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The Magical Forest (BBC Documentary 2012)

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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,
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    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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    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, 1'm going to what is, for me,
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    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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    And 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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    1t'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
    that if I stand here
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    and stay really quiet,
    I'll be in for a real treat.
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    1t's a creature 1've waited all my life
    to see, but they move so fast!
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    0h! 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-
    They can glide for up to 2OO metres!
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    When I was a kid, I was obsessed
    with things that were, you know,
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    not meant to fly.
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    Flying fish, flying frogs,
    flying lizards, flying squirrels.
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    And 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...? 0h! Did you see that?!
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    I felt it, it went right through my hair!
    Seriously! Centre parting!
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    It was like having 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 crisscrossing
    all of the trees.
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    And they immediately scamper up to the
    top and then take off and glide again,
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    and sometimes, I've noticed, they can
    even change direction during flight.
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    Urgh! 0ne 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 out and about
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    in the woods trying to find
    as much food as possible
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    before the weather turns nasty
    and the winter kicks in.
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    But what are they after?
    Well, they're after these - truffles.
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    They're the fruiting bodies of fungi
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    and they appear in the damp cool
    of autumn-
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    1n 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-
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    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,
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    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
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    by hordes of hungry squirrels either.
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    Because without these truffles
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    and all of 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 the leaves-
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    And, cunningly,
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    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,
    because the tree
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    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,
    clearly helps the tree grow,
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    but it's not only that.
    It greatly extends the reach of its roots.
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    Because in effect, they become
    as extensive as the fungal network
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    that they're connected to.
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    1n autumn, throughout the northern
    hemisphere, trees use fungi
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    to extend their roots
    and absorb sufficient nutrients
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    for the big freeze ahead-
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    1 love this little web of relationships-
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    The squirrels, the fungi, the trees-
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    1t 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
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    is seen on the far west coast of Canada,
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    as one of the world's most ancient forests
    prepares for the oncoming challenge-
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    Here, 1 can stand at the foot
    of thousand-year-old cedars
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    and 9O-metre tall sitka spruce trees-
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    The combination of large mountains
    and ocean winds
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    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 are 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
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    that this key to life is not here
    in the forest at all at the moment,
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    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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    And the swollen rivers
    make it easy for them
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    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!
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    Just look at this.
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    There's a female here,
    about 40 metres in front of me,
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    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
    that's just leapt off of the island there,
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    and caught a salmon, look at that,
    right in its mouth.
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    Overjust 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,
    one adult bear like this can eat
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    40kg of salmon, and during the course
    of the salmon run, 1,400kg.
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    That's just one bear's intake.
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    But every salmon caught by these bears
    increases their chances of survival-
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    And 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 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- 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
    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
    3O metres from the river-
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    Because here they're 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 of a football pitch-
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    But what have dead fish 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
    attracted by such a feast-
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    A banana slug- 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 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 the almighty change
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    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,
    all of the life here
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    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 just 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 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
    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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    The squirrels and other small mammals
    must keep their 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,
    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 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 have adapted to live in winter,
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    this stripped-down forest ecosystem -
    well, it's a wonderland.
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    1n 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,
    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.
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    Having said that,
    scientists have been tracking them
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    through the forest here
    for more than a decade.
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    Researchers from the Maine Department
    of Fisheries and Wildlife
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    have set a trap to catch one alive-
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    With those distinctly pointed ears,
    it can only be a Canadian lynx-
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    Lynx are the world's
    most northerly dwelling cats-
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    And this particular lynx is well known
    to chief scientist Jen Vashon-
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    The ear tags are blue with white.
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    - That indicates it's L1 -1 1 .
    - (LYNX BARKS)
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    He's called L 1-1 1
    and was born in May 2OO4-
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    They've discovered that he is just one
    of hundreds of lynx living here-
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    JEN: It's too intimidated
    with everybody right there.
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    1n fact, there are more lynx
    living in these eastern forests
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    than anywhere else in North America-
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    Now, the fact that L1 -1 1 has lived
    all of his life in this frozen forest
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    has to mean that this is
    a perfect place for a lynx to live.
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    But how can a top predator
    like this survive
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    in such a stripped-down environment
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    when there appears to be
    so little else here?
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    The tracks of their prey are everywhere,
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    but actually finding one
    is a real challenge,
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    because its winter camouflage is perfect-
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    It's taken some finding,
    but it's there - the snowshoe hare.
