Original subtitles

The biggest living thing

that exists on this planet is a plant.

The giant sequoia tree of California.

Plants, whether they are enormous, or microscopic,

are the basis of all life,

including ourselves.

We depend upon them for every mouthful of food that we eat

and every lung full of air that we breathe.

The plants of our planet flourish live remarkable lives

yet, for the most part,

the secrets of their world have been hidden from us...

...until now.

Now we have new ground-breaking technology that enables us

to enter their extraordinary world

and see their lives from their perspective.

In this series, we will uncover

the dramatic and unexpected behaviour of plants...

...and explore the beautiful...

(THUNDER CRACKS)

...but challenging landscapes in which they live.

The tropics - the richest and most competitive place

in which to survive.

The bizarre water world...

...where giants fight ferocious battles,

and plants eat animals alive.

Deserts...

...a world of extremes.

Seasonal lands...

...where survival depends on precision timing.

And everywhere,

there are intimate and critical relationships

between plants and animals.

This is a world that takes you...by surprise.

See our planet as never before -

from the plants' perspective.

This is The Green Planet.

(BIRDS AND ANIMALS CALL)

Rainforests, like here in Costa Rica,

are the richest and most dynamic environments on Earth.

They cover only a very proportion

of the Earth's surface...

...and yet they contain over half of all the world's

animal and plant species.

Up here, the forest's canopy is bathed by life-giving sunlight.

The branches of the great trees

carry rich, flourishing sky gardens...

...home to countless different kinds of beautiful plants.

Each species has evolved its own exquisite solution

to the challenges of survival.

This forest world may look peaceful,

timeless and unchanging,

but that is far from the truth.

The battle is at its fiercest on the forest floor...

...where only 2% of the sunlight filters through.

Plants here have to bide their time.

Their opportunity comes when an old tree dies.

When that happens, sunlight floods the forest floor

for the first time in perhaps 100 years.

The seedling's wait is over.

It must now race skywards

and claim a place in the canopy.

But it's not alone.

(LEAVES RUSTLE)

Rivals are everywhere,

each with its own survival strategy.

Some plants, like this monstera,

stretch out divided leaves to collect what light they can.

This vine is groping blindly around with its tendrils.

It attempts to reach the light by hitching a ride.

Its tendrils are highly sensitive to touch.

And a suitable target is in range.

Got it!

The vine tightens its grip

and begins to haul itself upwards.

But it's now overtaken

by the forest's fastest-growing tree.

A young balsa.

Its giant leaves are already 40cm across

and are stealing the light from its rivals below.

But the balsa's battle is not yet won.

Other, different vines are lying in wait.

Each is armed with dozens of claw-like hooks.

If just one hook gets a grip,

the vine will be able to smother its victim.

But the balsa is defended by a shield of slippery hairs.

The vine's hooks just can't get a hold.

The balsa brushes them aside...

...and continues to rush skywards...

...leaving the losers in its shadow

to fight among themselves.

This balsa has won its battle for the light.

And it's done so in a little over a year.

Balsa beat its competition

because of its extraordinary adaptations for swift growth.

Under the microscope, balsawood looks like a honeycomb.

It contains more air than wood,

so not only can it grow very fast,

but it gets the maximum height for minimum weight.

But fast growth needs something else.

Fuel...

...and lots of it.

That fuel is created in a plant's leaves,

as they soak up the sun.

It's a process called photosynthesis...

...a chemical reaction that is the basis of all life on Earth.

Leaves are covered by thousands of microscopic pores

called stomata.

When open, they extract carbon dioxide from the air,

and using energy from the sun,

combine it with nutrients to build the plant's tissues.

And critically for us, the process releases the oxygen

that we and all animals need in order to breathe.

(BIRD CALLS)

But for plants, there is a downside.

These precious, energy-packed leaves attract predators...

...in every shape...

...size...

...and agility.

A sloth can only move slowly,

but you don't need speed to gather leaves,

and it eats nothing else.

Plants are under attack from all kinds of leaf-eaters,

but the most voracious by far is hardly ever seen.

It consumes 50,000 leaves every day.

It's called leucoagaricus.

It's neither animal nor plant.

It's a fungus.

It lives five metres underground,

far from the leaves that it devours.

To get them,

it employs the best leaf-gatherers in the tropics.

Leaf cutter ants.

Millions of them provide the fungus with its food,

and in return, the fungus cultivates tiny mushrooms

as food for the ants.

The fungus releases chemical signals

that tell the worker ants what type of leaf it wants to eat.

Scouts are sent out with the latest orders.

Worker ants will travel hundreds of metres

to find the right kind.

Today's crop is being taken from a young bixa tree.

Just a few years old and still battling to reach the canopy,

it can ill afford to lose any of its leaves.

(CRUNCHING AND SLICING)

Between them, the ants can demolish a large leaf

in a matter of minutes.

The sound of cutting attracts more ants.

Now the pieces are carried back to the underground fungus.

The ants can run at speeds of two metres a minute.

