What is the theme in Rainbow Six by Tom Clancy?

Another theme in the book is radical environmentalism. The major plot of the story is based on the viewpoint by radical environmentalists that humans are ruining the earth. Their goal is to return the earth to Nature and the animals. John Brightling, CEO of Horizon Corporation, a behemoth in the pharmaceutical industry, is one of these extremists and uses the skills of his employees and resources of his company to develop a deadly Ebola-like flesh-eating virus that will all but end humanity. Of course, Brightling sees to it that his company develops a vaccine to inoculate himself and those he selects to survive the killer. These few survivors will be witness to the new world order where Nature takes over as the dominant force on earth and humans assume their rightful subordinate position.