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Ten million species live on
planet earth.

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Each one is remarkable.

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But none can survive on its own.

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All life depends upon connections.

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Unexpected, invariably complex,
beautiful relationships between
millions of plants and animals.

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This time, in our seasonal forests,

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why does this lynx need
a caterpillar?

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Why does the tree need the fish?

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And why does this truffle fungus
need one of these?!

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Flying squirrel!

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Connections like these form
the planet's great ecosystems.

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They're vital for all life.

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I want to show you our world
as you've never seen it before.

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JAUNTY MUSIC

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New England in autumn.

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There really can't be a more magical
place anywhere on earth,

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to appreciate that dramatic
transition between summer
and winter.

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But we mustn't get blinded by
this natural fiesta,

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because such an extreme
transformation
is a huge challenge for life.

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And autumn is just one of many
transformations the forest
must face.

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From summer to winter, this land
of plenty will appear to collapse,

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before attempting to rebuild itself
all over again in the spring.

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To see how, I'm going to, what is
for me, the greatest seasonal
forest on the planet.

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The wooded wilderness that stretches
right across North America.

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From the land of the Canadian lynx,

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to the land of the grizzly bear.

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Our story begins in autumn.

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As the days are drawing shorter,
less light is feeding the forests.

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Deciduous trees are shedding
their leaves.

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Many creatures are burrowing away
to escape the cold.

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Others are simply leaving.

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But there's one animal with
a crucial job to do.

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Now, before the winter sets in.

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It's a job the entire forest
depends upon.

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The best time to see them is in the
first couple of hours after dark.

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And what I'm hoping is,
if I stand here and stay really
quiet, I'll be in for a real treat.

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It's a creature I've waited
all my life to see.

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But they move so fast!

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Oh! Did you see that?!

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That was amazing, it went
right past my face!

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Flying squirrel!

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They really are expert gliders.

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They can glide for up to 200 metres!

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When I was a kid, I was obsessed
with things that were, you know,
not meant to fly.

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Flying fish, flying frogs,
flying lizards, flying squirrels.

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This is the first time I've ever
seen them.

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It was worth a 45-year wait.
Honestly!

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Did you... Did you see that?!

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I felt it. It went right through
my hair. Seriously!

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Centre parting!

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It was like a sheet of A4 coming
right over my face

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and as soon as they hit the tree
they're running and up they go.

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They're just criss-crossing
all the trees.

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They immediately scamper up to the
top, then take off and glide again,

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and sometimes, I've noticed, they
can even change direction in flight.

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Arghh!

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One hit me in the chest!

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It doesn't come better than that,
does it?

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It doesn't get more exciting.

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But what on earth have
they got to do with our story?

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Well, at the moment, these flying
squirrels are in the woods

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trying to find as much food as
possible before the weather turns
nasty and the winter kicks in.

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But what are they after?
Well, they're after these.

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Truffles.

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They're the fruiting bodies of fungi
and they appear in the damp cool
of autumn.

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In preparation for winter,

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the hungry squirrel needs
to hoard food such as truffles.

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But the truffles also need
the squirrel to eat them.

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As the squirrel moves through the
forest, the spores are dispersed.

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And that's crucial, not just
for the truffle, but for the trees.

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What's so special about these
truffles?

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They certainly don't look much,
and the smell can be
said to be an acquired taste.

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And they're not just here as another
organism to be eaten by hordes
of hungry squirrels either,

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because without these truffles,
and all the other fungi here
in the wood,

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this woodland simply couldn't
function. It couldn't exist.

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Why?

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Well, take a look beneath
the soil down here.

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Each truffle has thread-like roots
extending from it.

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The threads extract nutrients
in the soil,
from rotting material like leaves.

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And, cunningly,
they also tap into the roots
of the trees to siphon off sugars.

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But this is not a one-way
relationship,

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because the tree can now
tap into the nutrients
extracted by the fungal threads.

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This symbiotic relationship between
the trees and the fungus,

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where each is dependent on
the other,

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clearly helps the tree grow,
but it's not only that.

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It greatly extends
the reach of its roots

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because, in effect, they
become as extensive as the fungal
network that they're connected to.

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In autumn, throughout the northern
hemisphere, trees use fungi to
extend their roots

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and absorb sufficient
nutrients for the big freeze ahead.

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I love this web of relationships -
the squirrels, the fungi, the trees.

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It ensures that they're all ready
to face the winter.

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But for me, one of the most magical
relationships of all is seen
on the far west coast of Canada,

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as one of the world's
most ancient forests

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prepares for
the oncoming challenge.

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Here, I can stand at the foot of
1,000-year-old cedars

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and 90-metre-tall
Sitka spruce trees.

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The combination of large mountains

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and ocean winds generates
unusually heavy rainfall -

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earning this place the title
The Raincoast.

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There's so much rain in autumn
that the rivers swollen.

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And that is vital to
the forest's survival.

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There's a significant event
happening here,

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which allows the whole forest
not only to survive the winter,

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but also to flourish throughout
the course of the year.

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But you know, the really incredible
thing is this key to life

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is not here in the forest at all
at the moment, but it will be soon.

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After years at sea,
salmon are returning to spawn

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in the same forest streams
in which they were hatched.

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The swollen rivers make it easy for
them to swim deep into the forest.

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But the scent of home also draws
them irresistibly towards danger.

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Predators make the most
of this banquet of seafood.

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But none of them compare to the most
formidable fish eater of all.

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Grizzly bears. Just look at this -
there's a female here,

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about 40 metres in front of me,
in the shallows, fishing for salmon.

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Behind her, on the bar over there,
she's got three cubs.

