1. Introduction
Due to the Paris Agreement, much attention and research has gone into the question of how to limit global warming to 1.5 °C (see e.g. IPCC, 2018). In this context, several scenarios were introduced that include carbon dioxide removal (CDR) measures, most prominently the land-based CDR measure bioenergy combined with point source carbon capture and geological storage (BECCS). On average, scenarios that remain within the 1.5 °C temperature limit with no or only a limited (below 0.1 °C) temperature overshoot include 4.5 Gt CO2 per year of BECCS by 2050, and 12.4 Gt CO2 per year by 2100 (IPCC, 2018, Table 2.4). The latest IPCC assessment report emphasizes the need for CDR: ‘The deployment of CDR to counterbalance hard-to-abate residual emissions is unavoidable if net zero carbon dioxide or greenhouse gas emissions are to be achieved’ (IPCC, Reference Shukla, Skea, Slade, Al Khourdajie, van Diemen, McCollum, Pathak, Some, Vyas, Fradera, Belkacemi, Hasija, Lisboa, Luz and Malley2022, C.11, emphasis added).
CDR measures seemingly offer a solution to the shrinking carbon budget that comes with ambitious climate mitigation (Minx et al., Reference Minx, Lamb, Callaghan, Fuss, Hilaire, Creutzig, Amann, Beringer, de Oliveira Garcia, Hartmann, Khanna, Lenzi, Luderer, Nemet, Rogelj, Smith, Vicente, Wilcox and del Mar Zamora Dominguez2018). They offer the possibility to (i) support current mitigation efforts by reducing current net emissions, (ii) compensate for future residual emissions to achieve net zero CO2 or greenhouse gases (GHGs), and (iii) reverse a carbon budget overshoot with net negative emissions. When they first came to prominence, in the early days of the so-called ‘geoengineering’ debate, CDR technologies were largely regarded as somewhat benign, but it is now acknowledged that CDR measures raise a host of ethical questions (for an overview see e.g. Heyward, Reference Heyward and Letcher2019; Minx et al., Reference Minx, Lamb, Callaghan, Fuss, Hilaire, Creutzig, Amann, Beringer, de Oliveira Garcia, Hartmann, Khanna, Lenzi, Luderer, Nemet, Rogelj, Smith, Vicente, Wilcox and del Mar Zamora Dominguez2018). One of the first problems raised by commentators was that increasing discussion of CDR measures could distract attention from the essential task of reducing emissions – the objection popularly known as ‘moral hazard’ (Anderson and Peters, Reference Anderson and Peters2016; Fuss et al., Reference Fuss, Canadell, Peters, Tavoni, Andrew, Ciais, Jackson, Jones, Kraxner, Nakicenovic, Le Quéré, Raupach, Sharifi, Schmidt and Yamagata2014). Furthermore, if deployed at the scale specified in the 1.5 °C scenarios, land-based or terrestrial CDR (tCDR) such as BECCs would compete with other demands for land. Given that most of the biomass provided for BECCS in ambitious mitigation scenarios is projected to come from the Global South (Daioglou et al., Reference Daioglou, Muratori, Lamers, Fujimori, Kitous, Köberle, Bauer, Junginger, Kato, Leblanc, Mima, Weise and van Vuuren2020; Fajardy et al., Reference Fajardy, Morris, Gurgel, Herzog, Mac Dowell and Paltsevet2021), biomass-based CDR options have been identified as an agrarian challenge that would be imposed on developing countries (McElwee, Reference McElwee2022) that have contributed little to causing the problem. Therefore, the drive to develop and use tCDR options may provide an excuse for some parties to ride rough-shod over the land rights of indigenous communities, smallholders, or other local communities (Bluwstein & Cavanagh, Reference Bluwstein and Cavanagh2023), as has happened in the past (Neudert & Voget-Kleschin, Reference Neudert and Voget-Kleschin2021). Other side-effects associated with land-use demand include stress on water supply and negative effects regarding biodiversity and ecosystems (Boysen et al., Reference Boysen, Lucht, Gerten, Heck, Lenton and Schellnhuber2017; Heck et al., Reference Heck, Gerten, Lucht and Popp2018, Reference Heck, Gerten, Lucht and Boysen2016). Finally, a problem for BECCS approaches is the need for permanent storage of CO2 in geological formations, given previous controversy in Germany and the Netherlands (Akerboom et al., Reference Akerboom, Waldmann, Mukherjee, Agaton, Sanders and Kramer2021; Bürgerinitiative gegen CO2-Endlager e.V, n.d.; Mogelpackung CCS, n.d.). The topic of geological CO2 storage has since become a deal-breaker within the German political debate (Hahn et al., Reference Hahn, Szarka and Thrän2020).
