- The exploration of space, a symbol of our triumph, our success on Earth.

[dramatic music] But in truth, we have little control of this planet.

No matter how hard we try, there is nothing we can do when these powerful forces of nature are unleashed.

[thunder booming] For centuries, we've been struggling to predict and to control them, often with little success.

And today, the planet has a new force.

One with enormous strength and tenacity, humanity.

Our billions of citizens have begun to change the very planet we call home.

[gentle music] [soothing choral music] [impact booming] [dramatic music] [pleasant music] - [James] Planet Earth.

To our eyes unchanging, constant.

But on a different time scale, continents drift across the face of the globe.

Sea levels rise and fall.

Mountain chains come and go.

The land is cloaked in forests, or surrenders itself to the desert.

Ice ages have a rhythm of their own.

And everywhere, a spectacular variety of life.

[lively music] [woman singing in foreign language] As the world changes, so life changes with it.

The great process of evolution is simply nature's way of coping with new conditions.

But as life adapts to the world around it, so life itself creates more changes.

And the biggest changes are made by the smallest life forms.

Tiny microscopic creatures live everywhere, and in such large numbers, they can alter the whole world by influencing the levels of gases in the atmosphere.

But however much the earth changes, it never seems to change beyond certain limits, those needed to support life in one form or another.

It's as if the whole planet acts like a single creature, always adjusting itself, regulating itself, keeping things just right.

[water burbling] Some people now believe that life and the planet are part of one system, and if they weren't, all life would've become extinct millions of years ago.

This idea, that the Earth and the life on it, is one giant self-regulating organism was named after the Greek Earth goddess, Gaia.

But now, a new element has emerged.

One that could bring disruption to this balance, to Gaia, to Mother Earth herself.

[people chattering] Humanity.

But we owe our success, our very existence, to the changes that created this dynamic, yet balanced Earth.

We are also children of Gaia.

And our story starts millions of years ago, in Africa.

A time when forests stretched from coast to coast.

And in those ancient forests, our ancestors, the same as those of chimpanzees, lived out their lives.

[birds chirping] Chimpanzees are our closest living relatives.

98% of their genes are identical to ours.

They offer us a glimpse into our own past.

Chimpanzees aren't so different from us.

They live in close communities, in family groups, caring for each other.

They're intelligent.

They make friends, form alliances, establish who's in charge.

[birds chirping] Like us, they use tools.

Fishing for termites with a stick of just the right length takes skill.

It's not a skill that comes naturally.

It has to be taught to each new generation.

[birds chirping] And like us, chimps live in a changing world.

[lava burbling] [eruptions rumbling] Five million years ago, Africa began to tear itself apart, along a great rift that runs north and south.

[flames crackling] And it's still happening.

Active volcanoes are a result of Africa's turmoil, as it splits open at a rate of an inch a year.

[flames crackling] [lava burbling] This huge upheaval has created the Great Rift Valley.

It's so big that it runs north and south through 2/3 of the continent.

This was such a dramatic change that it altered the African climate.

To the east of the valley, forests were replaced by open savannah.

This was the original Garden of Eden.

[birds chirping] Some apes, our ancestors, adapted and survived.

Standing upright freed their hands to use tools, and they developed bigger brains.

With our new intelligence, we could now remodel the world, create our own habitats.

And, although the Earth is the cradle of humanity, we can't stay in the cradle forever.

[tense music] [rockets whooshing] [dramatic choral music] July, 1969, Apollo 11 took humans to the moon.

[dramatic choral music] That one small step for man was humanity's biggest step since leaving Africa.

For the first time, life reached beyond the surface of our own planet.

Looking through the eyes of the three astronauts was, for most of us, the first time we saw our home from space.

[somber music] But the technology that allows us to look down on our world is only a part of our success story.

There are more people on Earth now than ever before.

On the dark side of the planet, whole continents are outlined by city lights.

[soothing music] 5 1/2 billion people, growing by 100 million a year.

Technology now allows us to build our cities anywhere, whatever the nature of the land.

The cities of the American West, Los Angeles, Phoenix, Tucson, Las Vegas, are in the middle of deserts.

