01x01 - Source to Sea

[bunniefuu]

[music playing]

NARRATOR: To really
know something,

you have to enter its
world, learn its rules,

be prepared for anything.

Because there's more
here than meets the eye.

The Great Lakes
of North America--

at a time when fresh
water is running short,

they hold a fifth of the
world's entire supply.

These five lakes have
never been more important.

And yet there's still much
we need to learn about them.

The Great Lakes can
rage like a furious sea.

But they also nourish
a rich web of life,

above the surface and below.

They create around them
worlds of forest and wetland.

And they sustain great
cities of two nations.

To understand the Great Lakes,
you need more than a map.

You must travel with
the water on its

2,000-mile journey
across a continent,

all the way from source to sea.

[music playing]

We call them the Great Lakes.

But though they
are huge, they're

defined by countless
stories that

unfold on a much smaller scale.

From afar, they seem
permanent, unchanging,

as if they've always been
here just as they are.

But the water is
always in motion,

the lakes always in flux.

Each has its own
character, its own moods.

And each plays
its part in a much

larger system that drains 4/5
of North America's fresh water.

At the western extreme
sits Lake Superior--

cold, deep, pristine.

To the south, Lake Michigan,
one of the busiest shipping

lanes in the world.

It feeds into Lake Huron
through the treacherous Straits

of Mackinac.

Riddled with islands, Huron
drains into a calmer, warmer

Lake Erie.

It then plummets
down Niagara Falls,

170 feet into Lake Ontario.

Finally, the St. Lawrence
River carries the water

another 744 miles to the sea.

It's a journey spanning
half a continent

and more than three centuries.

A drop of water that splashed
into Lake Superior in 1715

still wouldn't have
reached the Atlantic today.

But arrive it eventually will,
thanks to a chain of events

that begins here--

the northwest region of
the Great Lakes watershed.

[thunder]

Here, crystal clear waters
start their journey, gathering

momentum as they flow, merging
with other brooks, streams,

and rivers in a vast
system that feeds

Lake Superior, the
wildest and most

unspoiled of the Great Lakes.

These are Superior's
headwaters in Ontario,

home to thriving
populations of wildlife,

among them, two animals
whose ancient relationship

shapes the wetlands surrounding
much of Lake Superior.

This is the largest
rodent in North America.

And he's on a mission.

Beavers spend much of their
time gathering construction

materials and building dams.

His goal is to help turn
a stream into a pond

where he and his family can
build a home, called a lodge.

Their lodge is
supposed to protect

his colony from predators.

Ironically, the lakes
and ponds he builds also

create the perfect habitat
for an age-old foe.

[howling]

[music playing]

By the early 20th century,
gray wolves had been brought

to near extinction in the US.

But the wetland habitat
surrounding the Great Lakes

gave them refuge.

[music playing]

Thanks to the beavers, there
are thousands of smaller lakes

here.

Their dams filter the water that
will end up in the Great Lakes.

But they alter the
surrounding forest, too.

Dams cause ponds to grow.

And soon, where once
there was dry forest,

marshy woodlands develop.

This means less
human development.

The wolves are here
because the wetlands

keep hunters out and bring a
diversity of prey animals in.

Unfortunately for the
beaver, wolves are at the top

of the food chain here.

And beaver is one of
their favorite foods.

[howling]

By thinning the ranks
of the dam builders,

wolves open up the rivers
the beavers had blocked,

and increase the flow of
water into Lake Superior.

Over time, beavers and wolves
forge a natural balance

between closing and
opening the waterways

that feed the Great Lakes.

[birds calling]

[music playing]

Below the surface,
there's a lot of life in

these clean, cold headwaters.

A school of emerald
shiners feeding

in the shallows near the shore.

With plenty of
plankton here to eat,

it's a paradise for
fish like these.

But the shiners can sense there
might be trouble in paradise

and quickly close ranks, forming
what's called a bait ball,

their chief defensive strategy.

Their nemesis, a common loon--

a swift, efficient hunter.

These agile swimmers
flock to the Great Lakes

headwaters every
summer to breed.

This pair has a family to feed.

She's a solitary,
skillful worker.

Loons are supremely
adapted to aquatic life.

Unlike most birds, their
bones are solid and dense,

which makes them less buoyant.

[music playing]

They can dive for
up to five minutes.

A streamlined body
with legs set far back

reduces water
resistance as they hunt.

[bird call]

They need very
clear water in order

to hunt, which is
exactly what they

get here in the pristine
wetlands feeding Lake Superior.

