All language subtitles for The.Green.Planet.S01E04.2160p.UHD.BluRay.x265-GREENFiNGERS

DAVID ATTENBOROUGH:
The Taklamakan Desert

in northern China.

A constantly shifting
landscape of sand...

(wmo WHOOSHES)

...temperatures that swing
from minus 20...

(SAND RUSTLES)

...to more than
40 degrees centigrade...

...and most critically,

almost entirely without rain.

Yet, here on the dunes...

...a Euphrates poplar tree.

And it's not alone.

Some of these trees have
lived here for 1,000 years.

They have exceptionally
long roots

with which to collect water.

And what is more,

those roots are connected to
neighbouring trees...

...so that if one strikes water...

...others can share it.

In every desert
across the planet,

plants have found ways to
not only survive...

...but flourish.

These dunes,
in the Gran Desierto of Mexico,

may appear to be virtually
barren...

...but there are seeds
of many kinds

hidden among
the grains of sand.

(THUNDER CRASHES AND ROLLS)

But rain may come
only once a decade,

and even then, the long-awaited
storm may be very brief.

So seeds must respond
immediately.

This is sand verbena.

It can grow from a seed to
a sweetly scented flowering plant

in just a few weeks.

Primroses and many other plants

soon join the race to flower
before the sand dries.

Desert blooms like this,
however, are rare.

This is the first year
for 20 years.

The combination of vibrant
colour and powerful scent

attracts migrating pollinators,

such as these painted lady
butterflies,

which fly into the middle
of what were only recently

barren dunes.

Everything is rushing
to complete their lives

before the moisture has gone.

Such spectacular blooms

transform deserts
all around the world...

...from the Atacama
in South America...

...to the dusty plains
of Southern Africa.

Rain in deserts, however,
never lasts long,

and all too soon, the flowers
wither and die.

But not before they've produced
the next generation...

...the seeds that will now wait
in the sand for the next rains.

(SAND RUSTLES)

In the Sonoran Desert
of North America,

the huge saguaro cacti

have a different strategy.

They store water in quantity...

...and can live to a great age.

But in their early years,

they are extremely vulnerable.

This young cactus
is about ten years old.

If it was living
out in the open,

it's likely it would have dried up
and died by now.

But this one is lucky.

It's been living in the shade
of this mesquite tree,

and it's got a very good chance
of surviving to maturity.

The young saguaro is protected
by the mesquite's branches.

They halve the amount of
scorching sunlight

reaching the cactus...

...and so keep it cool.

And the mesquite's
extremely long roots

draw up water,

bringing it within reach
of the young saguaro.

So the mesquite is known as
a "nurse plant",

and a very effective one it is,
too.

And a single tree like this

can nurture dozens of
young saguaros in its lifetime.

As a young cactus grows,

it needs the protection
of its nurse plant

not only from the heat,

but from the other hazards
of desert life.

Temperatures can drop to
minus 10 degrees overnight...

...and very occasionally...

...it even snows.

If the water stored inside
a young cactus should freeze,

the cactus will die.

But the nurse plant traps

a blanket of slightly warmer
air around it,

just enough to keep it alive.

Eventually, saguaros outgrow
their nurses,

but by that time,
they are robust enough

to face the elements
by themselves.

No matter how old
a desert plant is,

water is always precious,

whether gathered from
melting snow...

(THUNDER CRASHES AND ROLLS)

...or a shower of rain.

So cacti have developed
extraordinary adaptations

that enable them
to not only collect water...

...but to retain it.

Instead of leaves, which would
lose precious moisture

through evaporation,

they have spines.

Each spine has a tiny pad
at its base

where the water is absorbed...

...and then stored in
the great swollen trunk.

A large saguaro can hold
5,000 litres of water...

...and is able to do so

because it has another
special adaptation.

(SLOW CREAKING)

The ridges on its surface

are like the pleats
on an accordion.

They allow the saguaro
to change its shape.

After rain has fallen,

the pleats expand,

and the saguaro
fills up its water tank.

In the dry times,
it uses its water

to grow, produce flowers

and, eventually, seeds.

Fully loaded with thousands
of litres of water,

this saguaro won't need
to drink a single drop

for another year.

But such valuable stores
of water attract thieves.

Now the spines' function
changes from collecting...

...to guarding.

The spines of some species
are a quarter of a metre long.

Others are needle-like barbs

that grow in clusters,

and easily break off
in the skin of any animal

that touches them.

But perhaps
the most vicious cacti

belong to a group called
the chollas.

This is a teddy bear cholla,

but don't be deceived by
the name.

It has a nasty reputation

as one of the desert's
most lethal plants.

