In the biosphere, as in every ecosystem, there is a constant cycle of carbon, nitrogen, hydrogen, oxygen, phosphorus, sulfur and other substances.

Carbon dioxide is absorbed by plants and producers and, through the process of photosynthesis, is converted into carbohydrates, proteins, lipids and other organic compounds. These substances are used in food by animal consumers.

At the same time, the reverse process occurs in nature. All living organisms breathe, releasing CO 2, which enters the atmosphere. Dead plant and animal remains and animal excrement are decomposed by decomposer microorganisms. CO 2 is released into the atmosphere. Some carbon accumulates in the soil in the form of organic compounds.

During the carbon cycle in the biosphere, energy resources are formed: oil, coal, combustible gases, peat and wood.

When plants and animals decompose, nitrogen is released in the form of ammonia. Nitrifying bacteria convert ammonia into salts of nitrous and nitric acids, which are absorbed by plants. Some nitrogen-fixing bacteria are capable of assimilating atmospheric nitrogen. This closes the nitrogen cycle in nature.

As a result of the cycle of substances in the biosphere, a continuous biogenic migration of elements occurs: the chemical elements necessary for the life of plants and animals pass from the environment into the body; when the organisms decompose, these elements again return to the environment, from where they enter the body.

The basis of the biosphere is the cycle of organic matter, which takes place with the participation of all organisms inhabiting the biosphere, and is called the biotic cycle.

The laws of the biotic cycle contain the basis for the long-term existence and development of life on Earth.

Man is an element of the biosphere and, as an integral part of the Earth’s biomass, throughout all evolution he has been and is directly dependent on the surrounding nature.

With the development of higher nervous activity, man himself becomes a powerful environmental factor (anthropogenic factor) in further evolution on Earth.

Human influence on nature is twofold - positive and negative. Human activity often leads to disruption of natural laws.

The share of the mass of humanity in the biosphere is small, but its activity is enormous; at present it has become a force changing processes in the biosphere.

V.I. Vernadsky claims that the biosphere will naturally transform into the noosphere (from the gr. “noos” - mind” + gr. “sphere” - ball).

According to V.I. Vernadsky, the noosphere is a biosphere transformed by human labor and changed by scientific thought.

Currently, a period has come when a person must plan his economic activities so that it does not violate the established patterns in the gigantic ecosystem that is the biosphere and does not contribute to the reduction of biomass.

Cycle of nutrients. In addition to the basic elements considered, a number of others take part in the metabolic process of a living organism. Some of them are present in significant quantities and belong to the category of macronutrients, such as sodium, potassium, calcium, magnesium. Some elements are contained in very small concentrations (microelements), but they are also vital (iron, zinc, copper, manganese, etc.).[...]

Cycles of basic nutrients and elements. Let's consider the cycles of the most significant substances and elements for living organisms (Fig. 3-8). The water cycle is a large geological one; and the cycles of biogenic elements (carbon, oxygen, nitrogen, phosphorus, sulfur and other biogenic elements) - to small biogeochemical.[...]

The rate of cycles of nutrients is quite high. The turnover time of atmospheric carbon is about 8 years. Each year, approximately 12% of the carbon dioxide in the air is recycled into the cycle in terrestrial ecosystems. The total cycle time for nitrogen is estimated at more than 110 years, for oxygen at 2500 years.[...]

Biotic cycle. The cycle of nutrients caused by the synthesis and decay of organic substances in the ecosystem is called the biotic cycle of substances. In addition to biogenic elements, the biotic cycle involves mineral elements that are most important for the biota and many different compounds. Therefore, the entire cyclic process of chemical transformations caused by biota, especially when it comes to the entire biosphere, is also called the biogeachemical cycle.[...]

Biotic cycle is the circulation of nutrients and other substances involved in them in ecosystems, in the biosphere between their biotic and abiotic components. The most important feature of the biosphere biotic cycle is a high degree of isolation.[...]

On the other hand, biogenic elements as components of biomass simply change molecules, which include, for example, nitrate N-protein N-waste N. They can be used repeatedly, and cycling is their characteristic feature. Unlike the energy of solar radiation, the reserves of nutrients are not constant. The process of binding some of them into living biomass reduces the amount remaining to the community. If plants and phytophages did not eventually decompose, the supply of nutrients would be exhausted and life on Earth would cease. The activity of heterotrophic organisms is a decisive factor in maintaining the cycles of nutrients and the formation of products. In Fig. 17.24 shows that the release of these elements in the form of simple inorganic compounds occurs only from the decomposer system. In reality, a certain proportion of these simple molecules (especially CO2) is also provided by the consumer system, but in this way a very small part of the biogenic elements returns to the cycle. The decisive role here belongs to the system of decomposers.[...]

The driving forces of the cycle of substances are the flows of solar energy and the activity of living matter, leading to the movement of huge masses of chemical elements, concentration and redistribution of energy accumulated during the process of photosynthesis. Thanks to photosynthesis and continuously operating cyclic cycles of nutrients, a stable organization of all ecosystems and the biosphere as a whole is created, and their normal functioning is carried out.[...]

In the absence of external flows of biogenic compounds, the biosphere can exist stably only if there is a closed cycle of substances, during which nutrients perform closed cycles, alternately moving from the inorganic part of the biosphere to the organic and so on. vice versa. This cycle is carried out by living organisms of the biosphere. It is believed that the biosphere contains about 1027 living organisms that are not correlated with each other. In the process of evolutionary development of the biosphere, the following three groups of organisms were formed, differing in their functional purpose and participation in the cycle of nutrients: producers, decomposers and consumers.[...]

Material processes in living nature, cycles of biogenic elements are associated with energy flows with stoichiometric coefficients that vary within the most diverse organisms only within one order of magnitude. Moreover, due to the high efficiency of catalysis, the energy consumption for the synthesis of new substances in organisms is much less than in the technical analogues of these processes.[...]

A very important conclusion for practice, arising from many intensive studies of the cycle of nutrients, is that an excess of fertilizers can be just as unprofitable for humans as their deficiency. If more material is introduced into a system than can be used by currently active organisms, the excess is quickly bound by soil and sediments or lost by leaching, becoming unavailable just when growth of organisms is most desirable. Many people mistakenly believe that if 1 kg of fertilizer (or pesticide) is recommended for a certain area of ​​their garden or pond, then 2 kg will bring twice as much benefit. These more-is-better proponents would do well to understand the subsidy-stress relationship illustrated in Figure 1. 3.5. Subsidies inevitably become a source of stress if not applied carefully. Excessive fertilization of ecosystems such as fish ponds is not only wasteful in terms of results achieved, but can cause unforeseen changes in the system, as well as contaminate downstream ecosystems. Since different organisms are adapted to different levels of element content, prolonged overfertilization leads to changes in the species composition of organisms, and those we need may disappear and unnecessary ones may appear. [...]

