0:00:02 > 0:00:06Our planet is the greatest living puzzle in the universe.
0:00:06 > 0:00:09A collection of worlds within worlds.
0:00:09 > 0:00:13Each one a self-contained ecosystem, bursting with life.
0:00:18 > 0:00:20But how do they work?
0:00:20 > 0:00:23The intricate web of relationships
0:00:23 > 0:00:26and the influence of natural forces
0:00:26 > 0:00:29makes each microworld
0:00:29 > 0:00:33complex and unique.
0:00:33 > 0:00:36So, to discover their secrets,
0:00:36 > 0:00:39we need to explore them one by one,
0:00:39 > 0:00:43untangle their interlocking pieces
0:00:43 > 0:00:48and ultimately reveal the vital piece -
0:00:48 > 0:00:51the key to life itself, hidden deep within
0:00:51 > 0:00:53each of Nature's Microworlds.
0:01:01 > 0:01:05In the remote temperate region of the Pacific Northwest,
0:01:05 > 0:01:07there's a remarkable ecosystem.
0:01:11 > 0:01:17Canada's coastal forest has some of the largest trees on Earth,
0:01:17 > 0:01:20and they reach right down to the shoreline.
0:01:20 > 0:01:22But that's not all.
0:01:22 > 0:01:26This place is also jam-packed with wildlife.
0:01:37 > 0:01:41This coastline is an extraordinary merging of land and sea
0:01:41 > 0:01:46which showcases some of nature's greatest living spectacles.
0:01:46 > 0:01:50The forest is home to iconic species like bears...
0:01:52 > 0:01:54..eagles
0:01:54 > 0:01:56and wolves.
0:01:58 > 0:02:00In fact, these coastal areas
0:02:00 > 0:02:04are such great habitat for these top predators
0:02:04 > 0:02:08that they're here in some of the highest densities on the continent.
0:02:08 > 0:02:11Winters here can be harsh
0:02:11 > 0:02:15with blanketing snow and very little sunlight.
0:02:15 > 0:02:19Yet this forest is one of the most productive in the world.
0:02:19 > 0:02:23The sheer volume of plant material this forest accumulates
0:02:23 > 0:02:28outweighs even some of the world's tropical rainforests.
0:02:32 > 0:02:35So, where do all the nutrients come from
0:02:35 > 0:02:39that allow the trees of this forest to get so big?
0:02:41 > 0:02:45This coastal forest stretches for thousands of kilometres
0:02:45 > 0:02:47along the North American coast -
0:02:47 > 0:02:51from Northern California right up to Canada and southern Alaska.
0:02:55 > 0:02:58It's a landscape forged by glaciers
0:02:58 > 0:03:02and bordered by a mountain range stretching right along the coast.
0:03:05 > 0:03:08And to its west sits the Pacific Ocean.
0:03:08 > 0:03:10Thousands of kilometres of water
0:03:10 > 0:03:14that floods in to fill sheltered inlet and bays.
0:03:17 > 0:03:20This microworld is more than just a forest.
0:03:20 > 0:03:24And to see just what it is that makes this place tick,
0:03:24 > 0:03:27we'll need to explore all of these parts.
0:03:32 > 0:03:35In the North American Coastal Forest, there's one thing -
0:03:35 > 0:03:39or rather a few million things - that dominate the landscape.
0:03:40 > 0:03:43Spruce, cedar,
0:03:43 > 0:03:46fir trees and redwoods tower above the forest floor.
0:03:49 > 0:03:51These trees are huge.
0:03:51 > 0:03:54Many are 70 metres tall
0:03:54 > 0:03:57and some are over 1,000 years old.
0:03:58 > 0:04:01But the great coniferous forests of North America
0:04:01 > 0:04:03are more than just trees.
0:04:03 > 0:04:06They're homes for squirrels...
0:04:07 > 0:04:09..rich hunting grounds for pine martens...
0:04:17 > 0:04:21..and nest sites for Great Grey Owls to raise a family.