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They're not struggling
to catch the fish here.

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There's such a tremendous surfeit
of tired salmon out there.

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All she really has to do is
wander into those shallows

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until one comes close.

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And then she can grab it,
much to the delight of her cubs.

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For these cubs,
it's the first salmon run.

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They've got to learn how to catch
fish by watching their mother.

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Look at this! Look!

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This is the adult grizzly,

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that's just leapt off
the island there,

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and caught a salmon.
Look at that! Right in its mouth.

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Over just six weeks in autumn,

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tens of millions of salmon
are going to return to these rivers.

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And during the course of a day

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one adult bear like this
can eat 40kg of salmon,

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and during the course
of a salmon run 1400kg -

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that's just one bear's intake.

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But every salmon
caught by these bears

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increases their chances of survival.

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They are incredibly
important to these bears,

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particularly at this time of year,

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when it's essential that they
bulk up as quickly as possible

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before they slip into hibernation
with the winter coming.

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This cub hasn't quite got
the hang of it yet,

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but he hasn't got long -

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the salmon run has only got
a couple of weeks to go.

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Until they learn,
Mum has to work even harder.

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Every salmon caught
makes a real difference.

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These bears, those that are close
to a huge amount of salmon,

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grow 80% larger than
those in other areas.

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They have 25% more cubs,

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and occur at densities
50 times greater.

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So salmon, frankly,
are great news for bears.

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Exciting as it is to watch,

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there's a lot more going on here

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than simply bears catching fish.

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And the reason is thanks to
what happens next.

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And the only way to see it is with
remote cameras,

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positioned deep in the forest.

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These younger bears have carried
fish 30m from the river.

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Because here they are less likely
to be challenged by hungry adults.

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So they can eat in peace.

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There's so much fish available,
they just eat the richest bits

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to lay down enough fat
for hibernation.

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The rest appears to be wasted,
abandoned on the forest floor!

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Along with our camera.

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The aftermath of this feast
is unbelievable.

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Up to four tonnes of carcasses
are left in an area the size

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of a football pitch.

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But what have dead fish

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got to do with the forest
preparing for winter?

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Well, this is where it starts
to get really intriguing,

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because the catching of the salmon
is just the start of it.

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Bears aren't the only creatures

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attracted by such a feast.

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A banana slug.

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At 25cm long, it's one of the
largest slugs in the world.

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And masses of insects.

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These flies
won't survive the winter,

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but if they plant their eggs
in the salmon's flesh,

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their offspring might.

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This flurry of activity

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eventually breaks the flesh down
into simple nutrients

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that are absorbed into the soil.

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The significance of all
of this decaying fish

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goes far beyond it being just
a feast for scavengers.

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Without all of these rotting salmon
accumulating here every autumn,

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this forest would be
a very different place.

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The salmon nutrients in the soil
are taken up by the fungi.

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So this ancient forest
is better equipped to face

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the almighty change
that's fast approaching.

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For forests in the Northern
Hemisphere, time has run out.

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Every day the sun sinks
lower in the sky.

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Winter.

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And on the face of it,

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all of the life here seems
to have just gone away.

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Those truffles and the seeds,

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they're locked away underneath
all of this snow.

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The salmon run is over.

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The vegetation... look at it.
It appears to have shut down.

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Even the water is in short supply -
it's all frozen.

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All of those connections
appear to be broken.

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The fungi have reduced
their recycling to a bare minimum.

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And the trees they're connected to
are producing little in return.

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The deciduous trees pre-empted
the winter by shedding their leaves.

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The conifers are slowing down, too.

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The waxy coating on the needles
protects their leaves from the cold.

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But not everything here can

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exist in a state
of suspended animation.

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Some of the animals have to
remain active,

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and surviving in conditions
like this isn't easy.

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The icy cold
is the cue for the bears

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to leave the forest altogether.

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With the salmon run over,

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they are retreating to their
winter dens, up in the mountains.

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They must spend the entire winter
living off their fat reserves

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gained by feeding on
all of those salmon.

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00:22:19,600 --> 00:22:21,280
The squirrels,

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and other small mammals,
must keep activity to a minimum,

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only occasionally venturing out
to retrieve their autumn caches.

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The lower the temperature falls,

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the more vulnerable
creatures become.

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Winter has been too brutal for this
young white-tailed deer,

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but at least it's an opportunity
for some nocturnal scavengers.

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A racoon.

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Out of the forest, a fisher -
a relative of martens and weasels.

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And it's smart enough
to keep this meal to itself!

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But there is more to this
lifeless-looking forest

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than just the scavengers.

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For most creatures, winter is
a brutal and unforgiving time.

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But others actually
thrive in these conditions.

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You see, for animals
that are adapted to live in winter,

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this stripped-down forest ecosystem,

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well, it's a wonderland.

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In winter, here, there are beautiful
connections,

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between some of the forest's most
enchanting characters.

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There is one predator here,

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an incredibly important animal

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that has no intention of avoiding
the snow,

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because, unlike me,
it's perfectly adapted to it.

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But it's an enigma,
a really, really shy animal,

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one that's difficult to study.

238
00:24:55,200 --> 00:24:56,440
Having said that,

239
00:24:56,440 --> 00:24:59,840
scientists have been tracking them
through the forest here

240
00:24:59,840 --> 00:25:01,120
for more than a decade.

241
00:25:11,880 --> 00:25:15,520
Scientists from the Maine Department
of Fisheries and Wildlife

242
00:25:15,520 --> 00:25:20,160
have set a trap to catch one alive.

243
00:25:31,040 --> 00:25:36,440
With those distinctly pointed ears,
it can only be a Canadian lynx.