Many processes occurring in the soil are associated with the vital activity of soil microorganisms - cycles of nutrients, mineralization of animal and plant residues, enrichment of the soil with forms of nitrogen available to plants. Soil fertility is related to the activity of microorganisms. Consequently, soil microorganisms directly influence plant life, and through them, animals and humans, being one of the main parts of terrestrial ecosystems.[...]

Ponds and lakes are especially convenient for research, since over a short period of time the cycles of nutrients in them can be considered independent. Hutchinson (1957) and Pomeroy (1970) published reviews of work on the phosphorus cycle and the cycles of other vital elements.[...]

Transpiration also has its positive sides. Evaporation cools the leaves and, among other processes, promotes the cycling of nutrients. Other processes are transport of ions through the soil to the roots, transport of ions between root cells, movement within the plant, and leaching from leaves (Kozlowski, 1964, 1968). Some of these processes require metabolic energy, which can limit the rate of transport of water and salts (Fried and Broeshart, 1967). Thus, transpiration is not simply a function of exposed physical surfaces. Forests do not necessarily lose more water than grassy vegetation. The role of transpiration as an energy subsidy in humid forest conditions was discussed in Chap. 3. If the air is too humid (relative humidity approaches 100%), as happens in some tropical cloud forests, the trees are stunted and most of the vegetation consists of epiphytes, apparently due to the lack of transpiration. traction" (N. Odum, Pigeon, 1970).[...]

Energy cannot be transferred in closed cycles and reused, but matter can. - Matter (including nutrients) can pass through a community in “loops”. - The cycle of nutrients is never perfect. - Study of the Hubbard Brook Forest. ■-The input and output of nutrients is usually low compared to the amount participating in the cycle, although sulfur is an important exception to this rule (mainly due to “acid rain”), - Deforestation opens the cycle and leads to loss of nutrients.- Terrestrial biomes differ in the distribution of nutrients between dead organic matter and living tissues, - Currents and sedimentation are important■ factors affecting the flow of nutrients in aquatic ecosystems.[...]

All people consume food, being consumers of the 1st and 2nd order in food chains. They secrete products of physiological metabolism that are utilized by decomposers participating in the cycle of nutrients. Man is one of the 3 million currently known biological species on Earth.[...]

Any ecosystem can be thought of as a series of blocks through which different materials pass and in which these materials can remain for varying periods of time (Figure 10.3). In the cycles of mineral substances in an ecosystem, as a rule, three active blocks are involved: living organisms, dead organic detritus and available inorganic substances. Two additional blocks - indirectly accessible inorganic substances and precipitating organic substances - are associated with the cycles of nutrients in some peripheral parts of the general cycle (Fig. 10.3), however, the exchange between these blocks and the rest of the ecosystem is slow compared to the exchange occurring between active blocks .[...]

Carbon, nitrogen and phosphorus are important in the life of organisms. It is their compounds that are necessary for the formation of oxygen and organic matter in the process of photosynthesis. Bottom sediments play a significant role in the cycle of nutrients. In one case they are a source, in another - an accumulator of organic and mineral resources of a reservoir. Their supply from bottom sediments depends on pH, as well as on the concentration of these elements in water. With an increase in pH and a low concentration of nutrients, the supply of phosphorus, iron and other elements from bottom sediments into the water increases.[...]

An important task of studying the structure and functioning of communities (biocenoses) is to study the stability of communities and their ability to withstand adverse impacts. When studying ecosystems, it becomes possible to quantitatively analyze the cycle of matter and changes in energy flow during the transition from one nutritional level to another. This production-energy approach at the population and biocenotic levels allows us to compare various natural and human-created ecosystems. Another task of environmental science is the study of various types of connections in terrestrial and aquatic ecosystems. It is especially important to study the biosphere as a whole: determining primary production and destruction throughout the globe, the global cycle of nutrients; these problems can only be solved by the combined efforts of scientists from different countries.[...]

The periodic system in chemistry, the laws of motion of celestial bodies in astronomy, etc.) These patterns are manifested, for example, in the presence of the same species (or the same forms of growth, productivity, rates of circulation of biogenic elements, etc. ) in various places. This in turn leads to the creation of hypotheses about the reasons for such recurrence. Hypotheses can then be tested by further observations or experiments.[...]

All forms of relationships together form a mechanism of natural selection and ensure the stability of the community as a form of organization of life. Community is the minimal Form of organization of life. capable of functioning for an almost unlimited time in a certain area of ​​the territory. Only at the community level can the cycle of nutrients be carried out in a certain area of ​​the territory, without which it is impossible to ensure unlimited life expectancy with limited life resources of the territory.[...]

As a result of the life activity of organisms, two opposing and inseparable processes occur. On the one hand, living organic matter is synthesized from simple abiotic components, on the other hand, organic compounds are destroyed into simple abiotic substances. These two processes ensure the exchange of substances between the biotic and abiotic components of ecosystems and constitute the main core of the biogeochemical cycle of nutrients.[...]

Back in the seventies of the 20th century, chemist James Lovelock and microbiologist Lynn Margulis put forward a theory of complex regulation of the Earth's atmosphere by biological objects, according to which plants and microorganisms, together with the physical environment, ensure the maintenance of certain geochemical conditions on Earth that are favorable for life. This is a relatively high content of oxygen in the atmosphere and a low content of carbon dioxide, certain humidity and air temperature. A special role in this regulation belongs to microorganisms of terrestrial and aquatic ecosystems, ensuring the circulation of nutrients. The regulatory role of microorganisms in the World Ocean in maintaining a certain amount of carbon dioxide in the Earth’s atmosphere and in preventing the greenhouse effect is well known.[...]

The reproductive potential of living matter is enormous. If dying were stopped for some time and reproduction and growth were not limited in any way, then a “biological explosion” on a cosmic scale would occur: in less than two days, the biomass of microorganisms would be several times greater than the mass of the globe. This does not happen due to substance limitation; The biomass of the ecosphere is maintained at a relatively constant level for hundreds of millions of years. With constant pumping of a flow of solar energy, living nature overcomes the limitation of nutrient material by organizing cycles of nutrients. This ensures high productivity of many ecosystems (see Table 2. 1).[...]

