Namibia’s famous so-called fairy circles – circular and barren holes in the grassland – have fascinated researchers for decades. Now a German-Israeli team of researchers has been able to unravel the phenomenon.
Scientists from the University of Göttingen and Ben-Gurion University in Israel have investigated how and why newly germinated grasses in the fairy circle die. Their results show that a lack of water in the fairy circle causes them to wither away.
No traces of termite damage were found
According to the researchers, the topsoil, i.e. the top ten to twelve centimeters of the soil, would act as a kind of ‘death zone’ in which young grasses cannot survive permanently. Instead, they die between ten and twenty days after the rain. According to the scientists, the fact that they show no signs of termite damage disproves a competing theory.
For the study, the scientists examined 500 individual grass plants in four regions of the Namib using measurements of root and leaf lengths, statistical tests and comparative photo documentation. They also took hundreds of soil moisture measurements during and after the rainy season in 2023 and 2024.
This showed that the topsoil is very sensitive to dehydration. During and after the rainy season, the soil moisture here is three to four times lower than in the top 20 centimeters of soil. In addition, during the period of grass growth after heavy rain, the topsoil in the fairy circle is significantly drier than outside it (see animation below).
Roots of freshly sprouted grass are too short
Under these conditions, freshly sprouted grasses cannot survive in the fairy circle: they dry out because their roots, which are only ten centimeters long on average, cannot reach the deeper, moister soil layers (see animation below).
The large, perennial, so-called clump grasses, which grow on the edge of the fairy circle and quickly turn green after rain, benefit from the groundwater below a depth of 20 to 30 centimeters. After the rain, they have a huge competitive advantage over the freshly sprouted grass in the fairy circle.
Because the freshly germinated grasses release only a small amount of water through evaporation through their small leaves, “their suction power is too low to absorb new water from deeper soil layers,” explains Stephan Getzin from the Ecosystem Modeling Department at the University of Göttingen.
The round shape of the fairy circles is designed by the grasses themselves, which can thus provide themselves with a maximum amount of groundwater. “This self-organization can be called swarm intelligence. “It is a systematic adaptation to the lack of resources in arid areas,” say Getzin and his Israeli colleague Hezi Yizhaq.
Millions of barren spots in the Namib Desert
About 80 to 140 kilometers offshore in the Namib Desert are millions of so-called fairy circles, each only a few meters wide and together they form a distinctive pattern in the landscape that is visible for miles.
Source: Krone
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