Muhammad Fahad Ansari 12IEEM14

1. DESERTIFICATION
Muhammad Fahad Ansari
12IEEM14

4. DESERTIFICATION
• Desertification is the impoverishment of terrestrial
ecosystems under the impact / influence of human
beings.
• In other words the desertification may be defined as the
destruction of forest as a result of human activity.
• About 3.6 billion of the world's 5.2 billion hectares of
useful dry land for agriculture has suffered erosion and
soil degradation.
• In more than 100 countries, 1 billion of the 7 billion-
world population is affected by desertification, forcing
people to leave their farms for jobs in the cities.
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5. • Desertification takes place in dry land areas
where the earth is especially fragile, where
rainfall is nil and the climate harsh.
• The result is the destruction of topsoil
followed by loss of the land's ability to sustain
crops, livestock or human activity.
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6. • Climatic changes can trigger the desertification
process, but human activities frequently are the
proximate cause.
• Over-cultivation exhausts the soil.
• Deforestation removes trees that hold the soil to
the land.
• Overgrazing of livestock strips the land of grasses.
• According to a UN study, about 30% of earth's land
- including the 70% of dry land - is affected by
drought.
• Every day, about 33,000 people starve to death.
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7. • Desertification creates conditions that intensify
wildfires and stirring winds, adding to the
tremendous pressure to earth's most precious
resource, water, and, of course, the animals
dependant on it.
• According to the World Wide Fund for Nature,
the world lost about 30% of its natural wealth
between 1970 and 1995.
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8. • Dust from deserts and drylands is blown into
cities around the world.
• Dust from Africa reaches Europe through the
wind, and even reaches US cities.
• Dust particles, which are less than 2.5
millionths of a metre in size, are inhaled,
causing health problems and have been
shown to boost death rates.
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9. • Desertification is the process, which turns
productive into non- productive desert as a
result of poor land-management.
• Desertification occurs mainly in semi-arid areas
(average annual rainfall less than 600 mm)
bordering on deserts.
• In the Sahel, (the semi-arid area south of the
Sahara Desert), for example, the desert moved
100 km southwards between 1950 and 1975.
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10. • The desertification commonly appears as
degradation of plants, animals, soil and water
resources.
• The desertification is a continuous process
going through several stages before reaching
the final one.
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11. • The desertification is a process leading to
desert like conditions – Desert like conditions
are:
3.No or less vegetation
4.Poor or unfertile soil
5.Scarcity of water
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12. Causes of Desertification
• Overgrazing is the major cause of desertification
worldwide.
• Plants of semi-arid areas are adapted to being eaten by
sparsely scattered, large, grazing mammals which
move in response to the patchy rainfall common to
these regions.
• Early human pastoralists living in semi-arid areas
copied this natural system.
• They moved their small groups of domestic animals in
response to food and water availability.
• Such regular stock movement prevented overgrazing
of the fragile plant cover.
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13. • In modern times, the use of fences has
prevented domestic and wild animals from
moving in response to food availability, and
overgrazing has often resulted.
• However, when used correctly, fencing is a
valuable tool of good wild management.
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14. • The use of boreholes and windmills also allows
livestock to stay all-year round in areas formerly
grazed only during the rains when seasonal pans
held water.
• Where not correctly planned and managed,
provision of drinking water has contributed to the
massive advance of deserts in recent years as
animals gather around waterholes and overgraze the
area.
• Cultivation of marginal lands, i.e lands on which
there is a high risk of crop failure and a very low
economic return, for example, some parts of South
Africa where maize is grown.
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15. • Destruction of vegetation in arid regions, often for fuel
wood.
• Poor grazing management after accidental burning of
semi-arid vegetation
• Incorrect irrigation practices in arid areas can cause
salinization, which can prevent plant growth.
• When the practices described above coincide with
drought, the rate of desertification increases dramatically.
• Increasing human population and poverty contribute to
desertification as poor people may be forced to overuse
their environment in the short term, without the ability to
plan for the long term effects of their actions.
• Where livestock has a social importance beyond food,
people might be reluctant to reduce their stock numbers.
