Answer:
Thoreau describes the pine tree as an example of men’s enemy because it shows the human disdain for nature.
Step-by-step explanation:
A wild animal would have seemed like a dangerous element, and therefore a proper symbol of an enemy. A pine tree signifies the beauty and resources of nature that Western colonization has turned into a commodity through deforestation.
Thoreau is known as a philosopher of nature and its relationship with humanity and its development.