01x06 - When the Oceans Shrank

[bunniefuu]

[gentle music]

NARRATOR: The story
of life on Earth...

[chirps]

[roaring]

...has been marked by a series

of catastrophic
extinction events.

Natural disasters which
have threatened to wipe out

many of the creatures
that call our planet home.

[snarling]

But with each brush with death,

life has come back
even stronger.

[dramatic music]

One of the planet's
first great extinctions

took place


[majestic music]

In the shallow seas, life had
established an exotic foothold.

♪

But then, suddenly,

the climate cooled,

sea levels plummeted,

and 85% of all life died out.

♪

Eventually,
the seas rose again...

♪

...the survivors
rebuilt their world...

♪

...and some discovered
a whole new one.

[theme music]

[dramatic music]

NARRATOR: This is Earth,


This is a world that will not
see the first dinosaur

for another 200 million years.

The continents are mostly
in the southern hemisphere,

and all of them
are barren wildernesses,

devoid of all
but microscopic life.

No roars, no barking,

not even a chirp sounds
across the empty landscape.

[wind gusts howl]

Carbon dioxide is a staggering


in the atmosphere
than it is today,

and the days
are three hours shorter.

[mysterious music]

It is a truly alien world,

and yet, there is a place
where life is thriving.

[gentle music]

Hidden in the warm,
shallow sea,

lives a magical world,

[waves crash]

♪

Thousands of miles
of spectacular reefs.

These dazzling corals
are home to newly-evolved

complex creatures like starfish,
and horseshoe crabs.

Bug-eyed trilobites
swim upside down,

sifting the water for food.

♪

Yet one animal,

whose descendants
will one day fill the seas,

and a forerunner of every
bird, mammal,

and reptile on Earth,

is surprisingly hard to find.

[water laps gently]

[whimsical music]

This guy, a fish.

These are Sacabambaspis,

one of the first animals
on Earth to evolve a backbone.

These two young males
are here for lunch.

♪

The reefs are full
of things to eat,

but most creatures here
have hard shells,

and all these young fellas
can do is suck.

♪

[dramatic music]

Their search for food takes them
into a field of sea lilies.

These graceful lilies
aren't actually plants,

they're animals,
filter feeders,

that open their arms to catch
plankton in the water.

[majestic music]

Finally, one of our
little guys finds a snack.

He doesn't have jaws or teeth,

so he has to get his head
right inside.

[whimsical music]

And now, he's stuck.

♪

It is just not his day.

[music turns suspenseful]

His awkward jam
has caught the eye

of some squid-like predators.

♪

They don't know what
this strange object is,

just that it's worth
fighting over.

[thuds]

♪

Our hungry little Sacabambaspis
makes a break for it,

and finds a place to hide.

This cave should keep him safe.

[ominous music]

What he doesn't know
is that he has company.

[ominous music swells]

Hiding in the shadows
is the reef's top predator.

NARRATOR:


the land is empty,

but these shallow seas
are filled with coral reefs.

[dramatic music]

It is the only place
on the whole planet

that teems with complex life.

[ominous music]

Our little fish has taken
refuge in a cave,

only to discover he's not alone.

A giant sea scorpion.

This reef's apex predator.

But this scorpion
isn't hunting in this cave.

She's here to molt.

She can only get bigger
by shedding

one armored skin
and growing another,

but this makes her soft
and vulnerable

for a few hours.

[gentle music]

Sometimes, even apex predators
have to hide.

Looks like it's this guy's
lucky day.

♪

These endless
shallow seas have proved

the perfect nursery
for early life,

but something is happening
on land

that is about to spoil
this prehistoric paradise.

Across the empty landscapes,

the absence of vegetation
means wind and water

tear at its surface.

[waves splashing]

[thunder rumbling]

Massive dust storms,

and rivers laden with sediment

are dumping vast quantities
of materials into the sea.

[majestic music]

This onslaught of minerals
is feeding marine algae

on an expl*sive scale,

generating enormous blooms
across the oceans.

