The mysterious "fairy circles" speckled across the Namibian grasslands in Africa are not the work of sand termites, as previously thought, but rather self-organization.
These crop circle-style bare patches have baffled scientists for decades, but recent research published in the journal Ecography may offer a more plausible explanation than the former termite theory.
"The occurrence of such patterning in nature is rather unusual," study researcher Stephan Getzin, of the Helmholtz Centre for Environmental Research (UFZ) in Leipzig, Germany, said in a statement. "There must be particularly strong regulating forces at work."
These vegetation-free circles that inhabit the arid grasslands of southwest Africa can grow to be 65 feet (20 meters) in diameter and can linger for as long as 75 years.
Scientists have offered up many hypotheses to explain these bare patches that occur in millions at the transition to the Namib Desert. They range from grass-killing seeps of hydrocarbons to carnivorous ants to termite feeding patterns, according to Live Science, but most suspect termites are the culprits.
A past study revealed a species of sand termite, Psammotermes allocerus, lived at the majority of patches. Researchers concluded that the insects seemed to be feeding on the grass roots, creating the characteristic rings. The circles also established a reliable water source for the termites.
But the UFZ team behind this most recent study argues that termites are usually distributed in irregular clusters, and so could not have created patterns as consistent as the ones they observed in their aerial photos.
"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," Getzin said in his statement.
Getzin and colleagues believe the explanation for the fairy circles is that the grass grows in self-regulating patterns to deal with competition for water.
To support their claim, researchers note that in young forests, plants at first will grow close to one another, and then over the years spread out in a self-regulation process so the vegetation has more access to resources and space.
"We consider this at present being the most convincing explanation," authors concluded.