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Philip Cafaro discusses population growth and environmentalism.


Forty years ago, at the dawn of the modern environmental movement,

it was common to hear humanity’s rapid population growth spoken of as “cancerous” — dangerous and out of control — and even occasionally of humanity itself as a cancer threatening life on Earth. Since then, such rhetoric has largely disappeared from environmental discourse, along with serious attention to human overpopulation.

The notion of “humanity as cancer” grated over time. Who wants to think of themselves, or their children, as part of a sickening, life-threatening disease? Many of us know people who have suffered from cancer. The whole way of speaking about it seems in bad taste.

Yet the environmentalists of the past had the clarity of mind to realize that overpopulation was a problem and the courage to say so. Today we are ever so much more sensitive, well behaved and well spoken. Yet we are utterly failing to protect wild nature and future human generations from overpopulation — despite the fact that empirical evidence linking growth and environmental decline continues to accumulate.

In one area after another, environmentalists are documenting what Dave Foreman describes as “the Man Swarm” overwhelming biodiversity. They lament the losses and call for strong action: for human restraint in our appropriation of the habitats and resources of the world. They know that such restraint is impossible unless human numbers are curbed.


The ability to restrain ourselves lies at the core of humanity’s ostensible sense of superiority over the rest of nature. The great philosopher Immanuel Kant laid it out clearly over two hundred years ago: rationality -> choice -> freedom -> morality. Our ability to reason allows us to distinguish between different courses of action and to choose one over another. This constitutes a limited, yet real, freedom, which in turn demands that we act with justice and generosity in a world where we have the power to influence for good or ill.

We do not expect wombats, redwoods, or cancer-causing viruses to respect rights or appreciate limits. We do expect this from people. The claim is that humanity is different precisely because we can act with foresight, planning, restraint and higher ends in view. But can we? Can people act intelligently and with restraint as a species, a global community, which collectively holds the fate of Earth in its hands? That is far from clear.

Humanity gives every indication of being “out of control” in terms of our use and appropriation of the biosphere. It is clear that rapid economic and demographic growth is the primary, fundamental cause of our major environmental problems. The IPCC’s Fourth and Fifth Assessment Reports from 2007 and 2014 show this unequivocally for global climate change; several overviews in recent years document it for the ongoing worldwide mass extinction of species; and the comprehensive multivolume Millennium Ecosystem Assessment published in 2005 illustrates it for ecological degradation as a whole. Growth in human numbers and economic activity is causing these problems. Yet it is precisely growth that cannot be stopped or even slowed under the current economic regime, or questioned by the reigning economic ideology.

Cancer’s Voice

Economists — the secular priests of the current age — have developed an elaborate theology in which perpetual growth is necessary, good and inevitable. Those who acknowledge limits to growth are deemed pessimists who oppose human progress. They justify the rejection of limits by appealing to a view of human nature as greedy and insatiable and to a definition of freedom that (unlike Kant’s) limits the use of reason in the instrumental pursuit of arbitrary ends, rather than seeing the recognition and pursuit of higher ends as a key to real freedom. They have developed a metaphysics in which everything that is “not us” has value exclusively as a resource for us to exploit.

Modern economic theory reads as if cancer had found a voice. Why, here it is now, in the person of Larry Summers! In the late 1990s, as U.S. Deputy Secretary of the Treasury, Summers declared that the Clinton administration “cannot and will not accept any ‘speed limit’ on American economic growth. It is the task of economic policy to grow the economy as rapidly, sustainably and inclusively as possible.” Earlier, he had confidently stated: “there are no . . . limits to the carrying capacity of the Earth that are likely to bind any time in the foreseeable future. There isn’t a risk of an apocalypse due to global warming, or anything else. The idea that we should put limits on growth because of some natural limit is a profound error”.

Profiles of Summers habitually characterize him as highly intelligent. So, reading the words above, one might assume that he actually explored whether rapid growth really is sustainable and found good evidence that the answer is “yes,” or that his “foreseeable future” stretched out past the next quarterly earnings reports or election cycle, say fifty or a hundred years out, when many of our children and grandchildren will still be alive. But such is not the case. Summers literally does not know what he is talking about and words like “sustainably” or “the foreseeable future” are merely there for their soothing rhetorical effect. They are an invitation not to think about limits to growth and a subtle preparation to accept lost species and ecological degradation as inevitable.

