Status of GAP Components This section reviews the status of the constituent parts, or components needed, to conduct Gap Analysis. Gap Analysis was begun with a focus on the terrestrial environment, however, the development of information and analyses must logically be extended to the aquatic environment; the aquatic component of Gap Analysis is also treated in this section. The status of analyses of the GAP data layers is discussed in the "Products" section of this report. Land Ownership and Land Management Maps Since one purpose of GAP is to provide an assessment of the conservation status of species and their habitats, maps of lands that are managed for conservation must be compared with the distributions of species and habitats. Most states, however, do not have a current inventory of land management status. The first step toward developing a map of conservation lands is to map land ownership by the major categories of: (1) public lands by managing agency, (2) voluntarily identified privately owned conservation lands, and (3) all other privately owned lands. Then, as a second step, the attributes for land management categories are added to these tracts. All non-conservation privately owned lands (category 3 above) are simply labeled "private," and individual parcel boundaries are not delineated. The GAP state projects that were begun earliest resolved land management parcels with a minimum mapping unit of either 100 or 200 hectares, with areas of special concern (e.g., wetlands) being resolved at finer MMUs because of biological significance, rarity, or diminishing status. At that time, the reasoning for MMU size was that (a) natural communities less than 100 hectares were less likely to retain the integrity required to maintain the complement of organisms needed to maintain a clearly defined trophic structure, biotic diversity, and material cycles over the long term, and (b) Gap Analysis seeks to quickly and efficiently identify opportunities where the gaps in the current network of conservation lands can be filled. Resolving land parcels at smaller MMUs is more labor-intensive. Additionally, most of these earlier state projects occurred in Western states, where landscape grain size and the size of conservation lands are generally larger than in Eastern states. For most of the state projects begun after 1993, however, there has been a strong consensus among cooperators that the land ownership and land management maps should include land parcels that can be reasonably resolved at a 1:100,000 scale. Commonly this is one hectare, which is equivalent to one mm2 on a 1:100,000 scale map. This reflects the needs of cooperating organizations in environments where landscape grain size and the size of conservation lands are generally smaller than in Western states. For maps that are made using smaller MMUs, coarser MMU thresholds, such as 100 hectares, can be set to meet various analytical objectives. Beardsley and Stoms (1993) tested the California Gap Analysis Project land management data layer to see how much of the total Level 1 area was being omitted by using an MMU of 200 hectares for uplands. They compiled a size-frequency distribution of all Level 1 areas in California's Southwestern ecoregion, regardless of size. They found that of the 81 Level 1 areas, 25 are less than 200 hectares, and 45 are less than 1,000 hectares. However, nine of the 81 Level 1 management areas account for 76.4 percent of the total Level 1 surface area. They note, though, the risk in setting a large MMU threshold is that some biologically important areas will be overlooked. Conservation areas that are small in size may play invaluable roles in maintaining the natural values of a region. Although it would be ideal to map all conservation lands regardless of size, it is not practical because of limited funding and the short-term project nature of state Gap Analysis projects. Additionally, small conservation parcels tend to be focused on a particular feature or species rather than regional biodiversity. Descriptions of how the land management maps are developed are provided by Scott et al. (1993), Beardsley and Stoms (1993), and Edwards et al. (1994). Land management is ranked by the four levels shown in Table 1.
Table 1. The four levels of land management and their definitions. Over the past year there has been an ongoing discussion among GAP staff about the adequacy of these definitions. Many feel that a larger number of categories which use a wider variety of management activities undertaken on behalf of native species and ecosystems would be more useful. When a greater number of management categories were recognized during the Sierra Nevada ecosystem project, it greatly improved communication among cooperators (F. Davis, University of California, Santa Barbara, personal communication). Accordingly, at the 1995 GAP annual meeting, an ad hoc committee was formed and is now chaired by Dr. Bruce Thompson, Principal Investigator of the New Mexico Gap Analysis Project (NM-GAP). The committee is charged with developing a more explicit guide to promote greater national consistency. The NM-GAP developed a dichotomous key for categorizing land management, which the committee is reviewing for application as a national model. A flow chart for the NM-GAP dichotomous key is shown in Figure 4.
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