- hace 6 días
Categoría
📺
TVTranscripción
00:00Nuestro planeta es el más grande puzzle de vivienda en el universo.
00:05Un colección de mundos dentro de mundos.
00:09Cada uno un ecosistema de un ecosistema de vida.
00:13Pero ¿cómo funcionan?
00:20El intercambio web de relaciones y la influencia de las fuerzas naturales
00:26hace cada micro-world complejo y único.
00:33Así que para descubrir sus secretos,
00:35tenemos que explorarlos uno por uno,
00:39untargar sus piezas interlocking,
00:43y finalmente revelar la pieza vitala,
00:46la clave a la vida itself,
00:49hidden deep within
00:51cada uno de los micro-worldes.
00:56In the remote temperate region of the Pacific Northwest,
01:05there's a remarkable ecosystem.
01:11Canada's coastal forest
01:13has some of the largest trees on Earth.
01:17And they reach right down to the shoreline.
01:20But that's not all.
01:21This place is also jam-packed with wildlife.
01:26This coastline is an extraordinary merging of land and sea,
01:42which showcases some of nature's greatest living spectacles.
01:45In fact, these coastal areas are such great habitat for these top predators,
02:03that they're here in some of the highest densities on the continent.
02:06Winters here can be harsh,
02:11with blanketing snow and very little sunlight.
02:15Yet this forest is one of the most productive in the world.
02:19The sheer volume of plant material this forest accumulates
02:23outweighs even some of the world's tropical rainforests.
02:26So where do all the nutrients come from
02:35that allow the trees of this forest to get so big?
02:41This coastal forest stretches for thousands of kilometres
02:44along the North American coast,
02:47from Northern California,
02:49right up to Canada and Southern Alaska.
02:51It's a landscape forged by glaciers
02:57and bordered by a mountain range stretching right along the coast.
03:04And to its west sits the Pacific Ocean,
03:08thousands of kilometres of water
03:10that floods in to fill sheltered inlets and bays.
03:13This micro-world is more than just a forest.
03:20And to see just what it is that makes this place tick,
03:24we'll need to explore all of these parts.
03:31In the North American coastal forest,
03:34there's one thing,
03:35or rather a few million things,
03:38that dominate the landscape.
03:39These trees are huge.
03:52Many are 70 metres tall,
03:54and some are over a thousand years old.
03:58But the great coniferous forests of North America
04:00are more than just trees.
04:03They're homes for squirrels,
04:05rich hunting grounds for pine martens.
04:17And nest sites for great grey owls to raise a family.
04:20There are top predators here too,
04:35and the generally solitary brown bear
04:37can live here in surprising numbers.
04:44These brown bears manage to put on so much weight
04:47that they've become the largest in the world.
04:50Another top predator thrives here too,
04:56the grey wolf.
04:57This population has become particularly adapted
05:00to living in this unique forest environment.
05:04Each in their own way,
05:06these animals depend on the giant trees
05:08that stretch for thousands of kilometres
05:10along this coast.
05:14These trees are actually some of the largest living things
05:17on the planet,
05:18and they're still growing.
05:22But how do they get so big?
05:34Trees need nutrients
05:36in the form of phosphates
05:37and nitrates to grow.
05:38These are essential building blocks
05:45that fuel growth.
05:47And what growth?
05:55Each tree can weigh over 150,000 kilograms.
06:00And to get to this size,
06:04more than a million kilograms of nutrients
06:07are drawn up by the trees in this forest every year.
06:11But with so many trees,
06:13the available nitrates and phosphates
06:15are soon locked up in the forest's living tissue.
06:19So where do these building blocks come from
06:22to make these giant trees?
06:26It's too wet for forest fires
06:28that might release nutrients in ash.
06:31So the only way trees get recycled here
06:34is when strong winds and old age
06:36put an end to a giant's life.
06:38The nourishing chemicals locked up in its tissues
06:49provide a feast
06:50for decomposing lichens and fungi,
06:53which gradually break it down
06:55and return the life-giving elements
06:58into the soil.