0:04:33 > 0:04:35There are top predators here too,
0:04:35 > 0:04:37and the generally solitary brown bear
0:04:37 > 0:04:39can live here in surprising numbers.
0:04:43 > 0:04:47These brown bears managed to put on so much weight
0:04:47 > 0:04:50that they've become the largest in the world.
0:04:52 > 0:04:57Another top predator thrives here too - the grey wolf.
0:04:57 > 0:05:00This population has become particularly adapted
0:05:00 > 0:05:03to living in this unique forest environment.
0:05:04 > 0:05:08Each in their own way, these animals depend on the giant trees
0:05:08 > 0:05:11that stretch for thousands of kilometres along this coast.
0:05:14 > 0:05:17These trees are actually some of the largest living things
0:05:17 > 0:05:20on the planet, and they're still growing.
0:05:22 > 0:05:24But how do they get so big?
0:05:34 > 0:05:38Trees need nutrients in the form of phosphates and nitrates to grow.
0:05:43 > 0:05:47These are essential building blocks that fuel growth -
0:05:47 > 0:05:49and WHAT growth!
0:05:56 > 0:06:00Each tree can weigh over 150,000 kilograms.
0:06:03 > 0:06:07And to get to this size, more than a million kilograms of nutrients
0:06:07 > 0:06:10are drawn up by the trees in this forest every year.
0:06:12 > 0:06:16But with so many trees, the available nitrates and phosphates
0:06:16 > 0:06:19are soon locked up in the forest's living tissue.
0:06:20 > 0:06:24So where do these building blocks come from to make giant trees?
0:06:27 > 0:06:30It's too wet for forest fires that might release nutrients in ash,
0:06:30 > 0:06:34so the only way trees get recycled here
0:06:34 > 0:06:38is when strong winds and old age put an end to a giant's life.
0:06:40 > 0:06:42CREAKING
0:06:42 > 0:06:45CRASHING
0:06:46 > 0:06:50The nourishing chemicals locked up in its tissues provide a feast
0:06:50 > 0:06:55for decomposing lichens and fungi, which gradually break it down
0:06:55 > 0:06:59and return the life-giving elements into the soil.
0:07:05 > 0:07:08Thanks to the nutrients provided by these decomposers,
0:07:08 > 0:07:13these small seedlings might still be standing in 500 years' time.
0:07:18 > 0:07:23This slow process of death, decay and recycling feeds the new life
0:07:23 > 0:07:26that colonises gaps on the forest floor.
0:07:29 > 0:07:31But the death of one or two trees
0:07:31 > 0:07:35cannot justify this microworld's prolific growth.
0:07:37 > 0:07:41The nutrients that feed these trees must be coming from somewhere else.
0:07:44 > 0:07:47To find it, we need to go beneath the canopy
0:07:47 > 0:07:50and get to know some of the animals in this forest.
0:07:52 > 0:07:53Our journey begins in November
0:07:53 > 0:07:56when the ice-cold grip of winter is setting in.
0:07:58 > 0:08:01The cold can make this one of the toughest times of year
0:08:01 > 0:08:03for the animals in this forest.
0:08:05 > 0:08:07But there's still life here.
0:08:07 > 0:08:11SQUAWKING
0:08:13 > 0:08:17Bald eagles weather out the winter months in this coastal forest.
0:08:20 > 0:08:24The eagle is another of the forest's top predators.
0:08:24 > 0:08:28And in winter, these eagles group together around
0:08:28 > 0:08:31the open waterways on the lookout for carrion and live prey.
0:08:38 > 0:08:41These are the largest congregations of bald eagle
0:08:41 > 0:08:43found anywhere on Earth.
0:08:48 > 0:08:52The flowing rivers full of fish provide food year-round,
0:08:52 > 0:08:55allowing the eagle to prosper in the freezing conditions.
0:08:58 > 0:09:00But few other animals are so lucky.
0:09:02 > 0:09:06Amongst the trees, bears are nowhere to be found.
0:09:06 > 0:09:09They've escaped the brunt of the weather and have retreated
0:09:09 > 0:09:10to dens in the mountains.
