Introduction: what is unsustainability?

Several studies have charted a long history of ‘growth criticism’ (Hayes 1976; Kassiola 1990; Smith 1979). The problems of endless growth on a finite planet were recognized as long ago as Marsh (1864) and repeated by Vogt (1948), Boulding (1966) and Ehrlich (1968). However, in the 1970s, Meadows et al. (1972) pushed the ‘limits to growth’ perspective into the public arena, which has been revisited many times since (Wallich 1982; Turner 2008, 2014). Several scholars—perhaps most of all Georgescu-Roegen (1971) and Herman Daly (1991, 1996)—critiqued, in particular, the fundamental assumptions shared by otherwise rival schools of economic thought, ranging from Marxism to monetarism.

Such analysis highlighted that increases in the human population are the critical driver of environmental impact, normally as part of the so-called ‘I = PAT’ formula (Ehrlich and Holdren 1972; Ehrlich and Ehrlich 1991). In this, environmental impact is the product of the human population, per capita consumption (affluence) and technology (Ryerson 2010). Several studies have vindicated the fears expressed by ‘limits’ authors that the combination of these forces would generate a global crisis of unsustainability that could threaten the very viability of human society, as well as the survival of a myriad nonhuman species (e.g. MEA 2015; Turner 2008, 2014). While some authors argue that population growth in poor countries is not a problem, as the poor consume less than the rich in Western countries (Wijkman and Rockström 2012), such assumptions do not take into account the fact that the world is no longer divided into ‘rich’ and ‘poor’ countries—the middle classes (and the consumption patterns associated with them) are growing especially rapidly in developing countries (Cafaro and Crist 2012). While Malthus did not predict that developments in medical and food production technologies would help sustain billions of people on Earth, the presence of ultimate limits on growth on a finite-resource planet cannot be discounted (Ehrlich and Ehrlich 1991). Also, people from developing countries increasingly (attempt to) migrate to richer countries, which is certainly understandable from human rights and social justice perspectives (Cafaro and Crist 2012). Beyond Malthusian concerns about potential conflict and starvation, the link between population and sustainability is also apparent for one biological reason—whether rich or poor, Homo sapiens is a relatively large omnivore, consuming other plant or animal species on a much larger scale than, for example, ants, which are more numerous than humans but are no threat to the rest of the world’s species. Simply put, this Earth is not able to support 8 billion omnivores indefinitely without endangering (wild) species or enslaving domestic ones through intensive feeding operations (Crist 2012).

However, the radical measures that were proposed to address the limits to growth gave way to a more optimistic belief in what has been described as a ‘balanced’ approach to the economic, social and environmental dimensions of sustainable development in the Our Common Future report (WCED 1987). In that report, sustainable development is described as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” (WCED 1987, p. 4). However, the optimistic balancing of economic, social and environmental objectives has not worked. Climate change and biodiversity loss—as testified by the Millennium Ecosystem Assessment (MEA 2015), the Intergovernmental Panel on Climate Change (IPCC 2019) and the IPBES (2019) report on extinction—demonstrate worsening conditions.

Following the First Warning to Humanity issued by a group of concerned scientists in 1992 (UCS 1992), the Second World Scientists’ Warning to Humanity signed by thousands of academic researchers in 2017 states that:

We are jeopardizing our future by not reining in our intense but geographically uneven material consumption and by not perceiving continued rapid population growth as a primary driver behind many ecological and even societal threats … (Ripple et al. 2017).

One of the central issues is that of endless growth—particularly economic and population growth. Besides growth, the current sizes of our population and our global economy are the root causes of unsustainability. As Engelman (2016) has argued, even if it stopped growing now, our present production and consumption pattern is unsustainable. Thus, we should stop growing and then recede, demographically and economically. The question of population growth is a crucial one, simply because the more consumers there are, the more pressure there will be on the Earth’s life support systems. In the case of economic growth, suggested solutions include degrowth (e.g. O’Neill 2012) and the steady-state economy (Daly 1991, 2014). However, the population issue requires country-level solutions. This article will canvass the idea that understanding different countries’ barriers to addressing population growth might build on the generic warning to humanity. In that warning, Ripple et al. (2017) wrote that they:

… believe that prospects will be greatest if policymakers and the rest of humanity promptly respond to our warning and declaration of a climate emergency, and act to sustain life on planet Earth, our only home.

