"Water:" "Hundreds of thousands of tons of it, lying frozen on the world's mountains." "It covers not only the poles, but caps great peaks on the equator." "Water molecules, distilled from the sea by the sun's heat, condense in the sky." "As they fall through the air, they pack together into shapes that echo their six-fold symmetry and form infinitely varied crystals of ice." "They settle on the high mountains and compact into snow and ice that is, chemically, almost pure water, much purer than the sea from which it came." "On Mount Rainier in the United States, permanent snow begins at 7,000 feet." "You might think that this was one of the most inhospitable places on earth for life." "After all, no vegetation grows on these snowfields, so there can be no animals that feed on it, like marmots or mice or rabbits, and if there are no herbivores, there can't be any predators like hawks or weasels." "But in fact, there is a surprising amount of life here." "There is some life actually within this snowfield itself, because this snow is not white, but red." "The colour comes from microscopic plants:" "Algae." "The redness is produced by light reflected from their cell walls, and is almost invisible when, under the microscope, light shines through them." "Internally, they're green with chlorophyll." "With its aid, they convert carbon dioxide and water into sugars." "These, and the minerals dissolved in the melt water, are all the algae need to grow and reproduce." "The winter snow will bury them feet deep, but in spring, when the surface melts, they divide, develop tiny beating hairs and swim up towards the sunshine." "As they age and the minerals are used up, they change colour, forming huge smears of red in snowfields all over the world." "Eventually, the snow algae produce spores as fine as dust and in that form they are blown from one snowfield to another." "But other, bigger animals, also brought up by the wind, blow across the snows of Mount Rainier." "Ladybirds." "Thousands of them." "Nobody knows why they come up in such numbers and assemble like this." "But in late summer they fly up from the valleys up to these high peaks and here assemble in the rocks." "When the winter snows come, the ladybirds remain underneath the snow in the rocks, and then in the spring, as now, the snow melts and the sun warms the ladybirds, and they become active and fly off back to the valley to feed on aphids." "The ladybirds are only temporary residents of the Mount Rainier snowfields." "Other insects manage, almost unbelievably, to live all their lives in this seemingly inhospitable snow." "The best time to find them is at night." "A whole community lives here, feeding on pollen grains and the bodies of dead insects blown up on the wind." "Some, like this primitive relation of the cockroach, a grylloblattid, have a body chemistry so well adjusted to low temperatures that if you pick them up, your hand's warmth will kill them." "Permanent snow lies directly on bare rock, but lower down, where it comes and goes, there can be a little vegetation to be grazed." "Mountain sheep." "These on Mount McKinley are the kind known as Dall Sheep." "Little ground squirrels live up here too." "Unlike the sheep, which retreat to lower altitudes in winter, the squirrels are permanent residents, insulated in their burrows from the frosts by the cover of snow." "There are sheep like these in mountains all through North America, Asia and Europe." "All carry big horns, and the senior males, in autumn, indulge in the most alarming courtship battles." "It's hard for plants to grow on steep, high slopes" "The warming by day and freezing by night makes the gravelly soil slip downwards, so it's difficult for plants to keep a hold." "With few plants, grazing animals are rare, though there may be more than there appear to be at first sight." "These, in the Himalayas, are blue sheep, so nimble and sure-footed they can reach almost any vegetation on the steep slopes." "But if these are rare, rarer still is the animal that preys on them, the snow leopard." "In summer it stays at between 12,000 and 15,000 feet, hunting small rodents and birds as well as mountain sheep." "Snow leopards have been seen as high as 18,000 feet in summer." "But with winter's heavy snowfalls, it retreats to the valleys." "Game is now so scarce that there's barely enough to support more than one leopard, so this animal hunts alone." "Its thick, dense fur is now paler." "It has a thick, woolly undercoat and cushions of hair under its paws which prevent it from sinking in the snow." "The mountains of Africa, although so near the equator, are permanently snow-capped." "Kilimanjaro, 19,000 feet high, is a volcano." "Mount Kenya, also volcanic, is 2,000 feet lower but still has its own glaciers" "Each has its own animals and plants specially adapted to life at low temperatures." "Here, at about 13,000 feet, grow some most beautiful and dramatic plants:" "Giant groundsels and giant lobelias." "At these