The Mysterious Fairy Circles of Africa

The Namib Desert of southwestern Africa is home to a mysterious phenomenon called “fairy circles" – nearly circular barren patches within a sparse matrix of small, short-lived grass species. Despite 30 years of research, their origin remains unknown. Fairy circles vary in diameter between 2 and 15 metres (7 and 49 ft). They typically occur in essentially monospecific grassy vegetation, especially in Namibia, where conditions are particularly arid. Associated grasses are commonly species of the genus Stipagrostis. The origin and history of fairy circles have long been a puzzle, and their investigation has proved challenging.

Image credit PAULO PEDRO DE SOUSA

Unresolved questions remain about the soil at the centre of the circle inhibiting plant growth and the interactions of other species in the fairy circle as they relate to the local ecosystem. Furthermore, the received wisdom from about a century ago remarked on the "heuweltjies" as being anomalously rich in plant nutrients, raising the question of how many effectively different types or circumstances of circles or heuweltjies there might be. The circles have been recognised and informally remarked on for many years, first being mentioned in technical literature in the 1920s and intermittently thereafter, with the intensity of study increasing during the final quarter of the 20th century.

Image credit: Jeremy T. Hetzel

In 2013, Michael Cramer and Nicole Barger suggested that the circles were the consequence of vegetation patterns that arose naturally from competition between grasses. They examined the conditions under which fairy circles arise and found that they negatively correlate with precipitation and soil nutrition. This observation is consistent with resource competition being a cause of the crop circles. Grassy landscapes with a mixture of grasses can result in barren spots because of competition between different types of grasses. The patches are maintained because they form a reservoir of nutrients for the taller grasses at the periphery and possibly because of the activity of termites, as in the theory above. Using rainfall, biomass and temperature seasonality, they can predict with high accuracy the presence or absence of fairy circles in a region. According to Walter Schinkel, this theory accounts for all the characteristics of fairy circles, including the presence of tall grass species. The argument, however, is intrinsically inconclusive, and several points remain to be settled, for example, by research into differences between the types of circles in various regions and soils and the effects of excluding termites from participation in the formation of circles.

In the oral myths of the Himba people, these barren patches are said to have been caused by the gods, spirits, and/or natural divinities. The region's bushmen have traditionally ascribed spiritual and magical powers to them. Of specific beliefs, the Himba people note that their original ancestor, Mukuru, was responsible for the creation of the fairy circles, or that they were the footprints of gods. Another myth, believed by some scientists to be tied to tour guides, claims that a dragon in the earth forms the circles and that its poisonous breath kills the vegetation. [source]