Original subtitles

At the southern tip of Africa...

withstanding the full might of the Atlantic...

a tiny kelp plant grows up to take its place

in a forest like no other.

Racing for the sun,

it provides a home

for the secretive animals of this coast.

From sex-changing fish and spiky nursemaids

to the show-offs of the forest -

and the ancient hunters that stalk them.

All coming together to create one of the most fertile zones

on the planet.

Africa's Golden Forest.

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

It's a busy morning in the kelp forest.

In the canopy, Cape fur seals play and explore,

safe from the predators of the open ocean.

Further down, among the stalks,

Roman fish patrol their empires.

Among the roots of the forest,

urchins and rock lobster scour the rocks for food.

Unseen by all of them, new kelp plants are being born -

a unique species of giant algae.

In this underwater sanctuary,

thousands of tiny spores are making their way

down to the ocean bed.

Every hour, each square inch

of these gigantic blades

releases some 65,000 microscopic spores...

Resulting in tens of millions of spores being launched every day.

Those that survive will grow into adults,

expanding the forest

that fringes Africa's south-western shore,

stretching from southern Angola around the tip of the continent.

The huge extent and abundance of the kelp forest

seems to contradict the harshness of this landscape.

On land, life along this Atlantic coast is a struggle.

And the animals that live here, like Eland,

Springbok and reptiles,

have learned to get by with little food and even less water.

The ocean, too, seems brutal.

The Atlantic is unforgiving:

whipped up by oceanic winds, it breaks onto a rugged coast.

And yet it is these winds that make the forest

such an abundant place

and allow marine life to thrive along this shore.

Powerful south-easters

continually blast the sea surface,

causing an upwelling of water from the ocean depths.

Millions of years of plant and animal matter has decayed

and dissolved into this deep water,

and now it surges up to the surface,

as an incredibly rich soup of nutrients.

The compost heap of the Atlantic is drawn up

and dumped directly onto this forest.

And the result: enough food to support a diverse range of life

and huge expanses of seaweed.

For the spores drifting to the forest floor,

food will not be a problem.

But before they can fight for a place in the canopy,

they must claim their space down below.

A tiny new plant has one job to do:

hold on for dear life.

Once settled, it grows a holdfast,

a root-like structure that grips onto the rocky outcrops

of the ocean bed.

But these are no ordinary roots.

Unlike its earthbound relatives,

this little plant absorbs no nutrients from the sea bed.

Everything it needs is supplied

by the water and the sunlight above.

But if it's going to grow into a giant adult

and reach the surface it must first focus

all its energy into holding on.

The sturdier the rock to which it is attached,

the better it can grip against the sweep of the ocean.

But where the baby kelp can't anchor, it can't grow

and this forest is dotted with clearings.

They might look deserted,

but even a forest clearing is inhabited.

Here, a sandy bottom provides an ideal home

for one of this ocean's more elusive predators.

The Short-tail stingray, the largest in the world.

These solitary hunters can reach a length of 13 feet

and weigh up to 770 pounds.

Their lethal stinger, up to 12 inches long,

is easily capable of killing a human.

Yet despite their size and vicious blade,

these are docile animals,

quietly scouring the sand for their favorite meal

of crustaceans and hard-shelled mollusks.

Clearings on soft sand are no use to young kelp,

but a clear spot on rocky substrate is a different matter.

Boosting their chances of finding the ideal landing zone

are smaller species of seaweed

that endlessly sweep the forest floor clean.

But this sweeping is not just good housekeeping.

Their lashing fronds are also keeping at bay

a pack of particularly voracious neighbors.

Sea urchins.

Living in large groups, with as many as 50 urchins

crowding each square yard,

they slowly scour the sea bed,

grazing on young plants and tasty holdfasts.

Their spikes ward off would-be predators like starfish

and octopuses.

What's hidden beneath their body is even more imposing:

a small but ferocious mouth,

ringed with five self-sharpening teeth

that make short work of kelp.

Left unchallenged,

they can decimate entire expanses of young forest.

But one plant's predator is another creature's protector.

While the urchin presents a life-threatening problem

to the young kelp plant,

they act as nursery nannies for one rare cold-water snail:

the abalone.

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

They are part of the fabric of this forest,

their shells are so overgrown that they merge into the reef.

Abalones are slow developers.

They're only ready to reproduce when they're 8 years old.

Scientists believe that the stimulus to spawn

is a sudden change in water temperature.

