Original subtitles

Earth's great rivers...

..from source to sea...

..make extraordinary journeys.

Carving through continents...

..nurturing ancient civilisations...

..feeding and connecting life across our world.

From the mountains and deserts of the Nile...

..to the cities and mysterious swamps of the Mississippi...

..and the steaming waters and secret worlds of the tropical Amazon.

Great rivers are the lifeblood of Planet Earth.

The massive, muddy Mississippi.

The heart and soul of America's Deep South.

The river has inspired writers and musicians for generations.

It's the familiar face of the Mississippi,

known the world over.

Yet this is, in fact, just the last stretch of a truly

vast river system.

The Mississippi is an enormous network of waterways.

It reaches into 31 states,

gathering water from nearly half of the USA.

From unexpected beginnings in remote mountain streams,

winding tributaries sweep across open prairie.

Hundreds of rivers, coming together as one...

..linking animals and people across thousands of miles.

Nothing connects and unites the states of America

like the Mississippi River.

Most of the Mississippi's water comes from across a 1,500 mile

wide swathe of the northern United States,

bordered by mountains.

The Mississippi's longest tributary begins here,

in the north-west,

amongst the towering Rockies of Wyoming, over 3,500 miles upstream.

Winter here can last for five months.

Right now, billions of tonnes of water are trapped

as ice and snow.

In summer, this is a fast-flowing torrent.

But, for now, the otters and other animals who depend on it must search

for holes in the ice to allow them to fish.

But some choose to come to the Rockies to experience

the frozen headwaters of the Mississippi.

For climbers, there is no greater challenge than scaling a sheer

wall of ice.

You're basically chasing a hidden treasure...

..that somebody told you was up in the hills.

And every once in a while, you actually get to find it.

For Aaron Mulkey, one of the most experienced ice climbers

in the world, winter is his favourite time of year.

Here, the Mississippi is suspended in the form

of towering, frozen waterfalls.

These provide some of the best ice climbing in the whole of the USA.

I don't think people ever really imagine these things

would ever freeze.

100, 200 foot, massive,

just a spectacular chunk of ice.

And sort of crazy to think that, you know, when you're chopping away,

ice climbing at these things,

that that water may end up in the Gulf of Mexico at some point.

Every one of these frozen waterfalls is unique.

They never form the same way twice.

These waterfalls are very much alive, you know.

You're watching them with the little trickle of water.

They're constantly moving and shifting.

You can hear the ice crack and sometimes shift.

Some of those noises are OK.

Some of them are much more concerning.

ICE SHATTERS

Ice!

Ice climbing is pretty unique.

You know, if you go rock climbing, it's there, it's always

going to be there, but ice is there one day and gone tomorrow.

For now, though, this whole landscape is frozen.

But no matter how cold it gets, a few streams here in the Rockies

throw the local wildlife a year-round lifeline.

Yellowstone National Park's steaming geysers spew out boiling water

into the middle of this icebound wilderness...

..keeping precious streams flowing through the snow.

The Madison River,

a remote tributary of the Mississippi.

Despite the air sometimes dropping to 40 below,

the river never freezes over.

Winter is especially hard for Yellowstone's coyotes,

endlessly searching for something to eat.

A few have learned that this particular river

holds a potential meal.

Fishing doesn't come naturally to coyotes.

But it's a skill this female is determined to master.

The wetter she gets,

the greater the risk of hypothermia.

But after four hours of enduring the bitter cold

and catching nothing...

Finally, a half-metre-long rainbow trout.

She's one of the only coyotes in the world who's learned

to fish this way.

And it's only possible thanks to the steaming waters

of this unique Mississippi headwater.

All across the frozen north, the season starts to change.

In the mountains, the spring melt sometimes doesn't happen

until as late as June.

Slowly, the temperatures rise...

..and the thaw begins.

The headwaters of the Mississippi are finally unleashed.

Billions of tonnes of water are on the move.

They can engulf everything in their path.

This dramatic transformation marks the annual reawakening of life

across the Mississippi.

Nowhere is this more true than in the Appalachian Mountains,

1,500 miles east of the Rockies,

on the other side of the continent.

Here, in Tennessee and Virginia,

upland streams are a haven for an incredible variety of life.

Hellbenders, a rare species of salamander that can grow

to over 60 centimetres long.

Huge shoals of fish,

like these buffalo suckers,

mass to spawn.

While on the river beds,

chub build stony nests to protect their eggs.

