Aldo Leopold (1887–1948), who was born in Burlington, Iowa, on January 11, was a pioneer of the American environmental movement. His essay "The Land Ethic," published in A Sand County Almanac (1966 [1949]), has become a foundational text of American environmental ethics. Leopold challenges his readers to reevaluate their relationship to the land they inhabit and act in accordance with a "land ethic" that "enlarges the boundaries of the community to include soils, waters, plants, and animals, or collectively: the land" (Leopold 1966, p. 239). In his work the land and the biotic community become more than symbolic or abstract entities; they become beings with an intrinsic right to exist. Extending ethics and rights to the land, according to Leopold, necessarily "changes the role of Homo sapiens from conqueror of the land-community to plain member and citizen of it" (Leopold 1966, p. 240). Leopold died in Baraboo, Wisconsin, on April 21.

Leopold's love of the...