If you fly over the coastal dune belt  of the Namib Desert in southwest Africa,   for hundreds of kilometers you’ll  see almost nothing but sand.

But eventually, you’ll come across these: hundreds  of thousands of bare circles surrounded by grass. Like a tile mosaic in the middle of the desert.

It’s almost like someone, or some  thing, made this elaborate pattern. But what? For more than 50 years, scientists  have been trying to figure that out.

It’s probably not a mythical  dragon with poison breath — a story possibly cooked up by local tour  guides and it’s definitely not aliens! But how can a design this massive and precise  show up without anyone…or anything…in charge? And why are we suddenly  finding more of them elsewhere? [♪ INTRO] Scientists have seen bare patches in grass before, caused by termite mounds,  gas leaks, things like that.

But nothing like the Namib’s fairy circles. They only seem to form in this one sliver of   desert that gets between 50 and  100 millimeters of rain a year. And along this sliver, hundreds of thousands  of circles…ranging in size from 2 to 35 meters wide…  line up in a suspiciously organized pattern  where each circle has about six neighbors.

Researchers started looking for  scientific explanations back in the 1970s,   but for the first few decades, they came up empty. One guy suggested that fairy circles  were old, eroded termite mounds. Another proposed they were  caused by poisonous plants   that had died and released  their poison into the soil.

Still more wondered if gases rising up  from the Earth were killing off the grass. But based on all the gathered evidence, there  was no consensus for any of these ideas. So scientists eventually  came up with some fresh ones,   and by the 2010s, the search for an  explanation became a full-on debate.

Science beef! Science beef! In 2013, one researcher thought he’d cracked it.

After studying hundreds of fairy circles, he found  one thing they all had in common: sand termites. These tiny insects build elaborate underground  nests, and as they tunnel through the ground,   they eat the roots of freshly sprouted grasses. By killing plants that would otherwise suck   up all the groundwater, termites  create their own personal oasis.

The researcher also proposed they  consistently munch on the grass roots   at the edge of the circle, widening  the whole shape slowly over time. Eventually, these termites run into  neighboring nests, all doing the same thing. And instead of battling, or merging into one  megacolony, they all just stop expanding…leaving   a kind of Demilitarized Zone between them,  and capping how big each circle can get.

So mystery solved, right? Well, another camp of researchers wasn’t so sure. Mainly because they didn’t find termite nests  at all when they dug up some of these circles.

They mostly just found sand. Plus, even if there were termites  burrowed somewhere in there,   this camp of researchers just didn’t  see why termites would only create   fairy circles in this narrow strip of the  Namib Desert, since they lived all over it. So instead, they put a new idea out there:   fairy circles arise naturally  as plants compete for water.

The bare patches represent the spots  where competition is the highest. There’s not enough water to go  around, and the grasses die off. But wherever the grasses die, water can start  pooling underground without roots sucking it up.

Meaning, eventually, a new reservoir can  form…and maybe even attracts critters like   termites who also need some  amount of water to survive. This hypothesis explains both how you could get a  whole field of fairy circles evenly spaced across   the desert, as well as why we only see them  in this narrow strip of desert: there’s just   the right amount of rainfall to both form the  reservoirs and force the grasses to compete. But it also has its problems.

For instance, scientists in the  termite camp pointed out the   grasses seem to die off during times  when the soil is relatively moist,   not when it’s dry and competition  for water would be the highest. So which idea do you like better? Termites or Plants?

Go ahead and think about it while we show  you this ad to help keep the lights on: This SciShow video is supported by DeleteMe,  the hands-free subscription service that removes   your personal information from hundreds  of data broker and people search sites. DeleteMe is trusted by medical providers, judges,   podcasts hosts, and our  executive producer, Nicole! She signed up this year and said they’ve already  reviewed over 900 records and begun removing them.

And by “they,” I mean real people available  for custom requests and help when you need it. They use their own tech and don’t outsource  to third parties, so your data stays safe. To sign up for their service,  use the QR code on screen or go   to joindeleteme.com/SCISHOW and use  the promo code SCISHOW at checkout.

You’ll get 20% off DeleteMe US consumer plans. So researchers sparred over these ideas for years. And then in 2017, one team wandered  up to the controversy like, “Hey,   what if everyone’s kind of right?” First, the team ran some simulations  of termite colony interactions.

What happens when two expanding nests  finally encroach on each other’s territory? According to these simulations, the bigger  colony usually wins and engulfs the smaller one. But when two colonies are about the same  size, they can hold out indefinitely,   and create that aforementioned Demilitarized Zone.

The end result is circles that look a  whole lot like real-life fairy circles,   with tall grasses growing in the “I’m not touching  you” zones where no termites are foraging. While that sure sounds like a win for  Team Termite, the group also found that   to really match Namib’s grass pattern, you  need to factor in water competition, too. That’s because all of the clumps of grass  between the fairy circles also look a lot   like they do in a simulation  of plants competing for water.

Alas, their 2017 paper has  still not sealed the deal. As of at least 2023, the termite team and  the water competition team were still at it,   publishing contradicting papers, still  trying to end the debate once and for all. In the meantime, a new set of fairy circles  entered the fray, 10,000 kilometers away.

In 2016, researchers reported on what appeared  to be fairy circles in the Australian outback. And despite forming on a completely  different continent, they look almost   identical to the Namibian ones. Suddenly, it seemed like fairy circles  might not be so rare and special after all.

Then in 2023, a survey of the  whole globe found hundreds of   patterns that looked like fairy circles  spanning Africa, Asia, and Australia. But while they all seem to show up in dry places,  they have very different climates and ecosystems. This suggests there’s no  one cause for all of them.

So, the mystery of fairy circles is  maybe even less solved than ever. But here’s what we do know: Whatever’s causing them, it’s probably  a survival strategy: some way for   plants and animals to create a mini, stable  ecosystem in the midst of a much harsher one. And these tiny actions…  termites munching through roots,   plants competing for water… get  repeated over an entire landscape.

In the end, their simple mission  creates a massive pattern that   almost looks like a deliberate work of art. So while scientists argue amongst themselves,  I’m just gonna take in nature’s beauty…and think   of what kind of pattern I’d draw if I were  a dragon with poison breath… or an alien. [♪ OUTRO]