Marshes may soon flip from carbon sinks to carbon sources

A new study published in PLOS Climate paints a grim future for coastal areas in the mid-Atlantic. A modeling simulation predicts that the coastal marsh zones will go from carbon sinks to carbon emitters as the climate warms and ocean levels rise.

The marshes will expand into low-lying forests and freshwater wetlands, killing the trees, which will release carbon as they decompose. 

During the study, Katie Warnell of Duke University collaborated with seven natural resource agencies along the coast. She says her findings are significant for management. 

“This research and our conversations with the states raise lots of questions about options for managing coastal landscapes given these changes and emphasizes the importance of  reducing greenhouse gases and sea-level rise overall because that’s the main driver of all of this.”

Warnell also points out that losing marshes is not just a concern for climate change. 

“Carbon is one piece of the picture. There are many other reasons to keep marshes around, including coastal protection and nursery habitats for fisheries. We need to weigh all of these different factors in making decisions about managing our coastal habitats.”

Based on the model, a negative outcome is likely. In 16 out of 19 runs, the model forecasted that marshland will transition from carbon sinks to carbon sources, releasing more carbon into the atmosphere than the marshes can capture. 

But not all hope is lost, according to Warnell. “There might be some things that can be done to protect key areas from converting. In North Carolina, berms and pumps have been used to protect agricultural land and towns from sea level rise. While these are expensive, they might be worth it in certain areas.”

Another option would be to preemptively cut down trees in vulnerable areas before they are killed by salt water. However, the paper mentions this solution might be risky because the method has not been tested and because of the obvious ecological impacts. Let’s hope it doesn’t come to that.  

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By Erin Moody , Earth.com Staff Writer