The sand dunes and rocky plateaus of the Sahara Desert may seem ancient, but they’re actually not that old. This vast swath of North Africa transforms from arid desert to lush forest every 21,000 years, a new study shows.
The last period when the Sahara was a green forest area occurred between 15,000 and 5,000 years ago. This latest research confirms that this was not just a strange disruption, but part of a cyclical transformation that changes the region from arid to wet every about 21,000 years.
D., lead author of the study and climate scientist at the University of Helsinki and the University of Bristol. “The cyclical transformation of the Sahara Desert into savannah and forest ecosystems is one of the most remarkable environmental changes on the planet,” said Edward Armstrong in a statement. “Our study simulates African Humid Periods of a magnitude comparable to those shown by paleoclimatic observations and examines why and when these events occur.” “One of the first climate modeling studies to show that this is occurring.”
The new research aimed to better understand the so-called “North African Humid Periods” over the last 800,000 years using a recently developed climate model.
The research confirmed the idea that periodic rainy phases in the Sahara are caused by changes in the Earth’s orbit around the Sun. It is generally accepted that the “greening” of the Sahara is caused by the shaking of the Earth on its axis, affecting seasonality and determining the amount of energy this part of the planet receives. This change affects the strength of the African Monsoon, which helps control how much vegetation spreads across this vast region.
But the study also suggests that this cycle may also be influenced by distant high-latitude ice sheets in the Northern Hemisphere. The study notes that wet periods did not occur during the Ice Ages, when most of Earth’s high latitudes were covered by thick sheets of ice. They think these ice sheets help cool the atmosphere like a refrigerator, limiting the African Monsoon system and suppressing the growth of plant life in the Sahara Desert.
North Africa’s cyclical transformation is not only important for the Sahara, it also has major implications for the human story. After all, some of humans’ greatest early achievements (the migrations from Africa) were largely determined by the conditions of the Sahara. It looks like this area can be a tough obstacle or a pleasant path, depending on the situation you’re in.
“The Sahara region is a gateway that controls the distribution of species both between North and Sub-Saharan Africa and within and outside the continent,” said co-author Miikka Tallavaara, Assistant Professor of Hominin Environments at the University of Helsinki. The statement continues: “The door was open when the Sahara was green, closed when the deserts dominated. This alternation of moist and dry phases had important consequences for the distribution and evolution of species in Africa. “Our ability to model the wet periods of North Africa is a great achievement and means we can now better model human distributions and better understand the evolution of our species in Africa.”
The study was published in the journal Nature Communications.
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