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    You can just make out
    its beady little black eye
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    and the black tips to its ears.
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    And these things form 80%/
    of the lynx's diet,
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    but as you can see,
    they don't make it easy for that lynx.
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    Their camouflage is astonishing.
  • 28:42 - 28:44
    In the summertime, they're brown,
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    but in the winter,
    they moult through to a white coat.
  • 28:47 - 28:50
    But they also use this thick brush.
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    It provides them with excellent cover
    to hide from the lynx,
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    also hide from the elements,
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    but it's also crucial
    in keeping them alive,
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    because they climb on top of the snow and
    nibble at all of the shoots and the bark
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    growing from all of this brush.
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    Look at that - beautiful!
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    And with those big snowshoe feet,
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    it just sort of floats across
    the surface of the snow.
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    What the snowshoe hare needs most
    to survive the winter
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    is a specific type of vegetation-
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    1t must be the right height to eat
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    and provide enough cover
    to hide from all of those lynx-
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    So the vegetation here must be perfect-
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    And the reason that it does grow into
    this perfect environment -
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    well, you could never guess-
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    The most beautiful thing about this story
    is that the lynx, the hare,
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    patches of cover like this
    amongst the forest
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    didn't happen by chance.
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    They're all controlled
    by the most unlikely of creatures,
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    a tiny thing, less than the size
    of one of my fingernails.
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    And at the moment, it's hiding,
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    having burrowed into the bark
    of one of these trees,
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    or perhaps in a crack in a log
    lying on the forest floor,
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    covered with frozen snow.
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    But it's there and it's waiting.
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    It's waiting for springtime.
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    As the hours of daylight increase
    and the ground thaws,
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    as if by magic,
    the northern forests change again-
  • 31:45 - 31:50
    As new leaves appear,
    trees start producing sugars,
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    and that's good for fungus in the soil-
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    Entwined with the trees'roots,
    they can siphon off some of these sugars-
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    But not everything appears
    so harmonious-
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    1n the land of the lynx, something
    extraordinary is happening to the forest-
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    These trees may have endured the winter,
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    but now it's spring, they're under attack-
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    Some are even dying-
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    But what's happening here now is vital
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    for how this ecosystem functions
    over the year-
  • 32:34 - 32:38
    This defoliation is entirely natural.
  • 32:38 - 32:41
    And I might be able to find
    one of the culprits down here,
  • 32:41 - 32:44
    although they're quite tricky to spot.
  • 32:44 - 32:49
    They live in these fresh, green shoots.
  • 32:49 - 32:50
    Yes, here we are.
  • 32:50 - 32:55
    Now, wrapped delicately in these leaves
  • 32:55 - 32:58
    is a species that is single-handedly
  • 32:58 - 33:03
    influencing the ecology
    of this entire forest.
  • 33:03 - 33:07
    Inside this nest is the caterpillar
    of the spruce moth - the budworm.
  • 33:07 - 33:11
    And it hasn't only wrapped itself up
    in those leaves
  • 33:11 - 33:14
    to hide from predators,
    because it's eating them as well.
  • 33:14 - 33:16
    And it doesn't just eat the leaves.
  • 33:16 - 33:25
    It also eats the buds, the flowers
    and the cones on the tree here.
  • 33:25 - 33:28
    Up in the canopy,
    a tiny budworm caterpillar
  • 33:28 - 33:31
    has just emerged from hibernation
  • 33:31 - 33:43
    and it's racing to fatten itself up-
  • 33:43 - 33:48
    When it's finished on one branch,
    it releases a strand of silk
  • 33:48 - 34:12
    and abseils down to the next-
  • 34:12 - 34:15
    1t's a risky business
    being a juicy, fat caterpillar-
  • 34:15 - 34:30
    You're in danger of being spied by all
    of those birds just back from migration-
  • 34:30 - 34:32
    But the caterpillar has a plan-
  • 34:32 - 34:45
    1t uses its silk to weave the needles
    together and hide in a dense web-
  • 34:45 - 34:49
    Now, the springtime assault
    by these caterpillars
  • 34:49 - 34:51
    is bad news for the trees-
  • 34:51 - 34:55
    But for other inhabitants
    of these forests,
  • 34:55 - 35:00
    these caterpillars are heroes-
  • 35:00 - 35:03
    It's thanks to the behaviour
    of this species
  • 35:03 - 35:07
    that one of North America's most elusive
    and charismatic predators -
  • 35:07 - 35:09
    the Canadian lynx -
  • 35:09 - 35:14
    is enjoying a bit of a renaissance
    in forests like this one.
