EXECUTIVE SUMMARY

Of the entire state, 13% has been converted to agricultural uses, nearly 5% to urbanization, 3% is unvegetated, and 79% remains vegetated with natural communities. As there is no concensus on a definition of "adequate representation," a pratical solution is to report the percentages of each community type in status 1 and 2 areas and allow the user to determine which types they believe need additional conservation. Of the 194 community types mapped by CA-GAP, 73 have less than 10% representation, 46 types have between 10 and 20%, 44 have between 20 and 50%, and 31 have more than 50%. The types with less than 10% representation generally fall within several categories: coastal scrub, Great Basin scrub, prairie grasslands, hardwood woodlands, and a few conifer forests. The types that are best represented are communities characteristic of Mojave Desert scrub or subalpine conifer and alpine communities (Figure 2).

Figure 2. Plant communities that are least- and best-represented in managed areas in California.

Coastal scrub types are of great concern both because they are often prime land for urbanization along California's coastal plains and large proportions of their historical extent has already been converted. As a result, they harbor a large percentage of the state's threatened and endangered plant and animal species. Native grasslands have been similarly affected through conversion to agriculture, invasion by exotic Old World annual plants, and change in fire regime, so that all are considered highly threatened. Most hardwood types occur principally on private lands and are subject to a number of impacts such as grazing, fuelwood cutting, clearing for pasture or cultivation, and fire suppression. Several oak species, notably Valley oak (Quercus lobata), Blue oak (Q. douglasii), and Engelmann oak (Q. engelmannii), have exhibited low rates of recruitment in recent decades, adding to the concern about the long-term viability of these ecosystems. The under-represented conifer types tend to contain the most commercially valuable timber species such as redwoods, ponderosa pine, and douglas-fir. Even though these types have not been extensively converted to other uses, they have been heavily altered in composition or structure either by selective removal of favored species (e.g., sugar pine) and/or great reduction in the extent of late successional stands.

Forty-six types were found to have between 10-20% representation in GAP status 1 and 2. Many of these are chaparral types which in general were assigned low levels of threat in the NHD rankings. These tend to occur in steep terrain with few resource conflicts. The primary issue in preserving chaparral is fire management.

Also in the 10-20% group are some of the riparian forest types, most of which are considered threatened or very threatened in the NHD rankings. Several of the saltbush or sink scrub communities also are in this category. All are considered threatened by NHD due to past losses from irrigated agriculture and the accidental flooding of the Salton Basin at the beginning of the century.

Forty-four cover types have 20-50% representation in GAP status 1 and 2. Most of these types are from the deserts, marshes, and the upper conifer forest zone. Included here are the creosote scrub communities of both the Sonoran and Mojave deserts, Alkali Playas, Desert Dry Wash Woodland, Desert Sink Scrub, and Mojavean Pinyon and Juniper Woodland. The montane types include communities such as Big Tree, Jeffrey Pine and Red Fir Forests, Huckleberry Oak Chaparral, Canyon Live Oak Forest, and meadows. Most of these types are not considered threatened in the NHD rankings, but there are several notable exceptions such as Desert Sink Scrub, Valley Needlegrass Grassland, Sitka Spruce-Grand Fir Forest, Beach Pine and Bishop Pine Forests, Siskiyou Enriched Coniferous Forest, and the wetland types.

Thirty-one types out of the 194 that were mapped have over half of their distribution in status 1 or 2 managed areas. Of these, 8 were mapped over less than 25 km�. Two types (Northern Coastal Bluff Scrub and Santa Lucia Fir Forest) occur entirely within protected areas. The majority of types in this category are Mojave Desert scrub or subalpine conifer forests and alpine communities, corresponding to the areas where protected areas are most concentrated. The remaining types tend to be rather rare or highly localized and often the focus of conservation action. Examples of this are the Salmon-Scott Enriched Coniferous Forest, Port Orford Cedar, and Valley Sacaton Grassland. The latter is ranked as very threatened by the Natural Heritage Division (NHD) of the California Department of Fish and Game and has suffered extensive reductions from agricultural land uses. Some of the few remaining stands have been recently acquired by the California Department of Parks and Recreation, but additional management action may still be required to preserve this type.

