All language subtitles for Evolution Ep 3 Extinction

NARRATOR:
In the ongoing drama of
evolution, species come and go.

They live,
they compete, they die out.

MAN:
Extinction is the termination

of a species.

We can think of a species
having a birth date,

it lives for a while, it goes
extinct and it dies out.

95% to 99% of all species that
have ever been on the planet

have gone extinct.

NARRATOR:
On average

a species dies out after four
million years of existence.

It could take less time,
it could take much more.

But it's all part of the
normal process of extinction,

always there, always happening.

MAN:
Conditions change,
a new predator arises.

Perhaps the climate changes.

Perhaps a mountain range
suddenly appears geologically.

Through those processes

this particular species
is no longer able to live;

it dies out.

NARRATOR:
The extinction of species
that can't adapt or compete

creates opportunities for
new species, new forms of life

in an endless cycle.

So evolution and extinction
are in balance.

But what happens when
a planetwide catastrophe

kills off many species
in a great mass extinction?

(thunder crashing)

MAN 2:
The game of evolution has
changed its rules a little bit

when one of these massive
extinction events takes place.

Suddenly you've leveled
the playing field.

NARRATOR:
It was a level playing field

that made
our very existence possible

after a mass extinction
65 million years ago.

Now it's we
who may be causing a new one.

But this time,
we may not be as lucky

as we face
evolution's severest test.

NARRATOR:
Five times in the past
500 million years

a mass extinction wiped out

most of the species
alive at the time.

The Earth itself tells
the stunning story

with its geological
and fossil record

stretching back through time.

Today, sheep roam the highlands
of South Africa's Karoo desert

but 250 million years ago

the Karoo played host to
creatures we can barely imagine.

It was their world,
and then they were gone.

Geologist Peter Ward
is here to study the secrets

of history's
greatest mass extinction

which swept
those creatures away.

It's a challenge that anyone
would find daunting.

WARD:
In late 1999, I spent three
weeks camping in a tent

next to an old,
abandoned farmhouse.

And behind this farmhouse,
I wandered the grounds

and found
this beautiful old graveyard.

One of the tombstones
had a husband and his wife.

There were two sons
off to the right.

The dates on the tombstones
ranged from 1892, I believe

to about 1897.

The mother was the first to go,
and the youngest son,

who was only 42-years-old
at the time,

was the last to go in 1897.

All die out
in this five-year time span.

There's a tragedy
that has happened here

yet we have
so little record of it.

MAN:
Looking at the epitaph:

"Nem dom fry
mos stoffer adder."

Translated into English,
that is:

"Take my ashes
and set them free on Earth."

WARD:
So, a hundred years

these people are just wiped off
the face of the Earth.

And we have no idea
what killed them?
MAN: Yes.

And if that's the case

how am I going to figure out
what killed animals

that lived in those hills

the fossils of which we have
from 250 million years ago?

NARRATOR:
250 million years ago

marks the end of the geological
time period called the Permian.

It's the rocks of the Permian

that give Peter Ward
his first clues.

WARD:
These types of layered rocks
often have fossils.

In fact, here in the Karoo

we find within these green,
layered rocks lots of fossils.

There are two types:
we find skeletons

and we find the remains
of activity of animals.

Some animals burrow,

they make little tunnels
in the strata.

As a matter of fact

there's probably one sitting
right back here.

This is either
a bone or a burrow.

Here's the piece of a burrowing
organism of some sort.

Some animal was living and
digging through the strata.

It gives us a sense

that not only were there larger
vertebrate creatures here

but a wide diversity
of smaller animals.

Sometimes they died
or were killed

or predators took them down.

Their skeletons fall
in this sediment

and we find it as fossils.

NARRATOR:
At the South African Museum
in Cape Town

the fossils of dozens of species
have been recovered

from this lost Permian world.

MAN:
I was walking on a farm track

and there in the middle
of the farm track

was this little piece of bone
sticking out of the shale

and not a very exciting piece.

But I took my pick
and started to work around it

and revealed
the back of the skull here.

And then down towards the snout
and when finding the tusk here,

this beautiful faceted tusk,

I knew that
I had a complete skull.

Then I began the long task of
uncovering the back of the skull

uncovering vertebrae
after vertebrae

working down this way, with the
ribs beginning to develop here.

After 2� hours to three hours

I knew that it was a complete,
articulated lystrosaurus.

NARRATOR:
Lystrosaurs were the Permian's
most common plant eaters.

