The Fairy Circles mistery, Korina Tarnita: "Termites that feed on plants..."
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Among the Himba of northern Namibia it is believed that the fairy circles are a phenomenon related to divine intervention. They would represent the footprints of their God Mukuru who brings rain and heals the sick. Another legend of this people claims that the circles of the fairies are created by the poisonous breath of a dragon that lives underground.
The gas rises to the surface and kills the plants in the circles. Many hypotheses have been advanced on the causes of the formation of the circles and the most accredited concerns the presence of sand termites, of the Psammotermes allocerus species, held to be solely responsible.
Equally valid is the theory relating to a form of self-regulation among the plants existing in the sandy soil of the Namibian desert; as well as the presence in the subsoil of a toxic gas which would exterminate every form of life present in the circles when it rises to the surface.
But what are the Fairy Circles?
Fairy circles are circular areas devoid of vegetation surrounded by a ring of tall grass of the genus Stipagrostis. Irregularly distributed, they occur along a 2,000-kilometer belt that runs along the eastern edge of the southern Namibian desert, from Angola to the north-western part of South Africa.
Circles are not perennial. On average they live about 24 years, but some of them, especially the older ones, even reach the age of 75. With their variable diameter, fairy circles are a phenomenon with still unknown causes, even if in the last 40 years many scientific hypotheses have been proposed.
A similar phenomenon was also found in Sudan, eastern Kenya and in 2004 15 km from the city of Newman in eastern Australia. According to Korina Tarnita and the group of researchers who published the work in Nature, the termites of Namibia feed on the roots of the plants that are above their nests and this destroys the surface vegetation.
Where termite colonies are forced to live side by side, areas of untouched grass symbolize the boundaries of opposing factions. Tarnita said: "If a colony of termites encounters another smaller one, generally the first takes over the second and expands into its own territory.
But if two colonies of the same size come into contact with each other they prefer to define a boundary." Researchers said the herbs that form the circles are also important. In areas where water and moisture are scarce, some herbs would be able to overwhelm others, sending their long roots beneath the surface to steal it from their neighbors.
This system leads, in the long run, to the formation of patches of dry sand. Inside them, the humidity will be able to concentrate, giving way to the grass that has taken over to have sufficient nourishment for survival.