The vanishing bayou
Ever-larger levies keep the Mississippi confined to its main channel.Louisiana swamps are cut off from their source.
COCODRIE, L.A. — In this southern Louisiana hamlet you can tell the age of someone's house by how high up in the air it is.
New trailer homes hang 16 feet off the ground on wooden pilings, their wheels whistling in the breeze coming off the Gulf of Mexico. Older homes sit on 10- or 12-foot pilings, while the oldest - the ones that survived Hurricane Andrew - stand on short stilts just a few feet off the ground. Ground that's only three feet above sea level, and "sinking" fast.
The marshes that comprise virtually all of southern Louisiana are vanishing at a staggering rate of 25 to 35 square miles a year. Since 1930, the state has already lost more than a million acres - an area larger than the state of Rhode Island - as marsh and swamp turn into open ocean and lakes.
If the loss continues, Cocodrie and 18 other town sites will be underwater by 2050, along with most of the southern part of the state. The city of New Orleans will sit on an island abutting the hurricane-prone waters of the Gulf of Mexico, a nightmare for evacuation planners.
Those estimates don't take into account sea-level rise predictions due to global warming. Scientists estimate the world's seas will rise by one to three feet over the next century due to global warming. Southern Louisiana is the part of the United States that is most vulnerable to sea-level rise: a low-lying region already experiencing rapid land-loss due to human engineering and industrial projects.
"We're the poster child for climate change in the US," says Len Bahr, executive assistant to Louisiana governor Mike Foster Jr. "Southern Louisiana is sinking at an incredible rate. Any raising of global sea levels is going to jeopardize our efforts to save and protect the coast."
Southern Louisiana's dramatic land loss is due to a combination of man-made changes to marshes, swamps, and water circulation patterns across Louisiana and the 31 other states that share the Mississippi River watershed.
River expanded Louisiana
Much of Southern Louisiana is a vast, low alluvial plain created by the Mississippi River. This land was deposited here bit by bit in the form of river sediments carried from as far away as the Rockies and the upper Midwest. The Mississippi continually created more land at its mouth in a lobe-shape delta.
Every thousand years or so the river would change course, finding a more direct path to the Gulf of Mexico and would begin creating a new lobe-shape delta at its new mouth. The old river channel would become a sluggish bayou and some of the new lands would sink or erode away until the river changed course again. The coast would constantly change shape, but taken as a whole it was continually growing.
Until recently, that is.
Over the past 150 years, people have attempted to control the Mississippi in an effort to prevent flooding, improve navigation, and protect settlements, farms, and industry along the river and throughout the delta. Ever-larger levees have been constructed to keep the Mississippi confined to its main channel. Many branches and bayous were cut off from the main river by the enormous earthen levees, which now stand several stories high on both sides of the river.
"The delta has been sealed off from the river that created and sustained it," says Mark Davis, director of the Coalition to Restore Coastal Louisiana, a Baton Rouge-based nongovernment organization. "The landscape has to be reengineered to reunite the river and its floodplain."
Cut off from the river and spring floods, marsh plants no longer received the sediments, freshwater, and other conditions necessary to remain healthy. For the past century, they have been dying at a rapid rate, and the marshes have turned into lakes or sunk into the Gulf of Mexico.
In recent decades, scientists say the problem has been made much worse by the oil and gas industry, which cut vast networks of canals through the marshes to gain access to fossil-fuel deposits found throughout the delta. Marshes adjacent to the canals then collapsed because of seawater intrusion or died after being sealed off by the raised, artificial banks of the criss-crossing canals.
"If we're to reverse land loss, people need to look at wetlands as ecological systems," says Louisiana State University coastal scientist Gene Turner, who thinks canals - not Mississippi levees - are the biggest cause of wetland loss. "If water levels can't rise and fall naturally, these plants die and the land sinks away."
As wetlands vanish at a rate of more than 40 acres a day, the homes and livelihoods of tens of thousands of bayou residents are put into jeopardy. The enormous Gulf shrimp industry is threatened because shrimp - and most other commercially important fish stocks - rely on the marshes for critical phases of their life cycles.
Although surrounded by enormous levees, the City of New Orleans is becoming increasingly vulnerable to hurricanes as it loses the wetlands that shield it from Gulf storms. The city is home to 1.2 million people, but almost half of its metropolitan core is below sea level. Evacuation is difficult because only a handful of highways span the levees and planners rely on the Superdome and downtown office buildings to serve as "vertical evacuation" sites in the event of a severe hurricane.
"Given the loss of wetlands and the recent tendency toward more intense storms, there are serious questions about whether [hurricane defenses] provide the level of protection that people think they do," says Randy Hanchey, former director of engineering for the Mississippi Valley Division of the Army Corps of Engineers in Vicksburg, Miss.
There are also questions about how to respond to the land-loss crisis.
State and federal authorities are in the midst of an ongoing effort to fund and construct new levee structures that would divert some of the Mississippi's flow into adjacent basins and marshes. They hope this will slow or reverse land loss by rejuvenating marshes with sediments and freshwater.
Under the 1990 Coastal Wetlands Protection and Wetlands Act - sponsored by Louisiana Sens. John Breaux and J. Bennett Johnston - some $240 million in federal and state funds have been invested in 81 projects to protect the coast, including diversions, shoreline stabilization, and sand-dune construction. But complicated inter-agency relationships and a shortage of state matching funds have hampered progress.
These projects - together with two much larger federal diversion projects costing another $130 million - will only prevent an estimated 22 percent of the expected land loss over the next 50 years.
Order of magnitude
"It's not that nothing's being done, it's just that it's an order of magnitude less than what is needed," Mr. Bahr says. "We need to think on a much larger scale."
A joint federal-state task-force study proposes a vast array of projects to re-engineer the movement of water and sediment across the entire southern half of the state. Gates, locks, pumps, dams, diversion structures, and artificial reefs would be constructed; shorelines, river banks, and entire Gulf shore islands would be stabilized - all with the intention of restoring more natural drainage patterns to the region.
The price tag is an estimated $14 billion, much of which would have to come from federal coffers. Getting that kind of money would be tricky for any state. Louisiana is further handicapped by its "colorful" politics - a euphemism for a legacy of corruption and graft that has lowered the state's credibility.
Nor does it help that the state continues to issue new permits for canal dredging to the oil and gas industries - one of the largest causes of land loss in the state.
Oliver Houck, director of the environmental law program at Tulane University in New Orleans, says a great deal could be accomplished relatively cheaply, if state lawmakers required companies to backfill canals and other marsh facilities at the end of their productive life - a difficult move since the oil and gas industries have considerable political influence in the state.
"Louisiana argues that the country must help pay for wetland restoration, but refuses to take measures to protect marshes from further losses," Mr. Houck says. To have credibility when seeking billions in federal funds, skeptics argue, the state needs to show leadership in wetlands protection.
"We may have to wait for a major disaster before people will really want to do anything about this problem," says Mr. Davis, whose organization has played a leading role in rallying support for the issue. "We want to put everything we can in place so that when that day comes, we can tell people exactly what needs to be done."