These algae blooms, in turn,

absorb carbon dioxide
from the atmosphere,

and the levels
of this greenhouse gas

are now plummeting.

♪

Earth has reached
a tipping point.

It's cooling down fast.

Even the warmest seas
will soon feel the change.

[waves crashing]

Back at the reef, our little guy

has returned
to the sea lily field.

[gentle music]

This time he is here
looking for something else.

His bright red tail is a sign
he's ready to mate,

and he's searching for
the right spot to build a nest,

so he can attract a female.

♪

At last, a clearing
amongst the lilies.

Except all these other guys
had the same idea.

The competition is already
fighting over the best spots.

[intriguing music]

A female.

Her silvery stomach signaling
she's ready to lay her eggs.

So now, it's showtime.

♪

The males start to dance.

They're all trying to woo her,
to lay her eggs in their nest.

♪

She's chosen.

Our little guy
is late to the party.

To stand a chance,
he needs to find his own space.

♪

At last, an empty spot.

[music swells]

Our little fish can only watch
as a larger male settles in.

[ominous music]

A predatory bristle worm.

But it's bitten off
more than it can chew.

No wonder that bit of sand
wasn't taken.

[gentle music]

These coastlines might
look tranquil.

[waves crashing]

But twice a day,
beneath the water,

it's a different story.

[waves crashing]

The water is so shallow
that when the tides change,

they produce massive
rip currents.

[water roaring]

The nesting males hunker down,
protected by the sea lilies.

These early fish
are not strong swimmers.

So they stick close
to the seafloor.

[water roaring]

[tense music]

The giant sea scorpion.

Now that she's finished
her molting,

she's bigger and hungrier
than ever.

[ominous music swells]

But she's after a bigger meal.

The bristle worm.

But in the chaos,

our hapless little fish
is thrown up into the riptide.

[dramatic music]

The current up here
is too strong.

[dramatic music swells]

It drags him away over the reef.

Soon, he is swept out to sea.

[waves roar]

By the time the tide
releases him,

he is over a mile
from the reef.

Exhausted and alone, it looks
like his luck has run out.

Even worse, here be monsters.

[majestic music]

NARRATOR: For millions of years,

Earth has had high levels
of carbon dioxide,

which have heated the
atmosphere, and warmed the seas.

These shallow waters
have been perfect

for complex life to evolve.

But now, they are cooling fast.

♪

This crisis has not reached
our young fish yet,

but he is still in trouble.

[dramatic music]

He has been dragged
off the reef by strong tides.

Now, he is lost
in the open ocean,

a long, long way from home.

[somber music]

The waters here
are an unfamiliar deep green.

♪

He's on the edge
of a vast algae bloom,

one of many that are drawing
carbon dioxide

out of the atmosphere,
and cooling the planet.

The consequences of this
climate shift are extreme.

[tense music]

At this time,
most of the world's land masses

sit over the South Pole,

and as temperatures plummet,

a giant ice cap is formed.

All this ice is reflecting
the sunlight,

making the planet
cool even faster.

Even for the warmer seas
further north, change is coming.

[gentle music]

By sunset, our little fish

still hasn't found his way
back to the reef.

He will not last much longer.

Then, in the middle of nowhere,

he discovers something
he can rest on,

and there's food on it.

Things are looking up.

Clustered with hundreds
of clam-like Brachiopods,

it looks just like
part of a reef.

♪

[music turns ominous]

A giant orthocone.

At 30 feet long,

this is the largest creature
on the planet,

the ocean's top predator.

It has 10 long tentacles that
feed a powerful beak-like mouth.

Fortunately, our fish is too
small to be in any danger.

Sometimes, it pays to be tiny.

Orthocones are normally
solitary,

but now is a time of gathering.

Tonight, there is a supermoon.

[reverent music]

This long ago in prehistory,

the moon is closer to the Earth,

and larger in the sky.

