Fairy tales? A natural reason for mysterious circles in the desert
Research conducted by the University of Pretoria’s department of plant and soil sciences may have finally solved the mystery of the circular patches, known as fairy circles, which have for decades covered the Kalahari Desert which stretches to the Namib Desert and the northernmost part of the Northern Cape.
The hundreds of spread-out circular patches stretch for kilometres across the desert sand and where they are, vegetation hardly ever grows.
Folklore told the tale of how the circles were left by fairies or elves dancing in a circle, and that humans who stepped in these suffered punishment by fairies. But now there’s a more plausible explanation to why and how these form.
A five-year study by a group of masters’ students has found the fairy circles are most probably caused by dead euphorbia species or milk bushes.
These milk bushes had grown well in the area before the climate conditions on the desert plains changed. Because of heat and lack of water, the milk bushes and other vegetation died off. Research has shown the temperature increase in Namibia during the last two or three decades is roughly three times more than the global mean temperature increase reported for the 20th century.
“The decomposition of dead plants and the sticky latex altered the chemical properties of the sand, which manifested in the hydrophobicity of fairy circle soil, the research proposed.
“Various other compounds also entered the soil from the decaying euphorbias, some of which posed phytotoxic or allelopathic (the inhibition of growth by substances released by another plant) and antimicrobial activity.
Most of these compounds would have broken down in a relative short time, but the milky latex can stick to the sand, become hard and can persist in soil for a long time. These changes to the soil cause the formation of many fairy circles and the transition proceeds from a site with only plants, to a mixed site with plants and fairy circles, and then a fairy circles-only site. This then results in a regular spatial pattern.”
While seeds at times managed to grow within fairy circles after some rainfall they never survived long.
Research revealed this was because the water needed for those seedlings to properly germinate was quickly sucked into the soil, leaving none for the seed itself.
But this will not always be the case.
“In time, decades or even centuries, with the occasional rain, the effect left in the soil by euphorbias will slowly erode away, seedlings will survive for longer periods in the older fairy circles until they are eventually fully established and reach maturity, and the fairy circle will no longer be visible,” the research revealed.
And as the fairy circles disappear, most likely the tales and folklore of how they all came about will also adapt and evolve to tell a new story.