Despite these potential difficulties, most scientific articles detailing ambitious mitigation scenarios include large deployment of tCDRs, most usually BECCS; and alternative pathways entailing behavioral change and societal transformation rarely feature (Beck & Mahony, Reference Beck and Mahony2018; Bellamy, Reference Bellamy2016). It has been observed that in the history of climate change debates, some self-imposed so-called ‘taboos’ have been present in that certain kinds of response to climate change have been avoided, from adaptation to solar radiation management (Lawrence, Reference Lawrence2006; Lawrence & Crutzen, Reference Lawrence and Crutzen2017; Rayner et al., Reference Rayner, Pielke, Prins and Sarewitz2007). ‘Taboo’ is perhaps not the most accurate term, but it has been used loosely by these authors to describe collective explicit or implicit reservations about discussing or considering certain options with potentially highly undesirable consequences. Within the broad category of emission reductions, some particular strategies have been similarly tabooed; the most obvious example being the widespread avoidance of discussing limiting population growth (Cripps, Reference Cripps2012, Reference Cripps, Gardiner and Thompson2016; Heyward, Reference Heyward2012).
To a lesser, but still significant extent, talk about scenarios that more obviously require societal change is largely avoided. It is regularly assumed that such scenarios will be more difficult or costly to implement and/or that it is impermissible to implement policy measures that push people to adopt certain ‘green’ lifestyles. On a number of accounts, ‘telling people how to live’, for example, how to dispose of their income, how to spend their time, etc., is morally problematic in itself, being patronizing and disrespectful of the autonomy of adult citizens.
This implicit assumption is connected to the problem of ‘moral hazard’ referred to above: presumably the chances of anything ‘distracting’ from emission reductions would be vastly reduced if the latter were easy and cheap to implement and ethically unproblematic. This seems to be behind Pozo et al.'s (Reference Pozo, Galán-Martín, Reiner, Mac Dowell and Guillén-Gosálbez2020) claim that an ‘international CDR supply chain […] seem[s] to be necessary to meet the long-term Paris goals and avoid drastic demand side-measures and lifestyle changes’ (Pozo et al., Reference Pozo, Galán-Martín, Reiner, Mac Dowell and Guillén-Gosálbez2020; emphasis added). Relatedly, Healey et al. (Reference Healey, Scholes, Lefale and Yanda2021) state ‘[for] the majority of high emitting countries, [perceived] fungibility between emissions and CDR sequestration targets provides a temptation to delay efforts with the more lifestyle-challenging or expensive policies of emission reduction’ (emphasis added). Others, for example, Prinzing (Reference Prinzing2023) have called for a ‘reframing’ to emphasize the benefits of emission reduction measures and green lifestyles, which makes sense only if the dominant framings claim or imply that such lifestyles are unattractive. (Prinzing notes that much environmentalist discourse has long invoked notions of ‘self-sacrifice’ and simple, or even austere lifestyles. There has also been considerable use of apocalyptic rhetoric in environmental movements along the lines that [vast sections of] humanity must change its ways in order to avert catastrophe (Heyward & Rayner, Reference Heyward, Rayner, Crate and Nuttall2016). The use of a threat rhetoric implies that those to whom it is directed would be unwilling to make the changes without it.)
The tendency to assume that calling for social change is problematic and thus avoiding it is unhelpful – and perhaps even unnecessary. Achieving emission reductions through requiring or facilitating social transformation might, on closer inspection, not be as morally problematic as sometimes assumed. This study is a first attempt at providing a closer inspection. Van Vuuren et al. (Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018) are one of the relatively few who have modeled alternative pathways to 1.5 °C. We here discuss some key moral issues raised by the assumptions of their four alternative transformation pathways involving societal transformations, and their implications. The scenarios are called ‘lifestyle change scenario’, a ‘low non-CO2 GHGs scenario’, an ‘agricultural intensification scenario’, and a ‘low-population scenario’ (see info box for more information). All of the scenarios aim to be moderate in their assumptions, for example, reduction rather than abandonment of meat consumption, and decreasing population growth by means of policies aiming at a higher average level of education rather targeting procreation directly. However, as even these moderate scenarios seem vulnerable to ethical objections, it is helpful to examine whether such objections are warranted. This is the task of this article.
We limit discussion to the scenarios in Van Vuuren et al. and the analysis here is intended only as a starting point. We also limit our discussion to ethical permissibility, not political feasibility or any other political concerns. Moral permissibility and political feasibility are linked, but by no means co-extensive. Moral reasons are frequently invoked in political debates and a widespread perception that a policy is unfair, unjust, or morally impermissible will seriously affect public acceptability and therefore (in more democratic countries) political feasibility.
