Since 2003, Friends has been the local sponsor for the Invasive Spartina Project, the multi-agency project led by the Coastal Conservancy, to eradicate invasive cordgrasses from San Francisco Bay. Hal Brown Park was the introduction site for two of the four invasive species: S. densiflora and S. anglica. The S. densiflora had spread throughout the tidal areas of the watershed. S. anglica, at the extreme southern edge of its range, did not spread out of the park. An intensive effort using digging, mowing, and treatment with the herbicide imazapyr has eliminated over 98% of both infestations. The final push to document three years with no detections is underway.

The various cordgrasses found in San Francisco Bay have different growth habits and preferred locations in the marsh.

The North Bay Conservation Corps worked with Friends for nine years, digging out and hauling away non-native cordgrass.