NEWS bizarre speckled pattern in arid grasslands , the researchers needed hard evidence . They hauled 175 pounds ( 80 kilograms ) of drone equipment and environmental monitors 745 miles ( 1,200 kilometres ) to Newman , Australia , a remote outpost in Western Australia . They used the drones to get a bird ' s- eye view of the arrangement of the fairy circles outside of town , where the air temperature can reach 118 ° F ( 48 ° C ) in the summer .
They also monitored the fairy circles on a detailed scale , setting up a weather station and soil-monitoring equipment about an inch beneath both barren and vegetated parts of the landscape . The desert outside of Newman is dominated by a single group of grasses in the genus Triodia . This is key to the formation of the fairy-circle patterns , Getzin said , because if there were more grass species around , they would take advantage of different ecological niches and likely cover the barren spots .
The monitoring showed that brief , intense rainfall pounds the coarse sand on the surface into fine silt and clay . The clay acts like a plug between the grains of sand , sealing off the surface . It only takes a couple of hard rains to create this crust , Getzin said . After that , the rainwater runs off rather than penetrating the ground .
Circles of life
However , Getzin said , this runoff also creates the potential for plants to survive in gaps between the barren zones . The remarkably regular , honeycombstyle pattern of 13-foot-diameter ( 4 meter ) fairy circles forms because the plants are availing themselves of as much of this gap space as possible ; the barren circles in between end up as far from each other as they can be . The regular , circular structure benefits the plants , too , because each gap ' s runoff is taken in by the maximum number of plants .
The soil monitoring also showed that the soil under the vegetation is much , much cooler than that in the barren patches . Getzin and his team once measured the top centimetre of the barren crust at 167 ° F ( 75 ° C ), well into egg-frying territory . The new study , which measured soil temperatures 2 centimetres down , found that vegetation lowered the soil temperature dramatically in the midafternoon when temperatures were highest . The cooler soil temperature makes it possible for seeds to germinate and seedlings to grow , Getzin said .
The field monitoring happened to coincide with a wildfire that cleared the desert of grasses , but the same patterns re-emerged when the grasses started again from zero , the researchers found .
" We could show for the first time with many and very detailed field investigations that Turing ' s theory and all the assumptions in the model / theory are indeed met in nature ," Getzin wrote in his email .
Getzin and his team are now doing a similar project in Namibia , where the fairy circles look similar but grow in sandy , rather than clay-rich soil . The different soils mean that the mechanisms for the formation of the circles must be different , Getzin said , but they are still almost certainly forced by the limits on water in the arid environment .
" How else can , in Namibia , perfectly circular grass rings form if it is not the competition of the grasses ?" Getzin said .
Figure 3 : Drone image of the Australian fairy circles , taken at a flying altitude of 130 feet ( 40 meters ). © S Getzin , University of Göttingen
Grassroots Vol 20 No 4 December 2020 30