(Map may reflect historical as well as recent sightings)
Whitebark Pine was federally designated as a candidate species on July 19, 2011.
Historical Status and Current Trends
Whitebark Pine is declining throughout its range. Based on current mortality rates from populations in Canada, it is anticipated that populations of Whitebark Pine will decline 57 percent by 2100.
Description and Life History
Whitebark Pine is a five-needled conifer species typically 16 to 66 feet (5 to 20 meters) tall with a rounded or irregularly spreading crown shape. Oone of five species of stone pines (so-called for their stonelike seeds) worldwide, Whitebark Pine is the only stone pine that occurs in North America. The Whitebark Pine’s characteristic dark brown-to-purple seed cones are 2 to 3 inches (5 to 8 centimeters) long and grow at the outer ends of upper branches. The seeds are dispersed almost exclusively by Clark’s nutcrackers (Nucifraga columbiana), a jay-like bird of high altitude forest habitats. Consequently, Clark’s nutcrackers facilitate the regeneration of Whitebark Pine and influence its distribution and population structure through their seed caching activities. A single nutcracker can cache up to an estimated 98,000 seeds during a good seed crop year.
Whitebark Pine is a slow-growing, long-lived tree with a life span of up to 500 years and sometimes more than 1,000 years. Although Whitebark Pine can occur in pure or nearly pure stands at high elevations, it more typically occurs in stands of mixed species in a variety of forest community types. Whitebark Pine is considered a keystone or foundation species in western North America where it contributes to critical ecosystem functions. As an early successional species, it can be the first conifer to become established after disturbance, subsequently stabilizing soils and regulating runoff. In winter, snowdrifts around Whitebark Pine trees help to increase and hold soil moisture later into the season. These higher elevation trees shade, protect, and slow the progression of snowmelt, essentially reducing spring flooding at lower elevations. Whitebark Pine also provides important, highly nutritious seeds for at least 20 species of vertebrates including ground squirrels, bears, and numerous bird species.
Whitebark Pineoccurs on cold and windy high-elevation or high-latitude sites in western North America. The elevational limit of Whitebark Pine ranges from approximately 2,950 feet (899 meters) at its northern limit in British Columbia, up to 12,000 feet (3,658 meters) in the Sierra Nevada. The species is typically found growing at alpine timberline or with other high-mountain conifers just below the timberline and upper montane zone. In the Rocky Mountains, common associated tree species include lodgepole pine (P. contorta var. latifolia), Engelmann spruce (Picea engelmannii), subalpine fir (Abies lasiocarpa), and mountain hemlock (Tsuga mertensiana). Common associated tree species are similar in the Sierra Nevada and Blue and Cascade Mountains, except lodgepole pine is present as Sierra-Cascade lodgepole pine (P. contorta var. murrayana) and mountain hemlock is absent from the Blue Mountains. Stands of Whitebark Pine are typically fragmented and isolated from one another due to the elevational requirement.
The range of Whitebark Pine extends from Northern British Columbia south to Northern Nevada, and from the coastal mountains of the Pacific Northwest east to the Wind River Range in Wyoming. In Oregon, isolated stands of Whitebark Pine are known from the Blue and Wallowa Mountains in northeastern Oregon and the subalpine and montane zones of the Cascade and Klamath mountains in south-central Oregon, including Crater Lake National Park.
Roughly 44 percent of Whitebark Pine’s range occurs in the United States, with the remaining 56 percent of its range occurring in British Columbia and Alberta, Canada. In Canada, the majority of the species’ distribution occurs on private land but in the United States, approximately 96 percent of land where the species occurs is federally-owned or managed. The majority (approximately 81 percent) is located on National Forest lands, with another 13 percent located in National Parks and 2 percent on Bureau of Land Management lands. The remaining 4 percent is under non-federal ownership.
Reasons for Decline
The decline in Whitebark Pine populations began sometime following the 1910 introduction of the exotic disease White Pine blister rust. White Pine blister has successfully spread across almost the entire range of Whitebark Pine, and its frequency of occurrence and intensity of infection are increasing. In recent years, Whitebark Pine has faced an even greater threat, the mountain pine beetle. This insect is now recognized as one of the principal causes of Whitebark Pine mortality. Mountain pine beetles are true predators on Whitebark Pine and other western conifers because the beetle’s reproduction process results in the death of the host tree. Another factor in Whitebark Pine’s decline has been the destruction or modification of its habitat due to environmental changes from fire suppression. Fire suppression and the resulting shift away from a natural fire regime have led stands that were once dominated by Whitebark Pine to undergo succession to more shade tolerant conifers. Finally, it is anticipated that direct habitat loss from climate change will lead to further declines in Whitebark Pine as increased temperatures make current habitats unsuitable for the species.
References and Links
U.S. Fish and Wildlife Service. 2011. 12-Month Finding on a Petition To List Pinus albicaulis as Endangered or Threatened With Critical Habitat. Federal Register