Gorgons, ferocious predators
up to ten feet long

ruled the plains.

Then suddenly,
the Permian ended.

The rock record reveals
a cataclysmic change

at the threshold of the next
geological period, the Triassic.

WARD:
We geologists
can climb through time.

I'm going to climb
about 50 feet up, through here.

I'll go through 2,000 to 5,000
years of time when I do it.

This is the very last layer
of the Permian.

As soon as I climb above this,
I'm now in the Triassic.

We're sitting in the very bottom
beds of the Triassic.

In these beds,
we have no fossils whatsoever.

All the Permian creatures
that we saw right down there

have disappeared entirely.

A few of them,
we know, survived

because one or two species will
be found a little higher up.

But in these beds,
we found nothing.

Not only are there no fossils

there aren't any of
the burrows or the tunnels

or the traces
of animal activity.

We see instead, layers of rock

that could only have formed
in the absence of animal life.

So catastrophic
was that mass extinction

that even the small creatures
have died out,

it's not just the mighty,
it's the meek.

This place is dead.

NARRATOR:
What could destroy so much?

What could turn day into
a seemingly endless night?

It may have been a comet,
as some new evidence suggests

or a combination of factors.

(tremendous explosion)

Sea levels dropped.

There was a dramatic rise
in global temperature.

Volcanoes erupted

depositing a million
cubic kilometers of lava.

The atmosphere changed

as the level
of carbon dioxide increased.

Ecosystems around the world
were ravaged.

(thunder)

Mass extinction followed,

the most dramatic turn possible
in the course of evolution.

The Permian extinction
was a time

when, if you were playing
Russian roulette

and you had a gun
with ten chambers in it

you put nine bullets in it,
spin it, put it to your head;

you've got one chance
out of ten of surviving.

NARRATOR:
In a mass extinction

when species die,
they don't die alone.

The collapse of one species
helps bring down others.

WARD:
You could almost analogize
that to a house of cards.

Each species props up another,
in a sense.

Because
the creature that you eat

is that card
that is sitting under you

that gives you your energy.

Now, let's pretend

that we start kicking out card
after card after card.

And that's what a mass
extinction does, isn't it?

It starts knocking out
a species here

knocks out a species there

but pretty soon,
lots of species are gone.

And it's not just the
disappearance of species now

the whole house of cards
falls down.

You start really snowballing
in this effect;

and that's really
what a mass extinction is.

NARRATOR:
The rocks tell the extraordinary
story of what happened next.

Above the barren layer,
new signs of life.

WARD:
We know that very few animals
that were present

prior to the extinction here
survived it.

(blowing)

(blowing)

Wow...

I just found a carnivorous
mammal-like reptile

in strata that we have
just above the mass extinction.

This is a creature
that has survived it.

NARRATOR:
The mammal-like reptiles

looked like crosses
between dogs and lizards.

But they weren't
the only survivors.

WARD:
Two lineages that get through

have tremendous consequences
later in time.

Both are pretty small in size.

They start evolving
because the world was empty

and empty worlds really begot

tremendous amount of
evolutionary diversifications.

NARRATOR:
Evidence of what was to come

is in one
of the best fossil collections

of post-extinction survivors,
gathered by a single family

over three generations.

WARD:
Of all the skulls in this
museum, this is my favorite.

This creature
leads to the dinosaurs.

At the same time that it exists
in the earliest Triassic Period

right after the mass extinction

we find a second small
carnivore, very different.

This little skull is the species
that leads to us.

Two of these predators,
the small mammal

the larger reptilian creature
that becomes the dinosaurs,

really duke it out
in head-to-head competition.

In the Triassic Period, there's
a clear winner: the dinosaurs.

NARRATOR:
It took around 20 million years

for the first dinosaurs
to evolve

on their way to the giant
creatures we think of today.

MAN:
Dinosaurs get big.

They're baroquely diverse with
all kinds of weird adaptations,

with armor,
with predatory animals,

with birdlike animals,

the dominant animal features
of the landscape.

Mammals just scurry
around in the shadows.

They're small, shrew-like,
or rat-like, in many ways.

They look like some of the least
dramatic things we have today.

NARRATOR:
Michael Novacek has been
fascinated by dinosaurs

ever since he learned
of a series of expeditions

to the Gobi desert.

NOVACEK:
My personal history with the
Gobi started a long time ago,

I was seven years old.

