Climate Change & Whitebark Pine
Climate Change and Whitebark Pine: Compelling reasons for restoration
High elevation whitebark pine forests are rapidly disappearing throughout western North America because of the cumulative effects of historical and current mountain pine beetle (MPB) outbreaks, over 90 years of fire exclusion policies, and the introduced pathogen Cronartium ribicola, which causes the exotic disease white pine blister rust (WPBR) in five-needle white pines. Exacerbating an already stressed ecosystem, projected future climates may accelerate whitebark pine declines and further reduce whitebark pine habitat. However, magnitudes and directions of whitebark pine ecosystem responses to projected climate changes are largely unknown because of the species’ unique ability to survive fire, colonize disturbed environments, and tolerate drought. The high uncertainty of future climate predictions coupled with limited information on disturbance and climate interactions in whitebark pine forests may confound planning restoration activities in this valuable ecosystem.
Predicting responses of whitebark pine to projected climate change and restoration actions is quite complicated involving consideration of complex ecological interactions at multiple spatial and temporal scales. Climate warming, for example, may foster more high elevation fires that burn more whitebark pine forests, provide additional sites for nutcracker caching, and promote future regeneration. However, fires may also kill trees that are genetically resistant to WPBR thereby reducing regeneration potential and future adaptation to the rust. This complexity precludes traditional approaches for evaluating climate impacts, such as expert opinion, statistical modeling, and field experiments, because of the long time spans and large areas needed to properly assess vegetation, disturbance, and ecosystem responses to changing climates. Mechanistic ecological simulation of climate, vegetation, and disturbance dynamics in a spatial domain may be the best approach to evaluate the likelihood of potential ecosystem trajectories at this time even though the field of landscape modeling is still in its infancy.
Whitebark pine decline and climate change
Taking an historical perspective, whitebark pine was able to persevere through many major climatic cycles in the past. Historical analogs of warmer climates in the paleoecological record indicate whitebark pine was maintained and even increased in some places under past warmer and drier climates in some parts of its range. Whitebark pine can grow within a broad upper elevation zone in the west; the pines just happen to grow best at high elevations where there is little competition from other tree species. In fact, studies have shown that whitebark pine’s elevational range extended over 500 feet below its current lower elevation limit in the Bitterroot Mountains of Montana. Whitebark pine occupies the largest geographic range of any five-needled white pine in the U.S. and Canada, including about 18˚of latitude and 21˚ longitude, indicating a great deal of tolerance to different climates. Because whitebark seeds are bird-dispersed, it is planted and has the potential to grow in many environments where it may not currently exist. Moreover, the fact that it is long-lived provides the potential buffering against changing climates; periodic regeneration success over the lifespan of centuries-old trees maintains populations during periods of less optimal climates.
Whitebark pine trees may have other positive responses to warming climates. Anecdotal evidence shows that some whitebark pine forests are experiencing abnormally high growth and more frequent cone crops due to warmer summers and longer growing seasons. This is supported by recent modeling efforts that have shown that whitebark pine might be maintained on the landscape providing that predicted increases in large, stand-replacement fires create large, competition-free burned areas. And, if tree dispersal enables range shifts to occur, this will lead to a new northern distributional range. Moreover, whitebark pine also shows promise for being maintained in the Northern Rockies because of high levels of genetic diversity; moderate to high heritability in key adaptive traits demonstrated blister rust resistance; minimal inbreeding; and generalist adaptive strategies.
Climate-induced changes in disturbance regimes will overwhelm most vegetation responses to climate change. Many climate change studies consistently project drier conditions in the range of whitebark pine and that will result in large increases in the annual number, area burned, and severity of wildfires. With increased fire, whitebark pine will have a unique opportunity to maintain its range or even increase in distribution in the future because it has bird-mediated (Clark’s nutcracker) seed dispersal that can disseminate seed great distances into the large, severe burns predicted in the future. Under this scenario whitebark pine seeds would have the opportunity to colonize newly burned sites with reduced competition from wind-dispersed species that would have a lower likelihood of landing within large, burned perimeters. Whitebark pine is a fire-adapted species that readily regenerates in large burned areas and has morphology that enables it to survive low to moderate severity fires. Therefore, whitebark pine is uniquely positioned as a species that can increase under the more frequent fire regimes that result from warming climates provided that future fires do not severely diminish existing seed sources. And since nutcrackers may be harvesting seeds from trees that have survived blister rust, there is some chance that seeds from unclaimed nutcracker caches may become blister rust-resistant trees. It is entirely possible that as long as wildland fire creates areas where birds will cache seeds and resultant seedlings can grow without competition, whitebark pine will continue to thrive throughout its range.
