‘Fairy circles’ spotted in Australia

Kevin Sanders

‘Fairy circles’ spotted in Australia

Fairy circles have stumped ecologists for decades. The circular patches of denuded soil that dot the dry grasslands of southern Africa have several curious features. As seen from the sky, they cover the landscape in a regular hexagonal pattern similar to a beehive. The center of the circle is devoid of plants, whereas the edges are often fringed with a low wall of extra-high grasses that complete the impression of a gathering place built by wee fairies. Has a toxin accumulated in the soil at the center? Is it the work of burrowing insects wreaking havoc on the roots beneath? The cause is certainly not supernatural, but there are seemingly nearly as many proposed explanations as there are scientists who study the phenomenon. Last year, a study of a decade's worth of satellite imagery of Namibia showed that fairy circles wax and wane in relation to rainfall. After wet years, the circles shrink in both size and number, then grow after dry ones—until it becomes too dry and they start to disappear again. But if the fairy circles of southern Africa are due to such a universal mechanism, rather than something local and specific, then shouldn't they appear elsewhere on Earth? Indeed they do. Today in the Proceedings of the National Academy of Sciences, scientists report that fairy circles exist in the outback of western Australia. In spite of having completely different species of plants and animals, the dead spots found in this desolate Australian landscape (above) have the very same hexagonal distribution. A computer model of the ecosystem based on what is known about the feedbacks between precipitation and grass biomass generated the very same patterns of fairy circles, suggesting that the pattern-forming mechanism is the same in both Africa and Australia. 

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