Around 6,000 years ago, Egypt was home to 37 large-bodied mammals, including lions, elephants, giraffes and oryx. Today, however, only eight of these remain.
While the Nile Valley region north of Aswan today is mostly made up of a hot, arid desert today with very little vegetation, it was very different back then. It was cooler, wetter and probably covered with lush vegetation driven by monsoonal rains which made it a much better habitat for the mammals.
The sharp decline of mammals over the years was not random, however, according to research published in PNAS. The paper suggests that the decline that occurred over the past 6,000 years was coupled with a drying climate and the rise of human settlements in the region.
“The trajectory of extinctions over 6,000 years of Egyptian history is a window into the influence that both climatic and anthropogenic impacts have on animal communities,” write the authors in the paper.
Ancient Egyptian artwork depicted on monuments and tools that were radiocarboned helped the researchers trace the changes in the animal populations. For example, depictions or lions in artwork up to the Second Dynasty (~4,645 years ago) show a long-maned lion, while latter depictions after that and up to the Twentieth Dynasty (~2,430 years ago) show a short-maned lion instead, which are two separate subspecies.
The increased extinction of species led to a decline in the stability of animal communities around the Nile Valley. When one species in a rich ecosystem disappears the effect is less pronounced, but with fewer numbers of species remaining, it becomes much more profound, shifting the prey-predator ratio in the region.
The researchers identified three episodes of extinction over the past 6,000 years, the most recent one 100 years ago and coinciding with the rise of industrialisation in Egypt. Three of the other drops in animal populations were coupled with periods of sharp increase in aridity with the earliest 5,000 years ago.
During these events, smaller herbivores, such as gazelles, started to decline sharply. These species are important for the ecosystem since many different predators prey on them. Their decline and eventual disappearance can lead to further decline in the populations of predators, such as lions and wild dogs.
While the authors point out that the actual cause of extinction of any single species cannot be identified, they suggested three scenarios that may have caused the decline. The first suggests that herbivores may have declined due to human overkill as Egyptians shifted to agriculture and supported it through hunting. The second scenario suggests that competition for habitats from humans who wanted to move to the floodplains for agriculture could have pushed out the animals there and reduced the available resources to them. The final scenario suggests that the climatic changes during that period may have affected both the herbivores and the carnivores populations.