Deserts and semi-deserts of Africa wildlife. African natural areas. What animals live in the Sahara desert: African ostrich

Deserts and semi-deserts located mainly in tropical zones. They occupy the largest area in North Africa. Dry tropical air prevails here throughout the year. The annual rainfall is less than 100 mm everywhere. It happens that the annual norm falls in a few hours, and then for many years there is no precipitation at all.

In a tropical continental (desert) climate, when the temperature at night is less than +10 °C, and during the day it exceeds +50 °C in the shade, rocks quickly collapse, turning into stones and sand. Due to weathering, different types of deserts are formed. Most of the Sahara (Fig. 75) and the Namib desert are occupied by rocky deserts. In addition to them, sandy and clayey deserts and semi-deserts, such as the Kalahari, are common here.

How did the Sahara Desert come about? To the north of the Ahaggar plateau in the mountains, a drawing was found on sandstone, which is about eight millennia old. The picture shows hunters and wild animals. This indicates that the Sahara, oddly enough, was once a steppe covered with rich vegetation. The increasing dryness of the climate and the depletion of soils by agriculture led to the formation of the largest desert in the world.

Desert tropical soils in conditions of dryness and lack of vegetation cover are poorly developed and often saline. They contain little organic matter, in such soils there is almost no humus.

The vegetation of deserts and semi-deserts is poor and very sparse, although individual plants have adapted well to the harsh growing conditions. These are camel thorn, aloe, euphorbia, wild watermelons, wormwood, etc. Some plants sprout only after rain, grow quickly, bloom, and then dry up. A peculiar plant of the Namib desert is velvichia, living for about 100 years (Fig. 76).

Rice. 77. Oasis

At springs and in river valleys, where underground waters rise close to the surface, rich vegetation develops - palm trees, various shrubs. People live here. Such places are called oases (Fig. 77). The largest oasis in the world is the Nile Valley.

The main plant of the oases is the date palm. Tasty and nutritious palm fruits are eaten, drinks are made from the juice, the tree is used for construction, and the roofs of dwellings are covered with leaves of trees. About 100 kg of fruits are harvested from each tree annually. Africa accounts for 40% of the world's date production. material from the site

Animals have also adapted to life in the deserts (Fig. 78). Antelopes and gazelles cover hundreds of kilometers in search of water. Predators - hyena, jackal, fennec fox, cheetah - get moisture from food. Turtles, lizards and snakes can go without water for a long time, hiding in burrows. There are many birds in the deserts: ostriches, bustards, larks. For a person, poisonous stings of a scorpion and phalanx are dangerous.

In the conditions of a tropical continental climate, deserts and semi-deserts are formed.

Remember: 1. What weather conditions are typical for tropical and subtropical climatic zones? 2. How does the cold sea current affect the climate of the coast? Why do coastal deserts occur? 3. What is physical weathering?

Tropical deserts and semi-deserts. Where the dry period sometimes lasts all year round, and short-term rains fall irregularly, there is a natural zone of tropical deserts and semi-deserts. It occupies the largest area in Africa in the Northern Hemisphere. From the Atlantic Ocean to the Red Sea, the Sahara desert stretches for 5000 km in a wide strip from west to east. In the southern part of Africa, deserts occupy much smaller areas: the harsh Namib Desert stretches in a narrow strip along the coast of the Atlantic Ocean, and the Kalahari semi-desert is located a little further inland.

The Sahara is the largest desert in the world by area. In its hinterland, there has been no rain for years or even decades. Often even rain does not fall on the surface of the earth: it evaporates in the air from the high temperature. Great heat during the day is replaced by piercing cold at night, and sandy and dusty brown ones sweep away all living things in their path. During the day, the surface of the rocks heats up to +70 °C, and at night the temperature drops sharply by 20-30 °C. Even stones cannot withstand such sharp changes. Sometimes at noon, in the very heat, you can hear a loud crack. It cracks and shatters into fragments of stones, overheated.

