Soil the influence of human economic activity on the condition of the soil. The influence of economic activities on soil cover Man influencing the structure of the soil
II. Concept of agroecosystem
The concept of “ecosystem” was proposed by the Englishman Arthur Tansley in 1935. Knowledge of the laws of ecosystem organization allows you to use them or even change them without completely destroying the system of natural connections that have arisen.
The concept of “agroecosystem” as an agricultural version of the ecosystem appeared in the 60s. It denotes a piece of territory, an agricultural landscape corresponding to the farm. All its elements are connected not only biologically and geochemically, but also economically. Professor L. O. Karpachevsky, in the preface to the Russian translation of the American book “Agricultural Ecosystems,” emphasized the dual socio-biological nature of the agro-ecosystem, the structure of which is largely determined by man. For this reason, agroecosystems are among the so-called anthropogenic (i.e., man-made) ecosystems. However, it is still closer to a natural ecosystem than, say, to another version of anthropogenic ecosystems - urban ones.
Agroecosystems are anthropogenic (i.e., man-made) ecosystems. Man determines their structure and productivity: he plows part of the land and sows crops, creates hayfields and pastures in place of forests, and raises farm animals.
Agroecosystems are autotrophic: their main source of energy is the sun. The additional (anthropogenic) energy that people use when cultivating the soil and which is spent on the production of tractors, fertilizers, pesticides, etc. does not exceed 1% of the solar energy absorbed by the agroecosystem.
Like a natural ecosystem, an agroecosystem consists of organisms of three main trophic groups: producers, consumers and decomposers.
Agricultural ecosystems or agroecosystems (AgRES) are among the anthropogenic ecosystems that are closest to natural ones. These ensembles of species are artificial, since the composition of grown plants and bred animals is determined by a person standing at the top of the ecological pyramid and interested in obtaining the maximum amount of agricultural products: grain, vegetables, milk, meat, cotton, wool, etc. At the same time, AgRES, like natural ecosystems, are autotrophic. The main source of energy for them is the Sun. All anthropogenic energy introduced into the AgRES, spent on plowing the land, fertilizing, heating livestock buildings, is called an anthropogenic energy subsidy (AS). The AS constitutes no more than 1% of the total energy budget of the AgRES. It is AS that causes the destruction of agricultural resources and environmental pollution, which complicates the solution to the problem of providing FS. Reducing the AC value is the basis for ensuring FS.
The value of AC in an AgRES can vary over a wide range, and if we correlate it with the amount of energy contained in the finished product, then this ratio will vary from 1/15 to 30/1. In the primitive (but still preserved) gardens of the Papuans, one calorie of muscular energy produces at least 15 calories of food, but only one calorie of food is obtained by investing 20-30 calories of energy in intensive agriculture. Of course, such intensive farming makes it possible to obtain 100 centners of grain per hectare, 6000 liters of milk per cow, and more than 1 kg of daily weight gain in animals fed for meat. However, the price of these successes is too high. The destruction of agricultural resources, which has reached alarming proportions in the last 20-30 years, is contributing to the approaching environmental crisis.
The “Green Revolution” that occurred in the 60-70s of our century, when, thanks to its father, Nobel Prize laureate N. Berlaug, dwarf varieties appeared in the fields with yields 2-4 times higher than those in traditional crops, and new breeds of livestock - “biotechnological monsters”, dealt the most significant blow to the biosphere. At the same time, by the beginning of the 80s, grain production had stabilized and there was even a tendency to decrease due to the loss of natural soil fertility and a decrease in the effectiveness of fertilizers. At the same time, the planet's population continues to grow rapidly, and as a result, the amount of grain produced in the world per person began to decline.
III. Urban ecosystems
Urban ecosystems are heterotrophic; the share of solar energy fixed by urban plants or solar panels located on the roofs of houses is insignificant. The main sources of energy for city enterprises, heating and lighting of city residents' apartments are located outside the city. These are oil, gas, coal deposits, hydro and nuclear power plants.
The city consumes a huge amount of water, only a small part of which is used by humans for direct consumption. The bulk of water is spent on production processes and household needs. Personal water consumption in cities ranges from 150 to 500 liters per day, and taking into account industry, up to 1000 liters per day per citizen.
The water used by cities returns to nature in a polluted state - it is saturated with heavy metals, residues of petroleum products, complex organic substances like phenol, etc. It may contain pathogenic microorganisms. The city emits toxic gases and dust into the atmosphere, and concentrates toxic waste in landfills, which enter aquatic ecosystems with spring water flows.
Plants as part of urban ecosystems grow in parks, gardens, and lawns; their main purpose is to regulate the gas composition of the atmosphere. They release oxygen, absorb carbon dioxide and clean the atmosphere from harmful gases and dust that enter it during operation. industrial enterprises and transport. Plants also have great aesthetic and decorative value.
Animals in the city are represented not only by species common in natural ecosystems (birds live in the parks: redstart, nightingale, wagtail; mammals: voles, squirrels and representatives of other groups of animals), but also by a special group of urban animals - human companions. It consists of birds (sparrows, starlings, pigeons), rodents (rats and mice), and insects (cockroaches, bedbugs, moths). Many animals associated with humans feed on garbage in garbage dumps (jackdaws, sparrows). These are city nurses. The decomposition of organic waste is accelerated by fly larvae and other animals and microorganisms.
The main feature of the ecosystems of modern cities is that their ecological balance is disturbed. Man has to take on all the processes of regulating the flow of matter and energy. A person must regulate both the city’s consumption of energy and resources - raw materials for industry and food for people, and the amount of toxic waste entering the atmosphere, water and soil as a result of industrial and transport activities. Finally, it determines the size of these ecosystems, which in developed countries, and last years and in Russia, they are quickly “spreading” due to suburban cottage construction. Low-rise development areas reduce the area of forests and agricultural land, their "sprawling" requires the construction of new highways, which reduces the share of ecosystems capable of producing food and carrying out the oxygen cycle.
IV. Industrial pollution
In urban ecosystems, industrial pollution is the most dangerous for nature.
Chemical pollution of the atmosphere. This factor is one of the most dangerous to human life. The most common pollutants are sulfur dioxide, nitrogen oxides, carbon monoxide, chlorine, etc. In some cases, toxic compounds can be formed from two or relatively several relatively harmless substances emitted into the atmosphere under the influence of sunlight. Environmentalists count about 2,000 air pollutants.
The main sources of pollution are thermal power plants. Boiler houses, oil refineries and motor vehicles also heavily pollute the atmosphere.
Chemical pollution of water bodies. Enterprises discharge petroleum products, nitrogen compounds, phenol and many other industrial wastes into water bodies. During oil production, water bodies are polluted with saline species; oil and petroleum products also spill during transportation. In Russia, the lakes of the North of Western Siberia suffer most from oil pollution. In recent years, the danger to aquatic ecosystems from municipal wastewater has increased. In these effluents the concentration increased detergents, which are difficult for microorganisms to decompose.
As long as the amount of pollutants emitted into the atmosphere or discharged into rivers is small, ecosystems themselves are able to cope with them. With moderate pollution, the water in the river becomes almost clean after 3-10 km from the source of pollution. If there are too many pollutants, ecosystems cannot cope with them and irreversible consequences begin. Water becomes unfit for drinking and dangerous for humans. Contaminated water is also unsuitable for many industries.
