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Climate ethics and population policy: A review of recent philosophical work



It is well‐established that human population growth is a leading cause of increased greenhouse gas emissions and accelerating global climate change. After decades of neglect, philosophical ethicists have, over the past decade, taken up the issue of climate change and population policy and there are now numerous articles and books which explore the subject. Both rights‐based and consequentialist approaches seek to balance reproductive rights against other human rights and interests threatened by overpopulation and ecological degradation. While biocentric ethicists have additional reasons to advocate for smaller human populations, even anthropocentrists affirm the need to balance reproductive rights against reproductive responsibilities in order to promote the well‐being of future generations. There is a particularly strong consensus on the value of choice‐enhancing population policies that reduce fertility voluntarily, such as securing universal access to modern contraception and promoting equal rights and opportunities for women. There is strong support for government policies that incentivize smaller families, some support for policies that disincentivize larger ones, and little to no support for punitive policies. Many ethicists warn that failure to enact reasonable population policies now may necessitate harsher policies in the future, a common theme in climate ethics generally. This article is categorized under: Climate, Nature, and Ethics > Ethics and Climate Change
Climate ethics and population policy: A review of recent
philosophical work
Philip Cafaro
Department of Philosophy, Colorado State
University, Fort Collins, Colorado, USA
Philip Cafaro, Department of Philosophy,
Eddy Building, Colorado State University,
Fort Collins, CO 80523, USA.
Edited by: Megan Blomfield, Domain
Editor, and Mike Hulme, Editor-in-Chief
It is well-established that human population growth is a leading cause of
increased greenhouse gas emissions and accelerating global climate change.
After decades of neglect, philosophical ethicists have, over the past decade,
taken up the issue of climate change and population policy and there are now
numerous articles and books which explore the subject. Both rights-based and
consequentialist approaches seek to balance reproductive rights against other
human rights and interests threatened by overpopulation and ecological degra-
dation. While biocentric ethicists have additional reasons to advocate for
smaller human populations, even anthropocentrists affirm the need to balance
reproductive rights against reproductive responsibilities in order to promote
the well-being of future generations. There is a particularly strong consensus
on the value of choice-enhancing population policies that reduce fertility vol-
untarily, such as securing universal access to modern contraception and pro-
moting equal rights and opportunities for women. There is strong support for
government policies that incentivize smaller families, some support for policies
that disincentivize larger ones, and little to no support for punitive policies.
Many ethicists warn that failure to enact reasonable population policies now
may necessitate harsher policies in the future, a common theme in climate
ethics generally.
This article is categorized under:
Climate, Nature, and Ethics > Ethics and Climate Change
climate change, consumption, growth, limits, population
We have now had 30 years of extensive political debate and ethical reflection on global climate change (GCC) and
throughout this time, participants have largely ignored the role that limiting population growth could play in dealing
with it. On its face this might seem strange, since our scientific models have long identified population growth as one
of the two primary drivers of humanity's increasing greenhouse gas (GG) emissions (IPCC, 2013), while studies have
repeatedly shown that limiting population growth is among the cheapest, most effective means to mitigate (O'Neill
et al., 2010, 2012, 2015) and adapt (Barrett et al., 2020; Dodson et al., 2020) to GCC's impacts. On reflection the oddity
vanishes, since GCC policy discussions have been tightly constrained by conventional economic thinking, which
Received: 5 April 2021 Revised: 19 October 2021 Accepted: 23 October 2021
DOI: 10.1002/wcc.748
WIREs Clim Change. 2021;e748. © 2021 Wiley Periodicals LLC. 1of17
regards limits to growth as anathema (Broome, 2019). Until recently, neither the scientific nor the philosophical com-
munities have shown much interest in challenging this taboo, while among policymakers, proposals, and actions to
limit GCC have focused on technological fixes or efficiency improvements within the context of continued demographic
and economic growth.
This approach, however, has proven itself a failure. GG emissions have continued to increase and GCC has
advanced more quickly than expected (IPCC, 2018). Some impacts that scientists once predicted might show up in the
second half of this century are happening now; worries about how our grandchildren's lives might be constrained have
been replaced by worries about our children's lives, or our own. In the face of grave and imminent danger and an
unraveling global ecosystem, more people are starting to question once-sacred cows, such as the possibility of endless
economic growth at the expense of nature, or humanity's ability to safely manage unimaginably complex systems.
One example of this new open-mindedness (or panic) has been a surge in scientific and ethical discussions of popu-
lation in relation to climate change. Ten years ago, when I wrote a literature review on Climate ethics and population
policy(Cafaro, 2012) for this journal, it mostly noted the absence of such discussions in the philosophical literature.
Thankfully ethicists have taken up the topic of population and there are now numerous articles and books on which to
report. This review focuses on substantial philosophical contributions from the past decade, after first briefly reviewing
the science regarding our topic.
1.1 |The science
It is well-established that human population growth is a leading cause of GCC. According to the IPCC's 5th Assessment
Report,Globally, economic and population growth continue to be the most important drivers of increases in CO
sions from fossil fuel combustion(IPCC, 2014a). Between 1970 and 2000, these two drivers contributed roughly equally
to driving up GG emissions. Since 2000, economic growth has contributed more than demographic growth, but popula-
tion growth's contribution remains substantial and atmospheric carbon pollution continues to increase, far outstripping
all efficiency improvements. Total emissions, which need to trend sharply down to limit climate disruption, instead
continue to grow. According to the IPCC (2014a): Without additional efforts to reduce GG emissions beyond those in
place today, emissions growth is expected to persist driven by growth in global population and economic activities.
Baseline scenarios, those without additional mitigation, result in global mean surface temperature increases in 2100
from 3.7C to 4.8C compared with pre-industrial levels.In plain language, continued growth in human numbers and
wealth is set to cause a worldwide climate disaster within the lifetimes of many people alive today.
When the 5th Assessment Report turns from explaining the causes of climate disruption to analyzing policies to miti-
gate or adapt to it, the IPCC ignores direct efforts to limit its main drivers and instead focuses on technological changes
and efficiency improvements (Bongaarts & O'Neill, 2018). Nevertheless, over the past decade, numerous scientific publi-
cations have found significant potential for population policies to contribute to climate change mitigation and
Regarding mitigation, analyses show that limiting human numbers can contribute substantially to limiting GCC
(Cafaro & Götmark, 2019; Ripple et al., 2019; van Vuuren et al., 2018; Walsh et al., 2017). Comparing low, medium,
and high population projections from the UN under one plausible economic development scenario, one study found:
if the world population were to follow a low rather than a medium growth path, world-wide emissions would be
reduced by 1.4 GtC/year in 2050 and 5.1 GtC/year in 2100, or by about 15% and 40%, respectively(O'Neill et al., 2012).
Conversely, underfunding family planning and taking a high rather than a medium growth path was estimated to lead
to 17% and 60% higher emissions in 2050 and 2100. The fact that improved contraceptive availability takes time to pro-
vide significant mitigation benefits has led some to note that human population reduction is not a quick fix for envi-
ronmental problems(Bradshaw & Brook, 2014). But neither is reducing average consumption or deploying new
technologies. There are no quick or easy solutions for GCC. It seems strange to question policies whose environmental
benefits cumulate over time as insufficient or too slow, when there are no faster or more effective solutions being pur-
sued, and when limiting GCC is motivated in part by a desire to make life easier for our descendants in the future.
Limiting population growth is also important for climate adaptation, since higher population paths could expose
hundreds of millions more people to climate risks such as flooding (Hinkel et al., 2014), water stress (Satoh et al., 2017),
and drought (Ahmadalipour et al., 2019) during this century. Studies show that family planning policies that reduce
desired family size and increase contraceptive prevalence rates could increase global per capita water availability
(Gunasekara et al., 2013) and compensate for the likely effects of climate disruption on national food security
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(Moreland & Smith, 2012). Indeed, several studies have found that future food and water security problems will be
driven primarily by population increase raising demand, and only secondarily by GCC reducing supply (Hall
et al., 2017; Smirnov et al., 2016).
