How does Marjory Stoneman Douglas use imagery in The Everglades: River of Grass?

Examples of Imagery:

"The freezing northern airs kept the animals in the warm south and in that developing shape of Florida like a sack with no lower opening. Nowhere else in America was there to be a more crowded or richer or more varied animal life."

"The word was 'war'. It blazed all along the white settlements and echoed in panic as far as Georgia and Alabama, carried by frantic, galloping men."

"The air of expansion and progress hung only over the east coast. The Everglades, under the winds and storms, the rains and dews, and the constant work of the sun, lay unchanged."