A hundred years ago
there were one and a half billion people on Earth.
Now, over six billion crowd our fragile planet.
But even so, there are still places barely touched by humanity.
This series will take to the last wildernesses
and show you the planet and its wildlife
as you have never seen them before.
Imagine our world without sun.
Male Emperor Penguins are facing the nearest that exists on planet Earth
winter in Antarctica.
It's continuously dark
and temperatures drop to minus seventy degrees centigrade.
The penguins stay when all other creatures have fled
because each guards a treasure:
A single egg rested on the top of its feet
and kept warm beneath the downy bulge of its stomach.
There is no food and no water for them,
and they will not see the sun again for four months.
Surely no greater ordeal is faced by any animal.
As the sun departs from the Antarctic
it lightens the skies in the far north.
原版英语阅读网 http://www.en8848.com.cn/
It's March
and light returns to the high Arctic,
sweeping away four months of darkness.
A polar bear stirs.
She has been in her den the whole winter.
Her emergence marks the beginning of spring.
After months of confinement underground
she toboggans down the slope.
Perhaps to clean her fur,
perhaps for sheer joy.
Her cubs gaze out of their bright new world
for the very first time.
The female calls them,
but this steep slope is not the easiest place to take your first steps.
But they are hungry
and eager to reach their mother,
who's delayed feeding them on this special day.
Now she lures them with the promise of milk,
the only food the cubs have known since they were born
deaf and blind beneath the snow some two months ago.
Their mother has not eaten for five months
and has lost half her body weight.
原版英语阅读网 http://www.en8848.com.cn/
Now she converts the last of her fat reserves into milk for her cubs.
The spring sun brings warmth
but also a problem for the mother.
It starts to melt the sea ice.
That is where she hunts for the seal she needs to feed her cubs.
And she must get there before the ice breaks up.
For now though it's still minus thirty degrees
and the cubs must have the shelter of the den.
It's six days since the bears emerged
and spring is advancing rapidly.
But even now blizzards can strike without warning.
Being so small,
the cubs are easily chilled and they will be more comfortable resting in
the den.
But their mother must keep them out and active.
She's becoming weak from hunger
and there's no food on these nursery slopes.
The sea ice still holds firm,
but it won't last much longer.
Day 10,
and the mother has led her cubs a mile from the den.
It's time to put them to the test.
原版英语阅读网 http://www.en8848.com.cn/
They've grown enormously in confidence,
but they don't have their mother's sense of urgency.
At last it seems that they're ready for their journey
and they're only just in time,
for a few miles from the coast the ice is already splitting.
Now the mother can start hunting for the seals they must have,
but she's leading her cubs into a dangerous new world.
Nearly half of all cubs die in their first year out on the ice.
Summer brings 24 hours of sunlight
and the thawing shifting landscape.
Further south the winter snows have almost cleared from the Arctic tundra.
Northern Canada's wild frontier.
Here nature stages one of her greatest dramas Every year three million caribou migrate across the Arctic tundra.
The immensity of the herd can only be properly appreciated from the air.
Some herds travel over 2,000 miles a year in search of fresh pastures.
This is the longest overland migration made by any animal.
They're constantly on the move.
Newborn calves have to be up and running the day they are born.
But the vast herds do not travel alone.
Wolves.
原版英语阅读网 http://www.en8848.com.cn/
Packs of them, eight to ten strong, shadow the migration.
And they are hungry.
It's the newly born calves that they are after.
Running directly at the herd is a ploy to generate panic.
The herd breaks up
and now it's easier to target an individual.
In the chaos a calf is separated from its mother.
The calf is young,
but it can outrun the wolf if only it manages to keep its footing.
At this stage the odds are even either the caribou will make a mistake
or after a mile the wolf will give up.
Midsummer on the tundra
and the sun does not set.
At these latitudes the sun's rays are glancing
and not enough of their energy reaches the ground
to enable trees to grow.
You'll need to travel 500 miles south from here
before that is possible.
These stunted shrubs mark the tree line the beginning of the boreal forest the taiga.
原版英语阅读网 http://www.en8848.com.cn/
The needle-shaped leaves of the conifers are virtually inedible
so this forest supports very little animal life.
It's a silent place
where the snow is unmarked by footprints.
In the Arctic winter
snow forms a continuous blanket across the land.
But as spring creeps up from the south
the taiga is unveiled.
This vast forest circling the globe
contains a third of all the trees on Earth
and produces so much oxygen
it changes the composition of the atmosphere.
As we travel south
so the sun's influence grows stronger
and at 50 degrees of latitude a radical transformation begins.
Summers here are long enough for broadleaf trees to replace conifers.
Broadleaves are much easier to eat and digest
so now animals can collect their share of the energy
that has come from the sun.
It's summer
and these forests are bustling with life.
原版英语阅读网 http://www.en8848.com.cn/
But the good times will not last.