It's a remarkable event.

Males release a cloud of billions of sperm

into the surrounding waters.

When the cloud reaches the female,

she gives a dramatic response:

powerful contractions expel torrents of eggs

into the water.

Within a few minutes, millions are released to be fertilized.

The numbers are vast, but most fertilized eggs will perish.

This reproductive overkill has a vital function.

The odds are so heavily stacked against survival:

it's the only way to ensure a few eggs get the chance

to develop into adults.

The larvae swim close to the ocean floor.

They're incredibly vulnerable;

the perfect snack for filter feeders like shrimps.

But abalone larvae have a remarkable alliance

with one forest-dweller:

the urchin.

The larvae are waiting for their cue to attach to a rock.

Their green light is a chemical signal.

Encrusting coralline algae releases an amino acid

into the water, beckoning the abalone larvae

to settle and start to form a shell.

And once they are ready they meet their nursemaids.

Less than a half an inch long,

the abalone creep in under their nanny's prickly petticoats.

Here they will be protected from hungry octopuses,

fish, starfish and crustaceans - and get free nibbles

dropped by the urchin as it eats.

When the abalone is strong enough,

they'll venture out from under their spiny nursemaids

and grow thick, camouflaged shells.

It's a fragile equilibrium on the forest floor.

Too many urchins grazing these rocks

and no young kelp plants would survive.

Too few urchins and juvenile abalone

would be exposed to danger.

Nature's system is kept in balance.

And keeping the urchins in check is their nemesis:

the rock lobster.

The spiny defense of the urchin is no match

for its formidable claws and full-body armor.

The rock lobster has earned its tough reputation.

And it started young.

While the abalone were sheltering under their nannies,

this extraordinary animal was embarking

on one of the most incredible journeys of the natural world.

As soon as he hatched, just 1/16th of an inch across,

he floated out into the open ocean.

Drifting with the currents for up to seven months,

still no more than two inches long,

he journeyed in a great loop -

from Africa almost as far as the South American coast

before he rode the current back home.

By the time he returned to the kelp forest,

he had molted 11 times,

shedding his carapace again and again as he grew,

until he had transformed into a young adult.

As soon as he arrived in familiar waters,

he set up camp in a crevice in one of the vertical rock walls

that define this submerged landscape.

Here he grew into a formidable predator,

with thick armor,

a muscular tail and powerful claws.

He's not alone in his rocky lair.

Away from the surging sweep of the forest floor,

the water around this wall is relatively still

and steeped in microscopic plant detritus.

This allows filter feeders to thrive here,

from sea squirts to anemones...

soft corals to sponges.

They're a convenient snack for the lobster.

But for him, the main benefit of this perch is that it offers him

relative safety from a cunning hunter.

A predator that is not only agile, quick and dexterous,

but is also considered by many to be the most intelligent

invertebrate on the planet.

The octopus is a cephalopod,

a word which translates literally as

"feet around the head".

It's part of the mollusk family, a distant relative of the snail.

But there's nothing sluggish

about this brilliant master of camouflage.

It can adapt the color and texture of its skin

to ambush its prey.

And it has a taste for rock lobster.

Eight suckered arms can prize open any shell...

the lobster is wise to back away...

In the battle between predator and prey,

animals may vary the color of their skin,

like the octopus or their body shape,

like the rock lobster.

But one animal undergoes

the most dramatic transformation of all:

it changes its sex.

Roman are territorial.

This one's empire could be up to 32,000 square feet,

but it's worth putting in the effort to defend its borders.

This fish preys on crustaceans,

sea urchins and even octopuses,

and with a patch of this size,

there is plenty of food on offer.

If it manages to keep challengers at bay,

it could be a long and successful reign:

Roman can live up to 30 years.

Like all good emperors, he protects his subjects,

in this case, smaller females.

But he wasn't always emperor.

In fact, he wasn't always a male...

once, he was a she.

Roman are born as females,

growing up under the watchful eye of a protective male.

Little more than eight inches long,

they are content to be members of his harem.

But as soon as they reach twelve inches,

the stunning change occurs.

Females transform into males by modifying their sex organs

and suddenly what was a quiet harem

becomes a serious threat to his crown.

It's an effective strategy.

Smaller males could never compete with the emperor

and so by remaining female they benefit from his protection

while they grow strong enough to challenge him.

When night falls, this male will retreat to the rocky wall.

But until then there are borders to patrol, and worms to hunt.