But one group of animals has come up with an astonishing way

of giving their young the best possible start.

Freshwater mussels.

During the breeding season, part of the mantle which runs

along the edges of their shell is unfurled.

It begins to resemble a small fish swimming in the current.

A small fish that larger fish might want to eat.

Hidden inside these lures are sacs containing thousands

of tiny mussel larvae.

To disperse and find a new home,

the larvae need to latch onto the gills of a large fish.

For this to happen, the adult mussels need to trick

a fish into biting their lure.

The larvae clamp on and begin to suck nutrients from

the fish's blood.

They will hitch a ride on the fish's gills for a few weeks

before finally dropping off.

The fish unwittingly spread the young mussels

up and down the river bed.

Surely, one of the most extraordinary parenting strategies

on Earth.

The rising waters of spring provide opportunities for many river

creatures right across the north.

But, for others, the spring melt is not so welcome.

Beavers are found throughout the Mississippi Basin.

They build dams to create a watery moat around their homes,

which protects them from predators that could attack from the land.

Inside their homes, known as lodges,

adults and their kits stay safe and warm.

But their peace is about to be shattered.

The beavers can hear there's a problem.

Researchers have found that the sound of running water

is something that beavers are simply unable to ignore.

The sound means their precious dams are in danger of being swept away

by the swelling streams.

Their moats could drain away,

leaving their lodges high and dry and at risk from predators.

The beavers must gnaw, drag and pack as much fresh material

into the dams as they can,

to try and staunch the flow.

Beavers spend their whole lives trying to block the river.

But in the end,

the river always wins.

Humans have also tried to control the powerful waters

of the Mississippi's tributaries.

Building dams like these in the foothills of the Rockies.

Many are used to store meltwater for irrigation

in the dry summer months.

But not even these 100 metre high walls can entirely contain

the Mississippi's water on its journey downstream.

Damming rivers disrupts their natural flow.

But here, Marsh Lake in Minnesota, nearly 1,000 miles downstream

from the Rockies, it's created an unexpected opportunity for some.

American white pelicans.

They arrive here each spring on three metre wingspans.

Some of them have flown over 2,000 miles just to get here.

Their nests are protected from predators by the surrounding waters.

22,000 of them cram onto the islands.

As a sign that they're ready to breed, both males and females

grow a special horn on their bills,

which drops off after their eggs have been laid.

But Marsh Lake's dam offers more than protection.

It forces migrating fish to pass through a narrow gap,

concentrating them all in one place.

And pelicans are famed for their appetite.

Some of the carp funnelled across the dam can be over a metre long.

But when one pelican finds more suitably sized fish...

..it's the cue for them all to pile in.

MUSIC: The Barber of Seville Overture by Rossini

The bonanza provides a welcome meal for the hungry chicks.

After their young have fledged,

these pelicans will leave.

They'll fly towards the main channel of the Mississippi River,

using it to help navigate on their long journey south.

As they leave its wild, upper reaches, the Mississippi's

tributaries begin to funnel into the main channel.

Here, around 2,000 miles from the river's mouth,

the Mississippi passes into the farming heartland of the USA.

92% of America's agricultural exports are produced

within the Mississippi Basin.

States like Iowa, Illinois, Wisconsin, growing everything

from grain to soybeans to cranberries.

Wisconsin produces over half the world's cranberries.

Historically, this industry relied on the Mississippi's water.

When the fruit is ripe, the fields are deliberately flooded.

The cranberries float to the top,

ready to be skimmed off the surface and exported across the globe.

The central stretch of the Mississippi helps to feed

the entire nation and is a fertile home for wildlife, too.

Each year, around the 4th of July,

tiny insects put on an amazing show.

Mayflies.

Their nymphs have lived on the riverbed for up to two years,

slowly maturing, preparing to sprout wings and take to the air together.

Millions emerge simultaneously, in swarms so big, they can be seen

on weather radar.

But their independence from the river is short lived.

They emerge simply to mate,

after which the females must return to lay their eggs.

Just two days after they first appeared,

the final, spectacular stage of their life will be over.

Mayflies have risen from the river since long before people

settled here.

But those that emerge today are surrounded by the modern face

of the Mississippi.

This central stretch is the steepest section of the main river channel.

To keep the waters deep enough for transport,

giant locks and dams have been built right across it.

What was once a wild, rushing river

has become a huge, sluggish canal.

Today, an endless stream of massive barges move millions of tonnes

of the nation's produce up and down the length

of the country.