Look closely at the spine

and you can see very clearly
why they're so dangerous.

Each is like
a splinter of glass,

sharp enough to pierce flesh.

And they're covered
with backward-pointing barbs.

And it makes both the plant
and its buds

virtually invulnerable.

Most animals
know to keep clear.

(SNIFFS)

Cholla buds
grow like tiny barrels

from the top of the adult plant
and then drop off.

(BARKS)

If the young cholla
put down roots here,

it would compete
with its parent for water.

(BARKING)

Night falls...

...and this one is on the move.

The pack rat.

She knows how to
deal with a cholla.

She avoids the spines
by gripping it

at the place where it broke off
from its parent.

And she works fast.

There are pack rat hunters
here.

She uses the cholla to build
a spiny wall around her nest.

The flesh of the cholla
supplies her with water...

...and the severed spines
further reinforce the defences.

This cholla bud...

...might be next.

But one accidental nudge...

...and it escapes.

(SPINES CRACKLE)

The bud starts
to put down roots...

...so the cholla,
thanks to the pack rats,

finds new territory...

...and sets about claiming it.

- (BIRDSONG)
- (INSECTS BUZZING)

Few plants deal with
the problems of desert living

better than cacti.

There are almost 2,000
different species of them.

Copiapoa cacti grow as clusters

to provide shade for
each other.

Barrel cacti swell into
rounded forms,

which keeps their surface area
to a minimum

and so reduces evaporation.

And creeping devil cactus

search for water by crawling
over the ground

an inch a decade...

...absorbing its rear
in order to extend its front.

Yet in the desert world,

water thieves
can come in many forms...

...to exploit even the smallest
chink in a plant's defence.

In South America,

the ice-covered peaks
of the Andes

act as a rain barrier...

...beyond which lies
the world's driest desert,

the Atacama.

In the desert world, water thieves
can come in many forms

to exploit even the smallest
chink in a plant's defence.

One of the strangest
travels within the gut

of a fruit-eating
mockingbird.

(BURBLING CALL)

These are the seeds...

...of tristerix,

a kind of mistletoe.

Their goal is the water
inside this hedgehog cactus.

Using the spines as anchors,
the seeds start to germinate.

Each produces a long probe

with which to try and locate
the cactus's skin.

For most, that's a stretch
too far

and they perish.

But for this one,

the cactus's surface
is within reach.

It clamps onto it with
a special sucker...

...and then waits for darkness.

At night, the cactus
opens its pores

in order to respire.

Oxygen goes out,

carbon dioxide goes in.

And so does tristerix.

Once within,

its tissues spread throughout
the body of the cactus,

sustained by the precious store
of water that they find there.

Then, a year later,

it breaks through
the cactus's skin...

...and bursts into flower.

Hummingbirds come to drink
their nectar

and pollinate them
as they do so.

And then,
to complete the cycle,

tristerix produces hundreds of
white eye-catching seeds,

ready to be carried away
by a bird

to invade another cactus.

The Karoo Desert
in Southern Africa.

And although it may look bare,

its rocky ground contains
an unrivalled variety of plants

that, one way or another,
store water in their tissues.

They belong to
many different families,

but as a group,
they're known as succulents.

Some are small and low

and barely distinguishable
from their surroundings.

These look like little pebbles.

They resemble them so closely

that animals which might be

only too glad
to steal their water

just pass them by.

(RAIN PATTERS)

When rain does fall,
they absorb it

and quickly expand.

But even this doesn't spoil
their disguise.

They just look like
larger pebbles.

Nor are they green.

The cells on their top surface
are transparent

and allow sunlight
to pass through.

Deep within, and out of sight,

are the green cells
where photosynthesis occurs -

the process
which uses this light

to make food for the plant.

When the time comes
to reproduce, however,

the stone plant
abandons its disguise.

And now it blooms.

The flowers open and close
every 24 hours.

So, for a few dangerous days,

the plant advertises
for pollinators,

before returning
to life as a pebble.

(ANTLERS CLATTER)

Some desert plants
have developed

a very different way
of attracting pollinators.

This is stapelia.

It produces what is perhaps

the desert's
strangest disguise.

It uses water
stored in its stems

to grow buds
the size of tennis balls.

(CREAKING)

The flower, once opened,

is called a desert starfish.

Instead of releasing millions
of loose pollen grains,

as most flowers do,

the desert starfish produces
them packed in five tiny sacs.

But if its strategy
is successful,

just one of them will produce
hundreds of seeds.

And this depends on deception.

The flower
appears to have hair...

...wrinkly skin...

...and it produces a stench

like the carcass
of a dead animal.

