1. Learning Unit 5: Desertification

2. Disclaimer
Please note that the following PowerPoint representation DOES NOT replace the official Study Material. The purpose of this additional resource is to support, assist and enrich your learning experience

3. Learning Outcomes Define the term "desertification"
Classify and explain the causes of desertification
Locate the countries within the Sahel Region on a map of Africa
Analyse how population growth in the Sahel results in desertification

4. Definition of desertification
The UNCCD defined desertification as land degradation in arid, semi-arid and dry subhumid areas resulting from various factors, including climatic variations and human activities.

5. Causes of desertification
Pages in Middleton
Five physical processes contributing to desertification:
Intensive grazing
Overcultivation
Overexploitation of vegetation
Salinization
Drought

6. Causes of desertification
Intensive grazing
Overuse of pastures by allowing too many animals or inappropriate types of animals grazing on pastures
Removal of biomass by grazing animals and livestock trampling cause soil compaction
Decreased vegetation cover increases soil erosion
Invasion of desert shrubs contribute to formation of desert pavement
Examples: commercial ranches in North America and Australia; Sahel (southern Somalia region in particular)

7. Causes of desertification
Overcultivation
Short fallow periods cause nutrient depletion and reduced crop yields
Mechanisation causes decreases in soil stability
Use of soils in marginal areas, which are more prone to droughts
All of the above activities decreases soil organic matter and increases soil erosion
Examples: US Great Plains (1930s), Former USSR’s Virgin Lands (1950s) and Niger (1950s and 1960s)

8. Causes of desertification
Overexploitation of vegetation
Expansion of grazing or cultivation (agriculture)
Provision of firewood
Soil is deprived of nutrients and organic matter from decomposing leaf litter
Decline in soil structure and fertility
May affect water tables
Chacoan forests in Argentina example:
Use of wood for railways
Agricultural expansion
Harvesting firewood and fodder
Making charcoal

9. Causes of desertification
Salinization of irrigated land
The potential evaporation rate of water from soil exceeding the input of water, which allows salts to accumulate near the surface as the soil dries.
Salt build-up can occur in the root zone of plants or create saline water tables under irrigated fields
Irrigation techniques which lead to salinization are:
Water leaks from supply canals
Overapplication of water
Poor drainage
Insufficient application of water to leach salts away
Examples: Indus irrigation system in Pakistan, Aral Sea tragedy

10. Causes of desertification
Drought
A temporary dry period when precipitation is significantly below normal recorded levels.
Three types of drought (meteorological, agricultural, hydrological)
Drought and its effects on people vary depending on their coping capabilities.
The impact of drought is more severe in some developing countries as in developed countries
Examples: Botswana; Niger; Kenya; Ethiopia; Eritrea and Djibouti

11. Positive changes: Case Study
Page 101 in Middleton
Reforestation in southern Niger
The low-cost method of tree regeneration
Amendment of laws in Niger to transfer ownership of trees to farmers
Benefits from trees: reducing wind speeds, evaporation and limiting soil and moisture losses
Falling leaves used as natural fertilizer
Trees producing firewood, fruit and bark
Improvement of food security and reducing poverty during a time of rapid population growth
Highest tree densities found in areas of high rural population density