Soil surface contamination with solid waste. City landfills for industrial and household waste occupy large areas. The garbage may contain toxic substances, such as mercury or other heavy metals, chemical compounds that dissolve in rain and snow waters and then end up in water bodies and groundwater. Devices containing radioactive substances can also get into the trash.
The soil surface can be contaminated with ash deposited from the smoke of coal-fired thermal power plants, enterprises producing cement, refractory bricks, etc. To prevent this contamination, special dust collectors are installed on the pipes.
Chemical contamination of groundwater. Groundwater currents transport industrial pollution over long distances, and it is not always possible to determine their source. The cause of pollution may be the leaching of toxic substances by rain and snow water from industrial landfills. Groundwater pollution also occurs during oil production modern methods when, to increase the recovery of oil reservoirs, salt water that rose to the surface along with the oil during its pumping is reinjected into the wells. Saline water enters aquifers, and the water in wells acquires a bitter taste and is not suitable for drinking.
Noise pollution. The source of noise pollution can be an industrial enterprise or transport. Heavy dump trucks and trams produce especially loud noise. Noise affects nervous system people, and therefore noise protection measures are carried out in cities and enterprises. Railway and tram lines and roads along which freight transport passes need to be moved from the central parts of cities to sparsely populated areas and green spaces created around them that absorb noise well. Airplanes should not fly over cities.
Noise is measured in decibels. The ticking of a clock is 10 dB, the whisper is 25, the noise from a busy highway is 80, the noise of an airplane during takeoff is 130 dB. Noise pain threshold - 140 dB. In residential areas during the day, noise should not exceed 50-66 dB.
Pollutants also include: contamination of the soil surface by dumps of overburden and ash, biological pollution, thermal pollution, radiation pollution, electromagnetic pollution.
V. Soil pollution
Soil is the top layer of land, formed under the influence of plants, animals, microorganisms and climate from maternal soils. rocks on which it is located. This is an important and complex component of the biosphere, closely connected with its other parts.
Under normal natural conditions, all processes occurring in the soil are in balance. But often people are to blame for disturbing the equilibrium state of the soil. As a result of the development of human economic activity, pollution occurs, changes in the composition of the soil and even its destruction.
The fertile layer of soil takes a very long time to form. At the same time, tens of millions of tons of nitrogen, potassium, and phosphorus - the main components of plant nutrition - are removed from the soil every year along with the harvest. The main factor of soil fertility - humus (humus) is contained in chernozems in an amount of less than 5% of the mass of the arable layer. On poor soils there is even less humus. In the absence of replenishment of soils with nitrogen compounds, its supply can be used up in 50-100 years. This does not happen, since farming involves the introduction of organic and inorganic (mineral) fertilizers into the soil.
Nitrogen fertilizers applied to the soil are used by plants by 40-50%. The rest (about 20%) is reduced by microorganisms to gaseous substances - N 2, N 2 O - and volatilizes in the atmosphere or is washed out of the soil. Thus, mineral nitrogen fertilizers do not have a long-term effect and therefore have to be applied annually. Unfavorable changes in the soil also occur as a result of incorrect crop rotations, i.e. annual sowing of the same crops, for example potatoes. The inclusion of legumes in crop rotation enriches the soil with nitrogen. Crover and alfalfa crops, due to the binding of N2 by symbiotic nodule bacteria, make it possible to retain up to 300 kg of nitrogen per 1 ha in the soil. Crop rotations are also necessary to combat herbivorous nematodes, which significantly reduce crop yields. For example, bulb garlic nematodes can reduce onion yields by 50%.
Soil contamination with mercury (with pesticides and waste from industrial enterprises), lead (from lead smelting and from vehicles), iron, copper, zinc, manganese, nickel, aluminum and other metals (near major centers ferrous and non-ferrous metallurgy), radioactive elements (as a result of fallout from atomic explosions or during the removal of liquid and solid waste from industrial enterprises, nuclear power plants or research institutes related to the study and use of atomic energy), persistent organic compounds used as pesticides. They accumulate in soil and water and, most importantly, are included in ecological food chains: they pass from soil and water to plants, animals, and ultimately enter the human body with food. Inept and uncontrolled use of any fertilizers and pesticides leads to disruption of the cycle of substances in the biosphere.
Anthropogenic soil changes include erosion(from Latin erosio - to corrode). Destruction of forests and natural grass cover, repeated plowing of the land without following the rules of agricultural technology lead to soil erosion - destruction and washing away of the fertile layer by water and wind. Water erosion is widespread and most destructive. It occurs on slopes and develops due to improper cultivation of the land. Together with melt and rainwater, millions of tons of soil are carried away from fields into rivers and seas every year.
Wind erosion is most pronounced in the southern steppe regions of our country. It occurs in areas with dry, bare soil and sparse vegetation cover. Excessive grazing in steppes and semi-deserts contributes to wind erosion and rapid destruction of grass cover. It takes 250-300 years to restore a 1 cm thick layer of soil under natural conditions.
Significant territories with formed soils are withdrawn from agricultural use due to the open-pit mining method for minerals located at shallow depths.
VI. Anthropogenic impact on forests, forest management
In the development of anthropogenic impact on the forests of the European North of Russia, two main periods can be distinguished: before the start of intensive industrial development of the forest resources of the North, focused on the needs of other regions and exports, and after. Of course, the time boundary between these periods is quite vague, and changes from the southwest to the northeast (from regions that are more populated and close to large economic centers to less populated and more remote). In certain parts of the territory under consideration, intensive industrial development of forest resources began already in the 17th - 18th centuries (for example, in the region of Staraya Russa in connection with the active development of salt production or in the middle and southern Urals in connection with the development of charcoal metallurgy). However, in most of the territory under consideration, any intensive industrial development of forest resources begins in the middle of the 19th century and is associated with the beginning of rapid growth in the export of forest materials from northern ports to European countries.
Each of these periods was characterized by its own characteristics of the impact of human economic activity on taiga nature. It cannot be said unequivocally that the level of human impact on the natural ecosystems of the North in the first period, before the start of intensive forest exploitation, was negligible. Already in the very initial period of human settlement of the modern taiga territory, it was at least a significant additional source of forest fires - and in this way has already made a significant contribution to the formation of taiga ecosystems. Subsequently, a significant role in the formation of taiga landscapes was played by slash-and-burn agriculture and the clearing of hay lands in the floodplains of taiga rivers, logging for local economic needs, hunting and fishing and many other types of economic activities associated with the subsistence economy of northern villages and cities. Many forms and elements of the economy that were formed during this first period of human economic development of the territory of the North were preserved during most of the next - industrial - period. Thus, slash-and-burn agriculture existed in the North until the 30s. twentieth century and finally ceased mainly due to collectivization and the extermination of individual peasants. The use of small hayfields along the floodplains of small taiga rivers and streams continues in some places at the present time, although the vast majority of such hayfields were also gradually abandoned, starting in the 20s. The system of hunting huts and winter huts exists and is partially renewed in some places to this day, although it no longer has the same density and former importance and is not so often used by the local population. Obvious traces of “pre-industrial” human economic activity - abandoned and overgrown areas of clearing or small forest hayfields, the remains of old hunting huts, and sometimes even small settlements - can now be found in places in the very center of the now wild and completely uninhabited taiga territories.
