Fairy circles AREN'T created by termites after all
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It is as if the landscape is dotted with freckles. Huge swathes of grassland in Namibia is covered with mysterious vegetation-free patches that have been baffling scientists for decades.
While a number of studies have suggested the fairy circles are created by industrious termites, new research claims they are the result of resource competition for water among plants.
German researchers analysed the spatial distribution of the fairy circles and found that they are 'remarkably regular' in their distribution, which made them question the termite theory.
A freckled landscape: Has the mystery of the fairy circles finally been solved? While a number of studies have suggested they are created by industrious termites, new research claims they are the result of resource competition for water among plants
Experts from various institutions have previously claimed that termites nibble away at grassroots in certain grasslands of southwest Africa, causing the dieback of vegetation and creating a water trap.
Other theories to explain the circles - which can measure anything between 10ft and 65ft (a few metres in diameter to 20metres) - include hydrocarbons emanating from the depths of the earth to kill off patches of vegetation and some people even think they are made by aliens.
German researchers analysed the spatial distribution of the fairy circles (pictured in the Marienfluss Valley) and found that they are 'remarkably regular' in their distribution. This is a close-up of a fairy circle. There is a no vegetation growth within the circular area
THE TERMITE THEORY
Scientists claimed in 2013 that the sand termite species Psammotermes allocerus was the most likely suspect for creating the fairy circles.
Norbert Jürgens from the University of Hamburg said the insect was the only species consistently present across the 1,200 miles of desert which included the circles.
His theory centres around the termites eating plant roots before they can sprout through the desert soil creating a water trap - in a similar way that beavers create dams.
Because of the lack of foliage, rainwater is not lost through transpiration - the evaporation of water from plants - and instead stays below the surface.
This allows the sand termites to survive and stay active during the dry season and also helps grasses at the edge of the circle to thrive attracting other life forms.
The termites feed on those grasses, thereby gradually extending the circle.
Dr Jürgens concluded that the fairy circles are an astounding example of ecological engineering by the sand termite, designed to retain precious water in an otherwise arid landscape.
However, no one has so far observed these creatures actually grazing holes into the Namibian grasslands – let alone in such consistent patterns.
Dr Getzin said: 'There is, up to now, not one single piece of evidence demonstrating that social insects are capable of creating homogenously distributed structures, on such a large scale.'
In fact, a range of studies covering the distribution of ant and termite populations in arid territories suggests they create random and irregular patterns.
'Although scientists have been trying to answer this question for decades their mystery remains as yet unresolved,' Stephan Getzin from the Helmholtz Centre for Environmental Research (UFZ) in Leipzig said.
No one has been able to observe the genesis of a fairy circle. Their occurrence appears to be restricted to particularly arid zones right at the border of grassland and desert regions, according to the study published in the journal Ecography. There is intense resource-competition for water.
Dr Getzin's team was joined by experts from Göttingen in Germany, Italy and Israel who studied aerial images of the circles in north west Namibia to pinpoint the location and distribution of the barren patches within the surrounding landscape.
Using statistical methods, they found that the circles are distributed regularly across large areas.
'The occurrence of such patterning in nature is rather unusual. There must be particularly strong regulating forces at work,' Dr Getzin said.
He believes it is the local resource-competition among plants and vegetation, in a similar way to how young trees space themselves out in forests to ensure they have access to enough nutrients and water.
'A similar process of resource-competition may consequently also be the real cause for a self-organising formation of the mysterious fairy circle patterns,' the study says.
The scientists simulated underground competition for water and the spatial vegetation distribution patterns. They found that similar patterns emerged on the screen to those recorded in Namibia.
Termite trouble: Experts from various institutions have previously claimed that termites nibble away at grassroots in certain grasslands of southwest Africa, causing the dieback of vegetation and creating a water trap. This pile of sand is typical of the markings made by termites
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