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.
Hunter Cutting on 25 Jun 10Report in Science: "Three studies, using different remote-sensing methods, show that East Antarctica has already begun to lose ice. A survey of laser altimetry data from the ICESat satellite, published in Nature in October 2009, found ice thinning in several spots along the East Antarctic coast at annual rates as high as nearly 2 meters. Another study, published in Nature Geoscience in November 2009, used the gravity-sensing GRACE satellites and found two areas along the East Antarctic coast each losing about 13 km3 of ice per year. A 2008 study in Nature Geoscience that compared ice flux off the edges of the continent with new accumulation of snow in the interior found a loss of about 10 km3 of ice per year at two areas." "Three studies, using different remote-sensing methods, show that East Antarctica has already begun to lose ice. A survey of laser altimetry data from the ICESat satellite, published in Nature in October 2009, found ice thinning in several spots along the East Antarctic coast at annual rates as high as nearly 2 meters. Another study, published in Nature Geoscience in November 2009, used the gravity-sensing GRACE satellites and found two areas along the East Antarctic coast each losing about 13 km3 of ice per year. A 2008 study in Nature Geoscience that compared ice flux off the edges of the continent with new accumulation of snow in the interior found a loss of about 10 km3 of ice per year at two areas." "It's too early to know what the ice loss in East Antarctica really means, says Isabella Velicogna, a remote-sensing specialist at NASA's Jet Propulsion Laboratory in Pasadena, California. "What is important is to see what's generating the mass loss," she says. Reductions in snowfall, for example, might reflect short-term weather cycles that could reverse at any time. But thinning caused by accelerating glaciers-as seen in West Antarctica-would warrant concern."
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