New Worlds The Living Planet

The planet on which we live is in a state of perpetual change.

From cracks in its surface, molten rock is continually erupting.

The forces that drive this lava to the surface also cause the continents

to move round the globe, millimetre by millimetre, over thousands of years.

When they collide, the buckling, contorted rocks are pushed up

into great mountain ranges.

But just as they rise, so are they cut down by the erosion of ice

and snow and rushing water.

At the poles, where the sun's rays strike the glob only obliquely, it's bitterly cold.

Here glaciers grind their way across the land, gouge out deep valleys

and flow down into the sea.

At the equator, where the sun strikes the Earth four-square, the land is baked.

Over centuries, the amount of rain falling on it has varied.

As it diminishes, so the forests have dwindled and been

replaced by grassland.

And grassland, if it dries still further, turns to desert.

Throughout all these changes, living creatures have evolved

?with a speed that has matched that of the changing landscape.

In the hot deserts, animals have evolved ways of living in oven-like temperatures

without drinking any liquid whatsoever.

In the cold deserts around the poles, other creatures, with the ability to

generate their own internal heat, have grown insulating coats

of fur and fat so that they are not frozen to death.

Human beings, one of the last species of large animal to appear on the planet,

have spread with extraordinary speed to all corners of the globe.

They've be able to do so not so much because their bodies have changed to

match different extremes but because they've used their skills

and intelligence to exploit the adaptations of other living creatures.

The Eskimos survive in the Arctic by keeping themselves warm

with the skins of polar bears and seals.

In the equatorial jungles of the Amazon, the Indians have learned where to find

and how to collect everything they need to sustain themselves.

Even though today they may cook in metal pots traded from the

outside world, they still know how to make pottery from the clay.

In the hot deserts of southern Africa, the Bushmen survive droughts

by tapping the stores of liquid held in the bodies of animals

and the roots and the stems of plants.

Immediately after the rains, however, they can collect water

from natural hollows, but even that takes knowledge and skill.

Indeed, human beings, for nearly all the half-million year of their

existence as a species, have lived simply by gathering wild plants

and hunting wild animals.

And 10,000 years ago, people were doing so here in the Middle East,

just as they were everywhere else.

In these forests, there's quite a lot to eat.

There are pistachio nuts and wild almonds and acorns and juniper berries.

And 10,000 years ago there were quite a lot of wild animals -

wild goat, wild pig, wild horses, giant wild cattle and gazelle.

Even so, there are hardships to be endured. There could be torrential rains.

At night it can get crushingly cold and there could be snow.

And during the day it gets bakingly hot.

But about 9,000 years ago, man took a crucial step.

Until then, the environment through evolution had shaped his body,

as it had shaped the bodies of all animals.

But now, uniquely, man turned that around.

He began to change the environment to suit himself,

and one of the places where he first did so is in that valley down there.

This is Beidha in Jordan, and here were found the remains of one of

mankind's earliest villages.

This was no temporary encampment, but a permanent settlement

with alleys and houses of stone built adjoining one another.

They were half-dug into the ground, the floor and walls were covered with

a plaster of mud and lime,

and in the walls there were posts which supported a roof of thatch

which probably just cleared the top of the wall so that light could get inside.

So the people had created a snug home, protected from the rain and the sun,

a place where mothers could bear their children in safety.

There are lots of grinding stones, querns, here, in which the people

ground the seeds of grass,

a kind of wild barley that grows abundantly hereabouts.

They'd long since discovered that you could take such grass seeds

and scatter them on the ground and produce a crop.

Indeed, they'd been doing just that with the seeds of another wild grass,

wheat, for many centuries.

And now they were settled, it was inconvenient to have to scour the

countryside to look for places where the grass just happened to grow.

Much better to throw it onto the ground nearby the village, where they

could watch the growing crop, make sure that wild animals

didn't plunder it, and where it was convenient to gather.

So these people became farmers.