However, humanity seems to have been largely unable to act. Part of the difficulty is the fact that population growth is not the same in all locations. For example, some Mediterranean countries (Cyprus, Italy, Spain, Greece and Portugal) have the lowest fertilities in the world, while many countries in Africa and some in Asia, South America and the Middle East have stable but consistently high birthrates (above the replacement level of a total fertility rate below 2.1) (The World Bank 2017a). Campbell (2012, p. 46) points out that the issue of political correctness regarding population growth has caused the discussion of population growth to become taboo, with derogatory terms such as “Malthusian” and even “demographic” being used. Thus, the topic of population has become very politically loaded (Kopnina and Washington 2016; Washington et al. 2019). Why is it such a contested topic?

This article explores both issues: economic growth and population growth. We reflect on how we can best address environmental unsustainability and poverty through an effective, noncoercive population policy that is sensitive to social and cultural context. We propose a more nuanced and culturally/socially tuned-in reflection on how sustainable population levels may be reached. As this article will argue, demographic solutions must be voluntary and noncoercive, but cultural issues associated with reducing population growth must also be considered.

Economic growth and industrial development

The mantra of endless economic growth underpins neoclassical economics (e.g. Daly 1991; Washington 2014; Victor and Jackson 2015; Rees 2019). However, as noted above, many scholars have questioned the physical feasibility and social desirability of this. The fundamental alternative to growth-focused economics has been the steady-state economy developed by Daly (1991, 1996, 2014). A steady-state economy features three characteristics:

  • A sustainable population size for the carrying capacity of its region (Daly 1991)

  • A distribution of wealth that is fair and equitable on an intergenerational basis (Daly 1991, 2014)

  • Low resource use (Daly 2014).

Czech (2013), Dietz and O’Neill (2013), Washington and Twomey (2016) and Victor (2019) have variously discussed the steady-state economy, ecological economics and degrowth. Reflecting on degrowth, O’Neill (2012) proposes that society can sustainably improve wellbeing but only by discarding GDP growth as the key goal in favor of more comprehensive measures of societal wellbeing.

It seems that 100% decoupling may be just wishful thinking that allows business-as-usual growth to continue (Wallich 1982; Turner 2008; Bithas and Kalimeris 2016, 2018; Washington and Twomey 2016; Kopnina 2019). There is also a debate on whether ‘isms’ such as capitalism, socialism and communism are compatible with meaningful sustainability, as these political systems remain committed to further economic growth (Washington 2015; Kopnina 2016).

Other ecological–economic models relate to growth, or how growth might be achieved. Chief among these is UNEP’s (2011) green economy, the circular economy (building on the cradle-to-cradle approach) and ‘doughnut’ economics. As promoted by the Ellen MacArthur Foundation (EMF 2014), the circular economy supports further growth via absolute decoupling. However, this is impossible for material resources (Rammelt and Crisp 2014; Washington and Twomey 2016; Kopnina 2019).

The cradle-to-cradle framework (McDonough and Braungart 2002) poses that the current industrial system of production is unsustainable, but also argues that the focus on eco-efficiency and ‘cleaning up the debris’ does not consider the root cause of unsustainable production. Most products and packaging that are currently used are not made to be biodegradable or even recyclable, let alone infinitely reusable in a circular system in which no new raw material input is needed.

