Populations in the Anthropocene: Is Fertility the Problem?

Abstract

The article addresses the question of the relative importance of human population size and growth in relation to the environmental problems of planetary heating and biodiversity loss in the current, Anthropocene era. To what extent could policies to encourage lower fertility be justified, while observing that this subject is an inherently contested one. It is proposed that a helpful distinction can be made between specific threats to habitats and biodiversity, as opposed to those related to global energy use and warming. Pressures of over-population can be important in relation to the former. But with regard to the latter—rising per capita energy usage—reduced fertility has historically been positively, not negatively correlated. A case can be made that the high-fertility nations of sub-Saharan Africa could benefit from culturally respectful fertility reduction policies. However, where planetary heating is concerned, it is the hydrocarbon-based, per capita energy-consumption patterns of already low-fertility populations on the other five inhabited continents that is rather more critical. While it will be helpful to stabilise global human population, this cannot be viewed as a solution to the climate crisis problem of this century. That requires relentless focus on reducing hydrocarbon use and confronting the rising inequality since c.1980 that has been exacerbating competitive materialist consumerism. This involves the ideological negotiation of values to promote a culture change that understands and politically embraces a new economics of both human and planetary balance, equity, and distribution. Students of populations can contribute by re-assessing what can be the appropriate demographic units and measures for policies engaging with the challenges of the Anthropocene.

1. Preamble

Where thinking about human fertility is concerned, we are confronted with its Janus- faced character. Since its earliest debut in the field of demography in the hands of Thomas Malthus, discussion of fertility has been a subject addressed very directly and urgently to matters of current public policy. However, it is also a richly complex subject that is highly suitable—and, indeed, rewarding—for more purely academic, scientific, social scientific, historical, anthropological, and cultural research, as Malthus himself also increasingly realized, as can be seen in the five successive and ever-enlarging editions of his famous Essay [1].

And just to make things even more complicated, this Janus actually has a third face of equal importance. Human reproduction—and by extension the demographic study of fertility—is an intrinsically moral and highly charged emotional subject. That means it is multiply wrapped around with issues of both personal but also social identity. For this reason, it is rapt with ritual and theology by all the world’s religions. Some secular researchers may not feel themselves subject to this, but their subject—and subjects of study—mostly are.

A recent example of this is the incipient pronatalist movement. This is a quasi-eugenic, supposedly scientific (exactly as eugenicists supposed themselves to be in the past), hyper-rationalist project claimed to be popular in Silicon Valley and counting Elon Musk with his 11 children as a key supporter. It is also one where White supremacists were welcome at its first Natal Conference in 2023 and which, at least on women’s primary role as maximum child producers, shares its beliefs with the most hard-line patriarchs of the orthodox variants of the three Abrahamic religions [2]. And then there is the “great replacement theory”, a direct revival of Madison Grant’s notorious, 1916 racist text, Passing of the Great Race [3]. But there is also the more measured and reasoning version of pronatalism, for instance, from Paul Morland, who argues that material consumerist motives are primarily behind below-replacement fertility in countries as diverse as orthodox Russia, Catholic Italy, Protestant Finland, Islamic Iran, and Lebanon. Morland notes that it is those self-identifying as religiously active in each of these countries who tend to have more children. As for fertility policy, Morland argues that “only by having a high fertility rate can a country have both a dynamic economy and avoid dependence on immigration” [4].

This compressed formulation raises issues that bear much more debate and discussion. What is a dynamic economy? Why cannot it be demographically static or even contracting (see [5,6])? Does being open to immigration have to mean a form of undesirable “dependence”; or can it be viewed more constructively as inter-dependence? Maintaining reduced fertility among the resident, high-consuming populations of the fully developed world is helpful, ceteris paribus, to reduce environmental pollution. If the consequent ageing effect creates a need to balance their dependency ratios through a flow of young adults of working-age from poorer countries, provided those young adults are fairly paid and can remit a proportion of their incomes, this relieves the employment needs of richer countries while acting as a channel to raise living standards in the poorer countries. Indeed, a properly managed formal system of such “migratory exchange” could see repeated cohorts of young adults in their twenties from poorer countries working and acquiring skills and training for a decade in a “partner” developed country, with mandatory provision that they return to their country of origin for the rest of their working lives to enrich it further with the skills and contacts they have acquired. This would be a kind of reverse of the Peace Corps scheme—on a much larger scale of course. It would counter the pernicious “brain-drain” effect of richer countries permanently “poaching” the most able citizens from poorer countries.

The cornucopian pro-populationist Julian Simon argued that more people meant more human creativity [7]. Presumably, by that he meant more human diversity in play. So why would not greater diversity within the boundaries of each national polity through openness to migration, not also endow each of these countries with more creativity, without necessarily the need for more people being born in each of them? In history, it has often been observed that those polities and empires most open to embracing ethnic and religious diversity have been artistically and scientifically impressive (for instance, the Mauryan Empire over 2000 years ago, Baghdad of the Abbasid Caliphate, or the late mediaeval Vijayendra Empire of Deccan India).

So, as we venture into the aspect of “populations” that addresses the implications of the Anthropocene for human fertility, we enter a field in which most statements and most arguments and evidence are immediately interpretable along at least three fairly orthogonal axes of thinking: policy implementation, the quest for understanding, and the morality of the subject—with the latter viewed from the many various viewpoints of the eyes of so many different beholders [8]. A scholar or policy-maker can offer an argument that appears unidimensional and clear to its author, but it will always be the case that it can be heard and decoded in at least these three very different ways, with endless capacity for imputing a range of further meanings. And social media, as we know all too well, only amplifies, while caricaturing, the cacophonous potential.

To this heady cocktail, we now have added into the mix the dawning recognition, in recent decades, that everything humanity has been collectively striving for over the last 250 years, organised in its respective competitive nation-state economies, has now turned out to create the most colossal problem for us all on a planetary scale. An entirely valid human desire to be freed from the harshest insecurities of nature, apparently fulfilled by harnessing the previously untapped power sources of fossil fuels and turning them into useable technologies to ease and prolong and enrich our lives, is now threatening to render us more vulnerable to nature than our worst nightmares could ever have predicted.

