All language subtitles for The Living Planet s01e07 The Sky Above.eng

All living creatures on the earth
and all material objects on it

are subject to the pull of one great
force: The force of gravity.

Were that to be suspended,
even for a moment,

the most extraordinary
things would begin happen.

I, for example, would suddenly float
into the air because I at the moment...

...am flying in an aircraft on a very
special cours which in effect

cancels out the effect of gravity.
So I float easily through the air.

Our plane is climbing and diving as
though it were on a giant roller coaster,

and as it goes over the crest of
its climb, it really lifts you out

of your seat and keeps you there.

If there were no gravity on earth,
seas would rise from their beds

just as this water lifts out of its cup
and disintegrates into droplets.

Nothing would remain where it
was placed. There would be no

up and no down.

There would no longer be the
sense of earthly order that we take

so much for granted.

Some creatures have managed to
overcome the force of gravity

sufficiently to enable them to fly,
but the only ones that will be able

to match this total freedom
in the air that I have in the moment

are those that are so small
that they are, in effect, weightless.

And there are more of them...
both plant and animal...

...than you might think.

It's the force of gravity which holds
the clouds around the earth and

the air in which they float.

You can't touch air,like a solid object
it's invisible and all-pervasive,

so it's easy to forget that it has
real substance.

But it's only by exploiting the presence
of air that seeds, insects, birds and man

are able to overcome gravity
and float above the earth's surface.

Dandelion seeds rise because
a puff of air carries them up

and they fall slowly because their
parachutes catch the air beneath.

A tuft of fluff will serve
the same purpose.

Milkweed and cotton grass,
willowherb and thistles,

all provide their seeds
with downy floats.

These delay the fall of the seeds for so
long that currents in the air, winds,

can carry them for hundreds
of miles from their parents.

Seeds like these have crossed
the widest oceans and landed

on the loneliest islands.

Pollen grains are so small, they don't
even need fluff to keep in the air.

The microscopic roughness
of their surface is enough.

Spores, shot out from a puffball

and shed in tens of millions from
the gills of fungi, are smaller still.

The merest breath of air
sweeps them away like smoke.

The gossamer, that sometimes
carpets the meadows,

is the animal equivalent of downy seeds.

It's produced by thousand upon
thousand of tiny spiders.

The young of many species of
spider, soon after they hatch,

climb to the top of grass stems
or onto the tiny pinnacles of stones

and lift their abdomens upwards.

Then, from the spinnerets at the tip,
they produce a thread of finest silk.

As it lengthens and the wind catches
it, the spiderling turns,

grabs the thread with its forelegs
and away it goes.

Only the tiniest and the lightest
of animals and plants

can defy gravity in this way.

Many seeds are far too heavy
to be lifted by the breeze,

no matter how downy they are.

But if they are produced
at the top of a tall tree they can

exploit the pull of gravity.

These, hanging in the jungle
of Venezuela, grow wings.

The wing is so shaped and weighted,
with the seed at one end,

that as it falls through the air, it spins.

This protracted fall gives the breeze a
chance to deflect the seeds sideways

so that they will land some distance
away from the parent tree.

The seed is functioning like
the blade of a helicopter.

Its wing is so shaped that
as it sweeps round,

it puts pressure on the air below
and reduces pressure just above

so that the seed hangs in the air much
longer than it would otherwise do.

Sycamore seeds spin and
glide in the same way.

And animals glide too.

The flying frog of Central America
has a parachute on each foot,

formed by the web of skin
between its toes.

So one jump from a high branch
is enough to carry it from

one tree to another.

In South-East Asia lives a gecko that
not only has a parachute on each foot,

but flanges on its body and tail.

Another lizard glides through the
same forests by extending

even bigger wings of skin from its
flanks supported by elongated ribs.

And the best glider of all:
A flying squirrel.

Its huge cloak of floppy skin
sometimes serves as a simple parachute.

But in horizontal flight it does
more than just trap air beneath it.

