(完整word版)BBC经典-《行星地球》英文解说词(全集)

2021年2月10日发(作者：yellow)

行星地球英文解说词

第

1

集

PLANET EARTH From Pole to Pole

A hundred years ago there were one and a half billion people on Earth.

Now, over six billion crowd our fragile planet Earth. But even so, there

are

still places

barely

touched by

humanity.

This

series

will take to the

last wildernesses and show you the planet Earth and its wildlife as you

have

never

seen

them

before.

Imagine

our

world

without

sun.

Male

Emperor penguins are facing the nearest that exists on planet Earth Earth

-

winter

in

Antarctica.

It's

continuously

dark

and

temperatures

drop

to

minus

seventy

degrees

centigrade.

The

penguins

stay

when

all

other

creatures have fled because each guards a treasure: a single egg rested on

the top of its feet and kept warm beneath the downy bulge of its stomach.

There

is

no

food

and

no

water

for

them,

and

they

will

not

see

the

sun

again for four months. Surely no greater ordeal is faced by any animal. As

the sun departs from the Antarctic it lightens the skies in the far north. It's

March and light returns to the high Arctic, sweeping away four months of

darkness.

A

polar

bear

stirs.

She has

been

in

her

den

the

whole

winter.

Her

emergence

marks

the

beginning

of

spring.

After

months

of

confinement underground she toboggans down the slope. Perhaps to clean

her fur, perhaps for sheer joy. Her cubs gaze out of their bright new world

1

for the very first time. The female calls them, but this steep slope is not

the easiest place to take your first steps. But they are hungry and eager to

reach their mother, who's delayed feeding them on this special day. Now

she

lures

them

with

the

promise

of

milk,

the

only

food

the

cubs

have

known since they were born deaf and blind beneath the snow some two

months ago. Their mother has not eaten for five months and has lost half

her body weight. Now she converts the last of her fat reserves into milk

for

her

cubs.

The

spring

sun

brings

warmth

but

also

a

problem

for

the

mother. It starts to melt the sea ice. That is where she hunts for the seal

she needs to feed her cubs. And she must get there before the ice breaks

up. For now though it's still minus thirty degrees and the cubs must have

the shelter of the den. It's six days since the bears emerged and spring is

advancing

rapidly.

But

even

now

blizzards

can

strike

without

warning.

Being

so

small,

the

cubs

are

easily

chilled

and

they

will

be

more

comfortable resting in the den. But their mother must keep them out and

active.

She's

becoming

weak

from

hunger

and

there's

no

food

on

these

nursery slopes. The sea ice still holds firm, but it won't last much longer.

Day 10, and the mother has led her cubs a mile from the den. It's time to

put them to the test. They've grown enormously in confidence, but they

don't

have

their

mother's

sense

of

urgency.

At

last

it

seems

that

they're

ready for their journey and they're only just in time, for a few miles from

the coast the ice is already splitting. Now the mother can start hunting for

2

the seals they must have, but she's leading her cubs into a dangerous new

world.

Nearly

half

of

all

cubs

die

in

their

first

year

out

on

the

ice.

Summer brings 24 hours of sunlight and the thawing shifting landscape.

Further

south

the

winter

snows

have

almost

cleared

from

the

Arctic

tundra.

Northern

Canada's

wild

frontier.

Here

nature

stages

one

of

her

greatest

dramas

-

Every

year

three

million

caribou

migrate

across

the

Arctic

tundra.

The

immensity

of

the

herd

can

only

be

properly

appreciated

from

the

air.

Some

herds

travel

over

2,000

miles

a

year

in

search of fresh pastures. This is the longest overland migration made by

any animal. They're constantly on the move. Newborn calves have to be

up

and

running

the

day

they

are

born.

But

the

vast

herds

do

not

travel

alone. Wolves. Packs of them, eight to ten strong, shadow the migration.

And

they

are

hungry.

It's

the

newly

born

calves

that

they

are

after.

Running directly at the herd is a ploy to generate panic. The herd breaks

up

and

now

it's

easier

to

target

an

individual.

In

the

chaos

a

calf

is

separated from its mother. The calf is young, but it can outrun the wolf if

only it manages to keep its footing. At this stage the odds are even - either

the

caribou

will

make

a

mistake

or

after

a

mile

the

wolf

will

give

up.

Midsummer on the tundra and the sun does not set. At these latitudes the

sun's rays are glancing and not enough of their energy reaches the ground

to enable trees to grow. You'll need to travel 500 miles south from here

before

that

is

possible.

These

stunted

shrubs

mark

the

tree

line

-

the

3

beginning of the boreal forest - the taiga. The needle-shaped leaves of the

conifers are virtually inedible so this forest supports very little animal life.

It's a silent place where the snow is unmarked by footprints. In the Arctic

winter

snow

forms

a

continuous

blanket

across

the

land.

But

as

spring

creeps up from the south the taiga is unveiled. This vast forest circling the

globe

contains

a

third

of

all

the

trees

on

Earth

and

produces

so

much

oxygen it changes the composition of the atmosphere. As we travel south

so

the

sun's

influence

grows

stronger

and

at

50

degrees

of

latitude

a

radical

transformation

begins.

Summers

here

are

long

enough

for

broadleaf trees to replace conifers. Broadleaves are much easier to eat and

digest so now animals can collect their share of the energy that has come

from the sun. It's summer and these forests are bustling with life. But the

good

times

will

not

last.

Broad

leaves

must

be

shed

in

winter

for

their

damage by frost. As they disappear, so the land becomes barren with little

for

animals

to

eat.

The

inhabitants

must

migrate,

hibernate,

or

face

months of near starvation. The Amur leopard - the rarest cat in the world.

Here, in the deciduous forests of eastern Russia the winter makes hunting

very

difficult.

Pray

animals

are

scarce,

and

there's

no

concealing

vegetation. The cub is a year old and still dependent on its mother. Deer

are

frequent

casualties

of

the

harsh

winter

and

these

leopards

are

not

above

scavenging

from

a

corpse.

African

leopards

could

never

survive

here,

but

the

Russian

cats

have

thick

fur

to

shield

them

from

the

cold.

4

There

are

only

forty

Amur

leopards

left in the

wild and that number

is

falling.

Like

so

many

creatures,

the

cats

have

been

pushed

to

the

very

edge

of

extinction

by

hunting

and

the

destruction

of

their

habitat.

The

Amur leopard symbolises the fragility of our natural heritage. The future

of an entire species hangs on survival of a tiny number of mothers like

this one. All animals, rare or common, ultimately depend for their energy

on

the

sun.

In

Japan

the

arrival

of

the

cherry

blossom

announces

the

beginning of spring. The sun's energy brings colour to the landscape. The

earth, as it makes its annual journey around the sun, spins on a tilted axis.

And

it's

this

tilt

that

creates

the

seasons.

The

advance

of

the

seasons

brings constant change. As the sun's influence diminishes in the north, so

the deciduous forests of America begin to shut down losing their leaves in

preparation

for

the

dark

cold

months

ahead.

One

season

hands

over

to

another.

Some

organisms

thrive

on

decay,

but

most

must

make

special

preparations

for

winter

and

a

life

with

little

sun.

Whole

populations

of

animals

are

now

forced

to

travel

great

distances

in

pursuit

of

food

and

warmth. 300,000 Baikal teal gather to escape from the Siberian winter by

migrating south to Korea - the world's entire population in a single flock.

But there are parts of the world that have no seasons. In the tropics the

sun's

rays

strike

the

earth

head

on

and

their

strength

is

more

or

less

constant all year round. That is why the jungle grows so vigourously and

supports

so

much

life.

This

forest

covers

only

3

percent

of

the

planet's

5

surface, but it contains more than 50 percent of all its plants and animals.

The canopy is particularly rich. There are monkeys, birds and millions of

species of insects, exactly how many we have no idea. The character of

the

forest

changes

as

we

descend,

becoming

ever

darker

and

damper,

favouring different kinds of animals and plants. Less than 2 percent of the

sunlight reaches the floor, but even here there is extraordinary variety. In

the great island of New Guinea there are 42 different species of birds of

paradise,

each

more

bizarre

than

the

last.

This

forest

is

so

rich

that

nourishing

food

can

be

gathered

very

quickly.

That

leaves

the

male

six-plumed bird of paradise with time to concentrate on other matters like

tidying

up

his

display

area.

Everything

must

be

spick

and

span.

All

is

ready.

Very

impressive,

but

no

one

is

watching.

The

superb

bird

of

paradise calls to attract a female. And he has more luck. But what does he

have to do to really impress her? She retires to consider her verdict. It's

hard not to feel deflated when even your best isn't good enough. The sun

influences life in the oceans just as it does on land. Its richest parts are

those

where

waves

and

currents

bring

fertilising

nutrients

to

surface

waters that are bathed in sunlight. The seas off the Cape in South Africa

have this magic recipe and are hugely productive. Summer is the time of

plenty and it's now that the seals start to breed. The strike of a great white

shark

lasts

a

mere

second.

Slowing

it

down

forty

times

reveals

the

technique and immense strength of this massive predator. If surprise fails,

6

there will be a chase. The shark is faster on a straight course but it can't

turn as sharply as the seal, its agility versus power. Once the seals

have

finished breeding the giant sharks will move on. It's now becoming clear

that great whites migrate thousands of miles across the oceans to harvest

seasonal abundances in different seas. The sun, beating down on tropical

waters,

powers

the

weather

systems

of

the

globe.

