All language subtitles for Planet Earth (2006) - S01E05 - Deserts (1080p BluRay x265 Silence)

A third of the land
on our planet is desert.

These great scars on the face of the earth
appear to be lifeless.

But surprisingly, none are.

In all of them life manages, somehow,
to keep a precarious hold.

Not all deserts are hot.

Fifty-mile-an-hour winds blowing in from Siberia

bring snow to the Gobi Desert in Mongolia.

From a summer high of 50 degrees centigrade,

the temperature in mid-winter
can drop to minus 40,

making this one of the harshest deserts of all.

Few animals can survive these extreme changes.

Wild Bactrian camels,
one of the rarest mammals on the planet,

and perhaps the hardiest.

Their biggest problem is the lack of water,

particularly now in winter when the little there is
is locked up as ice.

Surprisingly, snow here never melts.

The air is just too cold and too dry for it to do so.

The sun's rays turn it straight into vapour.

It evaporates.

But it is the only source of water

so Bactrian camels eat it.

Elsewhere in the world,

a camel at a waterhole can drink
as much as 200 litres during a single visit.

Here, the strategy is to take little and often,
and with good reason

for filling the stomach with snow could be fatal.

The camels must limit themselves
to the equivalent of just 10 litres a day.

Winter is the time for breeding.

This extraordinary performance
is a male Bactrian camel's way

of attracting the attention of a passing female.

In summer, the camels can't stray
far from waterholes.

But now, with mouthfuls of snow lying everywhere,

they can travel widely in search of mates.

Today, less than 1,000 of these desert specialists
remain in the wild.

The Gobi, hostile though it is,
is their last stronghold.

There is no other desert quite like the Gobi.

But why is this place a desert?

There is one simple and massive cause.

The Himalayas.

Clouds blowing from the south
hit this gigantic barrier.

As they're forced upwards,

so they empty their moisture
on the mountain slopes,

leaving little for the land on the other side.

From space, deserts are very conspicuous.

Dunes of sand hundreds of miles long
streak their surface.

With no cloak of vegetation to conceal them,

strange formations are exposed in the naked rock.

Africa's Sahara is the largest desert of all.

It's the size of the United States

and the biggest source of sand and dust
in the entire world.

Sandstorms like these appear without warning

and reduce visibility for days
over areas the size of Britain.

Dromedaries, single-humped camels,
take these storms in their stride.

The heavy sand rises only a few metres
above the ground.

But the dust can be blown
5, 000 metres up into the sky.

The ferocious wind, armed with grains of sand,

is the agent that shapes all deserts.

Reptiles have armoured, scaly skins
that protect them from the stinging grains.

For insects, the bombardment
can be very severe indeed.

The only escape is below the surface.

As the winds rise and fall, swirl and eddy,

so they pile the sand into dunes.

These sand seas can be hundreds of miles across.

In Namibia, the winds have built
some of the biggest dunes in the world.

Star dunes like these can be 300 metres high.

Grains swept up the flanks
are blown off the crests of the ridges

so it's only the tops that are moving.

The main body of these dunes
may not have shifted for 5, 000 years.

Few rocks can resist the continuous blast
of the sand-carrying wind.

These outcrops are standing
in Egypt's White Desert.

But they will not do so for much longer.

They are being inexorably chiselled away
and turned into more sand.

Now lumps of heavily eroded rocks
have been marooned in a sea of sand.

These jagged pyramids, 100 metres tall,

were once part of a continuous rocky plateau.

The blasting sand will eventually
eliminate them altogether.

The relentless power of the wind

ensures that the face of a desert
is continually changing.

But there is one constant presence.

The desert sun.

The sun's heat and the power to evaporate water

has had a profound effect on the bodies
and habits of everything that lives here.

This sun, potentially, is a killer.

And the red kangaroos must acknowledge that.

Right now, while the sun is low,
there's no immediate cause for concern.

But this situation won't last long.

Australia is the world's most arid continent
with blistering daytime temperatures.

Every hour, the temperature rises
by five degrees centigrade.

Soon the heat will reach a critical point.

Any kangaroo out in the open
is in serious danger of overheating.

In the full sun, the temperature on the ground
soars to 70 degrees.

By midday, the radiation is so intense
they must take shelter.

In the shade, they are shielded
from much of the sun's energy

but their body temperature can still rise.

So they lick saliva onto their forearms

where there is a network of blood vessels
close to the surface of the skin,

and as the saliva evaporates, their blood is cooled.

This thermal image shows
just how effective the process is.

The blue areas on the body are the cooler parts.

As the saliva dries, it has to be replaced.

And this is a real drain
on the kangaroo's body fluids.

Even in the shade, the earth is baking hot.

So the kangaroos dig away the warmed topsoil
to get at the cooler ground beneath.

