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Along a broad expanse of southern Louisiana, between the Atchafalaya and Mississippi rivers, a million acres of wetlands have disappeared since 1900. ^ Scientists now estimate that an additional 60 sq. mi. are vanishing every year -- a rate that could double by 1995. "It's a catastrophe that's happening to the wetlands. You're looking at the genocide of an entire ecosystem," says Oliver Houck, a Louisiana environmental lawyer. Indeed, the loss of the state's marshes affects more than just local residents: the area provides almost 30% of the nation's fish harvest and 40% of the fur catch, and is a winter habitat for some two-thirds of the migratory birds in the Mississippi flyway. Says Oysterman Matthew Farac, speaking of the 32-mile stretch from the mouth of the Mississippi to Empire, La.: "There is no land left. It's all gone now."
In the bayou country, the intrusion of salt water from the Gulf has been aided by miles of canals and pipeline rights-of-way dredged by oil and gas companies. Ordinarily, much of the salty water would be forced out of marsh areas by seasonal freshwater overflows from the nearby Mississippi. But the river now rarely floods, thanks to massive levees built along its banks to protect riverside land. The combination of saltwater intrusion and freshwater cutoff, says Houck, leaves the wetlands "caught in a double whammy. You couldn't do a better job of screwing up Louisiana if you planned it."Wilma Dusenberry, a Chauvin, La., restaurant owner, reflects the fears of many who depend on the bounty of the wetlands: "If we lose the marsh, we lose our livelihoods."
Shoreline erosion, however, is exacerbated by less well understood -- and perhaps more ominous -- factors. Over the past 100 years, the ocean has risen more than a foot, a rate faster than at any time in the past millennium. Sea- level fluctuations are part of a natural cycle, but scientists suspect that this one may be different. They believe it is magnified by a fundamental change in world climate caused by a phenomenon called the greenhouse effect. Since the Industrial Revolution, people have been burning greater quantities of fossil fuels, such as coal, oil and gas. One by-product is carbon dioxide, which has entered the atmosphere in ever increasing amounts.
While carbon dioxide allows the warming rays of the sun to reach the earth, it blocks the excess heat that would normally reradiate out into space. As a result, the atmosphere is gradually growing warmer, thus melting the polar ice caps and raising sea levels. It may be years before scientists determine just how significant the greenhouse effect is -- but they know the process is accelerating. Sea levels are expected to rise at least a foot in just another half-century.