La. wetland losses: Already 'screwed'

Rising sea level, fueled by global warming, will eventually cover the remaining 5,800 square miles of Louisiana's coastal wetlands in the Mississippi River Delta. The question remains, how quickly, according to a study published May 22 in Science Advances. “This is a major threat” to one of the most ecologically-rich environments in America, and also for 1.2M inhabitants and associated economic assets surrounded by the marshland, the report concludes. The new study reviewed the rates of sea-level rise that caused wetlands to disappear beneath the waves along Louisiana delta's 8,500-year history. It found that at rates of relative sea level rise between 6-to-9-millimeters a year, the ancient coastal marshes would turn into open water in 50 years. At 3mm annually, it would take a few centuries. The global average of sea-level risings between 2006-15 was about 3.58mm per year. As a result, Louisiana’s wetlands have already exceeded a tipping point, the authors penned. "What it says is we're screwed," said lead author Torbjörn Törnqvist, a Tulane University geology professor. "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." Other recent studies have shown growth of wetland plant material is keeping pace with today's rate of subsidence and sea level rise, but base on 6-to-10 years of measurements. By studying the boring core record of dozens of decades and hundreds of years of ancient marsh growth and disappearance, researchers discovered that marsh growth won’t be able to 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. (Source: NOLA.com 05/22/20) https://www.nola.com/news/environment/article_577f61aa-9c26-11ea-8800-0707002d333a.html