Ian Lowe's essay makes a welcome and thoughtful case for population to be discussed without prejudice when considering pathways to “sustainability”—whatever that might mean.

My own approach emphasizes that values and human welfare must be at the center of any discussion of a transition to sustainability and therefore that population growth and size cannot be ignored as factors in achieving an environmentally sustainable good life for all. This clearly anthropocentric approach should not be confused with the caricature of anthropocentrism which is frequently broadcast. Indeed, the sort of narrow and arrogant anthropocentrism which is supposedly the dominant frame for our civilization actually militates against human welfare and a more expansively defined good life.

This ecologically enlightened anthropocentrism has no foundational pretensions, and the "good life" to which it aspires must be fleshed out and debated in fora such as this. Arguably, this is as true for conceptions of the "natural" world as it is for the social. My own concern is with the natural world that exists now or, more accurately perhaps, that which existed in some not-so-distant past. More broadly and abstractly, I am concerned with the preservation of the conditions of the Holocene, not with some other past or future epoch devoid of Homo sapiens.

This still leaves the question of what this future natural and social world looks like relatively open, but it seems clear that population size is central to the trade-offs between the level of welfare to be enjoyed and the kind of natural environment we wish for. Many have attempted to arrive at figures for a so-called "environmentally sustainable population" and furnished figures typically ranging from 1 to 3 billion depending upon their assumptions. I do not find most of these calculations particularly helpful since due to demographic momentum, the most optimistic reductions in fertility will mean that those reading this will be dust long before such figures are achieved. Moreover, and perhaps more importantly, such calculations are extremely sensitive to value and technical assumptions.

Nonetheless, a recent study suggests that a good life for all within planetary boundaries might be enjoyed by no more than 7 billion.¹ The authors show that redistribution alone cannot sustainably meet the basic welfare needs of the current population, and while a complete transformation of socio-technical systems could provide good welfare to 7 billion, it is not likely that this can be achieved for many billions more without further breaching critical planetary boundaries. Of course, the value assumptions of this model (and, indeed, the model upon which it draws) are just as critical as any other, but it does give us cause to be mindful of the potential trade-offs between welfare, population size, and environmental change.

Clearly, it is equally easy to imagine a range of future population sizes from that where the (perhaps uneven) meeting of basic human needs takes place under barely tolerable but stable environmental conditions to one where humans and other species might flourish. Again, these are questions for debate in fora such as this, but I take it to be axiomatic that we also aspire to have a role in actively shaping humankind's trajectory rather than surrendering to seemingly intractable abstract social or natural forces.

For this reason, the characterization of the debate as polarized between Malthusians and anti-Malthusians is not only unhelpful but misconceived: nobody contributing to this debate is, in fact, a Malthusian. Historically, the majority of discussions of Malthus's essay on population have not been focused upon population size or growth as such, but on his reactionary conservative insistence that poverty and low welfare are unavoidable for a large section of the population. Malthus's objective was to show that the “perfectibility of man” was mistaken and that a combination of natural limits and human nature would inescapably determine the poverty and misery of a significant proportion of society.

Marx's scathing critique of Malthus correctly pointed out that there is nothing "natural" about poverty and scarcity, that they are a product of exploitative social systems and can be solved through system change, technical progress, and equitable distribution—an argument which is still pertinent today and shared by many of those in favor of population policies as well as by those who oppose them. Marx's key insight is that there are no abstract natural laws of population, only ones arising from particular historical conjunctures. Clearly, this does not exclude the idea that there are natural boundaries to be negotiated, and indeed recent scholarship makes it clear that Marx's understanding of natural limits and the ability of humans to transcend them was more nuanced than traditionally portrayed.²

Joel Cohen makes a similar, although less structurally deterministic, point when he argues that the idea of "carrying capacity" is a specious notion when applied to human beings.³ He argues that the Earth's capacity to support human beings is the outcome of both natural factors and the aggregated choices made by individuals during the conduct of everyday life. Cohen's observation is important, but his emphasis on "choice" may convey too much of a sense of voluntarism. Environmental change is largely the unintended consequence of everyday social practices, some of which may involve a moment of choice, but the majority of which are habitual and conducted in socio-technical contexts regarding which agents may have limited knowledge and little or no control. This lack of control may in part be due to their structural position in the (global) social hierarchy, and as such, this approach accommodates the role of social power in the production and reproduction of social norms and practices.

Obviously, since habitual social practices are a result of deeply embedded social norms, they are potentially amenable to change via a range of different policy interventions. But most importantly for this discussion, social norms are also critical in perpetuating or slowing the reduction of high fertility rates.⁴ It is important to remind ourselves that the so-called "demographic transition" from high to low mortality and fertility is not a universal law of nature taking place behind the backs of agents but the intended and unintended outcome of actions and choices conditioned by norms and values as well as the operation of structures of power and domination.

Fertility outcomes may be the product of deliberative choice, but, as with all social practices, they are conditioned and influenced by the social context in which the agent is embedded. This context will include accepted social expectations, such as norms around family size and gendered roles, as well as much more overtly oppressive patriarchal structures and value systems such as perpetuating child marriage, restricting access to contraception, preventing female participation in the labor force, etc. That these social norms should be regarded as sacrosanct from the Western liberal tradition which regards the individual as sovereign, or the equally Western idea of absolute cultural autonomy, seems problematic. Perhaps most importantly, we know that in the face of environmental change, high rates of population growth have a negative impact on resilience and adaptive capacity, which especially adversely affects the welfare of children and women.⁵

I am aware that, at all levels, the power dynamics are problematic, but the fact that treading the path between individual liberty and collective good is a perilous and difficult task does not mean that we should not attempt it, and even less, that we should treat it as taboo and close our minds to critical examination of our own value assumptions.

1. D. W. O’Neill et al., “A Good Life for All within Planetary Boundaries,” Nature Sustainability 1 (2018): 88–95; Regarding planetary boundaries, see Johan Rockström et al., “A Safe Operating Space for Humanity,” Nature 461 (2009): 472–475.
2. Kohei Saito, Karl Marx’s Ecosocialism: Capital, Nature, and the Unfinished Critique of Political Economy (New York: Monthly Review Press, 2017).
3. Joel Cohen, “How Many People Can the Earth Support?,” The Journal of Population and Sustainability 2, no. 1 (2017): 37–42.
4. Partha Dasgupta and Aisha Dasgupta, “Socially Embedded Preferences, Environmental Externalities, and Reproductive Rights,” Population and Development Review 43, no. 3 (2017): 405–441.
5. Kathleen Beegle and Luc Christiaensen, Accelerating Poverty Reduction in Africa (Washington, DC: World Bank 2019), https://openknowledge.worldbank.org/handle/10986/32354; Roz Price, The Linkages between Population Change and Climate Change in Africa, K4D Helpdesk Report 900, (Brighton, UK: Institute of Development Studies, 2020).