Earth is a very old place. About 4.5 billion years old, it has undergone profound changes on its surface. If a person were to travel to a distant time in the past, they would find an entirely different scenario than today. Among these transformations is the formation of the Sahara, the largest hot desert on the planet – over 9 million square kilometers – which has existed for 000,000 years, it was home to lakes, rivers, pastures and even forests. What made this green and humid place one of the driest parts of the world?

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It’s important to note that accurately measuring what caused this profound change is a tall order, as everything on the planet is inextricably linked. Although there is no scientific consensus on the true transformation of what is today the Sahara Desert, some scientific evidence provides evidence that traces part of the distant past of this region.

Earth axis change

The main studies on the formation of the Sahara point to the change in the Earth’s axis as one of the main factors in its emergence. Many scientists agree that between 5 and 20,000 years ago, the African wet period arrived. at its end, a climatic period in Africa occurred at the end of the Pleistocene and the Holocene.

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Saloum Delta National Park, located in Senegal (Image: Reproduction / Saloum Delta National Park)

Until then, North Africa was humid and had vegetation very similar to the present-day region of Senegal. Fossils of animals that are no longer a part of the region, such as crocodiles, elephants and hippos, reinforce the humid past of the Sahara. In addition, in the rare and isolated water bodies that are still there, there are species of fish that can only be explained by the presence of watercourses, that is to say rivers.

The cyclical alteration of the Earth’s axis, which occurs every 20,000 years, has caused an increase in the amount of solar rays focusing on the region. However, some research suggests that the Sahara has turned from green to desert rapidly – a matter of centuries – due to the shift in the Earth’s axis, which has profoundly affected the global climate.

Yet some studies indicate that the Sahara formed only 2,700 years ago through much slower change. Even samples taken from Lake Yoa, located in the north of the Republic of Chad, have provided clues to build part of the local geological history, indicating that a gradual process of desertification continues today.

Human action

Only the change in Earth’s orbit would not be enough to explain the profound change in the Sahara region. In a study published in 1024 in the journal Frontiers in Earth Science, archaeologist David Wright of the University of Oslo analyzed a series of archaeological and environmental data.

(Image: Reproduction / Unsplash / Chris Khani)

Sediment cores and pollen records from the same period indicated a pattern: any location that had a record of human presence showed corresponding changes in plant variety. In the later periods of the Green Sahara, humans roamed the area and, along with their livestock, altered some of the remaining vegetation.

Another consequence of human presence in the region has been the increase in albedo – a kind of dust that floats in the atmosphere – known as one of the factors behind the aridity of the Sahara. Human action, on this scale, would not have been sufficient to collapse all remaining local vegetation, but it may have intensified the inflection point, triggering the end of the wet period.

Will the Sahara ever become green again?

With or without humans, the Sahara would inevitably become the great hot desert it is today. Thanks to the cyclical alteration of the Earth’s axis, from time to time certain configurations on the surface of the planet are repeated. An example of this is the different ice ages this world has gone through.

511578 (Image: Reproduction / Pixabay / Wikilmages)

The Sahara itself was not green only 20 thousand years ago, but the region went through a wet period about 125 thousand years ago and, even without any human intervention, nothing has prevented the landscape from changing. is completely transformed. So it is to be expected that in a few thousand years, the world’s largest hot desert will once again be home to rivers, lakes and forests.

However, the projections for this future must take into account the great human impact which extrapolates any natural variation of the climate, because the Sahara is not explained only by the alteration of the axis of the Earth, but a series of factors. The current climate crisis is already the result of an imbalance. Either way, it’s a reminder that nothing in the universe lasts forever.

Source: Smithsonian Magazine, BBC

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