The story of animals surviving one of the harshest seasonal changes on the planet continues. It is summer and the Yellowstone beavers have a new challenge. Will the young survive as the river dries up and the colony is forced to move home? As food becomes scarce, wolves have a surprising strategy to keep their pups fed and grizzly bears are unexpected visitors on a cowboy ranch. By midsummer, the hot dry conditions create a new danger - deadly wildfires burn out of control and threaten to engulf a family of great grey owls. 2016 was the hottest year on earth since records began, and across Yellowstone scientists reveal the effects of rising temperatures on the animals that live here.
The episode begins in the South American rainforest whose rich variety of life forms is used to illustrate the sheer number of different species. Since many are dependent on others for food or means of reproduction, David Attenborough argues that they couldn't all have appeared at once. He sets out to discover which came first, and the reasons for such diversity. He starts by explaining the theories of Charles Darwin and the process of natural selection, using the giant tortoises of the Galapagos Islands (where Darwin voyaged on HMS Beagle) as an example. Fossils provide evidence of the earliest life, and Attenborough travels a vertical mile into the Grand Canyon in search of them.
David Attenborough returns in this landmark series to his most magical place on earth exploring the Great Barrier Reef aboard the research vessel Alucia. Part 1: Builders David descends beneath the waves at night in the state-of-the-art Triton submersible, the first of its kind to visit the reef. He meets some of the tiny coral animals that built the reef and helped to turn it into an underwater wonderland. He then takes to the skies to witness the vast scale of their endeavour, a living structure that provides a home for thousands of species. Using cutting-edge technology to generate computer scans of the sea floor, David learns that the Great Barrier Reef we know today is much younger than scientists ever imagined. He meets some of the people that have lived alongside it and who have told stories of its origins for thousands of years.