Wednesday, 4 July 2012

Mysterious Fairy Circles Are 'Alive'

Walter Tschinkel may not have solved the mystery of the fairy circles, but he can tell you that they're alive. Tens of thousands of the formations—bare patches of soil, 2 to 12 meters in diameter—freckle grasslands from southern Angola to northern South Africa, their perimeters often marked by a tall fringe of grass. Locals say they're the footprints of the gods. Scientists have thrown their hands up in the air. But now Tschinkel, a biologist at Florida State University in Tallahassee, has discovered something no one else has.
Tschinkel first encountered fairy circles in 2005 on a vacation to the NamibRand Nature Reserve, a private nature park dedicated to conserving the local ecology and wildlife in southwestern Namibia, where his local guide introduced him to the strange land forms. "I looked at them and said, 'Obviously, they're caused by termites,' " he recalls. Perhaps the insects were killing the grass from below, or maybe they were giving off gases that were poisoning the vegetation. But when he and his wife returned to the region in 2007 and excavated a handful of fairy circles, they found no evidence of termites. Other experiments—adding essential nutrients such as zinc to the fairy circles or replacing the soil inside the circles with the soil from outside the circles—didn't cause the vegetation to grow back, suggesting the formations are not the result of a lack of nutrients.
So Tschinkel turned to satellite images. By comparing photos taken over a 4-year period, he confirmed something other scientists had suspected: The circles were alive—or at least they were dynamic. A number of circles appeared and disappeared over this time period. Extrapolating from the data, Tschinkel calculated that most smaller circles arise and vanish every 24 years, whereas larger circles last up to 75 years. Overall, the lifespan averaged 41 years.
To confirm his results, Tschinkel crunched data collected from the NamibRand Nature Reserve. Over the past 10 years, the park has sold fairy circles to ecotourists for about $50 each. The buyers don't actually get the land; they just adopt it—kind of like people who "purchase" stars. Each circle the reserve sells is marked with the date of sale, and new owners are given the latitude and longitude so they can check up on their purchase on Google Earth.

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