V. HABITAT LINKAGE CORRIDOR
(a)Corridor Special Management Area-- Under this alternative, a habitat linkage corridor is established between the proposed recovery zone and the Cabinet Mountains Wilderness Area in northwest Montana (see Figure 3).
The best hope for reestablishing a demographically sound, genetically diverse grizzly bear population in the Greater Salmon-Selway region is to recreate a land bridge between grizzly bear populations to the north and the Bitterroot Range. The Northern Bitterroot Range serves as a natural movement area for wildlife, and is comprised of the same habitat types used by grizzly bears in the Cabinet-Yaak and Selkirk areas.
The 9th U.S. Circuit Court of Appeals (1990) described corridors as:
...avenues along which wide-ranging animals can travel, plants can propagate, genetic interchange can occur, populations can move in response to environmental changes and natural disasters, and threatened species can be replenished from other areas.
Noss (1991) identified corridors as one of three essential elements in the design of regional reserve systems for protection of biological diversity.
The general area established as a linkage zone by this alternative has been identified by the U.S. Fish and Wildlife Service (1993) as a potential linkage corridor warranting further study. At least one grizzly bear has been known to use this general area. In 1984 a radio-collared male grizzly bear from the Cabinet Mountains area moved south and crossed Highway 200 and the Clark Fork River and denned in the Northern Bitterroot Range (Kasworm, pers. comm.). Groves (1987) documented 7 reliable observations of grizzly bears within this corridor area. Melquist (1985) found that suitable travel corridors existed which could concievably enable grizzlies to disperse from the Cabinet-Yaak area south into the Bitterroot Range.
Geographic Information System (GIS) analysis (Ecology Center 1995) shows that between the Cabinet Range and the Northern Bitterroot Range there are no core areas of roadless or low density roaded areas of sufficient size to provide adequate refugia necessary to support even a small number of grizzly bears. However, with improved habitat security and connectivity, the chances of natural inmigration, supplemented by human-aided translocations of bears, offers the best hope for successful reestablishment of a breeding population capable of sustaining steady population growth throughout the Salmon-Selway region.
While research on corridor effectiveness has been limited in regards to grizzly bears, leading researchers have recognized their importance. Jonkel (1987) stated that travel corridors are important units of grizzly bear habitat. He concluded that even where corridors feature extensive human disturbance, if they connect units of habitat, prevent the isolation of bears into "island populations," or enable bears to travel to key food sources, then corridors are an important habitat requirement. Picton (1986) concluded that functional linkage corridors for grizzly bear movements between Yellowstone and Glacier National Parks were possible. The potential linkages he analyzed were of far greater length and cross more substantial obstacles than the corridor established by this alternative. Craighead et al. (1995) suggest that corridor linkages for grizzly bears be established immediately before expanding resource use precludes them altogether. Bader (1991) presented a system of corridor linkages for the Northern Rockies region (see Figure 1), including the linkage corridor established by this alternative. This alternative recognizes the importance of these other corridor linkages and the Scientific Committee formed in Section 10 shall identify additional opportunities for establishing linkages between the Salmon-Selway grizzly population and other populations in the region.
Craighead and Vyse (1996) suggest that a functional grizzly bear metapopulation could be established in the Northern Rockies with the Salmon-Selway as an integral core reserve connected to other core reserves through a system of corridors. They concluded that male grizzlies, and particularly subadults, are most likely to use corridors for dispersal and can maintain genetic diversity. They found that recolonization of empty habitat patches depends upon female dispersals, which are typically over shorter distances, requiring design of corridors which contain habitat capable of supporting several females through their lifetime and the lifetimes of their offspring.
The effects of road densities and habitat fragmentation on grizzly bear populations and habitat use are well established in the literature. Maintenance and restoration of low road density habitat in the linkage established by this alternative is essential to establishment of a large subpopulation of grizzly bears in the Salmon-Selway and consequently, a viable Northern Rockies metapopulation. In order to assess the effectiveness of habitat linkages, they must be established now, and grizzly bear restoration in the Greater Salmon-Selway region provides the opportunity to study this concept out on the land.
(b) Boundaries--The southern boundary of the Corridor Special Management Area shall be the northern boundary of the population recovery zone. The boundaries shall extend generally 15,000 meters to the sides of the Idaho-Montana border. The eastern boundary extends to south of Interstate 90 then parallel to I-90 to south of Haugan, MT. From Haugan, north to a line generally parallel to Montana Highway 200 northwest to Noxon, then crossing Hwy 200 and extending to the Cabinet Mountains Wilderness Area. The western boundary extends southwest from the Cabinet Mountains Wilderness over Berray Mtn. and across Hwy 200 and the state border, then along the border southeast to Wallace, ID and south across I-90, then extends southeast along the border to rejoin the population recovery zone boundary in Idaho.
(c) Management--Within this established corridor area, a habitat conservation agreement would be formalized between the U.S. Fish and Wildlife Service and the U.S. Forest Service to establish this area as a Corridor Special Management Area. This corridor totals 1,391 square miles on the Clearwater, Lolo, Panhandle, and Kootenai National Forests. There are approximately 543 square miles of inventoried roadless area within this corridor (Ecology Center 1995). Within the Corridor Special Management Area, open road densities will be limited to an average of 0.25 miles per square mile. This density is based upon security requirements for female/cub grizzly bear groups described by Mattson (1991) and is the road density standard recommendation by Craighead et al. (1995). Interstate 90 and Montana Highways 200 and 56 are exempted from this density standard. A standard for cover requirements shall also apply to the Corridor Special Management Area. This cover standard shall be developed by the Scientific Committee established in Section 10 of this alternative.