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[radio static]

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[radio beeps]

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[indistinct chatter over radio]

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[narrator] Just 50 years ago,

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we finally ventured to the moon.

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For the very first time,

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we looked back at our own planet.

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Since then, the human population
has more than doubled.

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This series will celebrate
the natural wonders that remain

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and reveal what we must preserve

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to ensure people and nature thrive.

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Fresh water.

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Everything that lives on land,
animal or plant,

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depends upon it.

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Yet only one percent of it
is within reach.

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The desert of central Australia.

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One of the hottest, driest places
on Earth.

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Virtually nothing can live here
for any length of time.

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Yet once a decade,
this vast, empty desert is transformed.

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For that to happen,
a chain reaction has to be triggered

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two thousand kilometers to the north.

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There, each year,
the moisture-laden clouds of the monsoon

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begin to build.

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[thunder rumbling]

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Eventually they burst,
and the process begins.

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Riverbeds that have been dry for years
suddenly fill.

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[birdsong]

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The torrents join together
and race towards the interior

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and the lowest land on the continent.

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Here, they flood over the desert
and create Australia's largest lake,

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Kati Thanda, Lake Eyre.

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Huge numbers of fish
swim down these wide waterways

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and into the growing lake.

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Pelicans arrive from Australia's coasts,
hundreds of kilometers away.

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Many will only see the lake fill
once in their entire lives,

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so how they know the lake has formed,
and in which direction to reach it,

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is still a mystery.

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[pelicans cawing]

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These new waters now contain so much food
that the birds start to breed.

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But the clock is ticking.

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The pelicans feed...

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and feed...

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and feed.

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The chicks must grow quickly,

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for they have to be strong enough
to leave within a matter of weeks.

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But time is short,

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for the parents
will only be able to find food

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while the water remains.

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The young pelicans set off
on their first long journey.

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It will be a demanding one, to the coast,

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and the nearest is 500 kilometers away.

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The lake will soon dry,

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and water may not return here
for another decade.

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This boom to bust transformation
is an exceptional event.

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But everywhere,
the availability of fresh water

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is becoming increasingly unpredictable
and uncertain.

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Much of the planet's fresh water,
however, is locked away.

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Almost two-thirds of it
lies frozen around the poles.

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This ice is several kilometers thick

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and may have been lying here
for millions of years.

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Every summer, some of it melts

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and carves its way
into the heart of the glaciers.

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These great caves
are beautiful and dramatic,

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but they're also dangerous places,
for glaciers are always on the move.

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[glacier creaking]

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Even away from the poles,

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much of the land's fresh water
freezes each winter.

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But when spring arrives,
this vast snowy reservoir melts

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and a great journey begins.

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Racing down the steep mountain slopes,

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the ice-cold waters
collect a life-giving ingredient...

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oxygen.

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Here, on the rivers of the Andes
in South America,

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there is a living to be made

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for those that can cope
with the powerful currents.

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And torrent ducks can.

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[ducks squawking]

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These chilly headwaters
may be oxygen-rich,

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but they contain few nutrients.

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The torrent ducks collect
what little food there is

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from below the surface.

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Stonefly and mayfly larvae have gills,

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with which they extract oxygen
from the water.

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Their flattened bodies
resist the relentless pull of the current.

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Black fly larvae.

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One of the ducks' favorite prey.

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Their specialized mouthparts
filter out the tiny particles of food

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as they race by.

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Hooks at the rear end
anchor them to the rocks,

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but the current
is sometimes irresistible.

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However, they have a special safety line,
with which they can pull themselves back.

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Every year, visitors come
to these rushing, oxygen-rich waters.

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Salmon.

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They have spent most of their lives
in the Pacific Ocean.

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Now, fully grown, they're returning
to the particular rivers in North America

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where they will now lay their eggs.

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Salmon have an extraordinary ability
to leap up waterfalls,

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but even they cannot, unaided,
cross the dams that we have built.

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Today, Pacific salmon number less than
one percent of the numbers they used to,

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and that's causing problems
for many other animals.

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Alaskan brown bears
wait for them at the waterfalls.

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Without these fish,

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the bears cannot build up
the fat reserves they need

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to sustain themselves
through their long winter hibernation.

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There is fierce competition
for the best fishing spots.

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[growling]

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[gulls cawing]

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Where water flows over hard rock,
it collects few nutrients,

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so few plants can grow in it.