Broad leaves must be shed in winter for their damage by frost.
As they disappear,
so the land becomes barren with little for animals to eat.
The inhabitants must migrate,
hibernate,
or face months of near starvation.
The Amur leopard the rarest cat in the world.
Here, in the deciduous forests of eastern Russia
the winter makes hunting very difficult.
Pray animals are scarce,
and there's no concealing vegetation.
The cub is a year old and still dependent on its mother.
Deer are frequent casualties of the harsh winter
and these leopards are not above scavenging from a corpse.
African leopards could never survive here,
but the Russian cats have thick fur to shield them from the cold.
There are only forty Amur leopards left in the wild
and that number is falling.
Like so many creatures,
the cats have been pushed to the very edge of extinction
原版英语阅读网 http://www.en8848.com.cn/
by hunting and the destruction of their habitat.
The Amur leopard symbolizes the fragility of our natural heritage.
The future of an entire species hangs on survival
of a tiny number of mothers like this one.
All animals, rare or common,
ultimately depend for their energy on the sun.
In Japan the arrival of the cherry blossom
announces the beginning of spring.
The sun's energy brings color to the landscape.
The earth, as it makes its annual journey around the sun,
spins on a tilted axis.
And it's this tilt that creates the seasons.
The advance of the seasons brings constant change.
As the sun's influence diminishes in the north,
so the deciduous forests of America begin to shut down
losing their leaves in preparation for the dark cold months ahead.
One season hands over to another.
Some organisms thrive on decay,
but most must make special preparations for winter
and a life with little sun.
Whole populations of animals
原版英语阅读网 http://www.en8848.com.cn/
are now forced to travel great distances in pursuit of food and warmth.
300,000 Baikal teal gather to escape from the Siberian winter
by migrating south to Korea the world's entire population in a single flock.
But there are parts of the world that have no seasons.
In the tropics the sun's rays strike the earth head on
and their strength is more or less constant all year round.
That is why the jungle grows so vigorously
and supports so much life.
This forest covers only 3 percent of the planet's surface,
but it contains more than 50 percent of all its plants and animals.
The canopy is particularly rich.
There are monkeys, birds
and millions of species of insects,
exactly how many we have no idea.
The character of the forest changes as we descend,
becoming ever darker and damper,
favoring different kinds of animals and plants.
Less than 2 percent of the sunlight reaches the floor,
but even here there is extraordinary variety.
In the great island of New Guinea
there are 42 different species of birds of paradise,
原版英语阅读网 http://www.en8848.com.cn/
each more bizarre than the last.
This forest is so rich
that nourishing food can be gathered very quickly.
That leaves the male six-plumed bird of paradise
with time to concentrate on other matters
like tidying up his display area.
Everything must be spick and span.
All is ready.
Very impressive,
but no one is watching.
The superb bird of paradise calls to attract a female.
And he has more luck.
But what does he have to do to really impress her?
She retires to consider her verdict.
It's hard not to feel deflated
when even your best isn't good enough.
The sun influences life in the oceans just as it does on land.
Its richest parts are those where waves and currents
bring fertilizing nutrients to surface waters
that are bathed in sunlight.
The seas off the Cape in South Africa have this magic recipe
原版英语阅读网 http://www.en8848.com.cn/
and are hugely productive.
Summer is the time of plenty
and it's now that the seals start to breed.
The strike of a great white shark lasts a mere second.
Slowing it down forty times reveals the technique
and immense strength of this massive predator.
If surprise fails,
there will be a chase.
The shark is faster on a straight course
but it can't turn as sharply as the seal,
its agility versus power.
Once the seals have finished breeding
the giant sharks will move on.
It's now becoming clear
that great whites migrate thousands of miles across the oceans
to harvest seasonal abundances in different seas.
The sun, beating down on tropical waters,
powers the weather systems of the globe.
Moisture evaporates from the warming ocean
and rises to create great storms.
The winds generated out at sea
sweep inland across the continents.
原版英语阅读网 http://www.en8848.com.cn/
As they travel across the Sahara
they create the biggest of all sand storms
blowing sand halfway round the world
to fertilize the Amazon jungle.
Winds blowing across the Indian Ocean
collect moisture and sweep northwards towards the Himalayas.
As the air rises, so it cools.
The water it carries
condenses into clouds
and then falls as the life giving rains of the monsoon.
So air currents powered by the sun
carry wet air to the middle of continents.
Without water
there can be no life,
but its distribution over the land is far from even.
Deserts cover one third of the land's surface
and they're growing bigger every year.
This is the Kalahari Desert in Southern Africa.
It's the dry season
and thousands of elephants have started to travel
in desperate search for water.
原版英语阅读网 http://www.en8848.com.cn/
All across Southern Africa animals are journeying for the same reason.
Buffalo join the great trek.
Nowhere else on Earth are so many animals on the move
with the same urgent purpose.
