A chokehold on Oregon’s estuaries

By Oregon Invasive Species Council,

SALEM, Oregon—Non-native cordgrass begs the question, “Just how bad can a grass be?” You may not want to know the answer.

Although wild hogs, quagga and zebra mussels, and yellow starthistle tend to grab the invasive species spotlight, lesser known species, such as non-native cordgrasses (Spartina spp.), are invading salt marshes and mud flats, threatening some of the most productive ecosystems on the West Coast. Because of their ability to choke estuaries, the Oregon Invasive Species Council features non-native cordgrasses as the October Invasive Species of the Month at http://www.oregon.gov/OISC/calendar2009.shtml.

Invasive cordgrasses are native to the eastern United States, South America, and Europe, but only one species of cordgrass is native to the West Coast—Spartina foliosa. The native species is found in salt marshes from Baja California, Mexico to Bodega Bay in California. Unfortunately, the native species of cordgrass has hybridized with one of the invasive forms to create a headache for land managers keen on protecting productive estuaries. Mark Sytsma, director of the Center for Lakes and Reservoirs at Portland State University, works closely with the Oregon Department of Agriculture on aquatic weed management, and is responsible for implementing the Oregon Aquatic Invasive Species Management Plan.
He said, “Oregon has learned a lot from how our neighboring states have dealt with Spartina, and I think we are in a pretty good position with it. It is a species that we know how to control and even eradicate. We just need to keep up our early detection surveys and act quickly when we find a new stand.” How did non-native cordgrasses reach the West Coast? They were brought here intentionally, with the purpose of erosion control and forage production, and unintentionally—hitching rides in ship’s ballast water or in oyster packing material.

When they arrived, it didn’t take long for them to do what invasive species do best—replace native species. Invasive cordgrasses can clog flood channels, displace native vegetation, raise mudflat elevation, and reduce habitat of Dungeness crab, shorebirds, and migratory birds by trapping sediments with their dense stems and root-mats of dense rhizomes. Willapa Bay, a 47,000-acre national wildlife refuge in Washington, is one of 10 major feeding stops along the Pacific Flyway. Willapa Bay provides critical food and shelter for dozens of shorebird species as they migrate to and from the Arctic during the spring and fall. Peak winter and spring shorebird use in parts of the bay has declined over 60% in the past decade as Spartina meadows have replaced the tidal mudflats. Managers have spent millions of dollars attempting to eradicate the cordgrasses and return the bay to its natural condition of expansive mudflats.

While California and Washington battle non-native cordgrasses, Oregon remains vigilant, studying the movement of cordgrasses and eradicating them immediately when they are found. The Center for Lakes and Reservoirs at Portland State University launched a drift card release study in 2004 to better understand Oregon’s vulnerability to non-native cordgrass from neighboring states.

Vanessa Howard Morgan, a graduate student at the Center for Lakes and Reservoirs, has been studying non-native cordgrasses for four years. She organized the release of bright-yellow drift cards in the mouths of three estuaries—Willapa Bay, Washington and Humboldt and San Francisco Bays in California—to monitor the movement of water currents and their potential distribution of cordgrass seeds. Her results demonstrate that Oregon is likely the continual recipient of non-native cordgrass seeds from California and Washington. The results of the drift card study can be found at http://www.clr.pdx.edu/projects/ans/spartina.php. Her work demonstrated that the battle against non-native cordgrass cannot be won by one state.

As a result, the governor’s of these three states are committed, through the West Coast Governor’s Agreement on Ocean Health, to eradicate non-native cordgrasses from the West Coast by 2018. It’s a tall order and will require a great deal of work with local communities in neighboring states to stress the importance of complete eradication of these invaders. Morgan said, “We know that there is a high probability that seeds and rhizomes of Spartina are being transported into Oregon, so the key to Oregon keeping Spartina out of our estuaries is to do everything we can to make sure that California, Washington, and British Columbia have an aggressive eradication program for their established populations.” Tim Butler, the manager of the Oregon Department of Agriculture’s Noxious Weed Program, was on point a few weeks ago to check the status of a large patch of non-native cordgrass in Youngs Bay, Astoria that was sprayed last year. This year, they found only seven plants to treat, meaning they had a 99.9% success rate last year. But Butler isn’t content unless there is complete eradication.

“The Youngs Bay Spartina infestation is a perfect example of implementing an aggressive Early Detection and Rapid Response (EDRR) program,” said Butler. “The Youngs Bay site was detected by a scheduled helicopter survey of the estuary in July, 2008 and it was initially treated that September by Oregon Department of Agriculture staff. These are exactly the types of projects that are most critical for protecting Oregon’s natural resources and a good example of how we can be successful. It is essential to detect infestations when they are small and aggressively treat them before they gain a major foothold. This type of effort makes sense biologically and economically—for every $1 invested in this type of project, there is an estimated return of $33.”

The fight against non-native cordgrass is an uphill battle that will require cooperation, education and outreach, funding, and legislative support to achieve the goal of complete eradication by 2018, not only lessening the chokehold Spartina could have on Oregon’s estuaries, but eliminating it. Failure is simply not an option.

The mission of the Oregon Invasive Species Council is to conduct a coordinated and comprehensive effort to keep invasive species out of Oregon and to eliminate, reduce, or mitigate the impacts of invasive species already established in Oregon. ####

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