They are strange desert grass formations. They grow in the arid soil in the Namib Desert, Namibia. Their origin was unknown… until now. The Namibian fairy circles have finally been explained.
It is an area of circular hollows in the grasslands visible for miles around. It shows an extraordinary degree of spatial arrangement. A typical circle is between 2 and 10 meters wide, separated from the rest by a distance of up to 10 meters.
One theory holds that the circles are caused by termites feeding on the roots. Another, that the weeds self-organize to maximize water availability.
Research led by Stephan Getzin of the University of Goettingen (Germany) studied the issue. Rainfall is scarce and irregular in this area. The researchers stressed the importance of these. Ten days after the rains, the interior of the fairy circles in Namibia had very little growth, according to the study. About 20 days after the rains, all the grass inside the circles was dead. But the surrounding grass was “green and soft.”
“We proved that termites are not responsible. The weeds die immediately after the rains with no sign of termites,” Getzin said.
Something was happening once the surrounding weeds were robust. Soil moisture quickly disappeared everywhere. “Under the strong heat of the Namib, the grasses permanently transpire and lose water. So they create moisture voids in the soil around their roots. And water is attracted to them,” Getzin said.
This is an incredible example of “ecohydrological feedback.” The barren circles become reservoirs that help support the weeds at the edges. This self-organization seems to buffer the plants against increasing aridity. This problem is worsening in some places due to climate change.
“They are well-modeled landscapes of fairy circles evenly spaced. The grasses act as ecosystem engineers. And they benefit directly from the water resource provided by the vegetation gaps,” the scientist said.
The study was published in Perspectives in Plant Ecology, Evolution and Systematics..