It’s strange to think that the iconic Sahara Desert, known for its vast sand dunes and intense heat, was once not a desert at all, but a lush and verdant countryside complete with both lakes and grassland. The contrast inevitably begs the question, what exactly caused the drastic change in climate?
A wet period called the African Humid Period, which lasted 10,000 years, gave Northern and Eastern Africa lots of moisture. However, around 8,000 years ago, the moisture balance began to shift. Now, the sandy landscape sits atop signs of rivers and plants from a once-greener time.
According to Wright, humans were once thought to be passive agents in the African Humid Period, but he now believes they may have actually been active agents in the change.
Wright said, “In East Asia there are long established theories of how Neolithic populations changed the landscape so profoundly that monsoons stopped penetrating so far inland.” He believes such a phenomenon may have occurred in the Sahara as well, with agriculture changing the environment. For instance, the air could have been warmed from sunlight bouncing off exposed soil, and this atmospheric change could have led to reduced rainfall, ultimately causing the Sahara’s desertification.
To test his hypothesis, Wright analyzed archaeological evidence chronicling the initial sightings of pastoralism across the Saharan region. He then compared this with records exposing the spread of scrub vegetation, which points at an ecological shift toward desert conditions. What Wright found coincided with his original thoughts: About 8,000 years ago in the regions around the Nile River, pastoral communities arose and continued to branch out westward, each time at the same time scrub vegetation increased.
Wright’s idea, though intriguing, must build a stronger case if he hopes to change what the textbooks teach. He will need more evidence to prove his theory:
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.
Wright stresses the impact humans have had, for several thousands of years, on the environment and climate, noting that, along with possibly changing the landscape of the Saraha Desert, human activity has led to 15% of the world’s population now living in desert regions. He says that “the implications for how we change ecological systems have a direct impact on whether humans will be able to survive indefinitely in arid environments.”
Should his research pan out, Wright’s work could offer important insight into how we can adapt on a large scale to climate change.
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