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Spartina Infestation Contained
The tide may have turned in the struggle against one of San Francisco Bay’s worst invasive species, non-native cordgrasses of the genus Spartina. “The heart of the infestation is now under control,” said Maxene Spellman, the Conservancy’s project manager for the Invasive Spartina Project (ISP). “The 2005-2006 control program was very successful, thanks largely to the much longer time allowed for treatment by the U.S. Fish and Wildlife Service, a new, more effective herbicide [imazapyr], lessons learned from previous years, and increasingly stronger partnerships.”

Since 2000, the Conservancy has spent $7,772,507 on ISP, most of which came from various grants. In March it approved an additional $1,250,868 grant of Wildlife Conservation Board funds for treatment projects. The Conservancy also approved $949,907 to operate and manage the regionally coordinated project through spring 2008.

Native California cordgrass, Spartina foliosa, is an important component of marsh ecosystems. But the three species that were introduced to San Francisco Bay starting in the 1970s are highly invasive, spreading at a greater than exponential rate and altering the physical structure and biological composition of marshes, mudflats, and creeks. Non-native invasive spartina converts mudflats to cordgrass meadows and fills in channels and sloughs, destroying habitat for native plants and animals and disrupting marsh hydrology. One species in particular, Spartina alterniflora, hybridizes with the native Spartina foliosa, and has invaded every marsh restoration project in the south and central San Francisco Bay Estuary in the past 15 years. (See Coast & Ocean, Vol. 16, No. 2 and Vol. 19, No. 2 for more about the history and impacts of the spartina invasion.)

In the 1990s biologists began to realize the extent of the invasion, and in 2000 the Conservancy established ISP to coordinate eradication efforts among federal, state, and local agencies and organizations. In 2004, ISP partners began to apply mechanical and chemical treatment to infested acres. The following year, 1,010 acres--67 percent of the infestation at that time--were treated in just over a month. In 2006, 94 percent of the acreage estimated to be infested with spartina was treated. Early observations suggest that the 2006 effort killed 70 to 90 percent of the weed in treated areas.

Now that invasive spartina’s spread has been contained, ISP partners can focus on eradication. All remaining untreated stands--most of them in hard-to-reach areas--will be treated, and sites will be revisited as necessary.

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