A rain forest is the richest habitat on Earth. Exactly how many species rain forests contain is unknown, but it runs into millions. And new ones are discovered every week. There are some, like the clouded leopard, we still know virtually nothing about. Although they cover just seven percent of the world's land area, jungles play a vital role in the health of the planet .
Jungles and rainforests are home to an incredible variety of species like preening birds, intelligent orangutans and remarkably ambitious ants.

The search for climate change solutions requires passion, resources and a sense of urgency -- three qualities Bill Gates clearly possesses. Bill has founded a start-up called TerraPower. After extensive computer modelling, the idea showed promise. Its new reactor greatly reduced the chance of human error. Fuelled by depleted uranium, the travelling wave reactor functions like a slow-burning candle and requires refuelling only once every decade. Bill and his team believed they had finally developed the ideal energy source, a reactor that was clean, efficient, and most importantly, safe.

The polar regions of our planet may seem beyond the reach of most of us, but they are not beyond our influence. We, unintentionally, are changing these frozen worlds, and these changes will not just affect the poles but the whole planet. On the unforgiving frontier of climate change, polar bears, walruses, seals and penguins find their icy Edens in peril.

A fifth of the land on our planet is covered by desert. Deserts may appear to be barren and empty, but they are of crucial importance to life. For those that can overcome their challenges they provide a vital refuge. The Grasslands are one of our planet's most productive landscapes. They support the greatest aggregations of large animals on Earth. Cameras follow desert elephants seeking sustenance, bison roaming North American grasslands and caterpillars living the good life underground.

Everything that lives on land, animal or plant, depends on fresh water. Yet only part of it is within reach: Much of the planet's fresh water, is locked away, almost two-thirds of it lies frozen around the poles. Even away from the poles, much of the land's fresh water freezes each winter. The need for fresh water is as strong as ever. However, the supply is becoming increasingly unpredictable and uncertain for all manner of species. We are not alone in our need for water, but we have the ability to ensure the fresh waters of the world do flow, and we alone can determine how they are shared.

The last episode examines the fragile interdependence that exists between forests' wide variety of residents, including bald eagles, hunting dogs and Siberian tigers.
Over half of all the world's trees, evergreen and deciduous, stand in great assemblies. For many of us, they are places of mystery and darkness. They are key to our climate, and home to countless unique species. The boreal forest contains 750 billion trees, and it stores over 40 percent of the world's carbon, making it a vital element in the fight against climate change. In the past, we have destroyed them without hesitation. Yet, forests do have an astonishing ability to recover. If we choose to give forests time and space, they could reclothe the earth with much of the rich and varied communities of animals and plants of which we have, so recently, robbed it. A future with more forests is key to the resilience of our planet.