altitudes, plants like these have to face two totally conflicting problems every 24 hours." "Every night the temperature falls so low that they're in danger of freezing solid." "And every day the sun beats down so strongly in this very thin air that it threatens to rob them of their moisture by evaporation." "But look how this lobelia deals with those problems." "This little pond of water in the leaf rosette freezes over every night, and this shield of ice prevents the water beneath from freezing, so that it acts as a liquid jacket, preventing the frost from reaching the heart of the plant." "But as the day wears on and it gets warmer, this water is in danger of evaporating and the plant of losing its night-time insulation." "But it isn'tjust rainwater that's accumulated in this rosette." "It's been secreted by the plant itself and it's slightly slimy." "It contains pectin, a colloidal substance which greatly reduces evaporation." "But there's another kind of lobelia which deals with these two problems in a quite different way." "This one grows very tall and has extremely long leaves, each fringed with tiny hairs which act like an animal's fur, trapping air between them, insulating the stem from chills." "They also prevent the wind from robbing the plants of moisture." "Each group of lobelias is owned by a pair of sunbirds which collect the insects the plants attract." "They keep themselves warm with fluffed-up feathers." "And among the rocks are hyrax." "The reason these little creatures are so tame and I can get so close to them is just because they're living so high up." "Up here, there are few creatures to prey on them." "An occasional leopard may come up and hunt them, but apart from that, nothing." "And so they can come out during the few brief hours of sunshine and bask on the rocks without any fear, just as they're doing now." "Hyrax also live down on the hot plains below, but these, in response to the cold, have developed particularly long fur." "Despite their shape, they often climb trees to crop leaves." "But at these altitudes, there's only grass and lobelias, and they share it with the little furry-eared rat." "Mount Kenya, like its neighbours Kilimanjaro and Ruwenzori, is an isolated patch of snow and ice surrounded by the baking hot African plains." "But the great mountains of South America, like Cotopaxi, 19,000 feet high, are very differen" "These volcanoes, some active, some dormant, are not isolated peaks but part of a continuous range that runs the length of the continent and is surrounded by the high, cold plains of the altiplano, so their flanks support a large and varied population of animals," "all adapted to life at high altitudes and low temperatures." "Here lives a wild South American camel, the vicuna." "Its coat is fine, silky and protected so well from the cold, that it has, paradoxically, led to its near-extinction." "Men have recognised that vicuna wool has an unexcelled softness and warmth and hunted the animal for it until it's close to extinction." "The people of the Andes have domesticated another wild camel, the guanaco, to produce heavy-fleeced versions which produce excellent wool and serve as beasts of burden." "Here, in Ecuador and Peru, near the equator, wild camels live at around 14,000 feet." "But as you travel south down the Andes, the snowline gets lower." "Half-way down, 2,000 miles south of Cotopaxi, the line of permanent snow has dropped from 16,000 feet to 13,000 feet." "A thousand miles farther south still, the mountains are not so high but are almost completely covered with snow, to within a few hundred feet of the sea." "So, on the southernmost tip of South America, in Patagonia and Tierra del Fuego, the guanaco doesn't live at great altitudes, but almost at sea level." "Yet it needs its warm coatjust as much, for here, even in summer, it's very cold, and during the winter the whole land is snowbound." "The reason it gets colder nearer the pole is not complicated." "The sun's rays strike the earth at the equator at right angles." "But as you travel round the earth, the rays become more and more glancing." "So a given amount of heat falling on the equator is distributed over a much greater area in the polar regions and has to travel through more of the earth's atmosphere, which weakens it still further." "So down in Patagonia, the sun's rays are very much less intense and carry much less heat, and the glaciers flow right down to the sea." "Farther south still, across the near-frozen seas off Cape Horn, you reach chains of small volcanic islands that run down towards the Antarctic continent itself:" "Remote, little-known archipelagos such as the South Sandwich and, here, the South Orkneys." "There are only two flowering plants that can manage to survive in this bleak, icy country." "One is a kind of thrift and the other is a small, stunted grass." "And apparently, no land-living animals of any kind." "But when the snows melt in summer, they reveal that the rocks and the boulders