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According to U-Like C.B.S.E CCE Sample Papers with Solutions and Model Test Papers for Revision in SOCIAL SCIENCE, the Sahara desert resulted from overgrazing by herbivores. This happened because the Romans captured the lions. As there were no predators, the herbivores increased in number resulted in overgrazing and the desert was created.

Is this an accurate description of how the Sahara dried up, or is there a better (more current) explanation?

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A quick google search turned up the book Physical Geography: Biogeography By K. Bharatdwaj published by Discovery Publishing Pvt.Ltd in India. It gives herbivore overgrazing as the reason for the Sahara desert. –  Legion600 Jan 10 at 3:25
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If OP is indeed a student forced to learn from such a textbook, questioning it here demonstrates quite some intellectual courage I think. –  congusbongus Jan 10 at 4:26
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It's not really history, I think this would fit better on skeptics.SE. –  Lennart Regebro Jan 10 at 6:15
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IMHO this is one of those questions that belong here until a more appropriate stack can make it into beta (perhaps Earth Science ) –  T.E.D. Jan 10 at 14:02
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@MarkC.Wallace - It's asking for a different explanation. Sounds like science to me, not a conspiracy theory. And school textbooks aren't exactly paragons of scientific accuracy, on any topic. –  DVK Jan 10 at 17:02
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2 Answers

Best evidence to date suggests that the Sahara dried up about 5,000 years ago, possibly in as little as 300 years, due to climate changes resulting from the precession and rotation of the Earth's rotation axis.

... around 8,000 years ago, the Earth's orbit was slightly different to how it is today. The tilt changed from around 24.1 degrees to the present-day 23.5 degrees.
...
Given the very strong dependence of vegetation on water availability, the end of the 'Green Sahara' came about quite suddenly around 5,500 years ago," Schmidt said. "Thus, a very slow change in the orbit (led) to an abrupt collapse in that ecosystem.

Update:
As regards the claim that human hunting of large carnivores resulted in over-grazing by large herbivores:
I find it an incredulous suggestion that that stone-age humans were preferentially hunting large carnivores in an eco-system in which large herbivores were numerous.

Update #2:
The desertification of the Sahara, by all accounts, certainly occurred at least 2,000 years prior to the Founding of Rome in 753 BC.

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This is what my textbook said. I also learned the cycle repeats every 28000 years, and some proof for it is the existence of crocodiles in some oasis surrounded by dessert. –  Jeroen K Jan 10 at 7:20
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Yes, cooling climate causes the air over the area to dry, declining rainfall, deserts grow. The lion story however might be a contributing factor, like deforestation due to increased population pressure which led to the desertification of the interior of the Iberian peninsula in the golden age. –  jwenting Jan 10 at 12:52
    
@jwenting: See update. Human activity may be relevant, but stone-age culture and population density, especially in a marginal ecosystem, seems very unlikely to have been a dominating factor. –  Pieter Geerkens Jan 12 at 19:10
    
@jwenting: It's not like the Romans were there cutting down trees for a century to build fleets with which to fight the Carthaginians. –  Pieter Geerkens Jan 12 at 19:11
    
@PieterGeerkens not in Spain they weren't :) Those trees came from Italy (with a pretty similar effect in the southern coastal regions). And of course the Roman fleet was quite a bit smaller than the Spanish armada. –  jwenting Jan 14 at 14:24
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I have in the past seen claims that human activity, specifically overgrazing by domestic goats and salinification of the water table by repeated irrigation, has been responsible for the advance of the desert into previously habitable areas of North Africa. That's a far cry from your book's reported claim, but its at least a nod in that direction.

It appears that a temporary change in the monsoon rain pattern at that latitude caused the Sahara to temporarily become habitable from about 10,000 to 5,000 BP. Scientists have given it the rather uninspiring name Neolithic Subpluvial. Supposedly some inscriptions in Egypt and the Sudan depict this. Here's an article in Live Science from 2006 that discusses the matter. However, before that time the Sahara was actually larger than it is now. So we are still better off that where we started before the monsoon aberration, and can probably expect it to go back toward that larger size, human activity or no.

There are theories that these changes just happen periodically.

I found an article in The Globalist from 2008 that makes the slightly less extravagant claim that human activity accelerated the re-desertification process when the rains went away. So this is an idea that is floating around. I don't know how widely-accepted it is though. Coincidentally, I also heard a story on NPR this morning about "carnivorists", or scientists who study carnivores. They do make the claim that taking carnivores out of an ecosystem can lead to large changes in the vegetation.

Still, we find deserts naturally worldwide in regions where rainfall is less than about 250mm a year. At its current northern limit, the Sahara receives about 100mm a year, and 150 at it southern. So I think it is fair to say that it would be a desert, regardless of what the animals around it are doing.

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I upvoted both answers, but I think this one is better. –  Lohoris Jan 10 at 21:00
    
@Lohoris - Reasonable. I upvoted the other answer as well –  T.E.D. Jan 10 at 21:15
    
I have serious doubts that stone-age humans were preferentially hunting large carnivores in an eco-system in which large herbivores were numerous. –  Pieter Geerkens Jan 10 at 23:23
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