  • 35:14 - 35:20
    But the caterpillar lives all the way
    up there, in the canopy.
  • 35:20 - 35:24
    Whilst the cat with the pointed ears
    is prowling around down here.
  • 35:24 - 35:28
    So how can a humble insect like this
  • 35:28 - 35:31
    have any impact
    on a formidable thing like that?
  • 35:31 - 35:34
    I bet the lynx never even sees
    the caterpillar
  • 35:34 - 35:37
    throughout the course of its life.
  • 35:37 - 35:42
    Why does the lynx need the caterpillar?
  • 35:42 - 35:50
    The clue is how they affect
    the lynx's prey on the forest floor-
  • 35:50 - 35:55
    For decades, scientists have studied
    budworm caterpillars,
  • 35:55 - 35:57
    and a remarkable pattern has emerged-
  • 35:57 - 36:03
    They've discovered that the population
    of caterpillars fluctuates dramatically-
  • 36:03 - 36:07
    And at the peak of the cycle,
  • 36:07 - 36:18
    there can be tens of thousands
    of budworms in a single tree-
  • 36:18 - 36:26
    And this has devastating consequences-
  • 36:26 - 36:29
    Whilst these dramatic natural events
  • 36:29 - 36:32
    might be a catastrophe
    for the established trees,
  • 36:32 - 36:37
    for anything trying to grow on the
    forest floor, they are an absolute bonus.
  • 36:37 - 36:39
    In here, where it's dark,
    there's very little,
  • 36:39 - 36:44
    very poor diversity -
    just some mosses and a few ferns.
  • 36:44 - 36:46
    But as soon as
    there's a break in the canopy
  • 36:46 - 36:51
    and the sunlight can flood in -
    well, look at the difference.
  • 36:51 - 36:54
    Lots of wild flowers, there's young maple
    coming through here,
  • 36:54 - 37:03
    mountain ash and, most importantly of all,
    regenerating spruce and fir.
  • 37:03 - 37:10
    Now, the hares essentially need
    these regenerating conifers as shelter.
  • 37:10 - 37:17
    And, of course, what's good for the hares
    is also good for the lynx.
  • 37:17 - 37:22
    1t's such an elegant connection-
  • 37:22 - 37:25
    Without the spring emergence
    of the hungry caterpillars
  • 37:25 - 37:27
    to chew holes in the dense canopy,
  • 37:27 - 37:31
    there wouldn't be enough light
    flooding the forest floor-
  • 37:31 - 37:33
    And with less light down here,
  • 37:33 - 37:39
    there would be less growing for
    our snowshoe hare to forage and hide in,
  • 37:39 - 37:42
    and then there would be nothing
  • 37:42 - 37:47
    for L 1-1 1 and all of those
    hundreds of other lynx to eat-
  • 37:47 - 37:52
    And that's why the lynx
    needs the caterpillar.
  • 37:52 - 37:55
    And now it's spring,
    there's no better time
  • 37:55 - 38:16
    to see what the future holds
    for the lynx population-
  • 38:16 - 38:21
    Wildlife biologist Jen is doing a count-
  • 38:21 - 38:42
    She's detected a signal
    from a radio-collared female-
  • 38:42 - 38:44
    There she is-
  • 38:44 - 38:52
    But there might be something else here-
  • 38:52 - 38:58
    Safe inside a den, a lynx cub-
  • 38:58 - 39:00
    He's just a few weeks old-
  • 39:00 - 39:12
    (CUB SQUEAKS)
  • 39:12 - 39:15
    His eyes aren't even open.
