Ecological problems of desert and semi-desert. The advance of deserts is a global environmental problem

What is the very first association that arises in us when we say “desert” or see its image? "Lifeless." And, although this is not a completely fair definition, because it has “its own” flora and fauna, nevertheless, for humans this is exactly the case.

It does not live in the desert and can survive there only under certain conditions. According to some data, such “lifeless” spaces on Earth increased by 500 million hectares in the 20th century alone. Desertification is considered a global environmental problem; this process cannot be characterized in any other way.

This term was introduced by the French scientist Oberville in the mid-40s of the 20th century. It was understood that as a result of certain processes within the biosystem, including primarily under the influence of humans, the earth loses its fertile soil cover.

Wind erosion and climate change complete the process, and once fertile lands turn into sandy, rocky, clayey or saline deserts. And it will take at least 150 years to revive 1 cm of fertile layer.

Desert is an area characterized by flat surface with specific species of flora and fauna. The main factors underlying its occurrence, existence and development are temperature and water. More precisely, the abnormally high or low temperatures and minimum quantity water resources and precipitation.

Based on this, it is easy to determine that the greatest probability of the formation of such territories is in the subtropical and tropical zones of both hemispheres, the temperate zone of the Northern Hemisphere and the so-called “Arctic” deserts at the Earth’s poles.

They occupy more than 16.5 million km 2 or about 11% of the Earth's land, and with the territory of Antarctica - 20%. The most famous is the sandy Sahara Desert. First of all, one should distinguish by the nature of their occurrence. That is, formed due to natural causes and resulting from human activity.

It is difficult to reliably determine the cause of the emergence of deserts located in tropical and subtropical regions or the temperate zone of the Earth’s Northern Hemisphere.

Their common climatic characteristics these are the same as the Arctic ones, with only one difference - the temperature peaks have a positive value. IN summer period during the day up to +50ºС, and in the Sahara everything is +58ºС. The average annual precipitation does not exceed 200 mm.

Deserts are often surrounded by mountain systems that prevent the movement of cyclones and precipitation. Because the air here has low humidity and does not protect the soil from direct sun rays. The land dries out and succumbs to water and wind erosion.

River waters carry silt, sand, pebbles and gravel. Drying out during the hot period, they leave it all on the ground. Then the wind carries the sediment throughout its territory and beyond. And the winds blow there constantly. Their speed can reach 20 m/sec, and if more, they turn into dust or sandstorms.

There are sandy, loess, loamy, clayey, pebble, sand-pebble, gravelly, rocky and saline deserts, as well as coastal, Central Asian and Mediterranean deserts.

It is safe to say about the Arctic deserts that they were formed without human influence. They are located near the Arctic and Antarctic belts of the Earth. In the area of ​​snow and on the border of the glacier zone.

They occupy most of Greenland, the Canadian Arctic Archipelago, the North Islands Arctic Ocean, the northern coast of Eurasia and on the islands near Antarctica.

Air temperatures in winter are up to -60ºС, with an average of about -30ºС. In summer about +3ºС. Level atmospheric precipitation does not exceed 400 mm per year. The polar night lasts about six months and is accompanied by hurricane winds. In the polar summer, even though the sun shines around the clock, the soil does not have time to warm up and thaw. Vegetation is sparse. Mainly mosses and lichens.

The animal world matches it - unpretentious, hardy to severe frosts and large temperature differences. Only birds can boast of significant diversity, but they are not permanent residents arctic deserts.

People are increasingly invading the Arctic desert zones and therefore environmental problems in this already difficult for the survival of any, even adapted species of flora and fauna, are becoming impossible. Fishing, and in fact, extermination of such animal species as seal, walrus, polar bear and arctic fox, led to their almost complete destruction.

Geological exploration revealed a large number of minerals in the Arctic deserts, the extraction of which, as usual, has resulted in environmental problems. First of all, this is the production of hydrocarbons, which is accompanied by accidents with spills of oil and other pollutants.

