Original subtitles

(dramatic music)

Mountains define

our most spectacular landscapes.

As they climb, the changing altitude results

in a mosaic of dramatic habitats,

teeming with incredible wildlife.

(birds screeching)

Often used as political borders,

these giants even control the weather.

(thunder rumbling)

Mountains are crucial to life,

providing most of the world's fresh water,

housing unique and often extremely rare plants and animals

and providing a home to one in 10 people.

(dramatic music)

It's no wonder mountains are considered sacred,

the top of the world, and a gateway to the heavens

It takes a lot to move mountains,

but these ancient giants are in constant flux.

The planet's greatest forces are constantly at work,

building up and slowly taking down

our most dramatic skylines.

(suspenseful music)

There are two main ways that mountains are born.

(volcano rumbling)

Volcanoes literally blow up the earth's surface

Chucking magma, liquid rock, from the earth's searing core.

As it cools, it hardens.

The mounds can be thrown up quickly and violently,

(volcano rumbling) (dramatic music)

or gradually added for eons.

Some of the most iconic cone-shaped mountains are born

of the earth's fire.

Like Ol Doinyo Lengai,

whose plumes of ash enrich the grasslands of the Serengeti.

(awe-inspiring music)

Or Mount Fuji,

the unmistakable backdrop to Tokyo.

Many volcanoes around the world are still active,

including four in Italy.

Mount Etna is Europe's highest and most active volcano

that has been both feared and worshiped

by humans for thousands of years.

(birds chirping)

And one of the world's most active volcanoes

is just a stone's throw away.

Stromboli.

(dramatic music) (volcano rumbling)

With daily eruptions,

the molten lava can literally make the sea boil.

Fish and octopus here play Russian roulette

with the Earth's fury.

Molten rocks boil marine life.

And in the aftermath, they dash in to clear up the spoils

before the next eruption.

We often celebrate Everest as the tallest mountain on earth,

but there is another.

The tallest peak by far is Mauna Kea

on the island of Hawaii.

4,000 meters stands proud above the ocean,

(dramatic music)

but it's the tip of the iceberg.

(waves whooshing)

This volcano built up from the seabed.

We can only see the exposed summit, but from top to bottom,

this biggest of volcanoes is 10,200 meters tall,

more than 1300 meters taller than Everest

Everest, of course, is part of the Himalayas,

the crowning glory of mountains,

but one with totally different origins.

The earth's surface is made up of giant tectonic plates,

vast sections of the earth's crust

that constantly slide around on their bed of molten lava.

The movement is constant and barely noticeable,

but can sometimes have dramatic consequences.

(suspenseful music)

When two plates collide,

they fold and buckle,

like the bonnet of a car in a head-on collision

Whole mountain ranges can be thrust into the sky.

Some of the youngest, most jagged, and dramatic ranges

have been formed this way.

(awe-inspiring music)

The Alps,

America's Rockies,

and the magnificent Andes.

(birds chirping)

(crow caws)

Mountains don't only form where plates meet.

There can also be fault lines,

rifts and tears within the plate itself,

where friction has pushed up the Harz Mountains of Germany.

(dramatic music) (woman vocalizing)

The African Rift Valley,

and California's Sierra Nevada.

There are also dome mountains

where magma builds underground, pushing up the land,

but never actually eroding.

Like the famous Half Dome in Yosemite.

(dramatic music)

Bobcats and coyotes hunt on the valley floor,

but Half Dome offers safer lookouts for marmots,

the ultimate rock climbing rodents.

And pika, mini rabbits that hide out in the rocks.

And plateaus where plate tectonics have pushed up a plate,

but without it buckling.

These areas are high, but fairly flat.

The biggest of these is the Tibetan Plateau in Central Asia,

which is four times bigger than the state of Texas

Animals roam across this vast area,

undertaking huge animal migrations

that are just as impressive as on the plains of Africa.

(falls whooshing)

In terms of the age of our planet,

some mountains are babies.

You can spot these newcomers.

Their peaks are jagged,

not yet eroded down by the elements.

The Tetons in Wyoming are a mere 10 million years old.

Whereas on the other side of the United States,

the Appalachian Mountains are ancient

They may be a billion years old.

Over millennia, wind and water have eroded them down,

rounding them off into a series of rolling ranges

without a jagged peak in sight.