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Here, in South America, however,

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this plant, Macarenia,
manages to flourish.

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For a few months each year,

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when the water level is low enough
for sunlight to reach the bottom,

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the Macarenia bursts into bloom.

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This is the Caño Cristales,
Colombia's rainbow river.

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Sometimes, however,
water disappears underground,

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beyond the reach of light,

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and there, no plants can live.

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Thirty percent of the planet's fresh water
lies beneath the surface of the land,

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either within the substance
of porous rocks

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or as subterranean lakes and rivers.

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Made slightly acid by rain,

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it slowly dissolves limestone,
creating great caves.

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A labyrinth of such passages and chambers
underlies much of the state of Florida.

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For the most part, they're barren.

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But where the water comes to the surface,
it's full of life.

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Fish are abundant.

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And so are fish eaters.

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Otters.

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All over the state,
fresh water bubbles to the surface

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from the greatest concentration of springs
on Earth.

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They feed rivers and pools,
in which all kinds of life flourish,

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including one of Florida's specialities...

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manatees.

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Many spend the summer in the sea,

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but when winter approaches,
they swim up the rivers,

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which are relatively warm.

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And there they graze
on an abundance of freshwater plants.

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But human beings are now taking
so much water from these springs,

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and polluting many of the others,

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that the manatees
are losing their winter homes.

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Rivers, being comparatively shallow,
warm quickly,

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and in spring, across Europe,

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the rising temperatures
trigger a sudden surge of life.

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[tweets]

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On Hungary's Tisza River,
giant mayfly are starting to emerge.

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For three years,
they've lived underwater as larvae.

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Now, in just three hours,

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millions of the winged adults
dance together and mate before they die.

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This extraordinary spectacle
was once common in Eastern Europe,

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but so many rivers
now have stabilized banks

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and are badly polluted

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that the mayflies
have largely disappeared.

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But when the rivers are clean,
wildlife is quick to return.

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The kingfisher,
the most glorious of divers.

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The osprey, the most skillful of graspers.

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Iguazu, on the frontier
between Brazil and Argentina.

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These are
the largest waterfalls on the planet.

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Thousands of tons of fresh water
thunder over them every second.

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Much of Iguazu's water
comes from the Amazon rainforest,

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a thousand kilometers away.

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There, it rose as vapor
from the surface of the jungle canopy.

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A single tree can give off
a thousand liters a day.

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As the vapor rises into the sky,
it condenses into clouds.

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Twenty billion tons of water
leave the forest each day,

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more than travels
down the Amazon River itself.

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If the rainforest is destroyed,

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this life-giving cycle will be broken.

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As the clouds travel across the continent,
they shed their water,

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irrigating farmland and forest alike.

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And on the plains of Brazil,

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they create
the largest tropical wetland on Earth,

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the Pantanal.

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Each year, however,
seasonal changes reduce the river's flow,

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and the Pantanal shrinks
to just a few river channels.

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This suits the top predator very well.

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The jaguar.

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It's a competent swimmer, but in water,

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it can't make the killing pounce
which makes it such a fearsome hunter.

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[mewls]

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Now, in the dry season,

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the banks can get somewhat crowded.

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But the jaguar has spotted prey
on the river's edge.

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Capybara.

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It must get close to be successful.

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Two capybara incautiously
are standing in the shallows.

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They have seen one another.

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Which will run first?

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[barks]

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Farther along the river,
dense vegetation provides better cover,

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but the bank here is quite high.

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Capybara have acute hearing.

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-One noisy footfall...
-[branch snaps]

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...and the chance is lost.

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Another failure.

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[barks]

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Perhaps it's time to try a different prey.

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Tackling one of these would be risky,

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but the jaguar is really hungry.

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If a jaguar is to catch a caiman,

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it must bite its neck and then hold on
to prevent the caiman striking back.

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It has to get into a position
directly above its prey.

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This is dangerous.

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00:26:21,413 --> 00:26:24,583
The caiman rolls
to try and drown the jaguar.

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00:26:30,380 --> 00:26:32,632
Predator and prey seem evenly matched.

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00:26:39,973 --> 00:26:41,933
The jaguar won't let go.

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00:27:01,119 --> 00:27:06,750
After 20 minutes, and near to exhaustion,
the jaguar wins.

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Sometimes, a river's downward journey
is interrupted by lakes.

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Together, they contain 40 times more water
than all the world's rivers combined.

