Freshwater Britain The Nature of Britain

Do you know what?

I think it's going to rain.

Water.

Can you imagine anything more pure, more elemental?

There's not a plant or animal on earth that can do without it.

And when it falls as rain, it brings the entire British Isles to life.

Like water off a duck's back, it drips from the leaves.

The drips become trickles,

trickles become streams.

And before you know it, a roaring river is born.

Water seems such simple stuff,

yet when it interacts with the land, it creates such extraordinary variety.

Rushing streams and lazy rivers, reed beds and bogs, lakes and canals.

The only thing they have in common is that water runs through them.

But how can something so pure and simple create so many opportunities

for wildlife, and produce such a diversity of habitats?

Come with me on a journey from the source to the sea, as we discover Freshwater Britain.

What better place to start than Scotland?

So wet, they had to invent the Macintosh.

They say if you can see the hills, it's about to rain.

And if you can't,

it's raining.

The uplands are where most of our rivers start.

And with their heavy rains, comes drama.

The first thing that strikes you is the water's incredible power.

Tonnes of it come cascading over these rocks every second.

I've got to shout just to make myself heard.

CASCADING WATER THUNDERS

Now, you and I might be tempted to go with the flow.

But there's one creature that fights it all the way.

The Atlantic salmon.

It's such a Herculean effort.

Even though they were born to swim and born to do this, it must take so much energy out of them.

They started life in this very river, but at just a few months old were swept out to sea.

They spent up to four years in the open ocean, building up the strength to return.

But to make it, they need every ounce of energy they possess.

Only upstream will the salmon find a mate, and to get there

it must battle against the flow every step of the way.

Beyond these falls, nestled in the Highlands, is the river where they started life.

They're drawn back by its memory.

After four years, they can still remember the taste.

As their energy ebbs, it's that memory that drives them on.

They won't eat or rest until they've reached their birthplace, or died trying.

As the salmon risk their lives battling this torrent of water,

they pass another creature that actually takes advantage of the flow.

DIPPERS SING

This is a dipper.

It's related to the robins and wrens in your garden.

But would they do this?

The dipper is the only British songbird to hunt underwater.

It's even known to swallow stones to help it sink.

And the thing that makes life tough for a salmon keeps the dipper alive.

They say that still waters run deep, but the opposite's also true.

Fast-flowing water, on steep slopes, runs shallow.

And that's why you only find dippers here.

The water's shallow enough to dive down for their dinner.

DIPPERS SING

But water doesn't just flow over the landscape - it creates landscapes.

The riffles, pools and waterfalls that make up the dipper's home

have been carved out by the water's erosive power.

It's this power that makes the salmon's journey so difficult.

But it's also the very reason that it has to make the journey.

It's only here, in the very place where they were born,

that the water's fast enough to scour the gravel clean of silt.

Without fast water, the eggs they've come all this way to lay, would simply be buried alive.

The ones that made it now assume their breeding colours, a rich red.

And for the males, hooked jaws, because the battle is no longer

against the flow, but with each other.

On arrival, the females turn their tails from the task of swimming, to digging a nest.

The effort can leave them in tatters.

The males, meanwhile, fend off the local competition,

although having worked so hard to get here, rivals can prove rather persistent.

Once they've seen off all comers, they set to wooing their mate with a shivering caress.

But fighting the flow has hit them hard.

The fast water will keep their eggs alive, but battling it all the way has left them exhausted.

For almost every one of them, this is the last journey they'll ever make.

As the year ends, their bodies litter the banks.

And these fallen fish make a meal fit for the king of birds.

On the Isle of Mull, sea eagles feast on the dead and the dying.

But beneath the fast-flowing water, the salmon have left their legacy.

A legacy forged through raging rivers and towering falls.

Buried beneath the gravel are hundreds of thousands of developing eggs.

Next spring they'll hatch, and before long, they too will be swept out to sea.

Most will never make it.

But crucially, a handful will survive to return.

But it's not just wildlife that's affected by fast-flowing water.

Its erosive powers have created some of

Britain's most memorable scenery, like here in the Yorkshire Dales.

Water is powerful stuff.

Every cubic metre weighs a tonne.

So it's no surprise that it's had a greater impact in shaping our landscape than anything else.

Especially here, in a place close to my heart, the north of England.

If you did geography at school, chances are

you've studied this place - Malham in the Yorkshire Dales.

Nearby, Gordale Scar, carved out over millions of years by the Gordale Beck.