They have been like this for a long time

and are blanketed in ancient, old growth forest.

They are so old that the world they grew up in

would be unrecognizable to us today.

(birds chirping)

They are from a time

when the earth had just one great landmass, Pangaea.

(plates rumbling)

The plates gradually drifted apart,

creating new oceans in the gaps.

(dramatic music)

(waves whooshing)

And today, parts of the same range of mountains

as the Appalachians in America remain in Morocco

(birds screeching)

and the Highlands of Scotland

on the other side of the Atlantic.

(awe-inspiring music)

(stag roars)

Mountains are found on every continent on earth,

literally from pole to pole.

(peaceful music)

They cover 22% of the earth's surface.

A quarter of terrestrial animal

and plant species live in mountains.

And an incredible 85% of all amphibians, mammals, and birds.

The location of mountains around the world gives

them unique plant and animal communities

and distinctive zones.

(wind whooshing) (melancholy music)

At the extremities of the planet,

the highest latitudes, no trees can grow.

These are the polar zones,

where the average annual temperature

at the base of the mountains is below zero,

let alone at the top.

Only ice age specialists,

like the shaggy muskox, can thrive here.

These are some of the harshest places on the planet.

(wind whooshing)

(melancholy music)

Summers are short, a tiny window for plants to grow,

and there is hardly any rainfall.

The tundra-covered slopes

can only support hardy dwarf shrubs

and a carpet of lichens and mosses.

Compared to other parts of the world,

their biodiversity is low.

But the soggy landscape, once bathed with summer sun,

is a rich breeding ground for insects.

(birds chirping)

Enough to attract migratory birds to dash in from the south

and use the summer's bounty to raise their young.

(playful music)

(birds screeching)

These little auks are especially mountain dependent.

They will only nest on the loose scree slopes,

picking little gaps under boulders to lay their eggs in

that should be out of reach of Arctic foxes.

(birds screeching)

And rely on the precarious scree

to keep the heaviest of predators,

polar bears, away.

(suspenseful music) (birds screeching)

They spend the winter out on the open ocean,

but are early visitors,

dashing in as the snow clears to breed,

choosing to congregate in the hundreds of thousands.

They look like tiny penguins, but with one key difference,

the gift of flight.

(awe-inspiring music) (birds screeching)

Many of the world's great mountains are just outside

of the polar zone and are classified as boreal.

Rising from the vast pine forest known as taiga,

these giants cover 5% of the earth's surface.

They can appear bleak,

with strong seasons and harsh winters.

(eerie music)

There's not much rain.

Most of the water falls as snow.

The pines are tough with narrow needles

that help conserve water and a natural antifreeze

in their sap.

But even they struggle at altitude.

(wind whooshes)

As the mountains climb, the pine forests thin out

and are replaced by dwarf shrubs

and heath land with heathers.

Low to the ground,

these tough little plants are less battered by storms.

(wings whooshing)

Beyond that, the mountain landscape becomes the alpine zone.

(peaceful music)

Small and hardy frost-resistant sedges and rushes

are about all that can cope with the cold.

At altitude, the air is thinner.

There is less air pressure.

Thin air is less able to collect and retain heat

so the mountaintops are not only more exposed

to the elements, but air is cooler too.

(birds chirping)

The boreal mountains appear both sides of the equator

in the higher altitudes.

(llamas groaning)

Like here, the southern reaches of the Andes.

This vast chain of mountains are the longest

to straddle a continent,

stretching down almost the entire western side

of South America, some 7,000 kilometers long

and with the second tallest peaks after the Himalayas.

(awe-inspiring music)

To live in this alpine environment,

animals have multiple adaptations.

Guanacos, the wild llamas, of the Andes,

are related to camels and like camels,

they are experts in conserving water,

which is essential during winters at altitude

when all of the water can be locked away in snow and ice.

But living up to 4,000 meters above sea level,

they also need adaptations to the thin air.

They have extra red blood cells

and their hemoglobin has a stronger affinity to oxygen,

extracting more from the air

where oxygen levels are at least 20% lower

than at sea level.

Still, even guanaco have their upper limits.

(ominous music)

The peaks of the tallest boreal mountains go beyond

the reaches of plants.

