U.S. Environmentalism Since 1945: A Brief History with Documents - Hardcoverby Na Na (Author) By the end of World War II, Americans relationship with nature had changed dramatically. New consumption patterns drove an industrial economy that damaged the earth in new ways, and the atomic age heightened awareness of the earth s fragility. Environmental historian Steven Stoll identifies 1945 as the birth of American environmentalism the point when conservation and nature advocacy fused with activism to form a political movement.