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16. 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 tons of topsoil every year.
• As vegetation cover and soil layer are reduced,
rain drop impact and run-off increases.
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17. • 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.
• 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, and conditions are set for
continual deterioration.
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18. How to Control Desertification
• To halt desertification the number of animals on the land
must be reduced, allowing plants to re-grow.
• Soil conditions must be made favorable for plant growth
by, for example, mulching.
• Mulch reduces evaporation, suppresses weed growth,
enriches soil as it rots, and prevents runoff and hence
erosion.
• Reseeding may be necessary in badly degraded areas.
• Mulching and reseeding are expensive practices.
• However, the only realistic large-scale approach is to
prevent desertification through good land management
in semi-arid areas.
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19. Main Factors Responsible For Desertification in
Pakistan
• Unscientific land use practices and
mismanagement of land and water resources.
• Indiscriminate removal of trees, shrubs and
other vegetation to meet the fuel wood and
other needs
• Rapid growth in population resulting in
extension in cultivation and an increase in the
livestock pressure.
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20. Causes of Desertification in Pakistan
In Pakistan desertification usually happens due
to:
4.Natural Factors
5.Man Induced Factors
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21. Natural Factors
• The important natural factor responsible for
the desertification is climate.
• In this overall dryness of the atmosphere in
the arid regions causes low and sporadic
rainfall and high rate of evaporation.
• For example total geographical area of
Pakistan is 79.6 million hectares of which
41.00 million hectares is arid including 10
million hectares of sandy desert.
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22. The province wise break up is as under:
• Punjab --------------------> 12.0 Million Hectares
• Sindh --------------------> 13.5 Million Hectares
• Baluchistan ------------> 14.9 Million Hectares
• N.W.F.P ------------------> 0.6 Million Hectares
-----------------------
Total 41.0 Million Hectares
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23. Man Induced Factors
• The economic activity of man is the main reasons for over exploitation
of soil, plant, air and water resources causing desertification in
Pakistan.
• There are several factors, which enhance desertification due to man’s
interference with nature.
The two major may be grouped as:
• Primary Factors
• The man induced primary factors includes:
• Degradation of vegetative cover
• The degradation of vegetative cover causes desertification due to:
10.Tree cutting
11.Overgrazing
12.Bush Fires
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24. Water Erosion
• Water erosion results by the flow of water.
• When runoff passes over soil surface on which the
vegetation is not adequate it removes fertile soil
from the parent rock.
Wind Erosion
• The removal of finer soil particles by high wind is
serious in regions of low rainfall where there is not
enough vegetation to cover and protect the soil.
• The hazard is increased by destruction of vegetation
through overgrazing and cutting of wood for fuel.
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25. Water logging & Salinity
• Due to perennial canal irrigation system the
dynamic equilibrium between groundwater
recharge and discharge become unbalanced.
• The percolation of water from canals and irrigated
areas is greater than the rate at which water is
being discharged from the aquifer.
• This is because canals are unlined and irrigation to
agricultural crops is not done on scientific lines.
• As a result; water table raises rapidly, this results
in waterlogging.
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26. Total area under irrigation is 15 million hectares of
which 2.1 million hectares are affected by
waterlogging.
Climatic Zone Affected Area ( Million Hectares)
• Arid 1.87
• Semi arid 0.18
• Sub humid 0.05
--------------------------
Total 2.1 ( Million Hectares)
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27. Secondary Factors
• Expansion of cultivation to marginal lands
• Reduction in organic matter
• Urbanization
• Soil compaction & excess of toxic substances
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28. Visible Effects of Desertification
• Abandoned croplands affected by waterlogging and
salinity (Punjab & Sindh)
• Abandoned villages, traditional irrigation systems
and croplands deserted, deteriorated ground water
aquifers or lowering of the groundwater table
(Baluchistan)
• Siltation of rivers, irrigation systems and reservoirs
• Rock and soil slides on hill slopes
• Flush flooding
• Disappearance of physical infrastructure and
rangeland
• Socio economic problems.
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