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  • [David AttenboroughJust 50 years ago,

  • we finally ventured to the moon.

  • For the very first time, we looked back at our own planet.

  • Since thenthe human population has more than doubled.

  • This series will celebrate the natural wonders that remain,

  • and reveal what we must preserve

  • to ensure people and nature thrive.

  • The polar regions of our planet may seem beyond the reach of most of us,

  • but they are not beyond our influence.

  • We, unintentionally, are changing these frozen worlds,

  • and these changes will not just affect the poles

  • but the whole planet.

  • Antarctica.

  • The southern end of our planet, and the coldest place on Earth.

  • It has been frozen for 30 million years.

  • In its center, the covering of ice is over four kilometers thick.

  • Entire mountain ranges are buried beneath it.

  • Here, it is so cold that each winter

  • 19 million square kilometers of ocean freezes,

  • more than doubling the size of the ice cap.

  • But when, in spring, the sea ice melts,

  • life returns once again to the continent's shores.

  • The peninsula that stretches north towards South America

  • is the first part of it to be released from winter's grip.

  • As the sea ice breaks up,

  • life returns.

  • [gulls cawing]

  • There is a greater variety of living creatures here

  • than anywhere else in Antarctica.

  • Gentoo penguins spend most of their lives at sea,

  • but now, in spring, they have to come ashore to breed.

  • They're the fastest of all penguins in water,

  • but on land, life takes on a slower pace.

  • It's an uphill struggle to reach their nesting grounds...

  • [penguins honking]

  • ...but penguins never give up.

  • The paths they follow, carved by thousands of tiny footsteps,

  • lead to Antarctica's rarest commodity.

  • Bare rock.

  • Less than one percent of Antarctica is ice-free,

  • and these rocky patches

  • are the only places where gentoos can lay their eggs.

  • It's been a 30-minute struggle,

  • but he's almost at the top, where his mate is waiting for him.

  • [honking]

  • He presents her with a stone,

  • a gift to improve the nest and so win her favor.

  • [both honking]

  • He's back just in time.

  • There's another mouth to feed.

  • [chirrups]

  • Gentoo penguins used to be rare in this part of Antarctica,

  • but now, as temperatures rise, their numbers here are increasing.

  • Sea ice may appear to be flat and lifeless,

  • but beneath it there is another world.

  • As the ice melts, the light filters through,

  • and algae, that have been trapped within the ice all winterflourish.

  • This upside-down world

  • is the polar equivalent of the great grasslands.

  • The ice is the soil upon which plant life grows,

  • and the herds of grazers soon arrive.

  • Antarctic krill.

  • Trillions of them swarm in the waters around Antarctica.

  • Protected by the ice above, they graze on algae whilst the sun shines.

  • But the good times don't last long.

  • Once all the ice has melted, the krill lose their protection,

  • and predators appear.

  • Penguins may have lost their ability to fly,

  • but they still form flocks, as so many birds do.

  • The longer they dive,

  • the longer it takes them to catch their breath.

  • Ruffling their feathers traps air, which makes their bodies more streamlined.

  • One last breath...

  • and the whole group dives down together.

  • The gentoos follow the krill down to depths of over 200 meters.

  • What a flock can catch in one dive,

  • a giant traps in a single mouthful.

  • Humpback whales from the tropics

  • have traveled over 8,000 kilometers to get here.

  • This one chooses to feed alone.

  • This technique, part lunge, part pounce,

  • only works when the krill are close to the surface.

  • As more humpbacks arrive, they begin to work in teams.

  • By lunging together,

  • the overspill from one huge mouth is not lost but collected by another.

  • Some humpbacks regularly work in an even more coordinated way.

  • They do so when krill has descended to some depth.

  • Once in position, they blast air from their blowholes.

  • Working together,

  • they create a curtain of bubbles around their prey.

  • As the spiraling net tightens, the krill are driven closer together,

  • and then the whales lunge upwards and collect them.

  • Almost all humpback whales in the southern hemisphere

  • come to the Antarctic to feed on krill.

  • Since the ban on commercial whaling, their numbers have recovered dramatically,

  • but their food supply is now under threat.

  • In the last 50 years,

  • with warming temperatures and disappearing sea ice,

  • krill stocks in this part of the Southern Ocean

  • have more than halved.

  • Other sea hunters come here seeking bigger prey than krill.

  • Antarctica's top predators.

  • Orca, killer whales.

  • Over half of the world's orca patrol these polar seas.

  • This particular pod specializes in hunting penguins.

  • They shift into stealth mode.

  • Hunting without making a sound, so that their prey won't hear them coming.

  • A penguin can outmaneuver a single killer whale,

  • but it can seldom escape a pod.

  • This hunt may seem cruel,

  • but important life skills are being passed down the generations.

  • From killer whales to krill,

  • all life here ultimately depends upon Antarctica's sea ice.

  • The seas that surround Antarctica are the roughest on our planet.

  • These churning waters draw up nutrients from the deep

  • and create vast, rich fishing grounds for nomads like the wandering albatross.

  • Beneath the waves, currents are flowing away from Antarctica,

  • transporting nutrients across the planet, fertilizing the oceans

  • and helping to regulate global temperatures.