Vertebrates

For this gap analysis, we limited the predicted distributions of terrestrial vertebrates to habitats within each species� range that were rated as 4 or 5, i.e., most of the land-cover/habitat polygon was classified as moderate to high suitability. Several species have very low levels of representation (<5 %) in managed areas. These species fall into four general groupings:

1. adapted to human-dominated habitats (little or no action needed)

Inca dove
Bronzed cowbird
Black phoebe
Western kingbird
American crow
Red-winged blackbird
Hooded oriole
American goldfinch
Woodhouse�s toad
Black- and Yellow-billed magpies (commonly feed in agricultural habitats but also depend on riparian or oak woodland habitat for breeding and cover)

2. very limited ranges (very narrowly endemic species are best evaluated in a "fine-filter" approach to complement the "coarse-filter" gap analysis)

Townsend�s pocket gopher (subspecies found in California is restricted to the Honey Lake area in Lassen County)
White-footed vole
Fresno (or San Joaquin) kangaroo rat
Tiger salamander
Redbelly newt
Siskiyou Mountains salamander
Shasta salamander
Spotted frog (may, in fact, have never occurred in California; may be misidentified specimens)
Grasshopper sparrow (wider range than these other species, but its abundance is erratic from year-to-year)

3. marginal to the state (should be re-assessed in ecoregional gap analyses over their entire range)

Gila woodpecker
Cordilleran flycatcher
Cedar waxwing
Northern pocket gopher
Pronghorn
Short-horned lizard (most widely distributed lizard in North America but in California only occurs in the Modoc Plateau region at the margin of its range)

4. diminishing or degraded habitats (generally the most vulnerable group of species)

Swainson�s hawk
Black-chinned hummingbird
California kangaroo rat
Western spadefoot

Of all native vertebrates, the largest group has 10-20 % of their predicted distributions in managed areas, with about equal numbers with <10 and 20-50 % (Table 1). Very few species have >50 % protection and these tend to be species with very small ranges, such as the Alpine chipmuck (Tamias amoenus), which was predicted over only 444 km�, or <0.1% of California�s land area, in the rocky habitats above 2800 m in the High Sierra.

Priority Group	Rarity	% Status 1 and 2	Threat Index	Weight
A	Rare	< 20	�	1.0
B	Rare	>20	�	0.75
C	Common	�	high	0.75
D	Common	<10	low	0.5
E	Common	10-20	low	0.3
F	Common	20-50	low	0.1
G	Common	>50	low	0.0
H (non-vegetated)	�	�	�	0.0

Table 2. Vulnerability groups of plant communities from the statewide gap analysis based on a combination of current protection and threat and the weights used for scoring sites.

For widespread community types, priorities were set based on a combination of two factors: percentage of status 1 and 2 lands and an index of threat. The threat index was based on a combination of roadedness and projected population growth. The first group (Group C) of common communities was characterized by a high threat index, indicating a relatively high degree of either past disturbance or future loss. Note that this threshold level was selected as a natural break in the set of plant communities, not on any a priori or theoretical basis. It had the further advantage of allowing us to divide communities into approximately equal-sized groups. Virtually all Group C community types were also relatively under-represented (< 20% status 1 and 2). The remaining four groups all appear relatively less threatened by roads or future development (low threat index) and were categorized based on their level of protection into roughly equal numbers of types in each group. We used the same break points, i.e., 10%, 20%, and 50%, in decreasing order of priority. Five exceptions were made to these general rules. Four types that were rated as rare by NHD were mapped over extensive areas by CA-GAP, perhaps due to differences in interpretation. We therefore chose to assign Mojave Mixed Steppe, Upland Redwood Forest, Westside Ponderosa Pine Forest, and Eastside Ponderosa Pine Forest to groups G, E, E, and D respectively, as if they were not rare types. Also, we assigned Tamarisk Scrub to group G because it is not a native community type and in fact is generally considered a pest species. The remaining urban, agricultural, and non-vegetated land cover types were assigned to group H that has no conservation priority for its vegetation values. There may still be important habitats and other ecosystem values, however, in the non-vegetated types (e.g., water bodies, sand dunes, rock outcrops, etc.).

Of the 194 natural community types, we have ranked 41 as highest priority for conservation (Class A) based on their rarity and lack of protection. Another 20 community types are also rare but have greater than 20% protection. All of these rare types need to be examined in greater detail to determine more their true extent, which was only coarsely estimated by CA-GAP methods, and the actual threats they face. Some of the common types include rare subtypes. Coast Range Ponderosa Pine Forest, for instance, includes a maritime subtype that is restricted to sterile marine sand deposits in Santa Cruz County that may need additional management. These caveats underscore the need to complement the coarse-filter of gap analysis with a fine filter approach to catch these special cases.