The people were also meat-eaters, and in this one small chamber

have been found great quantities of the bones of wild goat, like this.

Domesticating animals must have been very much more difficult than

domesticating plants.

But in fact, the first steps towards doing so were probably taken

many centuries earlier when the people were still nomads.

A way in which that might have happened can be seen going on today

amongst the Lapp peoples in Scandinavia.

This is the most northerly living of all deer.

It's found right round the Arctic wherever there is land.

In America, it's called the caribou, in Europe, reindeer.

In North America the caribou are completely wild,

but here in northern Scandinavia they are, to some degree at least,

domesticated.

Man has managed to achieve that by becoming a nomad himself.

The reindeer during the winter have to keep on the move in a continuous

search for something to eat, and the Lapps, they want to keep an eye on

their herd and maintain their possession to it, have to move with them.

Traditionally, they do so on skis. Indeed, skis originated in this part

of the world.

But today the herdsmen are fully up to date with modern technology.

The reindeer's winter food is a kind of lichen which they find

growing beneath the snow.

When the reindeer were completely wild, young stags as they mature

would wander away from their parental group, taking a few

young females with them.

But the Lapps regarded the offspring of THEIR herd as their property.

So to prevent them being lost, they castrated the young males.

The few they left unmutilated in order to breed were those they

thought most likely to remain unaggressive and disinclined

to wander, even when adult.

So, consciously or unconsciously, the Lapps over centuries have

changed the reindeer from a nervous creature living in small family groups

to one that is so docile it can be kept in herds thousands strong

and can be moved from one snow slope to another simply by leading

the way with a stag on a halter.

It may well be that in some such way as this, the people who lived

9,000 years ago in the village of Beidha gradually turned the wild

goats of the surrounding mountains into tamed domesticated ones.

The techniques of domestication and maybe the domesticated

animals themselves, slowly spread westwards across Europe.

7,000 years ago, the people living in France had their own herds.

And around 6,000 years ago, the techniques and even perhaps

the herdsmen with some of their stock crossed the channel into Britain.

They must have landed somewhere in southern England,

but the land they found didn't look like this.

Like nearly all the rest of Britain, it was covered in trees.

There were people already here living in the forests, gathering fruit and nuts

and hunting the wild animals, deer and wild oxen.

But they hadn't changed the woodlands of Britain

any more than the Amazonian Indians have changed the jungle.

But these new arrivals did. They began to clear the forests

to make way for their farms.

So this landscape of the South Downs is not natural. It's their creation.

The people cut down the forests with stone axes.

And then the teeth of their flocks kept the land open.

Grazing sheep still prevent the seedlings of trees from growing

and keep the pastures clear for cowslips and clover, orchids and

buttercups, pipits and skylarks.

This was the beginning of a process that was to transform Britain.

Much of our apparently wild landscape is in fact man-made.

The Norfolk Broads, that wilderness of shallow lakes, reed beds and

winding waterways, are not natural basins but vast pits, dug by men

collecting peat some 600 years ago, that have subsequently flooded.

Many of the upland moors of northern England and southern Scotland

were cleared of their forests thousands of years ago,

but during the 19th century, men encouraged heather to grow there

by setting light to the moors by regular intervals,

for heather is the food of grouse,

and men want flocks of grouse for their guns.

Indeed, almost the only part of Britain that remains free of human influence

is the land over 2,500 feet high that is of little practical use to people.

It was scraped clean of soil by glaciers during the Ice Age 10,000 years ago

and still remains stony and barren.

As we transformed the landscape, of Britain, so we also rapidly

altered the community of animals that lived here.

Those that didn't suit us, we got rid of.

Brown bears were once common, but they were regarded as dangerous

and they could give good sport if they were baited with dogs

The last British bear was killed in the 10th century.

Wolves preyed on domesticated flocks and herds and even

threatened people.

The last English wolf had been killed by the year 1500

and the last Scottish one by the middle of the 18th century.

Beavers were hunted not so much because of the damage they did

to the woodlands, but because their fur was so highly valued.

