Last week we pointed out how a study showed pine beetle damaged forests didn’t have a greater burn risk than healthy forests, now this new study shows that the favorite ‘milder winter caused by climate change’ link is overblown.
Mild winters not fueling all pine beetle outbreaks in western United States
HANOVER, N.H. – Warming winters have allowed mountain pine beetle outbreaks in the coldest areas of the western United States, but milder winters can’t be blamed for the full extent of recent outbreaks in the region, a Dartmouth College and U.S. Forest Service study finds.
Milder winters have contributed to recent beetle outbreaks in Canada, but this is the first study to evaluate warmer winters as a factor permitting simultaneous outbreaks across the majority of its range in the western United States. In the last 15 years, bark beetles in the western U.S. have killed pine forests over more than 140,000 square miles (about the size of Montana), which exceeds the area killed by forest fires during the same years. Warming winters could be fueling these beetle epidemics, but large-scale tests have been limited and other explanations are possible, such as rising summer temperatures that accelerate beetle development and the legacy of forestry practices.
The findings appear in the journal Landscape Ecology. A PDF is available on request.
The researchers examined the long-term trend in minimum air temperatures across 23 ecoregions in western U.S. forests that have had bark beetle outbreaks and assessed whether increased beetle survival due to warming winters permitted the outbreaks. The results show the coldest winter night has warmed by about 4 degrees Celsius (7 degrees Fahrenheit) since 1960 across Western forests. “This amount of warming could be the difference between pests surviving in areas that were historically unfavorable and could permit more severe and prolonged pest outbreaks in regions where historical outbreaks were halted by more frequent cold bouts,” says first author Aaron Weed, a former postdoctoral researcher at Dartmouth and now an ecologist at the National Park Service.
Despite the trend for warming winters across western U.S. forests, not all beetle populations between 1997 and 2010 have responded to winter warming. In the 11 coldest ecoregions, winter temperatures lethal to the mountain pine beetle have become less frequent since the 1980s and beetle-caused tree mortality has increased significantly in these regions. But in the 12 warmer ecoregions, recent beetle epidemics cannot be attributed to warming winters because earlier winters were rarely cold enough to kill the beetles.
Although winter warming has been occurring across the western United States for decades, it has only permitted mountain pine beetle outbreaks in regions where winters historically killed more than 50 percent of the beetles — primarily in the Middle Rockies (Idaho, Montana and Wyoming), the Blue Mountains in eastern Oregon and northern Colorado. In these regions, winter temperatures during the 1980s were more likely than in recent years to drop below the lower lethal temperatures for mountain pine beetles. But in coastal and southern regions, winters dating back to 1980 were never cold enough to cause substantial beetle mortality. However, these warmer regions are undergoing sustained and, in some forests, increasing impacts from beetles. Other factors — such as warming temperatures that affect seasonal rhythms of beetle development and forestry practices that have influenced forest composition, primarily pine density and age in this case — are necessary to understand the broad extent of mountain pine beetle outbreaks across the western United States, the study finds.
###
The study, which was funded by the Forest Service, was conducted by scientists from Dartmouth and the Forest Service’s Rocky Mountain Research Station and Southern Research Station.
We live in the middle of a bunch of evergreen trees in the Pacific Northwest and have had some difficulty with bark beetles infesting fir trees on our property. I attributed it to dryer than normal conditions which after a couple of years left the trees weakened and more vulnerable to these pests. We have had above average precipitation for the past couple of years and the trees that survived all seem to be doing fine again.
Since the upper atmosphere is cooled by CO2, I’ve wondered for years, at what altitude does theory predict a break even point where GHG’s have no effect? –AGF
How is this bad news?
I’m all for biodiversity but Mountain Pine Beetles are not my highest priority.
Dartmouth…..nuff said.
But in coastal and southern regions, winters dating back to 1980 were never cold enough to cause substantial beetle mortality.
That is something that has long bothered me about the “warm winters are causing pine beetle outbreaks” theory. The southern interior of British Columbia has rarely been subjected to bitter cold over the last 50 years. The climate is dominated by Pacific, not arctic, air masses. And yet only in the last few decades is the lack of bitter cold supposed to have created a pine beetle outbreak.
The second problem is that pine beetle outbreaks have also occurred in western Alberta, which today is subject to far colder winters than the interior of B.C. has ever recorded. So if the cold used to protect the interior of B.C., why is not now protecting Alberta?
More or less west of the Great Plains, summer drought is an annual event. As well, this area is drought prone throughout history – a mega-drought during the 12th and 13th centuries is believed to been the main cause of the collapse of the Anasazi culture. Now, add in the criminal mismanagement of the federal forests in the west, and over time conditions develop that are primed for large bark beetle outbreaks. If you live in the US, your federal forest resources are being wasted, costing the American taxpayer billions.
But, the situation is worse if you happen to have the misfortune of living in a county dominated by a large National Forest. These counties have some of the highest poverty rates in the entire country, because the federal government has reneged on it’s implicit promise to return a portion of timber sale receipts to the counties. Now that Congress has failed to re-authorize the Secure Schools Act (=welfare instead of jobs from the forest), these counties are slowly wasting away. Which is what the progressive “elites” thousands of miles away want…
The first move to begin fixing what ails federal forests would be to repeal EAJA – the Equal Access to Justice Act, which has the unintended consequence of forcing the American taxpayer to fund the frivolous lawsuits again forest management on federal land. Then, and only then can we begin to address the problem of bark beetles in western, decadent, and dying forests.
We biked the Great Divide mountain bike route, and much of the worst pine beetle kills were in the colder higher areas, near 100% near Granby,Colorado “the icebox of the nation” The warmer forests of New Mexico were in much better shape.
