What are ‘fairy circles’, which intrigue scientists – 11/05/2023 – Science

Members of the Himba tribe in Namibia have said for generations that the strong breath of a dragon left marks on the earth.

These are semicircular marks, where vegetation never grew again. All that was left was the bare earth, surrounded by the grasses common to the arid terrain of southwest Africa.

In the 1970s, South African ecologist Ken Tinley noticed that those pieces of land were similar to the famous rings formed by mushrooms in Europe. He gave the formations the name “fairy circles”.

Tinley believed they might have been created by termites. But, to this day, these land formations remain a mystery. Scientists have been debating it for many years and have not yet reached agreement on its origin.

But new research has added a new component to the discussion. Fairy circles do not only exist in southwest Africa and northwest Australia, as was believed until now.

“From space, with the help of a model based on artificial intelligence, we found hundreds of places in the arid regions of the world that had never been described before, with vegetation patterns identical to fairy circles”, he explains to BBC News Mundo (the service in Spanish from the BBC) scientist Emilio Guirado, from the University of Alicante, in Spain.

The study revealed that fairy circles exist in at least 15 countries on three continents.

His research did not seek to uncover the origin of these formations. But the data presented can help find the answer.

Debate of years

Despite their name, fairy circles are often hexagonal formations in the ground. Vegetation does not grow inside it, but around it — at least, for the most part.

After Tinley’s research in the 1970s, scientific discussions about the origins of fairy circles moved toward two main theories.

One of them was presented in 2013, by German biologist Norbert Jürgens. After a decade of research, he concluded that fairy circles are formed by subterranean termites.

According to Jürgens, these insects feed on the roots of vegetation that begins to grow after rain, generating accumulations of water underground and allowing termites to survive.

“Termites are social insects that control their territory, where they have water and food, and colonies defend their area from neighbors, sometimes very aggressively,” Jürgens explained to BBC News Mundo in 2016.

The German biologist stated that fairy circles form a “system of competition between colonies”. He is “completely sure” about his theory, which, he says, has been confirmed by many of his colleagues.

Almost in parallel, German ecologist Stephan Getzin and Israeli physicist Ehud Meron teamed up to research fairy circles in Australia. They argued that its formation is explained by self-organization theory.

Meron explained to BBC News Mundo, after the publication of his study in 2016, that nature faces water scarcity with this phenomenon.

For the researcher, “organized in circles, the surrounding vegetation benefits from an additional source of water, as rain in the terrain’s clearings finds its way through various water transport mechanisms.”

“In Australia, this mechanism includes the flow of water over land, while in Namibia it is related to the diffusion of stored water,” said Meron.

With this, Meron and Getzin discarded Jürgens’ theory, since, according to them, there were no termites in the fairy circles studied in northwestern Australia. Jürgens disputed the conclusion, saying his colleagues would not have dug deep enough to find the insects.

What does the new research say?

The research by Emilio Guirado’s team did not seek to find the causes of the formation of fairy circles. They created a map of the places where these formations are found.

The scientist explained that they used two artificial intelligence models and found hundreds of places with fairy circles in the arid regions of the world (which correspond to 41% of the Earth’s surface).

They analyzed several factors, such as climate, soil and environmental factors. And they concluded that, in places where these variables are stable, there are fairy circles — particularly where the soil is sandy.

“We analyzed hundreds of thousands of images and discovered hundreds of vegetation patterns identical to fairy circles in the world’s arid zones,” explains Guirado. “This process took just over a month on a supercomputer with four graphics processing units [GPUs, na sigla em inglês].”

With the help of two artificial intelligence models, they searched 600,000 satellite images from global mapping services, such as Google Earth, Bing Maps and Mapbox, looking for photographs of the terrain with higher resolution.

With this, they were able to obtain clearer images of the arid spots on Earth where fairy circles are present.

As a result, researchers found fairy circles in 263 points on the planet, located in 15 countries in Africa, Asia and Oceania.

These regions include the Sahel in Africa, Western Sahara, the Horn of Africa, Madagascar, southwest Asia and central Australia.

Asked about the possibility of his research providing some explanation about the origin of these patterns, the Spanish scientist responds that the unknown remains. He neither discards nor defends the hypotheses that have already been presented.

What is certain is that this is an arid land phenomenon, as it would be almost impossible to observe it in other regions.

“Theoretically, in places where precipitation is greater, the circles would close”, explains Guirado.