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Nature is made possible by public television stations,
your gas company, and the gas industry,
whose respect for nature and the environment
is reflected in the underwriting of this series.
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Since World War II, man has destroyed half
of the world's tropical rainforests.
If this rate of destruction continues,
within the next 40 years,
tropical rainforests will totally disappear.
Our generation will have presided over the greatest
mass extinction since that of the dinosaurs
65 million years ago.
Hi, I'm George Page for Nature,
and if you're a regular watcher of our series,
you know that tropical rainforests are the greatest
storehouses of genetic diversity on Earth.
Although they cover only 7% of our planet,
they contain at least half of all our plant
and animal species, and scientists are really just
beginning to unravel some of their secrets.
This week, we visit Africa's most species-rich jungle,
Kharup, in the West African country of Cameroon.
Our film, which took five years to shoot,
reveals the delicate interdependence of the plants
and animals that together comprise what's left
of this great citadel of ancient life.
Remote.
Isolated.
Inaccessible.
Kharup is one of Africa's last untouched rainforests.
A million years ago, a mantle of rainforests
covered central and West Africa.
Then the tropics grew colder and drier
as the northern continents were gripped by the great ice age.
The forest contracted into refuges where some plants
and animals managed to survive,
and there the forests were
protected from the cold.
The forests were protected from the cold
and the cold was protected from the cold.
The ice age changed to survive,
and there the evolution of forest life continued.
Then the ice sheet retreated,
the warm rains returned,
the forest expanded again.
Through all those changes, the refuges endured.
Among these ancient rainforest remnants
of Cameroon, which harbor the richest variety
of plants and animals anywhere in all of Africa.
Beautiful, but still mysterious.
Storms sweep in from the Atlantic,
bringing Kharup some of the heaviest rainfall in the world,
more than 30 feet a year.
As the forest dries, heat and humidity create
near perfect conditions for plant growth.
Far below the forest canopy, it's a twilight world,
occasionally pierced by shafts of sunlight.
Here in the humid darkness, plants and animals
need to be especially equipped to survive.
Parasitic plants flourish in the roots of trees,
only the flowers appear above ground.
The dappled light is ideal for begonias and ferns.
The pygmy chameleon is a living clue
to the great age of Kharup.
It's one of many kinds of animals which are found
only in this part of Cameroon,
and it was here before the ice age.
On the forest floor, huge colonies of driver ants
prey on slower moving creatures.
Fearsome predators, they kill and consume
any animal unable to escape.
There are clouds of butterflies.
Butterflies of many species.
Always the search for food.
The drill is one of the few large animals
that survive on the forest floor.
It lives mostly on fallen fruit.
This is a young male.
Drills are rare baboons, now restricted
to a few forests in southwest Cameroon.
They forage over a wide area in noisy groups,
scouring the floor for roots and insects,
and finding food where they can.
Immediately above the floor,
the forest is surprisingly open.
Poor light discourages abundant plant growth,
but the trees have adapted to these conditions,
developing large leaves,
which serve as efficient collectors of light.
The flowers grow directly on branches,
on trunks,
and even on the leaves themselves.
As do their fruits.
But food is hard to find in this twilight world,
and large animals must search diligently for it.
The white-collared mangabe,
a close relative of the drill.
Eighty feet up, creepers form a forest highway.
From floor to canopy, the forest changes,
and each level provides particular opportunities
for plants and animals.
Some trees grow to more than 150 feet.
Just below the treetops,
troops of monkeys forage the canopy for food.
Proyces red colobus is found only in collop.
The colobus mix freely with other species of monkeys,
like the white-nosed grinnon.
There's safety in numbers.
A mixed group is quicker to detect potential danger.
It's usually a crowned grinnon, which gives the alarm.
The monkeys come to rely on their natural vigilance.
The highest level of the forest is made by huge trees
which rise into the sunlight, emerging clear of the rest.
Here, 200 feet up, is the nesting site of the crowned eagle.
It's mainly on monkeys.
Its huge talons can easily crush the skull of its victim.
The chick will be fed at the nest for more than a year
and strong enough to kill for itself.
The whole forest, from the floor to the top of the tallest tree,
seems to behave as a single organism.
The trees alone are not the forest.
The animals don't simply live in the forest.
Together, plants and animals are the forest.
Trees provide the framework for this carefully balanced community.
But the trees must protect themselves
to survive among so many hungry animals.
Red-eyed grasshoppers and caterpillars threaten the very existence
of the trees on which they feed.
Trees cannot run away, so over many thousands of years
they have developed other, more subtle methods of defense.
The trees' defenses and the animals' responses
are both prime factors in the evolution of tropical forests.
Trees have evolved special chemicals that protect their leaves,
so successfully that over 90% of forest animals
cannot feed on the leaves of living plants.
