Hot desert case study: the Sahara and Sahel

OCR J383 Paper 2 offers a choice of hot desert OR cold environment. Hot desert is the more popular option. You need to know the Sahara as a named case study and understand the adjacent Sahel as the zone threatened by desertification.

The Sahara Desert — characteristics

Location: North Africa; 9 million km2 — the world's largest hot desert; countries include Morocco, Algeria, Libya, Egypt, Mali, Niger, Chad, Sudan.

Climate:

• Average rainfall: under 25 mm/year (hyperarid zones: under 10 mm).
• Daytime temperatures: 40–50 degrees C; night-time temperatures can drop below 0 degrees C (extreme diurnal range due to lack of cloud cover and moisture).
• High wind speeds; dust storms (haboobs).

Landforms:

• Erg: large areas of sand dunes (only 25% of Sahara is sandy).
• Reg/Hamada: flat plains of gravel and bare rock (majority of the Sahara).
• Wadis: dry river valleys that flood briefly during rare rain events.
• Oases: areas where groundwater reaches the surface → vegetation and settlement.

Adaptations of plants and animals

Plant adaptations (xerophytes)

• Deep or widespread roots: to access groundwater or capture every drop of rainfall.
• Waxy/thick cuticle leaves: reduce water loss through transpiration.
• Storing water in stems: cacti (though native to Americas; Sahara has Euphorbia as equivalent).
• Small/no leaves: reduce surface area for water loss; spines instead of leaves.
• Short life cycle: seeds germinate, flower and set seed within days of rainfall.

Animal adaptations

• Camel: water stored as fat in hump (not water); can go weeks without drinking; wide feet for sand; long eyelashes for sand protection; kidneys concentrate urine.
• Fennec fox: large ears dissipate heat; nocturnal to avoid daytime heat.
• Jerboa: nocturnal; metabolic water from food; hibernates in burrows during hottest periods.

Economic opportunities in the Sahara

1. Mining

• Oil and gas: Libya, Algeria, Egypt — major reserves; key to national economies.
• Phosphates: Morocco and Western Sahara have some of the world's largest deposits.
• Uranium: Niger — Arlit mine; 7% of global uranium production.
• Iron ore: Mauritania — Zouerate mine; exported via a 700 km railway.
• Challenge: extreme heat + remoteness → high operational costs; limited labour pool.

2. Tourism

• Cultural tourism: Marrakech, the Atlas Mountains, Saharan dune experiences (Erg Chebbi, Morocco; Douz, Tunisia).
• Revenue: Morocco receives 13 million tourists/year; Saharan tourism contributes significantly.
• Challenge: political instability in parts of the Sahara (Libya, Mali, Niger) deters tourists; heatwave risk; infrastructure poor.

3. Renewable energy

• Solar potential: the Sahara receives more solar energy per m2 than almost any other region on Earth.
• Desertec project: proposed 2009 — solar panels across North Africa to power Europe via undersea cables. Stalled due to political and cost challenges.
• Morocco's Noor complex (Ouarzazate): world's largest concentrated solar power plant; powers 1 million homes.

4. Farming and pastoralism

• Oasis agriculture: date palms, vegetables using groundwater irrigation.
• Nomadic pastoralism: Tuareg, Berber and other groups move livestock seasonally following sparse rainfall.
• Challenge: water extraction for farming depletes fossil aquifers (Nubian Sandstone Aquifer System) — non-renewable; draining rapidly.

The Sahel: desertification challenge

The Sahel is the semi-arid transition zone south of the Sahara (Senegal → Ethiopia) — approximately 5,400 km wide; home to ~135 million people.

Desertification = the process by which fertile land at the desert edge becomes unproductive and more desert-like.

Causes of desertification

• Overgrazing: too many livestock strip vegetation → bare soil eroded by wind and rain.
• Deforestation: trees removed for fuel wood → reduced soil protection and transpiration.
• Population growth: more people → more pressure on the land → harder to manage sustainably.
• Climate change: reduced and more variable rainfall in the Sahel since the 1960s (Sahel drought 1968–85 killed 100,000+).
• Over-cultivation: continuous farming with no fallow period depletes soil nutrients.

Management: the Great Green Wall

• African Union initiative launched 2007: plant an 8,000 km belt of trees and vegetation from Senegal to Djibouti across the Sahel.
• Goal: restore 100 million hectares of degraded land by 2030.
• Progress: ~18 million ha restored so far; Senegal, Ethiopia, Niger leading.
• Benefits: carbon sequestration, food security, employment, halt desertification.
• Challenges: funding gaps, conflict zones (Mali, Niger), land tenure disputes.

Common OCR exam mistakes

1. Saying the Sahara is all sand dunes — only 25% is sandy erg; most is rocky reg/hamada.
2. Confusing the Sahara (desert) and the Sahel (semi-arid zone at the desert fringe).
3. Forgetting that camel humps store fat, not water.
4. Only describing opportunities without evaluation — always assess whether mining/tourism actually benefits local people or primarily benefits governments and multinationals.