What is the theme in Death in Yellowstone: Accidents and Foolhardiness in the First National Park by Lee Whittlesey?

The wilderness is the main theme in this book. Yellowstone National Park is 3500 square miles and have been a national park for one hundred and forty years. The large majority of the park has never been 'tamed' and remains as wild as it has been for ten thousand years. The author, Lee Whittlesey, thinks that preserving the wilderness is very valuable. However, he thinks that many people have an idyllic image of the wilderness as somehow friendly to human beings. Modern Americans have a romantic notion of the wilderness as 'natural' to man and therefore it won't harm them.