An international team of scientists, led by Dr. Stephan Getzin of the Helmholtz Center for Environmental Research in Germany, has announced the exciting discovery of the so-called ‘fairy circles’ in the remote outback of Western Australia.
Aerial view on the Australian fairy circles which spread homogeneously over the landscape. Image credit: Kevin Sanders.
According to plant biologists, ‘fairy circles’ are one of nature’s greatest mysteries.
The circles are devoid of vegetation and often surrounded by a fringe of tall grasses. Although seedlings are sometimes found in these barren patches after rainfall, they usually do not survive, leaving the patches completely bare for most of the time.
Until now the phenomenon was only known to occur in the arid grasslands of Namibia.
“There are various hypotheses about how these circles came about: (i) some researchers have explained them using termites or ants; (ii) other scientists believe that toxic carbon monoxide gas rises up from the interior of the Earth under the circles and kills the vegetation; (iii) a third camp thinks that the barren areas simply arise of their own accord under certain conditions,” said Dr. Getzin, who has for years supported the third hypothesis.
To investigate the phenomenon more closely, Dr. Getzin and his colleagues went to the mining town of Newman, in the Pilbara of Australia.
The scientists measured the barren circles, compared their surface temperatures with those of vegetated areas and charted indications of ants and termites in four parts of the almost uninhabited region.
They observed how the water drained away in these areas and took soil samples. They also added aerial image evaluations, statistical analyses of the landscape patterns and computer simulations.
“While in Namibia there are usually two to three species of termites or ants scuttling around in or on the fairy circles and opening up scope for speculation, the situation in Australia is clearer,” Dr. Getzin said.
“There we found in the majority of cases no nests in the circles and unlike in Namibia, cryptic sand termites do not exist in Australia. And the ones we did find have a completely different distribution pattern to the fairy circles.”
For the team this is a clear indication that the barren patches are not produced by animal activities but the way in which the plants organize themselves.
“We report that so far unknown fairy circles with the same spatial structure exist 10,000 km away from Namibia in the remote outback of Australia,” Dr. Getzin and co-authors wrote in a paper in the Proceedings of the National Academy of Sciences.
“Combining fieldwork, remote sensing, spatial pattern analysis, and process-based mathematical modeling, we demonstrate that these patterns emerge by self-organization, with no correlation with termite activity; the driving mechanism is a positive biomass–water feedback associated with water runoff and biomass-dependent infiltration rates.”
“The remarkable match between the patterns of Australian and Namibian fairy circles and model results indicate that both patterns emerge from a nonuniform stationary instability, supporting a central universality principle of pattern-formation theory.”
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Stephan Getzin et al. Discovery of fairy circles in Australia supports self-organization theory. PNAS, published online March 14, 2016; doi: 10.1073/pnas.1522130113