One further, crucial constraining problem, which the tragic hot wars in Ukraine and in Gaza, and the cold cyber wars waged between authoritarian and liberal democratic regimes all underline, is that mutual distrust, due to historic grievances between states and peoples, provides an insistent motivator, driving international military and technological rivalry, on grounds of “defence”. The cosmopolitan libertarian dream of the Enlightenment’s project of global free trade was of course to rid the world of bellicose mercantilist rivalry between imperialist hereditary monarchs, consumed by their pursuit of honour, perpetuating the ancient equation of population size with military power [9,10]. However, if mercantilism’s offense was its pro-populationist, zero-sum nationalist rivalry, instead of replacing it, modern macroeconomics has tended to view a population’s demography principally through the lens of assessing its contribution to the main goal of national economic growth through rising labour inputs, balanced against avoiding too great a dependency ratio (from excessively high fertility) [11]. This focus on dependency ratios was encapsulated in the Keynesian growth model influentially presented in the 1950s by Coale and Hoover to the government of India [12].

Meanwhile, the world of global capitalism has only added the further complication of zero-sum competition between trans-generational, trans-national corporations seeking the lowest labour costs and supercharging national rivalries, through their lobbying power. As Marx first critically analysed and as Piketty’s recent analysis confirms, in its pursuit of profitability, capitalism’s corporations relentlessly seek freedom from regulations and the whole system pits the interests of labour—those many working citizens who own little or no capital—against that of capital [13,14]. The Enlightenment rationalists, notably Adam Smith, aspired to sweep away such a hierarchical, unequal world, but extreme inequality is now back, and a powerful section of the financial elite (though by no means all—the Patriotic Millionaires are an example of a counter-inequality voice from within the financial elite [15]) believe their own self-interests trump the values and practices of liberal democracy, if they feel the latter is cramping their style [16,17].

As an academic and historian, I have spent a good part of my time critically examining how influential C20th social science models—purporting to explain how fertility decline had happened in the recent past and how it could be brought about in the immediate future—were constructed by public policy and demographic analysts to answer time-specific urgent political problems, usually defined as the supposedly excessive fertility of “others”. The problem in the late C18th was the labouring poor according to Malthus, and at the beginning of the C20th, it was once again the prolific British working-class according to early British eugenicists; by 1950, it was the less developed peasant populations of the postwar “Third World”, who might be prey to communist ideology [18]. And now, for some, it is the outsize scale of Asian and African populations; for others, it is the fertility refuseniks across the liberal democratic world.

Such models are not worthless, but their purposes and limitations do need to be interrogated since they are always abstracted simplifications, often informed implicitly, or even explicitly, by specific ideological and political assumptions or aims. Such simplifications have a functional fitness for public policy makers, whose primary role is to spend money and to act within time-constrained budgets, not to spend decades on exploratory research [19]. So, paradoxically, brevity of formulation guarantees longevity in the public policy world. The notion of “transition”—whether demographic or epidemiological—is a prime example of this [20,21]. A seemingly immortal concept in the public policy world, but one that has done precious little to enlighten us or to solve any policy problems. That is because ”transition” is little more than a framing device, which appears to provide a rationale for forms of research that are addressed to the available data on large aggregates—classically, whole nations or large geographic divisions of them. It assess the extent to which certain quantifiable characteristics are descriptively correlated with measured changes in demographic indices. But it does not attempt to interrogate the causal processes of change. In order to make academic progress with understanding the manifold considerations involved in human reproduction, especially those of past societies or of present societies living with a variety of different value systems, it is important to put aside this approach and its abstracted models and instead to investigate and explore—empirically, which means historically and anthropologically (exemplary studies include [22,23,24,25,26,27,28]).

In the rest of this article, I will not refer further to the contentious political and intellectual history of this subject, important though it certainly is. Instead, I will ask whether there is, today, a place for prioritizing a policy focus on human fertility reduction and for the further study of reproductive behaviour as an important aspect of the relationship between populations and the looming environmental crisis of the Anthropocene.

2. An Important Preliminary Distinction

It was in the 1960s, book-ended by two high profile alarm-ringing publications, Silent Spring in 1962 and The Population Bomb in 1968, when concern about the planet’s ecology first became a matter of such international public concern that the civic campaigning organisations Friends of the Earth and Greenpeace were founded in 1969 and 1971, respectively [29,30]. Widely read journals and newspapers, TV, and radio programmes began to address mass audiences on the subject. The Population Bomb firmly established a link in the public mind between the increasingly rapid rate of growth of the global human population total and the stresses being placed on the natural environment, foregrounded by Silent Spring. That link was also strongly tied to the high fertility found in much of the “Third World” (a term coined in 1952 by the pre-eminent French demographer Alfred Sauvy denoting the non-aligned countries, it rapidly came to be used as an economic one to designate all the less developed countries). The Population Bomb started with a graphic, first-person description of a taxi-ride through a teeming slum quarter in India; and all graphs of world population have continued to confirm that the main driver of the marked upturn in the rate of growth from c.1950 onwards was indeed the rapid rise in the population growth of Asia, already in 1968 the globe’s most populous continent, with 1.38 out of the world’s 2.50 billion persons [31].

So, given what we now know, after sixty years of further study and observation of the effects of substantial population growth, continuing high fertility in some parts of the world, and a range of destructions wreaked on the natural environment, both locally and more globally, what can be said about the relationship between demographic change, fertility decline, and the ecological planetary predicament of the Anthropocene era?

In approaching this question, it seems helpful to me to distinguish from the outset between, firstly, threats to the natural habitat of all other species with which we share this planet, which can be addressed as the issue of the need for the preservation of planetary biodiversity in the biosphere. Secondly, there is the issue of the stark rise in energy usage by the human species and its impact on planetary climate patterns, principally involving changes to the atmosphere and the hydrosphere and, through them, also to the pedosphere (for the best general introduction to these issues, see [32]).

The historical and continuing relationship of human fertility behaviour to the Anthropocene is not a straightforward one. Reduction to low levels can, at least, be positively looked to with respect to the first of the two distinctions offered above. Fertility decline to below replacement levels is likely, ceteris paribus, to contribute to an easing of the pressures on habitats for other species and so to assist with the preservation of biodiversity. This is currently projected to take considerable time on a world population basis, even if it is the case that a number of national populations are already registering population contractions, with Japan the most significant large economy among them, registering a 0.41% reduction in 2023 compared to 2022. Cook Islands and American Samoa registered the largest falls during these years, 2.31% and 1.74%, respectively. Most of the dozen or so Baltic and south-eastern European countries (though not Poland, Hungary, Czechia, or Slovakia) registered falls of between 0.35% (Greece) and 1.14% (Moldova), with the latter possibly reflecting effects of the war in Ukraine or economic migrant motivation [33].

