No Need to Dephrag the Bay

John Page Williams at CBM has A New Take on an Invasive Species

You’ve seen plenty of it along Chesapeake waterfronts: the common reed, with its tall, feathery seed heads. You probably even call it by the Latin name of its genus, Phragmites. If so, you probably also know that it’s considered an undesirable, invasive species scorned for crowding out native wetland plants. It grows well on disturbed soils, such as the waterfront edges of constructed sites like bridge crossings, laying down dense, tangled root mats and quickly developing thickets of tough, pale green stalks.

Although there is only one species, Phragmites australis, two subspecies live around the Chesapeake. Phragmites australis americanus is native, but here it lives only along rivers on Maryland’s Eastern Shore. The much more widespread subspecies, Phragmites australis australis, apparently turned up here late in the nineteenth century and took off. Today, conventional wisdom dictates removing it, but doing so turns out to be a difficult, expensive challenge. That challenge poses a serious question about what we are trying to accomplish when we talk about restoring the Chesapeake.

 

One time years ago, I asked a friend who was acting in a play at Hanover (VA) Tavern what he would “go back to” after the play completed its run. “I won’t go back,” he responded, “I’ll go on to something else.” That pretty much sums up our Chesapeake restoration efforts. We can’t ever go back to the Bay ecosystem that existed when the Jamestown colonists landed in 1607. About 50,000 people lived in the Chesapeake watershed then. We are 19 million now, and climbing, along with the ecological changes that we continue to create in the water, on the land, and in the air.

The most obvious water quality improvements we have made in the past fifty years have been with increasingly sophisticated treatment of “point source pollution” (pipe outflows), especially our sewage wastewater. That engineering has brought rivers near population centers back from the dead, including the Potomac River around Washington, DC and the James below Richmond. They are healthier today than they have been since 1870. The greater challenge, though, is more widespread and less readily controlled: rainwater runoff from land that we have modified from 1607’s old-growth forests, especially including along the shorelines of our vast network of waterways. Engineering offers some solutions here, but often they work best when carefully, artfully integrated with natural processes.

Such integration requires deep searches for, and attention to scientific details, as well as the enduring lesson that anyone looking for simple answers has come to the wrong estuary. It goes ‘way beyond blanket statements, like “Eradicate all Phragmites.” In that vein, a new study from Maryland’s Department of Natural Resources breaks down the pluses and minuses of ecosystem services provided or taken away by stands of Phragmites as opposed to native wetland plant communities.

Using cost/benefit analysis, the scientists carefully went through and compared studies from existing research of wetland community performance in the categories of carbon sequestration, nitrogen removal, and wildlife habitat. They contrasted data from natural brackish high marshes with those from stands of Phragmites australis australis. If you read the study, you’ll find that the data together provide ranges of performance, but there are clear trends. Phragmites stands tend to deliver greater carbon sequestration, while native high marshes provide greater nitrogen removal and offer better, more diverse wildlife habitat. On average, the introduced and native communities offer similar ecosystem service values, though under optimal conditions, native marsh communities are more valuable.

 

The catch comes when looking at the Chesapeake’s wetlands as they are, in June of 2026, with many, many stands of Phragmites well established all over the Bay ecosystem, and considering the high cost of eradicating the plants, which require repeated manual, year-on-year applications of herbicide. The big reed is here to stay in today’s Chesapeake, and it does offer valuable ecological benefits, especially in carbon sequestration. Those considerations bring to mind the first maxim attributed to Hippocrates: “First, Do No Harm.” As the study’s authors conclude, “it is not a net economic benefit to control for Phragmites, unless the cost is low to moderate and the benefit is high, i.e., the system can maintain or return to optimal wildlife habitat…we recommend that landscape factors and management goals be considered when making these decisions for marshes in the Chesapeake Bay Region.”

In other words, Phragmites appears to have some useful roles in the Bay and rivers of the future. One more time, there are no simple answers here, but there is fresh Chesapeake information to guide careful thinking about “going on to something else.”

I agree. 

The Wombat has Rule 5 Sunday: Rebel Yell up and garnering clicks at The Other McCain.

Beach Report 1/12/21

A pretty nice day; clear skies, temperatures in the high 30s to low 40s, and a 10 knot breeze, falling off. 

The stream at Matoaka made a sharp right turn parallel to the shore line.

Do you see it?

A pretty nice Snaggletooth just off the band of shell debris, right in Georgia's path.

This was by far the best of 16 teeth.

Sunlight shining through the Phragmite's heads. 

 

Invasive Species Fight Climate Change!

5-foot-tall Naomi Hamermesh, a former intern who
is now an employee of the Michigan Tech Research

Institute, dwarfed by a stand of Phragmites

Phragmites, other invasives help fight climate change - New study shows nonnative plants in coastal ecosystems can excel at carbon absorption

And now, a kind word about one of the Chesapeake Bay’s most hated invasive plants: phragmites.