They're all heading for the swamps of the Okavango,
a vast inland delta.
At the moment it is dry,
but water is coming.
The travelers are hampered by dangerous dust storms.
Females and calves can easily get separated from the main herd.
For this pair sanctuary lies in the patch of woodland a few miles ahead.
They can't rest until they reach it.
The main has already got there safely.
Finally, the stragglers emerge from the dust.
The exhausted calf is still blinded by sand.
Its mother does everything possible to help it.
The storm is now subsiding,
but not all the elephants have been so lucky.
One youngster has got lost.
Thirsty and exhausted,
it follows the tracks of its mother,
but sadly in the wrong direction.
原版英语阅读网 http://www.en8848.com.cn/
At the peak of the dry season in the Kalahari
water arrives in the Okavango.
It fell as rain a thousand miles away in the highlands of Angola
and has taken nearly five months to reach here.
The water drives out insects from the parched ground,
which are snapped up by plovers.
Catfish, traveling with the flood,
collect any drowning creatures the birds have missed.
It's a seasonal feast for animals of all kinds.
Birds are the first to arrive in any numbers wattled cranes,
then black storks.
Behind the birds come buffalo.
After weeks of marching their trek is coming to an end.
As the water sweeps into the Okavango
a vast area of the Kalahari is transformed into a fertile paradise.
Nowhere on our planet is the life giving power of water so clearly
demonstrated.
The Okavango becomes criss-crossed with trails
as animals move into its heart.
The new arrivals open up paths like arteries
along which water flows,
原版英语阅读网 http://www.en8848.com.cn/
extending the reach of the flood.
This is an Africa rarely seen a lush water world.
Some creatures are completely at home here.
These are lechwe antelope with hooves that splay widely,
enabling them to move its speed through the water.
For others the change is far less welcome.
Baboons are somewhat apprehensive bathers.
The water brings a season of plenty for all animals.
Hunting dogs.
These are now among the rarest of Africa's mammals,
but then nonetheless the continent's most efficient predators.
Their secret is teamwork.
Impala are their favorite prey.
They start to hunt
and the pack splits up.
An aerial viewpoint gives a new insight into their strategy.
As the dogs approach their prey
they peel off to take up separate positions around their target.
They seem to form a cordon around the impala.
原版英语阅读网 http://www.en8848.com.cn/
Moving in total silence
they take up their positions.
Those ears can detect the slightest rustle.
The hunt is on.
Three dogs close in on one impala.
Missed.
The lead dog drives the impala towards the hidden flankers.
Anticipating their line
the leader cuts the corner
and joins a flanker for the final assault.
It's all or nothing.
One on one.
The dog has stamina,
the impala has speed.
Leaping into the lake is an act of desperation impala can barely swim.
The dogs know their prey must come out or drown now it's a waiting game.
The rest of the pack are calling.
They've made a kill in the forest
and this is an invitation to join in the meal.
The impala is in luck.
原版英语阅读网 http://www.en8848.com.cn/
A pack this size kills once a day and everything is shared.
And this impala is reprieved.
The elephants are nearing the end of their long journey.
After weeks of marching they're desperately tired.
The matriarch can smell water
and encourages the herd to make one last effort.
The youngsters are exhausted
but their mothers have made this journey before
and they know that they're close to water.
After many hundreds of miles they've arrived.
The lives of these elephants are dominated by the annual rhythm of wet
and dry,
a seasonal cycle created by the sun.
At the southern end of the earth,
after four months of total darkness,
the sun once more rises over Antarctica.
Now at last the Emperor penguins abandon their huddle.
The males are still carrying the precious eggs
that they've cherished throughout the Antarctic winter.
With the returning sun the eggs hatch.
Other birds have not even arrived.
But the Emperors by enduring the long black winter
原版英语阅读网 http://www.en8848.com.cn/
have given their chicks a head start.
These youngsters are now ready and eager to make the most of the brief Antarctic summer.
Human beings venture into the highest parts of our planet at their peril.
Some might think that by climbing a great mountain
they have somehow conquered it,
but we can only be visitors here.
This is a frozen alien world.
This is the other extreme one of the lowest hottest places on Earth.
It's over a hundred metres below the level of the sea.
But here a mountain is in gestation.
Pools of sulphuric acid are indications
that deep underground there are titanic stirrings.
This is the Danakil Depression in Ethiopia,
lying within a colossal rent of the earth's surface
where giant land masses are pulling away from one another.
Lava rises to the surface through this crack in the crust
creating a chain of young volcanoes.
This one, Erta Ale,
is today the longest continually erupting volcano on the planet,
a lake of lava that has been molten for over a hundred years.
These same volcanic forces also created Ethiopia's highlands.
原版英语阅读网 http://www.en8848.com.cn/
70 million years ago
this land was just as flat and as deep
as the Danakil Depression.