However, there are at least two evident reasons why fertility decline, even to “ultra-low” levels, will probably have little net effect in reducing the rising per capita demand for energy consumption that has been such a strong characteristic accompanying Anthropocene population growth. These two are direct effects of the demographic ageing effect of populations with reduced fertility. The shift towards a higher proportion of elderly persons with relatively few kin is likely, ceteris paribus, to produce an expansion in the number of independent households per 1000 population, and this substantially raises the per capita energy consumption needs of the population. Secondly, due to their mobility and medical needs, an ageing population tends to have higher per person energy consumption requirements. In Japan, the Ministry of Environment has identified such patterns emerging ([34], citing from [35]).

These two consequences of ageing could in fact be addressed by intelligent government-supported policy. In India, for instance, in the recent past, it was most common for ageing persons to be accommodated in their children’s homes, and this was even mandated legally as recently as 2007 by the Maintenance and Welfare of Parents and Senior Citizens Act. But the reality of urbanizing India is that this pattern is now fragmenting with a much more well-educated younger generation of both sexes migrating for better-paid jobs and becoming independent (demonstrated in the research findings from different states in all the chapters in [36]). If the national or each of the 37 Indian federal state governments were to invest in a nationwide provision of optional, well-appointed old people’s homes in local communities, the latest evidence suggests many in the elder generation would elect to live with their peers; and this could be conducted in energy-efficient locations with accessible medical assistance.

3. Fertility Decline and the Anthropocene

A superficial, starting observation that an historian can offer on the subject of fertility decline and energy consumption is to note that the per capita consumption of energy rose relentlessly in all countries during the periods in which they experienced secular fertility declines. However, it is also relevant to point out that such rises in per capita energy usage were occurring in almost—but not quite—all cases for many decades before the date at which national fertility rates began to tumble; and, furthermore, that the increase in energy consumption has also continued unchecked for decades in all those cases since fertility stabilized at relatively low levels around the middle of the C20th—with some slight further correlative effect now visible in some cases (the emergence of ultra-low fertility).

This would tend to suggest that, while declining fertility may have some kind of relationship with the rising availability of cheap, inanimate energy sources that has characterized the last two centuries of global history, it is far from a precise cause–effect kind of relationship. Indeed, if we accept the seemingly incontestable point that the access of virtually all human beings to cheap, useful energy to perform various desired tasks has been the fundamental and still-continuing global transformation in living conditions during the last two centuries, then all aspects of the modern world will have this same logical relationship to this apparent prime-mover. Energy transformation has been a highly general, necessary condition for the coming into existence of practically everything in our world today, including fertility declines, but to state this truism offers no more specific explanation than that. How or why any or each of these processes has occurred requires much further enquiry.

This is especially true in the case of national fertility declines. As is well-known, French nationwide fertility declined substantially during a period of half a century before its national economic growth rate, and its per capita energy consumption began to rise significantly from the 1830s and 1840s. By stark contrast, in Britain, fertility did not fall at all but rose markedly during the first century or so of rising energy usage, c.1725–1825, during which inanimate energy derived from hydrocarbons (coal and then gas) was systematically extended from mines to industry, and in street, workplace, and domestic lighting, and so on. When the nation’s fertility finally began to fall in Britain, it did so in so many different ways [37]. In the diverse range of thoroughly proletarian communication communities, which constituted the vast majority of the population, some began to restrain their fertility from the 1860s, while others did not do so until the 1920s (textile towns fall into the former category, colliery towns into the latter. See [38,39,40,41,42]).

4. How to Approach the Population Challenge in the Anthropocene? A Thought Experiment

As is well-known, global population growth rates have been reducing since they peaked in the 1960s. According to the latest UN world population estimates, this does, nevertheless, mean that the human population total will continue to grow for the next 55 years until reaching a projected peak of approximately 10.4 billion in the 2080s [43].

To what extent, then, is there prima facie evidence that the world’s human demographic mass is the crucial public policy problem that needs to be addressed in order to avoid the worst planetary consequences of the Anthropocene era we now live in? If that were so, then the case for substantial reduction in fertility would be the only humane way to proceed, since there is no planetary scope for an emigration solution (billionaires dabbling with interplanetary colonization notwithstanding) and there is no moral case for increasing mortality.

But is human population size actually the critical problem? It would undoubtedly be helpful, ceteris paribus, if the world’s population was headed towards no more than half its current size by the end of the current century. A figure of between 0.5 and 5 billion is proposed as a range of possible viable optimum population numbers by Partha Dasgupta [44]; and see Phil Cafaro’s review [45]. But that is not quite the same thing as concluding that it is population per se that is the most significant and critical problem, whose reduction could, alone, solve our problem…if only things were so simple.

For the planet as a whole, the problem is, in fact, a compound product of human numbers multiplied by humans’ command over hydrocarbon-derived physical power to provide themselves with whatever they want in an apparently easy, cheap, and low-cost way. The problematic aspects of that power are the increased capacity with which it endows human beings to impinge on:

(a)

The natural environment—pedosphere, lithosphere, hydrosphere, atmosphere.

(b)

Other species—the biosphere.

(c)

Each other—the demosphere, fissured by its nations, religions, and other ideological groupings.

A brief historical thought experiment may be helpful. I should preface this by asking the indulgence of the temporary suspension of disbelief—as all such artificial exercises require. And, no, I do not seriously believe we could have had the current level of human population without the increasingly industrialised infrastructural support system (the “technosphere”) developed over the last three centuries.

The thought experiment is this: If there were 8 billion humans on the planet today but with the same physical power capacities that humans had just 400 years ago, we would not be talking of the Anthropocene. There would no doubt be a considerable type (c) impingement, as recorded history tells us that humans all too often fight each other when they feel there are too many “others” too near to them, though they may be happy to peacefully trade with them when they feel the “others” are at a safe distance. There would be a good deal of types (a) and (b) because, without oil, a larger proportion of the planet’s pedosphere and a greater extent of its hydrosphere would have to have been turned over to human food production to feed the 8 billion than is possible with today’s intensive and extensive oil-fed agriculture, wildly destructive though that is.