They can eat either fruit or decomposing matter or each other.
Inside some leaves, the veins are lined with thick deposits of tannins,
which make them indigestible.
In others, irritating crystals and poisons,
such as cyanide, occur throughout the leaf.
Lignin, seen here in red, strengthens the leaves,
making them fibrous and difficult to digest.
These chemical defenses have compelled animals like the colobus
to develop very specialized feeding behavior.
Bright red, young leaves have few protective compounds.
Protection develops later as they mature and turn green.
Monkeys have learned to select the young leaves
and reject the unpalatable older ones.
Colobus are agile and acrobatic, moving from tree to tree,
selecting choice leaves from many different species.
And with the monkeys continually on the move,
many young leaves do survive to maturity.
Guided by the noise, the crowned eagle waits for an opportunity to strike.
And then, the monkeys spot the eagle and sound the alarm.
Unsuccessful, the parent returns to the nest with a sprig of leaves.
The hungry chick is not impressed.
Forest monkeys live on small quantities of a great variety of plants,
because they're always on the move.
But for smaller and less mobile animals, like caterpillars,
the story's quite different,
and the fates of individual plants and animals are more tightly intertwined.
Down on the forest floor, a female butterfly emerges from her chrysalis.
After mating, her single purpose is to find aritia,
the only plant where her eggs have a chance of survival.
This may take several hours.
She searches for it, tasting individual leaves by means of special receptors on her forelegs.
Eventually, she finds aritia and lays a single egg on a young leaf.
After hatching, the caterpillar eats its own egg sac
and begins the complex pattern of behavior upon which its survival depends.
The full-grown leaves of aritia are indigestible,
so the caterpillar must develop on a young leaf.
First, it inspects the whole leaf.
If the leaf is not large enough to sustain its feeding,
the caterpillar actually will lie dormant until the leaf has grown,
but it must begin to feed before the leaf develops its chemical defenses.
Now the caterpillar starts feeding, but only on the non-growing parts, such as the tip and the midrib.
The caterpillar grows only as fast as its leaf grows.
The mature caterpillar now pupates, with the leaf still intact.
A fine balance has been achieved.
The aritia has survived the attentions of a predator.
The caterpillar has matured into a butterfly.
These monkeys appear to be eating the flowers of a pentadezma tree.
If the flowers were to be eaten, it would be a disaster,
because they contain the tree's vital reproductive organs, which must be protected.
But these monkeys are not actually eating them.
The flowers produce vast amounts of nectar, rich in nutrients,
to attract the animals which pollinate them.
In a forest where food is often scarce, nectar is a vital source of nourishment for the monkey.
The flowers' reproductive parts are protected by a high concentration of tannin, which makes them inedible.
While the monkey has been drinking, yellow pollen has brushed onto its chin.
When the monkey finds another pentadezma tree,
the pollen is brushed onto the receptive female flower parts.
Far from damaging it, the monkey is helping the species to survive.
In temperate zones, winter is a major selective force on the forest community.
Here in the tropics, the interaction between the plants and animals
is the most important influence on evolution.
Coexistence is the key to survival.
A spectacular example of this interdependence is the parchea tree,
which is crucial to the survival of many different animals.
High in the canopy, over a hundred feet up, at the tips of its branches,
the parchea produces extraordinary blossoms.
Over a period of three hours, from each of these buds,
three thousand tiny flowers will grow.
Again, it's the nectar which is important,
and a sunbird is attracted to the first drops produced at sunset.
Honeybees fly in too.
By nightfall, the parchea flowers are producing enormous quantities of nectar.
The nectar is a major attraction for the forest's hungry night animals,
and nocturnal ants.
The flowers have a rich, peach-like smell that attracts a pato.
The pato is a nocturnal primate. Although he has large eyes,
he relies on a keen sense of smell to locate food.
Once he finds the blossom, he licks up the nectar,
but leaves the rest of the flower intact,
protecting the parchea's defensive chemical compounds.
A door mouse sips nectar and retreats.
The parchea flowers are at the tips of its branches.
This leaves the door mouse vulnerable, but is ideal for the bats,
the main target of the tree's succulent advertising.
As the bat licks the nectar, its breast brushes up against the flowers,
and, covered in pollen, it flies away.
After a few hours, every bat has picked up pollen.
This is vital to the parchea, because the female flowers can only be fertilized
by pollen brought from another parchea tree.
Bats have excellent memories and follow regular feeding routes.
They visit many parchea trees in the course of a single night,
so the female flowers have a good chance of being pollinated.
By dawn, the flowers have wilted. Butterflies and bees come to feed
on the leftover nectar and pollen.
Over the next few days, the blossom gradually breaks down.
After a while, only the individual pollinated flowers are left.
