0:00:42 > 0:00:44In the course of making Blue Planet II,
0:00:44 > 0:00:48we've explored every corner of the underwater world.
0:00:50 > 0:00:53We've encountered extraordinary animals...
0:01:00 > 0:01:04..and discovered new insights into how life is lived beneath the waves.
0:01:11 > 0:01:15For years, we thought that the oceans were so vast
0:01:15 > 0:01:18and the inhabitants so infinitely numerous
0:01:18 > 0:01:22that nothing we could do could have an effect upon them.
0:01:22 > 0:01:25But now we know that was wrong.
0:01:25 > 0:01:31The oceans are under threat now as never before in human history.
0:01:32 > 0:01:36In this final episode, we will meet the pioneers
0:01:36 > 0:01:39who are striving to turn things around.
0:01:44 > 0:01:46People who are helping to save
0:01:46 > 0:01:49the oceans' most vulnerable inhabitants...
0:01:51 > 0:01:55..and dedicating their lives to protecting the seas.
0:01:58 > 0:02:00But is time running out?
0:02:02 > 0:02:08Many people believe that our oceans have reached a crisis point.
0:02:08 > 0:02:11So just how fragile is our blue planet?
0:02:27 > 0:02:30Winter in the Arctic Circle.
0:02:32 > 0:02:36Every year, the waters of Norway are the setting for one
0:02:36 > 0:02:39of the greatest wildlife spectacles in the ocean.
0:02:41 > 0:02:45Over a billion herring pour into these fjords.
0:02:47 > 0:02:50The Blue Planet II team spent three years
0:02:50 > 0:02:52documenting this astonishing event.
0:02:57 > 0:03:02Such a wealth of prey attracts predators in extraordinary numbers.
0:03:06 > 0:03:07Orcas...
0:03:12 > 0:03:14..and humpback whales.
0:03:34 > 0:03:39But this migration hasn't always been so bountiful.
0:03:40 > 0:03:44Leif Nottestad is a Norwegian fisheries scientist.
0:03:45 > 0:03:49It's been one of the most important fisheries that we had for centuries
0:03:49 > 0:03:54along the whole coast of Norway, but in the late 1960s the herring stock
0:03:54 > 0:03:57we see around us here was on the brink of collapse.
0:04:02 > 0:04:0550 years ago, fishing was so intensive
0:04:05 > 0:04:08that the herring had all but disappeared.
0:04:10 > 0:04:13Orcas were seen as rivals,
0:04:13 > 0:04:15and hundreds of them were killed.
0:04:22 > 0:04:24It was only after the Norwegian government
0:04:24 > 0:04:28imposed severe restrictions that the herring began to recover.
0:04:35 > 0:04:40Today, this is once again an immensely productive fishery,
0:04:40 > 0:04:44closely monitored by teams of scientists.
0:04:47 > 0:04:53Marine biologist Eve Jourdain is one of the resident orca experts.
0:04:54 > 0:04:57From 1982, orcas got protected in Norway and we have clearly
0:04:57 > 0:05:01one of the largest orca populations in the world out here.
0:05:04 > 0:05:09There are now over 1,000 orcas here, but with so many mouths to feed,
0:05:09 > 0:05:12including ours, can the mistakes of the past be avoided?
0:05:15 > 0:05:17To answer this vital question,
0:05:17 > 0:05:21Eve and her team are using multi-sensor camera tags.
0:05:24 > 0:05:29With the tags, we try to see how the orcas interact with their prey,
0:05:29 > 0:05:33how they hunt, and all about the underwater behaviour
0:05:33 > 0:05:35that we are not able to see from the boat.
0:05:37 > 0:05:42A tag has to be attached to the orca in exactly the right position.
0:05:45 > 0:05:47Here it comes, here it comes...
0:05:51 > 0:05:53Ah, that's a good shot!
0:05:58 > 0:06:01It is the least invasive method, it is suction cups,
0:06:01 > 0:06:03so there is not a scratch on the whale afterwards,
0:06:03 > 0:06:05which is something we really like.
0:06:08 > 0:06:10While studying the orcas,
0:06:10 > 0:06:13Eve noticed a worrying change in their behaviour.
0:06:15 > 0:06:19They had worked out the easiest way to get a meal.
0:06:19 > 0:06:22We have seen that the orcas are waiting
0:06:22 > 0:06:24for those fishing boats to drop the nets.
0:06:24 > 0:06:26ORCAS CALL
0:06:26 > 0:06:30It acts like a dinner bell, and then all the orcas of the area gather.
0:06:31 > 0:06:33Quite a lot of herring slip from the net,
0:06:33 > 0:06:36and this is exactly what the orcas are looking for.
0:06:39 > 0:06:43But this new tactic is dangerous, as Eve has witnessed.
0:06:45 > 0:06:48We were there to monitor the behaviour of the orcas
0:06:48 > 0:06:53scavenging around the net, and we realised that one large adult male
0:06:53 > 0:06:55was actually trapped inside the net.
0:06:56 > 0:06:59When the fisherman started to retrieve the net,
0:06:59 > 0:07:01the orca was obviously starting to panic
0:07:01 > 0:07:05and trying to pull as much as he could.
0:07:05 > 0:07:07This orca was really fighting for his life.
0:07:09 > 0:07:12Stringent rules require fisherman to get permission
0:07:12 > 0:07:14before they open their nets...
0:07:16 > 0:07:18..but that took time.
0:07:23 > 0:07:25It was such a long process.
0:07:25 > 0:07:29We thought that the whale was going to die of exhaustion.
0:07:33 > 0:07:36Thankfully, the fishermen finally got the clearance
0:07:36 > 0:07:39to release their net, freeing the exhausted orca.
0:07:51 > 0:07:56It was a huge relief to see that this orca made it until the end
0:07:56 > 0:07:58and finally got back to his family.