are covered with over 100 different kinds of mosses and lichens, some of them rounded green cushions, others like miniature trees." "The capacity of these simple plants to endure cold is phenomenal." "Some species can even survive being frozen solid for weeks on end." "Within this miniature tangled jungle lives a whole menagerie of tiny animals." "Primitive creatures little bigger than pinheads manage to survive by slowly chewing away at the lichens and mosses during summer." "In winter they almost grind to a halt, yet they survive unfrozen because their blood contains a kind of antifreeze and remains liquid even when the temperature falls well below zero." "The majority are vegetarians, but there are also carnivorous mites among them which clamber around the grazing herds, picking off individuals as they fancy." "In this extreme cold, the processes of life are greatly slowed down, not only those of growth, but those that lead to old age and death." "So such tiny creatures, which elsewhere might live for merely months, survive for two or three years within the green mossy carpets." "The seas around these Antarctic islands are strewn with ice." "The pack ice that litters the surface is frozen sea water, and in winter forms a solid cover to the sea." "The icebergs are different." "They're made of fresh water and have broken away from glaciers flowing into the sea." "This is the source of those bergs:" "The edge of a glacier." "Beyond it, the continent of Antarctica." "It's huge, bigger than the whole of Europe, and, for the most part, it seems totally devoid of life." "But not all of Antarctica is snow-covered." "In parts of the interior there are valleys where almost no snow ever falls." "This is as desolate a part of the earth as exists." "The cold is extreme, it's drier even than the centre of the Sahara, it's dark for half the year and it's scoured by a never-ending howling wind." "And the wind is responsible for these carvings in the solid granite." "Crystals of salt form beneath tiny flakes on the surface, and grow slowly, but so powerfully that particles are broken loose." "The wind then sweeps them up and hurls them at the rock face, eroding it still further." "Desolate though this waste of shattered rocks may seem, there is life even here." "Algae." "Beneath the stone, the wind doesn't dry it out, and it's protected from the cold." "It gets the light it needs to grow through the translucent rock." "There are also green patches actually within the rock." "Algae have penetrated the microscopic spaces between the rock's constituent particles and there managed to grow." "Glaciers flow down these dry valleys, fed by the ice cap covering the continent's centre." "They're among the world's fastest moving, advancing as much as 300 feet in a year." "As they surge downwards, their surface is torn into thousands of crevasses." "During the summer, even though the winds are bitterly cold, the sun is sufficiently strong to melt a little of the glacier's surface." "Where it accumulates in pools, blue-green algae grows vigorously, its dark colour enabling it to absorb a high proportion of the sun's feeble heat." "These pools and streams are the only places in all of Antarctica's interior where life flourishes in any abundance." "The earth, at the beginning of the history of life before any higher plants or any animals had appeared, must have looked something like this." "Yet here, mysteriously, lie the corpses of large animals." "A crab-eater seal." "It looks comparatively fresh, but examination of its tissues show that it is about 300 years old." "This extreme climate has freeze-dried it." "It must have lost its way, perhaps because of sickness, and misguidedly crawled up here from the coast, 25 miles away." "Although the land of the Antarctic is almost steri its waters are extremely fertile, so its margins, particularly the beaches of its off-shore islands, are rich in life." "These fur seals in South Georgia flourish in great numbers because the surface waters of the seas are thick with shoals of floating shrimp:" "Krill, which is their main food." "Every year they come ashore to the beaches to pup and mate." "They're not true seals but eared seals, for they have small external ears." "Their hind flippers can be brought forward, enabling them to move quite fast on land, something that true seals can't do." "These fur seals retained and thickened the fur of their land-living ancestors, so that now some of these big males have manes which give them the name sea lion." "This fur lies in two layers." "There's an outer guard hair and then a thick layer close to the skin, and that traps air in it and keeps the animals warm when they go swimming." "But the trouble with fur as an insulator is that if you dive too deep, water pressure squeezes out the air." "So fur seals, for the most part, fish in the surface waters." "True seals, like these elephant seal pups, have a different kind of insulation." "Their fur is sparse, but beneath the