Anthropogenic pressure on nature is not limited to pollution. Equally important is the exploitation of natural resources and the resulting disruptions to ecological systems. Environmental management is very expensive - much more than the usual monetary value of the resources consumed. First of all, because in the economy of nature, as well as in the human economy, there are no free resources: space, energy, sunlight, water, oxygen, no matter how inexhaustible their reserves on Earth may seem, are strictly paid for by any system that consumes them, paid for completeness and speed of return, turnover of values, closedness of material cycles - nutrients, energy, food, money, health... Because in relation to all this, the law of limited resources applies.

The activity of living organisms in the biosphere is accompanied by the extraction of large quantities of minerals from the environment. After the death of organisms, their constituent chemical elements are returned to the environment. This is how the biogenic (with the participation of living organisms) cycle of substances in nature arises, i.e., the circulation of substances between the lithosphere, atmosphere, hydrosphere and living organisms. The cycle of substances is understood as a repeating process of transformation and movement of substances in nature, which has a more or less pronounced cyclic nature.

All living organisms take part in the cycle of substances, absorbing some substances from the external environment and releasing others into it. Thus, plants consume carbon dioxide, water and mineral salts from the external environment and release oxygen into it. Animals inhale the oxygen released by plants, and by eating them, they assimilate organic substances synthesized from water and carbon dioxide and release carbon dioxide, water and substances from the undigested part of the food. When bacteria and fungi decompose dead plants and animals, additional amounts of carbon dioxide are formed, and organic substances are converted into minerals, which enter the soil and are again absorbed by plants. Thus, atoms of the basic chemical elements constantly migrate from one organism to another, from the soil, atmosphere and hydrosphere - into living organisms, and from them - into the environment, thus replenishing the inanimate matter of the biosphere. These processes are repeated an infinite number of times. So, for example, all atmospheric oxygen passes through living matter in 2 thousand years, all carbon dioxide - in 200-300 years.

The continuous circulation of chemical elements in the biosphere along more or less closed paths is called the biogeochemical cycle. The need for such circulation is explained by the limited supply of them on the planet. To ensure the infinity of life, chemical elements must move in a circle. The cycle of each chemical element is part of the general grand cycle of substances on Earth, that is, all cycles are closely interconnected.

The cycle of substances, like all processes occurring in nature, requires a constant flow of energy. The basis of the biogenic cycle that ensures the existence of life is solar energy. The energy bound in organic substances at the stages of the food chain decreases, because most of it enters the environment in the form of heat or is spent on processes occurring in organisms. Therefore, a flow of energy and its transformation is observed in the biosphere. Thus, the biosphere can be stable only if there is a constant cycle of substances and an influx of solar energy.

Natural resources

Each animal or plant is a link in the food chains of its ecosystem, exchanges substances with inanimate nature, and therefore is included in the cycle of substances in the biosphere. Chemical elements in various compounds circulate between living organisms, the atmosphere and soil, the hydrosphere and the lithosphere. Having begun in some ecosystems, the cycle ends in others. The entire biomass of the planet participates in the cycle of substances, this gives the biosphere integrity and stability. Living organisms significantly influence the movement and transformation of many compounds. The biological cycle primarily involves elements that make up organic substances: C, N, S, P, O, H, as well as a number of metals (Fe, Ca, Mg, etc.).

The circulation of compounds is carried out mainly due to the energy of the Sun. Green plants, accumulating its energy and consuming mineral compounds from the soil, synthesize organic substances. Organic matter spreads through the biosphere through food chains. Reducers destroy plant and animal organic matter into mineral compounds, closing the biological cycle.

In the upper layers of the ocean and on the land surface, the formation of organic matter predominates, and in the soil and depths of the sea its mineralization predominates. The migration of birds, fish, and insects also contributes to the transfer of the elements they have accumulated. Human activity significantly influences the cycle of elements.

The water cycle. The planet's waters, heated by the sun, evaporate. The moisture that falls as life-giving rain returns back to the ocean as river water or groundwater purified by filtration, carrying a huge amount of inorganic and organic compounds. Living organisms actively participate in the water cycle, which is a necessary component of metabolic processes (for the biological role of water, see § 1). On land, most of the water is evaporated by plants, reducing runoff and preventing soil erosion. Therefore, when deforestation occurs, surface runoff increases several times at once and causes intense erosion of the soil cover. The forest slows down the melting of snow, and the melt water, gradually flowing down, moisturizes the fields well. Groundwater levels are rising, and spring floods are rarely destructive.

Tropical rainforests moderate the hot equatorial climate by retaining and gradually evaporating water (a phenomenon called transpiration). Deforestation of tropical forests causes catastrophic droughts in nearby areas. Predatory destruction of forests can turn entire countries into deserts, as has already happened in northern Africa. The water cycle, regulated by vegetation, is the most important condition for maintaining life on Earth.

Carbon cycle. During photosynthesis, plants absorb carbon through carbon dioxide. The organic matter they produce contains a significant amount of carbon, which is distributed throughout the ecosystem through food chains. During the process of respiration, organisms release carbon dioxide. Organic residues in the sea and on land are mineralized by decomposers. One of the products of mineralization - carbon dioxide - returns to the atmosphere, closing the cycle.

Over the course of 6-8 years, living beings pass through all the carbon in the atmosphere. Every year, up to 50 billion tons of carbon are involved in the process of photosynthesis. Some of it accumulates in the soil and at the bottom of the oceans - in the skeletons of algae and mollusks, and coral reefs. A significant reserve of carbon is contained in sedimentary rocks. On the basis of fossil plants and planktonic organisms, deposits of coal, organic limestone and peat, natural gas and, possibly, oil were formed (some scientists suggest the abiogenic origin of oil). Natural fuels, when burned, add carbon to the atmosphere. Every year, the carbon content in the atmosphere increases by 3 billion tons and can disrupt the stability of the biosphere. If the rate of increase continues, the intense melting of polar ice, caused by the greenhouse effect of carbon dioxide, will lead to the flooding of vast coastal areas around the world.

Nitrogen cycle. The importance of nitrogen for living organisms is determined mainly by its content in proteins and nucleic acids. Nitrogen, like carbon, is part of organic compounds; the cycles of these elements are closely related. The main source of nitrogen is atmospheric air. Through fixation by living organisms, nitrogen moves from the air into the soil and water. Every year, blue-greens bind about 25 kg/ha of nitrogen. Effectively fixes nitrogen and nodule bacteria.