They had all gone by the 13th century.

Wild boar were once common in British woods,

grubbing up roots and bulbs, munching acorns and beech nuts.

But boars could be aggressive and dangerous, and the sows

and particularly the piglets made good eating.

By the 17th century, there were none of these left either.

The elk, known in America as the moose, once lived here too,

but it had been hunted into extinction even before the Romans arrived.

Men also introduced animals to Britain.

The Normans brought fallow deer from Europe.

And rabbits.

At first these creatures were carefully guarded in enclosures,

for they were valued for their fur and meat.

They only became really common in the countryside during the 19th century.

Pheasants are Asian birds, and were brought here soon after

the Norman Conquest.

Other introductions, however, were unintentional and much less welcome.

The house mouse from the Mediterranean may well have been

the first animal of all to be brought to Britain by man,

for the Romans found it living in British villages.

And other, much bigger animals were living around the settlements

of those early British tribes.

Aurochs, the giant cattle whose images were painted on the walls of

French caves during prehistory, also roamed in British forests.

By Roman times, some had already been domesticated,

and one of the early strains derived from them still survives

in the Cheviot Hills.

This herd at Chillingham was penned in a great park during the 13th century,

and has lived here ever since, with scarcely any interference

from human beings.

The animals may well be very similar to those that wandered

around the farms during Roman times.

They're formidable animals, very different from the gentle

Friesian of today.

One great bull rules the herd. He mates with all the cows

and fights every young male who challenges him.

Eventually, after two or three years,

he will lose and surrender his place to a younger, more vigorous animal.

Having changed a wild animal into a relatively docile one by

selective breeding, farmers now used the same techniques to modify

the animal's body.

They wanted meat, and soon they produced a very different-looking

kind of beast.

These portraits, commissioned by proud breeders 100 years ago,

show clearly that the characteristics they valued in their cattle

then are the same as those we prize today.

Today's bulls have such stunted legs that they can't run fast

to chase away a rival.

Many don't even have horns with which to fight a courtship battle.

But these won't be permitted to mate with a cow anyway.

Their semen will be taken from them and injected into cows by syringe,

so that each of them, without moving from his stall,

may father thousands of offspring on the other side of the world.

Under intensive feeding, such cattle can put on two pounds a day

and grow so fast that they can be profitably slaughtered within a year.

The new breeds of pig, direct descendants of the wild boars of the

European forests, now grow five times faster than their wild cousins

and are ready for slaughter within only six months.

Turkeys are descended from wild birds that lived in Central America.

They are produced entirely by artificial insemination and have

been turned into creatures that will live not in small family groups

but immense congregations.

Chickens, originally birds of the Asian jungles, have been converted

into egg-producing machines that can lay over 300 eggs a year.

The same techniques of selective breeding produced our food plants,

using species from all over the world.

The potato came from the Andes, where it was grown by the Incas.

The pea is a European plant first cultivated by the Italians

in the 16th century.

Beans came from Mexico, rhubarb from China, beetroot from Germany.

And this plant was first cultivated in the 7th century in Afghanistan,

taken from there to North Africa, then brought by the Moors into Europe,

where it was cultivated by the Dutch to produce...this, a carrot.

But wild plants from the family that is perhaps the most important

to man for food don't grow in this allotment because they would be

regarded as weeds - the grasses.

The grass we call rice was domesticated in Asia some

7,000 years ago, at about the same time that people were learning

to cultivate wheat in the lands around the Mediterranean.

Over the centuries, the people of Asia have perfected the techniques

of growing one kind of rice in flooded terraces.

And they do so with such skill that the rice will flower and ripen

and produce heads of swollen seeds several times a year.

As mankind's population grew, so more and more of the land

had to be taken into cultivation.

Today, 11% of all the arable land on earth is devoted to growing

just this one species of grass.

Now more than 2,000 million people depend on it,

half the population of the world.

