Price of Progress
From the Birmingham News, March 14, 2004, Page 10A.
The price of progress:
Some aquatic species dammed to extinction
News staff writer
The Coosa River remains a global hotspot for snails and mussels, the center of diversity worldwide and home to hundreds of aquatic animals.
For that reason, it has a more lethal distinction: the site of the largest extinction in the history of the United States.
"Roughly half the extinctions in the last 500 years were in the Coosa River basin in the 20th century just in one concentrated area - on our watch," said Paul Hartfield, endangered species biologist for the U.S. Fish and Wildlife Service.
As the river was dammed, dozens of fish, mussels and snails that evolved to live and breed in the fast-flowing water on the shoals and riffles of the Coosa reefs lost their niche.
Animals were drowned, stranded, cut off from each other or stuck in water so dirty that they could not reproduce, biologists say. Forty-nine snail and mussel species were lost.
More may be extinguished as the last members of some long-lived species die. Biologists tell of finding enormous mussels above some of the last dams, but no smaller members of the species.
Some snails lost their homes because they needed shallow or swift water. Nearly all required clean, rocky bottoms without the silt brought by the dams.
The mussel's story was less obvious. Each one reproduces by attaching its eggs to a specific host fish. After about three weeks, the eggs fall off the fish, hatch and spend the rest of their lives where they land. As a result the mussels are distributed throughout the rivers. Without that time living as parasites on the fish, the eggs will not hatch.
Some mussels developed 8-foot lures designed to look exactly like the food of the host fish. When the fish chomped down, it would be covered by the larvae. Others developed balloon-like clouds of eggs for the fish to swim through, or larvae that winked their bodies to attach themselves when they sensed the salty tissue of the fish.
But the more careful its connection to the ecosystem, the more easily a species is torn from it. When the dams were built, many mussels were separated from their host fish.
Some of the fish died, unable to climb over dams and swim as far upstream as they needed to reproduce. Other mussels and fish were kept apart by the newly deep, dark water where the fish could not see their lures.
The federal government built the Coosa's first three locks in the late 19th century, for navigation. But the early locks did not create deep reservoirs neatly sectioned off from one another.
The river still flowed free and life in it and on it was little changed, historian Harvey Jackson wrote in "Rivers of History." In the first decade of the 20th century, one biologist reported finding 150 specimens of mollusks in a space not 20 yards long, Jackson wrote.
The era of modern river-taming began after Alabama Power Co. formed and began to build dams as deep as 110 feet. The first, Lay Dam, was completed in 1917. Over the next 50 years, the company built six more.
"Nobody cared at that time," Hartfield said. "We were still in the frontier mode - the resources of the United States were limitless."
By 1967, the entire Coosa had been chopped into a series of pools that flow only during high water, said Stan Cook, chief of fisheries for the Alabama Department of Conservation and Natural Resources. "Basically, the river doesn't exist."