And each can carry a load ten times its own weight.

It's a river of leaves across the jungle floor...

...part of a vast network that extends for miles

through the forest.

To avoid congestion,

worker ants dig trenches around obstacles.

Thousands of pieces are delivered every hour

to the waiting fungus.

Fed by such a continuous supply,

the fungus grows rapidly,

filling the chambers in which it lives...

...so the ants excavate more space.

It seems that the fungus has the upper hand...

...and the bixa tree will not survive.

But it fights back...

...using chemical warfare.

The bixa tree floods its leaves with toxins

that could kill the distant fungus.

As the ants carry the fragments back, they are themselves

poisoning the fungus on the tree's behalf.

It's a long-distance attack.

As the poison takes effect, the ants sense

that their fungus is weakening...

...and they respond to its signals

by changing to another source of leaves.

So the plant's chemical response

forces the ants to constantly switch from tree to tree.

Strike and counterstrike.

And that ensures that enough leaves remain uneaten

for each tree to recover.

(BIRDS AND ANIMALS CALL)

Once a plant becomes adult,

it can switch its energies

from growth to reproduction.

The tropical forests of the Americas stretch from Mexico

to the southern reaches of the Amazon.

They contain more than 100,000 different species of plant,

each with its own particular survival strategy.

One species that has adopted a grow-fast lifestyle

flourishes throughout this vast region.

The balsa.

But it has to pay a high price for doing so.

The lightweight wood that enables it

to grow at such speed is not strong

and is easily broken.

Few balsas live longer than 20 years.

This one is approaching the end of its brief life,

so the time has come for it to reproduce.

It has used a huge amount of energy to produce

some of the most extravagant flowers in the forest

in immense numbers.

Each is the size of a human hand.

As night falls,

the tree prepares an enticing treat.

This is a kinkajou,

a kind of fruit-eating raccoon.

Each flower is filled with huge quantities

of exceptionally rich nectar,

supercharged with sugar.

Irresistible!

The kinkajous drink so greedily

that they get pollen all over their faces.

So, as they move from tree to tree,

they carry pollen with them.

But the balsa leaves little to chance.

The nectar might appear to have run out,

but this is just the first round.

Now the balsa refills its flowers,

enticing the kinkajous back to repeat the process...

...seven times a night.

Pollination is complete.

And the kinkajous - they also get well served,

with over 100 pints of nectar in just a few weeks.

Both plant and animal do well out of this arrangement.

But in the tropical world, that isn't always so.

(BIRDS AND ANIMALS CALL)

Borneo.

Here, on the slopes of Mount Kinabalu,

live plants that eat animals

using pitcher-shaped leaves full of water.

Insects are attracted by the expectation of nectar,

but tumble into the pitcher,

where they are drowned and absorbed.

On the lower slopes of the mountain,

a plant grows that has no leaves at all.

Or even a stem.

All that can be seen is this -

a bud.

It is a parasite.

(RUSTLING)

The rest of its body lies within the tissues of a liana,

on which it feeds.

After about five years,

the bud finally opens into a monstrous flower.

It now has only a day or so in which to be pollinated

before it starts to wither.

Its petals are the colour of blood.

Their surface is tough and warty.

It appears to have fur.

Even whiskers and teeth.

At first sight, it might be mistaken for a dead animal.

This is rafflesia,

the corpse flower.

A metre across, it's the world's biggest flower.

And this one is a male.

From its centre comes the pungent odour of death.

It's a scent that might not appeal to every animal.

But it's very attractive to carrion flies.

They lay their eggs on rotting flesh.

(FLIES BUZZ)

The scent lures the fly deep into the flower

in search of meat.

The fly finds nothing.

The rafflesia, however, has the fly exactly where it wants it.

It's stuck pollen to the fly's back.

If this male rafflesia's strategy is to work,

the fly carrying its pollen must now visit

a female corpse flower...

...such as this one.

(FLY BUZZES)

Success!

Once pollinated, plants are able to produce seeds,

the next generation,

but once again, there are animals all over the forest

that are eager to make a meal of them.

(BIRDS CALL)

The Malay Archipelago,

a vast tropical world of 1,000 islands.

It's home to giants -

the tallest trees in the tropics,

many of which live for centuries.

They produce seeds in enormous numbers,

but only do so when the time is right.

This individual hasn't produced a single seed

for nearly a decade,

but in the last weeks, it has become festooned

with more than 10,000 of them.

Each seed has the potential to produce a giant,

like its parent.

But success will depend...

...on timing.

(SNORTS)

Seed-hunters are gathering.

Bearded pigs.

(GRUNTS)

But these seeds have been produced by a dipterocarp...

...trees that create the tropical world's

largest seed nursery.

After years of waiting,

thousands upon thousands of individual dipterocarps

have synchronised to produce the next generation,

all at exactly the same time.

(BIRDS CALL)

And now these seeds will face the dangers below together.

By releasing billions of seeds all at the same time,

they swamp the pigs and any other animals

with more than they could possibly eat.

