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Welwitschia Plains

Date de soumission : 03/10/2002
Critères: (x)
Catégorie : Naturel
Soumis par :
Namibia National Commission for UNESCO
Coordonnées Central Namib Desert, western Namibia. 22°15' S/ 15°15'E along Swakop River 22°40' S/ 14°55'E along Khan River to 22° 32'S/ 15°03'E
Ref.: 1747
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Description

The Welwitschia Plains are situated approximately 30 - 50 km inland from Swakopmund, roughly lying between the Swakopmund River and Khan River. They form part of the hyper-arid gravel plains of the Namib Desert. Most precipitation is in the form of fog, blowing in from the sea to the west. The most notable feature of this area is the presence of the highest concentration of Welwitschia mirahilis plants (Welwitschia) in Namibia. Not only is the Welwitschia endemic to the Namib Desert and semi-desert, it is also taxonomically very distinct, being the only representative in its family, and only one of three species in the order Gnetales. Welwitschia holds affinities with both flowering plants and gymnosperms, though the order Gnetales belongs to the gymnosperm (cone bearing) plants. Welwitschia and the other Gnetales are regarded as the most closely related extant plants to the flowering angiosperms. Some of the larger specimens (like those on the Plains) may be close to 2000 years old. On the central Namib gravel plains at the site, the Welwitschia plants are the dominant perennial vegetation. They provide shelter for most 'of the smaller endemic and semiendemic resident fauna of the gravel plains, including birds such as Gray's lark, snakes and lizards, scorpions and spiders, and insects. The leaves of Welwitschia act as a litter trap, which allows organic material to accumulate in otherwise infertile desert soils. Some larger antelope species such as oryx and springbok may chew on the leaves or suck moisture from the plants for sustenance. The Plains and surrounding areas support a vast diversity of lichens endemic to the Namib Desert, but the true species richness is still to be determined, since there are no Namibian based lichenologists currently and studies are undertaken by visiting scientists. These include endolithic lichens (lichens growing inside porous rocks and in cracks), epilithic lichens (lichens growing on rocks) and "vagrant" lichens such as Xanthomaculina convoluta (lichens which blow around in the wind, and are not attached to any substrate). The area also supports many examples of succulent and other species of flowering plants, which display an array of adaptations to cope with the harsh conditions on the Plains. Many of these are endemic to the Namib Desert as well. The above mentioned plants are either habitat for, or support food webs which include, many endemic insects and arachnids. The Welwitschia has been extensively studied (and is currently under long-term study by Desert Research Foundation of Namibia), and its uniqueness is verified in many scientific articles. The Welwitschia Plains lie within the Namib Naukluft Park, a proclaimed statecontrolled protected area in Namibia since 1907.