Many of the studies cited above have been published since the IPCC's 5th Assessment Report came out. It will be
interesting to see whether the 6th Assessment Report in 2022 takes this literature seriously: for example, by commission-
ing full chapters on population policy from the working groups devoted to mitigation and adaptation. A pro-growth
economic ideology remains politically dominant, yet signs of ecological decline are leading more people to question it
(Götmark et al., 2018). A recent Warning of a Climate Emergency,signed by over 11,000 scientists, forthrightly
describes continued increases in human population and the world gross domestic product as profoundly troubling
signsof ecological decline, and states: The world population must be stabilizedand, ideally, gradually reduced
within a framework that ensures social integrity(Ripple et al., 2019). These scientists say that addressing population
must be part of humanity's response to GCC. Ethicists have also begun to acknowledge this.
1.2 |Philosophers recognize an issue
In a searching series of articles, Elizabeth Cripps illustrates how widely held commitments to cosmopolitan justice,
combined with realization of GCC's potential harms, support policies to limit the size of the global human population
(Cripps, 2015, 2016, 2017a, 2017b). Cripps (2015) stipulates support for minimal understandingsof global and inter-
generational justice: the former requiring that no one in current generations is unavoidably unable to live a [materi-
ally] decent human life: one with a secure opportunity to satisfy central human interests;the latter requiring the same
for members of future human generations. GCC creates a danger that within a few generations, basic global justice
and intergenerational justice could become incompatible if the human population grows fast enough.In fact, this situ-
ation may already exist.
The confluence of GCC, continued population growth and a commitment to basic justice, means that humanity
must make hard moral choices now, to avoid the need for tragic moral choices in the near future (Cripps, 2015, 2016).
Cripps sympathizes with those who find it morally suspect to focus on limiting population to deal with GCC, given that
most population growth in coming decades is projected to occur among poor people in the developing world, who have
done little to cause GCC. But the reality is that poor people do not want to stay poor and improving their basic living
conditions will increase GG emissions, at least in the short-term, ratcheting up already excessive human demands on
the biosphere.
Cripps (2017a) argues that assuming human population will stabilize or decrease on its own, without enacting poli-
cies designed to achieve this, is naïve and dangerous. Recent demographic studies that project a quicker end to global
population growth than the standard UN (2019) projections depend on substantial policy changes to improve access to
family planning and girls' educational opportunities, not continuation of the status quo (Lutz et al., 2018; Vollset
et al., 2020). Hoping new technologies will allow humanity to keep growing indefinitely while simultaneously reducing
our ecological impacts is even more naïve. As recent history shows, new technologies are just as likely to increase GG
emissions (greater computing power and new fracking methods) as they are to help decrease them (wind turbines and
solar panels).
These considerations justify proactive population policies designed to stabilize, and if necessary humanely decrease,
the global human population. (Here as throughout this review, population policiesare defined broadly to include
most government policies that influence fertility rates, including reproductive rights, contraceptive availability, and tax,
benefits and educational policies.) Like most ethicists writing on this topic, Cripps advocates for choice-providing poli-
ciesand soft-incentive changing policies,such as the education of women and the reduction of gender inequality,
as well as the wide provision of contraception,while rejecting coercive or punitive policies of any sort (Cripps, 2017b).
Such policies, which have reliably reduced fertility rates in many parts of the world, are not just morally permissible
and environmentally prudentthey also benefit recipients directly. Given the urgent need to limit population, Cripps
also supports educating people about the connections between population and the environment, and enacting policies
that incentivize couples to have fewer children, provided they can be implemented without harming those affected
(Cripps, 2017b).
A similar approach is taken by Colin Hickey and colleagues in their article, Population Engineering and the Fight
against Climate Change.Like Cripps, Hickey et al. (2016) believe that climate change is among the most significant
moral problems contemporary societies face, in terms of its urgency, global expanse, and the magnitude of its attending
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harms,and that population plays an important role in determining just how bad climate change will be.As they
note, it is possible to put forward plans for mitigating GCC that do not address population; in fact, that is the consensus
approach currently taken by the world's governments under the United Nations Framework Convention on Climate
Change. They find such an approach morally irresponsible, since it falls short of offering a clear and reasonably certain
pathway to avoiding dangerous climate change.While population policy may take us into morally fraught territory,
ignoring population policy may be even more problematic, given the high costs of failure to limit GCC.
Hickey et al. (2016) provide a helpful analysis of possible population engineering policies,which they locate on a
coercion spectrum,from policies with a low risk of coercion up through policies with a high risk. Straightforwardly
coercive interventions to reduce human population growth are almost always wrong,they write, unacceptable viola-
tions of the human rights to autonomy and bodily integrity, while choice-enhancing interventions are not only permis-
sible, but obligatory, as they are means of ensuring equal access to basic goods(Hickey et al., 2016). Policies in the
mid-range, which seek to adjust people's preferences or actively incentivize choices, may seem intrusive. Yet in practice,
all cultures influence their members' procreation choices and all governments have policies which influence their citi-
zens' fertility rates, even if they do not label them population policies.Autonomy should be protected in procreation
decisions, Hickey et al. believe, yet upholding individuals' choices cannot mean shielding them from all influence.
Responding to Hickey et al. (2016), Quill Kukla (2016) asks Whose Job is it to Fight Climate Change?Kukla
agrees that climate change is a serious threat and that providing incentives for smaller families can help address it. Yet
Kukla worries that such efforts could put the burden on those who have done the least to create the problem, especially
poor women in the developing world. Kukla also worries that public advocacy for small families will wind up stigmatiz-
ing children from large families. Such concerns are widely shared (e.g., Heyward, 2012) and ethicists attempt to address
them in various ways, from arguing that efforts to reduce fertility should focus on the developed world (Hedberg, 2020)
to proscribing positive arguments for smaller families and limiting policies to improving access to contraception and
girl's educational opportunities. These debates are ongoing.
Hickey et al.'s (2016) most valuable contribution may be coining the phrase population engineeringfor the inten-
tional manipulation of the size and structure of human populations.Dangerous proposals to engage in high-tech geo-
engineering have proliferated in recent years, as the magnitude of the threat posed by GCC has become clearer.
Population engineeringreminds us that there are more responsible alternatives focused on changing human behavior
and limiting our environmental demands.
Human rights concerns loom large in debates about population policy. On the one hand, opponents of population stabi-
lization efforts often point to past human rights abuses, such as forced abortions under China's one child policy, to jus-
tify their opposition (Angus & Butler, 2011; Fletcher et al., 2014). On the other hand, family planning proponents note
that most social pressure and government coercion, now as in the past, involves forcing women to have more children
than they want to have, not fewer (Cottingham et al., 2012; Echegaray & Saperstein, 2010). GCC brings further rights
concerns to the table since it directly threatens a number of human rights, particularly the rights to basic physical secu-
rity and sufficient food, water, and shelter (Caney, 2010, 2018). GCC indirectly threatens all human rights, since secur-
ing rights depends on a functioning social order, which in turn rests on essential ecosystem services that GCC is
degrading. Beyond human rights concerns, other species arguably have a right to continued existence free from
untimely anthropogenic extinction (Donaldson & Kymlicka, 2011; Staples & Cafaro, 2012). This right, too, is clearly
threatened by GCC and the full suite of environmental impacts caused by human overpopulation.
2.1 |Conly's rights-based approach
The most rigorous recent treatment of population ethics from an environmentally informed, rights-based perspective is
Sarah Conly's One Child: Do We Have a Right to More? (Conly, 2016). Conly begins by noting that humanity's current,
unprecedented numbers have led to great environmental damage, including GCC and massive biodiversity loss, with
the promise of worse to come, including potential shortages of food and water. In response to the oft-repeated refrain
that it is consumption, not population size, that is driving environmental harms, she responds, reasonably, that it is
both: the growing per capita consumption of ever more people. Her central conclusion is that under current
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circumstances, people do not have a moral right to have more than one biological child. Her argument hinges on the
claim that the harms of environmental degradation are significant enough to justify limiting the human freedom to
Not that Conly denies such freedom. A chapter titled The Right to a Familyargues for a right to procreate based
on basic human interests and the fact that in most societies, our standard model of a good life typically involves having
some children(p. 39). Another chapter, titled The Right to Control Your Body,argues for such a right based on per-
sonal autonomy and integrity, grounded in the respect we owe one another as persons. Conly's arguments for a right to
procreate thus incorporate the two main approaches in contemporary rights theory, interest-based and status-based.
