Beneath billowing clouds,
in China's far southwestern Yunnan province,
lies a place of mystery and legend.
Of mighty rivers and some of the oldest jungles in the world.
Here, hidden valleys nurture strange and unique creatures,
and colourful tribal cultures.
Jungles are rarely found this far north of the tropics.
So, why do they thrive here?
And how has this rugged landscape come to harbour the greatest natural wealth in all China?
In the remote southwest corner of China,
a celebration is about to take place.
Dai people collect water for the most important festival of their year.
The Dai call themselves the people of the water.
Yunnan's river valleys have been their home for over 2,000 years.
By bringing the river water to the temple,
they honour the two things holiest to them -
Buddhism and their home.
The Dai give thanks for the rivers and fertile lands which have nurtured their culture.
Though to some it might seem just an excuse for the biggest water fight of all time.
Dai lives are changing as towns get bigger and modernise
but the Water Splashing Festival is still celebrated by all.
The rivers which lie at the heart of Dai life and culture
flow from the distant mountains of Tibet,
southward through central Yunnan in great parallel gorges.
The Dai now live in the borders of tropical Vietnam and Laos,
but their legends tell of how their ancestors came here
by following the rivers from mountain lands in the cold far north.
Lying at the far eastern end of the Himalayas,
the Hengduan mountains form Yunnan's northern border with Tibet.
Kawakarpo, crown of the Hengduan range, is a site of holy pilgrimage.
Yet, its formidable peak remains unconquered.
Yunnan's mountains are remote, rugged and inaccessible.
Here the air is thin and temperatures can drop below minus 40 degrees.
This is home to an animal that's found nowhere else on Earth.
The Yunnan snub-nosed monkey.
It's found only in these few isolated mountain forests.
No other primate lives at such high altitudes
but these are true specialists.
These ancient mountain dwellers have inspired legends.
Local Lisu people consider them their ancestors,
calling them "the wild men of the mountains".
During heavy snowfalls, even these specialists cannot feed.
It seems a strange place for a monkey.
Between snows, the monkeys waste no time in their search for food.
At this altitude, there are few fruits or tender leaves to eat.
90% of their diet is made up of the fine dry wisps of a curious organism.
Half fungus, half plant - it's lichen.
How have monkeys, normally associated with lowland jungle,
come to live such a remote mountain existence?
This is not the only remarkable animal found within these isolated high peaks.
A Chinese red panda.
Solitary and quiet, it spends much of its time in the tree tops.
Despite its name,
the red panda is only a very distant relative of the giant panda.
It's actually more closely related to a skunk.
But it does share the giant panda's taste for bamboo.
Southwest China's red pandas are known for their very strong facial markings
which distinguish them from red pandas found anywhere else in the Himalayas.
Like the monkeys, they were isolated in these high forests
when the mountains quite literally rose beneath them
in the greatest mountain-building event in recent geological history.
Over the last 30 million years,
the Indian subcontinent has been pushing northwards into Eurasia.
On the border between India and Tibet
the rocks have been raised eight kilometres above sea level,
creating the world's highest mountain range, the Himalayas.
But to the east,
the rocks have buckled into a series of steep north-south ridges,
cutting down through the heart of Yunnan,
the parallel mountains of the Hengduan Shan.
These natural barriers serve to isolate Yunnan's plants and animals
in each adjacent valley.
While the huge temperature range between the snowy peaks
and the warmer slopes below
provides a vast array of conditions for life to thrive.
Through spring,
the Hengduan slopes stage one of China's greatest natural spectacles.
The forests here are among the most diverse botanical areas in the world.
Over 18,000 plant species grow here,
of which 3,000 are found nowhere else.
Until little more than a century ago, this place was unknown outside China.
But then news reached the West
of a mysterious, hidden world of the orient.
Hidden among the mountains, a lost Shangri-la paradise.
Western high society, in the grip of a gardening craze,
was eager for exotic species from faraway places.