Whole communities live and rely

on the industrialised Mississippi,

including captain John Hill Gardner.

All these people are dependent on the river for their livelihood.

We all have a living and it gives us a living.

The hours are long. The work's hard.

When you come back,

it's like you're coming back to your home.

It's just a way of life.

Fed by trade on the river,

bustling cities have grown up all along its banks.

Halfway down the Mississippi, St Louis was built where the longest

of the river's tributaries, the Missouri, joins the main channel.

Grain is trucked here from across the central USA,

destined for the rest of the world.

On the river, tugboat captains wrangle huge, empty barges.

A single barge can carry 1,500 tonnes of grain or soy.

Once loading is finished,

the barges are shuffled together in giant flotillas.

Each one can cover the area of four football pitches

and be over 350 metres long.

Thanks to the river's help, the whole flotilla can be pushed

by a single boat, hauling as much cargo in one journey

as over 2,500 trucks.

A boat trip down the Mississippi is nearly 2,000 miles long.

It can take two weeks and requires concentration,

experience and stamina.

We work out here in a nonstop operation.

It goes 24/7, 365 days a year.

We work six hours on, six hours off,

for a month at a time.

Searchlights guide the boats along the river.

Steering these giants through the locks becomes even

trickier at night.

Five hours and 59 minutes of sheer boredom, then you've got 60 seconds

of sheer terror, because you come down on a bridge or something

like that, you're not quite shaped up for it,

hoping you get through with your bad spot.

The equivalent of 49 million truckloads of goods are transported

on the Mississippi every year.

It's become a vast and hectic motorway,

bringing cargo from across the country and carrying it south

to the coast.

As the river reaches the last 1,000 miles of its journey,

its character changes.

It widens, slows and begins to flow through a vast natural flood plain.

Massive, meandering detours and shifting sandbanks mark

the beginning of the lower Mississippi, as it enters

the Deep South.

River guide John Ruskey has paddled this iconic section

of the Mississippi for over 35 years.

When we flow out of the cities and civilisation,

the land immediately becomes wild.

The place where the big water meets the big forest,

underneath the big sky.

Because the landscape here is so flat, when the river is swollen

by heavy rain or spring meltwater,

it regularly bursts its natural banks.

Over time, this flooding has helped create a vast labyrinth

of interconnected backwaters, lakes and swamps.

When you leave the main channel of the Mississippi and paddle into

the cypress swamps, it's like entering a whole new world.

You get this feeling that the river is getting lost as it meanders

into the belly of some mysterious, giant wilderness.

The Atchafalaya.

The largest swamp in the USA.

Over 2,000 square miles.

Much is flooded forest.

Huge swamp cypress trees, draped in Spanish moss.

Historically, the river just flooded everywhere across this,

at times, 100-mile-wide flood plain, and all these nutrients

that the river's carrying from the Rocky Mountains

to the Appalachia are all concentrated,

and as a result, these hardwood forests became the richest forests

in North America.

Here, in the waterlogged south,

beavers worry less about fast flowing torrents washing dams away

and more about predators hiding beneath the surface.

The swamps are also home to a vast array of other wildlife.

Egrets.

Herons.

And roseate spoonbills.

White ibis and anole lizards.

The swamp remains a haven for wildlife.

It is one of the few remaining wild places that's as wild as parts

of Alaska or the Rocky Mountains.

In early autumn, the swamp echoes with the endearing squeaks

of the young of one of its most famous and most feared predators.

Baby alligators...

SQUEAKING

..only recently hatched from their eggs.

Despite only being around 15 centimetres long,

they're already equipped to take on anything that they can wrap

their jaws around.

But, at this size, they can easily become a meal themselves.

Many around here would snap up a baby gator,

including great egrets, up to a metre tall.

But everyone must keep an eye out for Mum.

Nearly three metres long, she lies in wait, listening

to her baby's squeaks,

ready to attack anything that comes too close.

The youngsters can bask in safety, under her protective gaze.

The Atchafalaya is just a fragment of what was once a much larger

network of Mississippi swamps,

originally five times the size they are today.

Over the last 150 years, much of the fertile flood plain

has been cleared and drained to make way for farms and cities.

New Orleans, the final big city before the river meets the sea.

Originally, all this was swamp.

And today, parts of the city are over seven metres

below the river's highest water level.

It's become a never-ending battle to hold the river back.

1,600 miles of levees have been constructed,

hemming in 80% of the lower Mississippi, yet the flood defences

have been repeatedly breached by the stubborn river.

