RSS FeedsBiological Resources
Regional Context
Countywide Context
Biotic Communities
Special-Status Plants & Wildlife
Wildlife Movement Area
This chapter describes the biological resources found in Napa County. It allows accurate assessment of impacts, evaluation of conservation plans, and review of proposed enhancements to biological resources in Napa County. In addition, it provides a biological database that can assist in analyzing biological resources.
Napa County was divided into thirteen evaluation areas to facilitate the analysis of biological resources and management concerns in distinct regions of the County. Common and sensitive biological communities, wildlife movement, concentrations of valuable biological resources, fire ecology, and management concerns are discussed for each of the evaluation areas.
REGIONAL CONTEXT
California is considered a global “hot spot” for biological diversity, where species diversity, endemism, and threats to this diversity are all particularly high (Myers et al. 2000, Stein et al. 2000). California contains more native biological diversity than any other state, including more endemic species than any other state (1,295 species) (Stein 2002). Threats to this biological diversity are also high relative to the rest of the U.S. Napa County is located within the California Floristic Province, the portion of the state west of the Sierra Crest that is known to be particularly rich in endemic plant species (Hickman 1993, Stein et al. 2000).
COUNTYWIDE CONTEXT
Napa County has a high natural level of biodiversity compared to California as a whole. The County’s biodiversity provides valuable goods, services, and scientific information. More importantly, the plants and animals of the County provide many critical ecological and social functions. Napa County’s many species also represent a vast storehouse of scientific information, most of it unexplored and some of it endemic to the County.
The following are critical issues of concern for protecting biodiversity in the County.
- Planning and/or limiting development to avoid or minimize impacts on sensitive communities, special-status species, and wildlife movement between large and/or critical natural areas
- Protecting and enhancing the Napa River, Putah Creek, and the other streams in the County
- Controlling the spread of invasive exotic species
- Preventing type conversion of biotic communities through changes in natural disturbance regimes, such as fire and flooding
BIOTIC COMMUNITIES
 California contains more native biological diversity than any other state. Napa County has a high natural level of biodiversity compared to California as a whole. |
Ten general land cover types have been identified in Napa County: grassland, chaparral/scrub, oak woodland, riparian woodland and forest, coniferous forest, wetlands, open water, rock outcrop, agricultural cropland, and developed lands. Of these ten, all except for two—rock outcrop and developed lands—are considered biotic communities. Dominant plants, general distribution, common wildlife, and special-status species for specific biotic communities within each of these general communities are described in the body of the biological resources chapter of the BDR.
The California Department of Fish and Game (DFG) recognizes 21 sensitive biotic communities in the County, not all of which are mapped. Many of these communities are subtypes of the general biotic communities described above. An additional six communities are considered sensitive because they are locally rare. Sensitive communities in the County include native grassland, serpentine chaparral, riparian forest, and cypress woodland. Six communities of limited distribution have been identified on a countywide scale: redwood forest, wet meadows, mudflats, Brewer willow scrub, ponderosa pine forest, and tanbark oak forest. Of these six communities, redwood forest is also recognized by DFG as potentially sensitive.
Several biotic communities are considered important to protect because of their relatively limited extent in the County and their importance to a large number of special-status plant and/or wildlife species. These communities are riparian woodland, freshwater wetlands, salt marsh, serpentine grassland, and streams, which are critical for the County’s special-status plant and wildlife species. Rock outcrops are critical habitat features used by special-status plants and wildlife.
SPECIAL-STATUS PLANTS & WILDLIFE
Eighty-one special-status plant species occur or potentially occur in Napa County. Their distributions and habitat associations are summarized in the biological resources chapter of the BDR. Particular biotic communities, such as serpentine grasslands, are shown to have high importance to specialstatus plant species relative to their extent in the County.
Sixty special-status terrestrial wildlife species and 9 special-status fish species occur or potentially occur in the County. Associations of these species with particular biotic communities are discussed in the chapter, which highlights the importance of a few communities, such as salt marsh and riparian woodland. A detailed analysis of streams and the riparian corridors is also provided, including a discussion of which stream channels are supportive of sensitive fish species.
WILDLIFE MOVEMENT AREAS
Three major, regional north-south wildlife movement routes have been identified in Napa County: the Western Mountains, the Napa River, and the Blue Ridge-Berryessa Natural Area. Constraints to eastwest movement and the importance of riparian corridors are discussed in the BDR, as is the potential for zoning buildout to constrain wildlife movement in particular parts of the County. Maintenance of wildlife movement areas is important to conserve the diversity of wildlife and plants within Napa County.
