Global Warming, Dead Forests, Imperiled Grizzlies (Part II)

In a comment to my original blog entry on this subject, a reader asked a few good questions, which, to properly respond, warrant a new post. 

Specifically, the commenter questioned:  (1) global warming in the Northern Rockies, (2) whether there have been previous beetle attacks on whitebark pine, and (3) my concerns with the grizzly bear population in the Greater Yellowstone Ecosystem (GYE).

Here are my responses to the three issues raised:

(1)  Human-caused global warming is no longer in doubt; the science is unequivocal.  See the Climate Change 2007: Synthesis Report on the Fourth Assessment Report of the United Nations Intergovernmental Panel on Climate Change (IPCC), this Science Daily article on the IPCC's Fourth Assessment Report, and this New York Times article on the same.

And temperatures in the West have been rising faster than any other region in the United States outside Alaska -- and more than the world as a whole.  An article published yesterday on Nature.com titled "Hot times ahead for the Wild West" states that "[e]xtreme temperatures are expected to become more common in the western United States by 2040 if greenhouse gases continue to rise."

Here is a striking graph of average annual temperatures for the western United States:

 temp graph

(Graph courtesy of Western Regional Climate Center, adapted by Rebecca MaCaulay, CLIMAS.)  

Also see this presentation titled "Recent Accelerated Warming in Western United States Mountains," this L.A. Times article, and this New York Times article.

(2)  Because of the temperature spike in the 1930s, mountain pine beetles killed whitebark pine trees in the GYE.  But that was a spike, and the trees bounced back.  The concern today is the long-term increase in temperatures scientists are predicting.  See this Bozeman Daily Chronicle article.  Also see the links I posted above to the IPCC report, Science Daily article, and New York Times article.

(3)  There were more human-caused grizzly mortalities in the GYE in 2008 than any other year on record.  Mortalities are different than human-bear conflicts, which were also quite high.  Without whitebark pine seeds, grizzlies go looking for food at lower elevations in the late summer and fall.  As the 2008 Interagency Grizzly Bear Study Team (IGBST) Report says on page 40, "The frequency of grizzly bear-human conflicts is inversely associated with the abundance of natural bear foods."  On the same page, the Report also notes that "whitebark pine seed production was poor throughout most of the ecosystem" and "[t]he high number of bear-human conflicts and human-caused bear mortalities in October suggest that preferred high quality bear foods were scarce at that time."  Translation: it was a bad year for whitebark pine seeds, so grizzlies went looking for food, they encountered hunters, and a bunch of bears were killed as a result. 

Also, at page 36 of the Report, the IGBST states that "[n]ear exclusive use of whitebark pine seeds by grizzly bears has been associated with falls in which mean cone production on transects exceeds 20 cones/tree.  Typically, there is a reduction in numbers of management actions during fall months with abundant cone availability."  It goes on to say that the number of management actions in the fall of 2008 was just above average (11 in 2008; 9 is average), but the number of bear mortalities from self-defense kills by hunters was high. 

Summary: global warming is occurring, it is more pronounced in the West, whitebark pine trees are dying, and the loss of whitebark pine seeds for grizzlies in the GYE will have dire consequences for their population. 

Solution: reduce our greenhouse gas emissions as quickly as possible.

About the Authors

Matt Skoglund

Director, Northern Rockies office

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