There is of course a risk of a prospective or retrospective political backlash against implementation of any kind of social or technological change motivated by climate concerns. Serious backlashes can even jeopardize overall support for action on climate change and the move toward decarbonization. One possible way of minimizing such backlashes is to take seriously the fact that all climate response measures and initiatives will raise possible moral concerns and to acknowledge and discuss these from the outset. For the vast majority of possible measures – and certainly the pathways discussed in this article – none should be taken as inherently benign nor inherently problematic; their permissibility or lack thereof will depend mostly on context and implementation.
We start by examining four scenarios. Our analysis focuses whether policies assumed in the lifestyle change and in the low-population scenario could qualify as permissible (Section 2.1–2.2). Based on this discussion, and because the low non-CO2 and the agricultural intensification scenario seem to assume a significantly smaller extent of societal transformation, our analysis of the latter scenarios centers on more concrete pros and cons (Section 2.3–2.4). Section 3 draws out some implications of each scenario related to both intra and inter-generational justice. Section 4 concludes.
Figure 1. CO2 emissions for the 1.9 W/m2 mitigation scenarios. The plot shows cumulative emissions for the 2010-2100 period partitioned into positive fossil fuel emissions (black), negative emissions from BECCS (dark blue for net negative emissions, light blue for other BECCS) and land-use change emissions (dark green for positive emissions, light green for negative emissions). The yellow marker represents the net emissions. Source: Fig. 2c in Van Vuuren et al., Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018
2. Moral analysis of the scenarios
Before we begin our analysis, a note on the terminology and set up might be helpful. The ‘lifestyle change scenario’ is not about lifestyle changes per se. After all, any response to climate change, like climate change itself, will cause changes in at least some of the ways that at least some people live their lives. Instead, this scenario is limited to consumer habits connected to everyday economic consumption. (In particular, those consumption patterns associated with a relatively affluent [Western] lifestyle.) In this scenario, consumers reduce meat consumption and food waste. They also adopt less CO2-intensive transport modes, reduce ownership and use of domestic appliances, and less intensive use of heating and cooling systems in their homes. The second scenario, ‘low population’, is different in that it is not about individual consumer choices. Whilst having children clearly affects household consumption, it is not normally classified as a consumer choice. This is arguably for good reason: the decision to have a child is qualitatively and morally different from engaging in high-emission economic consumption and the two should not be treated as morally equivalent (e.g. Heyward, Reference Heyward2012). The third scenario, ‘low non-CO2’, turns from the realm of household choices to the production of goods. In this scenario, the focus is on reducing non-CO2 GHG emissions, in particular, the CH4 emissions associated with livestock farming and meat production. A key part of such reduction is the move from traditional livestock rearing for meat production to cultured meat and animal products. This scenario would not only lead to reduced emissions, but also increase animal welfare without opposition from people that do not want to switch to vegetarian or vegan diets. Finally, the fourth scenario ‘agricultural intensification’ retains the focus on meat production but does not envisage the replacement of traditional meat and animal-based food products.
2.1 Lifestyle changes
As noted above, Van Vuuren et al.'s ‘lifestyle change scenario’ assumes that consumers change their consumption habits: namely dietary changes, the use of less CO2-intensive transport, heating, and cooling, and an outright reduction of the use of domestic appliances. In many countries, there is already increasing vegetarianism and veganism, which has not been directly policy-induced. However, it is unreasonable to expect that sufficient numbers of consumers will make such changes without significant policy initiatives and incentivization. Therefore, to ensure sufficient change at scale, policy measures should aim at designing so-called ‘consumption environments’ that enable, support, and – in certain situations – demand climate-friendly consumption (WBAE, 2020).
However, such a substantial incentivization of low-GHG lifestyles and accompanying discouragement of high-GHG lifestyles are criticized in public debates as interfering with people's ability to freely choose how to live. According to such critique, the state ought to not tell people how to live fulfilling lives, as that is up to its citizens to decide for themselves (Food and Soft Drinks: Nanny State Index in the European Union [EU-28] 2021, 2021; Harrabin, Reference Harrabin2018; Schmidt and Engelen, Reference Schmidt and Engelen2020; Sugden, Reference Sugden2009; Tapsfield, Reference Tapsfield2021).
The political philosophy in which such arguments are rooted claims that the state ought to be neutral regarding questions of the good life. This is regarded by some as a key component in liberal democracies. According to John Rawls, state neutrality is achieved if the ‘aims of the basic institutions and public policy […] can be said to be neutral with respect to […] conceptions of the good’ (Rawls, Reference Rawls2001, p. 153). Such conceptions give meaning to one's life and entail ideas about, for example, whether and how to believe in a deity; whether, with whom and how to form a family and what occupation and hobbies are rewarding.