  • The island of South Georgia.

  • It's far enough north

  • to be beyond the reach of the sea ice even in midwinter,

  • and many animals live here the year round.

  • This wandering albatross chick has been sitting on its nest all winter,

  • and is entirely dependent on its parents returning with food.

  • It may have to wait a few days between meals, or even a couple of weeks,

  • but at least it's not the only one who's waiting.

  • Albatross chicks need to spend a whole year growing

  • before they're ready to take their first flight.

  • And then they spend several years at sea before they return to land.

  • [honking]

  • Coming in to land  on three-meter wings takes some practice.

  • Albatross don't have reverse thrusters.

  • [chirping]

  • The chick  is this female's first.

  • She's been raising it for six months, and has another six to go.

  • Her chick is smaller than it should be,

  • a sign that her mate has not been returning with food.

  • He may well have been one of the many that die,

  • entangled on longline fishing lines.

  • South Georgia is an ideal place for wanderers to raise their young,

  • but now fewer adults are returning here to nest,

  • and in recent years,

  • the breeding population has declined by 40 percent.

  • For now, waiting on its nest, the chick is safe.

  • There are no land predators here.

  • But the same cannot be said for South Georgia's seas.

  • Giant kelp flourishes in these ice-free waters.

  • The perfect place for an ambush.

  • Leopard seals overwinter here to escape Antarctica's frozen ocean.

  • They should have returned south by now,

  • but this year they've stayed longer.

  • And they've delayed their departure for good reason.

  • There are king penguins here.

  • Each is a substantial meal,

  • if you can catch it.

  • Returning to feed their chicks,

  • the kings have no choice but to run the gauntlet.

  • Kings rarely porpoise like this.

  • It uses more energy, but it's faster than traveling underwater.

  • It's hard to select a moving target in a panicking crowd,

  • but if there are stragglers, the odds change.

  • Razor-sharp teeth versus a stabbing beak.

  • It's stalemate.

  • Both are exhausted after the chase.

  • The hunter decides that the meal is not worth the fight.

  • [cawing]

  • For the penguin, it was too close for comfort,

  • but that was just the first hurdle in getting back to feed its chick.

  • [cawing]

  • It isn't going to be  a walk in the park.

  • [elephant seals snoring]

  • Luckily, penguin is not on their menu.

  • Still, it's best to let sleeping giants lie.

  • [penguin honks]

  • Elephant seal females  don't take kindly

  • to being disturbed from their slumber,

  • but it's the four-tonne males you need to look out for.

  • [rasping grunting]

  • They are fighting for access to the females.

  • Getting bulldozed under angry blubber is to be avoided at all costs.

  • An escape route.

  • Time to run for it.

  • At last, he's reached the nursery.

  • Now comes his final challenge.

  • Finding his chick in the crowd of half a million.

  • He calls...

  • [cawing]

  • ...and listens  for a recognizable reply.

  • [chirping]

  • His chick could be another mile or two away,

  • at the back of the colony.

  • But that's the trouble with chicks.

  • They're never where you left them.

  • Astonishingly, in all this racket,

  • a parent and its chick can recognize each other's calls.

  • [chirping]

  • The things parents go through to deliver a meal.

  • If only they knew.

  • For such a small island,

  • South Georgia supports an extraordinary quantity of life.

  • All these creatures ultimately depend on the krill

  • that develops under the sea ice around the Antarctic peninsula.

  • With sea ice disappearing,

  • so South Georgia's future is far from certain.

  • At the other end of the planet, in the north,

  • the effects of climate change are being felt even more intensely.

  • The Arctic is not a continent surrounded by sea

  • but a frozen ocean ringed by land.

  • Here, in spring, the sea ice is still at its maximum extent.

  • It's a vast, firm hunting ground for the planet's largest land carnivore.

  • A male polar bear in search of his next meal

  • on the frozen fjords of Svalbard in the high Arctic.

  • He's looking for seals, which make up the bulk of his diet.

  • He must eat two-thirds of the food he needs for the whole year

  • before the ice melts and his hunting platform disappears.

  • The ringed seal mother had no choice but to leave her pup alone on the surface.

  • In the past, she would have built a den inside a ridge on the ice,

  • but now the sea freezes so late that the ice is flat,

  • and she had to leave her pup out in the open.

  • These changes in the ice may benefit the bears for now,

  • but in the long term,

  • a crash in their most important prey will follow.

  • This new, flatter ice makes life difficult for the bears, too.

  • There's nowhere for them to hide in order to creep up on a seal.

  • And for a mother with a young cub in tow, being stealthy isn't easy.

  • The cub doesn't yet appreciate the need for care

  • when sneaking up on a seal.

  • With fewer seals hiding in dens,

  • learning this pounding technique, once so useful,

  • is now almost pointless.

  • Still, at least he's discovered what a seal hole looks like..

  • His mother knows that overcast conditions are good for hunting,

  • and he knows when she's serious.

  • Adult seals make a much better meal.

  • Her cub carefully treads in her footsteps,

  • and takes care not to break her outline.

  • Neither must put a foot wrong.

  • They must move as one.

  • Most seal hunts end in failure.

  • The bears must keep searching.

  • Her cub wanders off,

  • and gets another chance.