All language subtitles for Waterworld.Africa.Series.1.1of8.Tidal.Forest.of.Africa.720p.HDTV.x264.AAC.MVGroup.org.eng

NARRATOR:
Caught between land and sea,

at the heart of a secret,
subtropical shoreline,

is a forest like no other.

Mangroves.

Where changing tides rule

over one of the most abundant
ecosystems on the planet,

and one of the most hostile.

It is home
to extraordinary creatures,

fighting a daily battle
for survival

in one of nature's
last wildernesses.

South Africa's eastern coast.

A subtropical realm
where the warm Indian Ocean

meets a wild shoreline.

From offshore reefs

that teem with life,
to the inland lakes and rivers,

this is a pristine
natural kingdom.

A place rich enough
in food and diversity

to support giants...

from the ancient predators
of the ocean,

to the huge hunters
of the lakes and estuaries.

From the air,
the oceans and lakes

look like separate worlds.

But both are intimately bound
together by a third ecosystem

few humans ever explore.

The mangrove forest:
the living heart of this coast.

It's an incredible machine

poised at the meeting place
of fresh and salt water.

Sheltering in
and under its branches,

a variety of secretive
forest dwellers,

each one uniquely adapted
to life in this maze

of waterways and mud flats.

But the mangrove's presence is
felt far beyond these estuaries.

The forest is also a nursery

for fish that thrive
on offshore reefs,

an undersea wonder sustained
in part by the mangroves.

And almost all of this variety
and richness depends

on the toil of an army
of unsung heroes.

High in the canopy,

a family of vervet monkeys
begins its day.

It could be a forest anywhere
in eastern Africa,

except for one
remarkable detail.

This forest is flooded.

Not that the monkeys seem
to care.

Their attention is elsewhere.

Each one
of these mangrove flowers

hides a sweet drop of nectar.

And for this family,

that's free,
concentrated energy.

Satisfying their sugar craving
might seem like a hedonistic way

to spend a morning,
but the monkeys' sweet tooth

is also helping the forest.

Pollen dusted
around a greedy snout

will be transferred to the next
flower and pollinate the tree.

A sweet deal for both monkeys
and mangroves.

They're so focused
on their foraging

that they barely notice that the
forest is starting to change.

The first signs
are easy to miss.

The transformation starts
at a snail's pace.

These are mangrove snails.

At high tide they cluster
high above the water,

out of the reach of fish below.

But now they are
inching downwards.

It seems a fatal move.

The water below is full of fish
that would eagerly snap them up.

But the snails creep on,
undeterred.

Somehow they have sensed

that the sea is beginning
to drain away,

and they will be able to forage
on the mud below.

Just how the snails
predict the tides is unknown,

one of the mysteries
of this secret world.

The ocean is retreating.

Inch by inch,

the secrets of the mangrove
forest are revealed.

Two species
of tree dominate here,

white and black mangroves,

but both share the same
incredible survival skills.

Many of the world's trees
survive extreme conditions.

But for almost all of them,
salt water is a death sentence.

Too much salt around their roots
prevents plants

from absorbing water.

Salt also creates
a toxic build-up

around the root,

slowly poisoning the tree.

But the mangroves have
an elegant solution.

If salt around the roots
is dangerous,

then remove it as far
from the roots as possible.

Salt is drawn up and away
and deposited in the leaves,

safely away from the main
workings of the tree.

But salt is only half
the challenge.

This mud is also
life-threatening.

Like animals,
plants need oxygen

to break down stored food
to grow.

But the water
that saturates this mud

has very little oxygen in it.

The solution: a snorkel.

Aerial roots grow up
above the ground,

allowing the forest to breathe.

This is a living factory
working around the clock,

shunting salt up from the floor
to the leaves above

and sucking air down
into the roots.

But the snorkel isn't only
for inhaling oxygen.

Mangroves have
to vent carbon dioxide,

and so the roots
also act as chimneys,

keeping the whole factory going
even when the tide rises.