However, she goes on to argue that while these moral concerns provide reasonable groundsfor a right to procreate,
they do not entail a right to have more than one child.
Regarding interests, while many and perhaps most adults have strong interests in procreation, these interests can be
met fairly well by having one child. The kinds of interpersonal and intergenerational bonds cultivated in family life do
not require large families. While people may desire more children, this must be balanced by a consideration of potential
Similarly, respect for autonomy generally supports non-interference in individuals' reproductive lives. Again
though, this right to be left alone may be limited when our behavior threatens to harm othersincluding potential
harms to future generations. The dangers of overpopulation may be serious and pressing enough to outweigh claims to
a right to have more than one child. If they do not now outweigh such claims, Conly argues, they may do so in the
future, as humanity stumbles toward ecological catastrophe (see also Spears, 2015).
What then are reasonable and just population policies? Conly reminds readers that when it comes to stopping an
undesirable behavior, punishment should not be the first thing we think of.Education regarding the connections
between overpopulation and environmental problems can change behavior. Financial incentives have proven effective
in convincing people to have fewer children, although Conly discusses how such incentives have sometimes passed over
into coercion. Increasing contraceptive availability is a non-coercive, win/win approach, and regardless of our worries
about population, it seems the humane thing to doto further women's safety and health.
Most ethicists stop here, with an admonition against coercion and a plea for win/win solutions. But Conly notes that
it is an empirical question whether non-coercive means will be sufficient to keep human populations within sustainable
bounds and that when it comes to protecting the environment, we do not typically rely solely on education and volun-
tary action. For these reasons, she affirms that coercive laws regarding how many children people have may be justified.
However, she points out that any punishments for breaking such laws must themselves be morally justified. Sanctions
such as forced abortions or sterilizations are morally repugnant and never permissible, she argues, while substantial
fines may be acceptableparticularly if implemented on a sliding scale that impacts the wealthy equally with the poor.
That is her preferred approach, should coercion become necessary. In any case, we can discover the best approach,
once we stop refusing to look at the issue.Like Elizabeth Cripps, Conly argues that mild population regulation now
might spare our children and grandchildren more intrusive regulation in the future.
2.2 |Caney's alternative approach
An interesting critique of Conly's analysis comes from Simon Caney, a leading proponent of a rights-based approach to
climate policy. According to Caney (2010, 2018, 2020a), essential human rights to life, health, and basic subsistence
oblige the current human generation (particularly its richer members) to support robust climate mitigation policies, as
a matter of justice. Because population size is an important driver of GCC, such mitigation may and perhaps ought to
include population policies and like Conly, Caney's preference is rights-enhancing policies that improve women's lives
and increase freedom (Caney, 2020b). Still, Caney recognizes that voluntary approaches to limiting population size may
prove insufficient to avoid catastrophic GCC. Uncomfortable with restrictivistapproaches like Conly's or Christine
Overall's (2012) that deny a human right to unlimited procreation,Caney (2020b) crafts an ecologically liberal
approach which cushions possible demands to limit procreation by allowing trade-offs between more procreation or
more consumption, and by holding space open for techno-fixes which could alleviate the need for discipline in
either area.
Invoking Ehrlich and Holdren's (1971) I=PAT equation, Caney points out that population is just one of the three
crucial variablesdriving increased GG emissions. One thus cannot make any inference at all about how many chil-
dren persons are entitled to have without knowing the levels of consumption that people (including those to be born)
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would or could enjoy (the Avariable). Similarly, one cannot reach any conclusion about how many children persons
are entitled to have without knowing the levels of access to clean technology (the Tvariable) that people would, or
could, enjoy(Caney, 2020b). Caney's approach formally recognizes the importance of all three I=PAT factors, recog-
nizes that I must be reduced, and seeks to maximize people's freedom to choose their own fair contributions to environ-
mental sustainability.
Some policies demanded independently by justice will themselves help humanity address GCC and should be pur-
sued. Such policies include securing women's rights to education and reproductive autonomy, which will drive down
fertility rates (addressing P); taxing the GG emissions of the world's wealthiest inhabitants (A); and eliminating subsi-
dies to the fossil fuel industry, accelerating the shift to less harmful technologies (T). Beyond that, those who wish to
have children can do so, but they must pay for the privilege, and they must ensure that there is sufficient reduction in
consumption and use of clean technology to ensure that humanity lives within the Sustainability Frontier. By the same
logic, others can choose to consume more, but they too must pay for the privilege and ensure that their population size
and technology policy are such that they too live within the Sustainability Frontier.If reducing Aor Pwill both help
keep environmental impacts within bounds, we have no reason to mandate one or the other approach. Furthermore,
Caney (2020b) claims, by providing flexibility in how people discharge their responsibilities it makes it much more
likely [to compel assent] than one which calls for everyone to engage in a specific course of action.
This is an ingenious approach, but it seems unworkable and overly optimistic about managerial solutions to GCC.
To be effective, there would have to be cases where people could have a second or third child, for example, if they fore-
swore buying a car or a bigger house. Conversely, those who chose to remain childless might be free to take more over-
seas vacations or eat more meat. How would that work? Who would keep track? Caney seeks to make the bitter pill of
constraint more acceptable, but the same societies that have balked at limiting overconsumption or harmful technolo-
gies are unlikely to become more public-spirited by adding limits to procreation.
Caney's approach would internalize the cost of having children, an approach anticipated by Casals and
Williams (1995). It relies on the principle that individuals' discretionary consumption and discretionary procreation are
morally equivalent, a position argued for explicitly by Young (2001). This position is also tacitly assumed in several
studies comparing the GG emissions caused by having children and various personal consumption decisions
(Murtaugh & Schlax, 2009; Wynes & Nicholas, 2017). This view is questioned by Robeyns (2021) and denied by Pinkert
and Sticker (2021), who see greater moral seriousness in creating life than in buying a new Audi. However, these
authors stop short of advocating an unlimited right to procreate, and Burket (2021) argues contrarily that procreation's
emissions impacts are so harmful that most people have no right to any children. This debate is ongoing and is likely to
grow in importance as environmental constraints hit societies harder.
Building on Caney's valuable reminder that all three IPAT factors are important, societies that took GCC seriously
might work to shift the impact of all three factors downwards simultaneously, as quickly and humanely as possible.
Bourban (2019) notes that the validation of IPAT within climate science has allowed policy analysts to focus on which-
ever one of the three factors they chose, often to argue against action regarding the others. He believes this is a mistake,
writing: The IPAT equation should not be used to emphasize any one of its three main factors over the others: it
should be used to fully consider each of them. Without an institutional framework to promote technological innova-
tions, consumption changes, and reduced population growth through education, regulation and incentives, we risk cre-
ating a far more dangerous world.Bourban adds that the need to avoid rushing past any of nine planetary boundaries
for safe use of the biosphere, not just the single one of atmospheric carbon load, reinforces the imperative to attend to
population and consumption, since curbing them helps ratchet down human impacts in all nine areas (for similar argu-
ments see Mitchell, 2012; Ganivet, 2019).
2.3 |Meijers' rights-based approach
In Climate Change and the Right to One Child,Meijers (2016a) asks the question: To what extent is it fair to require
people to refrain from procreating as part of a strategy to make the world more sustainable?He rejects the idea that
the right to reproduce can be unlimited, since this would not be universalizable: in a world in which everybody had
many children, extreme scarcity would arise and stable institutions could prove unsustainable. This would lead to viola-
tion of (rather uncontroversial) rights such as the right to life and to health and subsistence.In the actual world today,
excessive procreation could also undermine our descendants' right to have children, since people are likely to refrain
(and perhaps should refrain) from bringing children into an insecure and dangerous world (Gheaus, 2016).
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Nevertheless, many adults have a fundamental interest in founding a family, as recognized in the UN's foundational
human rights charters. Meijers argues that this justifies, at a minimum, a non-defeasible moral right to have one child.