In her book Doughnut Economics, Raworth (2017) acknowledges the problems of growth but then states she is ‘growth agnostic’. However, as endless population growth and economic growth are the root causes of unsustainability (Daly 2014), an ecologically sustainable economy needs to operate within ecological limits (e.g. Rees 2019). This would require an overall strategy of degrowth (O’Neill 2012) to a steady-state economy, with an ecologically sustainable population and low resource use (Daly 1991). However, while is it true that growth itself cannot be sustained indefinitely on a finite planet, if we had a steady-state economy and population that overwhelmed the capacity and resilience of natural resources, ecosystems and species, these two influences would be unsustainable at their steady-state scales.

Overproduction, overconsumption and poverty

Following the devastation of the Second World War, the USA and Western Europe specifically focused on the expansion of a consumer economy as well as job creation (Assadourian 2013). The subsequent growth in population, consumption and resource use has caused pollution, rapid climate change and biodiversity loss. Critical scholars have noted that the idea of poverty alleviation through economic growth is a euphemism for a transition to an industrial consumerist monetary economy, which is entirely unsustainable in the long term (Daly 1991; Crist 2012). In the context of decolonization and “developing” countries, it was assumed that economic growth would solve poverty, as a ‘rising tide will lift all boats’ (Johnson et al. 2011). This assumption has been used to justify the excesses of overproduction and overconsumption (e.g. McDonough and Braungart 2002; Daly 1991).

While promoting growth appears to be an almost costless pursuit, the recurring issue is whether this growth reaches the poorest and most vulnerable sectors of society (Johnson et al. 2011). Often, economic growth only seems to benefit the rich or the corrupt as the ‘trickle-down effect’ is weak, so it does not reduce overall poverty (Ravallion 2001). Poverty due to unemployment is not going to be solved by economic growth, as unemployment occurs due to improvements in technology, automation, and the increasing need for fewer but more highly skilled professionals (Johnson et al. 2011).

Critics have also noted that economic growth cannot solve the root causes of poverty, especially considering that population growth accentuates the challenges of poverty (Washington and Twomey 2016; Washington and Kopnina 2018). Economic growth has resulted in rising income disparities, ignoring the disadvantages women face in many societies (Babacan 2010). The disadvantaged position of women has also often meant that they have no access to family planning, resulting in unwanted pregnancies and population growth (Engelman 2016; Crist et al. 2017; Lamme et al. 2017). This is not to suggest that gender equality should take priority over other barriers to demographic change or environmental management actions. However, as the literature examined here suggests, the reproductive rights of women and limits on their freedom to terminate unwanted pregnancies are crucially important for understanding population growth, as will be further expanded upon in this article.

Hence, we argue that governments should instead focus on and address the drivers of both population growth and economic growth. That means reducing overproduction and overconsumption, as these degrade the Earth’s life support systems, which all of us (especially the poor) rely upon (Washington 2015).

The population question

Population was raised as an issue by Thomas Malthus more than 200 years ago (Malthus 1826 [1798]). Paul Ehrlich (1968) pushed this issue back into the public arena, generating renewed controversy. What is new is the resistance to the idea that population pressure causes social and environmental problems (Kopnina and Washington 2016; Washington et al. 2019). Some critics have argued that Malthus and Ehrlich have underestimated human ingenuity, especially regarding technological innovations in medicine, food production and pollution prevention. They suggest that the Earth is presently able to support over 7.7 billion people, and could potentially support 10 billion by 2050 (e.g. Lam 2011; UN 2019). There is a general assumption that the population question will solve itself through a demographic transition (critically discussed in Campbell 2012). Hence, most countries seem to ignore or deny the connection between environmental damage and population.

However, as many scholars note (e.g. Catton 1982; Ehrlich and Ehrlich 1991; Daly 1991; Brown 2011), the Earth does not have unlimited resources if both the economy and the human population keep expanding. Demographic and population expansion, in today’s world, add to the risk of destructive interactions with these limits, many of which are already being felt at current population and economic scales. While medical and food production technologies already support a large and growing population, they have their limits on a planet of finite resources (Meadows et al. 1972; Mavrommati et al. 2006; Rees 2010). Currently, refugees are moving out of areas that cannot sustain them because local environmental tipping points have been exceeded due to a convergence of decades of higher than (the global) average population growth and a climate crisis that limits local food production and water supplies. One could argue that there is evidence that actual unsustainability is a driver of emigration, as in the case of climate refugees. This is overlaid on local political and societal systems that have long histories of ethnic or religious rivalries (Holland 2019).

