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Author: Eric Robert
The outstanding photographs in this book perfectly reflect the exquisite beauty of western Namibia, one of the earth's rare remaining wilderness regions with virgin lands and abundant wildlife. The photographs show the unique denizens of the Namib; the text explains how plants and animals have adapted to survive in such harsh surroundings and tells the story of the Himba: their strong tribal organization, their values, and how they resist modern civilization. This book encapsulates the breathtaking kaleidoscope of the Namib Desert, from sunrise to sunset.
The Namib desert extends along the southwest coast of Africa in a high pressure zone generated by Hadley's cells. The desert covers a coastal area of approximately 1.900 km long between the Olifants River mouth in the Cape Province of South Africa and the district of Namibe (originally Mocamedcs) in southern Angola. It is crossed by two perennial rivers, the Kunene and the Orange River, which mark the northern and southern borders of Namibia. To the south of the Orange River, the desert is usually less than 50 km wide; in Namibia, along the 1.400 km between the Orange and the Kunene Rivers, the Namib, stretching to the Great Escarpment to the east, reaches an altitude of about 1.000 m and a maximum width of 200 km. This central part of the desert is the most arid.
This region has a great landscape diversity: Immense gravel plains (hamada), dune fields, sand seas, inselbergs, chains of rocky hills, massive mountains to the east, salt flats, dry river beds, as well as the mouths of two permanent rivers which constitute the only oases in this endless aridity.
Above the Atlantic Ocean there exists a permanent anticyclone at 30'S in summer and 26°S in winter. This anticyclone causes southerly winds along the coast of the Namib Desert. The wind generates surface currents; as a consequence of the relatively stable meteorological conditions, a surface current flows NNW up the Namib coast. It is not a fast current, flowing between 6 and 30 m per hour. Yet this current is but one aspect of the Benguela "system" which is also characterized by powerful "upwellings". This welling up of deep, cold ocean water to the surface significantly lowers the surface temperature along the coast.
As a result, surface temperature is between 5°C and 8°C lower than water temperature at the same latitude further offshore, and temperatures of 12°C to 13°C are not rare at the Tropic of Capircorn. The presence of this mass of cold water profoundly influences the climate of the Namib Desert, resulting in moderate temperatures along the coast and limited rainfall. Temperature inversion at lower atmospheric levels is also a consequence of the cold water, creates favourable conditions for the formation of fog which fills the important ecological function of providing the main source of moisture for most species of plants and animals along the coast.
The Namib is a rather temperate desert. Temperatures above 40°C in the shade are rare and the annual average maximum temperatures is about 30°C; 12°C to 15°C the average minimum. As a result of sunshine, temperatures at ground level frequently exceed 60°C and at times 70°C. Temperatures can drop below 0°C by the end of the night in the central part of the desert. These drastic differences in ambient temperature render life particularly difficult for both plants and animals.
The Namib is very arid. The least dry area, the foot of the Great Escarpment to the east, receives an annual rainfall of only about 100 mm. Precipitation progressively diminishes across the width of the Namib from east to west and along the coast the average does not exceed 12 to 15 mm. The southern sector, particularly the area south of the Orange River, receives winter rainfall, while the northern sector is distinguished by summer showers. In the central area, rainfall is very scarce and not seasonal. It is not unusual for a locality to receive no rain at all for several consecutive years and then to receive several times the yearly average in one or two downpours.
The fog provides an important source of moisture in the coastal areas, which is in fact more predictable and reliable than rain. The fog is at its densest at ground level between 300 and 600 m above sea level, producing important condensation on the hillsides. During the night the fog can extend up to 50 km inland, often lingering during the morning but normally dissipating before noon.
Southerly and SSW winds prevail along the coast and blow between 40% and 60% of the time; they are also the strongest. They are responsible for the transport and the accumulation of sand in the dune fields and the sand seas. The westerly winds are more moderate and cause the penetration of fog far inland. Easterly and northeasterly winds are hot and desiccating and when they gust in the central part of the desert, the humidity level falls precipitously to between 5% and 0% while the ambient temperature rises several degrees in minutes. These winds are more frequent in winter.
Winds in the Namib Desert fill important functions both in the shaping of the landscape and in the ecology. It is the wind which carries and accumulates the sand and blows the fine elements from the surface of the plains, leaving behind only rocks and gravel. Loaded with sand, the wind erodes and polishes the rocks. The wind also distributes detritus of organic matter into the heart of the desert, providing food and nutrients for animals even in areas naturally devoid of all vegetation.