Methods and assumptions used in this impact analysis include the following:
Impacts to special status wildlife species are based primarily on potential impacts to habitats managed by the BLM.
Precise quantitative estimates of impacts generally are not possible because the exact locations of future actions are unknown, population data for special status wildlife species are often lacking other environmental variables, or habitat types affected by surface-disturbing activities cannot be predicted.
The more habitat available for a species, the greater the benefit to the targeted species.
Prohibiting all surface-disturbing and disruptive activities in greater sage-grouse seasonal habitats is more beneficial to greater sage-grouse than avoiding these activities, as avoidance provides discretion for each proposed activity and applies mitigations, where prohibition precludes all activity.
Within historical fire regimes, prescribed fire is used to manage vegetative communities and can result in short-term adverse impacts with long-term beneficial impacts to wildlife, certain desirable wildlife habitats, and in some cases to forage productivity and availability.
Measures to protect one species generally result in long-term benefits to other species in that habitat.
Short- and long-term surface disturbance are assumed to occur in vegetation types in proportion to the availability of these vegetation types in the Planning Area. Impact acreage for vegetation types are not absolute, but serve as a relative comparison among alternatives.
Because of the migratory nature and relative mobility of some special status wildlife species (e.g., waterfowl, neotropical migrants, and raptors), these species are affected by actions on non-BLM-administered land more so than other species. In the case of migratory species, impacts to winter and migration habitats could adversely impact the viability of some species. Winter and migration habitats are assumed to be at least as important to long-term viability of these species as breeding and nesting habitats.
Removal of sagebrush habitat will have a long-term adverse impact on sagebrush-obligate species in the 5- to 9-inch precipitation zone.
The USFWS may designate additional wildlife species as threatened and endangered as additional data are collected and evaluated. These species would be managed in accordance with the ESA and as directed by decisions in the alternatives.