(SNIFFS)

(FLIES BUZZ)

And when a carrion fly
investigates...

...the flower clamps a tiny sac
of pollen to its proboscis.

It's not easy to feed

with such encumbered
mouth parts.

But try as it might,
the fly can't get rid of it.

(LEAVES CREAK)

And it's still there

when the fly leaves
to try and feed

from another bogus carcass.

(FLY BUZZES)

This time, however,
when its clamped-up proboscis

slots into the flower,
the pollen sac is released.

With pollination complete,

the fly is no longer needed.

And just as well!

Not all desert plants store
large volumes of water.

Some have
very different strategies.

One of them is simply to wait.

Here, one particular plant

plays the waiting game so well

that it spends much of its life
looking dead...

...and certainly
not worth eating.

And it can survive like this
for a decade.

This is the resurrection plant.

It's a kind of moss.

It barely has roots

and it certainly can't store
much water.

But it can travel.

(WIND BLOWS)

After a particularly long
drought...

...it breaks away
from its roots...

...and becomes...

...a tumbleweed.

Blowing across the desert,
it can travel a mile in a week.

With luck, it may find water.

(THUNDER ROLLS)

Just a shower of rain
can bring it back to life.

As its fronds soak up
the water, they unfurl.

In its protected centre,
it still has green cells,

which absorb
both the water and sunlight,

and rapidly produce the food
it needs to resume its growth.

It will grow for just as long
as there is moisture.

(LEAVES CRACKLE)

But when that disappears...

...it closes up once more

and resumes its travels.

The great American deserts

cover
over a million square miles.

Here, baked by the sun
and blasted by the wind,

the rocks disintegrate
to create a landscape

of plunging canyons

and towering pinnacles.

If you look close enough,
you'll find plants...

...everywhere.

Here, in the Mojave desert
of California,

the creosote plant dominates
the landscape.

Its success is down
to the efficient way

in which it grows,

just a few millimetres
a decade,

to form a ring, within which

its roots have exclusive access
to water.

This individual
is 12,000 years old,

one of the oldest organisms
on the planet.

Here, in the canyon lands
of Utah,

lives a plant
that has developed

a finely balanced relationship

with the animals with which
it shares this dramatic desert.

Rain does occasionally
fall here,

and turns dust into mud.

(CRACKING)

But that doesn't last long.

A brief window of opportunity
opens.

Seeds that have been buried
for years

may now be exposed to light...

...and come to life.

This is coyote tobacco.

In just a few weeks,
it grows a metre tall

and produces dozens of flowers.

The night air becomes heavy
with their fragrance.

Soon, they attract hawk moths,

which sip their nectar,

and in doing so,
pollinate them.

But the moths also
lay their eggs on them.

Soon, their caterpillars
have hatched

and are munching the leaves.

Their nibbles expose
the plant's sap

to the drying air.

But the tobacco plant
has a defence.

The leaves under attack
produce nicotine.

This chemical
sedates the caterpillars

and slows them down.

And what is more, it makes them
give off a particular scent...

...one that summons others
to come to the plant's aid.

Big-eyed bugs -

miniature assassins
only 2mm long.

And whiptail lizards.

Big or small, they make
a meal of the caterpillars.

It's certainly effective.

But there's more
to this strategy

than meets the eye.

Scientists in the United States

have genetically modified
tobacco plants

in order to reveal how,
when a leaf is attacked,

it's able to communicate
with other leaves

so that the whole plant
can prepare its defences.

Signals are being transmitted
along the veins

that link the leaf
to the rest of the plant.

It's rather like a very simple
nervous system.

This signal warns each leaf
of the danger...

...so that it is ready
to produce nicotine

the moment it's attacked.

With this defence at the ready,
the tobacco plant

can continue to grow

until, eventually,
it produces seeds.

It's particularly important
in deserts

for seeds to be distributed
as widely as possible

so that some will have a chance
of reaching moisture.

And deserts have an excellent
agent to help them do that.

(WIND BLOWS)

The wind.

Many seeds have adaptations
to help them exploit it.

They have shells
to protect the seeds within

from abrasion...

...or wings
to help them catch the air.

As the temperature rises
throughout the day,

desert winds
increase in strength.

Here, in Arizona,
the land is regularly swept

by what is known as a haboob.

It's a giant sandstorm,

but also, in effect,
a seed storm.

Countless millions of them
are swept up into the air.

Some seeds can travel

thousands of miles
on the wind...

(THUNDER CRACKS)

...so that plants
may eventually reach

even the most isolated desert.