As air passes over the front edge,
it's deflected slightly upwards,

so creating a slight reduction in the
air pressure on the upper surface,

just as happens on an aircraft wing or
the spinning blade of a sycamore seed,

so the squirrel creates a little lift
and floats through the air.

All those creatures are gliders.

Some of them can control to some
extent the direction in which they glide,

but none of them can climb in the air
except with the help of rising air currents,

like the breezes which sweep up
these downs in southern England,

carrying with them whole populations
of seeds and spores and spiders.

But there are no such breezes
down below the grass stems.

Down there, if creatures want to
climb into the air they have to have

true powered flight.

The most demanding moment
is at take-off.

The insect has to haul itself into the
air by sheer unaided muscle power.

The downward sweep of the wings
produces greater pressure in the air

beneath than in that above,

so, in a slightly different way
from the gliding cloak of the squirrel,

beating wings also create lift,
and the insect is sucked upwards.

Bigger insects, like grasshoppers,
boost their take-off with

a powerful spring.

Birds are even bigger and heavier.

For them, too, getting into the air is
the most energetic and demanding

part of flying.

They also use their well-muscled legs
to assist their labouring wings.

They jump even before their wings
begin their downbeat.

But really big birds, to get airborne,
have to generate the extra lift

by increasing the speed of air
streaming over their wings,

so they get up quite a lot of speed
on the ground or over water,

just as an aircraft does,
before they can take off

Once in the air, a whole new
environment is open to them,

and flying animals of all kinds
exploit it to the full.

Damsel flies catch their food in the air,
mate in the air and even fight in the air.

As males squabble over territory,
they flutter their patterned wings

at one another in an aggressive display.

This hawkmoth lays its eggs on
flowers while it's still flying,

for it's too heavy to land on them.

It feeds by hovering in front of a
blossom and sucking out the nectar

with a tube-like proboscis
as thin as thread.

One of the smallest of all birds,
the bee hummingbird,

even smaller than a hawkmoth,
is equally skilled,

beating its wings 80 times a second

to keep itself stationary in the air
as it drinks from the flowers.

Bird wings are more versatile
than those of insects,

for their flight feathers fit so closely
alongside one another and slide

so easily past each other that the
bird can change the shape and size

of its wing while maintaining its
continuous air-deflecting surface,

so the wing can be spread wide
on the downstroke,

and then, on the upstroke, be made
small to offer less resistance to the air.

This kestrel is maintaining a steady
position in the sky, relative to the ground,

by facing into the wind and flying
with such accuracy that it exactly

matches the wind speed.

The reduction of air pressure, creating
lift on the upper surface of the wings,

can be seen quite clearly,
for it sucks up the smaller feathers.

The albatross also habitually gets lift
by gliding into the wind,

and again, the reduction in pressure
produced as the air blows over

the birds outstretched wings
ruffles its feathers.

When it wants to travel over the sea
against the wind, it drops down

close to the surface of the water,
where the roughness of the waves

slows down the wind
blowing over them.

Albatrosses spend most of their
lives in the air.

Occasionally, for a minute or so,
they alight on the water to collect food.

Once every year or so they come down
to their nesting grounds to meet their

mates again, greeting one another
with a charming courtship dance.

It's difficult to appreciate just
how big these magnificent birds are

when you see them
gliding over the ocean.

It's only when you come to one
of their nesting sites like this one

in South Georgia that you
really see how big they are.

When they open these wings,
they are 11 feet across,

the biggest wingspan of any bird.

Long, narrow wings are the most
efficient shape for uninterrupted gliding,

and no bird glides better
than the albatross,

but such wings are difficult to flap
sufficiently fast to give take-off,

so many species of albatross
nest on the edge of cliffs,

where they can just fall into the air.

Cliffs are much favoured by gliders,

for the wind from the sea striking
the cliff face is deflected upwards,

and an albatross can hang on it.

If it wants to fly a little slower and
prevent itself from being swept away

or carried too high by a sudden gust,

it uses its tail and webbed
feet as air breaks,

and reduces its lift by
pulling in its wings,

so making their surface smaller.

