Namibia’s fairy circle mystery still bewildering researchers
With its bone-dry grasslands and oppressive heat, the middle of the Namib Desert may seem like a strange place to go fishing. Yet there Jennifer Guyton and Tyler Coverdale were, standing in a sea of orange sand and brittle yellow grass with their 30-foot carp pole.
But the two Princeton graduate students were not trying to catch some sort of desert-dwelling dogfish or a literal “sand shark.” Instead, they had swapped the hook with a camera so they could investigate the scenery around something much more scientifically sensible: fairy circles.
That is what scientists call the mysterious bald spots speckled across Namibia’s grasslands. The rings are 6 feet to 115 feet wide and are regularly spaced out in a hexagon or honeycomb pattern.
The fairy circles’ origins have long bewildered researchers. But a new study published Wednesday in the journal Nature seeks to offer some insights into how the enchanting landscapes may have formed.
One side suggests that termites, locked in neverending competition with neighboring colonies, create the circles as they fight for dominance and resources. The other says that perpetually thirsty plants simultaneously assist and compete with their neighbors’ roots, causing the vegetation to “self-organize” into the patterns.
The new study suggests that termites and plants may be jointly responsible for forming fairy circle landscapes in Namibia. And it has received mixed reviews from scientists entrenched in the dispute.
“We thought both sides of the debate bring in compelling arguments for each of these mechanisms, so why should it be one or the other?” said Corina Tarnita, an ecologist from Princeton University and the study’s co-lead author.
Tarnita worked with Juan Bonachela, a mathematician from the University of Strathclyde in Scotland, to test the termite and plant explanations in a computer model. They found that either hypothesis could generate the fairy circle features. But when they tested both mechanisms together, the model revealed a second pattern hidden within the grass between the fairy circles.
“Everyone was focusing on the circles and not what was happening in between them,” said Robert M. Pringle, an ecologist at Princeton and another author of the paper.
The next step was to confirm that this second vegetation pattern existed in nature. So they sent Guyton and Coverdale to Namibia in 2015.
By comparing the photos with their model, the team verified that the second pattern did exist. That finding, they said, suggested that only by interacting together could insects and plants create the landscape that characterizes Namibian fairy circles.
Stephan Getzin, an ecologist at the Helmholtz Centre for Environmental Research in Leipzig, Germany, was not persuaded, saying the paper was unable to account for the presence of fairy circles where sand termites were completely absent.
“Logically, if there are fairy circles without the presence of termites, the termite theory cannot be considered as a strong explanation for the phenomenon,” he said.
Tarnita responded that either termites and plants could make the fairy circles, but that the entire system, which includes the vegetation and the smallscale patterns seen in the Namibian fairy circles, needed both.