Eventually, these develop into long bean-like fruits,
each containing the seeds which carry within them the future of the parchea
and of the animals that rely on it.
After pollination, trees need some means to disperse their seeds
to places where they can germinate.
The seeds are often contained inside a nutritious fruit,
which birds eat seeds in all.
The collared sunbird and the yellow-throated tinkerbird
depend on fruiting trees for a large part of their diet.
The seeds of the alcornea are indigestible, protected by chemical compounds.
They pass through the bird's digestive system intact.
Birds and fruiting trees often depend on each other,
but monkeys too help disperse the seeds.
The white-collared mangabey is vulnerable to predators
while feeding in exposed tree tops,
so he stores the fruit in special pouches in his cheeks
and takes it away to eat later in a safer place.
In falling, this forest giant has smashed out its own shape in the canopy,
allowing light onto the forest floor.
This tremendous destruction plays an important part
in maintaining the diversity of the forest.
Because of the light, many seeds can now germinate here.
Under the closed canopy, they wouldn't have had a chance.
The winged fruits of a red ironwood tree nearby
depend on these cleared areas,
which give them the opportunity to establish themselves.
These seeds are among the first to colonize and exploit gaps in the canopy.
Blown by the wind, some seeds land in ideal conditions.
Germinating quickly, the seedling must now compete against other trees
to reach and fill that vital new space above.
A bright red pigment protects growing leaves
against the harmful radiation of the sun.
The young tree grows rapidly upwards, toward the light,
much of its energy going into the production of leaves,
which fuel its swift ascent.
Eventually, the successful tree reaches the canopy.
Then it branches and shuts out the light,
which would have enabled other plants to compete.
In the full sunlight of the canopy,
the grown tree flushes into an entire crown of bright red young leaves.
After three days hunting, the mayo has killed a monkey.
The female displays over the kill.
They raise a single chick.
Occasionally, two eggs are laid, but if both hatch,
the chicks will battle it out until one dies.
In the hot, saturated conditions of a tropical forest,
trees suffer not only from browsing animals,
but also from other plants.
Often leaves are colonized by mosses and lichens.
This greatly reduces their ability to absorb light.
In such a keenly competitive environment,
it's essential for the tree to be healthy.
Orchids and creepers have a similar weakening effect.
Protective chemicals do not help here.
One tree in particular, the barteria,
has evolved a special relationship with one species of ant
that solves the problem of hangers-on.
On this young barteria tree, a queen ant arrives to start her colony.
She searches quickly to ensure that the tree is a barteria
and that it's not occupied by other ants.
The tree has hollow branches.
The queen chews her way into them to lay her eggs and found her colony.
And so the unusual relationship begins.
The ant can only survive in the barteria tree,
and the tree will only reach the canopy if it's protected by this ant.
As the first black worker ants emerge,
they're confronted by aggressive red weaver ants.
The red ants are foraging, not nesting here,
but will attack anything that crosses their path.
Black ants of the young colony back off into the hollow branches.
Some don't make it.
Survival of the barteria tree depends on the black ants' ability
to drive off the weaver ants and keep control of the tree.
Inside the hollow branches, scale insects feed on the sap.
These insects secrete a sugar solution,
which is the staple food of the black ants.
To obtain it, the ants milk them regularly.
As the black ant colony grows,
the balance of power shifts in its favor.
The battle may continue for several weeks
until the red ants are finally driven off.
The black ants have deadly stings,
which paralyze and eventually kill.
Below, on the forest floor,
the hemipteran bug searches for fallen ants.
It picks up the dead ants and sucks them dry.
Then, strangely, it sticks the corpses onto its back,
presumably camouflaging itself against predators.
The black ants, having driven off the red weaver ants,
now begin the task of cleaning up the tree.
Some descend to the base,
where they gnaw through the smothering creepers and kill them.
At the top of the tree, other worker ants clean up the leaves.
Beneath its protective silken mantle,
this caterpillar normally escapes the attentions of ants
and other predators and grazes in safety on the leaf.
But the black ants will have none of it,
and the caterpillar is evicted.
The ants clean up every piece of debris.
Cleared of all damaging insects and creepers,
the barteria can now compete effectively with other trees,
protected by its ants.
The ants benefit by using barteria's hollow branches
to tend their scale insects, their only source of food,
and to raise their young.
The red weaver ants make their way back to their nesting tree.
Their nests are compact structures of living leaves,
extraordinary nests built in an extraordinary way.
The worker ants use their own larvae to stitch the leaves together.
Squeezed gently like a tube of toothpaste,
the larva exudes a sticky thread.
The larvae are not harmed by this process.
Inside the nest, worker ants prepare a new winged queen for her nuptial flight.
Ants on the leaf outside beat out a warning to the workers inside
as their main predator, the tree pangolin, approaches.
The pangolin uses his long, sticky tongue to gather up the ants.