Molten lava rising from the earth's core
forced up a huge dome of rock 500 miles wide,
the roof of Africa.
Over millennia, rain and ice carved the rock
into a landscape of spires and canyons.
These summits, nearly 3 miles up,
are home to some very remarkable mountaineers Gelada baboons.
They are unique to the highlands of Ethiopia.
The cliffs where they sleep are for expert climbers only,
and Gelado certainly have the right equipment.
the strongest fingers of any primate
and an utterly fearless disposition.
But you need more than a head for heights to survive up here.
A day in a Gelado's life reveals how they've risen to the challenge.
For all monkeys morning is grooming time,
a chance to catch up with friends.
But, unlike other monkeys,
原版英语阅读网 http://www.en8848.com.cn/
Gelados chatter constantly while they do it.
It's a great way to network while your hands are busy.
But these socials can't go on for too long.
Gelados have a busy daily schedule
and there's work to be done.
Most monkeys couldn't live up here.
There's no food and few insects to feed on.
But Gelados are unique they're the only monkeys in the world that live almost entirely on grass.
They live in the largest assemblies formed by any monkeys.
Some groups are 800 strong
and they crop the high meadows like herds of wildebeest.
The Gelados graze alongside Walia ibex,
which are also unique to these highlands.
These rare creatures
are usually very shy
but they drop their guard when the Gelados are around.
You might expect that grazers would avoid each other's patch
but this is a special alliance from which both partners benefit.
It's not so risky to put your head down
if others are on the lookout.
Ethiopian wolves they won't attempt an attack in broad daylight.
原版英语阅读网 http://www.en8848.com.cn/
But at dusk the plateau becomes a more dangerous place.
With the grazing largely over
there's a last chance to socialise before returning to the sleeping cliffs.
An early warning system puts everyone on the alert.
Their day ends as it began, safe on the steep cliffs.
The Ethiopian volcanoes are dormant,
but elsewhere others still rage.
Volcanoes form the backbone of the longest mountain chain on our planet
the Andes of South America.
This vast range stretches 5,000 miles
Antarctic.
from the Equator down to the
It formed as the floor of the Pacific Ocean
slid beneath the South American continent, buckling its edge.
At the southern end stand the mountains of Patagonia.
It's high summer,
but the Andes have the most unstable mountain weather on the planet
and storms can erupt without warning.
Temperatures plummet
and guanacos and their newborn young must suddenly endure a blizzard.
Truly, all seasons in one day...
A puma -
原版英语阅读网 http://www.en8848.com.cn/
the lion of the Andes.
Pumas are usually solitary and secretive.
To see a group walking boldly in the open is extremely rare.
It's a family - a mother with four cubs.
She has just one brief summer
in which to teach them their mountain survival techniques.
Rearing four cubs to this age is an exceptional feat,
but she does have an excellent territory,
rich in food and water.
Although the cubs are now as large as their mother,
they still rely on her for their food.
It will be another year before the cubs can hunt for themselves.
Without their mother's skill and experience
they would never survive their first winter.
Battered by hurricane force winds,
these slopes are now lifeless.
Further north, they hold other dangers.
Moving at 250 miles an hour,
an avalanche destroys everything in its path.
In the American Rockies
a 100,000 avalanches devastate the slopes every winter.
This huge mountain chain continues the great spine
原版英语阅读网 http://www.en8848.com.cn/
that runs from Patagonia to Alaska.
The slopes of the Rockies, bleak though they are,
provide a winter refuge for some animals.
A mother grizzly emerges from her den
after six months' dozing underground.
Her two cubs follow her
and take their first steps in the outside world.
These steep slopes provide a sanctuary for the cubs.
A male bear would kill and eat them given the chance.
But big animals find it difficult to get about here.
Males may be twice the size of a female
and even she can have problems.
Her cubs, however, make light of the snow
and of life in general.
But the mother faces a dilemma:
it's six months since she last fed
and her milk is starting to run dry.
She must soon leave the safety of these nursery slopes
and lead her cubs away from the mountain.
If she delays, the whole family will risk starvation.
Summer reveals the true nature of the Rockies.
原版英语阅读网 http://www.en8848.com.cn/
Stripped of snow,
the peaks bear their sculpted forms.
Only now can mountaineers reclaim the upper reaches.
Two miles up the crumbling precipices seem devoid of life.
But there are animals here a grizzly bear.
It seems to be an odd creature to find on these high rocky slopes.
It's hard to imagine
what could have attracted it here.
At this time of the year bears should be fattening up for the winter.
Yet they gather in some numbers on these apparently barren slopes.
They're searching for a rather unusual food moths.
Millions have flown up here to escape the heat of the lowlands
and they're now roosting among the rocks.
Moths may seem a meager meal for a bear,
but their bodies are rich in fat
and can make all the difference in a bear's annual struggle for survival.