07:05Thanks to the nutrients provided
07:06by these decomposers,
07:08these small seedlings
07:09might still be standing
07:11in some 500 years' time.
07:18This slow process of death,
07:21decay and recycling
07:22feeds the new life
07:24that colonizes gaps
07:25on the forest floor.
07:28But the death of one or two trees
07:31cannot justify this microworld's
07:33prolific growth.
07:36The nutrients that feed
07:38feed these trees must be coming
07:40from somewhere else.
07:44To find it, we need to go beneath the canopy
07:47and get to know some of the animals
07:49in this forest.
07:50Our journey begins in November
07:53when the ice-cold grip of winter
07:55is setting in.
07:58The cold can make this one of the toughest times of year
08:01for the animals in this forest.
08:03But there's still life here.
08:07Wild eagles weather out the winter months
08:15in this coastal forest.
08:17The eagle is another of the forest's top predators.
08:24And in winter,
08:25these eagles group together
08:27around the open waterways
08:28on the lookout for carrion
08:30and live prey.
08:31These are the largest congregations
08:40of bald eagle
08:41found anywhere on earth.
08:48The flowing rivers full of fish
08:50provide food year-round,
08:52allowing the eagle to prosper
08:53in the freezing conditions.
08:55But few other animals
08:59are so lucky.
09:02Amongst the trees,
09:03bears are nowhere to be found.
09:06They've escaped the brunt of the weather
09:07and have retreated
09:08to dens in the mountains.
09:12But this freeze
09:14doesn't last forever.
09:15With the arrival of spring,
09:20the North American days
09:21begin to lengthen.
09:23Up in the mountains
09:25on the eastern flank of the forest,
09:27the bears are now emerging
09:28with their newly born cubs.
09:30The cubs were born
09:45in the heart of winter
09:46and this is their first journey
09:48outside the den.
09:51They're still finding their feet
09:53on the slippery slopes
09:54that descend down to the forest.
10:00The adult bears
10:04might not have eaten
10:05for over half the year.
10:08Yet in the next few months,
10:09they can pack on
10:10an impressive 100 kilograms
10:12and in this forest,
10:14they thrive.
10:17Bears are capable predators
10:19but they're also opportunists,
10:22able to eat
10:22a massive range of food.
10:26And they even eat grass.
10:30But for the bears,
10:33perhaps the best thing
10:34about these forests
10:35is that they're right on the coast.
10:41And bears that are after
10:43any protein they can find
10:44are able to walk
10:46right down to the sea
10:47to find food.
10:48Here bears can find valuable protein
10:59from clams
11:00that they dig up
11:01on the sandy shore.
11:08And there's plenty more food
11:10available on the shoreline.
11:12As the tide goes out,
11:15other forest creatures
11:17take advantage of the shallows.
11:24With forest cover
11:25just meters away,
11:27raccoon families
11:28catch crabs
11:29in the draining pools.
11:32These morsels of food
11:34gathered along the shoreline
11:35by forest creatures
11:37are a hint
11:38to the potential nutrients
11:39that the Pacific Ocean
11:41can offer this forest.
11:48For now,
11:49bears and raccoons
11:50must resign themselves
11:51to foraging
11:52at low tide.
11:53But the ocean
12:04has an important part
12:05to play
12:06in this forest story.
12:09And its great productivity
12:11may just hold the key
12:12to the nutrients
12:14that feed this forest.
12:17To understand this,
12:19we need to take a look
12:20at just how spectacular
12:21this ocean is.
12:24And this will help us see
12:26just how the ocean nutrients
12:28might be getting onto land.
12:32It's now early spring
12:33and the warming waters
12:35attract herring
12:36from the open Pacific Ocean
12:37to the bays and inlets
12:39along the coast.
12:40And they gather
12:41in their millions.
12:44It's an event
12:45that doesn't escape
12:46the attention
12:47of predators.
12:51Sea lions head
12:53towards the commotion
12:54and dolphins move
12:58into position.