However, the destruction and pollution relating to (a) would be so much less as to be almost trivial in certain key respects if the 8 billion people on the planet only had the power technology prevailing in c.1600. Although the pedosphere would have suffered with 16 billion human feet walking on it and eating from it, neither the hydrosphere nor the atmosphere would have succumbed to the same scale of degradation that is occurring today, because that is due almost entirely to the transformation of human physical power capacities, which have accelerated alarmingly since the invention of carbon-burning engines. This, alone, is the true original direct cause of global warming and of the salination of our oceans, which I think are the two most salient defining characteristics that cause us to invoke the new geological term we are addressing in this paper, the Anthropocene. Like previous epochal geological terms, it signals the recognition that, like an ice age, the environmental conditions are changing so abruptly that mass species extinction is occurring, and only the most adaptable are likely to survive into the new age. That certainly includes homo sapiens—probably in rather radically reduced numbers—but our grandchildren just a century from now may find themselves in the company of a far smaller diversity of other mammals or primates, and a somewhat unpredictable expansion in numbers of various other species fortuitously suited or adaptable to the new warmer, drier environment—not all of them pleasant bedfellows for humans. As we all know, cockroaches will also be one of them.

5. The Evidence on Population and Energy Consumption, C.1965–2021

So let us take a look at the overall, summary evidence on population growth and energy usage since the 1960s, the decade when the public at large was first alerted to an imbalance occurring between the natural environment and human technology and numbers, with Rachel Carson’s Silent Spring in 1962 and Paul Ehrlich’s Population Bomb in 1968. A selection of relevant data is presented in the accompanying table in the Supplementary Materials.

The evidence presented there indicates that the vast, immediate problem for the planet over the next 20–30 years is not so much rapid population growth per se, which is mostly confined to sub-Saharan Africa. It is more the energy demands of two much more moderately growing or even non-growing sets of populations. Firstly, the populations of the already highly populous Asian countries, in combination with their voracious appetites—and capability—to continue the trend of the last 5 decades to catch-up and match the high-energy consumption lifestyles of the West. Secondly, the relatively static populations of the West, enjoying high-energy consumption levels, now “normalised” into daily life (e.g., air con and car usage in USA, centrally heated homes at 20 degrees through the winter in Europe).

Column 15 in the table shows the product of the percentage growth in per capita energy consumption (column 6) multiplied by the percentage growth in population (column 11) in the 1965–2021 period. At first sight, this seems unequivocally to identify China as the standout problem, which has created most of the absolute volume of increase in energy usage and consumption over the last sixty years or so, with India occupying second place on the charge-sheet, followed by Iran and Brazil. By comparison, the likes of Germany, UK, and Poland seem to be “not guilty”.

Is all this correct? Not exactly.

Firstly, we should observe that column 13 shows that China is not alone in posting an extremely large dynamic factor of a composite 13-fold increase in its overall energy consumption footprint since 1965 (increase in per capita energy consumed multiplied by increase in population size). In fact, this rate of factorial increase is even substantially exceeded by Indonesia, Iran, Malaysia, S. Korea, Thailand, and Vietnam.

However, the combined population in 2021 of all six of these other Asian countries totals 617m. This is only 43% of China’s 1.43 billion population. Due to its extreme population size, column 17 shows that, in 2021/2, the population of China, with a total of 44 million kWhs burned, massively out-consumed by ten times or more the total energy usage of any of these six individual Asian countries. It even out-consumed India by a factor of 4, since, although India’s population growth rate had been twice that of China’s—so that their populations became identical in size in 2021—India’s per capita consumption was only a quarter that of China’s. This reflects both the difference in average household income of the Chinese relative to the Indians, but also the fact that the Chinese economy is the largest exporter of mass consumer goods in the world and the second largest economy.

Column 17 shows that the only country that comes near to China in terms of total annual energy footprint in 2021/2 is—not surprisingly—USA, which was, at this date, still clearly the largest national economy in the world by GDP value (40% more than China).

USA’s total annual energy footprint in c.2021 is 26.5 million kWh, that is, the product of its per capita energy usage in 2022 (78,754 kWh) multiplied by its population size (337 million in 2021). This is therefore mainly due to its very high level of per capita energy consumption, which was already the highest in the world as early as 1965, when it was nearly double that of its nearest rivals, UK and Germany. It is only the citizens of the Arab oil-producing nations that, in 2022, out-consumed the USA, with their eye-watering amounts of energy use per citizen—in the case of the tiny UAE (9.4 m popn, but per capita energy usage of 148,577 kWh), almost twice that of each US citizen.

It is noticeable in columns 2 and 3 that the three standout leaders in per capita energy consumption in 1965 have hardly changed their per capita consumption rates 60 years later (column 4), and in the UK’s case, this has apparently reduced by 30%. Should the UK be in line for a global sustainability gold medal?

Sadly not. This is a false picture, as is shown by column 20. This shows trade-adjusted energy consumption for a few selected populations, where this can be calculated. Unlike all the figures we have been dealing with so far in this paper, this now includes the whole consumer side of the economies in question, including the energy required to produce and transport all the commodities consumed within their borders. USA, UK, and Germany all record figures in this column 23% to 53% greater than their raw, non-trade adjusted figures in column 3 (NB column 19 is Mega-Watt hrs, so 1000 times greater than column 3 in kWh).

Since the 1960s, these three have all become off-shoring, de-industrialising domestic economies, whose citizens are nevertheless continuing to consume energy at even higher rates than back in 1965; but, now, an increasing part of how they achieve this is through the consumption of goods manufactured elsewhere. And of course that much-increased volume of cross-border trade, while economically virtuous according to the classical Ricardian liberal orthodoxy of comparative advantage, entails a vastly increased consumption of sulphurous heavy fuel used by shipping and of CO₂ and NO_x aero-kerosene.

By contrast, the massive economy and population of China, the world’s largest exporter supplying those manufactured goods consumed in USA, UK, and Germany, actually shows a substantial 10% reduction of its energy consumption in column 20 compared to column 3. Other smaller economies that are net global exporters—mostly of their oil and mineral natural resources—Australia, Brazil, and Russia, also register similar reductions to China.