Another battle is being waged here
but on a much longer timescale.
These loose boulders are the mountain's crumbling bones.
The Rockies are no longer rising
but slowly disintegrating.
原版英语阅读网 http://www.en8848.com.cn/
All mountains everywhere are being worn down by frost, snow and ice.
The Alps were raised
some 15 million years ago
as Africa, drifting northwards, collided with the southern edge of Europe.
These spires are the eroded remains of an ancient seabed
that once stretched between the two continents.
But these are just the Alpine foothills.
The range at its centre rises to 3 miles high
and is crowned with permanent snows.
The Matterhorn,
its summit too steep
to hold a snow field.
Mont Blanc - the highest peak in Western Europe.
The distinctive jagged shapes of the Alps
were carved by those great mountain sculptors the glaciers.
Immense rivers of moving ice,
laden with rock,
grind their way down the mountains,
gouging out deep valleys.
They're the most powerful erosive force
on our planet.
A moulin - a shaft in the ice opened by melt water
as it plunges into the depths of the glacier.
原版英语阅读网 http://www.en8848.com.cn/
Like the water running through it,
the ice itself is constantly moving,
flowing down the valley with unstoppable force.
Alpine glaciers may seem immense,
but they're dwarfed by those in the great ranges
that divide the Indian subcontinent from Tibet.
This is the boulder strewn snout
of the giant Baltoro glacier in the Karakoram mountains of Pakistan.
It's the biggest mountain glacier on Earth 43 miles long and over 3 miles wide.
This huge ice-filled valley is so large
it's clearly visible from space.
This is the greatest concentration of peaks over 5 miles high
to be found anywhere on Earth.
They're the most dangerous mountains of all.
K2 and her sister peaks have claimed more lives than any others.
The peaks here rise so precipitously,
the glaciers are so steep and crevassed
that few except the most skilled mountaineers can penetrate these ranges.
Markhor gather for their annual rut.
Males must fight for the right to breed,
but on these sheer cliffs any slip by either animal could be fatal.
原版英语阅读网 http://www.en8848.com.cn/
A snow leopard the rarest of Himalayan animals.
It's a female returning to her lair.
These are the first intimate images of snow leopard ever filmed in the
wild.
She greets her one year old cub.
Her den is well chosen.
It has exceptional views of the surrounding cliffs.
On these treacherous slopes
no hunter other than the snow leopard
would have a chance of catching such fragile prey.
A female with young makes an easier target.
Her large paws give an excellent grip
and that long tail helps her balance.
Silently she positions herself above her prey.
She returns with nothing.
Golden eagles patrol these cliffs in search of the weak or injured.
With a 2 metre wing span
this bird could easily take a young markhor.
Eagles hunt by sight
and the thickening veil of snow forces them to give up.
For the leopard the snow provides cover
原版英语阅读网 http://www.en8848.com.cn/
and creates an opportunity.
The worsening weather dampens the sound of her approach
allowing her to get within striking distance.
It was an act of desperation
to try and catch such a large animal.
Wolves have made a kill
giving other hunters
a chance to scavenge.
The worst of the blizzard brings success for the snow leopard,
but having descended so far to make the kill
she has a grueling climb to get back to her lair.
The cub must be patient.
It'll be a year before it has the strength and skill
to kill for itself on these difficult slopes.
The snow leopard is an almost mythical creature,
an icon of the wilderness,
an animal few humans
have ever glimpsed
for its world is one we seldom visit.
The Karakoram lie at the western end of a range
that stretches across a tenth of our planet the Himalayas.
These, the highest mountains of the world,
原版英语阅读网 http://www.en8848.com.cn/
like other great ranges,
were created by the collision of continents.
Some 50 million years ago
India collided with Tibet
thrusting up these immense peaks, which are still rising.
This vast barrier of rock and ice
is so colossal it shapes the world's climate.
Warm winds from India, full of moisture,
are forced upwards by the Himalayas.
As the air rises so it cools,
causing clouds to form
and the monsoon is born.
At high altitudes the monsoon rains fall as snow.
Here, at the far eastern end of the range in China,
one inhabitant endures the bitter winters out in the open.
Most other bears would be sleeping underground by now,
but the giant panda can't fatten up enough to hibernate.
Its food, bamboo, on which it totally relies
has so little nutritional value
that it can't build up a store of fat like other bears.
Most of the creatures here move up or down the slopes with the seasons
but the panda is held captive by its diet
原版英语阅读网 http://www.en8848.com.cn/
for the kind of bamboo it eats only grows at this altitude.
But these forests hold fewer challenges for the more mobile.
The golden snap-nosed monkey, like the giant panda, lives only in China.
Their thick fur allows them to survive at greater altitudes than any other
monkey
and when the cold bites they have these upper slopes to themselves.
Even if you have a warm coat
it apparently helps to surround yourself with as many layers as possible.
