Nature (1982–…): Season 38, Episode 2 - The Serengeti Rules - full transcript
♪
There's a sign when you
get off the airplane there...
"Not the end of the world,
but you can see it from here."
They ventured into the wild,
from the coasts of Alaska
to South American jungles.
I was stunned.
I had never seen
anything like this before.
In North American rivers.
And on African plains,
they followed their
passion to explore.
I'd longed to be in such a place
ever since I was a small boy.
Their quest pursued
over a lifetime
was to understand how
nature is put together.
I'd try to go out looking to
see how the world works.
I've always said that
science is detective work.
There's a mystery to solve.
Science can tell
us what's happening
when the naked
eye can deceive us.
And now, after 50
years of research,
their discoveries fit together.
Whether it was
terrestrial or aquatic,
whether it was
arctic or tropical,
it was all working
in the same way.
This was a major deal.
It is a blueprint to help
heal a battered planet.
It was a flashbulb moment.
Nature could heal itself.
I've never in my life
felt such an excitement.
We found the rules...
How systems work,
how the world works.
This is a story of hope
that will change the
way you see nature.
♪
It begins in the
Pacific Northwest.
Bob Paine is a newly-minted
biology professor
at the University of Washington.
It was exciting. I
was totally naive.
Basically hadn't seen any of
the Pacific coast ecosystems.
As a naturalist, he's trained
to observe and record,
but Bob is thinking
more radically.
He wants to see how things
work by manipulating nature.
♪
When Bob was in
school, the general idea
was that all natural communities
are arranged the same way.
The sun's energy
drives the structure of life.
Plants grow using sunshine.
Grazers eat the plants,
and they in turn are
hunted by predators.
Everywhere on earth, nature
is organized from the bottom up.
♪
♪
Yet Bob Paine is most fascinated
by the predators at the top.
♪
Could they play a
more important role
than simply eating a little meat
at the summit of a food pyramid?
♪
But how do you test that?
You can't just get
rid of all the bears
or eagles from a forest
to see what happens.
Bob Paine needs
a natural community
he can easily manipulate.
♪
♪
At the tip of Washington's
Olympic Peninsula,
he stumbles upon a
small but magical world.
Few biologists had
paid much attention
to the tide pools
along this rocky shore.
But for Bob, they
present the opportunity
he's been dreaming of.
There it was spread
out in front of me.
♪
It was Nirvana.
♪
He realizes these tide pools
are a complete ecosystem,
but in miniature.
This magnificent
array of organisms.
There were carnivorous
gastropods feeding on barnacles.
There were sea
urchins feeding on algae.
There was a lot of pattern.
For Bob, the tide pool
is a natural laboratory.
There are hunters
and filter feeders,
scavengers, and plants
giving food and shelter.
♪
And among the
mussels and barnacles,
anemones and snails,
a large predator lurks.
♪
Despite appearances,
starfish are skilled hunters.
♪
Each of their arms
carry eye-like sensors.
♪
Starfish use their tube
feet to pursue prey.
They can pry open mussels,
devouring them in their shells.
♪
♪
Here, Paine conducts one
of the simplest experiments
in the history of biology.
♪
He removes starfish
from one tide pool,
while leaving them in another.
♪
♪
Month after month,
Paine returns,
clearing out starfish.
♪
And he sees the
tide pool changing.
♪
There are more mussels,
but less of everything else.
♪
Eight years later,
the impact is dramatic.
♪
The mussels are all that remain.
♪
That indicates that the starfish
have been preventing the
mussels from taking over.
♪
The predator maintains
the entire community
from the top down.
Without them,
it all falls apart.
♪
♪
In other experiments,
Paine removes different
species from the tide pools.
But when he does
that, nothing changes.
The starfish alone
hold everything together.
So Bob christens them
a "keystone species."
I knew that I had discovered
something important.
I'd changed the
nature of the system.
I used the line in George
Orwell's "Animal Farm."
"All animals are equal,
but some animals are
more equal than others."
And that expresses the fact
that all species don't
have the same impact
on the system they're in.
♪
Bob's discovery of
a keystone species
prompts more questions.
Do they only
exist in tide pools?
What's the scale
of their influence?
♪
New revelations
will soon link starfish
to sea otters
living thousands of
miles farther north,
in the remote Aleutian
Island chain off Alaska.
♪
The connection will be
made by a young man
who has yet to hear
of Bob Paine's work
and isn't even sure he
wants to be a marine biologist.
Everybody has to do something.
I was actually thinking
about doing a lot of things
other than biology.
I was thinking
first and foremost
about surviving, you
know, making a living,
being able to make
my way in the world.
♪
One of my former professors
at Washington State
was a consultant with the
Atomic Energy Commission.
And they were looking
for somebody to go out
to Amchitka Island
and work on sea otters.
I had never worked in the ocean.
I was not a marine biologist.
I knew nothing about the ocean.
♪
And he said, "You know, I
think you'd be perfect for this."
♪
Two weeks later, I was on
my way to Amchitka Island.
There's a sign when you
get off the airplane there...
"Not the end of the world,
but you can see it from here."
♪
I had this feeling
of both excitement
for the beginnings of a new life
and also an incredible
sense of trepidation
over whether I
would succeed or not.
♪
In the seas off Amchitka Island,
Estes gets to
know the sea otters.
Highly social, they spend
their entire lives in the icy water.
♪
Without blubber for insulation,
they have evolved the
densest fur of any mammal.
♪
♪
Sea otters are masters
of their underwater realm,
the kelp forest.
♪
It is spectacular.
♪
It is absolutely one of
the most amazing scenes
that I've ever seen.
Kelp to the coastal ecosystem
is like redwoods
to a redwood forest
or oaks to an oak forest.
The kelp forest is an
important foundation
for the coastal ecosystem.
♪
Like any forest, kelp
is a rich source of food,
home to dozens of species.
♪
Estes is interested in
how kelp can support
everything from spiky urchins...
♪
To the large sea
otters that eat them...
how everything is
organized from the bottom up.
But his world view changes
the day he encounters Bob Paine,
who is visiting Alaska
to meet with a student.
The instant I met
him, I thought,
"There's no way I'm
going to talk to this guy."
He just scared me to death.
He was very smart,
very intimidating.
