New research finds that marshes in the Mississippi River Delta have hit a tipping point and will likely drown this century due to sea level rise. The study, which examined 8,500 years of marsh paleorecords, contradicts other research that suggests Louisiana’s remaining 5,800 square miles of marshes could survive climate change.
The study found that at rates of relative sea level rise — meaning the combination of rising water and ground subsidence — of 6 to 9 millimeters a year, the Gulf’s marshes would disappear underwater within a half-century. At rates of 3 millimeters a year, the marshes would drown within a few centuries. Globally, the current average rate of sea level rise between 2006 and 2015 was 3.58 millimeters a year, not including subsidence, The Times-Picayune/The New Orleans Advocate reported. That rate is expected to accelerate significantly this century as the world warms and polar ice sheets melt.
“What it says is we’re screwed,” said Torbjörn Törnqvist, a Tulane University geology professor and lead author of the new study, which was published in the journal Science Advances. “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.”
Törnqvist and his colleagues concluded that the disappearance of the Mississippi River Delta’s wetlands would not only “threaten one of the ecologically richest environments of the United States, but also the 1.2 million inhabitants and associated economic assets that are surrounded by [Mississippi Delta] marshland.” The findings also “raise the question whether coastal marshes elsewhere may be more vulnerable than commonly recognized,” they write. They also note, however, that a rapid reduction in greenhouse gas emissions could help slow down the acceleration of sea level rise, giving coastal communities more time to adapt.