Farm runoff is accelerating demise of protective coastal salt marshes

Robert S. Eshelman in E&E News: Pollution from agricultural production degrades coastal salt marshes more quickly than previously thought, according to a study published in the journal Nature. The decline of these ecosystems, the authors add, not only harms the plants and animals that inhabit them but undermines the storage capacity of one of the world's primary carbon sinks.

"Perhaps the most obvious [benefit that salt marshes provide] is they're nursery grounds for many fish, shellfish and birds, especially migrating birds that use them as feeding stops," said John Fleeger, an emeritus professor of biology at Louisiana State University and one of the researchers involved in the study. Coastal marshlands, he added, also provide protection for cities. As storms pass over marshes, they lose energy; the wetlands absorb storm surges that can batter coastal settlements. "That's a very important function, especially if you think of New Orleans and Katrina," Fleeger said. "Many people feel the strength of Katrina was heightened by the loss of salt marshes in the last 50 years or so."

Salt marshes also play a significant role, he said, in mitigating the onset of climate change and helping reduce the vulnerability of coastal cities to the impacts of rising sea levels. Just as these ecosystems buffer storm surges, Fleeger said, they also absorb the imperceptible rise in sea levels brought about by a warmer atmosphere.

Marshes also sequester carbon. Degrading marshes means less carbon is being pulled from the atmosphere but also that the carbon stored in those soils is emitted back into the atmosphere....

A salt marsh in Sachsen-Anhalt, Germany, shot by K. Retzlaff, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license