0:08:02 > 0:08:05With marine mammals and humans competing so directly,
0:08:05 > 0:08:07accidents are inevitable.
0:08:12 > 0:08:17Two days after tagging an orca, it's released and Eve collects it.
0:08:21 > 0:08:23This tag is full of secrets, you know,
0:08:23 > 0:08:25because it has been on the whale for several days
0:08:25 > 0:08:29and will just reveal exactly what the whales have been doing.
0:08:29 > 0:08:33Pictures from the tag reveal their hunting technique in detail.
0:08:40 > 0:08:42They dive below the ball of fish...
0:08:45 > 0:08:47..and then backflip.
0:08:51 > 0:08:54The powerful tail slap stuns the herring.
0:08:57 > 0:09:01Eve can even work out how many fish the orcas are taking.
0:09:02 > 0:09:06They can kill up to 30 herring with just one tail slap.
0:09:06 > 0:09:08And then what is pretty amazing
0:09:08 > 0:09:11is all the individuals of the group share the dead herring.
0:09:12 > 0:09:15And it's not just the orcas feeding here.
0:09:17 > 0:09:21Humpback whales are also drawn to the feast.
0:09:34 > 0:09:37They, too, are being tagged and monitored,
0:09:37 > 0:09:40giving fisheries scientist Leif a complete picture
0:09:40 > 0:09:42of how much herring is being eaten.
0:09:43 > 0:09:48The whales, they take probably less than 1%.
0:09:48 > 0:09:52The fishermen take less than 10%.
0:09:52 > 0:09:56So the balance there is that there is enough for everybody,
0:09:56 > 0:09:58given that we manage this stock
0:09:58 > 0:10:01in a sustainable and a long-term sustainable way.
0:10:10 > 0:10:14But it's estimated that almost a third of ocean fisheries
0:10:14 > 0:10:16are being over-exploited.
0:10:21 > 0:10:24The remarkable recovery of the herring here
0:10:24 > 0:10:27demonstrates what can happen if a fishery is carefully managed.
0:10:45 > 0:10:49Our maltreatment of the seas has many effects.
0:10:50 > 0:10:52Some are predictable.
0:10:53 > 0:10:56But there are others that are rather more surprising.
0:11:06 > 0:11:07South-east Asia.
0:11:09 > 0:11:13The coral reefs here are among the richest on the planet.
0:11:24 > 0:11:29Marine biologist Steve Simpson is discovering how important sound is
0:11:29 > 0:11:32to the animals that live in these bustling coral cities.
0:11:34 > 0:11:37We're only now just realising, by listening underwater,
0:11:37 > 0:11:39that the fish are making all these sounds.
0:11:39 > 0:11:44They use sound to attract a mate, to try and scare away a predator.
0:11:45 > 0:11:50You hear pops and grunts and gurgles and snaps.
0:11:50 > 0:11:52POPPING
0:11:52 > 0:11:54There's a whole language underwater
0:11:54 > 0:11:56that we're only just starting to get a handle on.
0:11:59 > 0:12:01BUBBLING AND SEALIFE CALLS
0:12:01 > 0:12:03CHIRRUPING
0:12:15 > 0:12:19Using an advanced, multi-directional hydrophone,
0:12:19 > 0:12:23Steve is trying to make sense of this extraordinary chorus
0:12:23 > 0:12:27by working out who is making which noise.
0:12:30 > 0:12:33One fish is especially talkative.
0:12:34 > 0:12:36LOW CHIRRUP AND POPPING
0:12:36 > 0:12:41It's perhaps the reef's most famous resident, the clownfish.
0:12:44 > 0:12:46While filming for the series,
0:12:46 > 0:12:50we followed this particular family of saddle-back clownfish
0:12:50 > 0:12:53as they searched for a suitable place to lay their eggs.
0:12:57 > 0:12:59It's a noisy affair.
0:12:59 > 0:13:03BUBBLING AND POPPING
0:13:11 > 0:13:14LOW CHIRRUPING
0:13:14 > 0:13:17For clownfish, sound really is everything.
0:13:17 > 0:13:20They spend all day talking to each other.
0:13:20 > 0:13:22You've got dominance and the submission,
0:13:22 > 0:13:24you've got all the others calling to each other.
0:13:26 > 0:13:28It seems that they also use sound...
0:13:30 > 0:13:31..in protecting themselves
0:13:31 > 0:13:35from the many predators that hunt around the reef...
0:13:40 > 0:13:43..including coral trout.
0:13:57 > 0:14:00Will this model trout fool the clownfish?
0:14:07 > 0:14:09They react almost immediately.
0:14:09 > 0:14:12RAPID POPPING
0:14:12 > 0:14:13By mimicking a predator,
0:14:13 > 0:14:18Steve manages to record their alarm calls without putting them at risk.
0:14:20 > 0:14:22You can really hear the deeper pulsing sound
0:14:22 > 0:14:25of the female as she tries to scare the coral trout away.
0:14:25 > 0:14:27DEEP, RAPID POPPING
0:14:27 > 0:14:30And all the little ones are just popping, "Pop, pop, pop,"
0:14:30 > 0:14:32as if to say, "I'm still OK, I'm still alive!"
0:14:34 > 0:14:37So they've got this real language of sounds that they're using
0:14:37 > 0:14:40just to try and defend the colony against this coral trout.
0:14:44 > 0:14:47But that discovery has led to a serious worry.
0:14:47 > 0:14:50MOTOR DRONES
0:14:50 > 0:14:53The fish were really popping away at the predator,
0:14:53 > 0:14:57but, as soon as the boat came over, they looked completely distracted.
0:14:57 > 0:15:01With all that noise, it completely changed how the fish were behaving.
0:15:02 > 0:15:05Unable to make themselves heard above the noise of boats,
0:15:05 > 0:15:08the family can't warn each other of danger
0:15:08 > 0:15:10and so they are now vulnerable to attack.