And he said, "You
want to sit down
and talk a little bit about
what you're doing?"
i told him that I was interested
in following this notion
of how kelp forests could
support so many otters."
He said, "It sounds
pretty dull to me."
♪
"Why don't you think about
these animals as predators?"
It just immediately
occurred to me
that this was a phenomenally
interesting natural experiment.
And that was sort
of the beginning
of the rest of my life.
♪
Paine's question turns
Estes' research on its head.
Instead of asking what the
kelp forest does for the otters,
Jim now asks
what are the otters
doing for the kelp forest?
When Bob planted the seed
of looking at the
effect of otters,
it naturally occurred to
me that the way to do that
would be to go to someplace
where they didn't occur
and compare that
with where they did.
♪
If the otters are having some
big effect, I ought to see it.
If I go to a place where they
don't occur, I ought to see it.
♪
Having nearly been
wiped out by the fur trade,
sea otter populations
are recovering
and spreading out across
the Aleutian Island chain.
But the otters have not
yet reached the shores
of the most remote islands.
One is called Shemya.
♪
The most dramatic
moment of learning in my life
happened in less than a second.
♪
I stuck my head in
the water at Shemya,
and I thought, "Oh, my God.
This is unbelievable."
♪
I'd never seen an urchin
barren before going to Shemya.
♪
From having watched otters
for extensive periods of time,
I knew they ate
a lot of urchins,
but it never really
occurred to me
until I actually saw a system
where otters were gone
that the effect was massive.
♪
Unchecked by the otters,
the sea urchins have
gorged on the kelp.
That has started a
devastating domino effect
right through the community.
The kelp forest and virtually
everything that lived here
is gone.
Jim has discovered that
sea otters, like starfish,
are keystone species.
♪
I sat there all night long.
I didn't sleep
at all that night.
All I did was write.
I think I had some
sort of visceral sense
that this was a major deal.
♪
I've never in my life felt such
enthusiasm and excitement
as I felt at that moment.
Jim Estes takes Bob
Paine's keystone discovery
to a new level.
Both large and
small marine habitats
seem to be held together
by single keystones,
whose removal is catastrophic.
♪
The potential power of keystones
begins to attract the
attention of other biologists,
who ask new questions
about how keystones work.
Freshwater ecologist Mary Power
now wonders if the
influence of keystones
goes beyond predators
simply eating prey.
♪
An underwater hunter would
help Mary see something
neither Jim nor Bob had.
♪
Ironic perhaps,
because growing up,
Mary couldn't see well at all.
♪
When I was a child, I
was severely myopic
from who knows what age.
♪
I didn't know that you
could see leaves on a tree
from the ground.
♪
But something happened
before I got glasses,
and that was
that I was let loose
with a mask and snorkel.
♪
For the first time, I
saw things clearly
because of the
refraction of the water.
♪
You can imagine how
beautiful it would be
when you see detail that you'd
never known you could see.
♪
What were pondweeds
above the water
were forests of
stems under the water.
And in this little forest,
there would be sun fish.
♪
Then occasionally, a big,
larger predator like a pickerel
or a perch or a bass goes by.
♪
♪
♪
It was a flashbulb
moment, as they say,
where I just had
to be underwater
looking at life that way,
for the rest of my life.
♪
♪
♪
Following her passion, Mary
Power focuses her studies
on fish in the rivers and
streams of Oklahoma.
♪
Her keen eye soon
notices a striking difference
between some stretches
of river and others.
♪
Some pools are like
mini green forests,
teeming with life.
♪
Here, largemouth bass
are the top predator.
♪
But other pools are barren.
Bass are nowhere to be seen.
♪
Here, small minnows
eat everything
right down to the bare rock.
♪
Power suspects bass
might be a keystone
holding the community
together in the lush, green pools.
To test her hunch, she
designs her own version
of Bob Paine's
starfish experiment.
♪
We split the green
pool into two halves.
♪
We netted out the bass,
and then we added
minnows just to one side.
♪
And we sat back and waited.
♪
♪
In just five weeks, on
the side without bass,
the minnows have reduced
the green pool to rubble.
♪
With the top predator gone,
the minnows
overgraze the plants.
♪
But there is something
more in the green pools.
The bass are not just
eating the minnows.
♪
Mary realizes the predators
instill a "fear factor."
♪
About half the effect of bass
is due to terrifying the minnows
so they not only stop
feeding, but they emigrate.
And that's a landscape of fear.
Bass are keystone
species just in the sense
that Jim's sea otters
or Bob's starfish are.
♪
But there is still a major piece
of the puzzle missing.
♪
No one has shown that
keystones exist on land.
♪
That search will turn up
something unexpected
and sound an urgent alarm.
♪
The scientist that will ring it
spent a lifetime in the forests,
beginning when he was a boy.
I loved being in the forest.
♪
Not see people,
just be in the forest.
Some of my fondest
memories of that period
were of catching
fireflies in the evening.
Every summer, they would
emerge about sundown
and then come up one by one.
There were birds that would
sing on into the night and frogs,
and I've always loved listening
to the evening and night sounds
in Virginia there.
♪
John Terborgh will go on
to become a forest ecologist,
working primarily
in the tropical jungles
of South America.
It is from here that
he will mull over
the concept of keystone species.
Mary Power's work in streams,
Paine's work in the intertidal,
and Jim's work in the ocean...
They did seem to work in a wide
range of aquatic environments.
So at that time, I
started daydreaming,
how could I expand on this?
Forests cover a
third of our planet.
If John can show keystones
holding together
communities here,
it will suggest that
their power is global.
♪
Yet to succeed,
John still has to overcome
the same basic challenge
Bob Paine had faced
25 years before...
♪
How to remove the predators.
♪
What I needed was
to do an experiment,
but on land instead
of in the water.
That meant finding fragments
of forests without any predators
but with everything
else still there.
I didn't know of any such
place until I learned about Guri,
and that's where it all began.
♪
Guri was an area
of tropical jungle
half the size of Connecticut,
flooded by the construction
of a new hydro-electric dam.
♪
Now wooded hilltops
are small islands.
♪
With little food to eat,
predators like
jaguars face starvation
and abandon the islands.
♪
Everything that should've
been there was there
except for the top predators.
It was the perfect system
so that you could
see what the response
to removing predators would be.
