Crossroads of wild nature and a rapidly growing human presence, Yellowstone to Yukon -- Y2Y for short -- is both a biogeographical region and a conservation initiative. It encompasses nearly half a million square miles along the craggy Northern Rockies, most of it above 3,500 feet. Y2Y's limited lowlands provide prime winter range for numerous wildlife species -- as well as prime ranchland and prime building sites for vacation homes. Wildlife biologist and acclaimed author Douglas H. Chadwick takes you on a voyage of personal discovery as he chronicles the burgeoning threats that face this region -- and the promise embodied by Y2Y.