Friends participates in a project that is underway throughout the tidal marshes of San Francisco Bay to eradicate invasive non-native cordgrasses (Spartina spp.). We receive funding from the California State Coastal Conservancy’s Invasive Spartina Project (ISP) to work toward eliminating three species of introduced cordgrasses and their hybrids with the native cordgrass in our estuary. These destructive plants alter both the structure and function of tidal creeks and wetlands, harming native bird, mammal and fish species. Invasive cordgrasses also clog open channels, increasing flood risk and reducing navigability of waterways.
The ISP has researched eradication methods and has followed standard Integrated Pest Management protocols to develop the current treatment techniques. In a few locations, spraying individual plants with an herbicide containing the active ingredient imazapyr has been effective. Increasingly, we remove the invasive Spartina manually, finding this more reliable. The ISP has carefully documented the project, including the staff’s thorough analysis of the various treatment methods; the documentation is available on ISP’s website at www.spartina.org.
We carried out a pilot project at Piper Park in Larkspur starting in 2003. In 2005 through 2008 we treated all of the infestations in the Corte Madera Creek estuary, except for a few isolated spots where individual property owners would not grant permission for the treatment; unfortunately, these untreated plants continue to produce seeds. Follow-up treatments—nearly all involving digging—will be done over the next few years to complete the project. Crews from the Conservation Corps and volunteers do the digging; any spraying is done by licensed contractors. For large marshes where California clapper rails breed, the treatment season is September through January. In other areas, we can dig throughout the year and spray when the plants are growing.
We wish to thank all those property owners who have participated in this project, the aim of which is to maintain the richness of plant and animal life in our marshes.