Despite the fact that human economic activity in the first period - before the start of intensive forest exploitation - was a very important factor influencing the structure and dynamics of taiga territories, in this work all this activity is considered as a historical factor in the formation of the taiga, and not as an anthropogenic disturbance (see . chapter "Background anthropogenic influences"). It goes without saying that the anthropogenic infrastructure created during that period and which has existed to this day (settlements, transport routes, industrial centers) was excluded from potential intact forest areas.
A significantly greater impact on the natural ecosystems of the North was associated with the subsequent period of development of economic activity - with the intensive industrial development of forest resources of the taiga.
Used Books
1. www.omsk.edu.ru/schools/sch004/ecolog/lit.htm.
2. Garin V.M., Klenova I.A., Kolesnikov V.I. Ecology for technical universities. Rostov-on-Don, Phoenix Publishing House, 2001.
3. Stepanovskikh A.S. General ecology: Textbook for universities - M: UNITY-DANA, 2001.
Plan
Introduction
2. Human influence on the soil
3. Soil erosion
3.1 Causes and types of erosion
3.2 Soil erosion control
4. Paths of contaminants entering the soil and classification of soil contaminants
5. Soil contamination with pesticides
6. Soil aridization
7. Land degradation
8. Protection of land resources
Conclusion
Bibliography
Introduction
Currently, the problem of interaction between human society and nature has become particularly acute. It becomes indisputable that solving the problem of preserving the quality of human life is unthinkable without a certain understanding of modern environmental problems: preservation of the evolution of living things, hereditary substances (gene pool of flora and fauna), preservation of the purity and productivity of natural environments (atmosphere, hydrosphere, soils, forests, etc.), environmental regulation of anthropogenic pressure on natural ecosystems within their buffer capacity, preservation of ozone layer, trophic chains in nature, circulation of substances and others.
The Earth's soil cover is the most important component of the Earth's biosphere. It is the soil shell that determines many of the processes occurring in the biosphere.
The main reasons for the decrease in the area of farmland are manifestations of soil erosion, insufficiently thought-out land allocation for non-agricultural needs, flooding, flooding and swamping, overgrowth with forests and shrubs, desertification and alienation for industrial and urban construction.
The most important importance of soils is the accumulation of organic matter, various chemical elements, as well as energy. Soil cover functions as a biological absorber, destroyer and neutralizer of various pollutants. If this link of the biosphere is destroyed, then the existing functioning of the biosphere will be irreversibly disrupted. That is why it is extremely important to study the global biochemical significance of the soil cover, its current state and changes under the influence of anthropogenic activities.
1. Soil: meaning and structure
An important stage in the development of the biosphere was the emergence of such a part as the soil cover. With the formation of a sufficiently developed soil cover, the biosphere becomes an integral, complete system, all parts of which are closely interconnected and dependent on each other.
Soil cover is the most important natural formation. Its role in the life of society is determined by the fact that soil is the main source of food, providing 95-97% of food resources for the planet's population. The world's land area is 129 million km 2 or 86.5% of the land area. Arable land and perennial plantings as part of agricultural land occupy about 15 million km 2 (10% of the land), hayfields and pastures - 37.4 million km 2 (25% of the land). The total arable suitability of land is estimated by different researchers in different ways: from 25 to 32 million km 2.
Ideas about soil as an independent natural body with special properties appeared only at the end of the 19th century, thanks to V.V. Dokuchaev, the founder of modern soil science. He created the doctrine of natural zones, soil zones, and soil formation factors.
Soil is a special natural formation that has a number of properties inherent in living and inanimate nature. Soil is the environment where most of the elements of the biosphere interact: water, air, living organisms. Soil can be defined as the product of weathering, reorganization and formation of the upper layers of the earth's crust under the influence of living organisms, the atmosphere and metabolic processes. The soil consists of several horizons (layers with the same characteristics), resulting from the complex interaction of parent rocks, climate, plant and animal organisms (especially bacteria), and terrain. All soils are characterized by a decrease in the content of organic matter and living organisms from the upper soil horizons to the lower ones.
The Al horizon is dark-colored, contains humus, is enriched with minerals and is of greatest importance for biogenic processes.
Horizon A 2 is an eluvial layer, usually ash-colored, light gray or yellowish-gray.
Horizon B is an eluvial layer, usually dense, brown or brown in color, enriched with colloidal dispersed minerals.
Horizon C is the parent rock modified by soil-forming processes.
Horizon D – source rock.
The surface horizon consists of the remains of vegetation that form the basis of humus, the excess or deficiency of which determines the fertility of the soil. Humus is an organic substance that is most resistant to decomposition and therefore persists after the main decomposition process has been completed. Gradually, humus also mineralizes into inorganic matter. Mixing humus with the soil gives it structure. The layer enriched with humus is called arable, and the underlying layer is called subarable. The main functions of humus come down to a series of complex metabolic processes that involve not only nitrogen, oxygen, carbon and water, but also various mineral salts present in the soil. Under the humus horizon there is a subsoil layer corresponding to the leached part of the soil and a horizon corresponding to the parent rock.
Soil structure is the shape and size of the lumps into which it breaks down. The best structure is finely lumpy. Inside the lumps, conditions are created for the activity of humifying microorganisms that form humus, and between the lumps - for microorganisms that decompose humus into mineral compounds accessible to plants.
Soil consists of three phases: solid, liquid and gas. The solid phase is dominated by mineral formations and various organic substances, including humus or humus, as well as soil colloids of organic, mineral or organomineral origin. The liquid phase of the soil, or soil solution, consists of water with organic and mineral compounds dissolved in it, as well as gases. The gas phase of the soil is “soil air,” which includes gases that fill water-free pores.
An important component of the soil that contributes to changes in its physicochemical properties is its biomass, which includes, in addition to microorganisms (bacteria, algae, fungi, unicellular organisms), also worms and arthropods.
From the above it follows that the soil includes mineral particles, detritus, and many living organisms, i.e., the soil is a complex ecosystem that ensures the growth of plants. Soils are a slowly renewable resource. Soil formation processes occur very slowly, at a rate of 0.5 to 2 cm per 100 years. The soil thickness is small: from 30 cm in the tundra to 160 cm in western chernozems. One of the features of the soil - natural fertility - is formed over a very long time, and the destruction of fertility occurs in just 5-10 years. From the above it follows that the soil is less mobile compared to other abiotic components of the biosphere.
soil erosion pollution pesticide
Human influence on soil
Human economic activity is currently becoming a dominant factor in the destruction of soils, reducing and increasing their fertility. Under human influence, the parameters and factors of soil formation change - reliefs, microclimate, reservoirs are created, and land reclamation is carried out.
The main property of soil is fertility. It is related to soil quality. There are several processes involved in the destruction of soils and the reduction of their fertility.
A special place among soils is occupied by arable land, that is, land that provides human nutrition. According to scientists and experts, at least 0.1 hectares of soil should be cultivated to feed one person. The growth in the number of people on Earth is directly related to the area of arable land, which is steadily declining. Thus, in the Russian Federation over the past 27 years, the area of agricultural land has decreased by 12.9 million hectares, of which arable land - by 2.3 million hectares, hayfields - by 10.6 million hectares. The reasons for this are the disturbance and degradation of soil cover, the allocation of land for the development of cities, towns and industrial enterprises.
Over large areas, soil productivity is declining due to a decrease in humus content, the reserves of which have decreased by 25-30% in the Russian Federation over the past 20 years, and annual losses amount to 81.4 million tons. The land today can feed 15 billion people. Careful and competent handling of land has become the most pressing problem today.
