Repelling the Green Invaders
Sea Grant-Funded Researchers and Outreach Specialists Work to Control the Non-Native Cordgrass Spartina on Washington's Shores
Dull green in color, about waist-high, with numerous spikes bearing pale yellow flowers in summer months — at first glance, Spartina anglica looks like any other grass in a coastal environment. Yet this unassuming plant is a harmful and unwelcome invader of Northwest coastal wetlands. Since 1961, when a well-intentioned farmer first brought this exotic cordgrass to Washington's shores, S. anglica has occupied at least 73 sites and affected over 8,000 acres of tidelands, primarily in central Puget Sound but extending as far north as the Fraser River Delta of British Columbia.
This particular species of Spartina was introduced from England, where it evolved nearly 150 years ago from the hybridization of two other Spartina species. Soon after, English farmers realized the potential of Spartina to turn mudflats into desirable grazing land for cattle. That's probably what inspired the Washington farmer to plant S. anglica here.
Similar motives may have encouraged the settlers of Washington's Willapa Bay, where another nonnative species, S. alterniflora, is growing at alarming rates. Some believe, however, that this plant arrived as packing material in shipments of oysters from its place of origin, the Atlantic Coast of North America. Since its introduction about 100 years ago, this close relative of S. anglica has colonized approximately 15,000 acres of previously unvegetated mudflats. In parts of the bay, S. alterniflora has expanded its mass by about 20 percent per year — a rapacious rate that has earned this organism its reputation as the Plant Kingdom's answer to Attila the Hun.
A Management Challenge
In the Pacific Northwest, neither Spartina species has a natural enemy or grazer to slow its invasion. Both of these worrisome plants accumulate sediments around their roots, gradually transforming diverse mudflats or native marshes into solid Spartina meadows. In the process, commercial shellfish growers have lost valuable acreage, while migratory waterfowl and other animals that depend on a diversity of native plants — not just homogenous Spartina meadows — are losing important feeding, breeding and resting habitats.
"S. anglica presents an unusual challenge for land managers because it is remarkably versatile and resilient," write Megan Dethier and Sally Hacker in the WSGP-funded report Improving Management Practices for Invasive Cordgrass in the Pacific Northwest: A Case Study of Spartina anglica.
Unlike most marsh plants, S. anglica is capable of establishing itself in different habitat types, the two scientists point out. It and S. alterniflora cause major changes in the ecosystem by shaping the habitats they invade, often making them less suitable for native plants and animals. Both are also quite effective at producing and dispersing seeds. Because they store nutrients in their large, underground root masses, S. anglica plants can also withstand most attempts at eradication by hand-pulling or mechanical removal.
A Seasonal Strategy
With funding from Washington Sea Grant, Dethier and Hacker have devoted the past several years to studying S. anglica's ecology. They collected data on the timing of seed production and germination and made observations of the many physical factors that contributed to S. anglica's success. By linking this information with data from previous control studies conducted by the Washington State Department of Agriculture (WSDA) and other state agencies, they could make recommendations for developing management plans to thwart S. anglica's spread.
"We learned that any efforts to eradicate this plant must be consistent and well-timed," says Dethier, a Research Associate Professor at the University of Washington's Friday Harbor Laboratories. "It takes a combination of mechanical efforts, such as mowing, and herbicide sprays for at least three to four consecutive years to have any real effects."
Best results can be obtained by matching these efforts with S. anglica's reproductive patterns, Dethier and Hacker maintain. This means that mowing and herbicide spraying should be timed for early in the growing season (July) rather than later in the season (after mid-August), when most new growth and seed production has taken place.
"Several of the lessons learned from our work with S. anglica may apply to the control of S. alterniflora, because of the similarities in the biology of the two species," says Hacker, an Associate Professor in the Department of Zoology at Oregon State University, previously with Washington State University in Vancouver, Washington.
"Any long-term strategy for controlling S. anglica in Puget Sound must involve concerted attempts to reduce the impact of the plant in low-salinity marshes and mudflats, and to monitor satellite populations that can act as 'stepping stones' to other suitable habitats," Hacker and Dethier's report concludes.
Search and Destroy
Recognizing that early detection and swift removal are instrumental in the control of Spartina and other aquatic invasive species, WSGP produced Identifying Spartina, a companion publication to the popular European Green Crab Identification Guide, printed on waterproof paper. This easy-to-use identification card contains color photos of four Spartina species, along with key characteristics for field recognition of these aggressive, non-native plants. Two of these species — S. densiflora and S. patens — are currently limited to a few sites in Washington state. "However, it will take vigilance and a real effort on all our parts to prevent these species from becoming widespread," says WSGP's Associate Director Andrea Copping.
Sea Grant funding has also enabled Susie Richards, Service Learning Coordinator and seventh grade teacher at Langley Middle School, Island County, to bring Spartina awareness into classrooms on south Whidbey and Camano islands. For the past three years, middle school students have compiled data on Spartina in intertidal habitats, for incorporation into GIS maps. After joining forces with Judy Feldman of the Island County 4-H Youth Development Program, the Spartina Eradication and Education Project was born. Through this broad effort, which draws strength from its partners — the Camano-Stanwood School District, South Whidbey School District, Island County Noxious Weed Control Board, Coupeville School District, North Whidbey Middle School and WSDA — students have amassed data, created texts for brochures and interpretive signs and produced a video documentary about Spartina control.
The highpoint of each year has been a conference at Fort Casey State Park on Whidbey Island, where students share their knowledge of aquatic invasive species with residents of the Puget Sound region. The most recent conference, in early May 2005, drew a crowd of about 200 students and volunteer monitors. On two occasions, Richardson escorted groups of students to Olympia, to make presentations for Valoria Loveland, Director of the Washington Department of Agriculture and State Senator (District 10) Mary Margaret Haugen.
"We've had an enormous impact on the community at-large," says Richards. "Especially when you consider that every time you educate a kid, you're also educating their parents."
Thus, with Washington Sea Grant's help, knowledge about Spartina and its control is spreading as fast as the invasive cordgrass itself.
Summer 2005
Contact David G. Gordon, Science Writer for Washington Sea Grant, for further information.