Original subtitles

[♪ enchanting music]

[narrator] When forests and water meet,

each can have a transformative effect upon the other.

Seaweed becomes a force field protecting an entire species...

A team of misfits convert a mudflat into a fortress...

Seasonal banquets turn opportunists into hunters...

And the promise of a new life beckons creatures

to magically reinvent themselves.

These are the powers

of our forested water worlds.

Take a journey through our planet's kaleidoscope

of forest realms.

From the frozen boreal in the north,

to the tropical jungles that hug our equator...

From mountain peaks,

to the ocean depths...

Marvel at the magic...

and drama...

that unfolds, as we reveal...

the secrets of the Enchanted Forests.

♪ ♪

Coastal South Africa,

where hot dry sand...

meets a cold, fertile ocean

is about as far away from a forest as possible.

And a colony of seals

are not generally considered to be forest animals

but they are, and their lives can depend on it.

[seals barking]

In these waters lies a hidden forest

that for these seals,

acts as a magical force field against the deep dark ocean.

Despite spending most of their lives at sea,

Cape Fur Seals are not natural born swimmers.

They have to learn to swim.

As pups they practice in shallow, nursery pools.

[pups squeaking]

These teenage seals have graduated from the baby pool.

Now strong swimmers,

they confidently head out into the Atlantic Ocean.

♪ ♪

But they are naive to its dangers.

Luckily, there is a safe space where they can go.

Between the beach and the perils of the open ocean...

is the Great African Sea Forest.

A wondrous place made not from trees...

but of kelp.

♪ ♪

This bamboo kelp is a superpowered seaweed,

growing as much as 20 inches a day,

fueled by the nutrients from the surrounding water.

Anchored to the rocky sea bed,

its hollow trunk filled with air,

keeps it buoyant and upright.

As it dances to the rhythm of the waves.

It creates a natural, safe playground

for the teenage seals.

Similar to land forests,

this kelp provides the foundation

for an entire ecosystem.

The fronds are constantly releasing spores.

Clouds of tiny creatures, known as zooplankton,

feed on the spores.

Fish and crustaceans feast on the zooplankton

and are in turn, snatched by the seals

who turn everything into a game.

But seals are not at the top of this food chain.

A seven-gill shark has entered the forest on the prowl.

But the kelp stems slow him down and obstruct his line of vision,

allowing the agile seals to easily out maneuver him.

But as this shark's missing tail is testament,

there are far more ferocious predators

that patrol the deep waters just beyond the forest.

The great white shark -

a specialized seal hunter.

It uses lightning acceleration to ambush its prey.

But the web of kelp acts like speed breakers.

So, this killing machine

sticks to hunting in open water instead.

Next year, these teens will have to venture out

beyond their kelp forest,

joining the other adults to brave these sharks

when fishing further afield.

But for now, they are safe.

Further along the coast, grows a formidable forest

that not only protects entire coastlines

but also safeguards

the future of coral reefs miles offshore.

On a vibrant and bustling reef,

new life is spawned daily.

But survival on the reef

is a never-ending cycle of eat... or be eaten.

For newborns, life expectancy here is dangerously low.

In desperate need of protection, they head towards land,

into the nurturing embrace of a mangrove forest.

Lining the coasts and estuaries,

these welcoming trees extend their limbs seaward,

inviting millions of tiny juvenile fish

into their fortress of roots.

But for a tree to thrive here

in a place that is not quite land, and not quite sea,

requires new levels of resilience and problem solving.

The only water available to drink is a hundred times saltier

than any other tree could withstand.

But these trees have the ability

to filter out the salt internally

and banish it into their leaves.

Here, it is either excreted through specialized glands

or stored and eventually discarded.

Being flooded twice a day

makes access to oxygen a challenge for the trees.

So they send their root tips to poke up through the mud,

allowing them to breathe through hundreds of tiny snorkels.

Even their seeds are specially designed

to anchor themselves in the mud

and prevent them from being washed away with the tide.

Over time,

they'll grow to add another set of buttress roots

to this forest barricade.

These mangroves don't just nurture life,

they also shield the coastline from the wrath of the ocean.

Safe in their fortified refuge,

the little fish are bulking up on nutrients

from the forest floor and growing strong.

This latest generation of reef inhabitants

will only leave when they are ready to fend for themselves.

But to support this underwater creche,

the mangrove forest relies on an entire team above the waterline

to keep the whole setup functioning.

[narrator] As the tide's ebb reveals last night's detritus.

it kickstarts a flurry of activity.

Red claw mangrove crabs fight over the unstuck seed pods.

♪ ♪

These are highly desirable, and tasty items.

Any leftovers will rot in the burrows,

returning the finite nutrients to the mud

for the trees to recycle.

Other seeds may be abandoned within a burrow

and inadvertently planted.

Either way, it's a positive outcome for the forest

Whilst the mangrove crabs wrangle,

the smaller fiddler crabs are all about showing off.

