In Africa's ancient south west corner, two extraordinary deserts sit side by side. Water is in short supply, yet these deserts are somehow full of life because the creatures that live here have turned the rules of survival on their head. This film celebrates nature's ingenuity, no matter how tough it gets. In the Kalahari scrublands, clever meerkats are outsmarted by a wily bird, solitary and belligerent black rhinos get together to party and giant insects stalk huge flocks of birds. Rain almost never falls in the Namib - instead it must make do with vaporous, vanishing fog. The creatures in this, the world's oldest desert, have gone to the extremes, as spiders wheel to escape and a desert giraffe fights to defend his scant resources in the greatest giraffe battle ever filmed.

Fourth episode examines how plants either share environments harmoniously or compete for dominance within them. Attenborough highlights the 1987 hurricane and the devastation it caused. However, for some species, it was that opportunity for which they had lain dormant for many years. The space left by uprooted trees is soon filled by others who move relatively swiftly towards the light. The oak is one of the strongest and longest-lived, and other, lesser plants nearby must wait until the spring to flourish before the light above is extinguished by leaves. Tropical forests are green throughout the year, so brute force is needed for a successful climb to the top of the canopy: the rattan is an example that has the longest stem of any plant. As its name suggests, the strangler fig 'throttles' its host by growing around it and cutting off essential water and light. Some can take advantage of a fallen tree by setting down roots on the now horizontal trunk and getting nutriment from the surrounding moss and the fungi on the dead bark. The mountain ash (eucalyptus regnans) grows so tall, that regeneration becomes a considerable problem. It is easily flammable, so its solution is to shed its seeds during a forest fire and sacrifice itself. It therefore relies on the periodic near-destruction of its surroundings in order to survive. Attenborough observes that catastrophes such as fire and drought, while initially detrimental to wildlife, eventually allow for deserted habitats to be reborn.

Northern Africa is home to the greatest desert on Earth, the Sahara. On the fringes, huge zebras battle over dwindling resources and naked mole rats avoid the heat by living a bizarre underground existence. Within the desert, where the sand dunes 'sing', camels seek out water with the help of their herders and tiny swallows navigate across thousands of square miles to find a solitary oasis. This is a story of an apocalypse and how, when nature is overrun, some are forced to flee, some endure, but a few seize the opportunity to establish a new order.

Dr Alice Roberts re-traces the greatest ever journey taken by our ancestors. Thousands of years ago one small group of our species, Homo sapiens, crossed out of Africa and into the unknown. Their descendants faced baking deserts, sweat-soaked jungles and frozen wildernesses and risked everything on the vast empty ocean. Within 60,000 years they colonised the whole world... How did they do it? Why do we, their descendants all look so different?

Take a dino's-eye view of life in the prehistoric past as cutting-edge filming techniques and hard science. When White Tip, a female velociraptor, loses the rest of her pack, she must struggle to survive on her own. In time, she locates a new pack, as well as a mate, only to find that her hardships are just beginning in the harsh desert environment.

David Attenborough comes face-to-face with a baby rhino and asks what the future holds for this little one. He meets the local people who are standing side-by-side with the wildlife at this pivotal moment in their history. We discover what it takes to save a species, hold back a desert and even resurrect an entire wilderness - revealing what the world was like before modern man.