Due to varying degrees of surface destruction in the Sahara, three types of deserts have formed: rocky, sandy and clay. Rocky deserts (hamads) are common on highlands, plateaus and elevated plains formed by solid rocks. Sandy deserts (ergs) occupy mainly low-lying plains and depressions (Fig. 30). They amaze with the endless "sea" of barchans and dunes, which are blown by the wind. Clay deserts (seriri) occur less frequently.

An insignificant amount of precipitation has led to the fact that there are no permanent watercourses in the desert (except for the Nile River), but dry channels - wadis are stored. They fill with water only briefly when it rains. The sun quickly evaporates the water, and after a few hours the river disappears.

Since the vegetation in the desert is not rich, there is little organic matter in the soil. Desert tropical soils have formed here.

They are poor in nutrients and form a very thin layer. Only in clay deserts, more water is retained in the soil and there are mineral salts necessary for plants.

All life in the Sahara is concentrated in oases. They occur where groundwater comes close to the earth's surface (Fig. 31). There are wells or springs, temporary lakes in hollows. Acacias grow in oases, ducks, turtledoves, pigeons, hazel grouses, desert larks, runners, falcons are found. The hospitable mistress of the desert oases is the date palm, which gives people shade and tasty fruits. Cool juice flows from an incision in the trunk. Baskets and shoes are woven from the leaves of the tree.

Explain why the areas of the tropical desert and semi-desert zones are not the same in northern and southern Africa.

Explain why rocks are destroyed in the desert. Remember the name of this process.

Rice. 30. Sandy desert in the Sahara

Rice. 31. Scheme of the formation of an oasis in the desert

However, such landscapes are extremely rare. There is almost no vegetation in the vast expanses of the Sahara. Efemeri, plants with a short period of active existence, have adapted to the harsh climate of the desert. The rain will rustle - and leaves and flowers immediately appear on them. Ephemeris ripen, wither and wither so quickly that their seeds are ripe by the next rain and are just waiting for water to germinate quickly.

Thanks to a long root system, camel thorn receives moisture from groundwater. Its leaves are modified into short needles, which reduces the evaporation of water.

Animals survive in the desert that can quickly run from one oasis to another (antelopes), accumulate water in their bodies (camels) or some types of predators that almost do not drink water, getting it with the blood of their victims (fennec fox) (Fig. 32 ). Reptiles are best adapted to life in the desert: snakes, lizards, turtles. They have dry, scaly skin that evaporates little water. From the sun, these animals hide in the sand or crevices, and feed on insects.

The Namib Desert is located in southern Africa. The climate here is extremely harsh, as evidenced by the name - "That which is bypassed." Rains here are quite rare, so most of the desert is devoid of vegetation. Only rocks, stones, sand and salt. High sand dunes, not anchored by plant roots, move in the direction of the prevailing wind.

Only along the rivers do acacias and tamarix grow. The most amazing plant of the Namib desert is velvichia (Fig. 33). This tree has a short (10-15 cm) and thick (up to 1 m in diameter) trunk, from which two leathery leaves up to 3 m long extend. Velvichia leaves absorb moisture from the fog. The plant lives up to 2 thousand years and never sheds leaves that grow all the time and spread along the ground.

Rice. 32. Fennec fox

Rice. 33. Velvichia

Rice. 34. Kalahari semi-desert

The strictest nature of the ocean coast of the desert. No wonder this area was called the Skeleton Coast. Thirst often killed diamond seekers and passengers on shipwrecks here.

The semi-desert Kalahari is covered with huge sand dunes, colored pink, red and dark red, almost brown, because the soil contains a lot of iron (Fig. 34).

There is more rainfall here than in the Namib Desert, so the Kalahari has a vegetation cover. In some places the desert resembles the steppe. The tops of the dunes grow tough grass that turns green during the rains and fades in the drought. On the slopes of the dunes, low shrubs covered with thorns can also grow. In the Kalahari, there are spurges, aloe and other plants that accumulate moisture in the stems, leaves and trunks. Kalahari is the birthplace of watermelons. Wild watermelons still replace water for people and animals.

The fauna of deserts and semi-deserts in southern Africa is lizards, snakes and turtles. There are lions, cheetahs and jackals. Fleeing from poachers, even elephants sometimes enter the Namib Desert. There are many insects here: various beetles, locusts, scorpions and the like.

The population of the desert zone of Africa is engaged in nomadic animal husbandry, in the oases - agriculture. There are industrial settlements for mining. A trans-Saharan automobile road was laid, caravan routes were preserved between the oases.

Human economic activity leads to the expansion of deserts at the expense of semi-deserts and savannahs.

Zone of evergreen hardwood forests and shrubs. This zone is located in the extreme north and south of Africa. In winter, it is under the influence of cyclones, which bring coolness and moisture. In summer, cyclones displace the dry and hot air of the tropics. It has a typical Mediterranean climate: enough rainfall for the development of plants (about 500 mm) and at the same time not so much to wash the nutrients out of the soil. Therefore, the brown soils that have formed in this zone are quite fertile because they contain a lot of humus.

Plants have small, hard, yellow-skinned leaves, making it easy to withstand heat. Therefore, these forests are called hardwood. Coniferous trees - Lebanese cedar, pine, cypress - dry air in summer also does no harm.

Think about the main branches of the economy characteristic of the desert zone of Africa. Name the areas of their distribution.

In South Africa, subtropical forests and shrubs occupy a small area. Laurel olive, southern beech, ebony, euphorbia, heather, daffodils, tulips, gladioli grow here.

Large areas of the zone of evergreen hardwood forests and shrubs have been mastered by man: citrus fruits, grapes, olives, and the like are grown here.

Briefly about the main thing!

The deserts and semi-deserts of Africa are located in areas of dry and hot tropical climate. The largest desert in the world - the Sahara - occupies most of North Africa. In the southern part of the mainland, the Namib coastal desert and the Kalahari semi-desert formed.

Tropical desert soils are infertile. Vegetation cover is very poor. Of the animals, lizards, snakes, turtles, and insects are common.

Evergreen hardwood forests and shrubs are located in the north and south of Africa, in areas of subtropical climate. Cedar of Lebanon, pine, cypress, olive, southern beech and other evergreen trees and shrubs grow here on fertile brown soils.

1. Name and show on the map the largest deserts and semi-deserts of Africa.

2. Tell us how the plants and animals of tropical deserts are adapted to the harsh conditions of existence.

3. What are oases? Where and why do they form?

4. Compare the natural conditions of the savannas and tropical deserts. How are they similar, what is their significant difference?

5. Why are there different types of deserts in Africa: rocky, sandy, clayey?

6. What natural areas of Africa are best mastered by man? Explain why.

The article contains information about the deserts of the black continent. Gives an idea of ​​the annual rainfall in these sparsely populated areas.

Deserts of Africa

The deserts of Africa are extremely diverse in many ways:

• appearance;
• environmental conditions;
• history of the formation of the organic world;
• the composition of their living organisms.

These unique creations of nature mainly occupy the tropical belts. They occupy the largest area in areas of North Africa, where the dry air of the tropics prevails almost all year round.

The amount of precipitation per year does not exceed 100 mm everywhere.

It happens that the annual rate may fall in a few hours, and then for many years there may be no precipitation at all.

At the southern tip of the mainland, deserts occupy smaller areas.

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In this area, the merciless Namib Desert runs in a narrow coastal strip along the Atlantic Ocean.

Rice. 1. Namib Desert.

In the depths of the mainland lies the Kalahari semi-desert.

In a tropical climate, the temperature at night does not exceed +10 °C, and during the day it reaches +50 °C in the shade, rocks are destroyed forming stones and sand.

The result of further weathering is the emergence of deserts.

A characteristic feature of the climates of all the deserts of Africa is insufficient moisture during the year with excessive heat supply. The meager supply of moisture is accompanied by exorbitant temperatures. In most of the Sahara, the annual rainfall is 50-100 mm. The rainy season here happens in 1-2 months. In the southern part of the Sahara, this happens in the summer, and in the northern it is in the winter. These are usually short showers. Deserts do not have permanent streams. There are only empty channels, which are occasionally filled with water. Only clay soils of deserts can hold water. They enrich scarce vegetation with minerals and salts necessary for life.

Deserts and semi-deserts of Africa

The continent is famous for its deserts and semi-deserts. Among them are such deserts as the Sahara and the Namib.

Rice. 2. Sahara desert.

Semi-deserts are a transition zone between shrouds and deserts. Here, the drought period lasts almost all year round. The norm of annual precipitation does not exceed 300 mm.

Rice. 3. Kalahari semi-desert.

The vegetation cover of semi-deserts looks like a mosaic - dark patches of lifeless soil areas are replaced by thickets of shrubs, grasses, cereals and wormwood.

The Namib is the oldest of the deserts. It is also the driest. Only in some coastal settlements there is life. The rest of the territory is practically uninhabited.

The area of ​​the desert is 100,000 sq. km. It stretches for 1900 km along the Atlantic Ocean from the city of Namibe to the mouth of the Olifants River; then the desert deepens into the interior of the continent. The Namib joins the Kalahari in the south.

The Sahara is the largest desert on earth, covering an area of ​​9,269,594 sq. km. In some of its areas, rain does not fall for years.

In Kebili, an extremely high temperature on the planet was noted - + 58 ° in the shade.

Both the flora and fauna of these places, as a result of evolutionary development, were able to develop mechanisms that allow them to survive in extreme conditions.

What have we learned?

We found out which of the deserts of Africa is considered the largest in terms of area in the world. We learned where on Earth the highest temperature in the history of mankind was recorded. We received information about the most ancient and cruel desert on the planet. We learned how plants and animals adapted to life in these territories.

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Deserts and semi-deserts are a natural zone, which is characterized by an almost complete absence of growth and a poor stomach. the world. this is due to the extremely harsh climatic conditions of the planet where they are located. Deserts can form in almost any climate zone. Their image is associated with low rainfall. That is why deserts are primarily common in the tropics. tropical deserts occupy the territory of most of the tropics. Africa and Australia, west. tropical coasts. belts South. America, as well as the territory of the Arabian Peninsula in Eurasia. their formation is associated with the year-round dominance of the tropical air mass, the influence of which is enhanced by the terrain and cold currents off the coast. a large number of deserts are located in the subtropical and temperate zones of the Earth. This is the territory of Patagonia in South. America, where their formation is due to the isolation of the south. the tip of the mainland from the penetration of moist air by cold currents, as well as in the interior of the North. America and Center. Asia. Here, the image of deserts is associated with a strong continental climate due to the great distance from the coast and mountain systems that prevent the penetration of moisture from the ocean. The image-e of deserts can be associated with extremely low temperatures on the planet, this type of deserts are called arctic and antarctic deserts.

Nature. Desert conditions are extremely harsh. The amount of precipitation does not exceed 250 mm per year, and on large areas - less than 100 mm. The driest desert in the world is the Atacama Desert, where precipitation has not been recorded for 400 years. The largest desert in the world is the Sahara, located in the North. Africa. Her name transl. from Arabic. like "desert". The highest was recorded here. air temperature on the planet + 58 ° C. with the sunset, the temperature in the desert drops sharply, the drops reach tens of degrees during the day, and frosts even occur here on winter nights. Everything is to blame for the constantly clear sky due to the downdrafts of the dry. air from the equator, because of this, clouds are almost not formed here. The vast open spaces of deserts do not at all prevent the movement of air along the surface of the earth, which leads to the emergence of strong winds. Dust storms come unexpectedly, bringing clouds of sand and streams of hot air. In spring and summer, a strong wind rises in the Sahara - samum ("poisonous wind"). It can last only 10-15 minutes, but the hot dusty air is very dangerous for a person, it burns the skin, the sand does not allow you to breathe freely. Also in con. winter-beginning spring in Sev. Africa from the desert almost every year begins to blow a seasonal wind-khamsin ("fifty"), since on average it blows for 50 days. Deserts of temperate latitudes are also characterized by strong temperature fluctuations throughout the year. Hot summers give way to cold, harsh winters. Fluctuations in air temperature during the year can be about 100°C. Winter frosts in the deserts of the temperate zone of Eurasia drop to -50 ° C, the climate is sharply continental. The flora of deserts in particularly difficult climatic conditions may be completely absent, where moisture remains sufficient, some plants grow, but the flora is not diverse. Desert plants usually have very long roots - more than 10 meters - in order to extract moisture from groundwater. In the deserts Asia grows a small shrub-saxaul. In America, a significant part of the flora is cacti, in Africa, spurges. Stomach. the desert world is poor. Reptiles-snakes, monitor lizards predominate here, scorpions live, there are few mammals. One of the few who was able to adapt to these difficult conditions was a camel, which was not accidentally called the "ship of the desert." By storing water in the form of fat in their humps, camels are able to travel long distances. For the indigenous nomadic peoples of the deserts, camels are the basis of their economy. Desert soils are not rich in humus, however, they often contain a lot of minerals and are suitable for agriculture. The main problem for plants is the lack of water.

Africa is known for its deserts, among which the tropical deserts - the Sahara and the Namib - stand out.

The Namib is the oldest desert located in southwestern Africa and is the driest - only in some coastal cities there is life, the rest of the territory is practically uninhabited.

Namib, with an area of ​​100,000 sq. km, stretches for 1900 km along the Atlantic Ocean from the city of Namibe to the mouth of the Olifants River (Cape Province of South Africa); from the ocean, the desert goes into the interior of the continent, reaching the foot of the intracontinental plateau; it joins the Kalahari in the south.

Despite the harsh conditions, in the desert you can find plants that surprise and delight. Among these are velvichia (its life can last up to 1000 years, and during all this time it grows only two huge leaves, the roots of this plant are 3 meters), a quiver tree (up to 7 meters high with sharp ends of branches), nara (a source of moisture and necessary substances for all the inhabitants of the desert).

Animals usually live near water sources and in the hollows of the inner Namib - antelopes, rhinos, elephants, jackals, hyenas, zebras, but the dunes of the outer Namib are home to spiders, beetles, geckos and a large number of reptiles.

Both plants and animals in the process of evolution have developed special abilities that allow them to survive in extreme conditions, for example, the Nabian gecko can move on sand heated to a temperature of 60 degrees, and plants have adapted to collect the necessary moisture from morning fogs.

The Sahara is the largest desert, covering an area of ​​9,269,594 sq. km - from northern Sudan and Mali to the Mediterranean Sea, in the east it meets the Nile and the Red Sea, and in the west it reaches the Atlantic Ocean. Thus, the Sahara occupies the entire northern part of Africa.

The Sahara is an arid desert, in some places it does not rain for years, and in Kebili the highest temperature on the whole Earth was recorded - + 58 ° in the shade.

Semi-deserts are a transitional zone between shrouds and deserts, here the dry period lasts almost the entire year, and annual precipitation does not exceed 300 mm.

The vegetation cover of semi-deserts looks like a mosaic - dark areas of empty land alternate with thickets of shrubs, grasses, cereals and sagebrush.

Among the animals, most of all are hares, rodents and reptiles, there are also many birds. And from ungulates you can meet antelopes, mouflons, kulans. Among predators, jackals, hyenas and fennec foxes stand out.