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

Matt Skoglund

Posted May 28, 2009

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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 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.

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Bernie CullenMay 29 2009 10:05 AM

Many thanks for the response. However, I think your conclusion that the mountain pine beetle infestation is due to global warming is not supported by the evidence that you cite. Moreover, there is a danger that simplistically linking the current infestation to AGW will delay a meaningful response to the problem.
First, as I pointed out earlier, the local GYE temperatures do not suggest the temperature trends that need to exist in order to show that the infestation of mountain pine beetles is due to a local increase in temperatures. You may be right, but the available data does not support this contention. The presentation you cite is not particularly helpful since it lacks citations to the actual data sources. I suspect, though I do not know, that many of the presentation graphics especially those mapping temperature trends with altitude reflect computer model simulations and are not straightforward summaries of actual observed temperatures. There is a big difference between observations and simulations. The density of weather stations is simply not great enough for the level of granularity and precision suggested in these graphics. The lack of proper footnotes to the slides is also very disappointing, frustrating and plain bad practice. Frankly the sloppiness of the presentation suggests “preaching to the choir”. (Note: I found the inclusion of the Mt Warren slides in the presentation a bit puzzling in that it is a new station and only has data since 2006. Perhaps it is meant to illustrate what is now being done to improve data coverage!) Moreover a significant portion of the increase in temperatures in the Mountain and Western States reflect fairly dramatic increases in metropolitan and urban areas as is readily visible in slides 5 through 9 of the presentation: Phoenix, Las Vegas, Denver and Santa Fe have all experienced tremendous growth in the last 40 years. They are visible hot spots on these slides. More importantly it is moot what is happening in other western states if the temperature trend in GYE is supportive of an infestation.
Second, I do not doubt the general relationship between food supply and human-grizzly conflicts. Human-caused grizzly mortalities were higher in 2008 than previously though I would be more circumspect in making generalizations about this data given the relative shortness of the data record and intervening changes in data collection procedures. However the recent data on conflicts – if not mortalities – does not support the robustness of the relationship between food supply and conflicts. Moreover, the relatively rapid expansion of the grizzly bear population is also a source of increased human conflicts, surely? Finally, a drop in the relative supply of whitebark pine seeds does not mean that the food supply is insufficient per se for the current grizzly population. Again I find the line of argument too simplistic.
My initial comment and this response is driven by what I believe is a flawed and over-simplistic line of reasoning and one that is potentially counter-productive. In my mind, the fundamental issue for someone concerned about the well-being of grizzlies has to be the actual causes of the mountain pine beetle infestation – and what can be safely done to address the infestation. Jumping to global warming is neither necessary nor helpful. Current suggestions for addressing AGW offer no short term mitigation. This does not mean we should not do anything about AGW but that our response should also address the specific presenting problem, namely, the mountain pine beetle infestation. Because you have a hammer, does not mean you are dealing with a nail!

Bernie CullenMay 29 2009 12:12 PM

A point of clarification. I just checked the USHCN Master Station list. By my count there is 1 official station above 9000 feet, 3 more above 8000 feet , 13 more above 7000 feet (including Yellowstone Lake at 7770') and 32 additional ones above 6000 feet. Clearly the density of the coverage is not great and unless the authors of the presentation have access to additional station data it is hard to figure out how they can be as precise as their slides suggest.

Matt SkoglundMay 29 2009 02:00 PM


Thank you for your comment and your interest in this very important issue. I am not jumping to conclusions or over-simplifying the problem; I’m merely relaying the science and facts. You are, of course, free to dispute it, but the science and evidence speak for themselves. The primary cause for the recent whitebark pine deaths from mountain pine beetles is warmer temperatures, especially winter temperatures. The warmer temps are allowing pine beetles to attack whitebark pine – a high-elevation tree – because the requisite prolonged cold snaps needed to kill large numbers of beetles are not occurring. Look at the stands of dead whitebark pine in the GYE and read what the experts are saying. This problem is so severe – and happening so quickly – that the U.S. Forest Service just provided some of the scientists with whom we work a six-figure grant to continue their over-flights of the GYE, so we can obtain a better picture of what percentage of whitebark pine trees in the GYE are dying or already dead. The question is not whether warmer temps are allowing beetles to kill whitebark pine (we know that’s happening), the question is how bad is it.

