Desert survival basics. Desert: environmental issues, desert life What actions of people open the way for the desert

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. This is the name of the process of loss of permanent vegetation, 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, evaporate in the air. In the Gobi and on the territory of Central Asia, in winter the temperature drops below 0 ° С. Significant amplitude is a characteristic feature of the desert climate. For a day it can be 25-30 ° С, in the Sahara it reaches 40-45 ° С. Other geographic paradoxes of the Earth's deserts:

precipitation that does not wet the soil;
dust storms and whirlwinds without rain;
drainless lakes 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 ever-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 \u200b\u200bthe harsh conditions of dry areas. The map shows that 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, Kyzylkum in Eurasia.

Zones such as semi-desert and desert, on the world map, occupy a total of 17 to 25% of all the 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! 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 is washed by its cold

Atacama is the most lifeless desert, with a record low rainfall of 0 mm. Light rains occur once every several 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 \u200b\u200bthe 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 - a 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 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, and by the 21st century it shifted even further. 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 \u200b\u200bagricultural 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 restoration are carried out on a small area.

Desertification is most often caused by human activities, the reason for the “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);
without restoring pasture productivity;
cutting down of forest stands that fix the soil;
irregular irrigation (irrigation) systems;
increased water and wind erosion:
drainage 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)

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 solonchaks, which are practically unsuitable for plants.
Dust and sand storms are the movements 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 mining, 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 pass. 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 environment 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.

In the Arctic and Antarctic
In the tundra and forest tundra
In the woods
In the steppe
In desert
In the mountains
On rivers and lakes
Underground
On the seas and oceans
Under water
Underwater orientation
In settlements

In the steppe

Plain * relief, bright contrasting color of vegetation, monotony of the landscape complicate orientation in the steppe. The main and most reliable landmarks in the steppes are the stars, the moon and the sun. Interesting compass plants can also serve as a reference point: in North America, sylphium; in Central and Southern Europe, lettuce or wild lettuce. If lettuce grows on moist or shaded places, then its leaves on the stem are located in all directions and cannot serve as a guide. If lettuce grows on a dry or open, unshaded place, then its leaves on the stem face west and east, and ribs - north and south, and serve as an excellent landmark, for which the plant was called the Steppe Compass.
* Plain terrain - a flat or slightly wavy surface. Absolute heights of up to 300 m, relative excesses of up to 25 m per 2 km, and a prevailing slope slope of up to 1 ° are characteristic. May be closed and rugged terrain.

In desert

Staying in the desert requires compliance with a number of security measures related to the effect of the Sun on the human body, air temperature (in the summer up to 35-40 ° C in the shade, sand heats up to 60-70 °). Dangers arise due to lack of water and landmarks, difficulties associated with the movement in the sands of poisonous reptiles and arachnids, as well as in connection with other features of the nature of the desert. Compass plants: the South European lettuce plant and the North American sylphium plant 1 and 3 - view from the east; 2 and 4 - view from the south

While in the desert, you need to know the location of the nearest bodies of water, wells, available landmarks along the route, as well as roads and trails. Orientation in the desert has its own specific features created by the unsteadiness of soils due to the movement of sand by winds, rare oases, mirages, etc.
Tracing lost in the desert is facilitated by the planned signs: small mounds of quadrangular, round or other accepted shape, traces and remains of a halt or overnight, etc. Cloudy days in the desert are rare, so orientation by stars, the moon and the sun is greatly facilitated. . Among the kingdom of stones and mountains of South Sahara, oases are scattered. Tuaregs inhabit them. They are engaged in cattle breeding, roaming with caravans of camels in the vast expanses of sand and stone. The Tuareg’s ability to navigate in the desert is surprising: during the day they find their way along the Sun and only noticeable landmarks to them, and at night - along the stars. The inhabitants of the desert are famous for their art of trackers, amazingly accurately reading footprints in the sand: tiny triangles indicate the paths of beetles, pits - hares, large prints - traces of a camel caravan, etc. Most of our deserts have coarse, hilly or flat terrain. Sands moved by winds form dunes and dunes, often connected by lintels, and also ridged sands. "You can navigate the sides of the horizon by ridges of sand if you know the direction of the prevailing winds in a given area. In summer, Kara-Kum dunes move to the southeast; in late autumn, when the winds blow in the opposite direction, their peaks move to the north-west until a new change in the direction of the wind in the spring, when the movement to the south-east resumes again. perpendicular to the strike of the ridge.In moving sands, even with a weak wind, the tops of the dunes are smoked, and with a strong wind and a storm, masses of sand rise into the air in such a quantity that the position of the Sun cannot be determined on a clear day, The storm usually ends in the evening, and after there is a mass of new dunes.
* Ridge sands
- the sandy surface of deserts in seeing ridges stretched along the direction of the prevailing winds up to 20-30 m high with a slope slope of up to 20 °. They are usually covered with sparse vegetation and are relatively easy to walk, especially along the ridges.
Afghan is a hot, dry wind typical of southeast Central Asia. He reaches the strength of a storm and carries with him clouds of dust; the midday sun is barely visible and appears dark red. Air temperature reaches 40 ° C. Leaves wither and die. Extreme dry air precedes the Afghan. The harbinger of a desert storm can be the disturbing behavior of animals and birds: camels look for a bush to hide their heads, birds hastily fly away. Phenomena similar to the Afghan are also observed in other deserts, such as the Sahara.
Russian traveler A. Eliseev says:
“Everything was quiet around ... But in the hot air there were some bewitching sounds, quite high, melodious ... they were heard from everywhere ... I involuntarily flinched and looked around ... The desert was also silent, but the sounds flew and melted in a red-hot atmosphere, arising from somewhere above and disappearing as if into the earth. “Do you hear the sands singing?” - said my guide Ibn Salah, - these are the sands of the desert; these songs are not good! The sand sings, the wind calls, and death flies with it! .. I tried to get out of the tent and inspect the place from which the mysterious songs of sand were heard. The desert was still silent, and the sounds froze immediately as they suddenly began ... Several minutes passed, and clouds of dust covered the sun ... The flying sand of the desert gradually began to move more and more; the moving peaks of the dunes soared into the sultry atmosphere and hung in it ... We all felt the approach of a terrible elemental monster and trembled before it, but not a single language dared to pronounce the fateful word - “sumum”. We waited for him like a fateful hour, having prepared as much as possible, but completely feeling our powerlessness in the fight against this terrible enemy; "Air poison", "breath of death", "fiery wind" - the terrible sumum was already "far away." He was approaching with quick steps, and after some half an hour from the moment the first sounds of the singing sands were heard, we were already at the very center of this terrible natural phenomenon. ”
... Mirages in the desert most often occur in half a day. This deceptive optical phenomenon disorients the traveler and sometimes causes the death of people who take, for example, an oasis mirage for reality.

