Highlights the extreme conditions endured by those filiming "Planet Earth." From the Blu-Ray series.

Describes technology used to film Planet Earth including specialized airplanes and night vision cameras. From the Blu-Ray version.

Highlights the dangerous situations the filmers of "Planet Earth' experienced while making this series. From the Blu-Ray series.

Highlights the extreme care the film crews had to take while filming "Planet Earth." Also shows how sometimes care was not enough--luck was also key. From the Blu-Ray series.

Saving Species asks if there really is an extinction crisis facing certain species. Alastair Fothergill, executive producer of Planet Earth, admits that making the series was a bittersweet experience since some creatures were filmed with the knowledge that their continued existence is under threat.

The second part looks at man's potential effect on the world's areas of wilderness. As the human population has grown, only a quarter of Earth's land now remains uninhabited (aside from Antarctica). Although around 12% is protected, this may not be enough — providing such places are not just 'enclosures' and bordering territories are also managed. Ethiopia's Semien Mountains are increasingly encroached upon for farming land, and this example leads to the question of overpopulation. Some interviewees argue that it is not just about numbers: how humans consume their natural resources is also important.

The last episode deals with the future of conservation. It begins by looking at previous efforts. The 'Save The Whales' campaign, which started in the 1960s, is seen to have had a limited effect, as whaling continues and fish stocks also decline. In the 1990s, as head of the Kenya Wildlife Service, Richard Leakey took on the poachers by employing armed units. Although it was successful in saving elephants, the policy was detrimental to the Maasai people, who were forced from their land. The need for "fortress" areas is questioned, and the recently highlighted Raja Ampat coral reef in Indonesia is an example.

Originally aired under BBC Natural World Collection. The BBC Natural History Unit explores a secret cave deep in the mountains of Pakistan where generations of snow leopards return each year to raise their young.

The freshwater pools that dot Mexico's Yucatan peninsula were believed by the Mayans to be portals to the underworld. For the first time ever, the BBC Natural History Unit explores this incredible, labyrinthine system of underground rivers.

Follow the struggle for survival of two female elephants trying to raise their young in one of the harshest climates on Earth.

Originally aired under BBC Natural World Collection. Many years ago lions thrived in the deserts of Namibia's Skeleton Coast, until they were exterminated by man. Six years ago maverick biologist Flip Stander discovered a tiny remnant population alive and well in nearby mountains, and started to study them. Their numbers have grown and they are now returning to the desert in increasing numbers. But if these lions are to continue roaming here, Flip will have to persuade local people that these lions are worth more alive than dead.

The Planet Earth team reveal their most memorable moments from the making of the series. We'll discover their high points, and their not so high points. And they'll tell us which sequences they consider to be their great Planet Earth moments. From the