Here are links to two articles on the issue by Dr. Jesse Logan, former head of the beetle research unit for the United States Forest Service at the Rocky Mountain Laboratory in Utah: (From the article’s Abstract: “Unprecedented outbreaks of native bark beetles are occurring in forests throughout the mountains of western North America. Any one of these events would be unusual; their simultaneous occurrence is nothing short of remarkable. Significant biogeographical events are occurring at a continental scale, and a warming climate is the one commonality across all of these spectacular outbreak events.”) (“To date, the majority of results assessing individual pest species’ response to climate change indicate intensification in all aspects of outbreak behavior, and this certainly characterizes our work with the mountain pine beetle, gypsy moth, spruce beetle, and spruce budworm. Perhaps this is the result of a bias in reporting. More likely, the combination of attributes that first caused the insect species to be considered a pest also makes them sensitive to climate change. Many climate change predictions seem remote and unlikely (for example, the flooding of major coastal, urban areas). However, the effects of climate change, magnified through biological and ecological feedback, will be expressed on a more immediate time scale. We will probably experience ecological catastrophes such as the loss of high-elevation five-needle pines long before we are paddling sea kayaks in Central Park.”)

As for the grizzlies in the GYE, whitebark pine seeds are a critical food source for them (especially for females – the science shows that good whitebark crop years lead to better cub production for females), which is why the IGBST Report dedicates an entire section to whitebark pine cone production. There are certainly other foods available to grizzlies in the GYE, but some of those foods are also quickly disappearing (e.g., Yellowstone cutthroat trout (see pp. 29-31 of the Report)). The huge concern with the loss of whitebark pine seeds is how it will impact the way grizzlies use the landscape. Without such seeds, the bears won’t be in the high country gorging on pine seeds in the late summer or fall. They’ll be looking for food at lower elevations, where they are more likely to encounter people and get into trouble (something that typically ends badly for the bear involved).

Again, the science speaks for itself, and I’m just reporting it. More research is certainly needed (as well as more resources, attention, and coverage of the issue!), but right now there are whitebark pine trees dying on a massive scale in the GYE from beetles that aren’t being killed by cold spells – and it’s a serious concern for GYE grizzlies. We need to be working on solving the problem and learning more about it, not nitpicking the worrying evidence that already exists.

Bernie CullenMay 29 2009 03:26 PM

I am not disputing what might be possible, I am simply asking for the data that indicates that increased temperatures at high elevations in GYE is in fact one of the trigger mechanisms for the infestation. The current GISS data does not provide support for Dr Logan's assertion. He may well have additional data from other weather stations that are not part of the USHCN net. If so, it would be interesting to see that data. If he doesn't then he and you have to account for the fact that the available temperature data does not suggest that a rise in temperature is the trigger mechanism for this outbreak - that in itself would be a very important finding. It is not that there is an absence of local temperature data, it is that the available local temperature data does not support your and his hypothesis. This is an argument about the actual temperature record. Simply claiming AGW is not good science.
There could be important alternative explanations that need to addressed if the temperature record shows no meaningful increase. For example, a not unreasonable hypothesis is that the current mountain pine beetle infestation is driven by beetles from western Canada that have developed a shorter breeding cycle allowing them to migrate to different elevations in GYE. Another hypothesis may be that the warm year of 1998 (akin to 1934, but not as warm) allowed the critters to get a hold and the absence of a cold year or two immediately following the warm year has allowed them to hang on. Perhaps you can get Dr. Logan to chime in?

William MacfarlaneMay 29 2009 05:40 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.

Bernie CullenMay 30 2009 01:11 AM

Thank you for the additional information on the earlier outbreaks. I remain puzzled by the absence of any temperature trend for the local USHCN stations. Logan and others have clearly documented a link between temperature and infestation. However, since 1948 there has been no significant increase in average temperature in Yellowstone (see for example especially The beetle may not need an increase in average temperature just an absence of -40C days - which does not necessarily translate into an increase in average temperatures. It just seems both unscientific and illogical to claim a general cause before more specific mechanisms are accounted for. So I do not see the available temperature data supporting global warming as a general cause, though I am certainly open to the possibility that additional local temperature data may exist that supports the increasing temperature hypothesis.