In the mountains

Mountains - uplifts of the earth's crust, markedly distinguished on the earth's surface among the plains, as well as among the plateaus or in the mountains. Most of the mountains have a tectonic nature of formation (fault, folded, block) and the subsequent partition mainly of the erosive activity of rivers. There are mountains with alpine, alpine, mid-mountain and low-mountain types of relief. In preparation for the mountain hike, you should carefully study the map of geographical points and objects (buildings and structures); outstanding natural elements of the terrain and their styles, which can serve as landmarks on the route. You need to make yourself clear about the relative position of the main valleys, ridges and peaks, select the prominent peaks, cliffs, rocks, screes and others, details and local objects as the main and intermediate landmarks. While in the mountainous regions, it is necessary to take into account the many unusual conditions for the mountain climate and the dangers that await him at every step. The main hazards in the mountains are considered:

1. Rockfalls (rolling stones over narrow crevices), ice landslides, avalanches (snow masses falling down from the mountains), snow cornices landslides, mountain river flow rate and strength, mudflows (short-term and turbulent water flows with stones and mud).
2. Fogs, snowfall, rain, frost and wind, which greatly impede movement and dull vigilance in difficult places of a route.

Each person going to the mountains should have information about the influence of the mountain climate on the body, about the dangers and precautions in the mountains, and be able to navigate.
The following factors are especially depressing for a person.
1. As you climb a mountain and lower the barometric pressure of the air, the oxygen concentration decreases, and this affects the composition of the blood.
2. Intense solar radiation, under the influence of which general overheating of the body, heat, sunstroke, burns of the skin and eyes is possible.
3. Precipitation, strong winds and low temperatures can cause a person to get wet, freeze and freeze.
4. Dry air in the mountains causes a loss of water in the body, heat regulation is disturbed, the mucous membranes of the respiratory tract and oral cavity become inflamed.
Therefore, before going to the mountains, special training is necessary to prevent an accident. It should be borne in mind that a frivolous attitude to the difficulties of the journey, poor discipline of the participants of the campaign, neglect of the basic rules of orientation, traffic techniques and insurance are the causes of accidents. Mountains are a very complex natural formation, and orienteering in mountainous conditions is unusually difficult. For example, N. M. Przhevalsky, while traveling in Central Asia, found it very difficult to navigate in the desert, rarely populated areas of Northern Tibet, where the path often disappeared, and the wrong version of the movement led to a dead end in the gorge and inability to cross through the high and inaccessible Tien Mountains Shan or Tibet.
He wrote:
   "The tour guide, taken by us from the Gamun-nor and poorly known at all ... the direction of the path, is now completely confused, having entered the mountains that do not have any sharp signs for orientation." "During ... night walks ... I had only to approximately put the direction of the path, guided by the stars." “From the place of our parking ... we undertook the search for the next path. For this, two riding horses were equipped ... ”*
* Przhevalsky N. M. From Zaysan through Hami to Tibet and on the upper Yellow River. - M., Geografgiz, 1948.
   Mountain rivers and streams flowing through the valleys serve as good linear landmarks. The noisy flow of rivers allows you to navigate along them at night and in fog, when it is impossible to use other local objects. Mountain rivers with a fast current usually do not freeze, so their role as landmarks in winter increases. In the mountains, relief details sometimes serve as the most important signs by which to navigate. However, without sufficient skills to understand the mountainous terrain is very difficult.
   When moving along the valleys, the points of confluence of the main valley with the transverse ones (decays), cliffs, steep cliffs of slopes, narrow narrowing of the valley and various local objects can serve as point and area landmarks. The mountains very close the apparent distances: sometimes it seems that it’s not far to a mountain - a stone's throw, in fact, you need to go a few days to it. The familiar outlines of mountain peaks can change beyond recognition if you approach the mountains from some other side, from where they had not been seen before. Landmarks are often lost sight of.
In winter, orientation conditions in the mountains deteriorate significantly. Many details of the relief, which in the summertime could serve as good landmarks, are covered with snow and become invisible. Under these conditions, individual cliffs, cliffs, cliffs where snow does not linger can be reliable guidelines. Usually they are distinguished by dark spots on a white background.
   For orientation in the mountains, it is useful to know some methods for approximate determination of the sides of the horizon. In spring, on the southern slopes, the snow mass is “tousled”, as it were, forming a kind of “stubble” separated by thawed areas. Snow cover descends from the southern slopes of the mountains faster than from the northern ones. In separate deep gorges on their southern slopes, snow lies throughout the summer, forming snowfields. In forest areas, oak and pine grow mainly on the southern slopes, and spruce and fir on the northern. Forests and meadows on the southern slopes usually rise higher than on the northern ones. In settled mountain valleys, vineyards are located on the southern slopes.
   In highlands, orienting at night is facilitated by the use of a light alarm, and during the day, along with the main ones, it is necessary to mark intermediate artificial landmarks by setting milestones, laying out pyramids from stones and other means.

On rivers and lakes

   Many natural features are associated with the life of the river, with the properties of the river flow and the river channel, which are constant and can be successfully used by boatmasters to navigate rivers and lakes. Despite the widespread use of artificial signals on rivers and lakes, the significance of natural landmarks is very great, and they successfully complement and control each other.
   Forest managers and rafters are well aware that the rafting forest, lowered into the river, is washed ashore during a spill, and when water falls, it floats in the middle of the river. The nature of the river surface depends to a large extent on the nature of the course and topography of the bottom, which makes it possible to judge its depth and determine the location of obstacles in the channel.
In calm weather, during the daytime, the surface of the water above shallow places - scythes, zastrugi, saddles, crests of riffles and underwater osyderki - is usually more even and light than over deep places where it has a dark color. A natural underwater obstacle is found on a surface where water ripples. If there is not much water above the obstacle, then it overflows through it, and below it “soars”. Usually the surface of the water above the obstacle is smooth. The greater the difference in depths, the more sharply the individual places in the channel differ in color and waviness of the surface of the water.
   At night, the shallow spots have a whitish hue, and the deep ones are dark.
   “Quiet” refers to places with a pronounced quiet course or stagnant water. They usually form behind large sand spits and in the backwaters. By
the surface of the quiet wall in the daytime and at night seems darker than the surrounding water surface, and is separated from the stream with a normal or fast flow of a strip of foam. The water surface changes under the influence of waves formed by winds and moving ships. On the one hand, they make it difficult to see the reflection of small details of the bottom topography on the surface, and on the other hand (during calm weather), ship waves help to detect the location of streamers, shrouds, etc. In strong winds in stormy weather, the bottom topography and the difference in depths on the surface water is difficult to determine. When studying the riverbed, the skipper is helped in navigating near distances by the coastal forest, a group of trees, individual trees or bushes overgrown directly on the coast, in the zone of near visibility from the side of the vessel. The protruding part of the concave washable shore, turning into a spit or adjacent to a straight section of the channel, serves as a good natural sign for skippers.
   The “Mountain Market” has the appearance of a high promontory protruding into the bed, sometimes covered with forest, or a steep, treeless shore. The "mountain market", or cape, visible far even at night, is an even more noticeable landmark than the shoulders of the spring. The mouth of the tributary or ravine can also be used as a omen, since in most cases, opposite to and below them are rashes (removal cone), consisting of soil particles deposited by water. They quite often violate the channel regime in the area of \u200b\u200bthe mouth of the tributary or ravine and represent a serious obstacle to navigation.

