Nav: Home

Researchers get to the bottom of fairy circles

February 21, 2019

Fairy circles are round gaps in arid grassland that are distributed very uniformly over the landscape and only occur along the Namib Desert in southern Africa and in parts of Australia. Various theories circulate about the actual cause of these unusual spatial patterns, ranging from poisonous Euphorbia plants or rising gases, to ants, termites or plant competition for sparse water resources. Scientists from the University of Göttingen, Australia and Israel have now got to the bottom of their cause with soil investigations and drones. The results suggest that the fairy circles in Australia were caused by processes such as the weathering of the soil by heavy rainfall, extreme heat and evaporation. The extensive data collected by the researchers argued against a causal relationship to underground termite structures.

So far, fairy circles are only known from southwestern Africa around the Namib Desert and from Western Australia near the miners' town of Newman. While the origin of Namibia's fairy circles has been puzzled over since the early 1970s, the Australian fairy circles were only discovered in 2014. Despite a distance of around 10,000 kilometers, both occurrences have an identical spatial pattern, which makes them direct "relatives".

Supported by the German Research Foundation (DFG), the scientists now dug a total of 154 holes in 48 fairy circles east of Newman over a length of twelve kilometers in order to assess the possible influence of termites objectively and systematically. With the help of drones, they mapped areas of 500 by 500 meters to compare typical vegetation gaps - such as those caused by harvester termites in large parts of Australia - with typical fairy circle gaps. In addition, they investigated the soil conditions in the area of the fairy circles and in adjacent reference areas, where no grass grows over large areas.

"The vegetation gaps caused by harvester termites are only about half the size of the fairy circles and much less ordered", explains Dr Stephan Getzin from the University of Göttingen. "And in most cases, we didn't even find any hard subterranean termitaria that elsewhere in Australia prevent the growth of grasses". According to the researchers, however, the high soil compaction and clay content in the investigated fairy circles and vegetation-free reference areas are indications that the fairy circles are formed by abiotic processes such as mechanical weathering of the soil by heavy rain in cyclones, extreme heat and evaporation.

"Overall, our study shows that termite constructions can occur in the area of the fairy circles, but the partial local correlation between termites and fairy circles has no causal relationship", explains Getzin. "So no destructive mechanisms, such as those from termites, are necessary for the formation of the distinct fairy circle patterns; hydrological plant-soil interactions alone are sufficient."

In Namibia, research has so far concentrated on typical fairy circles in homogeneous landscapes. With the support of the Schimper Foundation, in a pilot study the scientists now for the first time focused on extraordinary fairy circles in atypical environments in order to better understand the actual threshold conditions for circle formation. Using Google Earth imagery, they found unusual circles - huge ones more than 20 meters in diameter, chain-like oval ones more than 30 meters long in drainage lines, circles in car tracks and circles in particularly dry, disturbed or Euphorbia-rich areas.

"Here our soil moisture studies showed that under such varied conditions the fairy circles function less as water reservoirs than under typical homogeneous conditions where they are extremely well ordered", says Getzin. With this work, the scientists intend to open up a new thematic field, as they hope to gain further insights into the formation and persistence of the fairy circles from studying "extraordinary" fairy circles.
-end-
Original publications:

Stephan Getzin, Hezi Yizhaq, Miriam Muñoz-Rojas, Kerstin Wiegand & Todd E. Erickson. A multi-scale study of Australian fairy circles using soil excavations and drone-based image analysis. Ecosphere 2019. https://doi.org/10.1002/ecs2.2620.

Stephan Getzin & Hezi Yizhaq. Unusual Namibian fairy circle patterns in heterogeneous and atypical environments. Journal of Arid Environments 2019. https://doi.org/10.1016/j.jaridenv.2019.01.017.

Contact:

Dr Stephan Getzin
University of Göttingen
Faculty of Forest Sciences and Forest Ecology
Department Ecosystem Modelling
Buesgenweg 4, 37077 Goettingen, Germany
Email: stephan.getzin@uni-goettingen.de
http://www.uni-goettingen.de/en/112105.html

University of Göttingen

Related Termites Articles:

Phylogenetic analysis forces rethink of termite evolution
Despite their important ecological role as decomposers, termites are often overlooked in research.
Hard-working termites crucial to forest, wetland ecosystems
Soil bedding increases microbial and termite decomposition activity
X-rays reveal termites' self-cooling, self-ventilating, self-draining skyscrapers
New insight into termites' architectural strategies could help us design more energy efficient self-sustaining buildings for humans.
Researchers get to the bottom of fairy circles
Fairy circles are round gaps in arid grassland that are distributed very uniformly over the landscape and only occur along the Namib Desert in southern Africa and in parts of Australia.
Termites shape and are shaped by their mounds
Termite construction projects have no architects, engineers or foremen, and yet these centimeter-sized insects build complex, meter-sized structures all over the world.
How forest termites protect tropical forests from drought
The efforts of tiny forest termites have a big effect on the harmful ecological effects of drought in tropical rainforests, according to a new study, which reveals their important role in maintaining ecosystem function during periods of extended aridity.
Termites mitigate effects of drought in Tropical Rainforest
Termites are commonly regarded as one of the most destructive insect pests, yet its unknown side was recently revealed by a major new study published in the prestigious journal Science -- the collaborative research co-led by Dr Louise Ashton of the University of Hong Kong, with researchers from the University of Liverpool and the Natural History Museum, London, has discovered that termites actually help mitigate against the effects of drought in tropical rain forests.
Revealed: Termites mitigate effects of drought in tropical rainforests
A major new study by the University of Liverpool and the Natural History Museum has discovered that termites mitigate against the effects of drought in tropical rain forests.
4,000-year-old termite mounds found in Brazil are visible from space
Researchers reporting in Current Biology on Nov. 19 have found that a vast array of regularly spaced, still-inhabited termite mounds in northeastern Brazil--covering an area the size of Great Britain -- are up to about 4,000 years old.
Some female termites can reproduce without males
Populations of the termite species Glyptotermes nakajimai can form successful, reproducing colonies in absence of males, according to a study published in the open access journal BMC Biology.
More Termites News and Termites Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Risk
Why do we revere risk-takers, even when their actions terrify us? Why are some better at taking risks than others? This hour, TED speakers explore the alluring, dangerous, and calculated sides of risk. Guests include professional rock climber Alex Honnold, economist Mariana Mazzucato, psychology researcher Kashfia Rahman, structural engineer and bridge designer Ian Firth, and risk intelligence expert Dylan Evans.
Now Playing: Science for the People

#540 Specialize? Or Generalize?
Ever been called a "jack of all trades, master of none"? The world loves to elevate specialists, people who drill deep into a single topic. Those people are great. But there's a place for generalists too, argues David Epstein. Jacks of all trades are often more successful than specialists. And he's got science to back it up. We talk with Epstein about his latest book, "Range: Why Generalists Triumph in a Specialized World".
Now Playing: Radiolab

Dolly Parton's America: Neon Moss
Today on Radiolab, we're bringing you the fourth episode of Jad's special series, Dolly Parton's America. In this episode, Jad goes back up the mountain to visit Dolly's actual Tennessee mountain home, where she tells stories about her first trips out of the holler. Back on the mountaintop, standing under the rain by the Little Pigeon River, the trip triggers memories of Jad's first visit to his father's childhood home, and opens the gateway to dizzying stories of music and migration. Support Radiolab today at Radiolab.org/donate.