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【1】Spartina alterniflora, known as cordgrass, is a deciduous, perennial flowering plant nativeto the Atlantic coast and the Gulf Coast of the United States. It is the dominant native speciesof the lower salt marshes along these coasts, where it grows in the intertidal zone (the areacovered by water some parts of the day and exposed others).
【2】These natural salt marshes are among the most productive habitats in the marineenvironment. Nutrient-rich water is brought to the wetlands during each high tide, making ahigh rate of food production possible. As the seaweed and marsh grass leaves die, bacteriabreak down the plant material, and insects, small shrimplike organisms, fiddler crabs, andmarsh snails eat the decaying plant tissue, digest it, and excrete wastes high in nutrients.Numerous insects occupy the marsh, feeding on living or dead cordgrass tissue, and redwingblackbirds, sparrows, rodents, rabbits, and deer feed directly on the cordgrass. Each tidal cyclecarries plant material into the offshore water to be used by the subtidal organisms.
【3】Spartina is an exceedingly competitive plant. It spreads primarily by underground stems;colonies form when pieces of the root system or whole plants float into an area and take root orwhen seeds float into a suitable area and germinate. Spartina establishes itself on substratesranging from sand and silt to gravel and cobble and is tolerant of salinities ranging from thatof near freshwater (0.05 percent) to that of salt water (3.5 percent). Because they lack oxygen,marsh sediments are high in sulfides that are toxic to most plants. Spartina has the ability totake up sulfides and convert them to sulfate, a form of sulfur that the plant can use; thisability makes it easier for the grass to colonize marsh environments. Another adaptiveadvantage is Spartina’s ability to use carbon dioxide more efficiently than most other plants.
【4】These characteristics make Spartina a valuable component of the estuaries where itoccurs naturally. The plant functions as a stabilizer and a sediment trap and as a nursery areafor estuarine fish and shellfish. Once established, a stand of Spartina begins to trapsediment, changing the substrate elevation, and eventually the stand evolves into a highmarsh system where Spartina is gradually displaced by higher-elevation, brackish-waterspecies. As elevation increases, narrow, deep channels of water form throughout the marsh.Along the east coast Spartina is considered valuable for its ability to prevent erosion andmarshland deterioration; it is also used for coastal restoration projects and the creation ofnew wetland sites.
【5】Spartina was transported to Washington State in packing materials for oysterstransplanted from the east coast in 1894. Leaving its insect predators behind, the cordgrasshas been spreading slowly and steadily along Washington’s tidal estuaries on the west coast,crowding out the native plants and drastically altering the landscape by trapping sediment.Spartina modifies tidal mudflats, turning them into high marshes inhospitable to the many fishand waterfowl that depend on the mudflats. It is already hampering the oyster harvest and theDungeness crab fishery, and it interferes with the recreational use of beaches and waterfronts.Spartina has been transplanted to England and to New Zealand for land reclamation andshoreline stabilization. In New Zealand the plant has spread rapidly, changing mudflats withmarshy fringes to extensive salt meadows and reducing the number and kinds of birds andanimals that use the marsh.
【6】Efforts to control Spartina outside its natural environment have included burning,flooding, shading plants with black canvas or plastic, smothering the plants with dredgedmaterials or clay, applying herbicide, and mowing repeatedly. Little success has been reportedin New Zealand and England; Washington State’s management program has tried many ofthese methods and is presently using the herbicide glyphosphate to control its spread. Workhas begun to determine the feasibility of using insects as biological controls, but effectivebiological controls are considered years away. Even with a massive effort, it is doubtful thatcomplete eradication of Spartina from nonnative habitats is possible, for it has become anintegral part of these shorelines and estuaries during the last 100 to 200 years.