Underground

Traveling underground is a very difficult type of tourism, since it requires the life support of a beginner caver, good equipment, special equipment, drawing up a tactical promotion scheme and orientation skills. The underworld preserves thousands of secrets and all kinds of miracles, which not everyone can uncover.
The cave poem from the book “Call of the Abyss” deserves recognition:

* “There are underground places where, like on mountain peaks,
Suddenly you understand the futility of human passions
And you see how small you are in comparison with the great
The mystery of eternal darkness and formidable abysses.
There is no end to the night; in caves, in transitions,
Where once the boiling stream rumbled
Now everything is silent, only stone arches
Solemn solemnity raises into darkness. ”

Along the weakened, fractured zones of the rocks, narrow deep hollows are formed - to a rs, separated by pointed ridges. Expanded cracks, collecting trickles of water from a clumping small area - micro-catchment, gradually turn into absorbing ponors **, * Under the influence of melt snow and rain water, prolonged dissolution of the rock creates closed saucer-shaped or conical funnels. Underground cavities gradually form, represented by the most diverse in configuration and origin wells (depth up to 20 m), mines (depth over 20 m) and caves with many kilometers of labyrinths. The inlet openings of the cavities are located on those elements of the relief where there are conditions for the accumulation and thawing of snow or for the absorption of permanent or periodic surface streams.
Leaving the surface in the constant darkness of the dungeon, with the usual movement, the speleotourist *** turns on his little sun - headlamp ****. Under the ground, a wonderful, fairy-tale world appears before the cavers ... Their route is limited by the walls of galleries and wells, either diverging beyond the borders of a narrow light cone and lost in obscurity, then converging and tightening their chest into a hard stone hug. Echoing silence, sometimes broken by the sound of water, amazing acoustics, slight fluctuations in air temperature, high humidity, incomplete color scheme, devoid of the characteristic tones of wildlife. Overhead, hanging on the vault of the cave, icicles alert, growing drop by drop of water, forming stalactites. Tearing and splashing on the floor of the cave, drops of water give rise to stalagmites. A fantastic landscape is formed: huge columns, openwork draperies, sagging flags, a shoot of bizarre crystals. Caves, karst cavities attract a person to study them, due to geographical unrecognition, the ability to experience a keen sense of discoverer, despite the fact that it requires endurance, dedication, extreme self-awareness, high moral, psychological preparation and excellent knowledge of the rules of conduct underground and discipline.
When exploring caves, the main obstacles are water and, more often, vertical walls, sheer fireplaces, slippery slopes or narrow loopholes. Having discovered the failure, first of all, it is necessary to measure its depth, throwing a stone to the bottom and noting the duration of its fall, observing the time by the clock. This is not difficult to do using the table. BUT. * Bonfire Norber. The call of the abyss. - M., Thought, 1964.
** PONOR - an absorbing hole in the area of \u200b\u200bkarst formations — wells, funnels through which water flows under the ground of the water-resistant layer.
*** The term "speleology" (the Greek word "speleon" - cave) was proposed in 1890 by the French archaeologist Emil Riviere.
SELEOLOG - Specialist involved in the study of caves, their origin and use.
**** Two other light sources with spare parts should be available: an acetylene lamp mounted on a helmet (250-300 g of carbide is reliably provided with light for six hours), and a short candle with waterproof matches.

Table a - for a rough estimate of the depths of wells and cavities.

	Depth with free fall, m.
Observed time fall, sec	Theoretical in airless space	approximate in the air	Speed sound in the air
1	4,90	4	4
2	19,60	18	18
3	44,15	40	40
4	78,50	65	60
5	122,60	93	85
6	176,60	123	112
7	240,30	154	142
8	313,90	185	170

The specific conditions of a person’s stay and life underground are determined by the influence of the following factors at the same time.

1. Natural obstacles - large elements of karst cavities that determine their morphology (wells, shafts, narrow passages - “skaters”, labyrinths); various elements of the underground relief complicating them (ledges, cornices, narrowing - “gauges”) and fillers of karst cavities (block bulk, deposits of underground rivers and lakes, ice, water). The possibility of overcoming them is considered the simplest, since it is mainly determined by the skills and physical training of the speleotourist. Fireplace pipe - a stroke of approximately 0.3 to 3 m in diameter, leading upward from a cavity or another stroke. They move along the fireplace of medium width, wedging, alternately resting against the hips and soles, then the shoulders. In narrow fireplaces they rest against one wall with the soles and back, the other with knees and hands. In wide fireplaces, the “scissors” technique is used, that is, they rest against one wall with the left hand and left foot, and the other with the right hand and right foot.
The passages in the cave have a completely different look when you look in the opposite direction. If the side passages seem to merge into the main one when you enter the cave, then they seem to branch off on the way back, so you can easily get confused. It is easy to find the way to the large cavity from the small passage, but it may be difficult to find the small passage from the inside of the cavity. Cavern water cannot be drunk, since bacteria are not filtered out in it. In small simple caves, you can apply the rule of the right hand - when moving forward, turn into all right moves, when moving backwards - into all left moves. The orientation helps to conduct topographic surveys of the cave, in which special marking is performed. When leaving the cave, all marks are removed. On the walls of the cave you can not leave any inscriptions that can disorient the following groups.

2. The impact on the caveman; conditions. The individual psychological characteristics of each person become aggravated and act underground, for example, fear of darkness, confined space, loneliness, height and water; fear, discomfort. Some mental characteristics of a person can be overcome by training, but quite often their complex is the basis for the restriction (or prohibition) of speleotourism. The influence of strong stressful agents (low temperature, high humidity, peculiar acoustics, etc.) gives rise to erroneous technical and tactical actions, does not allow to take the correct, often the only possible (especially in an emergency) solution to the problem of human life support and its adaptation underground. The safety of being in caves is facilitated by the discovery of factors leading to an emergency, prediction of the most probable incidents and the adoption of preventive measures to prevent and eliminate them.