Population growth has been linked to multiple social and environmental issues, including poverty and environmental devastation due to the increased demand for natural resources (Meadows et al. 1972; UNFPA 1994; MEA 2015; Wijkman and Rockström 2012; IPCC 2019). However, only limited government action on population has been undertaken since the International Conference on Population and Development (ICPD) held in Egypt in 1994. Little action has been taken because it was assumed that a demographic transition would take place universally that would decrease fertility rates across the world, so the population issue would solve itself (Campbell 2012). This theory posits a transition from high birth rates and high infant death rates to low birth rates and low death rates as societies become wealthier. The lack of government concern about population growth and their unwillingness to spend money on a controversial arena of health care that some powerful political constituencies object to have prevented further action.

However, while the shift to low birth rates has occurred in many industrialized countries, and global mortality rates of mothers and infants have decreased, as reported by the World Health Organization (WHO 2018), demographic transition theory does not appear to apply globally. This is due to specific social, political and economic factors (Campbell 2012). While medical advancements have become universal, saving millions of lives, and GDP has risen across the world, including in poorer countries (The World Bank 2017a), not all countries have low birth rates. There are various possible reasons for this.

Some governments have provided access to family planning information and services, as recommended by ICPD conference resolutions (UNFPA 1994). However, the statistics indicate a population increase of more than two billion people between the time of that conference and the writing of this paper—the global population was around 5.5 billion in 1994, it exceeded 6 billion around 1998 or 1999, and is 7.7 billion today (The World Bank 2017a). We point out that it is significant that influential international agencies such as the United Nations and global financial institutions such as the International Monetary Fund (e.g. Kunmakara 2017) and The World Bank (2019b) assume that an increasing population is connected to economic growth, which in turn, is also seen as a good thing (Kopnina and Washington 2016).

While some of these international agencies recently seem to have realized that population growth might be more of a curse than a boon (The World Bank 2017a), even for economic growth, the global rhetoric of the population question remains overwhelmingly optimistic, so there is no concerted effort to address population growth as a problem (Kopnina and Washington 2016; Washington et al. 2019).

It has been argued that it is part of human nature to increase in number when food and medicine are readily available (Rees 2010; Salmony 2019). However, not all humans (or, for that matter, all cultures) behave the same in the age of effective contraception. Another significant issue with an increasing population is the lack or poor availability of contraceptives or a knowledge of how to obtain or use them, particularly in developing countries (Chipeta et al. 2010; Wijkman and Rockström 2012) and in communities with lower economic status in developed nations (Kelly and Fernandez 1993; Lamme et al. 2017). In some cases, there is a lack of basic human/women’s rights (e.g. Ratcliffe 2018) that could protect against child bride marriages (Ezer et al. 2006). These occur at a remarkable level of 39,000 a day (UN 2013) and often result in millions of unwanted pregnancies (Wijkman and Rockström 2012; Engelman 2016; Crist et al. 2017; Lamme et al. 2017). Other factors concern cultural or religious taboos against using contraception that promote large families (Chipeta et al. 2010; Sultan 2018).

Additional reasons are identified in the volume Life on the Brink: Environmentalists Confront Overpopulation (Cafaro and Crist 2012). This volume has many thoughtful contributions to the issue of population and underlines the realization that human expansion seems to have resulted in a denial of population growth. This is expressed as a crisis of perception in which humanity seems so

“ill-informed of its actual situation, so mesmerized by the imperative of infinite expansion, so deeply in denial of its suicidal trajectory, that it celebrates hitting seven billion … and looks forward to adding another two or three billion by the end of the century” (Hawkins 2012, p. 202).

