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It's been a hard few years for bats in the U.S. A disease called White Nose syndrome has killed millions of them. But in Texas, something else is threatening a massive bat colony. It's a planned housing development.
Ryan Loyd of Texas Public Radio reports on the debate over what's considered the world's largest bat cave.
RYAN LOYD, BYLINE: The Bracken Bat Cave is as rural as it gets. To get there you have to drive down a long two-mile rocky road. There's nothing nearby.
(SOUNDBITE OF KATYDIDS)
LOYD: The only thing you hear are the katydids.
The folks who oversee the cave, Bat Conservation International, want it to stay secluded. Director Andy Walker doesn't understand why there's any discussion to build a subdivision right next door with nearly 4,000 homes.
ANDY WALKER: And it really instills an even deeper sense of stewardship for this land and these bats.
LOYD: The cave is at the bottom of a valley and it has a wide-open mouth. The air is hot, 100 degrees or so. The bat colony is estimated to have been here for 10,000 years. Around sundown, the first of 10 million bats begin to emerge from the cave. Thousands fly in a vortex in the valley at a time. They form a black streak over the sky. If you listen closely, you can hear their flapping wings, which sound like a steady, gently falling rain.
(SOUNDBITE OF BATS)
WALKER: This is really a ballet, watching these bats come out of this cave in these millions of numbers, never once bumping into each other.
LOYD: Walker worries about these bats if the housing project is approved. The land for the proposed subdivision is just to the south, directly under their typical flight path. San Antonio developer Brad Galo bought the property several years ago and had kept quiet about his plans. But they became public in March, when the San Antonio Water System board approved a contract for water and sewer service there.
ANNALISA PEACE: It's certainly crazy.
LOYD: That's Annalisa Peace who runs the greater Edwards Aquifer Alliance, a group that fights for the area's water source.
PEACE: I can't tell you why they want to build over it. But I can tell you our aquifer is really a world-class aquifer. It's amazingly prolific but that also makes it extraordinarily vulnerable to pollution.
LOYD: Although the planned subdivision has its critics, the Water System's Greg Flores defends conservation efforts to keep the bats safe. He says the water system and Aquifer Alliance purchased hundreds of acres of land around the bat colony for conservation.
GREG FLORES: There's been a lot of effort and there have been a lot of resources put into protecting this natural feature.
LOYD: One major consequence could be on Texas agriculture. Cave coordinator and tour guide, Fran Hutchins, says the bats eat tons of bugs and save farmers money.
FRAN HUTCHINS: This colony alone is going to eat 100 tons of insects every night. Their primary food are agricultural pests, so those insects are very harmful to the local farmers.
LOYD: So far, no master plans have been submitted to San Antonio's development department. Mayor Julian Castro says there's been no decision whether the housing project will move forward.
MAYOR JULIAN CASTO: There is a science to figure out in terms of whether development would or would not actually harm the bats.
LOYD: Environmental advocates are taking Castro at his word. Again, here's Bat Conversation director Andy Walker.
WALKER: You'd like to think also, because this is Texas, where there is a will, there is a way. And people have good horse sense here and we can figure out a solution to this.
LOYD: The delicate balance between progress and conservation is a dance even more complicated than the nightly flight of these creatures.
For NPR News, I'm Ryan Loyd in San Antonio.