13:02The herring attempt
13:03to confuse their assailants
13:05by schooling together
13:06in great shoals.
13:07But attack
13:17comes from all angles.
13:27Herring
13:28are considered
13:31a keystone species
13:32along this coast.
13:34A species so important
13:35that the whole system
13:36could collapse
13:37if they were removed.
13:38and one massive creature
13:49has travelled over
13:514,000 kilometres
13:52to be here.
13:59The humpback whale.
14:00Although thousands of humpbacks
14:04migrate here
14:05in the spring
14:05only a few
14:07have developed
14:08a neat predatory trick.
14:14Working together
14:15these humpbacks
14:17use circular streams
14:18of bubbles
14:18and loud calls
14:20to corral the fish
14:21into tighter
14:22and tighter balls.
14:24lunging up from beneath
14:35their huge mouths
14:36engulf their prey.
14:40Humpbacks have to eat
14:41up to one and a half
14:42tonnes of food
14:43per day
14:44and these herring
14:46provide about 20%
14:47of the food they eat
14:48along this coast
14:49over the spring
14:51and summer.
14:53The whales
14:54don't feed
14:54over winter
14:55and the herring
14:56provide essential energy
14:57before they begin
14:58their long migration
14:59back to the tropics.
15:05With such a swathe
15:07of predators
15:07it seems madness
15:09that the herring
15:09come to this coast
15:10at all.
15:14But they need
15:15this coastline
15:16for the future
15:17of their species.
15:21The coastal winds
15:23pull nutrient-rich water
15:25from the ocean depths
15:26into the inlets
15:27and bays.
15:34And these fertile waters
15:36turn green
15:37with a plankton bloom.
15:38These vast quantities
15:52of microscopic plants
15:53and animals
15:54are potential food
15:55for thousands
15:56of tiny mouths.
16:00And this is why
16:01the herring are here.
16:03But the adult herring
16:04haven't come here
16:05so that they can eat
16:06the plankton
16:07but so that their offspring
16:08can.
16:10They're here
16:10to breed.
16:16In a spawning frenzy
16:17females coat the seaweeds
16:19and rocks
16:20along this coast
16:21with eggs.
16:22And the males
16:23follow with a fertilising
16:24liquid called
16:25milt.
16:29The small eggs
16:30are just over
16:31a millimetre across
16:32and with each fish
16:34producing up to
16:34130,000 of them
16:36they can coat
16:38rocks and vegetation
16:39more than
16:4020 layers thick.
16:42Coastal birds
16:43are quick to respond.
16:48Gulls pluck eggs
16:49from the shallows.
16:50And huge flocks
16:59of migrating birds
17:00feast as they
17:01journey northwards.
17:09The herring
17:11and their eggs
17:12provide huge amounts
17:13of food for animals
17:14along this coast
17:15allowing the nutrients
17:18in the open ocean
17:19and the plankton
17:20bloom
17:20to reach the land.
17:23But the fish
17:24and eggs
17:24are just a thin layer
17:25of potential nutrients
17:27that sit right
17:29on the shoreline.
17:31Their influence
17:33doesn't travel far
17:34into the forest.
17:38Forest animals
17:39like bears
17:39and wolves
17:40unable to join
17:41in the herring feast
17:42can only wait
17:43patiently
17:44on the beaches.
17:47For hungry forest animals
17:49life can become
17:51a bit of a waiting game.
17:53As the summer arrives
17:55the surviving herring
17:56move off
17:57into deeper waters
17:58but the key
17:59to this microworld
18:01is still out at sea
18:02waiting for the rains.
18:07And as the sea warms
18:09the Pacific winds
18:10carry water
18:11drawn up
18:11into clouds
18:12towards the North
18:14American coast.
18:17The gathering clouds
18:19hit the coastal mountains
18:20and release their moisture
18:22as rain.
18:29And lots of it.
18:31The forest is showered
18:41with three to five
18:42metres of rain
18:43every year
18:44filling the rivers
18:46into torrents.
18:56Their tributaries
18:58spread like arteries
18:59winding deep
19:00into the forest.