  • 39:15 - 39:36
    Jen must work fast before Mum returns-
  • 39:36 - 39:41
    Thanks to the timing of the budworm
    opening the canopy this spring,
  • 39:41 - 39:48
    there's going to be enough prey
    for these lynx to hunt next winter-
  • 39:48 - 40:02
    (CUB SQUEAKS)
  • 40:02 - 40:21
    Far away to the west, the Raincoast forest
    is coming back to life-
  • 40:21 - 40:25
    Thanks to the richness
    of the autumn salmon run,
  • 40:25 - 40:33
    the bears have survived the winter-
  • 40:33 - 40:38
    They've now returned to the forest,
    looking for something to eat-
  • 40:38 - 40:47
    They'll survive on vegetation
    until the next salmon run-
  • 40:47 - 40:49
    The emergence of the bears
  • 40:49 - 40:54
    is a cue for scientists to conduct
    a rather risky experiment-
  • 40:54 - 40:59
    They need a large, hungry bear-
  • 40:59 - 41:01
    1t's the only way to measure
  • 41:01 - 41:05
    the impact of
    all of those salmon on this ecosystem
  • 41:05 - 41:18
    and to understand why this vast,
    ancient forest has thrived for so long-
  • 41:18 - 41:20
    For such a big question,
  • 41:20 - 41:29
    the methods employed by senior researcher
    Chris Darimont seem a bit curious-
  • 41:29 - 41:32
    He's equipped
    with a can full of old salmon guts,
  • 41:32 - 41:38
    effusing probably
    the most disgusting smell known to man-
  • 41:38 - 41:44
    CHRIS: This is wonderful stuff.
  • 41:44 - 41:49
    But he hopes
    the bears are going to love it-
  • 41:49 - 41:51
    He's made an aerial lure,
  • 41:51 - 41:57
    so the wind will carry this distinctive
    perfume deep into the forest-
  • 41:57 - 42:05
    The wind - extra boost.
  • 42:05 - 42:10
    Now they surround the area
    with barbed wire-
  • 42:10 - 42:15
    And it's this that they hope will collect
    what they're so interested in -
  • 42:15 - 42:20
    - a single hair from a visiting bear-
    - (CAMERA BEEPS)
  • 42:20 - 42:27
    Now the site is prepared,
    it's time to set some remote cameras---
  • 42:27 - 42:34
    ---and beat a hasty retreat-
  • 42:34 - 42:38
    Personally, 1'm very happy to watch
    from a safe distance-
  • 42:38 - 42:45
    1t's not the smell -
    some of those bears are huge-
  • 42:45 - 42:53
    Look at the size of this bear!
  • 42:53 - 42:56
    As a trap, this is the perfect bait,
    it's working brilliantly.
  • 42:56 - 42:58
    The bears have come in
  • 42:58 - 43:01
    and they're snagging themselves
    on the wire there.
  • 43:01 - 43:06
    You can see it vibrating about.
    And that's justwhat we want.
  • 43:06 - 43:08
    Fresh out of hibernation,
  • 43:08 - 43:12
    it seems they can't resist
    this pile of stinking salmon.
  • 43:12 - 43:16
    This one's even rolling around
    in the stuff now.
  • 43:16 - 43:23
    No doubt it values the scent -
    I'm not sure we would.
  • 43:23 - 43:26
    The bear's coat has been growing
    for nearly a year,
  • 43:26 - 43:32
    but soon it will be moulted and lost-
  • 43:32 - 43:46
    The more bears we can attract, the better-
  • 43:46 - 43:48
    Now the coast is clear,
  • 43:48 - 43:58
    and it's time to retrieve any fur
    from the barbed wire-
  • 43:58 - 44:11
    So what on Earth can hair tell us
    about this forest ecosystem?
  • 44:11 - 44:13
    Well, hair is made of protein
  • 44:13 - 44:29
    sourced from whatever the bear
    has been eating over the last year-
  • 44:29 - 44:31
    And by analysing this hair,
  • 44:31 - 44:44
    science can reveal an astonishing level
    of detail about a bear's life-
  • 44:44 - 44:49
    We can learn so much
    from a single bear's hair.
  • 44:49 - 44:53
    So I know, for instance, that this one
    has come from a female grizzly.
  • 44:53 - 44:56
    I know exactly what it's been eating
    even on a week-by-week basis,
  • 44:56 - 45:01
    where that food has come from and even
    the impact on the quality of its life.
  • 45:01 - 45:04
    So this bear has been getting
    most of its protein,
  • 45:04 - 45:06
    not from the forest around here
  • 45:06 - 45:10
    but actually from the deep ocean,
    via the salmon.
