WRITING about his first summer in the high Sierra, naturalist John Muir declared that "when we try to pick out anything by itself we find that it is bound fast to everything else in the universe."This sense of the interconnectedness of the natural world and respect for the millions of species that inhabit it is a common feeling, a sense that in dealing with endangered species one confronts questions of values and ethics as well as biology and politics. In his annual message to Congress on the environment earlier this year, President George Bush pointed out "the seamless web of relationships between living organisms and the air, water, and land that surrounds them.... We must expand our efforts to understand and protect the functional integrity of the environment - and our place in it." As a young manager of public forests and rangelands in the Southwest early in this century, Aldo Leopold was an enthusiastic proponent of controlling species - like wolves and coyotes - that interfered with man's notions of productivity and efficiency. But by the time he wrote his best-known work, "A Sand County Almanac," his thinking had changed. "If the land mechanism as a whole is good, then every part is good, whether we understand it or not," he wrote. "If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering." In the forward to a 1989 handbook on the Endangered Species Act published by the Stanford Environmental Law Society, Rep. John Dingell (D) of Michigan likened wild species to "a library of books still unread. "Preventing the extinction of our fellow creatures is neither frivolity nor foolish environmental excess; it is the means by which we keep intact the great storehouse of natural treasures that make the progress of medicine, agriculture, science, and human life itself possible. Our heedless destruction of them is akin to burning that library without ever having read its books." Professor John Cobb, a theologian at the Claremont Graduate School, adds a religious dimension: "For God, every species has value," he writes in an essay titled "A Christian View of Biodiversity.To wipe out unnecessarily whole species of those creatures over whom we exercise stewardship is to betray that stewardship and to impoverish the experience of God. It is a crime against our Creator."