The Fairy Circles Mystery Gets a New Suspect

A small study suggests that soil microbes could play a role in the ring-like grass formations in parts of Australia’s wilderness.

In the Australian outback, certain grasses grow in eerie rings, with ramparts of dusty green standing at the edge of wide circles of bare red dirt. Often described as “fairy circles,” these rings of spinifex grass resemble structures first spotted in the Namibian desert, both creating enormous honeycomb patterns across the landscape that really pop out in aerial photos. In Namibia, scientists have deployed cameras on fishing rods, observed termite colonies and even used mathematical models to try to explain how this phenomenon arises. A small study published last month in the Australian Journal of Botany suggests that microbes living in the soil may contribute to the rings’ formation in Australia, rendering the dirt within the ring hostile to new seedlings and the dirt beyond the ring hospitable. Spinifex grasses start out as small round hummocks, said Angela Moles, an ecologist at the University of New South Wales and an author of the new paper. Then, as new seedlings sprout outward, the plants in the middle die, leading to the ring shape. Researchers have explored whether the bare inner soil becomes depleted of nutrients; whether it is too dry or compacted for new growth; and whether insects might be destroying the spinifex. But a consensus on what is driving the formation of rings has yet to emerge.