Just how green was the 'Green Sahara' and how did the human inhabitants respond to the climatic changes?
Savanna grassland, South Africa
At the end of the Late Pleistocene, full glacial hyperarid conditions prevailed over an unpopulated, barren Sahara. In just a few thousand years the Sahara underwent major climatic changes, prompted by slow changes in the precession of the Earth’s orbit, marking the beginning of the African Humid Period (AHP), ca. 11,500 years ago followed by its demise at ca. 5000 BP. At this time the Sahara was a vastly different environment from the desert that we know today. The so-called “Green Sahara” supported a humid savannah with herds of elephant and other large fauna, and abundant lakes and rivers, which were home to aquatic species, including crocodile and Nile perch. However, this climatic amelioration was transitory, and there was a return to full desert ecosystem conditions by ca. 5000 BP; remarkably, this cycle was complete within a period of only 6000 years.
Whilst the Holocene AHP is perhaps one of the most thoroughly documented and well-dated climate change events, the rate of terrestrial environmental change, its spatial distribution, and ecological implications for human settlement are poorly understood with important questions remaining unanswered. For example, did some parts of the Sahara begin ‘greening’ sooner than others, and did climatic amelioration extend to all parts of the desert, or did localised arid conditions persist? How did populations adapt to changes in
resource availability, and to what degree did they rely on the newly available aquatic species? Answering these questions is vital to advancing our knowledge about the ecological and human history of the Sahara and will help in understanding how humans responded to past environmental change, providing potentially valuable insights for future climatic change.