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Scientists confirm Alan Turing's explanation for Australian fairy circles

Researchers used drone images to analyze the grass growth patterns found in the Australian Outback, home to polka dot pattern of barren patches known as fairy circles. Photo by S. Getzin/University of Göttingen
Researchers used drone images to analyze the grass growth patterns found in the Australian Outback, home to polka dot pattern of barren patches known as fairy circles. Photo by S. Getzin/University of Göttingen

Sept. 22 (UPI) -- The Turing pattern theory, developed by mathematician Alan Turing, explains how patterns in nature can emerge naturally, via random disturbances, from a uniform state.

The theory has previously been used to explain the emergence of zebra stripes and leopard spots. Earlier this year, scientists also used Turing pattern models to account for the distribution and segregation of non-territorial passerine birds.

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In a new paper, published this week in the Journal of Ecology, ecologists confirmed, for the first time, that Alan Turing's model successfully explains Australian fairy circles, circular patches of barren land barren in arid and semi-arid environs.

To test the Turing pattern's applicability in the Australian Outback, researchers used a drone and multispectral camera to map the vitality of Triodia grasses across five plots, each roughly 2.5 acres large. Scientists classified each plot as either high or low vitality.

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Statistical analysis of the vitality patterns showed that -- just as the Turing model predicts -- random variability in vitality leads to pattern-forming interactions between grass and water, feedbacks that reinforce the development of fairy circles.

The formation of arid clay circles encourages runoff, which plants in arid environs rely on. As clumps of grass develop, they increase shading and water infiltration around the nearby roots, encouraging further grass seeding and growth. As grass density intensifies, the runoff from the fairy circles in more easily intercepted and absorbed by surrounding vegetation.

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The new data analysis showed fairy circles work like "ecosystem engineers," helping vegetation cope with the challenges presented by arid and semi-arid environments.

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"The intriguing thing is that the grasses are actively engineering their own environment by forming symmetrically spaced gap patterns," lead study author Stephan Getzin said in a news release.

"The vegetation benefits from the additional runoff water provided by the large fairy circles, and so keeps the arid ecosystem functional even in very harsh, dry conditions," said Getzin, an ecosystem modeller at the University of Göttingen in Germany.

Without the Turing pattern, researchers estimate grasses in such water-stressed environs wouldn't be able to survive.

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