Now, though, the chimneys
are high and dry

and the factory floor
is coming alive.

The monkeys are messy eaters.

What doesn't get swallowed
gets dropped.

Unwittingly they are helping
the forest to regenerate.

Discarded seed pods fall
onto recently exposed mud.

A black mangrove seed pod
detaches from the parent tree,

spearing into the mud.

This fruit has
already germinated,

and now it has somewhere
to grow.

If the tide
doesn't carry it away,

it will extend roots from one
end and shoots from the other,

and the forest will gain
a new tree.

But the odds are stacked
against the vulnerable seeds,

because in this factory,

the workers of the morning shift
are arriving.

They have lain hidden
while the tide was high.

Now, the first worker
cautiously appears.

The red-claw mangrove crab,

the unsung hero
of an entire ecosystem.

They move slowly at first,

but this worker
is racing the tide.

In a few hours
all this potential food

will be swept away.

Time isn't the crab's
only enemy.

The heat is building fast.

To stay alive in this cauldron,
the crabs have had to adapt.

They keep their
respiratory organs covered

in a thin film of water,
continually passing water

through their gill cavity
as if they were underwater.

It looks orderly
from a distance,

but with so much food on offer,
arguments are inevitable.

When two crabs eye
the same morsel,

it's every crab for itself.

These are high-stake battles.

The strongest crabs will get
to carry away the best pieces

of plant matter,

and the smaller crabs
will have to make do

with leaner scraps.

The morning's forage
has gone well for the monkeys.

Time for the youngsters
to burn off some excess energy.

Down below, though,
there's no time for play.

A vast clean-up operation
is underway.

What seemed to be a lifeless
stretch of mud is transforming

into a busy
industrial operation.

The crabs are not alone.

The retreat of the sea
has turned the mangroves

into a more recognizable
kind of forest,

and a more traditional forest
dweller makes a shy approach.

Standing just 16 inches
at the shoulder,

the red duiker is still
tall enough to reach some

of the mangrove's lowest-hanging
fruit and leaves,

and by now there are also
rich pickings on the ground.

There are leopards in this
region, so it treads lightly.

But here in the forest,

the duiker will not
be disturbed.

For now, it is safe.

The tugs-of-war between
the red claws are intense,

but for one character
of the forest floor,

it's not about
how tough you are,

but how tough you look.

It's late morning.

The mud is drying as the forest
becomes unbearably hot.

The perfect landscape
for a tiny gunslinger.

This is the fiddler crab.

The naturalists who named it
thought the males

with their outsized claws
looked as if

they were playing a fiddle.

They might be small,
just a few centimeters across,

but they're feisty.

And when it comes
to shows of force,

the claw definitely
calls the tune.

They've left their burrows
near the water's edge

to join the red claws scavenging
for food on the mud.

But there's more going
on here than just feeding.

Some of these males
have come out to find a mate.

Others are defending
their territory.

And in both scenarios,

the claw plays a starring role.

Female fiddler crabs
are less flamboyant,

having two equal-sized claws
and more subdued coloring

than their mates.

Now they watch
as the wooing starts.

As sales pitches go,
it's straightforward:

"I've got a huge claw
and my own burrow."

He's not exaggerating.

Fiddler crabs are small,
but their burrows

are comparatively vast,

sometimes
up to 2 feet long.

To sweeten the deal, males also
build small decorations

over the entrance
to their burrow

which serve
as enticement to females

and also help them
to identify their new home.

But in a crowded neighborhood
like this,

competition for homes
can be fierce.

A male who lets his guard down
can find his burrow invaded

by a rival.

Brandishing his claw is a way
of keeping his territory clear

of potential usurpers.

It looks threatening,

but the posturing
is also a strategy

to avoid physical conflict.

If things do escalate,
the males will try

to intimidate each other
into backing down

by squaring up and seeing
who has the bigger claw.

(birds and insects chirping)

Noon is approaching,

and the red claws are starting
to feel the heat.

