For the 50th anniversary of Silent Spring, William Souder looks back to the world that made Rachel Carson’s book so urgent and necessary. In 1962, the Cold War was being conducted via nuclear tests, while throughout the United States a new chemical war was under way against fire ants, gypsy moths, and other pests. These amounted to two massive, unregulated experiments with deadly materials, and that they seem so shocking today is partly due to Carson. On a Farther Shore (Crown, $30) describes the marine biologist’s rising alarm over radiation and DDT, and Souder discusses how Carson’s work marked the transition from the age of conservation—preserving wildlife—to a new era of environmentalism, which recognized that human activity poses dangers to people as well as to nature. And just who was Rachel Carson? A workaholic who supported her mother and adopted her orphaned great-nephew, Carson had always wanted to be a writer. She worked as an editor for the Department of Fish and Wildlife (and lived in Silver Spring). Her first book, The Sea Around Us, won a national book award in 1951 and has never gone out of print; if some of its science is dated, its prose still enchants, and its prescient warnings about climate change are dead on.