Humans May Have Played Very Active Role In Desertification Of The Sahara, Research Finds
Humans may have played a very active role in the desertification of the Sahara, according to new research from Dr David Wright of Seoul National University.
The new findings directly contradict the earlier supposition that the rapid shift from a heavily greened landscape to the modern Sahara desert, over just a few thousand years time, was driven entirely by “natural” processes. (Obviously, if one considers human behavior to be “natural,” than there is no real distinction, but that doesn’t change the fact that people may have played a major role in the desertification of the region.)
“In East Asia there are long established theories of how Neolithic populations changed the landscape so profoundly that monsoons stopped penetrating so far inland,” commented Wright. Wright then went on to note that evidence of human-driven climatic and ecological change has been documented in Europe, North America, and New Zealand as well, and that similar scenarios could well have occurred in the Sahara.
Nick Fraser, Journal Development Manager, Frontiers in Earth Sciences, provides more: “To test his hypothesis, Wright reviewed archaeological evidence documenting the first appearances of pastoralism across the Saharan region, and compared this with records showing the spread of scrub vegetation, an indicator of an ecological shift towards desert-like conditions. The findings confirmed his thoughts; beginning approximately 8,000 years ago in the regions surrounding the Nile River, pastoral communities began to appear and spread westward, in each case at the same time as an increase in scrub vegetation.
“Growing agricultural addiction had a severe effect on the region’s ecology. As more vegetation was removed by the introduction of livestock, it increased the albedo (the amount of sunlight that reflects off the earth’s surface) of the land, which in turn influenced atmospheric conditions sufficiently to reduce monsoon rainfall. The weakening monsoons caused further desertification and vegetation loss, promoting a feedback loop which eventually spread over the entirety of the modern Sahara.”
If true, that would make for simply yet another version of the age-old human story of unintended consequences. In other words, it’s yet another show of the fact that humans aren’t nearly as clever as most of us like to think we are.
To reiterate that last point, historical study clearly shows that soil erosion and desertification played a significant role in the collapse of many earlier civilizations. And since we’re talking about North Africa here … it should be remembered that after the Roman Republic had more or less depleted the soils of Southern Europe (and entered into the civil war period that led to the birth of the Roman Empire), it colonized the region — which still possessed good soil fertility at the time — at the expense of the mostly Phoenician locals. (The “Afri” were one of the Phoenician groups living there at the time, and served as the basis of the name “Africa.”)
For many of the years that followed, this colonization of North Africa functioned as the breadbasket of the Roman Empire. The current state of North Africa’s depleted soils is partly the result of the mass-scale agriculture of the time, and partly the result of the overgrazing and abandonment of the aqueducts that followed Islamic conquest. (There was also a brief period when the Germanic Vandals had control of some parts of the region, before the Arabs then pushed them out.)
Commenting on what comes next, Wright stated: “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. 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.”
Overall, Wright’s work makes for an interesting interpretation of the available data. Personally, I wouldn’t be surprised at all if humans were the primary driver of desertification in the region — aided by the climatic turbulence of the times. There’s probably a parallel to be drawn there with modern times…
The new findings are detailed in a paper published in the journal Frontiers in Earth Science.
Image by Sidy Niang (some rights reserved) CC BY SA license
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