Forest Investment Account (FIA) - Forest Science Program
FIA Project M075048

    Assessing the threat of mountain pine beetle outbreaks to whitebark pine in British Columbia
Project lead: Campbell, Elizabeth
Contributing Authors: Campbell, Elizabeth M.; Carroll, Allan L.
Imprint: [BC] : Ministry of Forests and Range, 2007
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Background/Rationale - In the United States, a large proportion of mature whitebark pine (Pinus albicaulis) were killed by mountain pine beetle during the 1940s and the 1980s when mountain pine beetle (Dendroctonous ponderosae) epidemics spread from low elevation lodgepole pine (Pinus contorta) forests upward into whitebark pine forests (Ciesla & Furniss, 1975). The effects of mountain pine beetle outbreaks on whitebark pine forests in British Columbia are poorly understood, but the potential for a major, negative impact is clear. Considering the extent of the current outbreak in low elevation lodgepole pine forests, we can expect that a massive decline of whitebark pine in British Columbia is imminent. Although mountain pine beetle outbreaks are natural disturbances in pine forests of western North America, the cumulative effects of a number of anthropogenic factors are putting whitebark pine at greater risk from beetles than ever before. Warming climates are expanding the geographic range of mountain pine beetle in British Columbia (Carroll et al., 2004), and probably creating more suitable habitat for the beetle at higher elevations (Amman, 1973). In addition, many whitebark pine forests throughout British Columbia are heavily infected by the exotic fungus white pine blister rust (Cronartium ribicola) (Campbell & Antos, 2000), which makes them more susceptible to attack by mountain pine beetle. Moreover, fire suppression activities over the last century have contributed to an increase in the extent of susceptible lodgepole pine over landscapes in BC, creating more 'sources' of beetles at low elevations (Taylor and Carroll, 2004). Considered a 'keystone' species, whitebark pine is a functionally important component of many high-elevation ecosystems in western North America and the consequences of its decline are numerous. In upper subalpine ecosystems, where harsh conditions limit the growth of other tree species, whitebark pine strongly influences patterns of snow accumulation and snowmelt, and its continued decline may alter watershed hydrology affecting slope stability and the timing, levels, and quality of stream flow. In these same harsh environments, whitebark pine also moderates microenvironments and facilitates the recruitment and growth of other plants. Whitebark pine is inexorably linked to Clark’s nutcracker (Nucifraga columbiana), which has evolved to exploit the highly nutritious seed of whitebark pine (Lanner, 1996). The pine is, in turn, entirely dependant on the nutcracker for seed dispersal and subsequent recruitment. The seed is also an important source of dietary fat for other animals such as red squirrels (Tamiasciurus hudsonicus) and grizzly bears (Ursus arctos L.), which have increased reproductive success in years of abundant seed production (Mattson & Jonkel, 1990). Any disruption of the symbiotic relationship between the bird and whitebark pine will have cascading effects, impacting many basic ecosystems processes and compromising the biological diversity of these communities (Tomback & Kendall, 2001). Expanding outbreaks of mountain pine beetle, due to warming climate conditions, or other factors, like more abundant susceptible lodgepole pine in landscapes, pose just this sort of threat. Indeed, it has been hypothesized that the current distribution of whitebark pine resulted from the inability of this species to ward off attacks by insects and pathogens that occur on pines in more climatically benign environments (Logan & Powell, 2001). The current beetle outbreak in British Columbia started in about 1992 and provincial outbreak simulations suggest beetles will reach many whitebark pine stands over the next few years (unpublished data; M. Eng, BC MoF, and E. Campbell, PFC, CFS). During a reconnaissance field tour of E. Campbell’s research plots in southern BC in 2005, we found active beetle infestations on whitebark pine and many trees that were dead or dying due to the beetle. Given that mountain pine beetles are now infesting some whitebark pine stands, and that the current extent and severity of beetle outbreaks in lower elevation lodgepole pine forests was much higher than predicted, we feel that whitebark pine may be under greater threat than previously thought. Declining whitebark pine represent a strong indicator of the effects that climate change, human land-use activities, and exotic species invasions can have on the biological diversity and functional integrity of forest ecosystems. The International Union for Conservation of Nature and Natural Resources has deemed whitebark pine a 'vulnerable' species, meaning it is at 'high risk of extinction in the wild in the medium-term future'. Whitebark pine is currently not considered at high risk of extinction by federal or provincial governments in Canada or the United States and has been given global and national rankings of 'apparently secure' (G4, N4), indicating that it is 'apparently not vulnerable in most of its range, but is possibly cause for long-term concern'. In Canada, whitebark pine is considered 'vulnerable' (S3) in Alberta and 'apparently secure' (S4) in British Columbia. However, in light of the apparent increased threat of mountain pine beetle to whitebark pine, we feel that these risk-of-extinction rankings, and risks to the ecosystems on whole, require review. It is generally agreed among scientists, forest and wildlife managers, and high-mountain recreationists that development of a conservation strategy to offset human influences on the decline of whitebark pine should receive high priority (Tomback et al., 2001). Fundamental to this is an assessment and quantification of the factors contributing to the decline and how the influence of these factors has changed over time. With the partnered support of the British Columbia Conservation Data Centre (CDC), British Columbia Parks, and the Whitebark Pine Ecosystem Foundation, we propose a study that assesses and quantifies past and current impacts of beetle outbreaks and uses simulation models to predict the threat of future mountain pine beetle outbreaks to whitebark pine in British Columbia. This study will parallel similar ongoing research the Canadian Forest Service is conducting in lodgepole pine forests of BC: including the beetle-climate modeling work of Allan Carroll et al., (2005), beetle disturbance history studies (Campbell & Alfaro, 2005) and stand dynamics research (Hawkes et al. 2004). As part of a network of whitebark pine study sites in Canada, it will build on recent findings (Campbell & Antos 2003) and compliment ongoing research about disturbance and forest dynamics in these ecosystems (E. Campbell, Can. For. Serv.; J. Antos, Univ. Victoria; and, L. Daniels Univ. BC). Through the Whitebark Pine Ecosystem Foundation, this work will also form part of an international bank of data and compliment ongoing whitebark pine studies in the US (cf. Tomback et al. 2001), the results of which will be used to guide conservation/ecosystem restoration efforts over the range of whitebark pine.
Related projects:  FSP_M086048


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Updated August 16, 2010 

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