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Africa's Lake Tanganyika

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holds almost a fifth
of all accessible fresh water on Earth.

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00:27:44,245 --> 00:27:49,376
But, considering its great size,
Tanganyika contains little life.

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00:27:55,548 --> 00:27:58,385
It's almost a kilometer and a half deep,

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00:27:59,094 --> 00:28:03,723
but at the bottom the water barely moves
and there is no oxygen.

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It's only close to the surface,
in its top 150 meters,

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that the water contains enough oxygen
for life to exist.

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00:28:17,821 --> 00:28:20,990
But here, it flourishes in abundance.

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00:28:24,077 --> 00:28:28,289
Two hundred and fifty species
of cichlid fish have evolved here,

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00:28:28,373 --> 00:28:30,542
many of which are found nowhere else.

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00:28:40,760 --> 00:28:44,597
Competition in these crowded waters
is intense.

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00:28:47,809 --> 00:28:51,730
A male callipterus cichlid
collects shells.

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00:28:53,940 --> 00:28:58,278
The more shells a male has,
the more females he will attract.

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00:29:02,991 --> 00:29:05,076
And this one is doing very well.

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00:29:34,647 --> 00:29:37,776
His neighbor has a rather smaller mound.

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00:29:43,740 --> 00:29:45,992
And the neighbor is a thief.

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00:29:52,123 --> 00:29:53,833
As soon as he turns his back,

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the thief swoops in...

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00:30:01,800 --> 00:30:03,384
and steals a shell.

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00:30:14,187 --> 00:30:18,650
The hardworking owner of the larger mound
doesn't seem to notice.

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00:30:21,402 --> 00:30:25,073
So, the thief commits the crime again...

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00:30:26,991 --> 00:30:27,826
and again...

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00:30:32,205 --> 00:30:35,667
until he has built the largest mound.

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The shells are not just for display.

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They will be used by the females
as cradles.

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One arrives.

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00:30:52,392 --> 00:30:55,603
She's tiny, only a tenth of his size.

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00:30:57,689 --> 00:31:01,276
She's so small,
she can slip inside a shell.

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00:31:10,243 --> 00:31:15,331
There, she lays her eggs,
and the male quickly fertilizes them.

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00:31:18,126 --> 00:31:23,423
She will then stay inside protecting them
for up to a fortnight until they hatch.

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The emperor,

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00:31:30,430 --> 00:31:33,057
the largest of all the cichlids
in Tanganyika.

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00:31:35,977 --> 00:31:40,398
At almost a meter long, this female
must raise her young in the open.

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00:31:46,321 --> 00:31:50,742
Guarding them is therefore
a full-time job for both parents.

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00:32:00,126 --> 00:32:03,630
But the future for all these fish
is uncertain.

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00:32:07,091 --> 00:32:11,387
As global temperatures rise,
Lake Tanganyika is warming.

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00:32:13,431 --> 00:32:16,726
Its waters are no longer mixing as well
as they once did,

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00:32:17,226 --> 00:32:20,563
so the top oxygenated layer is reducing.

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00:32:31,074 --> 00:32:33,493
The Mekong River in Southeast Asia.

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00:32:34,369 --> 00:32:39,207
Four thousand kilometers long
and with the widest falls anywhere.

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00:32:43,127 --> 00:32:47,882
Today, over 60 million people
depend upon it for their livelihood.

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00:33:11,114 --> 00:33:15,076
The monsoon rains create
such a colossal surge of water

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00:33:15,159 --> 00:33:17,787
that the falls themselves
almost disappear.

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00:33:20,832 --> 00:33:23,084
The water is loaded with sediment,

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00:33:23,167 --> 00:33:27,171
collected during the Mekong's long journey
from the Tibetan Plateau.

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00:33:30,508 --> 00:33:35,221
Even before the flood,
the water covers a vast area of land.

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00:33:41,352 --> 00:33:44,230
These exposed roots are evidence

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00:33:44,313 --> 00:33:47,275
of the great rise in water level
that is to come.

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00:33:52,780 --> 00:33:54,574
When the main flood does arrive,

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00:33:54,657 --> 00:33:57,660
the trees are submerged
up to their branches.

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00:34:02,540 --> 00:34:07,295
For a few months, the floodwaters create
the planet's greatest breeding grounds

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00:34:07,378 --> 00:34:08,713
for freshwater fish.