Oliver RamsayMay 30 2009 01:32 AM

In the eighties and nineties, I spent the winters killing mountain pine beetles and the springtime luring them to their deaths with pheromones. Dendroctonus ponderosae put bread on my table and I was quite fond of the little critter until he got carried away.
His natural range is from Belize to Alaska and he'll munch on lodgepole, white pine, ponderosa, whitebark pine and, if all else fails, spruce. In BC it's been the lodgepole pine that has been hit; the sub-alpine whitebarks very little. There's no argument about the scale of the infestation, but , already, there's an under-storey of juveniles appearing amidst the mature grey-backs. The beetles get pitched out of young trees. I'm pretty sad when old trees go down, but it's not inconsistent with the notion that the weakest are the hardest hit.
It's never been -35C in Belize. It always gets to be that cold in the Copper valley in Alaska. I worked throughout BC, baiting and burning MPB. The outbreaks first occurred in the colder regions and, only later, moved south. Most of the affected regions never did see the temperatures that are claimed to be essential for a control of the problem. There were very localized population explosions, that happened very suddenly right under our noses, at a time when we were overflying all the drainages looking for red trees.
I don't know how to account for the MPB epidemic, but I'm pretty sure the GW explanation is simplistic and wrong.
I also can't say too much about the Yellowstone Grizzlies, but I lived a lot of years in the Cariboo Mountains, which are serious Grizzly country, and I'm very uncomfortable with the statements that are made about bears and their behaviour. I've been charged by bears, I've chased bears, I've laughed at bears and been terrified by them, but I've never studied them, though I used to always poke a pile of poo to see how old it was and what he'd been eating.
It's not clear from Matt's posts whether the bears are starving, failing in fecundity or being driven into the arms of hunters by the diminution of whitebark numbers. None of that rings true in my experience; bears move around for food and they're very fond of berries and salmon. They do not turn their back on abundant low-elevation food unless they feel full. And hunters move around for bears. They don't just sit in the valley bottoms waiting for them to appear.
It's usual to invoke "the science" but, most of it is not science. It's a bunch of forest techs earnestly clambering over windfalls gathering very imperfect data to be delivered to academics with a hypothesis that they mistake for a theory.
Okay, that's a bit ungenerous, but the claims of infallibility are a little over the top.

Bernie CullenMay 30 2009 08:03 AM

Your observations from the field are interesting. If the beetle is common from Belize to Alaska then it seems to me that some strain will already have developed a single year life cycle rather than the two year cycle that seems to be prevalent among northern and higher elevation beetles. Is that correct?
You also seem to suggest that the little monsters survive really cold temperatures. This does not seem to me to jibe with dramatically different mortality rates between beetles infesting the northern and southern sides of the same tree.
How do forest fires affect their cycles?
Also can they be blown North and South by the wind. In Canada they already appear to have been blown East into Alberta - or were they there already?

Jesse LoganMay 30 2009 03:10 PM

Oliver - Interesting range, "His natural range is from Belize to Alaska" for the mountain pine beetle. Most authorities would rather say isolated collections from the mountains of extreme northern Mexico to central British Columbia. With some notable exceptions (extreme southern Alberta), the Canadian distribution was historically restricted to the west slope of the Canadian Rockies. Accompanying warming temperatures, MPB range expansion has recently extended further north in BC than historic records. In recent years, the previously impregnable barrier of the Rockies was breached at a low point (Pine Pass) into the Peace River drainage on the east slope. Range expansion has continued eastward in Alberta into the previous non-host jack pine, and for the first time, verified successful reproduction in spruce. Nothing in the historical record comes even close to the 13 million hectare (the last figure I heard) Canadian outbreak. Interestingly, no comparable southern range expansion has been reported (MPB is still a long ways from Belize!).

Bernie - (1) For pertinent high elevation weather weather data in the Greater Yellowstone Ecosystem, check SNOTEL sites. There are almost 100 SNOTEL sites in the GYE, of these, 51 are located at elevations greater than 8,000 ft., highly relevant to whitebark pine. This data is readily available on the www -
Another source of higher spatial resolution weather data is the Mesowest network also available on the www at:
Many of these sites are also at higher elevation.

(2) You skepticism about models is shared by many people, however, without models, either informal mental models or formal mathematical models, we are limited to historical observation. Limiting ourselves to past events is of little help in times of rapid change, like that occurring with global warming. I would contend that without some sort of model, we are codemed to making the mistakes of the past amplified by future uncertainty. I, for one, place greater faith in the rigor of formal mathematical models that encompass the best scientific knowledge available than purely mental models that often incorporate much hand waving.