And Malham Cove, looking for all the world like a waterfall without the water, which is exactly what it is.

At the end of the last glaciation, meltwater plummeted over these cliffs.

And during the last Ice Age, vast rivers of frozen freshwater - glaciers -

bulldozed their way through Britain, giving us the deep U-shaped valleys of the dales,

and the dramatic scenery of the Lake District.

Across the border, in County Durham, the River Tees is responsible for

creating one of the highest waterfalls in England.

The mighty High Force.

All over Britain, freshwater has created some of our most dramatic and beautiful landscapes.

And everywhere it flows it brings life to our British Isles.

But it's not all drama on a huge scale.

Spare a thought for the smaller creatures living up here.

I mean, life's no picnic for them either in fast running water, which is what I'm here to show you.

Now then, the place to look for them is underneath these rocks.

Oh, look at that. Caddis fly larvae.

They surround themselves with these lumps of stone,

to protect them from the water and from predators. Oh and here...

Oh, come on. Look at that.

Flat as a pancake. I haven't squashed it. It's a mayfly larva.

It's flat like that for a good reason so the water passes over it,

rather like air flowing over a Formula 1 racing car.

That's something that all the insects here share. They're clinging on for dear life.

When it's underwater and not stuck to my finger, you can really see

how perfectly shaped the mayfly larva is.

And here's another caddis.

This one builds a stone house to weigh it down, but lugs it around.

Not easy, but better than being swept out to sea.

So given the difficulties, what is it that makes fast-moving water so attractive to insects like these?

Well, it's another insect, and one of our most beautiful

freshwater creatures that can help us unravel the mystery.

And to see that, we have to leave the turbulent waters of our uplands

and journey south, to one of our gentler, lowland rivers.

Only here can we see another advantage that fast flow brings.

This is the River Thame in Buckinghamshire.

And on lazy summer days, damselflies dance over the water's surface.

These are banded demoiselles, and they love slow-moving rivers - except when it comes to mating.

Then, it's the faster-flowing areas that everyone wants.

And the males, in their shining metallic armour, are prepared to do battle over them.

By landing, they lay claim to a small stretch of river.

But that takes nerve in the face of an adversary's flashing wings.

Crucially, they've captured an area of slightly faster-flowing water.

It might only be the smallest riffle as the river races around a fallen branch.

In fact, to you or me, it may not look much different.

But believe me, to the female damselfly, this slightly faster water is incredibly important.

And the males gamble everything to show the watching females just how fast it is.

Risking attack from below, the males throw themselves on the water's surface and float downstream.

Only if she's suitably impressed will the relationship be consummated in a cartwheel embrace.

And the reason for her careful choice is finally revealed.

In this tiny patch of fast-flowing water, the female damsel struggles through the water's surface.

And there, she lays her eggs.

For only here, where the current runs swiftly,

is there enough oxygen to give her young the best possible start.

Imagine being locked in a room where all the doors and windows are sealed.

It wouldn't be long before the air became stagnant and you started to suffer.

But then imagine opening all those doors and windows,

and allowing a cool, refreshing breeze to blow through.

Well, that's what current brings -

lots of crystal-clear water that's packed with oxygen.

In the slower flow, insects like the diving beetle larva

rely on snorkels so they can breathe from the surface.

Or, like scuba divers, some insects take their air supply with them.

The silvery sheen on this water boatman is an air bubble it carries with it.

But the damselflies have chosen a different path.

By risking the faster flow, their young can thrive in water

rich with oxygen, which is just as vital to wildlife underwater, as it is for us above.

To discover the next factor affecting our freshwater habitats,

why don't you join me on the banks of another sun-drenched lowland river?

Oh no, sorry - that was just drenched!

Got your waders on? Come on then.

What I'm hoping is that I can get you close to one of Britain's best-loved animals.

It's one of the top predators on this river here, and there's one every few hundred yards.

But what we need is a lot of patience, some peace and quiet

and this branch.

What I need to do now

is tuck myself in here, make myself as invisible as possible, and then not move a muscle

because if it sees me, it won't come anywhere near.

Are you set?

All we've got to do now is wait.

It's just that nobody told me quite how long.

Glamorous business, isn't it, this telly lark?

But eventually, a familiar call.

BIRD CHIRPS

Can you hear? Can you hear that?

That's it.

It always sounds to me like a boatswain's whistle,

piping somebody aboard.

BIRD CHIRPS

Got to keep absolutely still.