With such techniques, an albatross
will glide all day above a line of cliffs

travelling effortlessly along this
highway in the sky.

Land birds also exploit the air currents
above cliffs in just the same way.

This is the coast of Paracas in Peru.

As the day wears on, the sun heats up
these desert sands, causing rising air,

and that in turn sucks in cold air from
the sea, often bringing mists with it.

And as this cold air hits the cliffs,
so it's deflected upwards,

providing just the sort of
conditions that soaring birds need.

The condor, one of the heaviest
of all flying birds

Yet its skill in soaring is so consummate

that it can remain in the air for hours
with scarcely a wingbeat,

sustained entirely by those air currents
swept upwards by the cliffs.

And something else produces
columns of rising air: Heat.

When we turn on these burners,
they will create a current of rising air

so powerful that it'll lift this balloon,
this basket and us up into the sky.

We are in Africa, floating over the
great game plains of the Serengeti.

I'm now about 100 feet up
and kept up entirely by hot air.

But gas burners aren't the only things
which produce rising currents of hot air.

The sun does the same thing,
as it rises, it heats up the landscape,

but all parts of the landscape
don't react in the same way.

Some parts absorb the heat.
Other parts, bare slopes of grass

or patches of rock, reflect the heat,
and that causes those uprising

currents of air, the thermals.

That's a moment those big birds
down there are waiting for.

They are vultures, and at the
moment they're grounded.

They're big birds with large wings,
so large that beating them is a very

laborious business, and the vultures
don't do so unnecessarily.

At this time in the morning,
they don't try to battle against gravity

and climb high in the sky,
but limit themselfs by flapping

from one low tree to another.

They're waiting for the land to heat
up and the thermals to form.

But we have our own thermal,
created by our burner, and up we go.

This bird begins to follow us.

An outcrop of rock is already warming

and providing it with the thermal
it needs for effortless flight.

And now the vultures are beginning
to come up here to join me.

They will be using the thermals to
provide them with an observation

post in the sky from which they
can scan the plains below,

and I'm getting just about the same
kind of view as they are, and it's

a very, very exciting one.

Below me must be the biggest
concentration of meat on the hoof

to be found anywhere in the world:
Wildebeest.

Last night or in the early dawn,
somewhere,

lions or hyenas or hunting dogs
will have killed.

The vultures, several thousand feet
up in the sky, can quickly spot a kill or

deduce its presence from the behaviour
of birds in a neighbouring thermal,

and when they do,
they swiftly glide down to it.

Once one bird finds a carcass,
dozens arrive within a few minutes.

These are tearing apart
the body of a wildebeest calf.

Most of these are medium-sized vultures:
Ruppell's griffon and white-back.

But among them is the biggest
and most powerful of African vultures:

The lappet-faced.

With a heavy load of meat,
on board, the vultures won't fly far,

back to a nearest tree, to perch and
digest and wait for tomorrow's

thermals to carry them effortlessly
aloft once more.

But all the sustenance has not yet
been extracted from the carcass.

In the African mountains,
as well as in Asia and Europe,

lives a species of vulture with
a very specialised diet indeed:

The lammergeier.

It feeds, though it sounds extraordinary,
not only on marrow but on the bones

themselves, and to do so,
it has developed a special technique.

First it brings bones from a carcass
to a special workshop which

several birds may share.

A patch of bare rock near the
top edge of a cliff.

It chooses a cliff top so that when
it takes off again with a heavy bone,

in its toes, it has the least difficulty
in getting into the air

Now it has to gain height.

And this is why it chooses a patch
of bare rock for its operations.

So that the bone will land
so heavily that it crack

One drop, however,
may not be enough.

White-collared ravens often hang
about the scene of operations.

The ravens are starting to learn the
same technique but haven't mastered it.

They tend to drop their bones on
grass, where they don't break.

The lammergeier eats the splinters
of bone, impossibly spiky though

they appear to be.

Some birds exploit the force of gravity
by dropping not their food but

themselves from the sky.

The pied kingfisher hovers
as it searches the water beneath.