My modeling work that was initiated in the 1990s (with both historic data and projected modeled climate data) corresponds closely with what has happened in subsequent years. Work using the recent winter survival model of Regniere & Bentz indicates a striking effect of warmer winter temperatures on beetle survival, both for individual observed SNOTEL sites and spatially extrapolated whitebark pine habitat. It is necessary to use some lens that focuses temperature through the eyes of the beetle rather than just average annual temperature since it is the seasonal pattern of temperature that is important, not simply mean annual temperatures.

I could go on, but enough for now

Bernie CullenMay 30 2009 09:47 PM

Dr. Logan:
Many thanks for the information on and link to the SNOTEL data set. I will take a look. As to models, I have no problem with models per se, having originally trained many years ago as an economist. But as you recognize any model has to be validated against the actual observational record, hence my request for the local temperature data that supports the general hypothesis of unprecedent warming in the GYE as a trigger mechanism for the most recent infestation. Let me take a look at the data and I will respond accordingly.

Oliver RamsayMay 31 2009 06:25 AM

I'm happy to concede that the Belize beetles are dendroctonus frontalis and not d. ponderosae, but you do acknowledge that MPB is found in Mexico, in regions that never come close to -35C. You refer to "isolated collections", which, of course, does not imply large outbreaks. Obviously, single tree disposal is also carried out on "isolated collections" of beetles. That's what you have before you have an outbreak.
It's not accurate to say that MPB was mainly confined to the BC side of the Rockies. Here's an interesting animation of beetle outbreaks from 1960 through 2002
The Omineca Plateau, Cariboo/Chilcotin, The Purcells, The Selkirks etc. have all hosted beetles for a long time.
The barrier of the Rockies was breached already in the seventies, with ongoing infestations in the Bow drainage of southern (not extreme) Alberta.
Range expansion is interesting, but the real issue is explosions in existing populations.
Unsurprisingly, I share Bernie's misgivings about models; the more so, when you say that past events are of little help.
It is not clear to me that a putative long-term positive trend in night-time min temps is what has caused beetle-mania. That's the only trend claimed for BC and, to my eye, recent values are very similar to those for the fifties and sixties. I find the warm winter of 1985 incongruous with the collapse of an outbreak that had been going on for several years prior in the Cariboo.
We were always led to believe that females would only fly 50 meters in their life. I never quite believed that but it's somewhat moot, since, of course, they can be carried by the wind. I suspect that most long beetle trips are made the way humans travel; in trucks and trains.
Trees are hardest hit at their base, below the moss and duff and three or four feet of snow.Certainly in major outbreaks, the entire tree is hit, even some of the limbs. I never thought to assess survival rates in comparison to winter temperatures, sun exposure etc. A dead beetle looks a lot like a sleeping beetle.What was noteworthy was that we thought we had killed every last beetle in the area and the next year, we'd have to do it all again in pretty much the same areas. Over the years, we wound up burning piecemeal, all the pine in some areas. We were not unconsciencious and neither were the ministry guys who checked every tree treated. As for forest fire, it does them in!

Matt SkoglundMay 31 2009 10:57 AM


Thank you for sharing your thoughts and experiences. I write to respond to your comments about GYE grizzlies. You say you’ve spent a lot of time in the Cariboo Mountains, which is grizzly country, but you’ve never studied grizzlies. The GYE is a very, very different ecosystem than the Cariboo Mountains of British Columbia. For example, you wrote that bears are very fond of berries and salmon. That is true, but there are no salmon in the GYE and the annual berry crop is not a major part of GYE bears’ diets (for bears in the Glacier ecosystem, northwest of the GYE, where Dr. Logan and I live, berries are, indeed, a big part of their diet).

And I never said GYE grizzlies are currently starving. I wrote in my above blog entry: “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."