Embracing Limits

Those of us who care about the future of life on Earth decline the invitation. We are committed to the idea that the human race can be more than an ever-gaping mouth swallowing the world. We want to work toward a future in which humanity limits its appropriation of the biosphere and wild nature continues to flourish. In this way, I believe, we stand up for what is best in humanity.

In the world serious environmentalists seek to create, polar bears continue to hunt seals along the Arctic pack ice. Sperm whales fight unseen duels-to-the-death with giant squids a mile below the ocean’s surface. Arctic terns knit together the North and South Poles in their twice-yearly migrations, covering forty-four thousand miles annually. The great forests of the Amazon, Borneo and the Congo remain standing, remain breathing, remain overflowing with life and are not cut down to accommodate displaced peasants or to grow sugarcane to fuel an ever-growing world auto fleet. In that world, many of the biosphere’s grasslands are restored to wild ecosystems brimming with wildlife. Rivers run free of dams, overexploitation and pollution, so they can become again (in the language of the Song of Solomon) “living waters.” Sea turtles and sharks are brought back from the precipice of extinction. Large land animals, from wolves and cougars to tigers and elephants, are also restored and granted the unbroken expanses of untrammeled nature they require to live and evolve. In the world we envision we stop cutting old growth, period; indeed we leave many of the world’s forests alone because our need for pulp, wood, land and fuel is so vastly reduced.

In the world environmentalists seek to create, our children’s and our grandchildren’s right to enjoy natural beauty remains secure, rather than being sacrificed upon the altars of greed, materialism, or desperate need. They can explore and enjoy wild nature, in parks and open spaces close to home, or backpack and canoe across great wilderness areas. Their pictures and memories need not become memorials to what has been lost, as so many of our own have become. Instead, they may share the experiences and the places they have loved with their own children and grandchildren and so on, in perpetuity.

Full World

Since I am an American, I have a special concern to preserve wild places in the United States and I do not apologize for that concern. That is how environmentalism works, when it works, with people standing up and fighting for those places that are near and dear to them. But like most of my fellow environmentalists, I do not seek to preserve our own beloved landscapes by displacing the ecological costs of Americans’ excessive consumption elsewhere. Instead, I strive to reduce such consumption myself and try to convince my fellow citizens to do likewise. At the same time I decline to support the folly of nations that have high fertility rates by encouraging them to send their excess inhabitants to the United States. The American frontier closed long ago; we are “full up.” The ecological damage to the North American continent has already been exorbitant and it is time to conserve the wild nature and nonhuman species that remain, many of which are in decline. From a global ecological perspective, the last thing the world needs is hundreds of millions more Americans.

Ending Growth

No country can preserve wild nature in the context of endless economic or demographic growth, nor can the world as a whole. Either of these tsunamis, by itself, will wash away the wild species, the wild places we love and will threaten essential ecosystem services. Hence we must commit to ending the endless growth economy and support the family planning, abortion, women’s empowerment, tax and immigration policies necessary to stabilize and then reduce populations around the world and in the United States. Anything less is neither ecologically sustainable nor fair to the rest of nature. For these reasons we should reject suggestions from the Left to focus on reforming the economy while ignoring population growth and reject suggestions from the Right to limit population growth, through reduced immigration, while maximizing per capita economic growth. Such recommendations betray a weak commitment to sustainability and a shallow understanding of what is necessary to achieve it.

Serious environmentalists are committed to an end to conventional economic and demographic growth. But we do not seek the creation of some static, unchanging reality. Humanity can and should continue to grow in all sorts of ways: morally, intellectually, spiritually, creatively. It would be great if we grew in our understanding and appreciation for nature and in our willingness to share the world with other species.

Is humanity really a cancer of the biosphere, unwilling or unable to control itself? We will likely find out this century.

— Philip Cafaro is Professor of Philosophy at Colorado State University. This essay is adapted from the epilogue in Life on the Brink: Environmentalists Confront Overpopulation.

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