2023-09-26 17:15:11
Mysterious geometric patterns surrounded by plants appear in desert areas around the world. This has been determined in a recent investigation. Previously, it was believed that they were only present in a few areas.
It turns out that what are popularly known as fairy circles are present in more than 250 sandy areas in 15 countries and 3 continents, despite the fact that they were believed to be exclusive to Namibia and Australia. This is reflected in this new study, in which the Higher Council for Scientific Research (CSIC) of Spain participates through the Laboratory of Biodiversity and Ecosystem Functioning (BioFunLab) of the Institute of Natural Resources and Agrobiology (IRNAS).
These enigmatic circular patterns are among the most mysterious natural formations that can be observed in the arid areas of our planet. They are circles of bare soil surrounded by rings of vegetation. Over the years, multiple hypotheses have been proposed to explain their formation, which have given rise to numerous discussions about the mechanisms that cause them. However, until this moment, the global dimension of this type of phenomenon and the environmental factors that explain them were unknown.
Until now, the climatic, edaphic and environmental factors that determine its distribution on a global scale had not been analyzed because they were only known in Namibia and a part of Australia. “Analyzing their effects on the functioning of ecosystems and discovering the environmental factors that determine their distribution is essential to better understand the causes of the formation of these vegetation patterns and their ecological importance,” indicates Emilio Guirado, the principal investigator of this study. , which is part of the Multidisciplinary Institute for the Study of the Environment of the University of Alicante (UA) in Spain.
With the help of models based on artificial intelligence, scientists classified satellite images and obtained 263 sites where patterns similar to the fairy circles described to date can be observed, those of Namibia and Western Australia, including the Sahel, Western Sahara, the Horn of Africa, Madagascar, southwest Asia or Central Australia. “Our study provides evidence that fairy circle vegetation formations are much more common than previously thought, which has allowed us, for the first time, to globally understand the factors that affect their distribution,” highlights Manuel Delgado Baquerizo, leader of the IRNAS-CSIC BioFunLab and co-author of this research.
The researchers found that the combination of certain soil and climate characteristics, such as having a low nitrogen content and an average rainfall of less than 200 mm/year, were related to the presence of fairy circles. Both termites and ants had low importance as predictors on a global scale. However, on a regional scale, termites were a more important predictor in Namibia than in regions such as the Sahel or Australia. “This study has taken into account multiple variables not considered to date, such as the albedo or the state of the aquifers,” says Jaime Martínez-Valderrama, scientist at the Experimental Station for Arid Zones (EEZA) of the CSIC and co-author of the study.
Fairy circles on a plain in Namibia. (Photo: Audi Ekandjo)
An unprecedented global atlas
The study authors also compared the stability of primary vegetation productivity of fairy circles with that of other ecosystems and found greater invariance when fairy circles were present. “These results provide the first empirical evidence of greater stability in the productivity of fairy circles, a key property of ecosystems that is related to the stable provision of ecosystem services such as the amount of forage,” details Fernando T. Maestre, professor at the UA. “These results also open the door to research into whether these spatial patterns can be indicators of the degradation of ecosystems with global climate change, as is the case with other spatial patterns of vegetation in arid areas,” says Miguel Berdugo, co-author. of the study.
The scientists are also making available a global atlas of fairy circles and a database that could be useful in determining whether fairy circle vegetation patterns are more resilient to climate change and other disturbances. “We hope that these unpublished data will be useful for those interested in comparing the dynamic behavior of these patterns with others present in arid areas around the world,” concludes Guirado.
The study is titled “The global biogeography and environmental drivers of fairy circles.” And it has been published in the academic journal Proceedings of the National Academy of Sciences (PNAS). (Source: CSIC)
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