By staying in the shade
and licking to control their body temperature,

kangaroos manage to get through
the hottest part of the day without heatstroke.

But for the majority of desert animals,
this strategy would not be enough for survival.

The extraordinary ears
of the fennec foxes of Africa radiate heat,

but the animals have another way of keeping cool.

They spend their days underground
and only emerge at sunset.

Darkness brings huge changes.

In the Sahara, the temperature can drop
as much as 30 degrees during the night.

So it's cool enough
to allow these desert fox cubs to play.

All sorts of creatures now appear,
including some really unexpected ones.

Toads have permeable skins

and would quickly die from desiccation
out in the daytime heat.

It's only now that they can leave shelter.

The same is true for scorpions,
even though their shells are actually watertight.

In fact, most small desert creatures are nocturnal.

So it's only now that you can judge
just how much life there can be in a desert.

But moisture lost, even at night,

has to be replaced sometime, somehow.

And that problem dominates the lives
of all desert dwellers.

The Atacama in Chile.
This is the driest desert in the world.

Some parts may not see rain for 50 years,
and with such a record,

you would expect the place
to be completely barren.

These are South America's camels, guanacos.

They are very good at conserving moisture

but they, nonetheless,
need a regular supply of water.

They get it partly from cactus flowers.

But that explanation raises another question.

How do the cacti survive without rain?

Hot winds suck all the moisture
from the surface of the land.

Clearly, there must be something else
that takes the place of rain.

The secret is a cold sea current
that runs parallel to the land.

The cold water cools the moist, warm air above it
and that produces banks of fog.

At the same time, wind blowing onto the shore
sweeps the fog inland.

Before long, the cacti are dripping with dew.

The fog is so regular

that moisture-loving lichens
are able to grow on the cacti

and they absorb liquid like a sponge.

In the land of almost no rain,

these precious drops are lifesavers
for many different creatures.

Further inland, the air remains so warm
that its moisture does not condense.

So this slender strip of desert
is virtually the only part of the Atacama

where life can exist.

And without the fog,
this land, too, would be empty.

The guanacos make the most of the dew.

But it will not remain for long.

In an hour or two, the sun will have burnt it off
and dried the surface of the cacti.

The Sonoran Desert in Arizona
is not quite so dry as the Atacama.

Some rain does fall.

But it is infrequent,

and when it does arrive, animals and plants
have to be ready to make the most of it.

And it's coming.

When the summer monsoon blows in,

the giant saguaros, one of the biggest of all cacti,

are ready to take full advantage of it.

After a rainstorm,

the saguaro's long, shallow root system
sucks up the water

and the pleats on its trunk
enable it to expand rapidly.

When full, a saguaro stem can store
up to five tonnes of water,

and that's enough to see it through
many months of drought.

The trunks of these huge plants
provide homes for the Gila woodpecker.

But birds are not the only animals
to benefit from the presence of the cacti.

During four weeks of the summer,
the saguaros bloom at night to attract visitors.

The pollen and nectar
with which these flowers are loaded

attract long-nosed and long-tongued bats.

The bats left Mexico a few days earlier
to escape the heat of summer

and are on their way north
to the southern United States.

To get there, they have to cross
the Sonoran Desert.

But the desert is so big that for most of the year
they would be unable to cross it.

Now, with the saguaro in bloom,
they can refuel on the way.

So the saguaro's success
in developing a way to store water

is now crucial to most of the animals
that live or even travel through this land.

The scarcity of rain determined
the shape of this icon of the desert.

But water, scarce though it is,
has also, like the wind, shaped the land itself.

In the deserts of Utah,
ancient rivers flowing across sandstone country

steadily widened their canyons

until now, the land between them
has been reduced to spires and pinnacles.

With little or no soil to retain the water
on the surface of the land,

life here is scarce indeed.

And when resources are limited,
conflict is never far away.

These are Nubian ibex
and they are squaring up for a duel.

And when trouble starts, a smart ibex knows
that the best thing to do is to gain higher ground.

These are actually subordinate male ibex,
but their fights are, nonetheless, serious.

Losing one might mean
never getting the chance to breed, ever.

When competitors are evenly matched,
as they are here,

duels can last for an hour.

In this heat, the effort is truly exhausting.

But victory here will gain important ranking points
on a male's way to the top.

There's so much at stake that not all play fair.

The battle has produced a winner.

But the ultimate prize is not his yet.

That currently belongs to the dominant male ibex.

His rank earns him the loyalty
of a harem of females

and they follow him closely

as he travels across this desert
searching for food and water.

He doesn't have to waste time looking for mates,
they're his for the taking.

So he can concentrate with them
on keeping fit and healthy.

Lizards are desert specialists.

But here, their numbers are extraordinary.