Moisture

evaporates

from

the

warming

ocean

and

rises

to

create

great

storms.

The

winds

generated

out

at

sea

sweep

inland

across

the

continents.

As

they

travel

across the Sahara they create the biggest of all sand storms blowing sand

halfway round the world to fertilize the Amazon jungle. Winds blowing

across the Indian Ocean collect moisture and sweep northwards towards

the Himalayas. As the air rises, so it cools. The water it carries condenses

into clouds and then falls as the life giving rains of the monsoon. So air

currents

powered

by

the

sun

carry

wet

air

to

the

middle

of

continents.

Without water there can be no life, but its distribution over the land is far

from

even.

Deserts

cover

one

third

of

the

land's

surface

and

they're

growing bigger every year. This is the Kalahari Desert in Southern Africa.

It's

the

dry

season

and

thousands

of

elephants

have

started

to

travel

in

desperate

search

for

water.

All

across

Southern

Africa

animals

are

journeying for the same reason. Buffalo join the great trek. Nowhere else

on Earth are so many animals on the move with the same urgent purpose.

They're all heading for the swamps of the Okavango, a vast inland delta.

7

At the moment it is dry, but water is coming. The travellers are hampered

by

dangerous

dust

storms.

Females

and

calves

can

easily

get

separated

from the main herd. For this pair sanctuary lies in the patch of woodland

a

few

miles

ahead.

They

can't

rest

until

they

reach

it.

The

main

has

already got there safely. Finally, the stragglers emerge from the dust. The

exhausted

calf

is

still

blinded

by

sand.

Its

mother

does

everything

possible to help it. The storm is now subsiding, but not all the elephants

have been so lucky. One youngster has got lost. Thirsty and exhausted, it

follows the tracks of its mother, but sadly in the wrong direction. At the

peak of the dry season in the Kalahari water arrives in the Okavango. It

fell

as

rain

a

thousand

miles

away

in

the

highlands

of

Angola

and

has

taken nearly five months to reach here. The water drives out insects from

the parched ground, which are snapped up by plovers. Catfish, travelling

with the flood, collect any drowning creatures the birds have missed. It's

a seasonal feast for animals of all kinds. Birds are the first to arrive in any

numbers - water cranes, then black storks. Behind the birds come buffalo.

After

weeks

of

marching

their

trek

is

coming

to

an

end.

As

the

water

sweeps into the Okavango a vast area of the Kalahari is transformed into

a fertile paradise. Nowhere on our planet Earth is the life giving power of

water so clearly demonstrated. The Okavango becomes criss- crossed with

trails as animals move into its heart. The new arrivals open up paths like

arteries along which water flows, extending the reach of the flood. This is

8

an Africa rarely seen - a lush water world. Some creatures are completely

at home here. These are lechwe - antelope with hooves that splay widely,

enabling them to move its speed through the water. For others the change

is

far

less

welcome.

Baboons

are

somewhat

apprehensive

bathers.

The

water brings a season of plenty for all animals. Hunting dogs. These are

now

among

the

rarest

of

Africa's

mammals,

but

then

nonetheless

the

continent's most efficient predators. Their secret is teamwork. Impala are

their favourite prey. They start to hunt and the pack splits up. An aerial

viewpoint gives a new insight into their strategy. As the dogs approach

their prey they peel off to take up separate positions around their target.

They seem to form a cordon around the impala. Moving in total silence

they take up their positions. Those ears can detect the slightest rustle. The

hunt

is

on.

Three

dogs

close

in

on

one

impala.

Missed.

The

lead

dog

drives the impala towards the hidden flankers. Anticipating their line the

leader cuts the corner and joins a flanker for the final assault. It's all or

nothing. One on one. The dog has stamina, the impala has speed. Leaping

into the lake is an act of desperation - impala can barely swim. The dogs

know their prey must come out or drown - now it's a waiting game. The

rest of the pack are calling. They've made a kill in the forest and this is an

invitation to join in the meal. The impala is in luck. A pack this size kills

once

a day

and

everything is shared.

And

this impala is reprieved.

The

elephants

are

nearing

the

end

of

their

long

journey.

After

weeks

of

9

marching

they're

desperately

tired.

The

matriarch

can

smell

water

and

encourages the herd to make one last effort. The youngsters are exhausted

but

their

mothers

have

made

this

journey

before

and

they

know

that

they're close to water. After many hundreds of miles they've arrived. The

lives of these elephants are dominated by the annual rhythm of wet and

dry, a seasonal cycle created by the sun. At the southern end of the earth,

after

four

months

of

total

darkness,

the

sun

once

more

rises

over

Antarctica. Now at last the Emperor penguins abandon their huddle. The

males

are

still

carrying

the

precious

eggs

that

they've

cherished

throughout

the

Antarctic

winter.

With

the

returning

sun

the

eggs

hatch.

Other birds have not even arrived. but the Emperors by enduring the long

black

winter

have

given

their

chicks

a

head

start.

These

youngsters

are

now ready and eager to make the most of the brief Antarctic summer.

第

2

集

PLANET EARTH Mountains

Human beings venture into the highest parts of our planet at their peril.

Some might think that by climbing a great mountain they have somehow

conquered it, but we can only be visitors here. This is a frozen alien world.

This is the other extreme - one of the lowest hottest places on Earth. It's

10

over a hundred metres below the level of the sea. But here a mountain is

in

gestation.

Pools

of

sulphuric

acid

are

indications

that

deep

underground there are titanic stirrings. This is the Danakil Depression in

Ethiopia,

lying

within

a

colossal

rent

of

the

earth's

surface

where

giant

land masses are pulling away from one another. Lava rises to the surface

through this crack in the crust creating a chain of young volcanoes. This

one,

Erta

Ale,

is

today

the

longest

continually

erupting

volcano

on

the

planet,

a

lake

of

lava

that

has

been

molten

for

over

a

hundred

years.

These same volcanic forces also created Ethiopia's highlands. 70 million

years ago this land was just as flat and as deep as the Danakil Depression.

Molten lava rising from the earth's core forced up a huge dome of rock

500 miles wide, the roof of Africa. Over millennia, rain and ice carved the

rock

into

a

landscape

of

spires

and

canyons.

These

summits,

nearly

3

miles

up,

are

home

to

some

very

remarkable

mountaineers

Gelada

baboons. They are unique to the highlands of Ethiopia. The cliffs where

they

sleep

are

for

expert

climbers

only,

and

Gelado

certainly

have

the

right

equipment.

the

strongest

fingers

of

any

primate

and

an

utterly

fearless disposition. But you need more than a head for heights to survive

up

here.

A

day

in

a

Gelado's

life

reveals

how

they've

risen

to

the

challenge. For all monkeys morning is grooming time, a chance to catch

up

with

friends.

But,

unlike

other

monkeys,

Gelados

chatter

constantly

while they do it. It's a great way to network while your hands are busy.

11

But

these

socials

can't

go

on

for

too

long.

Gelados

have

a

busy

daily

schedule and there's work to be done. Most monkeys couldn't live up here.

There's

no

food

and

few

insects

to

feed

on.

But

Gelados

are

unique

they're the only monkeys in the world that live almost entirely on grass.

They live in the largest assemblies formed by any monkeys. Some groups

are 800 strong and they crop the high meadows like herds of wildebeest.

The Gelados graze alongside Walia ibex, which are also unique to these

highlands. These rare creatures are usually very shy but they drop their

guard when the Gelados are around. You might expect that grazers would

avoid

each

other's

patch

but

this

is

a

special

alliance

from

which

both

partners benefit. It's not so risky to put your head down if others are on

the

lookout.

Ethiopian

wolves

-

they

won't

attempt

an

attack

in

broad

daylight. But at dusk the plateau becomes a more dangerous place. With

the grazing largely over there's a last chance to socialise before returning

to the sleeping cliffs. An early warning system puts everyone on the alert.

Their

day

ends

as

it

began,

safe

on

the

steep

cliffs.

The

Ethiopian

volcanoes

are

dormant,

but

elsewhere

others

still

rage.

V

olcanoes

form

the backbone of the longest mountain chain on our planet - the Andes of

South

America.

This

vast

range

stretches

5,000

miles

from

the

Equator

down

to

the

Antarctic.

It

formed

as

the

floor

of

the

Pacific

Ocean

slid

beneath the South American continent, buckling its edge. At the southern

end

stand

the

mountains

of

Patagonia.

It's

high

summer,

but

the

Andes

12

have

the

most

unstable

mountain

weather

on the planet

and storms

can

erupt

without

warning.

Temperatures

plummet

and

guanacos

and

their

newborn young must suddenly endure a blizzard. Truly, all seasons in one

day...

A

puma

-

the

lion

of

the

Andes.

Pumas

are

usually

solitary

and

secretive. To see a group walking boldly in the open is extremely rare. It's

a

family

-

a

mother

with

four

cubs.

She

has

just

one

brief

summer

in

which

to

teach

them

their

mountain

survival

techniques.

