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For over 50 years, ecologists have studied and debated the mystery of the Namib Desert’s “fairy circles,” circular patches of mostly grassless that have spread over 1,100 miles across the arid grasslands of southern Africa.
Despite their whimsical name, related to the term “Fairy Rings” for circular mushroom patterns found in wooded areas, there are no fairies in play here. Many theories have been put forward, however two have held the greatest merit. One theory has attempted to blame termites for these dry patches, while the other considers the evolution of grasses. Scientists have been going back and forth for decades, but a new study may finally provide evidence for a clear explanation.
Stephan Getzin, an ecologist at the University of Göttingen in Germany and lead author of the study, began researching the fairy circles in 2000. In the years since, he has published more articles on the circles and their origins than any other expert.
What makes the fairy circles distinctive are the barren patches in them, however The grass growth around them is also remarkable – they’ve found a way to thrive in one of the driest places on earth. In previous research, Getzin and his team hypothesized that plants in the outer rings of the circles had evolved to maximize their limited water in the desert.
And for the past three years, he’s spent time in Namibia following the growth of grasses to find more evidence for this theory. During the 2020 drought season, Getzin and his research team installed sensors that could record soil moisture at a depth of about 20 centimeters and monitor water uptake by grasses.
“We were really lucky because in 2020 there wasn’t much vegetation, or actually almost no grass vegetation, in the fairy circle area,” Getzin said. “But 2021 and this year, 2022, had a very good rainy season so we could actually see how the growth of the new grasses redistributed the soil water.”
Analyzing data from these rainy seasons, Getzin’s team found that the water inside the circles ran out quickly, despite the lack of grass to use it, while the grasses on the outside were as hardy as ever. Under the intense heat of the desert, these established grasses had evolved to form a vacuum system around their roots, drawing any water towards them, Getzin said. Meanwhile, the grasses from the counties that try to grow right after the rains could not get enough water to live.
“A circle is the most logical geometric formation you would create as a water-stressed plant,” Getzin said. “If these circles were squares or low, complex structures, then you would have a lot more individual grasses along the perimeter. … The proportional area is smaller than if you grow in a circle. These grasses end in a circle because that is the most logical structure to maximize the water available to each individual plant.”
The study called this an example of “ecohydrological feedback,” where the barren circles become reservoirs that help maintain grasses on the edges — albeit at the expense of central grasses. This self-organization is being used to cushion the negative effects of increasing drought, Getzin said, and can also be seen in other harsh arid regions around the world.
The termite hypothesis, meanwhile, suggested that fairy circles are created by sand termites that damage grass roots and has been well received by other scientists. However, a 2016 study of similar fairy circles in Australia found no clear links to the pests. Getzin’s latest research came to similar conclusions.
“We have an example where it only rained once, the grasses sprouted, and then after eight or nine days the grasses just started dying inside the fairy circles,” Getzin said. “When we carefully[digged up]these grasses and looked at the roots, none of these grasses had root damage from termites—but they died anyway. Our results are unequivocal, no, these grasses will die without termites.”
Getzin and his team also found the roots of young Plants inside the circles will be longer than those outside. According to Getzin, this suggests that the grasses had made longer paths in an attempt to find water – further evidence of their competition with the outer ring grasses in the arid desert.
While the evidence produced by the study is a step forward, scientists – including Getzin – believe more research could be done. Still, Getzin told CNN it was time for him to take on a new challenge.
“In the fairy circles in Namibia and Australia, the plants change the distribution of soil moisture and thereby increase their chances of survival, and we can call this kind of ‘swarm intelligence,'” Getzin said. “Plants form intelligent patterns and geometric formations, and I will continue to work in that direction.”
For example, near the Fairy Circle area of Namibia, researchers have also found another type of grass that forms in large, circular rings after rainfall. “It’s a completely different genus of grass, but it forms identical circular formations,” Getzin said. He wants to research this process during Namibia’s next rainy season in 2023.