There was this very dramatic
explorer, Roy Chapman Andrews

who wanted to go to Central Asia
to look for early humans

and ended up finding
a lot of dinosaurs.

He wrote books about it
and kids loved those books

and I was one of those kids.

NARRATOR:
In the 1930s

Roy Chapman Andrews
made several trips to the Gobi.

Traveling in style,
he brought along six motor cars

a team of scientists
and a hundred camels.

He didn't find evidence
of early humans

but he did find something
far more ancient.

Buried in the sandstone

were 80-million-year-old
dinosaur bones and eggs...

and fossils of tiny mammals.

NOVACEK:
Mammals were part
of the dramatic finds

that the Andrews expedition
uncovered.

They weren't
the biggest things,

a lot of these mammals are
little, nugget-sized creatures,

but they were very,
very important to science

because at that time

we knew virtually nothing
about mammals that old,

mammals so old that they lived
alongside of the dinosaurs

nearly 100 million years ago.

NARRATOR:
The Gobi Desert is one
of the most isolated places

in the world.

When China reopened it
to foreign scientists

more than a decade ago,
they flooded in.

Most, including members
of Novacek's team

were looking
for dinosaur fossils.

The desert had
what they wanted...

more of those extremely rare
dinosaur eggs.

But this time, Novacek was after
something even rarer.

NOVACEK:
We were actually
heading a little west

but en route,
our gas tanker got stuck

and so we had to dig it out.

And as the truck
was being excavated

a few of us took a couple
of jeeps up to a little hill.

And there I saw a mammal skull
just lying on the ground.

And about every 15 minutes

it seemed someone said,
"I got a mammal."

And then I'd say,
"I've got one, too."

We had about 50 mammal skulls
by lunchtime.

We had already matched
the amount

that's been recovered
from the Gobi entirely

over a period of seven decades.

This is about as big
as they get.

This is the skull, and you can
see the front teeth here.

It's really no larger
than a squirrel

or what we would call
a small mammal today.

It contrasts dramatically with
some of the smaller skulls.

This encompasses practically the
entire size range of mammals

during the time
of the dinosaurs.

NARRATOR:
Like many of
their descendants today

the mammals survived
by being nearly invisible.

They were nocturnal.

They scavenged.

They reproduced quickly.

NOVACEK:
Mammals are beginning to get
better-developed brains.

The eyes are becoming larger.

And even in the skeleton behind
the skull, we see a number

of very interesting
transitional features.

In the pelvic region, there's
evidence of splint-like bones

that suggest support
for the abdominal cavity.

And this probably
supported a pouch

very much like living marsupials
like opossums and kangaroos,

a transition between a more
primitive, egg-laying behavior

and a more advanced behavior,
a more advanced reproduction

that we see in today's
placental mammals, like us.

NARRATOR:
But mammals remained
second-class citizens

in a world
where dinosaurs ruled

until the inconceivable happened
again, 65 million years ago.

It's thought that an asteroid
larger than Mt. Everest

reached the Earth traveling
25,000 miles per hour.

The mammals were used
to avoiding dinosaurs

but an asteroid
was something else entirely.

(explosion)

Known as the KT Event

the impact changed
the face of life on Earth.

The small mammals survived

but in a landscape
of death and destruction.

The house of cards

built since the last mass
extinction collapsed

but this time,
it was the dinosaurs

that fell the furthest.

With few places to hide,
less food

and little ability to protect
their eggs or young

the dinosaurs died out, while
the mammals went on living.

NOVACEK:
Mammals that survived this event

stay small, maybe for
a couple million years.

They start to get slightly
larger and diversify.

We have a sort of a lag effect
with the KT event,

a recovery of,
perhaps, the ecosystem,

and then the mammals
really take off.

NARRATOR:
Mass extinction had provided
an unexpected opportunity.

NOVACEK:
You can think of mammals after
the KT event as colonizers;

they first landed and made
a toehold on a new land

where there are lots of
tremendous advantages to them

and they're not competing

with these large, big, plant-
eating or meat-eating dinosaurs.

NARRATOR:
They spread out
to all parts of the world.

They competed and diversified...

until most of the largest
animals on Earth were mammals.

About 35 million years ago,
mammal evolution produced

the first true monkeys and apes
from earlier, smaller primates.

Then, generation
after generation

the process of adaptation
and change,

of evolution, continued.

Around five to six million
years ago, in Africa

the first
humanlike primates emerged.

Some of their descendants would
play an unprecedented role

in evolution's future.