Rearing

four

cubs

to

this

age

is

an

exceptional

feat,

but

she

does

have

an

excellent

territory, rich in food and water. Although the cubs are now as large as

their mother, they still rely on her for their food. It will be another year

before the cubs can hunt for themselves. Without their mother's skill and

experience

they

would

never

survive

their

first

winter.

Battered

by

hurricane force winds, these slopes are now lifeless. Further north, they

hold other dangers. Moving at 250 miles an hour, an avalanche destroys

everything

in

its

path.

In

the

American

Rockies

a

100,000

avalanches

devastate the slopes every winter. This huge mountain chain continues the

great spine that runs from Patagonia to Alaska. The slopes of the Rockies,

bleak

though

they

are,

provide

a

winter

refuge

for

some

animals.

A

mother

grizzly

emerges

from

her

den

after

six

months'

dozing

underground.

Her

two

cubs

follow

her

and

take

their

first

steps

in

the

outside

world.

These

steep

slopes

provide

a

sanctuary

for

the

cubs.

A

male bear would kill and eat them given the chance. But big animals find

13

it difficult to get about here. Males may be twice the size of a female and

even she can have problems. Her cubs, however, make light of the snow

and

of

life

in

general.

But

the

mother

faces

a

dilemma:

it's

six

months

since she last fed and her milk is starting to run dry. She must soon leave

the

safety

of

these

nursery

slopes

and

lead

her

cubs

away

from

the

mountain.

If

she

delays,

the

whole

family

will

risk

starvation.

Summer

reveals the true nature of the Rockies. Stripped of snow, the peaks bear

their

sculpted

forms.

Only

now

can

mountaineers

reclaim

the

upper

reaches. Two miles up the crumbling precipices seem devoid of life. But

there are animals here - a grizzly bear. It seems to be an odd creature to

find

on

these

high

rocky

slopes.

It's

hard

to

imagine

what

could

have

attracted it here. At this time of the year bears should be fattening up for

the winter. Yet they gather in some numbers on these apparently barren

slopes. They're searching for a rather unusual food - moths. Millions have

flown up here to escape the heat of the lowlands and they're now roosting

among

the

rocks.

Moths

may

seem

a

meager

meal

for

a

bear,

but

their

bodies are rich in fat and can make all the difference in a bear's annual

struggle for survival. Another battle is being waged here but on a much

longer

timescale.

These

loose

boulders

are

the

mountain's

crumbling

bones.

The

Rockies

are

no

longer

rising

but

slowly

disintegrating.

All

mountains everywhere are being worn down by frost, snow and ice. The

Alps were raised some 15 million years ago as Africa, drifting northwards,

14

collided

with

the

southern

edge

of

Europe.

These

spires

are

the

eroded

remains

of

an

ancient

seabed

that

once

stretched

between

the

two

continents. But these are just the Alpine foothills. The range at its centre

rises

to

3

miles

high

and

is

crowned

with

permanent

snows.

The

Matterhorn, its summit too steep to hold a snow field. Mont Blanc

- the

highest peak in Western Europe. The distinctive jagged shapes of the Alps

were

carved

by

those

great

mountain

sculptors

-

the

glaciers.

Immense

rivers

of

moving

ice,

laden

with

rock,

grind

their

way

down

the

mountains, gouging out deep valleys. They're the most powerful erosive

force on our planet. A moulin - a shaft in the ice opened by melt water as

it plunges into the depths of the glacier. Like the water running through it,

the

ice

itself

is

constantly

moving,

flowing

down

the

valley

with

unstoppable

force.

Alpine

glaciers

may

seem

immense,

but

they're

dwarfed by those in the great ranges that divide the Indian subcontinent

from Tibet. This is the boulder strewn snout of the giant Baltoro glacier in

the Karakoram mountains of Pakistan. It's the biggest mountain glacier on

Earth - 43 miles long and over 3 miles wide. This huge ice-filled valley is

so large it's clearly visible from space. This is the greatest concentration

of peaks over 5 miles high to be found anywhere on Earth. They're the

most dangerous mountains of all. K2 and her sister peaks have claimed

more

lives

than

any

others.

The

peaks

here

rise

so

precipitously,

the

glaciers

are

so

steep

and

crevassed

that

few

except

the

most

skilled

15

mountaineers can penetrate these ranges. Markhor gather for their annual

rut. Males must fight for the right to breed, but on these sheer cliffs any

slip

by

either

animal

could

be

fatal.

A

snow

leopard

-

the

rarest

of

Himalayan animals. It's a female returning to her lair. These are the first

intimate images of snow leopard ever filmed in the wild. She greets her

one year old cub. Her den is well chosen. It has exceptional views of the

surrounding cliffs. On these treacherous slopes no hunter other than the

snow

leopard

would

have

a

chance

of

catching

such

fragile

prey.

A

female

with

young

makes

an

easier

target.

Her

large

paws

give

an

excellent grip and that long tail helps her balance. Silently she positions

herself

above

her

prey.

She

returns

with

nothing.

Golden

eagles

patrol

these cliffs in search of the weak or injured. With a 2 metre wing span

this bird could easily take a young markhor. Eagles hunt by sight and the

thickening veil of snow forces them to give up. For the leopard the snow

provides

cover

and

creates

an

opportunity.

The

worsening

weather

dampens

the

sound

of

her

approach

allowing

her

to

get

within

striking

distance. It was an act of desperation to try and catch such a large animal.

Wolves have made a kill giving other hunters a chance to scavenge. The

worst

of

the

blizzard

brings

success

for

the

snow

leopard,

but

having

descended so far to make the kill she has a grueling climb to get back to

her lair. The cub must be patient. It'll be a year before it has the strength

and skill to kill for itself on these difficult slopes. The snow leopard is an

16

almost

mythical

creature,

an

icon

of

the

wilderness,

an

animal

few

humans

have

ever

glimpsed

for

its

world

is

one

we

seldom

visit.

The

Karakoram lie at the western end of a range that stretches across a tenth

of our planet - the Himalayas. These, the highest mountains of the world,

like other great ranges, were created by the collision of continents. Some

50 million years ago India collided with Tibet thrusting up these immense

peaks,

which

are

still

rising.

This

vast

barrier

of

rock

and

ice

is

so

colossal

it

shapes

the

world's

climate.

Warm

winds

from

India,

full

of

moisture, are forced upwards by the Himalayas. As the air rises so it cools,

causing

clouds

to

form

and

the

monsoon

is

born.

At

high

altitudes

the

monsoon rains fall as snow. Here, at the far eastern end of the range in

China,

one

inhabitant

endures

the

bitter

winters

out

in

the

open.

Most

other bears would be sleeping underground by now, but the giant panda

can't fatten up enough to hibernate. Its food, bamboo, on which it totally

relies has so little nutritional value that it can't build up a store of fat like

other bears. Most of the creatures here move up or down the slopes with

the

seasons

but

the

panda

is

held

captive

by

its

diet

for

the

kind

of

bamboo it eats only

grows at this altitude. But these forests hold fewer

challenges for the more mobile. The golden snap-nosed monkey, like the

giant panda, lives only in China. Their thick fur allows them to survive at

greater altitudes than any other monkey and when the cold bites they have

these

upper

slopes

to

themselves.

Even

if

you

have

a

warm

coat

it

17

apparently

helps

to

surround

yourself

with

as

many

layers

as

possible.

But at least these monkeys have a choice

- if they tire of tree bark

and

other

survival

food

they

can

always

descend

to

lower

warmer

altitudes

and

not

return

there

till

spring.

As

the

snows

retreat

trees

come

into

bloom. Cherry blossom. Rhododendrons - here in their natural home they

form great forests and fill the landscape with the covers of a new season.

These forests are a host to a rich variety of springtime migrants. Beneath

the blooms - another display. It's the mating season for oriental pheasants,

Himalayan

monal,

tragopan

and

blood

pheasant.

Musk

deer

make

the

most of a short flash of spring foods. This male smells a potential mate.

The red panda, rarely glimpsed in the wild. It was once considered a kind

of

raccoon,

but

is

now

believed

to

be

a

small

mountain

bear.

By

midsummer its larger, more famous relative, has retreated into a cave. A

giant panda nurses a tiny week old baby. Her tender cleaning wards off

infection. She won't leave this cave for three weeks, not while her cub is

so

utterly

helpless.

Progress

is

slow

for

milk

produced

on

a

diet

of

bamboo is wretchedly poor. Four weeks old and the cub is still blind. Its

eyes do not fully open until three months after birth, but the chances of

the cub reaching adulthood are slim. The struggle of a giant panda mother

to raise her cub is a touching symbol of the precariousness of life in the

mountains.

On

the

highest

summits

of

our

planet

nothing

can

live

permanently. The highest peak of all, Mount Everest, five and a half miles

18

above sea level and still rising - the roof of our world. Of those humans

who've tried to climb it one in ten have lost their lives. Those that succeed

can stand for only a few moments on its summit. The Nepalese call it 'a

mountain

so

high

no

bird

can

fly

above

it.'

But

each

year

over

50,000

demoiselle cranes set out on one of the most challenging migrations on

Earth. To reach their overwintering grounds in India they must cross the

Himalayas. By late morning ferocious winds are roaring past the peaks.

The

cranes

must

gain

height

to

avoid

the

building

storm.

