Mystery of 'fairy circles'

They are one of nature's greatest mysteries, prompting local legends they are created by gods and generating wild theories about visits by UFOs.

These images show the vast areas that are covered by the mysterious fairy circles that pock the grassy desert of Namibia and why they have captivated the imaginations of visitors to the region.For decades it is a phenomenon which has left scientists stumped.Thousands of barren patches of land several meters wide, known as 'fairy circles', which are found across the Namib Desert in southern Africa for no apparent reason.

What are fairy circles?

Fairy circles are barren patches of land which can be found across the Namib Desert in southern Africa.They can be 6-40 feet (2-12m) in diameter, are found in the region’s arid grassland on sandy soils.A ring of vegetation around the edge of the ring is taller than the surrounding grassland. The mystery of how they got there, or why they stay there, has stumped scientists for decades. Theories have included grass-killing gas, termites and even UFOs while local myth holds that a dragon lives beneath the Earth and his fiery breath burns the vegetation.

The fairy rings, which measure between 6 feet and 40 feet across (2-12 meters), are essentially bare patches of earth in the stubby grass that grows across the Namib Desert.

Fairy circles are circular patches of land, barren of plants, though often encircled by a ring of stimulated growth of grass. They typically appear in the arid grasslands of the western part of Southern Africa. Fairy circles are particularly common in Namibia, but also occur in parts of Angola and South Africa.

Fairy circles vary between 2 and 15 meters (7 and 49 ft) in diameter. They typically occur in essentially nonspecific grassy vegetation, especially in Namibia, where conditions are particularly arid. Associated grasses commonly are species in the genusStipagrostis

The circles occur in a band lying about 100 miles (160 km) inland, and extending southward from Angola for some 1,500 miles (2,400 km) down to the Northwestern Cape Province of South Africa. It is largely a remote and inhospitable region, much of it over a hundred miles from the nearest village. The circles have been recognized and informally remarked on for many years, first being mentioned in technical literature in the 1920s and intermittently thereafter with the intensity of study increasing during the final quarter of the 20th century.

Studies show that these circles pass through a life cycle of some 30 to 60 years. They become noticeable at a diameter of about 2 meters, achieving a peak diameter of perhaps 12 meters,^[after which they mature and "die" as they undergo invasion, mainly by grasses.

Theories have included radioactive soil, meteorites or even UFOs while local myth holds that a dragon lives beneath the Earth and his fiery breath burns the vegetation. 

But finally, a German professor believes he has solved the mystery for good. After a six-year study, and more than 40 trips to the Namib desert, Norbert Jürgens from the University of Hamburg says a species of sand termite is responsible.

He examined hundreds of fairy circles in more than 1,200 miles of the desert and found that the Psammotermes allocerus, or sand termite, was the only species consistently present.Mr Jürgens theory is that they eat plant roots before they can sprout through the desert soil creating a water trap - in a similar way that beavers create dams.

Because of the lack of foliage, rainwater is not lost through transpiration (the evaporation of water from plants) and instead stays below the surface. This allows the sand termites to survive and stay active during the dry season and also helps grasses at the edge of the circle to thrive attracting other life forms. The termites feed on those grasses, thereby gradually extending the circle.

Mr. Jürgens concludes that the fairy circles are actually an astounding example of ecological engineering by the sand termite, designed to retain precious water in an otherwise arid landscape. ‘Fairy circles can be regarded as an outstanding example of allogeneic ecosystem engineering resulting in unique landscapes with increased biodiversity, driven by key resources such as permanently available water, perennial plant biomass, and perennial termite biomass,' he told South Africa's newspaper the Weekend Argus.

'The termites match the beaver with regard to intensity of environmental change, but they surpass it with regard to the spatial dimension of their impact.

'The sand termite turns wide desert regions of predominantly ephemeral life into landscapes dominated by species-rich perennial grassland, supporting uninterrupted perennial life even during dry seasons and drought years.'

