"NARRATOR:" "Of all the planets in our universe, we know of only one that can support life." "Just the right distance from the sun, it has a perfect climate." "Earth rests at an angle of exactly 23 and a half degrees to the sun." "Without that crucial tilt, everything as we know it would be different." "For by it, the seasons are created, the extremes of climate, hot and cold, and landscapes of spectacular beauty." "We spend a year with our fellow creatures as they struggle to raise their young in a world that is ever-changing." "January." "It's the dead of winter in the high Arctic, and there has been no sun for over a month." "A father, alone in an icy wilderness." "He scavenges for food in the permanent darkness." "But there is little to eat." "Every living thing is waiting." "At long last, the sun makes its first appearance over the horizon." "And something else makes an appearance for the first time too." "A mother polar bear has been underground in her den the whole winter." "It's fresh-powder conditions up here, and, after being cooped up under the snow for so long, she can't help but enjoy the slopes." "But she's not alone." "They're 2 months old now, and this is the very first time they've seen the light of day." "[CUBS BLEATING]" "It's breakfast time for the little ones." "Mom uses the promise of food to coax them across the slopes." "But it's not the easiest place to take your first steps." "Milk is the breakfast of choice here." "In fact, it's the only choice here." "It's all the cubs have known since birth." "Mom hasn't eaten for five months, and she's lost half her body weight." "But still, she'll stay at home on these slopes and nurse the cubs until they find their footing." "Which, as you can see, might take a little while." "Every year at this time, they need food desperately." "They'll have to get down and join Dad on the ice before it starts to melt in the warming sunlight." "The sea ice is the only place the bears can hunt for seals." "If they don't make it in time, they'll lose their hunting platform, and the family could starve." "So far, the ice is strong enough to support their dad." "But he won't be much help to Mom and the kids." "Instinct leads him to hunt for himself." "This race to reach the sea ice is more urgent than ever." "Our planet is warming, and the ice is melting earlier every year." "It's ten days later and time for Mom to lead the growing cubs down to the sea ice." "They've found their feet now, but they seem to be taking them in the wrong direction." "Unlike humans, polar-bear cubs don't always listen to their moms." "[MOTHER BEAR SNORTS]" "Finally, everybody is pointed in the right direction, and the journey to the ice begins." "[CRACKING]" "Just a few miles from the coast, the ice is already breaking up." "Mom leads her cubs to start their life at the edge of this increasingly dangerous new world." "What they don't know is the harsh reality of life in the Arctic." "It's unlikely that both cubs will survive their first year." "[CRACKING]" "A thousand miles south of the bears, stunted conifers are still locked in ice." "They mark the tree line of our planet and the start of the boreal forest." "This vast belt of trees forms an almost unbroken circle around the north of the globe." "These conifers have needle-shaped leaves, virtually inedible, so the forest supports very little animal life." "In this silent world, footprints rarely mark the snow." "And those who do live here are so hard to glimpse, they're like spirits." "The lynx roams hundreds of miles in search of prey." "It may never visit the same patch of forest twice." "This creature is the very essence of wilderness." "One-third of all the trees on Earth are here, as many trees as in all the world's rain forests combined." "As the planet tilts toward the sun, spring creeps up from the south, and the boreal is unveiled from a blanket of snow." "The forest produces so much oxygen that it refreshes the atmosphere of the entire planet." "[BIRDS CALLING]" "April, and life starts returning to the warming north." "Visitors flock to this haven from all corners of our planet." "They've come to make the most of the brief flush of spring food." "And to have their babies." "In our changing world, every new generation is precious." "As the snow melts and the days grow longer, caribou, more than three million of them, start their migration across the tundra." "It's the longest overland migration on Earth, with some herds traveling 2,000 miles in a single year." "And it's totally dependent on vast open spaces." "The herd stays on the move, so newborn calves have to be on their feet and running from the day they are born." "But these vast herds don't travel alone." "Wolves shadow them all along the way, and they're hungry." "At first, the attack seems casual and random, but this running at the herd is a tactic to generate panic." "In the chaos, a calf is separated from her mother." "[CALF BLEATING]" "The calf is young, but it's capable of outrunning the wolf as long as it keeps its footing." "At this point, the odds are even." "Either the caribou will make a mistake, or after a mile or so, the wolf will give up." "Spring in the Artic, and already the sun never sets." "And further south, the sunlight begins to work her glorious magic." "[BIRDS CHIRPING]" "These are the forests that we know well, the broadleaf woodlands of Europe and North America." "More than any other, these have been crowded out by towns and farmlands." "Only fragments remain." "The summers are longer here, and deciduous trees can flourish." "They're far