It was the year… Wait, let me check. 2011? Really? Has it been almost six years? Huh.
Ok, so it was almost six years ago when I took my first plane ride, to Namibia, and what a doozy it was. Something like nine hours with no personal little tv screen in the seat in front of me, an incredible gift I wouldn’t get to see until I went to Ethiopia the following year. It was a night flight as well, so no one I could really talk to since most people can actually fall asleep anywhere. But not me. Anyway, this post isn’t about that plane ride but about something specific I encountered during my stay in Namibia when visiting the Namib desert but apparently neglected to take a picture of. Shame on you, past Simon. Shame on you.
What we saw where these large, rather circular patches of barren ground in an otherwise grassy plain. “But” you might start, “Isn’t that normal? It’s a desert, grass is bound to be patchy”. And you would be right, mostly. Thing is these patches occur not in the true desert parts of Namibia, but actual arid grasslands. There’s plenty of grass, albeit the very dry kind and in many cases it’s members of Stipagrostis. And the open patches aren’t just open, like I said, they’re very circular. Just look at some pictures (besides the cover photo which probably gave you an idea already), I don’t doubt you’ll agree that something’s up with these things.
These patches are called fairy circles. As our tour guide (Franko. Best. Guide. Ever.) told us back then, no one was really sure what caused these things, but they’ve been described in literature as far back as the 1920s. They range from 2 to up to 12 meters in diameter and can be present for as long as 60 years before the patches are again overtaken by grass. It was also thought that the Namib desert was the only place this phenomenon occurred in, but in 2014 some ecologists found some similar circles in the Pilbara region in Western Australia. Not that this gave the absolute solution yet to the puzzle, at least not yet. But they had some more material to work with now. For example, Stipagrostis doesn’t occur in Australia, so it doesn’t necessarily have to do with the specific genus. Then again, it doesn’t have to be the same cause in both scenarios, of course.
Obviously there were some myths surrounding the rings told by the local tribes, the Himba and bushmen. The circles were made by the gods or other natural spirits. It was their footprints or they’ve been made by Mukuru (the allfather of the Himba) and the bushmen give the patches both spiritual and magical powers. Tour guides add another and pin it on dragons, although Franko never used that story. A pity, really, it sounds like the perfect Franko story. In any case, the fairy part is something that us foreigners called it, thinking of our mushroom circles. So what did make this strange pattern?
A popular theory linked it to the scarcity of water and that the big patches were a population-level consequence for competition of this valuable resource. The grass can’t grow everywhere, so it needs to organize itself in a way that makes sure it gets what it needs in the most efficient way. In this case, the rings act like a rain pipe, they capture the water and divert it towards the vegetation along the edge. In turn, this extra water makes it so the plants get a bigger root system which loosens the ground so that water has an even easier path to take towards the edges. Australia does have a much harder soil crust, so water can’t flow as deep as it could in Namibia, but it doesn’t dismiss the hypothesis. Add to this the fact that in Australia other patterns have been discovered, stripes and even labyrinths, that surround individual plants to the same effect. Despite all the evidence, this self-organizing theory has not been made conclusive just yet as it didn’t completely explain every aspect of a fairy circle.
Another theory blamed ants and termites who nibble on the roots of the plants which then die off, likened to the workings of a beaver. For Namibia, Psammotermes allocerus in particular was said to be the culprit, but this sand termite doesn’t occur everywhere that the circles do, so the critters can’t be responsible for all the circles. Furthermore, although the termite had been found in almost all of the patches in one study (and was the only insect to be found there as well), they didn’t in another. However, the latter had searched for harvester termites which are different from sand termites. Sand termites live deeper underground and make no conspicuous nests or mounds. Their activity is the more stealthy of sort. This activity also loosens up the soil so enough water trickles down for the termite to survive the dry conditions.
However, what about other plant species? Why don’t they just go fuck things up in these circles? Why don’t they just put themselves in that big rain pipe and scoop up all the water for themselves, if that first theory would be correct? And why are there sometimes taller grass species present? Why don’t they get eaten by the termites? Another study tries to explain this with resource competition yet again, with the battle taking place underground. The patch serves as a reservoir again for both nutrients and water which are used by the taller grasses at the edge (with possibly the termites doing their thing as well). It’s these tall grasses that also maintain the circle by competing with the root systems of other, making sure they are the ones staying at the edge. In their models, given rainfall, biomass and temperature seasonality, it could predict the occurrence of fairy circles with very high accuracy. With this, it felt like they finally found the solution. This study was done in 2013, before the discovery of the Australian fairy circles but it’s not impossible for the same mechanism being behind those as well as it’s not talking about specific grass or termite species.
Then on the 19th of January 2017, a new paper got published in Nature, one of the most prestigious scientific journals. A friend of mine sent me this news remembering me talking about those patches in Namibia, and is why I’m writing this post. So thank you, Clint, you da man. In this new study, they explained “these and other related self-organised vegetation patterns by means of a general theory which integrates scale-dependent feedbacks and the activities of subterranean ecosystem engineers such as termites, ants, and rodents”. Quite a mouthful. This study doesn’t just talk about the fairy circles in both Namibia and Australia but also other kinds of odd, unexplained phenomena including Mima mounds in Washington (the state), Murundus in Brazil and “heuweltjies” in South-Africa. Distinction between these two as well as the fairy circles isn’t always very clear in literature and still a source for debate with different origins for each pattern. This new study however, tries to unite it all. It talks about multi-scale patterning: both intraspecific competition between animals (between termites, ants and rodents) and the self-organizing plants (the clumping or spreading of themselves I described in the first theory) combined can cause a variety of different patterns, including fairy circles on the two different continents but also the Mima mounds, murundus and the heuweltjies. It combines the pre-existing theories into one big whole, even more so than the previous. Synergy, it’s important everywhere.
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P.S. I got a note from past Simon saying he couldn’t take a picture of the fairy circles because they were in the bus driving by so the picture would be blurry as hell and that I’m a poopoohead.