There are many alarming documents in “American Earth” (1,048 pages, $40), the Library of America’s new anthology of “environmental writing since Thoreau.” The main purpose of environmental writing, after all — the mission that distinguishes it from its tame cousin, nature writing — is to sound an alarm, to awaken the reader to the ecological crimes of the human race. And there is no doubt that, over the last century and a half, American environmentalists have done an important service with their bell-ringing. Without John Muir, there would be no national park at Yosemite; without Rachel Carson, we might still be poisoning ourselves with DDT. As Bill McKibben, the volume’s editor and himself a prominent environmental doomsayer, proudly writes in the introduction, “the movement — so often driven by a piece of writing — has won many great battles.”

But the most alarming piece in Mr. McKibben’s anthology, to my mind, is not a report on global warming or endangered species. It is a mere commencement address, delivered by a graduating senior at Mills College in 1969. Stephanie Mills used the occasion to warn the assembled parents and graduates that they were less than 10 years away from the apocalypse. “Our days as a race on this planet are, at this moment, numbered,” she declared, and went on to forecast “widespread famines and possible global plagues” within the decade. Were her listeners prepared to kill their neighbors in the fight for food, she inquired, or even to eat their neighbors, should the need arise? As for herself, Stephanie Mills promised, she would never bear children; this would be her small contribution to the future of the planet.

What inspired this fantastic prophecy, which should certainly have raised the audience’s fears, if not about cannibalism, then about the mental health of the speaker? Ms. Mills had been reading “The Population Bomb,” the 1968 best-seller by Stanford professor Paul Ehrlich, which forecast the imminent collapse of human civilization under Malthusian population pressures. Since Mr. McKibben also includes an excerpt from “The Population Bomb” in “American Earth,” it is possible to see just how faithfully Ms. Mills followed her source. “Mass starvation,” Mr. Ehrlich wrote, was “inevitable”: it was already “too late” to stop hundreds of millions of people from dying of hunger.

Forty years have passed since Mr. Ehrlich issued this warning. The world’s population then was about 3 billion; today, it is 6 billion, yet the promised famines somehow failed to materialize. In short, Mr. Ehrlich now looks rather like William Miller, the founder of Seventh-Day Adventism, who confidently announced that the world would end on October 22, 1844. Yet just as the Adventists continued to revere their prophet after “the Great Disappointment,” so Mr. McKibben honors Mr. Ehrlich for his conviction that “there was no emergency greater than the exponential increase in human numbers” — even though, he is compelled to admit, “some of his predictions have proven inaccurate.”

Yet with Mr. Ehrlich, as with Mr. Miller, it is the psychology of the duped disciples that raises the most questions. Ms. Mills, at least, demonstrates exactly the same ideological frenzy and moral vanity, the hatred of elders and the past, as a Red Guard denouncing his teachers in the Cultural Revolution. Even today, her speech has the power to frighten with its self-righteous malice. For while Ms. Mills is talking about the end of civilization, she is no more able than a Mao or a Savonarola to disguise her satisfaction at the prospect. If “mankind has spread across the face of the earth like a great unthinking, unfeeling cancer,” as she says, then surely it deserves to die of its own rapacity, like a tumor that kills its host. “Perhaps,” as Ms. Mills suggests, “we are unconsciously expiating our guilt.”

Indeed, Ms. Mills gives the game away at the end of her speech when she advises that, even if Mr. Ehrlich’s famine is a lie, we should still fear it: “You and I should believe that the famine can and will happen if for no other reason than that we still may be able to do something” (emphasis added). The collapse of logic as well as humanity is complete. Yet Mr. McKibben includes this text in “American Earth” on the grounds that “if you want to know what it felt like to be young and idealistic in the late 1960s, you could do worse than read Stephanie Mills.” It is unfair, of course, to pay so much attention to Ms. Mills’s short piece when “American Earth” contains so much sane and lovely writing. Here is Thoreau, building himself a house by Walden Pond for less money — he proudly calculates — than a Harvard student spends on rent each year; John Muir, rhapsodizing over the sights and sounds of a windstorm in the forest, and John Burroughs, teaching the reader to cultivate the art of noticing. Here too are the muckrakers, the yellow journalists of the environment: Berton Roueche’s report on the fog that settled over the mining town of Donora, Penn., in 1948, choking thousands and killing 20, reads like a horror movie come to life. And there are the theorists, urging the world to think about humanity and nature in new ways. Aldo Leopold’s “A Sand County Almanac” propounds a new “land ethic,” a golden rule for the environmental age: “Examine each question in terms of what is ethically and esthetically right, as well as what is economically expedient.”

Yet already in this unobjectionable formula we meet the questionable strain in environmentalist thought and writing. For once environmentalism is understood as an ethic — and there is no doubt that, since Thoreau, its claims have been ethical, even religious — then it can no longer be judged simply as a series of more or less accurate predictions about humanity’s effect on nature. Another way of putting this is that environmentalism is not scientific. The claims of scientists must be falsifiable and value-neutral; the claims of environmentalists, as we see them in “American Earth,” are neither.

Environmentalism is, rather, a philosophical worldview, a comprehensive vision of good and evil. As such, it marks a self-conscious break with earlier Western traditions, both religious and secular. In the Christian worldview, man is intrinsically depraved, but becomes precious because he is made in God’s image and receives God’s grace. To the humanist, man is precious because he is the only possible source of meaning and value in his world: As the ancient philosopher Protagoras put it, “man is the measure of all things.” Together, these ways of thinking have preserved hope and something like conscience in our civilization, giving humanity a high sense of its destiny and duties.

To the environmentalist, however, mankind is not precious. He is, in fact, the only part of nature that it is permitted to hate. When beavers build dams, or when wolves tear the throats out of deer, they are simply following their nature; but when men build cities or shoot down wolves, they are acting against nature. Man is the Satan of the environmentalist’s theodicy, the only evil force in an otherwise good creation.

That is why the dominant emotion in “American Earth” is a profound misanthropy, which takes a whole variety of forms. There is the snobbishness of Edward Abbey, a park ranger who deplores the laziness and vulgarity of people who visit national parks, or of Ellen Meloy, who refers to Las Vegas as a prize item in “the Stupidity of Man exhibit.” There is the authoritarianism of Garrett Hardin, coiner of the phrase “the tragedy of the commons,” who argues for state control of human reproduction by invoking the sinister dictum of Hegel, “freedom is the recognition of necessity.” There is the vicarious cruelty of even a John Muir, who takes pleasure in the thought of alligators eating human beings: “Honorable representatives of the great saurians of an older creation, may you long enjoy your lilies and rushes, and be blessed now and then with a mouthful of terror-stricken man by way of dainty!”

It is not so far from this to Stephanie Mills’s description of humanity as a cancer, or to Robinson Jeffers’s grimly contented metaphor: “the people are a tide / That swells and in time will ebb, and all / Their works dissolve. Meanwhile the image of the pristine beauty / Lives in the very grain of the granite.” “We must unhumanize our views a little,” Jeffers exhorts in this poem, “Carmel Point.” But on the evidence of “American Earth,” we have already granted too much moral authority to those who would unhumanize us altogether.

akirsch@nysun.com