Potential & Restoration
These two maps show changes in distributions of grizzly bears in the western United States between 1970 and 2016, coincident with when grizzlies were protected under the ESA. Yellow denotes areas where grizzly bears were present in 1800 and remain extirpated as of 2016. An estimate of total grizzly bear numbers at each time step is also shown (plus or minus the range of uncertainty), along with each of these values as a percent of what we had during the early 1800s. The thermometer graphs along the margins of each map provide a visual snapshot of how grizzly bear populations during 1970 and 2016 compare with those of 1800. Gray denotes areas too hot and dry to support grizzly bears. Although significant progress has been made in recovering grizzlies in the western US, total gains are small relative to the magnitude of losses between 1800 and 1960.
Progress in Recovery & Restoration
These maps show distributions of grizzly bears in the US Northern Rockies (dark green) relative to Recovery Areas (white lines) and current potential suitable habitat (light green) during (A) 1975 and (B) 2016. Locations of grizzly bears documented outside the bounds of core distributions are shown as red dots in (B). Representations of potential suitable habitat are a composite of 7 different models, with greater replication of results denoted by darker shading. The main take-away from theses maps are that, first, distributions of grizzly bears have expanded substantially since ESA protections were implemented in 1975; second, extensive areas of potential suitable habitat remain unoccupied, especially in central Idaho; and, third, Recovery Areas encompass only a minority of suitable habitat especially in the Yellowstone and Bitterroot areas. All of the models used to estimate distributions of potential suitable habitat accounted for intrinsic habitat productivity and remoteness from humans.
Distributions & Potential Suitable Habitat in the Northern Rockies
These two maps show the current (A) and potential future (B) distributions of grizzly bears in the contiguous United States and adjacent portions of Canada. Dark green shows current core distributions; light green shows peripheral distributions. Current US Recovery Areas are delineated in red in (A). Two existing or potential future populations are highlighted in bright green in (B): the Heart of the Grizzly Bear Nation, approximating the current Northern Continental Divide Ecosystem, and Grizzly Bear Promised Land, encompassing the considerable potential yet currently unoccupied habitat in central and northern Idaho. The Heart is a critical source for dispersers and colonizers through figurative connective arteries, whereas the Promised Land—is just that for grizzlies. If all of the potential suitable habitat in this region were occupied by grizzlies there would be a contiguous interbreeding population in excess of 9000 bears, sufficient to insure long-term viability.
Current Distributions & Potential Suitable Habitat in the Contiguous US & Adjacent Canada
This map shows potential suitable habitat for grizzly bears in the contiguous United States based on an amalgamation of results from 4 different modeling efforts. Areas shaded darker green denote greater replication of results from these modeling efforts. Current Recovery Areas are delineated in black and shaded with cross-hatching. Ample potential suitable habitat exists outside of current Recovery Areas, notably in central Idaho, west-central Wyoming, Arizona and adjacent New Mexico, the Sierra Nevada of California, and the Uintas in Utah. All models considered the effects of both habitat productivity and remoteness from humans.
Connectivity & Connectors
These three maps summarize the potential for restoration of grizzly bears in the US Northern Rocky Mountains, including: (A) an amalgamation of modeled potential suitable habitat from 7 different research projects (darker shades of green indicate greater replication of results); (B) modeled dispersal routes (orange-burgundy), documented locations of dispersing or colonizing grizzly bears (pink dots), and potential connectors superimposed on contiguous areas of suitable habitat; and (C) modeled dispersal routes censored because they intersect areas blocked by a heavy human footprint (shaded yellow to dark orange). Areas with the greatest potential for connecting current grizzly bear populations or Recovery Areas are shaded green in (C). Current Recovery Areas are delineated in red in (A) and (B). Key conclusions from all of this are, first, there is ample potential suitable habitat for grizzly bears in the US Northern Rockies and, second, this potential suitable habitat naturally provides for connectors among Recovery Areas. Moreover, most of these connectors are already being colonized by grizzlies.
These four maps identify specific areas encompassed by potential connectors among grizzly bear population in the US Northern Rocky Mountains (shaded green) that are candidates for mitigation, restoration, or focused coexistence efforts. Map (A) identifies locales where construction of highway crossing structures would ideally be prioritized (green ovals). Green boxes in map (B) encompass private agricultural lands candidate for focused coexistence efforts, whereas green boxes in map (C) delineate public land grazing allotments US Forest Service and BLM lands where active mitigation measures focused on improved husbandry and non-lethal deterrents need to be prioritized. Map (D) identifies areas on US Forest Services jurisdictions where management of lands currently devoted to timber production would logically prioritize road closures and other restrictions on access as means of restoring currently degraded habitat conditions. Each priority area has been given a unique identifier.