They left their bones
on the valley floor

in caves and on lake beds.

They began to walk upright.

They left their footprints
in volcanic ash that hardened.

One lineage branched,
some species went extinct

while others evolved into
the ancestors of modern humans.

Today, the world is bursting
at the seams with people.

(whistle blowing)

This is Bangkok, Thailand,

population ten million
and growing.

(whistle blowing)

There are now six billion of us
on the planet.

Even the dinosaurs
would run for their lives.

We have caused the rate
of extinction to soar.

It's now over 100 times
greater than normal.

Many scientists worry that
we are the new asteroid

bringing about the sixth great
mass extinction on Earth.

(birds singing)

This is Kaengkrachan
National Park, population zero

in an area
twice the size of Bangkok.

From all appearances

a hidden world,
unspoiled, timeless.

Just 300 miles from Bangkok

it's protected
by natural barriers.

The Tenasserim mountain range
runs through it

creating
a steep, rugged terrain.

The forest is dense.

The Petchaburi River can be
difficult to navigate.

But no one knows
if the animals living here

have found a sanctuary or have
disappeared from the forest.

MAN:
We're in grave danger of
the "empty-forest" syndrome,

having a beautiful, seemingly
intact forest, on the surface

but inside that forest
the natural components

which maintain the flow
of energy through the system

it's disrupted.

Now, people say

"So what does it matter
if one component's gone?

"What if you don't have
the Sumatran rhino?

What if the civet species
are all gone, or other things?"

But each thing has evolved

to play an incredibly important
role within this complex puzzle.

NARRATOR:
Alan Rabinowitz wants to know
if Kaengkrachan has escaped

the escalating rates of
extinction found elsewhere.

So he and his colleague,
Tony Lynam, collect data

on the actual number of animals
living in the park,

especially the carnivores.

RABINOWITZ:
Large carnivores,
such as tigers,

are often the first animals
to be wiped out from a system.

You go into an area and find

relatively abundant sign
of large carnivores

you know what you're dealing
with, by necessity

is a very healthy

at least seemingly stable
natural habitat.

NARRATOR:
A typical habitat
works this way:

sunshine, nutrients and water
make plants grow.

The plants are eaten
by herbivores

which in turn
are eaten by carnivores.

About a hundred pounds of plants
generally sustain

about ten pounds of herbivore

which sustain
about one pound of carnivore.

Healthy carnivores
mean a healthy forest.

When Alan Rabinowitz
was here last

the news about the forest
was good.

RABINOWITZ:
More than ten years ago

I landed here
in Kaengkrachan National Park.

We got down in here,
and I was very pleased to see

that the place
was beautifully intact

in terms of the vegetation

but more importantly

I was able to find tiger sign
virtually everywhere I looked.

I would hike
through small rivers

and there'd be
families of otters

starting to swim around me.

Elephants came
to my camp at night.

Gibbons sang
every single morning.

Hornbills flew overhead
all the time.

All the signs

of a healthy, intact, relatively
unhunted forest were there

which made it probably one
of the few places in Thailand

and, in fact, when I surveyed
throughout the entire country

at the end of the survey
it became even more clear

that Kaengkrachan was easily
the most pristine,

the most untouched
piece of forest left

in this entire country.

NARRATOR:
But is it the same today?

On a search for life,
every stop offers more clues.

Hmm, fresh elephant, nice size.

There's cat, small cat.

NARRATOR:
The group uses
well-traveled elephant paths

to navigate the forest.

It's an
elephant trail.

Here's a trail
that elephants

are walking on
constantly.

And every time they
walk past this vine

they just push it
back this way

and then push it
back this way

and all the bark
has started to come off.

NARRATOR:
Three other teams
are in the park

each retrieving special cameras
with motion sensors

which were carefully placed
a month before.

Called "camera traps"

they take a photo when triggered
by an animal walking by.

LYNAM:
Out of batteries, I guess.

The camera's taken a whole roll
of film and it's rewound.

So there's 36 shots taken.

RABINOWITZ:
What the camera traps
will help us do

is start wrapping some numbers
around these things

helping us quantify.

It's one thing to say, "Boy,
sign of tiger is everywhere."

It's another to say,
"Just on this one survey

we have taken pictures of a
minimum of X numbers of tigers."

NARRATOR:
The cameras serve
as an unseen observer.

In one day, a camera trap
can catch more tigers on film

than Rabinowitz's team
could see in months.

