Drought could push salamanders to brink of extinction
By _Marty Toohey_ (http://www.statesman.com/news/local/drought-could-push-salamanders-to-brink-of-extinction-1796490.html?service=popup&authorContact=1 796490&authorContactField=0) AMERICAN-STATESMAN STAFF Published: 9:26 p.m. Friday, Aug. 26, 2011 The nearly yearlong drought has been tough on the endangered Barton Springs salamander, so much so that city officials say survival prospects have notably diminished for the unofficial mascot of Austin environmentalism. Salamander numbers appear to have dwindled significantly since the drought started, according to Laurie Dries, the city biologist responsible for managing the salamander population. The 2008-09 drought greatly reduced the amphibians' numbers, and they had a weak recovery during the wet period between that drought and this one. Of particular concern is a lack of juvenile salamanders, which are especially sensitive to dry conditions. Dries' assessment comes with the standard range of scientific caveats. A prolonged wet period might swell their numbers. They might be more resilient than thought. Precise counts are impossible because some salamanders might be hiding in hard-to-reach caves. But the best evidence indicates trouble for the salamander, Dries said. Her analysis is backed by recent lab testing on how drought conditions affect similar salamanders. "I'm concerned that we didn't see their numbers bounce back from the '08-09 drought, which was tough on the salamanders, and we're in an even worse drought now," she said. The Barton Springs salamander was added to the federal endangered species list in 1997, after Austin environmentalists had pushed for its inclusion for years. The much-discussed, rarely seen creature is equally celebrated and scorned, as it has become an important, if not always successful, tool for combating development over the recharge zone of the Barton Springs portion of the Edwards Aquifer. It's unclear how the salamander's possible demise could effect the debate about development rules over the aquifer. The rainwater that seeps through fissures, caves and other porous features in the recharge zone filters into the Barton Springs portion of the aquifer. The aquifer replenishes Barton Springs Pool and is a source of drinking water for rural areas in Travis and Hays counties. Adult salamanders are about 21/2 inches long and live in the water. They have weak eyes and are gray, purple or brown with salt-and-pepper mottling on their backs. They live only in the outflows of the four springs that collectively make up Barton Springs, according to the Texas Parks and Wildlife Department. The city typically uses the salamander population in Eliza Springs as the main barometer of overall salamander health. Eliza, which is behind the pool's concession stand, is the most salamander-friendly habitat and the easiest place for the city to track long-term salamander trends. Heading into the previous drought, scientists counted about 600 salamanders living in Eliza Springs. During the 2008-09 drought, the number dropped to 35 adults and no juveniles, although some might have been living in the caves. The number climbed to a peak of 300 salamanders after the rains started falling. There are now about 140 living in Eliza Springs, nine of them juveniles, according to city monitoring data. It's impossible for the city to get a precise salamander count because it is difficult to find them, but lab tests support what the city is observing. Recently, researchers at the University of Texas and Baylor University performed tests on San Marcos salamanders, which are closely related to the Barton Springs salamander but are not endangered. The tests measured how much oxygen they need in the water around them; in droughts, when less water is flowing, the oxygen content drops. At 5 to 6 milligrams of oxygen per liter of water, the typical amount in Eliza Springs, the salamanders were fine. At 4.4 milligrams, growth rates for the salamanders dipped in the lab tests. At 3.6 milligrams of oxygen, about 25 percent of adults died. At 3.4 milligrams, half the salamanders died in the lab. At 1.9 milligrams, they all died. Eliza Springs is now at 3.6 milligrams. Kirk Holland, the general manager of the Barton Springs/Edwards Aquifer Conservation District, said the oxygen levels are likely to keep dropping. He said the flow of water into the springs will probably continue weakening for the foreseeable future, possibly to its lowest level ever. "We're assuming things will get a lot worse before they start to get better," he said. Holland said there is no evidence of how far oxygen levels would ultimately drop, but he added, "The city, rightly so, is making some worst-case assumptions." _http://www.statesman.com/news/local/drought-could-push-salamanders-to-brink -of-extinction-1796490.html_ (http://www.statesman.com/news/local/drought-could-push-salamanders-to-brink-of-extinction-1796490.html)