This gave rise to a new breed of celebrity adventurers,
intrepid botanist-explorers known as "the Plant Hunters".
Yunnan became their Holy Grail.
The most famous was Joseph Rock, a real life Indiana Jones.
Remarkable film footage captured his entourage on a series of expeditions,
as they pushed into the deepest corners of Yunnan.
In glorious colour he recorded the plant life he found
on special photographic glass plates.
Sending thousands of specimens back to the West,
the Plant Hunters changed the gardens of the world forever.
Rock's success was born of a massive effort.
For, to find his Shangri-la,
not only had he to traverse endless mountain ranges,
but some of the deepest gorges in the world.
The Nujiang is called The Angry River.
This 300-kilometre stretch of raging rapids
is as much a barrier to life as are the mountains above.
WAVES CRASH
But the plant hunters weren't the first people to travel here.
Along the Nujiang,
less than 30 rope crossings allow locals passage across the torrents.
Tiny hamlets cling to the slopes.
This morning, it's market day,
drawing people from up and down the valley.
PIG OINKS
GOAT BLEATS
Hanging from simple rope slings,
people have been using the crossings for many hundreds of years.
In such narrow, precipitous gorges
it's by far the easiest way to get around.
Once across, the steep sides mean it's still a hike.
Many trek for hours by foot before they get to the market.
The immense valley is home to over a dozen ethnic groups.
Some, like the Nu people, are found only here.
The markets bring the mountain tribes together.
To continue his expeditions,
Rock had to get his entire entourage across the giant Yunnan rivers.
He commissioned especially thick ropes made from forest rattan
and filmed the entire event.
With yak butter to smooth the ride, 40 men and 15 mules made the journey.
Not all made it across.
On the far side of the great Nujiang gorge,
the Plant Hunters made a remarkable discovery.
Far from the tropics,
they seemed to be entering a steamy, vibrant tropical jungle,
the forest of Gaoligongshan.
The flora here is unlike anywhere else in the world.
Next to subtropical species, alpine plants grow in giant form.
Crowning the canopy, rhododendrons, up to 30 metres high.
In April and May, their flowers turn the forests ruby red,
attracting bird species found only here.
Constant moisture in the air means that the branches are laden with flowering epiphytes,
fiercely guarded by tiny sunbirds, unique to these valleys.
Nectar feeders, these are the humming birds of the Old World tropics.
The forests of Gaoligongshan are home to some of China's rarest wildlife.
This is a female Temminck's Tragopan.
She has a colourful male admirer.
He's hoping to woo her with his peculiar peekaboo display
but she's not about to be rushed.
His colourful skin wattle reflects more light than feathers do.
To her, this is like a neon sign.
Seeing his chance, the male makes his move.
Constant moisture in the Gaoligongshan forests
means that throughout the year there are always fruits on the trees.
Such abundance of food encourages a high diversity of fruit eaters
more commonly found in the tropics.
The black giant squirrel is found only in undisturbed rainforest.
At close to a metre in length, it's one of the world's largest squirrels.
The mystery is that these forests are growing well outside the tropics.
By rights, none of this jungle, or its animals, should be here.
These are bear macaques.
They're found only in tropical and sub-tropical jungle.
With a tiny home range of just a few square kilometres,
they depend on the abundant fruit
that only true rainforests can provide all year round.
To the European plant hunters,
these northern rainforests must have seemed a fantastic and mysterious lost world.
Yet, when they came here, they would have found beautifully constructed ancient stone pathways
on which the forest could be explored.
Winding westwards into the hills,
these were once some of the most important highways in Asia,
the southwestern tea and silk road.
Built thousands of years ago,
the southwestern tea and silk road gave access to the world beyond China's borders,
carrying tradesmen and travellers from as far away as Rome.
Wars were fought over access to this tiny path,
the only sure route in or out of China,
that was guaranteed to be clear of snow all year round.
So, what causes Gaoligongshan's strange and remarkable climate?
In late May, gusts of wind arrive,
bringing with them the key to Gaoligongshan's mystery.
