Planet Earth (2006) s01e07 Episode Script

1
Vast open plains.
Immense spaces.
Eerie silence
but any feeling of emptiness
is an illusion.
The plains of our planet
support the greatest gatherings
of wildlife on Earth.
At the heart of all
that happens here
is a single living thing.
Grass.
This miraculous plant covers a
quarter of all the lands of the Earth.
Grasslands exist
wherever there is a little rain,
but not enough to sustain the forests.
Some are huge.
The Central Asian Steppe alone
extends one third of the way
around our planet.
It's summer,
and eagles effortlessly
cruise the thermals,
scanning the ground beneath
for signs of prey.
In the distant reaches
of Outer Mongolia,
one of the planet's great
migrations is underway.
Few people ever see this
extraordinary annual event.
Mongolian gazelle.
2 million are thought to live here,
but no one really knows.
For much of the time, they're scattered
through this vast landscape,
but once a year they come together
to have their young.
Nearly all will give birth
within the next 10 days.
Out in the open, communal calving
is the safest way to have young.
With so many pairs of eyes
keeping watch,
it's almost impossible
for predators to sneak up.
There are no bushes, no trees, there's
only one thing to hide behind —
grass —
and it's not very effective.
Predators also have a hard time
raising their young on open grassland.
Without trees, eagles have to nest
directly on the ground.
All inhabitants of the Great Plains
are exposed to the elements.
Fire sparks panic in the herd.
Gazelles are born to run, and even young
calves easily outpace the flames
if they can avoid being trampled.
With nothing to stand in it's way, the
blaze consumes anything that can't flee.
Huge quantities of grass,
valuable food have been lost,
and with it, the old and the weak.
The gazelles move on to new pastures
and leave the desolation behind them.
From the ashes rises the phoenix.
Grass, the incredible survivor.
Because it grows from a protected part
at the base of its stems,
grass is almost indestructible.
Able to repair
and reproduce itself rapidly,
it covers more of the Earth's land
than any other plant,
and feeds more wildlife than any other.
Red billed quelea —
one and a half billion swarm
across the savannas of Africa.
These are the most
numerous birds on Earth.
Some flocks are so vast, that they
could take 5 hours to pass overhead.
Only grass can feed plagues
of these proportions.
The ravenous hordes devour the seeds,
and the leaves and stems are cropped
by great herds of antelope.
The East African savannas alone
sustain nearly 2 million wildebeest.
They trim the grass down to it's roots,
leaving little in their wake,
but within days
the plant will recover
and continue to sustain
the biggest herds on Earth.
Grass is not confined to the tropics.
It manages to grow even in the
bitter conditions of the Arctic.
Beyond the limits of the last tree, the
planet is barren and ice locked —
the frozen "No Man's Land"
at the end of the Earth.
But, for a short time each year, the
long dark winter releases it's grip.
Temperatures rise, and grass that has lain
dormant and frozen throughout the winter
sprouts once more.
Green returns to the Arctic.
The receding ice reveals an immense
flat plain, the size of Australia.
This is the Arctic tundra.
It's a desolate silent wilderness,
but it's about to change.
Snow geese.
They winter along the Gulf of Mexico,
and in spring they fly the
entire length of North America
to reach the Arctic tundra.
5 million birds
make this journey every year.
Their marathon migration
is almost 3,000 miles long
and has taken them 3 months.
Exhausted and starving, they touch
down inside the Arctic Circle
back at their traditional
breeding grounds, at last.
Snow geese pair for life.
As soon as couples arrive, they must
stake a claim to a nesting patch.
Ideal sites are in short supply and
quarrelsome neighbors are all around.
Disputes can be vicious.
Point taken.
It's a long way to travel,
but for a short period the tundra
is the ideal place for a grazer.
The grass grows vigorously during
the short intense summer
and the are fewer predators
than farther south.
Here, geese can nest on the ground
in relative safety,
nonetheless this female must
incubate her eggs for 3 weeks
and throughout this time
she will be very vulnerable.
An Arctic fox surveys the colony.
She's been waiting
for the geese all winter.
Sneaking up unnoticed is impossible.