It has a huge influence on the
rhythms of life in the ocean.

On this special night,

the moon signals the start
of one of the sea's weirdest

and most spectacular events,

a mass mating.

♪

Our lost fish decides to take
a chance, and hitches a ride.

Luck is with him again.

The orthocones are heading
into shallower waters to mate.

They're taking our little
adventurer back to the reef.

♪

Under the light
of the supermoon,

the reef is putting on
its biggest annual spectacle,

as most of the animals
prepare to mate.

But is it all too late
for the little fish?

[waves crashing]

NARRATOR: 444 million years
before modern humans evolve,

most creatures on Earth
do not live by the seasons.

[reverent music]

Instead, it is the moon
and tides

that have the most profound
effect on the rhythms of life.

♪

Tonight, there is a supermoon,

and it is a time of mating
for all creatures.

♪

All along the reef,

every animal triggers a glowing
trail of phosphorescence

as their motion disturbs
algae in the water.

♪

Our lucky little Sacabambaspis
is right back where he started.

There's no place like home.

♪

It's mating time for many.

The corals and sea lilies
are spawning.

♪

Generating clouds
of eggs and sperm

that cloak the entire reef.

♪

Our eager youngster
heads back to his mating site.

It looks like he's too late.

But after all he's been through,
he isn't giving up yet.

He gets to work making a nest.

Just beyond the reef,

hundreds of orthocones
have now gathered.

Normally, these giants would
see another of their kind

as a threat, and attack.

But not tonight.

The males must woo a mate,

and they do this
with a spectacular light show.

[majestic music]

He lights up with luminescent
patches on his skin.

Then he spreads
his tentacles wide,

and begins a gentle,
mesmerizing dance.

♪

She accepts.

♪

Mating is brief.

He doesn't want
to push his luck.

[gentle music]

Our plucky Sacabambaspis
seems to have missed out.

Then, a solitary female appears.

This is his moment,
his last chance to dance.

[energetic music]

♪

With no other challengers
to distract her,

she lays her eggs.

And then our young male
fertilizes them.

Mission accomplished.

[waves lap gently]

All across the reef,

millions of animals have begun
their next generation.

But daybreak reveals
a sinister arrival.

[tense music]

A warning from the frozen south.

An iceberg has drifted all the
way up from the polar ice cap.

Life on this reef
is about to change forever.

[waves crashing]

NARRATOR: As temperatures
drop across the planet,

the oceans are cooling
down fast,

and a huge ice cap is growing
over the south pole.

[ice creaking]

Icebergs are breaking off,

and one has made it
all the way to the tropics.

[waves crashing]

Life here is living
on borrowed time.

[gentle music]

A female orthocone is looking
for somewhere to lay her eggs.

♪

She's not used
to these shallow waters,

and is a little unsteady
on her tentacles.

[upbeat music]

She's also being watched.

[music turns ominous]

A predatory sea scorpion
has picked up the scent

of her new eggs.

♪

They'd make a tasty meal.

♪

But this...

is the wrong mother
to mess with.

[gentle music]

Orthocones do not
abandon their eggs.

Standing guard,
she will not eat

or leave this spot
for six months.

Which means,
by the time they hatch,

she will have died.

A mother's ultimate sacrifice.

[somber music]

Back in the clearing,

the Sacabambaspis adults
have all moved on.

[gentle music]

But under the sand,

lie their abandoned,
translucent eggs.

[waves crashing]

As the days pass,

the iceberg that broke off
thousands of miles away

floats ever closer to the reef.

And the freezing cold fresh
water cascading down its sides

pours directly
into the shallows.

[dramatic music]

For these creatures
used to warm saltwater,

it means death.

Those that can move
try to escape,

like these trilobites.

♪

Eventually, the cold water hits
the Sacabambaspis nesting site.

They hatch at the worst moment.

But at least these newborns
are mobile.

♪

The damage caused by this
iceberg is only local.

