Mindy Weisberger, CNN
Thu, September 28, 2023
Thomas Dressler/imageBROKER/Shutterstock
Round discs of barren dirt known as “fairy circles” look like rows of polka dots that can spread for miles over the ground. The phenomenon’s mysterious origins have intrigued scientists for decades — and they may be far more widespread than once thought.
Fairy circles were previously spotted only in the arid lands of Southern Africa’s Namib Desert and the outback of Western Australia. But a new study has used artificial intelligence to identify vegetation patterns resembling fairy circles in hundreds of new locations across 15 countries on three continents. This could help scientists understand fairy circles and their formation on a global scale.
For the new survey, published Monday in the journal Proceedings of the National Academy of Sciences, the researchers analyzed datasets containing high-resolution satellite images of drylands, or arid ecosystems with scant rainfall, from around the world. The search for patterns resembling fairy circles used a neural network — a type of AI that processes information in a manner similar to that of a brain.
“The use of artificial intelligence based models on satellite imagery is the first time it has been done on a large scale to detect fairy-circle like patterns,” said lead study author Dr. Emilio Guirado, a data scientist with the Multidisciplinary Institute for Environmental Studies at the University of Alicante in Spain, in an email.
Hundreds of potential fairy circle sites
First, the study authors trained the neural network to recognize fairy circles by inputting more than 15,000 satellite images taken over 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 vegetation in those images and identified repeating circular patterns that resembled patterns of known fairy circles, evaluating the circles’ sizes and shapes as well as their locations, pattern densities and distribution.
Output of this analysis then required a human review, Guirado said. “We had to manually discard some artificial and natural structures that were not fairy circles based on photo-interpretation 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 spots were distributed across Africa (the Sahel, Western Sahara and the Horn of Africa) and were also clustered in Madagascar and Midwestern Asia, as well as central and Southwest Australia.
Circle pattern recognition
Fairy circles aren’t the only natural phenomenon that can produce round, repeated bare spots in a landscape. One factor that sets fairy circles apart from other types of vegetation gaps is a strongly ordered pattern between the circles, said Dr. Stephan Getzin, a researcher in the department of ecosystem modeling at the University of Göttingen in Germany.
Getzin and colleagues published a November 2021 paper defining fairy circles and what made them unique, emphasizing details of the overall pattern structure, he told CNN in an email. And according to Getzin, who was not involved in the latest study, the newfound patterns fall short.
“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 survey clear that high bar, Getzin said.
But in fact, there is no universally accepted definition of fairy circles, Guirado said. He and his coauthors identified potential fairy circles — gauging the size and shape of individual circles, as well as the patterns they formed collectively — by referencing guidelines established across multiple published studies. The metrics of those spatial patterns, in fairy circles old and new, “are virtually the same,” he said.
Of the new locations that were identified, some passed muster with Dr. Fiona Walsh, who as part of an international team has investigated fairy circles in the Australian outback. “Pattern distribution in Australia appears to be congruent with some of what we previously reported,” said Walsh, an ethnoecologist at the University of Western Australia. Walsh was not involved in the new survey.
Fairy circles’ mysterious origins
The study authors also compiled environmental data where circles were spotted, collecting evidence that might hint at what causes them to form. The researchers determined that fairy circle-like patterns were most likely to occur in very dry, sandy soils that were high-alkaline and low in nitrogen. The scientists also found the fairy circle-like patterns helped stabilize ecosystems, increasing an area’s resistance to disturbances such as floods or extreme drought.
But the question “What shapes fairy circles?” is complex, and factors that create fairy circles may differ from site to site, the study authors reported. Getzin previously wrote that certain climate conditions, along with self-organization in plants, generated fairy circles in Namibia, and while insects such as termites take advantage of the dry patches, their activities don’t directly produce the patterns, he said in the email.
Walsh, however, said that Australia’s fairy circles are inextricably linked to termite activity. Their team’s research, conducted in close collaboration with indigenous peoples, determined that in Western Australia and in the Northern Territory, termites are intrinsic to the functioning of fairy circles, called “linyji” in the Manyjilyjarra language, and “mingkirri” in the Warlpiri language, she told CNN in an email.
“Aboriginal people illustrated these patterns at least since the 1980s and said they knew of them for generations, probably millennia earlier,” Walsh said.
“In Australia, termites do not simply ‘play a role’,” she added. “They are the primary mechanism and interpretations need to be centred on termite-grass-soil-water dynamics.”
Many questions about fairy circles have yet to be answered, and the authors of the new study are optimistic that their global atlas will open a new chapter in the study of these peculiar barren spots.
“We hope that the information we publish in the paper can provide scientists around the world with new areas of study that will solve new puzzles in the formation of fairy-circle patterns,” Guirado said.
Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American and How It Works magazine.
Mysterious ‘fairy circles’ found dotting Africa and Australia now found in more parts of world
Vishwam Sankaran
Wed, September 27, 2023
Strange circular patches called “fairy circles” dotting the arid terrains of Namibia and Australia have puzzled scientists for decades and have now been mapped across 250 locations that span 15 countries.
