The Fairy Circles

Peculiar barren patches pepper southern Africa's grasslands...

Dotting the grasslands of the NamibRand Nature Reserve—and continuing toward Angola—are peculiar patches of barren land known as fairy circles. Some of the sandy, grass-ringed clearings stretch 65 feet (20 m) across. The unusual patterns have baffled scientists for decades, but the discovery in 2016 of similar phenomena in an uninhabited Australian outback reinvigorated the investigation. Researchers now suggest that plant response to water short-age causes the irregularities. 

From National Geographic's "Hidden Earth" which you can purchase here.