0:09:13 > 0:09:15But this freeze doesn't last forever.
0:09:18 > 0:09:20With the arrival of spring,
0:09:20 > 0:09:22the North American days begin to lengthen.
0:09:24 > 0:09:27Up in the mountains on the eastern flank of the forest,
0:09:27 > 0:09:31the bears are now emerging with their newly born cubs.
0:09:33 > 0:09:36BEARS BARK
0:09:44 > 0:09:47The cubs were born in the heart of winter,
0:09:47 > 0:09:49and this is their first journey outside the den.
0:09:51 > 0:09:54They're still finding their feet on the slippery slopes
0:09:54 > 0:09:56that descend down to the forest.
0:10:03 > 0:10:08The adult bears might not have eaten for over half the year,
0:10:08 > 0:10:10yet in the next few months, they can pack on
0:10:10 > 0:10:15an impressive 100 kilograms, and in this forest, they thrive.
0:10:17 > 0:10:21Bears are capable predators, but they're also opportunists,
0:10:21 > 0:10:24able to eat a massive range of food.
0:10:26 > 0:10:29And they even eat grass.
0:10:32 > 0:10:36But for the bears, perhaps the best thing about these forests
0:10:36 > 0:10:39is that they're right on the coast.
0:10:42 > 0:10:45Bears that are after any protein they can find
0:10:45 > 0:10:49are able to walk right down to the sea to find food.
0:10:49 > 0:10:52BEAR SNUFFLES
0:10:57 > 0:11:00Here, bears can find valuable protein from clams
0:11:00 > 0:11:02that they dig up on the sandy shore.
0:11:08 > 0:11:12And there's plenty more food available on the shoreline.
0:11:13 > 0:11:16As the tide goes out,
0:11:16 > 0:11:19other forest creatures take advantage of the shallows.
0:11:24 > 0:11:27With forest cover just metres away,
0:11:27 > 0:11:30racoon families catch crabs in the draining pools.
0:11:33 > 0:11:37These morsels of food gathered along the shoreline by forest creatures
0:11:37 > 0:11:40are a hint to the potential nutrients that the Pacific Ocean
0:11:40 > 0:11:42can offer this forest.
0:11:48 > 0:11:51For now, bears and raccoons must resign themselves
0:11:51 > 0:11:54to foraging at low tide.
0:12:03 > 0:12:08But the ocean has an important part to play in this forest's story.
0:12:09 > 0:12:12And its great productivity may just hold the key
0:12:12 > 0:12:15to the nutrients that feed this forest.
0:12:17 > 0:12:19To understand this,
0:12:19 > 0:12:23we need to take a look at just how spectacular this ocean is.
0:12:24 > 0:12:26And this will help us see
0:12:26 > 0:12:30just how the ocean nutrients might be getting onto land.
0:12:32 > 0:12:36It's now early spring, and the warming waters attract herring
0:12:36 > 0:12:40from the open Pacific Ocean to the bays and inlets along the coast.
0:12:40 > 0:12:43And they gather in their millions.
0:12:45 > 0:12:48It's an event that doesn't escape the attention of predators.
0:12:52 > 0:12:54Sea lions head towards the commotion...
0:12:57 > 0:12:59..and dolphins move into position.
0:13:02 > 0:13:05The herring attempt to confuse their assailants
0:13:05 > 0:13:07by schooling together in great shoals.
0:13:17 > 0:13:19But attack comes from all angles.
0:13:30 > 0:13:34Herring are considered a keystone species along this coast,
0:13:34 > 0:13:37a species so important that the whole system could collapse
0:13:37 > 0:13:39if they were removed.
0:13:44 > 0:13:46SEA BIRDS CRY
0:13:47 > 0:13:53One massive creature has travelled over 4,000 kilometres to be here.
0:13:59 > 0:14:01The humpback whale.
0:14:03 > 0:14:05Although thousands of humpbacks migrate here in the spring,
0:14:05 > 0:14:10only a few have developed a neat predatory trick.
