Biologists Battle Non-Native Marsh-Devouring Grass

Island’s shores infested with East Coast hybrid

Written by Ryan White
Published: Friday, 21 July 2006


Photo of Elsie Roemer Bird Sanctuary marsh
Marsh at the Elsie Roemer Bird Sanctuary may look healthy, but the fields of green lining the shore consist of a quickly spreading species of invasive cordgrass. Photo by Ryan White.

Islands of lush, green cordgrass wave in the wind and carpet the shore as lapping waves and foraging birds dance around their stems. It could be a page out of an Audubon calendar. But where the untrained eye sees verdant local marsh life, local biologists see wave upon wave of an invasive, life-choking mutant known as Spartina alterniflora, or East Coast cordgrass.

From Elsie Roemer Bird Sanctuary to San Leandro Bay to the fringes of Bay Farm Island, biologists say the invasive cordgrass has turned some stretches of shoreline into ecological deserts.

The city’s Public Works Department teamed with the California State Coastal Conservancy and the East Bay Regional Parks District to hold a public information meeting on the ongoing Spartina eradication project Wednesday evening at City Hall. The second phase of the three-year project gets underway this September.

Although the offending invader has spread throughout the Bay’s marshlands, it was first introduced in the 1970s when the Army Corps of Engineers imported it to shore up Bay Farm Island levees. The East Coast transplant flourished, growing taller, denser and faster than the native cordgrass.

Then, sometime in the 1990s, biologists discovered that nonnative Spartina had hybridized with the native Pacific Coast species, a fairly rare event, biologists say. The new mutant strain has since colonized marsh shorelines around the Bay, flooding native stands of cordgrass with hybrid pollen.

“We’ve seen an exponential spread of cordgrass in the marshes,” said Erik Grijalva, field operations manager for the San Francisco Estuary Invasive Spartina Project, in an interview Tuesday.

The hybrid occupies about 20 acres of shoreline in Alameda, and about 1500 acres of marshland Bay-wide, according to Coastal Conservancy numbers. Alameda is home to some of the most densely infested sites, said Grijalva, an Alameda resident.

The hybrid’s mixed genetics allow it to dominate a wide spectrum of ecological niches in the marsh, driving out other plants and animals, like the endangered California clapper rail and the salt marsh harvest mouse, that depend on a variety of micro-habitats. “It creates a dense, monocultural marsh,” Grijalva said.

And Alameda’s Spartina infestation can have Bay-wide effects, since the many clusters around the Island act as a seed-source for the plant’s continuing spread.

But biologists and environmentalists are hoping to halt its onward march. This September, members of the Spartina Project, founded in 2000 by the California State Coastal Conservancy, will refine their eradication strategy in an attempt to nudge area marshes back to their native state.

But that won’t be easy. With roots that delve up to 2 feet into the marsh bottom, manually removing the invasive cordgrass is not only arduous work, but all those boots trudging through the marsh can further damage the habitat. New technologies for applying a Spartina-killing herbicide might help, including the use of a Marsh Mog, an amphibious, GPS-guided vehicle that leaves behind a light footprint.

In addition, the project’s herbicide of choice, a newer chemical called imazapyr, will be applied differently this year in attempt to more effectively target the Spartina hybrid.

But at least one local environmental group has balked at the idea of adding another chemical to the Bay.

“We are concerned that not enough studies have been done on the chemical,” said Sejal Choksi, program director of Baykeeper, a San Franicsco-based environmental watchdog group. “What is the accumulated impact on aquatic species?”

Others offer qualified support for the chemical’s use.

“We don’t support herbicide use normally, but in this case it’s a necessary evil,” said Marilyn Latta, habitat restoration director for the Save the Bay organization, adding that, in the case of Spartina, hand-removal just isn’t feasible.

Grijalva is confident the herbicide is safe. “It’s one of the least toxic herbicides on the market,” he said, adding that the chemical specifically targets plants’ amino acids, and in such low concentrations, doesn’t pose a threat to humans or pets.

Even with the project’s increasingly fine-tuned plan of attack, Grijalva says it’s likely some of the infestations will return, which can then be targeted with periodic spot-treatments. His agency is hoping to eradicate Spartina to the point where volunteers and land managers can monitor flare-ups after the program’s state and federal funding expires in 2007.

Although other Bay habitats present a veritable soup of invasive species — often hitching rides into the Bay in the ballast water of container ships — Grijalva says that with the exception of Spartina, tidal marshlands are relatively invasive-free, giving this project a rare chance to fully restore large sections of shoreline.

“The opportunity we have is to control the plant and restore the marsh to its native conditions,” Grijalva said. “We can look forward to a day in the not-too-distant future when the native marsh is restored.”


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