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Threats To The Mississippi River
Threats to the Mississippi River basin affect more than birds and wildlife. They affect jobs, the economy, and public safety. About a quarter of the nation's seafood catch outside of Alaska comes from the gulf. Despite a sinking Louisiana coast that is rapidly eroding inland, more people continue to move toward the coast. Three million people now live along the Louisiana coast, and 90% of them in homes less than three feet above sea level. Further, the massive oil and gas pipeline infrastructure along the coast is increasingly vulnerable to storm surges as subsidence continues. And, as the Gulf dead zone grows and critical tidal wetland habitat erodes, coastal fisheries decline.
Threats to the Mississippi River Basin are primarily related to sediment, pollution, and habitat alteration:
- Sediment
Perhaps the most vulnerable points in the river system are the Louisiana coastal wetlands where the river enters the gulf. These coastal wetlands comprise one of the most important wetland ecosystems in the world. Totaling over 3 million acres, this area includes 25% of the nation's wetlands, and 40 percent of the country’s coastal marshes outside of Alaska. For eons, the Louisiana coast has benefited from the natural cycle of sediment-laden spring flows from the Mississippi Basin that re-nourished these wetlands to maintain a dynamic balance. Today, 29 locks and dams trap significant portions of that sediment upstream, and the 1,600 miles of levees channel what sediment that remains directly to the Gulf. As a result, the Louisiana coast is rapidly sinking into the Gulf, as the re-nourishing sediments no longer pass through the coastal marshes and wetlands. Some 16,000 acres of wetlands are lost there every year, totaling 80% of all wetland losses nationally. We have now seen the human and ecological cost of this increased vulnerability to major storms like Hurricane Katrina.
- Pollution
All municipal, industrial and agricultural runoff from the entire river basin is eventually deposited into the Gulf near the Louisiana Coast. This polluted runoff, which is no longer being trapped in coastal wetlands and wetlands throughout the river system that are isolated by levees, has produced a massive dead zone off the Louisiana coast. This dead zone size has averaged more than 5,000 square miles each year since 1985 - an area about the size of Connecticut - and engulfed nearly 8,000 square miles in 2008.
- Habitat Alteration
The Mississippi River and its major tributaries have been significantly altered for flood control and to support navigation. As a result, virtually all of the Mississippi floodplain has been developed, drained or modified. More than 90 percent of floodplains are blocked by levees, making landowners dependent on the Army Corps of Engineers for flood control, and destroying floodplain-associated habitats such as bottomland forests critical to many species of nesting and migrating birds. The majority of America's grain and 92% of its agricultural exports are transported on the Mississippi River navigation system, also managed by the Corps.
Habitat is also altered by oil and gas pipelines and associated energy development along the Louisiana Coast; the region delivers about 25% of the nation's energy supplies each year. Removal of underground oil and gas accelerates natural subsidence. A massive complex of canals has been dredged to service this energy infrastructure. These canals hasten erosion from storms, and encourage saltwater intrusion further inland, accelerating the die-off of critical soil-stabilizing wetland vegetation.
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