The impact shocks Terborgh.
♪
When I climbed up and
walked into the forest,
it looked like a hurricane
had been through there.
Wow.
With fewer and fewer predators,
plant eaters ravenously
devour the trees.
Whether it's howler monkeys
or iguanas makes no difference.
Even size doesn't matter.
On islands without
predatory army ants,
hoards of leafcutters
wreak havoc.
♪
On the mainland,
leafcutter ants are controlled
by a species of army ant.
Without them, the leafcutters
are 100 times more abundant
than they would
be on the mainland.
The foliage had been stripped
off the trees so many times
by this multiplicity
of leafcutter ants.
♪
A tree can only withstand that
so many times, and then it dies.
♪
It's all predation-driven.
You remove
predators, then it leads
to the deterioration
of the whole system.
♪
To Terborgh, it's a
chilling realization,
because we've been
systematically targeting
predators for centuries
all across the world.
Our planet has been
rapidly changing.
♪
We've transformed it.
As we take out the top
predators in our path,
nature is being decapitated,
the ties that bind entire
communities broken.
What humans have done
is take nature apart
layer after later.
From loss of top predators,
there's almost always
loss of diversity.
♪
After we understood that,
we coined the word
"downgrading" to describe it.
♪
John Terborgh's trained eye
now sees downgrading
all around us.
I can see it.
I'm not sure just
anybody can see it.
Science can tell
us what's happening
when the naked
eye can deceive us.
Remember we found at
Guri that with no predators,
the herbivores increased,
and the ants literally
ate down the forest.
We're seeing the
same thing here.
It's not ants, it's deer,
but out of control,
they can lead to the same
rather disastrous consequences.
The deer have reached
plague abundance.
And it's the deer
that create this effect
as if you had taken
a hedge clipper
and gone along on the
underside of the branches,
removing everything
between the ground
and what we call a browse line.
The deer plague started
as we removed wolves
to make room for people.
Now the forests
Terborgh knew as a boy
are collapsing.
If this forest were
whole and natural
and reproducing normally,
you wouldn't see
me from the camera.
There would be
things in between.
But you can look way out
there, and there's no obstruction.
The visibility is
100 feet or 200 feet.
It should be maybe
10 feet or 15 feet.
That's the difference.
There's nothing in the middle.
♪
It's a disappearing forest.
♪
These big, old trees, they're
the last of their generation.
When those oak trees die off,
there wouldn't be a
forest there anymore.
♪
I remember a better
world, and now I see things
going in a direction that
disturbs me enormously.
Every day of the week, I
can't stop thinking about it.
♪
♪
Downgrading is a
disturbing reality,
but is it earth's destiny?
♪
The fate of the natural world
is the last thing on the
mind of a young biologist
when he first arrives
in what appears to be a
pristine natural wilderness.
In 1965, the Serengeti
was not well-known.
There were hardly any tourists.
♪
People weren't aware
of the remarkable nature
of that ecosystem
as they are now.
♪
♪
♪
There was everything
around me...
All of these species
all mixed up together.
It was just too good to be true.
I'd longed to be in such a place
ever since I was a small boy.
♪
♪
Little doe Tony
realize, at that time,
the Serengeti is the
midst of a dramatic change.
Tony joins animal
counts that reveal
wildebeest and buffalo
numbers are rising rapidly.
♪
When I first started,
the wildebeest
were somewhere
around 250,000 animals.
♪
By the time I'd
finished three years,
there were 400,000 of them,
and everybody thought,
well, they must have
reached their limit.
And the next time we
looked, it was 700,000.
♪
Four years later, they
had doubled again
to 1.4 million.
We had a world record.
For a large mammal, they
just don't do that sort of thing.
Tony determines
the growing numbers
are the result of a rebound.
It turns out the wildebeest
had been decimated
by a virus spread from cattle.
But once the virus was
eradicated in livestock,
the wildebeest started to boom.
♪
But was this a
blessing or curse?
Our next speaker is a
Mr. Tony Sinclair from Tanzania.
When Tony goes public
with his
record-breaking results,
he thinks this is a
good news story.
To 1.4 million.
But park managers fear
these increases
can't be sustained.
Too many wildebeest
will overgraze.
There was a deathly hush.
I wasn't expecting
that reaction at all.
Everybody thought we
were being irresponsible.
We should have been
culling these animals
because they'll overgraze
the place, destroy the habitats,
and they were going to
cause a collapse of the system.
I just want to point...
It's already been proven!
But Tony believes
the cattle disease
had artificially kept the
wildebeest numbers low.
♪
What he's observing
is a natural reset.
The way I looked on it
was that animal populations
have been in existence
for millions of years
without having to have
humans control them.
We decided we were
going to stick to our guns,
and we prevailed upon
the park authorities
not to give in to culling,
but to wait and see
what was going on.
If we were wrong,
we could be destroying one
of the iconic places on earth.
♪
For the next three years,
Tony keeps a close
watch on the wildebeest,
looking for signs they're
overgrazing the grasslands.
♪
But after two more counts,
numbers remain
steady at 1.4 million.
♪
At that point, we
knew that the system
had leveled out
of its own accord,
and there was no
damage to the environment.
♪
The wildebeest find
their natural balance.
But what happens
next amazes even Tony.
♪
He and his colleagues witness
an incredible transformation.
♪
To our surprise, we
found that all of a sudden,
things started to
reconnect with each other.
Because the wildebeest
were eating up the grass,
there was less fuel, and,
therefore, less burning.
That allows young trees to grow.
Wildebeest, of
course, do not eat trees,
and that allowed the tree
populations to increase.
♪
Tree populations that probably
hadn't occurred since the 1800s.
♪
Those trees provided
more food for elephants,
for giraffes, and for
many, many bird species.
♪
And then there are
many more predators
because there's more
food for those, too.
♪
The wildebeest in
their huge numbers
were determining everything
else inside the park.
I realized that wildebeest
was a keystone.
♪
We had always assumed that
keystones had to be a predator,
but we realized that a keystone
could actually be herbivores.
♪
And if removing
keystones causes collapse,
returning them leads to rebirth.
We were seeing a recovery,
an upgrading of the whole
ecosystem for the first time.
Tony's work is marvelous.
I was delighted
because here is recovery,
here is upgrading.