People may have a moral right to have more than one child; however, in a crowded world with limited resources,
they may not. Focusing on climate change, Meijers (2016a) writes: The right kind of balance between limiting fertility
and per capita emissions will probably depend on how much value people attach to having large families as opposed to
being able to have high per capita emissions on which reduction can be enforced in a morally permissible way.In
seeking to create sustainable societies, governments can legitimately consider limiting both per capita consumption and
per capita procreation, although any measures undertaken to remain within such limits should respect human rights.
Like Caney, Meijers argues that poor individuals in the developing world do not have the same moral responsibility
to limit their procreation, given lower consumption levels and the fact that having large numbers of children may be
rational in traditional social milieux. Nevertheless, he believes that a decline in fertility rates is [generally] in the inter-
ests of the global poor,since high fertility perpetuates poverty and can lead to environmental degradation, which
harms poor people disproportionately. He concludes:
When striking a balance between lowering per capita emissions and limiting procreation, a priority should
be placed on limiting superfluous emissions that do not contribute to goals as important as parenting. This
is in order to protect the interest people have in there being sufficient births for continuity and to allow
people to become parents. Importantly, in an unequal world like ours, limiting fertility levels will have to
go hand in hand with addressing global poverty; this will decrease fertility as well as open up the possibility
for further fertility reduction because procreation becomes a choice rather than a necessity.
(Meijers, 2016a)
An intriguing follow-up article (Meijers, 2017) considers some of these ideas within a Rawlsian framework of justice
(see also Meijers, 2016b).
Meijers' position that poor people in the developing world do not bear responsibility for climate change is widely
shared. Applied to consumption, it supports the view that wealthy people should limit luxury emissionsto preserve
ecological room for increased consumption and emissions by the global poor (Shue, 1993); it also undergirds contract
and convergegoals under the UN Framework Convention on Climate Change. Many ethicists apply this view to popu-
lation matters, arguing that it is unfair to ask poor people to limit procreation to deal with a problem they did not create
and their children are unlikely to make worse (Okyere-Manu, 2016). Since most future population growth is projected
for the developing world and much attention focuses on reducing rapid growth in poorer countries, some maintain that
population stabilization is largely irrelevant to dealing with GCC (Gaard, 2015). Others go further, arguing that atten-
tion to population is a diversion by wealthy neo-colonialists who do not want to limit their own consumption (Angus &
Butler, 2011), or a racist plot to limit the numbers of brown-skinned people (Dyett & Thomas, 2019; Sasser, 2014).
In response, many population advocates join Meijers and argue that efforts to limit population growth should
emphasize reducing births in the developed world (Crist, 2019; Hedberg, 2020). Others, however, contend that people
everywhere have a responsibility to limit their procreation, given the potential harms of overpopulation, which fall dis-
proportionately on the poor (Cafaro & O'Sullivan, 2019; Hines, 2018). It is true, for example, that Africans have contrib-
uted little to GCC to date. Yet according to recent UN (2019) median projections, Nigeria is poised to grow from
206 million today to 733 million by 2100, Ethiopia from 115 million to 294 million, Congo from 90 million to 362 mil-
lion, and Tanzania from 60 million to 286 million. Because people in Africa understandably want to improve their stan-
dards of living, their per capita environmental impacts are likely to grow. This makes their reproductive decisions and
population policies significant both for their descendants' well-being and for future efforts to limit and adapt to GCC.
2.4 |Feminist concerns
Some of the strongest arguments against tackling population growth to address GCC come from feminist scholars
(Hartmann, 2016; Hendrixson, 2016). In part, this is justified by reference to past human rights violations in population
control programs. But critics also argue that any talk of limiting women's reproductive rights is disrespectful and dan-
gerous (Ojeda et al., 2019). For example, Hendrixson (2018) criticizes the 120 by 2020initiative to improve family
planning options in the developing world, because it set specific targets for increasing contraceptive use and because it
justified these, in part, by reference to the environmental benefits of smaller populations. Proponents saw increased
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contraceptive availability as necessary to secure poor women's reproductive rights, and the initiative explicitly dis-
avowed any form of coercion (Hardee et al., 2013). But skeptics believe that when governments promote smaller fami-
lies or populations, this itself represents a kind of coercion, and starts a process that is likely to cumulate. It also
obscures the real causes of the problems mistakenly blamed by populationistson overpopulation: excessive consump-
tion by wealthy westerners in the case of GCC (Hendrixson et al., 2019); distribution problems and unjust poverty in
the case of famines (Gaard, 2015); and an unfair and unsustainable capitalist economic system generally.
There are two issues here. The first is the relative importance of human numbers in generating environmental prob-
lems, and the role curbing our numbers might play in solving them. Feminist philosophers such as Cripps and Conly
tend to follow the science on this, while feminists from other disciplines often stipulate population's unimportance. I
certainly do not dispute that population has grown enormously in the last hundred years or that anthropogenic climate
change is threatening our very existence on Earth,writes Emily Merchant (2021), but research has shown that the
former is not the cause of the latter(for a similar statement see Hendrixson & Hartmann, 2019). Such blanket dis-
missals are implausible, given the scientific consensus on population's environmental importance described in
Section 1.1 and elsewhere (IPBES, 2019; Reid et al, 2005).
The second issue is how to fairly balance rights and responsibilities in the realm of procreation. As we have seen,
ethicists have begun to grapple with this difficult question. Critics outside philosophy, however, sometimes take the
view that any discussion of limits to procreation is disrespectful and unfair to women (Bhatia et al., 2019). But from an
ethical standpoint, this cannot be correct, since rights are claims on limited resources and always involve correlative
responsibilities (Conly, 2016; Cafaro, 2021). Successive UN population conferences in Bucharest (1974), Mexico City
(1984), and Cairo (1994) each declared couples had a right to responsibly choosewhen to procreate. Whatever bal-
ance societies wind up striking, their members, male and female, will have to live with the results of those choices
(Clarke & Haraway, 2018).
2.5 |Rights and responsibilities
We can take some provisional results from the work reviewed in this section. First, that the question of procreative
rights is an important one for climate ethics and policymaking, deserving further discussion. Second, that such discus-
sions should seek to balance reproductive rights against other rights, and rights with responsibilities. Some ethicists add
the need to fairly balance human and nonhuman interests (Cafaro & Crist, 2012; McShane, 2016). With the proviso that
preserving robust populations of other species is a moral imperative, affirming a proper balance between reproductive
rights and responsibilities becomes part of sustaining the flourishing of life in all its forms (Rieder, 2016). On this view,
the proper context for striking the balanceis the effort to create just and sustainable societies.
3.1 |Dasgupta's utilitarian approach
While Sarah Conly's book has set the agenda for debate among rights-based approaches to population ethics, Partha
Dasgupta's Time and the Generations: Population Ethics for a Diminishing Planet (Dasgupta, 2019), seems likely to do so
for many utilitarians. Dasgupta takes humanity's environmental predicament seriously, writing that the enormous eco-
nomic success we have enjoyed in recent decades may be a down payment for future failureas we spend down natural
capital and threaten essential ecosystem services. He believes it is a mistake to reduce these environmental threats to
GCC, writing: Global climate change attracts attention among intellectuals and the reading public not only because it
is a grave problem, but also because it is possible to imagine meeting it by using the familiar economics of commodity
taxation, regulation, and resource pricing without having to forego growth in living standards in rich countries.Focus-
ing narrowly on GCC also leads analysts to concentrate on technological solutions, rather than reducing consumption
or limiting human numbers. But while developing and deploying new technologies can play a role in reducing environ-
mental impacts, Dasgupta believes it is unlikely to lead to real sustainability in a world where the goal is more growth.
All this suggests a need to attend to Pand Aas well as T. Dasgupta (2019) does so by working out estimates for a
sustainable global population at various average income levels, with income standing in as a proxy for consumption. In
an article titled Socially Embedded Preferences, Environmental Externalities, and Reproductive Rights,written in
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2017 with Aisha Dasgupta and included in Time and the Generations, they calculate a maximum sustainable population
of 3.5 billion, based on sustainability criteria borrowed from the Global Footprint Network and stipulation of an average
annual global income of $20,000. The higher a desired or acceptable average income is set, the lower the number of
people who can be sustained globally. We can ignore this trade-off temporarily by decreasing Earth's long-term carrying
capacity, but that, according to the Dasguptas, represents a failure of stewardship and disregard for the rights of future
people. Reproductive rights are important, they believe, but to insist that the rights of individuals and couples to decide
freely the number of children they produce trump all competing interests is to minimize the rights of all those (most
especially, perhaps, future people) who suffer from the environmental externalities that accompany additions to the
Having children is an inherently social act involving claims on limited resources, which may need to be managed
for the common good (see also MacIver, 2015). Best to face this with an understanding of real limits and ethical goals.
