Researcher weighs in on fairy circles of Namibia

March 28, 2017
A fairy ring in Namibia. Credit: School of Science

A study conducted by researchers at Indiana University-Purdue University Indianapolis adds new insights into one of nature's great mysteries: the fairy circles of Namibia.

Numbering in the millions, the so-called fairy circles are in the eastern, interior margin of the coastal Namib Desert, stretching from southern Angola to northern South Africa. They range in size from about 12 feet to about 114 feet, consisting of bare patches of soil surrounded by rings of grass. The origins of the circles have long been debated by researchers.

There is more than solving a mystery at stake. Analysis on the formation, structure and growth of vegetation patterns and their interactions with Earth's water cycle can improve our understanding of important processes underlying the dynamics of water-limited ecosystems, said IUPUI researcher Lixin Wang.

Wang, an ecohydrologist in the School of Science at IUPUI, along with IUPUI Ph.D. student Kudzai Farai Kaseke, Sujith Ravi and Ilya Buynevich of Temple University, and Eugene Marais of the National Museum of Namibia, reports new findings in an article titled "Ecohydrological interactions within 'fairy circles' in the Namib Desert: Revisiting the self-organization hypothesis." The paper was published March 10 in the Journal of Geophysical Research: Biogeosciences.

The team's results provide support to the self-organization hypothesis of fairy circle formation.

Self-organization theory says that the circular vegetation pattern is created by competition for scarce water. It's believed that the bare patches percolate more rainfall and act as water reservoirs, which the grass along the edges of the circle can access.

A second major theory is that fairy circles are created and maintained by sand termites that clear vegetation in the area of their nests. By making the soil porous, it's believed, the termites establish permanent reservoirs of rainwater below the surface that sustain them and the surrounding plants.

The research team brought new equipment and research specialties to bear on the question of fairy circle formation as it conducted extensive measurements of infiltration rate, soil moisture, grass biometric and sediment grain-size distribution from multiple circles and spaces between the circles.

Water infiltration flow rates were measured inside and outside the circles, with very fast infiltration rates recorded within the inner portion of the circles. The faster infiltration rates were facilitated by coarser particle size inside the circles. The team also found the roots of grass around the circles were much larger on the inside of the grass ring compared to the outside.

"That means the grass puts its roots on the inner side of the ring, competing for water," Wang said. "When it does rain, water flows to the edge of the circles, where the grass's roots can take the water for their use.

"Our investigation provides new insights and experimental data on the ecohydrological processes associated with fairy circles."

With evidence in hand concerning the self-supporting theory, the team reached out to a termite expert to search for evidence of termites in and among the where the study was conducted.

"There was no sign of sand termite activity at all," Wang said. "Our results seem to provide support to the self-organization theory of fairy circle formation attributed to scale-dependent biomass- feedback loops," the researchers wrote in their paper.

Explore further: Fairy circles found in Australian outback

Related Stories

Fairy circles found in Australian outback

March 15, 2016

(Phys.org)—A small team of researchers from Germany, Israel and Australia has confirmed that fairy circles exist in a part of the Australian outback. In their paper published in Proceedings of the National Academy of Sciences, ...

Scientists dance around Pilbara's fairy circles

April 20, 2016

An extremely rare phenomenon known as fairy circles—a concept more at home in the pages of fantasy books—have sprung into the vast, arid expanse of the modern day Pilbara.

Mysterious desert fairy circles share pattern with skin cells

April 7, 2015

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 ...

Recommended for you

East Antarctic Ice Sheet has history of instability

December 13, 2017

The East Antarctic Ice Sheet locks away enough water to raise sea level an estimated 53 meters (174 feet), more than any other ice sheet on the planet. It's also thought to be among the most stable, not gaining or losing ...

Hydraulic fracturing negatively impacts infant health

December 13, 2017

From North Dakota to Ohio to Pennsylvania, hydraulic fracturing, also known as fracking, has transformed small towns into energy powerhouses. While some see the new energy boom as benefiting the local economy and decreasing ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

BrettC
not rated yet Mar 28, 2017
Not so sure....Gravity would come into play and some circles are not on level ground.

see pic in

https://phys.org/...tml#nRlv

Bare spots in those instances should be oval or crescent moon shaped.
BrettC
not rated yet Mar 29, 2017
Why do the plants at the outer edge flourish? It's almost if something is removing the nutrients in the soil and depositing it at the outer edges of the circle.
Maybe bacteria is collecting it and migrating outward but has a limited lifespan so is depositing the nutrients where it's perished and that's why the plants flourish at the edges.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.