But at least these monkeys have a choice if they tire of tree bark and other survival food
they can always descend to lower warmer altitudes
and not return there till spring.
As the snows retreat
trees come into bloom.
Cherry blossom.
Rhododendrons here in their natural home they form great forests
and fill the landscape with the covers of a new season.
These forests are a host to a rich variety of springtime migrants.
Beneath the blooms - another display.
It's the mating season for oriental pheasants,
Himalayan monal,
原版英语阅读网 http://www.en8848.com.cn/
tragopan
and blood pheasant.
Musk deer make the most of a short flash of spring foods.
This male smells a potential mate.
The red panda, rarely glimpsed in the wild.
It was once considered a kind of raccoon,
but is now believed to be a small mountain bear.
By midsummer its larger, more famous relative, has retreated into a cave.
A giant panda nurses
a tiny week old baby.
Her tender cleaning wards off infection.
She won't leave this cave for three weeks,
not while her cub is so utterly helpless.
Progress is slow
for milk produced on a diet of bamboo is wretchedly poor.
Four weeks old
and the cub is still blind.
Its eyes do not fully open until three months after birth,
but the chances of the cub reaching adulthood are slim.
The struggle of a giant panda mother to raise her cub
is a touching symbol of the precariousness of life in the mountains.
On the highest summits of our planet
原版英语阅读网 http://www.en8848.com.cn/
nothing can live permanently.
The highest peak of all,
Mount Everest, five and a half miles above sea level
and still rising - the roof of our world.
Of those humans who've tried to climb it
one in ten have lost their lives.
Those that succeed can stand for only a few moments on its summit.
The Nepalese call it 'a mountain so high no bird can fly above it.'
But each year over 50,000 demoiselle cranes
set out on one of the most challenging migrations on Earth.
To reach their overwintering grounds in India
they must cross the Himalayas.
By late morning ferocious winds are roaring past the peaks.
The cranes must gain height to avoid the building storm.
They've hit serious turbulence.
They must turn back
or risk death.
A new day
and a new opportunity.
The flock stay in close contact by calling one another.
Weak from lack of food and water,
they use thermals, rising columns of warm air, to gain height.
原版英语阅读网 http://www.en8848.com.cn/
For many this is their first journey across the Himalayas.
For some, it will be their last.
The golden eagles have been expecting them.
The eagles work in pairs to separate a young crane from the flock.
It escapes the touches of one,
and is caught by another.
But even a young crane is a heavy prize
and the eagle has to struggle to control it.
The mother can wait no longer this is a desperate race against worsening weather.
The rest of the flock battle on.
In the ascent every wing beat becomes an exhausting struggle.
At last they are over the highest barrier that lies in their way.
But like all who visit the world of the high mountains
they dare not linger.
Only 3 percent of the water on our planet is fresh.
Yet these precious waters
are rich with surprise.
All life on land is ultimately
dependent upon fresh water.
The mysterious tepuis of Venezuela isolated mountain plateaus
This was the inspiration
rising high above the jungle.
for Arthur Conan Doyle's 'Lost World,'
an imagined prehistoric land.
原版英语阅读网 http://www.en8848.com.cn/
Here, strange towers of sandstone have been sculptured over the millennia
by battering wind and torrential rain.
Moisture rising as water vapour from the surface of the sea
is blown inland by wind.
On reaching mountains, the moisture is forced upwards
and as it cools, it condenses into cloud and finally rain the source of all fresh water.
There is a tropical downpour here almost every day of the year.
Fresh water's journey starts here, high in the mountains.
Growing from humble streams to mighty rivers
it will travel hundreds of miles to the sea.
Angel Falls, the highest waterfall in the world.
Its waters drop unbroken
for almost a thousand metres.
Such is the height of these falls
that long before the water reaches the base in the Devil's Canyon
it's blown away as a fine mist.
In their upper reaches,
mountain streams are full of energy.
Streams join to form rivers,
building in power,
creating rapids.
原版英语阅读网 http://www.en8848.com.cn/
The water here is cold.
Low in nutrients, but high in oxygen.
The few creatures that live in the torrent
have to hang on for dear life.
Invertebrates dominate these upper reaches.
The hellgrammite, its body flattened to reduce drag,
has bushy gills to extract
oxygen from the current.
Black fly larvae anchor themselves with the ring of hooks,
but if these become unstuck,
they're still held by a silicon safety line.
There are advantages to life in the fast stream bamboo shrimps can just sit and sift out passing particles
with their fan-like forearms.
Usually, these mountain streams only provide enough food
for small animals to survive.
But with the spring melt here in Japan
monsters stir in their dens.
Giant salamanders, world's largest amphibian,
almost two metres long.
They're the only large predator in these icy waters.
They begin their hunt at night.
These salamanders have an exceptionally slow metabolism.