19:01But the flowing rivers
19:06carry the nutrients
19:07that trees need
19:08to grow
19:08out of the mountains
19:10out of the forest
19:12and into the ocean.
19:15So there must be
19:16one last piece
19:17to the puzzle.
19:20The key
19:21that allows
19:22the nutrients
19:23to flow
19:23from the highly
19:24productive ocean
19:25into the forest.
19:26and it's a fish
19:32that's building up
19:33in numbers
19:34along the North
19:35American coast.
19:39Salmon
19:39These five species
19:42of Pacific salmon
19:43may have travelled
19:44more than a thousand
19:45kilometres
19:45from the open ocean
19:46and are reaching
19:48the end
19:48of their journey.
19:49These mature salmon
19:53have spent
19:54their adult lives
19:55in the ocean
19:55building up
19:56their muscles
19:57and fat reserves
19:57for this one
19:59final reproductive moment.
20:03Mature salmon
20:04come to this coast
20:05every year
20:05to breed
20:06but unlike
20:07the herring
20:08which spawn
20:08along the coast
20:09these salmon
20:10adopt a bizarre
20:12reproductive strategy
20:13a strategy
20:15which underpins
20:16the productivity
20:17of this entire forest.
20:24They switch
20:25their biology
20:25moving out
20:27of the ocean
20:27into the freshwater
20:29streams
20:29along the
20:30North American coast.
20:32These fish
20:33will travel
20:33sometimes
20:34hundreds of kilometres
20:35in land
20:36to the rivers
20:37of their birth
20:37and only there
20:39will they lay
20:40their eggs.
20:59But the rivers
21:00running through
21:01these forests
21:02can be treacherous.
21:05such huge
21:12parcels
21:12of protein
21:13from the ocean
21:13don't go unnoticed.
21:23Bears
21:24line the rivers.
21:25These normally
21:52solitary predators
21:53congregate in huge numbers.
21:55you can find 25 individuals
21:57on a single waterfall.
22:01But space
22:02at these busy falls
22:03is at a premium.
22:06And mothers
22:06with cubs
22:07are often relegated
22:08to the quieter sections
22:09of the river
22:10where young bears
22:12can learn the art
22:13of catching a salmon.
22:14catching salmon
22:24in deep water
22:25can be a challenge
22:26even for the experienced.
22:35Most of the salmon
22:36arrive in autumn
22:36when the bears
22:37are preparing
22:38to retire to the mountains
22:39for another year.
22:40this is the bears
22:43big chance
22:43to put on body fat
22:45before the winter
22:46sets in.
22:48The fish feast
22:49is the key reason
22:50why these bears
22:51do so well
22:52in this forest.
22:54And there's no coincidence
22:55that there are so many bears here.
22:58Without the salmon
22:59nine out of every ten bears
23:02in this forest
23:02would probably not be here at all.
23:04bears are messy eaters
23:11and their scraps
23:12become food
23:13for other forest creatures.
23:17Grey wolves
23:18which normally hunt
23:19animal-like deer
23:20join the bears
23:21feeding along the riverbanks.
23:25They're more than capable
23:27of catching salmon themselves
23:28but often let the bears
23:30do the hard work
23:30and turn to scavenging.
23:34The wolves of this forest
23:38have developed
23:39such a strong relationship
23:40with the coast
23:41that they barely venture
23:42beyond its limits.
23:47This isolation
23:48could start them
23:50on the slow path
23:51towards becoming
23:52a new wolf species
23:54the coastal wolf.
23:58These wolves
23:59are not isolated
23:59on an island
24:00or in a valley
24:01but instead isolated
24:03by their unique behaviour.
24:05It's a life
24:06that's centred
24:07around the coast
24:08and the habits
24:09are passed on
24:10from mother
24:11to young.
24:13It's just another reminder
24:15of the importance
24:15of the marine ecosystem
24:17to the thriving
24:18of life here.
24:22But it isn't just
24:24the bears
24:24and the wolves
24:25that rely so heavily
24:26on the salmon.
