Louisiana’s coastal wetlands have had a rough time of it. They’ve been eroding away for years; when the nation’s attention was riveted on New Orleans as Hurricane Katrina hit in 2005, the entire country got a lesson in how important they are in providing a buffer against storm surges. Now they’re facing another threat from the oil leak in the Gulf of Mexico.
Louisiana, which has about 40% of the country’s coastal wetlands, is losing roughly 40 square miles or more of them each year. Manmade changes to the Mississippi River are part of the reason; the Mississippi drains 40% of the continental US, and it once carried huge amounts of silt that it deposited in the coastal marshlands. As levees were built beginning in the 1700s to protect settlements from the river’s flooding, and as more and more navigation channels were constructed, the river was able to deposit much less of the sediment and nutrients that had built up and maintained the wetlands. The forces of the sea and seasonal hurricanes, meanwhile, cause damage from the other direction that the natural processes are increasingly unable to repair.
It’s estimated that for every acre of coastal wetlands that is lost, the storm surge from a hurricane or tropical storm increases by about a foot. After Katrina, aerial surveys by the US Geological Survey showed that the Chandeleur Islands—one of the first places the oil reached—had lost about half of their land area in the storm.
The oil, of course, won’t erode the wetlands directly, but will more likely suffocate them. Oil on the leaves of marsh-dwelling plants can hinder their ability to absorb carbon dioxide and release oxygen, and enough oil reaching the roots can poison them—and, since the plants are what holds the fragile marsh together, loss of plants means greatly accelerated erosion.
This Associated Press article includes some insightful interviews with coastal protection officials, ecologists, and fisherman in Louisiana who are closely watching the oil spill and who speculate on its possible consequences.