(THUNDER ROLLS)

Some have landed on an island

in the middle of the world's
largest salt flat, in Bolivia.

(BIRDS CALL)

In the Galépagos,

they sprout on fields
of recently erupted lava.

(FIRE CRACKLES)

Along the dry eastern coast
of Madagascar...

...desert plants have created
the jungle-like spiny forest.

They've even reached

one of the most inhospitable
of all sites -

the tiny island
of San Pedro Mértir,

a scorched, lonely rook
off the coast of Mexico.

Over a thousand years ago,

a seed found itself
marooned here.

Exposed and with little water
orshade,

its chance of survival
was slim.

Yet, remarkably,

it grew into one of these.

A giant cardon.

A species of huge cactus

that can weigh up to 12 tonnes.

They're able to thrive here

because of
an extraordinary partnership...

(CLACKING)

...with brown
and blue-footed boobies.

The cardones here
can become so broad

that they provide cooling shade
for nesting birds.

As the booby chicks get older,
they repay the cardones...

...with their droppings.

Guano.

The digested remains
of vast shoals of fish.

This guano is of such strength
and quantity

that most plants
would be poisoned by it.

These cardones, however,

have evolved the ability
to tolerate

the toxins in the guano
and digest the nutrients.

As a result, the cacti now grow
in a dense forest

over a million strong.

But such relationships
are very finely balanced

and can only too easily
tip into catastrophe...

...as is now happening
in northern Zimbabwe.

For six months of the year,

the savannah here is kept
lush and green by daily rains.

(ANIMALS CALL)

But when the rainy season
is over,

it becomes
as dry as any desert.

Soto survive here, trees
must be able to tolerate

both conditions.

And these giants
are adapted to do just that.

They are baobabs...

...known here
as the tree of life,

such is their importance
as a source of shade and food.

This one might be
over a thousand years old.

It's survived here,
in part, thanks to

its ability to store
thousands of litres of water

within the spongy wood
of its trunk.

But its battered surface

is evidence of a very finely
balanced relationship.

These huge trees are a focus
for animals of all kinds.

(RUMBLING AND SNORTING)

And they're particularly
important for elephants.

In the wet season,
they eat the baobabs' fruit

and disperse the seeds
in their dung.

Now, as the dry season
begins...

(SNORTS)

...they migrate
to distant watering holes.

The baobabs
have damp inner wood...

...and the elephants use it

to quench their thirst
on the journey.

(ELEPHANT TRUMPETS)

(LOW RUMBLING)

This relationship can only work
because baobabs

have a remarkable ability
to heal themselves.

Between each damaging attack...

...they expand
their spongy wood

and grow new skin.

And they've done this
time and time again,

over centuries.

Today, however, it's harder
for the baobabs to recover,

as dry seasons
become longer and drier

due to climate change.

Not only that,
but the elephants are forced

to take ever more wood from
the trees in order to survive.

In some parts of Africa,

many of the largest
and oldest baobabs

have fallen in the last decade.

The loss of a vital species
like the baobab

strikes a blow
at all life in the desert.

In these hostile lands,

few living organisms
can survive

without help from others.

You can find an extraordinary
illustration of this

in Arizona's saguaro country,

with one of the natural world's
most peculiar structures.

It has been produced,
indirectly, by woodpeckers,

which regularly dig homes
for themselves

in the bloated trunks
of the saguaros.

In the next six months...

...the cactus heals the wound,

and so creates a safe, cool
and watertight nest hole.

Its tough lining
will persist for years,

even after the cactus itself
has died and rotted away.

A single saguaro may hold

several of these
extraordinary homes.

So over its lifetime,

it may provide accommodation

for some 3,000 chicks
of several different species.

(BIRD SQUAWKS)

But in the long term,
the saguaro benefits,

as their lodgers repay
the cactus

by pollinating its flowers...

...and dispersing its seeds.

It's relationships like these
that enable life to flourish

in some of the world's
harshest landscapes.

Our growing understanding
of the complex ways

by which desert animals and plants
rely on one another

is now helping us to protect them.

90 years ago, this photograph
was taken here.

However, in the last 50 years,

the population of saguaros here
has greatly diminished...

...not because of a direct assault
on the cactus,

but because many of
the shade-giving nurse trees

were harvested for firewood...

...leaving young saguaro
to die in the sun.

Now that this relationship
is understood

and the nurse trees are protected,

there are already signs

that the saguaro are recovering.

Wherever there's a desert,

plants have evolved
to meet its challenge.

But everywhere,
they need our help.

As we understand
more about them

and their intimate
and complex relationships...

...we will be better able to protect them

and all life in these beautiful

but increasingly fragile worlds.