Perhaps fortune will favor the bold.
The colony is well defended.
There are no easy pickings here.
She's driven away from every nest,
but hunger compels her to continue.
There are more eggs here
than she can possibly eat now,
but the nesting season is short,
so she stashes much of her plunder
for later in the year
when all the geese have gone.
Further south, other bigger
predators prowl the tundra.
Wolves.
For them, finding food on the plains
is an even greater challenge.
Not only is their prey seasonal,
it's also hard to find.
They've been searching for days
without a sign.
Somewhere in this immense landscape,
there is food for them.
This is it — Caribou.
Travelling 30 miles a day,
they can cover nearly 2,000 miles
during the summer months.
The wolves will starve
if they don't find the caribou,
but it's no easy task to locate
prey that never stops traveling.
Biting flies and the quest
for new pasture
drives the migration ever onwards.
A wolf has finally picked up the trail.
The caribou are close.
At last, a chance.
The hunt is on.
The wolf panics the herd,
and the weak and young are singled out.
A calf is separated from it's mother.
At the goose colony, it's high summer
and eggs are hatching.
The young all emerge within
a day or two. A marvel of timing.
The colony is now home
to a million goslings.
The fox is still gathering
all she can get.
Sometimes one mouth
simply isn't enough.
One will have to do.
Not all food is stored.
Some is needed right now.
She has 7 hungry cubs to feed.
As their appetites grow, the mother
must work tirelessly to raise her family.
Only fat healthy cubs
will survive the Arctic winter.
The vast majority of the goslings
are still flourishing.
Their parents lead them down
to the safety of the water
as soon as they're strong enough
to make the journey.
For the foxes,
boom time has come to an end,
but the mother has given her cubs
the best possible start in life.
The geese will continue
grazing the tundra
until the summer ends, and they're
forced to head south for the winter.
At these latitudes,
the Sun's rays are weak,
and grass can only grow here
for a few months a year,
but further south, summers are longer
and the grasslands flourish.
The prairies of North America.
This rich pasture once supported the
greatest herds ever seen on our planet.
There were once 60 million bison,
but no animal is immune
to intensive hunting by man
or the destruction of it's habitat,
and a century ago the bison were
reduced to barely a thousand.
Now, thanks to rigorous protection,
the species is recovering.
The growing season is long
and the grass here can support
herds all year around.
Male bison weigh in at 1 ton.
In high summer, the bulls are fat
from the rich grazing
and in prime condition,
but only a few will mate.
Exactly which few
is about to be decided.
On temperate plains
around the world,
summer is a time for
growth and reproduction.
Now the grass produces it's flowers.
New colors also come to the plains.
The northern flowering is mirrored by the
grasslands of the southern hemisphere.
And nowhere is more impressive
than on the velt of South Africa.
Not all temperate plains
are so rich and colorful in the summer.
This is midsummer
on the Tibetan Plateau.
the highest great plain in the world.
Despite the conditions, grass survives,
and in sufficient quantities
to support the highest
of all grazing herds,
those of the wild yak.
Even in summer, life is hard,
temperatures rarely rise above
freezing, and the air is thin.
It's also exceptionally dry
for one very big reason —
the Himalayas.
The great mountain range
acts as a barrier,
preventing clouds
moving in from the south,
and this casts a giant rain shadow
that leaves Tibet high and dry.
Grass clings to life
even as desiccating winds remove what
little moisture remains in the soil.
So long as grass can survive,
so can grazers.
Wild ass.
The males are fighting
to win territories,
those that hold the best, are more
likely to attract a herd of females.
It's a frisky business.
That counts as a victory,
but he can't assume the females
will actually turn up.
Female asses are mysterious creatures.
They come and go as they please and much
of their behavior seems unfathomable
to an outsider.
They're the great nomads of the plateau,
and will often trek vast distances across
these parched plains in search of oases.
But when they do find paradise,
they're liable to feed and drink
for just a few hours
and then head back to the dust
for no apparent reason.
Wild ass are the most conspicuous
pioneers of this high frontier,
but the most numerous grazer
in Tibet lives underground.
Pika —
a relative of the rabbit.
It too feeds on grass.