Not so the fiddler crabs.

In winter they stay buried
in their burrows,

but now,
as the temperature soars,

these rugged little show-offs
stay out to see and be seen.

It's thanks
to a superb adaptation

that allows them
to be equally comfortable

on dry land as well
as in the water.

They have gills
for breathing in the wet,

but they also have
a primitive lung,

which means they can spend
months out of water.

The heat is too much
for the regular workers.

The winners take their trophies
and head for their burrows.

Much of the morning's debris
has been cleared away

by the red claws,
but their work is more

than just gathering food.

By dragging the debris
underground,

they have radically sped up
the rate of decomposition.

Composting that would normally
take weeks takes days.

They're also aerating the soil
with thousands of burrows

they have excavated,

filling this landscape
with air pockets.

Stirred, aerated
and pumped full of compost,

this soil has been perfectly
prepared by the crabs

for the next mangrove sapling
to take root,

and for the next chapter
of the forest's story.

High noon.

The forest slows down
in the oppressive heat.

It's a time
for conserving energy.

The vervet monkeys have come
down to the shade for a siesta.

Only a baby monkey
fueled with pure nectar

still has the energy to play.

For the dominant male
of this group,

a fork in a tree provides
an ideal armchair.

It's dramatically cooler
down here on the forest floor

than up in the canopy and now,
safely out of the sun,

there's time
for some personal grooming.

Vervets are omnivores,
and any ticks or lice they find

on themselves
are small packages of protein.

They might look lazy,
but in this forest,

nothing is wasted.

Low tide.

The forest floor has become
a hostile environment,

too dry for fish,
too muddy for land dwellers.

But for one unique
mangrove dweller,

it's pretty much perfect.

The mudskipper is an eccentric
little amphibious fish

that lives comfortably
in both water and on land.

And, just sometimes, in the air.

Moving around
on its pectoral fins,

the mudskipper can survive
out of water

thanks to a special
breathing adaptation.

Not only can they breathe air
through their mouths,

but they can also absorb it
through their skin.

But this only works when the
skin and membranes are wet,

so this fish will take
a regular mud bath

to keep everything slick
and in working order.

And if all else fails,

the mudskipper has
an enlarged gill chamber,

which allows it to seal
a bubble of air inside its body

for extended visits
out of water.

Mudskippers are well named.

The "mud" part needs
no explanation.

To see the "skipper" part,
however,

you have to wait

until one of them
feels threatened.

And then...

That speed also comes
in useful for hunting.

The fly has quick reflexes...

but it's no match
for a lunging mudskipper.

Along the water's edge,

the others are waiting for their
own meals to fly too close.

The chances are good

they'll see their prey
long before it sees them.

Large eyes mounted
on top of their heads

give mudskippers a panoramic
view of their surroundings.

They don't have tear ducts
to keep their eyes moist,

but there are other ways
to wet an eyeball.

The mudskippers rule this
small muddy kingdom for now,

but soon they'll have
to surrender it once more.

The snails on the tree trunks
have turned

and are inching
their way upwards.

The tide is coming in again.

For the snails, it's a journey
of just a few inches,

but it's ruled by gigantic,
planet-sized forces.

The ocean is being heaved up
by an irresistible force:

the moon.

Where the earth faces the moon,

the oceans are pulled
slightly towards it,

creating a bulge of water
we call high tide.

On the other side of the planet,

the moon's pull is
at its weakest.

Here oceans bulge
in the opposite direction,

creating two synchronized high
tides, which rise twice daily

as the moon revolves
around the earth.

A tidal pattern

that is fine-tuned
by the sun's gravity,

global rotation,
and the shape of the coastline,

creating spring and neap tides.

The rising water is good news
for the red claws.

The seawater will bring relief
from desiccation.

But while the water
might be welcome

on their sensitive
breathing organs,

it will also soon be a threat
to their burrows.

Above the tide line, emergency
renovations have taken place.

