Diversion Critics Question Impact on Economy, Environment
TO THE MODERN mind accustomed to highway speeds, time in the Louisiana wetlands may appear as fixed and eternal as the unblinking eye of an alligator. But the rate of change is quickly accelerating as levees, canals and other manmade structures contribute to the wetlands' rapid decline.
To counteract their detrimental impact, advocates of coastal restoration strongly urge using diversions to replicate natural processes and rejuvenate the wetlands. However, when humans impose control over nature, disputes inevitably erupt over how to exercise that control and whom to hold responsible for the consequences. Debates over using diversions concentrate on four issues: fisheries, water quality, flooding and navigation.
Oyster fisheries benefit in the long run as diversions enhance and sustain Louisiana's coastal ecosystem.
Courtesy of LA Dept. of Tourism
Fisheries
Historically, oystermen have been proponents of river diversions, citing as benefits the reversal of saltwater intrusion, the increase in areas of optimal salinity for oyster production, and the decrease of predators found in high-salinity areas. Lately, however, oystermen have voiced concern that modern large-scale diversions damage present-day fisheries by changing the salinity of estuarine waters, resulting in the displacement of aquatic populations and the reduction of catch. "Restoring normal and healthy salinity levels throughout an estuary is an important goal of diversions," confirms Allen Bolotte, district conservationist for the Natural Resources Conservation Service. "We'd like to return marshes to the graduated levels of an earlier time, when the interface of fresh water and salt was optimal. This would promote vegetative growth, marsh development, and a greater diversity of plants, animals and fisheries throughout the coastal zone."
For Bolotte, and many others studying the issue, a key question is how to ensure the sustainability of coastal Louisiana while protecting the livelihoods of people who depend on the wetlands today. "In the long run, diversions enhance habitat and increase productivity," Bolotte says, "but in the short term, in the life of coastal fishermen relying on a daily catch, their effect can be costly and disruptive."
Because oysters grow in stationary beds, unable to move when salinity levels change, oystermen are especially vulnerable to the effects of diversions. Acknowledging that people who suffer economic damage are justified in seeking reasonable compensation, the state of Louisiana and other concerned parties have devised a method for calculating losses incurred by oyster leaseholders that considers the value of both the oyster beds themselves and the crops they support.
Oysters Available on the Public Grounds East of the Mississippi River
Courtesy of LaDNR CRD
Water Quality
By mid-20th century, pollution pouring into the Mississippi from agricultural run-off, municipal sewage systems and industrial wastes earned the river a reputation as a dirty toxic soup. Although the quality of river water began to improve after the passage of the Clean Water Act in 1972, fears about contaminants such as insecticides, herbicides and fertilizers persist.
Scientific studies over the past decade document the health of the river. Tests for 100 toxic chemicals revealed the presence of only five, and these in low concentrations. Trace minerals detected in fish are well within safe limits for edibility, and concentrations of modern pesticides fall below EPA standards for drinking water. Throughout the watershed, improvements to waste treatment facilities have dramatically reduced bacterial levels in the river.
Overabundance of nitrogen and phosphorus could cause excessive algal growth harmful to the marsh ecosystem, but, as Bolotte points out, "At their present scale, diversions simply do not convey enough water into the wetlands to make algal blooms a threat." Wetlands have been able not only to absorb river-borne nutrients but actually to benefit from them. Furthermore, preliminary research at Louisiana State University indicates that filtering river water through the marshes decreases the nutrient load carried by the Mississippi, thereby reducing the size of the hypoxic area, or "dead zone," in the Gulf of Mexico.
Flooding
A unified system of levees along the Mississippi River allows millions of people from Baton Rouge to the Gulf to enjoy safety from floods. To them, purposefully breaching the levees may appear to be folly.
The major diversions can control the release of water, however, adjusting the timing and volume to local conditions and to meet specific needs. For instance, increasing flow might counter saline-borne threats such as brown marsh and red tide, or restraining it could accommodate the needs of fisheries or seasonal sportsmen. Channel banks and physical barriers in the receiving basins regulate outflow speed and direction, further diminishing the threat of flood and preventing unintentional erosion.
Navigation
Reducing water levels in a navigation channel that cuts through the wetlands could restrict ship traffic and require more frequent dredging, or force the relocation of the channel. Presently, however, diversions do not draw enough water from the river to threaten navigation. Implementing a huge diversion such as the Third Delta at Donaldsonville would certainly increase federal navigation maintenance costs. Shipping might also have to adapt by utilizing new channels if large diversions cause changes in the geography of the coastal region.
Balancing Needs for Sustainability
Diversions attempt to replicate the natural processes that build healthy wetlands while limiting potential damage to the people and economy of coastal Louisiana. Inevitably there are conflicting opinions over setting priorities and managing change. "For the benefit of the entire region," says Bolotte, "we need to develop consensus among the various concerned parties and make wise choices that assure the vigor and sustainability of the wetlands."