Planeta Tierra es una aclamada serie de documentales creada por la BBC que nos muestra, en 11 episodios escritos por el prestigioso naturalista David Attenborough, la belleza de nuestro enorme planeta con imágenes nunca antes vistas. 5. "Deserts" UK broadcast 2 April 2006, 9.23 million viewers (34% audience share);[25] US broadcast 1 April 2007 This instalment features the harsh environment that covers one third of the Earth: the deserts. Due to Siberian winds, Mongolia's Gobi Desert reaches extremes of temperature like no other, ranging from -40°C to +50°C (-40°F to 122°F). It is home to the rare Bactrian camel, which eats snow to maintain its fluid level and must limit itself to 10 litres (2.6 U.S. gal; 2.2 imp gal) a day if it is not to prove fatal. Africa's Sahara is the size of the USA, and just one of its severe dust storms could cover the whole of Great Britain. While some creatures, such as the dromedary, take them in their stride, for others the only escape from such bombardments is to bury themselves in the sand. Few rocks can resist them either and the outcrops shown in Egypt's White Desert are being inexorably eroded. The biggest dunes (300 m or 1,000 ft high) are to be found in Namibia, while other deserts featured are Death Valley in California and Nevada, the Sonoran in Arizona, the deserts of Utah, all in the United States, the Atacama in Chile, and areas of the Australian outback. Animals are shown searching for food and surviving in such an unforgiving habitat: African elephants that walk up to 80 kilometres (50 mi) per day to find food; lions (hunting oryx); red kangaroos (which moisten their forelegs with saliva to keep cool); nocturnal fennec foxes, acrobatic flat lizards feeding on black flies, and duelling Nubian ibex. The final sequence illustrates one of nature's most fearsome spectacles: a billion-strong plague of desert locusts, destroying all vegetation in its path. Planet Earth Diaries explains how the hunt for the elusive Bactrian camels necessitated a two-month trek in Mongolia.