What’s Killing the Great Forests of the West?

j_b · March 17, 2010

by jim robbins

For many years, Diana Six, an entomologist at the University of Montana, planned her field season for the same two to three weeks in July. That’s when her quarry — tiny, black, mountain pine beetles — hatched from the tree they had just killed and swarmed to a new one to start their life cycle again.

Now, says Six, the field rules have changed. Instead of just two weeks, the beetles fly continually from May until October, attacking trees, burrowing in, and laying their eggs for half the year. And that’s not all. The beetles rarely attacked immature trees; now they do so all the time. What’s more, colder temperatures once kept the beetles away from high altitudes, yet now they swarm and kill trees on mountaintops. And in some high places where the beetles had a two-year life cycle because of cold temperatures, it’s decreased to one year.

Such shifts make it an exciting — and unsettling — time to be an entomologist. The growing swath of dead lodgepole and ponderosa pine forest is a grim omen, leaving Six — and many other scientists and residents in the West — concerned that as the climate continues to warm, these destructive changes will intensify.

“A couple of degrees warmer could create multiple generations a year,” she said, as she chopped off a piece of bark on a dead lodgepole pine to show the galleries of burrowing larvae. “If that happens, I expect it would be a disaster for all of our pine populations.”

Across western North America, from Mexico to Alaska, forest die-off is occurring on an extraordinary scale, unprecedented in at least the last century-and-a-half — and perhaps much longer. All told, the Rocky Mountains in Canada and the United States have seen nearly 70,000 square miles of forest — an area the size of Washington state — die since 2000. For the most part, this massive die-off is being caused by outbreaks of tree-killing insects, from the ips beetle in the Southwest that has killed pinyon pine, to the spruce beetle, fir beetle, and the major pest — the mountain pine beetle — that has hammered forests in the north.

These large-scale forest deaths from beetle infestations are likely a symptom of a bigger problem, according to scientists: warming temperatures and increased stress, due to a changing climate. Although western North America has been hardest hit by insect infestations, sizeable areas of forest in Australia, Russia, France, and other countries have experienced die-offs, most of which appears to have been caused by drought, high temperatures, or both.

One recent study collected reports of large-scale forest mortality from around the world. Often, forest death is patchy, and research is difficult because of the large areas involved. But the paper, recently published in Forest Ecology and Management, reported that in a 20,000-square-mile savanna in Australia, nearly a third of the trees were dead. In Russia, there was significant die-off within 9,400 square miles of forest. Much of Siberia has warmed by several degrees Fahrenheit in the past half-century, and hot, dry conditions have led to extreme wildfire seasons in eight of the last 10 years. Russian researchers also are concerned that warmer, dryer conditions will lead to increased outbreaks of the Siberian moth, which can destroy large swaths of Russia’s boreal forest.

While people in some places have the luxury to doubt whether climate change is real, it’s harder to be a doubter in the Rocky Mountains. Glaciers in Glacier National Park and elsewhere are shrinking, winters are warmer and shorter, and the intensity of forest fires is increasing. But the most obvious sign is the red and dead forests that carpet the hills and mountains. They have transformed life in many parts of the Rockies.

Much more here: http://e360.yale.edu/content/feature.msp?id=2252

StevenSeagal · March 17, 2010

Awhile back, I sat next to a fat, redneck woman on an airplane flight. She had a gigantic bible that she kept in her lap the entire flight, to which she continually pointed to and counseled, "it's all right here..." as her final say on every point of discussion.

One of the many topics we covered, somehow, was environmental issues, during which time she authoritatively asserted to me that "the pine beetles are God's punishment to environmentalists".

So j_b, get over yourself and get over the stupid resource. As this woman put it, "stop worshiping the creation and start worshipping the creator".

:crazy:

Mtguide · March 17, 2010

Forest entomologists have begun having some success with aromatic packets of pheremones which tell the beetles that the tree is already at its limit for the number of beetles, and to go elsewhere. That's right, the pine beetles themselves produce a pheremone that does this. Evidently when so many beetles have infested a particular tree, their population limit,( based on how much area of a tree each beetle needs to provide sufficient food for it's larvae) kicks in, and all the beetles on the tree begin to emit this pheremone, telling any more beetles "Sorry, the place is full, go to the next tree."

Just one packet per tree seems to be enough,they're being placed on miliions of trees throughout the West. A packet can last an entire season. They're now working on developing a spray that could be applied like cropdusting to entire stands, wouldn't weather off, and also a sterile beetle with a genetic code that interferes with the reproductive cycle, much as was done with the Medfly infestation about 15 years ago in California.

mtn_mouse · March 17, 2010

Yes, all bark beetles use pheremones, and the ones described above are called anti-aggretating pheremones. These are indeed produced when the population within the tree has reached capacity. I know that there has been an anti-aggregating pheromone on the market for a while now to be used against the douglas fir beetle (Dendroctonus pseudopsugata). However, one packet has to be attached to each tree. And they are spendy. So in a forest it has never been an option, only a band aid for small stands of especially desirable trees. I didnt know they had one for the mountain pine beetle, but since the main host tree is the lodgepole pine, and they pretty much wipe out entire forests it would not be feasable.

The current practice is to use controlled burns to thin out these forests and slow the spread of beetles.

G-spotter · March 17, 2010

Yes they have them for mountain pine beetles but it's too late for many trees.

http://www.flickr.com/groups/mountain_pine_beetle/

jon · March 17, 2010

I was amazed at how bad the problem was in Banff driving through this summer. I just figured it was cold enough there to avoid the problem.

Hey mtn_mouse what do you do for work? This is most intelligent thread on here in a while LOL.

Pete_H · March 17, 2010

How come there's no slide alder or devil's club beetle?

ivan · March 17, 2010

i'll give up the devil's club beetle for X2 slide alder ones, please

tvashtarkatena · March 17, 2010

Slide cedar: Accept no substitute.

j_b · March 17, 2010

Anybody knows if the beetle is spreading rapidly east of the Rockies? or are winters too rigorous?

G-spotter · March 17, 2010

the winter temperature has to be -30c for at least two weeks in october or november to kill it. it just does not get that cold anymore thanks to our fossil fuel addiction, and so there's no cold cold enough to kill the beetle anymore

jon · March 17, 2010

It's time for a genetically modified pine beetle virus.

tvashtarkatena · March 17, 2010

The pine beetle isn't the only pathogen at work, here. There are other insects (wood wasps, etc) and diseases that are benefiting from the global warming that we all know is a hoax.

j_b · March 18, 2010

it seems like it'd have been difficult to get 2 weeks at -30degC in Oct-Nov at lower elev West of the Rockies even before global warming.