Time and the Generations seeks to do that in a long technical essay written at the intersection of philosophy and eco-
nomics titled Birth and Death.This lies in a long line of utilitarian attempts to specify an optimal human population,
going back through Parfit (1984) and forward through Broome (2004, 2012, 2016) and Greaves (2017, 2018, 2019). An
intriguing part of this effort involves arguing for Generation-Relative Utilitarianism, Dasgupta's attempt to specify an
ethically plausible compromise between Average Utilitarianism (in which average human well-being is held all impor-
tant) and Total Utilitarianism (which takes aggregate human well-being as its central value), both of which generate
ethically counterintuitive implications regarding population policies (see Greaves, 2017 for an overview and Section 3.4
below). The basic idea is to discount the well-being of future generations, to facilitate practical planning and preserve a
focus on human flourishing rather than maximizing mere numbers, while not discounting it too much, to preserve a
strong moral commitment to our descendants' well-being.
Dasgupta develops a formal theory that relates population, per capita consumption and biospheric capacity,
suggesting, as in his earlier article, that we work out optima for the first two while respecting the third, keeping in mind
future generations who will bear the costs of diminished biospheric capacity. Calculating hard numbers under such a
framework necessarily involves considerable uncertainty: regarding total biospheric capacity, a proper discount rate for
future people's well-being, and how best to balance average consumption against number of consumers. Within a spec-
trum of plausible answers to these questions, Dasgupta delivers a range of optimal global populations between 0.5 and
5 billion. Like his earlier article, this more rigorous effort suggests that humanity is already grossly overpopulated, as
does a recent revision of the earlier article that defines per capita impact in terms of average production, rather than
average consumption, giving an optimal sustainable global population of 1.8 billion (Dasgupta & Dasgupta, 2020; see
also Tucker, 2019).
Dasgupta's central argument is strictly anthropocentric, in line with ongoing utilitarian debates about optimal popu-
lation (Broome, 2016; Greaves, 2018). The biosphere is essentially a resource (or source of all resources) for human use;
carrying capacity and optimal population are simply functions of what is possible or best for humans. Yet Dasgupta
himself rejects anthropocentrism; as he wrote in kind response to a query, he deliberately made minimalist assump-
tionsin developing his moral arguments, the better to show that even if all people care about is ourselves, we need to
limit our population. In examining our values and thus our lives,he writes at the conclusion of Dasgupta (2019), peo-
ple need to ask whether needlessly extinguishing other species is something we can live with comfortably.If not, we
should grant some portion of biospheric capacity to other species and thus accept a smaller optimal human population.
3.2 |Coole's circumspect consequentialist approach
In Too many bodies? The return and disavowal of the population question,Coole (2013) provides a clear explanation
of the shift from the population controldiscourse of the 1960s and 1970s to the Cairo consensusof the 1990s and
beyond. The UN Population Fund has described this as a shift away from a focus on human numbers to a focus on
human lives.Under the new approach, Coole explains, policies based on perceptions of a 'race between numbers and
resources' are eschewed as synonymous with a 'numbers game' presented as antithetical to human rights,while
reproduction is recast as a self-regarding act,justifying rights but not enjoining responsibilities. But the distinction
between attending to numbers and attending to lives was always questionable. Pre-Cairo, many countries saw limiting
future numbers as essential to improving their citizens' lives, and in recent decades developing countries that succeeded
in reducing birth rates have been more economically successful than countries that did not (Sinding, 2009). GCC and
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other global environmental problems call the Cairo consensus further into question, suggesting that attending to
human numbers could be a prerequisite for protecting human rights going forward.
In a concise follow-up, Should We Control World Population? Coole (2018) answers her book title's question in the
affirmative, on broadly utilitarian grounds. Contrary to some popular misconceptions,she writes, population control
does not mean culling superfluous people. The aim is to reduce current birth rates in order that smaller future genera-
tions might live better.An initial chapter summarizes the case that limiting human numbers is important in dealing
successfully with humanity's environmental problems, with a focus on GCC. Coole also flags potential social costs of
increased population density, even when it is ecologically possible. Referencing John Stuart Mill's classic statements
about the disutility of a wholly managed world with little opportunity for solitude, she notes that such concerns have
been largely ignored in sustainable development debates.
Subsequent chapters explore the ethics of population control. Coole argues that from a consequentialist perspective,
it is reasonable for citizens of modern democracies to support mildly coercive fiscal and legislative measuresto
decrease birth rates. Such measures could avoid more harmful outcomes, including more stringent coercion, later
(Coole, 2018). Once we accept the reality of ecological limits, unlimited procreation becomes a threat to human free-
dom, rather than a reasonable expression of it. But, aware of the potential dangers of overzealous government efforts,
Coole propounds a three-part account of reproductive rights, in line with her circumscribed consequentialist
Rights to life, liberty, and security are absolute: they can never be legitimately violated on consequentialist gro-
unds.Prohibiting violence and securing basic bodily integrity, in Coole's view these rights include the right to abortion
on demand and the right against forced abortion. In a second category, rights to full reproductive health services,
including contraception, are very strong, although actualizing them depends on general social and economic develop-
ment. Securing these rights will limit population growth and further women's agency and happiness, in complementary
ways. Finally, in a third category, comes the right to choose family sizean important right which is nevertheless con-
text dependent and balanced by an imperative need to choose responsibly. Serious environmentalists will want to limit
this right, Coole (2018) suggests, and though she refrains from explicitly joining them, she presents the central issue
clearly when she writes: The relative importance of rights and responsibilities remains vague here. Is there a right to
choose irresponsibly, regardless of the consequences for others?Many utilitarians, following Mill, would answer no:
responsible parents should consider the impacts of such choices on their existing children, their society, perhaps the
biosphere as a whole. Even (or especially) if they do not support governments restricting individual procreation deci-
sions, sensible utilitarians must make a place for government actions to incentivize smaller families, since reproductive
choices have clear implications for the well-being of other people.
Coole concludes that there are prima facie just means to pursue population stabilization or reduction, in light of cur-
rent liberal practices within reasonably just societies. She highlights the benefits of her approach for women, poor peo-
ple, and non-human beingsthe ones who will be most harmed if societies fail to achieve ecological sustainability. She
argues, too, that since contemporary societies continue to pursue economic growth and increased per capita consump-
tion, it makes even less sense to ignore continued population growth. At various points, Coole defines her approach in
contrast with Sarah Conly's, but she comes to fairly similar practical conclusions.
3.3 |Hedberg's broadly consequentialist approach
Like many recent treatments, Trevor Hedberg's The Environmental Impact of Overpopulation: The Ethics of Procreation
(Hedberg, 2020) strikes a note of urgency. We are now more than 25 years past the United Nations International Con-
ference on Population and Development,he writes:
the venue where explicit discussion of population policy became a political taboo. Evading the problem has
not helped us. Population growth has continued and made it more difficult to mitigate climate change,
slow down the rate of species extinctions, and adequately distribute the world's finite resources. Minimiz-
ing the harm that befalls present and future people requires confronting this reality and abandoning the
fiction that procreative choices are too private or intimate to be subjected to moral scrutiny.
Hedberg's approach does not rely on a particular ethical theory; instead, he appeals to general moral principles that he
believes most theorists and laypeople will accept. These include that current people have a duty to avoid causing
10 of 17 CAFARO
massive and unnecessary harm to future people, and that we have a duty to create sustainable societies. The central role
harm plays in his argument justifies treating it as consequentialist, broadly speaking.
