According to Muir what is the only thing that can save trees

According to john Muir, the only one who can save trees is Uncle Sam and not even God himself, even though he supposedly is the creator of all these beautiful species of trees. The "Uncle Sam" here refers to the common person, and by referring to him as Uncle Sam, John Muir is expecting the common person to have enough wisdom and sense to protect something that sustains us (wisdom and sense being things one would commonly associate with an uncle figure).