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Fairy Circles

April 9, 2013

Mysterious “fairy circles” on African plains are caused by termites, which destroy patches of grass but help the surrounding grass thrive.

Transcript

BOB HIRSHON (host):

Fairy circles’ cause and effect.  I’m Bob Hirshon and this is Science Update.

On the edge of the Namibian desert, mysterious so-called “fairy circles” appear. They’re circles of bare dirt, surrounded by a ring of thick perennial grass.  Now, University of Hamburg biologist Norbert Juergens has found that the circles are made by sand termites, which eat underground grass roots. Although that leaves the inner circle barren, it also helps the soil hold water – because there are no plants to take up the water and release it into the air. Through the long dry season, the water sustains both the termites and the grasses on the circle’s perimeter.

NORBERT JUERGENS (University of Hamburg, Germany):

The termites create a permanent water store, and a permanent plantation of grasses.

HIRSHON:
These perennial grasses also attract other insects and small mammals.  So the termites’ fairy circles actually create a rich ecosystem, in what might otherwise be a barren landscape.  I’m Bob Hirshon for AAAS, the Science Society.

"Fairy circles" in Namibia's Marienfluss valley. (Thorsten Becker/Wikimedia)