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Limitations and Discussion


To meet the analytical objectives of GAP, it is necessary to compare the mapped distribution of elements of biodiversity to a map of land stewardship and management. As will be explained in the Analysis section, the stewardship and management status of a species or community type is not a direct measure of that element's viability. However, it does provide some indication of the vulnerability of that biotic element to future habitat conversion or severe degradation ­the primary cause of biodiversity decline. We use the term "stewardship" in place of "ownership" in recognition that legal ownership does not necessarily equate to the entity charged with management of the resource, and that the mix of ownership and managing entities is a complex and rapidly changing condition not suitably mapped by GAP. At the same time, it is necessary to distinguish between stewardship and management status in that an area in a single category of land stewardship may be subdivided into many different kinds of managed areas. For example, a national forest may contain wilderness areas, research natural areas, lands that are administratively designated for extractive and/or recreational use, and so on.

The purpose of comparing biotic distributions to a stewardship map is to provide a method by which land stewards can assess their contribution to the management of a species or plant community relative to that of other stewards. This information can reveal opportunities for cooperative management of that resource. The weakest point in our analysis of stewardship is the assessment of private lands, which are treated as a single category and not differentiated by zoning class, easements or other restrictions on land use, or land owner ( unless the information was provided voluntarily to recognize a permanent commitment to biodiversity maintenance, as with lands owned by The Nature Conservancy.

The purpose of assessing the management status of biodiversity is to help prioritize biotic elements or areas of high diversity for additional conservation management efforts. These changes in management often can be accomplished without affecting the stewardship status. There are myriad resource management goals, approaches and techniques, and management impacts on biodiversity are generally element-specific. For the purposes of statewide and regional gap analyses, these different management regimes are greatly simplified and broadly applied to all elements of biodiversity. CA-GAP currently uses a scale of 1-4 to denote relative degree of maintenance of biodiversity for each tract. A status of "1" denotes the highest, most permanent level of maintenance, and "4" represents the lowest level of biodiversity management, or unknown status. This is a highly subjective area, and we recognize a variety of limitations in our approach, although we maintain certain principles in assigning the status level. Our first principle is that land ownership is not the primary determinant in assigning status. The second principle is that while data are imperfect, and all land is subject to changes in ownership and management, we can use the intent of a land steward as evidenced by legal and institutional factors to assign status. In other words, if a land steward institutes a program backed by legal and institutional arrangements that are intended for permanent biodiversity maintenance, we use that as the guide for assigning status.

The characteristics used to determine status are as follows:

· Permanence of protection from conversion of natural land cover to unnatural (human-induced barren, exotic dominated, arrested succession).

· Relative amount of the tract managed for natural cover.

· Inclusiveness of the management, i.e., single feature or species versus all biota.

· Type of management and degree that it is mandated through legal and institutional arrangements.

The four status categories can generally be defined as follows (after Scott et al. 1993):

Status 1: An area having permanent protection from conversion of natural land cover and a mandated management plan in operation to maintain a natural state within which disturbance events (of natural type, frequency, and intensity) are allowed to proceed without interference or are mimicked through management.

Status 2: An area having permanent protection from conversion of natural land cover and a mandated management plan in operation to maintain a primarily natural state, but which may receive use or management practices that degrade the quality of existing natural communities.

Status 3: An area having permanent protection from conversion of natural land cover for the majority of the area, but subject to extractive uses of either a broad, low-intensity type or localized intense type. It also confers protection to federally listed endangered and threatened species throughout the area.

Status 4: Lack of irrevocable easement or mandate to prevent conversion of natural habitat types to anthropogenic habitat types and allow for intensive use throughout the tract, or existence of such restrictions is unknown.


The stewardship and management status map was compiled at a cartographic scale of 1:100,000 to achieve the objectives of gap analysis. The base map is the USGS topographic map series at this scale but projected into the Albers Equal Area projection to be compatible with the other data layers in the California Gap Analysis database. Based on the regional scale of gap analysis and on the available resources for compiling data, a minimum size threshold or mapping unit (MMU) was established, such that only upland preserves at least 200 ha (500 acres) were mapped as Level 1 areas. An 80-ha (200-acre) MMU was established for wetland preserves, because in southern California these rare and diminishing habitats tend to be small. We recognize that there are many reserves smaller than our 200 ha and 80 ha MMUs and that these may be critical for short-term protection of individual species, or as stepping stones in a nature reserve network. Such areas would be important to consider in more local, finer-grained conservation assessments and conservation efforts.