0:14:10 > 0:14:13WHALES SING TO EACH OTHER
0:14:15 > 0:14:19Working together, these humpbacks use circular streams of bubbles
0:14:19 > 0:14:23and loud calls to corral the fish into tighter and tighter balls.
0:14:23 > 0:14:27WHALES CALL OUT TO EACH OTHER
0:14:33 > 0:14:37Lunging up from beneath, their huge mouths engulf their prey.
0:14:40 > 0:14:44Humpbacks have to eat 1,500 tonnes of food a day.
0:14:44 > 0:14:49And these herring provide about 20% of the food they eat
0:14:49 > 0:14:52along this coast over the spring and summer.
0:14:53 > 0:14:55The whales don't feed over winter,
0:14:55 > 0:14:58and the herring provide essential energy
0:14:58 > 0:15:01before they begin their long migration back to the tropics.
0:15:06 > 0:15:08With such a swathe of predators,
0:15:08 > 0:15:11it seems madness that the herring come to this coast at all.
0:15:15 > 0:15:18But they need this coastline for the future of their species.
0:15:23 > 0:15:27The coastal winds pull nutrient-rich water from the ocean depths
0:15:27 > 0:15:28into the inlets and bays...
0:15:34 > 0:15:37..and these fertile waters turn green with the plankton bloom.
0:15:50 > 0:15:53These vast quantities of microscopic plants and animals
0:15:53 > 0:15:57are potential food for thousands of tiny mouths.
0:16:00 > 0:16:03This is why the herring are here.
0:16:03 > 0:16:05But the adult herring haven't come here
0:16:05 > 0:16:09so that they can eat the plankton, but so that their offspring can.
0:16:09 > 0:16:11They're here to breed.
0:16:16 > 0:16:19In a spawning frenzy, females coat the leaves and rocks
0:16:19 > 0:16:22along this coast with eggs
0:16:22 > 0:16:26and the males follow with a fertilising liquid called milt.
0:16:29 > 0:16:32The small eggs are just over a millimetre across
0:16:32 > 0:16:37and with each fish producing up to 130,000 of them,
0:16:37 > 0:16:42they can coat rocks and vegetation more than 20 layers thick.
0:16:42 > 0:16:44Coastal birds are quick to respond.
0:16:48 > 0:16:50Gulls pluck eggs from the shallows.
0:16:58 > 0:17:02And huge flocks of migrating birds feast as they journey northwards.
0:17:10 > 0:17:13The herring and their eggs provide huge amounts of food
0:17:13 > 0:17:16for animals along this coast,
0:17:16 > 0:17:20allowing the nutrients in the open ocean and the plankton bloom
0:17:20 > 0:17:22to reach the land.
0:17:23 > 0:17:28But the fish and eggs are just a thin layer of potential nutrients
0:17:28 > 0:17:30that sit right on the shoreline.
0:17:32 > 0:17:35Their influence doesn't travel far into the forest.
0:17:38 > 0:17:42Forest animals like bears and wolves unable to join in the herring feast
0:17:42 > 0:17:45can only wait patiently on the beaches.
0:17:48 > 0:17:52For hungry forest animals, life can become a bit of a waiting game.
0:17:54 > 0:17:59As the summer arrives, the surviving herring move off into deeper waters.
0:17:59 > 0:18:02But the key to this microworld is still out at sea
0:18:02 > 0:18:05waiting for the rains.
0:18:07 > 0:18:12As the sea warms, the Pacific winds carry water drawn up into clouds
0:18:12 > 0:18:14towards the North American coast.
0:18:14 > 0:18:18WIND BLOWS, THUNDER RUMBLES
0:18:18 > 0:18:20The gathering clouds hit the coastal mountains
0:18:20 > 0:18:23and release their moisture as rain.
0:18:30 > 0:18:31And lots of it.
0:18:39 > 0:18:44The forest is showered with three to five metres of rain every year...
0:18:45 > 0:18:48..filling the rivers into torrents.