The scales of his body give excellent protection against their painful stings.
Most forest mammals are nocturnal.
The Anguantibo, a rare primate and cousin to the pato, forages only at night.
Despite his huge eyes, the Anguantibo has poor eyesight
and so relies on a keen sense of smell to locate food.
The Anguantibo is a rare primate.
Another strange inhabitant of this African forest is the pygmy flying squirrel.
It weighs less than an ounce.
The squirrels live in colonies of up to 30 inside hollow trees,
only emerging at night to forage for fruits.
Special wing-like membranes link its limbs, allowing it to glide short distances.
In forests like Kharap, where nutrients are scarce, trees which offer a home
to animals like the flying squirrel may actually benefit from being hollow.
Inside the tree, waste droppings from these animals act as a fertilizer.
This could be essential because, paradoxically,
this lush jungle grows on some of the world's poorest soils.
Almost all the nutrients are found in the first inch of soil.
It may seem incredible, but these enormous trees,
some 200 feet tall and perhaps a thousand years old,
just sit on the surface of the forest floor, supported by giant buttresses.
Their roots are often just below the leaf litter.
Dead leaves fall to the forest floor throughout the year.
Fungi break down and absorb vital nutrients from these leaves
and reduce them to skeletons.
Microscopic networks of fungal threads infiltrate the leaf litter
and feed on it, absorbing its nutrients.
It's from the fungus that the tree roots obtain their nutrients.
Some fungi weave a mantle of threads around the roots,
which passes on the essential minerals to the tree,
while receiving, in turn, a supply of carbohydrates.
This relationship is vital in returning nutrients from the leaf litter to the tree.
And when conditions are right, the fungal threads interweave
to form a fruiting structure, the mushroom.
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Because of the extreme age of forest-like crop,
many unusual relationships have evolved.
They all are of mutual benefit.
A solitary stink ant scavenges on the forest floor.
As the ant searches for food, it is infected by breathing in microscopic spores of a fungus.
In the days which follow, the fungus grows in its brain,
and the ant's whole pattern of behavior is changed.
For the first time in its life, it starts to climb.
Driven on by the growing fungus, it struggles to the top of the plant.
It sinks in its mandibles and dies.
Over the next few weeks, the fungus continues to develop,
feeding on the body of the dead ant.
Ants killed in this way are quite common.
From the orange tip, fungal spores are rained down to infect other ants.
Fungi are not the only organisms that break down plant and animal tissues.
Inside this fallen tree, a community of plants and animals is at work,
feeding upon the wood and breaking it down.
Fungi often enter first, creating chambers and channels,
which enable animals such as termites to enter.
Much of the fallen wood in this forest is broken down by termites.
However, they are unable to digest the wood themselves.
Inside the stomach of each termite, a mass of single-celled animals is at work.
They digest the dead wood the termite has swallowed and produce simple sugars,
food for the termite.
Without these animals, the termites would starve,
and this major root by which the nutrients locked up in the wood
are returned to the living forest would be blocked.
Beetle larvae are the first invaders of the heartwood.
With insatiable appetites, they force their way through the toughest wood,
opening up channels.
These channels are then used by other animals, including the driver ants.
Predatory driver ants are nomadic,
and their huge colonies roam over the forest floor in a constant search for prey.
Soldier ants protect the relentless column of workers.
There may be as many as 20 million ants in a single driver colony.
The sheer volume of what they consume is as much as any other predator in the forest,
and helps maintain the population balance.
It took this colony three whole days to cross this log.
The crystal clear water is almost devoid of nutrients
because the plants and soil organisms have been so successful in intercepting them
before they're washed into the river.
This huge community of plants and animals depends on the microorganisms of the forest floor.
With their help, the forest survives on some of the world's poorest soils.
Any upset in this fine balance could reduce the forest's ability to maintain itself,
and if the forest goes, only the poorest scrub could survive here.
Several months have passed, and the young eagle is now flying, but still being fed at the nest.
Its future as head of the food chain is closely linked to the survival of the forest community below.
A monkey skull, surprisingly perhaps, signals a healthy forest,
for monkeys are among the first to disappear if a forest is disturbed.
They and the rest of the forest community have responded successfully
to the challenges imposed by nature over millions of years,
but ironically, these responses have left them especially vulnerable
to the new challenges imposed by man and his modern technology.
Highly specialized, these species could not survive outside of the complex,
interdependent system that is the forest.
Africa has already lost more than half of her rainforests.
If forests like Kharap are not protected, the rest may disappear within 40 years.
So may most of the tropical forests of the world.
The resulting extinction of perhaps half of all the plants and animals on Earth
will alter irrevocably the course of evolution.
Nature is made possible by public television stations,
your gas company and America's gas industry, supplying natural gas across this land of ours,
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