Northern Coastal Salt Marsh

In this issue, I am focusing on another of San Francisco’s rarities, but this time it is a habitat, not a particular species. Northern coastal salt marsh is a highly productive plant community dominated by herbaceous, suffrutescent (subshrubby), salt- tolerant hydrophytes (water plants), typically forming a dense mat of vegetation up to three feet high. Species are segregated vertically into more or less distinct zones defined by the degree to which they are inundated by the tides. This plant community occurs along the California coast from Oregon to near Point Conception where it intergrades with southern coastal salt marsh. It is especially extensive around San Francisco Bay but is also well developed at Humboldt Bay, Tomales Bay, Elkhorn Slough, and Morro Bay.

Perhaps the plant that is most characteristic of northern coastal salt marsh is pickleweed (Salicornia virginica). This succulent, salt tolerant perennial forms a dense canopy over large expanses in the Bay. Other commonly encountered native plants include California cordgrass (Spartina foliosa), alkali heath (Frankenia salina), salt grass (Distichlis spicata), dodder (Cuscuta salina var. major), jaumea (Jaumea carnosa), sea lavender (Limonium californicum), and marsh gum-plant (Grindelia stricta var. angustifolia), among many others.

Northern coastal salt marsh provides habitat for numerous endangered, threatened, and rare animals and plants. Some of the rarest animals in the Bay that are dependent on salt marsh habitat include the California clapper rail, California black rail, salt marsharvest mouse, salt marsh common yellowthroat, Alameda song sparrow, and salt marsh wandering shrew.

Some rare plants, known from historical records to be associated with salt marsh habitats in San Francisco Bay, are Point Reyes bird’s-beak (Cordylanthus maritimus ssp. palustris), soft bird’s-beak (Cordylanthus mollis ssp. mollis), Marin knotweed (Polygonum marinense), Suisun marsh aster (Aster lentus), Humboldt Bay owl’s-clover (Castilleja ambigua ssp. humboldtiensis), Mason’s lilaeopsis (Lilaeopsis masonii), rose-mallow (Hibiscus lasiocarpus), Delta mudwort (Limosella subulata), marsh gum-plant (Grindelia stricta var. angustifolia ‹see September 1996 newsletter), California sea-blite (Suaeda californica), marsh horsetail (Equisetum palustre) and hairless popcorn-flower (Plagiobothrys glaber), among others.

In the past 150 years, filling and construction of dikes have reduced the area of San Francisco Bay by 37 percent. The fringes of the Bay have long been subjected to filling and diking for agriculture, salt production, and development. Currently, the San Francisco Bay covers 478 square miles at high tide and receives runoff from approximately 40 percent of California’s land area. Fewer than 45,000 acres of the San Francisco Bay estuary’s historic tidal marshes remain intact, a reduction of 92 percent. The San Francisco Bay Area is the fourth most populous metropolitan area in the United States and the Bay continues to fall under relentless assault. The region’s booming economy, high land and home values, and influx of people place a constant pressure to expand development ever further into the Bay.

San Francisco itself has few examples of northern coastal salt marsh, none of which are either extensive or unaltered. Salt marshes can be found north of Pier 94 and at Pier 98, South Basin, India Basin, and the Islais Creek Channel. There is a good potential to restore these sites. A wetlands creation effort is being proposed for Treasure Island. In the meantime, San Franciscans need to travel a bit to experience the natural beauty of our salt marshes. There are excellent salt marsh interpretive centers and wildlife viewing areas at Hayward, Newark, Alviso, Palo Alto, and Tiburon, among others. Fall is probably the most splendid season to visit the marshes as migratory birds begin their travels southward and the colors of the vegetation are most vivid. Marsh gum-plant will still be in bloom as are the bird’s-beaks, if you’re fortunate enough to see one. Bring your cameras and binoculars. Enjoy the fall.