Their one jacked up claw...

is not for fighting.

It's to impress the females

and beckon them over to their burrows.

But their giant claw can also help the forest.

To accommodate this outsized limb,

these tiny crabs dig larger and deeper burrows,

creating deep air pockets that turn into channels in the mud

helping the mangrove trees to stretch their roots further.

The tide has turned... and creeps back inland.

The working day is coming to an end

and the forest floor is ship-shape.

Now it's time to batten down the hatches.

This extraordinary mangrove environment

only functions through teamwork.

This curious band of misfits all work together

so that the forest can provide an invaluable service

to protect both land and sea.

[Birds singing]

As the mangroves trees stretch their reach further inland,

saltwater starts to mix with freshwater.

Found amongst these brackish estuaries of Sri Lanka

is a fish that hunts its forest prey

with fearsome accuracy.

These ants are looking for a new nest site.

But as they venture closer to the water,

they are entering the strike zone.

This seven-spot archerfish has a remarkable talent.

He can shoot a jet of water into the air

at precisely the right force and direction to hit his target.

Giving him access to food in the surrounding trees

that other species in this stream can only dream of.

The archerfish doesn't have any additional body parts

to achieve this technique -

just some extra special adaptations.

His mouth is modified like a water pistol.

By taking in water, and quickly closing his gills,

he creates a pressurized liquid bullet

with five times more striking power

than any vertebrate muscle can produce.

But it is his 'dual vision' that gives that powerful shot

such incredible accuracy.

The upper part of his eye is perfectly tuned

to the colors of his underwater environment.

While the lower part

is designed for looking up above the surface.

[water splatting]

However, his eyes do not correct

for the light refraction of the water.

This is something he has to calculate

and calibrate on his own.

All this talent still doesn't guarantee a meal.

Other fish are all too eager

to capitalize on his shooting skills.

These crack shot archerfish have found a unique way

to target their forest surroundings

and supplement their supper.

Nothing within spitting distance is safe.

[narrator] A river carving its path through

a forest is far more than just a source of water.

It serves as a superhighway

enabling a tree to plant its offspring hundreds,

sometimes thousands, of miles away.

[birds singing]

The Mighty Mekong

begins as a distant icy headwater

in the Tibetan Plateau.

From here, glacial streams turn into freshwater rivers

over 2700 miles long,

flowing into the forested Mekong delta.

Trees en route drop their seeds into the flow,

sending their offspring down river

to seek their own fortunes.

These waterborne seeds can last up to a year

on their river cruise,

spreading their species influence

over many countries and habitats.

But the seeds need to get off the ride

before they hit the sea.

And these long-tailed macaques are their way out.

They've learnt that the river

is a conveyor belt of seasonal delights.

And they are only too willing to dive right in!

[playful music]

As the macaques move about their forest range,

their droppings disperse the tree seeds further inland,

where they can take root.

So, a seed from China could be planted in Vietnam...

with the help of a formidable river...

and a hungry monkey.

During the monsoon season, riches from a distant forest

can turn a dedicated scavenger into a fisherman.

The air around this lake in Southern Sumatra

is heavy with expectation.

The arrival of a Brahminy Kite

to the lake's surrounding forest

is a sign.

The monsoon rains are coming.

He has flown here from the other side of the island.

He is an opportunistic scavenger,

usually content feasting on anyone's leftovers.

But he knows

that when torrential rains pour in this region,

it brings a different kind of opportunity.

The changing winds usher in moisture laden air

which builds up over the mountains.

[thunder clapping]

[rain pouring]

This sudden deluge of water breaks through the canopy,

flooding the forest floor,

and flushing rich organic matter down the mountains...

and into the lowland lakes.

This influx of water,

packed with vital nutrients from fallen and decaying trees,

acts as a fertilizer.

And the lake's aquatic life goes into overdrive.

The boom in insects and larvae at the surface

draws the freshwater fish up from the depths.

This is the moment the kite has been waiting for.

Feasting at the surface,

the fish are now within reach.

Well, almost.

Brahminy kites' talons are relatively weak

compared to other raptors.

So he just has to keep... on... trying.

But now he has competition.

[adventure music]

[narrator] Despite the crowds,

eventually perseverance pays off.

Forest nutrients move up the food chain,

from land, to lake, to sky

and eventually back to the forest once again.

The building blocks of life

being constantly transferred and recycled.

[majestic music]

Next monsoon season,

this rain chasing visitor

will be back to improve his skills.

In some regions, the humble woodland pond

can support an even greater range of plants and animals

than any lake or river.

♪ ♪

Down in the silt of a pond,

amongst the vegetation

live nature's real-life transformers.

Diving Beetles,

dragonflies,

salamanders,

all start their lives underwater,

waiting for the secret signal

for them to reinvent themselves from aquatic to forest creature.

But it's a nymph eat nymph world.

Each competing to make it out of the pond alive.