Their meager flora and fauna arouse virtually no commercial interest among humans. But it appeared in these regions in connection with the discovery of significant oil and gas reserves. And the environmental problems of the desert, in addition to natural expansion, which is rather a problem of the surrounding areas, are mainly associated with this.

If formulated correctly, the environmental problems of deserts and semi-deserts lie in the fact that semi-deserts are gradually turning into deserts.

And this happens under the direct influence of man. Semi-desert or a name that more accurately reflects its properties, “desert steppe” is an intermediate link between steppe in temperate latitudes and savannah and desert - in the tropical. It is characterized by landscape, soils, natural world and the climate of both.

The warm period is long, with average temperature up to +25ºС, and the amount of precipitation is insufficient, only about 300 mm per year. As a result, high evaporation and drying up of rivers.

In addition, the soils are rich in salts, which crystallize during dry periods. Most plants, especially cultivated ones, are unable to tolerate such conditions and die. Livestock farming depletes pastures. The soil is eroded and ceases to bear fruit.

Land degradation, global problem

Desertification, or land degradation of dry areas and regions of the Earth, occurs against the background economic activity human and natural natural processes. Land degradation is defined as the decline or complete loss of land productivity.

About a third of the entire surface of the Earth is exposed to it. About 20 million hectares of agricultural land are no longer used for this reason.


Considering that more than 41% of dry regions in the world, it is overestimated negative consequences this phenomenon is impossible. The global nature of the problem is reflected in UN decisions and conventions.

According to the Organization, its main reason is the inefficient use of land resources. And the most negative thing about these assessments is that desertification cannot be reversed; attempts can be made to stop it. The “leaders” of desertification are the USA, India, China and Russia.

Watch the video: Desertification of the earth is an environmental problem.

"Tropical Deserts" - Deserts of Africa. Tropical deserts. Rocky and sandy deserts. Velvichia is the “octopus” of the desert. Sahara Kalahari Namib. Oasis. Cause-and-effect relationships. "Ship" of the desert. Unique plant Namib Desert. Animals have adapted to desert climate conditions. Tuareg nomads. The leaves are used to make fences, hedges, and weave sandals and baskets.

“Steppes and Deserts” - Sage. Antelopes and goitered gazelles travel long distances in search of a watering hole. Deserts are the driest areas of the Earth. Vegetable world steppes. Where on Earth are steppes and deserts located? The grasses form a closed or almost closed cover. Jeyran. Steppe eagle. Animal world deserts. Saiga. Desert.

“Desert Zone” - Sandy. Bandaging mole rats. Tumbleweed. Sand lizard - round-headed constrictor. Winter in the steppe is warmer than in the forest zone. Juzgun cactus. Occupations of people: Ecology. Location: Location. Jerboa long-eared hedgehog. Camel thorn. Desert. Desert zone. Find and correct errors: List the natural zones from north to south:

"Arctic Deserts" - Fur seal. They sleep under the ice of the sea, Bears rub against the axis - The Earth turns. Polar bear. "... - The Kingdom of Ice and Snow." Arctic desert zone (4th class). Plants of the Arctic. What do you need to take with you for your trip? In the sea, on the rocks, on the stones. . E – bear I – ice. Where do polar bears live? (1 class).

“Life in the Desert” - Sahara desert. Giraffes. Previously havens for wild animals from elephant to giraffe. The Kalahari supports a variety of fauna and flora. Nearly half of Australia is a desert. People often travel by camel. Antelopes. The Gobi Desert is the coldest desert in the world. Covering much of Botswana and parts of Namibia and South Africa.

"Deserts" - The world– 2nd grade. 2. The fastest-footed animal: 6. Ship of the desert: 5. Can survive without moisture: 3. Large ears help escape the heat: A) fleet-footed foot-and-mouth disease; b) sand boa; c) midday gerbil; d) lizard – round-headed. 1. The desert crocodile was nicknamed: A) the long-eared hedgehog; b) foot and mouth disease; c) corsac.

