Rising seas, invasive species concern coastal property owners

Sally Knowlton-Keen lost her shoe in the logy muck of a Darien marsh back in 1959. She was 7, and her family had just bought a home on Edgehill Drive for $35,000. But losing her shoe wasn’t a horrific moment, as it might have been for some children. Instead it was the beginning of a deep reverence for this natural habitat; a reverence fueled by a curiosity and wonder that has stayed with her over the past half century.But these days, Knowlton-Keen fears something far worse than losing footwear — the death of the marsh itself.

• See other articles in the Sound Wisdom series

“Perhaps I began noticing the marsh changing 20 years ago,” she said. “Every year there has been an ever larger expanse of mud and sad, empty mounds where the grasses once flourished so tall.”

Sea levels on the northeastern coast are rising three to four times the global average, according to a recent study by the U.S. Geological Survey, forcing once thriving marshes to migrate inland. But in Darien, as in most New England communities, the coast is heavily developed, leaving little room for migrating marshes, one of the most biologically important ecosystems on the planet.

“For most of my life, the houses surrounding the marsh had never changed,” Knowlton-Keen said. “Then a series of tear-downs and additions began and I began to worry that the marsh was dying, not just changing.”

Just down the road from her house, on Tokeneke Beach Drive, a 2,100 square-foot home surrounded by water waits to be nearly tripled in size, pending approval by the Planning & Zoning Commission. Other large homes stand where smaller ones once did, leaving less space for migrating wetlands seeking fresh ground as sea levels rise and displace the flora and fauna.

“There is so much we need to learn and we are running out of time,” Knowlton-Keen said. “Maybe education is the place to start. If people knew more about the salt marshes, they would care for them.”

Invasive species

Her neighbor, Todd Robbins, agrees. Robbins’ bay window looks out onto an expanse of reeds that stop right at his backyard. These reeds, known as Phragmites, are not signs that the marsh is healthy, however. It is actually an indication of the opposite.

Dr. Mark Bertness, a biologist at Brown University and expert in marine shoreline communities, said that Phragmites flourish in nitrogen-rich environments and can lead to local extinction of native plants and animals.

“When marsh is developed — with roads, golf course, houses — it ends up spiking the nitrogen,” Bertness told The Times. “Once you spike that, you are basically farming Phragmites because it’s able to move in and displace other native plants.”

But there’s a catch. Phragmites is excellent at storm damage control, and also absorbs toxins from runoff. As they dry up marsh beds, Phragmites increases sedimentation and could provide a balance against rising seas because of how much water it absorbs, Bertness said.

Bertness advocates planting Phragmites to remediate and restore marshlands to mitigate rising seas, although he admits this position has its critics.

The Darien Land Trust, and the state of Connecticut, might be two of them. Shirley Nichols, executive director of the Land Trust, encouraged residents to participate in the state-supported removal of Phragmites, a practice that a few Darienites already engage in through the trust.

“We’ve removed a lot of Phragmites from coastal areas,” she said. “When it’s removed, you get more spartina, the native plants, [which] absorbs tidal flow much better than Phragmites.”

Invasive Phragmites poses a threat to the wetland ecosystems because its rapid growth requires it to absorb most soil nutrients, to the detriment of native species, according to a report by the state Department of Energy & Environmental Protection. It also grows too thick for nesting of most native birds, including the seaside sparrow and salt marsh sharp-tailed sparrow, both of which are on the state list of species of special concern, or two steps below being endangered.

A 2009 study by the University of Delaware found that Phragmites emits a toxic chemical into the soil that when combined with ultraviolet radiation from the sun can kill competing plant species in a process called allelopathy.

Bertness, however, doubted the validity of this claim, and said the Phragmites’ dominance is more likely because of how it absorbs nitrogen and water, creating an environment where native spartina are merely pushed out or shaded from the sun by the eight-foot tall Phragmites.

The Darien Land Trust eliminated several acres of Phragmites on its Tokeneke property by using aquatic herbicides that stick to the plant. The process can take up to three years because of the reeds’ hardiness. The state has employed this method to 1,497 acres as of 2007.

Restoring natural water flows can also help because Phragmites cannot thrive in salinities above 18 parts per thousand, according to the state. But as larger homes and structures are built, more freshwater runoff heads directly into the marsh without being filtered naturally, leading to thriving Phragmites, Bertness said.