But it's a long, long process.
We're almost 60 years down
from Bob Paine's
work with the starfish.
I think we're finally arriving
at a much better place,
but it has taken that long.
♪
They started out strangers,
each a witness to the
power of keystones.
By 2008, the small bands of
scientists has grown its ranks.
♪
What was once maverick thinking
is becoming mainstream science
with the discovery of more
keystones from around the world.
It was only by
listening to each other
that we realized we were
talking about the same thing.
Whether it was
terrestrial or aquatic,
whether it was
arctic or tropical,
it was all working
in the same way.
There wasn't anyone that argued,
"I don't see this in nature,"
not a single one of them.
Morphological...
Bob Paine was the
first one to show it.
Throw away the starfish,
and the biodiversity collapses.
The starfish is critical.
With new knowledge
comes opportunity
and a plan for action.
And so our challenge
will be to upgrade systems.
♪
What we need to do is put
the starfish equivalent back in.
♪
It's critical that
we replace species
that are central in holding
ecosystems together.
♪
Nature could heal itself
if a keystone is released.
You can get enormous
bang for the buck.
I can see now how to
translate this everywhere,
on just about every
ecosystem in the world.
♪
In Yellowstone National Park,
the starfish
equivalent is the wolf.
This keystone has
been reintroduced
after an absence of 70 years.
Wolves were reintroduced
and began to feed on the elk.
Then Io and behold,
the vegetation began to respond
and change in very,
very dramatic ways.
The willows and cottonwoods
began to sprout
along stream-sides.
♪
Birds came back that
had disappeared long ago.
Beavers re-colonized.
♪
Yellowstone's trees
thrive because of wolves,
just like Serengeti's trees
thrive because of wildebeest.
♪
And even where
predators are still missing,
like the Scottish Highlands,
simply fencing off grazing
sheep has a dramatic impact.
♪
Upgrading works
on land and in water.
♪
Add some bass,
and then add maybe a
big pickerel or walleye,
and suddenly you might have
a five- or six-level food chain.
The result?
In choked and barren lakes,
the waters clear
and life returns.
Suddenly, you have
an aquatic system
that produces both clean
water and a lot of food for us
and a lot of recreation for us.
♪
So far so good.
♪
But can anything be
done when a community
is not just downgraded,
but almost totally destroyed?
♪
This is Gorongosa National Park.
♪
Like the Serengeti,
it's home to an incredibly
rich mixture of animals.
♪
Until 1977.
♪
For 15 years, civil war
ravaged Mozambique
and destroyed Gorongosa.
♪
95% of all the large
mammals were wiped out,
whether predator or prey.
♪
Surely such devastation
was beyond repair.
♪
Or is it?
Paola Bouley, a former
student of Jim Estes,
thinks there is still
a reason for hope.
By the time I started
my career in ecology
at UC Santa Cruz,
Jim Estes was teaching
in our department
and that very year was just
completing his pioneering work
on sea otters.
20-plus years later, I'm here
in Gorongosa National Park,
trying to understand how
we can restore balance
to this ecosystem.
Once the war was over,
security was re-established.
Year by year, the plant
eaters began to return,
growing from small
surviving populations.
Within little more
than a decade,
there were more than 100,000
large mammals in Gorongosa.
It's a sign of the
resilience of these species
and the fact that
this ecosystem,
the habitats were
still really intact.
There was space for growth here.
Problem was, virtually
all the lions, leopards,
and hyenas...
the big predators...
Were missing.
There were not enough to keep
the large plant eaters in check.
Paola and her team were
going to have to bring them back,
reestablish their roles,
and resurrect the
"landscape of fear."
They began by protecting
the few remaining lions,
which start to recover.
But lions don't
hunt all grazers.
The park now needs more
predators of different stripes
and with different tastes.
That's why in 2018, after
months of complex planning,
they attempt to
reintroduce wild dogs.
But getting them to
Gorongosa is not simple.
For everyone's safety,
including their own,
these feisty meat eaters
have to be sedated.
The plane lands, and, of course,
I feel a huge sense of relief.
Yeah.
And it's the culmination
of months of intense work
by teams across
international borders,
so it's not a trivial operation.
It's hard to believe
they're really here.
♪
We transported them
now to their new enclosure,
where they'll spend the
next couple of months
just situating, getting
used to each other,
getting used to their new home.
After bonding in a
protected enclosure,
the dogs are
released into the park.
It doesn't take long for
them to make an impact.
♪
It's like a wave of teeth...
♪
That just flush out
animals, on termite mounds,
through grasslands,
through forests,
and they chase until they
tire down their prey and strike.
♪
They're already
fulfilling a unique niche
in the ecology of
predators here in this park.
So, instead of taking
warthog and waterbuck,
they're taking
impala and bushbuck
and these smaller species
that have been pretty safe
from predation from lions.
Introducing wild dogs
is a big undertaking,
but it's paying off.
The dogs force the plant
eaters to stay vigilant
and keep moving.
They're re-establishing
the landscape of fear.
Over time, and with the
return of more predators,
this should reduce overgrazing,
encourage trees and bird life,
and bring Gorongosa back
from the brink of oblivion.
What we're demonstrating is
these ecosystems are resilient.
If you give nature a
chance, it comes back.
And I think that gives you hope.
♪
Restoring our damaged
earth is possible.
A small band of scientists
has shown us how.
They've given us a new
way to think about nature
and our place within it.
These keystones
are really important
to the distribution and
abundance of species.
But all of that is under
the control of humanity.
Humans are hyper
keystones in the sense
that they are all controlling.
Humanity ultimately is
the driver of everything.
♪
The behavioral change in humans
that I think is most important
is changing
intolerance to tolerance.
There's a lot of progress that
I've seen in the last 20 years,
and so I'm really pretty hopeful
that we will sort of have
an interconnected landscape
that works for both
people and wildlife.
♪
Humans care. They don't
want a destroyed earth.
♪
But I don't think
you get depressed
if you're fighting with
some hope in your heart.
♪
An upgraded planet
is within reach.
A path forward is clear.
There are rules.
♪
We can harness them...
♪
To heal our damaged earth.
♪
The challenges ahead
are formidable and complex,
but we are not alone.
We now recognize a
powerful ally in nature itself.