The red claws are now sealed
inside their dry burrows,

where they'll sit out
the high water.

The incoming flood is also
causing major domestic problems

for some of the mudskippers.

It seems strange that water
should be a threat to a fish,

but mudskippers
are no ordinary fish.

Raising a family down in the
mud, with very little oxygen,

makes special demands
on the mudskipper.

A devoted father,

he has done most
of the parenting.

It was he who dug the burrow

and who tended the eggs
for the week they took to hatch.

But now he faces a force
beyond his control: the sea.

His burrow is flooded
with oxygen-poor water.

His young are in danger
of suffocating.

And so he is creating
an air-pocket inside his home,

turning himself
into a mobile oxygen tank

by taking big gulps of air,
before heading down

to save his family,
one breath at a time.

The Indian Ocean is on the move,

surging over the reefs
and pushing inland.

Salt water floods
into the estuary,

and at last it reaches
the mangrove forest.

The red claws and fiddlers
are deep in their burrows.

Along the banks,
the mudskippers lie waiting

for the transformation
of the forest.

The flooded forest appears
deserted.

But as the tide rises,

the mangrove is welcoming
a new cast of characters.

Thousands of tiny fish,
recently hatched,

have been swept in from the sea.

And suddenly the mangrove
transforms from a forest

into a nursery.

These juvenile fish have
survived a perilous journey,

hatching out at sea

and then cautiously
trekking upriver.

But now that they're here,
these warm waters

and the labyrinth of roots

are a sanctuary.

Safe from the ocean's predators,
they can feast

on the nutrient-rich
forest floor

until they are mature enough
to run the gauntlet

back to the ocean.

They're also small enough
to benefit

from the cocktail of bacteria

that are helping decompose
the mangrove's waste.

For a fish of this size,

even tiny microbes
make a good sized snack.

The fish aren't alone.

Shrimp thrive here,

protected from the currents
and predators of the ocean.

Of course, the old rules
still apply here.

The fish are still the hunter,
the shrimps still the hunted.

But at least
in these calm backwaters

they have a fighting chance
to reach maturity.

The success of the mangrove
forest in nurturing shrimp is,

unfortunately,
a double-edged sword.

Being one of the planet's

most biologically
productive ecosystems

makes it a prime target
for the one predator

no animal or plant can hide
from-- humans.

Every year, more and more
mangrove forests

are being hacked down
to make way

for shrimp farms and similar
aquaculture projects.

Here, at least, the human
footprint is relatively faint.

Out in the lake,
a young fish huddles

against what looks like
another mangrove shoot.

But for adult fish,

this isn't a sanctuary.

It's a death trap.

These delicate curves
are fish traps,

perfected a thousand years ago
by ancestors

of the local Tembe-Thonga
communities in this region.

They're elegant
and beautifully efficient.

As the tide retreats
and adult fish begin

to swim back downstream
towards the sea,

they naturally follow the large
network of guiding fences.

It's a wall no more threatening
than the bank of a river

or a growth of reeds,
but it funnels them directly

into the final corral,

where fishermen can spear them
at their leisure.

It's not
an indiscriminate harvest.

These juveniles are
small enough to escape,

meaning that this is a largely
sustainable technology.

Even the posts themselves
can become a living part

of this landscape.

Mangrove timber used
in the traps can take root,

and the forest extends
by a few more trees.

Importantly, the traps don't
only provide food for humans.

They also create a new habitat
in which smaller species thrive.

Like a man-made
miniature mangrove forest,

these posts provide cover
and even food

for a variety of fish
and crustaceans.

These baby parrot fish
follow the tide upstream

and graze in the palisades
that make up the traps.

Nearby, a group of much more
flamboyant babies.

These are lion fish,

their bright pattern announcing
loud and clear

that they are venomous
and definitely not on the menu.

They are great hunters,

fanning out their wide pectoral
fins to corner their prey.

The sun's rays illuminate
this underwater world.

Mid-afternoon light
that is too bright

for one secretive creature.