The authors of the chapters in Cafaro and Crist (2012) are correct to point out that population growth is a major force behind our most serious ecological problems. However, the question of policy in various countries, or the fact that in some countries the birth rates have not declined—is not discussed in detail in that book. One of the issues is that, simply put, population growth is distributed unevenly across the globe. In some countries, notably most sub-Saharan countries, women have more than 7 children on average (World Population Review 2017; UN 2019); however, as predicted by demographic transition theory (Campbell 2012), there are also countries below the replacement level, including Albania, Bahrain, Belarus, Bosnia and Herzegovina, Georgia, Iran, Italy, Japan, Korea (South), Lebanon, Macau, Malta, Portugal, Qatar, Russia and Australia (World Population Review 1997). The fertility rate in Niger (West Africa) is 7.1, but women on the Mediterranean island of Cyprus are having, on average, just one child (Gallagher 2018; UN 2019).

When discussing population growth, it is important to carefully consider exactly what it is that differentiates countries with high fertility rates. This subject is particularly sensitive in developing countries, as accusations of racism and Western colonial ‘meddling’ are commonly made, especially when it comes to limiting childbirth (even when noncoercive measures are explicitly proposed). A dialogue is thus especially important, since population growth has recently become a taboo topic that is charged with political correctness (Campbell 2012; Kopnina and Washington 2016). Some population-related policies, such as the one-child policy in China (The Economist 2016) and the former sterilization policy in India (Biswas 2014), have caused protests by human rights groups (Biswas 2014; The Economist 2016). Clearly, from almost any moral/ethical standpoint, coercive population measures can be seen as inhumane. Yet, the issue is not so much about misguided coercive policies but a total lack of any—voluntary, humane, noncoercive, positive—policy at all. Indeed, some countries actively stimulate greater population growth. One can argue that, historically, most of the coercion has been directed towards women—forcing them to have more children than they want due to limitations on birth control and abortion restrictions.

In some countries, having children is seen as a great investment in the economy, the military, etc. In many countries, high fertility is seen as a good thing, as demonstrated by the pro-natalism policies evident in, for example, France (Deutsche Welle 2005), Scandinavian countries (The Local 2019), Spain (BFSC 2007), Germany (Kirschbaum 2007), Russia (Theroux 2017), Canada (Serebrin 2018) and Chile (BAT 2019). Generally, higher population growth is seen as good for economic growth (which in itself is a problem if sustainability challenges are to be addressed). A young labor force is perceived as supporting pensioners or providing more people for the army, enhancing a military advantage over other countries.

It is important to get around this problem by stimulating noncoercive measures of family planning that can benefit both the planet and future generations of humans and nonhumans. One suggestion is provided by Eileen Crist (2012, p. 146), who has looked at the ‘best case studies’ of policies in countries like Iran:

In numerous countries where such measures have been spearheaded by governments, backed financially and implemented competently, fertility rates swiftly declined. Iran is perhaps the most striking case of the results of a successful population policy: from an average of 5.5 children per woman in 1988, fertility declined to 1.7 in 2009. The catalyst for this transition was the reinstatement of Iran’s family planning program in 1989, coupled with an educational, cultural and healthcare crusade to encourage and enable the choice of smaller families. Among other measures, this all-out effort included the creation of fifteen thousand health clinics to service rural populations, a campaign to raise women’s literacy, media programming to raise consciousness and disseminate information, and the provision of all forms of birth control free of charge (Brown 2011 in Crist 2012, p. 146).

When examining this successful policy, it is useful to understand the social and cultural climate that existed in Iran prior to the introduction of this policy, the types of motivation used by local politicians, the media, how was the policy was translated into a publicly shared understanding and actual practice, and how the policy was received (to ensure its long-term effects). In the well-documented case of Iran, there was a concerted approach that included education at all levels, the provision of family planning advice and contraceptives, the removal of financial incentives for large families, and even the inclusion of religious leaders to avoid a perception that limiting family size was inconsistent with the teachings of Islam (Derer 2019a).