Plants absorb nitrogen compounds from the soil and synthesize organic matter. Organic matter spreads through food chains down to decomposers that decompose proteins with the release of ammonia, which is further converted by other bacteria to nitrites and nitrates. A similar circulation of nitrogen occurs between benthos and plankton organisms. Denitrifying bacteria reduce nitrogen to free molecules that are returned to the atmosphere. A small amount of nitrogen is fixed in the form of oxides by lightning discharges and enters the soil with precipitation, and also comes from volcanic activity, compensating for the loss in deep-sea sediments. Nitrogen also enters the soil in the form of fertilizers after industrial fixation from the atmospheric air.

The nitrogen cycle is a more closed cycle than the carbon cycle. Only a small amount of it is washed out by rivers or goes into the atmosphere, leaving the boundaries of ecosystems.

Sulfur cycle. Sulfur is part of a number of amino acids and proteins. Sulfur compounds enter the cycle mainly in the form of sulfides from weathering products of land and seabed rocks. A number of microorganisms (for example, chemosynthetic bacteria) are capable of converting sulfides into a form accessible to plants - sulfates. Plants and animals die, the mineralization of their remains by decomposers returns sulfur compounds to the soil. Thus, sulfur bacteria oxidize hydrogen sulfide formed during the decomposition of proteins to sulfates. Sulfates help convert sparingly soluble phosphorus compounds into soluble ones. The amount of mineral compounds available to plants increases, and the conditions for their nutrition improve.

The resources of sulfur-containing minerals are very significant, and an excess of this element in the atmosphere, leading to acid rain and disrupting photosynthesis processes near industrial enterprises, is already worrying scientists. The amount of sulfur in the atmosphere increases significantly when natural fuels are burned.

Phosphorus cycle. This element is found in a number of vital molecules. Its cycle begins with the leaching of phosphorus-containing compounds from rocks and their entry into the soil. Part of the phosphorus is carried away into rivers and seas, the other is absorbed by plants. The biogenic cycle of phosphorus occurs according to the general scheme: producers→consumers→reducers.

Significant amounts of phosphorus are applied to fields with fertilizers. About 60 thousand tons of phosphorus are returned to the mainland annually through fisheries. In the human protein diet, fish makes up from 20% to 80%; some low-value varieties of fish are processed into fertilizers rich in useful elements, including phosphorus.

The annual production of phosphorus-containing rocks is 1-2 million tons. The resources of phosphorus-containing rocks are still large, but in the future humanity will probably have to solve the problem of returning phosphorus to the biogenic cycle.

Natural resources. The possibility of our life and its conditions depend on natural resources. Biological and especially food resources serve as the material basis of life. Mineral and energy resources, when included in production, serve as the basis for a stable standard of living.

Resources are usually divided into inexhaustible and exhaustible. The energy of the Sun and wind, atmospheric air and water are practically inexhaustible. However, with modern non-ecological industrial production, water and air can only be conditionally considered inexhaustible resources. In many areas, pollution has caused a shortage of clean water and air. In order for these resources to remain inexhaustible, a careful attitude towards nature is necessary.

Exhaustible resources are divided into non-renewable and renewable. Non-renewable resources include lost species of animals and plants, and most minerals. Renewable resources include wood, game animals and fish, plants, as well as some minerals, such as peat.

By intensively consuming natural resources, a person needs to maintain natural balance. The balance of resources in the cycle of substances determines the stability of the biosphere.

1. How do living organisms participate in the cycle of substances? Where does the formation of organic matter predominate, where does its mineralization occur?
2. Describe the water cycle. What is the role of forests in its regulation?
3. How does the carbon cycle occur? Is it possible to exclude plants from the cycle?
4. What are the features of the nitrogen, sulfur, and phosphorus cycles?
5. What resources require especially careful treatment?

Human economic activity and global environmental problems

About 10-15% of the land surface is plowed, 25% are fully or partially cultivated pastures. If we add to this 3-5% of the surface occupied by the transport network, industry, buildings and structures, and about 1-2% of the Earth's territory damaged by mining, it turns out that almost half of the land surface has been modified by human activity.

With the development of civilization, its negative contribution to biosphere cycles increases. For every ton of industrial products there are 20-50 tons of waste. Each person in large cities produces more than 1 ton of food and household waste per year. Disharmony in the biosphere affects both the flora and fauna, as well as human health. Many pollutants, entering the soil, atmosphere and water bodies, accumulate in the tissues of plants and animals and infect the human body through food chains. Toxic compounds can significantly increase the number of mutations leading to congenital and hereditary abnormalities. A comparison of data from different regions of the planet has led scientists to the conclusion that at least 80% of cancers are caused by chemical pollution of the environment.

Atmospheric pollution mainly comes from the combustion of natural fuels by transport, utilities, and industry. In cities, transport accounts for more than 60% of pollutants, thermal power plants account for about 15%, and 25% of emissions come from industrial and construction enterprises. The main air pollutants are oxides of sulfur, nitrogen, methane and carbon monoxide. In plants, air pollution leads to serious metabolic disorders and various diseases. Sulfur dioxide destroys chlorophyll and hinders the development of pollen grains, leaves and needles dry out and fall off. The effects of other pollutants are no less harmful.

Every year, about 100 million tons of sulfur oxides, more than 70 million tons of nitrogen oxides, and 180 million tons of carbon monoxide are emitted into the atmosphere.

Acid precipitation. High concentrations of pollutants lead to the formation of acid rain and smog. Acid precipitation (rain, snow, fog) is formed when sulfur and nitrogen dioxides (SO2, NO2) dissolve in water. Acidic precipitation washes proteins, amino acids, sugar, and potassium from plant leaves and damages the top protective layer. Acid solutions introduce an acidic environment into the soil, causing humus to be washed out, reducing the amount of vital salts of calcium, potassium, and magnesium. Acidic soils are poor in microorganisms, the rate of destruction of litter slows down, and a reduction in the number of decomposers disrupts the balance of ecosystems.

Acid rain destroys huge ecosystems, causes the death of plants and forests, and turns lakes and rivers into lifeless bodies of water. In the USA over the past 100 years, acid rain has become 40 times more acidic, about 200 lakes have been left without fish, in Sweden 20% of lakes are in a catastrophic state. More than 70% of Swedish acid rain is caused by emissions from other countries. About 20% of acid rain in Europe is a consequence of sulfur oxide emissions in North America.

Smog. In the lower layers of the atmosphere, under the influence of sunlight, pollutants form compounds that are extremely harmful to living organisms, observed as fog. In large cities, the amount of sunlight due to smog is reduced by 10-15%, and ultraviolet rays by 30%.

Ozone holes. In the atmosphere at an altitude of 20-25 km there are a large number of ozone molecules (O3), which absorb the hard part of the solar spectrum, which is destructive for living organisms. In 1982, scientists discovered a hole in the ozone layer over Antarctica, and in 1987 - over the North Pole. Scientists fear that holes may also appear above the inhabited part of the globe. This could lead to a surge in skin cancer, cataracts, and disruption of forest and marine ecosystems.

