All language subtitles for BBC.Natures.Microworlds.03of13.Amazon.720p.HDTV.x264.AAC.MVGroup.org Eng

Our planet is the greatest
living puzzle in the universe.

A collection of worlds
within worlds,

each one a self-contained ecosystem
bursting with life.

But how do they work?

The intricate web of relationships
and the influence of natural forces

makes each microworld
complex and unique.

So to discover their secrets,
we need to explore them one by one.

Untangle their interlocking pieces

and ultimately reveal
the vital piece,

the key to life itself,

hidden deep within each
of nature's microworlds.

The Amazon.
The largest rainforest on Earth.

Feeding the mightiest
river in the world.

It drains over 40%
of South America

and holds a fifth of
the entire world's river water.

Up to 12 metres of rain falls
in parts of the Amazon every year.

But what makes the Amazon even more
incredible is the life within it.

For sheer diversity of species,
it's unparalleled.

It is estimated to be home
to up to 3 million species.

and its plants produce
20% of the world's oxygen.

The Amazon River even holds
more kinds of fish

than the whole of
the Atlantic Ocean.

A complex ecosystem with infinite
connections and relationships,

but as we shall discover,
as in all our microworlds

there is one piece that this
entire system relies on to survive.

And without it, the rainforest
would look like this.

Areas that have been
slashed and burned for agriculture

fail rapidly, and before long
the land cannot even support crops.

All our microworlds
rely on nutrients,

they are the
building blocks of life.

Phosphorous, potassium and calcium,

vital elements
that plants need to grow.

But these nutrients are not
a stable part of any ecosystem.

Here they are either locked up
and unobtainable in living tissue

or washed out by the incessant rain.

And it's so poor
in available nutrients

that scientists refer to the Amazon
as a wet desert.

The endless rain affects
the trees, plants and soils

and are constantly washing
the building blocks of life away.

Life here is actually
surprisingly hard.

So how in such a nutrient-poor
microworld,

is there so much diversity and life?

The answer is that in nature,
adversity leads to adaptation.

Animals and plants have carved out
incredible niches

and formed vital relationships,

not just to survive,
but to thrive here.

But is there one that holds the key
to all this success?

Understanding the Amazon,
the most complex ecosystem on Earth,

is one of the greatest challenges
that ecologists have ever faced.

Our only chance is by unpicking
its web of connections

until we can hopefully discover
how the Amazon is able to support

such diversity
on such slim pickings.

The Amazon is so massive
and so intricate

that we are really going to
have to delve deep

and get under this microworld's skin
to search for the pivotal piece.

So in our investigation
we need to start small

and focus on the details first.

Like all microworlds, the Amazon
is a showcase of natural selection.

The inhabitants have evolved
over time to exploit every niche,

every opportunity
that exists within its world.

But what makes the Amazon special

is the vast number of relationships
that have developed.

Particularly compelling is
the interaction between flowers

and one of the most beautiful
groups of birds on the planet.

Hummingbirds.

Like bees,
they are attracted to flowers

for their energy-rich nectar.

But in a world where every nutrient
has to be locked up safely,

the flowers can't give
their valuable resources away

unless they get something in return.

The plants need to be pollinated.

So as the birds feed, they get
their heads sprinkled with pollen.

But this only works if
the hummingbird delivers the pollen

to another flower
of the same species.

And that's the clever bit.

Over thousands of years, the flowers
and the birds have evolved together,

so that only the species of bird
with the right-shaped beak

can get nectar
from their species of flower.

The birds are guaranteed food

and the plant guarantees
it gets pollinated.

Relationships like this
are born out of necessity

but they might not hold the key
to how this world works.

The pivotal piece in many
microworlds is a constant,

something that doesn't change much

so the rest of the world
can keep up.

So to find the key
in this complicated world,

first we need to find this constant.

And there is one thing you can
rely on in a rainforest -

rain.

Massive quantities of rain
fall on the Amazon.

An average downpour can dump
two-and-a-half centimetres of water
on the forest every hour.

This rain usually comes from water
evaporated from the sea.

However, the Amazon is so immense,
it literally makes its own rain.

70% of the rain that falls

has evaporated
from the trees themselves.

And this constant rain
has had a direct effect

on the shapes of things
in the forest.

Plants have developed
leaves with gutters and spouts

to get rid of as much water
as possible

because a leaf that doesn't dry off
will end up rotting alive.

Life can't survive without water,

so the rain is an essential part
of this system,

but as we've seen,
all the good it does

is balanced by the damage it causes,

literally washing away
the rainforest itself.

So if the rain's effect
is to carry the forest away,

what happens to it after this?

Well, it ends up being transported

by the most obvious force
in our microworld, the Amazon River.

It is a huge destructive force.

Each year it removes an enormous
one billion tons of sediment and mud

from the forest basin
on its march to the sea.

During the course of this programme,
it will have dumped the equivalent

of 150,000 Olympic-sized
swimming pools into the ocean.

