A study shows that Sahara desert in Africa was quite green and it made a slow transition to what it is now. It became world’s biggest hot desert some 2700 years ago after a very slow fade from green according to a new study.
Previously it was known that the transition was quick and abrupt but this new theory proves it wrong.
The study by European-US-Canadian team of scientists show that six thousand years ago, the massive arid green dominating northern Africa was quite green. It had patchwork of trees and savannas as well as many sparkling lakes. It has published in the latest issue of Science.
Sahara desert is larger than Australia.
The scientists studied layers of sediment in one of the largest remaining Sahara lakes, Yoa, in a remote spot in northern Chad, as most of the physical elements that could tell the tale of the Sahara’s geographic evolution have been lost.
They looked at sediments, did soil tests and reviewed biological indicators such as plant and tree pollen and spores that were present before the desert encroached. Remains of aquatic microorganisms also came under study.
According to Stefan Kropelin, a geogolist at the Prehistoric Archeology Institute of the University of Cologne, who took part in the new study:
These findings contradict previous modeling that indicated at a rapid collapse of vegetation in the region in a sudden end to the African humid period about 5,500 years ago.
Previous study was done by Peter de Menocal of Columbia University in 2000. They studied sediments in the west of Mauritania and found a sudden increase in wind-carried dust blown off the Sahara region, suggesting swift climate change.
But data from Lake Yoa shows the opposite, and the transition to desert took its time, said Kropelin.
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