What Causes Fairy Circles?

Thousands of "fairy circles" dot the landscape of the NamibRand Nature Reserve in Namibia. Why these barren circles appear in grassland areas has puzzled scientists for years.

 A scientist thinks it is termites:

If you fly from Angola down to South Africa you'll spot thousands of these fairy circles down below. They look like moon craters and are anywhere from the size of a manhole cover to 30 feet across.
Scientists have had some good guesses as to what causes them (none of which include fairies or people): poisonous plants, insects, seeping gas, even radiation. But no one could find evidence of any of these.
Then came one very determined biologist: Norbert Juergens. He traveled from the University of Hamburg in Germany to dig trenches inside the circles.
Juergens found that within every circle, the sandy earth beneath the surface was wet, even in the dry season. Juergens, who is not given to excitability, knew he was onto something extraordinary. "It was an exciting observation," he says, "because water is the most important resource in the desert. I sort of discovered 1 million little circular oases in the desert at that moment."
There was something else odd about the circles — they were ringed by tufts of year-round grass. "It was a plantation," he says. "It's a plantation of plants created by some organism."
Juergens had been commuting back and forth from Germany for a couple of years, examining scores of these circles, and still hadn't found the cause. An organism, yes, he figured, but what kind?
He found spiders, beetles, ants and even aardvarks in the circles. And termites — and only termites showed up beneath every circle.

It is amazing that it took this long to figure it out.  But, there is also this:

JONATHAN WILKER: This is what happens when I'm on an airplane, and it comes up that I'm a scientist, people say: What do you study? And I'll say, yeah, you know, when you're at the beach and you see all those creatures stuck to rocks. And they'll say, yeah, yeah. I said, so, we're trying to figure out how they do that. And the typical response is oh.
PALCA: And if that's not enough to get people interested, Wilker lets the other shoe drop.
WILKER: Look, these glues that these animals are producing, they're really strong and they set wet. Go to the hardware store, buy everything on the shelf and try to glue two things together underwater, and you're not going to be able to do it. And this is how we're going to learn how to do that.
PALCA: This highly serious search for the sticky secrets of shellfish - try saying that three times fast - is in a boring old lab building on the Purdue University campus. Inside one of the rooms, Wilker shows off three giant tanks of saltwater and an elaborate pumping system to keep the water moving.

The guy has been studying shellfish for 14 years while trying to figure out what chemicals the animals emit to glue themselves to piers and ships and rocks.  Pretty freaking amazing. Maybe we can learn something worthwhile from the damn zebra mussels that plague the Great Lakes.