Sex change is an extreme survival strategy.

For other species, however,

simply holding on tight is enough.

In this territorial forest, the Roman might be an emperor,

but this adult limpet has its own kingdom to patrol:

the growing stem of the kelp plant,

covered in the limpet's staple diet of algae.

Rival limpets are bulldozed off the stem.

But some neighbors are tolerated.

Kelp snails are only after the blades of the plant

and don't compete for the food on the stem.

The limpet moves imperceptibly,

rippling its muscular foot hidden beneath its shell.

To eat, it scrapes the algae off the kelp stem with its radula,

a ribbon-like tongue with rows of teeth.

The limpet has adapted to live exclusively on this plant.

The shell of an adult limpet

is shaped to fit its cylindrical home.

As young ones, they hide at the base of the fronds

only moving out onto the stem

when they are big enough to graze and claim ownership.

It's a large kingdom for a tiny limpet to patrol

and each day his territory is growing bigger.

Kelp grows at an incredible rate.

Light powers the Golden Forest

and it needs to get its chlorophyll-producing fronds

to the surface as quickly as possible.

As it races towards the sunlight,

it can shoot up by half an inch a day.

No wonder this type of kelp called the bamboo of the ocean.

The little plant that drifted down here

and locked onto the rocks has done well.

Now it is well on the way to growing to a height

of around 39 feet.

Enormously tall in relation to its narrow trunk...

this forest tree has developed a unique way to stay upright:

the stems are hollow and supported by gas bladders

called pneumatocysts.

The blades, too, are kept afloat.

A floating bulb just beneath the head of the plant

makes sure that the blades are held up to the precious light

at all times.

Ultimately all life here owes its existence to photosynthesis,

from algae to apex predators.

And enjoying life in the middle of this dynamic food chain

are the forest's most charismatic creatures.

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

South African fur seals.

The show-offs of the Golden Forest.

They thrive here in huge numbers,

living on the same rocky coastlines carpeted by kelp

and fed by the same bounty that nourishes the Golden Forest.

For youngsters, identifiable by their darker pelts,

the forest is a playground.

They're having fun, but they're also learning skills

that will mean the difference between life and death.

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

Soon they will be old enough to leave the protection of the kelp

and venture out into the Atlantic to hunt for fish,

squid and crabs.

When they do, they will be entering dangerous waters -

the territory of the ocean's ultimate predator:

the Great White shark.

This abundant ocean provides plenty of food for the seals;

adult males can grow to be over six feet long

and weigh up to 660 pounds.

But even the biggest seal is no match for a 16-foot,

one-ton Great White swimming at a top speed

of 31 miles an hour.

The super-predators have perfected

their hunting techniques,

often attacking seals from below with such force

that they can breach the surface of the water.

Once a seal is caught, escape is extremely unlikely.

In many instances, it takes less than two minutes

from the first impact until the victim has been eaten.

To survive, these animals will need agility

and lightning-quick reflexes.

The open water is still too scary for the youngest pups.

While the teenagers play in the deeper water,

they hang back in the canopy.

Close to their low-lying island home,

the seals can use the upper canopy as day-care

for their pups, as they go out to hunt.

Baby seals have to learn how to swim

and this shallow zone is a safe paddling pool

for the youngsters making their first tentative outings

into the sea.

But further out, the forest's dense cover

is a double-edge sword.

If it can hide seals, it can also hide predators.

Great White sharks tend to avoid

swimming into dense underwater vegetation.

But there are other hunters in these waters

that haunt the thick kelp.

Which might explain this peculiar behavior.

It seems nothing more than playful vandalism,

but there may be more to this than fun.

One possible theory is that this game of cropping kelp

might reduce the chance of surprise attacks by sharks.

By clearing kelp from certain areas

and opening up sight-lines,

it is possible that seals will be able to spot

an approaching predator sooner

and will have precious seconds to flee.

For now, though, these seals are safe to play.

A favorite game: tormenting a potential meal.

The lobster is wise to play dead.

His sharp claws can give seals a painful pinch

and they're handling him with care.

But even with his claws and tough shell

he's unlikely to come away from this unscathed.

Not that everything that wanders

into this forest is edible, though.

This box jellyfish might look like a treat to the adults

and a toy to the babies,

but all the seals know that it packs a vicious sting.

It swims on, unharmed.

But the seals must stay on their guard

because another stealthy visitor is slipping

into the forest unseen...

