When temperatures pass a certain threshold, however, the beetles lose their ability to synchronize and begin emerging sporadically. Unable to coordinate mass attacks, they have greatly reduced chances of success.
These basic processes became the building blocks for Logan's climate models. Because the beetles developed at more or less constant rates relative to temperature, Logan was able to describe the relationship between reproductive success and temperature as a series of mathematical formulas.
Simplified, they might look something like this: At temperature X, an approximate number of beetles (Y) should emerge simultaneously, giving the insects a Z percent chance that a significant number will reproduce successfully.
Having established that equation, predicting the beetle's expansion into any particular region was just a matter of plugging in the IPCC's temperature projections and crunching the numbers.
After running his models, Logan arrived at a grim conclusion: The temperature thresholds for sites like Railroad Ridge, the greater Yellowstone region and much of the American West -- thresholds at which climatically impassable habitats would suddenly become benign -- were well within the short-term projections of the IPCC.
Forecasting a fast-moving plague
In 2001, Logan published his findings, along with co-author James Powell, in the journal American Entomologist. Already, the insect's reach had begun to spread, with the area of forest affected by beetle kill more than doubling between 1999 and 2001. However, few alarm bells had yet begun to sound.
Railroad Ridge remained Logan's most important litmus test. He had set up a number of weather stations on the ridge after his first visit in the 1990s, and these indicated that the area was steadily approaching the "tipping point" established by his models.
Then, on a visit in 2003, he found his predictions borne out. Here and there among the whitebark stands, patches of burnt orange, the color of rust, were appearing. The implications were obvious -- the beetles were back.
"It was the most magnificent whitebark ecosystem I'd seen," Logan would later recall in an interview with The New York Times. "It broke my heart."
It took less than four years for Railroad Ridge's ancient ecosystems to collapse. By 2007, virtually no living whitebarks remained.
Across the continent, the beetles were taking new ground. By 2008, much of the whitebark population of Yellowstone National Park would be similarly afflicted. And the beetles were spreading north, expanding into the boreal forests of Canada and exploding through central British Columbia. The maps and models Logan had created were suddenly being recreated -- this time, as the chronicle of a phenomenon well under way.
A story 'more bitter than sweet'
Logan retired from the Forest Service in 2006, although he has since collaborated on a number of articles with fellow scientists. His work, particularly the 2001 paper, is among the most widely cited in research explaining the momentous devastation wrought by the mountain pine beetle.
Yet the signature achievement of his career brings Logan little satisfaction. An avid skier and fly fisherman, he spends most of his time in the outdoors; during the coldest months of the year, he and his wife winter in a remote cabin in the Beartooth Mountains of southern Montana. Increasingly, the beetle's expansion has left dead and dying forests throughout the region.
"For me, this story is more bitter than sweet," he wrote in a recent exchange.
He is currently part of a group of scientists and citizens pushing the government to confer protected status on the whitebark pine.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500