Life in the Sahara and the Sahel: Adapting to a Desert Region Chapter 20
I. Geoterms • A. Desertification: the process by which land becomes more and more dry until it turns into desert. This may be caused by climate change, human activities, or both. • B. Drought: an unusually long period in which little or no rain falls • C. Marginal Land: land that is not well suited for growing crops • D. Pastoral Nomads: groups of herders who move with their animals from place to place in search of pasture and water.
II. The Geographic Setting • A. The World’s Largest Desert • 1. 3.5 million square miles (size of USA) • 2. Daytime temperature is 136F. • 3. About 6,000 years ago climate started to change creating a desert • 4. Trade winds from the north eliminated any moisture • 5. Most plants, animals, people that live here, live near oases.
B. The Sahel: On the Sahara’s Edge • 1. Sahel is on the southern edge of the Sahara • 2. Sahel receives more rain than the Sahara but often has long droughts • 3. Sahel is marginal land which is not good for farming (subsistence farming) • 4. People living here are pastoral nomads (people moving from place to place looking for water and grazing land for their animals • 5. Desertification is causing the Sahara to expand
III. The Desert Environment • A. The Desert Landscape: More Than Just Sand • 1. Three landforms • A. Ergs: great seas of sand with tall sand dunes over 400 feet high • B. Regs: gravel-covered plains • C. Hammadas: high rock-covered flatlands • D. Nile and Niger rivers with sources in mountains beyond the desert • E. Wadis: dry riverbeds that can turn into raging rivers after a rain and then quickly dry up again
B. The Harsh Desert Climate • 1. Temperatures: daytime 100+ degrees, night time may drop below freezing • 2. Sandstorms can reduce visibility to nothing • 3. Rain is unpredictable with flash floods occurring • 4. Plants adapt to climate • A. deep roots to anchor it and get moisture • B. Small waxy leaves that retain moisture
Transparency 20B • Answer questions (20.3) page 150
IV. Adaptations to Life in the Desert • A. The Wandering Tuareg • 1. Nomadic Tuareg raise camels, goats, cattle, or sheep • 2. They move about in search of grazing areas (caravans) • 3. Known as “Blue Men of the Desert” because they wear long blue robes that project them from sun and sand
4. Live in family groups of <100 people • 5. Can pack all possessions on just one camel • 6. They trade (meat, cheese, milk) at oases • 7. They often travel at night by reading the stars – and it is cooler
B. Technology Makes Life Easier • 1. Use lightweight plastic and metal containers • 2. Some use satellite phones to talk to customers • 3. Drilling machines create new oases by drilling through rock to underground water sources • 4. Trucks and planes being used to transport people and goods
V. The Oasis environment • A. Islands of Water Surrounded by Desert • 1. Natural oasis: springs bubble up to surface from underground or low spots where land dips to underground stream • 2. Human made: hand dug wells or machine drilled
B. Large and Small Centers of Life • 1. Sahara has about 90 large oases that can support a village and many small ones that can only support a family • 2. Many different plants and animals • A. Acacia and Baobab trees and shrubs • B. Gazelles, butterflies, and insects • C. Date Palms (most important) for fruit, building materials, rope, and animal feed
Transparency 20C • Answer questions (20.5) on page 151
VI. Adaptations to Life in the Oases • A. The Traditional Ways of Oasis Settlers • 1. Trading and farming is the major economic activity of an oasis • 2. Most people are subsistence farmers • 3. Some grow cash crops (dates, wheat, barley, and vegetables) • 4. People stop here to trade and get water • 5. Homes made of mud brick to keep out heat
6. Most work is done in cooler part of the day • 7. Windbreaks planted to protect from wind and sand B. Water Problems Limit the Growth of Oasis Towns 1. As oases grow, water must be brought in by truck 2. If too much water is used for either people or crops, it will run out.
VII. The Sahel Environment • A. A Landscape Threatened by Drought and Desertification • 1. Sahel’s vegetation is mix of acacia trees, baobab trees and small shrubs • A. North of this is desert = lack of rain • B. South is greater variety of plants due to more rain
2. Droughts lasting >six years • 3. Desertification • A. Winds take away soil • B. Sahara desert is expanding
B. Over grazing by cattle is a major cause of desertification in the Sahel (causes destruction of cover plants, allowing wind or water to erode the soil)
Transparency 20D • Answer questions 20.7 on page 151
VIII. Adaptations to Life in the Sahel • A. Plant crops that require little water (grains like millet and sorghum) • B. “Shifting Agriculture”: farmers plant on field for 1-2 years and then change fields • C. Human Causes of Desertification • 1. Farmers plant crops (peanuts) that deplete soil faster, then soil blows away • 2. Herders expanding herds and animals overgraze, turning land into desert • 3. Deforestation: people cutting down trees so erosion occurs
D. Agencies trying to correct this problem • 1. Get people to burn coal rather than trees • 2. Plant windbreaks • 3. Conserve water • 4. Improved farming methods
IX. Globally – Desertification Happening Around Other Deserts of the World • Transparency 20E • A. China • B. Baja California • C. Peru • D. Kazakhstan • E. Australia
X. Global Connections • A. Are the world’s deserts growing or shrinking? • B. What human activities contribute to desertification? • C. How might people adapt to living in areas threatened by desertification?