[birds calling]

Loons are a canary
in the coal mine.

If the loons are
breeding successfully,

the whole aquatic
ecosystem is healthy.

And here in the Great Lakes
headwaters, they're thriving.

[thunder]

Because of their exceptional
size and stormy weather,

the Great Lakes are
often called inland seas.

None fits this
description better

than Lake Superior, the largest
freshwater lake in the world.

It's about the size of Austria.

Superior is also the deepest
by far of the five Great Lakes.

With an average depth
of almost 500 feet,

it holds more water than the
other four lakes combined,

enough to cover all of
North and South America

with a foot of water.

Superior's great depth
means water that enters it

takes two centuries to leave.

And when that much
water gets roiled up,

this is what happens.

Winds of 50 miles an hour
routinely buffet Lake Superior.

[birds squawking]

Its waves can climb as high
as 30 feet in the air--

ocean-sized waves.

More than 550 ships have gone
down in Superior's storms.

And that's just the
wrecks we know of.

But when its temper cools
and its mood softens,

Lake Superior changes into
something altogether different.

The clarity of its
water is legendary.

Visibility averages
27 feet, far more

than the other Great Lakes.

Historically, Lake Superior
has experienced the least human

impact of all the Great Lakes.

Parts of its
shoreline have changed

little for thousands of years.

But downstream, to the east,
things are very different.

Plunging far south
of Lake Superior,

Lake Michigan enjoys
a warmer climate.

As a result, it's
densely populated.

More than 12 million
people live here.

Giant freighters serve major
port cities like Chicago.

[music playing]

But Michigan is a lake
with more than one face.

On its eastern shore lies a
35-mile stretch of wilderness,

the Sleeping Bear sand dunes.

Most people associate
sand dunes like these

with oceans, not lakes.

But like the Great
Lakes themselves,

these dunes have their origin in
the glacier that came and went

during the last Ice Age.

Lake Michigan was once
much deeper than it is

today, and held huge quantities
of glacial meltwater.

As the lake drained and
its water level fell,

winds whipped the exposed
sandbars into giant dunes 450

feet high on its eastern shore.

They tower over long expanses
of the beach and offer cover

for one of the most
endangered birds in North

America, the piping plover.

[bird chirping]

This little male is on
the hunt for a mate.

[music playing]

He's only about six
inches long, and weighs

no more than a tennis ball.

But his ambitions are large.

[bird chirping]

She seems unattached.

[bird chirping]

To win her, he must, like all
male plovers, plead his case.

[bird chirping]

But the real test is whether he
can build an acceptable nest.

The sand dunes are
just the kind of place

the plover likes to breed.

But it's not the sort of bird
that builds nests in trees,

assuming there were
any trees here.

He'll dig a scrape--

a shallow bowl in
the sand the female

will camouflage with shells
and other beach debris--

[bird chirping]

--if she decides that he
and his scrape are worthy.

[bird chirping]

Apparently, he's
passed the audition.

Only now does she allow
him to mate with her.

[bird chirping]

Unfortunately, the scrape
is not much protection

against their most
common threat.

[dog barking, man yelling]

People and their dogs
often scare plovers

into abandoning their nests.

And a misplaced paw could
easily crush the eggs.

Either way, the
offspring are doomed.

A century ago, about 700 pairs
of nesting piping plovers

called the Great Lakes home.

But by 1990, only 13
remained, their numbers

decimated by development
and recreational use

of the beaches.

[music playing]

Today, there are up
to 70 nesting pairs

thanks to conservation
initiatives

that include fencing
off plover nests

and rescuing abandoned eggs.

[bird chirping]

When the eggs have
hatched, the scientists

release the young birds back
at the nest site in the hope

that a new generation of plovers
can repopulate the dunes.

Protecting the native
wildlife is an important part

of preserving the
Great Lakes watershed,

but so is keeping new
invasive species out.

[ominous music]

Today, an ominous threat is
approaching along the Illinois

Waterway, which connects Lake
Michigan to the Mississippi

River to the south.

In the 1970s, an alien species
escaped captivity and began

to run wild, first in
Arkansas, then to many parts

of the Mississippi.

Now, it's headed
for Lake Michigan.

Meet the silver carp--

60 pounds of
unappeasable hunger,

originally imported from
Asia to help control

algae blooms in fish farms.

Silver carp lack a stomach,
so they must eat constantly,

consuming up to 40%
of their body weight

in plankton every day.

They are also prolific breeders.

Each female can produce as many
as five million eggs a year.