♪
♪
♪
♪
♪
♪
♪
♪
♪
There's a sign when you
get off the airplane there...
"Not the end of the world,
but you can see it from here."
They ventured into the wild,
from the coasts of Alaska
to South American jungles.
I was stunned.
I had never seen
anything like this before.
In North American rivers.
And on African plains,
they followed their
passion to explore.
I'd longed to be in such a place
ever since I was a small boy.
Their quest pursued
over a lifetime
was to understand how
nature is put together.
I'd try to go out looking to
see how the world works.
I've always said that
science is detective work.
There's a mystery to solve.
Science can tell
us what's happening
when the naked
eye can deceive us.
And now, after 50
years of research,
their discoveries fit together.
Whether it was
terrestrial or aquatic,
whether it was
arctic or tropical,
it was all working
in the same way.
This was a major deal.
It is a blueprint to help
heal a battered planet.
It was a flashbulb moment.
Nature could heal itself.
I've never in my life
felt such an excitement.
We found the rules...
How systems work,
how the world works.
This is a story of hope
that will change the
way you see nature.
♪
It begins in the
Pacific Northwest.
Bob Paine is a newly-minted
biology professor
at the University of Washington.
It was exciting. I
was totally naive.
Basically hadn't seen any of
the Pacific coast ecosystems.
As a naturalist, he's trained
to observe and record,
but Bob is thinking
more radically.
He wants to see how things
work by manipulating nature.
♪
When Bob was in
school, the general idea
was that all natural communities
are arranged the same way.
The sun's energy
drives the structure of life.
Plants grow using sunshine.
Grazers eat the plants,
and they in turn are
hunted by predators.
Everywhere on earth, nature
is organized from the bottom up.
♪
♪
Yet Bob Paine is most fascinated
by the predators at the top.
♪
Could they play a
more important role
than simply eating a little meat
at the summit of a food pyramid?
♪
But how do you test that?
You can't just get
rid of all the bears
or eagles from a forest
to see what happens.
Bob Paine needs
a natural community
he can easily manipulate.
♪
♪
At the tip of Washington's
Olympic Peninsula,
he stumbles upon a
small but magical world.
Few biologists had
paid much attention
to the tide pools
along this rocky shore.
But for Bob, they
present the opportunity
he's been dreaming of.
There it was spread
out in front of me.
♪
It was Nirvana.
♪
He realizes these tide pools
are a complete ecosystem,
but in miniature.
This magnificent
array of organisms.
There were carnivorous
gastropods feeding on barnacles.
There were sea
urchins feeding on algae.
There was a lot of pattern.
For Bob, the tide pool
is a natural laboratory.
There are hunters
and filter feeders,
scavengers, and plants
giving food and shelter.
♪
And among the
mussels and barnacles,
anemones and snails,
a large predator lurks.
♪
Despite appearances,
starfish are skilled hunters.
♪
Each of their arms
carry eye-like sensors.
♪
Starfish use their tube
feet to pursue prey.
They can pry open mussels,
devouring them in their shells.
♪
♪
Here, Paine conducts one
of the simplest experiments
in the history of biology.
♪
He removes starfish
from one tide pool,
while leaving them in another.
♪
♪
Month after month,
Paine returns,
clearing out starfish.
♪
And he sees the
tide pool changing.
♪
There are more mussels,
but less of everything else.
♪
Eight years later,
the impact is dramatic.
♪
The mussels are all that remain.
♪
That indicates that the starfish
have been preventing the
mussels from taking over.
♪
The predator maintains
the entire community
from the top down.
Without them,
it all falls apart.
♪
♪
In other experiments,
Paine removes different
species from the tide pools.
But when he does
that, nothing changes.
The starfish alone
hold everything together.
So Bob christens them
a "keystone species."
I knew that I had discovered
something important.
I'd changed the
nature of the system.
I used the line in George
Orwell's "Animal Farm."
"All animals are equal,
but some animals are
more equal than others."
And that expresses the fact
that all species don't
have the same impact
on the system they're in.
♪
Bob's discovery of
a keystone species
prompts more questions.
Do they only
exist in tide pools?
What's the scale
of their influence?
♪
New revelations
will soon link starfish
to sea otters
living thousands of
miles farther north,
in the remote Aleutian
Island chain off Alaska.
♪
The connection will be
made by a young man
who has yet to hear
of Bob Paine's work
and isn't even sure he
wants to be a marine biologist.
Everybody has to do something.
I was actually thinking
about doing a lot of things
other than biology.
I was thinking
first and foremost
about surviving, you
know, making a living,
being able to make
my way in the world.
♪
One of my former professors
at Washington State
was a consultant with the
Atomic Energy Commission.
And they were looking
for somebody to go out
to Amchitka Island
and work on sea otters.
I had never worked in the ocean.
I was not a marine biologist.
I knew nothing about the ocean.
♪
And he said, "You know, I
think you'd be perfect for this."
♪
Two weeks later, I was on
my way to Amchitka Island.
There's a sign when you
get off the airplane there...
"Not the end of the world,
but you can see it from here."
♪
I had this feeling
of both excitement
for the beginnings of a new life
and also an incredible
sense of trepidation
over whether I
would succeed or not.
♪
In the seas off Amchitka Island,
Estes gets to
know the sea otters.
Highly social, they spend
their entire lives in the icy water.
♪
Without blubber for insulation,
they have evolved the
densest fur of any mammal.
♪
♪
Sea otters are masters
of their underwater realm,
the kelp forest.
♪
It is spectacular.
♪
It is absolutely one of
the most amazing scenes
that I've ever seen.
Kelp to the coastal ecosystem
is like redwoods
to a redwood forest
or oaks to an oak forest.
The kelp forest is an
important foundation
for the coastal ecosystem.
♪
Like any forest, kelp
is a rich source of food,
home to dozens of species.
♪
Estes is interested in
how kelp can support
everything from spiky urchins...
♪
To the large sea
otters that eat them...
how everything is
organized from the bottom up.
But his world view changes
the day he encounters Bob Paine,
who is visiting Alaska
to meet with a student.
The instant I met
him, I thought,
"There's no way I'm
going to talk to this guy."
He just scared me to death.
He was very smart,
very intimidating.
