Strange, circular bald spots called "fairy circles" have been found in Australia, which marks the first time the phenomenon has been seen outside of Africa. Researchers say soil and plants created the circles themselves, and the theory of these origins has been published in the Proceedings of the National Academy of Sciences.

Fairy circles are open spots of naked earth in areas otherwise covered with vegetation. When they appear, they appear in droves, and they’re typically pretty big; the circles in Namibia range from 7 to almost 50 feet in diameter apiece. From the air, they look like leopard spots on the landscape. (Their unusual appearance may even trigger trypophobia in some observers.)

Where do fairy circles come from? That depends on whom you ask. Two culprits are most commonly suggested: bugs and gas. The bug theorists say the spots are areas where the tiny bites of ants and termites have killed the grass. As evidence, they point to the fact that Africa’s fairy circles are indeed all located by termite and ant colonies. Other scientists say the spots are the product of lots of carbon monoxide leaks. The gas rises out of the Earth’s crust, they say, killing all the vegetation it touches.

But study author and fairy circle expert Stephan Getzin of the Helmholtz Centre for Environmental Research doesn’t buy either of these theories. He’s a believer in the self-organizing plants theory, which says that, under certain conditions, plants gravitate toward resources.

“Water is limited, and because water is limited it cannot sustain a continuous vegetation coverage,” he told Smithsonian. “So we have gaps and other patterns like labyrinths and stripes or even spots.” The self-organizing theory met with resistance for a long time. Some scientists said it wasn’t even possible. If such a thing could happen, they argued, why weren’t there fairy circles in places other than Africa?

In 2014, shortly after publishing a paper on Namibia’s circles, Getzin got an email and a photo from Bronwyn Bell, an environmental manager for a mining company. Bell had read Getzin’s paper and was sure she had seen something similar nearby. Getzin was astonished. “We couldn’t believe it,” he said. “The Namibia fairy circles are supposed to be the only ones in the world.”

Getzin assembled a team of colleagues and headed to Australia. They took soil samples, recorded detailed measurements, and snapped photos from the ground and in the air. They ran computer simulations and image analysis, looking all the while for some pattern or evidence.

Image Credit: Stephan Getzin

They found that the Australian fairy circles were identical in appearance to their Namibian counterparts, but there were some interesting differences.

For one, there were almost no ants or termites to be found. Cryptic sand termites, the prime Namibian termite suspects, don’t even exist in Australia, Getzin said in a press statement. “And the [insects] we did find have a completely different distribution pattern to the fairy circles." So much for the bug theory.

Getzin and his colleagues found that the Australian soil literally forced the plants out. In Western Australia’s intense sunlight, any earth not covered with vegetation is more or less cooked, and a hard crust forms on top. The baked earth is so hard, rain can’t get in—and no rain means no plants. It's a self-perpetuating cycle that Getzin says could explain the spots.

Smithsonian explains further:

Getzin and his team suggest that when it rains, water pools to the edges of any established gaps in vegetation, straight to the waiting roots of the plants on the gap’s edge. Those edge plants then grow bigger and put down more roots to collect even more water. That means these plants are pulling resources away from their neighbors, limiting their growth and driving the circular pattern of boom and bust.

"In Namibia, the sandy soils of the fairy circles are much more permeable and precipitation can drain away with ease," Getzin said. "The details of this mechanism are different to that in Australia, but it produces the same vegetation pattern because both systems of gaps are triggered by the same instability."

His theory bolstered, Getzin intends next to begin a worldwide search for other fairy circles.

[h/t Smithsonian]