Scientists in Australia believe they may have an explanation for the "fairy circle" phenomenon, and it doesn't involve termites—or fairies. The researchers say soil microbes appear to be a major contributor to the grassless circles long considered one of nature's greatest mysteries, the New York Times reports. In a study published in the Australian Journal of Botany, researchers say soil pathogens that harm seedlings apparently build up in the centers of hummocks of spinifex grasses, making it hard for new seedlings to sprout and causing the circles to form as plants in the middle die off. They believe other microbes in the region's soil might actually help the seedlings, leading to growth around the outside of the circle.
When researchers took soil from the barren inner ring and sterilized it, seeds were able to germinate. "Sterilizing the inner soil seemed to remove whatever was keeping plants from sprouting," per the Times. The study notes that previous research has established that plants "can accumulate pathogens in their root zones over time." Adult plants can tolerate these pathogens, but not seedlings. Study co-author Angela Moles, an ecologist at the University of New South Wales, says she got the idea for the research after learning about a European swamp grass that grows in circles due to a buildup of soil pathogens. The microbes involved—both the harmful and potentially beneficial ones—have yet to be identified. (Other researchers say the formations have a lot in common with skin cells.)