Fairy circles are strange patches of barren earth that arrange themselves in formations that look like honeycomb.
Until now they had only been seen in southwestern Africa, but a new paper shows the phenomenon in Australia. It is thought that competition for water causes the mysterious patterns.
Why do fairy circles form in arid environments?
The fairy circles were spotted by Bronwyn Bell, who works in environmental restoration in Perth, Australia. She emailed the images to Dr. Stephan Getzin, an ecologist at the Helmholtz Center for Environmental Research in Leipzig, Germany, who has been researching the phenomenon in Africa.
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Most scientists in the field believe that it is caused by competition for water or by termites, but other theories include noxious gases. Getzin believes the formations are caused by competition for water, where vegetation in harsh climates self-organizes into patterns.
The barren patches in Africa act as troughs, storing water which grasses can soak up over a long period of time from the sandy soil. In Australia, things are different as the soil is loamy, forming hard clay troughs. However these troughs serve to push water to the grasses that grow around them.
Termites, water scarcity, or noxious gases
“The gaps function as a source of extra water, like in Namibia,” Dr. Getzin says. “The mechanism of water transport is different, but the function of the fairy circles is the same.”
Researchers used spatial pattern analysis of aerial imagery to test their self-organization theory, creating computer simulations of interactions. Both the Australian and African fairy circles formed hexagonal patterns, like honeycomb.
They also found labyrinth and spot patterns nearby, which goes to show how bad the competition for water is among plants. Researchers also looked into insect activity, knowing that another group believed that termites were behind the formations.
In 2013, Norbert Jurgens, an ecologist at the University of Hamburg, published his research into termites as the cause of fairy circles. Other scientists said that just because termites were present, there was insufficient proof that they caused the patterns.
Debate rumbles on between opposing camps
Getzin and his team used GPS to map termite activity in Australia before comparing it to the fairy circles. They found no correlation.
The team also used electron microscopy to find that the hard center of the fair circles were caused by weather processes rather than insects. Jürgens does not accept that his theory has been proven wrong, and points out that they should be referred to as “clay circles” rather than fair circles.
Jurgens maintains that the Australian circles could be the work of termites. They contain more clay and fine silt than the surrounding earth, which could be the result of nests built by insects, he says.
According to Nichole Barger, ecosystem ecologist at the University of Colorado, the new research “moves us closer toward a unifying theory of fairy circle formation.” There may be more undiscovered fairy circles in other dry areas on other parts of the planet, she said.
Walter Tschinkel, an entomologist at Florida State University, says that the research points to the fact that the self-organization of plants is to thank for the fairy circles. He claimed that by controlling environmental factors like water and termites scientists could be more certain. However limited budgets and logistical constraints mean that such a huge undertaking has not been attempted.