Abstract: Western forests are experiencing unprecedented change with the loss of white pine communities from the introduced fungal pathogen, white pine blister rust (Cronartium ribicola). Whitebark pine (Pinus albicaulis), a subalpine conifer, is rapidly declining from the combination of blister rust, fire exclusion, and mountain pine beetle (Dendroctonus ponderosae) epidemics. Paradoxically, 98% of whitebark pine occurs in protected areas, such as national parks and wilderness, but losses of whitebark pine are anthropogenic in origin. Surveys in the northwestern United States and southwestern Canada indicate that more than 20% of the whitebark pine are dead, with some stands at nearly 100% mortality; and 40 to 100% of the living trees are infected with blister rust. These losses are compounded by the successional replacement of whitebark pine by shade-tolerant conifers on favorable sites. Rangewide, whitebark pine communities represent a variety of habitat types and considerable plant biodiversity. The large, wingless seeds of this pine are an important food source for many birds and small mammals, and particularly for the Clark’s nutcracker (Nucifraga columbiana), the primary seed disperser of the pine. The decline of whitebark pine threatens the security of the grizzly bear (Ursus arctos) in the Greater Yellowstone Area and the Bob Marshall Wilderness.