0:00:03 > 0:00:07Our planet is a place of constant change.
0:00:09 > 0:00:13Each year, the seasons shift and life is transformed.
0:00:16 > 0:00:20But there are places where the changes are so epic in scale
0:00:20 > 0:00:22they can be seen from space.
0:00:24 > 0:00:26In this series,
0:00:26 > 0:00:29we reveal three of the most miraculous transformations.
0:00:30 > 0:00:33The islands of Svalbard -
0:00:33 > 0:00:37within a few weeks, frozen wastelands burst into life.
0:00:39 > 0:00:42The African Okavango -
0:00:42 > 0:00:45a desert transforms into a magical water-world.
0:00:47 > 0:00:50And the mysterious forests of New England
0:00:50 > 0:00:53erupting in a blaze of seasonal colour.
0:00:56 > 0:01:02Life finds the most ingenious and surprising ways to thrive
0:01:02 > 0:01:05in the world's fastest changing landscapes.
0:01:20 > 0:01:22Svalbard -
0:01:22 > 0:01:25a frozen ice world,
0:01:25 > 0:01:29lying far beyond the Northern tip of Norway.
0:01:30 > 0:01:32A lonely group of islands,
0:01:32 > 0:01:34almost at the top of the world.
0:01:41 > 0:01:45For four months, because of the tilt of the Earth,
0:01:45 > 0:01:48Svalbard is cloaked in darkness,
0:01:48 > 0:01:51hidden from the life-giving light of the sun.
0:01:57 > 0:02:00But every year,
0:02:00 > 0:02:02a miracle happens here.
0:02:05 > 0:02:07As the sun returns,
0:02:07 > 0:02:11Svalbard undergoes an extraordinary transformation.
0:02:17 > 0:02:21From perpetual darkness to perpetual light.
0:02:22 > 0:02:27From frozen ice world to land of vibrant life.
0:02:30 > 0:02:33This is the story of how life survives one of the planet's
0:02:33 > 0:02:35most extreme changes.
0:02:48 > 0:02:50WIND HOWLS
0:03:03 > 0:03:05The Svalbard winter.
0:03:07 > 0:03:10A night that lasts for months.
0:03:13 > 0:03:15Without the sun's light,
0:03:15 > 0:03:16nothing can grow...
0:03:18 > 0:03:23..and ferocious winds are dragging temperatures to minus 40 and below.
0:03:28 > 0:03:30How can anything survive here?
0:03:40 > 0:03:43One animal is in its element.
0:03:47 > 0:03:51A polar bear has been sleeping peacefully through the storm.
0:03:55 > 0:03:59Its unique coat reflects heat back into its body just
0:03:59 > 0:04:03like a survival blanket,
0:04:03 > 0:04:06so it is quite comfortable, even at minus 40.
0:04:16 > 0:04:20And remarkably, for the polar bear,
0:04:20 > 0:04:22these are relatively good times.
0:04:25 > 0:04:28The sea ice is at its maximum,
0:04:28 > 0:04:32connecting the islands of Svalbard to the whole of the Arctic...
0:04:35 > 0:04:40..so the bear can stride out over the frozen ocean,
0:04:40 > 0:04:42its prey right beneath its feet.
0:04:56 > 0:04:57A ringed seal.
0:04:59 > 0:05:02Just a metre beneath the bear,
0:05:02 > 0:05:04but protected by the ice.
0:05:05 > 0:05:08Until it needs to breathe.
0:05:10 > 0:05:13The seal scrapes out a network of breathing holes
0:05:13 > 0:05:15dotted about the ice.
0:05:19 > 0:05:23It can hold its breath for 45 minutes,
0:05:23 > 0:05:26but then it must come up for air.
0:05:30 > 0:05:34The trick for the polar bear is guessing where it will appear next.
0:05:44 > 0:05:48But it only needs to catch one seal a week
0:05:48 > 0:05:51and it is very patient.
0:05:56 > 0:06:01Bears can wait at a single hole for days.
0:06:09 > 0:06:13Only a handful of animals are tough enough to survive the winter here.
0:06:20 > 0:06:26The Svalbard reindeer is the world's most Northerly herbivore,
0:06:26 > 0:06:30and that's a challenge when the land is locked in ice.
0:06:35 > 0:06:39They survive partly off their summer fat reserves,
0:06:39 > 0:06:43losing up to half their body weight during winter.
0:06:45 > 0:06:47But they do need to eat.