They've

hit

serious turbulence. They must turn back or risk death. A new day and a

new opportunity. The flock stay in close contact by calling one another.

Weak from lack of food and water, they use thermals, rising columns of

warm

air,

to

gain height.

For

many

this

is

their

first

journey

across the

Himalayas. For some, it will be their last. The golden eagles have been

expecting them. The eagles work in pairs to separate a young crane from

the

flock.

It

escapes

the

touches

of

one,

and

is

caught

by

another.

But

even

a

young

crane

is

a

heavy

prize

and

the

eagle

has

to

struggle

to

control it. The mother can wait no longer - this is a desperate race against

worsening

weather.

The

rest

of

the

flock

battle

on.

In

the

ascent

every

wing

beat

becomes

an

exhausting

struggle.

At

last

they

are

over

the

highest barrier that lies in their way. But like all who visit the world of the

high mountains they dare not linger.

19

第

3

集

PLANET EARTH Freshwater

Only

3

percent

of

the

water

on

our

planet

is

fresh.

Yet

these

precious

waters

are

rich

with

surprise.

All

life

on

land

is

ultimately

dependent

upon fresh water. The mysterious tepuis of Venezuela isolated mountain

plateaus rising high above the jungle. This was the inspiration for Arthur

Conan Doyle's 'Lost World,' an imagined prehistoric land. Here, strange

towers of sandstone have been sculptured over the millennia by battering

wind and torrential rain. Moisture rising as water vapour from the surface

of the sea is blown inland by wind. On reaching mountains, the moisture

is forced upwards and as it cools, it condenses into cloud and finally rain

- the source of all fresh water. There is a tropical downpour here almost

every

day

of

the

year.

Fresh

water's

journey

starts

here,

high

in

the

mountains. Growing from humble streams to mighty rivers it will travel

hundreds

of

miles

to

the

sea.

Angel

Falls,

the

highest

waterfall

in

the

world. Its waters drop unbroken for almost a thousand metres. Such is the

height

of

these

falls

that

long

before

the

water

reaches

the

base

in

the

Devil's

Canyon

it's

blown

away

as

a

fine

mist.

In

their

upper

reaches,

mountain streams are full of energy. Streams join to form rivers, building

in power, creating rapids. The water here is cold. Low in nutrients, but

20

high in oxygen. The few creatures that live in the torrent have to hang on

for

dear

life.

Invertebrates

dominate

these

upper

reaches.

The

hellgrammite, its body flattened to reduce drag, has bushy gills to extract

oxygen from the current. Black fly larvae anchor themselves with the ring

of hooks, but if these become unstuck, they're still held by a silicon safety

line. There are advantages to life in the fast stream - bamboo shrimps can

just sit and sift out passing particles with their fan-like forearms. Usually,

these

mountain

streams

only

provide

enough

food

for

small

animals

to

survive. But with the spring melt here in Japan monsters stir in their dens.

Giant

salamanders,

world's

largest

amphibian,

almost

two

metres

long.

They're the only large predator in these icy waters. They begin their hunt

at

night.

These

salamanders

have

an

exceptionally

slow

metabolism.

Living up to 80 years they grow into giants. The fish they hunt are scarce

and salamanders have poor eyesight. But sensory nodes on their head and

body

detect

the

slightest

changes

in

water

pressure.

Free

from

competition, these giants can dine alone. Pickings are usually thin for the

salamanders, but every year some of the world's high rivers are crowded

by

millions

of

visitors.

The

salmon

have

arrived.

This

is

the

world's

largest fresh water fish migration. Across the northern hemisphere salmon,

returning from the ocean to their spawning grounds, battle their way for

hundreds

of

miles

upstream.

Up

here,

there

are

fewer

predators

to

eat

their eggs and fry. A grizzly bear. From famine to feast

- he's spoilt for

21

choice.

This

Canadian

bear

is

very

special

-

he's

learnt

to

dive

for

his

dinner. But catching salmon in deep water is not that easy and the cubs

have

lots

to

learn.

The

annual

arrival

of

spawning

salmon

brings

huge

quantities of food into these high rivers that normally struggle to support

much life. Although relatively lifeless, the power of the upland rivers to

shape the landscape is greater than any other stage in a river's life. Driven

by gravity, they're the

most erosive forces on the planet. For the past 5

million

years

Arizona's

Colorado

river

has

eaten

away

at

the

desert's

sandstone

to

create

a

gigantic

canyon.

It's

over

a

mile

deep

and

at

its

widest

it's

17

miles

across.

The

Grand

Canyon.

This

river

has

cut

the

world's

longest

canyon

system

-

a

1,000

mile

scar

clearly

visible

from

space.

As

rivers

leave

the

mountains

behind,

they

gradually

warm

and

begin

to

support

more

life.

Indian

rivers

are

home

to

the

world's

most

social

otter

-

smooth-coated

otters

form

family

groups

up

to

17

strong.

Group rubbing not only refreshes their coats, but strengthens social bonds.

When

it

comes

to

fishing

there

is

real

strength

in

numbers.

Fishing

practice begins when the cubs are four months old. Only the adults have

the speed and agility needed to make a catch. Adults share their catches

with their squabbling cubs. Most otters are solitary, but these rich warm

waters

can

support

large

family

groups

and

even

bigger

predators.

Mugger crocodiles, four metres long, could easily take a single otter. But,

confident in their gangs, the otters will actively harass these great reptiles.

22

Team play wins the day. The Mara river, snaking across the plains of East

Africa.

As

the

land

flattens

out

rivers

slow

down

and

lose

their

destructive

power.

Now

they

are

carrying

heavy

loads

of

sediment

that

stains their waters brown. Lines of wildebeest are on their march. Each

year

nearly

two

million

animals

migrate

across

the

Serengeti

plains

in

search of fresh green pastures. For these thirsty herds the rivers are not

only a vital source of drinking water, but also dangerous obstacles. This is

one of the largest concentrations of Nile crocodiles in Africa, giants that

grow

over

five

metres

long.

From

memory,

the

wildebeest

are

coming

and gather in anticipation. The crocodile's jaws snap tight like a steel trap

- once they have a hold, they never let go. It took over an hour to drown

this

full-grown

bull.

To

surprise

their

prey

crocodiles

must

strike

with

lightning speed. Here, only the narrowest line separates life from death.

Most rivers drain into the sea, but some end their journey in vast lakes.

Worldwide lakes hold twenty times more fresh water than all the rivers.

The East African Rift Valley holds three of the world's largest: Malawi,

Tanganyika, and Victoria. Lake Malawi, the smallest of the three, is still

bigger

than

Wales.

Its

tropical

waters teem

with

more

fish species

than

any

other

lake.

There

are

850

different

cichlids

alone,

all

of

which

evolved

from

just

one

single

ancestor

isolated

here

thousands

of

years

ago. These two-metre wide craters are fish-made. Fastidiously maintained

by

the

males,

these

bowls

are

courtship

arenas.

Cichlids

are

caring

23

parents.

Brooding

young

in

the

mouth

is

a

very

effective

way

of

protecting them. This lake can be a dangerous place. After dark, predatory

dolphin fish emerge from their daytime lairs among the rocks. Like packs

of sharks, they're on the prowl for sleeping cichlids. In the darkness these

electric fish hunt by detecting distortions in the electric field they create

around their bodies. Any cichlid that trenches out will be snapped up. The

floor of Lake Malawi drops 700 metres into an abyss. Here, in this dead

zone the larvae of lake fly midges hide out away from predators. In the

rainy

season

they

balloon

up

to

the

surface

and

undergo

a

magical

transformation. At dawn the first adult midges start to break out. Soon,

millions upon millions of newly hatched lake flies are taking to the wing.

Early

explorers

told

tales

of

lakes

that

smoked,

as

if

on

fire.

But

these

spiralling columns hundreds if metres high are mating flies. Once the flies

have mated, they will all drop to the water surface, release their eggs and

die. Malawi may look like an inland sea, but it's dwarfed by the world's

largest lake - Baikal in Eastern Siberia. 400 miles long and over a mile

deep, Baikal contains one fifth of all the fresh water found in our planet's

lakes and rivers. For five months of the year it's sealed by an ice sheet

over a metre thick. Baikal is the oldest lake in the world and, despite the

harsh conditions, life flourishes here in isolation. 80 percent of its species

are found nowhere else on Earth, including the world's only fresh water

seal.

With this

seal

and

its

marine-like

forests of sponges

Baikal

seems

24

more like an ocean than a lake. There are shrimp-like crustaceans - giant

amphipods - as large as mice. They are the key scavengers in this lake.

The water here is just too cold for the bacteria that normally decompose

the dead. Most rivers do not end in lakes but continue their journey to the

sea.

The

planet's

indisputable

super-river

is

the

Amazon.

It

carries

as

much

water

as

the

next

top-ten

biggest

rivers

combined.

Rising

in

the

Peruvian Andes, its main trunk flows eastwards across Brazil. On its way

the system drains a third of South America. Eventually, over 4,000 miles

from

its

source,

it

empties

into

the

Atlantic

Ocean.

The

Amazon

transports a billion tonnes of sediment a year, sediment clearly visible at

the

mixing

of

the

waters

where

one

massive

tributary,

the

Rio

Negro,

flows

into

the

main

river.

Its

waters

are

wonderfully

rich.

