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The Jekyll and Hyde of the Marsh

PhragmitesPhragmites, an invasive species of reed introduced to North America from England, is often seen as a monster because the grass stalks grow up to 18 feet tall and drive out native plants and wildlife.

But some scientists suggest the plant is more of a Dr. Jekyll and Mr. Hyde, because while it is bad for plant and wildlife diversity it may be good at protecting shorelines from erosion caused by rising sea levels and climate change.

Patrick Megonigal, Deputy Director of the Smithsonian Environmental Research Center, is studying the effects of rising carbon dioxide levels on marshland plants, including phragmites.

“On the one hand, phragmites is very poor habitat for a lot of animals –- birds, and even fish.  But on the other hand, it is a champion soil builder,” Megonigal said among the reeds and measuring equipment at his wetlands research site, outside Edgewater, Maryland.  “And so we find places where the plant is dominant that the soil elevation rises very rapidly, and that could be a good thing from the point of view of preventing these marshes from drowning due to sea level rise.”

This is not to say that Megonigal or anyone else is advocating the intentional spreading of phragmites for erosion control purposes –- first, because the rapidly-growing grasses don’t need any help spreading; and second, because their roots emit a toxin (trihydroxybenzoic acid) that kills other plants nearby, according to research by the Delaware Technology Institute. Phragmites also crowds out wild rice, cattails, goldenrod, and other native plants that wildfowl, muskrats, and other marsh dwellers need to survive.

Phrag headsThe reeds, thought to have been brought to the Americas in the ballast of ships by English colonists, have proliferated across the Chesapeake Bay region and elsewhere in recent decades, because they thrive in disturbed soil caused by development.

Over the last three decades, the invasive plant has multiplied perhaps 10 fold to cover roughly 100,000 acres or about 10 percent of Maryland marshes, according to an estimate by the Maryland Department of Natural Resources. It has also spread widely across Virginia, Pennsylvania and other states.

Jonathan McKnight,  a biologist at the Maryland Department of Natural Resources, said that phragmites roots form thick masses that hold soil together.  But he said that it would be wrong to plant phragmites to protect shorelines, because the plant  does not play well with other forms of life.

“It would be great to find a silver lining in our phragmites infestation,” McKnight said. “But it would be a lot better for us to find a way to preserve marshes or maintain marshes with the native material.  Because even if you are protecting a phragmites marsh, a phragmites marsh is not as good as the real native Maryland marsh.”

SprayingThe Maryland Department of Natural Resources, with help from the U.S. Fish and Wildlife Service, spends about $30,000 a year spraying an herbicide (glyphosate, the active ingredient in Round Up) from helicopters onto selected stands of phragmites that are monopolizing the landscape in important wildlife areas.  Other states also conduct similar spraying.

Webster said glyphosate, which is used widely on farms and elsewhere, dissipates quickly and does not pose a threat to fish or wildlife.

On a recent morning, Webster directed a helicopter with a tank full of glyphosate as it launched from the top of a truck beside the Nanticoke River.  The helicopter swooped over green and gold marshlands, then released the herbicides when over a stand of phragmites, which are very tall reeds with fluffy seed heads.

Helicopter“A lot of homeowners on the Bay simply do not like phragmites just because they do not have a view of the water” when the reeds are in the way, Webster said. “But typically that’s not what we are out here to achieve.  We are doing this (spraying) to help  wildlife.”

Webster said the state’s spraying of the weed from helicopters is limited and not intended to totally eradicate the invasive species, which he said would be impossible. Webster said Maryland is simply trying to keep the phragmites in check in a few selected feeding grounds for migrating waterfowl.

Dr. J. Court Stevenson, a professor at the University of Maryland Center for Environmental Science who studies marshes, said in an email that he is not opposed to spraying phragmites with Round-Up, as long as it is done carefully, so the herbicide does not drift into other areas and kill endangered plants.

Dr. Stevenson added, however, that over-use of Round-Up is creating herbicide-resistant weeds that make farming more difficult.  And he also noted that spraying phragmites in some waterfront areas can increase erosion, because of the reeds’ ability to hold shorelines together with their dense roots.

“An example of where helicopter use appears to have been a problem is at the Cove Point (Liquid Natural Gas) plant property on the Western Shore, where the Phragmites rhizomes were holding the beach and protecting it from excessive erosion,” Dr. Stevenson wrote. “After extensive spraying over several years, the beach was breached causing many the freshwater marsh plant populations behind the beach strand to suffer.”

Officials with the Maryland Department of Natural Resources say they try to be careful about where they spray phragmites, to avoid erosion problems like this.

But the big picture is that sometimes it may be bad to kill the monstrous Mr. Hyde of the marshes, because you will also lose the good Dr. Jekyll. 

By Tom Pelton

Chesapeake Bay Foundation




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Great article on the pros and cons of phragmites! I also read a study, many moons ago, that phragmites is also very efficient at removing toxins from water. As you said, not a reason to plant phragmites, but a little silver lining in the cloud.

Thanks, Desiree. Yes, as in many things in life, it's often impossible to judge a species as "good" or "bad."

Exotic species often have a complex and unpreditable impact on our world. In this case, it is clear that phragmites infestations are bad for native plant and animal diversity. But whether they are bad for shorelines threatened by erosion, and the human built environment behind the shorelines, is not clear.

We have been working with government agencies to kill this off in Virginia. Fortunately we have not seen any increased erosion, and have actually seen a huge growth of native marsh grasses and a greater return of wildlife. Almost the entire area that was covered by this reed is now covered by various grasses - it's been a 6 year process, but good results.

It appears that phragmites are a danger to native species of grasses and plants. They need to be controlled. Phragmites are not a good habitat for animals, birds, and other creatures. Though they do control erosion, the trade off is not worth it since there are native grasses that can do as well a job.

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