244
00:25:39,040 --> 00:25:44,040
Lynx are the world's
most northerly-dwelling cats.

245
00:25:48,200 --> 00:25:51,080
And this particular lynx
is well-known

246
00:25:51,080 --> 00:25:53,480
to chief scientist Jen Vashon.

247
00:25:55,680 --> 00:25:59,200
The ear tags are blue with white.

248
00:25:59,200 --> 00:26:02,080
That indicates it's L1-11.

249
00:26:02,080 --> 00:26:07,440
He's called L1-11 and was born
in May 2004.

250
00:26:17,040 --> 00:26:20,440
They've discovered that he is just
one of hundreds of lynx living here.

251
00:26:25,120 --> 00:26:28,000
It's too early
with everybody right there.

252
00:26:43,680 --> 00:26:47,120
In fact, there are more lynx
living in these Eastern forests

253
00:26:47,120 --> 00:26:49,960
than anywhere else in North America.

254
00:27:09,040 --> 00:27:14,320
Now, the fact that L1-11
has lived all of his life

255
00:27:14,320 --> 00:27:16,880
in this frozen forest

256
00:27:16,880 --> 00:27:21,920
has to mean that this is a perfect
place for a lynx to live.

257
00:27:21,920 --> 00:27:25,120
But how can a top predator like this

258
00:27:25,120 --> 00:27:29,200
survive in such
a stripped-down environment,

259
00:27:29,200 --> 00:27:33,240
when there appears to be
so little else here?

260
00:27:45,000 --> 00:27:48,240
The tracks of their prey
are everywhere,

261
00:27:48,240 --> 00:27:51,880
but actually finding one
is a real challenge

262
00:27:51,880 --> 00:27:55,560
because its winter camouflage
is perfect.

263
00:28:16,280 --> 00:28:22,240
It's taken some finding,
but it's there - the snowshoe hare!

264
00:28:22,240 --> 00:28:26,600
You can just make out its beady
little black eye,

265
00:28:26,600 --> 00:28:29,280
and the black tips to its ears.

266
00:28:29,280 --> 00:28:34,360
And these things
form 80% of a lynx's diet.

267
00:28:34,360 --> 00:28:38,000
But, as you can see, they don't
make it easy for that lynx.

268
00:28:38,000 --> 00:28:40,800
Their camouflage is astonishing.

269
00:28:42,600 --> 00:28:44,320
In the summertime they're brown,

270
00:28:44,320 --> 00:28:47,120
but in the winter they moult through
to a white coat.

271
00:28:47,120 --> 00:28:49,000
But they also use this thick brush.

272
00:28:49,000 --> 00:28:51,840
It provides them
with excellent cover

273
00:28:51,840 --> 00:28:55,680
to hide from the lynx, also hide
from the elements,

274
00:28:55,680 --> 00:28:58,720
but it's also crucial
in keeping them alive,

275
00:28:58,720 --> 00:29:02,240
because they climb on top
of the snow and nibble at

276
00:29:02,240 --> 00:29:06,880
all of the shoots and the bark
growing from all of this brush.

277
00:29:12,360 --> 00:29:17,240
Look at that! Beautiful,
and with those big snowshoe feet,

278
00:29:17,240 --> 00:29:20,280
it just sort of floats across
the surface of the snow.

279
00:29:31,680 --> 00:29:36,120
But what the snowshoe hare needs
most to survive the winter

280
00:29:36,120 --> 00:29:39,360
is a specific type of vegetation.

281
00:29:39,360 --> 00:29:44,000
It must be the right height to eat,

282
00:29:44,000 --> 00:29:47,480
and provide enough cover
to hide from all those lynx.

283
00:29:49,080 --> 00:29:52,760
So, the vegetation, here,
must be perfect.

284
00:29:59,720 --> 00:30:03,720
And the reason that it does grow
into this perfect environment,

285
00:30:03,720 --> 00:30:07,200
well, you could never guess.

286
00:30:11,280 --> 00:30:15,520
The most beautiful
thing about this story

287
00:30:15,520 --> 00:30:18,320
is that the lynx, the hare,

288
00:30:18,320 --> 00:30:23,320
patches of cover like this amongst
the forest, didn't happen by chance.

289
00:30:23,320 --> 00:30:28,960
They're all controlled
by the most unlikely of creatures,

290
00:30:28,960 --> 00:30:32,480
a tiny thing, less than
the size of one of my fingernails.

291
00:30:32,480 --> 00:30:35,160
And at the moment it's hiding,

292
00:30:35,160 --> 00:30:39,200
having burrowed into the bark of one
of these trees,

293
00:30:39,200 --> 00:30:43,360
or perhaps in a crack in a log lying
on the forest floor,

294
00:30:43,360 --> 00:30:45,560
covered with frozen snow.

295
00:30:45,560 --> 00:30:48,720
But it's there, and it's waiting.

296
00:30:48,720 --> 00:30:51,520
It's waiting for springtime.

297
00:31:11,400 --> 00:31:17,080
As the hours of daylight increase
and the ground thaws,

298
00:31:17,080 --> 00:31:21,600
as if by magic, the northern forests
change again.

299
00:31:44,920 --> 00:31:49,600
As new leaves appear,
trees start producing sugars,

300
00:31:49,600 --> 00:31:52,240
and that's good for the fungus
in the soil.

301
00:31:52,240 --> 00:31:57,640
Entwined with the trees' roots, they
can siphon off some of these sugars.

302
00:31:59,320 --> 00:32:02,800
But not everything appears
so harmonious.

303
00:32:02,800 --> 00:32:04,240
In the land of the lynx,

304
00:32:04,240 --> 00:32:07,080
something extraordinary
is happening to the forest.

