperature probe.
His data is contributing to an international attempt
to chart the rise in both sea and air temperatures.
What shocks me about what all the data show
is how fast things are changing here.
We're headed into uncharted territory.
To truly comprehend
the effect of the temperature increases here,
John takes to the skies.
From here, he can record the number and size
of the icebergs being produced as the ice shelfs melt and break apart.
The bergs we're seeing all around us give you some idea
of how huge this process is that's taking place on the Antarctic.
As the floating shelves break up, they allow water,
which has been locked up on land as ice for thousands of years,
to empty into the sea.
And this is predicted to push up sea levels.
If the ice shelves break up, then that opens the flood gates.
Ice on land flows faster into the sea
and that's what pushes up the sea levels.
So, what's happening here right now affects all of us.
Already, cities like Miami here are under threat.
Scientists predict that by the end of the century,
the sea levels could have risen by a metre or even two.
Were that to happen, parts of this city would certainly be submerged.
Around the world, hundreds of millions of people live near the coast,
and as sea levels rise, their lives will be seriously affected.
It's now clear that our actions are having a significant impact
on the world's oceans.
During the four years it took to make this series,
we've witnessed many of these changes first-hand.
But we've also worked alongside men and women
dedicating their lives to safeguarding the ocean's future.
The oceans provide us with oxygen,
they regulate temperature,
they provide us with food and energy supplies.
And it's unthinkable to have a world without a healthy ocean.
I still think we have the capability
to change the manner in which we're wasting resources,
in which we're poisoning our oceans,
and we can look to a future with healthy oceans.
When I look forward, I believe that if what we are doing
can be duplicated just a little bit.
These animals will have a chance of surviving.
It comes down, I think, to us each taking responsibility
for the personal choices that we make in our everyday lives.
That's all any of us can be expected to do.
And it is those everyday choices that add up.
We are at a unique stage in our history.
Never before have we had such an awareness
of what we are doing to the planet.
And never before have we had the power to do something about that.
Surely, we have a responsibility to care for our blue planet.
The future of humanity,
and indeed all life on Earth,
now depends on us.