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Yellowstone National Park, WY, USA

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Trees destroyed by pine beetle in Yellowstone National Park, Wyoming, USA

Due to just slightly warmer temperatures, the destructive mountain pine beetles have multiplied quickly throughout the Rocky Mountains. From the mid–nineties through 2010, about 3.1 million acres (1.3 million hectares) of trees in Wyoming have been attacked by bark beetles, primarily mountain pine beetles. That is almost one–quarter of Wyoming's forests.

Key Facts

The mountain pine beetle's ability to survive and multiply rapidly is highly sensitive to temperature2,3 and precipitation.4 Slightly warmer temperatures allow pine beetles to complete their lifecycle in just one year instead of two.3,5 Also, more beetles can survive the winter as the minimum temperatures have increased in Wyoming.2,6

  • Average temperatures in the Yellowstone Park region of Wyoming have risen over twice as much as the global average—when comparing mean temperatures at the start of the 20th century to mean temperatures in the first decade of the 21st century.7,8
  • The mountain pine beetle in the Greater Yellowstone Ecosystem9 has devastated the high elevation whitebark pine, a critical food source for grizzly bears to fatten up prior to hibernation.10
  • By killing off millions of acres (hectares) of trees, the mountain pine beetle has turned infested lodgepole and ponderosa pine forests into a source of atmospheric carbon as the trees decay or act like a tinderbox for wildfires should they occur.11

Details

Yellowstone Park along with surrounding national forests form an area known as the Greater Yellowstone Ecosystem that covers an area about the size of South Carolina.12 It is one of the largest, nearly intact temperate ecosystems left on earth.13 In 2010, over three and a half million people visited Yellowstone National Park.14

Whitebark pines are a slow growing, long–lived tree. Whitebark pines are a critical food source for grizzly bears in the Yellowstone region where other food sources are not as abundant, especially prior to hibernation.10 The pine nuts provide a healthy amount of fat that helps sustain the grizzly population.15 Having enough fat on their bodies allows more bears to survive the winter and in particular it helps pregnant females stay healthy to be able to give birth to cubs in the spring.9

Mountain pine beetles bore through the bark of pine trees, killing the tree. When conditions are right, pine beetles can multiply rapidly, devastating large areas of forest. In Wyoming, from the mid–nineties through 2010, about 3.1 million acres (1.3 million hectares) of trees have been attacked by bark beetles, primarily mountain pine beetles. That is almost one–quarter of Wyoming's forests.16 In Wyoming their prime targets have been mature lodgepole pines, along with whitebark, ponderosa and limber pines.16

Historically the high elevations in this region were too cold for extensive mountain pine beetle outbreaks. There had only been shorter lived and limited scale outbreaks.12 Whitebark pines are the main pine tree at the higher elevations in the Greater Yellowstone Ecosystem.9 Because of the devastation and threats to the trees from mountain pine beetles, white pine blister rust and fires, in July 2011, the U.S. Fish and Wildlife Service determined the whitebark pine warrants protection under the Endangered Species Act.17

The mountain pine beetle's ability to survive and thrive is highly sensitive to temperature and precipitation. Outbreaks have been correlated with slightly warmer winter temperatures, which allow more beetles to survive.2 In one study of higher elevations, biologists found that warmer temperatures allow the pine beetles to complete a full generation in just one year instead of two, allowing the population to grow faster.3 Recent periods of drought have also stressed trees, making them more susceptible to attack.4

Based on climate records from Wyoming, the first decade of the 21st century was about 2.1°F (1.2°C) warmer than at the beginning of the 20th century (the 18851920 mean). However, through 1975, the average state temperature stayed approximately the same as the beginning of the century with an increase of about 2.0°F (1.1°C) since 1975.6 This is similar to the global warming pattern where two-thirds of the increase over the last century occurred since 1975.18

Warming has been even greater in the Yellowstone region of Wyoming. In that region, climate records show that the first decade of the 21st century was about 3.3°F (1.8°C) warmer than at the beginning of the 20th century (the 18851920 mean). Again, through 1975, the average temperatures in Yellowstone were approximately the same as the start of the century. However, the mean temperature since 1975 increased by about 3.0°F (1.7°C).7