On the exposed plateau,
pikas never stray far
from their burrows,
but even so, squatters will
move in given half a chance.
While ground peckers and snow finches
can be a nuisance,
they're worth tolerating, because they
provide a valuable early warning system.
The bizarre Tibetan fox.
The pika's nemesis.
When stalking,
it keeps below the skyline
perhaps helped
by it's curious body shape.
But why the square head?
In summer,
the Tibetan plateau heats up,
drawing in warm wet air
from the south,
but the water never arrives.
As the moist air approaches,
it's forced upwards by the Himalayas,
and condenses into huge rain clouds.
These clouds drop all their water
on the southern side of the mountains.
The very peaks that keep Tibet dry
are responsible for the monsoon
rains falling farther south,
and the greening of India.
Here, soaked by rain
and bathed in tropical sun,
grass reaches it's full potential.
Elephant grass
is the tallest in the world.
Grass that towers over an elephant,
can conceal all sorts of surprises.
The male lesser florican.
It's hard work getting noticed
when you go courting in the high grass.
The long grass plains of tropical India
are home to some of the largest
grass eating mammals on our planet
and some of the smallest.
Pygmy hogs are no bigger than rabbits.
They're the tiniest and rarest
of all wild pigs.
The female is busy collecting grass,
but not for eating.
She's building a nest.
Each piglet may be small enough
to fit in the palm of a hand,
but she does have 10.
This is how grass can grow,
given unlimited sunshine and water,
but on most tropical plains
across our planet.
the wet season is followed
by a dry one.
On the African savannas, grazers are
marching in search of grass and water.
Without rain, these plains can become
dust bowls. Grass can now lose it's hold.
Elephants are in immediate danger.
They must drink almost daily.
Driven on by thirst, they march hundreds
of miles across the parched plains.
Relying on memory, the matriarchs
lead their families
to those special water holes
that saved them in previous years.
This one still has water,
but they must share what remains with
desperately thirsty animals of all kinds.
These are tense times.
The elephants dominate
the water hole,
but as night falls,
the balance of power will shift.
Thirsty herds continue to arrive
throughout the night.
It's a cooler time to travel.
In the darkness the tables turn.
The elephant's night vision
is little better than our own,
but lions have
much more sensitive eyes.
The cats are hungry,
and the elephants seem to sense it.
Lions don't usually hunt elephants,
but desperate times
require desperate measures.
This herd contains calves —
easier targets.
But how to reach them?
The adults encircle their young.
It's an impenetrable wall of grey.
A few exhausted stragglers
are still arriving.
One of them is alone.
But it's too big
for the lions to tackle.
This one looks a little smaller.
A solitary lion stands no chance,
but the whole pride is here.
There are 30 of them, and they're
specialist elephant hunters.
This elephant will feed the
whole pride for at least a week.
Elephants know these drinking holes
are dangerous, but they have no choice.
The dramas that play out here
are a savage reminder
of how important water is
for all life on these plains.
As the dry season
finally draws to a close,
Africa's baked savannas
undergo a radical change.
Rain sweeps across the continent and
grass, the great survivor, rises again,
and the herds return.
For months, they've been
scattered over huge areas,
clinging to existence
around tiny water holes.
Now, the good times are back.
A few African savannas
are very special.
Here, rain water from far and wide
flows across the flat plains.
Grass is submerged,
but still it grows.
Flooded, burnt, baked and frozen
grass can withstand it all.
After 6 months of drought,
grass replaces dust over great areas.
Fresh new shoots draw animals
from great distances.
Many undertake epic migrations
to catch the boom time.
Some resourceful animals live here
all the year round.
Baboons are permanent residents, but
they have to change their behavior
if they are to gather what they need
on the newly flooded plains.
There's plenty to eat, but getting
to it can be a little uncomfortable.
New water poses problems
for the youngsters,
but they know
where to find a dry seat.
A juicy snail is ample recompense
for sodden paws.
Having survived the dry barren times,
animals can now reap the rewards.
On this seasonal planet, the great
plains are lands of feast and famine.
At their peak, they support the
greatest gatherings of wildlife
found anywhere on Earth.