Regression and impoverishment of the soil

The regression and degradation are processes of evolution associated with a loss with balance with a stable ground in ecology. The regression is primarily due to the erosion and corresponds to a phenomenon of renovation of a ground (return towards the state opposed at the stage climacic).

Degradation is a evolution different from the natural evolution related on the Climat and the local vegetation . It is caused by the replacement of the primitive vegetation (known as climacic) by a secondary vegetation, which modifies the Humus and the formation of the ground. It is generally directly related to the action of the man via for example;

  • a reduction in the rates of Organic matter: degradation can come from the destruction of the Humus and the argilo-humic complex insoluble by the Labor which hides and destroys the alive roadbases of the ground.
  • compaction and the asphyxiation, often accompanied by the appearance of a Sole of ploughing, in the cultivated grounds;
  • the Acidification, the Salinisation and possibly the Turning into a desert;
  • the erosion (hydrous or wind)…

Inventory of fixtures

UNO and FAO have alerted for several decades on the degradation of many tropical grounds, with in particular of serious phenomena of turning into a desert and of salinisation.
According to a study of the American professor of ecology David Pimentel, ten million Hectare S of cultivable grounds is carried by erosion each year.

In Europe

According to the European commission, the impoverishment of the soil became a serious problem in Europe, which is posed with a variable intensity according to the countries and ragions, but in a way important and increasing for each of the 25 countries of the EU, in particular in the Mediterranean zone (See the article devoted to with the Directive grounds )
As example, in France, with INRA and within the framework of the Gis Sol in charge of the information system on the grounds of France, IFEN has in November 2007 réalerté on the reduction (“ of 6 Mt/an on ten years ”) of the capacity of the agricultural grounds with to store carbon. A French average ground is according to the IFEN in 2°°7 composed of organic carbon 58%. The organic matter contributes to better a Fertilité, better a ecological Résilience and resistance to the Sécheresse (better retention of water and capillarity), with the erosion. It also contributes recalls the IFEN to a less circulation of certain contaminants, and to an important function of carbon well.

causes

The causes indexed by the commission are mainly husbandries and forestry “inadequate” , and the impacts of the development urban, industrial, tourism and “great work” which prevents the grounds from rendering the services ecological and agricultural that they returned. This is with an accelerated loss of Organic matter (Humus), of Fertilité and Biodiversité, which induces less function of Puits of carbon, a reduction in the retention of water and a disturbance of the biogeochemical Cycles (gas and Nutriment S in particular) as well as a less degradation of contaminants Biodégradable S…

Incidences

The commission estimates that these degradations have a direct incidence on the resources Eau, Air, Biodiversité, like on the Climate change. The commission identifies also possible impacts on the Santé of the Man and the animals, and on the Public health of the agricultural food products.
La commission, on the basis of available data estimated into 2006 that:
  • 12% of the European grounds (115 million ha) is subjected to hydrous erosion,
  • 42 million hectares undergoes a wind erosion
  • 45% of the European grounds poor or is impoverished today out of organic matters, especially in the countries of the south, but also in areas of France, the United Kingdom and Germany;
  • Environ 3,5 million sites “is potentially contaminated” by various pollutants in the UE-25

“Corine Land Cover”, the base of géoréférencéée data European watch the deep ones and fast changes in the use of the grounds of the EU: In addition to agriculture intensifies, 1990 to 2000, more than 2,8% of the grounds changed assignment with the profit of the periurbanisation. with an slight increase. This change concerns from 0,3% to 10% of the ground, according to the countries of the EU. The tendency, worsened by the prospects for climate change is with an aggravation of the impoverishment of the soil (aggravation being to some extent self-sustained, ground being him even a carbon well) the commission perhaps estimates “that the impoverishment of the soil in Europe will continue, at a faster rate/rhythm” (page 3/13 of the Strategy set of themes in favor of the protection of the grounds already quoted).

Evolutionary cycles

The ground is surface and alive layer, interface between the earth's crust, the surface waters and the atmosphere. It results from the transformation by the alive one of the Rock-mother and the organic contributions.