skin is a thick layer of oily fat, blubber, which surrounds their entire body." "Elephant seals dive to great depths to hunt squid, navigating in the dark with sonar and huge eyes, but they don't get chilled, for pressure has no effect on blubber's insulating qualities." "With every year, the blubber which kept them so warm in the freezing seas loses its power." "Because every year the sea elephants have to moult, and in order to grow new skin they have to bring a blood supply close to the surface." "Blood vessels open up through the blubber and the skin is flushed with blood just below the surface." "If they stayed in the sea like that, they'd chill very quickly." "But they don't." "Instead they haul themselves up onto the beaches or into mud wallows like this one." "And there, the big old bulls like that one must suppress the feelings of antagonism they felt only a few months ago and lie close together with their fellows in the interests of keeping warm." "These are the biggest of all seals." "The huge adult males develop a bladder on top of their noses, like a kind of trunk." "But they also justify their name of sea elephant by their immense size." "The bulls may grow to 20 feet long and weigh three tons." "If you wanted to pick a creature to symbolise the frozen Antarctic wastes, you might well choose a creature like this." "These are macaroni penguins on the island of South Georgia, halfway between the tip of South America and the Antarctic." "But it seems the original penguins evolved in relatively warm climates." "Even today, there are species of penguins that live on the equator, in the Galapagos islands." "So this dense coat of feathers with a layer of fat beneath it was probably developed to keep them warm in the seas anywhere, but it serves them just as well in the freezing Antarctic winds, standing on land or on a surging iceberg." "And they are superb swimmers." "Swift and agile through water, they come in to land through breakers that would smash any boat with the resilience of rubber balls." "These chinstrap penguins are only a couple of feet high." "King penguins are half as tall again." "Large size can be an advantage in cold climates." "The bigger a body, the smaller the surface area of its skin relative to its volum" "So big penguins retain heat better than small ones." "But their great size causes problems in breeding." "They lay just one egg, which they keep warm by the rather inconvenient method of holding it on top of their feet, covered by a fold of feathered skin, for eight long weeks." "When it does hatch, the chick takes so long to mature that they have to feed it for a further ten months" "These king penguins aren't the biggest of all penguins." "They have a cousin, living farther south, which grows even bigger." "It, too, has fearsome problems in raising its chic and it solves them in the most dramatic way imaginable." "They lay their eggs not in spring, but at the end of summer." "Their breeding grounds are on the permanent sea ice near the coast." "The females return to the sea to feed, leaving the males with the eggs." "They shuffle back and forth, each with an egg on his feet, held carefully above the ice." "The gales intensify as the winter advances and the sun sinks lower." "In the skies above, the aurora plays." "The male emperors stoically sit out the months of winter darkness." "The sea ice can offer them no nest." "Not even a scree for a few pebbles." "They have nothing to eat, and nothing to do except protect the precious egg and prevent it from freezing while the chick slowly forms inside it." "As the gales intensify, the males huddle together to give one another shelter." "Then, 65 days after it was laid, the chick begins to hatch." "The newly-emerged chicks are hungry." "All the male can provide is a little secretion from his throat and long-empty stomach." "He's close to starving himself, having been sustained only by the layer of fat beneath his skin." "He's lost a third of his weight." "But soon after, the female reappears with a full stomach and takes the chick onto her feet for its first proper feed." "Now the parents will take turns to trek to the sea and back, bringing food for their youngsters." "But now, at the end of winter, the ice has extended far out to sea, and the penguins may have to walk 50 miles to reach open water." "The adults have a powerful urge to cherish a chick." "Those that have lost one will try and adopt any that wanders by or incubate pieces of ice." "Repeatedly, the parent in charge manages to find something from the pit of its stomach to feed the ever-hungry chick." "Until the chicks lose their down and get their adult plumage, they can't swim and so can't feed for themselves." "But being so big, they, like the king penguins, take a long time to grow to full size, and so their parents must make the long march to the sea to collect food for them." "Though the winter is almost over, there is still bad weather." "Blizzards rage over the ice, and the young