However, the argument that the state ought not to promote low-GHG lifestyles because this would violate the principle of state neutrality must overcome several difficult challenges. To begin with, note that the argument against incentivizing low-GHG lifestyles can only get off the ground if the principle of neutrality is accepted. So-called perfectionist theories in philosophy reject this principle (Hurka, Reference Hurka1993; Wall, Reference Wall1998). Rather than being neutral, the state should advance the good life of its citizens based on an objective account of what is a valuable human life. The most prominent examples of perfectionism in politics are theocratic states, but other forms of perfectionism in politics are possible, including ‘liberal perfectionism’. (For a seminal critique of the neutrality principle and defense of liberal perfectionism, see Raz [Reference Raz1986].)
Putting this aside, we can note that low/high-GHG lifestyles as such do not seem to be ‘conceptions of the good’ at least as understood by Rawls. Such conceptions are ‘an ordered family of final ends and aims which specifies a person's conception of what is of value in human life […]. The elements of such a conception are normally set within, and interpreted by, certain comprehensive religious, philosophical, or moral doctrines in the light of which the various ends and aims are ordered and understood’ (Rawls, Reference Rawls2001, p. 19). Thus understood, low/high-GHG lifestyles are not themselves conceptions of the good but rather (partial) expressions or simply results of such conceptions. That is, these lifestyles may be rooted in more fundamental and comprehensive ideas of, say, autonomy, seeking pleasure, or how own relates to nature. Think of a person akin to Walter Faber in Max Frisch's novel Homo Faber: to such a person, living well may mean to distance oneself from the natural world via technology and he may cherish travelling in cars and planes, spend time in energy-intensive built environments, and use many electric appliances. Still, his conception of the good is not to emit lots of GHGs. The emissions rather are an unintended side-effect of how he chooses to live, not a constitutive element of it. (We are grateful to an anonymous reviewer who pressed us on this point.)
Take the examples of vegetarian days in canteens (De Keyzer et al., Reference De Keyzer, Van Caneghem, Heath, Vanaelst, Verschraegen, De Henauw and Huybrechts2012) or speed limits on auto-routes (Madireddy et al., Reference Madireddy, De Coensel, Can, Degraeuwe, Beusen, De Vlieger and Botteldooren2011). These policies do not restrict or disincentivize conceptions of the good such as living autonomous lives or seeking pleasure as there are many different ways of achieving these aims. By contrast, a policy that aims at incentivizing the adoption of certain religious (or atheist) practices would violate the principle of state neutrality. As current policy proposals for encouraging the adoption of low-GHG lifestyles do not touch upon the level of basic and comprehensive values, they do not favor conceptions of the good in the sense that concerns proponents of state neutrality. Hence, the objection from state neutrality fails, at least in the case of the policies discussed in the lifestyle change scenario.
Moreover, a key principle, in Rawls' theory and most contemporary accounts, is that each person possesses a set of basic rights compatible with the same set of rights for all (see Rawls, Reference Rawls2001, p. 42) and that a state may intervene to prevent transgressions of these rights, even if these interventions conflict with some conceptions of the good. It has long been acknowledged that climate change undermines key human rights for millions if not billions of present and future people (for an overview see Bell, Reference Bell2013). Thus, even if one assumes if emitting large quantities of GHGs is a constituent element of a conception of the good, it would nevertheless be permissible for the state to restrict them on the grounds that high-GHG lifestyles collectively undermine basic human rights. Correspondingly, at the political level, those who generally support state neutrality accept that policy measures can enable, support, and sometimes direct certain lifestyle changes, if current lifestyle choices harm others, or put others at considerable risk. For example, measures taken across EU countries to reduce smoking in public places are now largely accepted. (Such policies can draw on different legal resources. For instance, smoke-free legislation built on labor laws and might have been more difficult to advocate based on public health reasons.) Hence, the state may take action which compromises citizens' abilities to pursue their conceptions of the good provided that the reason is to avoid or reduce the violation of established principles of basic justice (e.g. regarding basic rights). Given that states are to protect their (and other) citizens from climate-related harms, they must severely limit GHG emissions, support adaptation, and more (Gardiner, Reference Gardiner2010).
To summarize, anyone who wishes to claim that policies to promote low-GHG lifestyles violate the requirement that states ought to be neutral between the conceptions of the good has to show that consuming high amounts of GHGs can count as a conception of the good in the relevant sense. Furthermore, they have to claim also that climate change will not involve transgressions of human rights. We consider the first challenge to be very hard and the second virtually impossible to overcome. Therefore, the neutrality objection is unconvincing.