It must be Britain's most brilliant bird.

Even on a dull day it seems to shine.

Suddenly the rain

and the numb bum don't matter any more.

It's an amazing sight.

But the fact that these kingfishers are here, and in such large numbers on these lowland rivers,

tells us something very important about this particular freshwater habitat.

To support so many kingfishers, the water here must be packed full of fish.

But why are there so many?

To answer that I need to find the perfect place to do a spot of fishing.

And where better than the Itchen, a chalk river in the heart of Hampshire.

You've only got to look closely at a fly fisherman's tackle to realise the diversity of species out here.

Perhaps I'd better rephrase that.

Come and look at this.

Sculpins and muddlers, zonkers and minkies.

Aren't they wonderful names?

And you've never seen so many different kinds of fishing fly.

Here we have things like a daddy long legs, all hand tied.

Here, larvae of different kinds of grubs and flies that might land on the water.

And the reason there are so many of these is that there are so many

insects on the river that the trout will take, and the fly fisherman has to do his best to emulate nature.

But why are there so many of them?

Why is this stream so rich in insect life?

The answer is because it runs over chalk.

It's all down to the rock.

The figures decorating these hillsides owe their colour to the chalk rock below.

But the rock does more than provide a palette for ancient artists.

Chalk rivers start life as springs, emerging from deep within these hills.

They're filtered crystal clear by the soft rock,

which also breaks down in the water, adding minerals.

These nourish a rich underwater garden, full of life.

Wherever the rock is soft, water can easily pick up minerals.

But chalk rivers are special.

It's their unique qualities that make the region famous for its water meadows, like these in Salisbury,

immortalised by the artist John Constable.

Beautiful views for which, ultimately, we have the surrounding rock to thank.

And if you want even further proof of how rich this habitat is, you need only take a peek

beneath the watercress beds for which this region is famous.

Lurking here in the quiet Hampshire countryside is one of Britain's most voracious predators.

An animal with a deadly venomous bite.

It's here because this is one of the few habitats in Britain

productive enough to support its terrifying appetite.

It's...

..a shrew.

A water shrew.

Not a reason to stay indoors, but it does have a venomous bite.

Harmless to us, but to its prey, quite deadly.

Water shrews have no time to hang about.

They're permanently ravenous -

attacking sticklebacks, and even small frogs.

Good job those venom-laden teeth aren't any bigger.

And they're here because of their favourite food.

Below the surface, like shoals of clockwork toys, swim tiny freshwater shrimp.

Crucially, the water is packed full of nutrients

dissolved from the soft rock.

It's the chalk, crammed with calcium,

that enables these tiny creatures to build their shells

and exist in such numbers.

Food enough to satisfy the most ravenous and rapid shrew.

It's only by slowing them down

that you can tell what on earth is going on.

Shrews can smell under water.

This is no mean feat for a mammal.

Noses don't usually work down here.

But by blowing tiny bubbles, and sucking the air back up that snout,

they can sniff out the sweet smell of even the smallest shrimp.

So without the soft rock, the plants wouldn't have the nutrients

they need to grow lush and thick,

nor the shrimp the calcium for their shells.

And without them, the most voracious predator in Hampshire

would soon run out of shrimp, and steam.

But not all our rocks are as easily broken down as those soft southern ones.

Let's leave Hampshire and travel back to Scotland,

this time to visit the most famous bit of freshwater in Britain...

..Loch Ness.

Loch Ness is big, very big.

It's so big that there's more water beneath my tiny boat

than in all the rivers of England and Wales combined.

It's enough to make you feel a bit vulnerable,

especially when you consider what most people come here looking for.

There's something mysterious beneath these dark waters.

Something that reveals a great deal about this particular freshwater habitat.

Oh, there you are.

No, I've not come looking for Nessie,

but there is a monster lurking down there in the depths of Loch Ness.

And here it is.

A ferox trout -

ferox from the Latin, meaning "ferocious".

And they are!

They start life feeding on insects,

but in Scottish lochs some of them turn, growing huge jaws

and swelling to twice their normal size, becoming...well, monsters.

They're the top predator in most Scottish lochs, and eating

their fellow fish boosts their growth and lengthens their lives.

Among fishermen, these ferocious ferox trout are almost as legendary as the great Nessie herself.

But to find out what makes them the monsters they are, I need to look

not down into the water, but back on the shore.

It's these - the very rocks of Scotland themselves.

Now, when water flows over soft rock, it picks up mineral nutrients that are vital for plant growth.