So, what all this evidence points to is that it is energy consumption per capita—and the polluting emissions that this entails with the current technological array—that is the primary direct cause of Anthropocene adverse effects on the atmosphere, the oceans, and the ice-caps. It is not population growth per se, and it is not the fertility of either of the two main continental population blocks (N. America and Europe) most responsible for the ecological problem that we face now and over the rest of this century. If one was simply to project forward the current global trends of population expansion along with energy consumption levels, it is the latter—per capita energy consumption—not the former, population growth, which is the chief policy problem. The world’s rate of population growth has been falling since 1971.

6. What About Fertility and Population Growth?

Does this mean fertility is irrelevant? Not entirely.

But it does indicate that, on a planetary scale, it is definitely a secondary problem—after the per capita fossil fuel energy consumption and consumerism of the wealthiest nations.

From a climate change point of view, there is almost no current “excess fertility” problem, but it can be argued there is a potential contributory one imminent among some of the poorest populations in the world, most of which are located in sub-Saharan Africa (SSA). With the exception of Pakistan and Afghanistan, it is only in sub-Saharan Africa that there are large national populations with very high fertility TFR’s of 4.0 and above (where a TFR of about 2.1 represents no long-term population growth; so, 4.0 implies a doubling every 25–30 years).

For much of sub-Saharan Africa and its relatively poor peoples, the principal way in which they currently contribute any negative impact on the world’s environment and on their own ecology is through their numbers and their rapid growth in numbers. For this part of the world, the full gamut of family planning activities and birth control technologies—but only if provided in a humane, gender-neutral, culturally respectful, and socially secure way—is the most appropriate, immediate, and current policy response needed to attempt to bring into balance their relationship with their local environments [46]. Unlike most of the peoples of the other continents, their ecological problems in this respect are not generally due to the polluting consequences of their own energy-consuming characteristics. However, they may well be subject to rising pressures on their livelihoods resulting from climate change, which can be exacerbated by their relatively high fertility, as documented in the Sahel region of Northern Nigeria, for instance [47]. Furthermore, it must be acknowledged that the “environmental” conditions among the poorest dwellers in Africa’s and Asia’s many urban centres are certainly often the most polluted and unhealthy on the planet ([48]. See the grim realities conveyed in the first-hand documentary account of a Mumbai slum, c.2007–11 [49]).

The per capita energy consumption statistics covering the 1965–2020 period are simply not available for the majority of SSA countries due to lack of reliable data for the early decades. However, it is clear from what is known about their most recent consumption patterns that they remain extremely low, by any comparative measures, even in the 2020s. Nevertheless, this is likely to rise over the rest of the century. It will be a critical test of global commitment to sustainable and renewable energy sources whether this fastest growing section of the world’s population will be effectively equipped with leap-frogging, low-emission energy technology, or not. According to the International Energy Agency, this is eminently feasible [50]. It is an extremely high policy priority.

While their communities remain very poor, there is a critical problem with any form of policy to encourage lower fertility for cultures that rightly value children and extensive kinship networks as their principal form of social security. This means that, in such impoverished contexts, in a superficial paradox, the key to fertility reduction probably lies in universal old age pensions. Probably, the only effective general policy to bring about a sufficient shift in common perceptions of personal and family security, which is necessary to radically reduce fertility, is the provision of widespread universal social security and health care to address and to satisfy fully, with an alternative state-funded and state-provided system, the security needs of the dependent elder generation [51]. Ever larger proportions of the elderly now do live into dependent old age in sub-Saharan African societies. They enjoy significantly extended average life expectancies, relative to those prevailing through to their recent past, for which their current cultures and reproductive practices have been adapted over millennia.

There is certainly a major role for the academic study of the multi-faceted aspects that reproduction plays in the many and various communication communities of sub-Saharan Africa, for any such policies to be implemented with the consent of the peoples in these poorer countries. Partha Dasgupta originally argued, in 1993, in a paper submitted to the Population Summit of the World’s Scientific Academies in New Delhi, for the importance of understanding why it is genuinely in the interests of poor parents and poor women in poor countries to have high fertility despite this being a disadvantage for the whole community, and consequently, that effective policies to reduce fertility needed to provide substitutes for the positive benefits of having children in the eyes of such poor parents [52].

For success, such policies will almost certainly require significant redistributionist financial resources, requiring at the very least a universal social security system, along with reproductive health facilities and an education programme to secondary level for both sexes to be put in place. Such publicly provided policies were being promoted in many African countries before the Washington Consensus and its structural adjustment programmes slashed all forms of public spending due to the dogma that the free market would be a better provider. It never was; and previously rising literacy rates stalled [53]. If universal female education to the completion of secondary schooling is one of the most dependable policies to bring down high fertility, then the lesson needs to be learned that the misguided and failed neoliberal policies of the Washington Consensus have been a major reason why high fertility remains today in much of SSA. The free market has never found a way to make a profit from the provision of universal education; it can only come from a national commitment to a funded public service.

In these countries, maternal mortality is probably the single most significant indicator of whether public health and population policies are, indeed, being delivered in a way that will encourage reduced fertility for humane and positive reasons. The perusal of this statistic makes for some salutary reading. In 2020, of 40 countries with the worst rates of MMR (>225 maternal deaths/100k births), all were in SSA, apart from Afghanistan, Haiti, and Venezuela (Pakistan’s rate was 154, India’s 103, China’s 23, Iran’s 22, USA’s 21, Russia’s 14, UK’s 10, and Germany’s 4). The three worst, with rates over 1000/100k, were South Sudan, Chad, and Nigeria [54].

But almost everywhere else in the world beyond Sub-Saharan Africa, apart from a small number of states where reactionary, patriarchal variants of the noble Islamic religion currently hold sway, to invoke the relationship between population and the Anthropocene in order to focus our attention primarily on numbers and fertility is something of a red herring.

7. The Immediate Ecological Problem Is Not Population and Fertility, but a Clean Energy Transition, Followed by Clean Energy Revolution

The bigger problem in the other five inhabited continents is, firstly, the extent of the carbon-emitting characteristics of the current, postwar legacy of the extant energy-producing industries and transport infrastructures serving many of these countries. Secondly, the tendency of liberal consumerist societies to encourage and even goad their citizenry into a dynamic of rising competitive mass demand for foods and for a wide range of consumer goods and services, so that measured GDP is seen to rise and leaders can stay in power. The problem is, of course, that all the goods and services delivering satisfied consumers and a rising GDP are produced and transported through unsustainable methods, which ignore the uncosted destruction of “natural capital”—the global environment—involved in their production and marketing.

