Our Planet

Just 50 years ago,

we finally ventured to the moon.

For the very first time, we look back at our own planet.

Since then, the human population has more than doubled.

This series will celebrate the natural wonders that remain,

and reveal what we must preserve

to ensure people and nature thrive.

When human beings built their first settlements

some 10,000 years ago,

the world around them,

on the land and in the sea,

was full of life.

For generations, this stable Eden nurtured our growing civilizations.

But now, in the space of just one human lifetime,

all that has changed.

In the last 50 years,

wildlife populations have, on average, declined by 60 percent.

For the first time in human history,

the stability of nature can no longer be taken for granted.

But the natural world is resilient.

Great riches still remain.

And with our help, the planet can recover.

Never has it been more important to understand how the natural world works,

and how to help it.

Wildlife still flourishes in astonishing numbers

in a few precious places.

Along the Peruvian coast of South America,

seabirds congregate in colonies millions strong.

They come here to breed.

Every morning, the birds leave their colonies

to fish in one of the richest seas on Earth.

It is an astonishing daily migration

of five million birds.

The huge flocks of cormorants and boobies are all seeking one thing:

anchovies.

The boobies carpet-bomb the shoals.

More and more birds join the feeding frenzy.

All in this immense assembly are here

because a powerful oceanic current, the Humboldt,

sweeps up from the Antarctic,

bringing with it rich nutrients from the ocean's depths.

90 percent of the life in the oceans

is found in the shallow seas close to the coast.

Away from the land,

the seas, for the most part, are a blue desert.

But even these distant waters may be enriched

by a most unexpected connection to the land.

Some deserts,

often hundreds of kilometers from the ocean,

provide the raw materials for life.

Every year, winds sweep up two billion tons of dust into the sky.

At least a quarter of it eventually falls on the sea,

providing nutrients needed by the microscopic organisms

that are the foundations of ocean life.

Dolphins explore the vast, open ocean

in search of the riches that distant deserts may have nourished.

A shoal of mackerel has discovered a swarm of krill...

the small crustaceans

that feed on the ocean's floating microscopic plants.

But the mackerel themselves are food for the dolphins.

They drive the mackerel towards the surface,

and into the range of birds.

Shearwaters.

The wings that normally propel the birds through the air

now drive them six meters down through the water.

Whilst the birds pick off the top of the shoal...

the dolphins attack the underside.

After 20 minutes of feasting,

the predators from both the sea and the air

have had their fill.

The stability of life on our planet

relies on such connections between different habitats.

Water evaporating from the surface of the sea

condenses to form great clouds.

And these eventually release the fresh water as rain.

But these life-giving rains are not evenly spread over the land.

This vast salt pan in Africa

is all that remains of an ancient lake.

It's totally waterless and oven-hot.

Few places on the land are more hostile to life.

A few tracks cross it, made by animals searching unsuccessfully for water.

But very occasionally, this whole landscape is transformed.

A huge deluge drenches the salt pan.

Triggered by some unknown signal,

flocks of lesser flamingos arrive from thousands of kilometers away.

The algae that the flamingos feed on

have lain dormant as spores in the dust.

But most importantly,

the birds are here to breed.

Perfect conditions might occur only once in a decade.

The birds nest on an island far from the shore.

They build mounds of mud that raise up their eggs

and so keep them just marginally cooler than they would be at ground level.

The water surrounding the island is so salty

that predators do not venture into it.

So the nests are safe.

Thirty days later, thousands of chicks start to hatch.

But there is no shelter from the scorching sun.

The water that once surrounded their island, protecting them,

has now dried up altogether.

The last to hatch step out into a desperately harsh world.

Somehow or other, the growing chicks must find fresh water to drink.

They cannot yet fly, so they must walk, guided by some of the adults.

They may have to trek for 50 kilometers.

Some... cannot keep up.

The salt has solidified around their legs.

Most of the chicks, in spite of everything,

and having walked for days,

eventually reach fresh water.

It is the end of a long journey...

but only the first of the trials that will be imposed on these flamingos

by the irregularity of the rains.

If rainfall is more predictable and certain,

then life can flourish more richly,

both in numbers and variety.

The Serengeti plains in East Africa support over a million wildebeest.

The herds follow the seasonal rains,

grazing on the newly-sprouting grass that comes in their wake.

Each year, within a three-week period,

the females give birth to over a quarter of a million calves.

This youngster is just a few days old.

Playing strengthens its legs for the long journey that lies ahead.

The calf must stay close to its mother.

Without her milk, it would starve.

And the herds are always traveling,

following the rains as they drift across the plains

in order to find fresh grazing.

Eventually, they reach woodlands.

Hunting dogs.

Wildebeest calves are a favorite prey.

And the dogs are hungry.

The calf must stay with its mother, protected within the herd.

The dogs have incredible stamina...

but the calf is defended by the herd.

They need the calf on its own.

The mother blocks the dogs, shielding her calf.

It makes a run for safety.

And it just manages to get back to the herd.

The future of this whole migration depends on the regularity of the rains,

but also on the continued existence of the great open grasslands

across which the herds make their immense journeys.

In places where rains fall abundantly throughout the year, forests grow,

and in the warmth of the tropics,

they support an unparalleled richness of life.

Half of all the species of land-living animals

live in these stable worlds.

The sheer diversity is breathtaking.

We still have not catalogued

all the species that live in the tropical forests.

The relationships between them all are multitudinous and complex.

Plants often depend on animals to pollinate their flowers.

And these intimate connections

are just as important as the great global ones.

These are traps.

Flowers shaped like buckets,

produced by an orchid.