0:06:50 > 0:06:54With their sharp hooves, they chisel through the crust of ice
0:06:54 > 0:06:58and then literally chew the rocks,
0:06:58 > 0:07:01scraping off the coating of frozen moss and lichen.
0:07:09 > 0:07:12But after just seven or eight winters
0:07:12 > 0:07:14their teeth start to wear out...
0:07:18 > 0:07:20..and that's when many struggle to make it.
0:07:31 > 0:07:34When winter claims one life,
0:07:34 > 0:07:36another is quick to profit.
0:07:40 > 0:07:43An Arctic fox.
0:07:45 > 0:07:48It scavenges its way through the winter,
0:07:48 > 0:07:51visiting frozen carcasses like this,
0:07:51 > 0:07:55and following polar bears to feed on their leftovers.
0:08:06 > 0:08:10And this is the only bird to over-winter in Svalbard.
0:08:13 > 0:08:18The ptarmigan, a relative of the grouse, but tougher.
0:08:20 > 0:08:25Like the reindeer, they pack on extra fat in the autumn,
0:08:25 > 0:08:27but not for energy -
0:08:27 > 0:08:31for insulation.
0:08:31 > 0:08:33So they are 50% heavier in the winter.
0:08:36 > 0:08:40But now they're too fat to fly any distance.
0:08:42 > 0:08:45On feathered feet, they scuttle across the tundra,
0:08:45 > 0:08:47seeking out the tiniest shoots of plants
0:08:47 > 0:08:50lying dormant in the frozen ground.
0:09:05 > 0:09:08For everything but the polar bear,
0:09:08 > 0:09:10such conditions are hard to endure.
0:09:16 > 0:09:21For the first explorers who came here from Europe 400 years ago,
0:09:21 > 0:09:24the Svalbard winter felt like an eternity.
0:09:27 > 0:09:31They must have wondered whether the sun would ever return.
0:09:33 > 0:09:36For many, it never did.
0:09:40 > 0:09:43But there is light here.
0:09:45 > 0:09:47When the moon rises,
0:09:47 > 0:09:49it can stay up for a week.
0:09:57 > 0:10:00And every so often,
0:10:00 > 0:10:04the solar wind coming from the other side of the planet
0:10:04 > 0:10:07collides with the Earth's magnetic field,
0:10:07 > 0:10:10creating magical colours in the Arctic sky.
0:10:13 > 0:10:16Aurora Borealis,
0:10:16 > 0:10:19the Northern Lights.
0:10:38 > 0:10:40It's now mid-February
0:10:40 > 0:10:43and after four long months,
0:10:43 > 0:10:46the sun finally returns.
0:11:03 > 0:11:07At first, the sun is only up for an hour at a time
0:11:07 > 0:11:11so it brings little warmth,
0:11:11 > 0:11:12but it signals the beginning
0:11:12 > 0:11:15of Svalbard's miraculous transformation.
0:11:45 > 0:11:49As the sun's light reaches out across the landscape,
0:11:49 > 0:11:51the true nature of this
0:11:51 > 0:11:53extraordinary wilderness is revealed.
0:11:55 > 0:11:58Beautiful but brutal.
0:12:01 > 0:12:05Vast glaciers flow from lonely peaks,
0:12:05 > 0:12:10pulverising mountains and bulldozing their remains to the frozen sea.
0:12:14 > 0:12:17There are no forests or woodlands.
0:12:21 > 0:12:24But surprisingly,
0:12:24 > 0:12:26the same titanic forces that make this place
0:12:26 > 0:12:30so inhospitable have also drawn people here.
0:12:36 > 0:12:37Coal,
0:12:37 > 0:12:42brought right to the surface by the scouring of Svalbard's glaciers.
0:12:44 > 0:12:46A source of great wealth for those
0:12:46 > 0:12:48who can survive here long enough to get it.
0:12:52 > 0:12:55Svalbard belongs to Norway today,
0:12:55 > 0:12:57but in the past, many nations came
0:12:57 > 0:13:00to exploit its rich coal deposits,
0:13:00 > 0:13:02including Soviet Russia.
0:13:04 > 0:13:08But one grand scheme after another succumbed to this frozen land.
0:13:12 > 0:13:15This is Pyramiden.
0:13:18 > 0:13:22Once home to over 1,000 people,
0:13:22 > 0:13:25now a ghost town.
0:13:36 > 0:13:40Inside these buildings, Russian workers lived with their families.
0:13:44 > 0:13:46But today it all lies abandoned.
0:13:55 > 0:13:58The plan was to give the people of Pyramiden everything
0:13:58 > 0:14:01they needed to survive here through the long, dark winter.