huddle together in groups of their own amongst the parent birds." "Many of the youngsters lack the strength to withstand the cold." "Many die." "As the sun rises higher each day, the adults suffer in a different fashion." "On sunny days they get too hot in their insulating blanket of feathers, and eat snow in order to cool themselves." "The chicks still have their downy feathers and can't swim." "But ten months on from laying, the chicks fledge, and over the next few weeks, they all walk down to the sea, which now, with the spring break-up of the ice, is close at hand." "Now, at last, the adults can feed entirely for themselves." "They've got two months in which to restore their weight before they start the whole process over again." "These birds, at first sight so penguin-like, live not near the south pole, but the north." "They're not penguins but guillemots, members of the auk family." "All auks, like penguins, are excellent underwater swimmers." "They use their wings like flippers, but they have not become such specialised swimmers as the penguins, for they can still fly." "These are the guillemots' smaller cousins, the little auk." "Auks and penguins, similar though they are, are not closely related." "They've come to resemble one another by adopting a similar lifestyle at opposite ends of the earth." "Unlike Antarctica, that isolated continent surrounded by sea, the Arctic is connected by land to more temperate regions." "So the land animals of Europe and North America have been able to colonise it and adapt to its particular demands." "Foxes have moved up here." "The Arctic fox's coat is lighter than its southern cousin, and in winter turns whit" "On land, it feeds on small rodents, and on ice floes, perhaps the odd bird." "It's just as well the little auks have kept their powers of flight." "The ice floes are also the hunting ground of one of the biggest of all carnivores." "The polar bear." "This one has killed a bearded seal." "A young bear is eager to take a share of the kill, but must be cautious." "Adults sometimes kill youngsters in squabbles." "The polar bear is clearly a close relative of the bears that live in Europe and America." "Its whiteness is an obvious adaptation to the snow and ice, but so is its huge size." "The principle of a big body retaining more heat applies to bears as much as penguins, and polar bears are very much bigger than their cousins in temperate lands farther south." "Polar bears, if forced to, will eat all kinds of t but their preferred food is flesh, particularly that of seals." "They especially like the blubber just below the seal's skin, and often leave the meat for the scavenging gulls and foxes." "Among the glaucous gulls is the much rarer and pure-white ivory gull." "The polar bear's white coat and great size are not its only adaptations to Arctic life." "It grips the ice with long, sharp claws and thick hair on the soles, which also makes them excellent paddles, for the polar bear spends a lot of time swimming during the summer." "Ringed seals are much hunted by polar bears, and when on the ice, must be constantly on the alert." "They need ice holes through which to leave the water, or at least stick up their heads to breathe." "A polar bear will wait for many hours, motionless, beside such a hole." "They also stalk seals that are rash enough to lie out on the ice." "The polar bear has lost, but about once in every five hunting days, it does kill, and that is enough." "The most powerful effective hunter of all, however, on the northern ice, is man." "Eskimo, or Inuit, as they prefer to call themselves, came up to the Arctic in very early times." "Superb hunters, they could live for many months in winter on nothing whatever but raw meat." "They were so skilled at living on the ice that with only a knife of bone they could make a waterproof house from snow in an hour or so." "A slab of sea ice made a window." "Inside, the igloo was lit with lamps fed by seal blubber." "Heat from the flame and from their bodies could raise the temperature enough for them to remove their heavy clothing and relax." "It was a life of extraordinary rigour and privatio" "These pictures were taken 20 years ago." "No Eskimo lives in this way today." "The poles have not always been so cold." "One explanation of why they've become so is the warming effect of ocean currents." "If they can circulate the waters of the polar seas down towards the equator, they would keep them relatively warm." "And maybe they did so 100 million years ago, when the continents were arranged like this." "But the continents have shifted, the polar seas become more enclosed and any such currents interrupted." "Meanwhile, during the same period, the Antarctic continent drifted south until it came to rest over the south pole." "Now ocean currents could not keep that part of the world warm either, and so an ice cap formed." "The whiteness reflected 90% of the heat in the already feeble rays of the sun." "So ice now covers all of