Original subtitles

My mom moved us to Indonesia for a few years as a kid.

We lived in a small house with the simple joys of nature.

A mango tree out front, whiffs of fruits and spices.

Paddy fields where water buffalo glanced up at you with mud-covered snouts.

Indonesia is home to some of the most important forests

and biodiversity in the world.

And there's nothing like the Leuser Ecosystem,

home to some of the most endangered species on Earth.

The rain forests of Gunung Leuser National Park

shelter countless plants and animals…

each with a role to play.

Leuser is also the last stronghold

of four of the planet's most threatened species.

Powerful and elusive tigers…

…the world's smallest rhinos…

…unique forest elephants…

…and orangutans, one of the smartest great apes in the world.

Once, these animals could be found together across southeast Asia.

But deforestation and poaching means that, today,

Leuser is the only place they still co-exist.

Will we allow something so precious to disappear forever…

or seize our last chance to protect it

for our children and grandchildren?

Join me in this most unique of wild spaces.

On the Indonesian island of Sumatra lies a vast tropical rain forest

and at its core, Gunung Leuser National Park.

Here, forest-covered mountains dominate,

reaching 10,000 feet tall.

They safeguard its inhabitants like a fortress.

But perhaps its greatest wildlife riches are found in its steamy lowland jungles.

In Indonesian, "orangutan" means "person of the forest."

And these trees are home to the densest population anywhere on Earth.

This is their forest.

There are several huge males.

With large, flanged cheek pads, they're more attractive to mates.

They're immensely powerful

with a bite force stronger than a lion's.

But there's an athletic and ambitious younger male coming up through the ranks.

Rakus.

His name, given to him by resident scientists, means "greedy."

Because he likes to eat pretty much everything.

Leaves,

bark…

fruit…

termites.

It's all on the menu.

If this gourmet ape can eat enough,

he may one day develop cheek pads

like the most senior males.

There's one food in particular that could fuel his ambition.

The neesia fruit.

About the size of a football,

it's packed with large, tasty seeds.

Before it ripens, it's as hard as concrete,

making it nearly impossible to get into.

Ripe neesia cracks open by itself.

But the succulent seeds are surrounded with thousands of sharp, irritating hairs.

To get this meal, Rakus must master

the most sophisticated skill in the jungle.

Many of the orangutans here

use an ingenious way of avoiding the neesia's prickly hairs.

First, they select a stick.

Then, maneuvering it with their extremely versatile lips,

they push it into the neesia's cracks.

Repeated movement of the stick dislodges the seeds

and in the process scrapes out the hairs…

…making the fruit ready to eat.

Orangutans are usually solitary animals.

But the neesia tree comes into season only rarely.

When it does, it draws in orangutans from far and wide.

As they gather, there's a chance to learn from each other.

Friska is a mature female

and is expert at preparing the fruit.

Rakus moves in for a masterclass.

There's enough food around for him to be tolerated.

These are the only wild orangutans

known to create and use tools in this unique way.

Rakus wants to have a go himself.

Carefully, he crafts his tool.

And Rakus selects the perfect neesia.

Then it's down to trial and error.

At last, with a little perseverance…

Rakus gets the delicacy he's been craving.

The more he perfects this extraordinary skill,

the bigger and stronger he'll become.

And one day, this greedy guy

may just rise to the top.

Leuser's abundance is partly thanks to its soil,

which is up to six times more fertile than other rain forests in the region.

And this is a reason why.

One of the world's most active volcanoes.

Mount Sinabung.

For millennia, its eruptions have showered the area with volcanic ash…

…rich in minerals and nutrients.

The ash acts as a fertilizer,

supporting a jungle of staggering complexity.

With thousands of species of plants,

it's one of the most diverse forests in the world.

The titan arum.

This is the largest flowering structure on the planet…

…growing up to ten feet tall,

the height of a basketball hoop.

It only emerges after the plant has been growing for a decade.

But producing this huge bloom saps a lot of energy.