305
00:32:09,880 --> 00:32:12,280
These trees may have endured
the winter,

306
00:32:12,280 --> 00:32:15,160
but now it's spring,
they're under attack.

307
00:32:18,280 --> 00:32:20,200
Some are even dying.

308
00:32:23,040 --> 00:32:26,520
But what's happening here
now is vital

309
00:32:26,520 --> 00:32:30,800
for how this ecosystem
functions over the year.

310
00:32:32,960 --> 00:32:37,040
This defoliation
is entirely natural.

311
00:32:37,040 --> 00:32:40,360
And I might be able to find
one of the culprits down here,

312
00:32:40,360 --> 00:32:44,240
although they're quite tricky
to spot.

313
00:32:44,240 --> 00:32:47,240
They live in these fresh,
green shoots.

314
00:32:47,240 --> 00:32:49,680
Yes, here we are.

315
00:32:49,680 --> 00:32:53,960
Now, wrapped delicately
in these leaves

316
00:32:53,960 --> 00:32:57,680
is a species that is single-handedly

317
00:32:57,680 --> 00:33:02,680
influencing the ecology
of this entire forest.

318
00:33:02,680 --> 00:33:06,960
Inside this nest is the caterpillar
of the spruce moth. The budworm.

319
00:33:06,960 --> 00:33:10,200
And it hasn't only wrapped itself up
in those leaves

320
00:33:10,200 --> 00:33:11,720
to hide from predators,

321
00:33:11,720 --> 00:33:13,920
because it's eating them as well.

322
00:33:13,920 --> 00:33:17,000
And it doesn't just eat the leaves,

323
00:33:17,000 --> 00:33:22,280
it also eats the buds, the flowers,
and the cones on the tree here.

324
00:33:22,280 --> 00:33:27,480
Up in the canopy,
a tiny budworm caterpillar

325
00:33:27,480 --> 00:33:30,720
has just emerged from hibernation.

326
00:33:30,720 --> 00:33:34,600
It's racing to fatten itself up.

327
00:33:42,920 --> 00:33:47,280
When it's finished on one branch,
it releases a strand of silk,

328
00:33:47,280 --> 00:33:50,400
and abseils down to the next.

329
00:34:11,560 --> 00:34:14,440
It's a risky business being a
juicy, fat caterpillar -

330
00:34:14,440 --> 00:34:18,040
you're in danger of being spied
by all of those birds,

331
00:34:18,040 --> 00:34:19,920
just back from migration.

332
00:34:28,000 --> 00:34:30,520
But the caterpillar has a plan -

333
00:34:30,520 --> 00:34:33,200
it uses its silk

334
00:34:33,200 --> 00:34:36,440
to weave the needles together
and hide in a dense web.

335
00:34:44,480 --> 00:34:48,920
Now, the springtime assault
by these caterpillars

336
00:34:48,920 --> 00:34:50,560
is bad news for the trees.

337
00:34:50,560 --> 00:34:54,200
But for other inhabitants
of these forests,

338
00:34:54,200 --> 00:34:56,640
these caterpillars are heroes.

339
00:34:59,920 --> 00:35:02,560
It's thanks to the behaviour
of this species

340
00:35:02,560 --> 00:35:06,600
that one of North America's most
elusive and charismatic predators -

341
00:35:06,600 --> 00:35:11,240
the Canadian lynx - is enjoying
a bit of a renaissance

342
00:35:11,240 --> 00:35:13,360
in forests like this one.

343
00:35:13,360 --> 00:35:19,160
But the caterpillar lives
all the way up there, in the canopy.

344
00:35:19,160 --> 00:35:23,640
Whilst the cat with the pointed ears
is prowling around down here.

345
00:35:23,640 --> 00:35:28,240
So, how can a humble insect
like this have any impact

346
00:35:28,240 --> 00:35:31,400
on a formidable thing like that?

347
00:35:31,400 --> 00:35:34,200
I bet the lynx never even sees
the caterpillar

348
00:35:34,200 --> 00:35:36,440
throughout the course of its life.

349
00:35:36,440 --> 00:35:39,240
Why does the lynx need
the caterpillar?

350
00:35:41,840 --> 00:35:46,720
The clue is how they affect
the lynx's prey on the forest floor.

351
00:35:49,680 --> 00:35:53,960
For decades, scientists have
studied budworm caterpillars,

352
00:35:53,960 --> 00:35:56,640
and a remarkable pattern
has emerged.

353
00:35:56,640 --> 00:35:58,600
They've discovered

354
00:35:58,600 --> 00:36:02,400
that the population of caterpillars
fluctuates dramatically.

355
00:36:04,280 --> 00:36:06,080
And at the peak of a cycle

356
00:36:06,080 --> 00:36:09,800
there can be tens of thousands
of budworms in a single tree.

357
00:36:17,840 --> 00:36:20,880
And this has devastating
consequences.

358
00:36:25,200 --> 00:36:29,320
Whilst these dramatic natural events
might be a catastrophe

359
00:36:29,320 --> 00:36:32,840
for the established trees,
for anything trying to grow

360
00:36:32,840 --> 00:36:35,760
on the forest floor
they are an absolute bonus.

361
00:36:35,760 --> 00:36:39,440
In here, where it's dark,
there's very little,

362
00:36:39,440 --> 00:36:42,880
very poor diversity - just some
mosses and a few ferns.

363
00:36:42,880 --> 00:36:45,520
But as soon as there's
a break in the canopy

364
00:36:45,520 --> 00:36:49,800
and the sunlight can flood in, well,
look at the difference.

