Deserts are dry spaces with high temperature and low humidity. Researchers consider such places on earth as territories of geographical paradoxes. Geographers and biologists argue that the deserts themselves - this is the main environmental problem of the Earth, or rather desertification. So they call the process of loss of permanent vegetation by the natural complex , the impossibility of natural recovery without human intervention. 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 activity.
Country of Geographical Paradoxes
Most of the arid lands of the globe are in the tropical zone, they receive from 0 to 250 mm of rain per year. Evaporation is usually tens of times greater than the amount of precipitation. Most often, the drops do not reach the surface of the earth, they evaporate in the air. In the stony Gobi desert and in Central Asia in winter, the temperature drops below 0 ° C. Significant amplitude is a characteristic feature of the desert climate. For a day it can be 25–30 ° , in the Sahara it reaches 40–45 ° . Other geographic paradoxes of the Earth's deserts:
- precipitation that does not wet the soil;
- dust storms and whirlwinds without rain;
- closed lake with a high salt content;
- sources that are lost in the sand, not giving rise to streams;
- rivers without estuaries, waterless channels and dry accumulations in deltas;
- wandering lakes with constantly changing coastlines;
- trees, shrubs and grasses without leaves, but with thorns.
The largest deserts of the world
Vast territories deprived of vegetation are assigned to the drainless regions of the planet. Here, trees, shrubs and grasses without leaves predominate or vegetation is completely absent, which reflects the term "desert" itself. 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 ° C. w. The largest deserts of 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, Kyzyl Kum in Eurasia.
Zones such as semi-desert and desert, on the world map occupy as a whole from 17 to 25% of the entire land of the globe, and in Africa and Australia - 40% of the area.
Sea Drought
An unusual location is characteristic of Atakama 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 territory is washed by the Pacific Ocean with its cold Peruvian current.
Atacama is the most lifeless desert, with a record low rainfall of 0 mm. Light rains occur once every few years, but in winter fogs often come from the coast of the ocean. About 1 million people live in this arid region. The population is engaged in animal husbandry: the entire high mountain desert is surrounded by pastures and meadows. The photo in the article gives an idea of the harsh landscapes of Atacama.
Desert species (environmental classification)
- Arid - zonal type, characteristic of the tropical and subtropical zones. The climate in this area is dry and hot.
- Anthropogenic - arises as a result of direct or indirect human impact on nature. There is a theory that explains that this is a desert whose environmental problems are associated with its expansion. And all this is caused by the activities of the population.
- Inhabited - the territory in which there are permanent residents. There are transit rivers, oases, which are formed in places where groundwater emerges.
- Industrial - territories with extremely poor vegetation cover and wildlife, which is due to production activities and disturbance of the natural environment.
- Arctic - snow and ice in high latitudes.
The environmental problems of deserts and semi-deserts in the north and in the tropics are very 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
About 150 years ago, scientists noted an increase in the Sahara area. Archaeological excavations and paleontological studies have shown that there was not always only desert in this territory. Environmental problems then consisted in the so-called "drying up" of the Sahara. So, in the XI century, agriculture in North Africa could be engaged up to 21 ° latitude. For seven centuries, the northern border of agriculture moved south to the 17th parallel, shifted even further by the 21st century. Why is desertification happening? Some researchers explained this process in Africa as “drying out” of the climate, while others cited the movement of sand falling asleep oases. The sensation was the work of Stebbing "Desert, created by man", which saw the light in 1938. The author cited data on the advancement of the Sahara to the south and explained the phenomenon by improper farming, in particular trampling of cereal vegetation by cattle, by irrational farming systems.
Anthropogenic cause of desertification
As a result of studies of the movement of sand in the Sahara, scientists found that during the First World War, the area of agricultural land and the number of cattle decreased. The woody-shrubby vegetation then reappeared, that is, the desert receded! Environmental problems are currently compounded by the almost complete absence of such cases when territories are withdrawn from agricultural circulation for their natural restoration. Reclamation measures and reclamation are carried out on a small area.
Desertification is most often caused by human activities, the reason for “drying out” is not climatic, but anthropogenic, associated with the excessive exploitation of pastures, excessive development of road construction, and irrational farming. Desertification under the influence of natural factors can occur at the border of existing drylands, but less often than under the influence of human activity. The main causes of anthropogenic desertification:
- opencast mining (in quarries);
- grazing without restoring pasture productivity;
- cutting down of forest stands fixing soil;
- irregular irrigation (irrigation) systems;
- increased water and wind erosion:
- drainage of water bodies, as is the case with the disappearance of the Aral Sea in Central Asia.
Ecological problems of deserts and semi-deserts (list)
- Water scarcity is a major factor that increases the vulnerability of desert landscapes. Strong evaporation and dust storms lead to erosion and further degradation of infertile soils.
- Salinization - an increase in the content of readily soluble salts, the formation of solonetzes and salt marshes, which are practically unsuitable for plants.
- Dust and sand storms - the movement of air that raises a significant amount of small clastic material from the surface of the earth. In salt marshes, the wind carries salt. If sands and clays are enriched with iron compounds, yellow-brown and red dust storms arise. They can span hundreds or thousands of square kilometers.
- “Desert Devils” are dusty sand whirlwinds that lift a huge amount of small clastic material into the air to a height of several tens of meters. Sand pillars have an extension at the top. Differ from tornadoes in the absence of cumulus clouds carrying rain.
- Dusty bowls - territories where catastrophic erosion occurs as a result of drought and uncontrolled plowing of the earth.
- Clogging, accumulation of waste - objects that are foreign to the natural environment that do not decompose for a long time or emit toxic substances.
- Exploitation and pollution by humans in the extraction of minerals, the development of livestock, transport and tourism.
- Reduction in the area occupied by desert plants, depletion of fauna. Loss of biodiversity.
Desert life. Plants and animals
Severe conditions, limited water resources and barren desert landscapes change after the rains have passed. Many succulents, such as cacti and Crassulaceae, are capable of absorbing and storing bound water in stems and leaves. Other xeromorphic plants, such as saxaul and wormwood, develop long roots reaching the aquifer. Animals adapted to get the moisture they need from food. Many representatives of the fauna switched to a nightlife to avoid overheating.
The world around , the desert in particular, is negatively affected by the activities of the population. The destruction of the natural environment occurs, as a result, man himself cannot use the gifts of nature. When animals and plants lose their habitat, this also negatively affects the life of the population.