What is the author’s purpose for her extensive discussion of beetles in "The Thirsty Tree"?

She wants to give a specific example of how interconnected the various tree, bird, and beetle species are, and show how complicated their interactions become.

She is showcasing a particularly interesting example of poor planning of ecological maintenance in the American Southwest.

She wants to provide an example of how one form of wildlife can be used with another to extensively restore an ecosystem.

She is showcasing a particularly good example of how ecological balance can be restored and maintained in the American Southwest.