A similar concerted approach successfully reduced the rate of population growth in Tunisia (Fig. 1) to replacement level (Derer 2019b). As in Iran, the education of women, the provision of family planning services and the enlistment of the support of religious leaders for what was described as a modern version of Islam were critical to the success of the program. These concrete examples show that culturally sensitive and intelligent policy that incorporates a long-term vision of both ecosystem and human wellbeing can succeed in stabilizing the human population in a developing country.

Fig. 1
figure 1

Tunisian family

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There are some other positive signs. Even organizations that were previously only interested in stimulating economic growth and industrial development in developing countries are starting to be more population conscious (Gates Foundation n.d.; however, we note that the Gates Foundation remains primarily focused on human welfare, as their slogan ‘all lives have value’ does not extend to billions of nonhuman beings). These include the World Bank (2017a), the IMF, and some NGOs that were formerly only concerned with improving the health and the economic position of poor people. However, we suggest that greater consideration of the cultural backgrounds of countries with high population growth rates is needed.

Noncoercive, voluntary solutions to reduce population growth

Robert Engelman (2016) has proposed several excellent noncoercive solutions to reduce population growth:

  1. 1.

    Assure universal access to a range of safe and effective contraceptive options and family planning services for both sexes

  2. 2.

    Guarantee education through secondary school for all, with a particular focus on girls

  3. 3.

    Eradicate gender bias from the law, economic opportunity, health, and culture

  4. 4.

    Offer age-appropriate sexuality education for all students

  5. 5.

    End all policies that reward parents financially if they are based on the number of children they rear

  6. 6.

    Integrate teaching about population, environment, and development relationships into school curricula at multiple levels

  7. 7.

    Put prices on environmental costs and impacts

  8. 8.

    Adjust to population ageing rather than trying to delay it through government incentives or programs aimed at boosting childbearing

  9. 9.

    Convince leaders to commit to ending population growth by exercising human rights and human development.

A key question is: how have these proposed solutions been received? Similarly, to what extent are these policies applied by governments? Table 1 indicates whether each solution is being applied in the three countries researched.

Table 1 Implementation of the nine solutions to reduce population growth, as suggested by Engelman, in three countries: Tanzania, Italy and Cambodia (data obtained from research on the internet; see the “Appendix”)
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Considering Engelman’s nine solutions for three case studies (Tanzania, Italy, Cambodia)

Explanations of the responses for each case study are shown in the “Appendix”.

Discussion of the case study results

The three countries discussed above are interesting examples to test Engelman’s (2016) nine solutions. In regard to Tanzania, the environmental outlook for this country is clearly unsustainable (The World Bank 2019b), as it has a high birth rate (5.2 babies per woman) that leads to an annual population growth rate of 3% (Worldometer 2019a), with 63% of the population aged 24 or below (Omondi et al. 2019; UN 2019). Among the nine suggested solutions, only solution five could be considered to be implemented in Tanzania, and even this is debatable given that the government actually encourages more births, although this encouragement is not financial in nature. The ‘bride price’ system in Tanzania encourages child marriages and associated high birth rates (Girls Not Brides 2017), and appears to be a cultural practice that strongly supports ongoing population growth. Notably, only 32% of the country’s households use any form of contraception, though many women express a desire for it that remains unmet. It is projected that by 2050 the population of Tanzania could rise from 58 to 138 million (The World Bank 2019b). Population growth in Tanzania is out of control, and while NGOs struggle to assist, the government is failing to attempt to stabilize this.