An existing digital map of land ownership was obtained from the Teale Data Center in Sacramento. This map was derived from the 1:100,000 scale Bureau of Land Management (BLM) Surface Management Status maps published in the 1970's. It distinguishes ownership by private, state, and federal categories. Federal and state lands are further divided by managing agency. The most recent National Forests maps had been used to update the base maps prior to digitizing. Teale Data Center registered the digitized map to the Public Land Survey System network. At UCSB, we further updated the ownership component of this map with current information (e.g., in the Santa Monica Mountains National Recreational Area where land acquisition by several agencies and private conservancy groups has been very extensive). Large county parks were also digitized from 1:100,000 scale USGS topographic map base sheets if the park appeared to be relatively undeveloped and might contribute to long-term maintenance of biodiversity. Other semi-public lands (e.g., lands owned by water districts and public utilities) were included where digital maps were readily available, but it would have been too time-consuming to compile consistent information for the entire state. It is recognized, however, that water district lands are sometimes maintained in a natural condition for watershed protection, and thus may be valuable for preserving biodiversity.

To compile the remaining managed areas, we obtained boundary maps for the areas listed in Appendix 4-1 from various agency and conservation group sources at scales approximately the same as the 1:100,000 scale ownership map. The Natural Heritage Division of the California Department of Fish and Game provided a digital map of many of The Nature Conservancy preserves and easements, Forest Service Research Natural Areas (RNA) (Keeler-Wolf 1990), and of Fish and Game Ecological Reserves and Wildlife Areas. Current land ownership of the Santa Monica Mountains NRA was supplied by the National Park Service. A digital map of ACEC's was provided by several BLM district or resource area offices. We drafted additional managed areas such as Federal wilderness areas and Audubon Society sanctuaries onto 1:100,000 scale topographic maps and digitized them. Most State Parks and National Wildlife Refuges were already part of the ownership coverage, but maps of recently acquired parks and refuges had to be located and digitized.

All lands were assigned to one of the four management status levels by a simple set of classification rules. Generally entire categories of managed areas were assigned to the same status level (e.g., all USFS wilderness areas were assigned to status level 1). Table 4-1 illustrates the general assignments. Some exceptions were made in special cases. For instance, large, mostly undeveloped Department of Defense military bases (such as Fort Hunter-Liggett and Camp Pendleton) were assigned to status 3, whereas small, developed DoD tracts were assigned to status 4 (e.g., Miramar Naval Air Station). See the Limitations and Discussion section below for a discussion of the consequences of this generic classification and the ideal for future gap analysis projects.

Table 4-1. Management status assignments to land management categories in California.

Status 1 Status 2 Status 3 Status 4
USFS Wilderness Areas, Research Natural Areas

NPS National Parks, Preserves, Monuments, Seashores, and Wilderness

BLM Wilderness Areas

State Park Wilderness Areas, Reserves

State Fish and Game Ecological Reserves

University of California Natural Reserves

Nature Conservancy preserves, Audubon sanctuaries

USFS Special Interest Areas, Experimental Forests

USFWS National Wildlife Refuges

National Recreation Areas, National Conservation Area

BLM Areas of Critical Environmental Concern

Wild and Scenic Rivers, Wilderness Study Areas

State Fish and Game Wildlife Areas

Some municipal water districts, open space districts, land trusts, conservation easements

Regional wilderness parks

USFS National Forests

BLM lands

Some large DoD military bases

Corps of Engineers

State Forests

State Recreation Areas, Historic Parks, Beaches

County and regional parks

Native American lands

Some DoD military bases

State trust lands, university campuses

Private lands


The following table presents summary statistics of area representation of stewardship and management categories in the state. We begin by comparing representation of various stewardship categories in management status categories. Table 4-2 provides information on the proportional make-up of management status categories by stewardship and vice-versa, so that land stewards can see how their lands, as classified by GAP, contribute proportionately to biodiversity maintenance in California. This table indicates the area for the following 1) area of the land stewardship category in each management status and total for the state, 2) the steward’'s percent of total area in each management category and of the state area, 3) total area of each stewardship category in the state and its percent of state area, and 4) mean elevation of the lands in each status category.

Table 4-2. Area and percentage of land surface by land steward and status level in California. Percentages in each Status sum to 100%, except for Total, which refers to the State as a whole.

