The seasonal cycle that drives the lives of elephants on land, is just as important in the oceans. It’s July and the humpback whales are in their breeding grounds in the tropics. This calf is no more than a few weeks old and as he begins to tire, his mother supports him close to the surface, so that he can breathe. These shallow equatorial waters make good nurseries. They are warm and calm and there are few predators. The playful calf is now drinking 600 liters of milk a day, but its mother is starving. There is nothing for her to eat in these crystal clear waters. To find food, she will have to lead her calf on an epic 4000- mile journey to richer feeding grounds at the southern extremes of our planet. This is the longest migration by any marine mammal, and it depends entirely on the healthy ocean all along the way.

Out in the open ocean, the whales meet others searching for food. Dolphins are closing in on their prey. A hundred sailfish join in the attack. Reaching almost 70 miles an hour, they are the cheetahs of the sea. Mother and calf swim on south through the vast open oceans. They have to cross half the globe from the equator all the way to the edge of Antarctica. The tropic seas are a long way behind them now. They’re heading for stormy seasonal waters. Strong winds and current draw nutrients up from the depths and life blooms wherever the sun’s rays can penetrate. The mother knows there are even richer feeding grounds further south and hurries her calf through these dangerous waters. The great white shark. Great whites attack whale calves, but they are not victims today. These magnificent predators, at the very top of the food chain, are the vital parts of a healthy ocean. Yet we slaughter almost 100 million of them every year. Their populations are in freefall.

August in the arctic and the ice is vanishing fast. The two cubs can’t cope with the shifting platform and their hungry mother is forced to lead them back to the shore. Out to sea, the ice is now too thin to support the cubs’ father. Glacial melt waters pour from the land, mix with the sea, and speeds up the thaw. Each year as the climate warms, there is less and less ice in the arctic. This is a disaster for polar bears. Without a solid platform, they struggle to hu nt the seals they need to survive. How will the father make it through the year now that the ice is almost gone?

September and the whales are 3000 miles from the equator. Water is getting colder and rougher. Mother and calf must stay close. So as not to lose track of each other, they slap their fins on the surface. They can hear these sound signals above the roar of the ocean.

The far south….. at last. October, and the whales are entering polar waters. Summer is drawing to a close in the north, but here it’s only just beginning. As the sun melts the ice, life returns. The whales have finally reached Antarctica in time for the summer. Adelie penguins and they are in a hurry to reach their nesting grounds.

December and the sun does not set. The Antarctic summer is all too short, but for a few brief months its warmth unlocks the sheltered bays. In the depths something stirs. At last after their 4000-mile journey, the humpback whales can feed. They harvest krill, shrimps that begin to swarm here as soon as the ice retreats. Now, at last the mother can replenish her reserves as she and her calf join the rest of the team. The whales create a spiraling net of bubbles, concentrating the krill into one gigantic feast. They work round the clock, for the boom will be short-lived. Summer is fading fast and they’ll soon have to return to the tropical waters. These whales and most of the life in Antarctica, ultimately depend on the krill. Without it, the far south would be almost deserted. But krill depend on the ice and ice is in decline. Winter in Antarctica and the greatest seasonal change on our planet is underway. The sun begins to retreat. Soon the continent will be plunged back into darkness. The aurora Australia illuminates the southern skies, but these spectacular lights bring no warmth to the wilderness of ice.

Back in the north of the planet where our story began, the sea ice has completely disappeared. Our male polar bear is in great danger now. If he doesn’t find land soon in this vast ocean, he will drown. After many days at sea, the exhausted bear is drawn by the pungent smells of the colony. He’s lost half his body weight. He’s desperate for food, but walrus are much larger than his usual prey. If the pups he’ll have to get to, the powerful adults can do terrible damage with their huge tusks. The walrus sense the danger. The adults close ranks around their young. He tests the barrier. It stands firm. He may be the world’s biggest land carnivore, but it looks like he’s met his match and he’s badly weakened by starvation. A pup hides behind its mother. If he can just prize her off. With the herd retreating to the safety of the water, the bear has little time to left. He tries again. And again, in sheer frustration now. he has to avoid the lethal tusks at all costs. It slips from his grasp. It’s only when bears are on the verge of starvation that they’ll risk attacking such dangerous prey. This one took the gamble and lost. The walrus are calm again. The bear is no longer a threat. Unable to feed, he can’t survive. As the global climate continues to warm and the arctic ice melts sooner every year, more of his kind will come to this sad end.

A year has passed and the two bear cubs have beaten the odds. They’ve left their mother and are thriving. Their ever-shifting world is changing faster by the day, but for now, they’re keeping one step ahead. Their father’s adventurous spirit lives on in these magnificent youngsters, the next generation and proof of the resilience of life.

The polar bear has become an emblem for the state of our planet and for all the creatures who are struggling to live alongside. Finally we’ve begun to understand how precarious the state of our once lucky planet is. If we are to go on sharing earth with such a rich variety of life and preserve its fragile balance for our own children, now, more than ever, it’s in our hands.