Sharks are some of the most ancient animals in the ocean.

Supremely equipped to survive in a variety of conditions,

they have changed very little

over hundreds of millions of years.

And one of the most primitive of all shark species is this -

the cow shark.

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

With is seven gills and smoothed features

it would look at home in ancient seas.

The cow sharks have come here to hunt seals,

but beyond the protection of the forest

they, too, are at the mercy of the Great Whites.

For one, a horrific reminder of what happens

when predator becomes prey:

most of its tail has been bitten off.

Without the ability to maneuver or accelerate,

hunting will be difficult.

It might even starve.

Unlikely to escape larger, faster sharks,

its next brush with a Great White

will almost certainly be its last.

Here, at least, it finds temporary sanctuary.

Among the soaring stalks, it is safe.

Kelp is a sun-loving giant.

Photosynthesis is the life blood of this forest

and up here in the canopy is where the work is done.

The blades are multi-dimensional synthesizers:

there is no top or bottom side.

It makes no difference how wildly

the ocean waves thrash them;

the entire surface of the fronds can take part in photosynthesis.

It is an endlessly renewable engine

that keeps the entire ecosystem running.

But more than that, it is a life-saving shield.

The waves that roll in off the Atlantic are highly destructive.

Each surge is packed with energy

and when they collide with the shore

they release that power in an unrelenting bombardment.

But where the kelp forest thrives,

it creates a huge buffer.

Instead of hitting the rocks with their full force,

the waves and their energy are absorbed and diffused.

By the time the Atlantic reaches the shore,

its destructive power has been subdued

and instead of wrecking the coast,

it brings a bonanza of food.

Species that would otherwise be washed away can flourish

in the intertidal zone.

Marine creatures are not the only ones

that owe their success to the kelp.

Evidence suggests that it was access to shellfish

along southern Africa's coasts

that enabled early humans to thrive -

A protein-rich diet that helped to increase their brain power.

Without kelp, the shellfish might not have flourished

on the rocky shores and without shellfish to harvest,

our ancestors might not have developed

their most potent tool: the human brain.

Kelp is tough, but sometimes the Atlantic wins.

Pounded to breaking point,

some plants are torn free and tossed up onto the shore.

But even in death, they support the life of this coast.

Sand hoppers appear from underground

to feast on the rotting kelp.

Up to 25,000 of these tiny animals

squeeze into every square foot of this beach -

all sustained by the rotting kelp banquet.

There's plenty to go around:

sand hoppers eat up to

700 pounds of kelp every year.

They're not the only creatures tucking in.

Once it's dark, giant isopods emerge.

These large crustaceans, related to crabs and shrimp,

have lain buried near the high-tide mark.

Now, they too join the feeding frenzy -

yet another species kept alive by this incredible plant.

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

(♪♪♪)

It's not only the shore and the kelp that benefit

from the Atlantic upwelling.

Nutrient-rich waters also feed huge schools of pelagic fish,

such as anchovy.

And a school of anchovy is a feast for a super-pod

of dolphins.

The Golden Forest is a world in balance -

a buffer against the violence of the ocean

and home for fragile animals.

But every year or two, for a few grim days,

this underwater heaven transforms into hell.

The oceans are full of algae, but sometimes

some microscopic species grow out of control,

reproducing in huge and unsustainable numbers.

Here on the southwestern coast of Africa,

these harmful algal blooms

are caused by a sudden lull in the winds.

With huge volumes of nutrients in the water,

but no wind to stir the surface,

algae multiply dramatically, devouring oxygen.

The murky water has become anoxic:

the animals of the Golden Forest are being suffocated to death.

Desperate, they go to the one place with plenty of air -

but it's the one place they can't survive.

The seagulls gorge until they can't eat any more.

Harmful algal blooms are an apocalyptic event

in the Golden Forest.

And yet, for all the destruction they cause,

they cannot kill the forest itself.

The kelp survives;

ready to nurture new life around its stalks and fronds.

The upwelling continues

and the nutrients flood the coast once again.

The forest is resilient.

The plant that started as a tiny spore

is itself flooding the ocean with spores.

Soon a new kelp plant will anchor itself onto these rocks.

The Golden Forest will be renewed.

In the teeth of the south wind

and the pounding waves of the Atlantic,

kelp is more than just a plant.

It is a nursery...

a provider...

a hunting ground...

a playground.

Africa's Golden Forest.

A world beneath the waves.