Staff Writer Houma Today
The annual pace of wetland loss increased by 25 percent between 2004 and 2009 compared to the previous six years, according to a study released late last year.
Battered by a series of hurricanes and ongoing subsidence, or sinking land, the 68 million acres of Gulf Coast wetlands had the most loss during this period. The study was conducted by the National Fish and Wildlife Service and the National Oceanic and Atmospheric Administration’s Marine Fisheries Service.
Those tasked with studying local wetlands say in a more long-term time frame, the pace has actually slowed simply because there are considerably fewer wetland acres to lose now than 60 years ago.
The study notes that in addition to providing habitat for wildlife, wetlands benefit humans by improving water quality and providing protection to coastal communities. A previous NOAA study found that coastal communities generated $6.6 trillion in 2011, contributing about half to the nation’s gross domestic product that year.
“If you live anywhere around here, you should be concerned about wetland loss. We are not talking about people living down here saying, ‘We need a place for the rabbits and birds.’ We need a place for us. The wetlands protect us,” Barataria National Estuary Program Director Kerry St. Pe said.
Between 1998 and 2004, there was a net loss of 361,000 acres in coastal watersheds of the Atlantic, Gulf of Mexico and Great Lakes wetlands. Losses in the Gulf Coast region at Atlantic watersheds occurred at a rate of 60,180 acres annually, while the Great Lakes region gained wetlands during that period.
There were about 41.1 million acres of wetlands in coastal areas in 2009. Coastal wetlands consisted of about 37 percent of the total wetland area in the first 48 states. About 84 percent of that was freshwater wetlands.
Between 2004 and 2009, wetland areas in coastal watersheds declined by 80,160 acres annually, representing a 25 percent increase over the previous reporting period from 1998 to 2004, according to the study.
In 2009, the 1,630 miles of Gulf of Mexico shoreline had 15.4 million acres of wetlands and experienced a loss of 257,150 acres between 2004 and 2009, accounting for about 71 percent of wetland loss in the U.S. The Gulf region also experienced the greatest rate of loss in the previous study used for comparison.
The Gulf area has the greatest acreage of saltwater wetland area, with 3.4 million acres and just more than 12 million acres of freshwater wetland.
Between 2004 and 2009, the Gulf region lost 161,870 acres of freshwater wetlands and saltwater wetland conversion to open water more than doubled during that time, losing 95,300 acres. Saltwater wetland losses accounted for 99 percent of such losses nationwide.
The study cites hurricanes Katrina and Rita in 2005 and Ike in 2008 as major drivers of wetland loss in the Gulf; residential and commercial development were pegged as the main culprits elsewhere.
St. Pe said a map of the Gulf Coast 300 years ago would look much different with land stretching all the way to the coast.
“The loss began to accelerate at the time we built levees on the Mississippi River,” St. Pe said. “Then you move forward, they didn’t really start to accelerate until the early ’60s and late ’50s into the early ’70s, when oil and gas extraction was really heavy.”
There is also the subsidence of land interacting with rising seas. Subsidence has measured in some parts of Louisiana to be more than a third of an inch annually in Grand Isle, according to NOAA studies.
“The good news is a lot of the subsidence and settling of the earth’s crust is not happening as much as it was because much of the production has moved offshore,” St. Pe said noting the prognosis still isn’t good.
As more saltwater is pushed in, the local lakes get wider. The next hurricane pushes more salt water into the fresh marshes. This kills the plants, destroys the binding root systems and eventually leads to the whole marsh washing away with the tide, St. Pe said.
To estimate the change, the study randomly selected four square-mile plots for high-resolution imagery to document change over each year. The study included more than 2,614 plots nationwide.