LiveScience: here's a predictable arc to many environmental debates. Step 1: Scientists observe a change in the natural world due to human activity. Step 2: A discussion ensues about what this change might mean for the natural world. Will it challenge the prosperity, or even the survival, of this or that species of plant or animal? This phase of the debate is well underway before we finally arrive at Step 3. Step 3: What does this observed change mean for people?That last one is usually the prerequisite for...