Status 1 Status 2 Status 3 Status 4 Total
Steward Area (km²) % Area (km²) % Area (km²) % Area (km²) % Area (km²) %
Federal 189,403 46.6
Bureau of Land Management 12,091 19.4 4,374 38.0 42,051 34.2 0 0.0 58,516 14.4
US Fish and Wildlife Service 0 0.0 1,101 9.6 0 0.0 0 0.0 1,101 0.3
National Park Service 29,429 47.2 705 6.1 0 0.0 10 <0.1 30,145 7.4
US Forest Service 18,267 29.3 954 8.3 63,775 51.8 0 0.0 82,997 20.4
Department of Defense 0 0.0 5 <0.1 12,740 10.4 3,568 1.7 16,313 4.0
Other agencies 0 0.0 4 <0.1 138 0.1 3 <0.1 145 <0.1
State 9,367 2.4
State Parks 1,850 3.0 2,235 19.4 619 0.5 0 0.0 4,705 1.2
Fish and Game 187 0.3 1,433 12.5 4 <0.1 0 0.0 1,624 0.4
State Forests 0 0.0 0 0.0 276 0.2 0 0.0 276 0.1
Other 75 0.1 52 0.5 1,103 0.9 1,531 0.7 2,762 0.7
Regional and County 2,967 0.7
Parks and preserves 0 0.0 68 0.6 888 0.7 0 0.0 957 0.2
Water districts 25 <0.1 358 3.1 1,466 1.2 0 0.0 1,849 0.5
Open space districts 0 0.0 137 1.2 0 0.0 0 0.0 137 <0.1
Other 0 0.0 0 0.0 3 <0.1 21 <0.1 24 <0.1
Private 203,085 49.9
TNC 419 0.7 3 <0.1 0 0.0 0 0.0 422 0.1
Audubon 26 <0.1 0 0.0 0 0.0 0 0.0 26 <0.1
Land trusts and other conservancies 17 <0.1 50 0.4 0 0.0 0 0.0 67 <0.1
Other 0 0.0 20 0.2 0 0.0 202,550 96.6 202,570 49.8
Native American Lands 0 0.0 0 0.0 0 0.0 2,047 1.0 2,047 0.5
Total 62,387 15.3 11,500 2.8 123,064 30.3 209,729 51.6 406,868 100.0
Mean Elevation (meters) 1,397 705 1,187 506 852

Just under 50% of the state is privately owned (Table 4-2). Stewardship of the remainder in public ownership is widely distributed among USFS (20.3%), BLM (14.3%), NPS (7.4%), military bases (4.0%), USFWS (0.3%), Indian reservations (0.5%), state parks (1.2%), California Fish & Game (0.4%), State forests (0.1%), other State lands (0.7%), local governments (0.7%), and private conservation groups (0.1%). Public land is highly concentrated in the eastern half of the state, with lesser amounts in the higher northern and southern coastal mountains. There is very little public land in the Great Valley or coastal areas. A similar table for management status by county is provided in Appendix 4-2.

Figure 4-1 shows the management status of lands in California. Three hundred seventy-one status level 1 managed areas were mapped for California, covering 62,387 km² or roughly 1/6 of the land area of the state. Status level 1 managed areas are dominated by 16 National Park units (29,431 km²), 54 USFS Wilderness Areas (17,319 km²), and 65 BLM Wilderness Areas (12,056 km²). Also mapped were 93 USFS Research Natural Areas (582 km²) and 3 wildlife sanctuaries or interest areas (363 km²), 57 California Fish & Game Ecological Reserves (200 km²), 13 state reserves (80 km²), 6 state park wilderness areas (1,767 km²), 15 University of California Natural Reserves (111 km²), 5 Audubon sanctuaries (26 km²), and 41 TNC preserves (426 km²). The distribution of status level 1 areas in the state is skewed towards the Sierra Nevada and desert regions, with some other large areas in northern California.

California Management Status Map

Figure 4-1. Map of management status of lands in California. See text for definitions of management levels.

Another 370 managed areas were classified as Status level 2. These Status 2 areas consisted primarily of 80 BLM Areas of Critical Environmental Concern and other conservation designations (3,695 km²), 32 USFWS National Wildlife Refuges (1,101 km²), 65 Wildlife Areas of California Fish & Game (1,336 km²) and another 196 km² of undesginated lands, and 76 state park units (2,231 km²). In addition, 6 BLM Wilderness Study Areas or proposed wilderness areas (633 km²), 18 USFS Special Interest Areas and other management areas (699 km²), 5 USFS Experimental Forests (97 km²), 5 Wild and Scenic Rivers (160 km²), 4 National Park units (National Recreation Areas or Seashores) (705 km²) were also mapped.

Appendix 4-1 identifies all management areas identified by CA-GAP categorized as a management status 1 or 2. These areas constitute the set of protected lands used in the representativeness analysis. Appendix 4-1 also identifies the entity charged with management implementation.