Antarctica and the seas of the north pole." "Over the past million years there have been other variations, due to the sun's varying strength, and the ice cover has waxed and waned." "Now we're in one of the warmer phases, but even so, Antarctica is still buried beneath ice a mile thick, and in the north, ice and snow extend for 1,000 miles away from the pole." "As you come down the mountain or away from the pole, the land becomes warm enough to prevent it being covered by ice and snow all year." "Beyond, the country is bleak enough:" "Boulders and gravel, rocks that have been ground to fragments by the glaciers and pushed in front of them." "This is the tundra, a land full of strange shapes and patterns." "Fine muds and sands retain more moisture than coarse gravel, so when they freeze, they expand more and push the gravel outwards to produce these geometric shapes." "A foot down, the soil is still frozen, permafrost, so the summer melt water can't soak away and the land is covered with bogs and ponds that lie within the polygonal ridges, so that the land looks almost as though it's been cultivated by man." "In places, the underground ice pushes upwards into a mountain called a pingo." "It looks like a small volcano, but instead of hot lava in its heart, it has cold, blue ice." "Although the ice relaxes its grip for only a few weeks in summer, a surprising number of plants and animals manage to find a permanent home here." "Small flowering plants keep low, for close to the ground there is little wind and the sun's rays can be quite warm." "One kind of tree manages to live up here in large numbers by adopting exactly the same policy." "This is the Arctic willow and it lies flat." "It grows extremely slowly in these cold temperatures, and this one may be a century or so old." "In shallow burrows in the topsoil live the harvesters of this meagre crop of leaves and grass:" "Lemmings." "In summer, when there's food about, they breed with great speed." "One female produces five or six babies in a litter, four or five times in a single season" "So in a few months she may produce 30 young." "The babies grow so quickly that the first to be born in the spring can themselves produce young before the winter returns." "In summer, all the tundra plants put out their leaves and there's lots to eat." "The swarming hordes of lemmings attract hunters:" "Snowy owls." "During the summer, lemmings are the owl's main food." "Abundant though the lemmings are, the hunting has been poor for this owl." "She may have laid as many as eight eggs, but only one chick has survived." "As the days lengthen, herds of caribou migrate up from the south." "Their calves were born early in the season and the herd moves up to 15 miles a day" "They have to keep traveling in order to find enough food to sustain them all." "They follow the same route each year." "In places, paths are worn 18 inches deep where the animals have passed, century after century." "Snow geese fly up, too." "They've come from as far away as Mexico, 3,000 miles distant, to claim a share in summer's brief crop and to breed." "They exist in two forms:" "Ones with dark feathers on the body, as well as pure-white ones." "But they're all the same species, and mixed couples are common." "Soon the tundra is thick with their nests." "Ptarmigan, now in their dark summer plumage, feed on the willow scrub." "The caribou take not only willow, but grasses and lichen." "The first snow geese to arrive already have goslings, and are foraging as a family." "Later arrivals are still on the nest, and can't leave until the last egg has hatched." "While there, the first goslings to emerge and their parents are plagued by hordes of voracious blood-hungry mosquitoes." "From the warming pools, more and more mosquitoes hatch." "They provide food for the red-necked phalarope, and there are plenty to gather." "A square yard of fresh water here can produce 100,000 insects in a season." "Now the blackfly larvae, which as eggs were attached to stones in the shallow pools, are also beginning to emerge." "Activity now is intense, for it is light for almost the whole 24 hours of the day." "But by late August, the snow geese sense the imminence of winter and start to head southwards again." "The caribou, too, end their grazing, and start to plod back across the tundra." "As they go, they continue to feed, building up the reserves of fat they will need to sustain themselves through the winter." "As the weather gets colder and colder, the need for shelter becomes more urgent and the herds may cover 25 miles in a day." "And then, at last, the returning travellers reach the first tall tree" "It's the start of the great coniferous forest that lies south of the tundra right round the globe." "The snow geese will fly on for thousands of miles, but the caribou have reached their wintering grounds." "The forest is a sanctuary which will protect them from the bitter winter col and it's here that we shall be coming in the next programme."