原版英语阅读网 http://www.en8848.com.cn/
Living up to 80 years they grow into giants.
The fish they hunt are scarce
and salamanders have poor eyesight.
But sensory nodes on their head and body
detect the slightest changes in water pressure.
Free from competition,
these giants can dine alone.
Pickings are usually thin
but every year some
for the salamanders,
of the world's high rivers
are crowded by millions of visitors.
The salmon have arrived.
This is the world's largest fresh water fish migration.
Across the northern hemisphere
salmon, returning from the ocean to their spawning grounds,
battle their way for hundreds of miles upstream.
Up here, there are fewer predators to eat their eggs and fry.
A grizzly bear.
From famine to feast he's spoilt for choice.
This Canadian bear is very special he's learnt to dive for his dinner.
原版英语阅读网 http://www.en8848.com.cn/
But catching salmon in deep water is not that easy
and the cubs have lots to learn.
The annual arrival of spawning salmon
brings huge quantities of food into these high rivers
that normally struggle to support much life.
Although relatively lifeless,
the power of the upland rivers
to shape the landscape
is greater than any other stage in a river's life.
Driven by gravity,
they're the most erosive forces on the planet.
For the past 5 million years
Arizona's Colorado river
has eaten away at the desert's sandstone
to create a gigantic canyon.
It's over a mile deep
and at its widest it's 17 miles across.
The Grand Canyon.
This river has cut the world's longest canyon system a 1,000 mile scar clearly visible from space.
As rivers leave the mountains behind,
they gradually warm
and begin to support more life.
Indian rivers are home to the world's most social otter smooth-coated otters form family groups up to 17 strong.
原版英语阅读网 http://www.en8848.com.cn/
Group rubbing not only refreshes their coats,
but strengthens social bonds.
When it comes to fishing
there is real strength in numbers.
Fishing practice begins when the cubs are four months old.
Only the adults have the speed
Adults share their catches
and agility needed to make a catch.
with their squabbling cubs.
Most otters are solitary,
but these rich warm waters
can support large family groups
and even bigger predators.
Mugger crocodiles, four metres long, could easily take a single otter.
But, confident in their gangs,
the otters will actively harass these great reptiles.
Team play wins the day.
The Mara river,
snaking across the plains
of East Africa.
As the land flattens out
rivers slow down and lose their destructive power.
Now they are carrying heavy loads of sediment
that stains their waters brown.
Lines of wildebeest are on their march.
原版英语阅读网 http://www.en8848.com.cn/
Each year nearly two million animals migrate across the Serengeti plains
in search of fresh green pastures.
For these thirsty herds
the rivers are not only a vital source of drinking water,
but also dangerous obstacles.
This is one of the largest concentrations of Nile crocodiles in Africa,
giants that grow over five metres long.
From memory, the wildebeest are coming
and gather in anticipation.
The crocodile's jaws snap tight like a steel trap once they have a hold, they never let go.
It took over an hour to drown this full-grown bull.
To surprise their prey
crocodiles must strike with lightning speed.
Here, only the narrowest line separates life from death.
Most rivers drain into the sea,
but some end their journey
in vast lakes.
Worldwide lakes hold twenty times more fresh water than all the rivers.
The East African Rift Valley holds three of the world's largest:
Malawi, Tanganyika, and Victoria.
Lake Malawi, the smallest of the three,
is still bigger than Wales.
原版英语阅读网 http://www.en8848.com.cn/
Its tropical waters teem
with more fish species
than any other lake.
There are 850 different cichlids alone,
all of which evolved from just one single ancestor
isolated here thousands of years ago.
These two-metre wide craters are fish-made.
Fastidiously maintained by the males,
these bowls are courtship arenas.
Cichlids are caring parents.
Brooding young in the mouth is a very effective way of protecting them.
This lake can be a dangerous place.
After dark, predatory dolphin fish emerge from their daytime lairs among the rocks.
Like packs of sharks, they're on the prowl for sleeping cichlids.
In the darkness these electric fish hunt
by detecting distortions in the electric field they create around their bodies.
Any cichlid that trenches out will be snapped up.
The floor of Lake Malawi
drops 700 metres into an abyss.
Here, in this dead zone
the larvae of lake fly midges hide out away from predators.
In the rainy season
they balloon up to the surface
and undergo a magical transformation.
原版英语阅读网 http://www.en8848.com.cn/
At dawn the first adult midges
start to break out.
Soon, millions upon millions of newly hatched lake flies
are taking to the wing.
Early explorers told tales
of lakes that smoked, as if on fire.
But these spiralling columns hundreds if metres high
are mating flies.
Once the flies have mated,
they will all drop to the water surface,
release their eggs and die.
Malawi may look like an inland sea,
but it's dwarfed by the world's largest lake Baikal in Eastern Siberia.
400 miles long and over a mile deep,
Baikal contains one fifth
of all the fresh water
found in our planet's lakes and rivers.