Status 1 areas are substantially larger than status 2 sites. The mean size for status 1 areas is 16,816 ha while status 2 areas average 3,091 ha. When combined they average 9,944 ha. The size-distributions are skewed heavily towards small size areas, however, with a median for status 1 of only 764 ha and for status 2 of 900 ha. Only 76 sites are greater than 10,000 ha in size. The largest are National Park units such as Death Valley at 1,343,591 ha, the new Mojave National Preserve at 540,563 ha, Sequoia-Kings Canyon National Parks at 348,473 ha, Yosemite National Park at 301,951 ha, and Joshua Tree National Park at 297,339 ha. The John Muir and Trinity Alps Wilderness areas are greater than 200,000 ha and Golden Trout Wilderness was mapped at 121,416 ha.

Size-frequency graph of managed

Figure 4-2. Frequency (bars) and cumulative area (curve) of aggregated management status 1 and 2 lands in California.

If Status 1 and 2 lands are assumed to be essentially equivalent for biodiversity conservation and if boundaries between contiguous managed areas are ignored, there are 1,019 individual tracts of land managed for biodiversity. Some of these tracts are extremely large aggregations of parks and wilderness areas as in the Death Valley region (over 15,000 km²) and in the higher elevations of the southern Sierra Nevada (over 12,000 km²). These tracts would be even larger if small separations caused by roads were ignored. Even after lumping Status 1 and 2 lands, half of the state's conservation areas are less than 200 ha. This is mainly because many managed areas are comprised of several isolated parcels. The skew towards many very small tracts can be seen in Figure 4-2, which also shows that 22 very large tracts contribute 75% of the total protected area in the state.

Elevation bias of managed

Figure 4-3. Proportion of managed areas and all lands in California by elevation zones.

Despite the relatively high level of overall representation of lands in status 1 and 2 managed areas in the state, the distribution of these areas is not uniform across all habitats. Figure 4-3 illustrates the bias in representation towards higher elevations, particularly above 2,000 m, and the poor representation of habitats in the 1-500 m zone, which is dominated by private land and by urban and agricultural land uses. In general, this zone contains the biodiversity elements with the least protection and that are most vulnerable to serious loss or degradation.

This pattern of greater protection in higher elevation zones and less protection at lower elevations is generally repeated within the biophysical regions of the state. We divided elevation into four zones that correspond approximately with lifezones for vegetation: <500 meters (valley grassland and riparian forest, coastal scrub) , 501-1500 meters (chaparral and oak woodlands), 1501-2500 meters (mixed conifer), and >2500 meters (subalpine and alpine). These elevation zones were intersected with the subregions described in the Jepson Manual (Hickman 1993) which characterize the variation in climatic and physiographic features in California, and therefore with range limits of vegetation types. This combination of elevation zone with general biophysical subregions was then overlaid with the management status map to calculate the proportions in each management status level for each zone. The results are shown in Figure 4-4 and Table 4-3. The desert regions have high levels of biodiversity management at all elevation levels, but especially in the Desert Mountains subregion of the Mojave region and the highest elevation zone in the Sonoran Desert. Similarly, the higher elevations of the southern and central Sierra Nevada are very well-represented in status 1 or 2 managed areas. In some cases the proportion of biodiversity management areas approaches 100% of the elevation zone. In contrast, the lower elevation zone of the Great Central Valley, the coastal regions, the Owens Valley, the foothills of the Cascades and Sierra Nevada, and the Modoc Plateau have less than 10%, and often close to zero, in status 1 or 2 areas. Two exceptions are the San Francisco Bay and Central Coast subregions, where the percentages are generally between 10-20.

Management status by elevation

Figure 4-4. Map of percentage of management status 1 and 2 lands in each elevation zone of subregions of California.

Table 4-3. Percent area of each subregion-elevation zone combination by management status level in California.