“But in the 12 warmer ecoregions, recent beetle epidemics cannot be attributed to warming winters because earlier winters were rarely cold enough to kill the beetles.”
They meant to say “…winters were NEVER cold enough…”
It’s no surprise they cling to their failed hypothesis, even as they back-pedal; warmer winters were still responsible for (now reduced to ‘contributed to’) outbreaks in Canada even though something else caused them elsewhere. Certainty abides!
When I was burning beetles for the BC government in the 80’s, conventional wisdom was that the beetles would never fly more than 50 meters from where they emerged before entering their new home. The epidemic moved a good deal faster than that.
There were considerable resources invested in the fall and burn program and it was interesting that we always wound up returning to the areas we’d treated the previous year because we hadn’t eliminated the beetle. Meanwhile, enormous tracts of forest produced no evidence of them at all.
It was often the case that we incrementally took out every pine in certain areas, especially in mixed stands with spruce and poplar. It was my impression that, in the big pine forests, there was no endemic population being held in check by winter kill-off or some such fully understood natural force, but, rather, they just hadn’t discovered the smorgasbord yet and as soon as they did, they tucked in.
I remember reading some studies on the pine beetle several years ago that seemed to make sense. The pine beetle survives the cold temperatures by changing its body fluid to an anti-freeze in a process that takes time and is triggered by temperature. The study showed that the beetles could survive temperatures down to 30 degrees F below zero, but did not determine a lower bound. Most beetle mortality was due to either early cold snaps, before the beetle could sufficiently convert its body fluid for protection or late cold snaps after warmer conditions triggered the return to normal body fluid.
The warming winter argument always struck me as odd since the range of the pine beetle stretches down into Mexico, without the decimation of their food source. Apparently the beetles make little headway if the trees are young and healthy.
The last time WUWT delved into mountain pine beetles and forest fires, it was triggered by a Joe Romm blog post which claimed 70,000 square miles. I looked into that figure and could not find any substantiation. Far from it, the cycle of references all seemed to lead to a 2011 US Forest Service report which claimed a total of 7 million acres in three states were affected by pine beetles, which translates into 10,938 square miles, or 28,328 square kilometers for the metrically-minded. Note the US Forest Service report said affected, which somehow got conflated into destroyed.
The earlier WUWT article is here. My comment (with references) is here .
I would say humans are the most fortunate and we can influence our faith, but the animals have to adapt or they will have no other way. At least, we can try and do something…. to care!
With a bit of common sense the problem is obvious. Look at this graph of beetle spread below. The green line is 2006, the red line 2011. What you are seeing in the advance is the spread of an INFECTION. This is the pattern of how disease spreads, with clustering and break-outs. From infected population to healthy population.
The most obvious answer is that we are looking at an improved blue stain fungus. A mutation has taken place and those trees that are susceptible will be killed. The remaining trees, those individuals that are naturally most resistant will pass along this resistance to the next generation.
https://www.nrcan.gc.ca/sites/www.nrcan.gc.ca/files/cfs/assets/file/1550
http://oi60.tinypic.com/25plsug.jpg
I’ve long maintained that forestry practices have been to blame for much of the beetle kill in Colorado, which suffers from a largely monocultural body of aging trees, beginning with the Colorado gold rush in 1859, with many areas of trees crowded together because of too little human understanding and too much fire suppression. It’s gratifying to see this confirmed, even if they don’t think they’re specifically confirming it.
errata
Checkered
BeatlesCheckered Beetles
(But what about Billy Shears?)
…but many of these
hostspredators may replay on woodpeckers…I think I better quit now while I’m behind.
I live in the southwest in one such forest. One thing I have noticed over the years is the more densely populated an area is with trees, the worse the beetle damage, with ALL areas Ive found with wider spacing having at worst only minor damage that isn’t killing trees. There is also the fact human actions have hindered the forest fires that used to routinely clear out the younger trees here, point being that your average spot used to burn every 7-15 years according to some sources. Not very hot fires, many trees would survive, or be by passed entirely. Older trees here show these fire marks. So previously the density of the trees was lower, which would mean stronger trees more impervious to the beetles. I have old pictures taken from all over the area, which also suggest thinner density of treestands was the norm in the past. I also see outbreaks of them at both very high elevations and very low which suggest to me temp isnt the major factor in the beetles dominance. Also some of the spots I know with thinner density and no issues are at the lower elevations of the forests range where it is warmer.
How odd that ‘nature lovers’ hate the fact that ‘nature eats nature’. They hate the Uroboros.
They talk about ‘wholeness’ yet only see fragmentation.
They fail to understand that the patterns we see — the forms — unity — emerge from opposing spirals.
See my painting: The Flower Sermon
http://www.maxphoton.com/flower-sermon/
Actually Rabbit central and northern BC has had temperatures of 50f below and extended periods around 40f below. These temperatures have been rare though for about the last 15 years and early cold freezes which also kill off the bugs has also been rare. PDO?.
This is the area where I live.
Speaking of mild winters how many feet of global warming are you buried under at the moment?
How far can a bark beetle fly? At least 2 miles, supposedly: http://cals.arizona.edu/extension/fh/bb_faq.html#5
Accordingly their spread should take human transport into account, by loggers and firewood collectors, and this should be added to artificial old growth due to fire suppression. Temperature must be a minor factor. –AGF
Beetle killed pine trees do burn better than green (uninfested) pine. In 2014 in B.C. on the west side of the Rocky Mountains, the largest fire in over 100 years occurred burning over 250,000 ha all of which was in beetle killed pine. Beetle killed trees that have been dead for 5 or more years are drier, have more fine fuels, burn with a higher fire intensity and through more sparks further than green stands. I and my compatriots in the fire control and research community can only shake our heads at this report.