Scientists: Rising seas threaten to swamp Louisiana’s coastal restoration efforts

Louisiana faces a double threat of higher ocean levels and a sinking delta
Published: Nov. 20, 2023 at 9:58 PM CST
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NEW ORLEANS (WVUE) - Louisiana is spending billions of dollars on, arguably, one of the world’s most ambitious environmental restoration efforts, restoring barrier islands, ridges and marsh along its rapidly-disappearing coastline.

Rising seas could threaten that massive effort.

The world’s coastal wetlands and coral reef islands could be swamped by sea levels driven by climate change, according to recent study by an international team which included researchers at Tulane University.

“We have to address climate change,” said Torbjorn Tornqvist, the Vokes Geology Professor in Tulane’s Department of Earth and Environmental Sciences.

“And for us, there is more at stake than for most other places around the world.”

The findings show that the future of marshes and other low-lying coastal areas depends heavily on whether global warming since the start of the industrial age can be limited to less than 2 degrees Celsius (3.6 degrees Fahrenheit).

The paper finds coastal areas are unlikely to keep pace with sea level rise exceeding about one-quarter of an inch per year.

“”How the global wetlands will look by the end of the century in the year 2100 will depend very, very much on how much warming is going to happen during that time,” Tornqvist said.

The study finds temperatures higher than 3.6 degrees Fahrenheit would likely lead to widespread collapse of the world’s marshy areas, mangroves and reefs, with sea levels rising at double today’s rates.

“Wetlands cannot keep up with those rates,” Tornqvist said. “They will probably drown within perhaps, half a century.”


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For his role in the research, Tornqvist examined the geological history of coastal wetlands through other periods of rising oceans.

Since 1932, for a variety of reasons, Louisiana has lost an estimated 2,000 square miles of land.

The most significant causes include loss from hurricanes, saltwater intrusion from oil field canals dug decades ago, interruptions in tidal flow, and erosion.

Long before it became a superhighway of commerce, the Mississippi River dumped mountains of sediment in annual spring floods to create the Louisiana delta.

Cut off from the river by its straightjacket of levees, the delta sinks.

The dramatic rates of land loss have, so far, had relatively little to do with what most people think of a sea-level rise.

Scientists tell us that since 1900, the seas have risen by an average of 5-8 inches. Some areas of Louisiana’s delta, disconnected from the river, sank by several feet during that time.

However, more rapid rates of sea level rise in the future threaten to swamp Louisiana’s ambitious efforts to restore the coastline.

“Sea level rise will continue even in the best-case scenario,” Tornqvist said. “But we still have an opportunity to prevent the rate of sea level rise to accelerate to really dangerous rates.”

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