more edible than the conifers of the north, so these forests bustle with life." "Spring also means flight school for the mandarin ducks." "Mom is in her nest high in the treetops, and it's her job to lead the way." "[CHIRPING]" "It's their first flight." "Actually, I wouldn't call it flying, as much as falling with style." "Wait." "There are two missing." "A perfect landing, sort of." "With one big adventure behind them, what other challenges are in store for our planet's newest recruits?" "The rhythm of the seasons is a glorious legacy that we've inherited, thanks to that all-important tilt of the Earth." "As the seasons parade past, the same forest will show her spectacular fall colors and eventually give up her leaves to the snows of winter." "There are parts of the world that have no seasons." "Here in the tropics, the sun shines for 12 hours a day every day of the year." "[ANIMALS CALLING]" "This is what allows the jungle to grow unchecked and support so much life." "Rain forest now covers just 3 percent of our planet's surface, but contains more than half of all the plants and animals on Earth." "The rain forests of New Guinea are especially precious." "They are home to 42 different kinds of birds of paradise, each more exotic than the last." "[WARBLING]" "[SQUEAKING]" "[CROAKING]" "[WARBLING]" "This is a particularly rich forest, so the six-plumed bird of paradise has no problem finding food." "He can concentrate on more important tasks, like cleaning up for his big date tonight." "He's obsessed with housework." "Everything has to be spick and span before she comes over." "Oh!" "Missed a spot." "Finally, the stage is set." "Get down, baby." "It's a virtuoso performance, but, unfortunately, she's a no-show." "[CAWING]" "This contender, called the superb bird-of-paradise, is a magician, with a special trick." "First, he advertises his show by calling to attract a female." "And then, with the audience in place, he begins to work his magic." "Now, that's impressive." "But she needs to step out for a moment to think." "How could a girl resist?" "Oh, boy." "Well, not today." "These tropical forests not only enjoy 12 hours of sunshine a day all year long, they also need lots of rainfall." "But as the weather patterns change, there are signs that these lush forests are starting to dry up." "Deserts cover one-third of the Earth's land surface." "They're getting bigger every year." "This is a land where only a few can survive, a special few." "Dry season in the Kalahari Desert of southern Africa." "Thousands of elephants have started on their epic quest for food and water." "The baby elephants stride alongside." "It's their first road trip with the family." "The mothers follow the same trails their families have followed for decades." "And all trails lead to one place:" "the Okavango, a vast inland delta in the heart of the desert." "At the moment, it's dry, but water should come." "All across southern Africa, millions of animals are on the move, on the same life-or-death quest for water." "This tiny calf struggles to keep up with Mom." "It's his first trip, and he has a desperate need for water." "All his mom can do is encourage him to keep going in the heat and impossible dryness." "A dust storm blows hard across the trail, making it nearly impossible to see." "The mother and son move slowly and become separated from the herd." "Without the protection of the herd, the mom and her baby are completely exposed to the dangers of the wild." "It looks like refuge just a few paces away." "But these dead trees offer no protection, and the herd is already a mile ahead." "But these dead trees offer no protection, and the herd is already a mile ahead." "Mom knows the herd can't afford to stop, so they move as fast as they can." "Finally, they emerge from the dust, but the herd is nowhere in sight." "Blinded by sand, the calf barely has the strength to go on." "This lone youngster got lost in the dust storm too." "Thirsty and exhausted, he follows the tracks of his mother, but in the wrong direction." "Where dust and water combine, the march of the deserts is halted." "Sand dunes give way to prairies and savanna." "Grass is the great unsung hero of our planet." "It keeps deserts in check and provides the stage for many of the greatest spectacles on Earth." "The great game herds of East Africa all rely on these vast life-giving grasslands." "But where there are herds, there's always someone watching." "Every day on wide open plains the world over, a timeless ritual plays itself out:" "the drama of hunter and hunted." "This is the circle of life that most of us, in our urban lives, have lost touch with." "They've been on the trail for two weeks now." "The baby elephant and his mom made it back to the herd, but they're exhausted and desperately thirsty." "The moms lead their herd to a temporary watering hole." "It's not exactly the paradise they were expecting, but they're only halfway on their journey, and this place looks safe, at least for tonight." "As the sun sets, the elephants are forced to share the water with others." "These are fragile alliances." "[GROWLS]" "[ELEPHANT TRUMPETS]" "By day, the elephants dominate the watering hole." "But by night, the balance of power shifts." "The baby and his mother are most at risk." "They are closer to the lions than they know." "In total darkness, an elephant's vision is no better than our own." "Lions can see easily." "The cats are ravenously hungry, and the elephants know it." "The lions can bide their time." "It's the calves they're after." "[GROWLS]" "The pride rallies