The rough, rocky surfaces, frozen most of the year

and blasted with ice, are some of the toughest places

on earth and little life can survive.

Because of their location in high altitudes,

causing fierce winters,

boreal mountains are places

where few humans have managed to settle.

(wind whooshing)

One exception is in the mountains of Northern Siberia,

where reindeer have enabled people to live nomadic lives,

traveling through the mountains as the reindeer migrate,

but retreating to the lower country before winter sets in.

(bell rings)

At first, they would have followed wild reindeer,

but the hardy deer were gradually domesticated.

They still roam and feed themselves,

but the herders keep them safe from predators

and in return, get all the food, leather,

and other materials they need from the animals.

People got a much stronger foothold

in the temperate mountains.

(peaceful music)

These ranges, like the American Rocky Mountains,

the Alps, Caucuses, Siberia's Southern Altai,

the Himalayas, and the Japanese Alps

are all strongly seasonal.

The European Alps are perhaps the most famous

and most populated,

with people flocking to the region for thousands of years.

The highest and most expansive of truly European mountains,

they run over 1000 kilometers

and form natural boundaries

between eight different countries.

In places, they are rugged and remote,

and therefore teem with mountain specialists

like the chamois and ibex.

These mountains still have very harsh winters,

but warmer and more productive summers

and more reliable rain.

(rain whooshing)

Because of the strong seasons.

The trees are often deciduous.

Their leaves bloom in summer to exploit the sun,

but to save energy and avoid frost damage,

they are shed for winter,

the trees shutting down to weather the cold.

(peaceful music)

Because of the frosty winter, many animals do the same.

(eerie music)

Australia is not a place

where many people imagine snow-capped peaks,

but the Australian Alps have cold winters,

too cold for most mammals.

(crickets chirring)

But the mountain pygmy possum is unique.

It is the only hibernating marsupial in the world,

enabling it to weather the cold.

It spends the summer and brief autumn fattening itself up

on a calorie-rich diet of insects and seeds.

It can double in body weight, which is just as well.

It may have to stay in hibernation for seven months.

(suspenseful music)

To do so, like other hibernators,

the possum shuts down its body into a state of torpor,

with its metabolism running at 5% normal levels.

It means their breathing

and heart rate are similarly reduced.

(wind whooshing)

There's an assumption that hibernators sleep through winter,

but this is different.

It's a state of suspended animation.

In fact, a lot of hibernators wake up during winter,

have a stretch, and then need to take an actual nap

before going back into torpor.

It means they can colonize the cold mountain slopes.

(birds chirping)

Though winters are tough,

summers on the alpine slopes reveal

a surprising diversity of flowers,

making the most of the high levels of ultraviolet.

(bright music)

Above the reach of plants,

the mountain slopes become known as the aeolian zone.

(wind whooshing)

Only microbes and algae grow here,

feeding a small invertebrate community.

(peaceful music)

Since prehistoric times,

people have used the temperate mountains,

especially in Eurasia.

(sheep bleating)

Ranges like the Pyrenees, Carpathians, Caucuses, and Alps.

To cope with the strong seasonality,

a practice known as transhumance developed

and continues to this day,

with farmers moving with their livestock

into the high country during summer

to exploit the rich grazing,

(cows mooing)

and retreating to small holdings

at lower elevations during winter.

But it was in the mountains of the subtropics,

closer to the equator, that humans really found their ways

to exploit mountain life.

The climatic conditions are termed Mediterranean,

though are not restricted

to the Mediterranean ranges of Europe.

(peaceful music)

The snowy mountains of Australia

and America's Sierra Nevada both fall into this category.

(birds cawing)

For eons, the native peoples of both ranges used

the natural plants and animals of the mountains

in a sustainable way.

(peaceful music)

Making the most of the cold wet winters with plenty of rain.

And the hot dry summers.

Like all mountains, they have their unique zones,

characterized by different plants.

Above the deciduous trees, there are alpine zones,

scrubs, and a unique habitat adapted to the heat.

This vegetation, found across the world

where Mediterranean climates occur,

are known as sclerophyllous forests.

Plants with tough, leathery, woody leaves,

like the characteristic evergreen oaks of Southern Spain.

But while the indigenous people of North America

and Australia worked with nature,

Europeans had different ideas.