  • 45:10 - 45:13
    And we know that,
    throughout the course of the year,
  • 45:13 - 45:17
    80%/ of that bear's protein
    has come from these salmon.
  • 45:17 - 45:19
    And that's surprising, because, remember,
  • 45:19 - 45:24
    they're only available to the bear
    for a few weeks during the autumn.
  • 45:24 - 45:28
    And yet the impact
    is clearly lasting all year.
  • 45:28 - 45:44
    So how come the bears appear to be
    so full of salmon?
  • 45:44 - 45:45
    Well, back in autumn,
  • 45:45 - 45:58
    we saw the bears scattering fish carcasses
    all around the forest floor-
  • 45:58 - 46:01
    As the protein
    in those rotting salmon broke down,
  • 46:01 - 46:05
    nitrogen from it accumulated in the soil-
  • 46:05 - 46:13
    And this salmon nitrogen
    is like fertilizer-
  • 46:13 - 46:17
    So in spring,
    nutrients all the way from the ocean
  • 46:17 - 46:23
    gradually appear
    in all the vegetation growing here-
  • 46:23 - 46:31
    Just in time for the hungry bears to eat
    as they emerge from hibernation-
  • 46:31 - 46:34
    And hungry bears have huge appetites -
  • 46:34 - 46:40
    they'll eat a third of their body weight
    every day-
  • 46:40 - 46:54
    That's why their bodies
    appear to contain so much salmon-
  • 46:54 - 46:58
    But the impact
    of this ocean-borne nitrogen
  • 46:58 - 47:04
    extends far beyond bears and their food-
  • 47:04 - 47:09
    This particular form of nitrogen
    can be found in almost all of the animals
  • 47:09 - 47:22
    and plants that appear here in the spring-
  • 47:22 - 47:27
    These rufous hummingbirds
    have migrated to the forest to breed-
  • 47:27 - 47:31
    They're drinking nectar from plants
    that have been fertilized by rotted fish-
  • 47:31 - 47:35
    So they'll carry the same salmon nutrients
    with them
  • 47:35 - 47:45
    as they fly through the forest-
  • 47:45 - 47:49
    And many of the insects
    pollinating the plants now
  • 47:49 - 47:55
    were incubated in that decaying flesh
    back in the autumn-
  • 47:55 - 47:56
    As they themselves are eaten,
  • 47:56 - 48:04
    the salmon nutrients
    are spread even further-
  • 48:04 - 48:07
    Thanks to the bears, the insects
    and the birds,
  • 48:07 - 48:12
    this salmon fertilizer is spread
    deeper and deeper into the forest,
  • 48:12 - 48:16
    sometimes as much as 800 metres
    from the river.
  • 48:16 - 48:19
    And this pulse of nutrients
  • 48:19 - 48:25
    then allows the organisms which define
    the forest itself to prosper...
  • 48:25 - 48:42
    ...its trees.
  • 48:42 - 48:47
    Dr Tom Reimchen
    can measure exactly how much
  • 48:47 - 48:52
    these vast old trees need the fish-
  • 48:52 - 49:07
    The secret is to look inside the tree
    by taking a core sample-
  • 49:07 - 49:18
    Written on it is the entire story
    of this 3OO-year-old tree-
  • 49:18 - 49:23
    T0M: The rings I see are two, three,
    even four millimetres,
  • 49:23 - 49:31
    which continues back to even the early
    parts of the 1 800s, late 1 700s.
  • 49:31 - 49:36
    Tom has taken similar samples
    from thousands of trees-
  • 49:36 - 49:40
    An entire forest is lined up in his lab,
  • 49:40 - 50:03
    each tree waiting to tell its own story-
  • 50:03 - 50:14
    1n this seasonal climate, annual rings
    are created as the tree grows-
  • 50:14 - 50:17
    From these rings, he can determine
    not just the age of the tree
  • 50:17 - 50:22
    but also the amount of growth
    in each year-
  • 50:22 - 50:25
    Some of the rings are thicker than others,
  • 50:25 - 50:34
    showing that the tree has grown more-
  • 50:34 - 50:39
    Like the bear fur,
    each annual ring can be analysed-
  • 50:39 - 50:42
    Tom can search
    for the same type of nitrogen
  • 50:42 - 50:44
    that's found in the bears'hairs -
  • 50:44 - 50:56
    it comes from the ocean
    and it's called nitrogen-1 5-
  • 50:56 - 50:58
    And the data will tell us
  • 50:58 - 51:10
    just how much nitrogen in those trees
    comes from all those salmon-
  • 51:10 - 51:13
    I think this is really exciting.