24:28Larger life forces
24:29in this forest
24:30depend on the salmon too
24:31but the bustling rivers
24:35full of fish
24:35are no use
24:36to them yet.
24:40The forest's
24:41waiting game
24:42continues.
24:43The surviving salmon
24:48move on
24:48driven by raging hormones
24:54which have now
24:55turned many of them red.
24:58They travel far
24:59into the forest
25:00some for over
25:02a thousand kilometres
25:03into the tiniest streams.
25:05Their incredible sense
25:10of smell
25:11carries them
25:11to the stream
25:12where they themselves
25:13were born
25:14and where now
25:15they'll mate
25:16and lay their eggs.
25:17This is their
25:25ultimate sacrifice.
25:29With their eggs
25:30safely tucked away
25:31in the riverbed
25:32their one way journey
25:33is at an end.
25:41They've exhausted
25:42themselves to get here
25:44and invested
25:45all their energy reserves.
25:47Their wasted bodies
25:49can swim no more.
25:55Salmon carcasses
25:57sprawl across the river
25:58but this seemingly
25:59useless death
26:00is not wasted.
26:06These carcasses
26:07represent the massive
26:09injection of nutrients
26:10that the forest ecosystem
26:11has been waiting for.
26:13The nutrients
26:14that are the elements
26:15of life.
26:17because even in death
26:23the salmon feed
26:24the animals
26:25of the forest.
26:34Carried onto land
26:35by scavengers
26:36salmon
26:37become soil.
26:39their nutrients
26:42seep into the water
26:43table
26:43and it's now
26:45the trees turn
26:46to feast
26:47on the salmon.
26:51These are the nutrients
26:52that drive
26:53the coastal forest
26:54and the supersized trees
26:57grow fast
26:58tall
26:59and strong.
27:00But the death
27:05of the salmon
27:06is not a completely
27:07selfless act.
27:09The nutrients
27:11in their bodies
27:12feed the streams.
27:14They feed algae
27:15and insects.
27:19That will be a
27:20miniature feast
27:20for the tiny
27:21baby salmon
27:22that will emerge
27:23the following year.
27:24The next generation
27:27of nutrient
27:28messengers
27:29that will live out
27:30their adult lives
27:31in the ocean
27:31and will one day
27:33return to this same spot
27:34in the riverbed
27:35to make the ultimate
27:37sacrifice
27:37of their own.
27:38life on every level
27:47from mosses
27:48to lichens
27:49trees to animals
27:51flourish
27:52in this coastal
27:53rainforest.
27:54The trees
27:55close to salmon
27:56streams
27:57grow taller
27:58and faster.
28:00The forest
28:01animals have
28:01more food
28:02and live in
28:03higher densities
28:04in these forests.
28:06Some have even
28:07become so
28:08tied to the ocean
28:09that they're
28:10truly becoming
28:11coastal specialists.
28:14But the secret
28:15of this forest's
28:16success
28:17doesn't come
28:18from the land
28:18at all
28:19but from the
28:20riches
28:20of the Pacific
28:21Ocean
28:21sitting just
28:23offshore.
28:25This is a
28:26forest
28:26fuelled
28:27by the ocean.
28:33And tomorrow night
28:34explore the
28:35Great Barrier Reef.
28:36Nature's
28:37Microworlds
28:38continues here
28:39at 7.30.
28:40Now a land of
28:41contrasts
28:42from billionaires
28:43to refugees.
28:45Simon Reeve
28:45follows Turkey's
28:46Aegean coast
28:47to the Syrian
28:48border next.
28:50Then we're
28:51Beirut bound
28:52here on BBC4
28:53an eye-opening
28:54art lover's guide
28:55to the Lebanese
28:56capital
28:57in an hour.
28:57in a
29:06year-obeyed
29:07to the
29:08world.
29:08It's very
29:09odd on you
29:09to go to the
29:10world.
29:11It's been a
29:11modern year-old
29:12time.
Sé la primera persona en añadir un comentario