Mysterious “fairy circles” have been identified in hundreds of locations around the world

Round disks of dry earth, known as “fairy circles” , they look like rows of balls that can spread for kilometers across the floor. The mysterious origins of the phenomenon have intrigued scientists for decades – and may be much more widespread than previously thought.

Fairy circles were previously seen only in the arid lands of the Namib Desert in southern Africa and the interior of western Australia. But a new study used artificial intelligence to identify vegetation patterns similar to fairy circles in hundreds of new locations in 15 countries across three continents. This could help scientists understand fairy circles and their formation on a global scale.

For the new research, published Monday (25) in the magazine Proceedings of the National Academy of Sciences, researchers analyzed datasets containing high-resolution satellite images of drylands, or arid ecosystems with little rainfall, from around the world. The search for patterns similar to fairy circles used a neural network – a type of AI that processes information in a similar way to a brain.

“This is the first time that artificial intelligence-based models have been used in large-scale satellite images to detect patterns similar to fairy circles,” said the study’s lead author, Dr. Emilio Guirado, a data scientist at the Institute Multidisciplinary Environmental Studies at the University of Alicante in Spain.

Hundreds of possible fairy circle locations

First, the study authors trained the neural network to recognize fairy circles by inputting more than 15,000 satellite images taken in Namibia and Australia. Half of the images showed fairy circles and half did not.

The scientists then fed their AI a dataset with satellite views of nearly 575,000 plots of land around the world, each measuring about 2.5 acres (1 hectare). The neural network scanned the vegetation in these images and identified repeating circular patterns that resembled known fairy circle patterns, evaluating the sizes and shapes of the circles, as well as their locations, pattern densities, and distribution.

The result of this analysis then required human review, Guirado said. “We had to manually rule out some artificial and natural structures that were not fairy circles based on photointerpretation and the context of the area,” he explained.

The results showed 263 dryland locations where there were circular patterns similar to fairy circles in Namibia and Australia. These arid zones were distributed throughout Africa (Sahel, Western Sahara and the Horn of Africa) and were also clustered in Madagascar and Central-West Asia, as well as central and southwestern Australia.

Circular pattern recognition

Fairy circles are not the only natural phenomenon that can produce round, repeated bare patches across a landscape. One factor that differentiates fairy circles from other types of vegetation gaps is a strongly ordered pattern between the circles, said Dr. Stephan Getzin, a researcher in the ecosystem modeling department at the University of Göttingen in Germany.

Getzin and colleagues published a paper in November 2021 defining fairy circles and what makes them unique, emphasizing details of the pattern’s structure, he told CNN . And according to Getzin, who was not involved in the latest study, the newly discovered patterns are insufficient.

“Fairy circles are defined by the fact that they have, in principle, the ability to form a ‘spatially periodic’ pattern”, which is “significantly more ordered” than other patterns – and none of the patterns in the research pass this high bar, Getzin said.

See also: Desert elephants are meeting friends in Namibia’s drylands