Anthropogenic impact on soil is divided into several types:
1) erosion (wind and water);
2) pollution;
3) desertification;
4) alienation of land for industrial and municipal construction, as well as secondary salinization and waterlogging.
The agricultural development of Russia is 13%, 2/3 of this territory is arable land (131.7 million hectares), but this area is decreasing from year to year. Every year, more than 1 million hectares are lost from agricultural use as a result of erosion and 100 thousand hectares are “eaten up” by ravines. Every year, Russian soils lose more than 0.5 tons of humus per 1 hectare. Of the 5.9 million hectares of irrigated land, more than half of these soils are secondary saline and produce extremely low yields. Every fourth hectare of arable land has acidic soils due to acid rain and the use of fertilizers, which also reduces yields. The area of arable land is decreasing as a result of urban sprawl and the construction of roads and industrial facilities.
Throughout history, the impact of human society on soil cover has continuously increased. In distant times, countless herds cleared away the vegetation and trampled the turf on a vast area of arid landscapes. Deflation (destruction of soils by wind) completed the destruction of soils. More recently, as a result of non-drainage irrigation, tens of millions of hectares of fertile soils have turned into saline lands and salt deserts. In the 20th century large areas of highly fertile floodplain soils were flooded or swamped as a result of the construction of dams and reservoirs on large rivers. However, no matter how great the phenomena of soil destruction are, this is only a small part of the results of the impact of human society on the soil cover of the Earth. The main result of human impact on the soil is a gradual change in the process of soil formation, an increasingly deeper regulation of the processes of the cycle of chemical elements and the transformation of energy in the soil.
One of the most important factors of soil formation - the vegetation of the world's land - has undergone profound changes. Behind historical time The forest area has more than halved. Ensuring the development of plants useful to him, man replaced natural biocenoses with artificial ones on a significant part of the land. The biomass of cultivated plants (unlike natural vegetation) does not completely enter the cycle of substances in a given landscape. A significant part of the cultivated vegetation (up to 80%) is removed from its place of growth. This leads to depletion of soil reserves of humus, nitrogen, phosphorus, potassium, microelements and, ultimately, to a decrease in soil fertility.
In ancient times, due to an excess of land in relation to a small population, this problem was solved by leaving the cultivated area for a long time after harvesting one or several crops. Over time, the biogeochemical balance in the soil was restored and the area could be cultivated again.
Slash-and-burn was used in the forest belt a farming system in which the forest was burned, and the liberated area, enriched with the ash elements of the burned vegetation, was sown. After depletion, the cultivated area was abandoned and a new one was burned. The harvest with this type of farming was ensured by the supply of mineral nutrition elements with ash obtained by burning woody vegetation on site. The large labor costs for clearing were paid off by very high yields. The cleared area was used for 1–3 years on sandy soils and up to 5–8 years on loamy soils, after which it was left to be overgrown with forest or used for some time as hayfield or pasture. If after this such an area ceased to be subject to any human influence (cutting, grazing), then within 40–80 years (in the center and south of the forest belt) the humus horizon in it was restored. To restore soils in the northern forest zone, a two to three times longer period of time was required.
The impact of the slash-and-burn system led to soil exposure, increased surface runoff and soil erosion, leveling of microrelief, and depletion of soil fauna. Although the area of cultivated areas was relatively small, and the cycle lasted a long time, over hundreds and thousands of years, vast areas were deeply transformed by slashing. It is known, for example, that in Finland in the 18th–19th centuries. (i.e. in 200 years) 85% of the territory passed through the cutting.
In the south and in the center of the forest zone, the consequences of the slash system were especially acute on sandy soils, where indigenous forests were replaced by specific forests dominated by Scots pine. This led to a retreat to the south of the northern borders of the ranges of broad-leaved tree species (elm, linden, oak, etc.). In the north of the forest zone, the development of domestic reindeer husbandry, accompanied by increased burning of forests, led to the development of a tundra zone of forest-tundra or northern taiga, which, judging by the finds of large trees or their stumps, reached the shores of the Arctic Ocean back in the 18th–19th centuries.
Thus, in the forest belt, agriculture has led to the most profound changes in living cover and the landscape as a whole. Agriculture was apparently the leading factor in the widespread distribution in the forest belt of Eastern Europe podzolic soils. Perhaps this powerful factor of anthropogenic transformation of natural ecosystems had a certain impact on the climate.
In steppe conditions, the most ancient farming systems were fallow and fallow. Under the fallow system, the used plots of land were left for a long time after depletion, while under the fallow system, for a shorter period. Gradually, the amount of free land decreased, the fallow period (break between crops) was increasingly shortened and, in the end, reached one year. This is how the fallow farming system with two- or three-field crop rotation arose. However, such intensive exploitation of the soil without the application of fertilizers and with low agricultural technology contributed to a gradual decrease in yield and product quality.
Vital necessity has confronted human society with the task of restoring soil resources. Since the middle of the last century, industrial production of mineral fertilizers began, the introduction of which compensated for plant nutrients lost with the harvest.
Population growth and limited areas suitable for agriculture have brought to the fore the problem of soil reclamation (improvement). Reclamation is aimed, first of all, at optimizing the water regime. Areas of excessive moisture and waterlogging are drained, and artificial irrigation is used in arid areas. In addition, soil salinization is being combated, acidic soils are limed, solonetzes are gypsumed, and areas of mine workings, quarries, and dumps are restored and reclaimed. Reclamation also extends to high-quality soils, raising their fertility even higher.
As a result of human activity, completely new types of soils have arisen. For example, as a result of thousand-year irrigation in Egypt, India, states Central Asia powerful artificial alluvial soils with a high supply of humus, nitrogen, phosphorus, potassium and microelements have been created. On the vast territory of the loess plateau of China, the labor of many generations created special anthropogenic soils - heilutu . In some countries, liming of acidic soils was carried out for more than a hundred years, which were gradually transformed into neutral ones. The soils of the vineyards on the southern coast of Crimea, used for more than two thousand years, have become a special type of cultivated soil. The seas were reclaimed and the changed coasts of Holland were turned into fertile lands.
Work to prevent processes that destroy soil cover has gained wide scope: forest protection plantations are being created, artificial reservoirs and irrigation systems are being built.
Structure of the planet's land fund.
According to V.P. Maksakovsky, the total area of the land fund of the entire planet is 134 million km 2 (this is the area of the entire landmass with the exception of the area of Antarctica and Greenland). The land fund has the following structure:
11% (14.5 million km 2) – cultivated lands (arable lands, gardens, plantations, sown meadows);
23% (31 million km 2) – natural meadows and pastures;
30% (40 million km 2) – forests and shrubs;
2% (4.5 million km 2) – settlements, industry, transport routes;
34% (44 million km 2) are unproductive and unproductive lands (tundra and forest-tundra, deserts, glaciers, swamps, ravines, badlands and land reservoirs).
Cultivated lands provide 88% of the food needed by humans. Meadows and pastures provide 10% of food consumed by humans.
Cultivated (primarily arable) lands are mainly concentrated in forest, forest-steppe and steppe regions of our planet.
In the first half of the 20th century. half of all cultivated lands were chernozems of steppes and forest-steppes, dark prairie soils, gray and brown forest soils, since it is most convenient and productive to cultivate these soils; in our time, these soils are plowed in less than half of the territory occupied by them, however, a further increase in the plowing of these land growth is constrained by a number of reasons. Firstly, the areas of these soils are heavily populated, industry is concentrated in them, and the territory is crossed by a dense network of transport highways. Secondly, further plowing of meadows, the rare preserved forest areas and artificial plantings, parks and other recreational facilities are environmentally dangerous.
Therefore, it is necessary to search for reserves in the distribution areas of other soil groups. The prospects for expanding arable land in the world were studied by soil scientists different countries. According to one of these studies, conducted by Russian scientists taking into account environmental conditions, an increase in agriculture is environmentally permissible due to the plowing of 8.6 million km 2 of pastures and 3.6 million km 2 of forests, while the plowing of forest areas is expected mainly during humid tropics and partly in taiga forests, and pastures - in the territory of seasonally humid tropics and subtropics, as well as in the humid tropics, semi-deserts and deserts. According to the forecast of these scientists, the largest amount of arable land in the future should be concentrated in the tropical zone, in second place will be the lands of the subtropical zone, while the soils of the subboreal zone, traditionally considered the main basis for agriculture (chernozems, chestnut, gray and brown forest, dark prairie soils) ) will take third place.
The uneven use of different types of soil in agriculture is illustrated by the picture of the agricultural use of the soil cover of the continents. As of the 70s, the soil cover of Western Europe was plowed by 30%, Africa - by 14%, on the vast surface of North and South America, arable land accounted for only 3.5% of this territory, Australia and Oceania were plowed a little more than by 4%.
The main problem of the world land fund is the degradation of agricultural land. Such degradation is understood as depletion of soil fertility, soil erosion, soil pollution, reduction in the biological productivity of natural pastures, salinization and waterlogging of irrigated areas, alienation of land for the needs of housing, industrial and transport construction.
According to some estimates, humanity has already lost 2 billion hectares of once productive land. Just because of erosion, which is widespread not only in backward but also in developed countries, 6–7 million hectares are lost from agricultural production every year. Approximately half of the world's irrigated land is salinized and swamped, which also leads to an annual loss of 200–300 thousand hectares of land
Soil destruction as a result of human activity.
The natural environment around us is characterized by the close connection of all its components, carried out thanks to the cyclic processes of metabolism and energy. The Earth's soil cover (pedosphere) is inextricably linked by these processes to other components of the biosphere. Reckless anthropogenic impact on individual natural components inevitably affects the condition of the soil cover. Well-known examples of unforeseen consequences of human economic activity are soil destruction as a result of changes in the water regime after deforestation, swamping of fertile floodplain lands due to rising groundwater levels after the construction of large hydroelectric power stations, etc. A serious problem is created by anthropogenic soil pollution. An uncontrollably growing amount of industrial and household waste emissions into the environment in the second half of the 20th century. has reached dangerous levels. Chemical compounds that pollute natural waters, air and soil enter plant and animal organisms through trophic chains, thereby causing a consistent increase in the concentration of toxicants in them. Protecting the biosphere from pollution and more economical and rational use of natural resources is a global task of our time, on the successful development of which the future of humanity depends. In this regard, the protection of soil cover, which absorbs most of the technogenic pollutants, partially fixes them in the soil mass, partially transforms them and includes them in migration flows, is of particular importance.
The problem of increasing environmental pollution has long acquired global significance. In 1972, a special UN conference on the environment was held in Stockholm, at which a program was developed that included recommendations for organizing a global environmental monitoring (control) system.
The soil must be protected from the influence of processes that destroy its valuable properties - structure, soil humus content, microbial population, and at the same time from the entry and accumulation of harmful and toxic substances.
Soil erosion.
If the natural vegetation cover is disturbed by wind and precipitation, destruction of the upper soil horizons may occur. This phenomenon is called soil erosion. When erosion occurs, soil loses small particles and changes its chemical composition. The most important chemical elements - humus, nitrogen, phosphorus, etc. - are removed from eroded soils; the content of these elements in eroded soils can decrease several times. Erosion can be caused by several reasons.
Wind erosion is caused by the movement of loose soil cover by the wind. The amount of soil blown out in some cases reaches very large sizes– 120–124 t/ha. Wind erosion develops mainly in areas with destroyed vegetation and insufficient atmospheric moisture.
As a result of partial dispersal, the soil loses tens of tons of humus and a significant amount of plant nutrients per hectare, which causes a noticeable decrease in yield. Every year, millions of hectares of land are abandoned due to wind erosion in many countries in Asia, Africa, Central and South America.
Soil movement depends on wind speed, the mechanical composition of the soil and its structure, the nature of vegetation and some other factors. The blowing of soils of light mechanical composition begins with a relatively weak wind (velocity 3–4 m/s). Heavy loamy soils are blown by the wind at a speed of about 6 m/s or more. Structured soils are more resistant to erosion than pulverized soils. Soil that contains more than 60% of aggregates larger than 1 mm in the upper horizon is considered erosion-resistant.
To protect soils from wind erosion, obstacles are created for moving air masses in the form of forest strips and scenes of shrubs and tall plants.
One of the global consequences of erosion processes that occurred both in very ancient times and in our time is the formation of anthropogenic deserts. These include the deserts and semi-deserts of Central and Western Asia and North Africa, which most likely owed their formation to the pastoral tribes that once inhabited these territories. What could not be eaten by countless herds of sheep, camels, and horses was cut down and burned by herders. The soil, unprotected after the destruction of vegetation, was subject to desertification. In very close time, literally before the eyes of several generations, a similar process of desertification as a result of ill-conceived sheep farming engulfed many areas of Australia.
By the end of the 1980s, the total area of anthropogenic deserts exceeded 9 million km 2, and this is almost equal to the territory of the United States or China and accounts for 6.7% of the total land fund of the planet. The process of anthropogenic desertification continues today. Another 30 to 40 million km2 within more than 60 countries are under the threat of desertification. The problem of desertification is considered a global problem for humanity.
The main causes of anthropogenic desertification are overgrazing of livestock, deforestation, as well as excessive and improper exploitation of cultivated lands (monoculture, plowing virgin lands, cultivating slopes).
It is possible to stop the desertification process, and such attempts are being made, primarily within the UN. Back in 1997, the UN International Conference in Nairobi adopted a plan to combat desertification, which primarily concerned developing countries and included 28 recommendations, the implementation of which, according to experts, could at least prevent the expansion of this dangerous process. However, it was only partially possible to implement it - for various reasons and, first of all, due to an acute lack of funds. It was assumed that to implement this plan, $90 billion would be required (4.5 billion over 20 years), but it was never possible to fully find it, so the duration of this project was extended until 2015. And the population in arid and semi-arid regions of the world, according to UN estimates, is now more than 1.2 billion people.
Water erosion is the destruction of soil cover that is not secured by vegetation under the influence of flowing water. Atmospheric precipitation is accompanied by planar washout of small particles from the soil surface, and heavy rains cause severe destruction of the entire soil thickness with the formation of gullies and ravines.
This type of erosion occurs when vegetation is destroyed. It is known that herbaceous vegetation retains up to 15–20% of precipitation, and tree crowns retain even more. A particularly important role is played by forest litter, which completely neutralizes the impact force of raindrops and sharply reduces the speed of flowing water. Deforestation and destruction of forest litter increases surface runoff by 2–3 times. Increased surface runoff entails vigorous washing away of the upper part of the soil, which is richest in humus and nutrients, and contributes to the vigorous formation of ravines. Favorable conditions for water erosion are created by the plowing of vast steppes and prairies and improper soil cultivation.
Soil loss (planar erosion) is enhanced by the phenomenon of linear erosion - erosion of soils and soil-forming rocks as a result of the growth of ravines. In some areas, the ravine network is so developed that it occupies most of the territory. The formation of ravines completely destroys the soil, intensifies the processes of surface erosion and dismembers arable areas.
The mass of washed away soil in agricultural areas ranges from 9 t/ha to tens of tons per hectare. The amount of organic substances washed away throughout the year from all the land on our planet is an impressive figure - about 720 million tons.
Preventive measures for water erosion are the preservation of forest plantations on steep slopes, proper plowing (with furrows directed across the slopes), regulation of grazing, and strengthening the soil structure through rational agricultural practices. To combat the consequences of water erosion, they use the creation of forest shelterbelts, the construction of various engineering structures to retain surface runoff - dams, dams in ravines, water-retaining shafts and ditches.
Erosion is one of the most intense processes of soil destruction. The most negative side Soil erosion is not the impact on the loss of a given year's crop, but the destruction of the structure of the soil profile and the loss of its important components, the restoration of which takes hundreds of years.
Soil salinization.
In areas with insufficient atmospheric moisture, agricultural yields are limited by the insufficient amount of moisture entering the soil. To compensate for its deficiency, artificial irrigation has been used since ancient times. Worldwide, soils are irrigated on an area of over 260 million hectares.
However, improper irrigation leads to the accumulation of salts in irrigated soils. The main causes of anthropogenic soil salinization are non-drainage irrigation and uncontrolled water supply. As a result, the groundwater level rises and when the groundwater level reaches a critical depth, vigorous salt accumulation begins due to the evaporation of salt-containing water rising to the soil surface. Irrigation with water with increased mineralization also contributes to this.
As a result of anthropogenic salinization, about 200–300 thousand hectares of highly valuable irrigated land are lost annually throughout the world. To protect against anthropogenic salinization, drainage devices are created, which should ensure that the groundwater level is located at a depth of at least 2.5–3 m, and canal systems with waterproofing to prevent water filtration. In case of accumulation of water-soluble salts, it is recommended to flush the soil with drainage to remove salts from the root layer of the soil. Protecting soils from soda salinity includes gypsuming soils, using mineral fertilizers containing calcium, and introducing perennial grasses into crop rotation.
To prevent the negative consequences of irrigation, constant monitoring of the water-salt regime on irrigated lands is necessary.
Reclamation of soils disturbed by industry and construction.
Human economic activity is accompanied by soil destruction. The area of soil cover is steadily decreasing due to the construction of new enterprises and cities, the construction of roads and high-voltage power lines, the flooding of agricultural land during the construction of hydroelectric power stations, and the development of the mining industry. Thus, huge quarries with dumps of mined rock, high waste heaps near mines are an integral part of the landscape of the areas where the mining industry operates.
Many countries are carrying out reclamation (restoration) of destroyed areas of soil cover. Reclamation is not just backfilling mine workings, but creating conditions for the rapid formation of soil cover. In the process of reclamation, soils are formed and their fertility is created. To do this, a humus layer is applied to the dump soil, but if the dumps contain toxic substances, then it is first covered with a layer of non-toxic rock (for example, loess) on which a humus layer is already applied.
In some countries, exotic architectural and landscape complexes are created on dumps and quarries. Parks are laid out on dumps and waste heaps, and artificial lakes with fish and bird colonies are built in quarries. For example, in the south of the Rhine lignite basin (FRG), dumps have been dumped since the end of the last century with the aim of creating artificial hills, later covered with forest vegetation.
Chemicalization of agriculture.
The successes of agriculture achieved as a result of the introduction of chemical advances are well known. High yields are obtained through the use of mineral fertilizers; the preservation of cultivated products is achieved with the help of pesticides - pesticides created to combat weeds and pests. However, all these chemicals must be used very carefully and the quantitative standards for the added chemical elements developed by scientists must be strictly observed.
1. Application of mineral fertilizers
When wild plants die, they return the chemical elements they absorbed to the soil, thereby maintaining the biological cycle of substances. But this does not happen with cultivated vegetation. The mass of cultivated vegetation is only partially returned to the soil (about one third). Man artificially disrupts the balanced biological cycle by removing the harvest, and with it the chemical elements absorbed from the soil. First of all, this applies to the “fertility triad”: nitrogen, phosphorus and potassium. But humanity has found a way out of this situation: to replenish the loss of plant nutrients and increase productivity, these elements are introduced into the soil in the form of mineral fertilizers.
The problem of nitrogen fertilizers.
If the amount of nitrogen introduced into the soil exceeds the needs of plants, then excess amounts of nitrates partly enters plants, and partly is carried out by soil waters, which causes an increase in nitrates in surface waters, as well as a number of other negative consequences. With an excess of nitrogen, there is an increase in nitrates in agricultural products. When entering the human body, nitrates can be partially transformed into nitrites , which cause a serious disease (methemoglobinemia) associated with difficulty transporting oxygen through the circulatory system.
The use of nitrogen fertilizers should be carried out with strict consideration of the need for nitrogen for the crop being grown, the dynamics of its consumption by the crop and the composition of the soil. We need a well-thought-out system for protecting soils from excess amounts of nitrogen compounds. This is especially relevant due to the fact that modern cities and large livestock enterprises are sources of nitrogen pollution of soils and waters.
Techniques for using biological sources of this element are being developed. These are nitrogen-fixing communities of higher plants and microorganisms. Crops of legumes (alfalfa, clover, etc.) are accompanied by nitrogen fixation of up to 300 kg/ha.
The problem of phosphorus fertilizers.
About two-thirds of the phosphorus captured by crops from the soil is removed with the harvest. These losses are also restored by adding mineral fertilizers to the soil.
Modern intensive agriculture is accompanied by pollution of surface waters with soluble compounds of phosphorus and nitrogen, which accumulate in the final runoff basins and cause rapid growth of algae and microorganisms in these reservoirs. This phenomenon is called eutrophication reservoirs. In such reservoirs, oxygen is quickly consumed by the respiration of algae and the oxidation of their abundant residues. Soon, a situation of oxygen deficiency is created, due to which fish and other aquatic animals die, and their decomposition begins with the formation of hydrogen sulfide, ammonia and their derivatives. Eutrophication affects many lakes, including the Great Lakes of North America.
The problem of potash fertilizers.
When applying high doses of potassium fertilizers, no adverse effect was found, but due to the fact that a significant part of the fertilizers is represented by chlorides, the effect of chlorine ions is often felt, which negatively affects the condition of the soil.
The organization of soil protection with the widespread use of mineral fertilizers should be aimed at balancing the applied masses of fertilizers with the harvest, taking into account specific landscape conditions and soil composition. Fertilizer application should be as close as possible to those stages of plant development when they need a massive supply of appropriate chemical elements. The main task of protective measures should be aimed at preventing the removal of fertilizers with surface and underground water runoff and at preventing the entry of excess amounts of introduced elements into agricultural products.
The problem of pesticides (pesticides).
According to FAO, annual losses worldwide from weeds and pests account for 34% of potential production and are estimated at $75 billion. The use of pesticides preserves a significant part of the crop, so their use is quickly being introduced into agriculture, but this entails numerous negative consequences. By destroying pests, they destroy complex ecological systems and contribute to the death of many animals. Some pesticides gradually accumulate along trophic chains and, when entering the human body with food, can cause dangerous diseases. Some biocides have a stronger effect on the genetic apparatus than radiation.
