1
In the Pacific Ocean lies
a very special place.
Essential to the health
of our planet.
I've come to Queensland, Australia,
to see one of the great natural
wonders of the world at a crucial
time in its history.
Out there is the Great Barrier Reef.
It's the biggest
coral reef on Earth.
It's the biggest living
organism on Earth.
It extends 2,400km -
that's nearly 1,500 miles -
But its future has become
a worldwide concern.
Recent reports have suggested
that almost a third of it
has been killed off,
and many believe it will be dead
within a century.
My name is Iolo Williams.
I'm a naturalist
and conservationist.
I'll be travelling over 1,000 miles
to see for myself
if there are any signs of hope
that this place can survive.
I've been invited to join a top team
of experienced divers
who know the reef well.
They'll be using their
specialist knowledge to guide me
to some amazing places
not many people get to see.
We're going to the far end
of the reef.
We're going to the outer reaches
of it.
So it's going to take us probably
about ten hours to get out there.
I'm really looking forward
to seeing the reef,
to seeing the wildlife there,
but also, to discovering
just how much of the reef
is being and has been destroyed,
It'll be nice to see with my own
eyes exactly what is going on there.
The Great Barrier Reef
lies off the tropical
north eastern coastline
of Australia in the Coral Sea.
There are just over 3,000 coral
reefs distributed along it,
covering an area of around
344,000 square kilometres.
That's about the same size as Japan.
These reefs are inhabited
by over 1,500 species of fish...
..together with six species
of turtles
and 17 species of sea snakes.
But all of this is under threat.
Aerial surveys in 2016 suggested
that over 50% of the reef
had been severely affected
by bleaching,
with almost 500 individual reefs
under major stress.
We've travelled up the coast,
over 20 miles,
to the area around Pixies Pinnacle
in the northern sector.
One of the sectors of
the reef worst affected.
On my first dive, I'm going to take
a close look
at the foundation of the reef.
The coral.
How's that feeling?
OK.
What an amazing view!
Whoa!
One of the first things
that hits you down here
is the fact that this is
a living reef.
The Great Barrier Reef extends
for 2,400km.
And many people think
that it's just one long reef,
but that's not true.
It actually is made up of
thousands of smaller reefs.
And some of them are
as small as this stack here,
which comes up from the depths,
almost to the surface.
And that means it's incredibly
attractive
to a whole host of wildlife.
20,000 years ago, this would
have been a limestone cliff,
with some green pasture,
probably with wallabies
and kangaroos on it.
And the Aborigines
would have hunted here.
Then the ice in the polar regions
melted, the sea level rose,
drowned this.
The Aborigines retreated
into what we know
as mainland Australia.
And this has become
the Great Barrier Reef.
Over time, the perfect conditions
have allowed coral to grow
on these cliffs.
This is a pink sea fan.
Really cool animal, really.
And these grow at 90 degrees
to the current.
They're filter feeders.
So as all this plankton
you can see before me runs through,
they filter that out of the water.
It's ideally placed here too,
in kind of a cavern,
where the water rushes through.
Plenty of food for it.
Look at this -
sea fans, fish everywhere.
Where else in the world
are you going to get this?
Scientists initially mistook
the coral reef for plants.
In fact, they are polyps,
small animals that look
like upside-down jellyfish.
These polyps are master builders.
Slowly converting chemicals
in the water into limestone.
The scaffolding of the reef.
Over thousands of years,
coral polyps can create massive,
robust reef structures.
All these colours, all these
patterns here - it's mind-blowing.
There are over 600
different types of coral.
Some, like fan corals,
resemble branches.
Others look like rocks.
This is what they call
a boulder coral, this one here.
It can grow to be about
the size of a small car.
And they grow incredibly slowly.
They're very hard corals too.
And just this one here is probably
hundreds of years old.
And the biggest ones -
who knows? - they may well be
a thousand years old.
This is an interesting coral. It's
what's known as stag's-horn coral.
It's a rapidly growing coral too.
It can grow anything between three
and ten centimetres per annum.
As you can see, these small fish,
they absolutely love it.
These are amazing little things,
these bright blue feathery things.
They're actually called
Christmas tree worms.
They look like bright blue
Christmas trees.
And that's just a part of the animal
sticking out
and they're filter feeding,
taking food,
taking nutrients out of the water.
If there's any threat coming by,
someone like me,
then they disappear, just like this.
Back into the safety of that tube.
Corals are totally dependent
on algae that live within them.
Algae use sunshine
to photosynthesise,
producing sugar that fuels
the polyp inside the coral.
There are several million single
cell algae
living in just one square inch
of coral.
