Following up on my 2012 post about fairy circles.
Rachel Nuwer writes at the NY Times, “When Stephan Getzin, an ecologist at the Helmholtz Center for Environmental Research in Leipzig, Germany, opened the email, his heart began to flutter. Attached was an aerial image of fairy circles, just as he had seen in countless photos before. But those images were always taken along long strips of arid grassland stretching from southern Angola to northern South Africa. These fairy circles — which looked nearly identical — came from Australia, not Africa. …
“The emailed photo came from Bronwyn Bell, who does environmental restoration work in Perth. She had read about Dr. Getzin’s research in Namibia and made a connection to the odd formations in her home state, Western Australia. …
“Scientists have been interested in fairy circles since the 1970s, but have not been able to agree on what causes the patterns to form. Researchers generally fall into two groups — team termite and team water competition — but there are other hypotheses as well, including one involving noxious gases.
“Dr. Getzin, like others on team water competition, explains the circles through pattern-formation theory, a model for understanding the way nature organizes itself. The theory was first developed not by biologists, but by the mathematician Alan Turing. In the 1990s, ecologists and physicists realized it could be tweaked to explain some vegetation patterns as well. In harsh habitats where plants compete for nutrients and water, the new theory predicts that, as weaker plants die and stronger ones grow larger, vegetation will self-organize into patterns …
“In the case of African fairy circles, the bare patches act as troughs, storing moisture from rare rainfalls for several months, lasting into the dry season. Tall grasses on the edge of the circles tap into the water with their roots and also suck it up with the help of water diffusion through the sandy soil.
“Although similar in appearance, Australian fairy circles turn out to behave differently, Dr. Getzin and his colleagues have found. … Aussie circles feature a very hard surface of dry, nearly impenetrable clay, which can reach up to a scalding 167 degrees during the day. Despite the differences, though, they believe the fairy circles’ function remains the same. When the researchers poured water into the circles in a simple irrigation experiment, it flowed to the edges, reaching the bushy grass …
“The new research ‘moves us closer toward a unifying theory of fairy circle formation,’ said Nichole Barger, an ecosystem ecologist at the University of Colorado, Boulder.
“It could be that more fairy circles are yet to be discovered in arid environments around the world, she said.
“According to Walter Tschinkel, an entomologist at Florida State University, the findings strengthen the claim that the circles are a result of self-organization by plants. He cautioned, though, that to be more certain, scientists would need to control environmental factors — water and termites, for example — to see which produce the predicted outcome.”
More here.
Photo: Norbert Jürgens
Tracks of Oryx antelopes crossing fairy circles in Namibia.
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