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The Arctic - five and a half million square miles

of land, water, and ice.

It's home to some of the world's most

spectacular landscapes and

most magnificent creatures.

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Spring's arrival triggers a mass migration north.

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For a few months, the Arctic teems with animals -

feeding, breeding,

nurturing their young,

and battling for survival.

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But the Arctic is changing.

The climate is warming.

The ice is retreating.

The delicate natural balance is threatened.

And what happens here in the Arctic affects us all.

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The Arctic has inspired the imagination

in legend and myth.

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Many picture the Arctic as a barren wasteland -

frozen and lifeless.

But it's home to a surprising diversity

of plants and animals.

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The Arctic encompasses all land and sea north of the

66th parallel - The Arctic Circle -

and the boundaries of eight nations.

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Two features characterize the Arctic:

fiercely freezing temperatures and

extremes of day and night.

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For much of winter, while the northern hemisphere

tilts twenty-three degrees away from the sun,

the Arctic is cloaked in darkness.

When the northern hemisphere begins to tilt

towards the sun, the Arctic enters spring.

The days grow longer, culminating in summer's

twenty-four hours of daylight.

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On the western shores of Hudson Bay,

the warming sunlight draws a hungry polar bear and

her two cubs from their winter den.

The cubs were born in the depth of winter,

between November and January.

In March, they emerge onto the ice and search for food.

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For the cubs, walking for long periods is exhausting.

But they're discovering and learning,

as their mother teaches them to survive.

One of the first lessons will be how to hunt seal.

The mother hasn't eaten in months.

She's ravenous to capture her first prey since fall.

Seals are a polar bear's staple food.

But they are hard to catch - especially with

these two clowns in tow.

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Her best chance will be to catch a baby seal.

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Below the sea ice off the coast of Greenland,

pregnant harp seals congregate in huge numbers.

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Harp seals dance between the worlds above and below,

supremely adapted to both.

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As many as five thousand females may gather in a

square mile to give birth.

Seal pups are among the fastest-growing infant

mammals, nurtured by milk that's 45% fat.

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The pup weighs around twenty-four pounds at birth

and can triple its weight in twelve days.

It has to grow fast.

This is when the pup is most vulnerable.

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The mother leaves her offspring unattended all day,

returning occasionally to nurse.

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The pup is camouflaged, but helpless should a

sharp-eyed polar bear or fox come along.

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The mother will soon leave the pup to fend for itself.

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While the pup lies on the ice,

the surrounding landscape transforms -

the Arctic Ocean is thawing.

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Expanses of ice break in a churning,

often violent, cataclysm.

As the temperature rises, wind and tides

smash vast ice sheets together.

Ice, several feet thick, is heaved into the air.

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Across the Arctic, the ice is moving.

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The spring days launch one of the great events

in the natural world -

The massive northward migration of millions of creatures.

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The cold, dark Arctic becomes a haven

bathed in sunshine,

where animals feast on lush vegetation.

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A primal urge drives them on arduous journeys over

thousands of miles to reach this

land of abundance.

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Exactly how these creatures time their journey

and precisely navigate their way remains a mystery.

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The caribou tackle one of the longest migrations

of any land mammal.

This herd's journey north can be more than 930 miles.

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They've wintered, safe from storms,

in the northern edges of Yukon forests.

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Now that spring is coming, they venture further north,

along paths migrating caribou hooves

have etched into rock over thousands of years.

They cross mountain passes still gripped by winter.

They ford rivers and cross plains.

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Further and further, on to the open tundra.

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During the weeks they've travelled,

snow and ice have melted away.

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They have one goal: to reach their

calving grounds on tundra near the Arctic Ocean.

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Timing is critical.

Female caribou are pregnant during the migration

and give birth soon after arriving.

They must reach their destination in time to

feast on tender spring grasses and buds.

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The wide, rolling tundra becomes a nursery for

thousands of calves.

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Caribou in a herd give birth within

hours of each other.

Newborns can walk almost immediately.

They must move quickly to keep up with the herd.

They're born into a dangerous life.

