Cattle are driven to their summer pastures in the Centennial Valley of Southwestern Montana in June 2012.  The age of the open range is gone and the era of large cattle drives  over. Today, very few ranches drive their cattle with horses, instead moving them by truck. Now, spurred by growing consumer concern over meat's environmental impact and concerned about the long-term viability of their livelihood, a cohort of ranchers is trying to apply the understanding gleaned from the science of ecology to livestock management.
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