For better or worse, invasive phragmites is here to stay

Cover photo: Serina Wittyngham of the Virginia Institute of Marine Science examines one of her phragmites research plots in Dorchester County, MD. (Dave Harp)

Few phenomena of the past century have altered the landscape and the ecology of the Chesapeake Bay, experts say, as much as the invasion of a straw-like saltmarsh weed from the opposite side of the world.

Its Latin name, Phragmites australis, presents something of a geographic misnomer. Australia is where the species was first fully described in scientific literature. But the genetic strain that now pervades the Bay area originated in Europe, Asia and North Africa, researchers say.

As far as scientists can surmise, the now-dominant variety probably crossed the Atlantic Ocean in a ship’s ballast water in the 1800s. Surveys began finding it in marshy patches in Maryland beginning in the 1910s.

Now, phragmites (pronounced “frag-MY-teez”) can be found just about anywhere the soil is typically wet: waving in the breeze along the Bay’s shoreline, engulfing abandoned homes on the rural Eastern Shore, sprouting in ditches outside suburban strip malls.

The last major survey of phragmites in the Bay region, led by College of William and Mary researchers in 2008, found that the weed covered 15% of shorelines in Maryland’s shoreline and 2% in Virginia. The highest coverage — encompassing 30% of a 200-mile stretch of serpentine coastline — was in an area along the middle Eastern Shore, above and below the Chesapeake Bay Bridge.

Land managers and researchers have long regarded the phragmites takeover as a negative change for the Bay. The plant grows in claustrophobic thickets too dense for most local wildlife. It easily crowds out native grasses. And its tall stalks are a scourge to waterfront property owners trying to preserve their views.

But as P. australis has gained an all but permanent foothold, that hardline consensus has softened. In perhaps the latest environmental exemplification of the phrase “if you can’t beat them, join them,” longtime phragmites critics are grudgingly acknowledging its positives.

“It’s a mixed bag,” said Dennis Whigham, a senior botanist at the Smithsonian Environmental Research Center in Edgewater, MD, who has published several studies on ways to fight phragmites. “You can look at it positively, and you can look at it negatively.”

To be sure, no one in the scientific community is advocating for surrendering to the plant’s spread. But recent developments, including a surge in research on potential environmental benefits and a shift toward less-ambitious management methods, signal a new chapter in the phragmites saga.

“In the Chesapeake Bay, it’s too late,” Whigham added. “There’s already so much phragmites that it’s not possible economically to eliminate it. It’s here to stay.”

A ‘perfect storm’ for phragmites

Also known as common reed, phragmites grows on every continent except Antarctica. There are native North American varieties, including in the Bay region. But before the introduction of the Eurasian variety, they were a rare sight around the estuary, scientists say. Today, the native phragmites remain few and far between, nowhere near as prevalent as their overseas counterparts.

Phragmites belongs to the grass (Poaceae) family. It can grow up to 13 feet tall. Usually, where there is one plant, there are many, forming tightly packed walls of green wisps in the summer that fade to yellow in the fall.

The species prefers fresh to brackish wetlands — partially accounting for their higher abundance in Maryland’s portion of the Bay versus Virginia’s — but can survive surrounded by waters saltier than the ocean. It spreads either by seeds or rhizomes, underground shoots from existing plants.

It’s no coincidence that phragmites has accelerated in lockstep with the human population around the Bay, said Serina Wittyngham, a post-doctoral research associate with the Virginia Institute of Marine Science. The reed is especially good at establishing itself in spots where the installation of bulkheads or other human disturbances have left behind bare earth.

“As soon as it ends up somewhere, it takes over,” she said. “It has a real competitive ability, and it outcompetes anything native.”

The intensification of farming in the region also has been a boon to phragmites. For decades, farmers spread more fertilizer on their fields than their crops could absorb, leaving behind nitrogen to nourish fledgling phragmites nearby. In the William and Mary study, researchers found that 17% of the phragmites-dominated shoreline in Maryland occurred adjacent to farmland even though that land accounted for just 11% of the total shoreline surveyed.

Whigham said research shows that phragmites is quicker to take up nitrogen than most marsh plants, providing it with a competitive advantage. High-nitrogen environments promote more-robust growth, including the production of more flowers (and, therefore, more seeds), he added.

“Humans have created a perfect storm for phragmites,” Whigham said.

Management strategies shift

The collective approach toward managing phragmites has shifted in recent years, experts say.

“I think a few decades ago, the standard response was all invasive species are bad, and there’s nothing good about it,” said Matt Whitbeck, a wildlife biologist at the phragmites-plagued Blackwater National Wildlife Refuge on the Eastern Shore. “But I think our understanding of phragmites has evolved since then.”

In 2001, the Chesapeake Bay Program — the multi-state and federal partnership overseeing the Bay’s cleanup since the early 1980s — drafted a questionnaire for state and federal government experts. It asked them to rank the invasive flora and fauna causing the biggest threats to the Bay’s aquatic ecosystem.

Only the top six would move on to the next stage: getting individualized management plans. Phragmites was selected as one of them.

After two years of drafting and discussions, the phragmites plan was ready. The report’s authors, a team of state, federal and academic wildlife and plant experts, set an ambitious goal of no net gain in phragmites acreage.