Hedberg stipulates that environmental degradation is the product of human population size and the average rate of
environmental degradation per person. That means we must address either population size or average consumption, or
both. Given humanity's current population momentum (we are adding roughly a billion people every dozen years) and
the evidence that we are already overpopulated relative to what Earth can sustain, there is no way we can humanely
reduce the global population fast enough to avoid having to cut back on per person consumption. Hedberg thus rejects
population reduction as an environmental panacea. But the obstacles to cutting average consumption fast and deep
enough to avoid catastrophe are perhaps even more daunting; most nations have decreased their fertility rates signifi-
cantly over the past half century, while literally no country has a lower per capita consumption rate than it did 50 years
ago, or desires one. Thus there appears to be no feasible way to cut average consumption enough to sustain a global
population of 812 billion people indefinitely.
Hedberg concludes that humanity must reduce both per person environmental demands and population size, sub-
ject to moral and practical limits. He develops this central argument with clarity and ingenuity in the first half of his
book (see also Hedberg, 2019, 2021). Its second half explores the practical implications regarding personal procre-
ation decisions and government population policies, and responds to likely objections. Like Caney (2020b), Hedberg
is centrally concerned to avoid making unjustified moral demands on people in developing nations, and this leads to
some policy differences with Sarah Conly. Most consequentially, while Conly (2016) argues for a right to only one
child for everyone, Hedberg believes people in the developing world with low personal consumption have a right to
more. Similarly, Hedberg would avoid incentives for smaller families in the developing world, only supporting them
in developed countries. These positions may be rhetorically effective, but they seem unrealistic about the grave dan-
gers growing populations in Africa, the Middle East, and South Asia pose to the people who live there and their
descendants. Hedberg's main argument is anthropocentric, but a short chapter titled What about the nonhuman
community?notes that if we extend moral consideration to other species, the incentives to reduce our numbers
increase significantly.
3.4 |Greaves, Broome, and population axiology
By taking limits seriously and emphasizing the need to act under conditions of uncertainty, Dasgupta (2019) makes a
compelling case for government policies to limit or reverse population growth. Other writers on population axiology
instead emphasize its ethical and empirical uncertainties, leaving us with admonitions for further study rather than
political action. A good example is Hilary Greaves, who provides a clear introduction to the topic. Greaves (2017)
defines population axiology as a betterness ordering of states of affairs, where the states of affairs include ones in
which different numbers of persons are ever born.The two most basic population axiologies are averagism (a state A
is better than a state B if and only if people's average well-being is higher in A) and totalism (a state A is better than a
state B if and only if the summed well-being of all people is higher in A). While averagism and totalism each have
appeal, both also generate negative or counterintuitive consequences for population policy, as do other possible
approaches such as variable value and critical level theories, and Greaves (2017) concludes that further study is needed.
Greaves (2018) applies a totalist population axiology to determine the optimum size of the global human population.
This effort founders on two problems; first, the implausibility of totalists' inclination to maximize human numbers at
the expense of life quality; second, uncertainty regarding the biosphere's human carrying capacity (Greaves assumes
without argument that human beings have no moral responsibility to share that capacity with other species). Despite
numerous signs of environmental decline, including melting glaciers, immense dead zones at the mouths of the world's
major rivers, the expanding Great Pacific Garbage Gyre, and so on, Greaves insists we do not know whether biospheric
carrying capacity is in danger of being breached. Again, further study is needed.
In Climate Change and Human Population,Greaves (2019) applies her general framework to the question of
whether humanity should limit population growth to deal with GCC. In addition to uncertainties already mentioned,
she explores further ones regarding the practical details of successfully limiting GCC. She concludes, tentatively, that
population reduction probably would, in the end, help with climate change.In addition, she notes that larger
populations might accelerate other aspects of environmental degradation and undermine the planet's future life-support
capacity. As is usually the case, widening the scope of environmental concern beyond GCC lends greater urgency to
limiting human numbers. Widening the scope even further, however, again deflates that urgency, as Greaves concludes
CAFARO 11 of 17
that theoretical uncertainties about the optimal timeless population sizethe total number of people who will ever
liveundermine all her previous conclusions.
John Broome, another population axiologist, has been influential in climate ethics through his own writings
(Broome, 2012, 2016, 2019) and as one of the few ethicists contributing to the IPCC's Fifth Synthesis Report (as a lead author
of a chapter in IPCC, 2014b). In the latter role, he brought a short discussion on population ethics into an IPCC publication
for the first time. Tellingly, though, this discussion did not treat any actual or proposed population policies, focusing
instead on the probably unanswerable question of how many human beings we should seek to sustain over humanity's
entire career. After providing a short summary of population axiology under the title Valuing Population,it concluded:
Each of the existing ethical theories about the value of population has intuitively unattractive implications.
So far, no consensus has emerged about the value of population. Yet climate change policies are expected
to affect the size of the world's population, and different theories of value imply very different conclusions
about the value of these policies. This is a serious difficulty for evaluating policies aimed at mitigating cli-
mate change, which has largely been ignored in the literature. (IPCC, 2014b)
In other words, as humanity hurtles toward catastrophic GCC, further study is needed. Given the chance to discuss the
pros and cons of actual population policies, which substantially influence one of the two main drivers of GCC, Broome
and his co-authors passed. Summarizing the uncertainties of population axiology was easier than forthrightly addressing
the ethics of growth on a finite planetthe inescapable problem at the root of GCC. This suggests that population axiol-
ogy, the approach pioneered by Parfit (1984) and developed at length by Greaves, Broome, and others (Fleurbaey
et al., 2019; Méjean et al., 2020; Scovronick et al., 2017), may be a dead end, at least as regards climate ethics.
Population axiologists call for greater rigor in thinking about the value of human numbers (Greaves, 2019). But their
inability to speak to actual policy choices renders their approach questionable, as does their over-reliance on main-
stream economic approaches to value. Consequentialism has done some of its best work when it questioned previously
unchallenged economic views and practices; that may be the sort of rigor needed now. Some economists take GCC to
show the need to radically rethink mainstream economics' emphasis on morein favor of enough(Daly &
Farley, 2010; Stuart et al., 2020). Perhaps ethicists also should replace optimizing and maximizing with satisficing and
gratitude in considering how best to respond to GCC.
3.5 |Looming consequences
Given the world's complexity, consequentialism is always vulnerable to paralysis by analysis. Yet when it focuses on
the likely consequences in the real world of actual policy choices, it is a powerful ethical approach providing useful
practical guidance. Within climate ethics, more grounded consequentialist approaches tend to support robust efforts to
limit human population growth to deal with GCC (Coole, 2018; Dasgupta, 2019; Hedberg, 2020; see also Gesang, 2013).
Their conclusions mirror the conclusions of most rights-based treatments (Conly, 2016; Meijers, 2016a; Rieder, 2016),
suggesting that the overall ethical case for such efforts is strong.
4.1 |Broadening the issue
GCC is often treated as a synonym for all of humanity's environmental challenges. Yet it only represents part of our
global environmental damage, as documented by the Millennium Ecosystem Assessment (Reid, 2005), the Global Assess-
ment Report on Biodiversity and Ecosystem Services (IPBES, 2019) and various scientists' warnings that have proliferated
in recent years (Bradshaw et al., 2021; Ripple et al., 2017, 2019). The planetary boundaries approach developed by the
Stockholm Resilience Centre identifies nine global ecological thresholds that humanity needs to avoid crossing to pre-
serve essential ecosystem services, several of which have already been breached (Higgs, 2017; Steffen et al., 2015, 2018).
Seeing GCC as part of a larger suite of environmental threats tempers hopes that technological or managerial fixes
alone might solve these problems, encouraging us to consider reductions in consumption, production, and human
numbers as well (Bourban, 2019; Cafaro, 2014).
12 of 17 CAFARO
Another frequent yet questionable assumption in climate policy debates is that stabilizing population will be sufficient
to deal with GCC, or that stabilization is all that is possible or desirable. As Kuhlemann (2018) observes, that a
population's size is stable in no way entails sustainability. It may be sustainable, or it may be far too large.Three recent
studies argue that two to three billion people might be sustainable globally if societies made heroic environmental
improvements in existing modes of consumption and production (Dasgupta, 2019; Lianos & Pseiridis, 2016; Tucker, 2019).