The amount of warm temperature during the spring and summer determine whether a mountain pine beetle will be able to complete its lifecycle in one year or two.5 The quicker lifecycle allows pine beetles to multiply more rapidly. Furthermore, if the beetles only have to survive one winter instead of two, more larva will go on to become full grown beetles. On top of that, if winter minimum temperatures do not fall below certain levels, the beetle larva will also survive at much higher rates.19

In the Yellowstone region, in the warm season—May to September—average temperatures have increased approximately 3.5°F (1.9°C) since the beginning of the 20th century.20 While in January, the coldest month of the year, when temperatures should drop the lowest to kill off the mountain pine beetles, average temperatures in the Yellowstone region have increased even more—by approximately 4.0°F (2.2°C).21

Part of a Larger Pattern

The mountain pine beetle story shows how a devastating insect can spread to new regions where the seasonal temperatures are no longer cold enough to keep this pest in check. Along with infestations in Wyoming, epidemic outbreaks of the mountain pine beetle have occurred in Colorado, Montana, Idaho and Alaska.22,4 And outbreaks are growing in California, Oregon, Washington, South Dakota, and just recently Nebraska.22

The mountain pine beetle has wreaked devastation on a scale beyond that of most other forest pests. Beetles attacked some 11.8 million acres (4.8 million hectares) of forests in the United States just in 2009, and some 75 percent of those losses stemmed from the mountain pine beetle alone.22

The warming trend in the mountainous interior and northern regions of British Columbia, has been much steeper than the global trend, particularly in winter.23,24 This set the stage for rapid mountain pine beetle expansion. The lodgepole pine forests of central British Columbia have been destroyed and the pine beetles are continuing to expand into northern British Columbia and across the Continental Divide into Alberta.25,26,27 There is potential for mountain pine beetles to spread across the continent through the jack pine forests to the east coast of the United States and Canada.27,28

What the Future Holds

A healthy forest normally stores significant amounts of carbon. By killing off millions of acres of trees, which then decay or provide fuel for wildfires, the mountain pine beetle has instead turned lodgepole pine forests into a source of carbon emitted into the already overloaded atmosphere.11

The pine beetle epidemic shows how warming temperatures can lead to a problem that, in turn, causes temperatures to rise even further. Such an effect is another example of amplification—or feedback loop—of global warming. The additional carbon in the atmosphere warms mountain temperatures even further, which allows the beetles to continue to multiply and destroy more trees, which give off more carbon. The feedback loop continues until the forests are so devastated that the mature stocks of pine the preferred target of pine beetles are no longer around and only younger saplings remain.4

The choices we make today can help determine what our climate will be like. Making significant reductions in our heat–trapping emissions and developing cleaner energy technologies, such as solar and wind power would help us to avoid even higher temperatures and the significant damage that would have on our forests and National parks.