As these invasive reeds flourish, the entire salt marsh can dry, leaving the numerous birds, fish and mollusks without a place to nest. It’s estimated that from one-half to two-thirds of the fish harvested from the Atlantic and Pacific oceans for food spent part of their lives in salt marshes or estuaries. Knowlton-Keen said she’s counted more than 60 bird species during her 50-plus years watching the marsh.

Although a few animals, such as the red-winged blackbird, can live in Phragmites patches, most other animals and birds avoid these areas because they cannot penetrate the thick growth. Eventually the alien reeds, along with rising seas, could overwhelm coastal communities. A native version of Phragmites exists in North America, but it is becoming increasingly pushed out by its invasive relative.

“It’s far more fragile than people realize,” Robbins said of the coastal wetlands. “Everyone wants to build a big house right on the water — and they’re entitled to, I don’t have a problem with that — but don’t do anything that jeopardizes the marsh.”


Darien wetland regulations require permits for any activity within a certain distance from a wetland, and require homes built near the water be at least one foot above the 100-year floodplain as determined by FEMA. If homes are subjected to continuous flooding, the federal Robert T. Stafford Disaster Relief & Emergency Assistance Act authorizes towns to use grant money to purchase these flood-prone properties, which then can only be used for open space, recreation or wetlands management, said First Selectman Jayme Stevenson.

Darien used this provision to purchase the building at 33 Cherry Street. Stevenson said she is confident that the current storm water runoff and construction regulations near the coast are adequate.

“At this point in time, I do not believe additional regulations beyond what we currently impose are needed,” Stevenson wrote in an email. “Only time will tell if sea level changes will be as predicted so, of course, we should be prepared to respond in the event conditions dramatically change.”

Most scientists predict sea levels to rise worldwide by up to three feet by the end of this century, according to a report by the International Scientific Congress on Climate Change. Sea level rise in this part of the country has increased by 2-3.7 mm per year since 1990 — or roughly a 10th of an inch — which scientists contend will continue and lead to an additional 8 to 11.4 inches of sea level on top of the global average. Variations in sea level rise are caused by changes in ocean circulation, variations in temperature and salinity, and from changes in gravity as the Earth’s rotation fluctuates.

Scientists estimate that approximately two-thirds of the coastal wetlands in the U.S. will be lost if the sea level rises three feet, which could lead to increased carbon dioxide in the atmosphere as salt marshes regulate climate and oxygen levels on a global scale.

Locally, the story isn’t much better for Knowlton-Keen and her husband Frank. Walking out onto her backyard that flanks the salt marsh, she points out the rows of high-tide bush that’s now flourishing in place of ornamentals planted by her mother years ago. Some eastern prickly pear, also a species of concern, winds underneath the high-tide bush, heading around a stone-encased pool that occasionally finds itself under water during strong storms.

Across the marsh, a herd of Phragmites encroaches a sizable home — a sign that lawn fertilizer was used, Knowlton-Keen said. “In our yard, we’ve never fertilized,” she said. “We let it be what it wants to be. It’s not your golf course any more.”

Knowlton-Keen has taught art at Hindley School since 1977, where she incorporates marsh birds into several art lessons per year. Frank Keen shares his wife’s passion for nature. He recently retired after 34 years of teaching social studies at Middlesex Middle School, and is credited for bringing the district-wide recycling program to town last year.

Her sister, Nancy, who also grew up on the salt marsh, became a renowned marine biologist, having recently penned a book, “Citizens of the Sea,” for National Geographic.

At a recent public hearing for a home on Tokeneke Beach Drive, Knowlton-Keen and Todd Robbins told P&Z they were concerned about the possible impact this new structure would have on the wounded salt marsh, especially since it will be on a septic system with five bathrooms. Knowlton-Keen said she has been to many such meetings making her voice heard, but the big homes keep being built.

“People feel like they have a right to build these homes, but I think in certain places where it’s very sensitive, I would take their plans and find a different property to build what they want to build,” she said. “It’s a beautiful home but I don’t think it’s right to be on a sensitive marsh that’s on the brink of extinction.”

The Millers, who own the Tokeneke Beach Drive property, could not be reached for comment. Robbins said the Millers are friends and good neighbors, but that he’s concerned solely about whether the marsh can withstand the additional stress from construction.

“I feel like I’ve made enemies saying [these things],” Knowlton-Keen said, “but I feel my loyalty is to the marsh.”

Originally published in The Darien Times.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s