That the planet is in environmental crisis is a truth(almost)universally recognized, but the nature of the crisis doesn't command nearly the same unanimity. Is it because our activities now threaten our survival, or because the weight of humanity -- all 6.5 billion planet-eating, carbon-spewing individuals -- lies too heavily upon the rest of what was once known as creation? Those who express the latter view are often dismissed, sometimes maliciously, as being anti-human, madmen who regard the fate of Amazonian butterflies or Arctic bears as having the same moral value as human life. Mostly such accusations are baseless -- you don't have to hate humanity to value the rest of nature -- but there are, in fact, a lot of people who think the most useful thing humanity could do is disappear, in whole or in part.

The Church of Euthanasia, for one, is proud to trumpet its four "pillars": abortion, suicide, cannibalism and sodomy.(By the last it means merely whatever form of non-procreational sex appeals to you.)The black humour carries through its website guide to butchering a human carcass, which comes complete with -- in case anyone's still missing the joke -- a recipe for barbecue sauce. Then there are the transhumanists, some of them eminent thinkers, who believe, in all seriousness, that we should upload ourselves into computers, an elegant solution that would leave the physical realm for nature to rule, while we gain personal immortality. If only there ever was a machine that could function, eternally no less, without human maintenance.

That's why serious anti-humans prefer a more traditional(if gradual)suicide. In Oregon, America's only euthanasia-friendly state, schoolteacher Les Knight, head of the Voluntary Human Extinction Movement, makes it all sound perfectly idyllic. Talking to Alan Weisman, author of The World Without Us(HarperCollins)-- a marvellous projection of what life would be like on a human-free earth -- Knight describes what he sees as the best path to the inevitable. Brutal resource wars, starvation and epidemics are going to mow us down anyway, as our growing numbers come up against the world's finite resources. So much the better that we should "all agree to stop procreating."

Abortion providers going out of business would be the first happy result, in Knight's opinion. Soon, "there would be no more children under five dying horribly. In 21 years, there would be, by definition, no juvenile delinquency." There would finally be enough to eat, even while nature was staging a recovery from our depredations; with nothing to fight over, war would end. "The last humans could enjoy their final sunsets peacefully, knowing they have returned the planet as close as possible to the Garden of Eden."

The logic is as absurd as it's unassailable. Yes, indeed, if there are no more children, there will be no more child tragedies. Or child triumphs, for that matter, or much reason to think childless humanity will spend its dying days as serenely as Knight predicts. In The Children of Men, P. D. James's scarifying 1992 dystopia, the dispiriting consequences of mass infertility(a collective loss of the will to live)are far more believably depicted. Yet, as Weisman notes, Knight's lament does catch some of "the weariness that genuinely humane beings feel as they witness the collapse of much biology and beauty." That's why Weisman has another suggestion, one "poignant and distressing, but not fatal": limit every human female on earth to one child only.

The math suddenly turns positive. If a gender-neutral one-child policy began tomorrow, our numbers at mid-century, currently projected to rise to nine billion, would drop to 4.5 billion. By 2075, we would have reduced our presence by almost half, down to 3.4 billion, and "our impact by much more, because so much of what we do is magnified by chain reactions we set off through the ecosystem." Keep it up for a century, and by 2100 our 1.6 billion descendants would be suffused with "the growing joy of watching the world daily become more wonderful."

Compared with what some are predicting for the future(from Armageddon-level catastrophe to grubbing out an ever meaner life), or are actually suggesting we do(see above), this sounds pretty good. In fact, only the alternative most of us seem to be hanging on to -- that somehow, in some unspecified way, we will muddle through -- can match Weisman's dream for hopefulness. Any number of terms could be applied to it, with utopian being the mildest, but one thing it's not is anti-human.