0:14:06 > 0:14:09Including the world's Northernmost piano.
0:14:14 > 0:14:16But it couldn't last.
0:14:20 > 0:14:23These mines were never profitable.
0:14:23 > 0:14:25The cost of survival
0:14:25 > 0:14:27here at the frozen ends of the Earth
0:14:27 > 0:14:29was just too great.
0:14:31 > 0:14:35Today, Arctic foxes roam the streets
0:14:35 > 0:14:39where people tried to tame the Svalbard winter.
0:15:04 > 0:15:06Mid-March.
0:15:06 > 0:15:09The days have been getting dramatically longer.
0:15:09 > 0:15:12Only four weeks since the sun's return
0:15:12 > 0:15:17and there are already 12 hours of sunlight every day.
0:15:20 > 0:15:23Though temperatures are still well below freezing,
0:15:23 > 0:15:27the sun's energy is now strong enough to trigger a chain
0:15:27 > 0:15:32of events, fundamental to life in Svalbard,
0:15:32 > 0:15:34under the sea ice.
0:15:43 > 0:15:47These strange colours are caused by ice algae.
0:15:52 > 0:15:54It lays dormant all winter,
0:15:54 > 0:15:57frozen into the fabric of the ice.
0:16:05 > 0:16:08Just like a plant,
0:16:08 > 0:16:11it has the power to turn the sun's energy into food.
0:16:17 > 0:16:20As the sunlight starts to penetrate the ice,
0:16:20 > 0:16:24it energises the algae's green cells.
0:16:35 > 0:16:38The switch is flicked.
0:16:44 > 0:16:49From the dark depths, tiny creatures are now drawn to the ice.
0:16:51 > 0:16:53Copepods,
0:16:53 > 0:16:56just a couple of millimetres long.
0:16:56 > 0:16:59They may look unimportant,
0:16:59 > 0:17:01but they hold a key to life here.
0:17:05 > 0:17:10They've been waiting to gorge themselves on ice algae.
0:17:15 > 0:17:19Very soon they are chomping away in their millions.
0:17:21 > 0:17:25Now they take the sun's energy from the algae
0:17:25 > 0:17:29and concentrate it into a clear drop of fatty oil,
0:17:29 > 0:17:34which they store in a sack inside their bodies -
0:17:34 > 0:17:36bottled Arctic sunshine.
0:17:44 > 0:17:49For now, all that energy is locked away beneath the sea ice.
0:17:53 > 0:17:55But not for long.
0:18:06 > 0:18:09The intensifying sun heats from above.
0:18:11 > 0:18:14The warming water melts from below.
0:18:14 > 0:18:17CRASHING
0:18:20 > 0:18:25It's April and the door to Svalbard's rich waters is opening.
0:18:41 > 0:18:44It starts slowly at first,
0:18:44 > 0:18:48the silence of winter broken
0:18:48 > 0:18:51by the distant calls of seabirds.
0:18:53 > 0:18:57But quickly their numbers build.
0:19:09 > 0:19:11Guillemots,
0:19:11 > 0:19:13little auks,
0:19:13 > 0:19:15eider ducks.
0:19:17 > 0:19:24Around six million birds return to Svalbard every spring,
0:19:24 > 0:19:26travelling many thousands of kilometres
0:19:26 > 0:19:29from their winter homes in Europe,
0:19:29 > 0:19:32timing their arrival for just this moment.
0:19:36 > 0:19:39Right away they start to refuel,
0:19:39 > 0:19:41diving into Arctic water to
0:19:41 > 0:19:44feast on the oil-rich copepods.
0:19:45 > 0:19:47And beneath them,
0:19:47 > 0:19:49other life is stirring.
0:19:50 > 0:19:56Vast shoals of fish now come for the copepods' bottled sunshine,
0:19:56 > 0:20:00and in turn become food for more birds.
0:20:04 > 0:20:08The light from the strengthening sun has kick-started spring.
0:20:15 > 0:20:18When the birds first reach their nesting cliffs,
0:20:18 > 0:20:20they find them covered in ice.
0:20:24 > 0:20:26It's still bitterly cold here,
0:20:26 > 0:20:30but they need to stake their claim early.
0:20:30 > 0:20:32Very soon there will be no more space available.
0:20:35 > 0:20:38And they've got less than four months to
0:20:38 > 0:20:42raise their chicks before they'll have to be off again.
0:20:42 > 0:20:46So immediately they get straight on with the business of breeding.