Almost half die in the first year -

from sickness, drowning, abandonment, or as victims

of hungry wolves and grizzly bears.

The skies are thick with millions of birds,

flocking from all over the Americas,

returning to their summer home.

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Thick-billed murres spend their winters on the

open seas of the North Atlantic.

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In May, they migrate over twelve hundred miles

back to their birthplace - steep cliff faces on

Coats Island in northern Hudson Bay.

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Over thirty thousand birds nest here.

By June, the barren cliffs are alive with the

chatter of their voices.

They come to mate and raise chicks.

Within a few weeks, the female lays one egg.

Both parents keep it warm.

When the chick hatches, mother and father take turns

watching and feeding: the mother during the day,

the father at night.

The waters around Coats Island teem with young cod -

rich in nutrients and the hatchlings' favorite food.

The murres spend their summer preparing their

offspring for a migratory life in the skies.

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Further north still, on high seas off Baffin Island,

icebergs calved from Arctic glaciers are

on a two-thousand mile journey.

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They drift south about six miles each day,

moved by winds, currents and tides.

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From the moment the iceberg calves off the glacier,

nature begins sculpting.

Wind and water chisel and polish the mass of ice,

molding soft hollows, cutting sharp angles.

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Among the bergs, one of the world's largest

mammals comes to feed - the bowhead whale.

Diving over five hundred feet

their giant mouths wide open,

they can stay in these depths for over forty minutes,

feeding on tiny plankton.

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In recent years, a sleek predator,

the orca, has intruded into their waters.

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Orcas are at home in all the world's oceans,

but are not typically seen so far north because

they're not best-adapted to heavily-iced waters.

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Unlike native Arctic whales, orcas have big

dorsal fins that scrape against sea ice.

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But climate change has caused longer ice-free

periods in the Arctic.

The orcas can roam freer in northern seas.

And there they hunt, kill, and eat bowhead whales.

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The increase of orcas in these waters poses a new

threat to the bowhead, which is already endangered.

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In the waters around Coats Island in Hudson Bay,

walrus hunt for mollusks and crustaceans on the sea floor.

Between dives, they rest on ice floes or small islands.

But, like the bowheads',

the world of the walrus is changing.

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In the last twenty-five years, rising temperatures

have caused sea ice to melt much earlier in spring.

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Diminishing ice affects polar animals

in a number of ways.

Polar bears use ice floes as platforms for hunting seals.

In many areas, the sea ice has completely disappeared.

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Bears like this one must swim further and more often

to find food.

Bears are used to fasting in summer,

but as summers last longer, the bears grow famished.

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This bear is desperate to satisfy its hunger.

It's willing to take risks.

For any polar bear, a walrus is a formidable foe.

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Their sharp tusks and strength can easily,

fatally wound a polar bear.

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It's rare for a polar bear to attack a grown walrus,

let alone a colony.

Chaos ensues... leaving a calf unprotected.

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Polar bears are excellent hunters,

but as their world is changing,

they seek new ways to feed themselves.

Some on Coats Island are desperate enough to

scavenge the murre colony.

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It's a lot of work that yields a small amount of

protein, and a few bones and feathers.

But it must be worth it.

In recent years polar bears have wiped out a

third of this colony.

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Cubs are learning from their mothers and bears

now return here every year.

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It's the peak of summer in the Arctic.

The sun is high in the sky.

Land and sea are bathed in twenty-four hours

of sunlight.

Bushes and grasses bloom.

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Creatures rush to take advantage of the

weeks of plenty.

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On the shores of Ungava Bay, muskoxen slip into

the rhythm of summer, as they have for millennia,

nurturing their young and fattening while they can.

The muskox was here when the wooly mammoth and the

saber tooth cat roamed the terrain.

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They are gone.

But the muskox remains.

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A herd moves slowly across the landscape -

as muskoxen have for thousands of years.

Calves born earlier this spring graze and play.

They won't be weaned for another year or so.

They closely follow their mothers.

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And while they nibble on leaves and grasses,

they still drink their mother's milk.

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The muskoxen are perfectly adapted to this severe land.