There is also a positive argument to promote low-GHG lifestyles. As a general rule, we maintain that climate mitigation measures should not be viewed in isolation from other goals, such as promoting human rights, sustainable development, or protecting biodiversity (Heyward, Reference Heyward and Letcher2019; following Caney, Reference Caney2013; IPCC, Reference Shukla, Skea, Slade, Al Khourdajie, van Diemen, McCollum, Pathak, Some, Vyas, Fradera, Belkacemi, Hasija, Lisboa, Luz and Malley2022). Some policies have greater potential for bringing about multiple benefits (including the benefits of GHG emission reduction) than others. For example, the substitution of meat by pulses and/or oil crops offers leeway to implement more extensive animal husbandry systems which will allow for improvements in animal welfare and biodiversity conservation, respectively. Against this backdrop, and as long as no other convincing critique is brought forward, we consider these ‘lifestyle change’ – or rather – ‘consumption change’ pathways in countries of the Global North as an important (and in our view compelling) alternative pathway to the 1.5 °C target. It therefore should be explicitly considered in both scientific and policy debates, including discussions about the need for CDR measures.
2.2 Low population
Calls for population-focused policies to reduce GHG emissions are perhaps the most controversial kind of mitigation measure. Early discussions of population and climate change referred to the topic as ‘the elephant in the room’ (Cripps, Reference Cripps2012), and pointed to the misanthropic veneer of policy discussions in the past as well as flawed framings in the philosophical discourse (Heyward, Reference Heyward2012). Coercive measures such as China's infamous ‘one child policy’ are unacceptable from the point of view of most normative frameworks. From a human rights perspective, they violate basic human rights such as women's right to decide freely and responsibly on the number and spacing of their children (see Final Act of the International Conference on Human Rights, 1968, p. XVIII, 3). Moreover, as population increase is highest in lower-income countries, advocating population reduction measures can be interpreted as shifting the focus from the Global North's responsibility to act to the Global South. (However, there is also some scholarly debate on lowering population in the Global North, given the higher per-capita emissions rates [Hedberg, Reference Hedberg2019; Rieder, Reference Rieder and Kim2016].)
However, there are indirect ways that can have the effect of reducing global population or rather the rate of population increase, particularly education of women, along with greater protection of women's rights and work opportunities for women outside the home (Sen, Reference Sen1997). Thus, the shared socioeconomic pathway 1 (SSP1) as chosen in the low-population scenario by Van Vuuren et al. (Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018) assumes a different trajectory of education in general by adding one further year of schooling, especially in the Global South (Samir & Lutz, Reference Samir and Lutz2017). This was projected to result in an earlier peak in global population and lower population, respectively, compared to the default SSP2 scenario in the Van Vuuren study. By 2100, the global population in SSP1 is 6.9 billion people, compared to a projected 9.0 billion in SSP2. One key driver for this development is increased female education attainment (Samir & Lutz, Reference Samir and Lutz2017). (Whether seven billion people can live sustainably on earth is disputed [see e.g. Dasgupta, Reference Dasgupta2019], but this strongly depends on consumption and production patterns.)
Moreover, increasing educational attainment for women in particular is also linked to reduced risk of domestic abuse, reduced child mortality (Balaj et al., Reference Balaj, York, Sripada, Besnier, Vonen, Aravkin, Friedman, Griswold, Jensen, Mohammad, Mullany, Solhaug, Sorensen, Stonkute, Tallaksen, Whisnant, Zheng, Gakidou and Eikemo2021), increased child educational performance (Mak Arvin & Summers, Reference Mak Arvin and Summers1999), and improved economic performance (Klasen, Reference Klasen2018). Realizing a higher average level of education among women thus contributing to realizing human rights and the sustainable development goals (SDGs) relating to both education and gender equality. In addition to improving education for women, other strategies, that is, those that target realizing the human right to reproductive choice, reduction of childhood mortality, human rights to an adequate standard of living, and human rights to equal employment opportunities can simultaneously contribute to the realization of human rights, SDGs, and GHG emission reductions (Caney, Reference Caney, Akande, Kuosmanen, McDermott and Roser2020; Heyward, Reference Heyward2012; Sen, Reference Sen1996, Reference Sen1997). (Counteracting racial, ethnic, or religious tension could also reduce the temptation for some group leaders to adopt ‘pro-natalist’ polices, in order to gain a demographic advantage over their rivals [see e.g. Morland, Reference Morland2014].)
Two further points should be noted here. The first is that education for men and boys is also important as female empowerment cannot happen without the support of men. Males with higher levels of education are typically more willing to endorse gender equality policies and practices (Barker et al., Reference Barker, Verma, Crownover, Segundo, Fonseca, Contreras, Heilman and Pawlak2012; Fulu et al., Reference Fulu, Warner, Miedema, Jewkes, Roselli and Lang2013; Marcus, Reference Marcus2014; UNESCO, 2022). (We thank an anonymous reviewer for raising this point.) The second is that realizing higher average level of education is desirable regardless of its impact on population. (The importance of education for human quality of life is the reason why education features as one of three dimensions in the United Nations Human Development Index [also see Anand & Sen, Reference Anand and Sen1997].) This is all the more true regarding the Global South which on average features a comparatively low level of education and a high level of illiteracy, linked to limited opportunities for employment and income generation and higher chances of poor health (see Cree et al., Reference Cree, Andrew and Steward2012; Maddox, Reference Maddox2008).
