Tom Yulsman is co-director of the Center for Environmental Journalism at the University of Colorado. His work has appeared in a variety of publications, including the New York Times, Washington Post, Climate Central, the Daily Climate and Audubon.
Listeners to National Public Radio, and readers of many newspapers, woke up yesterday morning to news that withering wetlands, rising sea level, and raging hurricanes have been causing cemeteries along the Louisiana coast to wash away. Here’s how the Associated Press described the situation:
LEEVILLE, La. — As a young adult, Kathleen Cheramie visited her grandmother’s grave in a tree-lined cemetery where white concrete crosses dotted a plot of lush green grass just off Louisiana Highway 1.
Now, the cemetery in Leeville is a skeleton of its former self. The few trees still standing have been killed by saltwater intruding from the Gulf. Their leafless branches are suspended above marsh grass left brown and soggy from saltwater creeping up from beneath the graves.
Wetland loss in Louisiana, and the resulting swamping of communities like Leeville, is not a particularly new story. In 2011, for example, a U.S. Geological Survey report found that the state had lost 1,883 square miles of coastal land between 1932 and 2010—an area almost the size of the state of Delaware. From 1985 to 2010, the report found a rate of wetland loss amounting to 16.57 square miles every year. That works out to the loss of an area the size of one football field every hour.
“Coastal Louisiana wetlands make up the seventh largest delta on Earth, contain about 37 percent of the estuarine herbaceous marshes in the conterminous United States, and support the largest commercial fishery in the lower 48 States,” according to the USGS report. “These wetlands are in peril because Louisiana currently undergoes about 90 percent of the total coastal wetland loss in the continental United States.”
Louisiana’s coastal wetlands began eroding when canals were dug for oil and gas exploration, allowing saltwater to intrude into freshwater marshes and kill them off. The problem was exacerbated by damming along the Mississippi, and construction of levees, which together tended to impede sediment from flooding out into the wetlands and replenishing them. In recent years, coastal Louisiana has taken big hits from strong hurricanes and other extreme storms, causing land loss to accelerate.
What about the role of sea level rise due to global warming? The 2007 report from the Intergovernmental Panel Report on Climate Change put global sea-level rise at about 1.7 millimeters per year over the past century. But along the Louisiana coast, the sea has risen almost 10 millimeters per year, according to the National Oceanic and Atmospheric Administration. The difference comes from subsidence: The mud of the marshes is sinking under its own weight and is not being sufficiently replenished with new sediment. This makes the coast ever more vulnerable to the impact of storms.
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