For what reasons do ozone holes occur? Scientists suggest that the main one is the accumulation of freons (chlorofluorocarbons СFCl3, СF2Сl2), used in the production of aerosols and in the refrigeration industry. These gases persist in the atmosphere for decades. Once in the stratosphere, they are decomposed by solar radiation to form chlorine atoms, which catalyze the conversion of ozone to oxygen.

Greenhouse effect. Some atmospheric gases transmit visible light well and absorb the planet's thermal radiation, causing overall warming. The greenhouse effect is 50% due to the presence of carbon dioxide, 18% from methane and 14% from freons. The increase in the amount of CO2 in the atmosphere is caused mainly by the combustion of fuel and the clearing of forests for plowing, as well as the intensive mineralization of humus in vast arable lands.

Methane enters the atmosphere from swampy areas, from waterlogged soils of rice plantations, from numerous livestock farms, and during the opening of coal deposits. Methane is one of the main metabolic products of ruminants, giving a characteristic pungent odor to their excretions. In the 20th century the amount of CO2 in the atmosphere increased by 25%, and methane by 100%, which increased the average temperature by 0.5°C. With this trend, temperatures could rise by 3-5°C in the next 50 years. Calculations show that the melting of polar ice will lead to a rise in sea levels by 0.5-1.5 m. In Egypt, 20-30% of the fertile lands of the Nile Delta will be flooded, and coastal villages and large cities of China, India and the USA will be under threat. The total amount of precipitation will increase, but in the central parts of the continents the climate may become drier and detrimental to crops, especially grains and rice (for 60% of the population of Asia, rice is the main product).

Thus, even small changes in the gas composition of the atmosphere are dangerous for natural ecosystems.

Disturbances in the hydrosphere. Large-scale mistakes in agricultural practices have led to the destruction of many natural ecosystems. The diversion of runoff from the Amu Darya and Syr Darya for irrigation of cotton plantations caused a catastrophic drop in the level of the Aral Sea. Dust storms in its drying bed caused soil salinization over vast areas. The degradation of the natural ecosystems of the Aral Sea region is the result of lack of water and desertification.

Predatory water withdrawal for irrigation, for the needs of industrial production (the smelting of 1 ton of nickel takes 4000 m3 of water, the production of 1 ton of paper - 100 m3, 1 ton of synthetic fiber - up to 5000 m3), the destruction of water conservation forests and the drainage of swamps have led to to the massive disappearance of rivers. If in 1785 there were more than 1 million rivers in the Kaluga region, then in 1990 there were only 200 of them left!

River ecosystems are very sensitive and vulnerable. A huge amount of fertilizers washed off from fields, livestock waste and sewage water causes an increase in the concentration of nitrogen and phosphorus compounds in water bodies. In aquatic ecosystems, the rapid development of blue-green algae begins, displacing diatoms necessary for zooplankton. The fish are dying of hunger. Blue-greens accumulate at the bottom and rot (decomposed by bacteria), poisoning the water and depleting oxygen supplies. Picturesque ponds turn into foul-smelling sewers covered with mud and foam. If the water is not poisoned, then on each square meter there are up to 15 mollusks, each of which carefully filters up to 50 liters of water per day. These creatures die when foreign chemicals enter the water bodies. The most resistant to water pollution are leeches, ascidians and dragonfly larvae.

The components of the biosphere are interconnected by the cycle of substances and food chains; disruption of one ecosystem causes a shift in the ecological balance in others. When insects began to be poisoned with DDT in the northern hemisphere, significant amounts of this poison were soon found in the bodies of Antarctic penguins who received it from fish. Many pesticides are very stable and can accumulate in the tissues of organisms for a long time, multiplying many times at each subsequent nutritional level.

Due to unreasonable human economic activity, natural reservoirs have become poisoned with salts of heavy metals - mercury, lead, as well as copper and zinc. These compounds accumulate in sludge, in fish tissues, and enter the human body through food chains, causing severe poisoning. The lead content in the tissues of organisms of residents of industrial areas of the United States has increased 50-1000 times over the past 100 years. Even in the glaciers of the Pamir-Altai, the mercury content has increased fivefold. Minute amounts of many chemicals disrupt the behavior of fish, lobsters and other aquatic species. The registration of minimum concentrations of copper, mercury, cadmium, and phenols is based on these characteristics. One of the most common pesticides - toxaphene - at a content of 1:108 (1 part per 100 million) causes the death of some fish (for example, gambusia), irreversible changes in the liver and gills of catfish and trout.

Oil leakage during production and transportation leads to the formation of an oil film on the surface of rivers and seas (more than 40% of all oil is produced on the shelf). According to satellite observations, about 10-15% of the surface of the world's oceans is polluted. Oil from the surface gradually evaporates and is decomposed by bacteria, but this happens slowly. Many aquatic birds are dying, plankton is being destroyed, and after it its main consumers - the inhabitants of the deep sea. " Benthic desert" in the Baltic Sea covers more than 20% of the bottom surface. Oil prevents the enrichment of waters with oxygen. As a result, the gas balance of the hydrosphere with the atmosphere is disrupted and the ecological balance is shifted.

Intensive fishing and shellfish harvesting has depleted many shelf ecosystems.

Soil destruction. The extensive plowing of the steppes in our country and the United States caused dust storms that carried away millions of hectares of the most fertile lands. It takes nature 100-300 years to recreate a centimeter layer of soil! Currently, about 1/3 of cultivated land has lost 50% of its fertile layer due to various types of erosion. Every year, about 3 million hectares are lost due to erosion, 2 million hectares due to desertification, and 2 million hectares due to poisoning by chemicals.

The soils of many agricultural areas became saline. In the Aral Sea region this happened as a result of dusty salt storms, in other areas - from improper organization of irrigation water flow. Excess water causes salt-rich groundwater to rise to the surface. Intense evaporation produces salinization of the upper soil horizons, and after a few years it becomes impossible to grow crops on such lands. Soil salinization led to the decline of agriculture in Mesopotamia 4,000 years ago. Irrigation waters initially provided good harvests there, but due to intense evaporation they caused chemical degradation of the soil.

A big problem is also associated with the physical degradation of cultivated lands - strong compaction by heavy agricultural machines.

