Thousands of mysterious circles dot the landscape of western Africa with strange precision, and for many decades people had no idea what caused them, until now.
The circles came to be known as "fairy circles," but according to ecologist Norbert Juergens of Germany's University of Hamburg, the circles aren't caused by fairies at all. Rather, based on a new study, it appears that the circles are the result of termites seeking to re-make the landscape.
"The circles, according to [Norbert Juergens], are water traps created by a sand termite," states Ed Yong in an article for "National Geographic." "The termites eat all the grass within a circular patch, exposing underlying sand grains that store any falling rainwater. These barren freckles are works of ecological engineering, designed to retain precious water in an otherwise dry land. They're like desert versions of beaver dams."
According to Juergens, the activity allows for additional benefits as well, as the termites are a valuable food resource for a number of other creatures like moles, geckos, jackals, aardvarks, spiders and ants.
Other proposed theories for the cause of the circles include toxins left by poisonous plants, "self-organizing" vegetation dynamics and ant species producing groups of plant-eating insects. None of these hypotheses, however, has resulted in convincing evidence.
Juergens came to his conclusion by counting insect species at fairy circles in Namibia, Angola and South Africa. He found that a desert-dwelling termite species called "Psammotermes allocerus" was found most frequently near the circles, and could even be discovered to burrow beneath them.
Afterward, Juergen measured vegetation composition and soil water content near the circles, discovering that the soil was surprisingly rich in water. He theorizes that the circles are formed when the termites feed on the roots of grass seedlings. This results in water collecting under the soil, which nourishes grasses that often surround the circles. Juergen states that the formations are part of a larger process involving other animals.
"Fairy circles, like oases in the desert, increase biodiversity," he says. "[The termites] turn wide desert regions of predominantly ephemeral life into landscapes dominated by species-rich perennial grassland, supporting uninterrupted perennial life even during dry seasons and drought years."
However, the reason for what causes the circles is still very much a topic for debate. Biologist Walter Tschinkel says that Juergens misinterprets correlation as causation and plant ecologist Mike Cramer says that only a small amount of termites has been found near the circles he's examined.
"The only way for this question to be properly answered is with more thorough investigations and focused experiments," Cramer states.
