New ‘time travel’ study reveals future impact of climate change on coastal marshes

Scientists are usually forced to rely on computer models to project the long-term effects of rising seas. But an unexpected set of circumstances enabled a real-world experience along the Gulf Coast.

An extensive network of nearly 400 monitoring sites was established along the Louisiana coast following Hurricanes Katrina and Rita. Since then, the rate of sea-level rise in the region has exceeded 10 mm (half an inch) – at least three times the global average. This exposes the region to the kind of sea level rise not expected until around 2070. The rapid rise created a unique opportunity to determine whether the marsh could survive this rate of coastal flooding.

“It’s the dream of every field researcher who does experiments — we can basically travel 50 years into the future to get a glimpse of what’s in store,” said Torbjorn, Vox Geology Professor in Tulane’s Department of Earth and Environmental Sciences. Tornqvist said.

The researchers used new techniques developed by European scientists to measure sea-level rise along the coast with satellite data, which was previously unavailable. The team then compared the rate of water level rise at each monitoring site to the rate of wetland elevation change determined by other instruments and found that about 90 percent of the sites were in deficit.

“To our knowledge, this is the first time climate impacts have been tested over a large area,” said Guandong Li, PhD candidate in Earth, based on hundreds of monitoring stations that have collected data for about 15 years. collected.” and environmental sciences at Tulane who led the study. “It also allowed us to study climate impacts on a heavily human-impacted landscape, rather than a more resilient ancient ecosystem.”

Lee was investigating the role of land subsidence in coastal Louisiana when a team led by Sonke Dengendorf, the David and Jane Flowerery Professor in Tulane’s Department of Coastal Science and Engineering, tracked sea-level rise along the Gulf and Southeast. demonstrated unprecedented rates of US shores since 2010.

“Guangdong immediately dropped everything it was working on to take advantage of this unique opportunity,” Tornqvist said. “They set out to answer the important question of whether coastal marshes can sustain this rate of sea-level rise, as some earlier modeling studies suggested they could.”

If the current climate scenario continues, the rate of sea level rise is expected to be about 7 mm (a quarter of an inch) per year by 2070. The study projects that about 75% of wetland sites will be lost by then, potentially resulting in a greater rate of wetland loss than has already occurred in the past century.

However, researchers emphasize that more favorable outcomes are expected if immediate action is taken. By meeting the targets set by the Paris Agreement and reducing carbon emissions, it is possible to move to a more sustainable climate path that will slow the rate of wetland loss.

This study was funded by the US Department of the Treasury through the Louisiana Coastal Protection and Restoration Authority’s Center of Excellence Research Grants Program (RESTORE Act).