skip to main content

→ Top Stories:
Clean Power plan
Safe Chemicals

Matt Skoglund’s Blog

Global Warming, Dead Forests, Imperiled Grizzlies

Matt Skoglund

Posted May 22, 2009

, , , , , , ,
Share | | |

Whitebark pine is a rugged, tough, resilient, beautiful tree that inhabits the high country of the Northern Rockies.  Whitebark pine is typically the last tree one sees before going above timberline.  Whitebark pine seeds - or pine nuts - feed Clark's nutcracker birds, red squirrels, and grizzly bears. 

In the Greater Yellowstone Ecosystem (GYE), whitebark pine seeds are the primary food source for grizzly bears during late summer and fall when the bears are trying to fatten up for their winter hibernation.  Bears in Alaska have salmon, bears in Glacier National Park have berries, and bears in the GYE have whitebark pine seeds.

But the whitebark pine population is being rapidly decimated by global warming. 

The main killer is the mountain pine beetle, which bores through the tree's bark, cuts off its supply of water and nutrients, and starves it to death.  A second killer is blister rust, a fungus accidentally introduced from Europe in the late 1800s.

While mountain pine beetles are native to the West, the high-altitude environment that whitebark pine trees inhabit has typically been too cold and harsh for the beetles to do any damage.  Prolonged cold snaps (i.e., 40 below zero for several days) in whitebark country previously prevented major beetle infestations. 

But global warming has changed that.

Milder temperatures have allowed the beetles to move to higher altitudes and prey on whitebark pine.  And while other trees evolved with the beetles and have natural defenses (e.g., lodgepole pine), whitebark pine have none.  As such, the beetles are literally destroying the whitebark pine ecosystem in the Northern Rockies. 

And it's happening alarmingly fast.

Earlier this week, I had the opportunity to see this devastation up close.  I was in Jackson, Wyoming, for an event on whitebark pine and grizzly bears.  NRDC and the Jackson Hole Conservation Alliance sponsored the event, which was held at the Teton Science School's Jackson Campus.  The event featured presentations by legendary grizzly expert Doug Peacock, renowned entomologist Dr. Jesse Logan, talented guide/writer/musician Thomas Turiano, and the delightful musicians Beth McIntosh and Phil Round. 

The next morning, Bruce Gordon of EcoFlight flew a few of us over the Teton Wilderness, which is east of Grand Teton National Park and south of Yellowstone National Park, to see some of the damage from the air.  What I saw was shocking: hundreds and hundreds of acres of red (dying) and gray (dead) whitebark pine forests.  Dr. Logan has seen such devastation all over the GYE and predicts that whitebark pine will be functionally gone from the GYE in less than ten years. 

Here are some photos I snapped from the plane:

wbp 4

wbp 2

 wbp 2

wbp 1

wbp 5

wbp 6

wbp 7

wbp 8

The decimation of whitebark pine in the Northern Rockies is a tangible manifestation of the harmful effects wreaked by global warming.  And the loss of whitebark pine will be catastrophic for grizzly bears and the Greater Yellowstone Ecosystem, which is why NRDC filed a petition with the U.S. Fish and Wildlife Service in December 2008 to list whitebark pine as an endangered species.   

Because whitebark pine is found at high elevations, it keeps grizzly bears in the high country in late summer and fall - and away from people.  Without whitebark pine, the bears will be forced to go to lower elevations to find food, and more human conflicts will occur, which often end badly for the bear involved.  (There were 37 human-caused bear mortalities in the GYE in 2008, the highest number ever recorded.)

The dismal scenario I've described is very real, but there is some good news.  Whitebark pine is doing well in the Wind River Range in Wyoming and on the Beartooth Plateau in Montana.  Both still have the requisite prolonged cold snaps (thanks to glaciers in the Winds and high elevation on the Plateau) needed to kill the beetles.  This points to one conclusion: we need to curtail global warming - quickly.

Yesterday, progress was made when the House Energy and Commerce Committee passed the most ambitious energy and global warming legislation ever debated in Congress, which NRDC helped shape.  But this bill still has a long way to go before it can be signed into law by President Obama.  And all of us still have a long way to go to curb our greenhouse gas emissions and reverse the warming trend. 

Whitebark pine and Yellowstone's grizzlies are two more reasons to care about global warming. 


(For more on the loss of whitebark pine, see this New York Times article and these Switchboard posts: 1, 2, 3, and 4.)

Share | | |


Bernard CullenMay 28 2009 11:19 AM

Matt, you say
"Prolonged cold snaps (i.e., 40 below zero for several days) in whitebark country previously prevented major beetle infestations.

But global warming has changed that.