Terns dive with such speed,
they can strike fish several feet

beneath the surface, pulling back
their wings at the last moment

so as to get a clean entry
into the water.

Gannets do the same thing.

During the nesting season,when
they concentrated in their colonies,

huge flocks of them set out on
fishing trips, and when they find

a shoal of fish near the surface,
they subject it to an aerial

bombardment of devastating intensity.

But the ace of dive-bombers,
which can reach at least

80 miles an hour in a dive,
is the peregrine falcon.

It patrols the skies, often high above
the flight path of other birds.

And when it has selected its victim,
it folds its wing

steering almost entirely with its tail,
and hurtles downwards.

Close the target the talons are
brought forward for the strike

and to make last-second adjustments
to the accuracy of its final run.

A hunter of the night.

Owls, this is a barn owl, don't rely
on speed like the peregrine,

but on a slow, silent approach

Their flight feathers have special soft
edges to them which serve as silencers.

Their wings are particularly large
and support the bird so easily

that there's no need for
any vigorous noisy flapping,

and the owl can waft its way
in silence through the trees.

Although owls hunt after dark,
they find their way with their large,

highly sensitive eyes, and, because
their flight is virtually soundless,

they can listen for the squeak
of unwary voles and mice.

But on the darkest nights,
even an owl can't see,

and it seldom ventures into the air.

Such nights belong to bats.

They are able to navigate
without the aid of vision.

Instead they use sonar, squeaking
ultrasonically and guiding themselves

by the reflected echoes.

They do this so skilfully that they
can pluck a flying moth from the air.

It's been known for a long time that
bats use high peak sounds in this way,

but it's less well known that just
one or two birds have, also

and quite independently,
evolved the same technique.

This cave in Venezuela is the
home of one of them.

These, flying all around me, are oilbirds.

Most of the noise that they're
making at the moment, is nothing

to do with navigation.

It's their alarm calls. They're alarmed
because of the brightness of my light.

So what I'm going to do is to
put on a deep-red filter.

That will disturb them much less,
but it will enable us to watch them

with a special electronic device
called an image intensifier.

They're big birds, relations of the
nightjars, and about the size of pigeons.

Their nests are compiled from their
droppings and bits of regurgitated food.

When their alarm calls subside, you can
hear the clicks by which they navigate.

These calls are much lower in
frequency than sonar the signals of bats,

although they have the longer
range they're much less accurate,

so the oilbirds can't detect objects
much smaller than a foot across.

That's quite good enough to
prevent the birds crashing into

the cave walls or one another.

Their favourite food is the fruit
of a jungle tree

and the cave floor is covered
by a soggy carpet of seeds.

Many germinate, though in the
dark they can't develop chlorophyll,

and they remain pallid,
leggy seedlings which soon die.

The fruits are too small for the
oilbirds to locate with their clicks,

but out in the moonlit forest,
where the fruit trees grow

there's enough light for the
birds to find them by eye.

The mastery of the air and the
strength to remain in flight for days

has enabled birds to become
the greatest of all animal travellers.

In the skies above Panama
every October and November,

there is a great aerial traffic jam.

Hawks and turkey vultures, fleeing
from the approaching winter in

North America, are on their way to
spend a few months in the south.

As the day warms up, they find
the thermals in which they can

spiral upwards,to give them the
altitude they need to make the day's

flight with the least effort.

These long journeys require a lot of fuel.

Big birds, like hawks,
can draw it from their body tissues.

But north-east of Panama,
across the Caribbean,

on the Atlantic coast of the
United States, smaller wading birds,

sandpipers and phalaropes,
are preparing for their journey.

They must put on a lot of fat before
they start off, and they find the food

in the quantities they need in the
rich waters of the Bay of Fundy.

In a few days of intensive feeding,
each tiny bird will increase its weight

by half as much again, and they will
need all that fat, for they are about

to travel across the open ocean,
and then they can't feed at all.

On the other side of the Atlantic, the
migration route also run predominantly

north and south, as birds move
back and forth to get the best

of the changing seasons.

