In this, the final episode, we follow water on a journey that will take us across the world – from the remote mountain streams, via luscious wetlands and swamps, to coral reefs and the deep ocean. We begin high in the mountains of Iceland, in the North Atlantic. We then travel across the world to South America, to the world’s greatest wetland – The Pantanal.

Seasonal forests are special. Their ecosystems have to cope with drastic change twice a year, in Spring and Autumn. Not only do the individual inhabitants have to deal with that change, but the entire ecosystem has to transform itself at exactly the same time – and it can only do this if all the animals work in perfect synchronicity.

In this episode, we travel to the savannahs of Kenya; the grasslands of Australia; and the Cerrado of Brazil to witness how one of our most important ecosystems works – grasslands. In Kenya we witness the surprisingly important role that rhinos play in making the grasslands fit for antelope. In the Brazilian Cerrado, we reveal how maned wolves get by on a low nitrogen diet, with the help of an odd dietary supplement – a fruit.

This film transports us around the emerald band that encircles our planet – our jungles. And begins by tackling one of the biggest puzzles about the world’s rainforests: why do these places have such a bewildering variety of life, far greater than any other habitat on Earth?