To

date

over

3,000 species of their fish have been described - more than in the whole

of the Atlantic Ocean. The Amazon is so large and rich in fish that it can

support

fresh

water

dolphins.

These

botos

are

huge

-

two

and

a

half

metres

long.

In

these

murky

waters

they

rely

on

sonar

to

navigate

and

hunt. They work together to drive shoals of fish into the shallows. Botos

are highly social and in the breeding season there is stiff competition for

mates. The males hold court in a unique way. They pick up rocks in their

jaws

and

flaunt

them

to

their

attending

females.

Maybe

each

male

is

trying to show how strong and dexterous he is and that he therefore is the

best father a female could have for her young. Successful displays lead to

25

mating. Even for giant rivers like the Amazon the journey to the sea is not

always smooth or uninterrupted. Iguassu Falls on the border of Brazil and

Argentina

is

one

of

the

widest

waterfalls

in

the

world

-

one

and

a

half

miles across. In flood 30 million litres of water spill over every second.

All the world's great broad waterfalls: Victoria, Niagara and here, Iguassu,

are

only

found

in

the

lower

courses of

their

rivers.

In their

final

stages

rivers broaden and flow wearily across their flat flood plains. Each wet

season here, in Brazil, the Parana river overflows its banks and floods an

area the size of England. The Pantanal

- the world's largest wetland. In

these slow-flowing waters aquatic plants flourish like the Victoria giant

water

lily

with

leaves

two

metres

across.

These

underwater

forests

are

nursery

grounds

for

fish.

Over

300

species

breed

here,

including

red-bellied

piranha

and

other

predators,

like

the

spectacle

caiman.

Ripening

fig

trees

overhanging

the

water's

edge

provide

welcome

food

for shoals of hungry fish. The commotion attracts dorado, known locally

as the river tiger. They patrol the feeding shoals, looking for a chance to

strike. And waiting in the wings, ready to pick off any injured fish, are the

piranhas. The feeding frenzy quickly develops. Piranha can strip a fish to

the bone in minutes. Great numbers of fish sustain vast flocks of water

birds. The rose-eared spoonbill is just one of the 650 bird species found in

the

Pantanal.

They

nest

alongside

wood

stocks

in

colonies

thousands

strong. Spectacle caiman linger below, waiting for a meal to fall out of

26

the sky. When rivers finally reach the sea they slow

down, release their

sediment

and

build

deltas.

In

Bangladesh

the

Ganges

and

Brahmaputra

rivers

join

to

form

the

world's

biggest.

Every

year

almost

2

thousand

million tonnes of sediment eroded from the Himalayas is delivered to the

ocean. At the delta's mouth - the largest mangrove forest in the world, the

Sundarbans. These extraordinary forests spring up throughout the tropics

in these tidal zones where rivers meet the sea. Crab- eating macaques are

mangrove

specials.

In

Indonesia

these

monkeys

have

adopted

a

unique

amphibious lifestyle

- they fish out fallen food. The troop also uses the

waters to cool off during the heat of the day. But the channels are also the

playground for restless young macaques. Some of the young have even

taken

to

underwater

swimming.

They

can

stay

down

for

more

than

30

seconds

and

appear

to

do

this

just

for

fun.

Yet

these

swimming

skills

acquired during play will certainly be useful later in life in these flooded

mangrove

forests.

In

cooler

climes,

mud,

laid

down

in

estuaries,

is

colonised

by

salt

marsh

grasses

and

form

one

of

the

most

productive

habitats on the planet. 400,000 greater snow geese flock to the estuaries

along

the

Atlantic

coast

of

the

United

States

to

rest

and

refuel

on

their

long

migratory

journeys.

This

is

the

end

of

the

river's

journey.

Collectively they've

worn down mountains and carried them

to the sea.

And all along the way, their fresh water has brought life and abundance to

planet Earth.

27

第

4

集

PLANET EARTH Caves

This

is

our

planet's

final

frontier,

an

inner

world

where

only

the

most

adventurous

dare

to

go.

Beneath

our

feet

are

countless

miles

of

cave

shafts and passages. The Cave of Swallows in Mexico, 400 metres to the

bottom,

deep

enough

to

engulf

the

Empire

State

Building.

This

is

the

biggest cave shaft in the world. Yet these depths were first explored only

two years before man landed on the moon. Today caves remain the least

explored places on Earth. However, human beings are seldom the first to

reach

these

black,

damp

places.

Here,

live

some

of

the

strangest

and

least-known animals on the planet. This galaxy of little lights is created

by thousands of living creatures. Any animal that lives in a cave has to

cope with complete blackness, but in New Zealand some have turned this

darkness to their advantage. A silicon strand is lowered from the ceiling,

alongside

hundreds

of

others.

Beautiful

though

these

threads

are,

they

have a sinister purpose. This is a cave glow worm. To trap its prey it goes

fishing with a line of silk. The silk comes from glands in the glow worm's

mouth and is loaded with droplets of mucus. Each glow worm produces

dozens of these threads. Once its lines are set, the glow worm hangs from

28

a

mucus hammock

and

waits, like

a patient angler. But the

glow

worm

doesn't leave everything to chance. That ghostly blue light is the result of

a chemical reaction taking place inside a special capsule in its tail. The

light

literally

shines

out

of

its

backside.

It's

a

lure

for

attracting

prey.

Insects seem irresistibly drawn towards the source and then get trapped

by the sticky lines. Once stuck, there is no escape. Now it's just a matter

of

reeling

in

the

line

and

slowly

consuming

the

catch

-

alive.

By

ensnaring

the

insects

that

hatch

in

this

cave,

these

glow

worms

have

solved the biggest challenge that permanent cave dwellers face - finding a

regular and reliable source of food. One kind of rock makes this whole

underground

world

possible

-

limestone.

Most

of

the

world's

caves

are

found

within

it

and

it

covers

nearly

10

percent

of

the

earth's

surface.

Limestone is composed of minerals derived from marine shells and corals,

so although this rocky escarpment in the United States is now hundreds of

metres above sea level it was actually formed under water. The limestone

towers of Vietnam's Ha Long Bay are a reminder of this link with the sea.

Originally, this whole area would have been one solid block of limestone,

the base of a coral reef. In Borneo, rain has sculptured the limestone into

extremely

sharp-sided

pinnacles.

But

the

dissolving

power

of

rainwater

has other, much more dramatic effects underground. Rivers that flow over

limestone

often

seem

to

completely

disappear.

When

the

water

reaches

the

more

resistant

bed

of

limestone

its

course

is

altered.

Once

29

underground, the water takes on a new,

more erosive power. During its

journey from the surface the water absorbed carbon dioxide from the soil

making it mildly acidic. And over millions of years this acid eats away

the limestone creating a maze of caverns and passages that sometimes go

on for miles. This is the biggest underground river passage in the world,

so big

a

jumbo

jet

could

fly

through

it.

It's

Deer

Cave, in

Borneo.

The

sheer

size

of

Deer

Cave

allows

some

animals

to

gather

there

in

huge

numbers. A staggering 3 million wrinkle-lipped bats live here. The bats

roost high on the walls and ceilings where they're well protected from the

outside elements and safe from predators. And while they're up here the

bats produce something very important. This hundred metre high mound

is made entirely of bat droppings - guano. Its surface is covered by a thick

carpet of cockroaches, hundreds of thousands of them. Caves are one of

the few habitats on Earth not directly powered by sunlight. In the absence

of plants this food chain is based on a continuous supply of bat droppings.

The

cockroaches

feed

on

the

guano

and

anything

that

falls

into

it.

The

droppings

also

support

other

types

of

cockroaches

which

spend

part

of

their day resting on cave walls. These in turn become food for giant cave

centipedes,

some

more

than

20

centimetres

long.

Bizarrely,

there

are

crabs

here,

too,

sifting

through

the

droppings

for

nutrients.

All

these

animals spend their entire lives within the cave. They're totally dependant

on

the

digested

remains

of

food

that's

brought

here

from

outside.

Each

30

evening in just two hours three million bats leave the safety of the cave to

hunt for insects in the forest outside. But not all will return. As they leave

the cave the stream of bats form a doughnut-shaped ring. The wheeling

bats seem to confuse a rufus-bellied eagle, but they must still survive the

attacks of other, more specialised, birds of prey. Peregrine falcons and bat

hawks are the jetfighters of the bird world. Good hunting will end as the

light fades so the bat hawks bolt their catches on the wing and fly straight

back

for

more.

Any

bat

separated

from

the

group

becomes

a

clear

and

obvious

target

and

is

asking

for

trouble.

Yet

the

nightly

onslaught

has

little impact on bat numbers

- by the morning the vast majority

will be

back in the safety of the cave. Bats are not the only commuters in these

Bornean caves. There's a day shift as well. Returning from hunting in the

sunlight

these

commuters

rely

on

their

loud

clicks

to

find

their

way

through the cave passages in total darkness. They're cave swiftlets. Like

bats they use echolocation to navigate. We need lights to see what's going

on, but in the pitch black the swiftlets manage unerringly to locate their

individual

nesting

sites,

which

are

only

a

few

centimetres

across.

It's

a

remarkable skill and one we still do not fully understand. These birds are

unusual

for

another

reason.

