The total area of the Land Fund is 134 million km2, or 13.4 billion hectares. If the total area of land taken for 100%, the share of processed (arable) land accounts for approximately 10%, 28% forest, meadows and pastures — 20%, ice sheets — 10%, deserts, bedlendov, built-up land is 32%. Thus, in the field of agricultural production used about 30% of the world land trust.
Most major regions of the Land Fund are Asia, Africa, North and South America. However, the per capita ranking of regions different: in the first place is Australia, whereas other regions (especially European) lag far behind. At the turn of the 80-90s in the world at an average rate of 1 person accounted for about 0.3 hectares of arable land, while in the United States is 0.79 HA, in Canada, 1.84, in France — 0.32 0.09 — in China, in Japan — 0.04 ha (table 21).
In terms of specific sectors of the rural (and forest) and then accelerated the degradation of land in rainfed agriculture is associated primarily with the wind-water erosion, deflation, acidification, etc.; in irrigated agriculture — from flooding, salinity, chemical pollution, osoloncevaniem, etc.; in the grazing livestock from water and wind erosion, ultimately a desertification control; in the industrial animal agriculture is soil pollution of waste production; by lesorazrabotkah from water erosion, wind, deflation, pancireobrazovaniem, mechanical erosion, etc.
Dwell in some detail on soil pollution of the planet. It is known, is one of the results of increasing anthropogenic pressure. The main pollutants are fertilizers and pesticides, metals and their compounds, radioactive.
The strongest influence on soils has a modern agriculture, widely using fertilizers, herbicides and pesticides. The number of substances involved in agricultural activities, measured values of the same order as in the process of industrial production. So, each year on the field comes about 40 million tons of fertilizer and 4 million tons of toxic chemicals, and their production is growing. Each year, the harvest is a huge amount of nutrients (most severely deplete the soil grains and tuberous crops). Expended stocks are replenished as fertilizer, containing nitrogen, phosphorus, potassium, copper, boron, etc. Thus, in global nutrient cycling includes the additional resources that may not be reflected on his violation.
Very dangerous soil pesticide contamination has scales. The global range of herbicides and pesticides has already more than 100 drugs. Volumes of manufacture of pesticides in the world is enormous, and their use is often disappointing. Herbicides and pesticides (at least many of them) are included in the ecological chain, moving from soil and water in the plants, and then animals and birds, and ultimately end up with food in the human body.
In the growing movement against the use of herbicides and pesticides. It has been suggested that chemical agents against obsolete and should be replaced by biological, since their use adversely affects the ecosystems of any level.
However, soil contamination is not limited to the use of herbicides and pesticides. Man develops and diffuses through the land the enormous mass of metal that disperse into the State, enter into an intensive migration again accumulate in the upper soil layer. Every year, from the depths of the Earth is not less than 4 KM3 of rocks and ores of almost all known elements. As a result of incomplete use of raw materials, direct losses, waste concentration of some metals in the soil by the middle of the next century could increase in 10-100 times-warn distinguished scientists.
So, for many steel works "loss" can reach 20% of the manufactured products. But if even consider them equal 5 per cent, while annual emissions to the atmosphere and the soil surface only, this industry is: 150000 tonnes of copper, zinc, etc. 89 120000 tonnes of lead, 765 t of cobalt, 30 tonnes of mercury.
One of the results of the technological migration is a gradual "ozeleznenie" of the Earth's surface. Each year, about 0.5 billion tonnes of smelted iron with irreversible losses of iron due to corrosion and abrasion reaches x/4 total quantity. The arrival of iron man caused significantly higher nutrient. Excessive ozeleznenie of soils leads to sequestration of organic acids on the sedentary complexes, thereby influencing the processes of soil formation.
Among the most hazardous soil pollutants include lead, mercury and their compounds. Until recently the lead compounds have been widely used as a gasoline additive, anti-detonation and road transport was virtually the main source of lead pollution of the natural environment. Not coincidentally, the lead content in the soils of the planet still largely depends on the density of roads, traffic density. (In fairness to note that in recent years in the leading countries of the world have abandoned the use of lead as an anti-knock additive.)
Mercury enters the environment when using mercury-containing pesticides, waste-paper mill industry, in the production of soda and chlorine, when technologies use mercury electrodes. Metallic mercury, as well as a variety of inorganic and organic compounds (in particular dimethyl mercury, which has even more volatile and toxic than the metallic mercury) often contain waste products and other industries. (Only in the United States over the past 25 years in the Biosphere has received about 30 thousand tons of mercury was no better situation. and in the former Soviet Union.)
Widespread soil pollution sources are non-ferrous copper. Soil contamination by industrial zinc dust from the mines and the use of superfosfatnyh fertilizers that contain zinc. Increase in the quantity of copper and zinc in soils in excess is detrimental to plants, leads to slower growth and lower yields. Other metallovzagraznitelej include manganese, nickel, and aluminum.
Finally, soil pollutants are highly dangerous radioactive elements. They intensively accumulated in the past (rainfall after nuclear tests) and accumulate today (transportation of liquid and solid waste, the nuclear industry). Increased risk of accidents at nuclear power plants. Radioactive isotopes are from soil into plants and organisms in animals and humans, accumulating in certain tissues and organs (90Sr in bones and teeth, 137Zs is a muscles, 1311 — in the thyroid gland, etc.).
Soil degradation and decline in their fertility are closely related to desertification processes in the modern world. There are two forms of desertification: dezertifikaciu — expansion of Deserts and dezertizaciu is a deepening of the desertification process in the previous limits. It is important to remember that desertification is not necessarily associated with arid regions: in some cases it may also occur on the water-logged areas. It all depends on what is meant by desertification, reduction or loss of the biological potential of the territory, the loss of continuous vegetation cover and so on.
Today, desertification processes are not the result of any climate change in a global or regional scale, as it happened before. The main factor in the current process of desertification is human activities that lead to a sharp fall or even complete destruction of biological potential of individual Territories. Among the most important anthropogenic causes of desertification will call excessive grazing, cutting down forests for firewood and timber farming podsecnoognevogo technique, excessive and incorrect operation of cultivated land (monoculture, ploughing Virgin soil, cultivation of slopes, etc.).
Almost a third of the Earth's land mass is desert and semi-desert areas, where more than 15% of the population. By the mid-1990s, the total area of man-made deserts was, according to various estimates, from 10 to 13 million km. In addition, under the threat of desertification is still at least 30 million km of land.
One of the most disturbing environmental phenomena of our times — a progressive desertification of the Sahel (the contact zone of the Sahara desert and Savannah). Never before has the pace of advancement of the Sahara to the South were not so fast.
All of the above leads to the great importance of the protection and regeneration of the soil on the planet. System of different measures practised in the world and to preserve the Earth's land cover, includes:
protection of soil against erosion (preventing any erosion processes, not only at the already-affected soils, but also on those which they threatened in the future);
soil protection from chemical, physical, biological, mechanical impurities;
prevention of soil salinization and waterlogging;
protection of the soil from the landslides, mudslides, etc.;
combating desertification;
land reclamation;
reclamation of land, that is a complex of works aimed at restoring the productivity of land, etc.