Southwestern California
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
South Coast <500M 0.5 0.8 2.0 96.7 9,383 1.3
South Coast 501-1500M 0.3 3.5 6.6 89.6 1,221 3.8
Western Transverse Ranges <500M 1.1 5.5 5.9 87.5 2,866 6.6
Western Transverse Ranges 501-1500M 17.1 1.6 46.3 35.0 4,480 18.7
Western Transverse Ranges 1501-2500M 39.1 0.0 51.7 9.2 1,118 39.1
Western Transverse Ranges >2500M 67.8 0.0 32.2 0.0 7 67.8
San Bernardino Mtns. <500M 0.0 0.0 5.5 94.5 2 0.0
San Bernardino Mtns. 501-1500M 3.0 0.0 66.0 31.0 834 3.0
San Bernardino Mtns. 1501-2500M 12.2 0.1 66.6 21.2 1,211 12.3
San Bernardino Mtns. >2500M 60.6 0.0 30.3 9.1 147 60.6
San Gabriel Mtns. <500M 0.0 0.1 32.8 67.2 73 0.1
San Gabriel Mtns. 501-1500M 10.0 0.1 75.9 14.0 1,523 10.1
San Gabriel Mtns. 1501-2500M 28.6 0.0 68.6 2.8 719 28.6
San Gabriel Mtns. >2500M 58.2 0.0 41.7 0.1 32 58.2
San Jacinto Mtns. 501-1500M 13.4 6.2 44.4 36.1 240 19.5
San Jacinto Mtns. 1501-2500M 44.4 14.6 20.8 20.3 177 59.0
San Jacinto Mtns. >2500M 100.0 0.0 0.0 0.0 31 100.0
Peninsular Ranges <500M 1.8 1.5 20.2 76.5 3,359 3.3
Peninsular Ranges 501-1500M 8.3 3.1 33.7 54.8 5,733 11.4
Peninsular Ranges 1501-2500M 15.4 7.6 41.4 35.6 660 23.0
Central Western California
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
Central Coast <500M 2.5 8.7 10.2 78.6 6,101 11.2
Central Coast 501-1500M 20.8 11.7 22.7 44.7 78 32.5
San Francisco Bay <500M 1.7 10.6 4.0 83.7 5,751 12.3
San Francisco Bay 501-1500M 2.3 13.9 5.8 78.1 2,089 16.2
Outer South Coast Ranges <500M 1.6 0.2 13.2 85.0 8,189 1.8
Outer South Coast Ranges 501-1500M 30.7 0.9 36.0 32.5 5,968 31.5
Outer South Coast Ranges 1501-2500M 70.9 0.0 28.9 0.1 194 70.9
Inner South Coast Ranges <500M 0.5 0.1 1.2 98.1 4,441 0.6
Inner South Coast Ranges 501-1500M 0.9 2.8 10.0 86.3 4,458 3.7
Inner South Coast Ranges 1501-2500M 0.0 100.0 0.0 0.0 1 100.0
Northwestern California
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
North Coast <500M 3.1 10.7 3.3 82.9 2,869 13.8
North Coast 501-1500M 0.0 28.5 2.7 68.7 187 28.5
Klamath Ranges <500M 3.2 4.1 55.1 37.5 1,593 7.4
Klamath Ranges 501-1500M 13.3 2.4 54.9 29.4 14,473 15.7
Klamath Ranges 1501-2500M 51.7 0.2 32.8 15.3 3,634 51.9
Klamath Ranges >2500M 57.0 0.0 7.2 35.8 6 57.0
Outer North Coast Ranges <500M 1.9 2.4 3.0 92.8 10,162 4.2
Outer North Coast Ranges 501-1500M 3.1 2.4 16.3 78.2 7,101 5.5
Outer North Coast Ranges 1501-2500M 18.0 0.0 69.7 12.3 121 18.0
High North Coast Ranges <500M 0.1 2.7 34.2 63.0 496 2.7
High North Coast Ranges 501-1500M 5.1 0.3 71.0 23.6 4,878 5.4
High North Coast Ranges 1501-2500M 32.8 0.0 48.4 18.8 1,220 32.8
Inner North Coast Ranges <500M 0.3 0.7 5.9 93.1 7,106 1.0
Inner North Coast Ranges 501-1500M 0.0 1.0 34.4 64.6 2,053 1.1
Great Central Valley
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
Sacramento Valley <500M 0.5 2.9 0.9 95.7 15,659 3.4
Sacramento Valley 501-1500M 0.0 0.0 0.0 100.0 2 0.0
San Joaquin Valley <500M 0.2 1.4 1.1 97.4 39,643 1.6
San Joaquin Valley 501-1500M 1.8 20.3 11.9 65.9 3,149 22.1
San Joaquin Valley 1501-2500M 0.0 0.0 55.0 45.0 8 0.0
Cascade Ranges
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
Cascade Range Foothills <500M 4.0 2.4 16.1 77.5 2,959 6.4
Cascade Range Foothills 501-1500M 4.4 2.6 27.7 65.3 4,746 7.1
Cascade Range Foothills 1501-2500M 8.6 0.2 62.2 29.0 1,391 8.8
Cascade Range Foothills >2500M 99.9 0.0 0.1 0.0 18 99.9
High Cascade Range <500M 0.0 0.0 28.3 71.7 2 0.0