Each time, people have rebuilt the barriers,

taller and stronger.

And where the water can't be held back, people have simply built

over the top of it.

The three longest bridges in the USA have been constructed

above these Mississippi wetlands.

Lake Pontchartrain Causeway, nearly 24 miles long,

the biggest of them all.

It leads across a vast, swampy lagoon into the centre

of New Orleans.

Down here, a 16-mile stretch of the river has been turned

into the largest port in the Western Hemisphere.

The cargo carried on the barges is transferred to huge

ocean-going ships.

The massive vessels steam through the final hundred miles

of wetlands on their way out to sea and around the world.

This is the last stage of the Mississippi's long journey.

A marshy delta of islands, channels and beaches which form

the final boundary between the land and the ocean.

It covers an area of over 11,000 square miles and is a rich fishing

ground - a draw for both people and wildlife.

White pelicans, many the same individuals that bred at the other

end of the Mississippi, have migrated here to take advantage

of the subtropical climate of the Gulf of Mexico.

Reddish egrets - a southern wetland specialist.

Once pushed to the brink of extinction for their crest feathers,

they are now making a comeback.

In the muddy waters,

small fish can be hard to spot.

When an egret does manage to find one, it doesn't let

it out of its sight.

SWAMP BLUES MUSIC

That one's got away.

All the dashing around was worth it in the end.

This entire landscape was formed by the Mississippi,

which picked up soil from across America

and deposited it here.

But it's now at risk of disappearing beneath the waves.

To tell the story of these wetlands, local photographer

and conservationist Ben Depp learned to paramotor.

The landscape is totally flat,

and the only way to get perspective is to go up in the air.

This whole landscape, hundreds of miles of wetlands,

were created from the Mississippi River.

This land is dirt from a soybean field in Iowa and a cornfield

in Ohio, a mountainside in Montana, and it's an incredible thought

that that sediment is being carried all the way down the Mississippi

River and is washing into wetlands here and building new land.

These coastal wetlands may be huge,

but what people have done to the Mississippi has had effects

that few could have foreseen.

The landscape here is naturally in a state of change.

The river spreads and slows, depositing sediment,

which builds new land.

The ocean currents then try to wash it away.

Historically, the Mississippi has always won this contest,

gradually forming this,

one of the largest deltas in the world.

But the balance between sedimentation and erosion

has been changed.

The flood defences that line the lower Mississippi mean

that the river can no longer

spread out to rebuild the wetlands,

and land is now being lost at the rate of a football pitch every hour.

Everywhere you look,

you can see what we've done to this landscape.

I think we didn't understand what we were doing,

and now we understand that we've really messed up

those natural systems.

Over the last 80 years,

we've lost 2,000 square miles of land.

Coastal wetlands help protect cities like New Orleans from storm surges

caused by hurricanes.

As the wetlands disappear,

hurricane damage becomes much worse inland.

We need to change our perspective, and we need to prioritise

these things that are going to help us continue living here long term.

Now, work is taking place to reverse this massive land loss.

Sediment is being pumped and diverted to replenish the marshes,

and sand is being dredged from the ocean to rebuild protective

barrier islands.

It's a constant battle against tide and wind,

but already over 55 square miles of land have been restored

or protected, and much more is planned.

Down here, at the end of the river's journey,

people are now forced to spend billions trying to do what the river

once did entirely by itself.

Throughout the Mississippi's enormous reach, stretching

the length of this huge country,

animals rely on its natural riches.

And for centuries, people have exploited its vast scale

to connect, enrich and unite the states of America.

The river is, and always has been,

a powerful and untameable giant.

The massive, muddy Mississippi

remains the lifeblood of this nation.

The huge Mississippi Basin encompasses a vast range

of habitats, from frozen mountains to subtropical marshes.

But it was here, in the swamps of Louisiana,

that cameraman Doug Gardner was most excited about filming.

I was born in South Carolina and raised in the heart

of the swamps, and pretty much I'm a swamp rat.

But, you know what, I don't apologise for it,

it's the place that I absolutely love.

Generally, people think of a swamp as a nasty,

dirty place, and, for me, I see it as one of the most special

ecosystems that our planet has to offer.

The Atchafalaya is the biggest swamp in North America.

Doug is here to find baby alligators, but getting

past their enormous mother won't be easy.

I think alligators are amazing animals,

and I'd never had a chance to actually film a mother

with babies, so I was really excited about getting out here.

