Every form of life on Earth
depends on the ability of plants...
...to capture the sun's energy
and transform it into food.
Sea birds feed on fish,
and bigger fish eat smaller fish.
But somewhere their food chain
began with plants.
Every food chain is started
by a vegetarian.
The great African herds
of wildebeest feed on grass.
And in their turn, they become food
for predators such as lions.
lt is plants, and plants alone, which
generate all the food we have on Earth.
Without them,
ours would be a dead planet.
And four billion years ago,
that's just what it was...
...dead.
A forbidding, hostile place...
...bombarded by ultraviolet radiation...
...the planet's surface
sealed with poisonous gasses.
Yet in such conditions,
strange carbon compounds formed...
...with power to reproduce themselves.
From them appeared the first
primitive cells of life.
Drawing energy from the sun,
they began to make their own food.
Some combining water with a chemical
we know as chlorophyll...
...and this produced an important
byproduct: bubbles of oxygen.
An atmosphere was being created
in which...
...you and l would eventually be able
to breathe and live.
Two billion years ago, this was
the scene where land and sea met.
ln the next billion years, the oxygen
was gradually accumulating...
...some of it forming a shield of ozone
in the upper layers of the atmosphere.
At last, the stage was set
for life in many forms.
And true plants swarmed
in prehistoric waters.
Now, filter-feeding animals
such as barnacles...
...could flourish
in the oxygenated water.
The secret of life was formed
in an unwritten contract...
...binding plants and animals
together: the green contract.
Some animals might live by
eating other animals...
...but every food chain must start
with animals eating plants.
That is the essence
of the green contract.
By the time fish had evolved...
...another stage in the story
of life was beginning.
The teeming life of the oceans
reached out to the dead land.
About 400 million years ago,
the first plants came ashore.
Tiny growths
clinging to rocks and mud.
ln time,
they took a firmer hold on land.
They developed roots.
Plants developed woody vessels within
their stems which made them rigid...
...and enabled them to grow tall.
Competition with other plants
compelled them to grow taller still.
With this dynamic lift off,
the first forests were born.
Plants had successfully
invaded the land.
Their roots broke the Earth's surface
and held together the topsoil.
The atmosphere they'd created made life
on land possible for many animals...
...among them, insects.
Wings meant that insects could follow
the plants upwards into the sky.
The first land plants
had swimming sex cells...
...and could therefore
thrive only in moist places.
But by degrees, plants developed
new methods of reproduction.
The conifers' male sex cells could be
carried on the wind to female cones...
...which produced seeds.
Since they reproduced in this way...
...the trees could move into new,
dryer territories.
Like an advancing army,
they swarmed the foothills...
...and occupied the mountainsides.
A far cry from the shoreline
of the ocean.
Today, one-third of all
the world's forests are conifers.
Among them, the largest living
organisms: the giant redwoods...
...capable of growing to the height
of a 20-story building.
A remarkable development...
...but there was an even more
spectacular one still to come.
The plant's male and female parts were
combined in a single marvelous device:
The flower.
Flower pollen is an attractive source
of food for insects.
They carry some of it on their bodies
as they move from flower to flower.
ln that way,
the flower's eggs may be fertilized.
Many flowers produce nectar,
which attracts insects...
...with guidelines
to help them find it.
Some flowers
favor particular insects.
The wild arum has a spike
with a fetid odor...
...which attracts small mosquitoes.
Many slide to the bottom
where the female parts are located.
They remain trapped overnight.
But next day,
the male parts exude pollen.
The bristles wilt and clear the way
for the mosquitoes to escape...
...well-coated with a dusting of pollen
that they carry to the next arum.
Again, temporary prisoners...
...they pollinate their captor
before escaping once more.
The size and shape of certain flowers
match the bills of particular birds.
Members of the parrot family,
like the rainbow lorikeet...
...have adapted
to eat certain flowers...
...and so
have become their chief pollinator.
Other flowers await pollination
at night.
ln Australia, small nocturnal
marsupials called honey possums...
...visit banksia flowers
for the sake of their nectar.
By chance, they carry pollen
on their fur...
...as they move from flower to flower.
The traffic to the flowers
that feed them...
...is an open invitation
to the secret hunters.
Some predatory mantes can disguise
themselves as flower petals...
...to fool their victims.
The killer, poised to strike.
Life in the world
of flowers became complicated...
...with many variations on the theme
of ''predator meets prey.''
ln the relationships
linking plant and animal...
...it was not always the plant
which was the passive partner.
ln some cases, the plants themselves
became the killers.
Growing on poor soil,
this sundew plant...
...gets the nitrogen
it needs digesting the insects...
...caught in its sticky leaves.
The leaves of another flesh-eating
plant form an even more ingenious trap:
The Venus flytrap.
Press the button,
and ''bang'' goes the trap.
Even so,
the plant has no guarantee of success.
''Win some and lose some''
is always nature's rule.
Each hair is a trigger.
Touch it twice and the trap shuts.
Once it has secured its prey,
the plant digests it.
ln all subcontracts written
into the green contract...
...there's a delicate balance
maintained between killer and victim.
lndividuals will perish,
but each species will survive.
ln the tropical forest
there is the richest variety...
...of relationships
between plants and animals.
The success of flowering plants
shows here more so...
...than anywhere else. They've
an ideal climate with warmth...
...and continuous moisture.
lt's the variety of plants
that provides such an abundance...
...of food and living conditions for
a greater number of animal species.
Over two-thirds of all
flowering plant species...
...are found in tropical forests.
Eat and be eaten,
so the food chain goes on.
Body color that matches the background
can be a good defense.