In Scandinavia, every autumn
great numbers make their way south.

Most land birds prefer to keep their
flights over water as short as posible,

and huge flocks assemble on the
shores of the narrow straits between

south of Sweden and Denmark to make
the crossing into southern Europe.

Small birds often fly in parties,
close to the water

Buzzards,
experts at soaring and gliding,

use the thermals to climb so high
that they eventually cover the whole

distance, in what amounts
to one long, shallow glide.

Red-breasted geese spend their
summer considerably farther east

in the tundra of western Siberia

They too move south in the autumn.

Their journey is almost entirely
over land, so they're able

to stop each night to refuel.

After several weeks, in travel they reach
their wintering grounds south of the

Caspian Sea, many of them on
the marshes of the Danube delta.

Birds are not the only creatures to make
these immense transcontinental flights.

Almost unbelievably, a few small,
seemingly frail creatures do so as well.

Insects, flying with just as steadfast
a purpose, achieve journeys

as long as many migrating birds.

Back in South America,
in a high valley in Mexico,

hundreds of thousands of
monarch butterflies roost in just

a few special trees.

They hatched in the autumn woods
of North America and have flown

some 2,000 miles down here
to hibernate.

They won't feed here, but they're spared
the lethal frosts and snows farther north.

In spring they will set off back,
travelling about ten miles a day,

feeding, courting and laying
eggs as they go.

But only a few will live long enough
to reach the northern woods where

they were hatched.

So the world is criss-crossed by
the flight paths of animal migrants.

In the Americas, nearly all pass
through Panama. A few hardy

travellers cross the Caribbean.

On the other side of the world there's
more land, and birds and insects have

greater choise of routes, travelling
north and south but also east and west

between Asia and Africa.

Although the journeys made by
these travellers may be thousands

of miles long, the earth's wrapping
of air thru which they move, is less

than six miles deep.

On rare occasions the gases from
which it's formed become visible.

Subatomic particles from space,
attracted towards the poles by the

earth's magnetic field, energise the
gases of the atmosphere so that they

glow and form shifting veils
of light the aurora borealis.

The atmosphere is not composed
entirely of gas

and at certain times you can see
evidence of the presence of other things.

Dust particles are scattered through
its lower layers, and when the setting

sun shines obliquely across
the earth, at dawn and sunset,

they scatter its white light,
turning it red.

Minute droplets of water, being
translucent, act like infinitive

tiny prisms and produce a rainbow,

and at high altitudes tiny ice
crystals create a similar effect.

As you climb up away from the earth,
the gases become thinner and the

temperature as a result,
becomes colder.

The balloon which is taking us to
these great heights must be

much bigger than that we used in
Africa for, as we climb, we will require

a greater volume of the rarefied air
to give us the necessary lift.

A rubber bladder, sealed with a cork,
on the ground will gives us a rough idea

of the drop in pressure
as we ascend.

We are now at 8,000 feet, and you
might think that no living creature

would come as high as this except
perhaps some rather foolhardy men.

But no. Some small creatures
are swept up as high as this

by the convection currents rising
from the surface of the ground,

and we're going to try and catch some
using this rather curious machine.

Inside there's a fan which will suck
in air through this end when I turn it

on here, and I'll lower it over
the side to see what we catch.

And now we're going to go higher still
and it's going to get very, very cold,

so I shall need all this
warm clothing I've got,

but, perhaps even more seriously,
the oxygen is going to get thinner

and thinner, and so I shall have to
put on this mask in order to breathe

oxygen as we go higher and higher.

And now an indication of our height
can come from this balloon.

Before it had those corners to it and
now it's swollen quite considerably,

so the pressure here is really very
considerably lower than it was when

we were on the ground.

We are now getting on for four
miles above the surface of the earth.

It certainly looks very far away. And
it's shrouded beneath a pall of clouds.

And we're getting very close to the
outermost frontier of life on earth.

It's very cold and I certainly wouldn't
be able to talk at all if I hadn't got this

oxygen, so conditions here are really
very much more severe than you might

imagine when you sit in your
aircraft flying comfortably

from one continent to another.

