Earth's Greatest Spectacles

Our planet is a place or constant change.

Each year, the seasons shift and life is transformed.

But there are places where the changes are so epic in scale they can be seen from space.

In this series, we reveal

three of the most miraculous transformations.

The island of Svalbard.

Within a few weeks, frozen wastelands burst into life.

The African okavango.

A desert transforms into a magical water world.

And the mysterious forests of new england

erupting in a Blaze of seasonal colour.

Life finds the most ingenious and surprising ways to thrive

in the world's fastest changing landscapes.

New england, home to the most colourful forest in america,

stretching across six states,

from Maine in the north to Connecticut in the south.

Every year, millions of people flock here

to witness one of the planet's greatest spectacles

known here as the fall.

When billions of trees explode into a riot of red,

orange, and gold.

There's nowhere else on earth quite like it.

But despite this beauty, there's a battle raging.

One that holds the secret

to this magical forest's most flamboyant display.

The story of the fall begins while winter still has a grip

on the forest.

17 billion trees rich with maples and oaks

wait in suspended animation.

Amongst them, many of new england's animals

are hibernating from the cold.

But america's tallest mammal remains at large.

Moose survive by chewing on twigs.

Their calves will be born in just two months,

and their survival will depend on the same chain of events

that will fuel the forest's climax of colour.

As the weather warms, water courses through every tree

and it picks up sugars stored in the wood.

This liquid energy is the life force of the entire forest.

It's so rich with sugar that maple syrup is made from it.

The spring sunshine warms the land,

and the sugar surges faster,

fuelling the growth of nutrient-rich buds.

These tiny packages contain everything needed

to build a leaf.

But from this point on, each tree faces a battle.

All across new england, twigs are coming to life.

These creatures spend the winter disguised as twigs.

Looper caterpillars.

They awake with the warmth and immediately begin to seek out

the freshest buds on a hunt for sugar.

Nearby, hundreds of baby tent caterpillars

hatch from their winter eggs.

Each smaller than a grain of rice,

they join the feast.

Swarming along the branches, a torrent of bud destruction.

This is just the first wave in a battle that will escalate

through the year.

The buds race to open before they can be attacked.

Gradually, the first flush of green spreads across the forest.

But it will be a few weeks before the leaves

are fully expanded,

and they will need a constant supply of sugary sap

from under the bark.

In some trees, that sap is also at risk.

The warming spring weather attracts and animal

with a serious sugar addiction.

All the way from Mexico...

The yellow-bellied sap sucker.

His beak hammers six times a second,

wounding the tree deeply and chiselling into the vessels

carrying the precious sugar.

His feathery tongue quickly laps up the weeping liquid.

On this tree last year, he dug hundreds of holes,

but now all the Wells are dry.

It's not enough to deter a determined sap sucker.

He can dig as many as 1,000 holes in a season.

And on another tree, he's excavating a nest.

If he finishes it and keeps his Wells running sweetly,

he could attract the attention of a female.

But there's another bird that could ruin his plans.

A Ruby-throated hummingbird.

He's followed the sap sucker all the way from Mexico.

His wings beat 80 times a second,

putting him on a calorific knife edge.

The weeping sap is the best source of sugar

currently available.

And feeding at 15 sips a second, he can quickly drain a well dry.

He's too fast for the sap sucker to chase off.

So the sap sucker opens more and more Wells.

Eventually, despite the interruption,

he finishes off his nest,

creating a deep hollow in the tree.

Now everything is prepared.

As the trees' leaves grow, they start to shade the forest floor.

In anticipation, the plants down below wake from their stupor.

The flowers must attract a pollinator

before all the light is stolen.

Now hummingbirds can feed on their favourite source of sugar,

nectar, in turn helping to pollinate the flowers.

A looper caterpillar feeds amongst the flowers too.

He's no longer hiding amongst the twigs.

This master of disguise has a different trick up his sleeve.

Swaying back and forth,

he mimics a flower moving in the breeze.

He sticks petals to his back

so he can feed unnoticed by predators.

And there's a whole army of flower arrangers

sporting the latest spring fashion.

As the sun strengthens the building sap finally forces

the leaves to fully unfurl.

As many as 200,000 leaves on every tree.

Together they grow enough foliage to blanket an area

six times the size of new england.

As the leaves expand,

they produce one of nature's most powerful chemicals.

Chlorophyll.

This green pigment catches the sun's energy

to power a reaction crucial to all life.

Photosynthesis, creating sugar from sunshine.

This sugar is essential for the tree to grow,

but it's now in easy reach of new england's hungriest animals.

A moose.

Named by the native Americans as moosu,

"he who strips off," they are leaf-eating machines

and can strip a branch clean in seconds.

But the trees can defend themselves.

In response, they flood their leaves

with a repulsive chemical called tannin.

So moose must constantly roam to seek out fresh ones.

But this female doesn't want to travel far.

She has twins, and they're just two weeks old.

Until now, they've remained hidden in the shade

of the forest.

With the leaves now loaded with unpleasant tannins,

she needs to find an alternative food source.

She leads the twins away from the cover of the trees

for the very first time.

Out here, it's a big new world.

The mother must stay close.

Another cow and her calf

are already enjoying the coolness of the lake.

Moose have the longest legs in North America,

which allows her to reach something that other animals

can't get to.

It's what makes this lake irresistible.

Water plants,

just what this mother needs to enrich her milk.

Because they're packed with nutrients

washed out of the leaf litter.

The twins will increase in weight tenfold

over the next few months.

It's not just the females who need the nutrients.

Big bulls are here to feed for a different reason,

to grow their antlers,

one of the fastest growing animal organs.

They keep a safe distance,

neither want to damage his prized possessions.

Because their racks are not just for fighting.

Male moose concentrate on looking good

and attracting females.

With females watching on, it's a chance to show off.

A good try, but at this time of year,

this female's attention is still fully on her calves.

It won't be until the fall

that she'll be back on the market for a mate.

Late spring, the busiest time

for the forest's most notorious tree eater.

Signs of his appetite surround almost every lake.

The beaver, new england's most industrious animal.

His lodge is his castle, built of sticks and hardened by mud.

But his masterpiece is his dam.

Over 50-metres long and built of thousands of logs and branches.

For 20 years, it has held back the water to create a moat,

a defence against predators.

But this security comes at a price.

The dam needs constant maintenance.

A leak, he's going to need supplies.

To avoid being spotted by predators,

beavers work under the cover of darkness.

Their iron-infused teeth make powerful tools

with which they can fell a tree ten-inches wide

in just a couple of hours.

Fixing a leak can take all night and into the morning.

He stirs up mud using this mortar to seal the cracks.

But fix one leak and another is sure to sprout.

A beaver's work is never done.

All this work isn't just for his own security.

In spring, a beaver's lodge is busy with the activity

of baby beavers and their sounds as they call for milk.

This is a crucial time to practise using their teeth,

before they, too, are unleashed unto the forest.

The beavers of new england fell millions of trees every year.

But surprisingly, it's this that makes them heroes of the forest.

By removing softer trees, they create large open spaces

where red maple saplings can take root,

and they leave bigger hardwoods standing,

like maples and oaks,

with space to spread their branches and grow more leaves.

Beavers have helped to create a forest