About
The Sahara — covering approximately 9 million km² across 11 African countries — is the world's largest hot desert, and yet 6,000-11,000 years ago (the 'African Humid Period' or 'Green Sahara'), it was covered by lakes, grasslands, and forests, and was densely populated by humans and wildlife (hippos lived in what is now the central Sahara). This dramatic transformation from wet to dry — caused by changes in Earth's orbital cycles (Milankovitch cycles) reducing summer insolation in the Northern Hemisphere — happened relatively rapidly over 1,000-2,000 years.
The Sahara's history is foundational to African and world history: the desiccation of the Sahara (beginning ~5,500 years ago) may have pushed human populations toward the Nile Valley, concentrating them in conditions that led to the development of Egyptian civilization. The Sahara was never completely impassable — trans-Saharan trade routes (gold, salt, slaves) connected sub-Saharan Africa to North Africa and the Mediterranean for 2,000 years, producing great empires (Mali Empire, Ghana Empire, Songhai Empire). The Tuareg people have navigated the Sahara for millennia using star navigation and knowledge of ephemeral water sources.
# Top 10 Sahara facts
- 19M km² (largest hot desert)
- 2Green Sahara (6,000-11,000 years ago, hippos in the Sahara)
- 3Milankovitch cycles caused desiccation
- 4trans-Saharan trade routes
- 5Tuareg people
- 6Saharan rock art (green period wildlife)
- 7Niger River
- 8Sand dune seas (ergs, 25% of Sahara)
- 9temperature extremes (50°C day, -0°C night)
- 10climate models predict possible re-greening
Fascinating Facts
- ◆The Sahara was a green, well-watered landscape with hippos, elephants, crocodiles, and dense human settlement as recently as 5,000 years ago — rock art in the Tassili n'Ajjer mountains depicts this vanished landscape — and its desiccation may have pushed populations toward the Nile, triggering Egyptian civilization
- ◆Trans-Saharan trade routes carried gold and salt in both directions for 2,000 years — gold from West Africa (Mali Empire) was so abundant that when Mansa Musa (Emperor of Mali) made a pilgrimage to Mecca in 1324 with 60,000 followers carrying gold bars, he caused inflation in Egypt that lasted 12 years
- ◆Climate models suggest that African greening (reduced Sahara) similar to the Green Sahara period may occur again by 2100 as global warming strengthens the West African monsoon — potentially transforming the region's ecology and carrying capacity within 80 years
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