Loss of natural species diversity. A significant part of animals and plants live in forest biocenoses. If 1500 years ago forests occupied 7 billion hectares of the planet, today they occupy no more than 4 billion hectares. Particularly barbaric is the deforestation of tropical forests, which contain about 80% of all plant species on the planet. Tropical forests are located mainly in underdeveloped countries, for which the sale of timber is one of the main sources of income. Forests in the tropics have decreased to 7% of the land area, and if the rate of destruction continues, then by 2030 only a quarter will remain.

In Central Russia, coniferous forests have been practically destroyed, and the most valuable and most accessible forest areas of Siberia and the Far East are being intensively cut down. With the destruction of forests, the climate is disrupted, soils are degraded, rivers die, animals and plants disappear.

The unique forest in the Amazon basin is being cut down at a rate of 2% per year. In Haiti, 20 years ago forests occupied 80% of the territory, today - only 9%. Due to predatory deforestation, thousands of plant species disappear irrevocably every year; about 20 thousand species of flowering plants, 300 species of mammals, and 350 species of birds are on the verge of extinction. With the disappearance of each plant species, from 5 to 35 species of animals (mainly invertebrates) ecologically associated with it become extinct.

Every year in Europe, about 300 million migrating and wintering birds, 55 million individuals of swamp, field and forest game are destroyed, in the USA - 2.5 million mourning doves, in Greece - 3 million starlings, on the island. Mallorca - 3.5 million blackbirds.

With the development of agriculture, the steppes in Eurasia almost completely disappeared. Tundra ecosystems are being barbarously destroyed. Coral reefs are endangered in many areas of the ocean.

Species diversity is not only beauty, but also a necessary factor in the stability of the biosphere. Ecosystems are able to withstand external biotic, climatic, and toxic influences if they are inhabited by a sufficiently large number of diverse species. In one study, scientists introduced the toxic substance phenol into ecosystems. Only bacteria neutralize phenol, but it turned out that neutralization is more effective in an ecosystem with a greater diversity of organisms. The extinction of species is an irreparable loss for the biosphere and a real danger to the survival of humanity.

A variety of vegetation expands the possibilities for maintaining health. A huge number of medicines today are made from wild plants. We do not yet know all the beneficial qualities of plants; we cannot assume which of them we will need. In 1960, only 20% of children with leukemia survived, today - 80%, because In one of the tropical forest plants of Madagascar, scientists managed to find active substances to combat this disease. By losing species diversity, we are losing our future.

Currently, there is an international program for the conservation of rare and endangered species of flora and fauna.

Radioactive contamination of the atmosphere. Radioactive particles in atmospheric currents quickly spread over long distances, contaminating soil and water bodies, plants and animals. Four months after each nuclear explosion on the Pacific atolls, radioactive strontium was detected in the milk of European women.

Radioactive isotopes are especially dangerous because they can replace other elements in organisms. Strontium-90 is similar in properties to calcium and accumulates in bones, while cesium-137 is similar to potassium and is concentrated in muscles. Especially a lot of radioactive elements accumulate in the bodies of consumers who have consumed contaminated plants and animals. Thus, an extremely large amount of cesium-137 was found in the bodies of Alaskan Eskimos who ate reindeer meat. Deer feed on lichens, which accumulate significant amounts of radioactive isotopes over their long lives. Their content in lichens is thousands of times higher than in soil. In the tissues of deer this amount increases threefold, and in the bodies of Eskimos there is twice as much radioactive cesium as in deer. The mortality rate of the population of some Arctic regions from malignant tumors is noticeably higher than average.

Radiation persists especially long after accidents at nuclear power plants. During the Chernobyl disaster, radioactive particles rose to a height of 6 km. On the very first day they spread over Ukraine and Belarus with atmospheric flows. Then the cloud split, one part of it appeared over Poland and Sweden on the second to fourth day, crossed Europe by the end of the week and reached Turkey, Lebanon and Syria on the 10th day. Another part of the cloud crossed Siberia within a week, on the 12th day it appeared over Japan, and on the 18th day after the accident the radioactive cloud visited North America.

The study of biosphere processes helps to understand the importance of every part of the created world and to understand the painful state of mind of modern man. In the West, and now in Russia, the desire for a comfortable American way of life as the highest good prevails. What is America through the eyes of an ecologist? This is 5.5% of the planet's population, 40% of natural resource consumption and 70% of harmful emissions! This is the price of a luxurious life at the expense of other peoples and the future of the planet.

The time has come to take a sober view of the desires for ever greater material wealth and understand that the strategy of the industrial-consumer society is leading us to disaster. If in the coming decades we do not move to the right spiritual guidelines, then our descendants will face the problem of survival. We must remember to take care of each other and our native planet - the priceless wealth entrusted to us by the Creator.

1. Describe the four main effects of air pollution. How are pollutants distributed?
2. Why is irrigation farming dangerous?
3. What are the negative consequences of excess fertilizer?
4. Why do scientists consider the reduction in species diversity of ecosystems dangerous for humans?
5. Is environmental pollution a consequence of the lack of spirituality of our civilization? Where do you need to start to improve the planet?

Global circulation in oh yea

Globally, the water and CO2 cycles are probably the most important biogeochemical cycles for humanity. Both are characterized by small but highly mobile funds in the atmosphere, highly sensitive to disturbances caused by human activity and which can influence weather and climate.

Although water is involved in the chemical reactions that make up photosynthesis, most of the water flow through an ecosystem is due to evaporation, transpiration (evaporation from plants), and precipitation.

The water cycle, or hydrological cycle, like any other cycle, is driven by energy. The absorption of light energy by liquid water represents the main point at which the energy source is coupled to the water cycle. It is estimated that about a third of all solar energy reaching the Earth is spent on driving the water cycle.

More than 90% of the earth's water is bound in the rocks that form the earth's crust and in sediments (ice and snow) on the earth's surface. This water enters the hydrological cycle occurring in the ecosystem very rarely: only during volcanic emissions of water vapor. Thus, the large reserves of water present in the earth's crust make a very insignificant contribution to the movement of water near the Earth's surface, forming the basis of the reserve fund of this cycle.

The amount of water in the atmosphere is small (about 3%). The water contained in the air in the form of vapor at any given moment corresponds to an average layer of 2.5 cm thick, evenly distributed over the surface of the Earth. The amount of precipitation that falls per year averages 65 cm, which is 25 times more than the amount of moisture contained in the atmosphere at any given moment. Consequently, water vapor constantly contained in the atmosphere, the so-called atmospheric fund, cycles 25 times annually. Accordingly, the time of water transfer in the atmosphere is on average two weeks.

