Stephen Fry explores how nearly all life on Earth is impacted by our annual journey around the sun. Northern winters bring notably harsh conditions for polar bears, for example.

As the North starts to face the sun, the great melt begins, and there's a baby boom. But for penguins and foxes in the South, conditions are getting harsher.

Summer can be extreme. In The Rockies, summers are short. Pika must harvest flowers to eat before the snow returns. For Marion Island’s king penguin chicks, life has frozen still.

Autumn signals change. For many, change brings opportunity, but also huge challenges. For some, like Monarch butterflies, it offers a chance to begin again or take a new path.

These are the stories of the scientists and conservationists who have have used pioneering techniques to uncover new behaviour, enabling us to film this extraordinary series.