Credits

Endnotes

  1. Photograph: Dena Adler. 2009. Collected as part of NRDC led citizen science effort.
  2. Powell, J.A., and J.A. Logan. 2005. Insect seasonality: Circle map analysis of temperature–driven life cycles. Theoretical Population Biology 67:161–179. Online at http://www.usu.edu/beetle/documents/Powell-Logan2005.pdf. Accessed August 16, 2011.
  3. Bentz B.J., and G. Schen–Langenheim. 2007. The mountain pine beetle and whitebark pine waltz: Has the music changed? Proceedings of a conference: Whitebark pine—A Pacific Coast perspective, E.M. Goheen, amd R.A. Sniezko, technical coordinators. R6–NR–FHP–2007–01. Portland, OR: U.S. Forest Service, Pacific Northwest Region. Online at http://www.treesearch.fs.fed.us/pubs/34086. Accessed June 30, 2011.
  4. Berg, E.E., J.D. Henry, C.L. Fastie, A.D. De Volder, and S.M. Matsuoka. 2006. Spruce beetle outbreaks on the Kenai Peninsula, Alaska, and Kluane National Park and Reserve, Yukon Territory: Relationship to summer temperatures and regional differences in disturbance regimes. Forest Ecology and Management 227:219–232. Online at http://www.sciencedirect.com/science/article/pii/S0378112706001599. Accessed August 16, 2011.
  5. Safranyik L. and B. Wilson (Eds.). 2006. The Mountain Pine Beetle: A Synthesis of Its Biology, Management and Impacts on Lodgepole Pine, Canadian Forest Service, Pacific Forestry Centre, Natural Resources Canada. Online at www.for.gov.bc.ca/hfd/library/documents/bib96122.pdf, accessed August 19, 2011.
  6. National Oceanic and Atmospheric Administration - National Climatic Data Center. Wyoming, All Climate Divisions, December 12–month average temperature plot, 1895–2010. Online at: http://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php?parameter=tmp&month=12&year=2010&filter=12&state=48&div=0. Accessed August 30, 2011.
  7. National Oceanic and Atmospheric Administration – National Climatic Data Center. Wyoming, Climate Division 1, December 12–month average temperature plot, 1895–2010. Online at http://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php?parameter=tmp&month=12&year=2010&filter=12&state=48&div=1. Accessed August 30, 2011.
  8. Hansen, J., R. Ruedy, Mki. Sato, and K. Lo, 2010: Global surface temperature change. Reviews of Geophysics, 48, RG4004, doi:10.1029/2010RG000345. Online at: http://pubs.giss.nasa.gov/abs/ha00510u.html. Accessed July 25, 2011.
  9. Logan, Jesse A. and William W. MacFarlane. 2010. Beetle Devastates Yellowstone Whitebark Pine Forests. American Institute of Biological Sciences. Online at http://www.actionbioscience.org/environment/loganmacfarlane.html. Accessed August 21, 2011.
  10. Mattson, D. J., B. M. Blanchard, and R. R. Knight. 1992. Yellowstone grizzly bear mortality, human habituation, and whitebark pine seed crops. Journal of Wildlife Management 56:432–442. As cited in: Logan, Jesse A., William W. Macfarlane, and Louisa Willcox. 2010. Whitebark pine vulnerability to climate–driven mountain pine beetle disturbance in the Greater Yellowstone Ecosystem. Ecological Applications 20:895–902. [doi:10.1890/09–0655.1] Online at http://www.esajournals.org/doi/abs/10.1890/09-0655.1. Accessed August 21, 2011.
  11. Kurz, W.A., et al. 2008. Mountain pine beetle and forest carbon feedback to climate change. Nature 452:987–990, April 24, 2008. doi:10.1038/nature06777. Online at http://www.nature.com/nature/journal/v452/n7190/abs/nature06777.html. Accessed June 30, 2011.
  12. Logan, Jesse A., William W. Macfarlane, and Louisa Willcox. 2010. Whitebark pine vulnerability to climate–driven mountain pine beetle disturbance in the Greater Yellowstone Ecosystem. Ecological Applications 20:895–902. [doi:10.1890/09–0655.1] Online at http://www.esajournals.org/doi/abs/10.1890/09-0655.1. Accessed August 21, 2011.
  13. Greater Yellowstone Coalition. Online at http://www.greateryellowstone.org/about/who-we-are.php. Accessed August 22, 2011.
  14. National Park Service. 2011. Yellowstone Fact Sheet Online at http://www.nps.gov/yell/planyourvisit/factsheet.htm. Accessed August 22, 2011.
