AUDIE CORNISH, HOST:
Now, we're going to travel to the middle of the desert in the United Arab Emirates. For centuries, it's been nothing but an expanse of red sand, but a new watery ecology is emerging as reporter Ari Daniel Shapiro reports.
ARI DANIEL SHAPIRO, BYLINE: Drive through the desert in the United Arab Emirates and all you see mile after mile are red, rolling dunes. Maybe some occasional trees or shrubs, but otherwise a dry, red sandscape. And then suddenly, a bright blue spot comes into view. You think it must be a mirage, but it's not. It's the most undesert-like of things, a lake, one the size of Walden Pond.
The wind whips across the blue water's surface, pushing it into a light chop. And wispy reeds in the center of the lake flutter in the breeze. Dave Clark is a hydrologist with the U.S. Geological Survey, and he says this lake emerged from the sand a few years ago.
DAVE CLARK: You see local families out here, and they're all just enthralled.
SHAPIRO: They're pleased or they're weirded out?
CLARK: Yeah, I think they're pleased. No, 'cause it's water in the desert, so everybody's pleased. But it's definitely water that's had a human touch to it. People have had their hand in this water maybe literally.
SHAPIRO: Here's how this lake got here. A desalination plant right on the coast pulls in saltwater from the Persian Gulf and makes that water drinkable and usable. The water is then pumped 150 miles inland to the city of Al Ain. The residents there drink it up, bathe with it and then flush it down their drains.
CLARK: It goes to the sewage treatment plant, and they treat it, and they bring it back into town. And they water the parks and the gardens and things like that, and that percolates down into the groundwater.
SHAPIRO: And then it ends up here?
CLARK: It ends up here.
SHAPIRO: Here in the desert, a short distance from Al Ain, by percolating back up from the ground. This water's clean. But still, it comes as a shock to some of the life here in the desert.
BRIGITTE HOWARTH: Just because the sand dunes look on the surface to be fairly barren doesn't mean that they are. They are full of life.
SHAPIRO: Brigitte Howarth is an ecologist at Zayed University in Dubai. She studies insects that evolved in the harsh, arid conditions out here, and she worries that some of them aren't faring so well in this part of the desert that's suddenly underwater, like the Mydas fly, which she spotted for the first time in October 2010.
HOWARTH: All of a sudden, this fly started to dip its abdomen into the sand. And so it's about an inch deep in the sand, and it's egg-laying.
SHAPIRO: The Mydas flies rely on dry, loose sand to lay their eggs. But the lake is flooding more and more of the sand. Howarth hadn't yet spotted any Mydas flies this year, and she's concerned that as the lake continues to swell, their habitat might disappear altogether.
HOWARTH: For them, the encroachment is, in fact, a death sentence.
SHAPIRO: The wind blows the sand off the top layer of the dunes to create a kind of granular fog in the air. But underneath that shifting surface, the world is more stable. So if the dunes are dry enough and warm enough to allow Mydas fly eggs to hatch, Howarth knows that a raft of other organisms will probably be in good shape too.
Howarth trains her eye on the lake. She's worried that this new source of water and the development pressures of a growing human population don't bode well for the dunes.
HOWARTH: With every species that we lose, it's like rolling the dice. The whole ecosystem could crash down.
SHAPIRO: But one expert told me he's not concerned about the desert ecosystem. He says amount of desert in this part of the world far exceeds the area awash with new lakes. He considers extinction of local species unlikely. And all this water spawned a whole new ecosystem. Here's Dave Clark again.
CLARK: If I look through the binoculars, there's, like, seven different kinds of herons. There's greater cormorants.
SHAPIRO: This year, three types of birds bred at this lake. They've never been able to breed before in the United Arab Emirates. But this lake has changed all that.
CLARK: Every year, we find two or three or four or five birds that have never been seen before in the UAE. So it's one of the few places in the world that the number of birds is actually increasing instead of decreasing.
SHAPIRO: There are fish appearing in these lakes as well. Fish eggs cling to the feet and legs of the herons. So as the birds shuttle between old and new lakes, the eggs fall off and hatch. That's how you get fish in a desert. Out here, one ecosystem is leaking into another and new lakes like this one are starting to appear in other parts of the desert. As new webs of creatures replace the ones that came before them, it might happen so quickly that we'll never know what was here in the first place.
For NPR News, I'm Ari Daniel Shapiro.