for an attack." "The elephants herd their young together, forming a protective circle." "The cats pace nervously, looking for an opening." "They're waiting for the call to attack." "[ROARING]" "The calves are too well protected." "The lions will have to risk it all and change tactics." "Against this elephant, a solitary lion wouldn't stand a chance." "But the whole pride is here, 30 of them, and they're expert elephant hunters." "Those who survive the night press on." "They're tired and frightened and can only follow their instincts." "The sun that scorches the desert also brings water to the land." "As it beats down on tropical seas, moisture rises from the warming oceans and fuels the global weather systems." "Moisture-filled clouds from the Indian Ocean sweep north toward the mountains." "As the air rises, the water cools and falls as snow." "This majestic sight is the backdrop for nature's most challenging migration." "In late summer, demoiselle cranes have to escape the harsh winters in Mongolia by flying south to the warmer climates of India." "To get there, they have to cross the highest mountain range on Earth:" "the Himalayas." "As the sun heats these great slopes, warm air rises from the valleys." "By late morning, it turns into ferocious winds." "The cranes hit violent turbulence that throws them off course." "They have no choice but to turn back for the night or risk certain death." "As the sun sets, the slopes cool, and the turbulence falls away." "After a long night in the frigid mountain air, the cranes are ready for their next attempt." "It's early morning, and the warm air is already rising fast." "But this time, the winds are calmer, and they can use the rising thermals to gain height." "But as the heat rises, the winds lock in again." "They're past the point of no return." "They're past the point of no return." "In the final ascent, every wing beat is a desperate battle against the freezing wind." "At last, they've made it." "They've conquered the highest peaks on Earth." "On the other side, there's a warm sanctuary for the winter." "The sun melts the snow, and the waters begin the long journey back to the oceans." "It's the great unending cycle of sunlight and fresh water that brings life to every corner of the Earth." "For generations, humans and animals alike have come to depend on the great rivers and their endless flow." "After months of drought, the buffalo reach the end of their long migration, and the rivers begin to flow again in the Kalahari." "As waters sweep through desert lands, the Okavango is transformed into a fertile paradise." "This is an Africa we rarely see, a lush water world totally reliant on a seasonal flood, originating from a tropical ocean thousands of miles away." "Most animals feel at home in this life-giving flood, but some aren't sure what to do with their new beachfront property." "After weeks of marching, the elephants are exhausted and struggle to stay focused on the road ahead." "Mom is sure she can smell the water in the distance and encourages everybody to make one last try." "They're just a few days away now." "The seasonal cycle that drives life on land is just as important in the oceans." "[WHALES CALLING]" "It's summer, and the humpback whales are in their breeding grounds in the tropics." "This calf is only a few weeks old, and, like any newborn, he needs a little help." "His mom holds him up to the surface so he can breathe more easily." "These shallow waters are great for raising kids." "They're warm and calm, with few predators to speak of." "The playful calf is now drinking 150 gallons of milk a day, but Mom is starving." "In these crystal-clear waters, there's nothing for her to eat." "To find food, she must lead her calf to richer feeding grounds at the southern extremes of our planet." "It's the longest migration of any marine mammal." "Out in the open ocean, the whales hit rush hour on the high seas." "Dolphins close in on their prey." "A hundred sailfish join in the attack." "Reaching almost 70 miles an hour, they are the cheetahs of the sea world." "The seas are churning now, and the going is slow." "Mom and her calf have to swim south across half the globe to reach their destination:" "Antarctica." "The tropics are hundreds of miles behind them as they head into stormy seas." "Winds and currents pull nutrients from the deep, and life blooms wherever the rays of the sun can penetrate." "To our whale calf on her first trip, this is all brand-new." "So far, their journey has been safe and far away from the dangerous predators who roam the high seas, at least until now." "The great white shark, the largest predatory fish on the planet." "Late summer in the Arctic, and the ice is melting fast." "Mom and her two cubs have had a hard time on the shifting ice, and she's forced to lead the hungry cubs back to shore." "Their dad has it even worse." "He's wandered miles from land, and the ice is too thin to support him." "He's in danger of being stranded in the frigid water, and, if he doesn't act fast, he could be lost at sea." "The glacial runoff pours from the land to mix with seawater and speed up the thaw." "Time is running out." "The father is starving and trying everything just to stay upright on the ice." "[ROARING]" "Each year, as our planet warms, there is less and less ice in the Arctic." "It's a disaster for polar bears." "Without a hunting platform, he'll struggle to survive." "Mom and her calf forge ahead through treacherous seas." "They're nearly 3,000 miles from the tropics now, and the winds are blowing hard." "The calf