Human Activities May Have Created Sahara Desert, Study Says

Posted: Mar 16 2017, 12:59pm CDT | by , Updated: Mar 16 2017, 1:06pm CDT, in News | Latest Science News

 

Human Activities may have Created Sahara Desert, Study Says
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New study suggests that ancient humans may have transformed Sahara from lush grassland to a dry region

Sahara desert used to be a lush, green landscape some 10,000 years ago. But then shifts in weather patterns transformed the green, vegetated land into some of the driest places on Earth. However, a new research suggests that humans had also played a role in Sahara’s transformation and turning it into a arid place as we know it today.

The new claim is based on the fact that humans have often emerged as a major contributor behind radical changes in the original state of many ecosystems, from extinction of Australian magafuana to the loss of Arctic sea ice to environmental changes in East Asia. 

“In East Asia there are long established theories of how Neolithic populations changed the landscape so profoundly that monsoons stopped penetrating so far inland.” Study author and archeologist Dr. David Wright from Seoul National University said

The evidences of human-driven ecological and climatic change have been documented in the historical records of Europe, North America and New Zealand due to th eintroduction of livestock. And Wright believes that similar scenarios could also be applied to the desert of Sahara. 

To test the hypothesis, the archeologist looked at the earliest known evidence of the raising of the livestock across the Saharan region and compared this with records showing the spread of scrub vegetation or low woody plants, which is an indicator of an ecological shift towards desert-like conditions. The record happens to coincide with evidence for the introduction of livestock in the region and it occurred somewhere between 8,000 and 4500 years ago.

Raising and grazing livestock had a severe effect on the region's ecology. As more sheep and camels fed on vegetation, it increased the proportion of sunlight reflected from the region back into space, which in turn reduced monsoon rainfall in inlands. The weakening monsoons caused further desertification and vegetation loss, creating a vicious which eventually spread over the entire region of Sahara.

The reflectance of the sun's rays off the earth or albedo depends on vegetation or grass cover, which slows down sunlight penetration to the ground. The lack of vegetation pushed the region of Sahara over the edge of an ecological tipping point.

A tipping point is encountered in an ecological system when local biotic environment undergoes a transformation in state from one condition to another. Once a shift has occurred, it is almost impossible to regain the previous state because of the involvement of so many variables - such is the case with Sahara desert.

“There were lakes everywhere in the Sahara at this time, and they will have the records of the changing vegetation. We need to drill down into these former lake beds to get the vegetation records, look at the archaeology, and see what people were doing there,” said Wright. “It is very difficult to model the effect of vegetation on climate systems. It is our job as archaeologists and ecologists to go out and get the data, to help to make more sophisticated models."

The study was published in journal Frontiers in Earth Science .

 

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Hira Bashir covers daily affairs around the world.

 

 

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