The mysterious circles in the desert explained by Alan Turing’s theory 70 years ago
It was 1952, and Alan Turing was on the verge of reshaping humanity’s understanding of biology.
In a landmark article, the English mathematician introduced what has come to be known as the Turing model – the notion that the dynamics of certain uniform systems could give rise to stable models when disturbed.
Such an “order of disturbance” has become the theoretical basis for all kinds of strange and repeated patterns observed in the natural world.
It was a good theory. So much so, in fact, that decades later scientists are still discovering stunning examples of it in unusual and exotic places: real-world Turing motifs that come to life in places Turing himself never had. the chance to see.
The latest incarnation of this theoretical phenomenon turns out to be fairy circles – mysterious desert grass formations that grow around distinctly circular patches of arid soil, first documented in the Namib Desert of southern Africa.
The explanations for their existence range from the mythical to the mundane, and just a few years ago their origins were still the subject of debate. At first, one view argued that the strange circles were due to termite activity under African soil – but the later discovery of fairy circles in the Australian outback complicated the account, demonstrating that fairy circles could be found not closely related to termites.
Alternatively, scientists have proposed that fairy circles are the result of plants managing to make the most of limited water resources in a harsh, arid environment.
It sounds plausible, and if true, it would be another natural example of a Turing model as well. But there isn’t much empirical evidence to actually support the hypothesis, the researchers say, because the types of physicists who tend to model the Turing dynamics of these systems rarely end up also doing fieldwork in the desert in support of their ideas.
“There is a strong imbalance between theoretical models of vegetation, their a priori assumptions and the paucity of empirical evidence that the modeled processes are ecologically correct, ”says a team led by ecologist Stephan Getzin from the University of Göttingen in Germany in a new article.
To close that gap, Getzin and other researchers walked the march, using drones equipped with multispectral cameras to monitor fairy circles from the sky near the mining town of Newman in the Pilbara region of Western Australia.
According to one of the team’s hypotheses, a Turing pattern arrangement of fairy circles would be stronger among herbs with a greater reliance on moisture.
By analyzing the spatial separation of high and low vitality grasses and using moisture sensors to verify ground readings, the team found that healthier, high vitality grasses were consistently more strongly associated with fairy circles. than low vitality grasses.
In other words, for the first time, we have empirical data suggesting that fairy circles correspond to Turing’s decades-old theory.
“What’s intriguing is that grasses actively design their own environment by forming patterns of symmetrically spaced spaces,” Getzin explains.
“The vegetation benefits from the additional runoff water provided by the great fairy circles, and thus keeps the arid ecosystem functional even under very harsh and dry conditions. Without the self-organization of the grasses, this area would likely become desert. , dominated by soil. “
According to the researchers, the grasses that make up the fairy circles grow together cooperatively, modulating their environment to better cope with the near-perpetual drought of an extremely arid ecosystem.
The team says even more fieldwork will be needed to further validate the mathematical models, but for now, it looks like we’re closer than ever to closing the book on this mysterious phenomenon.
“By forming periodic gap patterns, the vegetation benefits from the additional water resource provided by the fairy circle holes,” the authors explain, “and thus maintains the ecosystem functioning at lower precipitation values compared to a uniform vegetation. “
The results are reported in Ecology review.