John Noble Wilford, reporting for the New York Times:
The reddish barren spots, thousands of them, are called fairy circles, the name itself an invitation to try to solve the mystery of their origins. They dot a narrow belt of desert stretching from Angola through Namibia into northern South Africa. For no obvious reason, the round patches of sandy soil interrupt the arid grassland, like a spreading blight on the land.
The cause? Sand termites, ecologists think.