UK broadcast 5 March 2006, 9.41 million viewers (34% audience share); US broadcast 25 March 2007
The first episode illustrates a 'journey' around the globe and reveals the effect of gradual climatic change and seasonal transitions en route. During Antarctica's winter, emperor penguins endure four months of darkness, with no food, in temperatures of −70 °C (−94.0 °F). Meanwhile, as spring arrives in the Arctic, polar bear cubs take their first steps into a world of rapidly thawing ice. In northern Canada, the longest overland migration of any animal — over 3,200 kilometres (2,000 mi) — is that of three million caribou, which are hunted by wolves, and one such pursuit is shown. The forests of eastern Russia are home to the Amur leopard; with a population of just 40 individuals, it is now the world's rarest cat. This is primarily because of the destruction of its habitat, and Attenborough states that it "symbolises the fragility of our natural heritage." However, in the tropics, the jungle that covers 3% of the planet's surface supports 50% of its species. Other species shown include New Guinea's birds of paradise, African hunting dogs in their efficient pursuit of impala, elephants in Africa migrating towards the waters of the Okavango Delta, a seasonal bloom of life in the otherwise arid Kalahari Desert, and 300,000 migrating Baikal teal, containing the world's entire population of the species in one flock. The Planet Earth Diaries segment shows how the wild dog hunt was filmed unobtrusively with the aid of the Heligimbal: a powerful, gyro-stabilised camera mounted beneath a helicopter.
UK broadcast 12 March 2006, 8.57 million viewers (30% audience share); US broadcast 25 March 2007
The second instalment focuses on the mountains. All the main ranges are explored with extensive aerial photography. Ethiopia's Erta Ale is the longest continually erupting volcano — for over 100 years. On the nearby highlands, geladas (the only primate whose diet is almost entirely of grass) inhabit precipitous slopes nearly five kilometres (3 mi) up, in troops that are 800-strong: the most numerous of their kind. Alongside them live the critically endangered walia ibex, and both species take turns to act as lookout for predatory Ethiopian wolves. The Andes have the most volatile weather and guanacos are shown enduring a flash blizzard, along with an exceptional group sighting of the normally solitary puma. The Alpine summits are always snow-covered, apart from that of the Matterhorn, which is too sheer to allow it to settle. Grizzly bear cubs emerge from their den for the first time in the Rockies, while Himalayan inhabitants include rutting markhor, golden eagles that hunt migrating demoiselle cranes, and the rare snow leopard. At the eastern end of the range, the giant panda cannot hibernate due to its poor nutriment of bamboo and one of them cradles its week-old cub. Also shown is the Earth's biggest mountain glacier: the Baltoro in Pakistan, which is 70 kilometres (43 mi) long and visible from space. Planet Earth Diaries demonstrates the difficulty of obtaining the first ever close-up footage of the snow leopards: a process which took over a year.
3. "Fresh Water"
UK broadcast 19 March 2006, 8.83 million viewers (32% audience share); US broadcast 15 April 2007
The fresh water programme describes the course taken by rivers and some of the species that take advantage of such a habitat. Only 3% of the world's water is fresh, yet all life on land is ultimately dependent on it. Its journey begins as a stream in the mountains, illustrated by Venezuela's Tepui, where there is a tropical downpour almost every day. It then travels hundreds of kilometres before forming rapids. With the aid of some expansive helicopter photography, one sequence demonstrates the vastness of Angel Falls, the world's highest free-flowing waterfall. Its waters drop unbroken for nearly 1,000 metres (3,000 feet) and are blown away as a mist before they reach the bottom. In Japan, the water is inhabited by the biggest amphibian, the two-metre long giant salamander, while in the northern hemisphere, salmon undertake the largest freshwater migration, and are hunted en route by grizzly bears. The erosive nature of rivers is shown by the Grand Canyon, created over five million years by the Colorado River. Also featured are smooth coated otters repelling mugger crocodiles and the latter's Nile cousin ambushing wildebeest as they cross the Mara River. Roseate spoonbills are numerous in the Pantanal and are prey to spectacled caiman. In addition, there are cichlids, piranhas, river dolphins and swimming crab-eating macaques. Planet Earth Diaries shows how a camera crew filmed a piranha feeding frenzy in Brazil — after a two-week search for the opportunity.[