Mysterious ‘fairy circles’ in the Namib Desert have a scientific answer
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For more than 50 years, conservationists have studied and debated the mystery of the Namib Desert‘s “fairy rings”, circular patches, mostly devoid of grass, that stretched 1,100 miles across the arid grasslands of Southern Africa.
Despite their fanciful name, related to the term “fairy circles” for circular mushroom patterns found in wooded areas, there are no fairies in play here. Many theories have been put forward, but two had the most merit. One theory has sought to blame termites for these dry areas, while the other considers the evolution of grasses. Scientists have been back and forth for decades, but a new study offers what may finally be proof of a clear explanation.
Stephan Getzin, an ecologist at the University of Göttingen in Germany and lead author of the study, began researching fairy circles in 2000. In the years that followed, he published more papers on fairy circles. and their origins than any other. expert.
What sets fairy circles apart is the barren stains within them, but the grass growth around them is also remarkable – they have found a way to thrive in what is considered one of the driest places in the world. In previous research, Getzin and his team hypothesized that plants in the outer rings of the circles evolved to maximize their limited water in the desert.
And for the past three years, he has spent time in Namibia tracking grass growth to find more evidence for this theory. During the 2020 drought season, Getzin and his team of researchers installed sensors capable of recording soil moisture about 7.9 inches (20 centimeters) deep – and monitoring water uptake by the herbs.
“We were very lucky because in 2020 there was not much vegetation, or in fact almost no herbaceous vegetation, in the fairy circle area,” Getzin said. “But in 2021, and this year, 2022, there was a really good rainy season, so we were able to really follow how the new grass growth was redistributing water from the soil.”
Analyzing data from these rainy seasons, Getzin’s team found that the water inside the circles was running out quickly, despite having no grass to use it, while the grasses outside were as robust as ever. Under the high desert heat, these well-established grasses had evolved to create a vacuum system around their roots that drew water to them, according to Getzin. The grasses inside the circles, which try to grow right after the rain, could not receive enough water to live.
“A circle is the most logical geometric formation you would create as a plant with a lack of water,” Getzin said. “If these circles were squares or low, complex structures, you would have a lot more individual grasses along the circumference. … The proportional area is smaller than if you grow in a circle. These grasses end up in a circle because it is the most logical structure to maximize the water available to each individual plant.
The study called this an example of ‘ecohydrological feedback’, in which barren circles become reservoirs that help maintain grasses at the edges – albeit at the expense of grasses in the middle. This self-organization is used to buffer the negative effects of increasing aridity, Getzin said, and is also seen in other harsh arid areas around the world.
The termite hypothesis, meanwhile, suggested that fairy circles are generated by sand termites that damage grass roots, and was welcomed by other scientists. However, a 2016 study of similar fairy rings in Australia found no clear link to pests. Getzin’s latest research has come to similar conclusions.
“We have an example where it only rained once, the grasses appeared, and then after eight or nine days, the grasses just in the fairy circles had started to die,” Getzin said. “When we (excavated) these grasses carefully and examined the roots, none of these grasses suffered root damage from termites – but they died anyway. Our results clearly indicate that no, these grasses die without termites.”
Getzin and his team also found the roots of Young the plants inside the circles should be longer than those outside. This suggests, according to Getzin, that the grasses had created longer routes in an attempt to find water – further evidence of their competition with the grasses of the outer ring in the water-poor desert.
Although the evidence from the study is a step forward, scientists – including Getzin – believe there is still more research to be done. That said, Getzin told CNN it’s time for him to take on a new challenge.
“With fairy rings in Namibia, as well as those seen in Australia, plants are changing the distribution of soil moisture and thus increasing their chances of survival, and we can call this kind of ‘swarm intelligence'”, Getzin said. “Plants create clever patterns and geometric formations, and I will continue to work in that direction.”
Near the Fairy Ring area in Namibia, for example, researchers have also found another species of grass that forms into large circular rings after rain. “It’s a completely different kind of grass, but it forms identical circular formations,” Getzin said. He seeks to study this process during the next rainy season in Namibia in 2023.