At the national level, too, many populations in both the developing and developed worlds may need to shrink to achieve
sustainability: Lianos and Pseiridis (2016) found that 44 of the world's 52 most populous countries are currently over-
populated, based on plausible stipulations regarding per capita consumption and sustainability requirements. This puts
recent demographic studies that project global populations may peak sooner than expected in proper perspective (Lutz
et al., 2018; Vollset et al., 2020). Even if true, most nations and Earth as a whole will still be grossly overpopulated for the
foreseeable future, given likely human demands on the biosphere (see also Bravo & Tamburino, 2021).
A third necessary broadening of concern involves GCC's impact on other species (Lo & Brennan, 2018; Nolt, 2011).
As we have seen, anthropocentric analyses of climate policy can justify limiting human numbers, along with other miti-
gation and adaptation efforts. Yet many ethicists see anthropocentrism itself as a significant cause of humanity's harm-
ful environmental behavior (Kortetmäki, 2017; Rolston, 2020): a selfish and unjust approach to ethics that must be
transcended to successfully meet environmental challenges like GCC. Committing to generously sharing habitat and
resources with other species would have significant implications for the full suite of climate ethics issues, from geo-
engineering to population policy (Cafaro, 2010; McShane, 2016). Arguably, climate ethicists and policymakers should
broaden their discussions to take other species into account.
4.2 |Questioning growth and redefining success
Perhaps the most radical approaches to dealing with GCC are those that directly explore modern societies' obsession
with growth and try to frame alternatives. In Abundant Earth: Toward an Ecological Civilization (2019), Eileen Crist
argues that a false conception of the good is at the root of humanity's environmental destructiveness. She details the
many ways people have come to redefine the Earth as a storehouse of resources for our use, where wild species and
wild places have no integrity we feel compelled to respect. Along with this anthropocentrism goes a shallow, misplaced
conception of freedom built around high levels of irresponsible consumption. The only realistic solutions to GCC, mas-
sive biodiversity loss and other environmental problems, she believes, involve scaling back human numbers and eco-
nomic demands. Yet sociocultural conditioning into the precepts of human distinction and prerogative renders the
very notion of substantially scaling down and pulling back humanity's sprawl almost unthinkable from a mainstream
perspective(Crist, 2019). To date this unwillingness has been widespread among climate policymakers.
Reformist attempts to square continued growth with environmental protection are bound to fail, Crist argues. She
presents an alternative vision of social progress in which people accept and even welcome limits to growth, as an
expression of caring relationships with the biosphere and concern for future generations. A growing chorus of critics
makes similar arguments (Mills, 2003; Urry, 2010; Vieira, 2016). If they are right, we must choose between demographic
and economic degrowth, or an ecologically devastated world. Thirty years ago, such claims found little hearing, yet
research by climate scientists and conservation biologists appears to bear them out. In a recent Warning to
Humanity,more than 15,000 scientists assert: We are jeopardizing our future by not reining in our intense but geo-
graphically and demographically 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). Their suggestions for
creating sustainable societies include estimating a scientifically defensible, sustainable human population size for the
long term while rallying nations and leaders to support that vital goal,with no hint that merely stabilizing human
numbers will be sufficient (see also O'Sullivan, 2018).
Faced with the reality of GCC and its devastating impacts, climate ethicists have begun to address the role of population
and the need for limits to growth. Across all ethical approaches, there is a strong consensus on the value of choice-
enhancing policies that reduce fertility, such as securing universal access to modern contraception and providing equal
rights and opportunities for women. There is also strong support for government policies that incentivize smaller
CAFARO 13 of 17
families, considerable support for policies that disincentivize larger ones, and little to no support for punitive policies. It
appears that ethicists who ask what justice demands regarding population policy in a warming world may find reason-
ably clear answers. Whether our societies can discipline themselves to apply those answers is a further question.
The author has declared no conflicts of interest for this article.
Data derived from public domain resources.
Philip Cafaro
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How to cite this article: Cafaro, P. (2021). Climate ethics and population policy: A review of recent
philosophical work. Wiley Interdisciplinary Reviews: Climate Change, e748.
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... Yet the focus of population ethics, i.e., ethical research on moral issues regarding variable populations, has mostly remained anthropocentric. Ethical discussions that are more applied in nature mostly have sought to justify policies to reduce human population growth (Cafaro 2012(Cafaro , 2021Cripps 2016aCripps , 2016b. The more theoretically oriented population ethics aims to find an appropriate value theory of human populations that would avoid the infamous problems formulated by ...
... The environmental sustainability discourse in particular has emphasized the need to place upper "limits to growth" for human consumption and for the population to stay within (or return back to) the carrying capacity of the Earth. Population ethics with more applied motivations also discusses the morality of various population policies that aim to limit growth (Cafaro 2012(Cafaro , 2021Cripps 2016aCripps , 2016b. ...
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Current ecological threats, such as the sixth mass extinction or climate change, highlight the need to evaluate the moral implications of changing populations, both human and non-human. The paper sketches a non-anthropocentric and multispecies sufficientarian account of population ethics. After discussing several other options for multispecies population ethics, the paper proposes a two-level account of multispecies sufficientarianism, according to which the value of populations depend on two kinds of sufficientarian thresholds. First, there is a species-relativized individual-level threshold for what species-specific flourishing is for an organism. Second, there is a population-level threshold for a sufficiently viable population enough to support the species-specific flourishing of the current and future members of that population. The paper concludes by discussing some of the practical implications and concerns raised by the two-level account suggested.
... This approach is upheld in United Nations processes including the Aichi Targets of the Convention on Biological Diversity, and the 2030 Agenda and Sustainable Development Goals (SDGs). While MPAs are, and will continue to be, a fundamental and effective conservation tool when properly implemented and managed (see Edgar et al. 2014;Gownaris et al. 2019), human population growth, and activities contributing to unsustainable lifestyles, continue to threaten marine ecosystems beyond the boundaries of MPAs (Cafaro 2021;Halpern et al. 2019). Safeguarding marine biodiversity and ecosystems into the future will therefore require more holistic and inclusive approaches. ...
... Three important considerations affected what was considered within the scope of our methodological approach. 1) We note that up to and beyond 2030, the driver with the greatest impact on global marine ecosystems and biodiversity is anthropogenic climate change (Cafaro 2021;IPCC 2019;Trisos et al. 2020). Consequently, cutting greenhouse gas emissions is the action with the greatest potential benefit to the state of global marine ecosystems in the long term. ...
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Marine ecosystems and their associated biodiversity sustain life on Earth and hold intrinsic value. Critical marine ecosystem services include maintenance of global oxygen and carbon cycles, production of food and energy, and sustenance of human wellbeing. However marine ecosystems are swiftly being degraded due to the unsustainable use of marine environments and a rapidly changing climate. The fundamental challenge for the future is therefore to safeguard marine ecosystem biodiversity, function, and adaptive capacity whilst continuing to provide vital resources for the global population. Here, we use foresighting/hindcasting to consider two plausible futures towards 2030: a business-as-usual trajectory (i.e. continuation of current trends), and a more sustainable but technically achievable future in line with the UN Sustainable Development Goals. We identify key drivers that differentiate these alternative futures and use these to develop an action pathway towards the desirable, more sustainable future. Key to achieving the more sustainable future will be establishing integrative (i.e. across jurisdictions and sectors), adaptive management that supports equitable and sustainable stewardship of marine environments. Conserving marine ecosystems will require recalibrating our social, financial, and industrial relationships with the marine environment. While a sustainable future requires long-term planning and commitment beyond 2030, immediate action is needed to avoid tipping points and avert trajectories of ecosystem decline. By acting now to optimise management and protection of marine ecosystems, building upon existing technologies, and conserving the remaining biodiversity, we can create the best opportunity for a sustainable future in 2030 and beyond.
... Yet, ways to limit the increase of the human population without natural catastrophes also deserve further attention. Without curtailing human population growth, solutions to other aspects of ecological and social concern are far more difficult [2][3][4] . ...
