Arabia Weather – It’s hard to imagine, but the Sahara desert was a green forest a few thousand years ago.
Every 21,000 years the desert becomes fertile land
The sand dunes and rocky plateaus of the Sahara may seem as old as time, but that may be far from the truth. According to a new study, this vast area of North Africa changes from barren desert to lush forest every 21,000 years or so.
The last time the Sahara was a green forest occurred between 15,000 and 5,000 years ago. This latest research confirms that it’s not just a curious blip, but part of a cycle that changes an area from dry to wet every 21,000 years.
Dr Edward Armstrong, lead author of the study and a climate scientist from the University of Helsinki and the University of Bristol, said in a statement: “The transformation of the Sahara into different ecosystems and forests is one of the most significant environmental changes on the planet.”
“Our study is one of the first climate modeling studies that simulates African wet periods at a scale similar to what paleoclimate observations indicate, and reveals why and when these events occur.”
The new research seems to have a better understanding of what is being called “Wet Periods in North Africa”. It uses a recently developed climate model for the past 800,000 years.
Their work confirmed the idea that periodic wet phases in the Sahara are driven by changes in Earth’s orbit around the Sun. It is generally agreed that “Greening“The Sahara desert exists because of the Earth’s tilt on its axis, which affects the seasons and determines the amount of energy a part of the planet receives. This ultimately affects the strength of the African monsoon, which helps control the amount of vegetation spread across a wide area.
However, their work also suggests that this circulation may be influenced by distant ice sheets at high latitudes in the Northern Hemisphere. Wet periods did not occur during the Ice Ages, when most of Earth’s high latitudes were covered by thick ice sheets.
Experts speculate that these ice sheets served to cool the atmosphere like a refrigerator, controlling the African monsoon system and suppressing the growth of plant life in the Sahara.
Cycle change in North Africa is not only a big problem for the Sahara, but it has huge implications for our story. After all, humanity’s greatest early achievements—the migrations out of Africa—were largely dictated by conditions in the Sahara. Depending on his “mood”, it can act as a severe barrier or a welcoming path.
The door was open when the desert was green and closed when deserts prevailed
Mika Thalavara, co-author and assistant professor of hominin ecology at the University of Helsinki, explained: “The Sahara serves as a gateway to northern and sub-Saharan Africa, controlling the spread of species within and beyond the continent.”
The door was open when the desert was green and closed when deserts prevailed. This transition between wet and dry phases had serious consequences for the distribution and evolution of species in Africa. Modeling wet periods in North Africa is a major achievement, and we are now able to model human distributions and understand the evolution of our species in Africa.
Source: Science
Nature