Their biorhythms shift with the seasons,

conserving energy to survive winter.

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And no wool is more insulating than the

qiviut that covers them.

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Grizzly bears used to range throughout North America -

until hunting and the destruction of their habitat

pushed them to the last vestiges of wilderness.

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Across the entire Arctic mainland, the grizzly has

made its home from northernmost forests,

across open tundra, to the shores of the Arctic Ocean.

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A grizzly bear can eat virtually anything

this land has to offer.

This female grizzly on the Yukon North coast learned

from her mother where to dig for clams.

Now she's passing on that knowledge to her cubs.

They don't know it, but everything she does is a

lesson that can make the difference between

life and death.

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This male grizzly is pursuing a female in heat.

He's been wooing her for days,

following her every step.

She is now ready to mate.

Exhausted by the effort, he naps on the tundra.

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He's the predator on top of the food chain,

has little to fear, so rests wherever he pleases.

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His sensitive ears and nose provide quick alerts

to any change around him, even in the deepest sleep.

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Here on the tundra, the Arctic summer flaunts

its lushest greens.

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Meadows of flowers and cotton grass wave in the breeze.

Fields of fireweed brighten the hills.

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Herds of caribou graze across the tundra.

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This spring's calves are almost independent and

have begun to feed, alongside their mothers,

on grasses and sedges.

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The warming lakes and channels of the Mackenzie

River Delta produce one of the Arctic's most

ferocious creatures.

The mosquito - unchallenged ruler

of the Arctic summer.

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Stagnant ponds teem with millions of mosquito larvae.

They hang upside down, feeding on microorganisms.

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The larvae turn into pupae,

from which adults emerge to rest on the water's surface,

waiting for their bodies to harden.

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Their wings must dry and spread before they can fly.

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With Arctic temperatures rising twice as fast as

the rest of the globe, ponds and lakes on the

tundra are melting several weeks sooner than before.

As a result, adult mosquitoes are emerging

and taking flight earlier in the season.

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They threaten entire herds of caribou, which run to

snowy pockets or windy ridges to escape the onslaught.

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But the more time they spend fleeing swarming insects,

the less time they spend eating.

A caribou can lose a pint of blood a day to mosquitoes.

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For calves the attack can be fatal.

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In the precious few weeks of summer, plants make the

most of the generous sunlight.

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Low growing vegetation and trees have

adapted to survive the Arctic's harsh conditions.

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Shallow, expansive roots grip the meager soil.

Despite their small size, some of these trees are

hundreds of years old.

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They're armed with strategies for

surviving the chill.

Woolly stems and thick, small leaves retain moisture.

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Lichen has adapted to live on bare rock.

It's an important food for caribou,

the only creatures that can completely digest

its fibrous mass.

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Climate change is threatening this vital

food source in two ways.

Warmer temperatures push shrubs and bushes

further north, displacing the lichen.

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Now, freezing rain, instead of snow,

often covers the remaining lichen and

thick ice blocks caribou from their food.

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As a result, during the last thirty years,

Arctic caribou populations have plunged

by nearly sixty percent.

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In the golden light of late summer,

the land presents the last of its bounty -

blueberries,

cranberries, and cloudberries.

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The ptarmigan enjoys the late summer fruit.

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Its changing plumage foreshadows the

arrival of winter.

The feathers change from brown in summer to white

in winter, camouflaging it from predators.

It's only the beginning of September.

But fall comes early to the Arctic.

There's a chill in the air and frost on the ground.

The sun rises lower in the sky.

Leaves are changing color.

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Ponds start to freeze over.

Hoar frost covers grass and bushes.

Shadows grow longer.

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In about a month, the grizzly bears will dig

their dens and hibernate.

They must consume an immense amount of food

before their winter sleep.

Caribou calves, now four months old, are strong

enough to start the long journey south

for the first time.

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Though they may not know their destination,

the drive to go is inscribed in their DNA.

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Mature caribou bulls have fully grown their antlers.

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They'll fall off in winter or spring,

but are important now.

The size of the antlers signals a bull's virility

and dominance.

Bulls use them to challenge each other in a rut.