Louisiana has the largest alligator population in North America -

nearly 2 million of them.

But actually finding them in this flooded labyrinth

is not easy.

I'm pretty used to working in swamps, but I wasn't expecting

the Louisiana swamp mud to be as deep as it is.

Getting my steps in today!

The only difference is that one of these steps equals

about 400 regular steps.

I don't want to put my foot in an alligator's mouth,

cos often they will just lie on the bottom.

One of the main things, you've got to keep moving.

You can't just say,

"Oh, I'm freaking out because I'm bogging down."

If you stand still, you're going to sink even deeper.

A lot of times, you use sticks to get around.

One thing about this mud, it absolutely stinks.

It's such a vast area, and we had a lot of ground to cover.

It was tough going.

Rather than struggling through the quagmire,

Doug opts for a more comfortable form of transportation.

The deeper we ventured into the swamp, the thicker the vegetation

got, and to be honest with you,

my eyes really started to play tricks on me at that point.

There, there! No, that's a frog.

But then a sign - the telltale calls of baby alligators.

SQUEAKING

We can hear them, but I can't...

I can't pinpoint them yet.

They're so well camouflaged.

I was about to quit for the day, and I heard all this commotion

behind me, and I really wasn't prepared for what I was

about to see.

Mother alligators will attack anything that gets close

to their brood - even another gator.

I just grabbed the nearest camera

and started filming the best I could.

The mother alligator has got another, small alligator

in her mouth.

She's just... She's trying to eat it.

Trying to get this, sorry about the shake, there's a leg.

Even though the alligator was smaller than the mother,

it was still quite big enough to pose a threat to the babies.

There you go.

You know, a lot of times, I forget just how unpredictable

nature can be.

The babies must be nearby, but with the light fading fast

and a two-hour boat ride back, Doug can't hang around.

Nope.

After a long day of searching and trudging through the swamp,

the last thing I want to do is break down in the middle of nowhere.

The motor has overheated.

The water where we broke down really wasn't that deep,

but considering what I'd just witnessed 30 minutes earlier,

I wasn't about to get in the water and push.

So, Doug's only real choice was to stay on board

and paddle instead.

We have seen quite a few alligators as soon as the sun went down,

so that's a little unnerving.

I hear things in the water all around me.

And then, a light in the distance.

You know, there's this code when you're out on the water.

If you see somebody that needs help, you stop and help them,

because one day - I assure you - you're going to need help.

Any way you can pull us up there to the landing? Yeah.

All right, man, appreciate it.

I'm feeling quite relieved now.

Hey, thanks, bud, have a goodnight.

It's always an adventure.

Something was bound to happen today, because it is Friday the 13th.

And a black cat ran in front of me at the hotel,

so that's double jinxing.

A new day, and Doug decides to return to the same spot

where he heard the baby alligators.

Already, things are looking up.

I see a fresh slide,

it looks like she has been going up the bank.

Now, gators like to bask in the sun on the banks until their body warms

up, and then they'll just slide into the water.

And that slide looked very fresh to me.

And what I was hoping was that, if I could spot her,

then maybe she would lead me to her babies.

Doug is confident that mum is nearby

so takes position at what he hopes is a safe distance.

I don't know that she is in there, but I'm hoping she is.

I know the babies are back there, cos I can hear 'em.

I've done everything I can to try to alleviate

all the odds, being attacked by an alligator, and I think

that this log will give me some protection if a gator came up at me

and lunged out of the water.

But you're not going to go anywhere real fast in waders and in mud.

OK, I see momma, here's momma right here.

Finally, I spotted the mother coming across the canal,

and she looked like she was coming straight at me.

But, thankfully, you know, I wasn't close enough to her young

that she considered me a threat,

so she just turned around and went back.

I could feel her eyes on me all the time.

I think I see where they are.

As if by magic, she just led me right to them,

right where she had been hiding them all along,

and now I see why they were so hard to find, because they are so well

camouflaged, they blend into everything in their surroundings.

Despite everything the swamp has thrown at him,

Doug can finally capture an intimate view of these tiny predators.

You've got to look careful.

They have black, brown and yellow on them,

and everything out here has the same colours.

These babies will grow up in one of the most mysterious and exotic

regions found anywhere in the USA.

The Atchafalaya is just teeming with wildlife,

and it's full of surprises.

And, you know, that's the reason I love it here,

that's the reason I'll keep coming back here time and time again.