With much of it covered in ice all year round and with no daylight from October to March, the Arctic Ocean is one of the world's most remarkable oceans. Its home to a multitude of unique life forms, all highly adapted to cope with the extreme and seasonal conditions. The impacts of climate change are more strongly felt here than anywhere else in the world.

Over the last years, the world has experienced an energy revolution, driven by an urgent need to green the grid and save life on Earth as we know it. 50 years ago, a devastating oil crisis kicked off an energy revolution. The world set course to cut the costly habit of burning fossil fuels. With the urgent new threat of a changing climate, the drive to unleash the power of the sun, earth and wind has accelerated into a race for humanity's survival. Change is taken place but, is it happening fast enough to secure our future? Technologies are right here, right now, and they will enable the transition to 100% renewables, because winning the energy race means a win for the entire world.

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.

A new force threatens our perfect planet. In the past, five mass extinction events were caused by cataclysmic volcanic eruptions. It was not the lava or ash that wiped out life, but an invisible gas released by volcanoes: carbon dioxide. Almost every part of modern life depends on energy created by burning fossil fuels, and this produces CO2 in huge amounts. Humans are changing our planet so rapidly, it’s affecting earth’s life support systems: our weather, our oceans and the living world. The greatest change to be made is in how we create energy, and the planet is brimming with natural power that can help us do just that. It’s these forces of nature - the wind, the sun, waves and geothermal energy - that hold the key to our future.
Through compelling animal-led stories and expert interviews, we discover how CO2 is destabilising our planet. We meet rescued orphaned elephants in Kenya, victims of ever worsening droughts, and join ocean patrols off the coast of Gabon fighting to save endangered sharks. In the Amazon, we witness wildlife teams saving animals in the shrinking forests, and in San Diego we enter a cryogenic zoo preserving the DNA of endangered species before they become extinct.

Will explore the strategy, deception and feats of engineering plants use to thrive in the changing weather of different seasons. In the face of conditions ranging from ice and snow to raging fires, survival is often a question of perfect timing - particularly when contending with intense competition and surprising predators.
In this episode, David Attenborough travels to Finland to show one of the most extreme examples of seasonal plant life in the Arctic Circle. He also travels to California to see how climate change is affecting giant sequoias. These ancient trees like all other seasonal plants depend on the predictability of the seasons and our current changing climate threatens their survival.

As tides rise and fall twice a day, vast amounts of water swirl around the earth. This is a huge energy source that's currently largely untapped. An estimated 3000 gigawatts are available to be harvested globally, enough to power a third of the earth's homes. Yet compared to wind and solar, the technology needed to harness tidal power is still in its infancy. The power of the ocean’s tides is the last great untapped energy source on Earth. From sub-sea kites to floating platforms, teams of engineers are racing to perfect the technology to harness the vast flows of water.