365
00:36:49,800 --> 00:36:54,040
Lots of wild flowers, there's
a young maple coming through here,

366
00:36:54,040 --> 00:37:00,040
mountain ash, and, most importantly
of all, regenerating spruce and fir.

367
00:37:02,000 --> 00:37:07,920
The hares essentially need these
regenerating conifers as shelter.

368
00:37:09,440 --> 00:37:13,880
And of course what's good for
the hares is also good for the lynx.

369
00:37:16,960 --> 00:37:21,120
It's such an elegant connection.

370
00:37:21,120 --> 00:37:24,520
Without the spring emergence
of the hungry caterpillars

371
00:37:24,520 --> 00:37:26,360
to chew holes in a dense canopy,

372
00:37:26,360 --> 00:37:30,840
there wouldn't be enough light
flooding the forest floor.

373
00:37:30,840 --> 00:37:35,320
And, with less light down here,
there would be less growing

374
00:37:35,320 --> 00:37:38,840
for our snowshoe hare
to forage and to hide in,

375
00:37:38,840 --> 00:37:42,520
and then there would be nothing
for L1-11

376
00:37:42,520 --> 00:37:46,480
and all of those hundreds
of other lynx to eat.

377
00:37:46,480 --> 00:37:51,120
And that's why the lynx
needs the caterpillar.

378
00:37:51,120 --> 00:37:52,520
And now it's spring,

379
00:37:52,520 --> 00:37:55,400
there's no better time to see
what the future holds

380
00:37:55,400 --> 00:37:56,600
for the lynx population.

381
00:38:14,480 --> 00:38:18,520
Wildlife biologist Jen
is doing a count.

382
00:38:20,360 --> 00:38:25,080
She has detected a signal
from a radio-collared female.

383
00:38:41,080 --> 00:38:44,960
There she is.

384
00:38:44,960 --> 00:38:48,320
But there might
be something else here.

385
00:38:51,680 --> 00:38:56,800
Safe inside her den, a lynx cub.

386
00:38:56,800 --> 00:38:59,360
He's just a few weeks old.

387
00:39:11,920 --> 00:39:14,520
His eyes aren't even open.

388
00:39:14,520 --> 00:39:17,640
Jen must work fast
before Mum returns.

389
00:39:35,360 --> 00:39:40,240
Thanks to the timing of the budworm
opening the canopy this spring,

390
00:39:40,240 --> 00:39:44,400
there's going to be enough prey for
these lynx to hunt next winter.

391
00:40:01,720 --> 00:40:07,840
Far away to the west, The Raincoast
forest is coming back to life.

392
00:40:21,440 --> 00:40:24,360
Thanks to the richness of the autumn
salmon run,

393
00:40:24,360 --> 00:40:26,360
the bears have survived the winter.

394
00:40:33,440 --> 00:40:37,240
They've now returned to the forest,
looking for something to eat.

395
00:40:37,240 --> 00:40:40,600
They'll survive on vegetation
until the next salmon run.

396
00:40:45,000 --> 00:40:49,280
The emergence of the bears
is a cue for scientists

397
00:40:49,280 --> 00:40:52,680
to conduct a rather risky
experiment.

398
00:40:52,680 --> 00:40:55,680
They need a large, hungry, bear.

399
00:40:55,680 --> 00:41:01,000
It's the only way to measure
the impact of all those salmon

400
00:41:01,000 --> 00:41:02,760
on this ecosystem

401
00:41:02,760 --> 00:41:06,120
and to understand why this vast,

402
00:41:06,120 --> 00:41:10,400
ancient forest has thrived
for so long.

403
00:41:16,400 --> 00:41:18,120
For such a big question,

404
00:41:18,120 --> 00:41:23,160
the methods employed by
senior researcher Chris Darimont

405
00:41:23,160 --> 00:41:24,600
seem a bit curious.

406
00:41:27,640 --> 00:41:31,400
He's equipped with a can full
of old salmon guts,

407
00:41:31,400 --> 00:41:37,240
effusing, probably, the most
disgusting smell known to man.

408
00:41:37,240 --> 00:41:39,880
This is wonderful stuff.

409
00:41:43,520 --> 00:41:47,560
But he hopes the bears
are going to love it.

410
00:41:47,560 --> 00:41:52,240
He's made an aerial lure.

411
00:41:52,240 --> 00:41:54,520
So, the wind will carry this
distinctive perfume

412
00:41:54,520 --> 00:41:56,080
deep into the forest.

413
00:41:56,080 --> 00:41:57,120
Wind, extra boost.

414
00:42:04,960 --> 00:42:08,280
Now they surround the area
with barbed wire.

415
00:42:09,480 --> 00:42:11,160
And it's this

416
00:42:11,160 --> 00:42:14,560
that they hope will collect
what they're so interested in -

417
00:42:14,560 --> 00:42:18,840
a single hair from a visiting bear.

418
00:42:19,840 --> 00:42:22,160
Now the site is prepared,

419
00:42:22,160 --> 00:42:25,720
it's time to set some
remote cameras,

420
00:42:25,720 --> 00:42:27,720
and beat a hasty retreat.

421
00:42:33,080 --> 00:42:37,320
Personally, I'm very happy
to watch from a safe distance -

422
00:42:37,320 --> 00:42:41,200
it's not the smell - some of those
bears are huge!

423
00:42:44,440 --> 00:42:47,320
Look at the size of this bear!

424
00:42:52,120 --> 00:42:57,120
As a trap this is the perfect bait,
it's working brilliantly.

425
00:42:57,120 --> 00:42:58,360
The bears have come in,

426
00:42:58,360 --> 00:43:01,000
and they're snagging themselves
on the wire there.

