What is the author's tone in The Everglades: River of Grass by Marjory Stoneman Douglas?

The mood of the book is one of concern. The author is concerned with the damage done to the environment of the Everglades and the affects on the ecosystem of the area. She describes the history of the Everglades and how the Indians adapted to their environment without damaging the Everglades. The problems with the environment began with the modernization and the increased population in the southern Florida area. Speculators who thought they could develop and sell the Everglades land needed to have it drained.