High Cascade Range 501-1500M 0.4 1.0 28.9 69.7 4,803 1.4
High Cascade Range 1501-2500M 8.3 2.0 58.6 31.1 6,626 10.2
High Cascade Range >2500M 92.1 0.0 5.9 1.9 68 92.1
Modoc Plateau
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
Modoc Plateau 501-1500M 1.4 5.4 43.7 49.5 12,330 6.8
Modoc Plateau 1501-2500M 0.4 0.3 69.0 30.3 8,518 0.7
Warner Mtns. 501-1500M 0.5 0.9 8.5 90.1 45 1.3
Warner Mtns. 1501-2500M 14.0 0.0 69.9 16.0 1,578 14.1
Warner Mtns. >2500M 88.7 0.0 11.3 0.0 47 88.7
East of Sierra Nevada
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
East of Sierra Nevada 501-1500M 2.5 5.5 88.6 3.4 2,281 7.9
East of Sierra Nevada 1501-2500M 6.4 5.8 76.9 11.0 6,012 12.1
East of Sierra Nevada >2500M 41.4 1.7 55.1 1.8 3,262 43.1
White and Inyo Mtns. <500M 93.5 0.0 6.5 0.0 20 93.5
White and Inyo Mtns. 501-1500M 78.5 0.0 21.1 0.4 583 78.5
White and Inyo Mtns. 1501-2500M 44.1 0.1 55.3 0.5 2,082 44.2
White and Inyo Mtns. >2500M 24.6 10.6 64.7 0.2 1,101 35.1
Sierra Nevada
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
Northern Sierra Nevada Foothills <500M 0.0 1.9 8.8 89.3 5,212 1.9
Northern Sierra Nevada Foothills 501-1500M 0.0 1.7 24.5 73.7 4,608 1.8
Northern Sierra Nevada Foothills 1501-2500M 0.0 0.0 85.8 14.2 99 0.0
Northern High Sierra Nevada <500M 0.0 0.0 79.9 20.1 7 0.0
Northern High Sierra Nevada 501-1500M 1.0 1.3 57.1 40.6 4,338 2.3
Northern High Sierra Nevada 1501-2500M 7.4 1.0 64.3 27.2 11,921 8.5
Northern High Sierra Nevada >2500M 57.7 0.2 38.9 3.3 933 57.9
Central Sierra Nevada Foothills <500M 0.9 2.3 12.8 84.1 2,436 3.1
Central Sierra Nevada Foothills 501-1500M 0.1 0.4 37.3 62.1 3,198 0.6
Central Sierra Nevada Foothills 1501-2500M 0.3 0.3 55.6 43.7 223 0.6
Central High Sierra Nevada <500M 0.9 61.4 35.7 2.1 10 62.3
Central High Sierra Nevada 501-1500M 16.0 2.0 67.3 14.7 1,472 17.9
Central High Sierra Nevada 1501-2500M 47.6 0.2 46.9 5.3 4,248 47.8
Central High Sierra Nevada >2500M 93.9 0.0 6.0 0.1 3,654 93.9
Southern Sierra Nevada Foothills <500M 0.4 1.2 6.9 91.5 1,196 1.6
Southern Sierra Nevada Foothills 501-1500M 5.2 6.0 28.1 60.7 5,034 11.2
Southern Sierra Nevada Foothills 1501-2500M 22.1 4.7 62.1 11.1 2,616 26.8
Southern Sierra Nevada Foothills >2500M 90.4 0.0 9.4 0.2 325 90.4
Southern High Sierra Nevada 501-1500M 46.7 6.0 27.5 19.8 531 52.7
Southern High Sierra Nevada 1501-2500M 59.0 1.5 36.4 3.1 2,870 60.5
Southern High Sierra Nevada >2500M 88.4 0.1 11.3 0.2 3,739 88.6
Tehachapi Mtns. <500M 0.0 0.0 0.1 99.9 29 0.0
Tehachapi Mtns. 501-1500M 0.0 0.0 4.5 95.5 1,222 0.0
Tehachapi Mtns. 1501-2500M 0.0 0.0 12.9 87.1 471 0.0
Mojave Desert
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
Mojave Desert <500M 46.7 3.2 37.7 12.4 10,732 49.9
Mojave Desert 501-1500M 29.2 2.5 41.9 26.4 54,700 31.7
Mojave Desert 1501-2500M 62.2 0.5 31.9 5.4 3,043 62.7
Mojave Desert >2500M 100.0 0.0 0.0 0.0 5 100.0
Desert Mountains <500M 79.0 0.0 11.1 9.8 267 79.0
Desert Mountains 501-1500M 76.0 0.5 16.3 7.2 3,002 76.5
Desert Mountains 1501-2500M 65.7 0.0 32.1 2.1 2,174 65.7
Desert Mountains >2500M 93.6 0.0 6.2 0.2 54 93.6
Sonoran Desert
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
Sonoran Desert <500M 16.1 5.8 37.4 40.6 23,089 22.0
Sonoran Desert 501-1500M 54.1 8.6 12.2 25.1 5,081 62.6
Sonoran Desert 1501-2500M 65.2 11.9 5.2 17.8 71 77.1
Subregion Elevation Zone Status 1 % Status 2 % Status 3 % Status 4 % Total Mapped Distribution (km²) Status 1+2 %
All All 15.3 2.8 30.3 51.6 406,868 18.1