427
00:43:01,000 --> 00:43:05,600
You can see it vibrating about.
And that's just what we want.

428
00:43:05,600 --> 00:43:07,400
Fresh out of hibernation,

429
00:43:07,400 --> 00:43:12,200
it seems they can't resist this
pile of stinking salmon.

430
00:43:12,200 --> 00:43:15,200
This one's even
rolling around in the stuff now.

431
00:43:15,200 --> 00:43:17,720
No doubt it values the scent -
I'm not sure we would.

432
00:43:21,840 --> 00:43:25,600
The bear's coat has been
growing for nearly a year.

433
00:43:25,600 --> 00:43:28,120
but soon it will be moulted
and lost.

434
00:43:32,080 --> 00:43:35,440
The more bears we can attract,
the better.

435
00:43:45,040 --> 00:43:47,960
Now the coast is clear,

436
00:43:47,960 --> 00:43:52,280
and it's time to retrieve
any fur from the barbed wire.

437
00:43:57,360 --> 00:44:05,000
So, what on earth can a hair tell us
about this forest ecosystem?

438
00:44:09,760 --> 00:44:12,200
Well, hair is made of protein,

439
00:44:12,200 --> 00:44:17,040
sourced from whatever the bear has
been eating over the last year.

440
00:44:28,320 --> 00:44:31,160
And by analyzing this hair,

441
00:44:31,160 --> 00:44:36,560
science can reveal an astonishing
level of detail about a bear's life.

442
00:44:43,440 --> 00:44:47,760
We can learn so much
from a single bear's hair.

443
00:44:47,760 --> 00:44:51,960
So I know, for instance, that this
one has come from a female grizzly.

444
00:44:51,960 --> 00:44:55,640
I know exactly what it's been eating
even on a week-by-week basis,

445
00:44:55,640 --> 00:44:57,440
where that food has come from

446
00:44:57,440 --> 00:45:00,000
and even the impact
on the quality of its life.

447
00:45:00,000 --> 00:45:04,200
So this bear has been getting
most of its protein,

448
00:45:04,200 --> 00:45:06,400
not from the forest around here,

449
00:45:06,400 --> 00:45:09,880
but actually from the deep ocean,
via the salmon.

450
00:45:09,880 --> 00:45:13,120
And we know that throughout
the course of the year

451
00:45:13,120 --> 00:45:16,760
80% of that bear's protein
has come from these salmon.

452
00:45:16,760 --> 00:45:19,440
And that's surprising
because, remember,

453
00:45:19,440 --> 00:45:22,720
they're only available to the bear
for a few weeks during the autumn.

454
00:45:22,720 --> 00:45:26,400
And yet the impact is clearly
lasting all year.

455
00:45:27,680 --> 00:45:32,000
So, how come the bears appear to be
so full of salmon?

456
00:45:43,040 --> 00:45:47,240
Well, back in autumn, we saw
the bears scattering fish carcasses

457
00:45:47,240 --> 00:45:49,480
all around the forest floor.

458
00:45:57,000 --> 00:46:00,760
As the protein in those
rotting salmon broke down,

459
00:46:00,760 --> 00:46:04,520
nitrogen from it
accumulated in the soil.

460
00:46:04,520 --> 00:46:06,360
And this salmon nitrogen

461
00:46:06,360 --> 00:46:10,000
is like fertiliser!

462
00:46:12,000 --> 00:46:14,240
So, in spring,

463
00:46:14,240 --> 00:46:17,880
nutrients all the way from the ocean
gradually appear

464
00:46:17,880 --> 00:46:20,960
in all the vegetation growing here.

465
00:46:22,400 --> 00:46:24,640
Just in time for the hungry bears

466
00:46:24,640 --> 00:46:29,200
to eat as they emerge
from hibernation.

467
00:46:29,200 --> 00:46:33,800
And hungry bears
have huge appetites -

468
00:46:33,800 --> 00:46:36,600
they'll eat a third
of their body weight every day!

469
00:46:39,240 --> 00:46:44,840
So that's why their bodies appear to
contain so much salmon.

470
00:46:53,360 --> 00:46:56,880
But the impact
of this ocean-born nitrogen

471
00:46:56,880 --> 00:47:00,120
extends far beyond bears
and their food.

472
00:47:03,360 --> 00:47:05,480
This particular form of nitrogen

473
00:47:05,480 --> 00:47:08,280
can be found in almost all
of the animals and plants

474
00:47:08,280 --> 00:47:10,720
that appear here in the spring.

475
00:47:21,320 --> 00:47:26,120
These Rufous Hummingbirds have
migrated to the forest to breed.

476
00:47:26,120 --> 00:47:28,240
They're drinking nectar from plants

477
00:47:28,240 --> 00:47:30,720
that have been fertilised
by rotted fish.

478
00:47:30,720 --> 00:47:34,280
So, they'll carry the same
salmon nutrients with them

479
00:47:34,280 --> 00:47:36,520
as they fly through the forest.

480
00:47:44,080 --> 00:47:48,520
Many of the insects pollinating
the plants now

481
00:47:48,520 --> 00:47:51,400
were incubated in that decaying
flesh back in the autumn.

482
00:47:54,000 --> 00:47:57,280
As they themselves are eaten,

483
00:47:57,280 --> 00:48:00,040
the salmon nutrients are spread
even further.

484
00:48:03,120 --> 00:48:06,800
Thanks to the bears,
the insects, and the birds,

485
00:48:06,800 --> 00:48:12,080
this salmon fertiliser is spread
deeper and deeper into the forest -

486
00:48:12,080 --> 00:48:15,520
sometimes as much as 800m
from the river,

487
00:48:15,520 --> 00:48:20,000
and this pulse of nutrients
then allows the organisms

488
00:48:20,000 --> 00:48:27,720
which define the forest itself
to prosper - its trees.