But instead of being held in check over the past two decades, phragmites has continued to spread like a wildfire across most of the region’s tidal marshes — and beyond.

Management efforts have typically ended in frustration. One of the most aggressive control attempts took place in conservation areas on the Atlantic side of Virginia’s Eastern Shore. Between 2004 and 2008, land managers conducted a vast aerial spraying campaign, typically followed by applications at ground level. To get the most bang for the buck, the effort mostly targeted stands of phragmites covering 5 acres or more.

The result: Phragmites abundance fell by 34%, shrinking from 706 to 468 acres, in treated areas.

But in the smaller patches that didn’t receive aerial control, the plant’s coverage increased from 657 to 805 acres, a 22% jump, during the same span. Factoring in those gains, the net reduction in phragmites acreage was a disappointing 4%.

State land managers concluded in a status report that eradicating all phragmites at such sites “is neither feasible nor probable.” But keeping the plant at controllable levels while staving off its invasion of native marsh spans, they added, “is completely feasible and very possible.”

The treatment usually involves repeated applications of herbicides, such as Roundup. Even then, success has been limited across larger areas of infestation.

“We’re not even attempting to control it on the broad scale,” Whitbeck said. “We’re just trying to keep it out of certain areas.”

Researchers consider benefits

Phragmites research in the United States used to concentrate almost exclusively on exploring ways to control its spread. There is still plenty of that. But a new strain of inquiry has emerged over the past decade or so with a decidedly different outlook: If phragmites are here to stay, as it appears, perhaps the benefits can be maximized.

“When you hear [the term] ‘invasive,’ you immediately go to, ‘Oh that’s bad,’” said Daniel Coleman, a post-doctoral fellow and wetlands scientist at the University of Georgia. “But phragmites, in particular, offers ecosystem services that can benefit marshes, and it does some things really well.

“It’s hard to imagine a Chesapeake Bay without phragmites at this point,” Coleman added. “So, if we’re stuck with it, let’s look at these ecosystem services we want for marshes.”

While at Virginia’s George Mason University, Coleman led a study analyzing how well phragmites can prevent erosion caused by waves and storm surge. “If you’ve ever walked through a patch of phragmites, it’s tough going,” he said. “I thought a wave would have a difficult time moving through it.”

Using sensors placed in the Chesapeake’s waters off Franklin Point State Park in Anne Arundel County, MD, he and his team found that the native marsh grass Spartina alterniflora is better at knocking down waves. During the fall, when the differences between the two species were most pronounced, the spartina, likely because of its thicker stems, reduced wave heights by an average of 73%. Phragmites only mustered a 36% reduction — but Coleman said that’s better than no vegetation at all.

Phragmites also appears to be somewhat resilient when it comes to climate change, but that has a downside, too. With sea level expected to rise another 2 feet by 2100, according to some projections, the Bay region might lose as much as 167,000 acres of low-lying coastal marshes. The only hope for native marsh plants is to reestablish themselves on higher ground, researchers say.

Phragmites literally stand in the way of that happening. Their highly invasive ways are giving them a strong competitive advantage in these areas. If the weed takes over, the region stands to lose the wildlife that relies on native marsh habitat, particularly two rare bird species, black rails and saltmarsh sparrows.

“If we accept phragmites as the future [marsh grass] species of the Chesapeake Bay, we’re going to lose native wildlife because of that,” Whitbeck said. “I could see black rails disappearing from the Chesapeake Bay in my lifetime, unless we find a way to mitigate those changes.”

Wittyngham is leading a study at Blackwater trying to determine which management method works best: herbicides, controlled burns or salt. Her goal is to “hold that line” against the ongoing spread of phragmites into the pine-dominated forests as those forests give way to marshland, she said.

Nevertheless, she doesn’t see herself as completely anti-phragmites. “It still has ecosystem benefits, even if it’s not supposed to be here,” Wittyngham said. “My gut reaction when I started doing this work was, ‘Absolutely, get it out of here.’ But when I started digging into the literature and learning about it, I decided it has some benefits that shouldn’t be overlooked. And in some places, we should just let it stay.”

She pointed to research that has shown that phragmites can help slow erosion in places where nothing else is growing, even helping to raise the height of the land by trapping sediment. But again, a positive effect is accompanied by a negative one: Phragmites-invaded areas may not be as suitable as nursery grounds for young fish, as shown by reduced counts of juvenile and larval fish in their midst, according to a growing body of research.

Phragmites also has been shown to have some worth in capturing and storing carbon (a major greenhouse gas) and nitrogen (a nutrient that fuels harmful algae blooms). But in both cases, it is a poor substitute for native plants and trees.

Keryn Gedan, a coastal ecologist with George Washington University, has spent as much time as anyone in the Chesapeake region thinking about and studying phragmites. Her work on the Eastern Shore concentrates on the fate of marshes.

“I lost a student once in phragmites,” she said, with a quick pausing before adding, “Not permanently.”

Gedan admits that phragmites has benefits to offer. But she hopes that her work and that of others help to save some native marsh for future generations.

“I’m just suggesting we’re not going to drive phragmites extinct. It’s going to be part of the future, and I accept that. And the people who say there are advantages to phragmites, I agree with them,” she said. “What I’m promoting is keeping some areas for biodiversity, which is something we don’t get from heavily invaded phragmites areas.”