Louisiana is sinking

Scientists estimate that 1295 square kilometres of Louisiana's wetlands will disappear in the next 50 years. Image: Shutterstock

Though it may seem like a paradox, a lack of water could drown coastal Louisiana. Every hour, an area of land approximately the size of a football field disappears. Mostly to blame are the extensive levees built along the edges of the Mississippi River to prevent flooding of the surrounding areas and maintain navigation routes, which means the area does not have sufficient sediments to stay above water. Comprehensive plans have been made to save the endangered areas, and the first of them have already been implemented.

Albert Naquin’s home is often underwater. During the past six years, the southern Louisiana town he lives in has been flooded five times, and things only seem to be getting worse. Isle de Jean Charles is a small finger of land in the midst of one of the world’s most vulnerable wetland areas. Every day, the open ocean of the Gulf of Mexico is moving a little bit closer to the battered houses.

Channels that have cut through the surrounding wetlands have weakened the buffer zone for hurricanes, and now storms submerge the land, slowly eating away at the isle. Where there used to be land, people now sail around in boats, and the only road leading to Isle de Jean Charles is underwater several times a year.

“The road is probably flooded 30 per cent of the time,” says Albert Naquin, tribal chief of the Biloxi-Chitimacha Indians, who have lied in the area for centuries. But 250 residents have left the community since 2002, leaving only 70 today, many of whom are considering leaving before it’s too late. “Sooner or later our community will die,” Naquin says. “And with that, our Indian culture will die.” The problem of lost land is unfortunately not unique to the Isle de Jean Charles — Louisiana shrinks every day. The coastal wetlands, a unique ecosystem of marshlands and swamps filled with herons, alligators and trout, are being absorbed by the Gulf of Mexico — every hour, the area the size of a football field disappears. Since 1930, 4737 square kilometres of land have been converted into open water, and the coast has crept closer to New Orleans. Most modern maps of Louisiana show the coastline as it appeared in 1930, so relying on a roadmap could make for a very watery drive.

“It’s the largest land loss currently on the planet,” says Val Marmillon, the managing director of America’s Wetland Foundation, an organisation fighting to save wetlands.

The massive land loss is not only threatening to destroy an entire ecosystem, including dozens of endangered animal species, but it could also severely affects local residents as well as the greater U.S. economy. The fishing operations in the area, which account for an estimated 24 per cent of the fish, crayfish and oysters consumed in the United States, will likely be severely affected. Also, the oil and natural gas industry, which has an annual economic impact of approximately $365 billion (US $385 billion) and employs 1.3 million people, will be threatened. Finally, up to 2 million people are at risk of having to leave their homes. The problem is unfortunately not unique to Louisiana — most of the world’s largest river deltas are facing similar crises, derived largely from human development and modifications to the river’s natural flow.

Impact of the levees

In the late 1800s and early 1900s, New Orleans officials built up a levee system to protect the system from being inundated with water during the river’s seasonal flooding. Then, in 1927, the rest of the Mississippi River watershed, from Illinois to Louisiana, experienced some of the worst flooding in American history, due to a year of heavy rains. Portions of 10 states along the river were underwater. The American authorities reacted promptly, passing legislation that enabled the federal government to manage flood risks countrywide. Approximately $310 million (US $325 million) was appropriated to construct floodways, spillways and diversion channels throughout the region.

What wasn’t understood at the time, though, was the negative impacts of such development, which was widespread at the time and carried out with little thought given to the natural environment. The levees and diversion systems cut the wetlands of Louisiana off from the Mississippi River, their source of life. Seasonal flooding is necessary in the life cycle of these wetlands, which are deeply dependant on the nutrients and sediments that the river brings along. The seasonal influx of fresh water also keeps salt water at bay, maintaining the low salinity levels that wetland plants need to survive. With its soft soils, southern Louisiana has always been sinking under its own weight, but new layers of mud created by river sediments compensated for the sinking, stabilising ground levels and allowing the wetlands to flourish, which held the ocean at bay.

Coastal Louisiana has always been at the mercy of the Mississippi. The river is a dynamic builder, adding new land by depositing its sediments, but it has also left areas in a state of decay when it has been obstructed. The change before the levees were built, though, was gradual. In the past 5,000 years, the river has added an average of two to five square kilometres of land a year, up until the 1930s when the levees were built. Since then, approximately 33 square kilometres of land have been lost a year.

Both natural nutrients that fertilise the marsh plants and artificial ones from industrial complexes and agriculture — such as nitrate — are now being carried downstream, leaking into the Gulf of Mexico. That has created dead zones, where all life has disappeared because of oxygen depletion. As salt water invades the wetlands, freshwater plants die because of the high salt content, and without their roots, the soil slowly erodes. In 2005, Hurricanes Katrina and Rita dealt another devastating blow, transforming 513 square kilometres of marsh into open water. Even with restoration efforts, scientists estimate that another 1295 square kilometres could turn into ocean by 2060. By then, New Orleans will be close to open water, protected from future storm surges and ocean level rises only by its levees, which are already vulnerable because of riverbank erosion.

The unfortunate irony is that the wetlands themselves would protect against flooding, had they not been cut off from the Mississippi River. When a hurricane or storm surge hits, the wetlands function like a sponge, absorbing huge quantities of water and energy. Without this vital natural landscape, the levees must be taller, which leads in turn to further sinking of the soft soil. (Continued on page 2)