Over time, legs grow,

tails disappear

and the forest world calls to them.

This fire salamander

is going through his awkward teenage transition stage.

His nymph gills are shrinking, and he's covered in spots.

He is on the cusp of change.

When the length of daylight and temperature is just right,

after years spent underwater,

it's time to enter adulthood.

This dragonfly is undergoing

one of nature's most spectacular metamorphoses.

[magical music]

She'll only live another few months...

just enough time to find a mate and lay her eggs.

The fire salamander has also left the pond

and is exploring his new forested world.

His bright spots will help him in this unfamiliar environment,

by shouting out the message that his skin is now poisonous.

More than 80,000 known insect and amphibian species

start their life in freshwater.

They all need a clean, cool place

to spend their formative years.

But ponds are fragile places,

and in a warming and increasingly crowded world,

they are disappearing.

Without them and the life they nurture,

the entire forest food web would soon collapse.

[wildlife chattering]

[narrator] These are North America's steamy subtropics.

Here, a terrestrial forest

has been slowly shaping these wetlands for centuries,

giving birth to a swamp.

Fluctuating water levels are fed

by rainwater and underwater springs.

But it's the trees that truly shape these habitats.

The tree's extensive roots bolster the banks

and slow the flow of water,

allowing more plants and algae to bloom.

Creating the perfect home for the American alligator.

The surrounding forest offers shelter for many birds,

reptiles and small mammals.

[splashing]

A pantry of delights for this apex predator.

In stagnant water, forest debris doesn't wash away.

It simply sinks to the bottom.

Over time, layers of rotting vegetation build up,

creating an underbelly of thick sediment

which soaks up the water and slackens it even further.

Even this silt is a bonus to the alligator.

It not only colors the water to match his skin,

its murkiness raises the water temperature,

and gently warms his cold blood.

This male is so content in his swamp surroundings,

he is not prepared to share it.

Unless it's breeding season, of course.

[♪ flamboyant guitar music]

His low, guttural mating calls make the water dance...

[alligator growling]

...enticing a nearby female.

[growling]

[♪ flamboyant music]

He invites her in,

solely for courtship and mating.

After some brief moments of tenderness,

she retreats to her own swamp

to find a secluded spot amongst the vegetation to lay her eggs.

After months of watching over her nest,

she hears the distinct sound she has been waiting for.

[hatchlings purring]

For an alligator, swamps make the best nurseries.

As a little warmth can make a big difference

in her babies' gender.

[hatchlings purring]

The decomposing vegetation makes an ideal incubator.

If the internal temperature reaches 93° Fahrenheit or above,

mostly males will emerge,

whereas a cooler temperature

will produce predominantly female offspring.

The forest swamp ecosystem

will nurture these alligator hatchlings

as they move their way up the food chain.

As adults and top predators, they will rule these waters,

and keep all other populations of prey in check.

Swamps are often given a bad rap.

But they're an important and thriving habitat.

They store twice as much greenhouse gas

in their vegetation and mud than land forests.

And, along with rainforests and coral reefs,

swamps are some of the most productive ecosystems

in the entire world.

♪ ♪

[narrator] The ancient partnership between forests and water

has created many diverse settings,

enabling life on earth to flourish.

In Hawaii, these forest lined rivers

present the ultimate paradise for one tiny ocean fish...

who is prepared to undergo a full body transformation,

to take on the challenge of a lifetime.

These goby fish have spent the last six months

feeding out at sea,

and now the wooded wonderland of their birthplace

is calling them home.

But Hawaii is a volcanic island,

with steep rock faces and no easy route inland.

So the gobies gather in their thousands,

clinging to the rocks at the base of a steep waterfall

waiting for a miracle.

For an ocean dwelling fish,

the flow of freshwater has magical powers.

Just by allowing the falls to wash over it,

its juvenile body starts to change.

Its mouth, once positioned at the front of their heads,

migrates to the underside.

Now it has two clamps (mouth and belly sucker)

ready for rock climbing.

Legions of gobies inch their way out of the water,

and begin their momentous climb.

Propelled forwards by their pectoral fins,

they use their mouths to inch up the wet rock

while their belly sucker clings on for dear life.

The sheer force of water proves too much for some.

But the promise of a new forest home

is enough to keep the rest fighting for the summit.

♪ ♪

For the gobies who make it to the top,

this is their slice of heaven.

The woodland canopy keeps the water cool,

allowing in just enough sunlight for algae to grow,

ensuring the gobies won't go hungry.

And unlike the ocean, there are no predators here.

Having passed the ultimate endurance test to get here

the gobies never need to leave the forest again.

It's the perfect place to start a family

and live out the rest of their lives

in their Hawaiian Island paradise.

Forests like these are the guardians

of our planet's waterways.

Standing tall, they temper the water's force,

offering sanctuary and seasonal opportunities

whilst nurturing and protecting life

both above and below the waterline.