And that buys time for some of the seeds to take root

and sprout.

(CRACKLING)

The tree's strategy has worked.

But a seedling will have to overcome many more dangers

over the years if it, too, is to become a giant.

And there are many ways in a tropical forest

by which a tree's life can be ended

before it reaches its prime.

The northernmost tip of Australia.

This is the world's most ancient rainforest.

(BIRDS AND ANIMALS CALL)

(LOW GRUNTS)

Battles between animals and plants

have raged here for 180 million years.

(LOW CREAKING)

So the plants have had time to develop effective defences.

This is a poison arrow tree,

one of the tropical world's most heavily defended plants.

Its trunk is tall and slippery

and exudes a poisonous sap.

It appears to be almost invulnerable.

But even so,

just as this individual reaches maturity,

its life has become endangered.

(BIRDS TWEET)

Each monsoon season,

it is invaded from above.

It attracts hundreds of shining starlings.

Its immense smooth trunk makes its high branches above

a safe place to nest,

but over the years,

this has created a major problem for the tree.

After feeding, the starlings return to the nest

to digest their food,

with inevitable consequences.

Every year,

they produce almost a quarter of a tonne of droppings.

The toxic chemicals they contain

create a dead zone that completely surrounds the tree.

The toxins are absorbed by its roots

and travel up through the trunk and into every leaf.

(CRASHING)

Branch by branch,

the tree is slowly dying.

It has become a victim of its own success.

It has been poisoned.

Now a new battle begins...

...one to claim the tree's dead body

and the vast amount of nutrients that it contains.

It's a battle that is fought throughout the natural world...

...involving a group of organisms

that we rarely notice.

They exist for most of the time

hidden in the leaf litter and earth

as a network of fine white threads -

fungL

The threads of competing fungi envelop their victim's body,

releasing enzymes which digest the tree's tissues

and unlock the nutrients within.

There are a million or so different species of fungi

in the tropics.

Some feed on dead plants.

Others eat them alive.

And some reveal their existence in an eerily beautiful way.

In Africa, in the Congo,

this is known as chimpanzee fire.

The mysterious bioluminescent glow

becomes brighter as the fungus digests the tree.

When fungi have fed sufficiently,

they develop their reproductive organs.

Each can produce literally billions of spores...

...the tiny particles

that carry the species' genetic blueprint.

Each spore like this

has the potential to kill a tree.

(SPORES RUSTLE)

The spores are so light

they can be carried by the slightest air currents.

At least a billion

float above every square metre of rainforest.

Recently, it has been discovered that these spores

do far more than just bring death and decay.

They are, in fact,

at the very centre

of the rainforest's life support system.

(WIND WHISTLES)

High in the humid air,

the spores combine with molecules of water.

(RUMBLING)

Gradually, they collect into droplets,

which, when they are heavy enough,

- fall... - (THUNDER CRACKS)

...as rain.

Over two-and-a-half metres of rain falls every year

in a rainforest.

And in the centre of almost every raindrop,

there is a fungal spore.

The world's rainforests are the richest

and most dynamic environments on Earth,

built on complex connections and relationships.

(BIRDS SQUAWK)

But these connections,

competitive or collaborative,

are now becoming increasingly fragile.

(THUNDER RUMBLES)

(THUNDER CRASHES)

Today, 70% of all the world's rainforest plants

grow within a mile of a road or a clearing

that we have cut into the forest...

...and this is creating new battlefields

in the tropical world.

Alien armies of identical cultivated plants

now stand where thousands of different species once grew.

We have planted vast regiments of crops

in order to provide ourselves

with food and other commodities...

...and the ancient forest has been reduced

to ever fewer isolated fragments.

All, however, is not lost.

The fragments can still be sanctuaries...

...keeping alive the intimate relationships within them.

This is the seven-hour flower.

The plant produces its flowers at night.

They open for about seven hours

and then they die.

During that time,

they provide food for one particular animal.

Underwood's bat feeds almost exclusively on its nectar.

It is the plant's primary pollinator.

An individual seven-hour flower

only produces a small amount of nectar,

so a bat must visit as many as 300 flowers a night

to find enough food to survive.

And it pollinates them as it feeds.

But if a patch of forest becomes too small,

with too few flowers,

the bats will disappear,

and without the bats, the flowers can't reproduce

and will soon die out.

The partnership is broken.

Life in the forest depends on countless close relationships,

but they are increasingly under threat

as forests become more fragmented.

The solution, of course,

is to join these remaining fragments together again.

30 years ago, this forest in Costa Rica

was grazing pasture.

The cattle were removed,

and nature was allowed to take its course.

This new forest has become a bridge

that connects several fragments,

allowing plants and animals

to both renew old connections

and create fresh ones.

Of course, we urgently need to protect

the healthy forest that still remains.

But looking forward,

we must take what may well be our last chance

to re-build the lost rainforest...

...and preserve the treasures of the tropical world

for future generations,

and with it,

ultimately protect all life on this, our green planet.