A multicriteria assessment of the irreplaceability and vulnerability of sites in the Greater Yellowstone Ecosystem

We conducted a systematic conservation assessment of the 10.8-million-ha Greater Yellowstone Ecosystem (GYE), integrating three basic approaches to conservation planning: protecting special elements, representing environmental variation, and securing habitat for focal species (grizzly bear [Ursus arctos], wolf [Canis lupus], and wolverine [Gulo gulo]). Existing protected areas encompass 27% of the GYE but fail to capture many biological hotspots of the region or to represent all natural communities. Using a simulated annealing site-selection algorithm, combined with biological and environmental data based on a geographic information system and static (habitat suitability) and dynamic (population viability) modeling of focal species, we identified unprotected sites within the GYE that are biologically irreplaceable and vulnerable to degradation. Irreplaceability scores were assigned to 43 megasites (aggregations of planning units) on the basis of nine criteria corresponding to quantitative conservation goals. Expert opinion supplemented quantitative data in determining vulnerability scores. If all megasites were protected, the reserved area of the GYE would expand by 43% (to 70%) and increase protection of known occurrences of highly imperiled species by 71% (to 100%) and of all special elements by 62% (to 92%). These new reserves would also significantly increase representation of environmental variation and capture critical areas for focal species. The greatest gains would be achieved by protecting megasites scoring highest in irreplaceability and vulnerability. Protection of 15 high-priority megasites would expand reserved area by 22% and increase the overall achievement of goals by 30%. Protection of highly imperiled species and representation of geoclimatic classes would increase by 46% and 49%, respectively. Although conservation action must be somewhat opportunistic, our method aids decision-making by identifying areas that will contribute the most to explicit conservation goals.