0:15:12 > 0:15:15When you think about how many boats are driving around, all the ships,
0:15:15 > 0:15:18all of the offshore drilling, and all the noise that we're making
0:15:18 > 0:15:21in the ocean, you realise just how much we're drowning out
0:15:21 > 0:15:25this natural biological noise, robbing animals of their ability
0:15:25 > 0:15:27to be able to talk to each other.
0:15:31 > 0:15:35All this noise may have serious consequences for many reef fish
0:15:35 > 0:15:39because their babies, as soon as they hatch, are swept out to sea.
0:15:43 > 0:15:47There, they feed and grow until strong enough to swim back.
0:15:49 > 0:15:53And to find the reef, they use sound.
0:15:54 > 0:15:57They listen in, they eavesdrop to the noises that they can hear
0:15:57 > 0:16:01and they use that to choose which reef they want to make their home.
0:16:01 > 0:16:04But obviously because we're adding all this noise to the ocean,
0:16:04 > 0:16:07it's a wonder whether they can even hear the reef at all.
0:16:07 > 0:16:09SHIP'S HORN BOOMS AND ECHOES
0:16:11 > 0:16:15Man-made noise is now everywhere in the ocean,
0:16:15 > 0:16:18and it has an effect on marine creatures of all kinds...
0:16:21 > 0:16:22..from tiny fish...
0:16:24 > 0:16:26..to gigantic whales.
0:16:30 > 0:16:32But Steve believes there are solutions.
0:16:33 > 0:16:36Noise in the ocean is a real problem.
0:16:36 > 0:16:38But it's something that we can control -
0:16:38 > 0:16:40we can choose where we make the noise,
0:16:40 > 0:16:42we can choose when we make the noise.
0:16:42 > 0:16:45We can directly reduce the amount of noise that we make,
0:16:45 > 0:16:47and we could start doing that today.
0:16:55 > 0:16:59We're only now beginning to realise what an impact our noise
0:16:59 > 0:17:01is having on the inhabitants of the ocean.
0:17:04 > 0:17:07Other forms of pollution are only too familiar.
0:17:15 > 0:17:17Since its invention some hundred years ago,
0:17:17 > 0:17:21plastic has become an integral part of our daily lives.
0:17:21 > 0:17:27But every year, some eight million tons of it ends up in the ocean
0:17:27 > 0:17:29and there it can be lethal.
0:17:34 > 0:17:37While filming Blue Planet II,
0:17:37 > 0:17:40the crews found plastic in every ocean...
0:17:42 > 0:17:46..even in the most remote locations.
0:17:46 > 0:17:47PENGUINS CHATTER AND CALL
0:17:49 > 0:17:51South Georgia.
0:17:53 > 0:17:56900 miles North of Antarctica,
0:17:56 > 0:17:59this isolated wilderness is the breeding place
0:17:59 > 0:18:02for vast numbers of penguins and elephant seals.
0:18:02 > 0:18:04SEALS GRUNT
0:18:13 > 0:18:17It's also a favoured nesting site for the largest bird in the sky...
0:18:19 > 0:18:21..the wandering albatross.
0:18:25 > 0:18:29Here we learned of the extraordinary lengths aged parents go to
0:18:29 > 0:18:32give their chicks the best chance of survival.
0:18:35 > 0:18:38Each devoted parent travels thousands of miles
0:18:38 > 0:18:41searching for fish and squid to feed their hungry chick.
0:18:45 > 0:18:49But, despite all their efforts, the albatross colony here is in trouble.
0:18:52 > 0:18:56Lucy Quinn is part of the British Antarctic Survey team
0:18:56 > 0:18:59studying the birds here for the last 40 years.
0:19:01 > 0:19:03It's only through looking at long-term studies
0:19:03 > 0:19:05that you get a sense of these creatures,
0:19:05 > 0:19:11and the albatrosses here have, over the past ten years, been in decline.
0:19:12 > 0:19:15There are a number of possible reasons.
0:19:15 > 0:19:19While foraging at sea, albatross can get entangled
0:19:19 > 0:19:21and drowned by fishing gear...
0:19:22 > 0:19:25..but Lucy is particularly alarmed
0:19:25 > 0:19:29by what the parents are bringing back for their chick.
0:19:29 > 0:19:32Albatrosses have the ability to cough up bits of food
0:19:32 > 0:19:34that they can't digest,
0:19:34 > 0:19:36and from that we can tell what they've been eating.
0:19:38 > 0:19:40A healthy albatross chick in its diet
0:19:40 > 0:19:42should really have things like squid,
0:19:42 > 0:19:46so we can find the squid beaks that come out of the pellet,
0:19:46 > 0:19:49and also things like fish, so we can find fish bones as well.
0:19:52 > 0:19:56But these chicks are being fed something very different.
0:19:57 > 0:20:02We have some plastic that this poor chick has had to bring up.
0:20:03 > 0:20:04Plastic bag.
0:20:07 > 0:20:11Here we have some food packaging, looks like rice.
0:20:11 > 0:20:13Luckily for this chick,
0:20:13 > 0:20:16he has managed to get this out of his stomach,
0:20:16 > 0:20:18so fingers crossed he doesn't have any more plastic
0:20:18 > 0:20:20left in there before he fledges.
0:20:24 > 0:20:27For other chicks, plastic can be fatal.
0:20:29 > 0:20:32Unfortunately, there was a plastic tooth-pick
0:20:32 > 0:20:34that had actually gone through the stomach.
0:20:34 > 0:20:37Something just as small as that has actually...
0:20:37 > 0:20:40has managed to kill the bird. It's really sad to see.
0:20:43 > 0:20:48Lucy collects and records what plastic she finds around the nests.
0:20:51 > 0:20:56These are all items that were regurgitated just from last season.
0:20:56 > 0:20:59And that's going to be a vast underestimation,
0:20:59 > 0:21:02because that's just the ones that we happen to find.