But with rocks as hard as these, those nutrients remain locked up.

So if the plants can't grow, insects can't feed on them,

and the trout can't feed on the insects, so they turn into monsters.

The ferox trout turn to eating their fellow fish because there aren't enough nutrients

to support their normal prey, and this has big implications for the loch's more famous resident.

Much as we'd like to believe that a prehistoric monster lurks beneath the waters of Loch Ness,

the surrounding rocks mean that this sort of freshwater habitat

is just too nutrient-poor to support a resident colony of predators like Nessie.

< GURGLING

Probably nothing.

We've seen the importance of the rock to freshwater habitats.

But the other reason Loch Ness is so devoid of life is because it's dark.

The peat in the water makes great whisky,

but its dark-brown stain means sunlight struggles through.

And without light, not much can survive.

The reason divers spend a fortune travelling to the Mediterranean or

Red Sea is that the clear, shallow water lets in loads of light,

encouraging plant life, which in turn supports the shoals of fish the divers come to enjoy.

But this isn't the Med,

this is Britain, and about as far from the sea as you could get.

This is Stoney Cove, a flooded freshwater quarry

in the heart of England's Midlands, and a national centre for diving.

Cynical old sea dogs rather disparagingly call it the headquarters of the Birmingham navy.

Now, granted, this is not the most exotic location

I've ever brought you to, and this water is decidedly parky.

But, believe me, down there there is something every bit as amazing

as what you'd find on the Great Barrier Reef.

Come on, follow me.

Because large areas of the lake are shallow,

sunlight can reach the bottom, allowing plants to grow, insects to flourish and fish to thrive.

And where there are this many fish, you'll find one of freshwater Britain's top predators.

If you didn't know this was freshwater, you'd think the fish

cruising these wrecks were barracuda, but they're pike.

Their ferocity is legendary.

But for just a handful of days each year, perhaps only hours, they show a more sensitive side.

And for the first time ever, we can share it with you.

Even feared predators have to be parents, and in the spring, as the sunlight warms the water,

these solitary hunters throw aside their differences

and delicately woo their prospective partners.

As the time nears to shed her eggs,

the female resting in the reeds attracts a host of hopeful males.

And when the attention gets too much,

she leads an entourage around the lake...

..each attentive male vying to be the perfect partner.

The outcome - thousands of eggs.

The young pike will hatch and grow, until one day they, too,

will join the ranks of feared predators stalking Stoney Cove...

..in waters made rich with prey by the sunlight.

Well, it may not be the Med, but Britain's freshwater habitats

can be every bit as beautiful,

and our wildlife behaviour just as fascinating.

But after a quick dip in there, I ain't half ready for a cup of tea.

Thank you. I don't know whether to drink this or wear it.

Cheers.

Lovely.

From the still waters of flooded quarries,

let's join the river again, on its journey to the sea.

We're off to East Anglia to visit a freshwater habitat that rivals the richest on Earth.

And that means there's one animal that can thrive in greater numbers here than anywhere else.

This is its nest, but it's not made by a bird...

..it's made by a mammal.

And high in the reeds you'll find its newborn babies.

Each one is the size of a raisin.

The whole litter weighs less than a tuppenny piece.

When they're born, their eyes are closed to the dangers that lurk outside.

Their days are spent resting, perhaps dreaming, while their mother keeps them warm.

At just eight days old, they've grown fur and opened their eyes.

But it'll soon be time to leave this sanctuary.

At just two weeks old, they clamber up into the reeds

for the very first time, to face the big, wide, world.

And what a world!

Crowded with people.

And with powerful predators lurking just beneath the surface.

These are the Norfolk Broads.

And the mammal?

The commonest among the reeds isn't a water shrew, or a water vole,

but a harvest mouse, not only a farmland creature,

but a freshwater one.

These are the smallest rodents in Europe.

Even fully grown they can be as little as a couple of inches long.

They're superb climbers,

possessing something not one African monkey can boast -

a truly prehensile tail.

It allows them to clamber to the very tops of the reeds,

where they feed on the seeds.

It's these climbing skills that make the harvest mouse at home in our farmland crops.

But it does even better here among the reeds.

And it's the reeds that make this freshwater habitat so productive.

We've seen how the river's speed gives it the energy to pick up and sweep along nutrients.

But wherever it slows, it no longer has the strength to carry them.

These reeds act like a huge brake, slowing down the river and forcing it to drop its cargo.