At the beginning of the formation of a ground, the rock-mother is colonized little by little by the micro-organisms (bacteria, microscopic mushrooms) then by the vegetation (Algue S, Lichen S and foams, then herbaceous S, followed by a forest layer of shrubs and finally . In parallel a first humus-bearing horizon is formed (known as horizon has ), then subjacent mineral horizons ( horizons B ). Each successive stage is characterized by a certain association ground/vegetation and medium: the Ecosystem " sol" is regarded as one of the large compartments of the Biosphère, one of the stages of the biogeochemical cycle of the elements (carbon in particular).

After a certain time of evolution of the system ground-vegetation, a dynamic state of balance is reached, said “climacic”. One speaks about progression" before this stage.

The cycles of evolution of the grounds have very variable durations, between one millenium for the grounds with development rapide' (ground at horizon only has) with more than one million years for the grounds with slow development . Observation of the vegetable colonization of the volcanic rock small islands emerging at sea watch which the process is started very quickly, but that it is braked or prohibited by the too hot or too cold climates.

Ecological factors influencing the formation of the grounds

One jointly recognizes two large types of process to work; the Deterioration and the Humification, which explain in particular the evolution of the grounds with short development.
  • a first factor is the general climate of an area and the vegetation which is associated for him (Biome). This factor makes it possible to define the great zones of vegetation and ground.
  • a second factor is more local, and is relating to the rock of origin and the local conditions, but also to the work of the ground, and in particular to the drainage. It is at the origin of specialized vegetable associations (ex the Tourbière S).

Disturbances of the balance of a ground

When the theoretical state of balance (climax) is reached, the ground is theoretically stable in time, or tends to accumulate organic matter. Vegetation and the microfaune of the ground producing the Humus and ensuring the ascending circulation of the matters. The humus and the vegetable cover protect the ground from the erosion against water, dehydration and the wind. The plants, the bacteria and certain micro-organisms of the ground reduce also erosion by binding the particles of the ground between them and to the roots thanks to the complexes argilo-humiquese and various Mucus or Mucilage S secreted by the living organisms.
Ainsi, any modification light is quickly corrected and balances it restored.
Dans reality, the grounds are reorganized or disturbed by many “factors of disturbance” occurring occasionally.

In the event of important destruction of the ground or vegetation (avalanche, fires, deforestation, ploughing, flood of long life, Salinisation, Glaciation, Turning into a desert…), the Perturbation undergone by the ecosystem can not allow the impact strength system (on human scale of time). The ground can “die” , or erosion can then be faster than the formation process of the higher horizons of the ground; there is renovation of the ground (i.e the evolution turns over behind, towards the initial state). One also speaks about regression or involution .

The regression can be partial or total (only the rock-mother with naked remains then). A Clearing of inclined ground, follow-up of violent rains, can lead to the complete destruction of the ground. In Madagascar the thicknesses from 3 to 4 m of ground can be thus carried after deforestation, in one rain season where the forest ground had put million years to be made up.

the man modifies deeply and quickly the evolution of the grounds by the clearing, the close-cropped cuts abusive, the Surpâturage (including in forest), the raking of the Litière S, the Labor, the intensive use of chemical Engrais and of Pesticide S. the mechanization which developed after war 14-18 is at the origin of an impoverishment of the soil related to compressing or compaction operated by the agricultural and forest machines, increasingly heavy. Compressing is opposed to circulation water, air and organizations of the ground, the roots of the plants suffer from it and one attends losses of output and quality of the crop plants, which decay. The caused streaming also supports erosion. The sole of ploughing adds its effects to those of the compaction of the grounds.

Gradually, the forest climax is replaced by a secondary forest, much poorer and the ground is modified (example: the replacement of forests of leafy trees by moors or plantations of pines is source of acidification, Podzol isation and water and impoverishment of the soil). The regression is often related to very old husbandries, of which the use of the ploughing and/or the repeated use and with broad scale of fire. In Europe, the scrap-metal has during a few century produced a very effective and productive compromise, but it was destroyed by agricultural mechanization, the breeding out-ground and the regroupings, with the support of the agricultural lobbies most powerful.
La degradation is an evolution different from the natural evolution related on the climate and the local vegetation. It is caused by the replacement of the primitive vegetation (climax) by a secondary vegetation, which modifies the humus and the formation of the ground. It is directly related to the action of the man (example: agriculture).

