It’s not termites: new study gives fresh take on how “fairy circles” form

The fairy circles in Namibia seen from the air. New research asserts they form an additional source of water in this arid region, because the rainwater flows towards the grasses on the edge.

Enlarge / The fairy circles
in Namibia seen from the air. New research asserts they form an
additional source of water in this arid region, because the
rainwater flows towards the grasses on the edge. (credit: Stephan
Getzin)

Himba
bushmen
 in the Namibian grasslands have passed down legends
about the region’s mysterious
“fairy circles”
—bare, reddish-hued
circular patches
dotted along the 1200-mile long swath of land.
They can be as large as several feet in diameter. Dubbed
“footprints of the gods,” it’s often said they are the work of the
Himba deity Mukuru, or an
underground dragon whose poisonous breath kills anything growing
inside those circles.

Scientists have their own ideas, and over the years two
different hypotheses have emerged about how the circles form. One
attributes the phenomenon to a particular
species of termite
(Psammmotermes allocerus), whose burrowing
damages plant roots, resulting in extra rainwater seeping into the
sandy soil before the plants can suck it up—giving the termites a
handy water trap as a resource. As a result, the plants die back in
a circle from the site of an insect nest. The circles expand in
diameter during droughts because the termites must venture further
out for food. The other hypothesis holds that the circles are a
kind of
self-organized spatial growth pattern
arising as plants compete
for scarce water and soil nutrients.

Two new papers, one published in the
journal Ecosphere
 and
the other
in the Journal of Arid Environments, add yet another
dimension to the ongoing debate. The authors argue that—at least
in northwestern Australia, where fairy circles were first observed in
2014—termite activity may be present at such formations, so
there’s some correlation in the data. But it isn’t what’s causing
the fairy circles. The authors attribute the circles’ emergence to
natural weather-related processes like heavy rainfall, extreme
heat, and evaporation. These deplete the soil of nutrients, forcing
plants to compete for scarcer resources to survive.

Read 11
remaining paragraphs

Source: FS – All – Science – News
It’s not termites: new study gives fresh take on how “fairy circles” form