0:21:02 > 0:21:05There'll be many more that we never see being brought back.
0:21:09 > 0:21:11To find out where all this rubbish is coming from,
0:21:11 > 0:21:17Lucy and her team have attached GPS trackers to adult birds.
0:21:23 > 0:21:25It's showing where they're going to find food for themselves
0:21:25 > 0:21:28and to find food to bring back for their chicks.
0:21:29 > 0:21:32It really shows us that they could be picking up plastic
0:21:32 > 0:21:35from thousands of miles away.
0:21:35 > 0:21:38Plastic's coming from either being dumped at sea,
0:21:38 > 0:21:40or also from people's homes.
0:21:40 > 0:21:42Plastic gets into the rivers
0:21:42 > 0:21:45and then the rivers flow into the sea.
0:21:45 > 0:21:49So this isn't just a problem around these remote parts -
0:21:49 > 0:21:51this is happening world-wide,
0:21:51 > 0:21:53and it's our rubbish that's going into the oceans,
0:21:53 > 0:21:56and it's our problem that we need to solve.
0:22:01 > 0:22:05In some parts of the ocean, it's estimated that there are now
0:22:05 > 0:22:09over one million pieces of plastic for every square mile.
0:22:10 > 0:22:12And we're only beginning to discover
0:22:12 > 0:22:16just how seriously that affects marine life.
0:22:24 > 0:22:26On the east coast of the United States,
0:22:26 > 0:22:31researchers are investigating the mysterious deaths of young dolphins.
0:22:40 > 0:22:44The team is led by Dr Leslie Hart.
0:22:45 > 0:22:49It looks to be a young animal, maybe a little bit over a year.
0:22:49 > 0:22:51So we're going to try to find out more information
0:22:51 > 0:22:53on why this dolphin died.
0:23:01 > 0:23:05Looking at young dolphins, the very young dolphins,
0:23:05 > 0:23:06it's always heart-breaking.
0:23:14 > 0:23:16Leslie takes tissue samples.
0:23:17 > 0:23:21Their chemical analysis could provide crucial evidence.
0:23:22 > 0:23:26We are often shocked by the high levels of toxins
0:23:26 > 0:23:28that we detect in these animals.
0:23:30 > 0:23:33These young calves are dying for a number of reasons.
0:23:33 > 0:23:37But we suspect man-made toxins are playing a large role.
0:23:39 > 0:23:42And plastic could be part of the problem.
0:23:52 > 0:23:58Once in the ocean, plastic breaks down into tiny fragments,
0:23:58 > 0:24:00micro plastics.
0:24:03 > 0:24:05Along with all the industrial chemicals
0:24:05 > 0:24:10that have drained into the ocean, these form a potentially toxic soup.
0:24:16 > 0:24:21The really small organisms can mistake these tiny, tiny plastics
0:24:21 > 0:24:25as food, then the larger organisms eat the plankton,
0:24:25 > 0:24:29the larger fish eat the smaller fish and so on and so forth.
0:24:31 > 0:24:34Dolphins are at the top of this food chain,
0:24:34 > 0:24:38and it's now thought that pollutants may be building up in their tissues
0:24:38 > 0:24:41to such a degree that a mother's contaminated milk
0:24:41 > 0:24:43could kill her calf.
0:25:01 > 0:25:06Industrial pollution and the discarding of plastic waste
0:25:06 > 0:25:10must be tackled for the sake of all life in the ocean.
0:25:26 > 0:25:30Around the world, people are now devoting their lives
0:25:30 > 0:25:33to saving some of the most threatened sea creatures.
0:25:35 > 0:25:37As here in the Caribbean.
0:25:41 > 0:25:47Every year, on just a few islands, a remarkable event takes place.
0:25:57 > 0:26:02As the sun sets, giant reptiles begin to emerge.
0:26:16 > 0:26:20This magnificent creature, preparing...
0:26:20 > 0:26:22Whoops!
0:26:22 > 0:26:28..preparing to lay her eggs is the largest of all turtles,
0:26:28 > 0:26:30a leatherback.
0:26:30 > 0:26:34They can grow up to half a ton in weight
0:26:34 > 0:26:38and they have an ancestry that goes back 100 million years,
0:26:38 > 0:26:40to the age of the dinosaur.
0:26:41 > 0:26:46But, in recent times, their numbers have fallen catastrophically.
0:26:47 > 0:26:51Here, however, in the Caribbean, there is hope.
0:26:56 > 0:26:59Leatherback turtles leave the sea
0:26:59 > 0:27:01in order to lay their eggs in the dry sand.
0:27:04 > 0:27:07But, out of water, these huge creatures
0:27:07 > 0:27:08are easy targets for hunters.
0:27:13 > 0:27:16In a small fishing village in Trinidad,
0:27:16 > 0:27:19Len Peters has experienced this first-hand.
0:27:21 > 0:27:25I grew up in a household where the presence of turtle meat was normal,
0:27:25 > 0:27:27the fridge was always full of it.
0:27:27 > 0:27:30Everybody, everybody harvested turtles, including my parents.
0:27:31 > 0:27:35It's only when I became exposed to things that were being published
0:27:35 > 0:27:37about leatherbacks were on the verge of extinction,
0:27:37 > 0:27:40and nobody cares, that piqued my interest.
0:27:41 > 0:27:45Len took the leatherbacks' future into his own hands.
0:27:47 > 0:27:51He began patrolling the beach at night to protect the turtles,
0:27:51 > 0:27:53a brave thing to do.
0:27:57 > 0:28:00We were met with tremendous resistance -
0:28:00 > 0:28:02people would pelt us at night.
0:28:02 > 0:28:05I have had persons insult me, I've had persons curse me,
0:28:05 > 0:28:10I've had persons physically try to wrestle me with a machete.
