In a legal confrontation rooted in the meaning of a single word, twenty states and the District of Columbia have moved to defend a half-century of American conservation law against rules they say quietly dismantle it. At stake is whether 'harm' to a species can include the destruction of the places where it lives — a question whose answer will determine the fate of ecosystems, industries, and creatures that cannot speak for themselves. The 1973 Endangered Species Act once pulled condors and grizzly bears back from oblivion; now its reach is being contested in federal court, where the boundary