In this case, there are two distinct though related issues. Firstly, the sheer level of per capita consumption among today’s richest nations. But, secondly, among some large nations that do not currently consume anything like as much per capita, there is an extremely ominous trend.

The latter problem is that both the governments and the populations of Asia want their citizens to be able to catch up and match the lifestyles of the rich “West”. The Western governments of the ex-colonial world can hardly tell them not to do so, while the world’s trading corporations, CEOs, shareholders and pension funds, tech giants, and global financial centres are all devoted to servicing as profitably as possible these “growing markets”. The world’s international development efforts, during the last 75 years, have been devoted to helping them to do just that. This has been prompted by a mix of some well-meaning humanitarianism admixed with Cold War rivalry. Although USSR is no longer the economic power it once was, such geo-political rivalry is again being revived by an economically expansionist China, with its Belt and Road incursion westwards unsettling its giant neighbour, India, and through its extensive cyber and infrastructure investments and growing government links in Africa and Latin America, from Ethiopia to Peru (In November 2024, Chinese President Xi Jinping attended that Asia-Pacific Economic Cooperation (APEC) summit held in Lima, during which the largest deepwater port on the western coast of South America, funded with Chinese finance, was opened at Chancay, capable of docking container ships that cannot go elsewhere in South America and cutting shipping times from China in half, by up to 20 days [55]).

The politically unrealist approach, it seems to me, is to hope for an aesthetic change in the consumerist habits and hopes of most national populations on the planet, in the face of moment-by-moment bombardment by the commercial global advertising and social media industries. If that is right, then the only realist approach is to take up the urgent challenge to wean our entire complex global economy off carbon-based energy sources as soon as possible and voluntarily to leave most of it in the ground. Plastics should be used only where genuinely essential and should be truly recyclable (on the myths of recyclability perpetuated by the plastics industry for the last several decades and the commercially induced expansion of plastic consumerism during the same period, see [56]). Along with the to-date unknown effects of microparticles in our own bodies, we are already faced with a parody of plastic Barbie-land in the form of two “garbage patches” each covering an area larger than France swirling round in the Pacific Ocean [57].

To address the unhealthy hydrocarbon energy addiction we collectively suffer from will require massive investments right now, 2025–2035, in the alternative technologies that we already have at our disposal, such as hydro, solar, windfarms, electric storage and grid capacities and carbon capture. This is just to get us through the next two decades without melting the Antarctic and Greenland icefields and releasing the methane under the Permafrost Tundra [58]. It is at least encouraging to note that UN Secretary-General Antonio Guterres has proclaimed ahead of the Cop-30 summit in Brazil in November 2025 that ‘The sun is rising on a clean energy age’, reflecting on the fact that solar power is now 41% cheaper than any fossil fuel. It is already the case that the economics is no longer supporting further investment in fossil fuel [59]. This will of course only, at best, radically reduce the rate at which we pump any more carbon or methane into the atmosphere, but not reverse it.

It will be vital also to pursue and to implement as soon as possible the delivery over the next 10–30 years of entirely new, clean energy infrastructure requiring superior battery technology, super conductor transmission and ultimately nuclear fusion power generation. Meanwhile many other less well-known ideas are currently being researched in universities all round the world, such as the technologies of green ammonia, sustainable concrete, artificial leaves for photo- and electro-catalysis and upcycling plastics for a more circular economy (these examples are drawn from work known to me because it is conducted by three Fellows in just one college in Cambridge, where I happen also to be a Fellow: Prof. Laura Torrente Murciano, Prof. Janet Lees and Prof. Erwin Reisner). The ‘technosphere’ is not only the cause of our current environmental problems; it is probably the only realistic solution to them that we have in the short timescale available. But the political will is also vital to corral the world’s collective financial power and resources into the right kind of technology. That is not Musk Mars-shots or wasting each other’s time and energy with cyberwarfare or—worse—military expansionism. Some of our national leaders today are acting more like children intent on sticking their fingers in each other’s eyes, not noticing the whole playground beneath their feet is sliding into an abyss.

Secondly, specific human populations in particular ecological environments do need to be studied in relation to the populations of other species, and here again, studies of fertility and reproduction can play an important role. It is not just about those flora and fauna they cultivate, which is the history of agronomy and agriculture. Often, it is the species that are pushed aside and excluded by the demands of human cultivation that are the principal source of interest if we are concerned with biodiversity. In principle, this extends to all other species, from microbes, through insects to fungi, trees, and plant life, domesticated and non-domesticated animals, creatures of the sea and air. For example, the extension of rice paddies to feed the poor of Madagascar is directly endangering the survival of several of their 112 unique lemur species [60]. Furthermore, there is a dual aspect to this, since rice paddies produce excessive methane, although there is a technology for reducing their emissions by between 30 and 90% through drip irrigation, see [61]. On AWD (Alternate Wetting and Drying) and SRI (System of Rice Intensification, see [62,63]. George Monbiot has recently produced a bold thesis, ‘Fermenting a Revolution’, not that it seems to everyone’s taste [64]. He argues that, to return space for all our fellow creatures and species for them to thrive, the over-sized human population needs to turn to photosynthesis-free precision fermentation production techniques for its food source, radically reducing the land surface and harvesting of the oceans needed for human sustenance. Lab-grown meat is another land-saving innovation already licensed and underway in both Singapore and USA with apparent potential to satisfy the enormous US chicken-demand industry [65].

We need to look carefully at the inter-related history of all other species populations to be able to fully understand what ecological and environmental effects have resulted from this peculiar dynamic of exponential human population growth, evident on a global scale since c.1900 and accelerated since c.1950. But we also need to be clear that it is power—both in its physical and its political forms—that provides the only solution. This means we cannot avoid politics and, in particular, the complexities of international negotiations to achieve such crucial changes, notably such as an end to the tax havens that are the toxic machines building inequality of wealth and power [66,67,68,69,70], or an end to the global stupidity of tax-free aero-kerosene, which is positively encouraging everybody to use high-polluting aviation, rather than surface transport.

Kate Raworth has offered a helpful general formulation for rendering into economics an understanding of the predicament of population and environment that we now face on a planetary scale. It is an application of the systems theory thinking that she calls doughnut economics [71,72]. In relation to issues of population and ecology, the essence of the doughnut model is two propositions:

• That there is an agreed social foundation of satisfactory well-being that no-one should fall below (these are essentially the 1948 package of UN Human Rights, now defined as the UN’s Sustainable Development Goals (SDGs)).
• That there is an ecological ceiling of planetary pressure that we should not extend beyond [73].

These are helpful foundational principles for a negotiated inter-governmental agreement among reasonable people, since it’s not possible to disagree with proposition 1 without expressing indifference to the well-being of fellow humans; while not agreeing with proposition 2 is dangerously irresponsible. Most unfortunately there are powerful corporate interests and some governments, including the current administration of USA, the world’s second largest total energy user in the accompanying table, which continue to deny this ‘Inconvenient Truth’ as Al Gore termed it as long ago as 2006.

To subscribe to Raworth’s propositions makes it clear that if, we endorse 1, then much greater equity of distribution must occur to achieve 1, while staying within 2. The only way to stay within 2, while still continuing with a high degree of inequity of distribution, and yet at the same time continuing to subscribe to 1, is for a massive fall in the overall population total to relieve ecological pressure. This is the implied conclusion that Partha Dasgupta’s modelling exercise points towards [44]. However, Raworth’s propositions make clear that to focus on population numbers as the primary problem omits to engage with the thorny issue of changing the direction of economic redistribution of the current global economic system, away from the top 10% and towards the other 90% ([71], p. 59). As currently constituted, this pattern is as true of China’s and Russia’s economies and elites, as it is of USA’s and UK’s, to take the two leading examples each of authoritarian and libertarian regimes currently extant.

This is why, within Raworth’s application of a complex, dynamic systems theory approach (as an alternative to static general equilibrium models of old-fashioned conventional economics), the task of redesigning economies to be equitably distributive to all their citizens should be considered alongside their redesign to be ecologically regenerative, rather than degenerative, for the environment. It is also why this requires a redistribution of wealth—which is power and control—even more than a redistribution only of income. For a highly pertinent example of the way in which, otherwise, even the production of solar photovoltaic cells—an environmentally helpful development in and of itself—has exacerbated governance problems with respect to population, when delivered through a “normal” capitalist process, see [74].

The redistribution of wealth, both within and between societies, of course, raises the most difficult issues of all.

8. And So to Politics…and to Measures

Humans have always been political animals, and we have not got a great record, with conflict frequently—though not always—an outcome when politics and its international corollary—diplomacy—breaks down. But we humans are now facing political problems of an entirely new order of difficulty.

The relatively stable and warm Holocene lasted for 12,000 years, which is approximately 500 human generations. Archaeology is now showing us just how many extraordinary human civilisations have come and gone in this time on all the continents, without apparently altering the geosphere [75]. But, with the Great Acceleration since 1950, during just the two most recent of these 500 generations, humanity has become a geological force [76]. Thus, humanity has a new responsibility for the planet. Though we can find injunctions to stewardship of nature in all the major religions, humanity has never had responsibility at this scale before, requiring co-operation among members of all religions… and very diverse political entities [77].

Is it possible perhaps that the world’s religious leaders could potentially take as much responsibility as political leaders for leading us towards the much-needed co-operative solutions to planetary challenges? Certainly Pope Francis weighed-in with two Encyclicals: Laudato Si: On care of our common home (2015) and Fratelli tutti: On fraternity and social friendship (2020); and a co-authored book [78]. Given that so much of the world’s populations are religious believers, religious leaders agreeing a common message for their followers, rather than simply continuing to tread their separate, doctrinal paths, could have considerable cultural and political impact. The key message of the fundamental importance of interfaith mutual respect was preached to great acclaim at the Parliament of the World’s Religions in 1893 by the charismatic Hindu teacher Swami Vivekananda (1863–1902). His popular text of 1896, Rajah Yoga, launched the Indian Ramakrishna movement in USA and more generally the practice of Yoga in the West [79,80,81,82]. Tragically, as we know, the following 130 years has continued to see extremist forms of religious faith motivating conflicts, though many others among the faithful do seek mutually respectful collaboration.

In addition, as Raworth points out, thanks to Elinor Ostrom, we do also have, in principle, a starting point for good practical models—even translatable to the models of liberal economics—of how to go about caring for our commons and not allowing them to become the “tragedies”, which a previous generation of economists identifed as their inevitable fate [83]. Ostrom found the answer by a comparative ethnographic study of real communities managing their commons, instead of relying on deductions from economic theory premised on the behaviour of self-interested rational individuals. She examined robust common-pool resource systems persisting for many generations in mountain grazing in Switzerland and Japan, and in irrigation systems in Spain and the Philippine Islands [84]. This showed that the successful maintenance of the commons for the mutual benefit of all those involved required three conditions to be met: (a) clearly defined communities of participant users; (b) users operating according to collectively agreed rules; (c) with punitive sanctions accepted as just for those breaking those rules. Ostrom pointed out that, with these simple ground-rules in place, the continual harvesting of natural resources was possible in a manner that was far more sustainable and equitable than either leaving matters to the commercial free market or to central direction by authority from afar ([71], pp. 82–84).

But, of course, we have to be realistic about the treacherous international political inheritance of armed distrust and cultural and linguistic division. This has not been helped at all by the last several hundred years of nationalist–imperialist land-grabbing and rivalry for a global hegemonic status among the greatest of the powers.

Meanwhile, any persistent faltering in the rising living standards of populations in the already high-consuming, rich democratic West seems to produce votes for populist, nativist leaders pedalling dangerous, potentially war-mongering fantasies about national and racial purity and supremacy. This preys on a potential political vulnerability that appears to be harboured within any liberal democracy, as was first made starkly visible in Weimar Germany in the 1930s.

