Fairy circle (Africa)
Fairy circles are circular barren patches of land, typically found in the grasslands of the western part of Southern Africa. They are most prolific in Namibia, but are also present in Angola and South Africa. Their diameters vary between 2 and 15 metres (7 and 49 ft), and they occur amidst monospecific grassy vegetation, specifically in Namibia, of the genus Stipagrostis. Evidence suggests that the sand termite Psammotermes allocerus is responsible for their creation.
The circles are to be found in a band about 100 miles (160 km) inland, stretching south from Angola for about 1,500 miles (2,400 km). Located in a remote and inhospitable stretch of land that is over a hundred miles from the nearest village. The circles have been studied since they were reported on in 1971.
Studies done by scientists shows that these circles are under continuous development, with an estimated life-span of 30 to 60 years. They grow, ranging from 2 to 12 meters in diameter, where they mature and "die", filled in by invasive grasses.
Examples can be found at.
Formation and Controversy
The debate has been ongoing for some time as to the cause of the formation of the circles. The leading assumption is that the sand termite, Psammotermes allocerus is responsible for the creation of the circles. The investigation and development of theories behind the source of the circles has included numerous theories both mundane and supernatural.
In 2004, University of Pretoria's Botany professor Gretel van Rooyen ruled out termite activity along with radioactive soil and plant toxins. A theory put forth by Angelique Joubert in 2008 noted Euphorbia damarana as a possible origin of the circles.
In 2012, Eugene Moll suggested the termite species Baucaliotermes hainsei and Psammotermes allocerus as the creator of these circles. All rings have been found to contain termite casts, and radar investigations suggest that a moist layer of soil is situated beneath the fairy circles.
In 2013, this theory was reinforced by Norbert Juergens. Juergens found evidence that the sand termite, Psammotermes allocerus generates a local ecosystem which results in the creation of the fairy circle. The sand termite was found in 80-100% of the circles, and in 100% of newly formed circles and was the only insect to live across the range of the phenomenon. Sand termites create the faerie circle by consuming vegetation, and burrowing in the soil to create the ring. The barren circle allows water to percolate down through sandy soil and accumulate underground, allowing the soil to remain moist even under the driest conditions. Grasses grow on the edges of the circle due to the stored underground water, which the termites will feed upon and slowly increase the size of the circle. Because of this behavior, the sand termites cultivate their own sources of food and water, creating a local ecosystem in a manner similar to the common beaver.
Juergens' research while receiving interest in the media, has not been universally accepted as the cause of circles. Walter R. Tschinkel, a biologist at Florida State University who also researched the fairy circles, does not believe the termites to be the cause, noting that Juergens, "has made the common scientific error of confusing correlation (even very strong correlation) with causation." Previously, Tschinkel had searched for harvester termites without success. Juergens responded to the claim, noting that sand termites are different from harvester termites and live deep beneath the circle, do not create mounds or nests above ground and move in such a way as to leave no tracks in the sand. Because of these strange behaviors, the sand termite is unlike other species of termites.
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.
Later in 2013, Michael Cramer and Nicole Barger theorized that the circles were the consequence of vegetation patterns that arose naturally due to competition between grasses. They take the approach of examining the conditions under which fairy circles arise. Fairy circles are found to be negatively correlated with precipitation and soil nutrition which 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.
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.
The Himba people use the fairy circles for agricultural use. Because the fairy circle supports grasses in otherwise barren land, the circles provide a means for animals to graze. Temporary wooden fences are sometimes erected around the circles to corral young cattle overnight for protection against predators.
- BBC News - Enigma of Namibia's 'fairy circles'
- 'Fairy circles' of Africa baffle scientists - Telegraph
- "By building "fairy circles," termites engineer their own ecosystem". Ars Technica. Retrieved April 1, 2013.
- Investigation on selected biotic and abiotic factors in the maintenance of "fairy circles" (barren patches) in Southern Africa
- Nuwer, Rachel (28 June 2012). "Mysterious Fairy Circles Are ‘Alive’". Wired. Retrieved 30 June 2012.
- Njuguna, Wanja (27 November 2012). "Fairy rings – enigmatic features of Namibia". The Namibian.
- Juergens, Norbert (29 March 2013). "The Biological Underpinnings of Namib Desert Fairy Circles". Science.
- Wilford, John Noble (28 March 2013). "African Circle Mystery Solved? Maybe It’s Chewing". NY Times.
- Cramer, Michael; Nicole Barger (Aug 15, 2013). "Are Namibian "Fairy Circles" the Consequence of Self-Organizing Spatial Vegetation Patterning". PLoS ONE. 8 8. doi:10.1371/journal.pone.0070876.
- Castro, Joseph (September 4, 2013). "Mysterious "Fairy Circles" in African Desert Get New Explanation". livescience.
- Fairy circles - Namibia, South Africa
- 'Fairy circles' of Africa baffle scientists
- Scientist uses satellites to examine circles in African desert
- PLoS ONE: The Life Cycle and Life Span of Namibian Fairy Circles
- Media related to Fairy circles at Wikimedia Commons