A snail in Alabama has become the first in U.S. history to recover from the brink of extinction and is now merely threatened rather than an endangered species.
In 1991, the Tulotoma snail was barely clinging to one small place, extinct in 99 percent of its historic range. The snail now has expanded to 10 percent of its range.
"The Clean Water Act and improved land use conditions have allowed the snail population to start growing again," said Jeff Powell, senior biologist with the U.S. Fish and Wildlife Service.
Under the Clean Water Act, the federal government has implemented pollution control programs and set water quality standards for contaminants in surface waters.
At the bottom of the food chain, snails consume algae and provide food for other species. More snails indicate better water quality.
The orangish, two-inch long Tulotoma snail with elegant swirls was once prized by Native Americans for its beauty and crafted into jewelry. Its historic range was destroyed in the early 1900s, when dams emerged on Alabama's flowing rivers.
Snails and mussels thrive on flowing water, which has higher oxygen content. Powell described impounded lakes created by the dams as "bathtubs" where oxygen goes down and temperatures go up.
The Tulotoma snail's recovery resulted in part from an agreement with the Alabama Power Company to release a steady flow of water from its dam on the Coosa River.
"We changed to pulsing flows and installed aeration systems to raise the oxygen. It has had a dramatic impact on the river species," said Brandon Glover, a power company spokesman.
U.S. Fish and Wildlife biologists and others also embarked on a diligent search for the Tulotoma and other species. New populations have been found in three more tributaries, bringing the numbers from 10,000 to hundreds of thousands.
Dispersed populations ease the vulnerability of a single event wiping out the species, as was the case when pollution of a small creek wiped out one of four populations of the snail.
Alabama is among the leaders in extinctions, with 29 snails, 28 mussels and two species of fish already extinct, according to Michael Buntin, biologist with the Alabama Aquatic Biodiversity Center.
The state also holds the record for a single mass extinction, when a dam opened and wiped out 40 species.
One reason for the high numbers is Alabama's freshwater biodiversity, which includes 310 species of fish, 150 snails and 181 mussels, Powell said.
http://www.reuters.com/article/2011/07/26/alabama-snails-idUSN1E76P0M920110726