Their

little

cup- like

nests

are

made

entirely

from threads of saliva. It takes more than 30 days to complete one. The

nests are very precious objects, and not only for the birds. For 500 years

people have been harvesting the nests of cave swiftlets. It's a very risky

31

business. with virtually no safety equipment and using ladders made from

forest vines the gatherers climb into the highest reaches of the cave often

more than 60 metres from the floor. The work may be hazardous in the

extreme, but the rewards are great. The pure white nests of cave swiftlets

are the main ingredient of birds' nest soup and gram for gram are worth as

much

as

silver.

As

soon

as

its

nest

is

removed

a

bird

will

immediately

build another. So, as long as this valuable harvest is properly controlled,

the colonies will continue to flourish. These Bornean caves are among the

biggest in the world and they're still getting bigger as each year rainwater

eats away a little more limestone. But water in caves doesn't only erode.

It also builds. This water is loaded with dissolved limestone and when it

meets the air in the cave some of that is deposited as a mineral - calcite.

As it builds up so the calcite forms decorations that hang from the ceiling

- stalactites. Each drop leaves behind only a miniscule amount of calcite,

but

over

time

the

process

can

produce

some

spectacular

results.

If

the

water seeps though the ceiling quickly, then the calcite is deposited on the

floor of the cave and that creates stalagmites. Variations in water flow and

the air currents produce an infinite variety of forms, but all are created by

the same process - the slow deposition of dissolved limestone. And when

stalactite meets stalagmite a column is born. Structures like these in North

America's Carlsbad Cavern can take many thousands of years to develop.

But

sometimes

the formations

in

a cave stop

growing

altogether.

These

32

flooded

caves

in

Mexico

have

remained

virtually

unchanged

for

thousands of years. Since the last Ice Age they've become cut off from the

outside world. Yet their impact on life on the surface has been huge. 500

years ago they supported one of the world's great civilisations the Maya.

Mexico's Y

ucatan Peninsula has no rivers, lakes or streams so the Maya

relied

on

the

cenotes

-

the

flooded

entrances

to

the

water-filled

caves.

These flooded shafts are the region's only source of open fresh water. The

cenotes

are,

in

effect,

gigantic

fresh

water

wells.

Away

from

the

life-giving rays of sunshine one might not expect to find plants. But in the

darkness of the cave tunnels roots of giant tropical trees have pushed their

way

through

cracks

in

the

limestone

to

reach

the

flooded

caverns.

Without this water the Yucatan's forest could not grow so luxuriantly. The

Maya knew that their lives depended on this water, but it's only with the

help

of

today's

technology

that

we've

come

to

appreciate

the

full

significance

and

scale

of

these

flooded

passageways.

So

far,

more

than

350 miles of underwater galleries in the Yucatan have been mapped, but

still nobody

yet knows the true extend of this subterranean waterworld.

And

with

good

reason.

Underwater

caving

is

notoriously

dangerous.

When the nearest exit may be hundreds of metres or more away, running

out

of

air

down

here

would

be

fatal.

To

avoid

getting

lost

divers

carry

with them a spool of string. It becomes their lifeline - literally. The string

also doubles as a measuring tape - a technique that has been used here, in

33

Mexico, to chart the largest underwater cave in the world - all 100 miles

of it. Cave exploration often requires you to push yourself through narrow

gaps

in

the

rock.

Cavers

call

such

places

'squeezes.'

The

tighter

the

squeeze,

the

greater

the

chance

of

damaging

some

vital

life-support

system. In these conditions a diver could easily become disorientated and

that could be fatal. The flooded caverns can play tricks on you in other

ways. What seems like air, isn't. It's just another kind of water. This is a

halocline - a meeting of fresh and salt water. Fresh water from the jungle

flows

over

the

heavier

salt

water

from

the

sea.

The

saltwater

layer

is

extremely

low

in

oxygen

making

it

a

particularly

difficult

place

for

animals to live. Yet some have managed it, like the remiped, one of the

most

ancient

of

all

living

crustaceans.

The

Maya

understood

the

importance

of

the

cenotes,

but

they

could

never

have

known

that

these

flooded passageways were actually the beginning of subterranean rivers,

all of which eventually flow out to the sea. Salt water, unlike fresh water,

does

not

erode

limestone,

so

most

sea

caves

are

created

by

the

mechanical pounding of the waves. The rocky outcrops of New Zealand's

Poor

Knight

Islands

are

riddled

with

sea

caves

and

just

like

those

in

Borneo

they

have

become

important

shelters

for

many

species.

After

a

day feeding in the open water vast shoals of demoiselle fish return to the

caves, which they use as a refuge from predators. For these fish the caves

are a night time retreat, but they're not the only commuters in here. There

34

are

other

fish

working

to

a

different

schedule.

The

bigeyes

are

the

equivalent of bats. Night feeders leave the cave each evening. And like all

cave

commuters

they

are

most

vulnerable

at

the

scheduled

time

of

departure.

A

bottleneck

funnels

these

exiting

bats

into

dense

concentrations attracting the attention of others. The bats can detect the

snakes using echolocation, but the snakes are literally in the dark - they

can

see

nothing.

The

strikes

seem

to

be

largely

hit-and-miss,

but

the

snakes have a secret weapon. They can actually sense each bat flying past.

Receptors in the snake's head pick up the heat given off by the flying bats,

as

this

thermal

image

shows.

To

the

snakes

the

bats

are

apparently

glowing and this gives them something to aim at. This is the price that

these cave commuters must pay for their daytime sanctuary on the ground.

Small wonder then that there are other cave dwellers that stay put. Many

caves

are

like

islands

-

cut

off

from

the

outside

world

and

from

other

caves. This isolation has resulted in the evolution of some various strange

creatures. They are the cave specialists - troglodytes, animals that never

emerge from the caves or see daylight. These troglodytes from Thailand

are possibly the most specialised creatures on Earth for they live only in

cave waterfalls. The entire population of these cave angel fish seems to

be

restricted

to

just

two

small

caves.

It's

the

same

story

with

other

troglodytes.

There

may

well

be

less

than

a

hundred

Texas

cave

salamanders in the wild. And the Belizean white crab is another creature

35

that is unique to just one cave system. Living in perpetual darkness they

have all not only lost the pigment in their skin, but also their eyes. It takes

thousands of generations for eyes to be lost, so these species must have

been

isolated

for

a

very

long

time.

But

the

blind

salamander

has

other

highly

developed

sensory

organs.

Receptors

in

their

skin

detect

minute

movements in the water made by its prey. External gills help it to breathe

in water that is particularly low in oxygen. The cave angel fish feed on

bacteria

in

the

fast

flowing

water

keeping

their

grip

with

microscopic

hooks on their fins. Food is often in short supply and troglodytes like the

crab have to survive on whatever washes into the cave from outside. The

salamander

might

not

encounter

food

for

several

months,

so

when

something does come along it can't afford to miss it. It's astonishing that

these extraordinary cave dwellers manage to survive at all. But one cave

is

so

inhospitable

that

one

would

not

expect

it

to

contain

any

life

whatsoever.

The

water

flowing

out

of

the

Villa

Luz

cave

in

Mexico

is

actually

coloured

white

with

sulphuric

acid.

Explorers

entering

this

dangerous

cave

must

wear

respirators

and

carry

monitors.

Poisonous

gases

rise

to

fatal

levels

so

quickly

that

an

early

warning

system

is

essential.

Bats

survive

by

staying

close

to

the

skylights,

but

venturing

deep

into

the

cave

is

very

dangerous

indeed.

The

source

of

these

toxic

fumes lies several miles below. Hydrogen sulphide gas bubbles up from

oil deposits in the earth's crust. It mixes with oxygen and the water, and

36

forms sulphuric acid. These are not the sort of conditions in which you

would expect to find fish, yet these cave mollies seem to thrive despite

the

acid

and

the

low

levels

of

oxygen.

There

is,

in

fact,

more

life

here

than anyone would think possible, but the biggest surprise is something

altogether

more

bizarre.

These

strange

stalactite-like

formations

are

known, rather appropriately, as snotites, the drops dripping from the ends

are sulphuric acid, strong enough to burn skin. The snotites are, in fact,

vast

colonies

of

bacteria,

capable

of

going

a

centimetre

a

day.

In

this

world

without

sunlight

these

bacteria

extract

energy

from

the

hydrogen

sulphide

gas.

Bacteria

like

these

are

known

as

extremofile

because

of

their ability to survive in such extreme conditions. And these extremofiles

play another important role in this cave. Surprisingly, they are the basis of

a food chain which supports, amongst other creatures, the larvae of these

midges.

Villa

Luz's

ecosystem

was

certainly

very

remarkable,

but

cave

explorers

were

soon

to

make

an

even

more

astonishing

discovery.

Beneath

this

arid

landscape

lies

a

subterranean

wonderland.

Without

water one might not expect to find any caves, but beneath these rolling

desert slopes in the United States lies one of the longest, deepest and most

surprising caves in the world. Its secrets remained unknown until 1986,

when cavers dug through several metres of loose rock to the bottom of

this pit. They named the cave 'Lechuguilla' and since this discovery more

than

120

miles

of

passageways

have

been

mapped.

When

the

first

37

explorers

descended,

no-one

guessed

at

the

sheer size

of this

cave.