To summarize, a lower total world population correlates with significantly lower GHG emissions, especially in the long term. Furthermore, [a] ‘stabilising or even declining global population after 2050 (as often projected) could reduce the pressure from competing land claims, allowing for more bioenergy production or reforestation’ (Van Vuuren et al., Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018). While direct population policies potentially violate human rights, there exist a bundle of measures that contribute to realizing human rights and SDGs, respectively, and in addition result in lower total world population. Due to their multiple socio-economic and human rights benefits in addition to emission reduction, it is arguable that, rather than being tabooed, such strategies are preferable to CDR and any other measures that target only climate mitigation.
2.3 Low non-CO2
The low non-CO2 scenario assumes the implementation of the best available technologies for reducing GHG emissions other than CO2, like methane (CH4) and nitrous oxide (N2O), and a wide-spread adoption of cultured meat in 2050. Van Vuuren et al. (Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018, supplement) assume that 80% of meat-like products (including eggs) are replaced by cultivated meat and that dairy products are produced by the remaining 20% of animals still used for meat (product) production. In this section, we focus on the replacement of traditional meat products by cultured meat.
Animal husbandry is associated with CO2, CH4 (especially ruminants), and N2O emissions. Cultured or in-vitro meat is produced using stem-cell technology and inputs of energy and (plant) protein. And while the adoption of cultured meat is dependent on further research and requires the development of market-ready products, this option could become competitive in the long run (at least as a niche product with a premium price) (Garrison et al., Reference Garrison, Biermacher and Brorsen2022; Post, Reference Post2012). The fact that an increase in vegetarianism and veganism in some countries has caused a demand-driven uptake of such products by existing food companies as well as start-ups shows that the free market can already play a significant role in this development (see e.g. https://cellbasedtech.com/lab-grown-meat-companies). However, while some consumer-uptake is to be expected, the degree of uptake as envisioned by Van Vuuren et al. would require overcoming some continuing concerns by means of policy measures that support or even demand uptake. Such concerns include unnaturalness, safety, healthiness, anticipating inferior taste, texture, and/or appearance of cultured meat, expectation of high prices in comparison to conventional meat and societal concerns regarding the effects on traditional animal agriculture, distrust in companies producing cultured meat, and concerns regarding the energy required for production (see e.g. Bryant and Barnett, Reference Bryant and Barnett2018; Siegrist and Hartmann, Reference Siegrist and Hartmann2020).
Apart from consumer acceptability, there are a number of objections that could be raised against the large-scale replacement of traditional meat products by cultured meat. One objection points out that grasslands are important habitats for many animal and plant species and are therefore rich in terms of biodiversity. The habitat for these plant and animal communities depends on grazing, which means keeping ruminants for meat or dairy. However, Van Vuuren et al. assume that 20% of today's number of farm animals remain, mostly for the production of dairy. These could (theoretically) be raised in extensive, grass-based systems and thereby ensure the preservation of valuable highly biodiverse grasslands.
Another objection points to a loss of employment in animal husbandry. However, if we assume that the reason for cultured meat replacing conventionally produced meat is to reduce GHG emissions so as to protect individuals' basic rights in the face of climate change (see Section 2.1), employment in conventional meat production/animal husbandry is not as such deserving of protection. But like the phasing out of other unsustainable branches, such a transition should be accompanied by measures supporting affected people and regions. Does that mean that the adoption of cultured meat as assumed by Van Vuuren et al. constitutes a promising alternative to the 1.5 °C target compared to relying heavily on CDR measures? Here, we want to highlight two issues. First, as an alternative pathway to the 1.5 °C target, increasing production and consumption of cultured meat is only desirable if it results in fewer GHG emissions. However, producing cultured meat is energy intensive, and accordingly only reduce GHG emissions if energy generation is decarbonized (Lynch & Pierrehumbert, Reference Lynch and Pierrehumbert2019) and a decarbonized energy sector leaves enough energy for surplus demand to produce cultured meat. Second, in the low non-CO2 scenario, the GHG reductions ultimately result from the decrease of conventional meat production. The reductions are achieved by substituting conventional with cultured meat, which only describes one pathway to reduced conventional meat production. Alternatively, consumers could simply choose to demand less meat, conventional or cultured, by switching to already available plant-based products. The non-CO2 scenario thus entails the additional assumption that consumer demand for meat of whatever form will not change.