(peaceful music)

The mountains of the Mediterranean

were changed forever by farming.

People removed mountain species,

planting what they wanted to grow

and introducing domestic animals.

For hundreds of years,

small rural communities have nestled in the foothills

and today are considered charming, rustic idylls.

Places where people live out simple lives,

making their living from the land.

The reality today is

that these traditional methods can't compete

with the industrial farming

and don't return much of a profit.

(peaceful music) (birds chirping)

They are not financially viable,

and increasingly young people are leaving the mountains

to seek better career opportunities in cities.

(cows mooing)

As the small communities are deserted.

Wildlife has the chance to creep back in.

And with a bit more space,

even the top predators, like wolves and bears,

are becoming a more common sight

on Mediterranean mountain ranges.

(water whooshing)

There is one other mountain type,

those found closest to the equator,

tropical and subtropical mountains.

(awe-inspiring music)

Cloaked in lush forest, they straddle regions like Kenya,

the Democratic Republic of Congo, even Hawaii.

Often rising from a carpet of jungle,

the mountain slopes have their own forest.

Montane forests are much colder

than the jungle lower down the slopes.

With moisture condensing on the cold air,

they are usually shrouded in mist.

For this reason,

they're more famously known as cloud forest.

(mystical music)

The only seasons here are wet and dry,

though it's sometimes said they go

through the seasons every day.

Because it can be warm and humid during the day

and bitterly cold at night because of the elevation.

The trees rarely attain the height of rainforest species,

peaking at around 20 meters,

and they are less densely packed,

allowing light to penetrate,

fueling a rich understory of herbs and ferns.

(peaceful music) (birds chirping)

Orchids, lichens, and mosses use the trees branches

to bring them closer to the light

In Asia, the laurels and Quercus oaks

are interrupted by color.

The family now familiar

as garden ornamentals, rhododendrons.

At above 4,000 meters,

even the tropical and subtropical cloud forest

gets nightly frosts,

making it a challenge for animals.

There is less diversity than lower down the slopes,

but the creatures here are special.

Birds like monal pheasants use bright colors

to stand out in the dense, dark undergrowth.

The red panda, a unique cat-sized creature,

not at all related to giant pandas,

has dense fur with a wooly undercoat

to help it cope with the cold.

Even its paws are furry.

(birds chirping)

The long bushy tail makes a great blanket

during cold nights.

They eat a lot of bamboo, a low-calorie diet,

so have a slow metabolism and plod around gently

to save energy.

If it gets particularly cold,

they can even lower their metabolic rate more,

becoming temporarily dormant.

The tropical and subtropical montane forest

is also rich in primates.

(playful music)

Rubbing shoulders with the red pandas are gray langurs.

And Assam macaques.

And in the montane forests of Africa, our closest cousins,

chimpanzees and gorillas.

Humans too, have long exploited the riches

of tropical mountain slopes.

(machinery rumbling)

And increasingly convert the forests to plantations of crops

like bananas and coffee.

Above the forests,

even tropical mountains have an alpine zone,

montane grassland.

Some of which have been created by humans,

burning and grazing the landscape.

But others have been created naturally

by mountain slopes too harsh for trees to colonize.

Unique species have learned to exploit this high country

like the gelada a baboon-like monkey.

Without trees, the colonists sleep on cliff faces

to stay out of reach of predators.

(monkeys chattering)

(peaceful music) (birds chirping)

And by day, spread out to graze.

(bright cheerful music)

There's no doubt

that mountains are spectacular, unmissable features

of our landscapes, giants that keep us in awe.

(peaceful music)

But they do a lot more than just improve the skyline.

Mountains are a vital part of a functioning planet.

Mountains can even change the weather.

Moisture from the Pacific Ocean gathers

towards the shores of California.

But as the clouds climb the elevations of the Sierra Nevada,

they cool and can no longer hold onto the moisture,

so it falls as rain.

(rain whooshing) (bright music)

So the westward side of the range is blanketed in forest.

(bees buzzing)

In fact, the biggest trees on the planet,

the giant sequoias, only live here,

thriving in the warm, wet landscape

the mountains have helped provide.

(peaceful music)

But this process means

that the marine moisture doesn't make it further inland

than the mountains.

Air that passes over to the other side is dry

and as it flows over the land,

it actually sucks up moisture.