This reliance on the sun means
most hard corals only thrive
in warm, clear waters.
Over thousands of years,
the stable temperature and water
conditions here has provided
the perfect environment for
the Great Barrier Reef to thrive.
Oh!
I have never been in the sea
with one of these before.
Especially one as inquisitive
as this - look! Hello, boy.
This turtle has probably come here
to have algae cleaned off its shell
by small fish.
These have remained unchanged
since before the age
of the dinosaurs.
And they still wander the seas
today.
I don't know how old this one is.
Probably 20, 30,
maybe even 40 years old.
It's a lovely, smooth shell.
Oh, I feel almost as if I'm
a little cleaning station for it,
giving it a good old scratch,
getting some of the algae off.
There we go.
You going to head off now?
Go on, then. Off you go.
She's so chilled. Look at her!
This sea turtle has come
to feed on seagrass,
living between the reefs.
And on jellyfish that eat the algae
growing on the coral.
This whole ecosystem
is delicately balanced.
Everything that lives here
is reliant on healthy coral.
Just look at the size
of this anemone here.
And every now and again, you see
a little fish poking out its head.
Well, several of them, really.
It's called a pink anemone fish.
And what happens is that the female
stresses out the male,
hassles him constantly.
And the chemicals
then keep it as a male.
When the female dies,
the male changes to a female
and one of the smaller fish
then changes to a male.
How incredible is that?
And this association here
benefits both species.
The stinging cells of the anemone
obviously gives the fish protection.
But there are certain species
of fish
that'll nibble away
at these tentacles.
And the pink anemone fish will rush
out in defence of their homes.
Oh, just look at all these fish!
I've never seen anything like it
in my life before.
Thousands and thousands of fish.
And all these small fish
are feeding on plankton.
What's interesting is that some
will keep really close
in to the coral, while others will
venture out a bit further.
And you look at the tails, these
boys here that are venturing out
quite a way have got
like a V-shaped tail.
The ones that stay really close in
have got a more rounded tail.
And that's because these out here
are faster swimmers.
So when the predatory fish come in,
which they will, they can quickly,
as they are doing now,
zip back in to cover here.
Wow, look at this
impressive-looking fish.
Barracudas have got a bad
reputation. Undeservedly so, really.
He's just hanging around
off this stack,
waiting for an opportunity
to dive in and try and get
some of these smaller fish here.
It's basically a big tail,
all muscle,
and a mouth at the front.
So it is a killing machine, really.
Whoa!
That was absolutely amazing.
Absolutely amazing. I was...
I might be disappointed,
but there's no way. It was like...
The only way I can describe it
is like diving into the biggest
and the best aquarium
you've ever seen.
Absolutely amazing. Coral, colourful
coral, different colours everywhere.
And the fish, the fish
were mind-blowing.
This part of the reef
was one of the worst affected
by mass bleaching in 2016.
I came here expecting
to see dead coral.
But all I saw was healthy coral.
It seems reefs can recover
if the conditions are right.
But this was only one dive.
We've travelled south
to dive on Ribbon Reef 5.
This will be my first opportunity
to see what the reef is like
at night.
Most top predators are nocturnal.
I'll be looking for
many top predators hunting.
A clear indication of the health
of a reef's food chain.
It's completely different here
at night.
Immediately, you come down at night,
you see that the colour
all of a sudden looks very
different. The reds look redder.
The blues, the yellows...
Wow! Look at this.
Corals are spectacular
enough by day.
But under torchlight,
their colours become even richer.
Under UV light, they have
an amazing ability to fluoresce.
Beautiful fish here - look at this.
Probably one of the most beautiful
fish on the reef.
It's called the lion fish.
Beautifully marked colours
all along the body.
You can see all these,
what look like feathers,
they're actually spines,
make it a very dangerous fish
indeed to eat.
Two fish here, the beautiful lion
fish and the unicorn fish here.
It's a completely different set
of fish you get here at night.
The day shift has gone to sleep
and the night shift has now
come out to feed.
This is the fish I was really hoping
to see in front of me here now.
He's superbly well camouflaged.
It's called a stone fish.
It's the most venomous, the most
poisonous fish in the world.
It has 13 spines along its back,
with a double sac of venom
below each spine.
And if someone was to stand on that,
the spines act
as a kind of hypodermic needle
and inject the venom
into their skin.
Oh, wow! It's a Moray eel.
There she goes,
hiding beneath the rocks here.
Beautifully marked animal too.
Look at the size of that.
That animal has got to be, what,
the best part of two metres long,
I would think?
He's tucked himself right in there.
Wow! A reef shark.