There is considerable difference in the effects of roads on habitat quality within the four status levels. Road data from the 1990 1:100,000 scale TIGER files (Bureau of the Census, 1989) were buffered with a buffer width related to the class of road (Table 4-4). This buffer operation was used to estimate the area of land actually impacted by the presence of each road, where freeways were assumed to affect a greater spatial extent than dirt roads. A "roadedness" index was calculated for each Status level in each region by summing the area of buffered roads, dividing that sum by the total area in the Status level in the region, and multiplying by 100. The index itself does not account for whether roads are in pristine habitats or heavily disturbed sites, but its value for Status 3 and 4 lands provides an indication of the level of current human activities and conversely the extent of less roaded habitats with presumably higher ecological integrity. The index was calculated for status 3 and 4 lands, and for lands within a 10 km buffer surrounding status 1 and 2 tracts.

Table 4-4. Buffer widths assigned to road classes for calculating roadedness index.

Census Feature Class Code Description Buffer width (m)
A10-A18 Primary road with limited access or interstate highway 500
A20-A28 Primary road without limited access (US and state highway) 250
A30-A38 Secondary and connecting road (state and county roads) 100
A40-A48 Local, neighborhood, or rural road 100
A50-A53 Vehicular trail (4 wheel drive route) 25
A70-A73 Other-Biking or walking trail 0

Within the entire state, 21% of the land area is within road buffers, but it varies drastically as expected between management status levels. Status 1, the most protected areas, had only 3.3%. Status 2 and 3 were similar at nearly 15%, while status 4 had over 30% area. Thus current management, as reflected by construction of roads, is mirrored in the management status classification. The relatively large proportion of affected area in status 2 is probably due to the small size of many status 2 areas and the fact that they are often sites developed and managed for recreation and public access. In contrast, status 1 lands are frequently large, unroaded wilderness areas.

The same general pattern held in most of the ten regions as well, but with a number of interesting findings. For example, roadedness values for status 1 and 2 lands in the Great Central Valley are much higher than average, reflecting the small size of BMAs in that region and the high contrast with land uses on surrounding lands. Also, the percentage of road buffer on status 4 lands in the Southwestern California region was over 50%. This high value is due, of course, to the vast urbanized area of Los Angeles and San Diego. The roadedness index for all status levels was much lower than average in the Sonoran Desert region where the landscape still has been the least fragmented by road construction.

The percent area affected by roads within a 10 km buffer around status 1 and 2 areas is only slightly less than that for status 3 and 4 combined over the entire region. This finding suggests that, on average, the area adjacent to existing BMAs has already been impacted to a degree comparable to the remainder of the undesignated portion of the region and that there is generally no management buffer zone of the type recommended as the model for Man and the Biosphere reserves (Batisse 1982). Further, this suggests that to increase representation of biodiversity within designated BMAs, there is relatively little opportunity to do so by expanding existing sites into contiguous unroaded areas.

Limitations and Discussion

The statewide stewardship and ownership map is a compilation of ownership maps provided by a variety of sources who are individually responsible for their accuracy. It was created solely for the purpose of conducting the analyses described in this report and it is not suitable for locating boundaries on the ground or determining precise area measurements of individual tracts.

No single source can provide maps of all managed areas within a large region. Numerous difficulties can arise when combining information from a large number of sources into a single comprehensive map. Some digital map sources may use different map projections and have different scales. The quality, scale, map projection and date of production for different paper source maps will vary. When such maps are converted to digital form by a digitizing technician, additional error may be introduced as a result of human limitations and level of computer precision. Another problem is that computer-determined area rarely duplicates the area given by other sources, such as atlases or agency publications. Very often there is conflicting information about an area and it is not always clear which source is most recent, valid or reliable.

There is rarely a central source or contact person, even within a single organization, for maps of all an agency's managed areas. Thus, individual reserve managers must be identified and contacted. Maps are often roughly sketched, small-scale illustrations of the preserve boundaries, contained in a brochure and lacking the cartographic precision of our database. For these reasons, a well-designed digital managed areas map must be more than a mere snapshot in time of the areas for which data were available. It should be continually updated as new contacts are established; new sources are identified; and more recent, updated maps become available.

