I always enjoy reading Liz Durkee’s articles on climate change and commend her tireless efforts to increase awareness of the dire threat it poses on the Vineyard and beyond.

In her recent piece that appeared on the Gazette opinion page on Dec, 20, Liz postulated that the invasive non-native type of phragmites (Phragmites australis) may play a positive role in helping reduce the impact of global climate change.

My concern is that people may begin to view the non-native phragmites as benign or even consistently beneficial. While I recognize the situation is complex with multiple pluses and minuses, I believe that on balance the non-native phragmites is more harmful than beneficial, especially when it invades salt marshes that are crucial habitats for many plants and animals.

Liz does an admirable job of describing the important ecological role of salt marshes, especially for fish, shellfish and birds as well as a variety of plants. However, midway through the article she switches to a discussion of phragmites, an invasive species that she acknowledges “crowds out native plants and decreases biodiversity.” In doing so phragmites destroys the salt marshes and the habitat they provide for the fish, shellfish and birds discussed earlier.

She appears to equate stands of phragmites with salt marsh, when the opposite is true. Phragmites exude gallic acid, a toxin which inhibits germination and causes cell death, killing seedlings of native plants. Every year phragmites also produces new above-ground stems, the visible part of the plant with the familiar horsetail seed head. When these stems die, they cover the ground and over time they build up a thick layer of mulch that further inhibits growth of other plants. The end result of these two processes is an almost pure stand of phragmites and the absence of the plants that make up a salt marsh. Without these plants there is no salt marsh and no salt marsh habitat for fish, shellfish and birds.

She argues that phragmites provide other ecosystem services, such as absorbing nitrogen and sequestering carbon, that may compensate for the negative impacts on biodiversity. However, carbon is only sequestered when the phragmites decompose and create peat. During decomposition the nitrogen stored into the stems is released back into the environment. Unless the above ground stems are removed annually, the nitrogen is simply returned to the ecosystem when the stems die in the fall. It seems to me that carbon sequestration and nitrogen removal are mutually incompatible. Finally, there is now clear evidence that non-native phragmites increase the release of methane, a potent greenhouse gas. One study showed the rate of release from phragmites stands to be several times higher than adjacent native marsh and that the rate of methane release increased with increasing density of phragmites. To summarize, I believe that phragmites pose a real danger to our native plants and many fish and shellfish that are important for both recreational and commercial harvest. Whether phragmites can help in mitigating global climate change and its impacts is not clear. Given the well documented negative impacts on biodiversity, I believe it would be unwise to halt efforts to keep it from spreading.

Nonetheless, I believe there is a middle way. If we want to protect our marshes we should focus on preventing the establishment of new stands of phragmites and stopping the expansion of existing stands. Where nearly pure stands of phragmites have already destroyed the natural communities, we should focus on harvesting the stems annually as a way of removing nitrogen and reducing methane emmissions. While this will be expensive, it may help to hold the line while we deal with the root causes of excess nitrogen in our ponds and estuaries.

Richard Johnson

Oak Bluffs