On the seas and oceans

Sailors should not neglect the knowledge of the natural features and patterns of the nature of the sea, do not cease inquisitively studying it, regardless of the modern equipment of the fleet. Swimming in the seas and oceans is accompanied by a relatively rapid and abrupt change in natural phenomena, which for the attentive eye can serve as an important sign in orientation when the vessel approaches land, shallow water, ice, reefs, etc. The appearance of a cormorant diver and the usual jellyfish-aurelia off the unfamiliar shores warns of the proximity of reefs.
In the stormy Bering Sea, snowstorms and mists make navigation very difficult. Landmarks here can serve as large bird markets. During the fog, cries of birds warn of the proximity of rocks. Rocks from bird droppings acquire a white color and become more distinguishable against the background of the coast or sea. From top to bottom in the rocks of bird islands everything is occupied, to the smallest place, each ledge serves as a dwelling for a thousand birds; nests are located next to each other. There is an unimaginable noise. The whole rock is covered with a cloud of swirling birds merging into one spot. It is known that each pair only cares about its chicks, and it is incomprehensible how birds can find their nest and each other. The common tern moves away from the tropical islands of the Pacific Ocean, where it nests, no further than 20 miles (nautical mile equal to 1852 m); brown silly - 30 miles, and white tern - 100 miles. When these birds, before evening hours (their usual return to the nesting place) quickly, without dodging anywhere, fly high above the sea to the coast, a storm should be expected. If dolphins gather in schools and frolic more than usual - this also portends a storm.
   The emergence of large swarms of scraps on the southern shores of the Baltic Sea in late autumn predicts an early harsh winter. All seabirds, with the exception of the seagull gull (northern half of the Atlantic Ocean and the north of the Pacific Ocean), are silent in flight. Therefore, the night cries of seabirds give the right direction to land.
   During the first Russian round-the-world voyage on the ship "Nadezhda" in 1804, I.F. Kruzenshtern noticed at 17 ° C. w. and 169 ° 30 "W, there were a lot of birds and concluded that there should be an island nearby. Three years later, an island discovered in these places was named after Kruzenshtern.
   Sailors all over the world are aware of the natural lighthouse, which serves as one of the landmarks in the Pacific Ocean off the coast of Central America. Every eight minutes an underground rumble is heard here, and a club of smoke appears over the crater of Itzalko volcano, which grows into a huge column about 300 m high. Then the column begins to spread in the air. Such eruptions have been following one after another for more than 200 years. On dark tropical nights, volcanic eruptions are visible for hundreds of kilometers, as a column of smoke is illuminated: a purple glow of boiling lava.
In the Indian and Pacific Oceans, the appearance in the water of a motley colored, highly visible from the deck of poisonous sea snakes warns of the proximity of the coast. A sailor should double his attention when a green-yellow spot or streak suddenly appears on the ship's course against the background of sea blue, characteristic of an open water area, smooth or covered with small chipstones. This phenomenon, called the “blooming of the sea”, is most often observed in inland seas, bays and bays and indicates the proximity of the shallows. Quite often, when passing from one stream to another, a sharp change in the color of water is found, associated with an abundance of animal or plant plankton in some waters and a lack in others. For example, reddish water from crustaceans is replaced by greenish from microscopic algae or blue plankton-poor water. This phenomenon helps to notice the change of one current to another, which is important during the course of the ship.
   The underwater cliffs of Kukikonosaki off the coast of Japan, overgrown with algae, over which the water layer reaches 20 m of thickness, give themselves out in calm weather with a reddish shade of water, and the excitement in the area of \u200b\u200bthese rocks is completely different than near, above the depths. Sounds and noises in sea water from the movement of large marine animals, the passage of schools of fish, the sound of the surf can often serve as good guidelines.
   Malay fishermen off the eastern coast of the Malacca Peninsula use a very original way to search for fish and install nets. Every 50-100 m a fisherman on a sampan descends overboard and, plunging headlong into the water, listens to the noise from the movement of schools of fish and determines how much it is and how much it is. After making sure that there is no fish near the boat or there is not much fish, he gets into the boat and floats further until he finds a suitable place for fishing. Widely used in modern navigation, the hydrophone device - “underwater ears” - makes it possible to listen to sounds underwater. Hearing aids-hydroacoustics through training develop the skills of recognizing sounds originating from the movement of a convoy of ships or a submarine, from swaying a sunken ship at the bottom of the sea, passing schools of fish, dolphins, whales.

Under water

Swimming underwater is associated with limited visibility, which also often changes. The nature of the distribution of brightness in various directions of the body of water determines the features of visual observation. For example, in shallow water, near the bottom or near the surface of the deep sea, the brightness distribution depends on the nature of the lighting of the aquatic environment, the reflective properties of the seabed, etc. At the same time, in the layers of the deep sea remote from the surface, the brightness distribution approaches the steady state almost independent of the nature of illumination of the sea surface, the movement of the observation point horizontally and vertically. The intensity of natural light in sea (very clean) water decreases at a depth of 100 m to 1% compared with the illumination on the surface, and it acquires a pale green color. At a depth of 200 m, the light intensity drops to 0.01% and has a dark green color. At a depth of more than 300 m, it is almost dark. Thus, already at a depth of more than 200 m, artificial lighting is necessary. The brightness of the water is maximum in the direction of sunlight and minimal in the opposite direction. On underwater objects or at the bottom, bright sun glare from the wavy surface of the water is played. But as soon as the clouds close the solar disk, the picture under water changes: the play of light stops, the difference in brightness for different directions decreases, underwater objects become more monophonic. The same thing is observed with increasing depth of immersion.
   On a sunny day, in clear ocean water, the light regime is set at depths of 100-200 m and more. It is difficult to swim under water at night, as it is difficult to establish communication and underwater orientation, which are fundamental elements of safety engineering. When navigating under water, the submariner is deprived of the usual support - contact with the ground. When moving under water, the high density of the aquatic environment and poor visibility give the impression of great speed.
   When a person is swimming in muddy water, at night or with a blue veil, of all the sensory organs orienting him, one vestibular apparatus acts, on the otoliths * of which the force of gravity still acts. The human mass in water in set No. 1 due to the air contained in the mask and breathing tube is close to zero, so that the value of gravity is lost.
Under water, the speed of movement decreases. It is easy to roll over your head there, but it is impossible to make a sharp movement. For orientation underwater, even the pose of the submariner is important. The pose "lying on your back with your head bowed back" is considered the most unfavorable for orientation.
   Staying a person in free swimming is very limited to an aqueous medium devoid of gaseous oxygen, since oxygen under water has a higher density than in air. For example, diving - a person’s invasion of an unfamiliar aquatic environment — causes a corresponding compression of tissues and air enclosed in the body’s cavities. The pressure on the body when diving every 10 m dives increases by 1 kg / cm2. The mass of a person in water is not more than 2-3 kg. At the same time, the specific gravity of his body on inspiration will be less than the specific gravity of water (0.976), and on exhalation it will be slightly larger than the specific gravity of water (1.013-1.057). The ability to hold your breath under water for a long time and painlessly tolerate a sharp increase in ambient pressure is a determining factor in the physiological capabilities of a diver.

* Otoliths - a part of the organ of equilibrium located on the surface of cells perceiving various mechanical irritations.

The easiest way to determine the distance to a given landmark is to count the number of breaths or strokes with your feet. You can more accurately determine the distance under water using a distance meter (lag), the operation of which is based on the use of high-speed water pressure on a special turntable.
Underwater orientation- a kind of sport in which the advantage of one athlete over another is achieved not only due to better physical fitness, but also due to the technical skill of the athlete and the quality of his equipment. Orienteering sports combines several exercises underwater:

“Direct” - swimming without changing course;
“Zones” - swimming with a change in course without reference points;
"Landmarks" - swimming with a change in course along landmarks; performance of special group exercises. For example, swimming under water “with a change of course according to reference points” consists in the fact that at a given control time, a submarine athlete must go a certain route under water and find 5 landmarks in succession, the distance between which is 100-200 m. This type of underwater orientation requires a search a landmark representing a wooden cross 4 m high; it is attached at the bottom to the anchor with a hemp rope 2-3 cm thick with the help of navigation devices and special search devices.