And I wrote in my comment to Bernie: “As for the grizzlies in the GYE, whitebark pine seeds are a critical food source for them (especially for females – the science shows that good whitebark crop years lead to better cub production for females), which is why the IGBST Report dedicates an entire section to whitebark pine cone production. There are certainly other foods available to grizzlies in the GYE, but some of those foods are also quickly disappearing (e.g., Yellowstone cutthroat trout (see pp. 29-31 of the Report)). The huge concern with the loss of whitebark pine seeds is how it will impact the way grizzlies use the landscape. Without such seeds, the bears won’t be in the high country gorging on pine seeds in the late summer or fall. They’ll be looking for food at lower elevations, where they are more likely to encounter people and get into trouble (something that typically ends badly for the bear involved).”

Finally, regarding your comment about hunting bears, grizzly bears cannot be hunted in the GYE. The kills to which I’m referring in the GYE are hunter self-defense kills (i.e., elk hunters encountering a grizzly at the carcass of the elk they killed).

Thanks for your interest in this very important issue.

Bernie CullenMay 31 2009 12:28 PM

Well guys we seem to be working a lot of different and interesting threads of the argument here. I appreciate the helpfulness and civilized tone of the discussion.

I looked at the SNOTEL data that Dr. Logan pointed to. Unfortunately it is not in a form that I find easy to work with - I have just started to learn R. It also seems to be somewhat truncated starting only in the 70s and 80s. However, all was not lost. As I was poking around to find a map of COOP weather stations in and around Yellowstone, I came across a very interesting UWYO climate site ( and another very good visual summary of the same data ). Assuming that there is no systematic flaw in the way the temperature data is collected/recorded, the data clearly indicates is that there was no change in Annual Mean temperature when the decade of the 60s is compared to the decade of the 90s. This obviously is in line with the USHCN data I mentioned earlier.

More intriguingly with respect to the MPB infestation is that there was a clear warming across Wyoming in one month - March. This is a truly remarkable and I would bet hugely significant pattern. I assume that an earlier and/or milder spring, all other things being equal, could in some way contribute to the recent outbreaks. I have no idea why March trended warmer in the 90s (or even if it is still doing so in Wyoming) but it is clearly a more viable potential explanation of the current infestation than a non-observed global warming in Wyoming. I am less clear as to the potential impact of the clearly off-setting cooler October and November. Perhaps a UWYO climate specialist can chime in with more upto date information.

Eyeballing the map data it seems hard for me to see the relationship between GW and elevation - though a more detailed analysis may uncover something because there certainly is a significant amount of unexplained variance in mean temperatures across Wyoming.

Using this single and limited data set - not to mention my limited understanding of MPBs, MPB infestations seem to be, if anything, an indicator of earlier springs not GW.


Jesse LoganMay 31 2009 04:31 PM

Oliver - What about those Alaska D. ponderosae you referred to? Might be a new record!

The limit of mountain pine beetle distribution to the south is more problematic than to either the north or high elevation. Two reasonable hypotheses are (1) competition with other bark beetles with similar life styles (mainly D. brevicomis and D. mexicanus). (2) Asynchrony in timing of adult emergence resulting from too much thermal input (ref. Logan & Powell or Powell & Logan ). To the best of my knowledge, neither of these reasonable hypotheses have been rigorously tested. On the other hand, the limitation to elevation and northern distribution is clearly temperature/weather related; dating back to the pioneering work of G. D. Amman (in the US) and Les Safranyik (in Canada).

Oliver RamsayJun 1 2009 02:50 AM

Yes, Jesse, I have to give up the Tongass National Forest, too and retreat from Alaska with my ponderosae. Later, perhaps, I can tie back in with rufipennis, but for now, I'd like to toss out Idaho and Colorado and even Mexico as well, because I don't think I need them to make the point that, in the hundreds of kilometers of horizontal BC MPB range, the outbreaks and the climatic variation just don't suggest GW. Furthermore, there is no warming trend in BC apart from winter nightly minima and those have little bearing on mating flights and phloem warming.
I found your paper interesting and less emphatic in conclusion than I'd expected. There are a number of points for discussion; one of which is the heating of the tree stem, which, of course, would be very variable, not only in exposure, but also in height. Snow depth and wind-driven snow high up the trunk must belie any sampled data. Then, there's the premise that the beetles choose the sunny side. I am very sure that they start at the bottom and work up, and I would not be surprised if that were a big part of the inefficacy of fall and burn; there must be plenty of trees with no pitch tubes above the snow and colonies of toasty little bugs down below. If Les Safranyik is correct about a 5% survival doubling the population annually, then you don't need anything so grand as a boiling planet to account for tremendous swings.
Thank you also, for his name; here's a cut and paste from an address of his, that seems germane: "First, I will say a few words about mountain pine beetle generation mortality.

