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Newbury and Salisbury

Invasive plant poses threat to the Great Marsh

Mark Wilson/Globe Staff/file 2004

A recent study found that a portion of the Great Marsh in Newbury and Salisbury is vulnerable to phragmites, an invasive plant species, but steps can be taken to reduce the reed’s impact.

Geoff Walker has watched the phragmites Australis grow for years, but a new study has proven what he already knew.

Typically, the invasive species that is also called the “common reed’’ starts on the marsh border and spreads, sometimes to the point where it crowds other plant species out. In recent years, that pattern had changed.

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“About four of five years ago we looked out and saw tremendous amounts of emerging small stands of phragmites [spread around the marsh], which is atypical,’’ said Walker, a Newbury selectman whose home abuts the Great Marsh. “That is what that study brings to light, and that certain parts of our marsh are reaching a tipping point. Once that tipping point is reached, we could lose broad swaths of our productive, high marsh.’’

The study, released on Jan. 31, has confirmed anecdotal observations, and offered both bad and good news regarding the future of the Great Marsh.

The bad news is that the study found the rest of the northern portion of the marsh - in Newbury and Salisbury - was potentially vulnerable to the invasive plant species.

The good news is that it determined that efforts to contain the spread, including spraying, was an effective short-term solution. The suggestion from the report is that spraying and other techniques could be used to manage the species for the time being.

A more permanent solution generally involves the enlargement or replacement of culverts to allow greater tidal flow, which has shown to restore salt marshes over a number of years. The Argilla Marsh in Ipswich is one that has been restored.

“I don’t think any biologist is a cheerleader for the use of chemicals in a natural system, but we acknowledge that because the threat is seemingly quite dire and increasing every time we go the site - not just year to year, but month to month across the landscape - it is a good approach to buy managers and scientists some time to see what combination of approaches can be used,’’ said Gregg Moore of the University of New Hampshire, who led the team of researchers. “If herbicide is one of those tools in the toolbox, integrated with other approaches, it needs to be reviewed.’’

A third important finding was the confirmation of the anecdotal belief that the major factor in phragmites growth is the level of salt in the water.

The reed can grow in fresh water, but thrives in brackish water, which in general terms has some salt content, but a lesser amount than in sea water.

“What they’re finding is the most critical is that if you do not have good tidal flow, you run the risk of having phragmites,’’ Walker said.

There are myriad threats that come with thick spread of phragmites, most specifically the loss of other habitat.

“The danger is that it creates a habitat that doesn’t support the native biodiversity,’’ said Robert Buxbaum of Massachusetts Audubon Society, who also worked on the study. In the marsh, that could include native plant life, birds such as rails and salt marsh sparrows, and fish habitat that is lost as the plant’s thick root system dries out the marsh. That can cause a negative impact on the fisheries and ecotourism, including birding.

“Locally, people are also concerned because it can be a fire hazard,’’ Buxbaum said.

State Senator Bruce Tarr, a Gloucester Republican, one of four chairs for the Legislature’s Great Marsh Revitalization Task Force, said the report could be an effective tool.

“It defines the problem as being significant enough to be worthy of the support of the state and federal government,’’ he said. “It also makes the case that we can do something to effectively combat the problem.’’

The task force is preparing a comprehensive Mass. Environmental Policy Act filing to make it eligible for umbrella permits to conduct an array of activities to combat phragmites throughout the entire area of the marsh, which runs up the coast from Gloucester into New Hampshire.

Peter Phippen, coastal resources coordinator for the Eight Towns and the Bay Committee, a partner in the Great Marsh Alliance, said that further steps are planned to deal with phragmites all over the Great Marsh, including developing a short-term management plan that will include mapping the region and identifying areas threatened by phragmites spread.

David Rattigan can be reached at drattigan.globe@gmail.com.
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