In celebration of the 50th Earth Day, The Atlantic compiles 31 iconic photographs, “each a glimpse into some aspect of our environment, how it affects and sustains us, and how we affect it.” Included are pictures taken during the inaugural Earth Day protests in 1970: “Conceived as a national teach-in, patterned after the Vietnam teach-ins held on hundreds of campuses in the Spring of 1965, Earth Day is a nationwide demonstration of concern for the planet and all forms of life—not only man—who live on it.”