Once in the soil, pesticides dissolve in soil moisture and are transported with it down the profile. The length of time pesticides remain in the soil depends on their composition. Resistant connections last up to 10 years or more.
By migrating with natural waters and carried by the wind, persistent pesticides are distributed over long distances. It is known that insignificant traces of pesticides were found in precipitation in the vast oceans, on the surface of the ice sheets of Greenland and Antarctica. In 1972, more DDT fell in atmospheric precipitation in Sweden than was produced in that country.
Protection of soils from pesticide contamination involves the creation of possibly less toxic and less persistent compounds. Techniques are being developed to reduce doses without reducing their effectiveness. It is very important to reduce aerial spraying at the expense of ground spraying, as well as the use of strictly selective treatments.
Despite the measures taken, when fields are treated with pesticides, only a small part of them reaches the target. Most of it accumulates in the soil cover and natural waters. An important task is to accelerate the decomposition of pesticides and their breakdown into non-toxic components. It has been established that many pesticides decompose under the influence of ultraviolet irradiation, some toxic compounds are destroyed as a result of hydrolysis, but pesticides are most actively decomposed by microorganisms.
Nowadays, many countries, including Russia, monitor environmental pollution with pesticides. For pesticides, standards for maximum permissible concentrations in soil have been established, which amount to hundredths and tenths of mg/kg of soil.
Industrial and household emissions into the environment.
Over the past two centuries, human production activity has increased dramatically. Various types of mineral raw materials are increasingly being used for industrial use. Now people spend 3.5 – 4.03 thousand km 3 of water per year for various needs, i.e. about 10% of the total flow of all rivers in the world. At the same time, tens of millions of tons of household, industrial and agricultural waste enter surface waters, and hundreds of millions of tons of gases and dust are released into the atmosphere. Human production activity has become a global geochemical factor.
Such intense human impact on the environment is naturally reflected on the planet’s soil cover. Man-made emissions into the atmosphere are also dangerous. Solid substances from these emissions (particles from 10 microns and larger) settle close to pollution sources, while smaller particles in gases are transported over long distances.
Pollution with sulfur compounds.
Sulfur is released when mineral fuels (coal, oil, peat) are burned. A significant amount of oxidized sulfur is released into the atmosphere during metallurgical processes, cement production, etc.
The greatest harm is caused by the intake of sulfur in the form of SO 2, sulfurous and sulfuric acid. Sulfur oxide, penetrating through the stomata of green plant organs, causes a decrease in the photosynthetic activity of plants and a decrease in their productivity. Sulfurous and sulfuric acids, falling with rainwater, affect vegetation. The presence of SO 2 in an amount of 3 mg/l causes a decrease in the pH of rainwater to 4 and the formation of “acid rain”. Fortunately, the lifetime of these compounds in the atmosphere ranges from several hours to 6 days, but during this time they can be transported with air masses tens and hundreds of kilometers from pollution sources and fall in the form of “acid rain.”
Acidic rainwater increases soil acidity, suppresses the activity of soil microflora, increases the removal of plant nutrients from the soil, pollutes water bodies, and affects woody vegetation. To some extent, the effect of acid precipitation can be neutralized by liming the soil.
Heavy metal pollution.
No less dangerous for the soil cover are pollutants that fall near the source of pollution. This is exactly how pollution with heavy metals and arsenic manifests itself, which form man-made geochemical anomalies, i.e. areas of increased concentration of metals in soil cover and vegetation.
Metallurgical enterprises annually release hundreds of thousands of tons of copper, zinc, cobalt, tens of thousands of tons of lead, mercury, and nickel onto the earth's surface. Technogenic dispersion of metals (these and others) also occurs during other production processes.
Man-made anomalies around manufacturing enterprises and industrial centers have a length from several kilometers to 30–40 km, depending on the production capacity. The content of metals in soil and vegetation decreases quite quickly from the source of pollution to the periphery. Within the anomaly, two zones can be distinguished. The first, directly adjacent to the source of pollution, is characterized by severe destruction of soil cover, destruction of vegetation and wildlife. This area has a very high concentration of metal pollutants. In the second, more extensive zone, the soils completely retain their structure, but microbiological activity in them is suppressed. In soils contaminated with heavy metals, there is a clearly expressed increase in the metal content from bottom to top of the soil profile and its highest content in the outermost part of the profile.
Main source of pollution lead – motor transport. The majority (80–90%) of emissions settle along highways on the surface of soils and vegetation. This is how roadside geochemical lead anomalies are formed with a width (depending on the intensity of vehicle traffic) from several tens of meters to 300–400 m and a height of up to 6 m.
Heavy metals, coming from the soil into plants and then into the bodies of animals and humans, have the ability to gradually accumulate. The most toxic are mercury, cadmium, lead, and arsenic; poisoning with them causes serious consequences. Zinc and copper are less toxic, but soil contamination with them suppresses microbiological activity and reduces biological productivity.
The limited distribution of metal pollutants in the biosphere is largely due to the soil. Most of the easily mobile water-soluble metal compounds entering the soil are firmly bound to organic matter and highly dispersed clay minerals. The fixation of metal pollutants in the soil is so strong that in the soils of the old metallurgical regions of the Scandinavian countries, where ore smelting stopped about 100 years ago, high contents of heavy metals and arsenic still remain. Consequently, the soil cover acts as a global geochemical screen, retaining a significant portion of polluting elements.
However, the protective capacity of soils has its limits, so protecting soils from contamination by heavy metals is an urgent task. To reduce the release of metal emissions into the atmosphere, a gradual transition of production to closed technological cycles is necessary, as well as the mandatory use of treatment facilities.
Natalia Novoselova
Literature:
Soils of the USSR. M., Mysl, 1979
Glazovskaya M.A., Gennadiev A.N. , M., Moscow State University, 1995
Dobrovolsky V.V. Geography of soils with basics of soil science. M., Vlados, 2001
Zavarzin G.A. Lectures on natural history microbiology. M., Nauka, 2003
Soil is the main source of food, providing 95–97% of the food supply for the world's population.
Soil formation has been occurring on Earth since the origin of life and depends on many factors. The duration of the soil formation process for various continents and latitudes ranges from several hundred to several thousand years.
The main property of soil is fertility. Human economic activity is currently becoming a dominant factor in the destruction of soils, reducing and increasing their fertility. The following processes contribute to this.
Aridization of land– a complex of processes of reducing the humidity of vast territories and the resulting reduction in the biological productivity of ecological systems. Under the influence of primitive agriculture, irrational use of pastures, and indiscriminate use of technology on land, soils turn into deserts.
Soil erosion– destruction of soils under the influence of wind, water, technology and irrigation. Most dangerous water erosion - washing away of soil by melt, rain and storm water. Water erosion is observed at a steepness of already 1–2°. Water erosion is facilitated by the destruction of forests and plowing on slopes.
Wind erosion is characterized by the wind carrying away the smallest parts. Wind erosion is facilitated by the destruction of vegetation in areas with insufficient moisture, strong winds, and continuous grazing.
Technical Erosion is associated with the destruction of soil under the influence of transport, earth-moving machines and machinery.
Irrigation erosion develops as a result of violation of watering rules in irrigated agriculture. Soil salinization is mainly associated with these disturbances. Currently, at least 50% of the area of irrigated land is salinized, and millions of hectares of previously fertile land have been lost.