And they can live 20 years.

Wherever the silver carp goes,
native freshwater species get

starved out, which could put
the Great Lakes' $7 billion

fishing industry at risk.

Every day, the carp get a little
closer to the Great Lakes.

Dr. Jason DeBoer
from the Illinois

River Biological
Station is anxiously

monitoring their approach.

It's taken 50 years
for the invading carp

to spread 1,000 miles
up the Mississippi.

Now, they're here in
the Illinois River,

just nine miles
from Lake Michigan.

Fisheries ecologist Dr.
Jason DeBoer is anxiously

monitoring their approach.

JASON DEBOER: Ring goes down.

NARRATOR: A simple
jolt of electricity--

Brace yourself.

NARRATOR: --is all it
takes to find them.

[MUSIC - WAGNER, "RIDE OF THE
VALKYRIES"]

They're everywhere.

Just the sound of an engine can
launch these high-strung fish

into the air.

A 60-pound fish hitting
someone on a boat

has been known to
cause serious injury.

And there are a lot of
boats in the Great Lakes.

So far, electrified fences
have kept the intruder at bay.

But some experts think it's
no longer a question of if,

but when they find their
way into the Great Lakes.

300 miles to the north,
the water of Lake Michigan

feeds into Huron
through the Straits

of Mackinac, a
treacherous channel

that's claimed many lives.

[music playing]

As water drains from
Lake Michigan into Huron,

the raging torrent pours through
the Straits of Mackinac, only

three and a half miles wide.

Battered by winds, these straits
generate powerful currents that

can reverse direction
in just a few hours,

currents that move 100,000
cubic yards of water per second.

No wonder the
Straits of Mackinac

are considered one
of the most dangerous

waterways in North America.

But it's also a
major shipping lane

with one of the
greatest concentrations

of shipwrecks in the world.

BECKY SCHOTT: The
ships need to get

in and out through that area.

There's nowhere
else for them to go.

NARRATOR: Underwater
videographer Becky Schott

has dived on wrecks all over
the world, from the Pacific

to the Mediterranean.

OK.

All right, that's good.

NARRATOR: But there's something
about Great Lakes ghost ships

she finds haunting.

BECKY SCHOTT: It's like
diving on a time capsule.

NARRATOR: In the ocean,
wrecks like these

would have long
since rusted away.

The salt would have quickly
corroded the iron in the ships,

and the currents
would have dispersed

the pieces of the hull.

But the cold, fresh
water of the Great Lakes

has preserved the remains
of thousands of vessels.

BECKY SCHOTT: Some
of these wrecks

look like they sank yesterday.

[music playing]

NARRATOR: Today, these
waters are still perilous,

partly because of a geological
feature peculiar to Lake Huron.

Huron isn't the biggest or the
deepest of the Great Lakes.

It doesn't have the coldest
or most pristine water.

What it has is islands--

30,000 of them.

The rest of the Great
Lakes have 5,000 total.

During the last glacial advance,
the ice cut away softer rock,

but left unscathed a very
hard form of granite.

The area Lake Huron now occupies
had more of this tough rock

than any of the
other Great Lakes.

Every island in the lake is
made of the granite the glacier

couldn't gouge out
of the basin, which

is one reason so many ships
have been wrecked on Lake Huron.

And countless hidden islands
lurk just below the surface.

Before sonar, sailors
had no way to spot

them until they'd already
ripped a fatal gash

in the ship's hull.

Hundreds of ship
carcasses now rest

on Huron's lake bed, preserved
in crystal clear water.

The northern shore of Lake
Huron is largely undeveloped.

[owl hooting]

On the fringe of the
forest, in a beaver pond,

a pair of great horned owls
have built their nest in

the branches of a spruce tree.

The female patrols
the marshland below.

[music playing]

She's adapted to
hunt aquatic prey.

Her vision is 30 times
more powerful than humans,

able to detect the slightest
movement from a great distance.

She can hear the rustle of
mouse feet far underground.

But a mouse would only amount
to a between-meal snack

for these chicks.

Something bigger
would be better.

A muskrat-- perfect.

These aquatic rodents can swim
underwater for 20 minutes--

a great way to avoid predators,
but only if they know

they're coming.

She's evolved to fly
in absolute silence.

[suspenseful music]

Dinner is served.

[music playing]

The flow of water that
entered Lake Huron like a lion

at the Straits of Mackinac
leaves like a lamb,

meandering along the St.
Clair and Detroit Rivers

until it empties
finally into Lake Erie.

