Deserts are dry spaces with high temperatures and low humidity. Researchers consider such places on earth to be territories of geographical paradoxes. Geographers and biologists argue that the deserts themselves are the main environmental problem of the Earth, or rather, desertification. This is the name of the process of loss of permanent vegetation by the natural complex, the impossibility of natural restoration without human participation. Find out what territory the desert occupies on the map. We will establish the environmental problems of this natural zone in direct connection with human activities.
Land of geographical paradoxes
Most of the arid territories of the globe are located in the tropical zone, they receive from 0 to 250 mm of rain per year. Evaporation is usually ten times higher than the amount of precipitation. Most often, drops do not reach the surface of the earth, they evaporate in the air. In the rocky Gobi Desert and in Central Asia, temperatures drop below 0°C in winter. A significant amplitude is a characteristic feature of the desert climate. Per dayit can be 25–30 °С, in the Sahara it reaches 40–45 °С. Other geographic paradoxes of the Earth's deserts:
- rainfall that does not wet the soil;
- dust storms and whirlwinds without rain;
- endorheic lakes with high s alt content;
- springs that are lost in the sands, not giving rise to streams;
- rivers without mouths, waterless channels and dry accumulations in deltas;
- wandering lakes with ever-changing coastlines;
- trees, shrubs and grasses without leaves, but with thorns.
The world's largest deserts
Vast territories devoid of vegetation are referred to the drainless regions of the planet. It is dominated by trees, shrubs and grasses without leaves or completely absent vegetation, which reflects the term "desert". The photos posted in the article give an idea of the harsh conditions of dry territories. The map shows that the deserts are located in the Northern and Southern hemispheres in a hot climate. Only in Central Asia is this natural zone located in the temperate zone, reaching 50°N. sh. The largest deserts in the world:
- Sahara, Libyan, Kalahari and Namib in Africa;
- Monte, Patagonian and Atacama in South America;
- Great Sandy and Victoria in Australia;
- Arabian, Gobi, Syrian, Rub al-Khali, Karakum, Kyzylkum in Eurasia.
Zones such as semi-desert and desert on the world map generally occupy from 17 to 25% of the entire land area of the globe, and in Africa and Australia - 40% of the area.
Drought on the coast
Unusual location is typical for Atacama and Namib. These lifeless arid landscapes are on the ocean! The Atacama Desert is located in the west of South America, surrounded by the rocky peaks of the Andes mountain system, reaching a height of more than 6500 m. In the west, the Pacific Ocean with its cold Peruvian current.
Atacama - the most lifeless desert, there is a record low rainfall - 0 mm. Light rains occur once every few years, but in winter fogs often roll in from the ocean coast. About 1 million people live in this arid region. The population is engaged in animal husbandry: the entire alpine desert is surrounded by pastures and meadows. The photo in the article gives an idea of the harsh landscapes of the Atacama.
Desert types (ecological classification)
- Arid - zonal type, characteristic of the tropical and subtropical zones. The climate in this area is dry and hot.
- Anthropogenic - occurs as a result of direct or indirect human impact on nature. There is a theory explaining that this is a desert, the environmental problems of which are associated with its expansion. And all this is caused by the activities of the population.
- Inhabited - a territory in which there are permanent residents. There are transit rivers, oases, which are formed in places where groundwater comes out.
- Industrial - areas with extremely poor vegetation and wildlife, whichcaused by production activities and environmental disturbance.
- Arctic - snow and ice expanses in high latitudes.
The environmental problems of deserts and semi-deserts in the north and in the tropics are largely similar: for example, there is insufficient rainfall, which is a limiting factor for plant life. But the icy expanses of the Arctic are characterized by extremely low temperatures.
Desertification - loss of continuous vegetation cover
Approximately 150 years ago, scientists noted an increase in the area of the Sahara. Archaeological excavations and paleontological studies have shown that not always there was only a desert in this territory. Environmental problems then consisted in the so-called "drying" of the Sahara. So, in the XI century, agriculture in North Africa could be practiced up to 21 ° latitude. For seven centuries, the northern border of agriculture has moved south to the 17th parallel, and by the 21st century it has shifted even further. Why is desertification happening? Some researchers explained this process in Africa by the "drying" of the climate, others cited data on the movement of sands that covered the oases. The sensation was the work of Stebbing "Desert created by man", which was released in 1938. The author cited data on the advancement of the Sahara to the south and explained the phenomenon by improper agricultural practices, in particular, trampling of grass vegetation by livestock, and irrational farming systems.
Anthropogenic cause of desertification
As a result of researchthe movement of sands in the Sahara, scientists have found that during the First World War, the area of agricultural land and the number of cattle decreased. Tree and shrub vegetation then reappeared, that is, the desert receded! Environmental problems are currently exacerbated by the almost complete absence of such cases, when territories are withdrawn from agricultural circulation for their natural restoration. Ameliorative measures and reclamation are being carried out on a small area.
Desertification is most often caused by human activity, the cause of "drying out" is not climatic, but anthropogenic, associated with excessive exploitation of pastures, excessive development of road construction, and irrational agriculture. Desertification under the influence of natural factors can occur on the border of already existing arid territories, but less often than under the influence of human activity. Main causes of anthropogenic desertification:
- open pit mining (quarries);
- grazing without restoring pasture productivity;
- cutting down forest plantations that fix the soil;
- wrong irrigation systems (irrigation);
- increased water and wind erosion:
- drying of water bodies, as in the case of the disappearance of the Aral Sea in Central Asia.
Ecological problems of deserts and semi-deserts (list)
- Lack of water is the main factor that increases the vulnerability of desert landscapes. Strong evaporation and dust storms lead to erosion and further degradation of marginal soils.
- Salinization - an increase in the content of soluble s alts, the formation of solonetzes and solonchaks, practically unsuitable for plants.
- Dust and sand storms are movements of air that lift a significant amount of small detrital material from the surface of the earth. On s alt marshes, the wind carries s alt. If sands and clays are enriched with iron compounds, then yellow-brown and red dust storms arise. They can cover hundreds or thousands of square kilometers.
- "Desert Devils" - dusty sand whirlwinds, raising into the air a huge amount of small detrital material to a height of several tens of meters. Sand pillars have an extension at the top. They differ from tornadoes in the absence of cumulus clouds that carry rain.
- Dust bowls are areas where catastrophic erosion occurs as a result of drought and uncontrolled plowing.
- Clogging, accumulation of waste - objects foreign to the natural environment that do not decompose for a long time or emit toxic substances.
- Human exploitation and pollution from mining, livestock development, transport and tourism.
- Reduction of the area occupied by desert plants, depletion of the fauna. Loss of biodiversity.
Desert life. Plants and animals
Harsh conditions, limited water resources and barren desert landscapes change after the rains. many succulents,such as cacti and crassula, are able to absorb and store bound water in stems and leaves. Other xeromorphic plants such as saxaul and mugwort develop long roots that reach into the aquifer. Animals have adapted to get the moisture they need from food. Many representatives of the fauna have switched to a nocturnal lifestyle to avoid overheating.
The environment, the desert in particular, is negatively affected by the activities of the population. There is a destruction of the natural environment, as a result, the person himself cannot use the gifts of nature. When animals and plants are deprived of their usual habitat, this also negatively affects the life of the population.
