Our frozen planet is changing. In this final episode, we meet the scientists and people dedicating their lives to understanding what these changes mean, not just for the animals and people who live there, but for the world as a whole.
Our journey begins in the Arctic, where every summer huge quantities of ice calve from the edges of Greenland’s melting glaciers. On top of the ice cap itself, glaciologist Alun Hubbard descends into a moulin to try to understand the mechanisms that are driving this historic loss of ice.
Elsewhere in the Arctic, it’s not just land ice that is disappearing. In the Gulf of St Lawrence, Canada, biologists are trying to find out how the loss of sea ice will impact the lives of baby harps. In Arctic Russia, with the loss of summer sea ice, more and more polar bears are arriving on the island of Wrangel. Here, a local ranger and scientists are braving the hungry bears to assess their future survival.
Loss of sea ice impacts not just wildlife but people too. In the remote community of Qaanaaq, Greenland, local Inuit hunters are finding the ice too dangerous to travel and hunt on, risking their traditional way of life. And these changes happening in the Arctic have the potential to affect people far beyond. On Alaska’s open tundra, bubbling lakes hint at the gases being released from the previously frozen soil, including the potent greenhouse gas methane.
There is one place where the full scale of a melting Arctic can be best witnessed - from space. Based in the International Space Station, astronaut Jessica Meir looks down at forest fires across Europe and reflects how our changing weather patterns are interconnected.
Rapid ice loss is also happening across the high mountains of the planet’s continents. Glaciologist Hamish Pritchard uses a sophisticated helicopter-strung radar system to try to quantify how much ice is left in the previously uncharted glaciers of the Himalayas. It’s important as, downstream, some 1.2 billion people rely on glacial meltwater as their primary source of fresh water.
Finally, in Antarctica, we meet Bill Fraser, who has dedicated 45 years of his life to studying the Adelie penguin. Over this period, he has witnessed changes in weather conditions and the extinction of entire colonies. These ‘canaries in the coal mine’ are a sign that all is not well, even in the remotest place on earth. And changes here have the potential to affect all of us, so an international group of scientists is on an urgent mission to assess the stability of a huge body of ice known as the Thwaites ice shelf. If this plug of ice melts and slips into the ocean, it will raise global sea levels, impacting coastal communities across the planet.
The unprecedented changes our scientists are witnessing may be profound, but there is hope that, through a combination of technology and willpower, there is still time to save what remains of our frozen planet.

Chris turns to longevity doctor Peter Attia to find out how changing his eating habits can help his quest for longevity. Ironically, the answer is to eat no food at all for four long days. If he can bear the hunger, fasting will unlock his body’s own anti-aging powers and give Chris the edge he needs when he tries to hunt for his next meal … by spearfishing off the Great Barrier Reef.

Sir David Attenborough explores the incredible diversity of Britain’s woodlands, taking us on a seasonal journey through our forests, and revealing a host of spectacular animals and the hidden dramas that rule their lives.
In an ancient pine tree in the Cairngorms, two eagle chicks are on the verge of fledging their gargantuan nest. In winter in the Forest of Dean, the reintroduction of wild boar has given the robin a lifeline. As they root through the thick snow, the boar unearth the worms with their snouts, which the robins otherwise couldn't find.
Back in Scotland, a male capercaillie displays to gathering females. These birds are on the edge. With only around 500 left, they are some of the rarest and most threatened in the British Isles. In a beech woodland outside London, the deciduous trees burst to life in spring, and huge colonies of wood ants awaken and go looking for food. Also looking for sustenance is a female roe deer. With no large predators left in our woods, the deer are free to browse on new growth to the extent that they can damage the woodland itself.
In Sussex is an ancient-looking landscape, but one that has only been recreated in the past 20 years. This is the wood pasture of Knepp, created by using old grazing methods that generate a mix of scrub, open areas and ancient trees. In the Scottish Highlands, red squirrels battle it out for access to ripe pine cones at the top of a tree. It’s an acrobatic and energetic encounter, with more than a little cunning required to win the day. As the summer finally fades, we encounter a honey buzzard nest, where two chicks feast on wasp grubs, squabble between themselves and grow up before our eyes.
Autumn brings the fallow deer rut. The woods resonate with their calls, and bucks fight for supremacy. The season also brings colour, both in the leaves but also in the fungi that fruit at this time of year. The mushrooms are just a tiny part of their story, however, and we travel underground to see how the wood-wide web connects the whole forest together.