Current mountain pine beetle outbreaks are killing more whitebark pine than historical records indicate and these outbreaks are probably a result of warmer winter temperatures that facilitate expansion and establishment of beetle populations in the higher-elevation whitebark pine zone (Logan and Powell 2001, Logan and others 2003). A warmer climate may also accelerate the spread of blister rust.
In summary, whitebark pine is not expected to do well under future climates, not because it is poorly adapted to shifts in climate regimes, but rather because it is currently experiencing major declines from the exotic disease that preclude its immediate regeneration in future burned areas. Moreover, these declines from WPBR and MPB have served to reduce whitebark pine populations to severely low levels and now the nutcracker is acting more as a seed predator than a seed disperser. Climate shifts will only exacerbate this decline and complicate restoration efforts. Make no mistake; this species can thrive under future climates providing that there are extensive restoration efforts to overcome the devastating effects of the WPBR exotic epidemic. Whitebark pine is at great exposure to any climate changes because of its (1) confined distribution to the upper subalpine environments, (2) severely depressed populations, and (3) lack of an ability to regenerate when populations are low because of nutcracker and squirrel predation. However, the species has the genetic capacity to overcome both WPBR and new climates and be able to thrive over the next century, but only with extensive restoration efforts. The magnitude of climate effects will be quite high because climate change is occurring with a major WPBR outbreak. And, the likelihood of these effects has a low uncertainty, mainly because of the role that WPBR will play in the health of whitebark pine forests.
Restoration is the only course of action for managing whitebark pine ecosystems. The anthropogenic-caused loss of a major ecosystem is irreversible: with it goes tremendous biodiversity, ecosystem services, and ecosystem function, seriously impoverishing our biological heritage. Restoration will include the implementation of strategies that hedge the effects of climate warming on whitebark pine ecosystems. However, the high uncertainty inherent in most current climate and ecosystem models may limit predicted distributional shifts that are extremely coarse-scaled and should not be used as justification for a “no restoration” response, especially considering the resiliency exhibited by whitebark pine over time and across its range. We must use the best information available and the most efficient restoration approaches in our toolkit of restoration techniques. We also need to educate and recruit new generations of managers and researchers, as well as new generations of agency administrators and other government officials, so that they understand the value of restoring these ecosystems and the rich biological heritage we hope to leave for future generations.
The following are a list of references that were used to construct this article
Allen CD et al. (2010) A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests Forest Ecology and Management 259:660-684 doi:http://dx.doi.org/10.1016/j.foreco.2009.09.001
Arno SF, Reinhardt ED, Scott JH (1993) Forest structure and landscape patterns in a subalpine lodgepole pine type: A procedure for quantifying past and present conditions. USDA Forest Service, Intermountain Research Station, Ogden, UT, USA
Aston IW (2010) Observed and Projected Ecological Response to Climate Change in the Rocky Mountains and Upper Columbia Basin: A Synthesis of Current Scientific Literature vol Natural Resource Report NPS/ROMN/NRR—2010/220. Natural Resource Program Center, Fort Collins, CO USA
Belotelov NV, Bogatyrev BG, Kirilenko AP, Venevsky SV (1996) Modelling of time-dependent biome shifts under global climate changes Ecological Modelling 87:29-40
Bower, A. D., and S. N. Aitken. 2006. Geographic and seasonal variation in cold hardiness of whitebark pine. Canadian Journal of Forest Research 36: 1842-1850.
Bower, A. D., and S. N. Aitken. 2008. Ecological genetics and seed transfer guidelines for Pinus albicaulis (Pinaceae). American Journal of Botany 95:66-76.
