Mother Jones: In 1996 Colorado received a very unwelcome--and hungry--house guest, the mountain pine beetle, whose voracious appetite for pine has since killed off millions of acres of trees there. A few years later, the beetles came knocking in British Columbia and have now knocked out over half the province's pine timber. The full-bore invasion of these critters, each no bigger than a grain of rice, is now one of the most pressing ecological disasters in the West, and their spread, scientists believe, is driven...