Unprotected At-Risk Plant Communities of the Western U.S.

R. Gerald Wright, J. Michael Scott, Shannon Mann, and Michael Murray

University of Idaho, Moscow

Most analyses conducted to date using GAP data that cover large multistate regions have been limited to tabulating those plant communities at greatest risk within a particular geographic region (e.g., Stoms et al. 1997) or to identifying broad geographic zones where conservation efforts should be concentrated to maximize the conservation of biodiversity (e.g., Kiester et al. 1996). Few studies have identified specific lands that would be a high priority for conservation action, although we expect more as state projects are completed and data are distributed (e.g., Crist et al., in press). Thus GAP data so far have seen limited application to land-use planning because such efforts typically take place locally and at small ecological scales (Stevenson 1998). We believe that if GAP vegetation data are to be useful for land-use planning at the scales normally employed, they must be used to identify specific land parcels associated with a particular plant community where protection should be a priority. The intent of this ongoing project has been to develop a stepwise process to achieve that goal over a large geographic area. The geographic region we studied was a 2,090,000 km² area encompassing all or parts of the 11 U.S. states west of the Continental Divide.

We used the vegetation cover maps developed by the individual GAP state projects, aggregating the different map classifications to the alliance level where possible. We used land ownership and land management maps compiled by the respective state GAP projects and other sources. Two broad categories of land ownership were defined for each tract of land: public and private. Public lands were subdivided into two categories based on the degree to which biodiversity is protected. We focused our effort on the 42 plant communities that had less than 10% of their area on protected lands. These plant communities occupied 35% of the study area, and initially, we considered them to be inadequately protected and therefore potentially at risk. For each of these plant communities, we calculated the total land area occupied, the geographic range (number of states) the community occurred in, the number of patches (polygons) occupied, the average patch size, and identified all counties where the plant communities occurred as well as the recent population growth rate of those counties.

We calculated that to adequately protect all of the plant communities to the 10% level would often require substantial change in management on 2.2 million ha in the region. To put this figure in perspective, this would require the conversion to protected status of a land area (albeit dispersed) equivalent to three Yellowstone National Parks. We did not think this was a sociopolitically feasible starting point in a long-term conservation strategy for the West. Therefore, using the criteria of total land area occupied by a given vegetation type, its geographic range, and the number of patches occupied, we attempted to reduce the list of "at risk" plant communities and their associated land area to a more workable figure.

Through this process we identified 26 vegetation types assumed to be at great risk. We calculated their protection would require conversion of about 700,000 ha of public lands to a protected status and acquisition or protection of 111,000 ha of privately owned lands. These changes would be spread out over 43 counties in the region, so no one area would be disproportionately impacted.

We are attempting to prioritize the individual land parcels involved in this process by arbitrarily limiting our selection to land patches >2,500 ha to assure the ecological viability of those lands. In addition, we have sought to prioritize the protection of those patches that occur in counties where the population gain over the last decade exceeded 30%.

The end result of this study will be a prioritized list of specific land parcels in a given county, which we feel should receive additional protection in order to achieve the specified conservation goal for a given plant community.

Our approach is contrary to that of those who advocate the protection of very large land areas as a biodiversity conservation strategy (e.g., Noss 1996) since our experiences have shown that socioeconomic constraints often limit the success of such ambitious schemes (Wright 1996). As a result, many large reserves exist only in plans and on maps. A set of strategically placed reserves of a size which is consistent with resources available for their protection may be a more realistic option (Zuidema et al. 1996).

Literature Cited

Crist, P., T. Kohley, J. Oakleaf. In press. BEST: An expert systems tool for assessing land use impacts on biodiversity. Landscape Ecology.

Kiester, A.R., J.M. Scott, B. Csuti, R. Noss, B. Butterfield, K. Sahr, and D. White. 1996. Conservation prioritization using GAP data. Conservation Biology 10:1332-1342.

Noss, R.F. 1996. Protected areas: How much is enough? Pages 91-120 in R.G. Wright, editor. National parks and protected areas: Their role in environmental protection. Blackwell Science, Cambridge, Massachusetts.

Stevenson, M. 1998. Applying Washington GAP to county land use planning. Gap Analysis Bulletin 7:30.

Stoms, D.M., F.W. Davis, K. Driese, K. Cassidy, and M. Murray. 1997. Gap analysis of the vegetation of the intermountain semi-desert ecoregion. Great Basin Naturalist 58:199-216.

Wright, R.G. 1996. Expansion of the U.S. national park system in Alaska. Pages 165-173 in R.G. Wright, editor. National parks and protected areas: Their role in environmental protection. Blackwell Science, Cambridge, Massachusetts.

Zuidema, P.A., J.A. Sayer, and W. Dijman. 1996. Forest fragmentation and biodiversity: The case for intermediate-sized conservation areas. Environmental Conservation 23:290-297.