But the river is not as constant
as you might think.

It is so powerful
that it scours deep channels

barging its way through the forest,

constantly changing course
on its way to the Atlantic.

But as destructive as it seems, it
also creates opportunities for life.

As the river loops
through the forest,

these meanders become very curved

until eventually the neck of the
meander touches the opposite side,

cutting off a big loop
from the main river.

In creating these pools,
known as oxbow lakes,

the river creates a slightly
different habitat to be exploited.

These isolated bodies of water
are the ideal space

for one of the river's
top predators,

the two metre long giant otter.

The lakes are full of fish and
the waters are calm so the otters

use them to rear their young
away from the powerful main river.

So in a microworld where every
available space is to be exploited,

the otters have turned this dead end
feature of the river

to their advantage.

The river is actually a dynamic
element in this environment.

It's not the key to its existence,

but its destructive nature
does open up

a lot of opportunities to life.

Some of the sediment the river
picks up gets dumped again,

forming large banks.

The minute space becomes available,
something is there to exploit it.

Thousands of giant river turtles
use these banks to make their nests.

So many come here that each wave
digs up the nests
laid moments before

and in a world short on nutrients
this bounty is not missed for long.

At every turn,
another opportunity is created

and the black vultures are ready
to jump in and make the most of it.

Like their sea-dwelling cousins,

these turtles have a strategy
that involves producing so many eggs

that they can afford to lose
some casualties along the way.

But in this ever-changing world,

the turtles might have to look
for a new nesting site next year.

So the river is dependent
on the rains,

both are prominent players
in the Amazon's ecosystem

but they both play a role
in removing the most vital piece

of this puzzle, the nutrients.

So how does the forest keep hold of
enough of the good stuff

to stay alive?

In the Amazon, 99% of the nutrients
are locked up in living tissues,

so when any of this becomes
available it's pounced upon.

Nothing goes to waste -

trees, leaves, dung and dead bodies
are recycled almost immediately.

The recycling team are an ungainly
rabble of floor dwellers

that lurk and skulk in the dark,
damp recesses of the forest.

Like this giant metre-long
earthworm.

They methodically race against
the rains to reclaim
as many nutrients as possible.

Even so, commodities are scarce.

Phosphorus, potassium and calcium,
essential elements for life

are hard to find, and because of
the rain can be gone in a heartbeat.

But the recycling teams are good,

so good that sometimes things get
recycled before they're even dead.

Spores of the cordyceps fungus
float through the air

and find their way
inside an insect host.

The fungus attacks them
from inside their bodies,

killing them and consuming them
from within.

The fruiting body then erupts
out of the dead insect

and releases its spores
to float through the air

and infect other
unfortunate individuals.

But even here, there is
a dark interdependency.

Each strain of cordyceps fungus

only infects its own particular
species of insect.

These recyclers play a vital role,

keeping what little nutrients there
are moving around the ecosystem.

But this is certainly not enough

to have created this forest
of giants in the first place.

So where would the trees normally
get their nutrients from?

Here trees can grow
to over 50 metres tall.

There is enough light and water
in the Amazon to fuel rapid growth.

But it is not enough.
These giants like everything here

need those nutrients to grow
to these incredible sizes.

Trees usually get all the nutrients
they need from the soil,

but what is different
in this microworld

is that these are some of
the poorest soils on the planet.

Only 1% of the nutrients in this
ecosystem are found in the soil,

compared to 50% in temperate forests

so the Amazon trees
are really up against it.

Only the top 50 cm
has any nutritional value,

below this there is only clay
that is no use to plants.

So in response, the trees
send their roots not down,

but out through as much
of the fertile top soil as they can.

The only problem with this is that
it makes them pretty unstable.

One way around this
is to create huge buttress roots
that help stabilise them.

And they need a good foundation
because they are competing with

the other trees for the other
vital resource here - sunlight.

The trees are so successful
in exploiting sunlight

that the forest floor is
in constant shade.

Only 2% of sunlight
penetrates this canopy.

So how does a young plant
that's just starting out

get established here?

Cheese plant seedlings have
a strange solution to this problem.

Instead of heading for light,
they search for darkness.

The shadows created by
a buttress root of a big tree.

Once there
and using the tree for support,

they can race upwards
towards the light.

The cheese plant pours its energy
resources into thin and rapid growth

rather than strong stems, and leans
on the tree for a helping hand.

This gives it an advantage in a
world where nutrients are limited.

Other plants don't even bother
to start at the bottom.

Bromeliads grow high up
in the branches of trees

and so start life closer
to the light.

They have ponds in their centres

that fill with up to eight litres
of rain water,

offering a water source
30 metres above the ground.

And where there are ponds,
there are usually frogs.

One of the most poisonous
creatures on earth

relies upon the bromeliads
for their rooftop pools.