But

even that was not going to be the biggest surprise. Little did they realise

that Lechuguilla would soon be regarded by cavers the world over as the

most beautiful of all caves. They were about to discover some of the most

exquisite formations ever seen underground. The walls were covered with

the most delicate and fragile crystals. Many of these crystals were made

of

gypsum,

a

mineral

that

comes

from

limestone.

And

there

was

mile

after mile of them. Water is the creator of most caves, but, unlike all other

limestone caves, Lechuguilla's rock had not been eaten away by running

rainwater.

Something

else

was

responsible.

The

only

water

Lechuguilla

has are these wonderfully still clear pools. As the explorers went deeper

into

the

cave,

they

came

across

whole

galleries

filled

with

the

most

unusual

formations,

like

these

5-metre

cones,

frosted

with

the

most

delicate

crystals.

It

was

Lechuguilla's

gypsum

crystals

that

made

scientists question how these caverns were formed. They discovered that

Lechuguilla's limestone had actually been eaten away by sulphuric acid,

cutting

through

literally

miles

of

limestone.

And

when

sulphuric

acid

dissolves

limestone

it

leaves

behind

gypsum,

the

basis

of

Lechuguilla's

remarkable formations. And there was one set, more than a mile from the

surface,

that

almost

defied

belief.

The

Chandelier

Ballroom

was

the

ultimate

discovery.

With

its

six-metre

long

crystals

it's

surely

the

most

bizarre cave chamber in the world. And the walls had one further surprise.

38

Extremofile

bacteria

were

found

to

be

feeding

on

the

rock

itself.

The

discovery of life that exists without drawing any of its energy from the

sun

shows

us

once

again

how

complex

and

surprising

the

underground

world can be. Each year explorers chart over a hundred miles of new cave

passages.

But

with

half

the

world's

limestone

still

to

be

explored,

who

knows how many Lechuguillas are still waiting to be discovered?

第

5

集

PLANET EARTH Deserts

A third of the land on our planet is desert. These great scars on the face of

the Earth appear to be lifeless, but surprisingly none are. In all of them

life manages somehow to keep a precarious hold. Not all deserts are hot.

Fifty-mile-an-hour winds blowing in from Siberia bring snow to the Gobi

Desert

in

Mongolia.

From

a

summer

high

of

50

degrees

centigrade

the

temperature in midwinter can drop to minus 40, making this one of the

harshest deserts of all. Few animals can survive these extreme changes.

Wild

Bactrian

camels,

one

of

the

rarest

mammals

on

the

planet.

And

perhaps

the

hardiest.

Their

biggest

problem

is

the

lack

of

water,

particularly

now,

in

winter,

when

the

little

there

is

is

locked

up

as

ice.

Surprisingly, snow here never melts. The air is just too cold and too dry

39

for it to do so. The sun's rays turn it straight into vapour. It evaporates.

But it is the only source of water, so Bactrian camels eat it. Elsewhere in

the world a camel at a waterhole can drink as much as 200 litres during a

single visit. Here the strategy is to take little and often. And with good

reason, for filling the stomach with snow could be fatal. The camels must

limit

themselves

to

the

equivalent

of

just

10

litres

a

day.

Winter

is

the

time

for

breeding.

This

extraordinary

performance

is

a

male

Bactrian

camel's way of attracting the attention of a passing female. In summer the

camels can't stray far from waterholes. But now, with mouthfuls of snow

lying everywhere they can travel widely in search of mates. Today less

than a thousand of these desert specialists remain in the wild. The Gobi,

hostile though it is, is their last stronghold. There's no other desert quite

like

the

Gobi,

but

why

is

this

place

a

desert?

There

is

one

simple

and

massive

cause

-

the Himalayas.

Clouds

blowing

from

the

south

hit

this

gigantic barrier. As they're forced upwards so they empty their moisture

on the mountain slopes, leaving little for the land on the other side. From

the space deserts are very conspicuous. Dunes of sand hundreds of miles

long

streak

their

surface.

With

no

cloak

of

vegetation

to

conceal

them

strange formations are exposed in the naked rock. Africa's Sahara is the

largest

desert

of

all.

It's

the

size

of

the

United

States

and

the

biggest

source of sand and dust in the entire world. Sandstorms like these appear

without

warning

and

reduce

visibility

for

days

over

areas

the

size

of

40

Britain.

Dromedaries,

single-humped

camels,

take

these

storms

in

their

stride. The heaviest sand rises only a few metres above the ground, but

the dust can be blown 5,000 metres up into the sky. The ferocious wind,

armed

with grains

of

sand, is

the agent that

shapes

all deserts.

Reptiles

have armoured scaly skins that protect them from the stinging grains. For

insects the bombardment can be very severe indeed. The only escape is

below the surface. As the winds rise and fall, swallow and eddy so they

pile

the

sand

into

dunes.

These

sand

scenes

can

be

hundreds

of

miles

across. In Namibia the winds have built some of the biggest dunes in the

world. Star dunes like these can be 300 metres high. Grains, swept up the

flanks, are blown off the crests of the ridges so it's only the tops that are

moving.

The

main

body

of

these dunes may

not

have

shifted

for

5,000

years. Few rocks can resist the continuous blast of the sand carrying wind.

These outcrops are standing in Egypt's White Desert. But they will not do

so

for

much longer. They're

being inexorably

chiseled away

and

turned

into more sand. Now lumps of heavily eroded rocks have been marooned

in a sea of sand. These jagged pyramids a hundred metres tall were once

part

of

a

continuous

rocky

plateau.

The

blasting

sand

will

eventually

eliminate them altogether. The relentless power of the wind ensures that

the

face

of

a

desert

is

continually

changing.

But

there

is

one

constant

presence - the desert sun. The sun's heat and power to evaporate water has

had

a

profound

effect

on

the

bodies

and

habits

of

everything

that

lives

41

here.

This

sun

potentially

is

a

killer.

And

the

red

kangaroos

must

acknowledge that. Right now, while the sun is low, there's no immediate

cause

for

concern.

But

this

situation

won't

last

long.

Australia

is

the

world's most arid continent with blistering daytime temperatures. Every

hour the temperature rises by five degrees centigrade. Soon the heat will

reach a critical point. Any kangaroo out in the open is in serious danger of

overheating.

In

the

full

sun

the

temperature

on

the

ground

soars

to

70

degrees. By midday the radiation is so intense they must take shelter. In

the shade they're shielded from much of the sun's energy but their body

temperature can still rise. So they lick saliva on to their forearms where

there is a network of blood vessels close to the surface of the skin and, as

the

saliva

evaporates,

their

blood

is

cooled.

This

thermal

image

shows

just

how

effective

the

process

is.

The

blue

areas

on

the

body

are

the

cooler

parts.

As

the

saliva

dries

it

has

to

be

replaced

and

this

is

a

real

drain on the kangaroo's body fluids. Even in the shade the earth is baking

hot

so

the

kangaroos

dig

away

the

warmed

topsoil

to

get

at

the

cooler

ground beneath. By staying in the shade and licking to control their body

temperature kangaroos manage to get through the hottest part of the day

without heat stroke. But for the majority

of desert animals this strategy

would not be enough for survival. The extraordinary ears of the fennec

foxes of Africa radiate heat but the animals have another way of keeping

cool.

They

spend

their

days

underground

and

only

emerge

at

sunset.

42

Darkness brings huge changes. In the Sahara the temperature can drop as

much as 30 degrees during the night, so it's cool enough to allow these

desert fox cubs to play. All sorts of creatures now appear including some

really unexpected ones. Toads have permeable skins and would quickly

die from desiccation out in the daytime heat. It's only now that they can

leave shelter. The same is true for scorpions, even though their shells are

actually watertight. In fact, most small desert creatures are nocturnal. so

it's only now that you can judge just how much life there can be in the

desert.

But

moisture,

lost

even

at

night,

has

to

be

replaced

sometime

somehow and that problem dominates the lives of all desert dwellers. The

Atacama in Chile. This is the driest desert in the world. Some parts may

not see rain for fifty years and with such a record you'd expect the place

to

be

completely

barren.

These

are

South

America's

camels,

guanacos.

They're

very

good

at

conserving

moisture

but

they

nonetheless

need

a

regular

supply

of

water.

They

get

it

partly

from

cactus

flowers

but that

explanation

raises

another

question.

How

do

the

cacti

survive

without

rain?

Hot

winds

suck

all

the

moisture

from

the

surface

of

the

land.

Clearly

there

must

be

something

else

that

takes

the

place

of

rain.

The

secret is a cold sea current that runs parallel to the land. The cold water

cools the moist warm air above it and that produces banks of fog. At the

same time wind blowing on to the shore sweeps the fog inland. Before

long the cacti are dripping with dew. The fog is so regular that moisture

43

loving lichens are able to grow on the cacti and they absorb liquid like a

sponge. In the land of almost no rain these precious drops are life-savers

for many different creatures. Further inland the air remains so warm that

its moisture does not condense so this slender strip of desert is virtually

the only part of the Atacama where life can exist. Without the fog, this

land, too, would be empty. The guanacos make the most of the dew but it

will not remain for long. In an hour or two the sun will have burnt it off

and

dry

the

surface

of

the

cacti.