For five months of the year it's sealed by an ice sheet over a metre thick.
Baikal is the oldest lake in the world
and, despite the harsh conditions, life flourishes here in isolation.
80 percent of its species
are found nowhere else on Earth,
including the world's only fresh water seal.
With this seal
and its marine-like forests of sponges
原版英语阅读网 http://www.en8848.com.cn/
Baikal seems more like an ocean than a lake.
There are shrimp-like crustaceans - giant amphipods - as large as mice.
They are the key scavengers in this lake.
The water here is just too cold for the bacteria that normally decompose the dead.
Most rivers do not end in lakes
but continue their journey
to the sea.
The planet's indisputable super-river is the Amazon.
It carries as much water
as the next top-ten biggest rivers combined.
Rising in the Peruvian Andes, its main trunk flows eastwards across Brazil.
On its way the system drains a third of South America.
Eventually, over 4,000 miles from its source,
it empties into the Atlantic Ocean.
The Amazon transports a billion tonnes of sediment a year,
sediment clearly visible
at the mixing of the waters
where one massive tributary, the Rio Negro, flows into the main river.
Its waters are wonderfully rich.
To date over 3,000 species
of their fish have been described -
more than in the whole of the Atlantic Ocean.
The Amazon is so large and rich in fish
that it can support
fresh water dolphins.
These botos are huge - two and a half metres long.
原版英语阅读网 http://www.en8848.com.cn/
In these murky waters they rely on sonar to navigate and hunt.
They work together to drive shoals of fish into the shallows.
Botos are highly social
and in the breeding season
there is stiff competition for mates.
The males hold court in a unique way.
They pick up rocks in their jaws
and flaunt them
to their attending females.
Maybe each male is trying to show how strong and dexterous he is
and that he therefore is the best father a female could have for her young.
Successful displays lead to mating.
Even for giant rivers like the Amazon
the journey to the sea is not always smooth or uninterrupted.
Iguassu Falls on the border of Brazil and Argentina
is one of the widest waterfalls in the world one and a half miles across.
In flood 30 million litres
All the world's
of water spill over every second.
great broad waterfalls:
Victoria, Niagara and here, Iguassu,
are only found in the lower courses of their rivers.
In their final stages
rivers broaden and flow wearily across their flat flood plains.
Each wet season here, in Brazil,
原版英语阅读网 http://www.en8848.com.cn/
the Parana river overflows its banks
and floods an area the size of England.
The Pantanal the world's largest wetland.
In these slow-flowing waters aquatic plants flourish
like the Victoria giant water lily with leaves two metres across.
These underwater forests
are nursery grounds for fish.
Over 300 species breed here, including red-bellied piranha
and other predators, like the spectacle caiman.
Ripening fig trees overhanging the water's edge
provide welcome food for shoals of hungry fish.
The commotion attracts dorado,
known locally as the river tiger.
They patrol the feeding shoals,
looking for a chance to strike.
And waiting in the wings,
ready to pick off any injured fish,
are the piranhas.
The feeding frenzy quickly develops.
Piranha can strip a fish
to the bone in minutes.
Great numbers of fish sustain vast flocks of water birds.
原版英语阅读网 http://www.en8848.com.cn/
The rose-eared spoonbill is just one of the 650 bird species found in the Pantanal.
They nest alongside wood stocks in colonies thousands strong.
Spectacle caiman linger below,
waiting for a meal to fall out of the sky.
When rivers finally reach the sea
they slow down, release their sediment and build deltas.
In Bangladesh the Ganges
and Brahmaputra rivers join
to form the world's biggest.
Every year almost 2 thousand million tonnes of sediment
eroded from the Himalayas
is delivered to the ocean.
At the delta's mouth - the largest mangrove forest in the world,
the Sundarbans.
These extraordinary forests spring up throughout the tropics
in these tidal zones where rivers meet the sea.
Crab-eating macaques are mangrove specials.
In Indonesia these monkeys have adopted a unique amphibious lifestyle they fish out fallen food.
The troop also uses the waters to cool off during the heat of the day.
But the channels are also the playground for restless young macaques.
Some of the young have even taken to underwater swimming.
They can stay down for more than 30 seconds
and appear to do this just for fun.
原版英语阅读网 http://www.en8848.com.cn/
Yet these swimming skills
will certainly be useful
acquired during play
later in life in these flooded mangrove forests.
In cooler climes, mud, laid down in estuaries,
is colonised by salt marsh grasses
and form one of the most
productive habitats on the planet.
400,000 greater snow geese flock to the estuaries along the Atlantic coast of the United
States
to rest and refuel on their long migratory journeys.
This is the end of the river's journey.
Collectively they've worn down mountains
and carried them to the sea.
And all along the way,
their fresh water has brought life and abundance to planet Earth.
原版英语阅读网 http://www.en8848.com.cn/