These crevices in South Africa

contain the highest density of lizards in the world.

They're called flat lizards, for obvious reasons,

and they flaunt their multicoloured bellies
in territorial disputes.

He's made his point
and now it's time to find some food.

As the day warms up,
the lizards move away from their cracks

and head down to the bottom of the gorge.

Their goal is the river.

There is no food at the edge,
but this desert river holds a secret.

Each day, black fly rise
from turbulent stretches of the river.

This is what the lizards have come for.

The black fly never land

so the lizards have to leap for their food.

In one day, each of these acrobatic little lizards
may catch 50 flies.

There are plenty of flies to go around,
even with hundreds of lizards competing for them.

Away from these rapids,

flat lizard populations
are found in much smaller numbers.

But here, one unusual abundance
has produced another.

Deserts are created by the lack of water

but what actually kills animals here
is not heat or thirst, but lack of food.

So how on earth does a plant-eater this size

survive in a place apparently
totally devoid of vegetation?

Elephants in Namibia are the toughest in Africa.

And they need to be.

What little food exists is so dispersed

that these elephants walk up to 50 miles a day

as they travel up the dry river channels
searching for something to eat.

At times, the task looks truly hopeless.

Elephants may seem out of place
in this landscape,

but they're not the only ones.

Amazingly, lions live here, too.

In savannah country, huge herds of game
support prides containing 20 lions or more.

But to live here,
lions have had to change their habits.

Prides are much smaller
and their home ranges are very much bigger.

And there's an added problem.

Their food is always on the move.

Like the elephants,

the lions must travel great distances
to find enough to live on.

But lions can't go everywhere.

They won't attempt to cross
this field of sand dunes,

and the oryx know it.

The lions must wait for the oryx
to leave the safety of the dunes,

which eventually they must to find food and water,

and then the lions will ambush them.

The elephants have found
some of their favourite food.

Grasses are the staple diet of all elephants,

but this herd concentrates
on digging up the roots,

which have more nutrition and moisture
than the stems.

It's the sort of behaviour

that can make all the difference
in a place of serious shortages.

Yet all this can change in an instant.

The fortunes of many deserts
are ruled by distant rains.

This water fell as rain
in mountains more than 100 miles away.

It's known as a flash flood

and called that because the water may run
for just a single day.

It's an event that only happens
once or twice a year at the most.

The sandy riverbed acts like
a giant strip of blotting paper,

sucking up the water as soon as it appears.

But every square metre of soil
moistened by this river

will increase the chances of survival
for those that live here.

Waterholes are filled temporarily.

Elsewhere in Africa elephants drink everyday

but the lack of water here means that
desert elephants can only refill their tanks

once every four or five days.

Within a week, the flash flood has produced
a flush of green,

more than enough to draw the oryx
out of the dunes.

It's a rare chance for them
to build up their food reserves.

The flood has made life easier for the lions, too.

The flesh of this oryx will keep the family going
for a week at the most.

But for a while, the hunting will be easier
now that the river channel has turned green.

The good times for lions and oryx are brief.

But these are the short moments

that make it possible
to live in deserts the year round.

Death Valley is the hottest place on Earth.

Yet even this furnace
can be transformed by water.

A single shower can enable seeds
that have lain dormant for 30 years or more

to burst into life.

And there hasn't been a bloom like this one
for a century.

The periods of boom in Death Valley are short

but they're just frequent enough
to keep life ticking over.

A sudden flush of vegetation
is what every desert dweller waits for

and when it happens,
they must make the most of it.

There is no other species on the planet

that responds as quickly and as dramatically
to the good times

as the desert locust.

Eggs that have remained in the ground
for 20 years begin to hatch.

The young locusts are known as hoppers,
for at this stage they're flightless.

They find new feeding grounds
by following the smell of sprouting grass.

Normally it takes four weeks
for hoppers to become adults.

But when the conditions are right, as now,

their development switches to the fast track.

As the vegetation in one place begins to run out,

the winged adults release pheromones,
scent messages,

which tell others in the group
that they must move on.

And when groups merge, they form a swarm.

An adult locust eats
its entire body weight every day.

And a whole swarm can consume
literally hundreds of tonnes of vegetation.

They have to keep on moving.

The swarm travels with the wind.

It's the most energy-saving way of flying.

Following the flow of wind

means that they're always heading
toward areas of low pressure.

Places where wind meets rain
and vegetation starts to grow.

As they fly, swarms join up with other swarms
to form gigantic plagues

several billion strong
and as much as 40 miles wide.

They will consume every edible thing
that lies in their path.

This is one of planet Earth's greatest spectacles.

It's rarely seen on this scale and it won't last long.

Once the food has gone,

the steady roar of a billion beating locust wings

will once again be replaced by nothing more
than the sound of the desert wind.