The

Sonoran

desert

in

Arizona

is

not

quite so dry as the Atacama - some rain does fall. But it is infrequent and

when it does arrive animals and plants have to be ready to make the most

of

it.

And

it's

coming.

When

the

summer

monsoon

blows

in

the

giant

saguaros, one of the biggest of all cacti, are ready to take full advantage

of it. After a rainstorm the saguaro's long shallow root system sucks up

the water and the pleats on its trunk enable it to expand rapidly. When full,

a saguaro stem can store up to five tonnes of water and that's enough to

see it through many months of drought. The trunks of these huge plants

provide

homes

for

the

gila

woodpecker.

But

birds

are

not

the

only

animals to benefit from the presence of the cacti. During four weeks of

the summer the saguaros bloom at night to attract visitors. The pollen and

nectar

with

which

these

flowers

are

loaded

attract

long-nosed

and

long-tongued bats. The bats left Mexico a few days earlier to escape the

heat of summer and are on their way north to the southern United States.

44

To get there, they have to cross the Sonoran desert. But the desert is so

big that for most of the year they would be unable to cross it. Now, with

the saguaro in bloom, they can refuel on the way. So the saguaro's success

in developing a way to store water is now crucial to most of the animals

that live or even travel through this land. The scarcity of rain determined

the shape of this icon of the desert but water, scarce thought it is, has also,

like the wind, shaped the land itself. In the deserts of Utah ancient rivers

flowing across sandstone country steadily widen their canyons until now

the

land

between

them

has

been

reduced

to

spires

and

pinnacles.

With

little or no soil to retain the water on the surface of the land life here is

scarce indeed. And when resources are limited, conflict is never far away.

These

are

Nubian

ibex

and

they

are

squaring

up

for

a

duel.

And

when

trouble

starts,

a

smart

ibex

knows

that

the

best

thing

to

do

is

to

gain

higher ground. These are actually subordinate male ibex, but their fights

are nonetheless serious. Losing one might mean never getting the chance

to

breed

ever.

When

competitors

are

evenly

matched

as

they

are

here,

duels can last for an hour. In this heat the effort is trully exhausting. But

victory here will gain important ranking points on a male's way to the top.

There's so much at stake that not all play fair. The battle has produced the

winner, but the ultimate prize is not his yet. That currently belongs to the

dominant male ibex. His rank earns him the loyalty of a harem of females

and they follow him closely as he travels across this desert searching for

45

foof and water. He doesn't have to waste time looking for mates - they're

his

for

the

taking,

so

he

can

concentrate

with

them

on

keeping

fit

and

healthy.

Lizards

are

desert

specialists.

But

here,

their

numbers

are

extraordinary. These crevices in South Africa contain the highest density

of lizards in the world. They're called flat lizards for obvious reasons, and

they flaunt their multi-coloured bellies in territorial disputes. He's made

his point, and now it's time to find some food. As the day warms up, the

lizards move away from their cracks and head down to the bottom of the

gorge. Their goal is the river. There is no food at the edge, but this desert

river holds a secret. Each day blackfly rise from turbulent stretches of the

river. This is what the lizards have come for. The black fly never land, so

the lizards have to leap for their food. In one day each of these acrobatic

little lizards may catch 50 flies. There are plenty of flies to go round, even

with hundreds of lizards competing for them. Away from these rapids flat

lizard

populations

are

found

in

much

smaller

numbers.

But

here

one

unusual abundance has produced another. Deserts are created by the lack

of water, but what actually kills animals here is not heat or thirst, but lack

of food. So how on earth does a plant- eater this size survive in a place

apparently

totally

devoid

of

vegetation?

Elephants

in

Namibia

are

the

toughest

in

Africa.

And

they

need

to

be.

What

little

food

exists

is

so

dispersed that these elephants walk up to 50 miles a day as they travel up

the dry river channels searching for something to eat. At times the task

46

looks truly helpless. Elephants may seem out of place in this landscape,

but they're not the only ones. Amazingly, lions live here, too. In savanah

country huge herds of games support prides containing 20 lions or more.

But to live here lions have had to change their habits

- prides are much

smaller and their home ranges are very much bigger. And there's an added

problem - their food is always on the move. Like the elephants, the lions

must travel great distances to find enough to live on. But lions can't go

everywhere - they won't attempt to cross this field of sand dunes and the

oryx know it. The lions must wait for the oryx to leave the safety of the

dunes, which eventually they must to find food and water. And then the

lions will ambush them. The elephants have found some of their favourite

food.

Grasses

are

the

staple

diet

of

all

elephants,

but

this

herd

concentrates

on

digging

up

the

roots,

which

have

more

nutrition

and

moisture than the stems. It's the sort of behaviour that can make all the

difference

in

a place

of serious shortages.

Yet

all this

can

change

in an

instant.

The

fortunes

of

many

deserts

are

ruled

by

distant

rains.

This

water

fell

as

rain

in

mountains

more

than

a

hundred

miles

away.

It's

known as a flash flood and called that because the water may run for just

a single day. It's an event that only happens once or twice a year at the

most. The sandy riverbed acts like a giant strip of blotting paper sucking

up

the

water

as

soon

as

it

appears.

But

every

square

metre

of

soil

moistened by this river will increase the chances of survival for those that

47

live here. Waterholes are filled temporarily. Elsewhere in Africa elephants

drink

every

day,

but the lack

of

water here

means

that

desert elephants

can only refill their tanks once every four or five days. Within a week the

flash flood has produced a flush of green, more than enough to draw the

oryx out of the dunes. It's a rare chance for them to build up their food

reserves.

The

flood has

made

life

easier for the lions, too.

The

flesh of

this

oryx

will

keep

the

family

going

for

a

week

at

the

most.

But

for

a

while the hunting will be easier, now that river channel has turned green.

The

good

times

for

lions

and

oryx

are

brief,

but

these

are

the

short

moments

that

make

it

possible

to

live

in

deserts

the

year

round.

Death

Valley

is

the

hottest

place

on

Earth.

Yet

even

this

furnace

can

be

transformed

by

water.

A

single

shower

can

enable

seeds

that

have

lain

dormant for 30 years or more to burst into life. And there hasn't been a

bloom like this one for a century. The periods of boom in Death Valley

are

short.

but

they're

just

frequent

enough

to

keep

life

ticking

over.

A

sudden

flush

of

vegetation

is

what

every

desert

dweller

waits

for,

and

when it happens they must make the most of it. There is no other species

on

the

planet

that

responds

as

quickly

and

as

dramatically

to

the

good

times as the desert locust. Eggs that have remained in the ground for 20

years begin to hatch. The young locusts are known as hoppers, for at this

stage they're flightless. They find new feeding grounds by following the

smell

of

sprouting

grass.

Normally

it

takes

four

weeks

for

hoppers

to

48

become

adults,

but

when

the

conditions

are

right

as

now

their

development

switches

to

the

fast

track.

As

the

vegetation

in

one

place

begins to run out the winged adults release pheromones - scent messages,

which tell others in the group that they must move on. And when groups

merge,

they

form

a

swarm.

An

adult

locust

eats

its

entire

body

weight

every day, and a whole swarm can consume literally hundreds of tonnes

of vegetation. They have to keep on moving. The swarm travels with the

wind - it's the most energy-saving way of flying. Following the flow of

wind

means

that

they're

always

heading

toward

areas

of

low

pressure,

places where wind meets rain and vegetation starts to grow. As they fly,

swarms

join

up

with

other

swarms

to

form

gigant???ic

plagues

several

billions strong and as much as 40 miles wide. They will consume every

edible thing that lies in their path. This is one of planet Earth's greatest

spectacles. It's rarely seen on this scale and it won't last long. Once the

food is gone, the steady roar of a billion beating locust wings will once

again be replaced by nothing more than the sound of the desert wind.

第

6

集

PLANET EARTH Ice Worlds

Both

poles

of

our

planet

are

covered

with

ice.

They're

the

largest

and

49

most demanding wildernesses of all. Nowhere else on Earth is seasonal

change so extreme. It causes the ice to advance and retreat every year and

all

life

here

is

governed

by

that.

When

the

first

polar

explorers

headed

south giant cathedrals of ice marked their entry into uncharted territory.

Passing the towering spires they must've wondered what unearthly sights

lay in store. As they battled on the ice became increasingly dominant but

nothing could have prepared them for the ice world that finally loomed

into

view.

Terra

incognita

-

the

unknown

land.

At

the

southernmost

extreme of our planet the continent of Antarctica is as large as the United

States of America. Ninety percent of all the world's ice is found here. This

frozen world is largely deserted until the start of spring. Adelie penguins

in a hurry. The clock is ticking. Instead of waiting for the summer melt

the new arrivals hasten south over the frozen sea. They have come here to

breed but polar summers are so short they must be in position before the

thaw starts. As the sea ice retreats life can journey farther south. Antarctic

waters are so rich that visitors come from far and wide to harvest them.

Vast numbers of chinstrap penguins come ashore to breed. No bird will

lay their eggs directly onto ice so bare rock is a vital commodity. The best

patches are worth the climb. The clifftops are soon stained pink with the

droppings of tens of thousands of nesting penguins. Only in a land almost

entirely covered in ice could bare rock be reckoned an oasis. Some will

travel into the heart of the continent to find it. These are noon attacks the

50