From the south of Angola to the northern part of South Africa, tens of thousands of circular patches of empty land with a diameter of two to twelve meters, which are often surrounded by unusually tall grass, stretch along the perimeter.
Locals consider them to be the traces of the gods, and scientists just shrug their shoulders. Biologist Walter Chinkel from Florida State University in Tallahassee (USA) does not pretend to solve the mystery, but he managed to find something very interesting.
When the specialist was first shown this phenomenon - and it was in 2005 in the private Namibian reserve NamibRand - he immediately suspected that it was termites that eat up grass roots or produce toxic gases.
But excavations in 2007 did not reveal any traces of termites. What's more, the addition of nutrients to these circles did not result in the growth of grass - so it is not a lack of them. Then Mr. Chinkel turned to satellite imagery. Comparing photographs taken over four years, he came to the conclusion, which - as a hypothesis - has already been expressed: the circles are alive!
Photo: Mike and Ann Scott / NamibRand Nature Reserve
Extrapolating the data, the expert calculated that the smallest ones appear and disappear every 24 years, while the largest "live" up to 75 years. The average life expectancy is 41 years. Then it was the turn of the analysis of the information provided by the administration of the NamibRand reserve.
The fact is that enterprising landowners sell circles to ecotourists for $ 50 each. The deal, of course, is symbolic: the owners are told the geographic coordinates of the spot, which they can then admire using Google Earth.
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Park rangers regularly take photographs of the parcels sold, and according to images taken in recent years, Mr. Chinkel has calculated that the average life of the circles is about 60 years. Alas, the researchers who found the time for these circles can be counted on one hand, and, as a rule, their experiments were carried out in haste.
Unfortunately, no one has taken them seriously yet. In the future, Mr. Chinkel plans to return to the reserve again and perform tests at different times of the year: it seems to him that circles usually form after the rainy season.