Land Area Change in Coastal Louisiana (1932 to 2010)
Coastal Louisiana: A vast expanse of wetlands and fertile
habitats vital to the ecology and
economy of the region and Nation.
Coastal Louisiana wetlands contain over
one-third of the coastal marshes and
support the largest commercial fishery in
the lower 48 states. These wetlands protect human
populations and provide critical habitat to many threatened and
endangered species. However, these wetlands are in
danger as Louisiana currently experiences
more coastal wetland loss than all other states in the contiguous
United States combined.
Coastal Louisiana wetlands are critical to the
economy, the security, and the well-being of the
entire North American Continent. One-third of the oil
and gas production or transport in the
United States occurs in coastal Louisiana. Five of the
Nation’s largest ports, which support
approximately 20% of the Nation’s waterborne commerce, are
located here. More than 5 million
migratory birds traveling on the Mississippi and Central
flyways make this coastline their home
during the winter. These wetlands truly are one of America’s
greatest treasures.
Scientists at the United States Geological Survey’s National
Wetlands Research Center have been using many
data sources to study Louisiana’s wetlands.
In a recent study of land area change, wetland change has been
quantified over a 78-year period from 1932-2010.
The findings of this research have given scientists
the ability, not only to quantify the amount of
wetland loss, but also to identify the time period in which it
was lost. This temporal resolution, or
time sequence, helps scientists to understand what might have
caused these losses. The new
dataset provides the ability to observe patterns such as gradual
shoreline erosion, and distinguish
them from losses due to specific events, such as hurricanes. This
time series of data shows the
gradual loss of wetland areas in the deltaic Plain of the
Mississippi River. The red on the map
indicates land loss.
From 1932-2010, coastal Louisiana has experienced a net decrease
in wetland area of 1,883 square miles. This net
change in land area amounts to approximately 25% of the
1932 land area or an area approximately equivalent to
the entire state of Delaware.
In more recent analyses, the rate of wetland loss from
1985-2010 has averaged 16.6 square miles
each year. If this loss were to occur at a constant rate,
it would equate to losing more than a
football field every hour.
Despite multiple stressors and high rates of sea
level rise and subsidence, some land gain has
been observed in coastal areas that receive direct sediment
delivery from the Atchafalaya and
Mississippi Rivers. Two examples of active land and delta
formation occur in the Atchafalaya
River and Wax Lake Deltas. This time series of imagery
shows the gradual building of these
deltas, which receive regular sediment.
The new land is shown in green.
Deltas are dynamic and have the capacity to be resilient.
Subsidence, sea level rise, hurricanes
and other stressors affected the Mississippi River Delta for
centuries prior to alteration of the
system by humans, yet the delta built despite these stressors.
The staff of the U.S. Geological Survey National Wetlands
Research Center continually strives
to improve methods, models, monitoring, and technical expertise
needed by decision-makers to
remediate and save our rapidly disappearing coastal zone.
Scientists and policymakers are
beginning to harmonize natural landscape functions with human
needs to guide management of
healthy ecosystems and a sustainable delta.
Only by understanding our natural resources, can we
ensure the vitality of the Nation’s economy, the health of its
environment, and the well-being of its citizens.