Theory of the bio-rhexistasy/rhexistasy

The determining role of the climate in the deterioration of the rocks and thus in the formation of the grounds gave place to the formulation of the theory of the bio-rhexistasy (Erhart).
  • In stable period (biostasy), the vegetation covers the grounds. There is no mechanical erosion. Water of drainage involves towards the oceans of the chemical elements and soluble biological compounds which will give, by sedimentation or precipitation, of the fine deposits (clays, limestones…)
  • In period of imbalance (rhexistasy) the vegetation disappears, the grounds are eroded, the deposits lake or marine then consist of coarse detrital materials.

Thus Erhart has T it establishes the link between pedogenesis and sédimentogenèse what is very important. But he does not explain the reasons of imbalances which can assign the vegetable cover to the continental scale (major fires, climate changes…). The stratification of certain lake deposits or sailors seems to corroborate his theory: material fine then coal (= residues of the vegetable cover), finally coarser material.

Influence action of the man (anthropogenic factors)

Erosion, become primarily related to the human activity is now the independent factor of the impoverishment of the soil. Chemical, physical and biological degradation of the latter makes that they are carried by water and the wind. They then pollute the rivers, the estuaries and contribute to the eutrophication of the seas. Road and urban installations by increasing impermeable surfaces exacerbate the floods support the streaming and thus the drive of the ground. The disappearance of the ripisylves, the meanders and species such as the beaver which slowed down the river also exacerbated the cycles flood-drynesses which are also factors of erosion and impoverishment of the soil. But in fact the recent transformations of agriculture accelerated the erosion of the grounds on most of planet.

Agriculture increases the risks of erosion by disturbing the local vegetation. Among the practices accelerating the erosion of the ground:

  • Overgrazing
  • Monoculture
  • culture in row spaced (industrial corn, vine) without vegetable cover
  • Ploughing
  • naked ground in autumn and/or wintry time
  • Grubbing and Deforestation of great pieces to increase agricultural surface
  • furrow in the direction of the slope,
  • excessive use of Manure and Pesticide S, etc

Thus, for example, the Remembrement of the years 1960 in France has leads to the increase in the size of the pieces and correlatively to the removal of the hedges, the slopes and the ditches. Surfaces in cultures of spring, encouraged by the subsidies, increase (sunflower, corn, beet) and leave the ground to naked in winter. The sloping grounds are gradually colonized by the vine. Lastly, the destruction of the adventitious plants by the weedkillers leaves the ground to naked between the cultivated seedlings. The European premiums support the ploughing with the detriment of the meadows, which everywhere in the world are overexploited or tend to regress with the profit of the plowed grounds and the breeding except ground.
La mechanization of the work of the agricultural and forest ground also increased the erosion and the impoverishment of the soil. The overexploitation of the forests is also a factor of degradation or disappearance of the forest humuses.
La Fertilization by mineral manures with depends on organic manure increases the immediate output but déstructure little by little the ground. Agronomists such that Claude Bourguignon alerts since the years 1970 on the fact that one observes in the world a progressive total reduction in the content of the ground of Organic matter, as well as a strong reduction in the biological activity of the ground (in particular relating to the increase in the use of plant health Produits).

Consequences of the regression and the impoverishment of the soil

  • quantitative loss of grounds (via erosion and degradation)

  • Reduction in productivity: the recent increase in the World population is responsible for a strong pressure the grounds world. More than 5,5 billion human use approximately 10% of terrestrial surface for the livestock productions and vegetable. The majority of the grounds present signs of degradation biological, physical, chemical and of erosion, which states limit their productive potentialities. One speaks about degradation light when the potential output is decreased by approximately 10%, of degradation moderated between 15 and 50%. The strongly degraded grounds present a reduction in output of more than 50% compared to their initial potential. The most degraded grounds are in the countries in the process of development, in Asia and Africa, but in the hemispheres northern, the productivity often expensively and is artificially supported by artificial fertilizers and pesticides which contribute to degrade the grounds.


La situation as regards erosion is such as certain experts evoke the possibility that agriculture cannot because erosion nourish it any more the world population.

  • Degradation of the function of carbon well, knowing that the carbon stock strongly depends on the types of ground, and its use (husbandries in particular). Stock is made essentielleemnt surfaces some and especially (except in the plowed grounds) in the first 20 centimetres. The ground loses its carbon in intensive culture and preserves it or accumulates some under forests and meadows (with comparable grounds and climatic conditions). The conversion of meadows, peat bogs or forests in culture strongly decreases the pedological storage of carbon in the ground, and conversely.