Search under water can be carried out in several ways: circular, stripes, trawling, as well as towing a scuba diver on a gazebo suspended from a boat. Currently, three types of search are widespread - visual (the athlete, looking through the water column, determines the location of the landmark), circular and sector. The latter is more reliable, since sector search takes more than two times less time than circular search; moving cargo 2-3 m does not lead to a loss of reference. With probable errors in the distance of ± 1.5 m and in the compass of ± 1 °, the length of the sector search is reduced to 8-10 m. Underwater orientation includes preparatory work on the shore, performing exercises - swimming under water using instruments and underwater search.
Preparatory work on the shore is carried out in order to determine the direction of movement of the athlete under water and the distance that he must overcome. Data is applied to the water plane, which the athlete uses underwater. The swimmer determines the direction of movement underwater using a magnetic compass, the scale of which (card) is set in the direction of the compass meridian. The angle measured from the northern part of the compass meridian to the longitudinal plane of the compass clockwise from 0 to 360 ° is called the compass course, and the athlete reads its value from the compass scale when moving under water. Start in underwater orientation is carried out from the launch buoy, installed in the water at a depth of about 1.5 m, by shot.
In the initial position, an athlete in equipment (a mask on his face, a mouthpiece in his mouth) stands on the ground next to the launch buoy. The navigation hydroplane is held in outstretched or slightly bent arms and is directed in the direction of movement. On a starter’s shot, the swimmer crouches, feeds the body forward, vigorously repels from the ground and begins to move. Between underwater swimmers, communication is carried out using hand signals, a signal end, a control end with a signal float, sound or visual conditional signals.
A special signal table was developed and discussed at the VIII General Assembly of the World Confederation of Underwater Activities in Barcelona. Depending on the purpose, the signals were combined in three groups:

1) informing about what is happening, pointing to something and insisting on doing something;
2) testifying to the not quite normal condition of the submersible or its equipment, conveying certain wishes and even orders;
3) reporting emergency condition and assistance.

Eight signals have been approved as mandatory for submarine athletes around the world, and eleven signals are recommended for use, not counting them mandatory. The international signal code (mandatory) includes characters that are usually given by the right hand.

In settlements

   In 1782 a new building of the Odeon theater was built in Paris, on de Tournon street. The audience was crowded at the performances. With the onset of darkness, carriages moved along the streets lit by gas lanterns, and walking people walked. An incredible crush formed at the theater, carriages interlocked, theatergoers often found themselves in the hospital instead of the auditorium. And then they decided to divide the street for carriages and pedestrians. On both sides of the street they took small strips of land, fenced off them from the rest with curbstones, laid hewn granite slabs and posted an ad: “sidewalk”, which in Russian means “road for pedestrians”. Gradually, people got used to the sidewalk and began to walk only on it. "Fashion" was taken to build sidewalks in London, Berlin, Rome, Vienna, St. Petersburg. The construction of sidewalks has become mandatory. Thus, the street includes the roadway, sidewalks, green spaces and landscaping elements (lights, fences, signposts, etc.). The boundaries of the building are called “red lines”, the distance between which determines the total width of the street. The set of streets forms a street network and occupies 20-25% of the territory of a settlement.
In a modern large city, it is extremely important to be able to navigate, observing the established traffic rules for this city, being guided by the marking lines of the carriageway of streets and roads and inscriptions on direction signs. For a confident orientation within a settlement, you should first get its plan or scheme. According to the plan or scheme, you must first familiarize yourself with the layout, the system of highways, pay special attention to the distinguished buildings, historical monuments, churches, museums, parks, theaters and other landmarks of this settlement. The nature of settlements (cities, towns, villages, farms) is very different, but in them you can find general principles and features of building, planning, the order of names and numbering of streets, houses, etc.
   In cities with a radial-ring layout, the numbering of houses on radial streets is from the city center (central square) to the outskirts; on ring streets, numbering can be either in the direction of the clock or counterclockwise. There are several numbering systems - “Moscow” (more common), “Leningrad”, “Cartesian”. The latter was first introduced by the French mathematician Descartes (or Latin Sayeszs), so we are talking about "cities, broken down according to the Cartesian scheme."
According to the “Moscow” numbering, the odd numbers are located on the left side (in the direction of the street from the center of the village), the even numbers are on the right side of the street. According to the Leningrad system, the odd numbers are located on the right side of the street, and the even numbers are on the left. In many cities of the United States of America, a west-east demarcation line and a north-south demarcation line have been drawn, with all the streets running parallel to either one or the other demarcation line. Sometimes, for their distinction, streets parallel to one demarcation line are called "street", and parallel to another - "avenue". The first, second, third, etc. streets are elongated in the west – east direction and, again, the second, etc. streets (or avenue) are elongated in the north – south direction. Therefore, the address can be written, for example, as follows:
200 N, 200 W, which means the intersection of the second avenue in the north-south direction, with the second street in the west direction, stretched in the west-east direction.
For example, the former city of Alma-Ata has the correct rectangular layout. Long wide streets, with canals flowing along its sides and shady alleys stretch, are oriented along the north - south, east - west lines. The same layout and location of streets in the capital of Kyrgyzstan, in the city of Frunze (Bishkek). In small cities located on both sides of the railway, the numbering of houses begins in most cases from the railway, from the forecourt.
   In cities located on highways, the numbering of houses along the highway is carried out more often in the direction of increasing the count of kilometers along the highway, and in the transverse direction - on both sides of the highway. Sometimes the numbering goes on one side from one end of the settlement to the other, and then in the opposite direction on the other side. The numbering of houses on the embankments and streets parallel to them is usually carried out in the direction of the river, and on the streets located perpendicular to the embankments, on both sides of the main river bed.
   A decisive influence on the development and planning of rural settlements is provided by the terrain, water bodies, watercourses, etc. Large prominent rural objects can serve as local landmarks. These are silos, MTS, windmills, gardens, red flags over the buildings of the boards of state farms, collective farms, rural and district Soviets, etc.
   Plain settlements are distinguished by their large size, sparse buildings and relatively proper layout with a large number of uniform lanes and dead ends. Sometimes they have the names and numbering of houses. Most often, houses are determined by the names of their owners. Valley-ravine settlements are located on the slopes of river valleys, beams, ravines, the direction of which determines the shape and nature of the buildings.
   Dividing rural settlements are located on small hills, valleys and ridges. Coastal settlements are usually extended along the seashore, lake, large river. The main streets run parallel to the shore, driveways are perpendicular to it.
   Mountain settlements are usually located on the slopes of the mountains. The buildings are closely adjacent to each other, forming the so-called cornice structure in the form of steps. Quarters, as such, are absent. The streets look like walking and pack paths meandering between buildings.
On the streets of the city you need to be especially careful and develop skills in your way to notice everything. For example, lying heaps of snow on the sidelines after clearing the roadway, especially in early spring, can orient a person on the horizon. The ledges and depressions parallel to each other are inclined at the same angle to the ground, they are especially clearly visible on the slopes contaminated with snow and are directed to the south.

The journalist stayed in a hotel. In the morning I noticed a yellow layer of sand on the windowsill.

There’s a desert right behind the village, ”the local resident explained. - The wind will blow - close all the windows. It was so hard to get used to it ... I remember where the sands were now, there was grass to the waist.

They had to push the car: the road was blocked by a sandy “snowdrift” - a dune, outlined overnight.

The hot wind hurts the face with the smallest grains of sand. Not for a minute makes you forget: the desert is advancing. Where is all this going on? In the south of our country, in the so-called Black Lands.

Black ... Did the people who gave this name to this land a long time ago foresee misfortune? No, that’s not the point. In winter, there is usually no snow, and the terrain without it seems black. And now the Black Lands have become a victim of a terrible disaster - desertification.

