From PBS - The fascinating story of beavers in North America - their history, their near extinction, and their current comeback, as a growing number of scientists, conservationists and grass-roots environmentalists have come to regard beavers as overlooked tools when it comes to reversing the disastrous effects of global warming and world-wide water shortages. Once valued for their fur or hunted as pests, these industrious rodents are seen in a new light through the eyes of this novel assembly o...