1. Section Four
The spreading desert

2. Desert
Desert is a dry region. It receives less than 250mm of rain a year.
Climatic characteristics
Rainfall:
Less than 250mm rainfall a year.
Rainfall is irregular.There may be no rain for several years. When the rain comes, it occurs in the form of short and heavy thunderstorms.
Temperature:
Very hot during the day. Very cold at night. Large diurnal range of temperature.

3. Areas in danger of desertification
Major deserts in the world

4. What is desertification?
Five years later
Desertification is the process by which the desert spreads into
the surrounding areas.

5. Areas in danger of desertification
Major deserts in the world

6. Where is the Sahel?
The Sahel

7. Rainfall and natural vegetation in the Sahel
Desert
Grassland and woodland
Rainforest
Annual
rainfall
Less
than
250mm
,000mm
More than
2,000 mm

8. Where is the Sahel? The Sahel is a narrow belt of land in Africa.
It is located between the dry desert land to the north and the forest areas to the south.
Temperatures are always high and there is a long dry season.
Most rain comes during the summer. There is more rain in the south and rainfall decreases towards the desert in the north.
The natural vegetation is mainly grassland.

9. Causes of desertification in the Sahel
Long period of drought
Soil becomes loose and dry.
Land become bare.

10. Causes of desertification in the Sahel
Long period of drought
As a result . . .
Wind
Water
Soil erosion occurs.
Land becomes desert like-land.

11. Drought Rainfall is highly unreliable.
In this long period of drought, vegetation has died. The land has become bare.
The soil becomes dry and loose.
The loose soil is easily removed by wind and water.
Soil erosion takes place.
Areas without vegetation cover will turn into desert-like land.

12. Causes of desertification in the Sahel
Population growth and human activities

13. Causes of desertification in the Sahel
Population growth and human activities
demand for food increases
Expansion of farmland
overcultivation overgrazing

14. Causes of desertification in the Sahel
Population growth and human activities
Overcutting of fuelwood
Trees cannot grow fast enough to recover themselves.Soil erosion occurs.

15. Causes of desertification in the Sahel
Population growth and human activities
Poor irrigation
The soil becomes very
salty and crops die.
Irrigation water bring mineral salts to the surface.Salty soil is not suitable for crop growth.

16. A summary of the causes of desertification
Drought
Population growth
Land becomes bare
Overgrazing
Expansion of farmland
Soil erosion
Overcultivation
Overcutting of fuelwood
Poor irrigation
Desertification

17. What are the results of desertification?
Loss of soil fertility and
vegetation becomes damaged
Less food production
widespread malnutrition
and starvation

18. Ways to stop desertification in the Sahel
3. Birth control to reduce birth rates
4. Large-scale dams to store water for irrigation and HEP
6. Planting fast-growing trees for fuelwood
1. Rearing good quality cattle
7. Hand dug irrigation canals
2. Planting fast-growing grass
5. Growing high-yielding crops

19. Problems with the measures to stop desertification
Most Sahelian countries are politically unstable.Civil wars are frequent.It is difficult to carry out development plans.
Birth control has failed. Population pressure remains very high.
The countries in the Sahel are very poor and heavily in debt. Most of the money borrowed has been spent on developing industries and infrastructure.
The government lacks the experts to carry out the development plans. People do not know how to use the new technology.

20. How can we help? Desertification is a global problem Rich countries
offer financial and technical
help to poor countries
such as World Vision and Oxfam provide food and medicine to the local people
Voluntary relief organisations
donate money and join operations organised by the relief organisations
Individuals