In the western world, people still prefer the kind of grass they first learned

to eat during prehistory, but that too they have transformed.

Today's wheat grows tall, uniform and dense, so it can be easily

harvested by machines.

Selective breeding techniques have greatly increased its yield.

Even since the 1940s, its productivity has been doubled.

Today it bears ten times the weight of seeds on each stem than does its

wild ancestor that still grows in the parched lands of the Middle East.

But this change has a price. Wheat like this can't even reproduce

itself now without man's aid.

It's true that it is largely immune to pests like moulds and rusts,

but moulds and rusts also evolve very quickly,

naturally, into forms which can attack the new strains.

So farmers have to change the strain that they grow on average

about every ten years.

Today, in North America, over half the wheat comes from just four strains.

Were plant breeders to fail to produce new varieties from wild species,

then fields like this could be devastated and the western world

would starve.

To grow the vast quantity of grain needed by mankind's ever

increasing population, huge areas of the most fertile lands on Earth

have been turned over to its cultivation.

Gone are the rich communities of grasses and other small plants,

that once lived here together with hundreds different kinds

of insects and small creatures.

Now over thousands of square miles, all other plants and all other large animals,

except human beings, are rigorously excluded.

Intruders are poisoned or shot.

So mankind has introduced to the earth a completely new type

of environment, a monoculture, one which contains,

to all intents and purposes, just one species.

And this is another of mankind's virtual monocultures.

The species that proliferates here and congregates of its own accord

into dense swarms numbering millions is Homo sapiens himself.

The tallest building he's constructed so far is in Chicago, the Sears Tower.

It stands 1,454 feet high.

12,000 people daily come to work in it, and they live in an

artificial microclimate in which the temperature and humidity

are controlled by computers.

The whole structure is built of artificial man-made materials,

a framework of steel, with black-skinned aluminium

and bronze-faced glare-reducing glass forming a shell around it.

In such an environment as this, you might suppose that animals

and plants could have no place.

But not so.

Many human beings, it seems, don't wish to live totally out of

contact with other living species.

Once again, people have moulded their animals to match their particular

whim and fancy, altering their size, their proportions, their fur.

Even their smells.

Dogs first associated with man when he was a nomadic hunter,

accepting him as a leader in a chase, helping him to track and pull down

his quarry, and taking a share in the spoils, but now

that man no longer hunts, his dogs must play a very different role.

Cats are not, in the wild, social animals like dog

but solitary hunters with strong territorial instincts.

They probably decided of their own accord to move into peoples houses

and hunt rats and mice, and people accepted them because they

performed this useful service, and because they're so endearing,

but to this day they have remained independent operators,

aloof and haughty, even when people have bred them to exaggerate

the most cuddlesome of their characteristics.

PA: 'Five tremendous cats, the best of their own varieties.

'Our congratulations to the winners.'

A few other living organisms have discovered that the city suits them.

The well-drained sterility of a lava flow is not unlike that of a city street,

and back in the 18th century a botanist found a yellow ragwort growing

on the slopes of Mount Etna.

He took it back to Oxford, where it was cultivated in the

botanic gardens.

60 years later, the ragwort was noticed growing on the stones

of college walls, but for quite a time it spread no further.

Then, in the 19th century, railways were built across Britain.

The stone rubble on which the tracks were laid was exactly what

the ragwort liked.

And it spread along the railways to appear in all the cities along

the main lines, where it still flourishes today.

A few wild animals have also found what they need in the apparently

hostile wildernesses that man has created.

The sea otter swims happily in the waters of California's harbours.

Prairie dogs, driven off the prairies by ranchers, and farmers,

find new homes in urban playgrounds.

English foxes have discovered a rich source of food in city litter bins

and doze on suburban roofs.

And in the south-west of the United States, acorn woodpeckers

continue to store their acorns in the trunks of fir trees, even when

they've been turned into telegraph poles.

Ospreys habitually build their nests in the very tops of trees,

and telegraph poles also give them the kind of isolation they need.