The winds are hot and saturated with water.
They come all the way from the Indian Ocean.
Channelled by Yunnan's unique geography,
they bring with them the moisture of the tropical monsoon.
The giant river valleys, created millions of years ago,
act like immense funnels.
The gorges are so deep and narrow,
that the moist warm air is driven right up into the north of Yunnan.
The result is rain, in torrents!
Four months of daily rainstorms sustain luxuriant vegetation.
The arrival of the monsoon
awakens one of the forest's most extraordinary moisture-loving inhabitants.
The crocodile newt is one of the most unusual of the many amphibian species found here.
As the rains arrive, they emerge to mate.
The newts are said to leave an odour trail that potential mates can follow.
The crocodile newt gets its name from the bumps along its back.
These are its defence.
If grabbed by a potential predator,
the tips of its ribs squeeze a deadly poison from the bumps.
The deluge wakes another forest inhabitant.
This one is particularly astounding in its vigour!
It can grow up to a metre a day,
fast overtaking the other plants around it.
The taller it grows, the faster its growth rate,
so that in a matter of days it towers above the undergrowth,
and continues reaching for the sky.
Not bad for what is essentially a grass.
It's bamboo.
Given the chance,
bamboo will create immense forests, dominating entire areas.
Bamboo forests occur across southwest China,
all the way to Shanghai.
But probably the highest diversity of bamboos in the world
is found on the hills and valleys of Yunnan.
Though incredibly strong, bamboos have hollow stems,
a perfect shelter for any creatures which can find a way in.
This entrance hole was made by a beetle
but it's being used by a very different animal.
A bamboo bat.
The size of a bumblebee, it's one of the tiniest mammals in the world.
The entire colony, up to 25 bats,
fits into a single section of bamboo stem, smaller than a tea cup.
It's quite a squeeze!
Half the colony are babies.
Though barely a week old, they are already almost as big as their mums.
Feeding such a fast-growing brood is hard work.
The mums leave to hunt just after dusk each night.
Back in the roost, the young are left on their own.
Special pads on their wings help them to grip on the bamboo walls -
most of the time.
The young bats use the extra space to prepare for a life on the wing
by preening and stretching.
Packed in like sardines, they would make an easy target for a snake.
But the snake has no chance of getting in.
The entrance is thinner than the width of a pencil.
When the mothers return,
they can push through the narrow entrance only because of their unusually flattened skulls.
But it's still a squeeze.
Bamboos are exploited in a very different way by another forest dweller.
Fresh bamboo shoots are an important forest crop.
Ai Lao Xiang is of the Hani tribe,
from the mountain village of Mengsong.
Roasted, the tender shoots he gathers will make a tasty dish.
The Hani have many uses for the different bamboos they grow and find in the forest around.
Though flexible enough to be woven,
bamboo has a higher tensile strength than steel.
Succulent when young,
in maturity it's tough and durable, ideal for making a table
and strong enough for a pipe to last a lifetime.
The people of southwest China
have found an extraordinary number of ways to exploit this most versatile of plants.
THEY SPEAK IN NATIVE LANGUAGE
Part of bamboo's phenomenal success
is that it's so tough that few animals can tackle it.
Yet, bamboo does come under attack.
A bamboo rat.
Feeding almost exclusively on bamboo,
they live their entire lives in tunnels beneath the forest.
The thinner species of bamboo are easy to attack and pull below.
She has a fantastic sense of smell
and can sniff out the fresh growth through the soil.
Bamboo spreads along underground stems.
By following these, new shoots are found.
Once a shoot is detected,
she snips it free and drags it down into her burrow.
This female has a family.
At just a few weeks old,
the youngsters can already tackle the hardest bamboo stems
and are eager to try.
Bamboo's tough reputation is such,
that another bamboo specialist was known by the Chinese as, "The Iron Eating Animal".
The giant panda is famous for its exclusive diet.
Giant pandas are thought to have originated in southwest China, millions of years ago,
but they are no longer found in Yunnan.