0:28:10 > 0:28:13So it was really a hostile time back then.
0:28:13 > 0:28:16If Len was going to save these turtles,
0:28:16 > 0:28:18he needed to win over the whole community.
0:28:21 > 0:28:25We had to find a way to get the villagers to benefit
0:28:25 > 0:28:27from the presence of these animals.
0:28:30 > 0:28:34He began to encourage tourists to visit the beach,
0:28:34 > 0:28:36and trained some villagers to be their guides.
0:28:41 > 0:28:43To help secure the turtles' future,
0:28:43 > 0:28:47he took the message to the next generation.
0:28:47 > 0:28:51Now, what's the largest size a leatherback can grow to?
0:28:51 > 0:28:54Er, Charlene?
0:28:54 > 0:28:562,000 pounds?
0:28:56 > 0:29:00That's correct, leatherbacks can grow to 2,000 pounds.
0:29:00 > 0:29:02That's a big turtle.
0:29:02 > 0:29:07Len's hard work paid off, and now attitudes have changed.
0:29:07 > 0:29:09Just want to touch base on some of the things
0:29:09 > 0:29:10we want to accomplish tonight.
0:29:10 > 0:29:14It took us a while to reach out to the villagers.
0:29:14 > 0:29:16But gradually we got them involved as well -
0:29:16 > 0:29:19we got some of the poachers who would be hunting the animals
0:29:19 > 0:29:21to be part of the conservation programme.
0:29:24 > 0:29:26As well as protecting the adult turtles,
0:29:26 > 0:29:31the team also collect any eggs that might be flooded at high tide.
0:29:34 > 0:29:37If the eggs are laid too close to the sea,
0:29:37 > 0:29:39we relocate the eggs and re-bury them.
0:29:41 > 0:29:43Thanks to the efforts of this community,
0:29:43 > 0:29:47these turtles have had an extraordinary change in fortune.
0:29:49 > 0:29:51This is now thought to be
0:29:51 > 0:29:54one of the densest leatherback nesting beaches in the world.
0:29:58 > 0:30:02When we started at the height of the nesting season,
0:30:02 > 0:30:05the numbers will be 30, 40 turtles.
0:30:05 > 0:30:07A night. Now it's over 500.
0:30:07 > 0:30:13So we have seen an increase from 40 turtles to 500 turtles a night
0:30:13 > 0:30:14in just around 20 years.
0:30:17 > 0:30:21Precious new hatchlings are also given a helping hand.
0:30:25 > 0:30:27Any that emerge during the day
0:30:27 > 0:30:31are collected to be released safely back to the sea,
0:30:31 > 0:30:33away from hungry birds.
0:30:40 > 0:30:44This little leatherback will have to face 1,000 hazards,
0:30:44 > 0:30:50before it returns as an adult to this beach where it hatched,
0:30:50 > 0:30:53and those dangers will be greatly increased
0:30:53 > 0:30:57because of damage that we have done to the oceans.
0:30:58 > 0:31:00Good luck, little leatherback.
0:31:31 > 0:31:34Protecting breeding sites on beaches
0:31:34 > 0:31:38may improve the fortune of some marine animals.
0:31:38 > 0:31:41But safeguarding them while they roam the high seas
0:31:41 > 0:31:42is much more difficult.
0:31:47 > 0:31:50Out here, there is little protection.
0:31:59 > 0:32:03Every night, thousands of miles of fishing lines,
0:32:03 > 0:32:05laden with hooks, are set.
0:32:07 > 0:32:11There's enough, it's said, to wrap twice around the world.
0:32:16 > 0:32:19Nets large enough to engulf cathedrals
0:32:19 > 0:32:22trap hundreds of tons of fish at a time.
0:32:25 > 0:32:30Long-distance travellers, such as sharks, are particularly at risk.
0:32:36 > 0:32:40It's estimated that tens of millions are killed every year,
0:32:40 > 0:32:45including the biggest fish in the sea, the whale shark.
0:32:57 > 0:33:01Shark biologist Jonathan Green is concerned
0:33:01 > 0:33:05that time is running out for these extraordinary creatures.
0:33:05 > 0:33:08We know that they're being fished, possibly at a massive rate.
0:33:08 > 0:33:12They may be taken by the thousands, possibly tens of thousands a year.
0:33:12 > 0:33:15If that is indeed true, we don't know how long
0:33:15 > 0:33:18they can withstand that kind of fishing pressure.
0:33:20 > 0:33:23To save them, Jonathan is trying to solve the mystery
0:33:23 > 0:33:25of where they give birth.
0:33:32 > 0:33:36And, for the first time, he has a clue as to where this might be.
0:33:43 > 0:33:45Pregnant whale sharks are thought to be travelling
0:33:45 > 0:33:50from across the Pacific Ocean to Darwin Island, in the Galapagos.
0:33:58 > 0:34:00Jonathan is going to try
0:34:00 > 0:34:04and attach a multi-sensor camera tag to a pregnant female.
0:34:05 > 0:34:07OK, we good to go?
0:34:16 > 0:34:19These sharks only stay in the area for a few days -
0:34:19 > 0:34:21this may be his only chance.
0:34:34 > 0:34:36Jonathan has to attach the tag
0:34:36 > 0:34:39before the shark dives to dangerous depths.
0:34:58 > 0:35:02The tag will remain on the giant's fin for two days
0:35:02 > 0:35:04before it's automatically released.
0:35:06 > 0:35:10Once retrieved, it reveals some unusual behaviour.
0:35:13 > 0:35:14Beautiful, beautiful.
0:35:17 > 0:35:22There's a silky rubbing up against the front, next to her eye.
0:35:22 > 0:35:25The silky sharks are brushing up against her rough skin,
0:35:25 > 0:35:28perhaps to scrape off parasites.
0:35:30 > 0:35:33These predatory sharks make the surface waters
0:35:33 > 0:35:37very unsafe places for young fish of any kind.