Erie is the most southerly
of the Great Lakes.

It's also the shallowest, which
means the water here only takes

two years to pass
through, unlike Superior,

where it takes 200 years.

It's also the most
densely populated,

and not just with people.

In the fall, huge numbers of
migrating birds and insects

start heading south
to their winter homes

in Central and South America.

So do millions of
monarch butterflies.

They're heading for Mexico,
where winters are warm.

But somehow, they have to get
across the immense Great Lakes.

The shortest and safest
crossing is right here--

a peninsula jutting
from Lake Erie's

northern shore, Point Pelee.

It's the perfect pit
stop, warm and sheltered.

And it shaves nine miles off
the trip across Lake Erie.

But that still leaves
another 30 miles.

So the monarchs have
to choose their moment,

when the wind is just right.

[music playing]

From here, it's
2,000 miles to Mexico

and a well-deserved rest.

Butterflies aren't the
only travelers that must

make this Great Lakes crossing.

Two major bird migration routes
intersect over Lake Erie.

They use these corridors every
fall to travel to their winter

homes down south.

Five million blackbirds stop
en route for food and shelter.

Songbirds, hawks, and waterfowl
all arrive on Erie's shoreline

to fuel up before moving on.

While they take advantage
of the local resources,

they become temporary
members of the ecosystem.

They eat massive amounts
of fruit along the route

and distribute its seeds.

They consume countless
insects, helping to maintain

balance in the food chain.

[music playing]

And then, as suddenly as
they came, they're gone.

Well, most of them are.

Pelee Island lies about
halfway across Lake Erie.

Many of the migrants
will stop here to rest.

But this female red-tailed
hawk lives here year round.

The climate is relatively mild.

And there's plenty to eat--

small mammals, reptiles,
and smaller birds.

But it's been a while since
she's had a good meal.

[music playing]

Pelee Island is
home to a creature

that will more than satisfy
her if she can catch it.

The blue racer
snake has vanished

from most of North
America, its habitat

lost to human encroachment.

The last 200 blue
racers in Canada

have found refuge
here on Pelee Island.

It's a large snake, growing
up to five feet long.

And it lives up to its name.

It can slither at speeds
up to four miles an hour--

no mean feat for an
animal with no feet.

Under cover of rotting logs,
the blue racer is hard to spot.

But sooner or later,
it has to venture out

in search of its own dinner.

The hawk can pick out the
movement from hundreds of feet

away.

Now, it doesn't matter
how fast the snake is.

The hawk is faster.

[music playing]

Mission accomplished.

[music playing]

From Lake Superior in
Michigan, to Lake Huron,

and on into Lake Erie, water
has flowed unrelentingly

in its quest to the sea,
extending its influence

over thousands of square
miles of watershed,

shaping the landscape,
feeding its inhabitants.

As it reaches the eastern
shore of Lake Erie

and enters the Niagara
River, levels start to drop.

The water picks up speed,
hurtling down the river,

then plunges more than
180 feet over Niagara

Falls, the most powerful
waterfall in North America.

Nearly 200,000 tons of water a
minute cascade over the edge.

The flow is so powerful, it
grinds 12 inches off the cliff

face every year,
carving a gorge that's

now four and a half
miles long as the falls

gradually migrate upstream.

50,000 years from
now, the falls will

have eroded the rock another
20 miles, all the way back

to Lake Erie.

Erie and Ontario will
become one giant lake.

From here, the Niagara River
flows another 14 miles north,

dropping another 60 feet
before reaching Lake Ontario.

Ontario is the last in the
great chain of lakes stretching

eastward from Lake Superior.

It's the smallest Great
Lake, but a quarter

of Canada's entire population
lives along its northern shore.

It bears the brunt of
pollution from Toronto

and other surrounding
cities, as well

as whatever contaminants arrived
from the lakes upstream--

agricultural pesticides
and fertilizers,

industrial chemicals,
and human sewage.

As a result, Lake
Ontario is the most

polluted Great Lake of all.

Still, there are signs
it could rebound.

In the 1960s, the
City of Toronto

planned a three-mile-long
breakwater that would

allow it to enlarge its harbor.

But when the anticipated
rise in shipping traffic

failed to materialize,
the project was abandoned.

City planners didn't know
what to do with the peninsula

they'd built, but nature did.

Within just a couple
of years, vegetation

began to grow on the landfill.

Wildlife moved in-- mammals
like coyote, mink, and beaver,

and more than 300 bird species,
many of which nest on what

is now called Tommy
Thompson Park.

