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Desert Fairy Circles Caused by Rain

Desert Fairy Circles Caused by Rain

February 27, 2019

Desert & Water Research

Fox News – BGU research says that unusual bare circles, called “Fairy Circles,” in the grasslands of Australia and the Namib Desert are caused by just the right balance of rain and evaporation.

In a new study published in the Journal of Arid Environments by Dr. Hezi Yizhaq, from BGU’s Department of Geography and Environmental Development, and his colleague Dr. Stephan Getzin of the University of Göttingen, satellite imagery was used to study the patterns of fairy circles in Namibia. This showed that weathering caused by heavy rainfall and evaporation was the cause, not termites or plants competing for resources, as some scientists have claimed.

In drainage areas, the researchers noticed oval fairy circles more than 98 feet across. In extremely arid spots, they found very irregularly spaced circles. They also noted some “mega circles” more than 65 feet in diameter. “That research was just a pilot study,” said Dr. Yizhaq. “But it highlights questions about the plant and soil dynamics outside of the eye-catching, very regular fairy-circle patterns.”

In a study on fairy circles in Australia, they wrote in the journal Ecological Society of America that in unvegetated soil heavy rainfall washes fine clay into empty spaces within the soil, essentially sealing it off with a hard crust impervious to new plant growth.

“No destructive mechanisms, such as those from termites, are necessary for the formation of distinct fairy circle patterns,” they said. “Hydrological plant-soil interactions alone are sufficient.”

Drs. Yizhaq and Getzin argue that to have fairy circles, a region must have very homogenous soil, just one or two plant species with particular growth patterns and a just-right balance of rain and evaporation. Those requirements could explain why fairy circles are seen in only two deserts on Earth.

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