The tall, feathery-plumed marsh reed is the bane of waterfowl lovers around the Chesapeake Bay region, as it crowds out native wetland plants, depriving ducks, geese and swans of nourishment. Landowners and resource managers alike spend a lot of time and money trying to control its spread, if not eliminate stands of it.

But a new study finds that Phragmites australis and some other invasive plants help to fight climate change by enhancing the storage of “blue carbon” — the carbon that’s accumulated and kept in oceans and coastal environments like salt marshes, mangroves and seagrasses.

Size comparison

“We were aware of the effects of invasions on other facets of these habitats, but this was the first time we really delved into blue carbon storage,” said Ian Davidson, a marine invasions biologist at the Smithsonian Environmental Research Center in Edgewater, MD. He is the lead author of the new study published Monday in the journal Global Change Biology.
. . .
Davidson and colleagues, including Smithsonian marine biologist Christina Simkanin and two researchers from Ireland, performed a “meta-analysis” of 104 relevant studies. They found a 40 percent net gain in carbon storage in invaded coastal vegetated habitats compared with similar ecosystems free of nonnative plants. And where invaders performed similar ecological roles in coastal habitats to the plants they were replacing, the carbon storage more than doubled, by 117 percent.

“When you have these essentially ‘ecosystem engineers’ come into the system, not only are they helping build habitat, they seem to be doing it more aggressively and more efficiently,” Davidson said in a release describing the study.

Note Phragmites in background

Phrag (the name insiders generally use) is an interesting plant. It really isn't a invasive species. The same species, Phragmites australis, is native to the United States. However, the type of Phrag that is invading, and spreading rapidly is a sub-species from Eurasia that is only slightly different in appearance from the native plant. It is, however, much better at doing a lot of things than our native clone, collecting nutrients, photosynthesizing, and growing. It's sort of the Genghis Khan of marsh grasses; marching continuously into new territory.

By definition, an invasive species is a species, that having been introduced to a new region, begins to spread rapidly, and makes a significant impact on the existing ecology. It is guesstimated that of 100 species introduced to a new area, 10 are successful in becoming established, and 1 of those will become "invasive."

It's not a great surprise then, that the invasive Phragmites, wildly successful at turning wetlands in to wetlands covered with Phrag, is also successful at making carbon and putting it into the ground.

Wombat-socho has Rule 5 Sunday: Brennschluss ready and waiting.

Can Goats Save the Bay?

Gabrielle Marquez, is using goats to get rid of

 invasive phragmites and reclaim the Pleasant Plains

 community beach tidal marsh. 

Prolly not, but they might make a dent in all the Phragmites that's cropping up:

It turns out that goats, and their voracious appetites and hearty digestive systems, are pretty good for Maryland’s wetlands.

On Wednesday morning a herd of around 20 of the four-legged eating machines were unleashed on Whitehall Bay’s shores where they were crucial players in an effort to eliminate invasive plants.

Their job? Eat their way through a ¼-acre lot filled with phragmites, an invasive grass that arrived from Europe in the 19th century. After the goats do their thing, volunteers will hand-plant native grasses to help reclaim the shoreline.

Gaby Marquez, a rising sophomore at St. Mary’s High School, organized the project and paid for it with a $5,000 grant from the Chesapeake Bay Trust and matching funds from her neighborhood’s homeowners association. She said she wants to eventually have a career in environmental protection and this seemed like a good way to enjoy her passion.
. . .
The herd was taken from their trailer into a temporary corral at the water’s edge in St. Margaret’s Pleasant Plains neighborhood. Some of the reeds were about three times as tall as the biggest goats and this summer’s rainstorms made the vegetation green and lush.

But through a combination of trampling and voracious eating the vegetation in the community association-owned land was visibly thinner within minutes. It will take about three days for the goats to eat their way through the lot their owner, said Mary Bowen, president of Browsing Green Goats in Sunderland.

Goats are ideal for this type of work, Bowen said. Not only can they eat all day, but between their dental structure and digestive system they destroy the plants’ seeds, so it’s impossible for a second generation of grasses to sprout from the animal’s droppings
“When they chew and bite, they’re dismantling the seeds in there,” Bowen said.

One alternative, mowing, doesn’t completely eliminate seeds while another option, herbicides, can pollute the water and harm nearby landscaping, she said.

Goats are efficient grazers, but Kevin Haines, president of Holly Oak Consulting, an environmental engineering firm working pro bono on the project, said it’s unusual to see those animals eat the invasive grasses.

“I’ve never seen goats used in Anne Arundel County to remove phragmites,” he said.

A herd of "Eco-Goats" clears land of invasive plants at Sandy Point State Park this week.

People will often excavate areas filled with non-native species, a method that effectively eliminates the unwelcomed plants but destroys the subsoil in the process. Goats, he said, don’t come with that side effect.