  • 51:13 - 51:16
    You see, the annual growth rings here
  • 51:16 - 51:19
    show the presence
    of the stable isotope nitrogen-1 5,
  • 51:19 - 51:23
    which significantly comes from the oceans.
  • 51:23 - 51:26
    It could only have been carried here
    by the salmon.
  • 51:26 - 51:29
    Now, look. Here is the present,
  • 51:29 - 51:33
    the bark on the outside of a tree.
    So these rings here represent perhaps
  • 51:33 - 51:36
    about the last 1 5 years
    and they're very closely packed together.
  • 51:36 - 51:41
    But here, back in the 1 980s,
    the rings are twice as thick.
  • 51:41 - 51:46
    The trees have been growing twice
    as much during the course of a year.
  • 51:46 - 51:49
    So perhaps the salmon runs then
    were even more productive
  • 51:49 - 51:52
    than they have been recently.
  • 51:52 - 51:53
    But that's not the best thing.
  • 51:53 - 51:55
    Come and have a look at this.
  • 51:55 - 52:00
    By measuring the abundance of that
    nitrogen isotope in this material,
  • 52:00 - 52:05
    I can tell you that majestic old giants
    like this beauty here
  • 52:05 - 52:15
    are actually composed of up to
    85%/ material that's derived from salmon.
  • 52:15 - 52:21
    Now, when I was a teenager, I remember
    learning that I was made of carbon,
  • 52:21 - 52:24
    and carbon could only be formed
    when stars died.
  • 52:24 - 52:29
    Effectively, I was made of dead stars,
    and that struck me as terribly romantic.
  • 52:29 - 52:36
    But look at this.
    This is a forest made of the ocean!
  • 52:36 - 52:42
    That's why the tree needs the fish.
  • 52:42 - 52:46
    Without this
    unlikely sounding relationship,
  • 52:46 - 52:53
    this magnificent ancient forest
    just wouldn't be the place it is today-
  • 52:53 - 52:56
    But there is one more relationship
  • 52:56 - 53:00
    crucial to seasonal forest
    all around the world
  • 53:00 - 53:05
    when it comes to surviving
    constant change-
  • 53:05 - 53:09
    And it's one that reaches
    its greatest intensity now,
  • 53:09 - 53:14
    at the height of summer-
  • 53:14 - 53:21
    1t's the driest time of year,
    and the trees need water-
  • 53:21 - 53:24
    Fortunately,
    united with their fungal partners,
  • 53:24 - 53:28
    the trees
    have massively extended their roots-
  • 53:28 - 53:31
    Fungal threads in the soil
    are absorbing water
  • 53:31 - 53:35
    and passing it to the tree-
  • 53:35 - 53:38
    But what has only recently
    been discovered
  • 53:38 - 53:44
    is the sheer scale
    of these fungal root networks-
  • 53:44 - 53:48
    A single cubic centimetre of the soil here
  • 53:48 - 53:53
    can have a mile of these
    white fungal threads running through it -
  • 53:53 - 53:56
    they're called mycorrhizae.
  • 53:56 - 53:58
    And for me,
  • 53:58 - 54:05
    it's these organisms that are
    the real secret of the forest here.
  • 54:05 - 54:06
    1n the lab,
  • 54:06 - 54:18
    the genetic fingerprints of individual
    mycorrhizae have been identified-
  • 54:18 - 54:22
    By mapping an area 3O metres across,
    it's been discovered
  • 54:22 - 54:29
    that individual fungi
    connect to more than a single tree-
  • 54:29 - 54:30
    Just one fungus
  • 54:30 - 54:37
    can be joined to 8O%
    of all of the plants growing here-
  • 54:37 - 54:40
    And, amazingly, these physical links
  • 54:40 - 54:46
    enable different species of plants
    to exchange nutrients-
  • 54:46 - 54:51
    Older established plants
    are even nurturing younger weaker ones-
  • 54:51 - 54:56
    1t acts like
    an underground welfare system-
  • 54:56 - 55:01
    These giant webs connect all of the trees
    in this forest,
  • 55:01 - 55:07
    and keep them, and all of the things
    that are dependent upon them, alive.
