David Attenborough takes a look at deserts, which cover a third of the Earth's land surface. From space they appear lifeless but a closer look reveals a different picture.

Deserts, in fact, are surprisingly varied; from Mongolia's Gobi desert where wild Bactrian camels have to eat snow in lieu of water, to the Atacama in Chile where guanacos survive by licking the dew off cactus spines.

Changes are rare in deserts but they play a crucial part in their story; from Saharan sandstorms nearly a mile high to desert rivers that run for a single day; from the brief blooming of Death Valley in the USA, to a plague of desert locusts 40 miles wide and 100 miles long - two events that might occur once in 30 years.

The highlight of the programme is a unique aerial voyage over the dunes and rocky escarpments of a Namibian desert. From this lofty viewpoint, we follow elephants on a desperate trek for food and - most amazingly of all - desert lions searching the wilderness for wandering bands of oryx.

The programme unravels the secrets behind desert survival - and reveals the ephemeral nature of this stunning environment.

The great plains are the vast open spaces of our planet. These immense wilderness areas are seemingly empty. But any feeling of emptiness is an illusion - the plains of our planet support the greatestgatherings of wildlife on earth: two million gazelles on the Mongolian steppes, three million caribou in North America and one and a half million wildebeest in East Africa. Close on their heels come an array of plains predators including eagles, wolves and lions.

At the heart of all that happens here is a single living thing - grass. Flooded, burnt, baked and frozen - grass is almost indestructible, able to survive from the baking savannahs of Africa to the frozen tundra of the Arctic, from the floodplains of India to the high altitude steppes of the Tibetan plateau. Together, these hugely productive grassland plains encompass a quarter of the land on earth and bear witness to some of the most dramatic wildlife stories on our planet.