Church towers, to kestrels, are just as good nesting sites as rocky crags.

While kittiwakes apparently regard modern buildings as little more than

particularly regular sea cliff.

Swallows learned to tolerate man for the sake of the nest sites

beneath his eaves, and now few nest anywhere else.

But not all people's urban companions are so welcome.

There are still plenty of creatures, mammals and insects,

that manage to claim a share of mankind's food.

Many insects eat cellulose, and find it in abundance in wood

and in the paper with which people surround themselves.

Grubs chew the sheep hair with which clothes are made.

And this whole community of insects is in turn preyed upon

by other unwelcome creatures: Spiders.

So we wage war on the animals that have come to live with us.

Brown rats originated somewhere in Asia and spread

to Europe some 300 years ago.

Today, rats are found in every large city in the world.

They will eat almost anything, tackling meat with as much relish

as grain and vegetables.

They gnaw electric cables, causing short circuits, and even,

in consequence, fires.

They not only consume huge quantities of mankind food, but contaminate

much of what they leave, and they spread disease.

So if we're not to be overrun, we have to pursue them wherever they go.

We created the city, and if it's to function properly

and be neither oppressively sterile on the one hand nor infested with pests,

on the other, we have to manage the living organisms that live in it,

encouraging some, exterminating others.

But our influence now spreads far wider than we often choose to recognise.

Now we're changing the whole of the globe, and we must equally

accept our responsibilities of managing that,

but so far we are making a very poor job of it.

We have to rid our cities of the vast quantity of rubbish we create.

New York City produces 22,000 tonnes of refuse every single day.

Half of that is taken by barge down the Hudson River

and dumped on Staten Island.

The rubbish is laid down in a layer several feet thick and 200 feet wide.

Every day it advances 100 feet. When the land is covered,

then another layer is dumped on top.

But this is a very expensive way of getting rid of our rubbish.

If there are cheaper ways of doing so, we unhesitating will take them,

telling ourselves if it's out of sight, it doesn't matter what happens to it,

assuming that somehow the world is so large

that our poisons will simply be lost in its immensities.

So we pour our waste chemicals and detergents into our rivers.

Suds may or may not have been valuable in a kitchen sink.

In a river they can be lethal, killing the plants and the fish.

We spill oil into the sea, in spite of all the precautions,

and set the waves aflame, and now there are patches of oil

polluting even the remotest parts of the widest oceans.

And we poison the very air we breathe.

Fumes belched from our engines fill the atmosphere of the city.

Steam rising from the cooling towers of power stations is relatively harmless,

but the gases produced by burning coal and oil are certainly not.

Our solution to this problem has been quite simple -

to build chimneys even taller, so that the gases are blown

farther away from our cities, but they don't disappear.

They're carried by the prevailing winds to countries hundreds of miles away.

The lakes of Scandinavia have, over the past few decades,

become more and more acid

until now fish and plants can no longer survive in many of them.

In Norway alone, there are now 1,800 lakes without fish,

and hundreds more that are dying,

shameful monuments to our carelessness and lack of concern.

In Germany, 10% of the forests are seriously damaged,

almost certainly as a consequence of industrial pollution of the atmosphere

and the collection of the poisons from it by rain.

But we don't only despoil the natural world by accident.

We do so quite deliberately.

These islands, just off the coast of Peru, may seem, on the face of it,

to be the very picture of fertility and ecological success

They're the home of a great variety of seabirds -

cormorants and pelicans, boobies, terns and gulls.

But 30 years ago, another bird was also living here.

These, a kind of cormorant called the guanay.

When these pictures were taken in the 1950s,

five and a half million of them were nesting on just one of these islands.

The guanay lives exclusively on anchovies and, oddly,

excretes an unusually high proportion of the fish it eats as droppings or guano.

No rain ever falls here, so the guano wasn't washed away

but accumulated on the rocks.

A 100 years ago the world realised that this was a fertiliser

of unparalleled richness

It was collected and sold for such high prices that the guanay

cormorant became known as the most valuable bird in the world.