Recently, their specialised diet has had dire consequences.
Bamboo has a bizarre life cycle,
flowering infrequently, sometimes only once every hundred years or so.
But when flowering does occur, it's on a massive scale,
and it's followed by the death of all of the plants.
Sometimes an entire bamboo forest may die.
In undisturbed habitat, pandas simply move to another area
where a different bamboo species grows.
But as human activity has fragmented their forest home,
pandas find it increasingly hard to find large enough areas in which to survive.
Wild pandas are now found only in the forests of Central China,
far to the east.
But in the hidden pockets of lowland jungle in Yunnan's tropical south,
live one of China's best-kept wildlife secrets.
DEEP BELLOW
The wild Asian elephant.
Elephants once roamed across China as far north as Beijing.
But it's only in the hidden valleys of Yunnan that they have survived.
Elephants are the architects of the forest.
Bamboos and grasses are their favourite food
but saplings, tree leaves and twisted lianas are all taken, with little care.
As they move through the forest,
the elephants open up clearings, bringing light to the forest floor.
This has a major impact on their home.
The richest forests are now known to be those which from time to time experience change.
The Jinou people are incredibly knowledgeable about their forests
and claim to have uses for most of the plants that they find there.
They have names for them all,
those good for eating and some which even have strong medicinal qualities.
By working here, the Jinou play a similar role to the elephants,
opening up the forest, bringing space, light and diversity.
Green, fast growing species are encouraged.
Insects are in high abundance here,
together with the animals that feed on them.
Knowledge of the forest enables the Jinou to find not just plants,
but other tasty forest food too.
Forest crabs are common here, feeding on the abundant leaf litter.
This will be a tasty addition to the evening meal.
Flowing through Yunnan's southern valleys,
the once angry rivers are now swollen,
their waters slow and warm.
These fertile lowland valleys are the home of the Dai.
The "People of the Water"
live along streams which originate in the surrounding hills.
Each family keeps a kitchen garden
modelled on the multi-layered structure of the surrounding forests,
which the Dai hold sacred.
The gardens are made more productive by inter-planting different crops.
Tall, sun-loving species give shelter to plants which thrive in the shade.
As companions, the plants grow better.
Yunnan's forests are home to more than a dozen wild banana species
and banana crops grow well in most Dai gardens.
The huge banana flowers are rich in nectar for only two hours a day,
but it's enough to attract a range of forest insects, including hornets.
With their razor sharp mandibles,
they find it easy to rob the flowers of their nectar.
But hornets are predators too.
They hunt other insects and carry them back to their nest.
An ideal target,
but this grasshopper is no easy meal.
There may be a price to pay.
The Dai men, Po and Xue Ming, take advantage of a hunter's instincts.
A hornet sting is agony.
But for now it's distracted, intent on cutting away
a piece of grasshopper small enough to carry back home.
Success!
The white feather hardly slows the hornet,
and, more importantly,
it can be seen.
Now the hunter is the hunted.
So long as Po and Xue Ming can keep up!
Back at the nest, the other hornets
immediately begin to cut the feather free.
But it's too late. The nest's location has been betrayed.
The relationship between the forest animals and the people who live here
was never one of harmony.
Yet the fact that the Dai and other ethnic groups considered these forests to be sacred,
has ensured their survival
and now many have been given extra protection as nature reserves.
Ingenuity and hard work pays off at last.
The fattened larvae are considered a delicacy by the Dai.
Although these forests have experienced a great deal of change,
they are still host to some ancient and incredible relationships.
Almost 60 centimetres high,
this is the immense flower of the Elephant yam.
Locals call it the "Witch of the Forest".
As the stars rise, the witch begins to cast her spell.
The forest temperature drops, but the flower starts to heat up.
A heat sensitive camera reveals the flower's temperature
rising by an incredible ten degrees Celsius.
At the same time, a noxious stench of rotting flesh fills the forest air.
As the flower's heat increases, a cloud of odour rises up.
The foul perfume carries far and wide.
