Published By: Sayan Paul

Sahara Turns Green: Did You Know The Desert Was Covered In Lakes And Vegetation 5000 Years Ago?

NASA's satellite images reveal greenery flourishing in several regions of theSahara Desert.

Thanks to a rare natural phenomenon, the Sahara Desert, usually dry and barren, is now experiencing patches of greenery. According to NASA's Earth Observatory, this happened due to an extratropical cyclone that brought heavy rainfalls in areas of northwestern Africa on September 7 and 8. As revealed in NASA's satellite images, vegetation is popping up (especially in low-lying areas, like riverbeds) in Morocco, Algeria, Tunisia, and Libya - regions that rarely receive rain.

Credit: NASA Earth

Well, the exceptional rainfall event in Africa was due to a northward movement of the tropical rain belt, influenced by factors like high Atlantic Ocean temperatures and the transition from El Niño to La Niña. And this led to flood-like situations in several areas in North Africa. On the other hand, lakes that are usually empty have been filled up.

Credit: ABC News

These plants are short-lived, however, are remarkably significant as far as studies about changing climate patterns are concerned. What's also essential to note is that this is not the first time the Sahara is experiencing greenery. In this article, let's have a throwback to the time when the present-day desert was entirely covered in lakes and vegetation.

The Green Sahara

With an area of 9,200,000 square kilometers, the Sahara is the largest hot desert in the world. However, not many know that this desert was completely green about 11000-5000 years ago, packed with lakes, rivers, grasslands, and forests. Birds were flocking across the region, while flora and fauna thrived in what are now Chad, Libya, Niger, and Mali. Moreover, some archeological evidence suggests that there were human settlements as well.

Credit: the.world.in.maps

But What Caused This?

Approximately 11,000 years ago, the Sahara experienced a significant climatic transformation, creating what’s now known as the African humid period. The changes in the Earth's axial tilt and orbital patterns strengthened the African monsoon; and increased greenhouse gases. As a result, these regions received incessant heavy rainfalls, leading to green and fertile land, allowing rivers and lakes to flourish.

This formed what is now known as a "Green Sahara". The vegetation cover spread over almost all of the Sahara and consisted of an open grass savannah with shrubs and trees. This fauna included baboons, cane rats, catfish, clams, cormorants, crocodiles, elephants, frogs, gazelles, giraffes, hartebeest, hares, hippos, mollusks, Nile perches, pelicans, rhinoceroses, snake-eagles, snakes, tilapia, toads, and turtles among others. In fact, the Lake Chad expanded to tenfold of its present-day size.

Credit: Abu Hadza

However, that period didn't last forever. Around 5000 years ago, the Earth's orbital tilt shifted once again, putting an end to the African humid period. As a result, the Sahara became dry and barren.

Some Interesting Facts To Know

Interestingly, this was not the first instance of a Green Sahara. According to archeological evidence, about 230 such periods happened in history, with the first dating back to 7–8 million years ago.

The Sahara was much larger (spreading 500–800 kilometers farther south) before the African humid period and had been extremely dry. And there were little to no human activities at that time.

A similar phenomenon took place in tropical America, China, India, the Makran region, the Middle East, and the Arabian Peninsula.

The transition from the green Sahara to the present-day dry Sahara is widely considered the "greatest environmental transition of the Holocene in northern Africa".

Credit: Fact Maniac

Well, the ‘desert’ is expected to turn completely green again in about 15,000 years.