This poison arrow frog
carries its tadpole,

hatched from an egg laid on a leaf,
to a pool in a bromeliad heart.

Here the tadpole has its own private
pool, tended by its parents.

So the frogs rely
on the bromeliad for a home

but give the plant nutrients in the
form of faeces and leftover food,

and the bromeliad relies upon the
tree to keep it near the sunlight.

The tree tops are where
it's really at.

So successful are these
high-rise communities

that researchers discovered
a single tree in the Amazon

to be home to nearly 2,000 species
of insect and spider.

Only 100 of these
were already known to science.

With such limited resources
and so many mouths to feed,

once the plants
have secured nutrients,

they have to keep hold of them.

Many Amazon plants use poisons
to protect their leaves

from the hungry vegetarians.

But again nature finds a way.

The piping guan only eats the tender
new tips that hold the least poison.

Most leaf eaters eat some
then move on

before they get too large a dose
from any given tree.

The white faced saki monkey,
however,

has evolved a highly specialised
digestive system

that can cope with virtually
any toxin found in the rainforest.

And there is another primate here,
one of the smallest in the world,

that has found a different way
around the tree's
poisonous defences.

Pygmy marmosets are omnivorous,
eating both plants and insects

but their favourite food
is tree gum,

produced by the trees
when their trunks are damaged.

The marmosets have learnt to keep
this food supply going

by reopening previous wounds
on the tree

and they have evolved
special teeth to do so.

These tiny monkeys,
which could fit inside a tea cup,

have learnt how to exploit
a particular food source

at the tree's expense.

Rather than fighting back,

some plants have developed
relationships with animals

that benefit both parties.

They grow tasty, energy-rich fruit.

44 different species of bird and
monkey can feed on a single tree.

And the benefit for the tree
is that contained inside the fruit

are seeds that cannot be digested.

So as the vegetarians
move off through the forest,

what has gone in has to come out.

And the minute it hits the floor,
in come the forests street cleaners.

Dung beetles detect
the bounty immediately.

The males meticulously ball it up

and roll it away
with their hind legs.

However, it is a lot easier
to steal someone else's

than to make your own.

And the bigger the ball, the better
the chances of attracting a female.

Once he's clear, the beetle
rolls his ball away,

burying it in a safe place so that
the female can lay her eggs inside

and the tree's seed is planted
with its own source of fertiliser.

So in this relationship,

the trees are connected to both the
fruit eaters and the recycling team

and they all benefit.

There is one species of plant that
has taken this one stage further

and developed a much more direct
and surprising relationship
to get ahead.

This might appear to be
a natural forest clearing,

but in fact it is inhabited
by only one species of plant.

One species of plant
and thousands of ants.

In this bizarre relationship, the
plant has enlisted the ants' help

in a very surprising way.

The ants inject formic acid
directly into the leaves and stems

of any other plants that try
and grow in the clearing,

killing off all
but their host plant.

And the ants don't stop there.
They also provide protection.

They attack any animals that try
and feed on the plant's leaves.

Even giants
many thousands of times their size

are not immune to
a bit of ankle biting.

This is a great service
if you are a plant in this
competitive environment,

but what do the ants get in return?

The plant has small openings
and swellings along its branches.

These tiny cavities
provide the ants with a home,

protecting them from predators
and giving them a safe place

to rear their young.

It's a collaboration developed over
millennia and another example

of how to survive out here, by
building a successful relationship.

And it is one of these relationships
that holds the key

to the success
of this entire ecosystem.

But it is not colourful, or obvious,
and happens completely out of sight.

Within the soil, the trees
hide a symbiotic relationship

The fungus are attached
to their roots

and absorb the available nutrients
far faster than the trees

because they have
a huge surface area.

They efficiently take elements
like phosphorus, potassium

and calcium out of the soil
and into the tree

before the rain gets a chance
to wash it all away.

But this relationship is mutually
beneficial. Both parties benefit.

In return, the tree supplies
the fungus with sugars and starches

that it can't obtain itself.

One could not survive
without the other

and the rainforest as we know it
would not exist.

The delicacy of this relationship

and the importance it has on this
microworld is clearly demonstrated

where the rainforest has been
cut down for agriculture.

The rain quickly washes away the
little goodness held in the soil,

and the sun bakes the ground solid.

With no trees to shade the ground
or to provide essential sugars,

the fungus in the soil dies out.

Leaving the soil barren,
untenable for trees to recolonise.

Without this partnership
there would be no rainforest

and so many species
rely on this ecosystem.

The Amazon rainforest is
a complex web of inter-connectivity,

where many organisms rely on
the others to survive.

The more diverse the microworld,
the more robust it is to change.

But as we have discovered, even our
biggest and most diverse ecosystem

relies on a fragile balance

between the environment
and the species that live within it.

And without one surprising alliance
between a tree and a fungus,

life in our microworld
would not exist at all.

But it does and it has created

one of the most incredible and
intricate microworlds on our planet.