The water content in soil, rivers, lakes and oceans is hundreds of thousands of times greater than in the atmosphere. However, it flows through both of these funds at the same rate, since evaporation is balanced with precipitation. The average time of transport of water in its liquid phase over the Earth's surface, equal to 3650 years, is 105 times longer than the time of its transport in the atmosphere.

Particular attention should be paid to the following aspects of the water cycle:

1. The sea loses more water due to evaporation than it receives through precipitation; on land the situation is the opposite. That. Much of the sediment that supports terrestrial ecosystems, including most agroecosystems, consists of water evaporated from the sea.
2. An important, if not the main role of plant transpiration in the total evapotranspiration (evaporation) from land. The effect that vegetation has on water movement is best revealed when the vegetation is removed. Thus, the experimental cutting down of all trees in small river basins increases the flow of water into the rivers draining the cleared areas by more than 200%. Under normal conditions, this excess would be released directly into the atmosphere in the form of water vapor.
3. Although surface runoff replenishes groundwater reservoirs and is itself replenished by them, these quantities have an inverse relationship. As a result of human activities (covering the earth's surface with materials impervious to water, creating reservoirs on rivers, building irrigation systems, compacting arable lands, clearing forests, etc.), runoff increases and the replenishment of such an important groundwater fund is reduced. In many dry areas, groundwater reservoirs are now being pumped out by humans faster than they are being replenished by nature.

Biogeochemical cycles of carbon, nitrogen and oxygen are the most complete. Thanks to large atmospheric reserves, they are capable of rapid self-regulation.

Global carbon cycle

In the carbon cycle, or rather its most mobile form, CO2, a trophic chain is clearly visible: producers that capture carbon from the atmosphere during photosynthesis, consumers that absorb carbon along with the bodies of producers and consumers of lower orders, decomposers that return carbon back into the cycle. Only organic compounds and carbon dioxide participate in the biological carbon cycle. All carbon assimilated during photosynthesis is included in carbohydrates, and during respiration, the carbon contained in organic compounds is converted into carbon dioxide.

Vast pools of inorganic carbon—atmospheric carbon dioxide, dissolved carbon dioxide (mainly in the form of HCO3-), carbonic acid, and carbonate deposits—participate in the carbon cycle to varying degrees. The exchange between carbon contained in igneous rocks, calcium carbonate deposits, coal and oil, and other more active carbon stocks occurs so slowly that the effect of this carbon on the short-term functioning of ecosystems is negligible.

The atmospheric pool of CO2 in the cycle is very small compared to carbon reserves in the oceans, fossil fuels and other reservoirs of the earth's crust. It is believed that before the advent of the industrial era, carbon flows between the atmosphere, continents and oceans were balanced.

This balance is based on the regulating activity of green plants and the absorption capacity of the sea carbonate system. When life appeared on Earth more than 2 billion years ago, the atmosphere consisted of volcanic gases. There was a lot of CO2 and little oxygen (or perhaps none at all), and the first organisms were anaerobic. As a result of the fact that production, on average, slightly exceeded respiration, oxygen accumulated in the atmosphere over geological time and the CO2 content decreased. Geological and purely chemical processes also contributed to the accumulation of oxygen, for example, its release from iron oxides or the formation of reduced nitrogen compounds and the splitting of water by ultraviolet radiation with the release of oxygen. Low CO2 content, as well as high O2 concentrations, serve as limiting factors for photosynthesis: most plants are characterized by an increase in the intensity of photosynthesis if the CO2 content increases or the O2 content decreases in the experiment. Thus, green plants turn out to be a very sensitive regulator of the content of these gases.

The Earth's photosynthetic "green belt" and the sea's carbonate system maintain a constant level of CO2 in the atmosphere. But in the last century, the rapidly increasing consumption of fossil fuels, together with a decrease in the absorption capacity of the “green belt,” begins to exceed the capabilities of natural control, so that the CO2 content in the atmosphere is now gradually increasing. Indeed, the flows of substances at the input and output of small exchange funds are subject to the greatest changes. It is believed that at the beginning of the Industrial Revolution (around 1800), the Earth's atmosphere contained about 290 parts per million (0.029%) of CO2. In 1958, when accurate measurements were first taken, the content was 315, and in 1960 it rose to 335 parts per million. If concentrations double the pre-industrial level, which could happen by the middle of the next century, the Earth's climate is likely to warm: temperatures will rise on average by 1.5 to 4.5°C, and this along with sea level rise (as a result of the melting of the polar caps) and changes in rainfall distribution can ruin agriculture.

It is believed that in the next century a new but precarious balance may be established between increasing CO2 levels (which contribute to warming the Earth) and increasing atmospheric pollution with dust and other particles that reflect radiation and thereby cool the planet. Any significant resulting change in the Earth's heat budget will then affect the climate.

The main source of the greenhouse gas CO2 is the combustion of fossil fuels, but agricultural development and deforestation also contribute. It may be surprising that agriculture ultimately loses CO2 from the soil (that is, it contributes more to the atmosphere than it takes out), but the fact is that CO2 fixation by crops, many of which are active only part of the year, does not compensate the amount of CO2 released from the soil, especially as a result of frequent plowing. Forests are important carbon sinks, since forest biomass contains 1.5 times more carbon, and forest humus contains 4 times more carbon than in the atmosphere. Deforestation, of course, can release the carbon stored in the wood, especially if it is immediately burned. Destruction of forests, especially with the subsequent use of these lands for agriculture or city construction, leads to the oxidation of humus.

In addition to CO2, two more carbon compounds are present in small quantities in the atmosphere: carbon monoxide (CO) - about 0.1 parts per million and methane (CH4) - about 1.6 parts per million. Like CO2, these compounds cycle rapidly and therefore have a short residence time in the atmosphere - about 0.1 year for CO; 3.6 years for CH4 and 4 years for CO2.

Both CO and CH4 are formed during incomplete or anaerobic decomposition of organic matter; in the atmosphere both are oxidized to CO2. The same amount of CO that enters the atmosphere as a result of natural decomposition is now introduced into it during incomplete combustion of fossil fuels, especially with exhaust gases. The buildup of carbon monoxide, a deadly poison to humans, poses no threat globally, but in cities where the air stagnates, rising levels of the gas in the atmosphere begin to become alarming, reaching levels of 100 parts per million.

Methane production is one of the most important functions of the world's wetlands and shallow seas. Methane is believed to have a beneficial function: it maintains the stability of the ozone layer in the upper atmosphere, which blocks the sun's deadly ultraviolet radiation. The biotic cycle of carbon is an integral part of the larger cycle; it is associated with the life activity of organisms. The turnover rate of CO2 is about 300 years (its complete replacement in the atmosphere).

