Planet Earth (2006) s01e10 Episode Script

1
Trees.
Surely among the most magnificent
of all living things.
Some are the largest
organisms on Earth
dwarfing all others, and these
are the tallest of them all.
The deciduous and coniferous
woodlands that grow
in the seasonal parts
of our planet,
are the most extensive
forests on Earth.
Their sheer extent
stuns the imagination.
The barren snows of the Arctic.
A thousand miles from the North Pole,
and heading south.
This is the very first place
that trees can grow.
To begin with,
the conifers are sparse,
but soon they dominate the land.
This is the Taiga Forest.
There are as many trees here, as in
all the world's rainforests combined.
The Taiga circles the globe and contains
a third of all the trees on Earth.
It produces so much oxygen,
that it refreshes the atmosphere
of the entire planet.
At the Taiga's northern extent,
the growing season can last
for just one month a year.
It can take 50 years for a tree
to get bigger than a seedling.
It's a silent world
where little stirs.
But there are occasional signs of life.
Stories written in the snow.
The prints of an Arctic fox and
the hare it might've been stalking.
A female polar bear and her two cubs.
Some animals are so difficult to
glimpse that they're like spirits.
One could live a lifetime in
these woods, and never see a lynx.
The cat must roam hundreds of miles
in search of prey
and may never visit
the same patch of forest twice.
It's the very essence of wilderness.
With so few prey animals here, life
for a hunter is particularly hard.
Creatures are scarce because
few can eat conifer needles.
The moose is an exception.
Growth is so difficult
that conifers protect their precious
leaves by filling them with resin.
That reduces water loss, but it
also makes them very distasteful.
At least the conifer's seeds
are edible.
but they're protected within
armor plated cones
and it takes a specialist
to reach them.
The crossbill's
extraordinary beak
can prise apart the scales, so that
it's tongue can extract the seeds.
Birds are fortunate.
When the seasonal crop is gathered,
they can fly south.
But one animal is so expert at
survival in this frozen forest,
that it stays here and is active
all year long.
In local folklore, the wolverine
is a link to the spirit world
and a cross between
a bear and a wolf.
In reality, it's a huge weasel.
It's bulk helps to conserve body heat
and also broadens it's menu.
It's so big and powerful, it can
even bring down an adult caribou.
For it's size, it's said that the animal
can eat more in one sitting than any other,
which is why it's also known
as the glutton.
Being gluttonous here
is a very effective strategy.
It's wise to eat all you can,
when you can,
and when even a glutton
can't eat more,
it stores what's left for later,
in the surrounding deep freeze.
Spring in the ice forest.
The capercaillie can also
digest conifer needles,
but feeding is not
it's priority at the moment.
Like gladiators,
the males square up for a battle.
Each may have just a single chance
to impress a female.
Neither can afford
a lapse in concentration.
The injured loser may not survive.
The inhabitants
of this great wilderness
may live and die without ever
having contact with humanity.
Long may it be that way.
The northern forest
may be the largest on Earth,
but to see coniferous trees that
have reached their full potential,
you must travel
a thousand miles south of here.
The Pacific Coast of North America.
The land of hemlock, douglas fir
and giant redwood.
Here, water is never
locked up in ice,
and even if rains fail,
the needles can extract moisture from
the fogs that roll in from the sea.
The Sun's energy
powers these forests,
not for one month as it does in
the Taiga, but for half the year.
These conifers grow at 10 times the
rate of those near the Arctic
and they live for thousands of years.
One grove of redwoods
in California
contains 3 of the tallest trees
on Earth.
This one is over a 100 meters high,
the size of a thirty-story building.
These forests were growing here
long before humans walked the Earth.
They were in their prime
20 million years ago,
and existed before the Swiss Alps or
the Rocky Mountains were even raised.
There is more living matter in
a forest of giant conifers,
than in any tropical rainforest,
but it's all contained within the trees.
These are as inedible
as those in the Taiga,
so animals are still scarce,
but they are present.
A pine marten. It's spring, the best
time of year for a marten to find food.
Bird's eggs are a seasonal snack and for
a short time, there's plenty of them.
Sometimes perhaps, too many.
But to live here permanently,
the marten needs a more
reliable food source.
Squirrels fit the bill.
They thrive here on the pine cones,
and although these are also seasonal,
they can be stored and eaten
throughout the year.
The squirrels are busy mating.
Good news for the hunter. A distracted
squirrel is a vulnerable squirrel.
But, this time,
the amorous couple is safe.
There is a loner stocking his larder,
who will be the easier target.
Early summer, and great
grey owl chicks are fledging.
Adults can only raise
young here
in years when the seasonal vole crop
is big enough to support them.
The moment has arrived
for their first flight.
Leaping from the world's tallest
trees is not for the faint-hearted.