0:35:39 > 0:35:41There is a surprise in store.
0:35:44 > 0:35:46The tag's depth sensor reveals
0:35:46 > 0:35:49that she dived to a depth of 600 metres.
0:35:51 > 0:35:54But down there it's too dark for the camera.
0:36:01 > 0:36:05The only way Jonathan can prove if they're giving birth
0:36:05 > 0:36:07is to go down and look.
0:36:19 > 0:36:21- RADIO:- Deep Rover, Deep Rover Control -
0:36:21 > 0:36:23you are clear to vent, clear to vent. Have a good dive.
0:36:31 > 0:36:34Out of the gloom, a shape materialises.
0:36:37 > 0:36:39Another massive whale shark.
0:36:41 > 0:36:44Look at that, she's having a look at us, she's looking right at us!
0:36:49 > 0:36:51She is huge!
0:36:51 > 0:36:54And look at the belly - absolutely massive.
0:36:55 > 0:36:59That's a large, pregnant female and she's sticking around,
0:36:59 > 0:37:00she's staying around.
0:37:05 > 0:37:08It goes to show we can follow them, we can follow them in a submarine.
0:37:12 > 0:37:16She leads them down into the darkness.
0:37:18 > 0:37:22- RADIO:- Deep Rover Control, passing one-zero-zero metres descending.
0:37:24 > 0:37:28Heading down, I think she accelerated slightly.
0:37:32 > 0:37:33She's too fast.
0:37:35 > 0:37:37And with a strong current running against them,
0:37:37 > 0:37:39the sub can't keep up.
0:37:44 > 0:37:45But, for the first time,
0:37:45 > 0:37:49Jonathan can see for himself exactly where she's headed.
0:37:52 > 0:37:55What specifically Darwin could provide is a safe refuge
0:37:55 > 0:37:59for those newborn pups where predators can't access.
0:38:00 > 0:38:03Perfect conditions for the formative years
0:38:03 > 0:38:05of these ocean-travelling giants.
0:38:12 > 0:38:14Ah! That was unbelievable.
0:38:16 > 0:38:18Ah! Dream of a lifetime.
0:38:20 > 0:38:23His discovery that pregnant whale sharks
0:38:23 > 0:38:26are visiting this very deep patch of the sea floor
0:38:26 > 0:38:28is strong evidence that this is indeed
0:38:28 > 0:38:31where the giants produce their young.
0:38:33 > 0:38:36If I can actually prove that they are giving birth in this area,
0:38:36 > 0:38:39then we'll have the information necessary
0:38:39 > 0:38:41to go to governments to actually say,
0:38:41 > 0:38:44"You must preserve those routes that they're migrating through."
0:38:44 > 0:38:47And then and only then can we really truly afford protection
0:38:47 > 0:38:49to this beautiful ocean traveller.
0:38:57 > 0:39:02Today, less than 1% of our international waters are protected.
0:39:05 > 0:39:08And the creation of marine reserves is vital
0:39:08 > 0:39:12if we're to safeguard the future of many ocean creatures.
0:39:18 > 0:39:21It will require international cooperation.
0:39:22 > 0:39:24But here, too, there is hope.
0:39:27 > 0:39:29We can turn things round.
0:39:29 > 0:39:31We've done so once before.
0:39:32 > 0:39:37For centuries, the sea-going nations of the world hunted the great whales
0:39:37 > 0:39:40until they were close to extinction,
0:39:40 > 0:39:44and then, in 1986, those nations got together
0:39:44 > 0:39:48and agreed to put a stop to commercial whaling.
0:39:52 > 0:39:56Today, although a few nations continue to hunt whales,
0:39:56 > 0:39:59some of the great whales are making a recovery.
0:40:07 > 0:40:10In the tropical seas surrounding Sri Lanka,
0:40:10 > 0:40:13there are stories of vast gatherings of whales.
0:40:18 > 0:40:21When the civil war ended in 2009,
0:40:21 > 0:40:26locals here were able once again to fish these waters.
0:40:28 > 0:40:31There were soon reports of assemblies of sperm whales,
0:40:31 > 0:40:34the likes of which had not been seen for centuries.
0:40:37 > 0:40:41Marine guide Daya was determined to get to the truth
0:40:41 > 0:40:43behind these fishermen's tales.
0:40:44 > 0:40:46The fisherman told me there were lots of whales,
0:40:46 > 0:40:48a little bit north from here.
0:40:48 > 0:40:53They didn't actually tell me a number, but in big numbers.
0:40:53 > 0:40:57Not ones or twos. Er...many.
0:41:01 > 0:41:03It took him three years,
0:41:03 > 0:41:08but eventually he found evidence to support these rumours.
0:41:54 > 0:41:57We saw about 15 sperm whales go past us.
0:42:07 > 0:42:09Then another pod came past us.
0:42:13 > 0:42:16After about 40 went past me, I started counting.
0:42:21 > 0:42:23Still they kept coming, so I lost count.
0:42:26 > 0:42:29I estimated that we saw about 300 sperm whales.
0:42:36 > 0:42:40Sperm whales were once killed in vast numbers,
0:42:40 > 0:42:43and it's thought that if the slaughter had continued,
0:42:43 > 0:42:47the species would be in danger of extermination.
0:42:50 > 0:42:55But now, here at least, they are being seen in huge numbers.
0:42:56 > 0:43:00I believe they come here to feed, mate, raise their young.
0:43:00 > 0:43:04So this must be a holiday spot for them, you know?
0:43:04 > 0:43:07At the moment, I don't know of any other place in the world
0:43:07 > 0:43:09that sperm whales gather like this.
0:43:13 > 0:43:16Although some whale populations are still in decline,
0:43:16 > 0:43:21scenes like this prove that when sea-going nations come together,
0:43:21 > 0:43:24they can achieve astonishing results.