And he said, "You
want to sit down
and talk a little bit about
what you're doing?"
i told him that I was interested
in following this notion
of how kelp forests could
support so many otters."
He said, "It sounds
pretty dull to me."
♪
"Why don't you think about
these animals as predators?"
It just immediately
occurred to me
that this was a phenomenally
interesting natural experiment.
And that was sort
of the beginning
of the rest of my life.
♪
Paine's question turns
Estes' research on its head.
Instead of asking what the
kelp forest does for the otters,
Jim now asks
what are the otters
doing for the kelp forest?
When Bob planted the seed
of looking at the
effect of otters,
it naturally occurred to
me that the way to do that
would be to go to someplace
where they didn't occur
and compare that
with where they did.
♪
If the otters are having some
big effect, I ought to see it.
If I go to a place where they
don't occur, I ought to see it.
♪
Having nearly been
wiped out by the fur trade,
sea otter populations
are recovering
and spreading out across
the Aleutian Island chain.
But the otters have not
yet reached the shores
of the most remote islands.
One is called Shemya.
♪
The most dramatic
moment of learning in my life
happened in less than a second.
♪
I stuck my head in
the water at Shemya,
and I thought, "Oh, my God.
This is unbelievable."
♪
I'd never seen an urchin
barren before going to Shemya.
♪
From having watched otters
for extensive periods of time,
I knew they ate
a lot of urchins,
but it never really
occurred to me
until I actually saw a system
where otters were gone
that the effect was massive.
♪
Unchecked by the otters,
the sea urchins have
gorged on the kelp.
That has started a
devastating domino effect
right through the community.
The kelp forest and virtually
everything that lived here
is gone.
Jim has discovered that
sea otters, like starfish,
are keystone species.
♪
I sat there all night long.
I didn't sleep
at all that night.
All I did was write.
I think I had some
sort of visceral sense
that this was a major deal.
♪
I've never in my life felt such
enthusiasm and excitement
as I felt at that moment.
Jim Estes takes Bob
Paine's keystone discovery
to a new level.
Both large and
small marine habitats
seem to be held together
by single keystones,
whose removal is catastrophic.
♪
The potential power of keystones
begins to attract the
attention of other biologists,
who ask new questions
about how keystones work.
Freshwater ecologist Mary Power
now wonders if the
influence of keystones
goes beyond predators
simply eating prey.
♪
An underwater hunter would
help Mary see something
neither Jim nor Bob had.
♪
Ironic perhaps,
because growing up,
Mary couldn't see well at all.
♪
When I was a child, I
was severely myopic
from who knows what age.
♪
I didn't know that you
could see leaves on a tree
from the ground.
♪
But something happened
before I got glasses,
and that was
that I was let loose
with a mask and snorkel.
♪
For the first time, I
saw things clearly
because of the
refraction of the water.
♪
You can imagine how
beautiful it would be
when you see detail that you'd
never known you could see.
♪
What were pondweeds
above the water
were forests of
stems under the water.
And in this little forest,
there would be sun fish.
♪
Then occasionally, a big,
larger predator like a pickerel
or a perch or a bass goes by.
♪
♪
♪
It was a flashbulb
moment, as they say,
where I just had
to be underwater
looking at life that way,
for the rest of my life.
♪
♪
♪
Following her passion, Mary
Power focuses her studies
on fish in the rivers and
streams of Oklahoma.
♪
Her keen eye soon
notices a striking difference
between some stretches
of river and others.
♪
Some pools are like
mini green forests,
teeming with life.
♪
Here, largemouth bass
are the top predator.
♪
But other pools are barren.
Bass are nowhere to be seen.
♪
Here, small minnows
eat everything
right down to the bare rock.
♪
Power suspects bass
might be a keystone
holding the community
together in the lush, green pools.
To test her hunch, she
designs her own version
of Bob Paine's
starfish experiment.
♪
We split the green
pool into two halves.
♪
We netted out the bass,
and then we added
minnows just to one side.
♪
And we sat back and waited.
♪
♪
In just five weeks, on
the side without bass,
the minnows have reduced
the green pool to rubble.
♪
With the top predator gone,
the minnows
overgraze the plants.
♪
But there is something
more in the green pools.
The bass are not just
eating the minnows.
♪
Mary realizes the predators
instill a "fear factor."
♪
About half the effect of bass
is due to terrifying the minnows
so they not only stop
feeding, but they emigrate.
And that's a landscape of fear.
Bass are keystone
species just in the sense
that Jim's sea otters
or Bob's starfish are.
♪
But there is still a major piece
of the puzzle missing.
♪
No one has shown that
keystones exist on land.
♪
That search will turn up
something unexpected
and sound an urgent alarm.
♪
The scientist that will ring it
spent a lifetime in the forests,
beginning when he was a boy.
I loved being in the forest.
♪
Not see people,
just be in the forest.
Some of my fondest
memories of that period
were of catching
fireflies in the evening.
Every summer, they would
emerge about sundown
and then come up one by one.
There were birds that would
sing on into the night and frogs,
and I've always loved listening
to the evening and night sounds
in Virginia there.
♪
John Terborgh will go on
to become a forest ecologist,
working primarily
in the tropical jungles
of South America.
It is from here that
he will mull over
the concept of keystone species.
Mary Power's work in streams,
Paine's work in the intertidal,
and Jim's work in the ocean...
They did seem to work in a wide
range of aquatic environments.
So at that time, I
started daydreaming,
how could I expand on this?
Forests cover a
third of our planet.
If John can show keystones
holding together
communities here,
it will suggest that
their power is global.
♪
Yet to succeed,
John still has to overcome
the same basic challenge
Bob Paine had faced
25 years before...
♪
How to remove the predators.
♪
What I needed was
to do an experiment,
but on land instead
of in the water.
That meant finding fragments
of forests without any predators
but with everything
else still there.
I didn't know of any such
place until I learned about Guri,
and that's where it all began.
♪
Guri was an area
of tropical jungle
half the size of Connecticut,
flooded by the construction
of a new hydro-electric dam.
♪
Now wooded hilltops
are small islands.
♪
With little food to eat,
predators like
jaguars face starvation
and abandon the islands.
♪
Everything that should've
been there was there
except for the top predators.
It was the perfect system
so that you could
see what the response
to removing predators would be.
The impact shocks Terborgh.