  15. Mattson, D.J. and D.P. Reinhart. 1994. Bear use of whitebark pine seeds in North America. Pages 212-220 in W.C. Schmidt and F.K. Holtmeier, editors. Proceedings of an international workshop on subalpine stone pines and their environments: the status of our knowledge. U.S. Forest Service General Technical Report INT–GTR–309. As cited by Podruzny, Shannon R., Daniel P. Reinhart, and David J. Mattson. 1999. Fires, red squirrels, whitebark pine, and Yellowstone grizzly bears. Ursus 11:131–138. Online at http://www.bearbiology.com/index.php?id=ursvol11. Accessed August 21, 2011.
  16. USDA Forest Service –Rocky Mountain Region–Forest Health Protection and Wyoming State Forestry Division. 2010 Wyoming Forest Health Highlights. Online at fhm.fs.fed.us/fhh/fhh_10/wy_fhh_10.pdf. Accessed August 21, 2011. U.S. Fish and Wildlife Service Mountain–Prairie Region. 2011. Whitebark Pine. Online at http://www.fws.gov/mountain-prairie/species/plants/whitebarkpine/. Accessed August 21, 2011.
  17. U.S. Fish and Wildlife Service Mountain–Prairie Region. 2011. Whitebark Pine. Online at http://www.fws.gov/mountain-prairie/species/plants/whitebarkpine/. Accessed August 21, 2011.
  18. Hansen, J., R. Ruedy, Mki. Sato, and K. Lo, 2010: Global surface temperature change. Reviews of Geophysics, 48, RG4004, doi:10.1029/2010RG000345. Online at: http://pubs.giss.nasa.gov/cgi-bin/abstract.cgi?id=ha00510u. Accessed July 25, 2011.
  19. Carroll, A.L. et al. 2004. Effects of climate change on range expansion by the mountain pine beetle in British Columbia. Pages 223–232 in T.L. Shore, J.E. Brooks and J.E. Stone, eds. Challenges and Solutions: Proceedings of the Mountain Pine Beetle Symposium. Kelowna, British Columbia. October 30-31, 2003. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, British Columbia, Information Report BC–X–399. 298 p. Online at http://www.for.gov.bc.ca/hfd/library/MPB/carroll_2004_effects.pdf. Accessed August 19, 2011.
  20. National Oceanic and Atmospheric Administration–National Climatic Data Center. Wyoming, Climate Division 1, September 5–month average temperature plot, 1895–2010. Online http://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php?parameter=tmp&month=9&year=2010&filter=5&state=48&div=1. Accessed August 30, 2011.
  21. National Oceanic and Atmospheric Administration - National Climatic Data Center. Wyoming, Climate Division 1, January single month average temperature plot, 1895–2011. Online http://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php?parameter=tmp&month=1&year=2011&filter=1&state=48&div=1. Accessed August 30, 2011.
  22. Man, G. 2010. Major forest insect and disease conditions in the United States: 2009 update—Forest health protection. Washington, DC: U.S. Forest Service, FS–952. Online at http://www.fs.fed.us/foresthealth/publications/ConditionsReport_2009.pdf. Accessed July 6, 2011.
  23. Osborn, Liz. 2008. Seasonal temperature trends in Canada. Current Results Nexus. Online at http://www.currentresults.com/Weather-Extremes/Canada/trends-temperature-seasonal.php. Accessed July 7, 2011.
  24. Hansen, J., et al. 2006. Global temperature change. Proceedings of the National Academies of Science 103(39):14288–14293, doi: 10.1073/pnas.0606291103. Online at http://www.pnas.org/content/103/39/14288. Accessed July 7, 2011.
  25. Westfall, J., and T. Ebata. 2010. 2010 summary of forest health conditions of British Columbia. Victoria, BC: Ministry of Forests, Mines and Lands. Online at http://www.for.gov.bc.ca/hfp/health/overview/2010.htm. Accessed June 30, 2011.
  26. Walton, A. 2011. Provincial–level projection of the current mountain pine beetle outbreak: Update of the infestation projection based on the 2010 provincial aerial overview of forest health and the BCMPB model (year 8). Victoria, BC: British Columbia Forest Service. Online at http://www.for.gov.bc.ca/hre/bcmpb/Year8.htm. Accessed August 16, 2011.
  27. Alberta Sustainable Resource Development. 2009. Beetle facts. Edmonton, AB. Online at http://www.mpb.alberta.ca/BeetleFacts/Default.aspx. Accessed June 30, 2011.
  28. Cullingham, C.I., et al. 2011. Mountain pine beetle host-range expansion threatens the boreal forest. Molecular Ecology 20:2157–2171, doi: 10.1111/j.1365–294X.2011.05086.x. Online at http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2011.05086.x/full. Accessed June 30, 2011.
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