* Assuming an average sex ratio of two females per male, and an average of 60 eggs produced per female beetle, mountain pine beetle populations remain stable at 97.5% mortality.
* On a one-year life cycle and at about 95% generation mortality, population and damage levels will double each year.
* Thus, contrary to popular belief, during epidemics generation survival is only a few % higher than during the endemic state. This modest increase in generation survival, however, will remain steady for a number of generations.
* The challenge to research is to identify the factor or factors responsible for this small increase in generation survival during the beginning stages of outbreaks.
* As we can attribute only about 60-70% of generation mortality to known factors, there is a lot of room for improvement in our understanding of population dynamics.

The following statements relate to epidemiology.

* Secondary bark beetles are important factors of mortality in unmanaged, mature lodgepole stands, especially in the smaller DBH classes. At low endemic levels, mountain pine beetle often infests trees that are colonized by these secondary species. Therefore, it appears that stand hygiene is an important factor affecting mountain pine beetle survival at endemic levels.
* Mountain pine beetle outbreaks are loosely synchronized over much of the beetles range where the one-year cycle dominates, indicating that population change may be governed by the so called Moran effect.
* Although we can describe the changes in host conditions and weather factors that should occur as a precursor for a change from the endemic state to the beginning stages of epidemics, we still cannot predict the timing of such event.
* The main factors mostly responsible for the development of outbreaks are host susceptibility and suitability of the climate for beetle establishment and survival.
* Of the host factors, the presence of mature /over mature stands at the landscape level appears to be the most important.
* Of the climatic factors, unseasonably low temperatures, and temperature conditions during the growing season that affect mass attack and univoltine cycling of populations appear to be most important.
* Once outbreaks develop at the landscape level, the population's very size becomes a major factor in maintaining its momentum.
* In areas where mountain pine beetle outbreaks are most damaging, the beetle generally has a univoltine life cycle.
* Therefore, it does not necessarily follow that sustained increased temperatures such as those associated with climate warming would invariably result in greater average level of damage.
* The adverse effects of the very factors that are responsible for the development of the outbreak will eventually cause it to decline, namely reduction in susceptible hosts, increasing adverse climatic conditions, or a combination of these factors."

No quarrel with the northern limitations, but insects are strange and until I understand why there are almost no mosquitoes on Vancouver Island, I will suspect them of everything. Except sensitivity to GW.

Oliver RamsayJun 1 2009 03:13 AM

Your point is well-taken that bear lifestyle is different in different locales . As I said, I don't know much about the GYE. Are there really no marmots, ground squirrels, sheep to go with those pinecones?
How about in the spring? They've already cleaned up the pines in the fall, and the grass in the slides isn't going to be much.
Is there a spring hunt, too?
Reading briefly on the web, I saw blister rust mentioned more than MPB and saw that The Grizz was removed from the list in 2007.
I know nothing of that story but I'll look some more.

Bernie CullenJun 1 2009 07:35 AM

Oliver & Jesse:
What differential effect will a warmer March have on infestations?

Matt SkoglundJun 1 2009 02:51 PM


There are other foods available to GYE grizzlies, but few are as abundant and calorically rich as whitebark pine seeds in a good crop year. Grizzlies are omnivores; it’s amazing how they work the landscape for food. In the spring, there are carcasses of winter-killed ungulates (e.g., bison and elk) and fresh grass. Whitebark pine seeds are key in late summer and fall. Army cutworm moths are another large food source for GYE grizzlies. Yellowstone cutthroat trout were once a key food source for GYE grizzlies, but their population has been decimated by the introduction of non-native lake trout. Losing whitebark pine seeds in the GYE, and the resultant effects on how bears will use the landscape without whitebark, would be dire for GYE grizzlies.