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00:34:12,675 --> 00:34:16,721
One species
has a particularly ingenious solution

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00:34:16,804 --> 00:34:20,641
to the problems of living
in shallow, oxygen-poor water.

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00:34:23,936 --> 00:34:26,147
The Siamese fighting fish.

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00:34:31,611 --> 00:34:35,073
The male breathes
by gulping air from the surface,

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00:34:35,156 --> 00:34:36,699
and during the breeding season

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00:34:36,783 --> 00:34:40,703
he uses that ability
to build a raft of bubbles.

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00:34:42,580 --> 00:34:45,166
Day after day he labors.

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00:34:52,048 --> 00:34:56,886
A female, waiting nearby,
rises to inspect the raft.

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00:35:11,859 --> 00:35:16,906
They wrap themselves around one another
in a tender embrace.

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00:35:26,874 --> 00:35:30,628
This union encourages her
to release her eggs.

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00:35:33,631 --> 00:35:37,093
As they sink downwards,
the male fertilizes them.

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00:35:42,932 --> 00:35:44,934
Both carefully collect them,

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00:35:49,730 --> 00:35:54,902
and then blow them, one by one,
into the bubble nest.

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00:35:58,865 --> 00:36:01,868
Oxygen is scarce in these stagnant waters,

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00:36:01,951 --> 00:36:04,328
but the eggs
will get enough from the bubbles

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00:36:04,412 --> 00:36:05,788
to allow them to develop.

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00:36:08,457 --> 00:36:11,335
The climax of the flood is still to come.

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00:36:14,005 --> 00:36:17,675
Eventually,
so much water surges down the Mekong

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00:36:17,758 --> 00:36:23,389
that the Tonlé Sap Lake expands
to five times its dry-season size.

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00:36:25,766 --> 00:36:30,438
Vast numbers of fish now swim
into these new feeding grounds.

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00:36:32,440 --> 00:36:36,277
People have harvested this seasonal event
for millennia.

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00:36:37,820 --> 00:36:40,114
They set nets across half of the river,

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00:36:40,615 --> 00:36:42,533
leaving the other half free

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00:36:42,617 --> 00:36:45,453
for the rest of the fish
to swim on and breed.

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00:36:49,540 --> 00:36:55,171
The Mekong, in fact, supports
the largest inland fishery in the world.

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00:37:01,552 --> 00:37:06,015
One-fifth of all the freshwater fish
caught by people worldwide

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00:37:06,515 --> 00:37:08,643
comes from this one river system.

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00:37:11,020 --> 00:37:13,064
But the future of the Mekong,

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00:37:13,147 --> 00:37:15,650
like that of so many other rivers
around the world,

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00:37:15,733 --> 00:37:17,693
is increasingly at risk.

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00:37:21,113 --> 00:37:23,157
We have changed the natural flow

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00:37:23,241 --> 00:37:26,786
of more than two-thirds
of the planet's longest rivers

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00:37:26,869 --> 00:37:30,998
by, amongst other things,
building dams across them.

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00:37:39,507 --> 00:37:44,136
So now, many rivers across the world
no longer flow.

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00:37:50,977 --> 00:37:54,897
Here in East Africa, in Ruaha, Tanzania,

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00:37:55,856 --> 00:37:58,317
these elephants are searching for water.

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00:38:01,779 --> 00:38:08,077
Each needs to drink 200 liters every day,
and there doesn't seem to be any here.

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00:38:09,704 --> 00:38:14,709
But the elephants know that baobab wood
contains a lot of moisture.

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00:38:17,211 --> 00:38:21,215
And in an emergency,
they eat it in great quantities.

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00:38:28,514 --> 00:38:31,100
Lions also need water.

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00:38:35,771 --> 00:38:41,027
And conveniently for the lions,
water is where their prey will gather.

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00:38:44,905 --> 00:38:48,868
So both predators and prey
head for the rivers.

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00:38:54,832 --> 00:38:56,334
Until 30 years ago,

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00:38:56,417 --> 00:38:59,337
rivers in this part of Africa
never ran dry.

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00:39:04,717 --> 00:39:08,637
Now, agriculture upstream
is taking great quantities,

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00:39:08,721 --> 00:39:13,351
and during the dry season,
the rivers shrink into isolated pools.

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00:39:30,493 --> 00:39:36,207
Hippos rely on flowing water
to keep themselves cool during the day,

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00:39:36,832 --> 00:39:40,211
but now they have to make do with mud.

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00:39:44,465 --> 00:39:48,427
As the water level falls still further,
they cram together.

