What is the theme in Refuge: An Unnatural History of Family and Place by Terry Tempest Williams?

Another theme in the book is the animal refuge. The Bear River Migratory Bird Refuge, a nesting place for a wide variety of waterfowl, is located in northern Utah. The Bear River Migratory Bird Refuge is aptly named as it sits at the point where the Bear River flows into the northeast sector of the Great Salt Lake. The Refuge serves many purposes, including the protection of the marshes around the Bear River, particularly those located at the mouth of the river. The Great Salt Lake ecosystem depends upon the marshes, which are the largest freshwater component of the system. Because the marshes are surrounded by desert, waterfowl routinely flock to the area which they see as an oasis.