The Sea Will Claim All 5,800 Sq. Miles Of Louisiana's Coastal Wetlands; Only Question Is How Quickly
Because of increasing rates of sea level rise fueled by global warming, the remaining 5,800 square miles of Louisiana's coastal wetlands in the Mississippi River delta will disappear. The only question is how quickly it will happen, says a new peer-reviewed study published Friday in Science Advances. “This is a major threat not only to one of the ecologically richest environments of the United States but also for the 1.2 million inhabitants and associated economic assets that are surrounded by Mississippi Delta marshland,” the report concludes.
The new study reviewed the rates of sea-level rise that caused wetlands to disappear along Louisiana's coast during the 8,500-year history of the current Mississippi River delta. It found that at rates of relative sea level rise -- the combination of rising water and ground subsidence -- of between 6 and 9 millimeters a year , ancient coastal marshes would turn into open water within 50 years. At rates of 3 millimeters a year, it would take a few centuries. The globally averaged rate of sea-level rise between 2006 and 2015 was about 3.58 millimeters a year, and that doesn't include local subsidence rates along Louisiana's coast. As a result, the state's wetlands already have exceeded a tipping point, the study's authors say.
"What it says is we're screwed," said lead author Torbjörn Törnqvist, a Tulane University geology professor, in an interview. "The tipping point has already happened. We have exceeded the threshold from which there is basically no real way back anymore, and there probably won't be a way back for a couple of thousand years." Recent studies that show that growth of wetland plant material is keeping pace with today's rate of subsidence and sea level rise have been based on just six to 10 years of measurements. That brief period of time is not long enough to determine that wetlands can literally outgrow sea rise.
By studying the boring core record of dozens of decades and hundreds of years of ancient marsh growth and disappearance, the researchers found that marsh growth could not keep up with the rising water levels. However, the report said additional research is needed to understand how rapid sea-level rise over decades causes the wetlands to disappear.
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https://www.nola.com/news/environment/article_577f61aa-9c26-11ea-8800-0707002d333a.html
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