Mysterious Desert Fairy Circles Share Pattern with Skin Cells

Patterns appearing on both the very large and very small scale are extremely rare, but researchers at Okinawa Institute of Science and Technology Graduate University (OIST) in Japan have found a similar pattern in two apparently unrelated systems -- skin cells and fairy circles in the Namibian desert.

“It's a completely amazing, strange match,” said Prof. Robert Sinclair, who heads the Mathematical Biology Unit at OIST.

Desert fairy circles are considered one of nature’s greatest mysteries because no one knows how they form. Different from mushroom rings, these fairy circles are large barren patches of earth ringed by short grass dotting the desert like craters on the moon or big freckles. Several groups are racing to figure out this bizarre phenomenon. Sinclair and his collaborator, Haozhe Zhang, believe they have identified a small, but vital piece of the puzzle.

The distribution of fairy circles throughout the desert may look random, but turns out to have a pattern that very closely matches the distribution pattern of skin cells. A pattern spanning such drastically different size scales -- microscopic skin cells and the desert landscape -- is almost unheard of in nature.

“It is still difficult to say why exactly they are similar, but the fact that they are similar is already very important,” Sinclair said. “This is suggesting there may be such types of patterns that cover really different size scales.”

To conduct the analysis, Sinclair and Zhang compared the number of neighbors adjacent to fairy circles and skin cells. They took satellite images of fairy circles, and a computer drew lines halfway between each pair of circles to designate invisible boundaries, much like cell walls. The computer then counted how many neighbors surround each fairy circle. Other researchers had calculated skin cell neighbors several years ago.

The results were almost identical. Both the majority of fairy circles and majority of cells have six neighbors. But the similarity gets even more specific -- the percentage of fairy circles with four, five, six, seven, eight and nine neighbors is essentially the same as the skin cells.

“I didn’t expect it to be so close,” Sinclair said. “We spent a lot of time checking because it really looked too close to believe.”

Many theories about how fairy circles form -- from rolling zebras to underground gases to dying trees -- have been proven incorrect. Now, some scientists are developing mathematical models attempting to explain the origin of fairy circles.

“These models have to incorporate our results,” said Zhang, a Ph.D. student in the Department of Statistics at Iowa State University, who conducted the research at OIST with Sinclair in 2013.

The researchers suspect the patterns might be similar because both skin cells and fairy circles are fighting for space. If true, scientists might one day be able to glean information about systems just by analyzing patterns. For example, they could search for signs of life on other planets or moons, where images are usually the only data initially available.

Finding such a pattern could also benefit ecology and biology in general. Understanding processes on one scale could illuminate what is happening at the other end of the spectrum. “Otherwise, we need a whole new theory for each type of system we study, and may miss general principles, or, as some say, not see the forest for the trees,” Sinclair said.

Myths

In the oral myths of the Himba people these barren patches are said to have been caused by the gods, spirits and/or natural divinities. The region's Bushmen have traditionally ascribed spiritual and magical powers to them. Of specific beliefs, the Himba people note that their original ancestor, Mukuru was responsible for the creation of the fairy circles, or that they were the footprints of gods.

Another myth put forth, believed by some scientists to be tied to tour guides, is that the circles are formed by a dragon in the earth and that its poisonous breath kills the vegetation.

Local legends say the fairy circles are the footsteps of the gods while others have suggested they are burn marks from dragons living beneath the ground. Some have suggested they may be the landing spots of UFOs or the sleeping spots of Namibia's national animal the Oryx.

There are some scientists who have suggested the circles are created by radioactive patches of soil that prevent the grass that covers the landscape from growing

One oral myth says the circles are the footprints of the gods; another that a dragon living beneath the earth’s crust breathes fiery bubbles which, when they hit the surface, burn the vegetation into the near-perfect circles.

No matter what is found in the field, all hypotheses on fairy circles need to account for both their small- and large-scale patterns. ‘This is the great thing about having multiple disciplines involved – trying to assemble the puzzle with just one doesn't always work.'

But the circles haven’t just confused the Himba. Despite decades of investigation, and a multitude of theories, scientists still haven’t come up with a definitive explanation for their existence. To this day, the circles remain one of nature’s greatest mysteries.