LYNAM:
I'd say, tonight, camp here.

Tomorrow morning, go down the
stream and check out this area

and check out what we've got
in terms of Siamese crocs.

And that's
where you think

we might have
Siamese crocodile?

Yeah.

That would be neat.

That would be something else.

NARRATOR:
The Siamese crocodile
is a species that, 30 years ago

lived throughout
the tropical forests of Asia

but they have been relentlessly
hunted for their skins.

Not a single one has been seen
in over a decade.

Is this it, Tony?

LYNAM:
Yeah...

These are
some fresh ones, right?

Oh, yeah,
those are fresh.

RABINOWITZ:
Siamese crocodile,

a species thought to be either
virtually extinct

or extinct in this country
and incredibly endangered

throughout all
of its existing range.

If we prove the existence

of a population of Siamese
crocodile in Kaengkrachan

that in itself, apart from
everything else, will make this

one of the most important areas
in the entire country.

Over on the other side
of the bank there

we saw tracks
of Asiatic Black bear

which is the largest
bear species in Thailand

and also tracks
of a large tiger.

So we call this place
Carnivore Corner

because it's got all
of the three carnivores.

NARRATOR:
With another roll of film and
sightings of carnivore tracks

the team presses on to pick up
the rest of the cameras.

But suddenly, there's a hitch.

Camera's gone.

You're kidding.

The camera's gone.

Where the hell
is it?

Somebody...

Somebody stole it.

Damn it, somebody
stole it.

Yeah, you can see
it's been cut.

It's been cut
right here.

Somebody's come and cut
the bamboo and taken the trap.

It could mean we have
a thieving problem

or it could mean that
this area's being more hunted

than we think it's being hunted.

It's gone.

It's gone.

The camera trap is gone.

And that one?

It's gone.

I can't believe this.

This is stupid.

Why is this happening?

Why would they want
to take the cameras?

RABINOWITZ:
Ramifications of losing
these cameras...

there's a lot of ramifications.

In terms of data,
it's a major loss.

It takes an incredible amount
of planning

and time and effort to even
get to do an area like this.

This area was chosen
for its remoteness.

The fact that it's quite obvious

that these cameras are being
both stolen and vandalized

is very bad.

I've never seen this in my
20-plus years in the field.

It looks
like somebody
has come along

in front
of the camera

taken a picture
of themselves.

They didn't want
that to happen.

So they tried to take
the camera

tried to slash
the lock

but the lock has got
a steel cable on it.

And they couldn't
take it off.

So instead of
taking it off

they tried to
destroy the picture,
destroyed the film.

So they got a knife

and they've just
slammed the knife

into the top
of the camera.

It doesn't surprise me

that people are anywhere anymore
in this world.

I'd be more surprised
if we found a spot

where there really weren't
any people penetrating there.

It's a male.

It's a male.

It's a young male.

It looks like two years old.

RABINOWITZ:
A lot of people ask me
why I do the work I do.

There's a lot of reasons.

But basically, I'm just tired
of watching animals die.

NARRATOR:
A fisherman from a village next
to the park may have information

on just how much hunting
is going on.

(man speaking Thai)

(speaking Thai)

LYNAM:
So now there are
fewer tigers than before

because there are
more people here

and the tigers are found
further into the forest.

RABINOWITZ:
Ask him about snares.

(Lynam speaking Thai)

(speaking Thai)

RABINOWITZ:
He says that they
don't use snares

that they don't hunt,
that there's no hunting.

It's probably the truth

somewhere a little in between.

NARRATOR:
Rabinowitz's team has retrieved
only three cameras out of ten.

The expedition could be
a failure

unless the other teams have
better luck.

The journey ends
at the village of Bongluek

a settlement of 70 families
near the park border.

If there's anything more
to learn

the local headman will know it.

Ask him if he's ever seen
this animal.

Does he know what
this animal is?

(speaking Thai)

Ah, okay.

So there used to be
rhinos here

but hunters have
wiped them out.

(headman speaking Thai)

(Lynam and headman
speaking Thai)

RABINOWITZ:
There's no doubt that
the major cause of extinction

on a global level is
human-related.

Everything from clear-cutting
forests

to removing intact habitats

to just desecrating them,
changing them.

NARRATOR:
Habitat destruction is now the
number one cause of extinction

people spreading out, or just
trying to survive in a world

where most of the habitable land
is already occupied.