Butler DR, Malanson GP, Cairns DM (1994) Stability of alpine treeline in Glacier National Park Montana, USA Phytocoenologia 22:485-500
Callaway R, A. Sala, Keane RE (1998) Replacement of whitebark pine by subalpine fir: Consequences for stand carbon, water, and nitrogen cycles. USDA Forest Service, Fire Sciences Laboratory, Missoula, MT., USA
Cansler CA, McKenzie D, Halpern CB (2016) Area burned in alpine treeline ecotones reflects region-wide trends International Journal of Wildland Fire:- doi:http://dx.doi.org/10.1071/WF16025
Carroll AL, Taylor SW, Régnière J, Safranyik L Effects of climate change on range expansion by the mountain pine beetle in British Columbia. In: Shore T, Brooks JE, Stone JE (eds) Mountain pine beetle symposium: Challenges and solutions, Victoria, British Columbia, 2003. Natural Resources Canada, Canadian Forest Service,, pp 223-231
Chang T, Hansen AJ, Piekielek N (2014) Patterns and Variability of Projected Bioclimatic Habitat for Pinus albicaulis in the Greater Yellowstone Area PLoS ONE 9:e111669 doi:10.1371/journal.pone.0111669
Crimmins SM, Dobrowski SZ, Greenberg JA, Abatzoglou JT, Mynsberge AR (2011) Changes in climatic water balance drive downhill shifts in plant species’ optimum elevations Science 331:324-327
Dullinger S, Dirnböck T, Grabherr G (2004) Modelling climate change‐driven treeline shifts: relative effects of temperature increase, dispersal and invasibility Journal of ecology 92:241-252
Flannigan MD, Krawchuk MA, de Groot WJ, Wotton BM, Gowman LM (2009) Implications of changing climate for global wildland fire International Journal of Wildland Fire 18:483-507 doi:http://dx.doi.org/10.1071/WF08187
Goeking S, Izlar D (2018) Pinus albicaulis Engelm. (Whitebark Pine) in Mixed-Species Stands throughout Its US Range: Broad-Scale Indicators of Extent and Recent Decline Forests 9:131
Hansen A, Ireland K, Legg K, Keane R, Barge E, Jenkins M, Pillet M (2016) Complex challenges of maintaining whitebark pine in Greater Yellowstone under climate change: A call for innovative research, management, and policy approaches Forests 7:54
Hansen AJ, Phillips LB (2015) Which tree species and biome types are most vulnerable to climate change in the US Northern Rocky Mountains? Forest Ecology and Management 338:68-83
Iglesias V, Krause TR, Whitlock C (2015) Complex Response of white Pines to Past Environmental Variability Increases Understanding of Future Vulnerability PLoS ONE 10:e0124439 doi:10.1371/journal.pone.0124439
Johnstone JF, Chapin FS (2003) Non-equilibrium succession dynamics indicate continued northern migration of lodgepole pine Global Change Biology 9:1401-1409 doi:10.1046/j.1365-2486.2003.00661.x
Keane RE, Holsinger L, Mahalovich MF, Tomback DF (2017) Restoring whitebark pine ecosystems in the face of climate change. USDA Forest Service Rocky Mountain Research Station, Fort Collins, CO General Technical Report RMRS-GTR-361
Keane, RE, Holsinger, LM, Mahalovich, MF, Tomback, DF (2017) Evaluating future success of whitebark pine ecosystem restoration under climate change using simulation modeling. Restoration Ecology 25, 220-233.
Keane RE et al. (2018a) Effects of Climate Change on Forest Vegetation in the Northern Rockies. In: Halofsky JE, Peterson DL (eds) Climate Change and Rocky Mountain Ecosystems. Springer International Publishing, Cham, pp 59-95. doi:10.1007/978-3-319-56928-4_5
Keane RE et al. (2018b) Effects of climate change on forest vegetation in the Northern Rockies Region [Chapter 6]. . In: Halofsky JE, Peterson DL, Dante-Wood SK, Hoang L, Ho JJ, Joyce LA (eds) Climate change vulnerability and adaptation in the Northern Rocky Mountains – Part 1. , vol RMRS-GTR-374. . U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fort Collins, CO, pp 128-173
Keane RE et al. (2012) A range-wide restoration strategy for whitebark pine forests. USDA Forest Service Rocky Mountain Research Station, Fort Collins, Colorado
Koteen L (1999) Climate change, whitebark pine, and grizzly bears in the greater Yellowstone ecosystem. In: Schneider SH, Root TL (eds) Wildlife responses to climate change. Island Press, Washington DC USA, pp 343-364
Landguth EL, Holden ZA, Mahalovich MF, Cushman SA (2017) Using Landscape Genetics Simulations for Planting Blister Rust Resistant Whitebark Pine in the US Northern Rocky Mountains Frontiers in Genetics 8 doi:10.3389/fgene.2017.00009
Larson ER (2009) Status and dynamics of whitebark pine (Pinus albicaulis Engelm.) forests in southwest Montana, central Idaho, and Oregon, USA. Dissertation, University of Minnesota
Loehman RA, Corrow A, Keane RE Modeling climate changes and wildfire Interactions: Effects on whitebark Pine (Pinus albicaulis) and implications for restoration, Glacier National Park, Montana, USA. In: Keane RE, Tomback DF, Murray MP, Smith CM (eds) The future of high-elevation, five-needle white pines in Western North America: Proceedings of the High Five Symposium, Missoula, MT, 2011. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, pp 176-188
Logan, J. A., and Powell, J. A. 2001: Ghost forests, global warming, and the mountain pine beetle (Coleoptera: Scolytidae). American Entomologist 47:160-172.
