Our Liiini; Riwoimfs — Habitat Assessments 



465 



The Gap Analysis Program (GAP), coordi- 

 nated by the National Biological Service, 

 provides a regional screening of elements of 

 biodiversity (plant communities and wildlife 

 species) to identify elements most at risk and to 

 identify general areas of highest concentrations 

 of the at-risk elements. Data collection and 

 analysis have been completed for southwestern 

 California, the first of 10 regions to be analyzed 

 in the state. This region covers roughly 8% of 

 the land area of California, spanning the south- 

 ern coast from Point Conception to the 

 U.S. -Mexico border and from the western edge 

 of the Sonoran and Mojave deserts to the Pacific 

 Ocean. Urban growth has been exceptionally 

 rapid in this region at the expense of species and 

 habitats, particularly in the Coastal Plain. This 

 article summarizes the gap analysis of this 

 region and identifies plant communities and 

 wildlife species considered at risk. Further 

 details can be found in Davis et al. ( 1994). 



Land Management Status 



hi this analysis we defined three levels of 

 management to determine the protection status 

 of elements of biodiversity. Level I represents 

 areas managed for the long-term protection of 

 biodiversity, such as wilderness areas, research 

 natural areas, state parks, and some private pre- 

 serves. Level 2 includes publicly owned lands 

 not specifically designated for Level 1 manage- 

 ment, and Level 3 contains lands with no formal 

 management for biodiversity. 



The amount of Level 1 areas managed to 

 preserve biodiversity is 9.6% of the region, 

 mostly in national forest wilderness areas. 

 Other public lands managed at Level 2 account 

 for another 30%, while the remaining 60% is 

 private land. Lower elevations, where most 

 urban and agricultural development occurs, are 

 predominately private land. Government agen- 

 cies manage most higher elevation lands, that is, 

 lands at l,500-2,500^m (4,920-8,200 ft), 25% of 

 which is managed at Level L 



Vegetation Status 



A team from the University of California, 

 Santa Barbara (UCSB) produced a map of actu- 

 al vegetation. The California Natural Diversity 

 Data Base staff has identified some plant com- 

 munities of special concern; they generally have 

 less than 10% of their distribution in Level 1 

 areas or over 70% of the mapped distribution in 

 privately owned Level 3 areas. We used these 

 criteria to identify other plant communities that 

 are at risk. 



Communities restricted largely to the lower 



elevations, like coastal sage scrub (Figure) and 

 non-native annual grasslands, are at consider- 

 able risk (Table I ). Although grasslands are 

 dominated by non-native species, they can be 

 rich in native plant species and are habitat to 

 many animal species. Roughly 88% of areas 

 below 500 m (1.640 ft) have no fonnal protec- 

 tion status; most low-elevation land has already 

 been converted to agricultural or urban uses. 

 and most remaining low-elevation land is 

 zoned for future urbanization. 



Especially alarming is the condition of the 

 California black walnut woodlands. The south- 

 ern variety of this species is endemic to this 

 region and its current distribution is highly frag- 

 mented and reduced compared with its original 

 distribution. Sagebrush steppe shrubland, 

 although widespread elsewhere in California, 

 appears vulnerable in this region. A significant 

 proportion of the sagebnash steppe habitat is on 

 Level 2 lands, and conservation concern for 

 these communities can probably be adequately 



Biodiversity in 



the 



Southwestern 



California 



Region 



by 

 David M. Stoms 

 Frank Davis 

 University of California- 

 Santa Barbara 



Figure. Gap analysis of coastal sage scrub in Ihe southwestern region of California. Highlighted 

 are landscapes where coastal sage scrub is the primary and secondary upland vegetation type. 



Table 1. Natural communities 

 identified as at risk by using 

 Gap Analysis Program criteria. 

 The list is ordered from highest 

 to lowest percentage of the com- 

 munity that occurs on Level 3 

 private lands. 



"Mapped distribution totals less than 50 km^ (19.3 mi^). 



