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How are Louisiana Wetlands Changing?
New Map Shows Losses and Gains Since 1932
Released: 6/2/2011 2:00:00 PM

Contact Information:
U.S. Department of the Interior, U.S. Geological Survey
Office of Communication
119 National Center
Reston, VA 20192
Jennifer LaVista 1-click interview
Phone: 303-202-4764

Gabrielle Bodin 1-click interview
Phone: 337-266-8655

Reporters: Want an aerial or boat tour of Coastal Louisiana Wetlands? Contact Jennifer LaVista at 720-480-7875. 

Coastal Louisiana has lost a wetland area the size of Delaware, equaling 1,883 square miles, over the past 78 years, according to a new U.S. Geological Survey National Wetlands Research Center study. 

Twenty-five percent of the wetland area present in 1932 was lost by 2010. If this trend were to continue, Louisiana would lose a wetland area larger than the size of the island of Manhattan every year. 

The USGS National Wetlands Research Center has developed a new map that illustrates wetland losses and gains on the Louisiana coastline from 1932-2010. This product provides opportunities to better understand the timing and causes of wetland loss, which are critical for forecasting landscape changes in the future. This color-coded map can be found online

"This issue is vital to the citizens of southern Louisiana, and Terrebonne Parish in particular," said Louisiana Representative and Chair of the House Natural Resources and Environment committee, Gordon Dove. "Products like the USGS wetlands change map are essential for the protection and restoration of our coastal areas." 

"By understanding land change on the Louisiana coast, decision makers can make informed choices about how to actively manage the land to help reduce future loss," said Phil Turnipseed, Director of the USGS National Wetlands Research Center. "We can’t manage what we don’t measure."

Louisiana currently experiences about 90 percent of the total coastal marsh loss in the contiguous United States. Land loss rates on the Louisiana coast have slowed from an average of more than 30 square miles per year between 1956 and 1978, to an estimated 11.76 square miles per year from 1985 to 2004. When the hurricanes of 2005 and 2008 are factored in, the trend increased the amount of land lost to 16.57 square miles per year from 1985 to 2010. If this loss were to occur at a constant rate, it would equate to losing more than a football field every hour. The combined loss from the storms of 2005 and 2008 equal a land area the size of Chicago. 

The areas undergoing the greatest wetland loss include the Breton Sound, Barataria and Terrebonne basins, south of New Orleans. Communities in that vicinity include New Orleans, Thibodaux, Houma, Golden Meadow and Grand Isle. The impacts on human populations, the oil and gas infrastructure, fisheries and wildlife will be considerable if coastal wetlands continue to disappear. 

There are many causes of wetland loss, but one of the primary causes is sediment deprivation caused by the dams, levees, and channels erected along the Mississippi River and its tributaries. These projects, including the Louisiana facilities initiated in response to the flood of 1927, have resulted in a 50 percent decrease in sediment delivered to the Louisiana coast. 

In areas where sediment has been allowed to reach coastal wetlands, land gain has been observed.  The Wax Lake and Atchafalaya Deltas receive regular sediment deliveries and have steadily gained land from the 1970s to present. 

The current land area decrease estimate of 1,883 square miles is slightly less than some previous measurements of loss. Previous studies had estimated total loss of 1900 square miles, which does not include the effects of hurricanes in 2005 and 2008. Improved methodologies and techniques have enabled the USGS to quantify coastal land and water changes more accurately. Scientists can now distinguish these changes from normal environmental variability, such as wind and tide driven changes, which can affect the aerial photography and satellite imagery on which the current estimate is based.

Coastal Louisiana wetlands support the largest commercial fishery in the lower 48 states and provide critical habitat to many threatened and endangered species. The delta is the seventh largest on Earth and the wetlands help to buffer populations and property from hurricanes and other storms. The U.S. Census Bureau estimates that about half of Louisiana’s 4.5 million people live in coastal parishes.

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