DESERTIFICATION

Muhammad Fahad Ansari 12IEEM14

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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• 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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• 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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• 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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• 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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• 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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• 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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• The desertification is a process leading to desert like conditions – Desert like conditions are:

1.No or less vegetation2.Poor or unfertile soil3.Scarcity of water

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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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• 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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• 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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• 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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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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• 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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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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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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Causes of Desertification in PakistanIn Pakistan desertification usually happens due

to:1.Natural Factors2.Man Induced Factors

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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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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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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:1. Tree cutting2. Overgrazing3. Bush Fires

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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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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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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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Secondary Factors • Expansion of cultivation to marginal lands• Reduction in organic matter• Urbanization• Soil compaction & excess of toxic substances

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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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