Facts About the Salt Marsh Dieback in Louisiana
What is a “marsh dieback”
and why is it called a “brown marsh”?
Recent aircraft reconnaissance and field surveys indicated that large
areas of salt marsh are turning brown across Coastal Louisiana. This
phenomenon could have profound consequences for economically important
renewable resources and for the citizens of the region. Researchers
and environmental planners from across the state are addressing this
extraordinary and serious process.
What is the cause of the dieback?
Smooth cordgrass (Spartina alterniflora) is the most abundant
plant in the salt marsh of Louisiana. Therefore, any factors that affect
these plants have the capacity for wide area impact. The precise cause
of the current large area browning is not yet known, but there are working
hypotheses that are being evaluated. Researchers are checking historical
and scientific records for similar occurrences in Louisiana and nearby
coastal states. Under normal circumstances smooth cordgrass is highly
resistant to saltwater; however, several climatic factors, especially
the current prolonged drought, interact to stress the plants beyond
their ability to recover. It may be that the stress weakens the plants,
rendering them more susceptible to naturally occurring pathogens. Perhaps
disease factors independent of climate are at play. Each of these possibilities
is being evaluated. As other hypotheses present themselves, they too
will be subject to rigorous scientific scrutiny.
 What
area is affected?
The salt marshes between Point Au Fer near Atchafalaya Bay (Terrebonne
Parish) and Timbalier Bay (Lafourche Parish) are most seriously affected
at present.
If marshes sometimes dieback
naturally, why is this dieback different?
Small areas of marsh are continually and naturally changing,
dying, and regenerating. Also, most of the salt marsh in coastal Louisiana
has been eroding and subsiding for decades from a variety of causes.
The changes witnessed recently are over a much larger geographic area
and much shorter time than current resource managers, fishermen, and
scientists have previously noticed.
What are some of the possible
outcomes?
It is important to realize that any answers to this question
at this time are highly speculative. Coastal marshes, including islands,
tidal pools, and ponds, that provide breeding and nursery habitat for
Louisiana's economically and ecologically important fisheries are still
intact. These areas also serve to protect coastal communities from the
full fury of tropical storms and hurricanes. In the most optimistic
view, the current brown marsh will recover quickly as the dead areas
are recolonized by living plants still in the area. However, if the
dieback continues and recovery does not take place in a timely fashion,
coastal Louisiana's renewable natural resources will be threatened through
large-scale habitat loss. Loss of the vegetation would also result in
rapid subsidence and erosion of the unstable marsh soils, threatening
coastal communities with direct exposure to the catastrophic force of
hurricane winds and tidal surge.
What is being done?
Although we currently do not know the cause of the marsh dieback,
scientists believe it is related to a combination of stressors, possibly
including prolonged drought conditions combined with other unknown biological
or environmental stress factors. A working group of resource managers
and scientists has been established to address the problem of the marsh
dieback.
Satellite Image with the Salt Marsh Study
Area Boundary in Red
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