Flowering can only last two nights.

So it has a clever way

of rapidly attracting the insects it needs for pollination.

It produces a powerful scent.

But this is no fragrant beauty.

It reeks of rotting flesh.

The huge red bloom stretches up to five feet,

adding to the illusion of a fresh animal corpse.

Then as night falls, its greatest deception begins.

Channeling ten years of stored energy,

the arum pumps heat into its central column,

becoming as hot as blood.

Like a chimney, rising heat carries its stench up into the cool night air.

For hundreds of scavenging insects,

the draw is irresistible.

They're lured into the arum's inner chamber.

A cavern filled with male and female organs.

As the insects search for the rotting meat they've been promised…

they find themselves coated in pollen they will carry with them

to other arums.

And if they've already visited another of these giants,

they will pollinate this plant.

Ten years of preparation for a two-night show.

The flower's energy is exhausted.

The stragglers file out…

before finally,

in a matter of seconds…

…the entire structure collapses.

Successfully pollinated, another ten-year cycle is set in motion,

toward more gigantic blooms.

Even within Leuser's lowlands,

there are extraordinarily different landscapes.

The park's rivers transport its nutrient-rich soils

downstream to the coast…

where the forest meets the Indian Ocean…

giving rise to a muddy mangrove swamp.

A mudskipper.

This fish is not confined to the life aquatic.

Taking a big gulp of air…

and using fins that have a shoulder joint,

he propels himself around.

A fish that can walk.

He spends most of his life here on the mudflats.

His periscope-like eyes have a lens like land-based animals,

allowing him to see far better out of water than in.

His favorite meal is a formidable foe

with razor-sharp pincers.

If he can catch one without getting nipped.

Perhaps something softer?

These crabs are very agile…

especially for a fish out of water.

Finally, all that remains is to disarm his prey.

Holding it in his mouth, he uses a neat trick.

Shake a crab hard enough and it will sacrifice its claw,

the tastiest bit.

But the loss is only temporary.

Within a month, the crab will have grown a new claw.

Maybe even bigger than before.

For this land-loving fish, life is a never-ending crab-claw buffet.

Heading inland, Leuser quickly becomes mountainous.

The forest here is much more impenetrable.

Steep hills provide a last refuge to Leuser's most endangered creature…

the rarely-glimpsed and surprisingly small

Sumatran rhinoceros.

Although only four feet tall, it still weighs a ton.

Perfect for bulldozing through thickets in search of lush foliage.

By pruning plants, these rhinos benefit the forest,

making room for new tree growth.

They dig out mud wallows, which help them stay cool in the midday heat…

…benefiting a range of neighbors.

So the more rhinos, the healthier the whole forest becomes.

Illegal hunting and habitat loss

have reduced numbers to just a handful in the wild.

To save them from extinction, rangers are constantly on patrol,

deterring poachers

and bringing the few remaining rhinos into captivity outside the park.

These rhinos now live in large, guarded natural enclosures…

where a breeding program

hopes to reintroduce their descendants into Leuser…

and eventually restore the balance of rain forest life.

There are many extraordinary relationships between the creatures that live here.

Some, we are only just discovering.

Deep in Leuser's foothills,

one of its smallest inhabitants is unwittingly helped

by its largest.

The Sumatran elephant.

As they travel, they carve a network of pathways hundreds of miles long.

Many species rely on these paths to get through the dense jungle.

But one resident depends on these elephants more than most.

A wart frog.

She's only the size of a chicken's egg,

but she has incredibly sharp senses.

It's thought she detects vibrations of the approaching herd

using special cavities in her lungs.

You'd expect her to get out of the way.

Instead, she heads towards them.

Straight into the crush zone!

But it's not the elephants themselves she's drawn to.

The frog has a belly full of eggs,

and she needs to lay them in still water.

The elephant's footprints make the perfect pop-up nursery.

She's given her eggs the best start in life

and leaves them to hatch.

Within two weeks, they've become tadpoles.

But until they transform into froglets,

survival in their flooded footprint is under threat.

The tropical sun can quickly dry out these pools.

So, if water levels drop, these tadpoles must get themselves out of trouble…

by doubling the speed of their transformation.

As froglets, they can finally escape the drying ponds.

As long as they don't get squashed.

Up in the treetops, the stakes are even higher.

Many of Leuser's animals have mastered living up here.

But perhaps none are more daring than the Thomas leaf monkey.

Found only in Northern Sumatra,

they roam in groups of up to 20.

One male leads the troop,

and the rest are females and young.

The adults are supremely agile.

Able to zip around the branches,

they can leap large gaps with ease.

But this two-year-old is still developing the strength in his leg muscles…

and he can't navigate the canopy with the confidence of his elders.

His mother used to carry him everywhere,

but she has a new baby.

And the youngster must now find his own way in the world.

Today, he faces one of the biggest challenges of his life.

The troop have exhausted supplies in this tree,

so they have to move on.

But it will take a giant leap across a gap of more than 20 feet.

It's a three-story drop.

One mistake

could be fatal.

The older monkeys have spent years perfecting such large jumps.

Climbing to the topmost branches, they launch…

maneuvering their limbs to control their descent.

Even Mom, with her new baby on her belly,

tackles the distance with grace.

The two-year-old is up next.

But it's all too much.

With the rest of the troop feasting on the other side…

…he's stranded.

Mom can't come to his rescue.

There's only one way to find out if he's got what it takes.

Nailed it.

The first of many such giant leaps he'll make on his journey to adulthood.

And he gets a well-earned reward.

Animals like the leaf monkeys

help maintain the health of Leuser's rain forest,

spreading seeds and natural fertilizers as they move.

Every species here is important.

Even the smallest

that lurk in the dark underworld of the forest floor.

The leafy gloom is home to a hunter,

the hammerhead worm.

This species of flatworm with its distinctive bands

is so new it's yet to be named.

As predators go, it's extremely small.

The length of a fingernail.

But it is deadly.

It's on the hunt for a juicy slug or snail.

They're everywhere in Leuser,

devouring microscopic plants and organisms…

and also the fungi that's essential for recycling plant debris.

And this is where the hammerhead plays its part,

keeping their numbers down, and so protecting the greenery.

Using chemical sensors in its hammerhead,

it tastes the ground for signs of a victim.

Slugs and snails can't help but leave an unmissable trail of slime.

With just a hint of a shell on its back,

this curious creature is called a semi-slug.

The perfect prey.

Wrapping around its victim, the flatworm pumps out mucus to trap it.

Once the prey is disabled,

it attacks the semi-slug with toxins and digestive juices,

breaking down its flesh…

…finally, swallowing it through a mouth in the middle of its body.

Within a matter of minutes, all that remains is the translucent shell.

There are predators of all shapes and sizes across Leuser.

But perhaps the most important sits right at the top of the food chain.

To find it, you have to travel even higher…

…to the remote, fortress-like mountaintop,

which gives the park its name…

Mount Leuser.

Towering over 11,000 feet above sea level…

often shrouded in mist…

the forest is stunted…

with patches of open moorland.

It can be up to 60 degrees Fahrenheit colder here

than the humid jungles far below.

Only the toughest of plants can survive.

Clinging onto the rocks, they hold the soil in place…

preventing erosion and retaining rainwater,

which then flows steadily into the forests far below.

It's eerily quiet.

Only a few animals venture this far up the mountain.

The muntjac. A type of deer that browses on the moorland plants.

Scientists hope research cameras might finally record

the predator which hunts them…

filming it here for the first time.

But it is almost never seen.

So it takes patience.

At last…

in a high mountain pasture…

a Sumatran tiger.

This adult male is checking out the scientific equipment

left to record it.

The terrain is so inaccessible

that almost no studies have been made into the Sumatran tiger's behavior.

But it's believed that as they patrol the mountaintops,

these tigers stop deer and other animals from overgrazing the delicate vegetation.

And these precious images prove that they're still here.

As long as we protect the park,

Sumatra's biggest cat can remain king of the jungle.

While Leuser's mountainous terrain offers some natural protection…

…on the fringes of the park, the risk to the wildlife is greater.

Leuser's ecosystem continues into an area twice the size of the park.

Much of it is protected…

but millions of people live in towns and villages amongst these forests.

So having the support of local communities

is crucial to keeping Leuser's wildlife safe.

Hidden in the trees on Leuser's southern border

is a rarely-seen Sumatran slow loris.

She's got huge eyes

that help her to see in almost complete darkness.

This mother has a young baby just a few weeks old,

but he's already too big for her to carry as she feeds.

Leaving him seems risky.

Rival lorises can be viciously territorial.

And the forest here is full of snakes.

But lorises have a secret weapon.

Their bite contains a deadly toxin,

making them the only venomous primate on the planet.

Even this youngster.

So Mom can just hide him among the leaves

while she goes foraging on her own.

It's extremely unusual to see slow lorises venture to the ground.

But she has to to get to one of her favorite foods,

the calliandra.

Its sweet-smelling nectar is packed with the energy she needs to nourish her baby.

But these flowering bushes have been planted by farmers

to shade their coffee crops.

And lorises' proximity to humans has given them a problem.

Traffickers in the illegal pet trade

have hunted these cute creatures to the edge of extinction.

But fortunately, this community is part of a new scheme that protects them.

The farmers get a better price for their coffee

for leaving the lorises alone.

And the lorises help the farmers,

because when they eat the calliandra,

they pollinate it.

As dawn approaches, she must return to her baby

and get back to the business of being a mom.

Local communities can also help to combat the biggest threat…

deforestation.

Leuser is so vast, it's almost impossible to patrol.

Every single hour,

more than a football field of forest is cleared,

much of it illegally,

to make room for growing palm oil.

Palm oil is used in up to 50% of products on our supermarket shelves,

from cookies to shampoo.

These plantations are lifeless

compared to the richness of the rain forest.

But some communities are taking part in a fight back…

…working with conservationists to remove the plantations.

A small subsidy and a chance

to grow a few profitable fruit trees within the forest

gives an incentive and helps safeguard their futures.

On the recovered land, Leuser quickly produces wonders.

The wind brings seeds from healthy forests nearby.

Microorganisms help to heal the soil.

In just a matter of months,

ferns and other plants grow over the old site.

The pollinators move in.

Mammals and birds spread more seeds.

And in as little as four years,

a thriving forest reappears.

As it does so, animals start to return.

Eventually, giant trees will grow.

They'll absorb more and more carbon dioxide from our atmosphere,

enriching it instead with oxygen,

which benefits us all.

By protecting this forest,

Asia's most endangered creatures will still have a home.

While still an infant, this Sumatran orangutan was taken from the forest

and sold into the pet trade.

After years of captivity,

she was finally rescued

and brought back to live freely again in the treetops.

And now, she has another to care for.

Less than two weeks old.

So small she could fit in the palm of your hand.

These tender moments are the beginnings

of one of the closest motherbaby bonds in nature.

For eight years,

she will live within arm's reach of her mother,

who will teach her everything she needs to survive.

Gunung Leuser National Park

and the vast ecosystem that surrounds it

is a place of hope

and an opportunity to protect its unique wildlife…

in this, their last precious refuge.

National parks are one of our greatest achievements.

Over time, we've created nearly a quarter of a million protected spaces

in almost every country on Earth.

But in this world that's getting warmer and more crowded, we've got to do more.

And if we're going to hang on to more of these wild places we depend on,

each of us has a role to play.

Demand to protect our last wildernesses

for future generations.

Campaign to create more, wherever you live,

and insist they're accessible for everyone.

Push your own communities to adopt smarter climate practices.

And vote like the planet depends on it.

There's no more time to waste.

The world we leave to our children is too important.

The time to act is now.