Spartina alterniflora is a fast-growing, rapidly-spreading perennial grass found in estuaries. Native to North America’s Atlantic and Gulf Coasts, the grass probably came to the West Coast in the late 19th century in shipments of oyster transplants that may have been packed in spartina.
Once established, spartina or cordgrass grows in tight clusters, or clones, that trap sediment and raise the height of the substrate.
Left alone, spartina clones eventually coalesce and grow together, forming a meadow of high marsh grass where once there were mud flats.
The worst spartina infestation is in Willapa Bay, arguably the most productive commercial oyster-producing area in Washington. Invasive cordgrass also has made inroads into Puget Sound, Grays Harbor, and rivers on the Olympic Peninsula. Uncontrolled, spartina will crowd out native species, reduce biodiversity, and alter wetland ecosystems.
For decades, spartina has threatened to overtake the inter-tidal mud flats and natural salt marshes of Willapa Bay. The bay provides habitat for thousands of shorebirds, waterfowl, and other animals.
In 1970, spartina clearly had established itself in the bay and covered about 75 acres. By 1988, it infested about 1,200 acres. In 2003, the peak of the infestation, more than 8,500 solid acres of spartina covered 20,000-plus acres of the bay’s intertidal zone.
Starting in the early 1990s–long after spartina had been established–agencies began efforts to manage the noxious weed. The state Departments of Natural Resources, Fish and Wildlife, and Agriculture, and the U.S. Fish and Wildlife Service used mechanical, chemical, and biological techniques to control spartina.
In the early days, these techniques were met with varying degrees of success. Field workers were applying herbicide using small-scale tools, such as backpack sprayers. Small crews of three to four people were using brush cutters to treat massive spartina meadows. Boats were unable to travel across the mudflats so workers often were forced to walk great distances, in soupy mud, just to reach and treat spartina.
Agencies developed more efficient and effective tools. They turned to airboats to traverse mud flats, high-pressure spray systems that could treat greater areas of infestation in a shorter amount of time, and a new herbicide that yielded better and more consistent results. With the new herbicide also came aerial (helicopter) treatment of huge spartina meadows.
For the first time, and in just a few days, crews treated massive spartina meadows in their entirety. After years of little progress, the control effort had begun to reduce the size of the infestation.
Today the infestation totals about 1 acre of the 80,000-acre bay.
Despite the early challenges tackling spartina, the story of its eradication is considered a success today because Willapa Bay is nearly free of the invasive plant.