  • 55:07 - 55:24
    That's why scientists
    are calling this the wood-wide web.
  • 55:24 - 55:28
    1t's thanks to this natural phenomenon,
    the wood-wide web,
  • 55:28 - 55:34
    that together the trees
    in the forest ecosystems are resilient-
  • 55:34 - 55:38
    Resilient enough to cope
    with the dramatic changes
  • 55:38 - 55:49
    they encounter every year-
  • 55:49 - 55:57
    And what's really amazing
    is how the web is built-
  • 55:57 - 56:01
    It's thanks to hungry mammals
    like our flying squirrels
  • 56:01 - 56:07
    that this essential life-support system
    is effectively maintained.
  • 56:07 - 56:12
    It's actually fair to say that these trees
    wouldn't be standing here,
  • 56:12 - 56:18
    wouldn't be thriving,
    unless a squirrel had eaten a truffle.
  • 56:18 - 56:24
    And thatis fantastic!
  • 56:24 - 56:25
    1t is fantastic-
  • 56:25 - 56:29
    1t's fantastic to think
    that what animals do in one season
  • 56:29 - 56:38
    influences the forest ecosystem
    throughout the year-
  • 56:38 - 56:47
    1t's almost as if all of these stories
    are choreographed-
  • 56:47 - 56:50
    The arrival of the salmon
    at exactly the right time
  • 56:50 - 56:54
    to fatten the bears for winter.
  • 56:54 - 56:57
    Then the emergence
    of the lush green vegetation
  • 56:57 - 57:03
    fertilized by those salmon to sustain the
    bears when they emerge from hibernation.
  • 57:03 - 57:08
    The squirrels foraging for truffles
    in the autumn time,
  • 57:08 - 57:10
    and sowing their spores
    throughout the forest
  • 57:10 - 57:16
    to grow a fungal network that joins
    all of the trees and all of the plants,
  • 57:16 - 57:20
    and provides them with nutrients.
  • 57:20 - 57:25
    The budworm chewing a hole
    in springtime in the canopy,
  • 57:25 - 57:30
    so that in summer, sunlight floods down
    to the forest's floor
  • 57:30 - 57:35
    and produces the perfect hunting habitat
    for lynx.
  • 57:35 - 57:38
    It's all in the timings.
  • 57:38 - 57:41
    And it's this that makes
    these temperate forests
  • 57:41 - 58:02
    such magical places.
  • 58:02 - 58:06
    If you'd like to know more about the
    fascinating web of links between species,
  • 58:06 - 58:12
    the 0pen University has produced some
    material both to inform and inspire you.
  • 58:12 - 58:22
    For your free copy, or to find out more
    about 0pen University programmes, ring...
  • 58:22 - 58:27
    0r go to the website...
  • 58:27 - 58:31
    And then follow the links
    to 0pen University.
  • 58:31 - 58:35
    And join me next time
    when 1'll be travelling
  • 58:35 -
    to some of the world's
    greatest water habitats-
Title:
The Magical Forest (BBC Documentary 2012)
Description:

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http://www.youtube.com/EvolutionDocumentary

Broadcast 2012. In this episode, Chris travels to North America to witness the annual miracle of the temperate forest: the destruction of its ecosystem in winter, followed by it rebuilding itself in spring. Chris marvels at the exquisite timing that is necessary in two particularly wonderful stories - the story of how the Canada lynx depends for its prey on a caterpillar high up in the canopy, and the story of why the giant trees of the north-west are dependent on bears and salmon.

Secrets of Our Living Planet showcases the incredible ecosystems that make life on Earth possible. Using beautifully shot scenes from all over the world, naturalist Chris Packham reveals the hidden wonder of the creatures that we share the planet with, and the intricate, clever and bizarre connections between the species, without which life just could not survive. For him, what is really beautiful about nature is not the amazing animals and plants that we share the planet with but the hidden relationships between them. Discover why a tiger needs a crab; or why a gecko needs a giraffe. Each week Chris visits one of our planet's most vital and spectacular habitats and dissects it, to reveal the secrets of how our living planet works.

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Video Language:
Sinhala
Duration:
59:01
Amara Bot edited English subtitles for The Magical Forest (BBC Documentary 2012)
Amara Bot added a translation

English subtitles

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