♪
When I climbed up and
walked into the forest,
it looked like a hurricane
had been through there.
Wow.
With fewer and fewer predators,
plant eaters ravenously
devour the trees.
Whether it's howler monkeys
or iguanas makes no difference.
Even size doesn't matter.
On islands without
predatory army ants,
hoards of leafcutters
wreak havoc.
♪
On the mainland,
leafcutter ants are controlled
by a species of army ant.
Without them, the leafcutters
are 100 times more abundant
than they would
be on the mainland.
The foliage had been stripped
off the trees so many times
by this multiplicity
of leafcutter ants.
♪
A tree can only withstand that
so many times, and then it dies.
♪
It's all predation-driven.
You remove
predators, then it leads
to the deterioration
of the whole system.
♪
To Terborgh, it's a
chilling realization,
because we've been
systematically targeting
predators for centuries
all across the world.
Our planet has been
rapidly changing.
♪
We've transformed it.
As we take out the top
predators in our path,
nature is being decapitated,
the ties that bind entire
communities broken.
What humans have done
is take nature apart
layer after later.
From loss of top predators,
there's almost always
loss of diversity.
♪
After we understood that,
we coined the word
"downgrading" to describe it.
♪
John Terborgh's trained eye
now sees downgrading
all around us.
I can see it.
I'm not sure just
anybody can see it.
Science can tell
us what's happening
when the naked
eye can deceive us.
Remember we found at
Guri that with no predators,
the herbivores increased,
and the ants literally
ate down the forest.
We're seeing the
same thing here.
It's not ants, it's deer,
but out of control,
they can lead to the same
rather disastrous consequences.
The deer have reached
plague abundance.
And it's the deer
that create this effect
as if you had taken
a hedge clipper
and gone along on the
underside of the branches,
removing everything
between the ground
and what we call a browse line.
The deer plague started
as we removed wolves
to make room for people.
Now the forests
Terborgh knew as a boy
are collapsing.
If this forest were
whole and natural
and reproducing normally,
you wouldn't see
me from the camera.
There would be
things in between.
But you can look way out
there, and there's no obstruction.
The visibility is
100 feet or 200 feet.
It should be maybe
10 feet or 15 feet.
That's the difference.
There's nothing in the middle.
♪
It's a disappearing forest.
♪
These big, old trees, they're
the last of their generation.
When those oak trees die off,
there wouldn't be a
forest there anymore.
♪
I remember a better
world, and now I see things
going in a direction that
disturbs me enormously.
Every day of the week, I
can't stop thinking about it.
♪
♪
Downgrading is a
disturbing reality,
but is it earth's destiny?
♪
The fate of the natural world
is the last thing on the
mind of a young biologist
when he first arrives
in what appears to be a
pristine natural wilderness.
In 1965, the Serengeti
was not well-known.
There were hardly any tourists.
♪
People weren't aware
of the remarkable nature
of that ecosystem
as they are now.
♪
♪
♪
There was everything
around me...
All of these species
all mixed up together.
It was just too good to be true.
I'd longed to be in such a place
ever since I was a small boy.
♪
♪
Little doe Tony
realize, at that time,
the Serengeti is the
midst of a dramatic change.
Tony joins animal
counts that reveal
wildebeest and buffalo
numbers are rising rapidly.
♪
When I first started,
the wildebeest
were somewhere
around 250,000 animals.
♪
By the time I'd
finished three years,
there were 400,000 of them,
and everybody thought,
well, they must have
reached their limit.
And the next time we
looked, it was 700,000.
♪
Four years later, they
had doubled again
to 1.4 million.
We had a world record.
For a large mammal, they
just don't do that sort of thing.
Tony determines
the growing numbers
are the result of a rebound.
It turns out the wildebeest
had been decimated
by a virus spread from cattle.
But once the virus was
eradicated in livestock,
the wildebeest started to boom.
♪
But was this a
blessing or curse?
Our next speaker is a
Mr. Tony Sinclair from Tanzania.
When Tony goes public
with his
record-breaking results,
he thinks this is a
good news story.
To 1.4 million.
But park managers fear
these increases
can't be sustained.
Too many wildebeest
will overgraze.
There was a deathly hush.
I wasn't expecting
that reaction at all.
Everybody thought we
were being irresponsible.
We should have been
culling these animals
because they'll overgraze
the place, destroy the habitats,
and they were going to
cause a collapse of the system.
I just want to point...
It's already been proven!
But Tony believes
the cattle disease
had artificially kept the
wildebeest numbers low.
♪
What he's observing
is a natural reset.
The way I looked on it
was that animal populations
have been in existence
for millions of years
without having to have
humans control them.
We decided we were
going to stick to our guns,
and we prevailed upon
the park authorities
not to give in to culling,
but to wait and see
what was going on.
If we were wrong,
we could be destroying one
of the iconic places on earth.
♪
For the next three years,
Tony keeps a close
watch on the wildebeest,
looking for signs they're
overgrazing the grasslands.
♪
But after two more counts,
numbers remain
steady at 1.4 million.
♪
At that point, we
knew that the system
had leveled out
of its own accord,
and there was no
damage to the environment.
♪
The wildebeest find
their natural balance.
But what happens
next amazes even Tony.
♪
He and his colleagues witness
an incredible transformation.
♪
To our surprise, we
found that all of a sudden,
things started to
reconnect with each other.
Because the wildebeest
were eating up the grass,
there was less fuel, and,
therefore, less burning.
That allows young trees to grow.
Wildebeest, of
course, do not eat trees,
and that allowed the tree
populations to increase.
♪
Tree populations that probably
hadn't occurred since the 1800s.
♪
Those trees provided
more food for elephants,
for giraffes, and for
many, many bird species.
♪
And then there are
many more predators
because there's more
food for those, too.
♪
The wildebeest in
their huge numbers
were determining everything
else inside the park.
I realized that wildebeest
was a keystone.
♪
We had always assumed that
keystones had to be a predator,
but we realized that a keystone
could actually be herbivores.
♪
And if removing
keystones causes collapse,
returning them leads to rebirth.
We were seeing a recovery,
an upgrading of the whole
ecosystem for the first time.
Tony's work is marvelous.
I was delighted
because here is recovery,
here is upgrading.
But it's a long, long process.