Lorenz, T. J., C. Aubry, and R. Shoal. 2008. A review of the literature on seed fate in whitebark pine and the life history traits of Clark’s Nutcracker and pine squirrels. General Technical Report PNW-GTR-742, USDA Forest Service Pacific Northwest Research Station, Portland, OR.
Lonergan ER, Cripps CL, Smith CM Influence of Site Conditions, Shelter Objects, and Ectomycorrhizal Inoculation on the Early Survival of Whitebark Pine Seedlings Planted in Waterton Lakes National Park. In, 2013. Society of American Foresters,
Mahalovich MF (2013) Grizzly bears and whitebark pine in the greater Yellowstone Ecosystem: Future status of whitebark pine: blister rust resistance, mountain pine beetle and climate change vol 2470 RRM-NR-WP-13-01. Norhern Region, Missoula, MT
Mahalovich MF, Hipkins VD (2011) Molecular genetic variation in whitebark pine (Pinus albicaulis Engelm.) in the Inland West The future of high-elevation pines in western North America (Keane RE, Tomback DF, Murray MP and Smith CM, eds) RMRS-P-63 USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO:118-132
Matthews SN, Iverson LR, Prasad AM, Peters MP, Rodewald PG (2011) Modifying climate change habitat models using tree species-specific assessments of model uncertainty and life history-factors Forest Ecology and Management 262:1460-1472
McKinney ST (2004) Evaluating natural selection as a management strategy for restoring whitebark pine. Master of Science, University of Colorado
McLane, SC, Aitken, SN (2011) Whitebark pine (Pinus albicaulis) assisted migration potential: testing establishment north of the species range. Ecological Applications 22, 142-153.
Millar CI, Westfall RD, Delany DL, Bokach MJ, Flint AL, Flint LE (2012) Forest mortality in high-elevation whitebark pine (Pinus albicaulis) forests of eastern California, USA; influence of environmental context, bark beetles, climatic water deficit, and warming Canadian Journal of Forest Research 42:749-765 doi:10.1139/x2012-031
Mohatt K, Cripps CL, Lavin M (2008) Ectomycorrhizal fungi of whitebark pine (a tree in peril) revealed by sporocarps and molecular analysis of mycorrhizae from treeline forests in the Greater Yellowstone Ecosystem Botany 86:14-15
Morris MS, Kelsey RG, Griggs D The geographic and ecological distribution of big sagebrush and other woody Artemisia in Montana. In: Proceedings of the Montana Academy of Sciences, 1976. pp 56-79
Schneiderman J, He H, Thompson F, III, Dijak Fraser (2015) Comparison of a species distribution model and a process model from a hierarchical perspective to quantify effects of projected climate change on tree species Landscape Ecology 30:1879-1892 doi:10.1007/s10980-015-0217-1
Six, DL, Vergobbi, C, Cutter, M (2018) Are Survivors Different? Genetic-Based Selection of Trees by Mountain Pine Beetle During a Climate Change-Driven Outbreak in a High-Elevation Pine Forest. Frontiers in Plant Science 9,
Smith-McKenna, EK, Malanson, GP, Resler, LM, Carstensen, LW, Prisley, SP, Tomback, DF (2014) Cascading effects of feedbacks, disease, and climate change on alpine treeline dynamics. Environmental Modelling & Software 62, 85-96.
Warwell MV, Rehfeldt GE, Crookston N Modeling contemporary climate profiles of whitebark pine (Pinus albicaulis) and predicting responses to global warming. In: Proceedings of the conference whitebark pine: a Pacific Coast perspective, 2007a. Citeseer, pp 139-142
Warwell MV, Rehfeldt GE, Crookston NL Modeling contemporary climate profiles of whitebark pine (Pinus albicaulis) and predicting responses to global warming. In: Goheen EM, Sniezko RA, tech. coords. (eds) Proceedings of the conference whitebark pine: a Pacific Coast perspective, 2006 August 27-31; Ashland, OR, 2007b. Ashland, OR, Ashland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region., pp 139-142
Wong CM, Daniels LD (2016) Novel forest decline triggered by multiple interactions among climate, an introduced pathogen and bark beetles Global Change Biology:n/a-n/a doi:10.1111/gcb.13554