Just keeping his distance
over there.
Oh, look! Look, look, look!
Here he is, here he comes.
Look, he's coming to have a look.
Look at that. Look at that!
Coming right down underneath us.
He came right beneath my fins,
a 2.5 metre shark!
Look how sleek it is.
What a beauty!
They move through the water
so gracefully.
They make it look so easy.
It makes me feel
like a cumbersome ox down here.
During the day, sharks are often
found lying motionless on the reef.
But by night, they transform
into ruthless hunters,
scouring the reef in packs,
in search of their prey.
Oh, yeah, yeah, here we go!
Look, there are at least three
sharks joining us now.
Two more. One down there
and one's just gone off to my right.
It's a party of sharks here now.
Could be four or five,
maybe even six.
All their senses are perfectly tuned
for the hunt.
Electro receptors detect
the faintest of electrical signals.
Such as the heartbeat
of a scared fish.
Even fish tucked tightly into cracks
and crevices in the coral
are a target. You see this shark,
every now and then,
putting his head right
underneath some of these rocks.
He's looking for sleeping fish
to prey on.
Look!
Right underneath me! Wow!
And off he goes!
This really is their habitat
down here.
And this is their time of night,
as well. It's when they come out
hunting.
Sometimes when you jump in,
and it's pitch-black,
you ask yourself, "Wow, do I really
want to go down there tonight?"
But look at this. When you do come,
you see all of these things.
Well...
I've been granted my wish...to get
within three millimetres of a shark.
Or rather six sharks, more like!
That was fabulous.
That was absolutely fabulous.
Spending time with sharks,
they get a hell of a bad name.
And unfairly so. They say there's
something like, I don't know,
a million sharks killed every year,
and there's four people killed
by sharks on average every year.
You know, that puts it
into perspective for me.
They're amazing animals,
and if you can get a reef
that's got a good population of
sharks, then it's a healthy reef.
But it doesn't matter how much
your brain tells you,
the sharks are fine, you know,
the sharks really are fine,
always, always, always
at the back of your mind,
you've got the music
from Jaws all the time!
From what I've seen,
the outer reefs have recovered well
from the 2016 mass bleaching
event...
..with healthy coral,
and many top predators
feeding on a robust food chain.
But the worst affected areas
were on the coast.
We've travelled 11 miles
to Lizard Island,
to see how these coastal areas
are today.
The Great Barrier Reef is a complex
and resilient structure.
It relies on healthy coastal waters
to keep it alive.
And the mangrove forests
that fringe the coast
play a crucial part in keeping
the water clean.
Just nice to get firm ground
beneath my feet.
It's incredibly hot and humid
underneath the canopy
of this mangrove forest.
And these mangrove trees
are very specialist.
One of the few species
that can grow in saltwater.
And the mangroves, along
with the Great Barrier Reef,
they defend the land,
because you get some cyclones,
some hugely powerful storms
coming through here.
But first of all, they hit the reef,
and then they get this mangrove,
so the power's all gone out of them
by the time they hit the land.
With their complex root systems...
..mangrove forests also filter water
from fast-flowing rivers...
..trapping sediment
where it moves out into the ocean,
and onto the reef.
Without the mangroves purifying
the water and depositing nutrients,
the reef would find it
almost impossible to survive.
Oh, wow. That's pretty cool.
Thousands and thousands
of little bait fish,
small, small fish just hanging
around the mangroves here.
And once I get anywhere near them,
they start to move in.
That's a real mass of
branches and leaves there,
so, they can hide away pretty well.
It's a good place for them,
cos it's full of food as well.
It's a very rich place.
It's the ideal nursery
for these small fish
before many of them decide,
"OK, I'm big enough now,
"I can head out
onto the coral reefs out there."
Wow! Did you see that?
Following a shark - I think
it was a tawny reef shark.
It was a little bit too far away
for me to see.
Just heading its way out of the
mangrove slowly, slowly, slowly,
out into the sea. Probably about 1.5
metres long, something like that.
Because the mangroves
are a really important nursery
for sharks too, particularly
the blacktip reef sharks.
They'll probably be further in.
The mangrove is more extensive
in there. We've been told not
to go up there. There might be
a crocodile up there.
But, er, that's where they'll be.
Small, small sharks,
and as they grow, they get more
confident, they'll start heading out
then towards the reefs out here.
But, that was cool.
That was nice to see.
The mangrove creeks are healthy.
But if the inner reefs are not,
then the juvenile fish growing here
will have nowhere to go.
I'm off to see how healthy
the local reefs are here.
It's absolutely heartbreaking
down here.
It's the first time I've seen it,
like 100% killed.