It doesn't go unnoticed.
Carrion beetles arrive on the scene.
The beetles come in search of a feast of warm decaying flesh,
but they've been tricked.
Slippery sides ensure they tumble
straight into the centre of the monster flower.
There's not enough room to spread their wings
and the waxy walls ensure that there's no escape.
But there's nothing sinister in the flower's agenda.
The beetles will be its unwitting helpers.
Dawn arrives,
but the flower remains unchanged, holding its captives through the day.
As the second night falls, the witch stirs again.
In a matter of minutes, the flower's precious golden pollen
squeezes from the stamens and begins to fall,
showering onto the captive beetles below.
Now, at last, the prisoners are free to go.
The flower's wall changes texture, becoming rough
to provide the ideal escape ladder.
Loaded with their pollen parcels, they can now climb to freedom,
just as other forest witches are beginning to open.
Seduced by the irresistible perfume, the beetles are sure to pay a visit,
so ensuring pollination,
and another generation of incredibly big, smelly flowers.
As dawn arrives, forest birds claim their territories in the canopy.
BIRDSONG
But there's one call which stands out among the rest -
virtuoso of the forest symphony.
STRANGE CALL RINGS OUT
It's a gibbon.
UNDULATING CALL CONTINUES
Living on a remote mountain range in south central Yunnan
is one of the few remaining wild gibbon populations in China.
The black-crested gibbons of Wuliangshan.
They are confined to these forest mountains,
so remote and steep that few hunters ever come here.
The Wuliangshan gibbons are unusual for their social structure.
Most gibbons live in small family groups
consisting of a mating pair and their offspring.
But these gibbons exist in troops.
One male can have two or sometimes three females
and all of these can have young.
Often even the juveniles stay in the community.
BABY SQUEAKS
Rarely glimpsed, this baby may be only a day old.
If it survives infancy, then it has a promising future
in these few valleys with its close-knit family.
GIBBON CALLS RING OUT
Gibbon song once inspired the ancient poets of China,
their glorious calls echoing far across the hills.
But now, new, strangely quiet forests have come to Yunnan.
These trees are here to produce an important and valuable crop.
When the tree bark is scored, it yields copious sticky sap,
so bitter and tacky that nothing can feed on it.
It's the tree's natural defence against attack.
It's collected daily,
bowl by bowl.
It will be boiled and processed into one of the most important materials
to a fast developing nation - rubber.
The expansion of the rubber forests began in the '50s when China,
under a world rubber embargo,
had to become self-sufficient in this vital product.
Beijing turned to the only place where rubber could grow,
the tropical south of Yunnan.
With efficiency and speed,
some of the world's richest forests were torn up and burned.
Replaced with mile upon mile of rubber plantation.
But there was a problem for the rubber growers.
While Yunnan's unique natural forests
can survive on the valley slopes which stretch to the north...
..just one severe frost will kill off these delicate rubber trees.
So Yunnan's terrain puts a limit on how far the plantations can spread,
halting at least their northwards advance.
The jungles of Yunnan are increasingly under pressure.
HORN BEEPS
New roads criss-cross the tiny remnant forests,
the infrastructure needed for trade, industry and, increasingly, tourism.
It's a meeting of two very different worlds.
ELEPHANT TRUMPETS
That elephants still exist in China is remarkable
considering the immense pressures
in the world's most highly populated country.
The 250 or so wild elephants which still live here
are now strictly protected.
And each year young are born to the small herds.
If elephants were to survive anywhere in China,
it could only have been here, in Yunnan.
The same mountains which guide the monsoon rains north
and which made Joseph Rock's journeys so treacherous,
also guarded Yunnan's forests and its wildlife.
ELEPHANTS GRUNT AND TRUMPET
For the moment, the mountains are still carpeted in a rich green,
deceptive in its simplicity.
Below the canopy lies perhaps China's richest natural treasure.
Delicate and unique,
a complex world of intricate relationships
between animals, plants and people, beneath the clouds.