The floral moray eel
is a night hunter.

It waits out the day,
coiled up in a crevice

where it can remain undisturbed.

Later, as darkness falls,

it will come snaking out
of its lair in search of prey.

For now, though,
the baby fish are safe.

Only a handful of the fish
in this system

end up in the traps.

The rest have safely
made their way downstream,

flushed out into the estuary
and then into the ocean,

where they were born.

Their destination is the reefs,
underwater islands

of abundant life, where brightly
colored tropical fish

dart between blooming anemones.

A hawksbill turtle pauses
on its oceanic journey

to graze on sponges.

The reefs are fertile ground

for a variety of marine plants,

providing abundant food
for the animals that live here.

For adult parrot fish, the reef
itself is a tasty treat.

It's an undersea garden,

far more vibrant than the somber
mangrove forests upstream.

And yet most of this spectacle

owes its existence
to the mangrove.

In fact, some species
of tropical fish

are twice as plentiful on reefs
that border mangrove forests,

a testament to their value
both as nurseries

and giant factories
producing nutrients.

Out on the open water,
a paradise for birds.

Flamingos thrive here,

sifting for shrimps
and small fish.

They look less pink
than their relatives,

the lesser flamingo.

But when they take to the air,

a beautiful flash
of famous flamingo pink.

The pinkness of flamingos
is a byproduct of their diet.

Shrimp contain an organic
pigment called a carotenoid.

But not all the birds
in these skies

are as benign as the flamingos.

High tide has pushed
the vervets back up

into their treetop haunt again.

Now, in the heat
of the late afternoon,

the monkeys have to move
carefully in the top canopy.

A young vervet

wandering too far
from the adults

or distracted by a flower

would be easy pickings
for the largest raptors

that haunt these skies.

At dusk,
smaller aerial predators

return to the mangroves
to roost.

These are yellow-billed kites.

They're secretive animals,

and the dense, tangled branches
provide an ideal hiding place.

But privacy isn't the only
reason the kite migrates here.

It's an opportunistic hunter
and scavenger.

When low tide returns,
the mangroves will provide

a wealth of options,

from fish and crabs to insects.

As the light fades, it's time
for a new phase in the life

of the mangrove forest and
the lake system that it feeds.

Hippos begin to stir.

These great beasts have been
lying in the water all day,

keeping cool and socializing.

Now, they leave
their watery haunts

to spend their nights alone,

foraging in the grassland
that surrounds the lakes.

They're mostly herbivorous,

and from a distance
they seem slow and lazy.

But looks can be deceptive.

Africa is home to a variety
of dangerous predators,

but hippos are the continent's
most feared killer,

responsible for nearly 2,000
human deaths every year.

As dusk falls
over the mangroves,

the landscape changes
once again.

Soon the snails will signal
the turn of another tide

and migrate slowly downwards.

The moon is tugging
at the earth's oceans,

starting to drain the water
out of the mangroves.

The bright face of the eternal
clock that runs this factory.

The monkeys are settling down
for the night.

Tomorrow will be a long,
hot day of foraging,

and they need their rest.

But the forest floor
beneath never rests.

Tonight, only a few seed pods
and flowers

will drop into the mud.

But when they do,
announcing themselves

with a soft vibration
on the mud,

the red-claw mangrove crabs
will stir in their burrows,

and the night shift
will go to work.

Mangroves are an enigma,
incredibly resilient

and also surprisingly fragile.

Forever in flux
between high tide and low tide,

land and sea,
salt and fresh water,

they are the foundation

for a dazzling variety
of life on this coast.

And keeping the entire system
working,

the red-claw mangrove crab,

the unsung hero
of the mangroves.

A tireless worker helping
to maintain and sustain

this unique forest,
ultimately feeding

the incredible diversity
in the ocean beyond.

And a living reminder
that our own survival depends

on our connectedness

with the great
life-giving machine

we know as planet Earth.

Captioned by Media Access Group
at WGBH, access.wgbh.org