Namibian owls: Creatures of the nightJuly 19, 2016
Shark Island – reflecting a dramatic historical pastJuly 21, 2016
Text by Antje Burke
Photos by Amy Schoeman
The so-called fairy circles are a prominent and enigmatic feature of the Namib Desert that has puzzled scientists and environmentalists for many years.
F or several decades scientists, farmers and nature lovers have puzzled over the mysterious ‘fairy circles’ of the Namib Desert. These strange, bare, circular patches found in grasslands range from about 2 to 10 metres in diameter and occur along the periphery of the Namib Desert from southern Namibia and the Sperrgebiet up to the Kaokoveld and north into Angola.
Well worth visiting – and seen best from the air – are the concentrations of circles in the dunes of the NamibRand Reserve, south of Sossusvlei. They are also prominent in the grasslands of the Giribesvlakte, north of Sesfontein and are particularly unmistakable when they are encircled by grass that is noticeably taller than that in the surroundings. While this phenomenon can be explained – the grass at the edge of the circle benefits from the extra water that is not used by a competing plant inside the circle and therefore grows taller – the origin and persistence of the circles are shrouded in mystery.
There is certainly no shortage of theories about the phenomenon. The more esoteric ones suggest that the enigmatic fairy circles were caused by underground energy waves similar to those that guide water diviners, or that they were sacred places for Bushman marriages, UFO landings and other extraterrestrial forces. More scientifically based explanations suggest they were caused by termites, toxic compounds in the soil and radioactivity.
Intrigued by the unusually regular spacing, many scientist, have argued that biological agents may be involved. Such agents could be rodents, or termites foraging in a circular pattern around their nests, as suggested by Professor Moll and the young German researchers Becker and Getzin. As yet no conclusive evidence has been provided by their studies. The lack of recent termite activity certainly rules out the possibility that termites are responsible for maintaining the existing fairy circles. Whether or not they were involved in their creation is still open to debate.
South African researchers such as Barry Lovegrove and Roy Siegfried have suggested that the fairy circles may well be the desert version of the conspicuous ‘heuweltjies’ or mica mounds that are scattered in a similarly regular fashion throughout South Africa’s semi-arid Karoo and fynbos regions. Despite a long history of arguments regarding their origin, it is accepted today that these mounds are created and maintained by mole-rat and harvester termite activities. These industrious diggers alter soil conditions and induce a different suite of plants to grow on them. Based on their observations on the mica mounds, South African researchers favour the termite theory apropos the Namib’s fairy circles.
Other scientists have proposed that toxic substances could be released into the soil by decaying plants, for example the poisonous milky sap of Euphorbia species. Damara milk bush (Euphorbia damarana) and milk bush (Euphorbia virosa) occur near areas with fairy circles and it is conceivable that under slightly different environmental circumstances, these may have been growing in areas that are covered in fairy circles today. However, plants grown in soil taken from beneath milk bushes, whether dead or alive, do extremely well. Their growth is certainly not inhibited.
In the Kalahari Desert activities of rodents and antelope also create bare patches. “Could the fairy circles not be zebra rolling pits?” suggested one of my colleagues from Etosha. Furthermore, soils have been tested for disease-related and other fungi, microbes and bacteria, radioactivity and toxic chemical compounds – without success. I was involved in investigations at NamibRand under the auspices of the Gobabeb Research Station. We compared physical and chemical properties of the soil inside and outside the circles and found no evident differences in water infiltration rates or any other of the tested properties of soil.
Although a study of fungi activity by Eicker and his colleagues from Pretoria carried out in the early 1980s raised more questions than answers, the ‘mushroom theory’ has not been completely discarded. This theory was likened to the dreaded fairy rings caused by mushrooms that often develop on lawns in higher rainfall regions. Yet Eicker and colleagues found no fungal evidence to support this theory. A team of scientists from Britain developed the theory further. They suggest that, as in the process of fairy-ring development in lawns, subterranean mushroom cells exude a toxin and prevent grasses and herbs from developing, also depriving the grass of the soil moisture necessary for growth during the rainy season. This process apparently initiates the bare patches. The researchers suggest that in addition there may be a high trace-metal content in the soil that is inside the circles, which could be caused by wind depositing mica-enriched sand into these open patches. Inside the circles the mushroom toxins could then form an inorganic agent with the trace metals and this toxic compound would prevent further establishment of plants. If this is true, testing for signs of present or past fungal activity, such as in Eicker’s study, could have left the actual toxic compound undetected. To prove this, the British scientists would have to come to Namibia to discover this elusive compound.
Professor van Rooyen from Pretoria University and Dr Jankowitz of Namibia’s Polytechnic revisited many of the old theories, trying to find evidence to support one or more of them. They found they had to reject every single one! However, when they grew English ryegrass (Lolium perenne) in soils from fairy circles and from the surroundings they found that this grass did not do well in the fairy-circle soil, whereas it thrived in soil from outside the circles. This, after all, indicates that there are differences in the soil.
Whether we can ascribe this to an as yet undiscovered substance or to a physical phenomenon in the soil, still needs to be established. Van Rooyen and her colleagues also introduced a theory, based on competition and vegetation dynamics, into the debate. Their suggestion is that the bare patches may be a result of severe water and nutrient limitations in this arid environment and that competitive forces have lead to the very regular spacing. At present this hypothesis lacks hard evidence.
What all these studies indicate is that the mystery is far from solved. Yet, if a substance of some form or another is responsible for inhibiting growth in the fairy circles, there could even be an industrial use in stock, for example, in the form of pest or disease control or some as yet unknown application.
The Namib is clearly not going to give its secret away easily and will undoubtedly keep us wondering and speculating for a long while yet!
This article was first published in the Flamingo January 2005 issue.