Why are deserts less populated
Info sheet Sahara
With a size of 8 million km², the Sahara is the largest desert on earth.
The name "Es-ssah-ra" was once introduced by the immigrant Arabs. This name describes the colors yellow and red as well as the character of a "desert plain". The special thing that distinguishes it from other deserts is its diversity in terms of climate, vegetation, precipitation and surface forms, which is caused by its location and size, as it extends over two climate zones, tropics and subtropics.
Geological and historical review
The latest research suggests that the Sahara appeared in the early and middle Holocene, around 7,000 BC. BC, was largely covered with vegetation. It is possible that continental drift and changes in solar radiation have gradually turned the area into a desert. It can be proven today that large river networks were once widespread in this area. The oldest traces of human settlement found in Libya, for example, fell during this "fertile" period in the Sahara. The original inhabitants of the Sahara are the Tuaregs. It is estimated today at around 1 million people, whose settlement areas extend over five African states.
Location and structure
The Sahara is located in northern Africa. It extends from about 17 ° W to 37 ° E and extends over 15 degrees of latitude from 32 ° N to 17 ° N. The west-east extension is about 6,000 km and the north-south extension is about 2,000 km. The Sahara comprises the eleven countries Morocco, Algeria, Tunisia, Libya, Egypt, Western Sahara, Mauritania, Mali, Niger, Chad and Sudan.
It is bounded in the west by the Atlantic Ocean and in the east by the Red Sea. In the north the Atlas Mountains and the Mediterranean Sea represent the borders and in the south the Sahel zone and Sudan represent the borders.
It becomes difficult when one tries to structure the entire area of the Sahara. They can be divided zonally or according to the habitus of the landscape. Zonal there is a West-Central and East Sahara. Furthermore, the altitude or the pending surface according to sand, scree or rock desert can be used as delimitation criteria. It should be mentioned that the sandy deserts only make up the smallest proportion of 10%. The greater part of the Sahara is occupied by rubble and pebble desert. According to the habitus of the landscape, a distinction is made between full desert, which extends from the north to around 22 ° N, and the less dry semi-deserts south of it.
In general, the Sahara is one of the tropics or trade deserts. Their dryness is due to the trade winds, which are hostile to precipitation. These arise from the Passat circulation between the equator and the subtropical low pressure channel.
However, on the west coast of the Sahara you can also find the coastal desert type, here due to the cold Canary Current directed towards the coast. In some regions, however, the desert effect is also reinforced by the rain shadow effect that higher mountains can exert. So in the case of the 4,000 m high Atlas Mountains in the northwest of the Sahara.
As is the case with all deserts, the Sahara also has a low rainfall, high levels of solar radiation and low humidity. There is a pronounced time of day climate. The days are very hot, while the nights can cool down to minus degrees.
Due to the size and location of the Sahara, the climate can vary greatly from region to region. A distinction is made between a continental, maritime and mountain climate zone (due to the many and high mountains).
The continental, central areas are characterized in the north by great summer drought and in the south by winter drought. The very rare precipitation occurs in the north mainly during winter and in the south mainly in summer.
The maritime influence of the coastal deserts suggests that the probability of precipitation is increasing. The west and east coast, however, have in common the low precipitation with a remarkably high humidity (arid-humid coastal climate). The temperatures on the west coast are, however, much milder than those on the rather hot east coast on the Red Sea.
The desert mountain climate is associated with severe drought and a rapid drop in temperature at altitude. However, clouds accumulate abundantly at the highest peaks, which can lead to snowfalls in winter.
Wind and a wealth of forms
For the entire desert, there is almost always wind. It often blows from the north-east, is dry and can reach speeds of over 100 km / h. In summer it is very dry, in winter it can turn into an ice-cold storm. It leaves behind huge dunes and carries the sand into large areas outside the desert into the Atlantic and the Alps. By wind grinding, mushroom rocks and honeycomb-like formations on columns and stones are created.
Flora and fauna
The flora with only 1,400 species is species-poor. Individual species are very far apart. A distinction is made between mainly herbaceous plants that have a root system close to the surface. This can expand to over 100 m² in order to absorb as much moisture as possible. The long and deep-rooted trees, on the other hand, feed their water supply from the groundwater. Due to the climate, the trees grow very slowly. As the seasons change only slightly, there are almost no annual rings in the tree trunks. Their adaptation phenomena to the climate are extremely diverse. Small, hard leaves with a rolled edge to prevent evaporation or light, silvery-white hairy leaf surfaces for better reflection of the sun's rays. There are also water-storing species (succulents) and onions, which can store nutrients and water for a long time. The tamarisk has adapted to the often high salt content due to the strong evaporation by means of salt-secreting glands.
The fauna of the Sahara is limited to a few species of beetles, snails and ants. There are just 50 mammals that are mostly nocturnal. They are all exposed to the constant risk of overheating and the extremely limited water supply. The symptoms of adaptation are so diverse that only a few can be named here. Dromedaries store water in the form of fats, and camels can also do without water for days. Many animals are cold-blooded. Nomad animals migrate to distant water holes or oases.
Every year the Sahara penetrates 600 m south. Dunes destroy agricultural land as well as oases and water points. This process, mainly due to desertification, is becoming increasingly serious and hardly seems to be reversible. Even broad, man-made belts of vegetation south of the Sahara do not prevent the desert from spreading beyond these "barriers".
Source: Geography Information Center
Author: Petra Müller
Published by Klett
Source date: 2003
Processing date: 05/18/2012
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