0:20:48 > 0:20:51They don't have the luxury of time.
0:21:00 > 0:21:03It's now the middle of April
0:21:03 > 0:21:07and Svalbard's transformation is moving into a whole new phase.
0:21:12 > 0:21:15As the Earth travels further round the sun,
0:21:15 > 0:21:19spinning on its axis once every 24 hours,
0:21:19 > 0:21:23Svalbard now moves into permanent day.
0:21:33 > 0:21:37Welcome to the land of the midnight sun.
0:21:46 > 0:21:50Now that the sun is shining all the time,
0:21:50 > 0:21:54it starts to have an impact on the land.
0:21:57 > 0:21:59Under the snow,
0:21:59 > 0:22:02small plants are already absorbing the sun's light.
0:22:04 > 0:22:06As they warm up,
0:22:06 > 0:22:09they start to melt themselves out of their icy prison.
0:22:12 > 0:22:15The summer is short and it pays to get a head start.
0:22:21 > 0:22:25One strange plant has taken this trick to an extreme.
0:22:28 > 0:22:31This is the compass plant,
0:22:31 > 0:22:34one of the great survivors of the Svalbard tundra.
0:22:34 > 0:22:38It can live for over 300 years.
0:22:41 > 0:22:45Its success is down to a secret weapon -
0:22:45 > 0:22:46a central heating system.
0:22:48 > 0:22:52The spongy dome catches the sun around the clock,
0:22:52 > 0:22:55absorbing its energy.
0:22:57 > 0:23:01Though the air temperature is still hovering around freezing,
0:23:01 > 0:23:05the inside of the dome can rise to 30 degrees Celsius.
0:23:09 > 0:23:12But it doesn't heat up evenly.
0:23:15 > 0:23:20As the sun circles the horizon, its intensity varies.
0:23:22 > 0:23:26The south side of the plant gets much more warmth than the north.
0:23:28 > 0:23:31So when the flowers come,
0:23:31 > 0:23:35they erupt in synch with the sun,
0:23:35 > 0:23:38from south to north.
0:23:40 > 0:23:44It was the early explorers who first noticed this and
0:23:44 > 0:23:49used the strange plant to help find their way,
0:23:49 > 0:23:51just like a compass.
0:23:59 > 0:24:02As the snow melts further,
0:24:02 > 0:24:05it reveals a pile of old mining carts.
0:24:09 > 0:24:13For plants that don't have their own central heating,
0:24:13 > 0:24:15the carts offer shelter from the biting wind.
0:24:28 > 0:24:33A tiny walled garden where spring can really start to take hold.
0:24:50 > 0:24:55And as the sun's warmth increases further,
0:24:55 > 0:24:57the whole tundra starts to bloom.
0:25:08 > 0:25:11By the end of May,
0:25:11 > 0:25:13a greener Svalbard is emerging from the ice.
0:25:24 > 0:25:26After such a long wait,
0:25:26 > 0:25:30for Svalbard's animals, the arrival of spring is miraculous.
0:25:42 > 0:25:49The reindeer desperately need the grass that the melt is uncovering,
0:25:49 > 0:25:53but at first they seem a little unsure of this new, green world.
0:25:56 > 0:25:59They still have their thick winter coats.
0:26:01 > 0:26:04As temperatures rise,
0:26:04 > 0:26:07it's getting a little hot for them.
0:26:07 > 0:26:10So whenever they can,
0:26:10 > 0:26:12they take a break from eating
0:26:12 > 0:26:16and settle down on the remaining islands of cool snow.
0:26:23 > 0:26:26It's the latest arrivals who first really take
0:26:26 > 0:26:28advantage of the opportunities here.
0:26:33 > 0:26:36Barnacle geese.
0:26:36 > 0:26:38They've come all the way from Scotland,
0:26:38 > 0:26:40where they spent the winter.
0:26:44 > 0:26:47As the tundra is revealed,
0:26:47 > 0:26:50it offers an untapped source of rich energy,
0:26:50 > 0:26:53worth coming over 2,000km for.
0:27:01 > 0:27:04This little bird is a snow bunting.
0:27:08 > 0:27:11He too has come far -
0:27:11 > 0:27:13all the way from Russia.
0:27:14 > 0:27:17And this is the object of his affection.
0:27:19 > 0:27:23Together, they have set up home in an abandoned miner's cabin.
0:27:32 > 0:27:34In the middle of a whale vertebra,
0:27:34 > 0:27:37hanging on the wall, is a cosy nest,
0:27:37 > 0:27:43and in that, a ball of soft reindeer fluff, ready to nestle tiny eggs.
