The Living Planet

A strangely shaped mountain catching the clouds high above

the jungles of Venezuela.

Its summit rocks have been carved into a multitude of grotesque shapes.

The sculptor, an agent that is continuously at wor on much of the

landscape of our planet: Rainwater.

It washes over the rock, eroding it chemically.

It permeates the cracks, freezes, and chips it off in flakes and splinters.

As the water flows downwards, it starts on a long journey

that will take it from the mountains to the sea,

and here, with a leap of over 3,000 feet, the highest made by any river,

it forms the Angel Falls.

Our journey begins not far from that towering waterfall

on the high moorlands of Peru, 15,000 feet above the sea.

Water is a very extraordinary and very precious substance,

the only one on earth, apart from mercury,

which remains liquid at normal temperatures and pressures,

and because of that, it is an essential part of the bodies of all living organisms,

animals and plant.

Without it, life would come to an end.

But this particular water is a very rare kind.

97% of the water on earth is salty, the sea,

but this was distilled from the surface of the sea by the heat of the sun,

rose into the sky as vapour, condensed to form clouds and then

fell again as rain and snow to form streams of pure, fresh, sweet water.

But this particular stream is on its way to the sea a very long way away,

because these are the Andes, and this is one of the many streams

that can claim to be a source of the biggest river on earth, the Amazon.

The difficulties of living in this young and violent river are formidable.

Its waters are thick with powdered rock and mud, but they have

gathered few nutrients,

and they rush down the valley at tremendous speed.

Anything that lives here has to be a prodigious swimmer.

And these are. They're torrent ducks.

They exploit the swirls and eddies with consummate skill,

paddling with powerfull strokes of their large webbed feet.

They head always upstream, bracing themselves against rocks with their stiff

quilled tail,and using small horny spurs on the wrists of their wings

to give them purchase.

A pair owns a stretch of the river, working their way up it to the frontier

of their territory when they abandon themselves to the flood and are swept

downstream to begin all over again.

Anchored firmly to the rocks is a kind of moss.

Mosses are primitive, ancient plants that appeared on earth

long before flowering plants.

This torrent moss is found in young rivers and streams all over the world,

and wherever it grows, whether in the Andes or here in Europe,

it provides shelter for a multitude of insect larvae

In summer, these creatures will become transformed and fly briefly above

the river to mate, but most of their lives are spent underwater.

Some are streamlined against the current.

The caddis fly larvae live in protective tubes, the hollow stem of a reed,

or a construction of bits of wood stuck together with silk.

Some weight themselves down so that the current doesn't

shift them by building their shelters from heavy grains of sand.

The larva of the blackfly holds on to a pebble with its back end,

while it grabs at food particles that are swept past it

with the antennae on its head.

It grips the rock with a ring of hooks, but even if it loses its hold, all is not lost.

It has a lifeline of silk which it has attached to its chosen pebble.

Having hauled itself back, it now has to get a new grip.

First it spins a tiny pad of silk from a spinneret just beneath its mouth,

then it fixes its hooks into that.

The nets with which it collects its food are modified antennae,

and the larva brushes off what they catch with alternate flicks

of its mouthparts.

Not all caddis larvae live in solid tubes.

This one builds a construction that serves both as a home and

a food-gathering device.

It uses its silk to produce a funnel-shaped scaffold

of criss-crossing threads.

Undulating its body is a way of aiding its breathing,

for the movement speeds the flow of oxygen-bearing water through the funnel.

It holds on with the hooks at the back...

...leaving its jaws and front legs free to do the construction work.

This blackfly larva wasn't saved by its lifeline.

But the caddis fly larva itself, ferocious and art trapper though it is,

is also at risk.

The dipper relishes it.

Dippers live both in the rivers of North America and Europe.

Underwater, their swimming technique is quite different from

the torrent ducks in the Andes.

Its feet are not webbed like a duck's, so it propels itself with its wings,

flying underwater.

In similar cold, fast-flowing streams in North America

lives a kind of giant newt, the hellbender.

When it's young, it also, like a dipper, takes insect larvae,

but it can grow to over two feet long, and then it seeks much bigger prey.

A crayfish would suit it admirably.

A narrow escape. The crayfish saved itself at the last moment by a convulsive

snap of its tail, but the hellbender doesn't give up easily.

Both animals try to keep out of the current and habitually

creep into crevices.

But that sometimes is a mistake.

Streams that tumble down the sides of the valleys and feed young rivers

have their own population.

In Malaysia, the big-headed turtle clambers around the waterfalls,

using its tail as a prop.

