The “fairy circles” of the Namibian desert have confused onlookers and sparked myths for centuries. These crisply shaped circles of bare dust in arid grassland have been explained away through tales of underground dragons, the footsteps of Gods, aliens and, of course, fairies. But the two scientific explanations – termites and insect life or water competition – have long divided scientists.
Until recently, the circles were only thought to be found in Africa. However, the discovery of rings over 10,000 kilometers (6,200 miles) away in the depths of the Australian outback has opened up a new enquiry into the mystery. For a study recently published online in PNAS, researchers went to Australia to investigate and see if its fairy circles could shed any light on the wider puzzle.
First of all, the scientists set out to probe the termite and ant hypothesis. Their fieldwork and aerial imaging showed that there was very little correlation between the position of termite or ant nests in the area and the location of the fairy circles.
Aerial image of Australia's fairy circles. Stephan Getzin et al/PNAS
They then moved onto the water competition hypothesis – the idea that these rings emerge as the plants compete for water and nutrients. Within this battle for resources, they undergo a process of self-organization to maximise access to scarce supplies and form these circular patterns.
The data from a combination of remote sensing, spatial pattern analysis, and mathematical modeling seems to support this idea. Curiously, however, the findings from Australia showed that though the rings shared the same characteristics as their counterparts, they are driven by a very different mechanism to those in Namibia.
In Australia, the top layer of soil in the circle was hard and tough for water to penetrate, allowing only plants and roots on the peripheral to receive water and thrive. In Namibia however, the upper layers of soil in the circle are sandy and loose, which caused water to quickly flow down and form a reservoir for plants growing on the circle’s edges.
Importantly, the research shows that the mystery of the fairy circles is indeed all down to water competition and biomass self-organization. However, the question of their origin and their exact relationship to different soils remains unclear.
“You should never claim to put an end to the mystery,” Stephan Getzin, an ecologist who led the study, told New Scientist. “We’ve just made one significant step forward in solving the problem.”