Wednesday, February 8th, 2023
Wednesday, February 8th, 2023

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Coastal Louisiana has Lost Vast Wetlands

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

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

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.

“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

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 1,900 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

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


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