0:27:46 > 0:27:48Now they are here, they are the Northern-most
0:27:48 > 0:27:51songbirds in the world.
0:27:53 > 0:27:56And theirs is the song of Svalbard's spring.
0:28:07 > 0:28:11As the Arctic fox trots out of winter,
0:28:11 > 0:28:14she sheds her coat quickly to avoid overheating.
0:28:16 > 0:28:18She has a lot to do.
0:28:21 > 0:28:24Foxes are nomadic in the winter,
0:28:24 > 0:28:28but now the race is on to establish her summer breeding territory.
0:28:35 > 0:28:39She even rolls up a ball of her fur,
0:28:39 > 0:28:42adding a dash of urine to help signpost her patch.
0:28:47 > 0:28:51And every so often she makes time to meet up with her mate.
0:28:53 > 0:28:55They got together in the middle of the winter.
0:28:57 > 0:29:00Very soon she'll be giving birth.
0:29:01 > 0:29:06And then she will have just 90 days to raise her family.
0:29:16 > 0:29:20It's now already June
0:29:20 > 0:29:24and off the coast of Svalbard the sea ice is breaking up fast.
0:29:48 > 0:29:51The polar bear's world is changing.
0:29:59 > 0:30:03Though a polar bear can smell a seal from over a kilometre away,
0:30:03 > 0:30:08in this constantly moving landscape, it's much harder to track it down.
0:30:20 > 0:30:22It must take to the water to navigate
0:30:22 > 0:30:24through the drifting maze of ice.
0:30:35 > 0:30:38Bears are excellent swimmers,
0:30:38 > 0:30:39but no match for a seal.
0:30:45 > 0:30:48Life is getting harder.
0:30:48 > 0:30:53As the ice cover falls below a critical 50%,
0:30:53 > 0:30:56the bear spends more energy catching seals
0:30:56 > 0:30:59than he gets from eating them.
0:31:08 > 0:31:12While the breaking ice makes life more difficult for the bear,
0:31:12 > 0:31:16it allows Svalbard's heaviest resident to access the land.
0:31:24 > 0:31:27Walruses.
0:31:27 > 0:31:29At one and a half tonnes,
0:31:29 > 0:31:31they can be three times the weight of a polar bear.
0:31:34 > 0:31:37After spending the winter at the edge of the sea ice,
0:31:37 > 0:31:41they now return to Svalbard's shores.
0:31:41 > 0:31:44They haul out on their favourite beaches for the first time
0:31:44 > 0:31:45since last autumn.
0:31:48 > 0:31:52Both males and females have tusks,
0:31:52 > 0:31:53some over a metre long.
0:31:55 > 0:31:58The bigger the tusks, the more important you are.
0:32:00 > 0:32:05They're also a good defence against polar bears,
0:32:05 > 0:32:10and useful props for a heavy head.
0:32:10 > 0:32:13THEY GRUNT
0:32:17 > 0:32:19It's their handsome whiskers
0:32:19 > 0:32:23and extraordinary mouths that are their most important assets.
0:32:25 > 0:32:29But they don't come into their own until they go out foraging.
0:32:31 > 0:32:34And they're in no hurry.
0:32:35 > 0:32:40Walrus siestas can last a week.
0:32:54 > 0:32:58When they finally decide to go for a swim,
0:32:58 > 0:33:02there are some novel ways of getting all that way down to the water.
0:33:33 > 0:33:35Once they're in,
0:33:35 > 0:33:38their strange features begin to make sense.
0:33:40 > 0:33:43The giant body becomes weightless.
0:33:43 > 0:33:46With just its nose on the seabed,
0:33:46 > 0:33:50it blasts away the mud with high-pressure jets of water
0:33:50 > 0:33:55forced through its nostrils, feeling around with its 500 highly
0:33:55 > 0:33:59sensitive whiskers for its favourite food -
0:33:59 > 0:34:01clams.
0:34:01 > 0:34:04It just loves clams.
0:34:17 > 0:34:19When it finds the clams,
0:34:19 > 0:34:21it sucks the flesh right out of them
0:34:21 > 0:34:23with its unique vacuum mouth.
0:34:27 > 0:34:30A walrus can consume over 1,000 clams a day
0:34:30 > 0:34:32without eating a single shell.
0:34:43 > 0:34:46But these extraordinary animals have
0:34:46 > 0:34:48only recently been making a comeback.
