The Fairy Circles confirmed
In the Namibian desert, along a 1500-mile sliver of land in southwestern Africa, one can see almost perfectly round circles of bare sand surrounded by rings of tall grass. The circles vary in size from 7 to 49 feet in diameter. The local nomadic Himba people believe that the circles were created by the spirits, that they are the footprints of the gods. They call this pattern of bare patches surrounded by rings of tall grass Fairy Circles.
Modern scientists do not believe in spirits, or in African gods, but not unlike the Himba people, when faced with a pattern, they search for an explanation. What is the cause of the Fairy Circles? They ask. Then, they take part in strident, long-lasting debates, presenting numerous arguments and counter-arguments, and debates simmer.
In the case of Fairy Circles, there are two competing explanations. The first is that plants arrange themselves, or self-organize, in specific patterns. They do so by facilitating the growth of neighboring plants and competing with distant plants. The second explanation is that large societies of sand-termites engineer the Fairy Circles by killing the plants in their centers. Scientists believe that the bare circles of exposed sand allow the termites to preserve moisture and to survive through periods of drought.
In a recent letter to Science Magazine, one of the world’s top academic journals, Corina E. Tarnita and her colleagues presented their solution to the long lasting debate. Tarnita holds a Doctorate degree in Mathematics from Harvard University and serves as a faculty member in the Department of Ecology and Evolutionary Biology at Princeton University. In a picture posted on the Princeton website, she is standing authoritatively with her arms crossed in front of her and a wide smile plastered on her face. In my search for the causes of patterns in nature – Fairy Circles and rings of tall grass – I wholeheartedly trust her.
Tarnita did not go on an expedition to the Namibian desert. She did not dig into the Namibian sand and did not delve into the social behavior of termites in their natural habitat. Instead, she studied low-altitude aerial images of vegetation patterns in the Namibian desert and images from Google Earth showing the distribution of insect nests.
Tarnita made assumptions like: each colony of termites starts with two termites, a queen and a king; and each colony grows, and reproduces, and seeds the rest of the system with new colonies. Tarnita considered such factors as territory area, the shape of the nest, the rate in which colonies grow, and the competition with other colonies. She put all of this data into several equations.
Then she did the math and Bam!!! Just like that, she proved that the formation of Fairy Circles cannot be explained by the self organization of plants alone, nor by the activity of termites alone. Rather, it is the effect of both self-organizing plants and that of the hard-working termites that contribute to the formation of Fairy Circles.
Will Tarnita’s research put an end to the strident, long-lasting debates on the formation of Fairy Circles? I think not, for when it comes to patterns, when one dispute resolves, another arises.
On the day after I read Tarnita’s article, on my way to work, I saw patterns everywhere: Driving along US 41, I saw the trees and the forest (trees have patterns, forests too); I saw the waves of Teal Lake breaking onto the shores, and the icy sand dunes form into crescent shapes; I turned on the wipers and cleared millions of snowflakes from my windshield – they too have a pattern, a sixfold symmetry. And I thought of patterns of other kinds: zebras that count each other’s stripes and leopards that could not change their spots.
When I arrived at the hospital and donned my white coat, I realized that as all doctors, mine too is the duty to notice patterns, and to detect disturbances in pattern: a spiking fever; an unexplained weight loss; a red, itchy skin rash over the neck; an irregular heart rhythm; and a sudden, intense abdominal pain.
In my next column I will tell you about a 58 year old man with a history of fevers and drenching night sweats. His eyes were yellow and his urine was dark. In short, a man whose normal health patterns were distrusted. It would take a group of physicians to make the correct diagnosis, and a liver biopsy that when examined under the microscope showed a pattern of rings not unlike the Fairy Circles in the Namibian Desert.