There's nothing to do now

but wait to hear from the other
teams, and hope for the best.

Thailand isn't alone.

Hawaii is another
once-isolated place.

For centuries,
it's had to battle

the number-two cause
of extinction:

biological invaders,

foreign species that can
overwhelm native life.

Born of lava
from undersea volcanoes

the Hawaiian Islands
were barren at first

and every species
was an invader.

The ocean swept in life.

Spiders, lifted into the air
by their own webs

were carried here.

Birds arrived
on the back of storms

carrying animal hitchhikers
and the seeds of plants.

Thousands of visitors made it
by sea or by air

and evolved into species

that were found nowhere else
on Earth.

With little competition
and few predators

they had found a paradise.

But now the paradise
is under siege.

Paleoecologist David Burney,
here with his son

is exploring the Hawaiian island
of Kauai

to better understand
what happened

after the Polynesians arrived
around 600 A.D.

BURNEY:
I'm trying to find sites
that will really give

a general picture of what
the whole landscape was like

where you have a record
of plants and animals

and human activity

and everything that you
could possibly reconstruct

about the whole landscape,

what I call my
"poor man's time machine."

(engine rumbling)

NARRATOR:
The time machine is a sinkhole

where mud and water
have preserved

10,000 years
of Hawaiian evolution.

With two small generators
and hoses

Burney drains it every day.

BURNEY:
I like to think of it

as sort of like trying to open
a window into the past

downward into the past

in order to get all of these
different kinds of fossils

that would give you details

of nearly everything
that was there.

We often recover

a very large amount
of very well-preserved material

including, in this case,
for instance

bones of a number of birds
and snails

possibly even a few plants
that were unknown to science.

NARRATOR:
It's a tedious, messy job

but the mud preserves
the evidence perfectly.

In a given day, Burney carries
a thousand pounds of sediment

out of the sinkhole.

Volunteers then wash, screen
and pick through it

for fossils and artifacts.

BURNEY:
As soon as the Polynesians
get here

we see evidence in the sediments
for big changes.

NARRATOR:
That's because the Polynesians
didn't come alone.

They brought with them
biological invaders:

plants, dogs, pigs, rats

new predators that fed on
and displaced

Hawaii's native species.

Ah, there's one of our culprits.

Jawbone of the Pacific rat,
probably about 1,000 years old.

Once we start finding these

a lot of the native species
start rapidly disappearing.

NARRATOR:
The sediment tells the tale.

BURNEY:
Over the ensuing
1,000 years or so

the human population grows.

You know, at first,
we're talking about

a relatively small number
of people

who came in outrigger canoes.

There couldn't have been
that many.

But over time,
the population on this island

in prehistoric times built up

to probably something like the
population of the island today.

There were a lot of people here.

People have a big job
transforming the landscape

cutting down trees

burning off the grasslands
and the brush lands.

And as a result of these impacts

then smaller creatures began
to go extinct.

At the time
that Captain Cook arrived

the wave of biological invasions
really crests.

Suddenly there are all these
goat bones and goat teeth

in that layer.

Suddenly there's a lot fewer
birds and trees around.

The Polynesians brought only

a small number of species
with them.

Europeans have brought hundreds
and hundreds of species.

We're now to the point

where there are about 1,000
native species of plants

in the Hawaiian islands

and over 1,000 naturalized
invasive species

things that have been
introduced by people.

The evolution
has now entered a new mode.

Something new altogether
is happening, and it has to do

with what humans do
to the evolutionary process.

NARRATOR:
The invasion of Hawaii
is a microcosm

of what's happening
throughout the world today.

At any moment, 100,000 people
are suspended in planes

over the Atlantic Ocean

traveling from one continent
to another.

Cargo is sent to the furthest
corners of the earth

in a matter of days,
or even hours.

And with it comes other,
smaller passengers

who are not going to get back
on the plane and go home.

(ship's horn blasts)

In ships, ballast water
is taken up in one port

and discharged in another.

With it comes invasive species
like the zebra mussel

which arrived
in the United States in 1988.

Quick to reproduce

these two-inch-long mollusks
encrust spawning grounds

clog water pipes
and consume plankton

which native fish and mussels
need to survive.

In the past decade,
the U.S. government has spent

four billion dollars
trying to control them.

Many animals and plants
that find their way in

can easily adapt to new
environments and flourish.

Some of them don't
cause problems

but there are others we'd rather
were not so good at sneaking in.

