This document discusses deserts and desertification. It defines deserts as arid regions with little vegetation that receive less than 10 inches of rainfall per year. There are different types of deserts classified by factors like rainfall, temperature, and location. Desertification is the process by which productive land becomes desert, threatening over 850 million people across more than 100 countries. Reclamation techniques to address desertification include controlling sand dunes, afforestation, and irrigation methods to enhance vegetation cover and protect soil.

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Samir BENZERGA Professor : Chris YUKNA

2.  What is desert ?
 Kinds of Deserts
 Where Deserts are Found
 Desertification
 What are the effects of desertification
 Reclamation techniques :
* Control of sand dunes
* Afforestation
* Irrigation techniques
 Conclusion

3. What is desert ?
Desert, an arid region with little or no vegetation. The
word comes from a Latin word meaning abandoned or
forsaken, signifying lack of human habitation. Although
deserts seem to be uninhabited, some kinds of plants and
animals have adapted to the harsh conditions. People, too,
live in or near deserts traditionally as oasis dwellers or
nomads. In the 20th century, permanent settlement in
some deserts has increased, largely due to improved means
of obtaining water and to such inventions as air
conditioning.

4. The term desert usually refers to areas that, in addition to
being extremely dry, have high daytime temperatures,
particularly in the summer. Many scientists also consider
polar regions to be deserts, since they are arid and sustain
little or no vegetation.
Deserts occupy between 15 and 20 per cent of the earth's
land area. They usually receive less than 10 inches (250
mm) of precipitation yearly. Precipitation, usually rain,
tends to come in a few heavy storms of short duration.
Deserts are often bordered by semiarid areas.

5. Kinds of Deserts
Though most scientists who study deserts agree that there
are several types of deserts, they do not agree on how to
classify these types. Some scientists classify deserts
according to the amount of annual precipitation received.
Others classify them according to the types of vegetation
and soil present. Still others classify deserts by average
summer and winter temperatures. In a general
sense, deserts can be categorized by where they are located.

6. Where Deserts are Found
• Rainfall
• Temperature
• Atmospheric Pressure

7. Desertification
The term desertification has been in use since 1949, yet still
there is no generally accepted definition.
Most definitions suggest:
• desserts increasing
• loss of resource potential
• depletion of soil and vegetation cover.
Reached wider audience after international concern of
famine in West Africa.
Affects about 65 million hectares of once agricultural land.
Threatens livelihood of 850 million people.
Affects more than 100 countries world wide – 27 in Africa
alone.

8. What are the effects of desertification
Desertification reduces the ability of land to support
life, affecting wild species, domestic animals, agricultural
crops and people. The reduction in plant cover that
accompanies desertification leads to accelerated soil
erosion by wind and water. South Africa losing
approximately 300-400 million tonnes of topsoil every year.
As vegetation cover and soil layer are reduced, rain drop
impact and run-off increases.
Water is lost off the land instead of soaking into the soil to
provide moisture for plants. Even long-lived plants that
would normally survive droughts die.

9. A reduction in plant cover also results in a reduction in the
quantity of humus and plant nutrients in the soil, and
plant production drops further. As protective plant cover
disappears, floods become more frequent and more severe.
Desertification is self-reinforcing, i.e. once the process has
started, conditions are set for continual deterioration.

10. Reclamation techniques
Control of sand dunes is a traditional technology
originating from the Ming Dynasty (1368-1644). Flood
water is used to reclaim deserted land, flattening sand
dunes, thus controlling wind sand erosion and creating
farmland.Oil in areas of water shortage.
Afforestation is an effective method used to enhance areas
that are affected by drifting sand.Air-seeding allows the
distribution of seeds into regions that would otherwise be
ecologically unreachable.

11. Irrigation techniques are inexpensive, the equipment is
user-friedly, plants are guaranteed to grow in all
seasons and the permantly wet roots deter termite
infestations.

12. Examples :
The Mongolian tradition of combating desertification :
Involves tree planting which reduces sand movement and
provides.
Algeria Green Wall :
The "Green Wall" was to halt the advancing desert to the north,
creating a barrier of greenery, that protects the steppe from the
Moroccan border to that of Tunisia. A total of 3 million hectares
were to be afforested. 160 000 hectares have been only. 160 000
hectares which are most often the appearance of large fields
withered the colors more than gray green

14. Conclusion :
rehabilitation becomes increasingly
lengthy and expensive and degradation may reach
a threshold beyond which it is reversible and
in practical .

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