The Coastal California Region (Region 25*) extends from Bodega Bay south to northern Mexico and includes the important San Francisco and San Diego Bays. The Coast Mountain Range is also considered in this region as is the Central Valley and the Salton Sea. The most important waterfowl habitat in the region is the Central Valley where DU has an extensive program of habitat restoration, protection, and enhancement.
The Central Valley of California averages 64 km wide by 644 km long and consists of the two lesser valleys, the Sacramento in the north and the San Joaquin in the south. One of the largest freshwater deltas in the world is formed at the confluence of the Sacramento, San Joaquin, Mokelumne, and Cosumnes Rivers. These waters then flow through Suisun Bay (Marsh) into San Francisco Bay. Wetlands in the Central Valley historically have hosted some of the largest concentrations of wintering waterfowl in the world. Estimates from the 1800s place waterfowl numbers between twenty and 40 million birds. More recently, population objectives for the Central Valley have been stepped down from the North American Waterfowl Management Plan (NAWMP). These population objectives call for the Central Valley to sustain peak wintering populations of nearly six million ducks and one million geese. Up to 60% of all Pacific Flyway waterfowl rely on the Central Valley during some portion of the migration or wintering period. Nowhere in North America do so many waterfowl winter on such a small wetland base.
Prior to the Gold Rush period of the mid-1800s, an estimated 5 million acres of wetlands were present in the state (Heitmeyer et al. 1989). However, the loss and degradation of these habitats has been dramatic. More than 95% of the historic wetland area and over 90% of the riparian corridors in California have been destroyed or modified (Gilmer et al. 1982). Although habitat loss in the Central Valley has slowed or even been reversed in recent years, population growth and urbanization continue. Human populations in California are expected to nearly double by 2040. Much of this growth will occur in the Central Valley where human populations are projected to increase from 5.7 million to 13.1 million over the same period.
*Region 25 - NABCI Bird Conservation Region 32