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List> ● For 8000 years, agricultural practices have affected atmospheric CO2 concentrations. ● Paddy rice cultivation has impacted atmospheric CH4 concentration since 5000 years ago. ● Modern agricultural practices must include carbon storage and reduced emissions. ● Sustainable management in agriculture must be combined with decarbonizing the economy and reducing population growth. Since humans started practicing agriculture at the expense of natural forests, 8000 years ago, they have affected atmospheric CO2 concentrations. Their impact on atmospheric CH4 started about 5000 years ago, as result of the cultivation of paddy rice. A challenge of modern agricultural practices is to reverse the impact cropping has had on greenhouse gas emissions and the global climate. There is an increasing demand for agriculture to provide food security as well as a range of other ecosystem services. Depending on ecosystem management, different practices may involve trade-offs and synergies, and these must be considered to work toward desirable management systems. Solution toward food security should not only focus on agricultural management practices, but also on strategies to reduce food waste, more socially-just distribution of resources, changes in lifestyle including decarbonization of the economy, as well as reducing human population growth.
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A dominant narrative in the climate change debate is that addressing population is not relevant for mitigation because population is only growing in the poorest countries, whose contribution to global carbon emissions is negligible, while the largest contribution comes from rich countries where the population no longer grows. We conducted an analysis of 30 years of emission data for all world countries showing that this narrative is misleading. Splitting the countries into four income groups according to the World Bank’s standard classification, we found that: (i) population is growing in all four groups; (ii) low-income countries’ contribution to emissions increase is indeed limited; (iii) the largest contribution to global carbon emissions comes from the upper-middle group; (iv) population growth is the main driver of emissions increase in all income groups except the upper-middle one; (v) the successful reduction in per capita emissions that occurred in high-income countries was nullified by the parallel increase in population in the same group. Our analysis suggests that climate change mitigation strategies should address population along with per capita consumption and technological innovation, in a comprehensive approach to the problem.
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The human enterprise is in overshoot; we exceed the long-term carrying capacity of Earth and are degrading the biophysical basis of our own existence. Despite decades of cumulative evidence, the world community has failed dismally in efforts to address this problem. I argue that cultural evolution and global change have outpaced bio-evolution; despite millennia of evolutionary history, the human brain and associated cognitive processes are functionally obsolete to deal with the human eco-crisis. H. sapiens tends to respond to problems in simplistic, reductionist, mechanical ways. Simplistic diagnoses lead to simplistic remedies. Politically acceptable technical ‘solutions’ to global warming assume fossil fuels are the problem, require major capital investment and are promoted on the basis of profit potential, thousands of well-paying jobs and bland assurances that climate change can readily be rectified. If successful, this would merely extend overshoot. Complexity demands a systemic approach; to address overshoot requires unprecedented international cooperation in the design of coordinated policies to ensure a socially-just economic contraction, mostly in high-income countries, and significant population reductions everywhere. The ultimate goal should be a human population in the vicinity of two billion thriving more equitably in ‘steady-state’ within the biophysical means of nature.
This chapter focuses on four root causes that could be the most important causes that are rarely addressed by governments, industries, and many environmental professionals who continue to accept the ideology that technological innovation will allow endless economic growth on a finite planet. The four root causes are: limits of human evolutionary strengths and our psychological biases; human population; anthropocentrism; and the myth that technological innovation allows endless growth in consumption of materials, energy, and land on a finite planet. There are other root causes, but unless we address these root causes, we are unlikely to make progress on addressing the global environmental crises we have created. KeywordsAnthropocentrismCognitive biasesPopulationEvolutionConsumptionEconomic growthTechnology limitations
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This paper outlines a moral framework for the debate on global population policy. Questions of population, climate justice and global justice are morally inseparable and failure to address them as such has dangerous implications. Considerations of population lend additional urgency to existing collective duties to act on global poverty and climate change. Choice-providing procreative policies are a key part of that. However, even were we collectively to fulfil these duties, we would face morally hard choices over whether to introduce incentive-changing procreative policies. Thus, there is now no possible collective course of action which is not morally problematic.
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The idea of physical limits to human economic systems is advanced by physical scientists and ecological economists, as well as appealing to the common sense proposition that unending growth in physical processes such as material extraction and waste disposal will ultimately be inconsistent with any finite entity, even one as large as the Earth. Yet growth remains the central aim of business and government almost everywhere. This paper examines the history of the idea of economic growth and the many influences and interests that supported – and still support – its enshrinement as the principal aim of human societies. These include the apparatus of propaganda in favour of corporate interests; the emphasis on international trade; the funding of environmental denial; and, underlying all these, the corporate requirement for profit to continue to increase. The dominance of these influences has serious consequences for the natural world while growth has failed to solve the problems of poverty.
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Clear indicators and evaluation criteria are essential to keep humanity’s environmental impact within planetary boundaries. We introduce a new criterion based on two constraints, accounting for both ecological and human sustainability. The ecological constraint is defined through a novel indicator, the eco-balance, grounded on the well known concept of ecological footprint and the new concept of population biodensity. The human sustainability constraint is based on the estimated level of biocapacity consumption needed to achieve an acceptable level of human development. The application of our criterion to world countries shows where technological improvements and changes in consumption patterns are sufficient to reach sustainability, and where actions on population and/or restoring ecological capital are also needed. This highlights synergic patterns going beyond simplistic schemes, such as overconsumption vs. overpopulation or developed vs. developing countries.
This handbook presents up-to-date theoretical analyses of problems associated with the moral standing of future people in current decision-making. Future people pose an especially hard problem for our current decision-making, since their number and their identities are not fixed but depend on the choices the present generation makes. Do we make the world better by creating more people with good lives? What do we owe future generations in terms of justice? Such questions are not only philosophically difficult and important, but also directly relevant to many practical decisions and policy issues, including on climate, health, population control and taxation. If we are to adequately assess such issues, we must be able to determine the value of differently sized populations. The aim of this handbook is to shed light on the value of population change and the nature of our obligations to future generations, and to offer practical guidance to policy-makers as to how our duties to future generations should be discharged. It contains an extensive and accessible introduction for those unfamiliar with the topic of population ethics as well as original work from key figures in academic debates on population ethics covering three main themes: (1) ways out of the paradoxes of population ethics, (2) questioning some philosophical and methodological assumptions underlying these paradoxes, and (3) several applications of population ethics to real world issues.
Chapter: Unlike many of the discussions about population in philosophy, this chapter does not focus purely on whether too many people inhabit the world. Instead, it discusses that issue in a wider context, especially in the context of competition and collision between human, animal, and plant populations in a world experiencing a scarcity of freshwater, good soil, and other basic requirements for the flourishing of human and nonhuman life. <URL =>
Building the Population Bomb examines how human population came to be understood as a problem in the twentieth century, how it became an object of intervention for governments, scientists, and nongovernmental organizations, and how some forms of intervention got coded as legitimate while others were recognized as coercive. It traces the emergence and growth of two scientific perspectives on population from the 1920s to the present. The first, rooted in the natural sciences, considered the world’s population as a whole in relation to natural resources. The second, rooted in the social sciences, considered national population growth rates in relation to economic growth. These two perspectives converged briefly after World War II, convincing world leaders that population growth posed a barrier to economic development and a threat to worldwide peace and environmental integrity. The book documents how this overpopulation consensus attracted vast sums of money to demography and population control, and teases out the differences between population control, birth control, and family planning. It concludes with the fracturing of this consensus at the end of the 1960s, constituting the factions that structure today’s debates over whether the world’s population is growing too quickly or not quickly enough, and over what should be done about it. The book documents how population growth came to take the blame for the world’s most complex and pressing problems, and how efforts to solve “the population problem” have diverted attention and resources from the pursuit of economic, environmental, and reproductive justice.
There is growing acknowledgement of a moral obligation to curb our personal carbon emissions. However, while much has been said regarding certain kinds of carbon‐intensive behaviours, the philosophical literature has – until only very recently – been largely silent regarding one of the worst things that a person can choose to do from a climate perspective: namely, have a child. I contend that procreation is an inessential high‐emission activity – one that results in inordinately greater emissions than other activities like joyguzzling or flying. Given this, I argue that if we believe that individuals bear moral responsibility for their personal carbon emissions, then we have strong moral reasons to refrain from choosing to procreate, reasons which – for many – amount to a moral obligation to refrain from choosing to have children. I also consider whether our climate duties might also be discharged by offsetting the climate burden of any children we do choose to have and providing a concrete quantification of what that offsetting might look like.