The Collapsing Delta, Part II

The levees on the river and the navigational canals are probably the largest culprits behind the loss of wetlands in coastal Louisiana. But there are other factors at work:

Oil and Gas Infrastructure: The Delta is home to thousands of offshore oil rigs and onshore wells, significant refinery capacity and thousands of miles of pipelines connecting it all. Canals cut to service these wells have acted as a highway for salt water intrusion. Over the decades, these activities have directly impacted thousands of acres of coastal wetlands, speeding up erosion.

Dams Upriver: Valuable land-building sediments are trapped behind locks and dams on the Missouri, Mississippi and Ohio Rivers. Since 1850, the amount of sediment in the Lower Mississippi River has decreased by more than 70 percent.

Subsidence: Land formed by river sediments naturally subsides and sinks over time. Historically, sediment deposition and build-up from plant growth outpaced the natural subsidence, resulting in coastal land gain. Without land-building deposits from the river, subsidence dominates and massive areas of land are sinking below sea level and disappearing.

Sea level rise: Scientists say that the level of the world’s oceans will rise from one to three feet over the next century. Rising seas combined with subsiding land (called “relative sea level rise”) makes the threat of submergence even greater for the Mississippi River Delta. When wetlands receive sufficient sediment from the river, they can stay above the rising seas.

Hurricanes: Storm surge from Hurricanes Katrina and Rita destroyed hundreds of square miles of coastal wetlands. The continued loss of wetlands will make coastal communities such as New Orleans even more vulnerable to storms.

Oil spill: The BP Macondo well spewed 206 million gallons of oil into the Gulf, affecting hundreds of miles of delicate shoreline, thousands of acres of coastal marsh, and disrupting the communities, economy and wildlife of the coast. The spill will continue to impact the coast and its inhabitants for decades to come.

Nutria: These fast breeding, voracious rodents were introduced into Louisiana for the fur trade, but their impact on coastal wetlands has been disastrous. They burrow into the ground, eat the roots of marsh plants, and devour cypress seedlings, harming wetlands as they go.