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Sunday, 22 February 2015

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 yr of research their origin remains unknown. Fairy circles vary between 2 and 15 meters or 7 and 49 ft in diameter. They typically occur in essentially mono-specific grassy vegetation, especially in Namibia, where conditions are particularly arid. Associated grasses commonly are species in the genus Stipagrostis. The origin and history of fairy circles have long been a puzzle and their investigation has proved challenging. 

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.
Image credit PAULO PEDRO DE SOUSA

Unresolved questions remain about the soil from the center 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" 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 recognized and informally remarked on for many years, first being mentioned in technical literature in the 1920's and intermittently thereafter with the intensity of study increasing during the final quarter of the 20th century.

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.
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 fairy circles are negatively correlated 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 as a consequence of under-ground 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 put forth, believed by some scientists to be tied to tour guides, is that the circles are formed by a dragon in the earth and that its poisonous breath kills the vegetation. [source]

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.
Image credit dreizehn28

Fairy Circles in the Namib Rand Nature Reserve.
Fairy Circles in the Namib Rand Nature Reserve. Image credit Christoph Schröer

Fairy circles, Sossusvlei.
Fairy circles, Sossusvlei. Image credit KSHoffman

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.
Image credit robert miles

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.
Image credit Elaine Pye

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.
Image credit Don Fletcher

Fairy Circles Sossusvlei, Namibia.
Fairy Circles Sossusvlei, Namibia. Image credit Karen Clark

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.
Image credit Rafael Hernández

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.
Fairy circle. Image credit Kit Wilde

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