What is desertification? This is the gradual transformation of drylands into desert. Like rust on a metal surface, the desert is expanding, expanding its borders, capturing more and more new areas. Over the past 50 years, an area equal to half of South America has turned into barren deserts around the world. On the verge of desertification, U is now part of the entire land of the Earth in more than 100 countries of the world. The African Sahara desert, for example, moves south annually to a distance of 10 km!

Why does desertification occur? To answer this question, we will return to the Black Lands.

The local pastures for centuries fed flocks of sheep. People knew: the layer of fertile soil here is very thin, under it is sand. Therefore, land cannot be plowed here. And cattle should not be too much. In addition, you can not graze it in the same places all year round so that the grass fastening the soil is not eaten and trampled by domestic animals. Violate these conditions, and the sand will break out of the centuries-old captivity.

In these parts, to this day, disaster would not have happened if people had not decided to neglect the laws of nature. Took to plow the earth! And so many sheep were bred that willy-nilly had to graze them all year round in the same pastures.

Yes, from plowed lands received watermelons, corn, wheat, barley. But a thin layer of soil quickly collapsed. Sand became the master here. And people were plowing a new plot.

Yes, they got meat and wool from the sheep. But the places where it was still possible to graze, became less and less. People from year to year increased the number of sheep! Unhappy exhausted animals ate everything that was still growing, and hundreds of thousands died of hunger ...

So why does desertification occur? The example of the Black Lands and the observations of scientists in other parts of the world show that people themselves are most often to blame for this. Land plowing and overgrazing play a major role.

Having understood the causes of desertification, we can decide how to stop it or at least slow it down.

It is necessary to stop the plowing of lands in areas undergoing desertification.
It is necessary to restore order in animal husbandry. Keep as many sheep as the pasture can feed. So drive animals so that pastures rest for a part of the year.
It is necessary to sow herbs and plant forests so that a vegetative cover protecting the soil appears.

Of course, turning into a real desert does not threaten the entire Earth. This is a disaster in arid climates. But this ecological disaster can be considered a symbol of what is happening now with the Earth. People are devastating their planet. Does air and water pollution not bring disease and death to the living? Doesn't deforestation and the extermination of plants and animals make the planet lifeless? Does any of us, thoughtlessly killing mushrooms or slamming innocent insects, impoverish the environment? People cannot live in a ruined, ruined natural house. Around the Sun, 8 dead planets revolve, and only one still bears life. We urge you to save this life by doing everything you can to do this.

Test your knowledge

What is desertification?
In which area of \u200b\u200bour country is desertification particularly rapid?
What actions do people open the way to the desert?
How can desertification be stopped?

Think!

In the early 70's. XX century in one of the regions of the Black Lands there were 850 thousand hectares of pasture. After 15 years, 170 thousand hectares remained. On the remaining lands it was already impossible to farm. Calculate how many hectares of land have been lost over the years.
According to scientists, the pastures of the Black Lands in the mid 80-ies. XX century could feed no more than 750 thousand sheep. But in fact, more than 1 million 500 thousand sheep were kept here. Give a rough estimate: how many times have pastures been overloaded?

Desertification is occurring in many parts of the world - the gradual conversion of arid lands to desert. Among the main causes of desertification are plowing and excessive grazing of animals that eat and trample vegetation. To stop desertification, you need to stop plowing, restore order in animal husbandry, sow grass and plant forests.

Vegetation. Desert vegetation, represented by xerophytes and halophytes, does not form a closed cover and usually occupies less than 50% of the surface, differing in a great peculiarity of life forms (for example, tumbleweed). Ephemers and ephemeroids occupy an important place in plant communities. Many endemic. Leafless shrubs and semi-shrubs (white saxaul, sand acacia, Circassian, ephedra) are common in Asia on sand; succulents (cacti, yucca, prickly pear, etc.) are common in America, as well as in Africa. A variety of wormwood, hodgepodge, and black saxaul dominate the clay deserts.

Animal world. Animals that have adapted to life in the open spaces of the desert can quickly run and remain without water for a long time. For example, a long-time domesticated camel, which for its endurance and reliability is called the "desert ship." Many of the animals are marked with a yellow or gray-brown “desert” color. Most of the animals in the summer lead a nocturnal lifestyle, some hibernate. Rodents (jerboas, gerbils, ground squirrels) and reptiles (lizards, snakes, etc.) are numerous and ubiquitous. Of ungulates, gazelles, antelopes, including gazelles, are often found; from predators - a wolf, a fennec fox, hyenas, jackals, coyote, caracal, etc. There are numerous insects and arachnids (phalanx, scorpions, etc.).

Impact on business activities

As already noted, deserts are distinguished by natural contrasts. Many natural processes occur in them in extreme conditions or on the verge of them. For this reason, they are characterized by violent reactions in case of imbalance in ecosystems. Each of the desert phenomena in its own way affects the terrain, soil, vegetation, wildlife, man and his economic activity. Like any extreme phenomenon, desert phenomena are unfavorable for people, sometimes dangerous. They cause crop failures of fodder plants; Sand buildings, roads, wells, etc. Dust storms stop work in the fields for several days in a row, dry winds have a depressing effect on living organisms, not excluding humans, causing them to be depressed. Even light winds set the sand in motion.

Extreme events in winter are manifested in severe frosts, followed by thaws and icy conditions. A feature of extreme events is that they are irregular, always unexpected, which makes them even more dangerous in their consequences. For example, stable snow cover more than 0.5 meters high is not every year, but in adverse

rare years it stays in separate lowland areas of Central Asia for 40 - 70 days, which is dangerous for sheep.

Human influence

Sharp changes in the existing natural complexes of the desert arise under the influence of natural processes and anthropogenic factors. In the first case, the natural environment changes temporarily and not fundamentally. The influence of man manifests itself differently: in conditions of hunting, it is slower than with nomadic animal husbandry, with the latter less noticeable than with the development of large areas in irrigated areas.

The largest and most noticeable transformations in the deserts took place in the 20th century, when the mining industry, and in the cities and manufacturing, the construction of railways, followed by roads, mechanization of agriculture, brought modern machinery into the desert. This significantly increased the intensity of its transformation, demanding to highlight a special category of impact on the territory - anthropogenic factor. Being part of the influence of the anthropogenic factor, man-made forces have their own distinctive features. In desert conditions, this is very noticeable, since the action of technogenic forces dramatically worsens the appearance of the area and, moreover, changes the natural processes that form ecosystems.

The construction of roads crossing the desert, the digging of large trunk canals, the laying of gas and oil pipelines - all this is possible only with the use of modern technology: tractors, bulldozers, excavators, hydraulic monitors, cars and other technical means. Producing a lot of useful work, they simultaneously cause significant and not easily repairable damage: when they move, vegetation is destroyed, the fixed sands become mobile, they revert. At the same time, wind and dry hot air dry them, and the sands lose their water-physical properties, the groundwater level below them decreases. In this case, phytomelioration does not give the desired result. The bare sands fall from the pasture fund. They generate dusty winds, sand tornadoes, create drifts on the roads, expand the area of \u200b\u200bloose, moving sands. But not only man-made forces, but also any excessively intensive use of nature in the desert can lead to similar results. So, a pasture, when overloaded with sheep or a very long permanent grazing of cattle, with a strong felling of shrubs, turns into a focus of waving sand.

