How P.E.I.'s salt marshes could join the battle against climate change

Salt marshes in the world's coastal areas could be an important resource for pulling carbon out of the atmosphere, but recent research suggests that resource could be limited on P.E.I.

The potential for salt marshesfor carbon sequestration, known as blue carbon, is even better than for forests, because trees will hold the carbon only as long as they live.

"The plants in salt marshes, like P.E.I. salt marshes that are grassy, store lots more carbon in their roots into the soil," said Gail Chmura, a geography professor at McGill University.

"It makes it a very important carbon sink, because once it's in the soil it gets stored for a long time. We've shown, on P.E.I. hundreds of years, and in other places it's thousands of years."

Chmura was co-author on a paper published last month in Environmental Research Letters that compared the salt marshes of four river systems on P.E.I.

• DeSable
• Indian
• Tryon
• Wilmot

These were studied alongside Kouchibouguac in New Brunswick. The idea was to compare salt marshes from watersheds with heavy agricultural use to one with virtually none.

Gains from carbon storage could be lost

The researchers found a problem related to nitrogen, a chemical common in fertilizer.

"We found nitrogen in the water in the marsh, but we found nitrogen being transformed into nitrous oxide," said Chmura.

As a greenhouse gas, nitrous oxide is 298 times more powerful than carbon dioxide, so while the salt marshes are still absorbing carbon, their overall value in mitigating climate change is greatly reduced.

"They're releasing a greenhouse gas that's much more potent," said Chmura.

In contrast, the salt marsh at Kouchibouguac was actually absorbing nitrous oxide, rather than emitting it. In some cases, the production of nitrous oxide in the marshes may entirely counterbalance the absorption of carbon dioxide.

Chmura believes there may be a solution to this problem as world carbon markets mature. If nitrogen loading is decreased through changed farming practices such as different crop rotations or larger buffer zones that could increase the value of the salt marshes on carbon markets.

"[I want] to see if there's ways to allow the farmers to get funds for them, because everything they do costs money," she said.

Chmura is announcing a project in June connected to the value of salt marshes around the Bay of Fundy. She hopes further research could lead to similar projects on the Island.

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