Their populations are measured in millions in a land that should only be able to support thousands.

[whistles trilling] Las Vegas, built in the middle of nowhere to provide the ultimate playground.

Created out of nothing, it's a testament to humanity's triumph over nature.

[cars honking] We've even built an artificial volcano.

It seems there's nothing we can't do.

[water splashing] When the first pioneers arrived here, they called it the wild west.

And the first thing they wanted to do was transform the desert, to conquer the land.

Nature here was an adversary, not an ally.

They pushed the frontiers of modern civilization west at a rate of 30 miles a year.

[water splashing] But people and cattle need water, lots of it, and the deserts of the West had no water to spare.

[water splashing] This land gets less than seven inches of rain a year.

To live here means bringing water from somewhere else.

[water splashing] Uncountable billions of dollars, and untold human efforts, have been poured into transforming this land.

[whistles trilling] [water splashing] The ancient civilizations of the Anasazi and Hohokam Indians lived with the desert, rather than against it.

[gentle music] Yet, even they mysteriously disappeared.

[gentle music] Nothing stays the same.

It seems the expanding desert forced them to abandon their towns.

[gentle music] But since the days of the first pioneers, we've imposed our technological might on the desert, and built a symbol of our victory.

[water splashing] Fountain Hills, Phoenix, and the highest fountain in the world.

Somewhere so hot and so dry that over half of the water evaporates before it hits the ground.

[water splashing] Phoenix is so named because it rose out of the ashes of an ancient, abandoned Hohokam town.

Have we now finally conquered the desert?

To water the desert means controlling the rivers.

The Hoover Dam is only one of 20 dams that strangle the Colorado River.

But this masterpiece of engineering is nowhere near as ambitious as trying to dominate the mightiest river in North America.

Old Man River himself, the Mississippi.

People have always lived alongside this river, but it's only in the last few centuries that it's been tamed, straightened, its banks raised, its waters contained.

All this meddling has increased the river's flow.

Much of the sediment it carries would normally settle in the delta to build islands.

Now, it's carried farther out to sea.

[tender music] These coastal islands, no longer fortified by sediment, are disappearing underwater.

The whole delta region is sinking.

Louisiana is losing its rich coastal wetlands at a rate of about 40 square miles a year.

[tender music] [birds chirping] The river also brings nutrients, drained from a large part of the American continent.

This delta is very threatened.

Pelicans, terns, skimmers.

Each fish these waters in their own way.

[birds chirping] [tender music] The Mississippi is a dynamic river.

Every 1,000 years or so, it has changed course naturally, creating new landscapes and destroying the old.

[tender music] [waves crashing] [wings flapping] [birds chirping] As the delta changes, the wildlife simply adapts to the new conditions.

The birds find new places to nest, and carry on as before.

But people don't see things the same way.

A river should be constant, unchanging, especially if we've built cities like New Orleans on its banks.

[thunder booming] When storms bring torrential rain, the river does what it always does, it floods.

[water rushing] In 1993, Old Man River rolled over 20 million acres of farmland in the most destructive floods in its history.

It is natural for a river to flood like this, and the more we try to prevent it, the more disastrous it is for us when the river does break free.

[water rushing] However much money and energy we spend trying to control rivers, they will flood.

And it seems the more we interfere, the more destructive the floods become.

Some people now believe that we've wasted our time and money trying to tame the Mississippi.

We'll always be fighting a losing battle.

There are more than 1,500 levies trying to keep the Mississippi where we want it, but in 1993, the river refused to be held in chains.

It overflowed, and damaged more than 1,000 of these artificial barriers.

75 towns were submerged, and 50,000 homes were lost.

Nine states were declared disaster areas.

[water trickling] And floods aren't the only devastation we face.

There are forces even more impossible to control.

- [Observer] Here now is the Montserrat Volcano Observatory report for the period four o'clock, April fifth to four o'clock April 6th.

The Soufriere Hills volcano has been highly active during this period.

A series of explosive eruptions have occurred, including the largest seen so far, which started at 14:45 on the sixth of April.