An obvious problem is the attitude of the government. Fertility rates have come down from almost 7 in the 1960s to the present level of 5.2 (The World Bank 2019a; UN 2019). However, in 2018, Tanzanian President Magufuli said that Western governments with ‘their family planning’ should not meddle in population affairs, and actually urged Tanzanian citizens to have more children (BBC News 2018). As is clear from news articles, the Tanzanian President assumes that having more children is not counterproductive to reducing poverty—that a larger population will in fact serve the economy the way he thinks it did in China and Nigeria (Ng’wanakilala 2019). Ironically, he forgets about China’s one-child policy, which has only recently been altered, and about the fact that the >175 million-strong population of Nigeria is one of the world’s poorest and most unequal (The World Bank 2019a). Magufuli seems to believe that having a larger population will help stimulate economic growth and lift people out of poverty (Ng’wanakilala 2019). He reassures citizens that they are safe to have more children in his supposedly healthy economy by denying free access to contraception (Ratcliffe 2018), despite data from the UN Population Fund (UNFPA) showing that Tanzania’s population is growing by about 2.7% a year while most public hospitals and schools are overcrowded and many young people lack jobs (Ng’wanakilala 2019). Tanzanians’ own perceptions (prior to the present President’s ‘stimulus package’) (e.g. Mosha et al. 2013) as well as limitations on access to health care (Mbeba et al. 2012), perceptions of early marriages (Mosha et al. 2013) and the social acceptability of certain sexual behaviors (Stark 2013) in Tanzania may all be contributing to the relatively high birth rate in this country.

Italy provides an interesting case study, as its population is officially in slow decline, though this may reflect poor statistics on the extensive influx of illegal immigrants. Indeed, the Italian government is seeking to boost childbirth (Wyatt 2018). However, despite government policy, the Italian TFR remains one of the lowest in Europe at 1.34 children per female. The most interesting aspect of the nine Engelman strategies for Italy is that only the first three are actually implemented (and the third not fully so). This suggests that the first three solutions are key to slowing population growth and then stabilizing the population. In an email, Engelman (2019, personal communication, 21 October) suggested that nonstrategic factors are the main reasons for the low fertility in Italy and some other countries—especially a lack of housing, the realization by women of the unfairness of male refusal to bear childrearing and housekeep burdens, etc. Thus, access to contraception (and safe and legal abortion) is essential, but it must be combined with a strong interest by women in not having more pregnancies and births than they desire (R Engelman, 2019, personal communication, 21 October). It should be noted that environmental education (solution six) is improving in Italy, but it is clear that the low TFR in this country is not due to environmental education, as it has only been implemented for a few years. The same applies to the repricing of environmental costs—changes are underway, but it is hard to say how serious those changes are. They have clearly not caused the low TFR. Although Italian society may be adjusting to population ageing, it is apparent that the Italian government has no formal programs to facilitate this (at least at this stage). Also, while the Italian Department of the Environment is encouraging green growth and the green economy, both are arguably dubious in terms of their ability to sustain the environment (Twomey and Washington 2016; Washington and Maloney 2020). Overall, the results of the case study of Italy suggest that the first three of Engelman’s solutions are the most critical for stabilizing the population, while the other solutions can help Italy to become more sustainable as a society without necessarily being essential for population stabilization.

The horrendous genocide of the Khmer Rouge regime claimed two million Cambodian lives out of a population of just over 8 million between 1975 and 1979 (Fitch 2015). Cambodia’s population has been recently on the rise, reaching over 16.5 million in 2019 (World Population Review 2019). In 2016, its youth aged between 10 and 24 comprised 35% of its population (UNFPA 2016a, b). The recovery and rise in population are still greeted as signs of political, economic and social success in overcoming the recent traumas of war, and also as a boon—a ‘demographic dividend’. This term refers in this case to the (incorrect) perception of a high birth rate as a driving force for financial development, although it can also refer to the reduction in the dependency ratio caused by decreased fertility (Kunmakara 2017).