If you're going to fall here it's
quite a good idea to do it in stages.
The ground is no place for an owl.
If he's to climb to the top of his
class, he'll need to persevere.
So now, let's have another go.
The American conifer forests may
not be the richest in animal life,
but their trees are extraordinary.
This giant sequoia,
a relative of the redwood,
is the largest living thing
on Earth.
Known as General Sherman,
it's the weight of ten blue whales.
Higher up in the nearby mountains,
bristlecone pines,
the oldest organisms on the planet.
Some have been here for 5,000 years.
They were alive before
the pyramids were built
and were already 3,000 years old
when Christ was born.
Across the Equator,
in the southern hemisphere,
there are forests
that mirror those of the north.
Here in South America,
araucaria trees or monkey puzzles
are like the conifers of the Taiga.
They have waterproof scales,
instead of needles,
and their cones look a little different
but the principles are the same.
Slender billed parakeets rather than
crossbills, extract their seeds.
Where the growing season is longer,
there are alerce trees,
the redwoods of the south.
As in the frozen north,
the Valdivian forests of Chile
support very few animals,
but that is the end of the similarity.
This is a bizarre world
of miniature creatures.
The pudu, the world's
smallest deer,
feeds on the giant leaves
of the gunnera plant.
The female is just 30 centimeters
high at the shoulder
and her infants are hardly
bigger than kittens.
The male must stay alert. There are
hunters here who would snatch his young.
Another miniature. The kodkod cat.
It's the smallest cat in all the Americas
and a young pudu would be a feast for it.
But, with the male on guard,
the kodkod must lower his sights.
Moths are hatching.
They're the last of the summer.
The tiny cat should be able
to score with these.
No one knows why the creatures
here are so small,
but at least they can
survive on meager rations.
You might call this
a game of cat and moth.
As winter approaches in Chile, spring
is arriving in the northern hemisphere.
These are the deciduous
forests of Home.
Dormant throughout the winter,
they now undergo
one of the most magical transformations
in the natural world.
By late spring, the landscape is
wrapped in a vibrant fresh green.
Here, instead of conifers,
there are broad leaved trees,
and that makes the character of
this forest entirely different.
Being broad, these leaves trap
much more light than needles,
but they're also thin,
soft and edible.
And others can eat the leaf eaters.
It's spring in the great
broad leaved forests
of Eastern Europe
and Asiatic Russia.
The mandarin ducks are courting.
The female mandarin nests
in a tree hole,
and when it's time for everyone
to leave, she leads the way.
The ducklings are only 24 hours old.
It's a long drop, and a few calls
of encouragement are required.
2 down, 7 to go.
There are still 2 missing.
All present and correct.
But they won't be safe
until they reach water,
and the forest pool
is almost a mile away.
By June, the days are at their longest,
and all across the northern hemisphere
the broad leaves are hard at work.
On the east coast of North America, it
seems like any other summer's evening
but tonight is special.
After 17 years underground,
creatures are stirring.
The nymphs of the periodical cicada
have been biding their time.
Now they march like zombies towards
the nearest tree, and start to climb.
At first, there are merely thousands,
but soon, more than a billion
swarm all over the forest.
The biggest insect emergence
on the planet is underway.
They invade the upper branches,
where they climb out of their
external skeletons
and assume their adult winged form.
At first they're white and soft,
but they have until dawn to
complete their transformation.
After an absence of 17 years, the
forest is now overrun by cicadas.
The adults are clumsy and very edible.
For turtles and other
inhabitants of the forest,
this is a feast they're lucky
to see once in their lifetime,
and they gorge themselves
while they can.
Times have never been so good.
The cicadas have no defenses
and virtually offer themselves
to their attackers.
The stream of insects
is so relentless
that soon all the predators are
full to the point of bursting,
and still the cicadas come.
With the predators overwhelmed, the
survivors can achieve their purpose.
After mating, the adults lay their
eggs and then their job is done.
In just a few days they will all die
and the forest will fall silent.
The cicadas here, will not be heard
again for another 17 years.
Having fed the predators, the cicadas
leave one final gift for the forest itself.
The nutrients in a generation of cicadas
are returned to the soil, all at once,
and the trees enjoy a
marked spurt in growth.
This may be the single largest dose
of fertilizer in the natural world.
In the great broad leaf forests
of Eastern Europe,
the days are beginning to shorten,
and a primeval sound heralds
the onset of autumn.
Male red deer are starting their rut.
The air is heavy
with the scent of females.
The rules are simple.
Winner takes all.
Across the northern hemisphere
the deciduous forests are changing.
Leaves that have provided food and
shelter since the spring, are now shed.
In the broad leaf forests of Russia,
winter is particularly severe,
but there will always be some
who benefit from hardship.
Black vultures scavenge from the
carcass of a seeker deer
that has died of cold or starvation.