Assessing map accuracy also presents a problem because there are many different types of errors and potential sources of error. The map source may contain errors or obsolete information. Registering all maps to a consistent coordinate system provides additional error, as does changing map projections. Often these inaccuracies are difficult to identify quantitatively. Choosing a map scale determines the amount of simplification used when abstracting from the real world to a computer representation.

The stewardship map has not been formally validated for accuracy of boundaries or of attributes. A relatively thorough quality control was used to track the addition of managed areas to the database. During the analysis process, some errors in labeling managed areas were discovered and corrected. Nevertheless, additional errors and omissions may occur. Two sources of error are virtually impossible to control. First are the constant changes in administration of properties, either as new managed areas are acquired or as areas are transferred to other agencies. For example, many of the military bases in California are being privatized or transferred to other public agencies. The other limitation in the stewardship database is caused by crude source maps for some managed areas. Some agencies and private conservation organizations have only rough maps used for tourist brochures for some parcels. We transcribed these as best as we could, and are satisfied that any inaccuracies in boundaries will not significantly impact the Gap Analysis results.

One case where boundary uncertainty could be more troublesome is that of wilderness areas in the Mojave and Sonoran regions that were designated in the California Desert Protection Act of 1994 . At the time our database was compiled, the best digital source maps of their boundaries was from a 1:1,000,000 scale map for the 1991 version of the legislation. Some areas proposed in the 1991 version and not designated by the approved act were included in the gap analysis database. We recognize that some of the boundaries underwent revisions in the final negotiations, but were unable to obtain the final boundaries in time to include them in our final database or analyses.

In order to maintain data consistency, we attempted to adhere to a set of explicit rules in compiling the map of sewardship and ownership. There were instances, however, when decisions had to be made on a case-by-case basis. For example, different source maps often disagreed on boundaries, ownership, or management status. Problems in classification also arose in relation to the spatial configuration of land parcels. For example, we exercised judgement in including or excluding protected areas that fell below our MMU but that were contiguous withother protected areas.

The digital map of land stewardship and management is spatially exhaustive and includes ownership and management level attributes for all land. It does not, however, include detailed records for individual privately owned parcels (i.e., most status 4). County agencies keep detailed maps and records that are beyond the scope of our needs for gap analysis. A closer look at land ownership will be required when reserve networks and corridors are designed.

Creating the digital map described in this report required several pragmatic choices to satisfy the project objectives. Beardsley and Stoms (1993) offered a vision of the characteristics of an ideal GIS database for management status. Specifically, three aspects were discussed: delineating sections within managed areas, encoding additional attributes, and accommodating multiscale representations of managed areas.

Individual areas are not managed uniformly. Many state and national parks, for example, have sections managed for intensive public recreation, which should be classified at a lower management level than their natural surroundings. In some cases this differentiation has been done (e.g., wilderness areas distinguished from non-wilderness in national forests), but ideally, all developed sections should be mapped and labeled as different from undeveloped sections. Similarly, areas managed as roadless, undeveloped areas on public lands (but not legislatively established as wilderness) should still be distinguished from lands managed for intensive resource extraction (Davis and Stoms 1996b). The classification of management status described here assumes that all units of a managed area system (e.g., all state parks) have the same management, and yet this is clearly an oversimplification. Crops are planted in some wildlife refuges and grazing is allowed in some wilderness areas. An ideal database would include attributes describing management practices for each area. Specific activities to be recorded include whether grazing, logging, off-road vehicles, and mining occur; if fire is suppressed (or the role of fire); and whether management favors individual species. This information could be used to classify managed areas more precisely.

Klubnikin (1979) compiled a similar list of parks and preserves (analogous to GAP's status 1 and 2) almost two decades ago. Many protected areas have been acquired or designated since that survey. In 1979, she recorded 30,000 km² of parks and preserves. For CA-GAP, using similar criteria, we have mapped 74,000 km², nearly a 150% increase of status 1 and 2 managed areas. In Southwestern California, land managed for protection of biodiversity nearly tripled during that period (Beardsley and Stoms 1993). While the total area has increased dramatically, the average size has shrunk. In 1979, the mean size of parks and preserves was 13,172 ha (Klubnikin 1979), while currently the mean is 9,944 ha. Klubnikin (1979) reported that protection of vegetation was highly biased towards desert scrub and montane forests in the Sierra Nevada. In the following chapter of the report, we will analyze how this increase in protection of land has changed the protection of plant communities and terrestrial vertebrates.

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