What creates “fairy circles” in dry regions? A German researcher walks the trail of the puzzle.

The circular spots in the desert floor look like they were drawn by magic. Standardizing the honeycomb pattern, these “fairy circles” adorn parts of the Namib in South Africa and areas of the Australian Outback. Satellite images show that there are several million of them. “They typically consist of 20 to 30 individual plants and are typically four to eight meters in diameter,” explains Stefan Getzen from the Department of Ecosystem Modeling at the University of Göttingen, who and his team want to unravel the mystery of the imaginary circles.

Human imaginative circles have always fascinated me. In 2000, Getzin and a colleague founded the international scientific term “Fairy Circles”. Recently, a Göttingen researcher worked on The world’s first sharp scientific definition of the term. The problem is that the term fairy circle has been used in a very inflated way for some time. But not everything that is green and grows in a circle can be considered a fairy circle, ”confirms Getzen. “For a long time I knew only real fairy circles from the Namib Desert, where they are formed from the annual resinous grasses. In 2014, an Australian ecologist contacted me who found very similar formations in the outback of northwest Australia. Unlike the Namib, it is formed from perennial Triodia grasses and reaches a maximum diameter of only seven meters. Otherwise, however, they have the same characteristics as in the Namib, including an exceptional spatial order.

Aquatic competition as a possible explanation

How are imaginary circles created? Many ecologists, geologists, and even physicists and mathematicians have worked on the answer. Getzin has also been trying to solve this fascinating nature mystery for two decades. The ecologist believes that “there is no absolute certainty yet” about the actual reasons for the formation of circles. But he and his team see himself and his team on a hot path: “Our self-organizing theory says that the circular growth formations provide up to 30 grassy beaches that form a fairy circle the best conditions for survival in this dry environment,” explains the scientist. “When it is dry, slopes of grass placed directly on the bare inner circle have the best access to the water. One might casually say: marginal grasses form a common cause by forming a stable circle in competitive equilibrium. In the middle, the grass germinates briefly Only when it is rainy, as Geetzen notes on the site: “What we can already say is that the weeds in the middle of the imaginary circles, which sprout temporarily after a little rain, begin to die soon after it has rained, but the termites have not eaten their roots, Nor are its roots shorter than the roots of vital herbs on the edge of the circles.”

Getzin sees ecological engineering as effective in self-regulation: “Without this remarkable ability of weeds in the Namib and Australian Outback, the regions would likely be completely devastated and silted up.” However, the term “self-regulation” is somewhat misleading: no plant voluntarily offers anything here to do a favor for those of its kind. Alternatively, some plants have better survival chances than others due to their more favorable location.

As reasonable as Getzin’s self-regulatory theory may be, testing it is hard work. Especially since critics complain that there must be superstitious circles in other similar climatic regions of the Earth, not only in the Namib and the Australian outback. But Getzin is working hard to support his hypothesis: “We have now been following rainfall in the Namib for more than a year to investigate its effect on imaginary circuits,” the researcher reveals. “We have to learn to better understand the water cycle in the vicinity of circuits. At the beginning of 2022 we will have the third rainy season behind us in the Namib. Until then, we hope to be able to work out how and why the imaginary circuits form. At least we want to be very close. of the solution.”

This brief article is from the December 2021 issue of bild der Wissenschaft. Read more about fictional circles and how the Göttingen research team studies them in the full article.

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