Oxygen cycle

The second most abundant element in the atmosphere after nitrogen is oxygen, accounting for 20.95% by volume. A much larger amount of it is found in a bound state in water molecules, in salts, as well as in oxides and other solid rocks of the earth’s crust, but the ecosystem does not have direct access to this huge pool of oxygen. The transport time of oxygen in the atmosphere is about 2500 years, if we neglect the exchange of oxygen between the atmosphere and surface waters. In the primary atmosphere of the earth, the content of O2 was very low, but with the advent of photosynthetic organisms it became an important component of the atmosphere. Over the course of many million years, the concentration of O2 in the atmosphere gradually increased, reaching 21% (by volume) by now. Almost all of the O2 was formed as a result of photosynthesis by cyanobacteria, and subsequently by green plants. The removal of oxygen from the atmosphere occurs as a result of its absorption by living organisms through aerobic respiration, the combustion of fossil fuels, and the formation of oxides (oxides). Respiration and combustion of fossil fuels produces carbon dioxide (carbon dioxide, CO2), which is used again in photosynthesis, a process that in turn releases oxygen into the atmosphere, thus completing the cycle. The oxygen cycle in nature is basically similar to the carbon cycle in nature.

Biogeochemical nitrogen cycle.

Of course, the nitrogen cycle is one of the most complex and at the same time the most vulnerable cycles (Fig.). Despite the large number of organisms involved, it ensures rapid circulation of nitrogen in various ecosystems. As a rule, in quantitative terms, nitrogen follows carbon, together with which it participates in the formation of protein compounds. Nitrogen, which is part of proteins and other nitrogen-containing compounds, is converted from organic to inorganic form as a result of the activity of a number of chemotrophic bacteria. Each type of bacteria does its part of the job, oxidizing ammonium to nitrites and then to nitrates. However, nitrates available to plants “escape” them as a result of the activity of denitrifying bacteria, which reduce nitrates to molecular nitrogen.

The nitrogen cycle is characterized by an extensive reserve fund in the atmosphere. Air by volume is almost 80% molecular nitrogen (N2) and represents the largest reservoir of this element. At the same time, insufficient nitrogen content in the soil often limits the productivity of individual plant species and the entire ecosystem as a whole. All living organisms require nitrogen, using it in various forms to form proteins and nucleic acids. But only a few microorganisms can use nitrogen gas from the atmosphere. Fortunately, nitrogen-fixing microorganisms convert molecular nitrogen into ammonium ions available to plants. In addition, nitrates are constantly being formed in the atmosphere by inorganic means, but this phenomenon plays only a supporting role compared to the activity of nitrifying organisms.

Biogeochemical cycles of phosphorus and sulfur

The biogeochemical cycles of phosphorus and sulfur, the most important biogenic elements, are much less perfect, since the bulk of them are contained in the reserve fund of the earth's crust, in the “inaccessible” fund.

The sulfur and phosphorus cycle is a typical sedimentary biogeochemical cycle. Such cycles are easily disrupted by various kinds of influences and part of the exchanged material leaves the cycle. It can return again to the cycle only as a result of geological processes or through the extraction of biophilic components by living matter.

Phosphorus

Phosphorus is found in rocks formed in past geological eras. It can enter the biogeochemical cycle (Fig.) if these rocks rise from the depths of the earth’s crust to the land surface, into the weathering zone. Through erosive processes it is carried out to the sea in the form of the well-known mineral apatite.

The general phosphorus cycle can be divided into two parts: aquatic and terrestrial. In aquatic ecosystems, it is assimilated by phytoplankton and transmitted along the trophic chain up to third-order consumers - seabirds. Their excrement (guano) returns to the sea and enters the cycle, or accumulates on the shore and is washed into the sea.

From dying marine animals, especially fish, phosphorus returns to the sea and into the cycle, but some fish skeletons reach great depths and the phosphorus contained in them again ends up in sedimentary rocks.

In terrestrial ecosystems, phosphorus is extracted by plants from the soil and then distributed through the trophic network. Returns to the soil after the death of animals and plants and with their excrement. Phosphorus is lost from soils as a result of water erosion. The increased content of phosphorus in the waterways of its transport causes a rapid increase in the biomass of aquatic plants, “blooming” of water bodies and their eutrophication. Most of the phosphorus is carried into the sea and is lost there irretrievably.

The latter circumstance can lead to depletion of reserves of phosphorus-containing ores (phosphorites, apatites, etc.). Therefore, we must strive to avoid these losses and not wait for the time when the Earth will return the “lost sediments” to land.

Sulfur

Sulfur also has a main reserve fund in sediments and soil, but unlike phosphorus, it also has a reserve fund in the atmosphere (Fig.). In the exchange fund, the main role belongs to microorganisms. Some of them are reducing agents, others are oxidizing agents.

In rocks, sulfur occurs in the form of sulfides (FeS2, etc.), in solutions in the form of an ion (S042~), in the gaseous phase in the form of hydrogen sulfide (H2S) or sulfur dioxide (S02). In some organisms, sulfur accumulates in its pure form (S2) and when they die, deposits of native sulfur are formed on the bottom of the seas.

In the marine environment, sulfate ion ranks second in content after chlorine and is the main available form of sulfur, which is reduced by autotrophs and included in amino acids.

The sulfur cycle, although it is required by organisms in small quantities, is key in the overall process of production and decomposition (Y. Odum, 1986). For example, when iron sulfides are formed, phosphorus goes into a soluble form that is available to organisms.

In terrestrial ecosystems, sulfur returns to the soil when plants die and is captured by microorganisms, which reduce it to H2S. Other organisms and exposure to oxygen itself cause these products to oxidize. The resulting sulfates dissolve and are absorbed by plants from the pore solutions of the soil - this is how the cycle continues.

However, the sulfur cycle, like nitrogen, can be disrupted by human intervention and this is primarily due to the combustion of fossil fuels, and especially coal. Sulfur dioxide (S02t) disrupts photosynthesis processes and leads to the death of vegetation.

Biogeochemical cycles are easily disrupted by humans. Thus, when extracting mineral fertilizers, it pollutes water and air. Phosphorus enters the water, causing eutrophication, highly toxic nitrogen compounds are formed, etc. In other words, the cycle becomes not cyclic, but acyclic. The protection of natural resources should, in particular, be aimed at turning acyclic biogeochemical processes into cyclic ones.

Thus, the general homeostasis of the biosphere depends on the stability of the biogeochemical cycle of substances in nature. But being a planetary ecosystem, it consists of ecosystems at all levels, so the integrity and sustainability of natural ecosystems are of primary importance for its homeostasis.