Milder temperatures have allowed the beetles to move to higher altitudes and prey on whitebark pine. "

In checking available GISS temperature records for GYE (e.g.,, I do not see the increase in temperatures you allude to. Also what evidence do you have that whitebark pine has not been subject to these little killers previously - say during the 30s when there was a definite uptick in temperatures (visible in the GISS data for variouos Yellowstone locations) throughout the West accompanied by drought conditions that would have stressed the trees and reduced resin production.

In addition, your concerns about the Grizzly Bear population seem not to comport with the facts. The 2008 Interagency Grizzly Bear Study team ( )indicates that the population is still expanding at the planned 4% p.a. rate and for 2008 is estimated at 596 - up from an estimated 571 in 2007(~ 4% increase). On page 40 of the same report, the authors note that human-bear conflicts were similar to the average between 1992 and 2007 - which given the increase in bear population must represent a decline.

Matt SkoglundMay 28 2009 08:18 PM


Thank you for your comment. Please see my new blog entry, which addresses the issues you raised. Here is the link:

William MacfarlaneMay 29 2009 05:01 PM

Hi Bernard,

You ask, "Also what evidence do you have that whitebark pine has not been subject to these little killers previously - say during the 30s?"

Historic outbreaks in GYE whitebark pine - During the 1930s, a widespread outbreak of mountain pine beetle occurred across the U.S. distribution of whitebark pine (Perkins and Swetnam 1996), including the GYE. This past mortality event has been used to support the view that the current event is not unprecedented (Gibson et al. 2008), i.e. that it is within the historical range of variability. In particular, in a 1934 report, Chief Ranger George Baggley wrote, “The mountain pine beetle epidemic is threatening all of the white bark and lodgepole pine stands in Yellowstone Park. Practically every stand of white bark is heavily infested...and will be swept clean in a few years (emphasis added). If the insects spread from the white bark pine to the lodgepole stands, it seems inevitable that much of the park will be denuded.” (Evenden 1944 in Furniss and Rankin 2003). The key to Baggley’s observation is the, "will be swept clean in a few years," - obviously this did not happen, instead the outbreak was relatively short-lived and limited in scale and intensity. However, if we evaluate the underlying driving variable of temperature, we see that the current situation is vastly different from the 1930s. This prior event also resulted from warm temperatures, unusually warm temperatures occurred throughout the west during the 1930s, and in particular the winter of 1933-34 was the warmest in the historical record. However, this warm period was short lived, and temperatures quickly returned to historical ranges. Something very different is occurring today with global warming. Instead of a short term weather event, we are experience a climate trend that started in the 1970s or 1980s and continues unabated. What was an anomalous event in the 1930 has become the norm of today, and the historical temperature range of the 1930 has now become the anomaly. Ranger Baggley's "in a few years" has, in fact, happened, but occurring much later than he thought. With this shift in climate, the impacts of warming weather mentioned above are prolonged and chronic rather that the episodic events of the past. With warming climate, the ongoing outbreak is the fire that doesn’t go out with onset of winter; instead it continues year after year.
Mountain pine beetle disturbance legacy in GYE whitebark pine - Whitebark pine is an exceptionally slow growing species; in the GYE they typically take a minimum of 50 years to reach cone-bearing age, and in many sites, much longer. The slow growth rate of this species combined with the slow decomposition rates of cold, xeric climates of high mountains guarantees that evidence of mountain pine beetle disturbances in whitebark pine will remain on the landscape for decades if not centuries (Millar et al. 2006). There are large landscapes in the GYE where essentially all the whitebark pine overstory has been killed during the current outbreak episode and these landscapes are widely distributed across this vast area. The standing dead trees will eventually weather into massive "ghost forests" that will remain an obvious landscape attribute for many years to come (Furniss and Renkin 2003), clearly spanning a time period greater than that from 1930 to present. We are unaware (with extensive combined on-ground and aerial survey experience) of any place in the GYE where ghost forests even remotely approaching the magnitude of the current disturbance exists. In a recent editorial, Diana Tomback, Director of the Whitebark Pine Ecosystem Foundation, wrote, "We discovered massive whitebark pines, at least a thousand years of age, hit this year by mountain pine beetles. Given that they had survived numerous past beetle outbreaks, including those of the 1930s and 1970s, this was a disheartening find." Even more disheartening from an ecological perspective is the complete removal of the reproductive component (cone-bearing tree) of the population over large areas. In conclusion, the current disturbance (threats) to the WBP ecosystems of GYE due to global warming appears to be well beyond the rare and brief events of the historical past.

Comments are closed for this post.


Switchboard is the staff blog of the Natural Resources Defense Council, the nation’s most effective environmental group. For more about our work, including in-depth policy documents, action alerts and ways you can contribute, visit

Feeds: Matt Skoglund’s blog

Feeds: Stay Plugged In