But then, in the 1950s, chemical fertilisers were developed in Europe,

the price of guano began to drop and the people here started to harvest

not the guanay's cormorant droppings, but its food, anchovies.

In one year, 14 million tonnes of anchovies were taken out of these waters.

They were sold not to feed people but cattle, and chickens and pets.

The fishing was so intense that the anchovies were almost wiped out.

That in turn brought about the collapse of the guanay cormorants' population.

And now for every 50 cormorants that used to live here,

you're lucky if you find one.

And these walls that would be filled with guano to the top inside two years,

now seldom accumulate more than an inch or so.

But the cormorants shed their guano not only on the land but in the sea.

Indeed, for every drop they put on land, they shed 20 into the sea.

And there it fertilises water just as it fertilises the land,

promoting the growth of floating plants, plankton, the food of the anchovy.

So it's not only that if you get less anchovies you get less cormorants,

and if you get less cormorants, you get less anchovies.

Anchovies are food not just for cormorants but for sea fish

like tuna and sea bass.

So, with that one rash act of overfishing 30 years ago,

Peru has lost anchovies,

cormorants, guano and sea fish.

It's a major blow to the nation's economy.

Nor does it seem that we are learning from our mistakes.

We're in the process of making similar catastrophic misjudgements,

and on an even greater scale, in the world's tropical rainforests.

This, the richest of all living communities, has been

of enormous value to us.

It's provided industry with rubber, craftsmen with hardwoods,

and our larders with bananas, nuts, chewing gum and chocolate.

Nearly a quarter of our drugs are based on animals and plants that live here.

And still we have only investigated in detail the biochemistry of less

than 1% of the rainforests' plants.

And here, too, live some of the most beautiful and bizarre creatures

to be found anywhere on the planet.

These animals are the product of millions of years of evolution

here, in these forests.

They can't live anywhere else. The numbers of each different species

within a given area remains remarkably stable, but over the past

few centuries one species of animal outside the forest has suddenly

started to increase in numbers in a way that is without parallel.

In South-East Asia, as in South America and Africa,

thousands of extra people every year

are seeking land on which to grow food for themselves and their children.

They take it from the forest. The labour is huge.

After the trees have been felled and burnt, the people sow their crops,

in this case, hill ruts.

After a month, it's as tall as this, and in only five months it will be

ready to be harvested,

and it will have been sustained by this, the ash from the burnt forest.

But there are only enough nutrient in this to sustain one crop.

So next year the people plant not rice but this, cassava or tapioca,

as it's called here.

This is a different kind of crop, a root crop, which gets its nutrients

from deeper in the soil, but even this can only produce for one year.

After that, the seeds from the wild forest will come in and new plants will grow,

producing a landscape like that.

But they will have to grow for eight to ten years before they are big enough

to be felled and produce enough ash and nutrients to refertilise the soil

and allow the people to take a second crop.

And the true forest, with all its original richness of animals and plants,

will never be restored.

It's not only the local people who cut down the forest.

So, indirectly, do the people of the developed world.

The huge trees are in perpetual demand

to provide timber for furniture, for constructing buildings and crates

and above all for the paper for which the world has an unquenchable appetite.

So a tree that took 200 years to grow is now cut down by a

chain saw in five minutes.

The gigantic trunks, which once could only be shifted by elephants

and only be extracted from forests growing on relatively flat country,

are now handled with terrifying ease by modern machinery.

Sometimes only the biggest trees are taken, leaving smaller ones standing,

but the damage is such that the forest is largely beyond recovery.

As the international price of timber increases, so more and more of the

tropical forest is destroyed.

In South-East Asia, it's been reduced to about a third of its original size,

and, in the world at large, an area the size of Switzerland

is being destroyed every year.

But this may be a ray of hope.

This is the fastest-growing tree in the world. It's called Albizia

and comes from eastern Indonesia, and can be planted immediately

after the felling of the jungle.

