The remaining marshes in Mississippi Delta may not be able to withstand the impacts of sea-level rise and may be gone in the years to come. 

The study revealed that 2,000 square miles (5,000 km2) of wetlands in coastal Louisiana are already gone, and the remaining 6,000 square miles of marshlands may drown as it may not be able to survive the rapid sea-level rise. 

There is a tipping point for coastal marshes, wherein the rising of sea levels may lead to its submergence. This was the key finding of a new study by a team of researchers from Tulane University lead by Torbjörn Törnqvist, a Geology Professor of Tulane Department of Earth and Environmental Sciences. The study has been published recently in Science Advances. 

How did this study come about?

Previous studies point that marshes can withstand sea-level rise to as high as half an inch per year. The period of observation of these studies are of a concise period, mostly ten years or less, Törnqvist emphasized. For this particular study, the research team examined the condition of marshes more than 7,000 years ago, when the global sea-level rise was rapid but at the range expected within this century. 

Hundreds of sediment cores were examined to study the relationship between marshes and sea-level rise for the past 8,500 years.

The Tipping Point for Coastal Marshes 

The study concluded that in Mississippi Delta, a rate of sea-level rise exceeding about one-tenth of an inch per year (3 mm/yr) would submerge marshes in a few centuries. 

When the rate of sea-level rise is more than a quarter of an inch per year (7.5 mm/yr), most marshes drown in about half a century. 

"The scary thing is that the present-day rate of global sea-level rise, due to climate change, has already exceeded the initial tipping point for marsh drowning," Törnqvist said. He added that considering the way things are now, it is expected that the rate of sea level will continue to increase rapidly, ensuring the fast disappearance of the marshes in the future.

Urgent, Meaningful Actions 

Despite the prospect of losing the remaining marshes in coastal Louisiana soon, there is still a way to avert the grim scenario. Törnqvist suggests that the most critical action is to radically reduce greenhouse emissions. This will help prevent sea-levels from increasing to rates where marshes will drown and eventually disappear in a matter of decades.

Törnqvist also recommended major river diversions the soonest time possible as it may save at least some portions of the Mississippi River Delta.

This window of opportunity for these actions, however, Törnqvist warns it is nearly fading.

The importance of the Mississippi River Delta 

 Mississippi River Delta has an array of interconnected habitats that are home to more than 2 million people, various endangered wildlife such as the American alligator, Louisiana black bear, piping plover, and green sea turtle. It is also an essential flyway for neotropical migratory songbirds that migrate to the Gulf of Mexico. More importantly, it provides ecological services such as filtering pollutants and absorbing nutrients, replenishing aquifers, preventing erosion, and dissipating storm surges.