The boreal forest is like a green banner draped around the northern hemisphere. It is the world's largest expanse of intact forest, covering nearly 11 percent of our planet's surface. Every breath we take is in part a gift from this immense, earth-circling ecosystem. Now the renewed Mackenzie Valley pipeline proposal, the Alaska Pipeline and escalating energy and mineral exploration in the north all threaten this last world-scale refuge of natural values--and conservationists around the world are mobilizing to defend it. "Three Rivers" focuses on one of the most strategic undisturbed regions left in the world, an oceanic wilderness that is under threat from gas and mining development.