These endangered birds are visitors.
They've come down from the north
to escape the even colder
conditions in Siberia.
An Amur leopard.
The rarest cat on Earth.
Winter is a difficult time
for this hunter.
There are no leaves for cover
and no young prey animals.
This female has the added pressure, of
having to provide for her 1-year old cub.
It'll be another 12 months, before
he'll be able to fend for himself.
The bickering vultures
have abandoned the carcass.
It's a valuable discovery
for the leopards.
But the cub doesn't share
it's mother's sense of urgency.
The vultures have left behind
plenty of good meat,
but it's stiff with frost.
The mother works to open the hide, and
make feeding a little easier for her cub.
There are only 40 Amur leopards
left in the wild,
and that number is still falling.
The harshness of the winter here
hinders their increasing numbers.
It takes one of these females longer
to raise her young to independence
than it does a leopard in Africa.
If the mother can sustain her cub
for a few more weeks,
spring will bring an increase in
prey and her task will lighten.
For all the inhabitants
of this seasonal forest,
the long, cold wait is nearly over.
Spring in a deciduous woodland
is special.
With no leaves overhead, the rays of the
sun strike the forest floor directly,
and their warmth rouses plants
from their winter sleep.
The ground living plants
are in a hurry.
Before long, the trees above will
come into leaf and steal their light.
Their flowers decorate
the forest floor
as they advertise their sweet nectar
to the newly emerged insects.
The spring blooms of the deciduous
woodlands have no equivalent
in either the great conifer forests,
or the tropical jungles.
Within a matter of weeks,
the canopy has closed,
and only a few wheeling shafts
of light penetrate the woodland.
In the treetops, the broad leaves
rapidly expand to their full size
to make the most of summer
while it lasts.
Then, after a few months,
the days begin to shorten again,
and the trees must shut down and
shed their leaves in preparation
for the cold dark time ahead.
Great tracts of North America flush
red as the season progresses.
The effect is so spectacular
and so extensive
that it can be seen from space.
The threat of winter frost is not the
only reason for trees to shed leaves.
These forests stand in the tropics.
Here, day length never changes,
but the dry season
is so severe
that the trees can't afford
to loose the amount of water
that would evaporate from their broad
leaves, so the leaves must be shed.
The forest resembles a European
woodland in midwinter,
but the heat is overpowering,
and it's inhabitants, unfamiliar.
For the creatures of India's teak
forests, these are desperate times,
but salvation is at hand.
The mahwa tree is about to bloom.
It's flowers are full of liquid,
making them irresistible.
The mahwa is an oasis
in a hot dry desert.
Those that fly or climb are not
the only ones to get a share.
Chital deer follow
the langur monkeys,
collecting the flowers that fall.
The monkeys welcome the deer, for deer
are unrivaled at spotting predators.
If they are relaxed, it must be safe
to come down to the ground
and gather the food that lies there,
but it's not wise to travel far
from the sentinels.
Tropical Madagascar.
The wet season.
It's now that the baobab trees
regrow their leaves
and collect water to store in their huge
trunks, ready for the dry season ahead.
The prehistoric shape of these trees
is rightly famous,
but few have ever witnessed
the baobab's real magic
for that happens at night
and high in the treetops.
Flush with water, the baobab prepares
itself for an unforgettable display.
Once started, the foot-long flowers
can open fully in less than a minute.
As the flowers open,
the creatures of the forest wake.
The mouse lemurs have been hibernating
throughout the dry season.
With the return of rains,
it's time to get busy.
A dozen share this tree hole,
but there's plenty of room.
The world's smallest primate
is no bigger than your hand.
High in the branches above, the
baobab's nectar is starting to flow.
A drink of this sugary
energy packed liquid
is an ideal way for the lemurs
to start their day.
Liquid oozes from the flower's center
and trickles down the petals.
But the nectar is not
intended for lemurs.
These giant hawk moths are the
drinkers the tree needs to attract.
As they sip,
moving from tree to tree,
so they transfer pollen
and fertilize the flowers.
Nectar was an excellent first
course for the lemurs,
but moths are the main dish.
The moths are very important
to the lemurs.
for they will replenish
the fat reserves
that the lemurs need to survive
the barren dry season.
The lemurs might seem to be a pest
for the baobab.
They kill it's pollinators
and rob it of it's nectar,
but they do give something in return.
For, as the wrestle with the moths, their
fur inevitably becomes dusted with pollen,
so they, too, become pollinators.
As the alternation of wet and dry seasons
brings change to some tropical forests,
so the progression of summer to winter
dictates life in more temperate regions.
Whether trees have needles
or broad leaves,
it is their ability
to survive annual change,
that has enabled them to cover
such vast areas of the Earth,
and made the seasonal forests
the greatest forests of all.