It was some 10,000 years ago, that the Sahara Desert was a wondrous expanse. Predictably, the dawn of anthropogenic age appeared to have brought about a metamorphosis that has left the world astounded.
Once upon a time, one of the planet's desert was idyllic synonymous to the biblical phrase, The Promised Land which no longer exists making us inquisitive about the inevitability of, what happened?
An archetypical desert is a landscape of endless stretches of sand, relentless sun and all that the caravans yearn for, an elusive oasis. However, 11,000 years ago this geographical feature was more like a phantasmagorical location; most of northern Africa, comprised of what is today called the Sahara Desert.
In the past it was a locale with lush green vegetation, dotted with lakes, and meandering rivers; there were grasslands and forests, a touchstone of Africa's environment. How did these water bodies and vegetation disappear? Archaeologist, David Wright, presents a study in the journal, Frontiers in Earth Science focusing initially on the termination of the African Humid Period. In the past era, the AHP was a period of enhanced moisture over northern and eastern Africa.
It was about 8,000 years ago when the moisture balance began to shift due to changing orbital precession and changes in the balance of vegetation. Precession refers to any of the several slow changes in an astronomical body's rotational parameters. Precession is caused by gravitational pull of the sun and moon on the earth.
These are changes that occur over millenniums. Humans were identified as agents for the disappearance of the AHP. They responded to changing conditions of the climate by following a practice of animal husbandry and introducing agriculture. Pastoralists were suspected to have precipitated a decline in vegetation. Wright further emphasises that human factor must be “contextualised,” against other global occurrences, related to neolithisation, a period marked by the systematic practice of farming and animal husbandry.
It was the Holocene epoch that witnessed the end of the AHP and was one of the most significant landscape changes that occurred on the African continent. In the northern half of Africa, rainfall dramatically decreased thus leading to new creation of plants and animals. Human communities shifted their practices from foraging to agricultural based economies, observed Alan Marshall, an author and scholar, in environmental studies.
After the AHP period was over, new social systems evolved in North Africa and South-Western Asia in which areas of irrigation, agricultural resources, and redistribution of food networks were managed by hierarchical leaders (Kruper and Kropelin, in 2006). It was accepted by researchers that the AHP occurred variably across Africa, 8,000 to 4,500 years ago, due to a weakening of the monsoon over the Sahara, causing desertification.
The area of the Sahara Desert is vastcovering 9.4 million km and is compared to an area of the US. This posed as a challenge to conduct studies linked to the region's past. It is known that reduction of moisture had brought about a change in the biotic environment. Regime shifts occurred where trophic or nutritional absorption level changed in response to external dynamics. Notwithstanding moisture, plants also depend on insects.
David Attenborough, an eminent naturalist, writes, “Plants begin to turn the flying skills of insects to their own advantage. Spores can develop if they fall on ground with sufficient moisture and insects carry pollen necessary for fertilization of plants; they place the pollen on the exact spot in a female flower.”
When a regime shift has taken place, a return to the previous state cannot occur due to many variables, such as, reproduction of identical conditions of a bygone period. Attenborough’s word on the role of insects has highlighted a crucial factor- – nature works in harmony with other species and organisms to form the pyramid of life. The pyramid of life interprets the flow of food in a community.
Different levels are categorised to different groups of organisms or species that composes a food chain. This brings out the significance of interdependence of many creatures that existed in the Sahara, to maintain a balance for the existence of that beautiful landscape, long ago. Lake Chad is further South in Africa and a study of its sediment core provides evidence of an abrupt switch to arid conditions about 5,000 years ago.
Hitherto, the area was dominated with flora and fauna, wrote Maceachern, professor, department of Earth Sciences, Canada. The termination of the AHP points towards the potential anthropogenic influences, inducing changes in local ecological threshold limits which catalysed de-vegetation.
Agricultural practices often follow monoculture and this system eliminates all the functions that nature attributes to plants and soil. It expatriates a range of insect species and a single dominant species can damage many plants for example one type of a plant species like wheat will not provide a range of bacteria for the soil to benefit.
A diversity of plant species in the Sahara enabled nature to function in harmony and with the advent of agriculture, with monoculture, a disturbance in the balance of nature began.
David Attenborough’s thoughts reflect what many naturalists will yearn for, “I just wish the world was twice as big and half of it was still unexplored.”