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Migration is dwindling worldwide, Middleton says, and preserving some of the last large mammal migrations in North America has become a key conservation concern. Satellite images of where the elk roam now suggest what’s gone wrong with their migration, Middleton reported June 14 at the annual meeting of the American Society of Mammalogists. Images show that the period when grasslands are thriving and green with prime nutrition for grazers shrank by 40 percent between 1989 and 2009, he said. This premature grassland brownout fits with weather station data showing that over the past 21 years, the average July temperature in the migrants’ high-elevation summer range has risen more than 4 degrees Celsius, Middleton said. On top of that, nearly a decade of drought worse than the Dust Bowl dry-out has parched the Yellowstone region. In contrast, satellite images show little change in the greening of vegetation at the lower elevation, Middleton said. Elk remaining there not only have a more stable summer food source, but can nip over to some scattered agricultural outfits to take advantage of irrigated vegetation.

global warming has only recently allowed beetles to flourish in high-elevation whitebark pine forests, where the trees have not evolved strong defenses. Until recently, harsh winters have kept mountain pine beetles (which are the size of a grain of rice) at bay. Warmer temperatures have dramatically increased the beetles’ numbers and allowed them to move upwards to attack the whitebark pines, a number of which have been made more susceptible due to weakening by blister rust. The result is the loss of more than half of historical whitebark stands across their range, with far worse numbers in some areas. In the eastern portion of the Greater Yellowstone Ecosystem, for example, whitebark pine forests have been already functionally lost.

Whitebark pine forests have been hit particularly hard in the Northern Rockies. NRDC and the US Forest Service helped fund an unprecedented aerial survey of the entire 20 million acre Greater Yellowstone Ecosystem to investigate mortality levels of whitebark pine throughout the region. A groundbreaking pairing of airplane overflights with GIS and field-based evaluation techniques have given a new and more detailed understanding of the impact being felt by the region’s whitebark population. The data was brought together by prominent academics leading the research team, to map out the beetle carnage and evaluate the pattern of tree mortality in the region. Released today, the report shows 82% of the Greater Yellowstone whitebark pine forests of Wyoming, Idaho, and Montana dead or dying (high to medium mortality rates). The mundane title, Using the Landscape Assessment System (LAS) to Assess Mountain Pine Beetle-Caused Mortality of Whitebark Pine, Greater Yellowstone Ecosystem, 2009 belies the explosive results, which imply that the problem is far worse than had been previously known. The study was written by prominent experts Wally Macfarlane, Dr. Jesse Logan and Willie Kern. Based on these data, and considering the rapid changes, the report authors believe it is likely that whitebark pine will be functionally extinct in the ecosystem within the next 4-7 years.