This polygon shapefile depicts the division of the nine county San Francisco Bay Area Region, California into 34 landscape units, or subregions, to ensure that conservation targets are conserved across latitudinal and elevational gradients (redundancy), onto which other thematic data can be layered.Delineation of the landscape units followed major physiographic features, primarily mountain ranges and intervening valleys. Discrete mountain ranges, such as Mt. Diablo, Sonoma Mountains, Southern Mayacamas and Marin Coast Range became a landscape unit. Where discrete valleys did not exist, major highway corridors were used to subdivide mountain ranges as in the cases of the East Bay Hills landscape unit (Highways 24, 580, and 680), Santa Cruz Mountains landscape unit (Highway 17) and American Canyon landscape unit (Highway 12). Major valleys such as Napa, Sonoma and Santa Clara were delineated manually with the use of slope and topographic hillshade. The urbanized plains around the Bay were included as four landscape units labeled "urban" - San Mateo, Alameda, Contra Costa and Santa Clara - and were excluded from the broad planning exercise. However, key remaining habitats occur within these urban areas, especially riparian corridors, and will be targeted during the fine filter analyses. A fifth landscape unit, incorporating lands at the Bay's edge that were the subject of the Baylands Ecosystem Goals Project, were considered outside the study area. This geographic stratification captures genetic variability and provides multiple representations of conservation targets, both of which assist with resilience and ensure redundancy in the event of major habitat loss or disturbance. The primary conservation network design, therefore, is being done within landscape units so that representation and integrity of local networks is achieved. This approach focuses attention first on filling out and connecting existing reserve networks in each landscape unit, and then maintaining linkages between landscape units. This coverage can be used as general reference, for cartography and for geospatial applications developments. This layer is part of the Conservation Lands Network regional biodiversity GIS database. This dataset was developed/compiled for use in the San Francisco Bay Area Upland Habitat Goals Project, a Project used to identify a Conservation Lands Network (CLN) for biodiversity preservation to inform conservation investments and lasting cooperative conservation partnerships. The Conservation Lands Network GIS Database is the primary output of the Project. The data depicts the spatially explicit CLN that is recommended for the nine county San Francisco Bay Area Region, California. Bay Area Open Space Council, GreenInfo Network, Conservation Lands Network, and San Francisco Bay Area Upland Habitat Goals Project. (2011). Landscape Units: San Francisco Bay Area, California, 2011. Bay Area Open Space Council. Available at http://purl.stanford.edu/fr188bj5334. This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.