Goats have been introduced in many areas where they aren't natural, and they often become a serious invasive species, stripping islands of natural vegetation. But using them this way, under control, I don't see a problem. But who is going to wrangle all the goats? There's an awful lot of Phragmites around.

The Good and Bad of Phrag

Jekyll or Hyde? The Many Faces of Phragmites

It’s easy to dislike Phragmites. The invasive brown reed can grow over 15 feet tall and tends to crowd out anything in its shadow. But in the story of global change, Phragmites is a gray character, like Mad Men’s Don Draper, or the enigmatic Professor Snape. Beneath the surface, Phragmites australis—a European reed sweeping over East Coast wetlands—can empower wetlands to grow higher soils and possibly survive rising seas. Biogeochemist Pat Megonigal of the Smithsonian Environmental Research Center (SERC) prefers an analogy from classic literature: Jekyll and Hyde.

“The Jekyll part is that Phragmites helps marshes maintain elevation and keep pace with sea level rise,” he said. “The Hyde part is that they are poor habitat for native plants and animals.”

The latest discovery in Megonigal’s lab could tip things in favor of Hyde. Phragmites’ deep-growing roots were once thought an advantage that helps wetlands build soil. But those same roots could be disturbing ancient soils deep underground—triggering them to release planet-warming carbon dioxide (CO2).

Soils are the third largest carbon pool on Earth. However, they release carbon dioxide when the carbon they hold decomposes. Surface soil carbon decomposes all the time as microbes feast on newly-deposited plant material. But carbon in deeper, older soils was supposed to be locked away, because deep soils were thought to contain tougher material microbes couldn’t decompose well.

Blanca Bernal with a sediment core

“When you get into the deep stuff, that stuff is considered to be sequestered. Nobody can eat that,” said Blanca Bernal, former SERC postdoc and lead author of the new study in Global Change Biology. Except, she added, that’s turning out to not be true. “Several studies have shown that it’s actually not that recalcitrant. It’s just a matter of recreating the right conditions down in the soil for the microbes to start consuming that old carbon pool.”

For the first time, ecologists caught Phragmites in the act of releasing carbon from ancient soils.

They launched the study on the Global Change Research Wetland, a 170-acre experimental wetland in Maryland run by the Smithsonian Environmental Research Center. First, researchers grew Phragmites and native wetland plants in white PVC pipes partially submerged in a tidal creek. At the end of the growing season, they sealed the pipes and sampled the CO2 inside. Their goal: Uncover how much CO2 came from the plant, from microbes in the surface soil (40 centimeters or less) and microbes in the deep soil (40 to 80 centimeters).

In total, soil with Phragmites emitted just slightly more microbe-made CO2than soil with a native sedge, Schoenoplectus americanus. But location made all the difference.

Almost all the microbe CO2 from the soils with native plants—87 percent—came from the surface. Meanwhile, Phragmites triggered microbes in its soils to emit 80 percent of their CO2 from deeper soils, where CO2 was supposed to be safely buried. Phragmites released five times more deep-soil carbon than the native plant or pipes with no plants at all.

No great surprise, since the release of CO2 requires oxygen to oxidize the organic matter, and very little oxygen penetrates to any depth in wetland soils without being used up.

Most plants don’t have roots deeper than 30 centimeters, or one foot, underground, says Tom Mozdzer, a Bryn Mawr assistant professor of biology who also worked on the study. That’s a problem with plants like Phragmites that can go far deeper.

“We’ve been underestimating the potential influence of Phragmites, because we haven’t looked at what’s happening below that typical rooting depth,” Mozdzer said. The figures in the new study might still have underestimated how much carbon Phragmites can release, the scientists noted, because the Phragmites plants in this study weren’t fully mature.

What makes Phragmites so powerful? Having roots that stretch deeper underground helps, but that alone wouldn’t be enough to release deep carbon. Their roots also pipe oxygen below ground, which can stimulate microbes to decompose more. Phragmites roots also transport other compounds microbes find easier to digest, spurring them to release even more CO2.

There you go!

But Phragmites has power to save wetlands as well. Its roots, while releasing deep-soil carbon, can also build wetlands up when facing sea-level rise. This puzzle is forcing conservations to decide whether it’s better to preserve native plants Phragmites crowds out, or ensure a wetland’s survival, period.“What are we managing for?” Mozdzer asks.

“Is it ecosystem services, or plant community?”

“At least for now, the Phrag-invaded areas are gaining elevation faster than the native areas,” said Megonigal. “So that suggests that on balance, they’re more Jekyll than Hyde.”

Another complication is that Phragmites in Chesapeake Bay area has two populations, the smaller, original native morph, and the  Eurasian immigrant, which is larger, more vigorous, and which his largely pushed the native variety out of it's original range, as well as claiming expanded range of it's own. So, should that function exist?