We suggest that without talking about birth rate, policy and cultural differences between countries, the generic recommendation to curb population for the sake of future generations (not to mention the environment) will not work. Tanzania has a 3% growth rate (Worldometer 2019a) while Cambodia has a 1.46% growth rate (Worldometer 2019c); Italy, in contrast, has a slightly negative growth rate (Worldometer 2019b). It is clear that family planning and contraceptive use is low in Tanzania and Cambodia (as it is not strongly supported by the government) and that child bride marriage is common, with bride price driving this practice. Italy has virtually no (legal) child bride marriages and has excellent access to contraceptives and family planning plus guaranteed access to female education. Italy has also largely addressed the worst aspects of gender bias, while Tanzania has not done so, and Cambodia has only partially addressed them.

From these case studies, it seems clear that there are major cultural barriers in Tanzania and Cambodia that keep population growth rates high. The key cultural practice is child bride marriage, and one can only wonder what a difference it would make if this was made illegal. The other obvious problem in Tanzania and Cambodia is poor access to contraceptives and family planning, in part due to the failure of their governments to support them. The failure to educate girls in Tanzania and Cambodia is also clearly a major problem, along with the failure to eradicate most gender bias. It is notable that NGOs seem to represent the positive path for change to reduce cultural barriers in both Tanzania and Cambodia. Understanding such cultural barriers is crucial to successfully implementing Engelman’s (2016) nine noncoercive solutions to overpopulation.

In addition to these solutions, the cases above warn us to be sensitive to social and cultural contexts. There can be traditional or religious taboos against using contraception or a historical and political background that influences the positive perception of having a large number of children. In Cambodia, for example, which has suffered war and genocide, having children can also be seen as a symbol of literal ‘revival’ or ‘regeneration’. In the case of Tanzania, the traditional practice of child bride marriages and teenage pregnancies conflicts with what can be seen as a Western idea of basic human/women’s rights.

The cases of Italy, Iran and Tunisia, which may be considered ‘best practices’ for lowering fertility to some degree, require an understanding of the roles of local politicians, the media and public perceptions in encouraging smaller families. We suggest here that intelligent and humane policy that is sensitive to country and cultural contexts is needed to achieve a global reduction in population growth. The successful case studies listed above reinforce Lowe’s (2016) conclusion that the birthrate is low in countries where women are well educated, secure and in control of their fertility.

Conclusion

We note that past and present growth in population, consumption, resource use and the economy are the key drivers of unsustainability, and that degrowth, the steady-state economy and the circular economy (and the cradle-to-cradle vision) offer solutions for reorienting our economy to one that is ecologically sustainable because it operates within ecological limits.

Regarding population, we praise Engelman (2016) for his nine noncoercive solutions to population growth. However, his strategies, arranged in order of what he perceived to be decreasing effectiveness, require more evidence in order to measure their strength and to identify which of them matter the most (R Engelman, 2019, personal communication, 21 October). However, the case study of Italy suggests that the first three strategies are most important for stabilizing the population. This is consistent with Lowe’s (2016) criteria. The cultural practice of child bride marriage in Tanzania and Cambodia is clearly a key barrier to reducing population growth. This could be addressed by introducing a government ban, or perhaps more successfully by changing what society deems to be acceptable, which could be catalyzed by the education of girls to at least to full secondary level. Education of girls (and their families) thus remains essential (Crist et al. 2017). However, there is a clear political block in Tanzania and Cambodia regarding support for readily available contraceptives and family planning and for eliminating the worst aspects of gender bias. The UN and international organizations can play a role, but national governments and educational campaigns, as well as local media, need to be leaders in this change.

In the case of population growth, we note the fact that birthrates are not equal throughout the world. While the Tanzanian and Cambodian governments might be convinced that having more children is good for their countries, if the citizens themselves can be educated and helped to change, the birthrates in those countries may reduce markedly. We believe that statistics of poverty, mortality and unemployment do not lie, and that smaller families do indeed tend to be healthier, wealthier and certainly much better for the environment. In this regard, some of the countries in the Mediterranean present good examples of best practices. We thus suggest that greater consideration of the cultural backgrounds of countries with high population growth rates is needed. Translating the Scientists’ Warning to Humanity into culturally acceptable rhetoric is, however, an ongoing challenge.