In case of excessive irrigation, an equally irrigated plot turns into solonchak or, at least, into an array of saline soils unsuitable for cultivation without complex reclamation.

As you can see, natural processes and the anthropogenic factor can, each in their own way, significantly modify, transform the desert, and the stronger, the more intensively nature management takes place. Undoubtedly, in this respect, technogenic forces are in first place, but other factors cannot be discounted. Therefore, economic activity in the desert, more than in any other landscape, should be closely linked with the protection of nature, with measures to compensate for the damage caused.

The problem of desertification. As a result of prolonged and intensive anthropogenic impacts (shift-cultivating land system, overgrazing

cattle, etc.) the offensive of the desert, the expansion of its area. This process is called desertification, or desertification. This is a real threat to many peoples of North and East Africa, South Asia and tropical America. For the first time, the problem of desertification attracted special attention after the tragic events of 1968-73, when a catastrophic drought swept the southern regions of the Sahara, the Sahel zone, where thousands of local residents died of starvation. In such extreme environmental conditions, the problems of food, feed, water and fuel are extremely acute. Pastures and agricultural land cannot withstand overload. Territories adjacent to the desert themselves become a desert. Thus, the process of desertification begins or intensifies. Sugar, moving south, annually takes away 100 thousand hectares of arable land and pastures. Atacama moves at a speed of 2.5 km per year, Tar - 1 km per year. Together, scientists from many countries have developed an integrated approach to the study of desertification in the framework of the UNESCO program “Man and the Biosphere”.

The expansion of the boundaries of deserts and desertification problems are characteristic of areas directly adjacent to deserts, where human activity is manifested actively.

From table 4 of potential desertification across continents, it can be seen that the largest areas of landscapes, highly degraded, are in Asia, Africa and Australia, where the largest

desert. The smallest areas are located in Europe, North and South America.

Table 4 Territories of potential desertification by continent (thousand square kilometers)

Degree of desertification	Australia	North America	South America	World at large


Very strong

The factors leading to desertification in the arid regions of the globe are quite diverse. A special role in enhancing desertification processes is played by the following:

the destruction of vegetation and the destruction of soil during industrial, municipal and irrigation construction;

2) degradation of vegetation by overgrazing;

destruction of wood and shrubbery as a result of fuel harvesting;

soil deflation and erosion during intensive rainfed cultivation;

secondary salinization and waterlogging of soils in conditions of irrigated agriculture;

intensification of takyro - and solonchak formation in foothill plains and drainage hollows;

landscape destruction in mining areas due to industrial waste, discharge of sewage and drainage water.

Natural processes leading to desertification are many. But among them the most dangerous are:

climatic - increase in aridity, reduction in moisture reserves caused by changes in macro- and microclimate;

hydrogeological - precipitation becomes irregular, groundwater supply - episodic;

morphodynamic - geomorphological processes become more active (weathering of salts, water erosion, deflation, the formation of moving sand, etc.);

soil - drying out of soils and their salinization;

phytogenic - degradation of vegetation;

zoogenic - reducing the population and number of animals.

Desert protection. To protect and study the typical and unique natural landscapes of the world's deserts, a number of nature reserves and national parks have been created, including Etosha, Joshua Tri (in the Death Valley - one of the hottest places in the world), Repetek, Namib and others.

Zones called “deserts” range from salty to sandy. Wherever you find yourself, know that deserts are places of extremes: extreme heat during the day, extreme cold at night, very few plants, trees, lakes and rivers. Deserts can be found all over the world, they cover about one fifth of the Earth’s surface. Among the most famous are the Sahara, the Gobi, the Arabian Desert and the flat plains in the southwestern United States.

Movement

Water is the main factor for survival in the desert. Carry it with you as much as you can, even if you have to leave something else. If you decide to move around:

- move only in the evening, at night or in the early morning; - go along the coast, to a known route, to a source of water or to a village. Sweating can be weakened by wetting your clothes

- Choose the easiest route possible, avoiding loose sands, difficult terrain, paths along the tracks of roads.

In the sand dunes, walk along the hard sand in the valley between the dunes or along the crests of the dunes:

- Avoid following along streams in order to reach the sea, with the exception of coastal deserts or those areas where large rivers cross them. In most deserts, valleys lead to an enclosed body of water or a temporary lake;

- Dress appropriately to be protected from direct sunlight and excessive sweating. If there are no sunglasses, make yourself slit glasses. Clothing is needed in the desert to keep warm, as cold nights are very common there;

- watch your legs. Boots are the best desert shoes. Cross the dunes barefoot only in cool weather, otherwise the sand will burn your feet. Follow the tracks of caravans in order to avoid loose sands or rocky areas;

- check the card if possible. Maps of desert areas are usually inaccurate;

- Take refuge in sandstorms. Do not attempt to move when visibility is poor. Mark the direction by drawing deep arrows on the ground, laying them out with stones or whatever is at hand. Lie on your side with your back to the wind and lie until the end of the storm. Cover your face with cloth. Do not be afraid to be buried under the sand. Even in dune areas, it takes years to fall asleep on a dead camel.

If possible, look for shelter on the leeward side of the hill;

- Multiply distance calculations by 3, since the absence of landmarks often leads to incorrect calculations;

- In the summer, mirages can often appear when you are facing the sun, although it is difficult to generalize under what conditions they appear and what forms they take.

Shelter

Shelter from the sun, heat and possible sandstorms is necessary in order to survive in the desert. Since there is basically no material for building a shelter, use the following methods.

1. Provide yourself some protection from the sun by covering the body with sand.
Burrowing in sand also reduces moisture loss.
2. If you have a parachute or other suitable material, dig a recess and cover its edges. In rocky deserts or deserts where there is a bush, thorns or there are tubercles overgrown with tall grass, throw a parachute or blanket over stones or bushes.
3. To create a shadow or shelter, use both natural and human-created features of the terrain - a tree, rock, a pile of stones or a cave. The wall of a dry riverbed can serve as a shelter, but if clouds run in, your shelter may be suddenly flooded with water. The banks along the dried up riverbeds, valleys and ravines are especially good places for finding caves.
4. If possible, use native shelters.

Water

General Provisions The value of water cannot be overestimated. It is significant, regardless of how well your food supplies are matched.

In hot deserts need at least 3.5 liters per day. If perspiration is moderate and movement in the desert occurs on a cold night, this supply is enough for 30 km. In the heat of the day you can walk only 15 km.

Keep water.
1) Stay always dressed. Clothing helps control
sweating, does not allow sweat to evaporate so quickly, which is why its ability to cool is lost. It will seem cooler without a shirt, but you will sweat harder and can also get sunburn.
2) Do not rush. With less water, if you sweat less, you will last longer.
3) Do not use water for washing until you have a reliable source of its production.
4) Do not swallow water in one gulp. Drink it in small sips.
If water is running out, use it only to moisten your lips.
5) As a means of relieving heat, keep small pebbles in your mouth or chew grass. You can reduce water loss by breathing through your nose. Do not speak.
6) Use salt only with water and only if there is enough water.
Salt enhances thirst.
7) Limiting water consumption to 1-2 liters per day leads to disaster (at high temperature), since such an amount of water does not prevent dehydration. In such cases, limit sweating, not water.

