Atlantic cordgrass (Spartina alterniflora), also known as smooth cordgrass, was introduced by an employee of the U.S. Army Corps of Engineers who had limited understanding of biology and no knowledge of the hazards he was creating; the other offender, dense-flowered cordgrass (S. densiflora), was introduced by a geneticist working with a landscape designer who didn’t understand that there was a difference between the native San Francisco Bay cordgrass (S. foliosa) and one he had found growing in Humboldt Bay. Once introduced, both cordgrasses have naturalized, spread, and now further degrade the San Francisco Bay ecosystem, particularly its shorebird habitat and its native marsh flora.

In the late 1960s, Tom Harvey, a biology professor at San Jose State University, conducted an experiment to see whether marsh vegetation would grow on land that was once a tidal wetland, then diked and left to dry out, and subsequently reopened to tidal activity. Until this time the general belief was that once gone, wetlands were gone forever. Before dikes were breached at the Faber Tract (no relationship to the author) in Palo Alto, Harvey transplanted a few sprigs of the native San Francisco Bay cordgrass into an area that had been made tidal. To his delight, the plants became established and grew. This success pointed the way toward restoring a number of diked former tidal marshlands in San Francisco Bay. The era of marsh restoration had arrived. The question then became how to do restoration work.

A few years later, in the early 1970s, several young men at the San Francisco Division of the U.S. Army Corps of Engineers took a field course in wetland ecology given by Ida Geary, a private biology instructor from Mill Valley. One of her students, Paul Knudsen, a returning Vietnam marine, soon became involved with a potential restoration project on a 75-acre site at Pond 3 adjacent to Alameda Creek in the south Bay. Knudsen met and talked with Professors Emeritus Herbert Mason from the University of California and Curtis Newcombe from San Francisco State University, who were experimenting with methods for restoring cordgrass along Alameda Creek. Should one sow seed, plant sprigs, or transplant clumps of cordgrass? They agreed that, for large-scale restoration, sowing seed was the least labor-intensive method and least likely to disrupt donor marshes.

The seed set for Spartina foliosa harvested in San Franciso Bay is frequently poor, so Knudsen turned to Ed Garbish, director of Environmental Concern, a private consulting firm and nursery in St. Michael’s, Maryland, on the east shore of Chesapeake Bay. Garbish had worked extensively on methods for handling the seed of Atlantic cordgrass, an eastern native. He had found that overwintering seeds at a constant temperature in refrigerated fresh water resulted in the highest rates of germination, and that seed sowed directly over exposed mudflats gave good establishment success. This was particularly important along the eastern seaboard, where erosion threatens the shoreline. It was hoped that through proper seed management, large stands of Atlantic cordgrass—a perennial that grows to six to eight feet in height, twice as tall as our native cordgrass—would stabilize large areas.

Paul Knudsen wanted to experiment on the Corps’ Pond 3 site to demonstrate large-scale establishment of cordgrass. He arranged to buy some of the Environmental Concern seed of Atlantic cordgrass collected in Maryland that had been properly overwintered. The imported seeds were spread across the mudflats in Pond 3, and many germinated and became established. Dikes at Pond 3 were breached soon after the planting; Atlantic cordgrass quickly naturalized, and it is now aggressively spreading around the Bay. Paul Knudsen transferred to the Corps facility in Mississippi soon after this planting and several years later left the Corps to work in his wife’s antique store in New Jersey.

According to Don Strong at the Bodega Marine Lab, Atlantic cordgrass spreads by dispersal of seeds on the tides. Because it is apparently hybridizing with native cordgrass (S. foliosa), largely through its windblown pollen, it is a particularly aggressive and disturbing invader. Atlantic cordgrass grows at somewhat lower elevations than the native plant, reducing the area of intertidal mudflat—shorebird feeding grounds—at low tides. Its dense growth also clogs flood control and navigation channels.

By 1988 Atlantic cordgrass had spread 15 miles north to the bayfront at Alameda, where Brit Larson, a graduate student of wetland biologist Michael Josselyn of San Francisco State University’s Tiburon Centers, studied its habitat and growth patterns. By 1990 it had also spread 15 miles south into Alviso and Mud Creeks, where it now densely lines creek edges. Debra Ayres, a postdoctoral student in Strong’s lab and lead author of a study published in 1999, reported that Atlantic cordgrass is competitively superior to native cordgrass and that all categories of hybrids exist in marshes colonized by water-dispersed seed. The study predicts that proliferation of cordgrass hybrids could grossly alter the character of San Francisco Bay.