0:34:51 > 0:34:55Not long ago, they were brought to the brink of extinction.
0:35:00 > 0:35:03Just beyond their beach
0:35:03 > 0:35:06are strange lumps of what appears to be concrete.
0:35:13 > 0:35:16In the middle of these rings were once great
0:35:16 > 0:35:20cauldrons in which the blubber from Svalbard's sea creatures was
0:35:20 > 0:35:23melted down into precious oil.
0:35:26 > 0:35:30Year after year, as the oil spilled over,
0:35:30 > 0:35:35it congealed with the surrounding sand and set into stone.
0:35:40 > 0:35:44Nearby is the evidence of the scale of this destruction.
0:35:49 > 0:35:53The bones of thousands of beluga whales.
0:36:01 > 0:36:04Long before it was known for its coal,
0:36:04 > 0:36:09Svalbard was one of the places to hunt whales and walruses.
0:36:15 > 0:36:17Their oil once lit the lamps
0:36:17 > 0:36:20and lubricated the machinery of industrial Europe.
0:36:25 > 0:36:29For 300 years, the slaughter continued
0:36:29 > 0:36:32until there was almost nothing left to kill.
0:36:40 > 0:36:43But it took its toll on humans too.
0:36:44 > 0:36:47As the ground repeatedly freezes
0:36:47 > 0:36:50then thaws every year,
0:36:50 > 0:36:53anything buried is pushed to the surface.
0:36:59 > 0:37:01A whaler's grave.
0:37:09 > 0:37:12Though the promise of wealth
0:37:12 > 0:37:16and adventure drew many to these remote whaling stations,
0:37:16 > 0:37:19life expectancy was so short,
0:37:19 > 0:37:22you even had to bring your own coffin.
0:37:43 > 0:37:46July is the hottest month.
0:37:49 > 0:37:51Even the great fjords that cut
0:37:51 > 0:37:55right into the mountains are free of sea ice
0:37:55 > 0:37:57and the summer heat kick-starts
0:37:57 > 0:38:00another chain of events that benefits life here.
0:38:02 > 0:38:06For so long, the land and sea were united by ice.
0:38:09 > 0:38:15Now open water laps against the faces of Svalbard's great glaciers.
0:38:25 > 0:38:27Behind the face, the glacier
0:38:27 > 0:38:30stretches into the distant mountains.
0:38:32 > 0:38:36Billions of tonnes of ice pushing down towards the coast.
0:38:40 > 0:38:45As the sun starts to melt the ice on the glacier's surface,
0:38:45 > 0:38:48water funnels downwards and lubricates the junction
0:38:48 > 0:38:52between rock and ice under the immense weight of the glacier.
0:38:57 > 0:39:00For some glaciers, the pressure gets too much.
0:39:01 > 0:39:04They start to accelerate.
0:39:07 > 0:39:09Svalbard's glaciers are unusual.
0:39:11 > 0:39:15Many remain motionless for years and then suddenly take off.
0:39:20 > 0:39:25These surging glaciers are some of the fastest on Earth,
0:39:25 > 0:39:29especially when summer melt-water lubricates them.
0:39:29 > 0:39:33They can reach speeds of up to 25 metres per day.
0:39:44 > 0:39:50At the face, the colossal weight of ice pushes from behind,
0:39:50 > 0:39:54while below, the warming sea erodes the base.
0:39:55 > 0:39:58Something has to give.
0:39:58 > 0:40:01CREAKING
0:40:55 > 0:40:57But this is not just a destructive force.
0:40:59 > 0:41:02Where the glacier meets the sea,
0:41:02 > 0:41:04it enhances life.
0:41:07 > 0:41:10In spite of the danger,
0:41:10 > 0:41:14kittiwakes and gulls are flocking in their thousands to the ice front.
0:41:16 > 0:41:18Right in the impact zone,
0:41:18 > 0:41:21they start to feed.
0:41:28 > 0:41:34Where the melt water flowing under the glacier reaches the sea,
0:41:34 > 0:41:38it billows upwards, right in front of the falling ice.
0:41:42 > 0:41:48As this plume of freezing water rises, it stuns tiny plankton
0:41:48 > 0:41:51and brings them to the surface.
0:41:55 > 0:41:58A microscopic feast,
0:41:58 > 0:42:01so rich it's worth risking your life for.
0:42:05 > 0:42:07But you've got to keep your wits about you.
0:42:40 > 0:42:43It's not only birds that come here.
0:42:46 > 0:42:49Beluga whales.