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00:39:52,640 --> 00:39:54,475
Tempers begin to fray.

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00:40:03,901 --> 00:40:05,569
[roaring]

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00:40:14,787 --> 00:40:20,709
Each day, the mud pools shrink further,
and the hippos' plight worsens.

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00:40:33,806 --> 00:40:36,976
Buffalo, in the urgent search for water.

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00:40:49,071 --> 00:40:52,950
The lions are already here
at this water hole.

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00:41:01,834 --> 00:41:07,131
However, the buffalo are driven on
by their desperate need for fresh water.

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00:41:20,936 --> 00:41:23,314
They need to drink every day.

318
00:41:38,787 --> 00:41:41,081
Every drink is now a risk,

319
00:41:42,833 --> 00:41:44,793
but the buffalo have no choice.

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00:42:59,743 --> 00:43:03,747
As the drought continues,
the buffalo begin to weaken.

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00:43:05,624 --> 00:43:08,586
The odds are changing,
in the lions' favor.

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00:43:24,476 --> 00:43:27,187
The elephants have reached their river.

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00:43:31,025 --> 00:43:35,112
Nothing else is here because it's dry.

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00:43:47,207 --> 00:43:50,878
But elephants can find water
where others can't.

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00:43:52,671 --> 00:43:57,051
They use their trunks to dig holes
in the sand of the riverbed.

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00:44:06,560 --> 00:44:09,271
The extraordinary sense of smell

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00:44:09,355 --> 00:44:13,067
that enables them to detect open water
from kilometers away

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00:44:13,776 --> 00:44:17,404
also helps them
to locate places underground

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00:44:17,488 --> 00:44:20,282
where it lies closest to the surface.

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00:44:25,037 --> 00:44:29,291
In severe droughts,
the wells they dig can be their lifeline.

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00:44:38,592 --> 00:44:42,471
The hardships of the dry season
have always been part of life

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00:44:42,554 --> 00:44:44,306
on East Africa's plains,

333
00:44:45,182 --> 00:44:46,850
but as the planet warms,

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00:44:46,934 --> 00:44:50,604
and we ourselves take so much water
for our own purposes,

335
00:44:51,188 --> 00:44:54,692
the droughts are becoming more frequent
and more severe.

336
00:45:08,997 --> 00:45:12,876
The Platte River,
in Nebraska, North America.

337
00:45:30,894 --> 00:45:36,358
Each year, sandhill cranes arrive here
as they travel north across America

338
00:45:36,442 --> 00:45:40,446
on one of the last great migrations
made by any animal.

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00:45:42,781 --> 00:45:45,325
It's one of their crucial staging posts.

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00:45:53,959 --> 00:45:58,547
The river once flooded the prairie
for a mile in all directions.

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00:46:02,134 --> 00:46:06,680
This was a perfect place
for them to feed and rest.

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00:46:12,519 --> 00:46:14,980
Now, we have dammed the river

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00:46:15,439 --> 00:46:18,484
and taken so much of its water
for our own use

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00:46:19,026 --> 00:46:22,404
that there is little space left
for the cranes.

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00:46:36,919 --> 00:46:41,507
But conservationists
now manage the river's flow in such a way

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00:46:42,049 --> 00:46:45,803
that it still creates the sandbanks
the cranes need.

347
00:46:57,981 --> 00:47:00,984
We are not alone in our need for water,

348
00:47:06,949 --> 00:47:12,830
but we have the ability to ensure
the fresh waters of the world do flow,

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00:47:14,915 --> 00:47:19,378
and we alone can determine
how they are shared.

350
00:47:29,888 --> 00:47:34,393
Please visit ourplanet.com
to discover what we need to do now

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00:47:34,476 --> 00:47:36,728
to ensure fresh water keeps flowing.

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00:47:39,231 --> 00:47:45,153
♪ I can hear the whole world
Singing together ♪

353
00:47:47,781 --> 00:47:53,704
♪ I can hear the whole world
Say it's now or never ♪

354
00:47:56,582 --> 00:48:00,836
♪ 'Cause it's not too late
If we change our ways ♪

355
00:48:00,919 --> 00:48:04,423
♪ And connect the dots to our problems ♪

356
00:48:04,798 --> 00:48:10,888
♪ I can hear the whole world
Say we're in this together ♪

357
00:48:10,971 --> 00:48:12,723
♪ We're in this together ♪