Deserts of Africa

Africa contains some of the most diverse desert ecosystems in the world, ranging from the hyper-arid Sahara in the north to the coastal fog deserts of the south. These arid regions are primarily the result of atmospheric circulation patterns (Hadley Cells), cold ocean currents, and rain-shadow effects.

The Sahara Desert: The Great Arid North

The Sahara is the largest hot desert in the world, covering approximately $9$ million km² and spanning nearly one-third of the continent.

Key Characteristics and Features

• Geographical Scope: It touches 11 countries: Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan, and Tunisia.
• Topography: Contrary to popular belief, only about 25% of the Sahara is sand (Ergs). The rest consists of barren rocky plateaus (Hamada), gravel plains (Regs), and salt flats (Shatts).
• The Tibesti and Ahaggar Mountains: These are volcanic highland regions within the desert that receive slightly more rainfall and host unique biodiversity.
• The Nile River: This is the only permanent river that crosses the Sahara, acting as an “exotic” stream that originates outside the desert.

The Sahel: The Desert Frontier

The Sahel is a semi-arid transition zone between the Sahara to the north and the Sudanian Savanna to the south. It is currently the focus of the Great Green Wall initiative, an African-led project to combat desertification and land degradation.

The Namib Desert: Coastal and Ancient

Located along the Atlantic coast of Namibia, Angola, and South Africa, the Namib is considered the oldest desert in the world (at least $55$ million years old).

Distinctive Features

• Benguela Current: The cold Benguela current flowing along the coast prevents rainfall but creates heavy fog, which is the primary source of moisture for the desert’s flora and fauna.
• Sossusvlei: Famous for its high, red sand dunes (some among the tallest in the world) and “Deadvlei” white clay pans.
• Welwitschia mirabilis: A unique “living fossil” plant endemic to the Namib that can live for over $1,000$ years.

The Kalahari Desert: The Semi-Desert

Located in the Southern African interior, the Kalahari covers much of Botswana and parts of Namibia and South Africa.

Characteristics

• Rainfall Pattern: It is technically a “fossil desert” or semi-desert because it receives more rainfall ($120$ to $250$ mm annually) than a true desert.
• Vegetation: It supports more plants and animals than the Sahara, including acacia trees and various grasses.
• The Okavango Delta: While the Kalahari is arid, it houses the Okavango Delta, one of the world’s largest inland deltas, where the Okavango River drains into the desert sands rather than the sea.

Other Notable Arid Regions

• Danakil Desert: Located in the Afar Triangle (Ethiopia/Eritrea). It is one of the lowest and hottest places on Earth, known for sulfur springs and active volcanoes.
• Nubian Desert: The eastern region of the Sahara, situated between the Nile and the Red Sea in Sudan. It is primarily a high sandstone plateau.
• Libyan Desert: The north-eastern part of the Sahara, known for being extremely dry and containing the Qattara Depression.

Comparison Table of Major African Deserts

UPSC Prelims Trivia

• Hamada vs. Erg: UPSC often tests landform terminology. Hamada refers to a rocky desert, while Erg refers to a sea of sand dunes.
• The Great Green Wall: An African Union initiative spanning $8,000$ km across the width of Africa to restore $100$ million hectares of currently degraded land.
• Endemic Species: The Dromedary Camel (one-humped) is native to the Sahara/Arabian regions, whereas the Bactrian Camel (two-humped) is found in Central Asian deserts.
• Qattara Depression: Located in Egypt, it is the second-lowest point in Africa at $133$ meters below sea level.