Most people think about Rachel Carson's book, Silent Spring, written in the 1960s as a key turning point or perhaps even the birth of the modern environmental movement in the United States. Rachel Carson was a biologist and author (http://www.rachelcarson.org/) who brought forward the belief that the pesticide DDT (especially), widely used in agricultural applications post WWII, was having a serious negative impact on wildlife, especially birds--hence, the ultimate culmination of such practices being a spring season without the music of songbirds.
