1. SOIL , FORESTS AND
WATER
GROUP-4

2. THE SOIL SYSTEM
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Soil is a composite environment which is the result of
abiotic factors (independent of human actions), such
as:alterations to the bedrock (which provides soil's
mineral elements),
atmospheric content (oxygen fixation, nitrogen cycle,
water cycle).
The composite environment of soil also consists of
biotic factors such as :the content of vegetation cover and
the decomposition of living things.
The analysis of a section of soil shows a
superimposition of layers made up of different colours,
different chemical compositions and different sizes of
material. Each superimposition of layers creates a

3. TYPES OF DEGRADATION
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By 2050, the world population will have
reached 9 billion. Soil has therefore
become a fundamental resource that must
be protected as a matter of urgency.
The degradation process can take different
forms:
hydraulic erosion,
wind erosion,
changes in the soil's composition
physical degradation.

5. Soil provides living things with food, fibres and
fuel. It supports wildlife and rural and urban
activities. From late 1940s to the early1990s,
over 90% of the degradation of productive land
was due to overgrazing, deforestation and
inappropriate agricultural practices. These
changes in the soil affect over 2 billion people,
most of the 852 million people suffering from
hunger in particular.

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According to the ISRIC World Soil Information
data:46.4% of soil is experiencing an important
decrease in productivity and partially destroyed
biological functions. A third of it is in Asia and a
fifth is in Africa.
15.1% of soil can no longer be used for farming
as its biological functions have been seriously
destroyed and it would take large investments to
restore them.
About 9.3 million hectares (0.5%) of soil is
irreparably damaged and no longer has any

8. CAUSES OF SOIL DEGRADATION
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Human activity is the main cause of soil
degradation.
Agriculture plays a large part in soil
degradation, especially clearing, irrigation, the
spreading of chemical fertilisers and pesticides,
overgrazing and even the passage of heavy
farming equipment.
Irrigation and soil drainage can cause soil
acidification and salination whilst the use of
chemical fertilisers and pesticides contributes
to reducing soil capillarity (runoff) as well as its
consistency.
Overgrazing by cattle threatens the productive
capacity of soils thus making them more

9. IMPACT OF URBANISATION ON
SOIL
A large percentage of the global population reside
in urban areas. Thus cities are important driving
forces in environmental trends.As the world
continues to urbanize, however, humans have lost
contact with soil and the services it provides to
sustain life. The ability of urban activities to
influence the physical conditions and pollution
levels in soils at a distance is increasing. Cities
and urban processes have had dramatic but
varying impacts on soil physical and biochemical
properties and pollutant loads, all of which affect
the life-supporting services of soils. As developing
countries continue to industrialize, soil pollutant
contamination in their cities continue to increase to
levels warranting immediate action. In urban
areas, pollutants such as heavy metals which are
dumped can affect soils, just as old industrial sites

10. CONSEQUENCES
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A third of all cultivated land is losing its arable layers faster than it is gaining
them and this lessens its productivity.
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Using pesticides and chemical fertilisers destroys soil fauna which is
necessary for aerating soil. The well-known consequence of this
phenomenon is soil runoff which causes floods and mudslides.
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Wind erosion which has been worsened by overgrazing and tillage in some
cases, causes dust storms like in the USSR in 1960 or in Africa where 2 to 3
billion tons of soil particles leave the continent every year, thus gradually
wearing away the soil's fertility.
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By changing the composition and structure of soils, agriculture makes it
more difficult for CO2 to be stocked in soil. Indeed, the conversion of
meadows, forests and peat bogs into crops significantly reduces the amount
of pedological carbon storage in soil.
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As well as the loss of biodiversity (climax vegetation and environmental
habitats) which comes with soil degradation and regression, there are also
effects on climate change, especially through changes in the albedo on a
local level and greenhouse gas emissions (soil asphyxiation).