0:43:32 > 0:43:37But today the oceans face threats on a truly global scale.
0:43:43 > 0:43:45The Great Barrier Reef...
0:43:47 > 0:43:51..the largest coral reef system in the world.
0:43:54 > 0:43:59Here, we filmed stories which reveal just how smart fish can be.
0:44:05 > 0:44:08This ingenious tusk fish, for example,
0:44:08 > 0:44:12used a favourite coral anvil to smash open shellfish.
0:44:14 > 0:44:18This astonishing behaviour has been closely studied
0:44:18 > 0:44:20by local scientist Alex Vail.
0:44:22 > 0:44:26We call him Percy, Percy the Persistent,
0:44:26 > 0:44:29because he took, like, an hour to open the first shell.
0:44:34 > 0:44:37He must have hit it well over 50 times,
0:44:37 > 0:44:40but he just kept on going and finally he got it open.
0:44:49 > 0:44:52Alex grew up on the Great Barrier Reef,
0:44:52 > 0:44:55on one of its more remote islands, Lizard.
0:44:57 > 0:44:59He knows the reef intimately.
0:45:05 > 0:45:09But in 2016, while he was filming for Blue Planet II,
0:45:09 > 0:45:11Alex witnessed a catastrophe.
0:45:13 > 0:45:16When we started filming, everything was pretty much fine,
0:45:16 > 0:45:19all of the corals were basically healthy.
0:45:21 > 0:45:24But, in the last few weeks, everything changed.
0:45:25 > 0:45:28I have never seen anything like this before.
0:45:31 > 0:45:33A combination of a warming ocean
0:45:33 > 0:45:37and an unpredictable weather event called El Nino
0:45:37 > 0:45:39raised sea temperatures to record levels...
0:45:44 > 0:45:47..and this had a disastrous effect on the corals.
0:45:49 > 0:45:54The heat causes reef-building corals to lose their nourishing algae,
0:45:54 > 0:45:57exposing their white skeletons.
0:46:02 > 0:46:06When temperatures remain high, bleached corals die off.
0:46:09 > 0:46:12The bleaching this year has been the worst in history
0:46:12 > 0:46:13for the Great Barrier Reef.
0:46:13 > 0:46:16About 90% of the branching corals
0:46:16 > 0:46:18on the reef out here at Lizard Island are dead.
0:46:21 > 0:46:23It also has disastrous consequences
0:46:23 > 0:46:26for the other creatures that live here.
0:46:30 > 0:46:33Percy, swimming around out there,
0:46:33 > 0:46:36the really sad thing is that his castle is starting to bleach.
0:46:37 > 0:46:38If we lose our coral,
0:46:38 > 0:46:41there's a chance we're going to lose our tusk fish.
0:46:42 > 0:46:45It's incredibly sad to see areas
0:46:45 > 0:46:47that you have dived on since you were a little kid
0:46:47 > 0:46:49just turn to rubble.
0:46:52 > 0:46:54I cried in my mask when I saw, you know,
0:46:54 > 0:46:57some of the devastation from this bleaching.
0:47:04 > 0:47:06In the last three years,
0:47:06 > 0:47:09over two thirds of the world's coral reefs
0:47:09 > 0:47:13are thought to have suffered from rises in ocean temperatures.
0:47:26 > 0:47:28This is not the only challenge they face.
0:47:31 > 0:47:32Research is revealing
0:47:32 > 0:47:36how the fundamental chemistry of the ocean is changing.
0:47:39 > 0:47:42Professor Chris Langdon shows me what this might mean
0:47:42 > 0:47:45for the future of our seas
0:47:45 > 0:47:47by pouring dilute acid over shells.
0:47:52 > 0:47:56And how much more acidic is this than the present ocean?
0:47:56 > 0:48:01This is more concentrated than the pH of the ocean,
0:48:01 > 0:48:04but it accelerates the process so we can see something visually.
0:48:04 > 0:48:06So what's happening is these shells,
0:48:06 > 0:48:08they're made out of calcium carbonate,
0:48:08 > 0:48:11and the acid is dissolving them,
0:48:11 > 0:48:15and coral reefs are made out of the same material as these shells here.
0:48:15 > 0:48:19But surely this is not happening in the ocean now, right now?
0:48:19 > 0:48:21What we're seeing here is more dramatic
0:48:21 > 0:48:23than what's happening in the ocean.
0:48:23 > 0:48:27But the shells and the reefs are really, truly dissolving.
0:48:28 > 0:48:31Coral reefs could be gone by the end of this century.
0:48:34 > 0:48:36And the cause of this?
0:48:36 > 0:48:37Carbon dioxide.
0:48:39 > 0:48:44Dissolved in the seawater, it forms carbonic acid.
0:48:44 > 0:48:46The more carbon dioxide in the atmosphere,
0:48:46 > 0:48:48the more acidic the ocean becomes.
0:48:51 > 0:48:55Evidence points to the burning of fossil fuels as the primary cause
0:48:55 > 0:48:58for these increasing levels of carbon dioxide.
0:49:00 > 0:49:03And this is man-made, beyond question?
0:49:03 > 0:49:04Beyond question.
0:49:08 > 0:49:11But Chris believes all is not lost.
0:49:13 > 0:49:17All we have to do - I say "all" - is reduce our CO2 emissions.
0:49:17 > 0:49:19We can switch to renewable fuels,
0:49:19 > 0:49:23wind and solar instead of fossil fuels,
0:49:23 > 0:49:27and so none of this has to devolve to the worst case.
0:49:27 > 0:49:28And that could fix it?
0:49:28 > 0:49:31Yeah, absolutely. So this future does not have to play out.
0:49:31 > 0:49:33It's-it's up to us.
0:49:39 > 0:49:43THUNDER CRACKS AND RUMBLES
0:49:44 > 0:49:47As the climate changes and the seas warm,
0:49:47 > 0:49:50our oceans are being seriously affected...