  • Natural disasters: flow mud, floods responsible for died for many living beings each year. The erosion of the grounds dehydrated of the Central Asia is with the orgine of a chronic pollution (dust and aerosols) of the air in China of the West, often visible of satellite.

  • qualitative and quantitative degradation of the water resource: the increase in the cycles floods/dryness, and the Turbidity of water and the contribution of Nitrogen and Phosphore can be at the origin of phenomenon of Eutrophisation and development of pathogenic microbes, or appearance of dead Zones at sea and in certain lakes. The entrainment of the particles of grounds in surface waters is also accompanied by that by the agricultural inputs (produced plant health and manures) and by pollutants of industrial, urban and road origin (Heavy metals in particular). The ecological impact of the plant health products is recognized but difficult to evaluate because of multiplicity and of the interactions of the products and their broad spectrum of action.

  • loss of the Biological diversity: the impoverishment of the soil involves the disappearance of the vegetation climax and the disappearance of many habitats for fauna. One can speak here about disappearance of ecosystems, and all that implies from an environmental point of view: reduction in the vegetable Biodiversity, extinction of animal species, reduction in the ecological Impact strength.

  • an example: In Pas-de-Calais (Northern of France), in the years 1980-1990, certain farmers lost usually 10 t/an/ha grounds, with " records" reaching 100 tons: year in the most fragile zones of the basin of Canche. Not far from there, in the area catchment of Judicious (Nord-Pas-de-Calais), the erosion of the grounds caused the progressive filling of the pond of Lécluse which, between 1963 and 1980 saw its surface decreasing by half passing of 8,7 ha to 4,5 ha.

In the world, the Fossé S, many channels and Barrage S whose eutrophic water shelters dangerous bacteria (Cyanobactérie S in particular), must be more and more often quarries, but their sediments (formerly of manures) are now contaminated by metals (of which Cadmium of manures) and the Pesticide S, at the point sometimes to kill during one or two years seeds that one plants there.

Measures of struggle

The erosion and the impoverishment of the soil can be fought by:
  • of measurements and tools legal (Ex: Directive Ground, in Europe).
  • of measurements and tools of the effective techniques improving or to correct the situations of degradation (ex: true Fallow (that which lets the grounds rest), direct Semis after Sous-solage, fragmented Bois raméal…).

Legal tools and means

Many countries have more or less a legislation treating protection of the grounds

Example of the level European

After the Directives on water and the air, and after long negotiation with the Member States the European ground is little by little with being taken into account on this scale of Subsidiarité since the years 2000, with;
  • a strategy set of themes on the protection of the grounds, preaching the protection and the restoration of the grounds degraded “so as to bring back them to a level functionality corresponding at least to their current use and their envisaged use, by holding account also financial implications of the restoration of the grounds”.
  • the Commission presented in 2002, a communication which collected the favorable conclusions of the other European institutions.
  • the adoption (496 votes for, 161 against and 22 abstentions) on November 14th, 2007, by the European Parliament of the project of a “ Directive grounds ” prepared by the commission, fixing a European framework of protection and restoration of the grounds, with objectives and a calendar, but leaving a great flexibility to the États-membres in the choice of the means of achieving these goals. It modifies the directive 2004/35/CE of April 21st, 2004 relating to the environmental civil responsibility with regard to the prevention and the compensation for the environmental damages.

Technical measures

Although généralemnet simple, they require a minimum of technicality, competence in ecology of the grounds and times.
Dans the facts, they only are not seldom applied, because ignored farmers, or requiring important changes of practice (ex: abandonment of the ploughing) and several years to bear their fruits. The ecological Génie showed its capacity to allow spectacular rebuilding of grounds. Certain agronomic techniques, used much in agriculture bio, improve in a few years the structure of the ground, and the outputs. Techniques such as the contribution of fragmented Bois raméal seem carrying hope.
L' regular contribution of organic matter, nonthe ploughing and the limitation of erosion and the streaming (by a permanent vegetable cover and a ground having found a good capacity of infiltration and retention of water) are principal the key. These techniques cannot nevertheless completely restore grounds (including their own fauna and flora) which required more than 1000 years and of the endemic species disappeared to reach their state of stability.

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