From USGS staff: “Significant loss of whitebark pine due to blister rust (Reinhart et al. 2001) or mountain pine beetle (Dendroctonus ponderosae; Haroldson et al. 2003) would reduce survival rates for bears, especially conflict-prone individuals. Should whitebark pine decline rapidly, we speculate we would witness a scenario similar to what occurred when dumps were closed in YNP; more management problems, particularly outside the [Grizzly Bear Recovery Zone], with a substantial increase in measurable bear mortality.” (Schwartz, C.C., M.A. Haroldson, G.C. White, R.B. Harris, S. Cherry, K.A. Keating, D. Moody, and C. Servheen. 2005. Temporal, spatial, and environmental influences on the demographics of grizzly bears in the Greater Yellowstone Ecosystem. Wildlife Monographs 161.)

Also, check out this recent article on warming at high altitudes in Montana with quotes from U.S. Geological Survey ecologist Dan Fagre:
(“‘During the past 15 years, there has been a faster rate of temperature increase for mountains than for lower elevations,’ said [Fagre]. . . . [W]estern Montana’s nine weather stations have found the average daily low temperature has gone up 2.79 degrees since records were first kept in 1892, Fagre said.”)

Grizzlies in the GYE cannot be hunted in any season. There are, however, spring and fall hunts for black bears, and some misidentified grizzlies are occasionally killed in these hunts.

Thanks again for your interest in GYE grizzlies and whitebark pine.


Bernie CullenJun 1 2009 08:07 PM

Is there a more formal citation for Dr. Fagre's finding? I am not sure where to find minimum daily temperature data and which 9 stations he referred to, so
I checked the GISS data for 12 high elevation Montana stations and, using the unhomogenized data and very simple Excel tools, I found no overall trend in average daily temperature beyond that which could be accounted for by a recovery from the 19C LIA - approx 1C per 100 years. As the stunning photographs make clear, there is no doubt that Western Glaciers have been retreating and they are retreating because of a warming trend, but the GISS temperature data I looked at does not suggest any alarming or accelerating rate of warming. It simply is not visible in the Montana data for these 13 high elevation stations (Hebgen Dam, Red Lodge, Virginia City, Anaconda, Philipsburg, Dillon WMCE, White Sulphur Springs, Ennis, Livingston, Bozeman (State University), Norris Madison, Moccasin Exp St'n and Big Timber.)
Interestingly with respect to MPB, there was a significantly greater increase in March mean temperature just as I reported for the Wyoming Coop Station data. Again I have no idea why there is this early Spring effect.
Perhaps this is the effect that Dr. Fagre is alluding to?

Matt SkoglundJun 1 2009 08:46 PM


I am not aware of any scientific journal or publication that has published Dr. Fagre's recent findings discussed in the article.

And, yes, the photographs of the receding glaciers on the following website are, indeed, shocking:


Oliver RamsayJun 3 2009 01:58 AM

I don't know. However, March would be early for beetles to resume feeding. Equally, no larvae that had survived until March would then freeze.
Conceivably, aberrant warmth could disrupt synchronous emergence of adults, which would reduce beetle numbers, but, perhaps it could enhance that timing. I know Jesse has a much better understanding of to what degree sap flow, for example, might influence development. March is closer to the cusp for the tree's return to growth; there's no sap flow below 0C.
It seems eminently reasonable to expect more warmth to equate to more beetles, however, I'm not convinced that's what's happened. I think it would be interesting to travel to the northernmost beetle trees and see if the beetle survival patterns, with regard to sun exposure and height relative to snow depth would correspond to accurately measured local isotherms.
I think the emotional response to forest devastation interferes with objective analysis. It's similar with fires; people drive for miles through a burn and are aghast at what they see. I am not suggesting that researchers in the field are so unsophisticated. I am truly impressed by the erudition and sedulity of scientists, but you can be really clever and still wrong.

Bernie CullenJun 3 2009 08:28 AM

I agree. I am simply an old numbers guy who likes puzzles and who just happens to have a beetle problem with some of my own trees. One of the unfortunate aspects of the focus on AGW is that it seems to distort the discussion of many interesting issues such as MPB infestations. I guess I am also non-plussed by the tendency to discount contrary evidence such as the actual absence of any appreciable warming trend in Wyoming and Montana. The warming trend in the introductory graph is readily accounted for by UHI than by AGW - especially given that the two most rural states, Wyoming and Montana, show less than a 0.1C per decade trend. At the same time the March warming pattern for Wyoming and Montana really does stand out and deserves some further analysis.