489
00:48:41,800 --> 00:48:46,400
Doctor Tom Reimchen
can measure exactly how much

490
00:48:46,400 --> 00:48:50,040
these vast old trees need the fish.

491
00:48:52,080 --> 00:48:59,400
The secret is to look inside
the tree, by taking a core sample.

492
00:49:06,200 --> 00:49:10,360
Written on it is the entire story
of this 300-year-old tree.

493
00:49:17,080 --> 00:49:21,280
The rings I see are two, three,
even four millimetres,

494
00:49:21,280 --> 00:49:23,720
which continues back

495
00:49:23,720 --> 00:49:29,600
to even the early parts
of the 1800s, late 1700s.

496
00:49:29,600 --> 00:49:35,240
Tom has taken similar samples
from thousands of trees.

497
00:49:35,240 --> 00:49:38,840
An entire forest is lined up
in his lab,

498
00:49:38,840 --> 00:49:42,480
each tree waiting
to tell its own story.

499
00:50:02,320 --> 00:50:07,440
In this seasonal climate, annual
rings are created as the tree grows.

500
00:50:13,240 --> 00:50:17,520
From these rings, he can determine
not just the age of the tree,

501
00:50:17,520 --> 00:50:20,360
but also
the amount of growth in each year.

502
00:50:20,360 --> 00:50:23,200
Some of the rings
are thicker than others,

503
00:50:23,200 --> 00:50:26,920
showing that the tree
has grown more.

504
00:50:33,440 --> 00:50:38,920
Like the bear fur,
each annual ring can be analyzed.

505
00:50:38,920 --> 00:50:42,280
Tom can search for
the same type of nitrogen

506
00:50:42,280 --> 00:50:45,320
that's found in the bear's hairs.

507
00:50:45,320 --> 00:50:47,440
It comes from the ocean

508
00:50:47,440 --> 00:50:51,120
and it's called nitrogen-15.

509
00:50:55,400 --> 00:51:01,320
And the data will tell us just
how much nitrogen in those trees

510
00:51:01,320 --> 00:51:03,840
comes from all those salmon.

511
00:51:09,360 --> 00:51:13,480
I think this
is really exciting.

512
00:51:13,480 --> 00:51:15,880
You see, the annual
growth rings here

513
00:51:15,880 --> 00:51:19,400
show the presence of
the stable isotope Nitrogen-15,

514
00:51:19,400 --> 00:51:22,400
which significantly
comes from the oceans.

515
00:51:22,400 --> 00:51:25,920
It could only have been carried here
by the salmon.

516
00:51:25,920 --> 00:51:29,720
Now look, here is the present,
the bark on the outside of the tree,

517
00:51:29,720 --> 00:51:32,640
so these rings represent
perhaps the last 15 years

518
00:51:32,640 --> 00:51:35,400
and they're very closely
packed together.

519
00:51:35,400 --> 00:51:40,480
But here, back in the 1980s,
the rings are twice as thick.

520
00:51:40,480 --> 00:51:44,120
The trees have been growing twice
as much during the course of a year.

521
00:51:44,120 --> 00:51:48,720
So, perhaps the salmon runs
then were even more productive

522
00:51:48,720 --> 00:51:51,080
than they have been recently.

523
00:51:51,080 --> 00:51:54,480
But that's not the best thing.
Come and have a look at this.

524
00:51:54,480 --> 00:51:58,760
By measuring the abundance of that
nitrogen isotope in this material,

525
00:51:58,760 --> 00:52:04,840
I can tell you that majestic old
giants like this beauty here

526
00:52:04,840 --> 00:52:10,400
are actually composed
of up to 85% material

527
00:52:10,400 --> 00:52:14,280
that's derived from salmon.

528
00:52:14,280 --> 00:52:16,080
Now, when I was a teenager,

529
00:52:16,080 --> 00:52:20,080
I remember learning that I was made
of carbon,

530
00:52:20,080 --> 00:52:22,920
and carbon could only be formed
when stars died.

531
00:52:22,920 --> 00:52:25,200
Effectively I was made of dead stars

532
00:52:25,200 --> 00:52:29,440
and that struck me
as terribly romantic.

533
00:52:29,440 --> 00:52:31,240
But look at this.

534
00:52:31,240 --> 00:52:33,080
This is a forest made of the ocean!

535
00:52:36,080 --> 00:52:40,000
That's why the tree needs the fish.

536
00:52:40,000 --> 00:52:45,040
Without this unlikely-sounding
relationship,

537
00:52:45,040 --> 00:52:49,400
this magnificent ancient forest just
wouldn't be the place it is today.

538
00:52:52,600 --> 00:52:56,840
But there is one more relationship,

539
00:52:56,840 --> 00:53:00,800
crucial to seasonal forests
all around the world,

540
00:53:00,800 --> 00:53:04,560
when it comes to surviving
constant change.

541
00:53:04,560 --> 00:53:08,680
And it's one that
reaches its greatest intensity now,

542
00:53:08,680 --> 00:53:10,880
at the height of summer.

543
00:53:13,600 --> 00:53:17,560
It's the driest time of year,
and the trees need water.

544
00:53:21,240 --> 00:53:24,520
Fortunately,
united with their fungal partners,

545
00:53:24,520 --> 00:53:27,560
the trees have massively
extended their roots.

546
00:53:27,560 --> 00:53:30,440
Fungal threads in the soil
are absorbing water

547
00:53:30,440 --> 00:53:32,680
and passing it to the tree.