0:42:49 > 0:42:52Young calves that don't yet have the white colour of adults.
0:42:57 > 0:43:01They swim in their family pods, feeding on fish that in turn
0:43:01 > 0:43:05eat the plankton at the foot of the ice cliff.
0:43:07 > 0:43:10Though the years of whaling almost wiped them out,
0:43:10 > 0:43:14in 1961 they were finally given protection.
0:43:16 > 0:43:21Today they are becoming a much more common sight,
0:43:21 > 0:43:24especially where the glaciers meet the sea.
0:43:38 > 0:43:40By mid-summer,
0:43:40 > 0:43:44there is more life on Svalbard than at any other time of the year.
0:43:45 > 0:43:48The bird cliffs are now at full capacity.
0:43:48 > 0:43:50Every ledge is taken.
0:43:53 > 0:43:56The chicks hatched three weeks ago
0:43:56 > 0:43:59and the race is now on to feed them fast enough.
0:44:00 > 0:44:03In just three more weeks, they must be out of here.
0:44:12 > 0:44:16Down below, the tundra too is alive with new life.
0:44:41 > 0:44:45The reindeer have finally got their cool summer coats,
0:44:45 > 0:44:49and the males are sporting impressive new antlers.
0:44:57 > 0:44:59The fox couple are busier than ever.
0:45:01 > 0:45:05They've had six pups and the pressure is on to feed them.
0:45:07 > 0:45:11They will need to be fully grown in less than a month.
0:45:15 > 0:45:17Arctic fox cubs don't like to share food.
0:45:19 > 0:45:23When the winter comes they will be completely on their own,
0:45:23 > 0:45:26so they need to learn to fend for themselves right from the start.
0:45:36 > 0:45:39But for the parents, now is the crunch time.
0:45:41 > 0:45:44As they work 24 hours a day,
0:45:44 > 0:45:48making many thousands of journeys to the den with food, they become
0:45:48 > 0:45:53exhausted, using up more energy than through the whole of the winter.
0:46:02 > 0:46:05In the skies above,
0:46:05 > 0:46:07aerial traffic has reached fever pitch,
0:46:07 > 0:46:10as the birds frantically try
0:46:10 > 0:46:12to keep up with the demands of their offspring.
0:46:15 > 0:46:18But as they shuttle back and forth,
0:46:18 > 0:46:21bringing food from the ocean to the cliffs,
0:46:21 > 0:46:24they do much more than feed their chicks.
0:46:31 > 0:46:36Some of the ocean's rich nutrients passes straight through the birds.
0:46:44 > 0:46:48As all that fertiliser is washed down from the bird cliffs,
0:46:48 > 0:46:51it has a profound effect on the land below.
0:46:56 > 0:47:01The grass that now fattens up the reindeer for winter.
0:47:01 > 0:47:05The soil that nourishes the plants.
0:47:05 > 0:47:08The richness of Svalbard's land,
0:47:08 > 0:47:11ultimately, comes from the sea.
0:47:20 > 0:47:23It's now late July
0:47:23 > 0:47:28and the last of Svalbard's summer visitors are only just settling in.
0:47:30 > 0:47:33Arctic terns have come all the way
0:47:33 > 0:47:36from the other end of the Earth, from Antarctica,
0:47:36 > 0:47:39the longest migration of any animal -
0:47:39 > 0:47:42over 30,000km.
0:47:45 > 0:47:52But in three weeks, they'll have to fly all the way back again
0:47:52 > 0:47:55and their chicks have only just hatched.
0:47:57 > 0:48:00In only 21 days' time,
0:48:00 > 0:48:05this ball of fluff will need to fly 30,000km.
0:48:09 > 0:48:13But it's well worth the parents travelling all this way.
0:48:20 > 0:48:24Svalbard's super-rich waters contain all the energy required.
0:48:25 > 0:48:30All they have to do is transport it from ocean to beak.
0:49:07 > 0:49:09As the adults fish nonstop,
0:49:09 > 0:49:13sometimes they have to leave a chick on its own,
0:49:13 > 0:49:17and because terns nest on the ground,
0:49:17 > 0:49:18that can make it vulnerable.
0:49:22 > 0:49:26The retreating sea ice has now forced Svalbard's largest
0:49:26 > 0:49:29predator onto the land
0:49:29 > 0:49:31and it's coming this way.
0:49:34 > 0:49:38Now is the toughest time for polar bears.
0:49:39 > 0:49:43It loses a kilo of body weight for every day it spends on the land.
