Global Climate Change and Its Impact on Louisiana's Coastal Wetlands

HEAT, HEAVY RAINS and occasional storms, floods and droughts have always been part of coastal Louisiana's climate. But global climate change could intensify this historical pattern, damaging the region's vital but already stressed wetlands.

In this special issue of WaterMarks, we examine this emerging, and at times controversial, subject. We ask questions, talk to scientists, look at models, and explore how this worldwide phenomenon may harm the fragile estuaries, marshes and mangroves that form the largest delta in the United States. We also consider how global climate change could affect current and future efforts to restore these coastal resources.

A satellite image of North America with Hurricane Andrew making landfall on the Louisiana coast

Hurricane Andrew as it makes landfall on the Louisiana coast.
Courtesy of NASA

International Concern

Natural and human forces drive climate. Although Earth's climate has been evolving naturally for millions of years, evidence suggests that human activities such as burning fossil fuels and clearing forests are altering global climate at an alarming rate.

Areas of Coastal Erosion

This map is a preliminary classification of annual shoreline erosion throughout the US, in coarse detail and resolution. The areas most vulnerable to future sea-level change are those with low relief which are already experiencing rapid eroison rates, such as the Southeast and Gulf Coast.

Louisiana's coastline is eroding more rapidly than any other coastal area of the United States.
Courtesy of NOAA

Because changes in global climate — warming temperatures, rising sea level, and variations in rainfall and storm patterns — could have tremendous human and ecological impacts, scientists and policymakers around the world have embarked on an unprecedented effort to study and address this issue.

Leading this effort is the Intergovernmental Panel on Climate Change (IPCC), an international consortium of scientists established by the United Nations in 1988. Charged with the task of reviewing and assessing the state of climate change science, the IPCC has published three comprehensive reports, in 1990, 1996 and 2001. Seventeen national academies of science, including the U.S. National Academy, recognize the IPCC assessments as the most comprehensive and objective reports on this controversial subject.

1956 – 1990 Louisiana Coastal Land Loss

A map showing land loss and gain over coastal Louisiana

Looked at in detail, the red areas of this map show those parts of Louisiana that were lost between 1956 and 1990.
Courtesy of USGS

Consensus Among Scientists

There is widespread consensus today in the international scientific community that the world's atmosphere is warming. The IPCC reports that global average temperature has increased by about 1 degree F in the last 140 years, and is expected to rise by 2.5 to 10.4 degrees F by the end of this century.

Scientists also agree that sea level is rising. Studies show that sea level has increased by 10 to 25 cm — 3.9 to 9.75 inches — in the last hundred years. The IPCC predicts that sea level will continue to rise into the next century, a crucial factor for Louisiana's coastline and wetlands.

Uncertainty remains, however, regarding patterns of precipitation. The two climate models generally used by scientists differ dramatically on projections of rainfall. Because fresh water is an essential ingredient for the survival of wetlands, this will be a key issue for future restoration projects.

Predictions of storm patterns are also uncertain. Even if the frequency and intensity of storms remain constant, those considered minor by current standards could have major consequences in Louisiana as rising sea levels intensify tidal surge, erosion, flooding and saltwater intrusion.

Potential Inundation of Louisiana

A map of Louisiana with the southern fourth colored red indicating an inundation of 1.5 meters

A 20-inch rise in sea level would have devastating consequences for the Louisiana coastline, much of which would be inundated (area in red).
Courtesy of EPA

Summary of Articles

In the following articles, we explore what climate change could mean for Louisiana's coastal wetlands. First, we look at the science behind climate change projections and provide predictions for the region in our article "Grappling with the Unknown."

In "Defining the Threat," we describe how Louisiana's low elevation, high rate of subsidence and deteriorating wetlands make it more vulnerable to the effects of climate change than any other part of the U.S. We consider how Breaux Act projects such as barrier-island marsh restorations and river diversions may help address the consequences of climate change in our article "Searching for Solutions."

Finally, in the "WaterMarks Interview," we talk with Dr. Robert Twilley, a biologist at the University of Louisiana in Lafayette and a leading expert on climate change in the Gulf Coast. Twilley emphasizes the need and value for decision-makers to include climate change as they plan and fund future projects.