The "fairy circles" of Namibia
detrimentum 2014/12/01 16:50
detrimentum 2014/12/01 16:50
Fairy circles are circular patches of land, barren of plants, though often encircled by a ring of
stimulated growth of grass. They typically appear in
the arid grasslands of the western part of Southern Africa. Fairy circles are particularly common in Namibia, but also occur in parts of Angola and South Africa.
Fairy circles vary between 2 and 15 metres (7 and
49 ft) in diameter. They typically occur in essentially monospecific grassy vegetation, especially in Namibia, where conditions are particularly arid.
Associated grasses commonly are species in the
genus Stipagrostis. Like the causes of heuweltjies and Mima mounds, the origin and history of fairy circles have long
been a puzzle and their investigation has proved
challenging. One controversially favoured
suggestion is that the activity of the sand termite Psammotermes allocerus is adapted to create locally favourable ecosystems that improve the supply of moisture and food.
Location
The circles occur in a band lying about 100 miles
(160 km) inland, and extending southward from
Angola for some 1,500 miles (2,400 km) down to
the Northwestern Cape province of South Africa. It is largely a remote and inhospitable region, much of it over a hundred miles from the nearest village.
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.
stimulated growth of grass. They typically appear in
the arid grasslands of the western part of Southern Africa. Fairy circles are particularly common in Namibia, but also occur in parts of Angola and South Africa.
Fairy circles vary between 2 and 15 metres (7 and
49 ft) in diameter. They typically occur in essentially monospecific grassy vegetation, especially in Namibia, where conditions are particularly arid.
Associated grasses commonly are species in the
genus Stipagrostis. Like the causes of heuweltjies and Mima mounds, the origin and history of fairy circles have long
been a puzzle and their investigation has proved
challenging. One controversially favoured
suggestion is that the activity of the sand termite Psammotermes allocerus is adapted to create locally favourable ecosystems that improve the supply of moisture and food.
Location
The circles occur in a band lying about 100 miles
(160 km) inland, and extending southward from
Angola for some 1,500 miles (2,400 km) down to
the Northwestern Cape province of South Africa. It is largely a remote and inhospitable region, much of it over a hundred miles from the nearest village.
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.
detrimentum 2014/12/01 16:54
Formation and controversy
There has long been debate about the causes of
the circles. The investigation and development of
theories have included numerous theories both
mundane and supernatural. One favoured
assumption is that the sand termite, Psammotermes allocerus is responsible, but the range of the phenomena is much wider than that of the termite
species, and details of the effects vary, so to ascribe
all circles to any such single cause would be
unrealistic.
In 2004, University of Pretoria's Botany professor
Gretel van Rooyen rejected proposals of termite activity, radioactive soil, and of plant toxins. In 2008 Angelique Joubert proposed that residual
plant toxins remaining in the soil after the death of Euphorbia damarana plants, might be the cause of the barren interiors 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 supported by Norbert
Juergens. Juergens found evidence that the sand
termite, Psammotermes allocerus generates a local
ecosystem that profits from and promotes 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. Grass growth around the circle is promoted by the accumulated
soil water, and in turn the termites feed on the
grasses, slowly increasing the diameter of the circle. This behavior on the part of Psammotermes allocerus amounts to creation of a local ecosystem
in a manner analogous to behaviour of the common beaver.
Juergens' research aroused interest in the media,
but has been criticised. Walter R. Tschinkel, a
biologist at Florida State University who also
researched the fairy circles, remarked 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 that sand termites differ from harvester termites and live deep
beneath the circle; they do not create mounds or
nests above ground, and they leave no tracks in the sand In such respects the sand termite is unusually inconspicuous in its activities.
Formation and controversy
There has long been debate about the causes of
the circles. The investigation and development of
theories have included numerous theories both
mundane and supernatural. One favoured
assumption is that the sand termite, Psammotermes allocerus is responsible, but the range of the phenomena is much wider than that of the termite
species, and details of the effects vary, so to ascribe
all circles to any such single cause would be
unrealistic.
In 2004, University of Pretoria's Botany professor
Gretel van Rooyen rejected proposals of termite activity, radioactive soil, and of plant toxins. In 2008 Angelique Joubert proposed that residual
plant toxins remaining in the soil after the death of Euphorbia damarana plants, might be the cause of the barren interiors 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 supported by Norbert
Juergens. Juergens found evidence that the sand
termite, Psammotermes allocerus generates a local
ecosystem that profits from and promotes 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. Grass growth around the circle is promoted by the accumulated
soil water, and in turn the termites feed on the
grasses, slowly increasing the diameter of the circle. This behavior on the part of Psammotermes allocerus amounts to creation of a local ecosystem
in a manner analogous to behaviour of the common beaver.
Juergens' research aroused interest in the media,
but has been criticised. Walter R. Tschinkel, a
biologist at Florida State University who also
researched the fairy circles, remarked 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 that sand termites differ from harvester termites and live deep
beneath the circle; they do not create mounds or
nests above ground, and they leave no tracks in the sand In such respects the sand termite is unusually inconspicuous in its activities.
detrimentum 2014/12/01 16:56
Myths
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.
Use
The Himba people use the fairy circles in their
agriculture. Because fairy circles support grasses in otherwise barren land, they provide grazing.Sometimes they erect temporary wooden fences
around the circles to corral young cattle for overnight protection against predators.
Myths
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.
Use
The Himba people use the fairy circles in their
agriculture. Because fairy circles support grasses in otherwise barren land, they provide grazing.Sometimes they erect temporary wooden fences
around the circles to corral young cattle for overnight protection against predators.
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