- [James] In 1996, on the holiday island of Montserrat in the Caribbean, a dangerous volcano lost its temper.

[volcano rumbling] Dangerous because there's little or no lava.

Instead, a boiling cloud of burning ash, steam, and fragments of rock is hurled into the sky.

This deadly combination, a pyroclastic flow, is unstable and unpredictable.

It can pour out in a continuous flow, or explode without warning.

- [Observer] Activity built up again, with continuous ash emission, and several ash plumes.

A significant explosive eruption started at 14:45, and continued for about an hour.

It consisted of two main pulses, which sent ash to about 15,000 to 20,000 feet above sea level, and generated a large pyroclastic flow.

This flow, however, did not- - [James] The only possible response is to evacuate.

The town of Plymouth was abandoned.

There was no telling when the volcano would erupt again.

- [Observer] 25 feet short of Chance's Peak, the spine has grown by about 200 feet since yesterday, and is now visible from many points around the island.

The scientists at the Montserrat Volcano Observatory remain gravely concerned about the current level of activity, because it may be leading towards a climactic eruption of the Soufriere Hills volcano, which would affect most of the areas of the evacuated zone.

The scientists therefore urge people still in the evacuated zone to leave immediately.

The Tar River, Long Ground, and Weekes areas are- - [James] But the soil around the volcano is very fertile.

So from Pompeii to Montserrat, people have risked everything to farm volcanic slopes.

And in spring 1997, the volcano erupted again.

[volcano rumbling] This time, 19 people were killed, all having refused to evacuate.

[volcano rumbling] The searing pyroclastic flow annihilates everything in its path, and when the flow reaches the sea, it is so hot, it boils the water underneath.

[water burbling] The whole cloud slides across the sea on a cushion of steam.

[eruption rumbling] Moving over 90 miles per hour, a searing wall of heat reaches temperatures of hundreds of degrees, leaving in its wake a scene resembling the aftermath of a nuclear holocaust, charred ruins covered in ash.

Montserrat could stay active for years, a continuous threat to the people who choose to stay.

[volcano rumbling] And it may be, in the long run, the whole island will have to be abandoned, the people finally conceding defeat to the volcano.

But creation and destruction are two sides of the same coin.

There wouldn't be an island here at all, if it wasn't for the volcano.

The islands of the Caribbean arc were created by volcanoes, formed as two of the great plates of the Earth's crust crashed into each other.

But some plates don't collide, they slide past each other.

That is happening along the West Coast of North America, creating the world's most famous fracture zone, the San Andreas fault.

Yet it was movement along the fault that created the great natural harbor of San Francisco Bay.

When the Spanish arrived here in the 18th century, they founded their city of St. Francis, on what they thought was a perfect site.

They had found a golden gate to the North American continent.

The Spanish didn't know about moving plates, but modern San Francisco does.

As these plates slide and scrape past each other, they don't produce volcanoes.

They generate earthquakes.

[bowl clinking] Tuesday, October 17th, 1989, a serious earthquake rocks San Francisco.

[earthquake rumbling] [glass tinkles] Measured at 7.1 on the Richter scale, the quake lasts only 11 seconds.

[earthquake rumbling] [glass tinkling] [rice clattering] [glass tinkles] [pasta clattering] [glass tinkles] [earthquake rumbling] [dishes clattering] [wood creaking] [glass tinkling] [dishes clattering] [pasta clattering] [wood creaking] [glass crashing] [dishes clattering] [earthquake rumbling] At the turn of the century, this city was devastated by a huge earthquake, and another, the same size, was overdue.

As bad as the '89 quake was, it was not the big one.

[sirens wailing] As the plates continue their relentless journey past one another, it's only a matter of time before San Francisco is once more shaken like it was in 1906.

The Marina District, on the edge of the bay, was built on sand.

Shock waves traveling through the sand turned it momentarily to liquid.

Some buildings survived the earthquake, but still had to be demolished, as the foundations became unstable.

[sirens wailing] [debris crashing] The whole Pacific Ocean is surrounded by colliding continental plates.

This is the Ring of Fire, a circle of earthquakes and restless volcanoes.