We have argued above (Section 2.1) that policies such as those aiming to motivate consumers to adopt low-GHG lifestyles are permissible, if not even imperative. Policies to encourage consumers to limit or forego consumption of conventional meat are part of this. If, however, both dietary changes and the increase of consumer demand for cultured meat require policy measures, one can ask which kind of behavioral change is preferable: a change toward less consumption of both conventional and cultured meat products or a replacement of conventional meat by cultured meat. With regard to this, studies show that the environmental impact (including GHG emissions) of cultured meat is better than some (e.g. beef) and comparable to other (e.g. pork, chicken) traditional meats but worse than that of plant-based meat alternatives (see Jetzke et al., Reference Jetzke, Richter, Keppner, Domröse, Wunder and Ferrari2020; Van der Weele et al., Reference Van der Weele, Feindt, Van der Goot, Van Mierlo and Van Boekel2019; Vural Gursel et al., Reference Vural Gursel, Sturme, Hugenholtz and Bruins2022). Given that some kinds of measures to discourage meat consumption overall are permissible (see Section 2.1), it seems that policies to incentivize this should be preferred to encouraging replacement of conventional by cultured meat.
The possibility to reduce GHG emissions via an increase in production and consumption of cultured meat as an alternative to conventional meat thus could be another promising alternative to a corresponding increase in CDR, since the measures would have benefits for animal welfare, as well as human and animal health. However, it only is an alternative if the energy sector is decarbonized and leaves enough energy for surplus demand to produce cultured meat. Moreover, we regard the possibility to reduce GHG emissions via an increase in production and consumption of cultured meat as inferior to doing so via dietary changes to a more plant-based diet.
2.4 Agricultural intensification
The agricultural intensification scenario assumes increasing livestock efficiency and increasing yields to the most efficient levels globally. Increasing livestock efficiency allows reducing cattle stock, which plays an important role for reducing non-CO2 GHGs (Van Vuuren et al., Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018).
The potential for agricultural intensification is highest where the ‘yield gap’ is highest. The yield gap designates the gap between what is actually produced and what could be produced under intensive animal husbandry systems and given agro-climatic conditions. (The concept of yield gap is widely used in production ecology and can also be applied to livestock science [see Van de Ven et al., Reference Van de Ven, de Ridder, van Keulen and van Ittersum2003; Van der Linden et al., Reference Van der Linden, Oosting, van de Ven, de Boer and van Ittersum2015].) Globally, crop yield gaps are highest in Sub-Saharan Africa, followed by South-East Asia and South America. Quantifying the yield gap in livestock is more difficult (see Gerber, Reference Gerber2016) but generally, the productivity of livestock in the Global South is low (Herrero et al., Reference Herrero, Mayberry, van de Steeg, Phelan, Ash, Dizyee, Robinson, Henderson, Gilbert, van Wijk, Godde, Blummel, Prestwidge, Stephenson, Power and Parsons2016). Accordingly, agricultural intensification primarily involves increasing livestock efficiency and yields in the Global South.
The potential ethical problem for this scenario is that given the above, this may lead to ‘rescaling of the land rush’ (Bluwstein & Cavanagh, Reference Bluwstein and Cavanagh2023, p. 288). Starting with the financial crisis in 2008, countries in the Global South, especially Sub-Saharan Africa experienced a stark increase in (large-scale) land acquisitions (LSLAs) by domestic and foreign investors that aim at rapidly increasing (crop) productivity through high inputs of capital, new technologies, and agrochemicals (Behrman et al., Reference Behrman, Meinzen-Dick and Quisumbing2014). (To our knowledge, the majority of the literature focuses on LSLA that aims to produce crops, but the evidence shows that there are also LSLA aiming at producing livestock [e.g. Borras et al., Reference Borras, Franco, Kay and Spoor2011; Schneider, Reference Schneider2014, see also https://landmatrix.org, Land Matrix, n.d.].) Whilst this was legitimized as ‘much-needed investment’, Borras and Franco conclude that the land rush largely favored the landed classes and elite actors (Reference Borras and Franco2018, p. 7).
In contrast to intensification based on high inputs of capital, new technologies, and agrochemicals, pro-poor, low-input, and sustainable intensification focuses on improved management of existing inputs rather than drawing on higher external inputs such as mineral fertilizer or agrochemicals. Sustainable intensification ‘is defined as a process or system where agricultural yields are increased without adverse environmental impact and without the conversion of additional non-agricultural land’ (Pretty & Bharucha, Reference Pretty and Bharucha2014, p. 1578). It causes less perturbation of the nitrogen and the phosphorus cycles than intensive agriculture and is more aligned to the needs and possibilities of the poor.