In our new, interconnected world

the invasive species
we carry with us

are dramatically increasing

the rate of extinction
of native life.

MAN:
Some of these animals
were brought in

by private individuals, as pets.

Some were brought in either for
resale as far as food products.

And some of these
actually stowed away

on some of our aircrafts
and ships

that arrived here in Hawaii.

NARRATOR:
The brown tree snake
is one of them.

Originally from New Guinea,
it can grow up to 11 feet long.

During World War II

the snakes began to climb
the landing gear of planes

and curl up
in the wheel housings

or hitchhike rides
on cargo ships.

When they arrived in Guam

the snakes would slither off
and head for the jungle.

Then they would climb trees
in search of food.

The eggs of the native birds
were easy targets

and nine of Guam's
11 forest bird species

were driven to extinction.

That's it, over here.

NARRATOR:
Hawaii's Department of
Agriculture now has to use

trained beagles to sniff out
the snakes.

Where is it?

NARRATOR:
This time it's a test
for training.

But the next time,
it will be for real.

That a girl, good girl!

MAN:
The last brown tree snake
that showed up here

was found in the wheel well

of a Continental Micronesia
747 aircraft

that arrived the day before
from Guam.

It does show that the snakes
are getting up there.

The main worry for the Hawaiian
Department of Agriculture

is that the Brown Tree snake
becomes established in Hawaii.

Hawaii leads the nation

in the amount
of endangered species

and many of those species
are birds.

If Hawaii loses our native birds

we also lose a lot
of our native plants

and the whole ecosystem in
Hawaii will be affected forever

and the paradise we know
might not be in years to come.

BURNEY:
My suspicion is that

of all of the things that we've
done to the planet so far

whether it's climate change

things we've done
to the atmosphere

things we've done to the water,
pollution problems,

all of those are bad things.

But I think, as it stands
right now, at least

that the thing we've done,
which will be most visible

in the fossil record
in a million years

is going be
these biological invasions.

NARRATOR:
Scientists have a term
for biological invaders.

They call them weed species.

Like weeds, they survive
and adapt almost anywhere

and push out
the native competition.

They are the ultimate survivors.

NOVACEK:
There's quite a bit of
speculation and theorizing

about why invaders seem
to be so successful

in moving into a new area.

The animals that tend to invade
are more mobile

maybe more adaptive to more
general changes in habitats

more flexible
with environmental change.

That confers some kind
of competitive advantage.

NARRATOR:
Of all the weed species
on Earth

we are the most mobile,
the most adaptable

and the most flexible by far.

The good news is we'll probably
be around for a long time.

The bad news is the world
around us may be very different.

As the rate of extinction
accelerates

every species that disappears

leaves one less
to prop up others.

So the question is,
in our own modern world

with our own house of cards,

how close are we to that
whole edifice coming down?

Have we reached that threshold?

NARRATOR:
This is the Great Plains state
of North Dakota, farm country.

It's where one of the battles
against human-caused extinction

is being fought

only this time by pitting
two biological invaders

against each other.

The enemy here is a weed
called leafy spurge,

so well-adapted and tenacious

it threatens to kill off
native grasses.

It's already spread
across a million acres.

A century ago

pioneers accidentally brought it
with them in bags of seed.

Now the settlers' descendants
are faced with the consequences.

MAN:
The leafy spurge limits
the number of cattle

that I can put in a pasture.

I mean, they'll eat the grass
that's in there

but if it's infested with leafy
spurge they just won't touch it.

There's a milky substance to it
and it's pretty bitter.

They don't like it.

NARRATOR:
Cy Kittleson's great-grandfather
homesteaded the land.

Today, Cy and his father
own 4,000 acres.

The weed covers
over a third of their ranch.

They've tried spraying it
with a weed-killer

but leafy spurge
is not easily beaten.

I look at it
as cancer to the land

and it makes the land
just totally useless.

The chemicals, it costs
between $90 and $100 a gallon

and it takes about a gallon
to cover one acre of land

and so that's $100 an acre

and that's not counting
your time.

And that's
about all the land is worth.

How many acres
would that cover?

NARRATOR:
Chuck Wiser, the local bank's
agricultural loan officer

understands the financial toll
of a biological invasion.

He has battled leafy spurge
in one way or another

for 25 years.

WISER:
Leafy spurge is

a very deep-rooted perennial

that is competitive
for nutrients and moisture

with our native grass.

And so it has an advantage

both in food storage
in its root system

and ability
to regenerate growth.

