I am grateful for the variety of thoughtful responses to my contribution. There is a rich diversity of views about the population question: some see it as central to any discussion of a sustainable future, some think it is important but not the highest priority, some believe it is being resolved such that discussion is irrelevant (e.g., Peter Sterling, Michael Platt), some argue that it is largely an excuse for inaction on other issues (e.g., Brian Murphy, Robert Fletcher), and others view that even discussing it risks a dangerous slide into eco-fascism (e.g., Manisha Anantharaman, Betsy Hartmann). Several have made the undeniable point that population growth is not “an independent variable that drives environmental problems,” as Gwendolyn Hallsmith puts it. Of course, we need to recognize the forces that promote population growth: patriarchy, poverty, some influential religions, the capitalist economy, and the legacy of colonial exploitation. Recognizing those forces does not, however, require us meekly to accept that we cannot work to weaken them.

Let me start with the fundamental problem. Eileen Crist, David Korten, Riane Eisler, Gus Speth, Alexander Lautensach, John de Graaf, and others all make the point that the environmental crisis is the product of increasing numbers and growing per capita consumption. In Crist’s words, “Excessive consumption is the problem; population growth spirals consumption upward and eventually out of bounds.” As Aaron Karp says, for every symptom of ecological overshoot, “the unifying cause is the scale of human consumption.” Lautensach observes that “all three variables [of the I = PAT equation] are still increasing,” while Speth notes that the P term “is especially important when A and T are large, as they are in the United States.” Eileen Crist and Guy Dauncey both underscore the role of the food system as a major driver of this increased human impact on the environment. Indeed, barring systemic change, we are heading toward the disaster which Rees euphemistically calls “a major population correction.” That is the gloomy conclusion I reach: unless we reduce our demands on the natural systems of the planet, we risk Breakdown and a calamitous collapse of civilization.

It should be uncontroversial to argue that family planning ought to be universally available since, as Celine Delacroix observes, “nearly half of all pregnancies around the world are unintended” and, as Jane O’Sullivan reminds us, family planning access is essential for equity. While Giorgos Kallis makes the reasonable point that I was not specific about the methods of making family planning available, David Korten responds with a detailed description of successful initiatives in many countries, drawing attention to the case book he and Fran Korten wrote. The basic point is that when every woman can choose if and when she will bear a child, birth rates decline, fewer women die in childbirth, and the prospects of the children improve. Speth correctly notes that I gave insufficient attention to the “headwinds” preventing access to family planning. The recent Great Leap Backwards by the US Supreme Court demonstrated the capacity of the patriarchy in general and theocratic forces in particular to deprive women of the ability to manage their fertility. As Speth points out, population growth in such affluent countries as the US does much more to accelerate environmental decline than increasing numbers in poorer parts of the world. The forces opposing family planning in the US have also been influential in halting or slowing programs to provide those services in poorer countries. Marth Van Der Bly signals hope for “the end of the global patriarchy,” which is necessary not only for equity reasons but for existential ones.

As several critics of my essay argue, poverty is the critical issue that needs to be addressed if we are concerned about population. Poverty is significant in two important ways. First, we need to change the circumstances that encourage large families, such as lack of old age security, economic instability, and high infant mortality rates. We should, like David Korten and Eileen Crist, strive for a future civilization in which wealth is distributed equitably to secure material sufficiency for all. But ending poverty is just one part of the solution.

Second, in the Global North, discussion of population often slides into an argument about migration, since that is a major contributor to population growth in affluent countries. What is rarely discussed is the role of poverty as a driving force. While there continue to be huge differences in material living standards between Europe and Africa, between North America and the countries to their south, between Australia and Asia, there will continue to be millions of people wanting to migrate, as Gustave Massiah makes clear. Wendy Harcourt and Lyla Mehta correctly point out that “scarcity is socially generated,” and Biko Agozino argues that developing countries need more equitable distribution of resources. As David Samways reminds us, they are restating Marx’s observation that poverty and scarcity “are a product of exploitative social systems and can be solved through system change, technological progress and equitable distribution.” This is really the crux of the population issue. With current human consumption more than 150 per cent of what can be sustainably provided by the planet’s natural systems, we are pushing those systems into very dangerous territory. Climate change is the most urgent problem, but the most serious is the dramatic decline in biodiversity, since that trend is irreversible. Shifting from an economic system based on growth to the steady state economy which Herman Daly has been advocating for decades, and which Heikki Patomäki intimates is necessary, makes ecological sense. But the growth model provides at least a glimmer of hope to the poor that their material circumstances might improve. Freezing in the present inequality to enable us to live within natural limits would be the politically and socially indefensible future of Fortress World.

We are forced inevitably to accept the conclusion that our predominantly national forms of governance cannot cope with the problems we now face. Even in the most affluent countries, elected leaders promise further growth, when it is clear that material demands in those nations need to be curbed to have any chance of a civilized future. If poverty is to be eliminated while the total demands of the human population are within what natural systems can provide, wasteful consumption in the minority world and obscene levels of military spending must be drastically reduced.

As Karp says, we “underestimate the extent to which society must change in order to be sustainable and the significant limits that we’ll need to place on our consumption.” That is the inescapable conclusion of the population debate.