We're almost 60 years down
from Bob Paine's
work with the starfish.
I think we're finally arriving
at a much better place,
but it has taken that long.
♪
They started out strangers,
each a witness to the
power of keystones.
By 2008, the small bands of
scientists has grown its ranks.
♪
What was once maverick thinking
is becoming mainstream science
with the discovery of more
keystones from around the world.
It was only by
listening to each other
that we realized we were
talking about the same thing.
Whether it was
terrestrial or aquatic,
whether it was
arctic or tropical,
it was all working
in the same way.
There wasn't anyone that argued,
"I don't see this in nature,"
not a single one of them.
Morphological...
Bob Paine was the
first one to show it.
Throw away the starfish,
and the biodiversity collapses.
The starfish is critical.
With new knowledge
comes opportunity
and a plan for action.
And so our challenge
will be to upgrade systems.
♪
What we need to do is put
the starfish equivalent back in.
♪
It's critical that
we replace species
that are central in holding
ecosystems together.
♪
Nature could heal itself
if a keystone is released.
You can get enormous
bang for the buck.
I can see now how to
translate this everywhere,
on just about every
ecosystem in the world.
♪
In Yellowstone National Park,
the starfish
equivalent is the wolf.
This keystone has
been reintroduced
after an absence of 70 years.
Wolves were reintroduced
and began to feed on the elk.
Then Io and behold,
the vegetation began to respond
and change in very,
very dramatic ways.
The willows and cottonwoods
began to sprout
along stream-sides.
♪
Birds came back that
had disappeared long ago.
Beavers re-colonized.
♪
Yellowstone's trees
thrive because of wolves,
just like Serengeti's trees
thrive because of wildebeest.
♪
And even where
predators are still missing,
like the Scottish Highlands,
simply fencing off grazing
sheep has a dramatic impact.
♪
Upgrading works
on land and in water.
♪
Add some bass,
and then add maybe a
big pickerel or walleye,
and suddenly you might have
a five- or six-level food chain.
The result?
In choked and barren lakes,
the waters clear
and life returns.
Suddenly, you have
an aquatic system
that produces both clean
water and a lot of food for us
and a lot of recreation for us.
♪
So far so good.
♪
But can anything be
done when a community
is not just downgraded,
but almost totally destroyed?
♪
This is Gorongosa National Park.
♪
Like the Serengeti,
it's home to an incredibly
rich mixture of animals.
♪
Until 1977.
♪
For 15 years, civil war
ravaged Mozambique
and destroyed Gorongosa.
♪
95% of all the large
mammals were wiped out,
whether predator or prey.
♪
Surely such devastation
was beyond repair.
♪
Or is it?
Paola Bouley, a former
student of Jim Estes,
thinks there is still
a reason for hope.
By the time I started
my career in ecology
at UC Santa Cruz,
Jim Estes was teaching
in our department
and that very year was just
completing his pioneering work
on sea otters.
20-plus years later, I'm here
in Gorongosa National Park,
trying to understand how
we can restore balance
to this ecosystem.
Once the war was over,
security was re-established.
Year by year, the plant
eaters began to return,
growing from small
surviving populations.
Within little more
than a decade,
there were more than 100,000
large mammals in Gorongosa.
It's a sign of the
resilience of these species
and the fact that
this ecosystem,
the habitats were
still really intact.
There was space for growth here.
Problem was, virtually
all the lions, leopards,
and hyenas...
the big predators...
Were missing.
There were not enough to keep
the large plant eaters in check.
Paola and her team were
going to have to bring them back,
reestablish their roles,
and resurrect the
"landscape of fear."
They began by protecting
the few remaining lions,
which start to recover.
But lions don't
hunt all grazers.
The park now needs more
predators of different stripes
and with different tastes.
That's why in 2018, after
months of complex planning,
they attempt to
reintroduce wild dogs.
But getting them to
Gorongosa is not simple.
For everyone's safety,
including their own,
these feisty meat eaters
have to be sedated.
The plane lands, and, of course,
I feel a huge sense of relief.
Yeah.
And it's the culmination
of months of intense work
by teams across
international borders,
so it's not a trivial operation.
It's hard to believe
they're really here.
♪
We transported them
now to their new enclosure,
where they'll spend the
next couple of months
just situating, getting
used to each other,
getting used to their new home.
After bonding in a
protected enclosure,
the dogs are
released into the park.
It doesn't take long for
them to make an impact.
♪
It's like a wave of teeth...
♪
That just flush out
animals, on termite mounds,
through grasslands,
through forests,
and they chase until they
tire down their prey and strike.
♪
They're already
fulfilling a unique niche
in the ecology of
predators here in this park.
So, instead of taking
warthog and waterbuck,
they're taking
impala and bushbuck
and these smaller species
that have been pretty safe
from predation from lions.
Introducing wild dogs
is a big undertaking,
but it's paying off.
The dogs force the plant
eaters to stay vigilant
and keep moving.
They're re-establishing
the landscape of fear.
Over time, and with the
return of more predators,
this should reduce overgrazing,
encourage trees and bird life,
and bring Gorongosa back
from the brink of oblivion.
What we're demonstrating is
these ecosystems are resilient.
If you give nature a
chance, it comes back.
And I think that gives you hope.
♪
Restoring our damaged
earth is possible.
A small band of scientists
has shown us how.
They've given us a new
way to think about nature
and our place within it.
These keystones
are really important
to the distribution and
abundance of species.
But all of that is under
the control of humanity.
Humans are hyper
keystones in the sense
that they are all controlling.
Humanity ultimately is
the driver of everything.
♪
The behavioral change in humans
that I think is most important
is changing
intolerance to tolerance.
There's a lot of progress that
I've seen in the last 20 years,
and so I'm really pretty hopeful
that we will sort of have
an interconnected landscape
that works for both
people and wildlife.
♪
Humans care. They don't
want a destroyed earth.
♪
But I don't think
you get depressed
if you're fighting with
some hope in your heart.
♪
An upgraded planet
is within reach.
A path forward is clear.
There are rules.
♪
We can harness them...
♪
To heal our damaged earth.
♪
The challenges ahead
are formidable and complex,
but we are not alone.
We now recognize a
powerful ally in nature itself.
♪
♪
♪
♪
♪
♪
♪
♪
♪