Slow movers often rely on camouflage.
lt's a strange fact that this wealth of
life thrives on the poorest of soils.
The plants survive because scarce
minerals are constantly recycled.
Decay, helped by insects and fungi...
...returns everything to the soil...
...ready to be taken up again by
new life forces in plant and animal.
One more relationship between the
plants and animals can be found here.
After pollination, the flowers
are transformed into fruits...
...succulent and often colorful,
they have evolved to be eaten.
Here, wild figs attract
large fruit-eating mammals...
...known as flying foxes.
While the fruit's
fleshy part is digested...
...the seeds will pass through
the animal's body to be dispersed...
...and germinate where they fall.
This is very effective
for dispersing seeds...
...and so creating
and regenerating forests.
Each seedling will struggle
to become a fruit tree...
...and compete for a place
in the sunlight.
Fruits and berries were an important
survival food for our early ancestors.
But more crucial
to human development...
...were the seeds of another
special group of flowering plants...
...which provided the staple food
of grazing animals: the grasses.
Most plants grow from the tip,
but grass leaves grow from the base.
So after they have been cropped
by grazing animals...
...the grass will continue to grow
and make more food.
All grasses and sedges are flowering
plants. lt's easy to overlook that.
No need for insects.
Grass pollen is carried by the wind.
When the seeds are set...
...they contain a nutritious substance
which gives them a good start.
Grind it up and it becomes flour...
...a basic human food
that can be stored for months.
The wild grasses that we know
as rice, oats, barley and wheat...
...were the key to the growth
of human civilization.
What drives the combine harvesters
is energy from the sun...
...processed and stored...
...in billions of microscopic marine
plants in prehistoric times...
...as oil,
one of the so-called fossil fuels.
Another fossil fuel is coal...
...the carbonized remains
of some of the earliest forests.
lt provides more than 40%
of the world's industrial energy.
And it takes energy to operate
the great thrust into the depths...
...where the prized black seam lies.
Fossil fuels, coal and oil...
...contain energy which can
be released so easily by fire.
ln 1 991 , the Gulf War focused
our attention on what happens...
...when nature is wantonly put
into reverse.
Originally, when plants first gathered
this energy from the sun...
...carbon dioxide was used and oxygen
given off to enrich the atmosphere.
Now, fire uses up oxygen...
...while carbon gases
pour back into the air.
Less violently, it goes on
in peacetime too.
Modern transport relies
on the burning of oil.
The carbon gases discharged
by city traffic and industry...
...build in the atmosphere and prevent
the release of heat by radiation...
...thereby causing
a greenhouse effect.
Other harmful chemicals
attack the ozone...
...which shields us
from ultraviolet rays...
...damaging to human skin and also
to the plant life of the oceans.
Trash, garbage, litter.
The dead end of life.
What is biodegradable is transformed
into a new life cycle...
...but mankind has introduced
the non-biodegradable...
...the junk outside
nature's regeneration...
...which poisons land and sea.
For the first time, a single species,
the human species...
...is threatening
the life-support systems.
We have broken the green contract.
But we are learning
to be less wasteful.
As the world's resources shrink,
we are recycling more and more.
This factory already uses 30%
wastepaper.
Soon it will recycle 60% waste
into new paper.
We are also learning to capture energy
without burning fossil fuels or timber.
Besides nuclear energy,
there is tidal power...
...solar panels, wind power.
We can harness the elements.
Our space-age technology can monitor
the damage we are inflicting.
Satellites report the frightening speed
of loss of vegetation...
...particularly in the rainforests.
This is a stretch of forest in Brazil,
about 1 00 miles across.
Forest clearance and roads
are clearly visible.
Three years later, the view provides a
grim record of the rate of destruction.
Time is running out
for research scientists...
...at work in the canopy
of a threatened forest.
Locked away in the rare plants
and insects the scientists collect...
...are secrets, perhaps, of medical
cures still to be discovered.
Our heritage is a pool
of genetic material beyond price.
This periwinkle comes
from the forests of Madagascar...
...not very important, we might think.
But now it is cultivated
and harvested...
...to make a drug used
to treat leukemia in children.
Any species we exterminate
may be an opportunity lost.
Lost forever.
By discovering how plants
and animals relate...
...we can enrich our
own understanding of life.
The rainforest shows us that true life
sustains itself...
...within the available resources
that it can recycle perpetually.
Living in harmony with nature
instead of abusing and degrading it...
...may demand a change in our habits,
but it will bring new benefits.
Some of our world's most beautiful
sights are under the sea.
Even these are no longer denied to us.
lt seems to be a natural human desire
to make contact with wild animals.
This desire is gratified each day...
...for visitors to a remote beach
in Western Australia by wild dolphins.
Oh, yes. He's so beautiful.
You wanna step out, young man,
and feed this dolphin?
They're encouraged with food...
...but the dolphins do seem to enjoy
contact with humans...
...as much as the humans enjoy it.
She's saying hello again.
She wants some more dinner.
Know what her name is?
What?
Our world has developed
over many millions of years.
What gave it stability
and increasing variety...
...was an unwritten contract
between plants and animals...
...acknowledging
their interdependence...
...within a system nourished
entirely by the sun.
But we can no longer take for granted
the age-old rhythms of nature.
The growth of human knowledge has given
us a decisive influence everywhere.
From the depths of the oceans...
...to the sky's final, delicate skin
of our atmosphere.
lt is our actions which will change
the world for good...
...or for evil.
ln the sheer joy of our existence,
we must love and cherish...
...those delicately balanced forces of
nature enshrined in the green contract.
They formed the rules
of the created world...
...before we joined the long march
of evolution.
They hold the secret
of our life on Earth.