On the other side of the Pacific, Mount Fuji in Japan, is the most famous of these volcanoes.

Although Mount Fuji hasn't erupted since the 1700s, Japan itself is still in the hot zone.

Water, heated by molten rocks, gushes up from deep underground, forming pools where Japanese macaques, snow monkeys, keep warm in the winter.

[water burbling] [monkeys chitter] But these luxurious baths are signs of powerful forces at work, just below the surface.

The same forces that produce hot pools can also produce earthquakes.

We certainly can't control earthquakes, but we can try to predict them.

Vast amounts of time and money are spent on the technology of earthquake prediction.

And in 1995, the world's experts met in Osaka, Japan to share their knowledge and results.

But at 5:47 a.m., on the 17th of January, Osaka and nearby Kobe were hit by a huge, unpredicted earthquake.

[people screaming] [earthquake rumbling] [things clattering] In Osaka, the scientists were caught by surprise.

In Kobe, more than 5,000 people died.

[earthquake rumbling] [people screaming] [somber music] Broken fuel tanks and electric fires set the city ablaze, and with water supplies disrupted and pipes burst, people were helpless.

The Japanese have lived with earthquakes for thousands of years.

They seem more philosophical about natural disasters.

[flames crackling] [somber music] As one Japanese writer pointed out, it isn't the earthquake that kills people.

It's their possessions.

[somber music] It has been said that civilization exists by geological consent, subject to change without notice.

Nowhere is that more apparent than in the aftermath of a big earthquake.

[dramatic music] Not far from Kobe is Tokyo, and like San Francisco, Tokyo is waiting for a big one.

If, some say when, that big one destroys Tokyo, the implications are unthinkable.

Rebuilding Tokyo could cost trillions of dollars, money that Japan has invested in the rest of the world.

If the Japanese withdrew those investments, there'd be a financial crash that could cripple the whole world economy.

But some geological events already disrupt the entire planet.

[eruption booming] Ruapehu in New Zealand.

Volcanoes this powerful hurl dust several miles into the upper atmosphere, where it stays for months, blocking the sun's light.

[eruption rumbling] And really powerful eruptions can change the climate of the whole world, cooling the Earth for years afterwards.

[eruption rumbling] It may be that in the past, volcanoes produced so much dust that the temperature of the Earth fell dramatically.

It's even possible that huge eruptions play a role in triggering even greater world-changing events, ice ages.

The Earth has been through several ice ages in its time.

[gentle music] Each one lasts for millions of years, and each one completely reshapes the landscape.

[gentle music] Nothing, not even life itself, was left unchanged by the ice.

Around the ice sheets, big arctic tundra replaced thick forests.

[ice splashing] And the enormous amounts of water locked in the ice sheets dramatically lowered the sea level.

[gentle music] [ice splashes] [ice splashes] As the glaciers slowly crept across the face of the Earth, they gouged out deep valleys and ground down mountains.

[ice creaking] [wind whistling] [dramatic choral music] But an ice age is not just millions of years of unrelenting cold.

There are brief warm periods.

[ice crashing] 100,000 years of bitter cold is followed by 10,000 years of relative warmth.

These oscillations continue for millions of years within a single ice age.

[ice crashing] Today, we are in the middle of such an ice age, but we're at the end of a 10,000 year warm period.

Civilization, everything we know, from agriculture to Apollo 11 has happened in this brief retreat of the ice.

If the pattern continues, we'll plunge once again into a long, everlasting winter, where polar bears will roam as far south as London, Paris, and New York.

So far, the cycle has repeated itself for two million years.

But, the Earth isn't cooling down as we expect.

It appears to be warming up.

And the cause of this break in the pattern?

It seems to be us.

As we burn fossil fuels to generate power, we release carbon dioxide into the atmosphere.

Carbon dioxide traps the sun's heat near the surface, warming the planet.

[tense music] Carbon dioxide isn't the only such greenhouse gas.

Nitrous oxides from the exhausts of cars also warm the Earth.

[tense music] In the industrial world, we see the planet as our playground.

There are no limits, no restrictions, no dues to pay.

But all of these displays of our progress have an impact on our planet.

