A Gap Analysis of the Management Status of the Vegetation of Idaho (U.S.A.)

Abstract

We compiled a 1:500,000‐scale map of the actual vegetation of the state of Idaho from existing vegetation maps, LANDSAT MSS satellite imagery, and aerial photography. An accuracy assessment showed 92.7% of the polygons to be correctly classified. The map was digitized as a layer in a Geographic Information System (GIS) using ARC/INFO software. Land ownership was also digitized from existing maps. Ownership tracts were assigned a protection level based on opportunities provided for management for conservation of biological diversity. We then compared the vegetation and management status layers to assess the extent and degree of protection afforded to 71 vegetation and land‐use categories. We identified six vegetation complexes with no protection and five vegetation complexes for which protection is less than 1000 ha each. An additional 18 vegetation types have total protection in the ranges between 1001–5000 ha and 5001–10,000 ha. Most of these 29 vegetation types are shrub‐steppe complexes or conifer/steppe mosaics. Economically valuable montane forests of western redcedar, western hemlock, and grand fir, as well as subalpine woodlands and forests of mountain hemlock, are also poorly represented in protected areas. Most opportunity for increasing protection of these types lies on land managed by federal agencies. Other trends in the data include poor geographic representation, small area of individual protected occurrences, relatively good protection in Idaho but less outside of the state, and protection poor in Idaho but widespread elsewhere. The major limitation of our analysis is a lack of detail on the ecological status of vegetation types. Information on the structure of the forest types as well as data on the understory composition of the shrub‐steppe complexes are lacking. Our study shows gap analysis to be an efficient and useful method of assessing the extent and degree of protection of land‐cover types and associated biodiversity over an area exceeding 200,000 km2.