According to statistics, in our country, in the vast territories occupied by deserts and semi-deserts, less than one million people live. One person per 4-5 square kilometers of desert land, this is the approximate population density in these areas. You can walk for hours, days, weeks and not meet a single living soul. However, in modern times Deserts attract people with their natural resources and riches that have been hidden for many thousands of years. Of course, such attention cannot do without consequences for the environment.

It is the discovery of natural raw materials that can attract Special attention, after which, as is known from many examples and bitter experience, only problems remain, both for humanity and for nature. They are connected, first of all, with the development of new territories, scientific research, and the impact on the ancient balance of natural systems. Ecology is the last thing people remember, if they remember it at all. The development of technological progress and the unlimited supply of natural resources have led to the fact that man has reached the deserts. Scientific research has shown that in many semi-deserts and deserts there are considerable reserves of natural resources, such as oil, gas, precious metals. The need for them is constantly increasing. Therefore, equipped with heavy equipment and industrial tools, we are going to destroy the ecology of previously miraculously untouched territories. Construction of roads, laying highways, extraction and transportation of oil and other natural raw materials, all this creates environmental problems in deserts and semi-deserts. Oil is especially dangerous for the environment. Contamination with black gold occurs both at the mining stage and at the stage of transportation, processing and storage. Release into the environment also occurs naturally, but this is the exception rather than the rule. Natural penetration occurs much less frequently and in quantities that are not destructive to nature and all living things. Pollution is the appearance in an ecosystem of components that are not characteristic of it, in unusual quantities. There are many known accidents on oil pipelines, in storage facilities and during transportation, the consequences of which were damage to the ecology of deserts.

The deserts themselves, however, are a serious environmental problem, or rather desertification. Desertification is an extreme degree of erosion. This process can occur naturally, but in nature it happens extremely rarely (except in areas on the border of existing deserts) and rather slowly. The spread of a process under the influence of anthropogenic factors is a completely different matter.

Anthropogenic desertification occurs for several reasons: deforestation and shrubs, plowing of lands unsuitable for agriculture, haymaking and grazing for long periods of time, salinization and improper irrigation methods, long-term construction and mining, drying up of entire seas, and as a result the formation of desert land. areas, an example is the drying up of the Aral Sea. In the second half of the 20th century, according to various sources, about 500 million hectares of land were subject to desertification. In modern times, desertification can be classified as a global environmental problem. The world leaders in the rate of erosion spread are the USA, India, and China. Russia, unfortunately, is also among them. Approximately 30% of the soils in these countries are subject to erosion, and only sufficient periodicity of climatic moisture does not allow the final stage of desertification to occur. In environmental and economic terms, the consequences of desertification are quite noticeable and negative. Firstly, it is the destruction of the environment natural environment, its formed ecosystem, which already makes it impossible to use the usual natural gifts. Secondly, this is damage to agriculture and a decrease in productivity. Thirdly, many species of animals and plants are deprived of their usual habitat, which in turn affects people. Ultimately, problems are observed both in semi-deserts and in the deserts themselves. An extremely small amount of time, resources, and material components are devoted to their solution. Perhaps in the future everything will change and more attention will be paid to combating desertification and solving environmental problems. Most likely, this will happen when the area of ​​land suitable for agricultural needs becomes insufficient to feed us. In the meantime, we are only seeing an increase yellow spots on the planet map.

Deserts are dry areas with high temperature indicators and low humidity. Researchers consider such places on earth to be territories of geographical paradoxes. Geographers and biologists argue that deserts themselves are the main environmental problem of the Earth, or rather desertification. This is the name given to the process of loss of permanent vegetation, the impossibility of natural restoration without human intervention. Let's find out what territory the desert occupies on the map. Ecological problems we will establish this natural zone in direct connection with human activities.

Country of geographical paradoxes

Most dry areas globe is in 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 and evaporate while still in the air. In the Gobi and in the territory Central Asia in winter the temperature drops below 0 °C. Significant amplitude - characteristic desert climate. During the day it can be 25-30 °C, in the Sahara it reaches 40-45 °C. Other geographical paradoxes of the Earth's deserts:

• precipitation that does not wet the soil;
• dust storms and whirlwinds without rain;
• endorheic lakes with high salt 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 constantly changing shorelines;
• trees, bushes and grasses without leaves, but with thorns.