The circumstances surrounding the introduction of dense-flowered cordgrass (Spartina densiflora) into San Francisco Bay are quite different, but provide another example of good intentions gone awry. In this case, the problem involved mistaken identity: the Humboldt form of Spartina was thought to be a growth form of the native cordgrass species, S. foliosa. For aesthetic reasons it was selected for a landscaping plan, and as it turned out, another exotic was thus introduced into San Francisco Bay.

This tale begins in 1972. Property between Marin Catholic School and Corte Madera Creek in Marin County was slated for development. Barbara Boxer, now a U.S. senator from California, was then running for county supervisor and made protecting this land part of her political campaign. She won, and the County subsequently acquired the site, now called Creekside Park. The County contracted with landscape architects Royston, Hanamoto & Abbey to create a park. They in turn subcontracted with Curtis Newcombe, of the San Francisco Marine Resources Center in Richmond, to develop and carry out a vegetation plan. Newcombe, formerly a professor of biology at San Francisco State University, had recently hired a former colleague and genetics professor, Kenneth Floyd; Floyd would create the vegetation plan.

In preparation, Floyd visited tidal salt marshes along the northern California coast. He was attracted to the gray, clumped appearance of the cordgrass growing in Humboldt Bay and incorporated it into his plan. He thought it was a growth form of the San Francisco native, S. foliosa. Not being a botanist, he did not question the species identification. During this period, Tom Harvey had mentioned to various people that the plant he saw on Humboldt Bay looked different from the San Francisco native, but no significant attempt was made to further identify it until after it had been introduced into Creekside Park. Landscaping for Creekside Park was carried out in 1976–77.

In 1983, I collected cordgrass specimens from Humboldt Bay and, using specimens in the California Academy of Sciences collections, tentatively identified the Humboldt plant as Spartina densiflora. Biology professor Beacher Crampton, a grass specialist at the University of California, Davis, later confirmed this identification. I then carried out transplant experiments to determine if the Humboldt form of cordgrass would revert to a more typical form when grown in San Francisco Bay. It did not. I also collected the cordgrass S. densiflora from three locations along the coast in Chile and from a fourth on Chiloe Island, also in Chile. In 1985 Josselyn and Douglas Spicher published a description of the Humboldt S. densiflora as part of Spicher’s master’s thesis—along with his hypothesis that the plant had arrived in California aboard a lumber ship from Chile that emptied its ballast water into Humboldt Bay.

In the meantime, dense-flowered cordgrass—now known to be an introduced species—was growing well in Creekside Park in Greenbrae. Too well. Dense-flowered cordgrass is distinguished from the native cordgrass by more than its color, narrower leaf blades, and earlier bloom. It grows at a higher elevation than the native cordgrass and outcompetes other plants; it thus threatens mid-elevation species such as alkali heath (Frankenia salina), marsh rosemary (Limonium californicum), and Jaumea carnosa. After almost 30 years, this plant has spread along Corte Madera Creek to the San Francisco bayfront.

So in San Francisco Bay, where 90 percent of tidal marsh habitat has been lost over the past 120 years, we now have two new introduced nonnative species of cordgrass disrupting a vitally important ecosystem. Smooth cordgrass is reducing the feeding grounds for migrating shorebirds, while dense-flowered cordgrass is reducing the tidal marsh flora. The public will foot the bill either for the removal of these invasive grasses or for the damage their spreading will cause. Certainly there was no criminal intent in either introduction; however, it is also clear that each was preventable. No professional botanists were involved in these two introductions. Had they been, their plan review might have discouraged either or both.

Accidental introductions such as occurred in Humboldt Bay over a hundred years ago may become more preventable if there are requirements to empty ballast water at sea. Accidental introductions by well-meaning landscapers are no longer acceptable: people need to be aware of the risk of moving plants from one place to another. As stewards of our land we must work hard to discourage the inadvertent moving of plants that naturalize easily, and if mistakes do occur, we must act promptly and aggressively to control introduced populations. Each of us is guilty of watching weedy plants spread—and conversely, each of us could help in their control or elimination. Sadly, through human carelessness or ignorance, the biodiversity of this once rich ecosystem is being reduced by the introduction of exotic species. We need no more good deeds gone awry.

Phyllis M. Faber is a founding member of the League of Coastal Protection, a former chairman of the North Central Coastal Commission, and the general coeditor of the Natural History Series for the University of California Press.