But let's see what we've caught...

in our apparatus.

Turn it off.

And...

...take off the end.

Well...

We certainly haven't caught
anything large.

But if we examine this mesh, when we
get down to earth, with a microscope,

it's very likely that, at the very least,
we shall have some pollen grains

and spores of fungus.

But bigger creatures are found
at these heights

and I've some of them here,
in this phial, that were caught here.

I'll pour them out on a dish
to get a better look at them.

There are tiny spiders that must
have sailed up hanging from their

threads of gossamer.

And winged aphids. At these
altitudes they can be carried halfway

around the world and,
amazingly, be frozen solid,

and yet revive when they fall
to lower altitudes.

But now we are very close to
the top of our environment,

for all the weather goes on
within these five brief miles,

the envelope of atmosphere
that wraps round the world.

It's here that the weather
is manufactured.

Molecules of water, evaporating in
the heat of the sun from the surface

of the sea and from lakes,
or breathed out by plants as vapour,

rise up from the land and as they
do so,they cool and condense

into clouds of droplets.

Driven by the winds, the clouds
evaporate and condense,

form and re-form.

The summit of Mount Everest is
less than six miles above the surface

of the sea, yet few clouds
ever sail much above it.

The earth, as it spins, creates
vast eddies within the atmosphere.

If they become intense,
they will develop into hurricanes.

From a satellite
22,500 miles away from the earth,

the build-up and dissipation
of these huge storms over 15 days

can be seen with pictures taken
every hour and run continuously.

Away to the east of Brazil in the
Atlantic, a hurricane is forming.

As it spins, it moves west
across the Caribbean.

Northwards it goes towards Florida,
while up in the north, air sweeping

over North America moves across
the Atlantic towards Europe

in another immense, swirling storm.

Other major disturbances in the
atmosphere are caused when the sun

builds up gigantic thermals in a
sky already loaded with moisture.

As the air is driven upwards,
the tops of the towering clouds

burgeon with fearsome speed.

The water molecules within the
clouds condense to form

bigger and bigger droplets, but
the speed of the rising air is now

so great that it keeps them
suspended within the cloud.

Eventually, the droplets become so
big that they can no longer

be supported,
and they fall as torrential rain.

The molecules of gas and water
vapour surging upwards create

a build-up of electricity that
eventually becomes so great,

it discharges down to earth.

The water droplets may have been
carried so high by the great thermals

that they freeze and eventually
tumble out of the cloud as hail.

If the storm is really intense,
they may rise and fall several times.

In the lower parts of the cloud,
the ice accumulate forms relatively

slowly and is clear and black.

But when they get to the top again,
it's so cold that the ice forms quickly,

trapping tiny air bubbles,
which makes the ice look white.

So really big hailstones may be banded,
like an onion, with alternate rings

of black and white ice.

Really big hailstones are often a sign
that a trully devastating storm

is about to strike the earth.

A strong, high-altitude wind, linked
with a severe storm such as this,

may vacuum up lower-level air,
increasing the updraught dramatically,

and beginning a spiral motion
in part of the storm.

If these converging winds are
powerful enough,

the vortex at the centre of this
great whirl reaches down

to the surface of the earth
as a suction funnel, a tornado.

Winds up to 300 miles an hour
devastate the land, tearing things apart,

ripping the roofs from buildings,
sweeping animals and trees and

sometimes even people high into
the sky and throwing them down.

When it strikes the land, it's
seldom more than 500 yards across,

but within this area it lashes the
earth with the most powerful

and destructive of all
atmospheric forces.

Storms like that may bring
death and destruction,

but they also bring life, because
the rain that comes from them,

distilled by the sun from the surface
of the ocean is fresh water, salt-free,

and that is something that all
life on land must have.

And when that rain, that sweet fresh
water, accumulates in rivers and lakes,

then it supports a community
of plants and animals all of its own,

and it's those communities
that we're going to be looking at

in the next programme.

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