HOW TO: Fish in the desert

In the United Arab Emirates, a freshwater lake has appeared in the middle of the desert. The oasis is beautiful and full of life, and it's risen 35 feet since 2011. It's also probably accidentally man-made.

Hydrologists believe the lake formed from recycled drinking water (and toilet water). The nearby city of Al Ain pumps in desalinated sea water, uses it for drinking and flushing the toilet, cleans it in a sewage treatment plant, and then re-uses it to water plants. All of that water ends up in the soil and, at the lake site, it comes back up.

The water is clean, writes Ari Daniel Shapiro at NPR. Don't worry about that. Instead, the major side-effect of the lake is change, as scientists watch the desert ecosystem that used to exist on the site decline, and a new one rise to take its place. It's a great story that shows how complicated discussions about ecology can be. On the one hand, you're losing something valuable. At least in this one spot. On the other hand, you're definitely gaining something valuable, too.

"With every species that we lose, it's like rolling the dice. The whole ecosystem could crash down," Howarth says.

But Clark, with the U.S. Geological Survey, says he's not so worried about the desert ecosystem. He says the lake is tiny compared to the vast amount of desert in this part of the world. "If I look through the binoculars, there's, like, seven different kinds of herons. There's greater cormorants. There's ferruginous ducks, which are another very rare worldwide species," Clark says. "There's about 15 of them out here."

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, and the others like it, have changed all that. 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.

Read the full story at NPR