[music playing]

One resident is the
double-crested cormorant.

50 years ago, it was almost
extinct in the Great Lakes,

a victim of pesticides like DDT.

DDT concentrates and becomes
more deadly to wildlife

as it moves up the food
chain, from plankton, to fish,

and ultimately birds like
gulls, herons, and cormorants.

In 1985, Canada banned DDT.

Now, Tommy Thompson Park has the
world's largest nesting colony

of double-crested cormorants--

30,000 of them in a park on a
landfill, in the most polluted

of the Great Lakes.

After a journey of 1,600 miles,
taking centuries to complete,

the water finally
leaves the Great Lakes

and enters the mighty
St. Lawrence River.

By the time it gets
to Quebec City,

the water level has
dropped by almost 300 feet.

Just west of Montreal, the
800-mile-long Ottawa River

joins forces with
the St. Lawrence,

boosting its flow with a
massive surge of clean water.

At times, there's more water
draining down the Ottawa

than travels out of
all five Great Lakes,

earning the Ottawa River the
nickname, the sixth Great Lake.

But much of this
water is hidden,

flowing beneath the
surface as groundwater,

and even through caves.

Many are yet to be explored.

ANDRE MARTEL: Let's
talk about diet plan.

JILL HEINERTH: Yeah.

NARRATOR: Dr. Andre
Martel has been studying

these caves since 2015.

JILL HEINERTH: The
feeders are set.

Tanks are full.

31, 71, and 3205.

NARRATOR: Cave
diver Jill Heinerth

is helping him gain
a clearer picture of

these subterranean ecosystems.

We'll go from there.

Have a great dive.

OK.

ANDRE MARTEL: Jill
truly is the eyes

of science as a cave diver.

It's the only way that we
can gain data about what life

forms living inside the caves.

[music playing]

NARRATOR: Jill has
already explored six

miles of this hidden habitat.

And there's no telling how
much farther the caves extend.

She's discovered an
extraordinary world

bursting with life.

JILL HEINERTH: It's
absolutely incredible.

The biodiversity and density
of life inside this cave

is like nothing I've
seen anywhere else.

NARRATOR: Millions of mussels
carpet the cave floor.

ANDRE MARTEL: Freshwater
mussels are your natural water

filter in your river.

Here, there are
millions of mussels.

And each and every
one of them filters

liters of water each day,
up to two liters an hour.

They are providing an amazing
free ecosystem service to us.

NARRATOR: Filter-feeding
mussels remove algae,

bacteria, and metals,
earning the moniker,

the livers of the rivers.

The water might look cloudy
because the strong currents

stir up the silt. But in
fact, it's remarkably clean.

Many fish, such as
sturgeon and bass,

thrive in the
Ottawa River thanks

to the filtering effects
of these native mussels.

Perhaps if native mussels
were left to work their magic,

the water quality
could rebound elsewhere

in the Great Lakes watershed.

ANDRE MARTEL: Hello there.

How was the dive?

Great.

[music playing]

NARRATOR: From Montreal,
the St. Lawrence

River flows another 550 miles
to the Gulf of St. Lawrence.

Together with the five Great
Lakes and its surrounding

catchment area, the watershed
now contains one quarter

of our planet's fresh water.

Finally, the St.
Lawrence River starts

to mix with saltwater
from the Atlantic

as it pours into
Earth's largest estuary.

It's the end of a
journey that began

2,000 miles away, in
the headwaters west

of Lake Superior.

The water has picked up man-made
contaminants along the way.

And these all flow via the St.
Lawrence River into the gulf.

But the water has
also leached minerals

from the countless
rocks, sand, and gravel

through which it's
passed, and gathered

organic matter along the way.

For thousands of years,
this nutrient-rich water

has flooded into the
salty gulf, creating

one of the world's most
productive and diverse

marine habitats.

One million seals and 14
species of whale are found here.

[whales calling]

Humpbacks, belugas,
fin whales feasting

on plankton, krill, and vast
schools of herring and capelin.

But the survival of all
the creatures in the gulf

depends upon the health of
the water that nourishes them.

The story of the Great
Lakes began in a moment

of cataclysmic climate change.

And they continue to
embody change today.

[music playing]

The water itself changes on
its long journey to the sea.

It transforms the
landscape as it goes,

nourishing its flora
and fauna, and is

transformed by them in turn.

The greatest lakes on Earth
are a repository of the past,

as well as our best
hope for a future

where there is still
clean water to drink,

and pristine natural
worlds to discover.