The largest deserts in the world

Vast areas devoid of vegetation are classified as drainage regions of the planet. It is dominated by trees, shrubs and grasses without leaves or completely absent vegetation, which is reflected in the very term “desert”. The photos posted in the article give an idea of harsh conditions dry areas. The map shows that the deserts are located in the Northern and Southern Hemispheres in hot climates. Only in Central Asia is this natural area is located in the temperate zone, reaches 50° N. w. The most large deserts 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 occupy in general from 17 to 25% of the total land area of ​​the globe, and in Africa and Australia - 40% of the area.

Drought on the sea coast

The unusual location is typical for the Atacama and Namib. These lifeless, arid landscapes are located on the ocean! The Atacama Desert is located in the west South America surrounded by rocky peaks mountain system Andes, reaching a height of more than 6500 m. In the west, the territory is washed by Pacific Ocean with his cold

The 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 move in from the ocean coast. This arid region is home to about 1 million people. The population is engaged in livestock farming: the entire high-mountain desert is surrounded by pastures and meadows. The photo in the article gives an idea of ​​the harsh landscapes of the Atacama.

Types of deserts (ecological classification)

1. Arid - zonal type, characteristic of tropical and subtropical zones. The climate in this area is dry and hot.
2. Anthropogenic - occurs as a result of direct or indirect human impact on nature. There is a theory that explains that it is a desert whose environmental problems are associated with its expansion. And all this is caused by the activities of the population.
3. Populated - a territory in which there are permanent residents. There are transit rivers and oases that form where groundwater emerges.
4. Industrial - territories with extremely poor plant cover and fauna, which is due to production activities and disruption of the natural environment.
5. Arctic - snow and ice expanses in high latitudes.

The environmental problems of deserts and semi-deserts in the north and in the tropics are in many ways similar: for example, there is insufficient rainfall, which is bad for plant life. But the icy expanses of the Arctic are characterized by extremely low temperatures.

Desertification - loss of continuous vegetation cover

About 150 years ago, scientists noted an increase in the area of ​​the Sahara. Archaeological excavations and paleontological studies have shown that this territory was not always only desert. Environmental problems then consisted of the so-called “drying” of the Sahara. Thus, in the 11th century, agriculture in the territory North Africa it was possible to practice up to 21° latitude. Over the course of seven centuries, the northern border of agriculture moved south to the 17th parallel, to XXI century moved even further. Why does desertification occur? Some researchers explained this process in Africa by the “drying out” of the climate, others provided data on the movement of sands covering oases. Stebbing’s work “The Man-Made Desert,” published in 1938, became a sensation. The author cited data on the advancement of the Sahara to the south and explained the phenomenon by incorrect Agriculture, in particular, trampling of cereal vegetation by livestock and irrational farming systems.

Anthropogenic cause of desertification

As a result of studies of the movement of sands in the Sahara, scientists found that during the First World War, the area of ​​agricultural land and livestock cattle decreased. Tree and shrub vegetation then reappeared, that is, the desert retreated! Environmental problems are currently aggravated by the almost complete absence of such cases when territories are withdrawn from agricultural use for their natural restoration. Land reclamation and reclamation measures 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 agricultural practices. 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. The main causes of anthropogenic desertification:

• mining open method(in quarries);
• without restoration of pasture productivity;
• felling forest plantations, fixing soils;
• improper irrigation systems;
• increased water and wind erosion:
• drying up of water bodies, as in the case of the disappearance of the Aral Sea in Central Asia.

