Environmental restoration is a global pursuit and a major political concern. Governments, nonprofits, private corporations, and other institutions spend billions of dollars each year to remove invasive species, build wetlands, and reintroduce species driven from their habitats. But restoration has not always been so intensively practiced. It began as the pastime of a few wildflower enthusiasts and the first practitioners of the new scientific discipline of ecology. Restoration has been a touchstone of United States environmentalism since the beginning of the twentieth century. Diverging from popular ideas about preservation, which romanticized nature as an Eden to be left untouched by human hands, and conservation, the managed use of natural resources, restoration emerged as a “third way.” Restorationists grappled with the deepest puzzles of human care for life on earth: How to intervene in nature for nature’s own sake? What are the natural baselines that humans should aim to res...