Louisiana's salt marshes, which had already been degrading at an alarming pace due to human activities, have suffered tremendous losses, in some cases leading to permanent marsh ecosystem loss due to BP's 2010 Deepwater Horizon oil disaster, according to a study published Monday by the Proceedings of the National Academy of Sciences.
The study found that "oil concentrated on the marsh edge enhanced the rate of decline of Louisiana salt marshes" and some areas had double the natural rate of erosion because of the effects of the oil.
“Louisiana is already losing about a football field worth of wetlands every hour, and that was before the spill,” said Brian Silliman, a University of Florida biologist and lead author of the study, referring to the "oilpocalypse" when 4,900,000 barrels of crude poured into the Gulf of Mexico.
“When grasses die from heavy oiling, their roots, that hold the marsh sediment together, also often die. By killing grasses on the marsh shoreline, the spill pushed erosion rates on the marsh edge to more than double what they were before. Because Louisiana was already experiencing significant erosive marsh loss due to the channelization of the Mississippi, this is a big example of how multiple human stressors can have additive effects," states Silliman.
The study's findings warn that further oil damage and human activity will bring about increased destruction of this important ecosystem.
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Marshes are the life’s blood of coastal Louisiana because they act as critical nurseries for the shrimp, oysters and fish produced in these waters while helping to sequester significant amounts of carbon. They also protect coastlines from flooding and guard estuarine waters from nutrient pollution.
But the marshes have been suffering for decades as a result of the channelization of the Mississippi River, which has starved them from needed sediments to deter erosion.
Then came the oil spill.
Researchers observed minimal oil on the surfaces of grasses located more than 45 feet from the shoreline, indicating that significant amounts of oil did not move into interior marshes.
Instead, the researchers found that the tall grasses along the marsh edge acted as wall-like trap to incoming oil slicks, concentrating oil on the marsh edge. This concentration of oil on the shoreline protected interior marshes from oiling but worsened already extreme erosion on the shoreline. As oiled plants died, their roots that hold tight to the sediment perished as well. Already eroding sediment was now exposed to wave action without the effect of the gripping plant roots.
The result: elevated erosion rates for 1.5 years that averaged more than 10 feet of shoreline loss per year — double the natural rate for this area.
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GRITtv: Unheard Voices From the Gulf Coast
About this episode One region supplies the nation with 30% of its oil and gas and 30% of its seafood. Yet, a football field?s worth of land is lost every 40 minutes in the southeast bayous due to pipeline canals made by big oil companies. The land is severed, raped, and disjointed from commercial interests capitalizing without consideration for its people, namely the United Houma Nation. Now add the BP oil spill into the equation. Suddenly prosperous Mother Nature is choked by exploitive enterprise.
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Gulf Coast Restoration Network:
Throughout the Gulf States, and the entire United States, we have been losing wetlands at an alarming rate. The U.S. Fish and Wildlife service estimates that over half of the wetlands in the Gulf of Mexico were lost between 1780 and 1980. An estimated 396,800 acres of freshwater wetlands were lost between 1998 and 2004 in the Gulf of Mexico. For comparison, this rate of loss was 6 times higher than the rate of freshwater wetlands losses in the coastal watersheds of the U.S. Atlantic Coast. The estimated wetland losses for all wetland types in the Gulf of Mexico were almost 25 times higher than those estimates for the Atlantic (371,000 acres versus 15,000 acres lost).
This rampant wetland loss is due to many reasons, most of which are caused or exacerbated by human influence. Some of the causes of wetland loss include:
- Construction and Development
- Salt water intrusion
- Oil and Gas Canals
- Sea level rise
- Hurricanes and other storms
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Wetlands are extremely valuable to society. Wetlands can decrease flooding , remove pollutants from water , recharge groundwater, protect shorelines, provide habitat for wildlife , and serve important recreational and cultural functions. Taken as a whole, it is estimated that the aggregate value of services generated by wetlands throughout the world is $4.9 trillion per year (Costanza et al. 1997).
If wetlands are lost, the cost of replacing them can be extremely expensive, if at all possible. Lost wetlands can result in a city having to invest more money in drinking water treatment or higher costs to citizens for flood insurance.