It is a researcher specialized in the interaction between man and the environment in which he lives who affirms it: a change in the way of life of Neolithic populations could have had an aggravating impact on the desertification of the Sahara.
The Green Sahara
We knew that around 10,000 years ago the Sahara was still green and humid. It was then a space with a climate more favorable to human occupation. For several millennia a population of hunter-gatherers thrived there. At his side lived a large number of wildlife: elephants, giraffes, buffaloes, rhinos. Abundant rock art is there to testify to this prosperous period. However around 6200 BC. JC then around 2200 BC. JC, the region experienced phases of aridification of the soil which is still perpetuated today on the borders of the Sahel. In a few thousand years, this area favorable to human life has thus become the largest desert in the world.
Until now, scientific hypotheses on the causes of desertification from the Neolithic did not take into account the human factor to explain this upheaval. The “classic” explanation pointed above all to the influence of the orbital cycle which had seriously compromised the beneficial presence of the monsoons on part of the African continent. No doubt the advent of the concept of the Anthropocene, a still controversial scientific term designating a geological era in which human activity strongly modifies the biosphere, has contributed to opening up a new perspective on the desertification of the Sahara.
The impact of human activity on the desertification process
In an article published in the journal Frontiers in Earth Science, Richard D. Wright is the first to show that human activities could already have played a determining role in the desertification of the Sahara during the Neolithic era. To support his theory, the archaeologist took into account the environmental history of different regions of the world. Thus the introduction of pastoralism among the Saharan populations was an aggravating factor in the climatological crisis in which the Sahara found itself: “ pastoralism in particular is supposed to increase the loss of vegetation and disturbances in imbalanced ecosystems. To support his point, he takes the example of the impact of the introduction of livestock on the environment in New Zealand or North America. It always translates to » a marked reduction in primary productivity, a homogenization of the flora, a transformation of the landscape into a biosphere dominated by shrubs, an overall proliferation of xerophyte plants. »
8000 years ago, the Saharan region experienced an episode of generalized aridification which lasted approximately 1000 years. While the monsoon ensured a certain level of humidity in the south, the north began a long drying phase. It is after this period that the populations would have adopted a way of life based on nomadic or semi-nomadic pastoralism. It is precisely animal domestication and the introduction of livestock that would have had a negative impact on an environment already weakened by global drying up, according to Richard D. Wright: “ The key ingredients for anthropologically induced changes in the ecological regime include natural or man-made processes, population increase or the proliferation of landscape modifications sufficient to drive the system into a new state. »
Neolithic pastoral activity would therefore have been an accelerator of “natural” environmental and climatological trends favoring the desertification of the Sahara. Perhaps we have entered the Anthropocene era a little earlier than expected.
Sources: Journals, Phys.org, Nature.com