(awe-inspiring music)

On the eastern side of the mountains is hostile desert

It's a phenomenon known as rain shadow

and is repeated by mountains across the world.

The eastern coast of Australia is buckled

by endless ranges of mountains.

(peaceful music)

Between the peaks and the coast,

Eastern Australia is lush and green,

eucalyptus forests, rich in wildlife,

giving way closer to the tropics

to dense and ancient rainforest.

The combination of ocean atmosphere, warm climate,

and the mountain rains created this paradise,

but the rain shadow on the other side of the mountains

(awe-inspiring music)

is the Australian Outback.

Because of their size and challenging

and changeable conditions,

mountains also influence evolution.

They create physical barriers,

stopping the spread of animals and plants

and creating isolated ecosystems

where unique species can evolve.

(birds chirping)

And because they trap rain and snow,

they are the birthplace of all of the world's great rivers.

(water whooshing)

Rain runoff and the melting of snow and ice fuel

the torrents that bring moisture

and nutrients across all land masses.

It's an essential component of life,

and not just to animals and plants, but to people too.

(peaceful music) (water whooshing)

Every day, water from mountains directly provides water

for half of all humanity.

Mountains are vital to us.

20% of the crop species now eaten

by 80% of the world's humans originated

from wild species like potatoes, sorghum,

tomatoes, apples, maize, and barley

that came from mountains.

(goats bleating)

Mountains even house 15% of the world's human population.

Over 915 million of us.

It's hardly surprising that throughout the world,

mountains are revered, considered sacred.

(peaceful music)

Often considered the homes of the deities,

like the mountains of Tibet, Japan, China,

Sinai, and Greece.

In Australia, they are the forms of the creators

who have laid down on the ground.

Throughout the world, they have long been shrouded

in myths and legends.

A source of spirituality.

And today, many of us seek them out for recreation,

knowing that their scale and fresh mountain air

can lift our spirits and are good for our souls.

But although they seem like immovable, timeless giants,

mountain habitats are surprisingly fragile.

(melancholy music)

Challenging climates, thin air, and poor loose soil

make it hard for life to survive.

Their remoteness and inaccessibility has protected mountains

for most of human history.

But now people move ever more into them

for recreation, to live,

and to exploit resources like timber.

Today, many mountain landscapes are degraded

and under threat.

70% of mountain land is used for grazing.

Highland farming practices have been going on

for so long that in many regions.

they have altered environments and now define them.

(sheep bleating)

People use different livestock in different areas,

and over hundreds of years have carefully bred animals

with the best genes to thrive in the tough conditions.

To small communities, the animals provide meat, milk,

and other products, but also produce dung

that can enrich the poor mountain soils.

In recent years, the drive for profit

has pushed farming into less sustainable models

that can destroy the delicate landscapes.

Commercial mining, logging, and poaching

are reducing biodiversity.

Mountainscapes are being threatened by over-exploitation.

The damaged landscapes are even more fragile

than the ones before, increasing the chance

of natural disasters like landslides and flooding.

(melancholy music)

Traditional mountain communities are often very poor.

They are often forced to abandon the failing landscapes.

When they go, unique culture and ancient knowledge is lost.

Mountains are under threat from our direct action.

But there's another impact from our huge population

whose consequences we are only just beginning to understand.

Mountains and the plant and animal communities

are very sensitive to climate change.

Mountains are sometimes dubbed the third pole,

because after the Arctic and Antarctic,

they hold most of the world's snow and ice,

a huge reserve of fresh water.

Much of it has been stored for tens of thousands of years

in massive glaciers.

(wind whooshing)

The giants are spectacular, food for the soul,

but they are far more important than that.

They are reservoirs, water storage tanks,

that very slowly and gently release just the right amount

of water to feed streams and rivers,

providing much of the vital fresh water to the world.

(water whooshing)

The increase in average global temperatures is ravaging

these ancient giants.

They are shrinking fast, and taking away the water supply

to millions of people.

We need to seriously change the way we interact

with our environment.

Mountains have been held in reverence

throughout human history.

They are our deities and a source of endless inspiration,

our gateway to the heavens.

Surely if there's anything

that deserves our respect and protection,

it's these defining magnificent giants.

(awe-inspiring music)