article_snippet.sent: Several teams of scientists are trying to explain the bizarre markings, and suggestions have included termites nibbling grass, zebras rolling in circles, competition for resources, hydrocarbons emanating from the depths of earth to kill off patches of vegetation and even aliens.
article_snippet.sent: Experts from various institutions have previously claimed that termites nibble away at grassroots in certain grasslands of southwest Africa, causing the dieback of vegetation and creating a water trap.
article_snippet.sent: There is a no vegetation growth within the circular area .
article_snippet.sent: German researchers occurrence appears to be restricted to particularly arid zones at the border of grassland and desert regions, according to the study published in the journal Ecography, where there is intense resource-competition for water.
article_snippet.sent: Dr Getzin believes it is the local resource-competition among plants and vegetation, in a similar way to how young trees space young trees out in forests to ensure young trees have access to enough nutrients and water.
article_snippet.sent: The scientists simulated underground competition for water and the spatial vegetation distribution patterns.
highlights_snippet.sent: Clue may lie in the distribution of the barren circles of Earth in grassland .
  