Main soil pollutants
Unlike air and water pollution, soil pollution is only technogenic in nature. Technogenic intensification of production contributes to pollution and dehumification (destruction of the fertile soil layer - humus), secondary salinization, and soil erosion.
Soil pollutants are pesticides, used to control weeds.
The soils around large cities and large enterprises of non-ferrous and ferrous metallurgy, chemical and petrochemical industries, mechanical engineering, thermal power plants at a distance of several tens of kilometers are polluted heavy metals, petroleum products, lead and sulfur compounds and other toxic substances.
Soil pollution oil in places of its extraction, processing, transportation and distribution exceeds the background level tens of times.
Thus, the intensive development of industrial production leads to an increase in industrial waste, which, together with household waste, significantly affects the chemical composition of the soil, causing a deterioration in its quality. Severe soil contamination with heavy metals, together with zones of sulfur pollution formed during the combustion of coal, leads to changes in the composition of microelements and the emergence of technogenic deserts.
Changes in the content of microelements in the soil affect the health of herbivores and humans, lead to metabolic disorders, and cause various endemic diseases of a local nature. For example, a lack of iodine in the soil leads to thyroid disease, a lack of calcium in drinking water and food leads to joint damage, deformation, and growth retardation.
The removal of industrial and household waste to landfills leads to pollution and irrational use of land, creates real threats of significant pollution of the atmosphere, surface and ground waters, increased transportation costs and irretrievable loss of valuable materials and substances.
Cleaning the soil from harmful substances is impossible - self-purification occurs naturally over several thousand years. It is also impossible to prevent the indirect impact of soil on human health through animal meat and plants. They accumulate harmful substances that accumulate in them over time. Mechanisms for effective protection against the indirect influence of poisoned soils have not been found, since heat treatment does not remove heavy metal salts from meat, vegetables and grains.
The impact of human society on soil cover represents one aspect of the overall human influence on the environment.
Throughout history, the impact of human society on soil cover has continuously increased. In distant times, countless herds cleared away the vegetation and trampled the turf on a vast area of arid landscapes. Deflation (destruction of soils by wind) completed the destruction of soils. More recently, as a result of non-drainage irrigation, tens of millions of hectares of fertile soils have turned into saline lands and salt deserts. In the 20th century large areas of highly fertile floodplain soils were flooded or swamped as a result of the construction of dams and reservoirs on large rivers. However, no matter how great the phenomena of soil destruction are, this is only a small part of the results of the impact of human society on the soil cover of the Earth. The main result of human impact on the soil is a gradual change in the process of soil formation, an increasingly deeper regulation of the processes of the cycle of chemical elements and the transformation of energy in the soil.
One of the most important factors of soil formation - the vegetation of the world's land - has undergone profound changes. Over historical time, the forest area has more than halved. Ensuring the development of plants useful to him, man replaced natural biocenoses with artificial ones on a significant part of the land. The biomass of cultivated plants (unlike natural vegetation) does not completely enter the cycle of substances in a given landscape. A significant part of the cultivated vegetation (up to 80%) is removed from its place of growth. This leads to depletion of soil reserves of humus, nitrogen, phosphorus, potassium, microelements and, ultimately, to a decrease in soil fertility.
In ancient times, due to an excess of land in relation to a small population, this problem was solved by leaving the cultivated area for a long time after harvesting one or several crops. Over time, the biogeochemical balance in the soil was restored and the area could be cultivated again.
In the forest belt, a slash-and-burn farming system was used, in which the forest was burned, and the liberated area, enriched with the ash elements of the burned vegetation, was sown.
After depletion, the cultivated area was abandoned and a new one was burned. The harvest with this type of farming was ensured by the supply of mineral nutrition elements with ash obtained by burning woody vegetation on site. The large labor costs for clearing were paid off by very high yields. The cleared area was used for 1-3 years on sandy soils and up to 5-8 years on loamy soils, after which it was left to be overgrown with forest or used for some time as hayfield or pasture. If after this such an area ceased to be subject to any human influence (cutting, grazing), then within 40-80 years (in the center and south of the forest belt) the humus horizon in it was restored. To restore soils in the northern forest zone, a two to three times longer period of time was required.
The impact of the slash-and-burn system led to soil exposure, increased surface runoff and soil erosion, leveling of microrelief, and depletion of soil fauna. Although the area of cultivated areas was relatively small, and the cycle lasted a long time, over hundreds and thousands of years, vast areas were deeply transformed by slashing. It is known, for example, that in Finland in the 18th and 19th centuries. (i.e. in 200 years) 85% of the territory passed through the cutting.
In the south and in the center of the forest zone, the consequences of the slash system were especially acute on sandy soils, where indigenous forests were replaced by specific forests dominated by Scots pine. This led to a retreat to the south of the northern borders of the ranges of broad-leaved tree species (elm, linden, oak, etc.). In the north of the forest zone, the development of domestic reindeer husbandry, accompanied by increased burning of forests, led to the development of a tundra zone of forest-tundra or northern taiga, which, judging by the finds of large trees or their stumps, reached the shores of the Arctic Ocean back in the 18th-19th centuries.
Thus, in the forest belt, agriculture has led to the most profound changes in living cover and the landscape as a whole. Agriculture was apparently the leading factor in the widespread distribution of podzolic soils in the forest belt of Eastern Europe. Perhaps this powerful factor of anthropogenic transformation of natural ecosystems had a certain impact on the climate.
In steppe conditions, the most ancient farming systems were fallow and fallow. Under the fallow system, the used plots of land were left for a long time after depletion, while under the fallow system, for a shorter period. Gradually, the amount of free land decreased, the fallow period (break between crops) was increasingly shortened and, in the end, reached one year. This is how the fallow farming system with two- or three-field crop rotation arose. However, such intensive exploitation of the soil without the application of fertilizers and with low agricultural technology contributed to a gradual decrease in yield and product quality.
Vital necessity has confronted human society with the task of restoring soil resources. Since the middle of the last century, industrial production of mineral fertilizers began, the introduction of which compensated for plant nutrients lost with the harvest.
Population growth and limited areas suitable for agriculture have brought to the fore the problem of soil reclamation (improvement). Reclamation is aimed, first of all, at optimizing the water regime. Areas of excessive moisture and waterlogging are drained, and artificial irrigation is used in arid areas. In addition, soil salinization is being combated, acidic soils are limed, solonetzes are gypsumed, and areas of mine workings, quarries, and dumps are restored and reclaimed. Reclamation also extends to high-quality soils, raising their fertility even higher.
As a result of human activity, completely new types of soils have arisen. For example, as a result of thousands of years of irrigation in Egypt, India, and the countries of Central Asia, powerful artificial alluvial soils with a high supply of humus, nitrogen, phosphorus, potassium and microelements have been created. On the vast territory of the loess plateau of China, through the labor of many generations, special anthropogenic soils - heilutu - have been created. In some countries, liming of acidic soils was carried out for more than a hundred years, which were gradually transformed into neutral ones. The soils of the vineyards on the southern coast of Crimea, used for more than two thousand years, have become a special type of cultivated soil. The seas were reclaimed and the changed coasts of Holland were turned into fertile lands.
Work to prevent processes that destroy soil cover has gained wide scope: forest protection plantations are being created, artificial reservoirs and irrigation systems are being built.