From the wheel of a vehicle, one might just miss the very existence of Namibia’s ‘fairy circles’, but take to the sky in a light aircraft or hot air balloon and they jump out of the desert like a blanket of polka dots. Each circle of barren red sand – ranging in diameter from three metres to 25 metres – is fringed with golden grasses of varying length. Why the grass, which is extensive throughout these area, fails to grow in these patches has long been a mystery.
The local explanations of their formation are based on folklore, and vary from them being the footprints of the gods to patches of desert poisoned by the breath of dragon living beneath the Namib’s surface. Science has been studying the phenomenon for years, with some projects focused on colonies of subterranean termites, which potentially reduce the fertility of the desert floor above them, while others have looked at the chance the patterns were simply the result of desert grasses naturally competing for space and limited water resources (known as self-organisation). However, no single theory has shown any concrete success.
The latest shot at a scientific answer involves ecologists from Princeton University using computer models. At first, they created various simulations to mimic the impact of the grasses, on which termites would build their underground colonies. The results showed up dead zones in the grasses, which were the result of conflicts between neighbouring termite colonies of a similar size. But these behaviours did not explain the tell-tale patterns of fairy circles completely. Next the Princeton scientists created a computer model that simulated a combination of warring termites and self-organisation of the various desert grasses. And it was this simulation that resulted in fairy circle-like patches. The Princeton team, who recently reported its findings in Nature, have stopped short of claiming to have solved the long-standing mystery, but it believes its models shed light on the complexity of all the natural interactions involved in the process.