This is happening again because, as Thomas Piketty and colleagues have shown, unregulated capitalism—pursued both without significant redistribution through high levels of marginal taxation on wealth and income and also with insufficient heft from the mitigating effects of an equitable, well-funded universal education system—will inherently and repeatedly exert a compound growth effect on inequality [85,86]. As Piketty demonstrated, and as independent reviews have confirmed, during the last several centuries in Europe and North America, the trans-war and postwar era in the twentieth century, c.1914–1980, was exceptional in the degree of restraint placed on capital accumulation [87,88]. We are today continuing to live with the political after-effects of a de-regulated, low-tax capitalism that was globally extended from its heartland in the USA by the growing dominance of the “Neoliberal Order”, c.1980–2008, especially intensifying after 1989 with the collapse of Soviet communism ([89]. For the most wide-ranging account, see [90]). Furthermore, the period since the Financial Crash of 2008 has seen no significant reduction in the extreme inequality built-up over the previous decades and no significant reduction in the political power of financial capitalism [91,92].

Research has now shown how this neoliberal order was a political project built by clandestinely funded organizations such as the Heritage Foundation, supported by wealthy right-wing extremists such as the Koch Brothers, and also by sections of corporate finance and industry in the USA [17,93]. It was intensively lobbying government and effectively aiming to influence public opinion from the 1970s onwards [94,95,96]. Its activism was triggered in the 1970s less by worries about supposed sympathisers with communism (which had been the cue two decades earlier for the McCarthyism in which the young Ronald Regan served his political apprenticeship), and more by fears of an articulate “enemy within”, in the form of the incipient anti-pollution and environmental protectionist movement that arose in the 1960s following Rachel Carson’s warning in Silent Spring [97,98,99].

It is important also for all citizens to fully absorb the implications of the “Pollution Paradox”. This is that “The dirtiest, most anti-social and damaging companies have the greatest incentive to invest in politics, as they are the ones most likely to face the heaviest regulation, if exposed to full democratic scrutiny” ([17], p. 75). Thus, such industries have consistently considered it entirely legitimate to spend vast amounts on agnatological denial and legal delay when faced with the harmful findings of public health and environmental science concerning the products and modes of operation through which they maximises profits [100,101]. This follows a strategy visible in the machinations of General Motors and the Ethyl Corporation from the early 1920s onwards, which successfully delayed for decades the science opposing lead in petrol [102].

The first priority of demographic social scientists today in contributing constructively to responses to the climate crisis is to be clear that neither population numbers per se, nor low fertility in rich countries, nor immigration to them are the key and most urgent environmental problems we face. Provided most of the world’s nations continue with the low and ultra-low fertility that they now exhibit, fertility is only a problem with respect to two sets of populations. Firstly, a good number of sub-Saharan African countries, whose economies and populations were severely damaged for several decades from the 1980s onwards by the exploitative, pro-corporate policies of structural adjustment imposed by the IMF, World Bank, and WTO. This misguidedly made life insecure for large proportions of these mostly rural and low-income urban migrant populations by setting its face against the provision of public services in the decades in which HIV-AIDs struck (see [103,104]; and note 11 and pp. 61–65 in [21]). Secondly, a small number of other countries, whose political regimes are actively suppressing the egalitarian rights and education of women due to the reactionary, patriarchal variants of religious ideology to which their current governments subscribe.

The more general key problem is extremes of economic inequality both within many high-income countries (notably USA with a Gini income coefficient well over 0.4) and between the OECD block and most other countries. Fixation on comparative average national GDP growth rates, on the one hand, and by individuals on their commercially-induced preoccupations with their personal materialist consumerism, on the other hand, both exacerbate this key problem. Demographers can contribute to helping resolve this by reaching out beyond their own discipline to their closest sister in the professional world, the Institute and Faculty of Actuaries, and by collaborating with other social, political, medical, public health, psychological, economic, and environmental scientists to construct alternative authoritative measures of well-being among the many populations which compose a national aggregate. These should include not only physical health but mental health. As Jonathan Haidt has shown there is an unfortunate relationship between planet-threatening commercial capitalism, competitive individualism, and mental health, notably among adolescents [105].

A relevant issue of political demography, which exemplifies the need for such multidisciplinarity, is that of whether an ageing population of ultra-low fertility would produce less interest in long-term environmental concerns, since less voters would be young or have their own children and grandchildren to consider. Current opinion polls show younger persons more sensitized to the issue. However, in the UK, for example, across the age range, the importance of the issue has risen substantially, especially during the last 15 years. Further research would be needed, but it seems that it is the salience of the environment in the news, which has grown significantly with rising global temperatures and frequency of adverse climate events, rather than age or fertility-related cohort effects, which will most strongly determine future political attitudes and the democratic will to address the problems [106].

Amartya Sen’s capabilities approach and the U.N.’s derivative Human Development Index introduced in 1990 by Mahub ul-Haq were certainly a step in the right direction. But its influence was stymied because it was side-lined over the following decades by neoliberalism’s Washington Consensus and the GDP-focused, free-market structural adjustment policies of the World Bank and the IMF. Today, students of populations can contribute by re-engaging fully with the capabilities approach and with the complex systems approach of Kate Raworth. Also with the related ideas of Elinor Ostrom and others [107,108]; and with the several other important new departures in the field of economics, such as Partha Dasgupta’s focus on “natural capital” [109] and Diane Coyle and colleagues’ additional attention to knowledge capital, human capital, and social and institutional capital [110,111].

What this means in practice is a drive by students of populations towards compositional demography. It is already known that it is not population size per se, but the number of households that is a primary demographic unit where resource consumption is concerned [112]. But compositional demography involves far more, sociologically. We need an historically sensitive appreciation of the multi-dimensional significance of reproduction outlined at the outset of this article. We need to understand the perceived relative costs and benefits of childrearing and child-care in different settings, which requires studying the complexities of the values and religious convictions held by communication communities (of which online Influencers are also a new example) and the relationships among them as they change [113,114]. This is in order to identify more precisely how pressures on the well-being of groups within larger national aggregates occur, while others within those same aggregates may be contributing most to unsustainable pressures on the environment.

These compositional populations and the different communication communities within a national population (and, indeed across national populations, facilitated by the internet and social media) are key items of socio-demographic intelligence for understanding the evolving politics, culture, and economics of populations. It is certainly a challenge, as they require a more politically attuned and sociologically and anthropologically discriminating approach to data collection (see the many examples of the gains to be had from this in the various chapters in [115]). This is needed for students of populations to provide fully informed advice for public policy to political and religious leaders on the realistic and effective remedial population and economic policies required to help navigate safely and with equity the relationship between populations and the environment in the Anthropocene century that lies ahead.