Using acreage data from the Gap Analysis Project CD-ROM and the habitat classes from the California Wildlife Habitat Relationships Database (CWHR) we developed these tables of rangeland acreage for California's 58 counties. The Gap Analysis Project used remotely sensed data to classify the habitat types. Because this method is different from the estimation methods used in the past these numbers may differ from those reported from other sources. To determine county rangeland acreage the rangeland habitat types in the CWHR for each county were combined. Twenty-six of the CWHR habitat types were classified as rangelands based on the Society for Range Management's definition of rangelands that includes natural grasslands, savannas, shrublands, most deserts, tundra, alpine communities, and wet meadows. We included pinon-juniper and juniper habitat types but not other forest habitat types that may be grazed.
This classification results in a total rangeland acreage of 62.9 million acres for California. The figure of 40 million acres of rangeland is often used, however that is not correct. California has about 40 million acres of grazed land. In 1988 the California Department of Forestry and Fire Protection reported that about 41 million acres of California land was grazed and 17.9 million of those acres were privately owned and provided more than 90 percent of the state's grazed forage (CDFF 1988).
There are some inaccuracies in the mapping of habitat types. Satalite imagary is not very accurate for distinguishing some habitat types and ground truthing is not possible for a project of this scale. However, used at the county to regional level these maps can provide a better assessment of rangeland acreage than any method that has been used in the past.
The California Gap Analysis Project (CA-GAP) was initiated in 1990 as a cooperative effort between the U.S. Fish and Wildlife Service and researchers at the University of California, Santa Barbara. Dozens of public and private organizations also provided invaluable support. The objectives of the project were to 1) develop new geographic information system (GIS) databases of land-cover, wildlife habitats, predicted distributions of native wildlife species, and land stewardship and management; 2) identify land-cover types and wildlife species that are inadequately represented in existing biodiversity management areas (i.e., the "gaps"); and 3) make all CA-GAP information available to users to encourage and facilitate its use so that resource managers may be more effective stewards of California's biological heritage.
CDFF. 1988. California's Forests and Rangelands: Growing Conflict Over Changing Uses. Forest and Rangeland Resources Assessment Program (FRRAP), Calif. Dept. of Forestry and Fire Protection. Pg 99.