Oliver RamsayJun 5 2009 02:44 AM

My commiserations with regard to your beetle problem. I don't know if you're talking about a lot of pine in a woodlot or just a handful in a residential landscape. Other than trying to restrict the number of trees targeted with pheromone lures and then paying close attention in the summer when the beetles are flying, I know of nothing but philosophical resignation. The irony of bait trees is that the little pests often have a mind of their own and enter adjacent unbaited trees in greater numbers with utter disregard for your plans.
As for the anomalous temperatures in Wyoming and Montana in March, that can only be bad data or variations in atmospheric circulation. The thing about UHI is not that those places are not warmer than they used to be, but that they're not representative of the much larger area that is not sampled. Stephen Chu's inspiration to paint urban roofs white would, perhaps, help make the weather data more representative, but it's hard to imagine how it would cool down the forests and kill bark beetles. You should be able to see whether these means arise from night-time temperature increases or daytime. Prime suspect is cloud cover, though I would look for patterns affecting the individual weather stations, first.

Bernie CullenJun 5 2009 01:43 PM

Fortunately the visible beetle infestation is on a single Austrian pine. What you said though makes me wonder whether I should take the tree down or leave it as a kind of Judas Goat? I was just about to have it cut down and hauled away.

As for temperatures, I have been stimulated into looking at GISS data for the last two years by 3 pretty heavy duty climate science and statistics sites: the NASA-related folks at, Steve McIntyre's and Anthony Watts' . I guess my view is that the differential apparent warming in the western states as represented by Matt's initial chart largely reflects the population and urban growth in selected parts of these states in the last 30 years. Las Vegas, Phoenix and Santa Fe are three classic examples of humans affecting the local temperature and they show up very visibly in the diagram. And, of course, you are right that their inclusion distorts the overall trends in the region even with geographic weightings. Hence the data for GYE, Wyoming and Montana when looked at in isolation shows a much less visible and remarkable trend. But being true to the data I had to note that the March pattern of warming was significant and I am curious as to what might explain it. If it is CO2, which I doubt, it would have to be a pretty unusual physical mechanism.

I have not seen any data to suggest that temperature trends are in themselves triggering the MPB infestation. I do think the microclimate studies in part described by Jesse Logan would shed light on the question -- but the time period covered by the available data seems to me to be way too short to draw any conclusions. The epidemiological spread of the critters that you pointed to suggests some other, possibly random, factors.

Oliver RamsayJun 6 2009 01:21 AM

If this is the first year you've seen sign of the beetles in this tree, then they're still home but getting ready to leave. The next generation will not return to this tree, because, even though they don't really have a brain, those bugs are smart enough to know that there will be nothing for them. The tree is either dead or dying.
I'm assuming you're seeing lots of pitch tubes all over the trunk; little resin bubbles with a hole in the middle and sawdust. The needles will be a faded green or completely chlorotic, depending on how hard hit it is. I think you should burn that tree asap. If the tree was hard hit, there will be lots of beetles and they will take up residence in pine(s) nearby. Now would be the time to nail up a pheromone bait in the hopes that you can reduce how much they spread out.
I can't imagine that your warming has anything to do with CO2 in the region. The AGW story is so much about averages over time and space that the mechanics of atmosphere and ocean seem to be lost in the desire to see a trend in everything.Clouds and ascending or descending air have somehow become irrelevant.
Thank you for the websites. I'm already familiar with all of them and I dare say you can tell which appeal to me most.
Thanks, too, to Matt for indulging our posts. I am, at least, very sympathetic to conservation of the natural world.

Bernie CullenJun 6 2009 01:51 PM

Burning the tree ASAP sounds like good advice. I will check with the arborists with whom I am dealing.

Like you, I am also a believer in conservation and I am very sympathetic to evironmentalists. But I also place heavy emphasis on critical thinking, real empirical data and the scientific method including the importance of transparency and replicability. These are tough but absolutely necessary standards to ensure policy decisions reflect reality not someone's hypothetical possibilities or normative preferences. It is too easy to conjure up disasterous outcomes that panic people into unreasonable decisions. I remember in 1963 in grammar school being asked to calculate what would happen to London IF all the ice in Antarctica melted. A great antidote to sloppy and emotion-driven thinking and one of my favorite books is the late Aaron Wildavsky's But is it true? It is a bit dated now, but at a psychological level it is still very much on target and illustrative of what can happen when everybody makes assumptions that a not unreasonable assertion is in fact the truth.

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