In just one year it can grow to 10 or 11 metres tall, 35 feet.

This one is some two years old and in only another six years

it will be ready for logging.

Albizia will grow well on the relatively poor land that once supported

rainforest, and many sawmills actually prefer small, easily handled

logs of uniform size.

So if it were possible to produce this kind of timber on a really

large scale, it might no longer be necessary to continue

the extremely expensive and appallingly destructive business

of felling the wild trees.

And were that to happen, then, in some parts of the world,

away from the coasts, away from the rivers, in remote and

mountainous country, the tropical rainforest might still survive.

The great rivers of the world can also yield riches to mankind,

not simply food but power.

We've known for almost a century how to turn the force of

tumbling water into electric power.

We've made mistakes in doing so. The dams we've built have filled up

with silt and become useless within decades, and fields downriver,

robbed of their annual supply of fertilising mud, have turned to desert.

But we're getting better at it, and we're doing it on a greater scale.

This dam, at Itaipu between Paraguay and Brazil,

will harness the power of one of South America's greatest rivers, the Parana.

I am walking across what was once the bed of that river.

And above me rises the biggest dam ever built by man.

It contains enough concrete to construct a whole city to house

four million people.

It will make a lake which will stretch upstream for 140 kilometres.

And the power it will produce will be enough to supply the whole of Paraguay

and the great cities of southern Brazil, Sao Paolo and Rio de Janeiro.

And the astonishing thing is that it will have taken only seven years to build.

There will, of course, be a heavy price to pay.

44,000 people will have to be moved and their villages and fields submerged,

fields that produce 200,000 tonnes of food a year,

and that will create further demands on the rainforest.

Even so, this major reshaping of the surface of the earth

is likely to be one of the less damaging of those that mankind

has inflicted on the planet.

A million trees of 50 different forest species will be planted

around the lake to prevent silt from washing down into it.

The water will slowly clear and develop a population of fish.

And the turbines in the dam, will produce power without poisoning

the atmosphere or leaving behind radioactive waste.

They will not deplete the Earth's irreplaceable reserves of fossil fuel,

and the dam will continue to produce electricity, it's estimated,

for the next 300 years.

The scale of this immense construction is awe-inspiring

evidence of the power that we now have in our hands

with which to transform the face of the Earth.

When, in prehistoric times, these stones were first put up

to build this temple in the west of England at Avebury, they too

must have been an astonishment to the local people, an amazing

demonstration of how clever, how powerful, human beings had become.

And yet that was less than 5,000 years ago, a mere moment

in the history of life.

And in the brief period since then, men have gone on to learn how to

build dams like Itaipu, how to mould animals and plants to suit

their needs or their fancies, how to transform whole landscapes.

Immensely powerful though we are today,

it's equally clear that we're going to be even more powerful tomorrow.

And what's more, there will be greater compulsion to use our power

as the number of human beings on Earth increases still further.

Clearly, we could devastate the world.

If we're not to do so, we must have a plan.

And just such a plan has been formulated by environmental scientists.

They called it the World Conservation Strategy

and it rests on three very simple propositions.

One - that we shouldn't so exploit natural resources that we destroy them.

Common sense, you might think. And yet, look what we've done to the

European herring, the South American anchovy,

and are still doing to the whales.

Two - that we shouldn't interfere with the basic processes of the Earth

on which all life depends, in the sky, on the green surface

of the Earth and in the sea.

And yet we go on pouring poisons into the sky, cutting down

the tropical rainforest, dumping our rubbish into the oceans.

And third, that we should preserve the diversity of life.

That's not just because we depend upon it for our food, though we do,

nor because we still know so little about it that we won't know what

we are losing, though that is the case as well, but it is surely that we

have no moral right to destroy other living organisms

with which we share the Earth.

As far as we know, the Earth is the only place

in the universe where there is life.

Its continued survival now rests in our hands.

Subtitles by Red Bee Media Ltd