Ok, trigger warning: There’s a high chance of getting Toto’s “Africa” stuck in your head by reading this post. But, the truth is, there used to be plenty of rains down in Africa. Enough to have made the Saraha Desert a rainforest.
It’s not a huge shock, since we know the Earth has gone through different climatic periods, but this was one far more recent and accounts for a more radical change than scientists ever could have imagined. In other words, it really takes a lot to turn a vibrant forest into a bone-dry desert, and this happened a mere 6000ish years ago! It’s pretty interesting.
How did the Sahara go from forest to desert?
So, what’s the deal here? Well, since we don’t have a time machine, we can’t know for certain. It could have to do with the tilt of the Earth’s orbital axis changing, it could also be part of a longer, larger pattern of transition.
African Humid Periods in the distant past meant….you guessed it…more rains down in Africa. In particular, northern Africa (which is where the Sahara is, in case you don’t have a map handy). But at some point, those rains went away.
As Smithsonian Magazine (cited below) explains:
“With more rain, the region gets more greenery and rivers and lakes. All this has been known for decades. But between 8,000 and 4,500 years ago, something strange happened: The transition from humid to dry happened far more rapidly in some areas than could be explained by the orbital precession alone, resulting in the Sahara Desert as we know it today.”
Cool use of archaeological data
We can see from archaeological data (which is not perfect, but is overwhelmingly in favor of showing past water and trees in certain areas) that the area was once forest, and even rainforest. But what’s also interesting – and seals the deal for most people – is that in this period there is also evidence of pastoralists. That means people were raising and herding animals. And you definitely can’t do that in a desert.
Are humans to blame?
If it wasn’t solely an axial issue (regarding the Earth’s tilt), some scientists believe that humans could have played a big role in changing the climate due to overgrazing.
There have been suggestions that the end of the humid period in northern Africa could have been brought about by humans letting domesticated animals eat up all the moisture-loving plants. They would have probably had to use fire as a land management tool as well. And that may have been enough to trigger the big change that turned the forest into a desert.
It’s not that easy, of course, but that’s the general idea. There are also hypotheses that humans had nothing at all to do with it. And neither one of those would be related to whether or not humans are affecting the climate currently, so it’s not a political discussion (thankfully). – WTF fun facts
Source: “What Really Turned the Sahara Desert From a Green Oasis Into a Wasteland?” — Smithsonian Magazine