The bigger threat is that
the entire planet is cooling.

As the polar ice cap
in the south grows,

it captures water as ice.

[wind gusts howl]

Eventually, reaching eight times
the size of today's Antarctica,

it locks away so much water
that global sea levels

drop by 300 feet.

♪

Thousands of miles of vibrant
and colorful reefs

are left high and dry,

deprived of the one
and only habitat

in which it has evolved
to thrive.


the life on Earth

is driven to extinction.

♪

[gentle music]

Ultimately, it is the Earth
itself that comes to life's aid.

Over hundreds
of thousands of years,

volcanic activity
from beneath the ice

spews out carbon dioxide,
warming the atmosphere.

The giant ice cap melts.

[water splashes]

and sea levels rise
as fast as they fell.

From their scattered
sanctuaries,

survivors begin to recolonize,

and new versions of the old
animal groups return.

♪

♪



life roars back.

But there is a crucial
difference.

[waves roar]

For the first time,

creatures are leaving the water
for the land.

[dramatic music]

NARRATOR: It is 15 million years

since the oceans
suddenly cooled.

Volcanic activity warmed
the planet and its oceans again,

but the temperature shock caused
a catastrophic mass extinction.

However, enough life
survived to recolonize,

and now, at last,
the shallow seas

are teeming with exotic
creatures again.

[gentle music]

Many remain unchanged.

But one group
has been through a revolution,

the descendant of our little
Sacabambaspis.

Fish.

There are now many,
many more of them.

♪

These new fish
have jaws and teeth.

Unlike the timid Sacabambaspis,

they are strong swimmers,

and are the fastest
predators in the sea.

The scorpion is now their prey.

♪

But these scorpions have
a trick up their sleeves,

and there is still a place
where they can rule.

Scorpions are among the first
complex lifeforms

to leave the sea behind,
and crawl up onto land.

[majestic music]

Or at least,
the first predators.

♪

Up here, there's new prey
to hunt.

An array of hard-shelled animals
have followed plants onto land.

And animals aren't the only
ones thriving.

Both plants and fungi
have started

to break down the rock,

creating soil,

[reverent music]

towering over it all.

Giant fungi,
called Prototaxites,

the largest living things
on the planet,

forming Earth's first forests.

♪

Plant growth has raised oxygen
levels in the atmosphere.

[thunder booms]

High enough to fuel fire.

In fact, the first forest fire
is a sign of life's success.

[thunder booms]

[fire crackles]

It is the start of a journey

that will take living things
to every habitat on Earth.

[gentle music]

Today, one of the most
challenging habitats for life

remains the coasts.

Every day, they change
with the tides.

Every year, they grow
or shrink from erosion.

And on a much longer timescale,

they are drowned,

or left high and dry
by changing sea levels.

♪

Since the last ice age,

sea levels have risen 300 feet.

Around the world,

low-lying coastal plains
were replaced by shallow seas.

In Australia, this proved
an ideal habitat for coral.

♪

We now call it
the Great Barrier Reef.

♪

Life has evolved to cope
with changing sea levels.

For humans, the story
is different.

During the short period
of recorded history,

sea levels
have been quite stable.

Vast cities have spread
along our coasts,

some even below sea level.

[majestic music]

But now, because of global
warming, that is changing.

Sea levels are predicted to rise

by around three feet
by the end of the century.

We can build barriers
against storms.

[water roaring]

But we cannot protect all cities

from the relentless power
of rising oceans.

However, we are learning
from nature.

♪

In some coastal cities,

rather than fighting the threat,

they aim to let the water in,
and manage it.

They are taking a strategic
approach to the future.

[gentle music]

Life has shown us the way.

To survive, we must adapt.

♪

♪ I see trees of green ♪

♪ Red roses too ♪

♪ I watch them bloom
for me and you ♪

♪ And I think to myself ♪

♪ what a wonderful world ♪

♪ Yes, I think to myself ♪

♪ what a wonderful world ♪