The common types were divided into roughly equal-sized priority groups, with between 23 and 31 types in each. Twenty-four types were ranked as Group C, with low protection and relatively high level of threat. Group C types include the coastal scrub, chaparral, and woodland types of southern California where population growth pressures are the greatest. Group D contains communities that are not well-represented in biodiversity management areas but face less threat than Group C according to our simple index. These communities include Great Basin scrub, non-native grassland, oak woodlands, and mixed conifer types, although they all face other forms of threat that our index does not address. Group E is the types with relatively low threat and greater than 10% in status 1 and 2 management areas. This group includes many of the common chaparral types, forests of the coastal mountains, and some Great Basin communities. Types with low threat and moderate protection are in Group F, which consists of many of the desert communities and montane shrub and forest types. Group G has the most well-represented communities, which therefore have the lowest levels of threat. These communities generally are from the desert and subalpine areas, which are the best protected in California.

A few plant community types deserve special mention where the CA-GAP is insufficient to evaluate them adequately. One group of communities that need to be highlighted are those that could not be mapped reliably at the resolution of GAP. Most important of these are the wetland types, such as marshes, vernal pools, riparian scrub, and other aquatic habitats. Joshua Tree Woodland is another example. It was not mapped as a specific plant community in the land-cover database of the Mojave Desert region where it is most common. The presence of Joshua Tree was only recorded as present where known. Frequently the density of Yucca brevifolia is so low (or unknown) that the community was classified as a scrub type. Many of these locations may actually be Joshua Tree Woodland, but our analysis is unable to evaluate its current management status reliably at this time.

• Assign weights to the vulnerability categories described in Table 2
• Calculate the area in a quadrangle of each category in status 3 and 4 lands
• Multiply the area in a category by its weight
• Sum weighted area for all categories in the quadrangle

The map of site scores is shown in Figure 3. The highest scoring quadrangles tend to occur in a ring around the Great Central Valley, particularly in western Kern County, and in Glenn, Colusa, and Tehama counties. Western Santa Barbara County and Solano County contain other particularly high scoring clusters of quadrangles. Other relatively high scoring areas include the Sierra Nevada foothills, much of the Central Western region, parts of Shasta County, undeveloped areas throughout the Southwestern California region, and a small area along the border with Nevada in Lassen County. Low scoring sites occur throughout the Great Central Valley, Los Angeles Basin, and the Imperial Valley near the Mexican border where agriculture or urbanization have eliminated most of the native vegetation. Other low scoring areas occur in the higher elevations of the southern Sierra Nevada and the majority of the Mojave and Sonoran Desert regions where the plant communities are well-represented in managed areas and thus tend to have low priority. Readers should note that a quadrangle could have a low score and yet contain a rare community type that only occurs at that site.

Appropriate Uses: The following is a general list of applications:

• Statewide biodiversity planning
• Regional (Councils of Government) planning
• Regional habitat conservation planning
• County comprehensive planning
• Large area resource management planning
• Coarse-filter evaluation of potential impacts or benefits of major projects or plan initiatives on biodiversity, such as utility or transportation corridors, wilderness proposals, regional open space and recreation proposals, etc.
• Determining relative amounts of management responsibility for specific biological resources among land stewards to facilitate cooperative management and planning.
• Basic research on regional distributions of plants and animals and to help target both specific species and geographic areas for needed research.
• Environmental impact assessment for large projects or military activities.
• Estimation of potential economic impacts from loss of biological resource based activities.
• Education at all levels and for both students and citizens.

Inappropriate Uses: It is far easier to identify appropriate uses than inappropriate ones, however, there is a "fuzzy line" that is eventually crossed when the differences in resolution of the data, size of geographic area being analyzed, and precision of the answer required for the question are no longer compatible. Examples include:

• Use of the data to map small areas (less than thousands of hectares) typically requiring mapping resolution at 1:24,000 scale and using aerial photographs or ground surveys.
• Combining GAP data with other data finer than 1:100,000 scale to produce new hybrid maps or answer queries.
• Generating specific areal measurements from the data finer than the nearest thousand hectares (minimum mapping unit size and accuracy affect this precision).
• Establishing exact boundaries for regulation or acquisition.
• Establishing definite occurrence or non-occurrence of any feature for an exact geographic area (for land cover, the percent accuracy will provide a measure of probability).
• Determining abundance, health, or condition of any feature.
• Establishing a measure of accuracy of any other data by comparison with GAP data.
• Altering the data in any way and redistributing them as a GAP data product.
• Using the data without acquiring and reviewing the metadata and this report.

The California Department of Fish and Game will be the long-term custodian of the CA-GAP database, both for its distribution and its maintenance. Ultimately it is anticipated they will establish a web site for users to download the data. Check the CA-GAP web site at: