Far away, cut off by vast oceans...
..Lie Earth's tropical islands.
Home to remarkable animal castaways...
..That have evolved in isolation.
And human cultures that have adapted in extraordinary ways.
From the jungles of Borneo with their staggering wild diversity...
..To Hawaii, the most remote island chain,
colonised by only the hardiest pioneers.
And Madagascar, the oldest island of all...
..Where time has given rise to thousands of unique species.
These tropical islands
have developed into astonishing and unique worlds.
Cradling precious life .
found nowhere else on Earth
In the tropical waters of the Indian Ocean...
..Lies the oldest island on Earth.
Madagascar.
Isolated for longer than any other island.
Life has had time to evolve in the most surprising ways.
With over 15,000 species found nowhere else.
Madagascar boasts more unique plants and animals
than any other island on the planet.
Madagascar was formed nearly 90 million years ago.
Giant landmass, known as Gondwana, broke apart.
As India split from Africa,
Madagascar was cast adrift.
It's a vast island almost the size of France.
And home to an astonishing array of ancient habitats.
At its heart lie the highlands,
an immense mountainous spine
that determines the island's climate.
Warm, wet air blows in off the Indian Ocean,
drenching the east of Madagascar with rain.
But the mountains block this rain from reaching the west,
creating a great expanse of desert.
This arid landscape stretches halfway up the west coast.
It was here, around 55 million years ago,
that a few animal castaways washed ashore.
Having somehow survived the 300-mile crossing from Africa.
One of the very first mammals to arrive
was an ancient species of primate.
And their direct descendants still live here in the desert today.
Ring-tailed lemurs.
It's dawn.
And a family of nine soak up the warmth of the early morning sun,
preserving vital energy for the day ahead.
This young lemur
is just six months old...
..And born into the harshest habitat on the island.
Known as the Spiny Forest.
Tiny leathery leaves provide little nourishment.
The troop spends up to eight hours a day
scouring the desert for food.
Tackling even the most hostile vegetation.
The sticky sap that oozes out of Euphorbia plants
can be caustic,
and burn human flesh.
Yet ringtails are resistant to their corrosive powers.
Euphorbia sap is also rich in fats.
Much-needed fuel
that will help this young lemur survive this inhospitable desert.
Ringtails are just one of the many species of lemur.
These primates are found only on Madagascar.
Their ancient ancestors gradually spread east across the island.
Adapting to each of Madagascar's varied habitats.
They now number more than 100 different species.
Humans are thought to have arrived on this island
just a few thousand years ago.
First from Asia, and then from Africa,
they settled on the coast.
Pushing inland,
those in the west faced the hostile desert.
Just 20 miles from the coastline lies the village of Ampotaka.
It's the dry season.
Temperatures often reach 40 degrees Celsius.
It hasn't rained for ten months now.
With their nearest water supply over 40 miles away,
life is a daily struggle.
The remains of this year's melon harvest
provide just enough water to cook with.
At 62, Adolphe has lived through the driest of years.
Today, Adolphe is joined by his son Leris...
..To visit the secret to their survival.
The baobab.
Known as "The Tree Of Life."
They can live for over 1,000 years.
Growing up to 30 metres high,
baobabs can hold vast
quantities of water in their immense trunks...
..And can survive for years without a single drop of rain.
For Adolphe, this baobab provides a lifeline.
By hollowing out the soft trunk, they created a tank,
which they could fill with water during the brief rainy season.
This living reservoir can store thousands of litres of water.
But this dry season has
lasted so long that the tree is already empty.
Still, it's an important opportunity to trim back the growing bark,
maintaining the tank's size
ready for the rain they hope will come soon.
This tank may have run dry.
But Adolphe inherited seven of these wells from his father.
Only one still holds any water.
With only enough water to last a few more weeks,
it's a worrying time for Adolphe and his family.
Survival in this desert depends on the arrival of the rains.
On the forest floor,
there are signs that the weather is changing.
Tiny Labord's chameleons,
only three centimetres long, begin to hatch.
They live for only four months.
The shortest lifespan of any land vertebrate.
For this young male,
it's a race against time.
In the dry season, there is little food.
But his hatching is perfectly timed.
It's the start of the rainy season.
The parched landscape is transformed
into a flush of green.
Just what this growing chameleon needs.
As his eyes can move independently...
..He can spot a meal in any direction...
..And, by locking both eyes onto a target, judge distance.
With deadly accuracy.
With so much food on offer,
the male Labord's chameleon can grow five times his size