These sparring matches determine which males are

worthy to mate with the females.

The rut starts when the herd begins

its southward migration.

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With the herd on the move, bulls don't stake out

a fixed territory.

They become increasingly aggressive, and display

their dominance in brief, ferocious outbursts.

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Weak bulls are quickly dispatched.

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For two weeks in October, alpha bulls with the

largest, most robust antlers fight sparring

matches that can seriously injure them.

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One match after another decides the dominant bull.

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The victor wins the right to mate with most of the

females in the herd.

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As the days shorten and temperatures drop,

birds prepare for the long journey south.

At Coats Island, the thick-billed murre

colony is crowded.

Chicks have grown and are almost too big for their ledges.

It's time to follow their parents out to sea and

take their first flight ever.

This chick has never flown but knows instinctively

it must make the jump.

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The first landing may be rough, but soon enough,

water becomes a natural element.

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The murres fly away over twelve hundred miles

southeast to their winter home, the high seas

of the North Atlantic.

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Throughout the Arctic the days grow shorter.

The brutal winter is advancing.

The ocean churns with high tides.

The seas and weather are volatile.

Storms thrust ice floes into coves and bays.

The big freeze has begun.

Snow begins to fall.

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Wind drives the snowflakes into interlocking

formations of ice crystals.

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The gathered blanket shelters and warms

small mammals that live and forage close to the ground.

The snow cover insulates heat from the earth,

while above it is brutally cold.

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In the bush of the Northern Yukon,

fast-flowing waters keeps some creeks open,

long after the lakes they join have frozen solid.

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These streams are known to wolves and otters

whose tracks cross the distances between them.

Here, even weak sunlight reaches the bottom,

where plants, algae, and bacteria feed a diversity

of insects, crustaceans and fish.

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As the days wane, early in the afternoon,

grey shapes move into the riffles.

Whitefish have swum to these gravel beds from

nearby lakes to lay their eggs.

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In a few weeks, the whitefish run is over.

In the gravels, the fertilized eggs will

hatch into tiny fry

and the creek will become their nursery.

They share the creek with the tiny American Dipper,

which is hardy enough to stay in the Arctic all year.

When most other birds its size have long-since

migrated, the dipper stays by its favorite streams.

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It's the only North American songbird to spend

all its time on or beside water.

It fearlessly dips into freezing water up to

sixty times a minute.

Staying warm and dry in a feathered suit,

waterproofed with oil.

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Dippers have unusual eyelids, protected with

tiny feathers that make the eyes flash white

when it blinks.

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The dipper feeds on rich aquatic insects to keep it

warm when temperatures plunge to negative sixty.

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As the days grow shorter, animals that remain for

the winter hunker down.

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Over millennia, muskoxen have evolved to endure

near-starvation and blinding Arctic blizzards

in temperatures sixty below.

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In recent years they've been fighting a foe even

more treacherous than Arctic winter.

Warming temperatures have encouraged the growth of

a parasite - the muskox lungworm.

It infests their lungs and weakens them.

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They seek areas with shallower snow and

forage persistently through winter.

Their fodder has little nutrition, but their

strategy is to eat a lot and conserve energy

by moving very little.

Their metabolism slows to half the rate it is in summer.

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It's December.

The ptarmigans' plumage has turned almost pure white,

blending with the snow banks that now carpet

their home.

They seek shelter along slopes facing away from

the wind and usually stay close to patches of Arctic

willow, where they nip off twigs and little leaves.

Sometimes their presence can only be detected by

the elaborate pattern their feathered feet

draw in the snow.

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Day by day, the northern hemisphere grows darker.

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But new light brightens the winter sky...

The Aurora Borealis - the Northern lights.

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The Arctic's inhabitants have evolved through

millennia of seasonal rhythms.

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Now, with each passing year, the weather

fluctuates more wildly.

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Summers lengthen,

temperatures warm,

and the ice retreats further.

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Animals may not be able to adapt to this

unprecedented change.

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We've wounded the Arctic.

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Our challenge is to restore the balance -

to mend and preserve this Land of Extremes.

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