Local wells. A minimum of four quarts of water per day may be difficult to find unless there is a well or oasis nearby. Since wells are the main source of water in the desert, the best way to find them is to travel along a local road. There are other ways to find water in the desert.

Be guided by the following:

1) dig a hole along the sandy shores or desert lakes in the first depression behind the first sand dune. At this point, local rain water will collect. Once you find the raw sand, stop digging, let the water leak. Further digging can lead to salt water;
2) wherever you find raw sand, dig a well;
3) dried streams have water immediately below the surface. If the creek
dries up, water descends to the lowest point on the surface at the turn of the channel. In search of water, dig along these turns;
4) dew can be a source of water, especially in some areas. Chilled stones or any metal surface is suitable as a dew condenser. Remove the dew with a piece of cloth and squeeze it. The dew evaporates immediately after sunrise and must be collected before that;
5) look for natural places that can be under the roots in ravines and side canyons, under the tops of rocks. Often near them is a strong stone or earth compaction. In the absence of such landmarks, look for sources of animal litter;
6) watch the flight of birds, especially at sunset and dawn. In areas of real deserts, birds fly over wells. Wild sand pumpkin can be seen as a source of water in the Sahara. A large cactus, similar to a gun barrel, in the American desert contains a large amount of moisture that can be squeezed out of its pulp. This is sometimes difficult to do. An alternative to this may be a well or other source;
7) do not take into account the romantic stories of poisoned wells. In these stories, it is mainly assumed that water contains salt, alkali and has a bad taste;
8) disinfect any water. This is especially important in native villages and where there is civilization.

It's hard to find food in the desert. But it still ranks second in importance in comparison with water. And you can do without it for several days without any health consequences. Distribute food from the start. Do not eat anything during the first 24 hours and do not eat until you have water.

Natural sources.

1) In the desert, you can rarely meet animals. Rats and lizards can be found at water sources, and they can make up your only food. Artiodactyl animals can be found in the desert, but it is difficult to approach them. The most common animals are rodents (rats), rabbits, jackals, snakes and lizards, which can usually be found near shrubs or water. Look for sand snails on rocks and bushes.
2) In the desert, you can find some birds. Try kissing the back of your hand, making a sound when sucked to attract them. On some lakes in the desert sand grouse, bustards, pelicans and even gulls were seen. Use traps or a hook and try to catch them well.
3) Usually, where there is water, there are plants. Many desert plants look dry and unappetizing. Look for the soft part that is edible on them. Try all the soft parts growing on the surface of the earth - flowers, fruits, seeds, young shoots and bark. At some times of the year, grass seeds or pods can be found. These pods grow on acacia trees, which are often prickly and look like a mosquito tree or “cat claw” growing in the southwestern United States. There is a prickly pear (a variety of cactus), whose homeland is North and South America, it is often found in North Africa, the Middle East and the Australian deserts.
4) All grass is edible, but some of its species growing in the Sahara or Gobi are tasteless and nutritious. Try any plant you find; it's not deadly. In northern Africa, Southwest Asia, and parts of India and China, dates can be found.

The food of the natives.

1) The food of the natives in the Sahara is both tasty and nutritious. In the Gobi, the Mongols do not really monitor the cleanliness, so the food is unhygienic. Take advantage of the natural hospitality of the natives, do not steal food.
2) The natives' daily food is extremely dangerous, as are the fruits and other cooked food offered by the locals. If possible, exchange or buy raw food and cook it yourself.

Fire

Palm leaves and similar fuels are found everywhere near oases. In the depths of the desert, however, use any piece of dry plant found. Camel dry manure can be used when there is no tree at hand.
Probably the most effective way to make fire without matches is to direct the sun's rays through a magnifying glass. Other simple ways to make fire may not be possible.

clothing

Protect yourself from direct sunlight, excessive sweating and numerous annoying insects living in the desert.

1) Well cover the body and head during the day. Wear long pants and a long sleeve shirt.
2) On the neck, wear matter that protects it from the back from the sun.
3) If some part of the clothes needs to be left to make it easier to wear, keep that part of the clothes that is necessary for protection from the night cold in the desert.
4) Wear loose clothing.
5) Unfasten clothing only in a thick shadow. Reflected sunlight can cause sunburn.

Leg protection can be a matter of life and death. It is useful to know the following.

1) Avoid getting sand and insects in shoes and socks, even if frequent stops are needed to clean the shoes.
2) If you do not have shoes, make some windings from any material that is at hand. To do this, cut two strips, each 3-4 inches wide and 4 feet long. Wrap their legs in a spiral, starting from the foot, from the bottom up to the lower leg. This will protect you from sand.
3) Make a pair of sandals from the wall of an old car tire if there are cars nearby. However, it is best to reinforce the sole of the shoe with a solid cloth if worn out soles cause problems.
4) When resting in the shade, take off your shoes and socks. Do this carefully, as your legs can swell and put on socks again can be very difficult.
5) Do not try to go barefoot. Sand can cause burns on your feet. In addition, barefoot movement along a hard, salt or marshy surface can lead to alkaline burns.
6) Make shoes with wooden soles to protect your feet while walking. Nail the strap to pieces of wood and tie to the leg. Protect your upper legs from the sun.

Dehydration

General Provisions
1) In desert heat, thirst alone is an inaccurate indicator of the amount of water you need. If you consume only the amount of water necessary to quench your thirst, then dehydration can still continue slowly. Drink more water whenever possible, especially with meals. If you drink water only during meals, you will have a tendency to dehydration between meals, but the normal state will be restored after eating and water; however, you will often feel tired due to loss of energy along with loss of water.
2) Forces lost as a result of dehydration are quickly restored if you drink water.
3) Losing water does not entail any irreversible complications, even if you lose up to 10 percent of your weight. At 70 kg - 7 kg can be lost due to perspiration, provided that you drink enough water afterwards to restore them. Cold water causes pain in the stomach if swallowed quickly.
4) At 25 percent fluid loss, you can survive if the air temperature is 30 degrees or cooler. At a temperature of 32 degrees and above, 15 percent fluid loss is dangerous.

Signs of fluid loss. First, thirst and general malaise appear, followed by a desire to slow down any movement and loss of appetite. With further loss of water, drowsiness prevails. Your temperature rises and by the time you lose 5 percent of your weight, you begin to feel nauseous. When you lose 6-10 percent of your body weight, the symptoms will increase in the following order: dizziness, headache, shortness of breath, trembling legs and hands, dry mouth, bluish body color, speech impairment, loss of walking ability.

How to prevent water loss. Water cannot be replaced with anything. Alcohol, salt water, gasoline only increase dehydration. In emergency cases, it is possible to drink salt water (containing half the amount of salt present in seawater) and get a clean increase in body fluid. Any liquid containing a higher percentage of unsuitable elements can only disrupt the body's cooling system. Chewing gum or stones in the mouth can be a pleasant way to delay the thirst pain, however, they cannot replace water and do not help maintain normal body temperature.