There's a lot of coral bleaching.
Vast areas of it are just white.
It's a bit like coming
to a coral graveyard.
This is the most obvious sign
that the reef here is under stress.
The water temperature
has increased too much,
forcing the algae out of the coral,
leaving the bleached white skeleton
behind.
Without the algae providing
oxygen and nutrients,
this coral will eventually die.
And rising sea temperatures
are not the only threat.
Coastal reefs are also vulnerable
to the damage caused
by local agriculture.
And even the mangroves
are powerless to stop it.
Pesticide runoff from intensive
farming methods flow into the sea,
increasing the nitrogen level
in the water.
This can lead to outbreaks of one
of the most damaging creatures
to coral reefs.
The crown of thorns starfish.
Large numbers of these predators
consume too much coral within
a very short time.
To give you an indication
of just how dead this place is,
I've been swimming around here now
for 15, maybe 20 minutes,
I've seen eight fish. Eight fish!
Could you imagine in a living coral
reef, it would be more like 8,000,
or even 80,000.
It's tragic, really.
Absolutely tragic.
Do you know, I can't believe how
naive I was when I first came out
here, because ever since I was a
young child,
I'd watch programmes on TV,
read magazine articles,
newspaper articles about the reef,
taken a great interest in it,
because it's one of the seven
natural wonders of the world,
after all.
And I thought, "Yeah, well,
I'm going out there, well prepared.
"I'm going to
know quite a bit about it."
I now feel as if I came out
here with one eye shut,
and it's only after diving it myself
that the other eye
is finally opened.
And now, finally I'm just
beginning to understand.
The Great Barrier Reef
is a massive structure made up
of many different parts.
Human impact on the planet is
increasing the challenges it faces.
Some areas are coping,
whereas others are clearly not.
And it's not only rising sea
temperatures and water pollution
that it has to cope with.
We're travelling 15 miles
down to Ribbon Reef 10,
a place known for cyclones.
Freedom, this is Argyle.
Argyle 167.
Where we're heading has seen
some of the worst storms on record,
with an increase
in their intensity and frequency.
That's going to be
an interesting day, this one.
We're right out,
right on the edge of the reef.
The open ocean is over there,
and the main reason
we are going down here is,
is that the cyclone two years ago
ripped through just
this fairly narrow path here and
decimated the reef,
so we're going down to see
the effects of that.
In particular, I'll be looking
to see any signs of the reef
recovering.
The big boat drifts
in the strong currents,
so we need to use this smaller one
to get to the right place.
Cyclones are nothing new,
and the Great Barrier Reef
has been ravaged by them
for thousands of years.
Occasional storms clear out
the faster-growing corals,
allowing slower growing coral
enough time to survive.
This allows large robust
reef structures to be built.
But scientists now believe
that the frequency of these storms
caused by rising temperatures
in the atmosphere,
could cause permanent damage.
Wow, look at this damage.
Look at this.
Huge boulder coral here...
..ripped apart,
and these are strong things.
It's just ripped apart by the last
cyclone a couple of years ago,
and look at it.
Just left it here for dead.
It's devastating.
It does look like a war zone
in parts out here.
What living coral still remained
after the storm had passed
has been killed off by a thick layer
of sediment covering it.
This has stopped the sun's rays
from reaching the coral,
preventing it from
photosynthesizing.
Here's evidence that
the reef can resurrect.
The boulder coral here, a small one,
surrounded by devastation,
it's got scars all over it,
but if the environment is right,
it will come back.
The more I dive, the more you learn
that the reef
really is a living, breathing thing.
Not just the wildlife,
but the reef itself.
And it's something that's changed
over hundreds of years too,
with changing water levels.
The problem you've got now
is that the changes are rapid ones,
so it's very quick one.
It's driven by man.
All of the reefs I've seen so far
have developed
over thousands of years.
I'm now on my way to visit
a very different reef.
Heading 200 miles further south
to one of the newest additions
to the Great Barrier Reef.
The English-built freighter,
the SS Yongala, sank in a storm
13 miles off the coast of
Queensland, just over 100
years ago.
She went down in a cyclone in 1911,
and everybody on
board was killed. 122 people.
And, nobody really knew
what happened to her.
They found some shipwreck
a few days later,
but she wasn't discovered down here
till the late 1950s,
and now it's a very popular dive.
And, the main reason
I'm going down, really,
is because it's become
an artificial reef.
I'm diving down to discover how well
this new reef is doing in such
a challenging place.
This will be my deepest
dive on the reef.
Because the shipwreck lies over
30 metres deep on the sea bed,
I'm unable to wear
the full face mask.