0:49:53 > 0:49:57..and this is nowhere more apparent than at the poles.
0:50:06 > 0:50:07Antarctica.
0:50:12 > 0:50:16For the Blue Planet II team, this was their most ambitious expedition.
0:50:19 > 0:50:21For the first time in history,
0:50:21 > 0:50:26a manned submersible will try to dive to a depth of 1,000 metres
0:50:26 > 0:50:29and reach the Antarctic seabed.
0:50:30 > 0:50:33A true journey into the unknown.
0:50:33 > 0:50:38- RADIO:- Deep Rover, Deep Rover Control. Comms check, over.
0:50:38 > 0:50:42SO, Rover. Hatch secure. Life support running.
0:50:49 > 0:50:53Control Rover, passing four-zero metres, over.
0:50:59 > 0:51:02Leading the team on this historic dive
0:51:02 > 0:51:04is deep-sea scientist Jon Copley.
0:51:12 > 0:51:16We get our first glimpse of this landscape...
0:51:18 > 0:51:23..and the carpet of life around us is astounding.
0:51:23 > 0:51:24That's beautiful.
0:51:33 > 0:51:38Diving in a submersible gives Jon an entirely new understanding
0:51:38 > 0:51:40of how this rich ecosystem works.
0:51:42 > 0:51:45But it also offers him a unique opportunity
0:51:45 > 0:51:48to investigate how the ocean here is changing.
0:51:49 > 0:51:51While we're observing the marine life down there,
0:51:51 > 0:51:54the subs are also recording what the environment's like,
0:51:54 > 0:51:56so we're getting measurements of temperature, of salinity,
0:51:56 > 0:51:58that's hopefully going to enable us to understand
0:51:58 > 0:52:01the changes that are happening in this vital part of our planet.
0:52:04 > 0:52:05To get a fuller picture,
0:52:05 > 0:52:08Jon also lowers a deep-sea temperature probe.
0:52:14 > 0:52:17His data is contributing to an international attempt
0:52:17 > 0:52:21to chart the rise in both sea and air temperatures.
0:52:25 > 0:52:27What shocks me about what all the data show
0:52:27 > 0:52:30is how fast things are changing here.
0:52:32 > 0:52:35We're headed into uncharted territory.
0:52:42 > 0:52:46To truly comprehend the effect of the temperature increases here,
0:52:46 > 0:52:48Jon takes to the skies.
0:52:50 > 0:52:54From here, he can record the number and size of the icebergs
0:52:54 > 0:52:57being produced as the ice shelves melt and break apart.
0:53:00 > 0:53:04The 'bergs we're seeing all around us give you some idea
0:53:04 > 0:53:08of how huge this process is that's taking place on the Antarctic.
0:53:09 > 0:53:12As the floating shelves break up,
0:53:12 > 0:53:14they allow water, which has been locked up
0:53:14 > 0:53:18on land as ice for thousands of years, to empty into the sea.
0:53:20 > 0:53:23And this is predicted to push up sea levels.
0:53:28 > 0:53:32If the ice-shelves break up, then that opens the flood gates.
0:53:32 > 0:53:34Ice on land flows faster into the sea
0:53:34 > 0:53:36and that's what pushes up the sea levels.
0:53:38 > 0:53:41So what's happening here right now affects all of us.
0:53:56 > 0:54:00Already, cities like Miami here are under threat.
0:54:01 > 0:54:04Scientists predict that, by the end of the century,
0:54:04 > 0:54:08the sea levels could have risen by a metre or even two.
0:54:08 > 0:54:13Were that to happen, parts of this city would certainly be submerged.
0:54:18 > 0:54:21Around the world, hundreds of millions of people
0:54:21 > 0:54:22live near the coast,
0:54:22 > 0:54:27and, as sea levels rise, their lives will be seriously affected.
0:54:40 > 0:54:42It's now clear that our actions
0:54:42 > 0:54:46are having a significant impact on the world's oceans.
0:54:51 > 0:54:54During the four years it took to make this series,
0:54:54 > 0:54:57we've witnessed many of these changes first-hand.
0:55:06 > 0:55:09But we've also worked alongside men and women
0:55:09 > 0:55:13dedicating their lives to safeguarding the oceans' future.
0:55:21 > 0:55:26The oceans provide us with oxygen, they regulate temperature,
0:55:26 > 0:55:30they provide us with food and energy supplies
0:55:30 > 0:55:35and it's unthinkable to have a world without a healthy ocean.
0:55:38 > 0:55:43I still think we have the capability to change the manner in which
0:55:43 > 0:55:46we're wasting the resources, in which we're poisoning our oceans
0:55:46 > 0:55:50and we can look to a future with healthy oceans.
0:55:53 > 0:55:57When I look forward, I believe that if what we are doing
0:55:57 > 0:56:00can be duplicated just a little bit,
0:56:00 > 0:56:03these animals will have a chance of surviving.
0:56:04 > 0:56:08It comes down, I think, to us each taking responsibility
0:56:08 > 0:56:11for the personal choices in our everyday lives,
0:56:11 > 0:56:14that's all any of us can be expected to do
0:56:14 > 0:56:17and it is those everyday choices that add up.
0:56:32 > 0:56:35We are at a unique stage in our history.
0:56:36 > 0:56:40Never before have we had such an awareness
0:56:40 > 0:56:42of what we are doing to the planet...
0:56:43 > 0:56:48..and never before have we had the power to do something about that.
0:56:50 > 0:56:54Surely we have a responsibility to care for our blue planet.
0:56:55 > 0:56:58The future of humanity,
0:56:58 > 0:57:03and indeed all life on Earth, now depends on us.
0:57:09 > 0:57:14To find out more about our oceans with this free poster, call...
0:57:16 > 0:57:18..or go to...
0:57:22 > 0:57:25..and follow the links to the Open University.