0:49:46 > 0:49:50The great ice bear turned scavenger -
0:49:50 > 0:49:52and he's starving.
0:50:16 > 0:50:19Not a good moment to break your cover.
0:50:35 > 0:50:38SQUEAKING
0:50:38 > 0:50:42But the chick's cries for help have been heard.
0:50:47 > 0:50:51Terns may look dainty but they are highly aggressive,
0:50:51 > 0:50:54and totally fearless.
0:50:59 > 0:51:03Repeated attacks draw blood from the bear's sensitive nose.
0:51:10 > 0:51:13The Arctic's top predator,
0:51:13 > 0:51:17driven away by one of its smallest birds.
0:51:34 > 0:51:37As August arrives,
0:51:37 > 0:51:40Svalbard's transformation reaches its maximum extent.
0:51:43 > 0:51:45It's only a fleeting transition.
0:51:47 > 0:51:49By the end of the month,
0:51:49 > 0:51:51the sun will be setting again.
0:51:55 > 0:51:59The winter is just around the corner.
0:52:08 > 0:52:13But as Svalbard's yearly miracle prepares to come full circle,
0:52:13 > 0:52:17the summer sun helps trigger a final dramatic change.
0:52:20 > 0:52:24In the far north east of Svalbard
0:52:24 > 0:52:26is a place where it always feels like winter.
0:52:28 > 0:52:30A massive ice cap.
0:52:30 > 0:52:34A frozen monster.
0:52:34 > 0:52:37Like a giant fridge, it cools this whole area of Svalbard.
0:52:39 > 0:52:44Only now in late summer does the sun start to have any effect here.
0:52:47 > 0:52:51On the surface of the ice, melt water pools together
0:52:51 > 0:52:53and starts to flow.
0:53:18 > 0:53:20Where the ice cap meets the sea
0:53:20 > 0:53:23is one of the world's greatest wonders.
0:53:25 > 0:53:28The ice cliffs of Austfonna.
0:53:35 > 0:53:39For nearly 200km, they rise uninterrupted from the ocean.
0:53:53 > 0:53:57But recently, these cliffs have been changing.
0:54:00 > 0:54:03Something we can see most clearly from space.
0:54:08 > 0:54:12The very latest satellites can make precise measurements of ice
0:54:12 > 0:54:14thickness and speed of movement.
0:54:17 > 0:54:19What they reveal
0:54:19 > 0:54:21is astonishing.
0:54:25 > 0:54:30A massive tongue of ice, 50km long,
0:54:30 > 0:54:33is on the move,
0:54:33 > 0:54:38sliding downwards from the centre of the ice cap out into the ocean.
0:54:41 > 0:54:45A wall of ice, advancing half a metre every hour.
0:54:48 > 0:54:504km a year.
0:54:55 > 0:54:59It's thought that massive events like this are part
0:54:59 > 0:55:03of a natural surge cycle lasting several years,
0:55:03 > 0:55:06but no-one knows exactly what sets them off.
0:55:09 > 0:55:12The latest research suggests that summer meltwater
0:55:12 > 0:55:16penetrating the ice cap may be a trigger.
0:55:21 > 0:55:25Svalbard's ice world is incredibly delicately balanced.
0:55:33 > 0:55:37Just tiny rises in global temperatures could have profound
0:55:37 > 0:55:41effects on the whole seasonal cycle of life here.
0:55:52 > 0:55:57Today, as Svalbard heads for the winter once more,
0:55:57 > 0:56:01its future lies on a knife-edge of just a few degrees.
0:56:21 > 0:56:24It's now the end of August
0:56:24 > 0:56:26and Svalbard is returning to the dark time.
0:56:30 > 0:56:34Svalbard's summer visitors must now leave.
0:56:36 > 0:56:41They've reaped the benefits of the rich summer,
0:56:41 > 0:56:43but if they stay here any longer
0:56:43 > 0:56:45they'll die.
0:56:51 > 0:56:55As parents now force their young to take flight,
0:56:55 > 0:56:57some before they're really ready...
0:57:01 > 0:57:04..foxes get a last feast before the lean time.
0:57:11 > 0:57:13Reindeer just keep on grazing.
0:57:15 > 0:57:18What they eat now decides whether they will make it through.
0:57:38 > 0:57:42Only one creature here welcomes the coming winter.
0:58:00 > 0:58:05As the sun drops below the horizon for the last time
0:58:05 > 0:58:09and Svalbard moves back on to the dark side of the Earth,
0:58:09 > 0:58:12the big change
0:58:12 > 0:58:14comes once more.