By Victoria Brito

Dr. Juan L. González, associate professor in UTRGV School of Earth and Environmental Sciences. (UTRGV Archival Photo by David Pike)

RIO GRANDE VALLEY, TEXAS – Dr. Juan L. González, associate professor in UTRGV School of Earth and Environmental Sciences (SEEMS), is part of a research team that examines the longevity of coastal wetlands on the Mississippi Delta.

The research, titled “Tipping points of Mississippi Delta marshes due to accelerated sea-level rise” was published in Science Advances, a high-impact journal of the American Association for the Advancement of Sciences. Other members of the research team include:

• Torbjorn E. Tornqvist, lead author, Tulane University. 
• Krista L. Jankowski, Coastal Protection and Restoration Authority of Louisiana. 
• Yong-Xiang Li, Nanjing University in China.

Coastal wetlands are important to society because they provide benefits such as storm surge protection, enhance water quality by removing excess nutrients and provide habitat for marine and terrestrial species. As a result, their subsistence is of great concern to society, particularly in the context of climate-driven accelerated sea level rise.

“Our study area is coastal Louisiana, but we argue that we can extend our findings to other wetlands around the world,” González said. “There are coastal marshes in the Mediterranean and South East Asia that we predict will also be impacted by fast rates of sea level rise.”

ABOUT THE STUDY

The team studied hundreds of sediment cores from the Mississippi Delta that showed changes in wetland response to changing rates of sea level rise, dating back more than 7,000 years.

“We basically look at a very large dataset of sediment cores and radiocarbon ages from the Mississippi Delta,” González said. “This allowed us to infer, for any one time in the past 7,000 years, how fast sea level was rising. And by looking at the different sediment layers in the cores, we could see whether the marshes were drowning or keeping up with sea level rise.”

González said this study differs from past studies in that it looks at a long-term record, rather than short-term. Recent studies claim coastal wetlands can adapt to a rate of rise in sea level as high as 10 millimeters per year. However, our findings show coastal wetlands actually are more vulnerable than hypothesized and already have crossed the threshold of survival.

The main finding of the study is that, once a rate of sea level rise of about 3 millimeters per year is exceeded, widespread marsh drowning occurs within a few centuries. And when rates increase to 6 to 9 millimeters per year, a likely scenario later this century due to the current sea-level acceleration is that drowning will occur in about 50 years.

“Most concerning is that the present-day rate of global sea level rise already exceeds the 3 millimeters per year threshold,” he said, “and drowning of the remaining marshland in coastal Louisiana seems unavoidable.”

Read more about this study:

• https://thehill.com/policy/energy-environment/499329-loss-of-louisiana-marsh-lands-highly-likely-as-sea-levels-rise    
• https://www.washingtonpost.com/climate-environment/2020/05/22/new-orleans-wetlands-climatechange/  
• https://www.nola.com/news/environment/article_577f61aa-9c26-11ea-8800-0707002d333a.html    
• http://news.sciencenet.cn/htmlnews/2020/5/440275.shtm