0:18:48 > 0:18:52WATER ROARS
0:18:57 > 0:19:00Their tributaries spread like arteries
0:19:00 > 0:19:01winding deep into the forest.
0:19:04 > 0:19:08The flowing rivers carry the nutrients that trees need to grow
0:19:08 > 0:19:14out of the mountains, out of the forest and into the ocean.
0:19:14 > 0:19:18So there must be one last piece to the puzzle.
0:19:20 > 0:19:23The key that allows the nutrients to flow
0:19:23 > 0:19:26from the highly-productive ocean into the forest.
0:19:30 > 0:19:33It's a fish that's building up in numbers
0:19:33 > 0:19:36along the North American coast.
0:19:39 > 0:19:41Salmon.
0:19:41 > 0:19:44These five species of Pacific salmon may have travelled
0:19:44 > 0:19:47more than a thousand kilometres from the open ocean
0:19:47 > 0:19:49and are reaching the end of their journey.
0:19:52 > 0:19:55These mature salmon have spent their adult lives in the ocean,
0:19:55 > 0:19:58building up their muscles and fat reserves
0:19:58 > 0:20:00for this one final reproductive moment.
0:20:03 > 0:20:07Mature salmon come to this coast every year to breed,
0:20:07 > 0:20:09but unlike the herring, which spawn along the coast,
0:20:09 > 0:20:13these salmon adopt a bizarre reproductive strategy.
0:20:13 > 0:20:19A strategy which underpins the productivity of this entire forest.
0:20:24 > 0:20:28They switch their biology, moving out of the ocean
0:20:28 > 0:20:32into the freshwater streams along the North American coast.
0:20:32 > 0:20:36These fish will travel sometimes hundreds of kilometres in land
0:20:36 > 0:20:41to the rivers of their birth and only there will they lay their eggs.
0:21:00 > 0:21:04But the rivers running through these forests can be treacherous.
0:21:11 > 0:21:16Such huge parcels of protein from the ocean don't go unnoticed.
0:21:23 > 0:21:26Bears line the rivers.
0:21:51 > 0:21:55These normally solitary predators congregate in huge numbers.
0:21:55 > 0:21:59You can find 25 individuals on a single waterfall.
0:22:01 > 0:22:04But space at these busy falls is at a premium.
0:22:06 > 0:22:08Mothers with cubs are often relegated
0:22:08 > 0:22:10to the quieter sections of the river,
0:22:10 > 0:22:15where young bears can learn the art of catching a salmon.
0:22:23 > 0:22:28Catching salmon in deep water can be a challenge,
0:22:28 > 0:22:32even for the experienced.
0:22:34 > 0:22:38Most of the salmon arrive in autumn when the bears are preparing
0:22:38 > 0:22:40to retire to the mountains for another year.
0:22:42 > 0:22:44This is the bears' big chance
0:22:44 > 0:22:47to put on body fat before the winter sets in.
0:22:47 > 0:22:50The fish feast is the key reason
0:22:50 > 0:22:54why these bears do so well in this forest.
0:22:54 > 0:22:58There's no coincidence that there are so many bears here.
0:22:58 > 0:23:03Without the salmon, nine out of every ten bears in this forest
0:23:03 > 0:23:05would probably not be here at all.
0:23:09 > 0:23:11Bears are messy eaters,
0:23:11 > 0:23:15and their scraps become food for other forest creatures.
0:23:17 > 0:23:21Grey wolves which normally hunt animal like deer
0:23:21 > 0:23:23join the bears feeding along the riverbanks.
0:23:25 > 0:23:28They're more than capable of catching salmon themselves,
0:23:28 > 0:23:33but often let the bears do the hard work and turn to scavenging.
0:23:37 > 0:23:40The wolves of this forest have developed such a strong relationship
0:23:40 > 0:23:44with the coast that they barely venture beyond its limits.
0:23:48 > 0:23:51This isolation could start them on the slow path
0:23:51 > 0:23:55towards becoming a new wolf species -
0:23:55 > 0:23:57the coastal wolf.
