Alhambra Creek - Habitat and Conservation

Habitat and Conservation

Two plant communities each comprise about half of the Alhambra Creek watershed, Coastal Oak Woodlands on north and east facing slopes and California Annual Grassland on drier high ridges and west and south facing slopes. The most common trees found in the oak woodlands are coast live oak, blue oak, California bay laurel, Toyon, and buckeye. In these woodlands, a wide variety of other plants grow beneath the trees, forming an understory. These plants include a variety of native and introduced grasses, herbaceous forbs, and small shrubs. Among the more common native understory plants are purple needle grass, soft chess grass, California yarrow, and poison oak. Native grasses that evolved over millions of years once dominated the grasslands of California. But changes in the fire frequency and intensity, the introduction of competitive grasses from the lands surrounding the Mediterranean Sea, and changes in the way the grasslands were grazed by animals led to a complete conversion in the species make-up of our grasslands. Now annual grasses introduced from Europe dominate California’s grasslands, while the native grasses cover only a minor fraction of the grassland area. The grasslands of the Alhambra Creek watershed support a wide array of wildflowers as well. Many of these wildflowers grow best when grazed moderately by wildlife and livestock.

Deer use the dense woodlands for forage, cover and shade. Coyotes and mountain lions prey on the deer. A huge number of bird species utilize the trees and shrubs for food, cover, and nesting habitat. Skunks and raccoons also live in the coast live oak woodlands, feeding on small mammals (like mice), insects, and vegetation. The coast live oak woodland of the Alhambra Creek watershed also supports at least one mountain lion, which feeds upon the deer that live there. One frequently used feeding spot is located near Carquinez Scenic Drive, just west of the watershed boundary. The ground squirrel is a keystone species in the annual grasslands, serving as an important food source for the coyote, red-tailed hawk, kestrel, and golden eagle.

Along Alhambra Creek's riparian corridor, trees like willows, cottonwoods, sycamores, big-leaf maples and valley oaks dominate riparian areas. Growing underneath the trees are a variety of shrubs including elderberry, California blackberry, and California rose. The American beaver has recently recolonized Alhambra Creek and is a keystone species as its ponds support steelhead trout and other fish, birds, otter and mink. Historically, Alhambra Creek likely supported a population of salmon and steelhead, as was typical of free flowing Bay Area streams. The Martinez Packing Company was established in 1882 and canned and shipped about 350 cases of salmon per day. The local commercial fishery thrived on huge runs of salmon up the Sacramento/San Joaquin River system.

Coastal marsh is another type of plant community found at the mouth of Alhambra Creek. Above the mudflats salt grass and pickleweed dominate the marsh. The salt marsh harvest mouse, a state and federally listed species, lives in these areas. A number of shore birds also nest in the coastal marsh community. They build their nests on the ground since no trees can survive in the salty soils. That is why dogs are not allowed in the Martinez Regional Shoreline at the mouth of Alhambra Creek.

The area was formerly roamed by the California grizzly bear (Ursus arctos horribilis ssp. californicus) and the black bear (Ursus americanus). The sighting of black bears in the upper watershed area near Bear Creek Road was a common occurrence up to the 1930s and ‘40’s. By the 1950s however, it was generally assumed that the bears had all disappeared from the region. In 1965 however, a bear was hit by a car and killed on San Pablo Dam Road. The memory of this last bear in Contra Costa is now preserved as a bearskin rug on the floor of a ranch house in the area.

In 1997, watershed conservation began in earnest when the Alhambra Creek Watershed Council was established to produce the Alhambra Creek Watershed Management Plan (2001). The group’s mission is to protect and enhance the health of the Alhambra Creek Watershed by educating the public about the watershed, acting as a community resource, and providing a forum for new ideas and projects. By representing diverse stakeholder interests and promoting healthy natural systems, AWC seeks the health and vitality of the entire watershed community. The County, Friends of Alhambra Creek, National Park Service, Muir Heritage Land Trust, residents, Martinez Planning Commission, and Alhambra Valley Improvement Association are all active participants.