In the hunt to solve the “Fairytale Circle” mystery, one suspect is fired
Strange, barren patches pepper the Namib Desert, which stretches from southern Angola to northern South Africa. They are known as “fairy circles”, and for a natural phenomenon with such a strange name, there has been heated scientific debate about their origin.
“Going back and forth between opposing camps has often been nothing short of abhorrent,” says Michael Kramer, an ecophysiologist at the University of Cape Town who has studied fairy circles.
Although decades of research, there is no consensus on the origin of the mysterious formations. Theories included poisonous gases, noxious shrubs, and plant-killing microbes or fungi. Two explanations, whether the circles are made by termites or they arise as a result of plant competition for limited water, have dominated the scientific debate.
“Each publication has been hailed as having finally ‘solved’ the ‘mystery’ of the popular media fairy tale frame,” Dr. Cramer said in an email, calling such reporting an approach that is “not the norm for science.”
A rigorous study published in October won’t end this battle, but it appears to be giving it a go the water-related hypothesis is a clear lead on the theory of termites.
“Plants have to create these frameworks to redistribute water in order to maximize their chances of survival,” said Stefan Götzin, an ecologist at the University of Göttingen in Germany and an author of the study. “We call it ecosystem engineering.”
The Namib Desert is one of the driest places in the world, typically receiving only a few inches of rain each year. Researchers was first proposed in 2004 that plants, competing for water in this harsh ecosystem, can self-organize into fairy circles; pattern formation theory developed by mathematician Alan Turing.
Over the past decade, Dr. Getzin and others have published more than a dozen papers to support a hypothesis known as plant water stress.
For their latest study, Dr. Getzin and his colleagues studied fairy circles for three years at 10 study sites across 620 miles of desert. One of those years, 2020, was a drought, while 2021 and 2022 were exceptionally rainy; a lucky break that allowed researchers to compare different conditions, Dr. Getzin said.
They used soil moisture sensors to collect continuous readings of water content in the sand every 30 minutes in and around the fairy circles. They also examined hundreds of individual grass shoots and roots that were excavated at various intervals from the frames and surrounding areas.
After the rain, the scientists found that grass sprouted both inside and outside the fairy circles, but within about 20 days, almost all the young shoots inside the circle had died. They also found that the top eight centimeters of soil inside the fairy circles dried out quickly, which they hypothesize is caused by established plants surrounding the fairy circles actively drawing water toward them.
Plants constantly absorb or lose water through their leaves. At the same time, their roots take up water. In the sandy soil of Namibia, this creates a vacuum effect that moves water from inside the fairy circles to the plant roots at the edge of the circle and beyond. “It’s like you open your window in the winter and the warm air comes right out,” Dr. Getzin said.
The new paper also discusses the termite hypothesis, which was advocated by Norbert Jürgens, an ecologist at the University of Hamburg in Germany. He reported in 2013 that there were actually fairy circles caused by sand termites which damage grass roots.
In the new paper, Dr. Getzin and his colleagues noted that termites were conspicuously absent from their study sites, and that they found no signs of root damage in grass that had died after rain.
“You could say termites weren’t the cause, because there were no termites at all,” Dr. Getzin said. “The reason is drying.”
Dr. Jurgens declined a request for comment.
Florida State University entomologist Walter Zchinkel, who was not involved in the research but has published papers to support the water stress hypothesis, said the new findings “put more nails in the termite’s coffin.”
“Support for a hydrodynamic explanation is now very strong, and support for a termite cause is very weak,” Dr. Tschinkel said.
Yvette Naude, an analytical chemist at the University of Pretoria in South Africa who was not involved in the research, agreed that the new study seems to confirm that “contrary to popular belief, termite activity does not cause fairy circles.”
But he does not consider the mystery revealed. “Many questions remain unanswered,” he said.
Proponents of the water stress hypothesis still have to come up with other explanations, says Dr Naude. He continues to suspect, based on earlier studies, that something about the composition of the fairyland’s soil inhibits plant growth.
Marion Meyer, a plant scientist at the University of Pretoria, says that while the new study “definitively” shows that termites are not a factor, fairy circles can occur; another plant, Euphorbia. According to published research by Dr. Meyer, it produces a milky, toxic sap that can kill grass where it previously grew, resulting in fairy circles.
According to Dr. Cramer, one of the reasons there are so many different fairy-tale framework theories is that it is extremely difficult to prove “causality for a long-standing ecological pattern that cannot be replicated in the laboratory.” To finally end the debate, he called for “some manipulative experiments to test the ideas in the field.”
But someone other than Dr. Getzin will have to conduct such difficult experiments because he has decided to leave fairyland research.
“After more than 20 years, I consider this chapter closed,” he said.
He plans to turn his attention to the investigation.”plant rings”, another strange natural phenomenon in the Namib desert. Plant rings look like fairy circles, but are a distinct phenomenon, says Dr. Getzin, and have so far escaped the attention of other scientists.
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