548
00:53:34,200 --> 00:53:38,440
But what has only recently been
discovered

549
00:53:38,440 --> 00:53:43,360
is the sheer scale
of these fungal root networks.

550
00:53:43,360 --> 00:53:47,240
A single cubic centimetre
of the soil here

551
00:53:47,240 --> 00:53:53,320
can have a mile of these white
fungal threads running through it.

552
00:53:53,320 --> 00:53:56,160
They're called mycorrhizae.

553
00:53:56,160 --> 00:53:58,000
And, for me,

554
00:53:58,000 --> 00:54:02,000
it's these organisms that are
the real secret of the forest here.

555
00:54:04,080 --> 00:54:07,360
In the lab, the genetic fingerprints

556
00:54:07,360 --> 00:54:11,200
of individual mycorrhizae
have been identified.

557
00:54:17,080 --> 00:54:20,360
By mapping an area 30m across,

558
00:54:20,360 --> 00:54:22,560
it's been discovered

559
00:54:22,560 --> 00:54:27,960
that individual fungi
connect to more than a single tree.

560
00:54:27,960 --> 00:54:33,880
Just one fungus can be joined to 80%
of all of the plants growing here.

561
00:54:35,680 --> 00:54:42,680
And, amazingly, these physical links
enable different species of plants

562
00:54:42,680 --> 00:54:45,440
to exchange nutrients.

563
00:54:45,440 --> 00:54:48,040
Older established plants
are even nurturing

564
00:54:48,040 --> 00:54:50,400
younger weaker ones.

565
00:54:50,400 --> 00:54:53,960
It acts like an underground
welfare system!

566
00:54:55,480 --> 00:54:57,000
These giant webs

567
00:54:57,000 --> 00:55:02,000
connect all of the trees
in this forest,

568
00:55:02,000 --> 00:55:06,240
and keep them, and all of the things
that are dependent upon them, alive.

569
00:55:06,240 --> 00:55:11,680
That's why scientists are calling
this the Wood Wide Web.

570
00:55:22,880 --> 00:55:27,840
It's thanks to this natural
phenomenon, the Wood Wide Web,

571
00:55:27,840 --> 00:55:33,160
that, together, the trees in the
forest ecosystems are resilient -

572
00:55:33,160 --> 00:55:37,720
resilient enough to cope with
the dramatic changes

573
00:55:37,720 --> 00:55:41,200
they encounter every year.

574
00:55:48,920 --> 00:55:52,960
And what's really amazing is how
the web is built.

575
00:55:56,240 --> 00:55:59,360
It's thanks to hungry mammals
like our flying squirrels

576
00:55:59,360 --> 00:56:04,720
that this essential life support
system is effectively maintained.

577
00:56:06,680 --> 00:56:12,680
It's actually fair to say that these
trees wouldn't be standing here,

578
00:56:12,680 --> 00:56:17,120
wouldn't be thriving, unless
a squirrel had eaten a truffle.

579
00:56:17,120 --> 00:56:20,040
And that is fantastic!

580
00:56:23,040 --> 00:56:24,240
It is fantastic.

581
00:56:24,240 --> 00:56:28,720
It's fantastic to think
that what animals do in one season

582
00:56:28,720 --> 00:56:33,800
influences the forest ecosystem
throughout the year.

583
00:56:36,640 --> 00:56:42,720
It's almost as if all of these
stories are choreographed.

584
00:56:46,120 --> 00:56:50,560
The arrival of the salmon
at exactly the right time

585
00:56:50,560 --> 00:56:53,400
to fatten the bears for winter.

586
00:56:53,400 --> 00:56:56,920
Then, the emergence of the lush
green vegetation

587
00:56:56,920 --> 00:56:58,920
fertilised by those salmon

588
00:56:58,920 --> 00:57:03,040
to sustain the bears when they
emerge from hibernation.

589
00:57:03,040 --> 00:57:07,120
The squirrels - foraging
for truffles in the autumn time,

590
00:57:07,120 --> 00:57:10,360
and sowing their spores
throughout the forest

591
00:57:10,360 --> 00:57:12,200
to grow a fungal network

592
00:57:12,200 --> 00:57:15,840
that joins all of the trees and all
of the plants,

593
00:57:15,840 --> 00:57:18,480
and provides them with nutrients.

594
00:57:18,480 --> 00:57:24,160
The budworm - chewing
a hole in springtime in the canopy,

595
00:57:24,160 --> 00:57:29,240
so that in summer, sunlight
floods down to the forest floor

596
00:57:29,240 --> 00:57:34,720
and produces the perfect
hunting habitat for lynx.

597
00:57:34,720 --> 00:57:37,360
It's all in the timings.

598
00:57:37,360 --> 00:57:41,440
And it's this that makes these
temperate forests

599
00:57:41,440 --> 00:57:43,240
such magical places.

600
00:58:00,960 --> 00:58:02,560
If you'd like to know more

601
00:58:02,560 --> 00:58:05,760
about the fascinating web of links
between species,

602
00:58:05,760 --> 00:58:07,000
the Open University

603
00:58:07,000 --> 00:58:11,280
has produced some material
both to inform and inspire you.

604
00:58:11,280 --> 00:58:12,520
For your free copy,

605
00:58:12,520 --> 00:58:15,960
or to find out more about
Open University programmes -

606
00:58:30,800 --> 00:58:32,600
And join me next time,

607
00:58:32,600 --> 00:58:36,040
when I'll be travelling to some of
the world's greatest water habitats.

608
00:58:52,720 --> 00:58:54,880
Subtitles by Red Bee Media Ltd