Until now, the enigmatic circular patterns of bare soil surrounded by plants generating rings of vegetation had only been described in Namibia and Australia.
Multiple theories have been proposed over the past five decades to explain their formation, but the global dimension of the phenomena has remained elusive, said researchers, including those from Universidad de Alicante (UA) in Spain.
The new study, published on Tuesday in the journal PNAS, used artificial intelligence to classify satellite images, obtaining 263 sites where patterns similar to the fairy circles have been described to date, including from Namibia and Western Australia.
The analysis found these patches in places like the Sahel, Western Sahara, the Horn of Africa, Madagascar, southwest Asia and central Australia, suggesting fairy circles are “far more common than previously thought”.
“Analyzing their effects on the functioning of ecosystems and discovering the environmental factors that determine their distribution is essential to better understand the causes of the formation of these vegetation patterns and their ecological importance,” study co-author Emilio Guirado from UA said.
Scientists found that the combination of certain soil and climate characteristics, such as low nitrogen content and an average rainfall of less than 200 mm/year, are associated with the presence of fairy circles.
The fairy circles seen from the air. They form an additional source of water in this arid region, because the rainwater flows towards the grasses on the edge. (Stephan Getzin)
“This study has taken into account multiple variables hitherto not considered, such as albedo or the state of the aquifers,” said Jaime Martínez-Valderrama, another author of the study.
“This is a particularly relevant factor, since the massive use of groundwater in arid areas around the world, including deserts, could disturb these formations,” Dr Martínez-Valderrama said.
Drone image of car driving through the NamibRand Nature Reserve, one of the fairy-circle regions in Namibia where the researchers undertook grass excavations, soil-moisture and infiltration measurements (Stephan Getzin)
The new findings, according to researchers, also open the door to research on whether these patterns on the soil can be indicators of ecosystem degradation with the climate crisis.
With the new study, scientists have also made available a global atlas of fairy circles and a database that could be useful in determining whether these vegetation patterns are more resilient to climate change and other disturbances.
Mysterious 'fairy circles' may appear on three different continents
Laura Baisas
Wed, September 27, 2023
The natural circles that pop up on the soil in the planet’s arid regions are an enduring scientific debate and mystery. These “fairy circles” are circular patterns of bare soil surrounded by plants and vegetation. Until very recently, the unique phenomena have only been described in the vast Namib desert and the Australian outback. While their origins and distribution are hotly debated, a study with satellite imagery published on September 25 in the journal Proceedings of the National Academy of Sciences (PNAS) indicates that fairy circles may be more common than once realized. They are potentially found in 15 countries across three continents and in 263 different sites.
These soil shapes occur in arid areas of the Earth, where nutrients and water are generally scarce. Their signature circular pattern and hexagonal shape is believed to be the best way that the plants have found to survive in that landscape. Ecologist Ken Tinsly observed the circles in Namibia in 1971, and the story goes that he borrowed the name fairy circles from a naturally occurring ring of mushrooms that are generally found in Europe.
By 2017, Australian researchers found the debated western desert fairy circles, and proposed that the mechanisms of biological self-organization and pattern formation proposed by mathematician Alan Turing were behind them. In the same year, Aboriginal knowledge linked those fairy circles to a species of termites. This “termite theory” of fairy circle origin continues to be a focus of research—a team from the University of Hamburg in Germany published a study seeming to confirm that termites are behind these circles in July.
In this new study, a team of researchers from Spain used artificial intelligence-based models to look at the fairy circles from Australia and Namibia and directed it to look for similar patterns. The AI scoured the images for months and expanded the areas where these fairy circles could exist. These locations include the circles in Namibia, Western Australia, the western Sahara Desert, the Sahel region that separates the African savanna from the Sahara Desert, the Horn of Africa to the East, the island of Madagascar, southwestern Asia, and Central Australia.
Fairy circles on a Namibian plain. CREDIT: Audi Ekandjo.
The team then crossed-checked the results of the AI system with a different AI program trained to study the environments and ecology of arid areas to find out what factors govern the appearance of these circular patterns.
"Our study provides evidence that fairy-circle[s] are far more common than previously thought, which has allowed us, for the first time, to globally understand the factors affecting their distribution," study co-author and Institute of Natural Resources and Agrobiology of Seville soil ecologist Manuel Delgado Baquerizo said in a statement.
According to the team, these circles generally appear in arid regions where the soil is mainly sandy, there is water scarcity, annual rainfall is between 4 to 12 inches, and low nutrient continent in the soil.
"Analyzing their effects on the functioning of ecosystems and discovering the environmental factors that determine their distribution is essential to better understand the causes of the formation of these vegetation patterns and their ecological importance," study co-author and University of Alicante data scientist Emilio Guirado said in a statement.
More research is needed to determine the role of insects like termites in fairy circle formation, but Guirado told El País that “their global importance is low,” and that they may play an important role in local cases like those in Namibia, “but there are other factors that are even more important.”
The images are now included in a global atlas of fairy circles and a database that could help determine if these patterns demonstrate resilience to climate change.
"We hope that the unpublished data will be useful for those interested in comparing the dynamic behavior of these patterns with others present in arid areas around the world,” said Guirado.
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