and her mom slap their fins on the water to stay in close contact with each other." "The calf can hear her mom above the roar of the ocean." "It keeps her calm and on course during the storm." "The frozen beauty of the Southern Ocean." "It's October, and here in the southern hemisphere that means summer is on its way, and life returns." "Adélie penguins, and they're in a hurry to reach their nesting grounds." "You may not know this, but they're one of the few animals with a built-in toboggan." "[BLEATING]" "December, and here in the southern extremes of our planet, the sun does not set." "The Antarctic summer is short, but, for a few brief moments, the sun's warmth unlocks frozen bays." "In the depths, something stirs." "They've made it." "At last, after a 4,000-mile journey, our calf and her mom have arrived, joined by their friends." "They celebrate by dining on their favorite food, krill, shrimp that begin to swarm here as soon as the ice retreats." "Mom and her calf can finally eat their fill." "The whales use a fishing technique that's been handed down through generations." "They blow bubbles while swimming in circles to create a bubble net." "The net encircles the krill and pulls them in." "Then the whales swim up through the bubble net, swallowing thousands of krill in one gulp." "In a few months, the summer will fade, and it'll be time for the long swim home." "Winter in Antarctica, and the greatest seasonal change on our planet is under way." "The sun begins to retreat, and soon the continent will be plunged back into darkness." "And the penguins?" "Well, don't feel sorry for them." "They have front-row seats for the most amazing light show on Earth:" "The aurora australis." "In the north of our planet, back where our story began, the sea ice is almost gone." "It's the cubs' dad, and he is in desperate trouble." "Hunger has driven him far out to sea to search for seals among the remaining fragments of ice." "He seems at home in the water, but he's exhausted." "If he doesn't find land soon in this vast ocean, he will drown." "[SNORTING]" "After many days at sea, the exhausted bear pulls up on shore at this pungent public beach." "He's lost half his body weight and now is desperate for food." "But a walrus is much larger than his usual prey." "It's the pups he'll have to get to, but the powerful adults can inflict fatal damage with their tusks." "The walrus sense danger and close ranks around their young." "He tests the barrier, but it stands firm." "He may be the world's biggest land carnivore, but he's met his match here, and he's clearly weakened by his ordeal at sea." "A pup tries to hide behind her mother." "If he can just pry her off." "Now the herd is fleeing to the water, and there's no time left." "He tries again and again, in sheer frustration." "Their tusks strike like knives, and he must avoid them at all cost." "The walrus flee on all sides, forcing him to a choice he didn't want to take:" "to attack in the water." "But it slips from his weakened grasp." "He gambled and lost." "He would never have attacked such dangerous prey had he not been so starved and desperate." "The walrus are calm again." "The bear is no longer a threat." "But unable to feed, the cubs' father cannot survive." "Wind and rain and fire and ice have come and gone." "A year has passed, and the cubs are old enough to be on their own." "They've left their mother and are thriving." "Their father's brave spirit will always live on in their young hearts." "Like all of our children, they are the hope of the future and proof of the resilience of life in this place we all share." "Yes, it's full of harsh realities, but sometimes it's just paradise." "[TRUMPETS]" "[CHIRPING]" "I've never been in anything like this before, and, of course, I'm slightly nervous of it." "Partly because it's basically a deck chair with a balloon on top, and partly because I can see where my head's gonna be." "It's gonna be incredibly close to that burner." "I do have a fear of heights." "I mostly have a fear of falling through them onto the ground." "But I think I'm happy with this." "It's got a little seatbelt and everything." "Set for takeoff." "[SPEAKING IN FOREIGN LANGUAGE]" "[LAUGHING]" "Oh, finally, they're off." "MAN 1:" "Yeah?" "MAN 2:" "Say when." "MAN 1:" "Pan." "Keep it locked." "I'll just go check the window." "MAN 1:" "Hang on." "He's coming back that way." "This is just a bit of a problem when we get bears as close as this to the cabin." "MAN 1:" "Day one." "MAN 2:" "Day one." "A bear outside the cabin." "MAN 1:" "Oh, hang on." "Polar bear at 11 o'clock." " There he is." "Keep going." "MAN 1:" "I got him." "MAN 2:" "They got him." "Big old bear." " He's awesome." " That's fantastic." "Stop." "MAN:" "She's gonna go." "She's coming in now." "Nice start." "Yes, here, here, here." "That's pin sharp." "WOMAN:" "Right here." "MAN:" "Yeah." "WOMAN:" "There's a lion right next to the door." "Very nice lions out here." "[LION ROARING]" "MAN 1:" "Now, this is a lot harder than I thought it was on the first day." "Michael, 9 o'clock?" "Just off to left." "Pan left." "And left." "And all right, you've got it bang in the middle of the frame." "Good." "Phew." " Just in time." "MAN 2:" "All right." "[WHALES CALLING]" "The port side." "It's gonna come back to you at 7 o'clock." "Whoa, unbelievable." " Got it?" "MAN:" "Yes." "That should be on." "Ohhh...." "Ohh!" "[BRANCHES CRACKING]" "MAN:" "I go down." "Sorry." "Stupid." "I'm stupid." " You okay?" " Yeah, just" "MAN:" "Captain for me?" " Yeah, I think so." " Leg okay?" " Just minor flesh wounds."