African Humid Period

The African Humid Period was an interval, roughly 14,500 to 5,000 years ago, when much of North Africa had stronger summer rains, extensive lakes and grasslands, and expanded human settlement.

African monsoon: Seasonal winds and rainfall systems that bring most of tropical Africa’s annual precipitation. Stronger summer monsoon rains supplied much of the period’s increased precipitation.
Lake Mega-Chad: A vast prehistoric lake occupying the Chad Basin during wetter intervals of the late Quaternary. Its shoreline deposits document an enormous lake in the humid Sahara.
Holocene pastoralism in the Sahara: The keeping of livestock by Saharan communities during the African Humid Period and subsequent drying. Pastoralism spread as grasslands and seasonal water supported herding.
Termination of the African Humid Period: The gradual decline of North African rainfall and vegetation that ended the African Humid Period. This transition converted many lakeshores and grasslands into increasingly arid terrain.
Abrupt climate change: A substantial climate shift occurring over a timescale much shorter than the changes that drive it. Some records suggest rapid local changes within the broader, uneven drying trend.
Precession: The slow change in the orientation of Earth’s rotational axis, altering the timing of seasons relative to its orbit. Precession increased Northern Hemisphere summer sunlight during the humid interval.
Tassili n’Ajjer rock art: Paintings and engravings in Algeria’s Tassili n’Ajjer plateau depicting people, animals, and changing environments. Its depictions of cattle and aquatic life evoke landscapes unlike today’s desert.
Nabta Playa: A prehistoric archaeological site in Egypt’s Western Desert with evidence of seasonal occupation and cattle herding. Its archaeological record captures early communities using a now-arid landscape.
Sahara desertification: The long-term expansion and intensification of arid conditions across the Sahara. The humid period’s end contributed to the modern desert’s establishment.
Green Sahara hypothesis: The proposal that vegetation feedbacks can help produce abrupt transitions between desert and vegetated Saharan states. It offers an alternative emphasis to explanations centered on orbital forcing alone.

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