NARRATOR:
If a chemical won't stop it

how can farmers fight an invader
that's taking over

the ecological niche
of native grasses?

The solution may be
another invader

discovered
when scientists learned

what kept leafy spurge in check
in its native Russia.

It's the flea beetle,

a case of fighting
evolutionary fire with fire.

WISER:
Flea beetles feed on the roots
and in the crown of the plant

and bore holes
allowing molds to get in.

They deplete the food reserve
in the root

and so they're just
kind of beating it up

so it's weaker and weaker

and eventually does not produce
any top growth.

NARRATOR:
Flea beetles were first brought
to Ward County in 1984.

Each summer,
teams harvest beetles

and move them to infested areas.

The beetles reproduce so rapidly

that a release of a hundred
in one year

yields a harvest
of two million the next.

That just leaves the challenge

of actually getting them
to the right place.

WISER:
We found that on the large
infestations of spurge

in really rough country
that's hard to get into

we can put out
more beetles faster

using a light airplane,
than any other method.

Our flight today consisted
of 150 canisters we dropped

with approximately 5,000 beetles
in a canister.

We put out somewhere
around 750,000 beetles.

Weeds grab life from us.

If we don't do something,
we'll be taken over by them.

KITTLESON:
It started out small.

And now, every spring now,
I go out and harvest these bugs

and spread them around

and I can really see
some good results with it now.

It's going to take a while,
it's going to take a long time

but I can see the results.

NARRATOR:
The story of Cy's farm
is a story of hope.

It means that we can do more

than just watch native species
go extinct.

We can fight back.

But that requires information
we may not have.

In Thailand, the research
expedition is still waiting

for the data it needs.

Will the scientists discover
that it's already too late

for Kaengkrachen?

Has it become an empty forest?

The other teams have collected
all their cameras

without trouble,
33 rolls of film in all.

(laughs)

Oh, look at this.

That's a beauty, but I got
a better one for you.

Look at this.

Wow.

Now, that's
a nice picture.

Tiger and leopard.

Another leopard.

Another tiger!

(laughs)

Holy cow!

Look at that.

I'm assuming this
is a sambar deer.

That's a nice tiger.

Boy, that's
a nice shot.

Oh, this is really
interesting.

Poachers or local people
or something or other.

This is the Petchaburi River.

This is the second route.

This is the one where
I walked up ten years ago?

That one?

That is some area.

Look at this tapir.

Tapir, yeah.

Phew.

Look at that.

We've got great...

Look at this.

Siamese crocodile.

Oh, there it is.

Look at that!

Crocodile.

This is the first
recent photo

of a Siamese crocodile
in Thailand.

RABINOWITZ:
While we were sleeping,
while we were walking,

while we were swimming
in the river

all these animals
were wandering around us.

The tigers were walking
around us, the leopards.

The Siamese crocodile
might have been in the water

at another part of the stream

at the same time we were
jumping in and cooling off.

It was definitely near us when
we were standing on its beach.

I know the tigers heard us.

Probably several saw us.

I know that the elephants
froze there in the forest

when we went by as if,
"Wow, what a neat forest."

There are still places left

where the natural evolutionary
processes are going on.

Most of my career involves
documenting species

on the verge of extinction.

But every now and then,
you get a place like this

and you say,
"It's not lost yet.

It's not gone yet."

Really, it's that close.

RABINOWITZ:
Knowledge is definitely
our greatest tool

against extinction.
There is no doubt about it.

Many species are on
a very quick, downward slide

possibly to extinction, faster
than they would be normally

because of human-related
activities.

But we're not at an endpoint
here by any means.

We're still in the middle

of a completely complex,
changing scenario.

Evolution is going on around us.

NARRATOR:
If we can slow the rate
of human-caused extinction

and avoid a mass extinction
by our own hands

then the natural cycle
of death and life

extinction and evolution

can play itself out
at its own speed

as we try to learn more
about it.

In 1859, Charles Darwin wrote

"We need not marvel
at extinction.

"If we must marvel, let it be
at our own presumption

"in imagining for a moment
that we understand

"the many complex contingencies

on which the existence
of each species depends."

"The appearance of new forms and
the disappearance of old forms

are bound together."

Continue the journey

into where we're from
and where we're going

at the Evolution web site.

Visit www.pbs.org.

The seven-part
Evolution boxed set

and the companion book

are available
from WGBH Boston Video.

To place an order, please call: