Original subtitles

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 a forest.

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.

Two 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 the 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 its 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 savannahs of Africa.

These are the most numerous birds on Earth.

Some flocks are so vast

that they can take five 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 savannahs alone sustain nearly two million wildebeest.

They trim the grass down to its 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.

A frozen no-man's land at the end of the Earth.

But for a short time each year, the long, dark winter releases its 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.

Five million birds make this journey every year.

Their marathon migration is almost 3, 000 miles long

and has taken them three 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 neighbours 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 there are fewer predators than further south.

Here, geese can nest on the ground in relative safety.

Nonetheless, this female must incubate her eggs for three 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 favour 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 travelling.

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 its 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 seven 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 its habitat.

And a century ago, the bison were reduced to barely 1, 000.

Now, thanks to rigorous protection, the species is recovering.

The growing season is long,

and the grass here can support herds all year round.

Male bison weigh in at one 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 its flowers.

New colours 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 veldt of South Africa.

Not all temperate plains are so rich and colourful 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 behaviour 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 are 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 its 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 its 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 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 savannahs,

grazers are marching in search of grass and water.

Without rain, these plains can become dust bowls.

Grass can now lose its 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 are 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 savannahs 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 savannahs are very special.

Here, rainwater 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 six 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 behaviour

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.