0:23:58 > 0:24:01These wolves are not isolated on an island or in a valley,
0:24:01 > 0:24:06but instead isolated by their unique behaviour.
0:24:06 > 0:24:08It's a life that's centred around the coast
0:24:08 > 0:24:13and the habits are passed on from mother to young.
0:24:13 > 0:24:16It's just another reminder about the importance
0:24:16 > 0:24:19of the marine ecosystem to the thriving of life here.
0:24:23 > 0:24:25But it isn't just the bears and wolves that rely
0:24:25 > 0:24:27so heavily on the salmon.
0:24:27 > 0:24:32Larger life forces in this forest depend on the salmon too.
0:24:34 > 0:24:37But the bustling rivers full of fish are no use to them yet.
0:24:40 > 0:24:43The forest's waiting game continues.
0:24:46 > 0:24:49The surviving salmon move on...
0:24:52 > 0:24:57..driven by raging hormones which have now turned many of them red.
0:24:58 > 0:25:01They travel far into the forest,
0:25:01 > 0:25:05some for over 1,000 kilometres, into the tiniest streams.
0:25:09 > 0:25:12Their incredible sense of smell carries them to the stream
0:25:12 > 0:25:15where they themselves were born and where now,
0:25:15 > 0:25:17they'll mate and lay their eggs.
0:25:23 > 0:25:27This is their ultimate sacrifice.
0:25:29 > 0:25:32With their eggs safely tucked away on the riverbed,
0:25:32 > 0:25:35their one-way journey is at an end.
0:25:41 > 0:25:44They've exhausted themselves to get here
0:25:44 > 0:25:47and invested all their energy reserves.
0:25:47 > 0:25:50Their wasted bodies can swim no more.
0:25:55 > 0:25:59Salmon carcasses sprawl across the river,
0:25:59 > 0:26:03but this seemingly useless death is not wasted.
0:26:06 > 0:26:09These carcasses represent the massive injection of nutrients
0:26:09 > 0:26:13that the forest ecosystem has been waiting for -
0:26:13 > 0:26:17the nutrients that are the elements of life.
0:26:21 > 0:26:26Even in death, the salmon feed the animals of the forest.
0:26:34 > 0:26:39Carried onto land by scavengers, salmon become soil.
0:26:41 > 0:26:44Their nutrients seep into the water table
0:26:44 > 0:26:48and it's now the trees' turn to feast on the salmon.
0:26:51 > 0:26:55These are the nutrients that drive the coastal forest
0:26:55 > 0:27:00and the super-sized trees grow fast, tall and strong.
0:27:05 > 0:27:08The death of the salmon is not a completely selfless act.
0:27:10 > 0:27:13The nutrients in their bodies feed the streams,
0:27:13 > 0:27:17they feed algae and insects...
0:27:18 > 0:27:21..that will be a miniature feast for the tiny baby salmon
0:27:21 > 0:27:24that will emerge the following year.
0:27:26 > 0:27:29The next generation of nutrient messengers that will live out
0:27:29 > 0:27:32their adult lives in the ocean
0:27:32 > 0:27:35and will one day return to this same spot in the riverbed
0:27:35 > 0:27:39to make the ultimate sacrifice of their own.
0:27:44 > 0:27:51Life on every level, from mosses to lichens, trees to animals,
0:27:51 > 0:27:53flourish in this coastal rainforest.
0:27:55 > 0:27:59The trees close to salmon streams grow taller and faster.
0:27:59 > 0:28:02The forest animals have more food
0:28:02 > 0:28:05and live in higher densities in these forests.
0:28:05 > 0:28:10Some have even become so tied to the ocean
0:28:10 > 0:28:13that they are truly becoming coastal specialists.
0:28:14 > 0:28:18The secret of this forest's success doesn't come from the land at all,
0:28:18 > 0:28:23but from the riches of the Pacific Ocean sitting just offshore.
0:28:25 > 0:28:30This is a forest fuelled by the ocean.
0:28:50 > 0:28:54Subtitles by Red Bee Media Ltd