The energy to power our modern lifestyle is not free.

[tense music] Pollution hangs over Los Angeles like a guilty conscience.

Legislation is beginning to control the notorious smog, but it's much harder to legislate against invisible gases that do their damage unseen.

And we don't really know how all this will affect the world in the long run.

We know that polluting our atmosphere is likely to warm up the Earth, and that can melt some of the polar ice caps.

Ice that plays a key role in driving deep ocean currents.

Ice at the poles chills the water around it.

The cold water sinks, to form a deep ocean current, that moves very slowly towards the equator.

We don't know how the deep ocean currents will be affected if the ice melts, but we do know that they play a crucial role in moving heat around the planet, and regulating our climate.

But since we've only recently invented the technology to explore these depths, we're just beginning to understand the hidden world of the deep ocean.

A strange, dark world full of creatures that have never known sunlight.

Lives we simply can't imagine.

[eerie music] We don't know how or if global warming might disrupt these deep ocean currents, but we do know that when surface currents change, they affect the whole planet.

Normally, the trade winds in the Pacific push the warm water of the equator away from South America.

But every four years or so, the winds die, and the tropical water backs up, warming the Eastern Pacific.

The change in the wind and water patterns usually happens around Christmas, hence its name, El Nino, the boy child.

A change in the Pacific Ocean currents affects rainfall patterns all around the globe.

The western coasts of the Americas receive torrential rain, but elsewhere, the rain clouds dry up.

Even as far away as Africa, there are devastating droughts.

[sand crackling] [winds whistling] Unlike America, Africa hasn't had the luxury of taming its deserts, and during severe El Ninos, people, as well as wildlife, die.

To make matters worse, the pattern of El Nino has recently changed.

In the early 1990s, there were five El Ninos in six years.

Australia, already a desert continent, suffered a series of terrible summer droughts.

[somber music] Huge herds of emus were driven out of the interior in their search for water and food.

Their only hope is to head for already parched farmland in the south.

But farmland is protected by a manmade barrier.

A fence, hundreds of miles long, built to keep dingoes away from livestock.

It kept the emus out, too.

[dramatic music] But the droughts from El Nino bring worse problems than starving emus, dust storms.

[woman singing in foreign language] Choking clouds of dust brought whole cities to a standstill.

[woman singing in foreign language] [baby crying] Parched, tinder dry land can easily flare up in devastating bush fires.

[helicopter whirring] The El Nino sequence of the 1990s resulted in the most terrifying fires Australia has known.

The suburbs of Sydney was surrounded by walls of flames.

By Christmas Day, 1994, there were 145 separate fires burning.

Is this a glimpse of things to come?

[flames crackling] Is global warming the cause of the repeating pattern of El Nino?

Are we already causing changes in ocean currents and climate?

[firefighters shouting] [flames crackling] [haunting choral music] As yet, nobody knows.

Like children playing with matches, we have no idea of the consequences of what we're doing.

[flames crackling] [somber music] And we're not the first.

The Maya of Central America were one of the many sophisticated civilizations before us that disappeared, leaving ruined cities as a testament to their passing.

What happened to this great civilization, that for hundreds of years, dominated the world around it?

Some now think they simply failed to adapt to changes that swept over their land, changes they caused themselves.

In the Mayan sacred writings, the Popol Vuh, their gods, their creators, were no longer pleased with their creation.

They know all.

What shall we do with them now?

Let their sight reach only to that which is near.

Let them see only a little of the face of the Earth.

Are they not, by nature, simple creatures of our making?

Must they always be gods?

[lively music] [woman singing in foreign language] [water splashing] We owe our existence to elemental forces that shape and mold this planet.

But now, we try to control them.

In doing so, we may change our world beyond recognition.

Nature, Gaia, will survive, with or without us.

Are we set to follow the Mayan civilization?

Or can we step back, look at the Earth, and understand our place?

Must we always be gods?

[woman singing in foreign language] Meet the people who come face to face with the powers of nature, and find out why they are literally playing with fire.

Next time on "Forces of the Wild."

[lively music] [dramatic music] [pleasant music]