Arid regions occupy about one third of the earth's surface. Most of these lands are confined between 15 ° and 30 ° latitude, where the masses of air transported along the intertropical convergence zone form, by subsidence, semi-permanent high pressure cells, which condemn them to constant intense solar radiation. But there are also deserts "cursed" because they are positioned in the rain shadow of imposing mountain ranges or in continental areas so inland that they cannot receive the influence of the humid sea currents.

What unites the heterogeneous multitude of environments that we call deserts is the almost total absence of precipitation. At first glance these places seem totally refractory to life: desertum comes from the Latin verb deserere which means to abandon, to untie . But life always finds a way to make the most of very few resources. Plants have tuned their biochemical rhythms, animals sharpened their senses: imposing African elephants walk through invisible paths generation after generation in search of the few sources of water. Under the arid and sandy surface, or the sunburnt crust, teeming communities take advantage of the cool microclimate of the subsoil.

At over 55 million years, the Namib Desert is considered the oldest in the world, a arid coastal strip located between Namibia, South Africa and Angola. Annual rainfall amounts to only 5 millimeters: the only source of water is the fog banks that sporadically form from the meeting of Atlantic ocean currents and the hot and dry eastern winds. It is precisely because of these mists that for centuries ships and vessels have been stranded in the northern part, "the skeleton coast", blocked by the slow advance of the sands into the ocean.