Herbicide plan for Bo Lagoon

04/10/2014

Despite previous eradication efforts, last year two colonies of spartina, commonly called cordgrass, invaded 1,000 square feet of mudflats on the eastern shores of Bolinas Lagoon. Last week Marin County’s Open Space District released a study and draft negative declaration of environmental impact for a plan to use a single targeted application of the herbicide imazapyr, which has been used in San Francisco Bay. The invasive grass in Bolinas likely escaped from that bay, where the Golden Gate National Recreation Area has fought the plant that at one point covered 800 acres. The grass threatens populations of native spartina, and ecologists say it could overtake the lagoon’s mudflats and turn them into cordgrass marsh that would spread to other estuaries. “If left unchecked, [invasive spartina in Bolinas Lagoon] would not only take over Bolinas’ upper mudflats, they would rain hybrid seeds to all of Drakes and Limantour Esteros, Tomales Bay, and also back to the Golden Gate, re-infesting San Francisco Bay,” according to Peter Baye, a coastal ecologist who wrote the initial study of the lagoon’s cordgrass and the draft impact declaration. The lagoon attracts over 35,000 birds each year, many stopping over on the Pacific Flyway migration route. Although the county battled previous colonies of invasive spartina by pulling them out by hand or covering them with tarps, the grass’s presence on the water-logged upper mudflats makes those options infeasible, the plan says. The eradication plan mitigates the potential impacts of the herbicide on nearby rare plants by spraying on low-wind days, avoiding the season when those plants are sprouting, covering those plants with tarps if needed and applying the herbicide directly on the invasive plant, as opposed to a blanket application. Comments on the study and draft negative declaration are due by May 5 at 4:30 p.m. They can be emailed to jraives@marincounty.org, or mailed to Marin County Parks, Attn: James Raives, Senior Open Space Planner, 3501 Civic Center Drive, Suite 260, San Rafael CA 94903.