Instead, I'm wearing
a regulator to breathe.
Lying in the middle
of a shipping channel,
the SS Yongala is the only solid
structure for miles around.
Despite the depth,
bright sunlight can pierce
all the way down.
Swirling currents bringing plankton
for the sea fans to feed...
..providing the perfect environment,
for an explosion of life.
It feels like this reef has been
here for thousands of years.
But in fact, cyclones
regularly destroy it.
In a very short time,
the coral grows back,
and the wildlife returns.
This olive sea snake is hunting
for fish inside the wreck.
It's one of the most venomous snakes
on the planet.
Just a few drops can kill
up to ten people.
The Great Barrier Reef has taken
a man-made structure,
transforming it into an established
part of the reef.
Every surface of the old ship,
has been covered with coral...
..attracting all this wildlife.
Amongst all of the colours,
I see something dark gliding
in through the shadows.
An ocean giant.
I'm dwarfed by this huge,
black bull ray.
The bigger brother of the stingray.
The fact that this reef
has regularly regenerated itself
in such a short space of time
suggests that when the conditions
are right, even new reefs
like this one can flourish.
It's amazing to think that that is
an artificial reef, you know?
It's a ship, and it's,
it's covered in wildlife.
It really raises your spirits
when you think that after a cyclone,
a lot of that would be killed.
A lot of that would have been wiped
off, but it keeps coming back.
You know, nature keeps coming back.
I think that's the lesson there.
One of the best dives of my life.
Amazing, amazing dive.
I'm coming to the end of my journey,
heading from north to south
along the Great Barrier Reef.
I've covered over 1,000 miles.
What I've seen is that a healthy
reef needs a combination
of different factors,
all working in harmony.
It needs clean water,
and a constant temperature
to support a variety of corals.
These corals support
a robust food chain
that sustain top predators.
But it also requires some natural
destruction to help clear out
fast-growing corals, allowing
slower-growing corals to thrive.
This place has survived
because it has adapted to different
environmental challenges
over thousands of years.
Now I've reached my
final destination.
Lady Elliot Island,
the most southerly point
on the reef.
This is my final dive.
In a very different habitat
to what I've experienced so far.
In a remote location
without any reported serious damage
from bleaching or cyclones,
I'm hoping to see a pristine reef.
The water depth here
is only 14 metres,
but the reef looks
like an alien planet.
This enormous blowhole
was formed during a storm,
by water surging upwards
through the rock.
Look at this place.
It's like a tunnel full of fish.
Amazing.
This water is the richest
I've seen yet.
The green colour is caused
by the chlorophyll in the plankton,
suspended in the ocean.
The reef here is full
of these small fish,
thousands and thousands of them.
You see the bigger fish
hanging around the reef.
Every now and again...
These are trevallies.
Every now and again they all
dash in, causing panic amongst
the smaller fish, and hoping to
disorientate one or two,
isolate one or two so they can
dash in and get a good mouthful.
From what I'm seeing here,
the condition of the reef
is every bit as good
as it was up in the North.
This is quite beautiful.
Whoa.
Look at this.
You can see why it gets
its name, leopard shark.
All those spots all along its body.
Couple of remora
hanging underneath it.
Beautiful.
Beautiful animal.
Look at it gracefully climbing up,
coming right past me,
having a good look.
That was a lovely day,
but it's, er...
..much wilder up here
than it is down below.
It's nice and peaceful down below.
And thousands of fish,
just the whole reef
is just covered in fish.
Lovely day. Beautiful day.
During my journey,
I've seen signs of hope that many
parts of the Great Barrier Reef
are still healthy.
This is still an incredibly rich
habitat, that must be protected
at all costs.
Well, my journey along
the Great Barrier Reef comes
to an end on another
beautiful Australian beach.
And when I came out here,
I was incredibly excited,
but also that was tinged with quite
a bit of apprehension
because I thought I was
going to find a reef
that was dead and dying.
But that's not true.
Yes, the reef has its problems -
I've seen bleaching,
I've seen examples where global
warming has had its effect,
I've seen algae
growing over the reef,
I've seen where cyclones
have killed parts of the reef,
but I've seen resurrection as well.
I've seen the reef growing back.
The reef is an amazing survivor.
But it may not be able to cope
with the rapid changes
we are causing in the oceans.
Recent scientific reports suggest
sea temperatures are rising...
..and will continue to do so,
if we don't slow down the pace
of global warming.
A further 1 degree rise
will almost certainly result
in the loss of everything
I've just seen within this century.
Unless we radically change
how we live our lives,
places like the Great Barrier Reef
will disappear for ever.