As a result, reeds are among the fastest growing plants on Earth.

They make these wetlands almost as productive as a tropical rain forest.

It's the perfect place to hide one of our strangest creatures.

For thousands of years, this has been a place of mystery.

It's almost prehistoric.

So perhaps it's no wonder that tusked beasts still roam the reeds.

These are Chinese water deer.

In their native China, they're so rare that Chinese scientists wanting

to learn more about them came to Britain to study them instead.

They're considered rather primitive, having no antlers, only tusks,

sported by both the males and females.

They're solitary for most of the year, but come December, the time of the rut,

they stake out their territories, marking the boundaries with scent from a special gland on their face.

When you lead such a secretive life, these scented messages

can be read by others for days, warning them to steer clear.

But some males just don't get the message.

Those tusks aren't just for show, you know.

This tangled forest of reeds means it can be really hard to find anyone.

The deer may leave scented messages, but the birds have another solution.

WARBLING

That's how they do it. Did you hear that?

That chug, chug, chug, chukachukachuk.

A reed warbler, which has come over here from Africa to nest.

And like all birds that live in reeds

and tall undergrowth like this, it needs a loud and penetrating call to advertise its presence.

But in so doing, it lays itself open to outrageous deception.

Carefully woven into the reeds is the reed warbler's nest,

and inside, the first chick has already hatched.

It's weak and helpless, until its mother's back is turned.

The parent looks on, seemingly in disbelief.

This isn't normal for a young reed warbler.

But blind to junior's behavioural problems,

like all good parents Mum and Dad work from dawn to dusk

to provide for what's now their only child.

Who is perhaps growing a little overweight on all their attention.

The parents, as always, seem to be the last to realise.

Until one day, surely even they can't deny

that a terrible mistake has been made.

Of course, this isn't a reed warbler at all.

It's a cuckoo.

It would be wrong to judge the cuckoo's life of deception by our standards.

But if you did, I'd blame the parents.

After laying its egg in as little as ten seconds,

its mother deserted and upped sticks to Africa.

The young cuckoo will never meet Mum and Dad, and has to make the long journey south alone.

IT CUCKOOS

Despite their skill, cuckoo numbers are in decline.

But not here. Reed warblers, unlike other cuckoo hosts, are doing well.

So this is one of the few places where the cuckoos are sure to find

enough surrogate parents to make the long journey from Africa worthwhile.

The dumping of the river's nutrient cargo

doesn't just happen in reed beds, it occurs wherever the river slows,

and there's one habitat it creates that's so lush

it tempts one winter visitor hundreds of miles across the ocean.

Every year, thousands of whooper swans travel to Britain from Iceland.

And it's here that most of them come - the Ouse Washes of East Anglia.

As rivers near the flatter areas toward the coast,

they slow, spread out, and can flood the low-lying land.

This is the biggest area of flooded grassland in Britain,

and the swans come here in their thousands,

taking advantage of grass growing lush due to the seasonal floods.

THEY HONK

It's the freshwater that attracts the whoopers,

and thousands of other birds, from as far away as Arctic Russia,

making this not just one of the most important areas for birds in Britain,

but in the world.

From the Ouse Washes, it's just a few miles to the end of the river's journey,

and ours.

We've finally reached the sea.

This is the Wash - one of the biggest estuaries in Britain, and a favourite holiday destination.

But I wonder how many of the sun- seekers along this stretch of coast

realise that it's freshwater that makes this such a special place?

Not now,

but in the depths of winter.

For a drop of freshwater heading downstream,

the seaside marks the end of the ride.

All that playful tumbling over rocks and rapids, and the gliding lazily by grassy banks is over.

The coast is the start of a new life, as part of something much bigger - the ocean.

But before embarking on this new adventure, the river has one last thing to do.

Ever since it first began to flow, it's toyed with sand and silt,

carried it from far inland.

But at the coast, as it comes of age,

it leaves those play things behind, creating the estuary.

And drawn here, every winter, are huge flocks of wading birds that swirl in the sky.

But that's a different story.

Our journey is over,

a journey that started with a single drop of rain.

So the next time you raise your eyes to the heavens

and see rain clouds building on the horizon, don't be downhearted.

Remember that it's rain that supplies the kingfisher with food

and allows the salmon to swim upstream.

It's rain that keeps the damselflies dancing

and the Loch Ness legend alive.

Every last drop brings life to the land and, for me,

it seems that that is a small price to pay

for getting a little bit damp.