In West African waterfalls, and nowhere else,

lives the extraordinary hairy frog.

Its so-called hairs are filaments of skin on its flanks which act as gills,

helping it to absorb oxygen from the water.

And, almost as unusual, it has claws that help it grip the slippery stones

The many sources of the Amazon began as rivulets on the eastern

flanks of the Andes.

Now, 5,000 feet lower down, each has grown beyond recognition

and cut its own zigzag valley.

White water, tumbling down the valley wall, joins the brown water

of a larger tributary,

heavy with mud and sediment.

And as it gets bigger and bigger, so it becomes more and more powerful.

It's the dry season at the moment and the river is comparatively low.

But during the rains, when it's in spate, its waters rise up over here

and the sheer volume and weight and force of them can shift boulders

the size of these.

The volume and speed of its waters are not the river's only weapons.

It also has teeth.

And in this empty rainy-season part of its bed, you can see them.

Sand and gravel, fragments of rock that have been eroded from higher

up in its course

and which the river hurls with enormous force at the rocks of its river bed.

With such tools, it can carve away the sides of mountains.

Young, vigorous rivers transform the land, demolishing the mountains,

breaking down the debris into smaller and smaller particles and carrying

them away downstream.

This river in China is perpetually so turbid that it's called the Huang Ho,

the Yellow River.

It carries a bigger load of sediment than any other river in the world.

During floods, each cubic yard of water contains over 2,000 pounds

of soil and pulverised rock.

Rivers in the full vigour of their youth are terrifyingly strong.

They roll great boulders along their beds,

they cut away at the banks, undermining trees which crash into

the waters and are swept away.

When a river encounters a band of unusually hard rock, such as an

ancient flow of basalt lava, its progress is temporarily slowed.

It spreads out across the barrier and then tumbles over the front edge.

So are formed some of the loveliest cascades.

These are the falls of Iguacu on the border of Brazil and Paraguay.

They can't compare in height with the Angel Falls,

but in terms of the volume of water that passes over them,

they are incomparably bigger.

The falling waters pound away at the base of the falls,

undercutting the basalt until blocks split off the face.

So the falls steadily work their way upriver, leaving downstream a deep

gorge, and animals live even here, within the falls themselves.

Swifts perch on the rock face behind the cascade.

Every evening they congregate high above Iguacu.

After a day of hawking for insects, they're ready to roost.

And where safer than behind a screen of falling water?

Some dive down with such speed that they shoot right through the fall.

And now the river has left the mountains far behind

and has changed its character considerably.

It's bigger, it's broader, and its waters carry not only sand and gravel

but rich nutrients washed in from its vegetation-covered banks.

And after it's gone over its last rapids and tumbled over its last fall,

it becomes a very different river indeed.

It's middle-aged: Ampler, less violent, more sluggish and richer.

On the banks of the Amazon tributaries, the jungle stands thick.

Birds like the sun bittern stalk quietly in search of a meal.

Huge fish cruise through the slow waters.

The arapaima, one of the largest of freshwater fish,

grows over six feet long.

The Amazon contains over 3,000 different kinds of fish.

That's more than live in all the Atlantic

Rays almost certainly evolved in the sea,

but this species has managed to make the change to fresh water

and lives high up the Amazon.

Many fish have evolved here in fresh water

and have become suited to all its variations of depth, speed and chemical

composition, to muddy water and to clear, to stretches that are

thick with plants and places where there are none.

Their variety is enormous.

Take, for example, just one family: The catfish.

They're bottom-dwelling fish, with feelers or bubbles on their snouts

that have sense organs on them, so the fish can feel and taste

their way through the thick, muddy water or at night.

There are small ones and immense ones,

some that give electric shocks and others that swim upside down.

Those who lives in fast-flowing waters have suckers on their chins

or undersides with which they cling to rocks.

In South America alone, there are 1,200 different species of catfish.

In these crowded waters, many fish give special protection to their young

for the first few weeks of their lives.

This fish, the discus, goes even further.

It provides its fry with special food.

The parents exude a nutritious slime from their skin

and the young graze over their flanks, feeding on it.

After a week, they're big enough to feed on small particles

floating in the water.

These are now a month old and have already assumed the disc-like

shape of their parents.

They're becoming independent, but they've strayed past the lair

of an electric eel

The eel has poor eyesight,

but it detects the presence of objects around it with short electric discharges,

a kind of radar.

It rises for a gulp of air. This time the young discus

seem to have escaped detection.

But the eel can also produce a major electric shock which stuns its prey.

It releases its capture. Perhaps so small a fish is not worth eating.