Environmental problems of deserts and semi-deserts (list)

1. Lack of water is the main factor that increases the vulnerability of desert landscapes. Heavy evaporation and dust storms lead to erosion and further degradation of marginal soils.
2. Salinization is an increase in the content of easily soluble salts, the formation of solonetzes and solonchaks, which are practically unsuitable for plants.
3. Dust and sand storms are movements of air that lift a significant amount of small debris from the surface of the earth. On salt marshes, the wind carries salts. If sands and clays are enriched with iron compounds, then yellow-brown and red dust storms occur. They can cover hundreds or thousands of square kilometers.
4. “Devils of the Desert” are dusty sand whirlwinds that lift huge amounts of small debris into the air 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 carrying rain.
5. Dust bowls are areas where catastrophic erosion occurs as a result of drought and uncontrolled plowing of the land.
6. Clogging, accumulation of waste - objects foreign to the natural environment that long time do not decompose or release toxic substances.
7. Human exploitation and pollution from mining, livestock development, transport and tourism.
8. Reduction of the area occupied by desert plants, impoverishment of the fauna. Loss of biodiversity.

Desert life. Plants and animals

The harsh conditions, limited water resources and barren desert landscapes change after the rains fall. Many succulents, such as cacti and crassulas, are able to absorb and store bound water in their stems and leaves. Other xeromorphic plants, such as saxaul and wormwood, develop long roots that reach the aquifer. Animals have adapted to obtain the moisture they need from food. Many representatives of the fauna switched to night look life to avoid overheating.

The environment in particular experiences bad influence activities of the population. The destruction of the natural environment occurs, as a result of which man 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.

2. (p. 57) Using the textbook, write the digital data into the text. Use this data when talking about the nature of deserts.

In the desert in summer, the surface of the earth heats up to 700, and the air temperature rises above 400. The roots of camel thorn penetrate to a depth of almost 20 meters and extract water from there. Jerboas can jump up to three meters, which is 20 times the length of the animal’s body. Saigas can run at speeds of up to 80 kilometers per hour.

3. (p. 57) Our erudite Parrot is in a hurry to talk about the desert. Is everything true in his story? Find and correct errors in the text (cross it out and write correctly).

Valuable plants of the desert are corsac (correctly: brassica) and juzgun. Their roots anchor sand well. In the desert there is a small fox - the saiga (corsac fox). Of the larger animals are remarkable eared hedgehogs(saiga). They live in herds, wandering in search of food and water.

4. (p. 58) Seryozha and Nadya’s dad, as in the last lesson, prepared an assignment. Find out desert animals from fragments. Write the names of the animals. Ask the student sitting next to you to test yourself.

5. (p. 58) Draw a diagram of the food chain characteristic of the desert. Compare it with the diagram proposed by your desk neighbor. Using these diagrams, talk about the ecological connections in the desert zone.

Plant seeds – jerboa – corsac.

6. (p. 58) Think about what environmental problems of semi-deserts and deserts are expressed by these signs. Formulate and write down.

1) Soil salinization.

2) Formation of shifting sands.

3) Poaching.

7. (p. 59) Here you can draw a desert according to the instructions in the textbook (p. 125).

8. (p. 60) And here you can write down a story about your imaginary expedition into the desert.

We managed to travel into the desert. This is an amazing place. At first glance, it is absolutely lifeless. There are no seas, rivers, or lakes in the desert, so it rarely rains here. Sometimes there are real downpours in deserts, but due to the heat the water quickly evaporates. But if you look closely, the desert is full of life.

Desert plants have very long roots. This is due to the fact that the water here is very deep and the plants need to get to it. Desert animals have features unique to them. Thus, they are characterized by a “desert” color - yellow, light brown and gray tones; it makes the animals invisible against the background of sand. To hide from enemies and hide from the heat, a number of animals have highly developed adaptations for digging in the sand (for example, rodents have sharp claws on their front paws). They dig holes or are able to quickly burrow into loose sand (lizards, some insects). Many desert animals (lizards, snakes, ungulates) are able to move very quickly.

The camel – the “caravan of the desert” – makes a special impression. A camel can go without water for a long time, losing up to 40 body weight. Having reached the water, a camel can immediately drink up to 57 liters to compensate for the loss of fluid.