The biggest living thing
that exists on this planet is a plant...
..like this giant sequoia tree in California.
Plants, whether they are enormous, like this one,
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.
Plants flourish in remarkable ways,
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.
This series will reveal the extraordinary
and dramatic ways in which plants behave...
..and we will explore the challenges demanded by
the very different 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...
Agh!
A world of extremes.
Seasonal lands...
..where survival depends on precision timing.
And everywhere, we will explore the critical
and intimate relationships between plants and animals,
including ourselves.
Join me in a world that takes you by surprise...
..and see our planet as never before...
..from the plants' perspective.
This is The Green Planet.
I'm in Costa Rica, in the heart of a rainforest,
the richest and most dynamic environment on Earth.
Rainforests only cover a very small proportion
of the Earth's surface,
yet they contain over half of all known
species of animals and plants.
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.
This is a battlefield.
Throughout this forest, plants are competing ferociously
with one another to claim the light.
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.
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.
Most trees would have grown an inch or so in that time,
but this one is already 30 feet - 10 metres - tall.
Balsas owe their success
to the special character of their wood.
If this section of tree trunk came from a hardwood tree,
it would be really quite heavy.
But as it is,
it's from balsa,
and it's really very light,
and that's because of its internal structure.
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.
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.
The plants here are under constant 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 created this great clearing in the forest...
..and it lives just beneath my feet.
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.
Leafcutter 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.
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.
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 plants,
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 racoon.
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.
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.
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.
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.
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.
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.
Seed-hunters are gathering.
Bearded pigs.
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.
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.
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.
Battles between animals and plants
have raged here for 180 million years.
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.
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 ton 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.
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.
Here, on the floor of a tropical rainforest,
it's dark, it's humid
and it's hot -
ideal conditions for fungi.
We normally think of fungi as things like this.
Mushrooms of one kind or another.
But these are just the fruiting bodies.
They exist for most of the time
hidden in the leaf litter and the earth
as a network of fine white threads.
The threads of competing fungi envelop their victim's body,
releasing enzymes which digest the tree's tissues
and unlock the nutrients within.
There 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.
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.
High in the humid air,
the spores combine with molecules of water.
Gradually, they collect into droplets,
which, when they are heavy enough, fall...
..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.
But these connections,
competitive or collaborative,
are now becoming increasingly fragile.
When Charles Darwin was exploring the tropical world
nearly 200 years ago,
he wrote this in his diary.
"Among the scenes which are deeply impressed on my mind,
"none exceed in sublimity
"the primeval forests undefaced by the hand of man."
He would struggle to find such a place today.
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.
Their size is nonetheless critical.
This is the seven-hour flower.
This plant produces its flowers at night.
They open about six o'clock,
and each blossom only lasts that night.
It opens for about seven hours
and then it dies.
But during that time, it provides food
for one particular animal.
A bat.
And here it is!
During the seven-hour flower's flowering season...
..Underwood's bat feeds almost exclusively on its nectar.
It is the plant's primary pollinator.
It might seem that this is
a fairly evenly balanced relationship,
but not so.
The bat likes this nectar because it's sweet,
but it's not very nourishing.
So the bat must visit hundreds of flowers a night...
..and it pollinates them as if 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, I came to this exact spot.
This land belonged to
a scientific research establishment
and it was covered with grass being grazed by cattle.
The scientists got rid of the cattle
and allowed nature to take its course.
Just look at it now!
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
what healthy forests still remain.
But looking forward,
we must take what may well be our last chance
to re-establish the lost rainforest...
..and help the tropical world to heal itself.
It will take the co-operation of nations around the world,
but it is the only way in which we'll be able to
preserve the treasures of the tropical rainforest
for future generations.
And with it,
ultimately protect all life on this,
our green planet.
The aim of The Green Planet team was to take the viewer
into the world of plants, so that it could be seen
from the plants' perspective
in a way that had not been possible till now.
That meant developing an entirely new camera system.
And this is the game-changer -
a specially designed robot camera
that we affectionately call "the Triffid".
The Triffid started life in the garage of an American
ex-military engineer, Chris Field.
I'd seen quite a few of these
Planet Earth style documentaries,
and they always absolutely blew my mind,
especially the botanic time-lapse really spoke to me.
In his spare time, Chris spent a decade
building elaborate motion-controlled
time-lapse camera rigs
and teaching himself how to film plants.
Plants often behave like animals in so many ways,
and being able to see it through time-lapse is one thing
but using the motion-control brings you into that timescale.
We could really see the potential
in how we could use this sort of movement
to bring plants alive
and film them in the same way that we film animals.
Soon, Chris joins the team
in a quiet corner of the Devon countryside
and the robot army begins to take shape.
After 40 years of filming time-lapse,
these rigs have opened up a whole new world for us.
So, it'll be like hovering around something
with a drone or helicopter, but in a time-lapse speed.
The holy grail for us is being able to take this technology
out into the wild, try and get the same sorts of dynamic moves
in some of the most extreme environments in the world.
So, what we needed to do
was to develop this technology even further.
Six months later, the Triffid is born...
..and with slight trepidation, they hand me the controls.
That makes it go away.
And this makes it come back.
And this sends it up.
Ooh!
I think I'd better hand it over to the experts.
Now it's time to put this new member of the team
properly through its paces.
The aim here is for Ollie to find a target, aim for it
and fly through it, as if he is a tiny fly
going through a hole in a leaf.
Easier said than done.
Oops! I'm trying to find a target.
Whether the kit's going to stand up to that sort of use
and the abuse that we throw at most pieces of kit
has yet to be seen.
In the studio, it seems to be working pretty well.
But this is only a dress rehearsal.
It's time for the Triffid to face the challenges
of the Costa Rican rainforest,
and leafcutter ants.
We want to film their journey all the way
down the trunk and along this buttress root
and down to their nest.
The team and the Triffid need several days
of dry weather,
but a storm can hit at any moment...
..and rain is one thing the Triffid does not like.
The conditions that we're working in now
are a little bit more challenging than the studio.
All the ground is really bumpy.
We've got loads of plants in the way.
I know we're making a series about plants,
but sometimes they're a complete pain in the neck!
The Triffid needs to be programmed
to capture images from 7,000 different camera positions
on the ants' trail.
Just one drop of rain on the lens,
or a wobble,
and the whole process will have to start again.
I think this is when we're going to find out
if our ambition outweighs our ability.
For the crew, the ambition is certainly high.
Fortunately, it's all down to the Triffid now.
We've been filming the ants with the Triffid
for eight days now, and we're on our third set-up.
It's pretty slow going.
While the Triffid seems to be handling the pressure well,
for the crew, trying to take a tree's-eye view of ants
is turning into a bit of a nightmare.
Wake up, film ants, go to sleep, dream of ants.
Wake up, film ants, sleep, dream of ants.
Wake up, film ants,
go to sleep, dream of ants.
After two weeks in the jungle,
ambition and ability finally come together,
for the Triffid, at least.
Thousands of individual images
creating a single extraordinary time-lapse...
..one that follows a river of leaves
across the jungle floor from a unique perspective.
For the Triffid, this was just the beginning.
Take a bow, Triffid.
Next time on The Green Planet...
..the wonder of water worlds...
..where plants hunt...
..go on the move...
..fight...
..and create the air we breathe.
The Open University have produced a poster
that explores the vital role that plants have for our planet.
To order your free copy, call...
..or go to...
..and follow the links to The Open University.