Part of the negative consequences of high-input agricultural intensification results from background injustice. That is, investments in land take place in the context of strong and rigid intra- and intercommunal inequities that systematically privilege certain actors (Kleemann et al., Reference Kleemann, Lay, Nolte, Ott, Thiele and Voget-Kleschin2013; Nolte & Voget-Kleschin, Reference Nolte and Voget-Kleschin2014). This is one reason why successful pro-poor and/or sustainable intensification requires ‘a holistic cross-sectoral harmonization of policies – i.e. in agricultural, land, and urban industrial policies, as well as public investments in physical infrastructure, health, education, family planning, etc.’ (Jayne et al., Reference Jayne, Chamberlin and Headey2014, p. 12). While such cross-sectoral governance changes that aim at alleviating injustice are desirable, they are also complex and will take time. In other words, they require substantial societal transformations promoting social justice and sustainable development. As such, pro-poor intensification can be understood as a building block of an encompassing sustainable development strategy. This also means that it is desirable not only for its effects regarding emission reductions but its multiple benefits, that is, its contributions to reaching the SDGs (FAO, 2018).
To summarize, increasing livestock efficiency and increasing yields to the most efficient levels primarily requires implementing corresponding measures in the Global South. To avoid negative social consequences requires that this be done in a pro-poor way. This presupposes substantial societal transformations, that is, addressing the encompassing institutional background against which agricultural development takes place. Therefore, it represents a long-term strategy for sustainability.
2.5 Overarching reflections on social transformation and state neutrality
The upshot of the above discussion is that while state neutrality is an important principle, it should not mislead us into foregoing the discussion of any scenarios requiring societal transformation. Nor should it lead to the unquestioned assumption that scenarios that (allegedly) require less societal transformation such as agricultural intensification or CDR are generally preferable to those that quite obviously involve societal transformation such as the lifestyle change and low-population scenarios.
Moreover, as our discussion of agricultural intensification has demonstrated, pathways that seem to primarily build on technical approaches may well involve societal transformations. Interestingly, some of the issues raised here, for example, negative social consequences of agricultural intensification or the assumption of a decarbonized energy sector for increasing production and consumption of cultured meat, are also raised in the context of large-scale CDR. Our study highlights the need to look closely at the ways different pathways could be implemented and the need for reflection on what kinds of societal transformations are compatible with taking state neutrality seriously (also see Fragnière, Reference Fragnière2014).
3. Some remarks on burden sharing
As mentioned above, the topic of burden sharing has been extensively discussed and it is not our intention to contribute to that debate here. However, different mitigation pathways and policies will inevitably have implications on the distribution of economic and non-economic costs. We would like to make a few remarks in this regard because a burden-sharing perspective sheds further light on the moral permissibility of the scenarios and related policies.
Economic and non-economic costs of climate policies will be distributed within states, across states (matters of global justice), and across generations (matters of intergenerational justice). With regard to global justice, the prevailing view is that the lion's share of costs and burdens of dealing with climate change should be shouldered by states in the Global North (see e.g. Hayward, Reference Hayward2012), or the global elite regardless of where they live (Caney, Reference Caney2005, Reference Caney2013; Chakravarty & Ramana, Reference Chakravarty and Ramana2012).
In the lifestyle change scenario, consumption rates converge globally, meaning that the burden of change falls on current high consumers, both in the Global North and South. In the low non-CO2 scenario, persons in all countries are asked to take up cultured meat. However, as global elites tend to consume more meat, the main burden falls upon them. By contrast, in both the population scenario and the agricultural intensification scenario, changes predominantly affect the Global South. Accordingly, mitigation scenarios requiring social transformation in the Global South are only acceptable if they primarily aim at improving the quality of life for non-elite individuals in the Global South. From a global justice perspective, the lifestyle change and the low-population scenarios as well as agricultural intensification via pro-poor growth strategies are clearly preferable to the low non-CO2 and agricultural intensification scenarios.
With respect to the distribution of costs over generations, there is no strong prevailing view equivalent to that found in the context of global justice. However, it is widely agreed that impacts of climate change will be more severe over time and thus disproportionately burden future generations. From the perspective of intergenerational justice, pathways that take seriously the problem of cumulative CO2 emissions and avoid putting even greater climate burdens on future generations are more attractive.
Cumulative CO2 emissions determine long-term warming (Rogelj et al., Reference Rogelj, Forster, Kriegler, Smith and Séférian2019) since their impact on atmospheric warming is occurring on much longer time scales compared to shorter lived GHGs or climate forcers (see Arias et al., Reference Arias, Bellouin, Coppola, Jones, Krinner, Marotzke, Naik, Palmer, Plattner, Rogelj, Rojas, Sillmann, Storelvmo, Thorne, Trewin, Achuta Rao, Adhikary, Allan, Armour, Zickfeld, Masson-Delmotte, Zhai, Pirani, Connors, Péan, Berger, Caud, Chen, Goldfarb, Gomis, Huang, Leitzell, Lonnoy, Matthews, Maycock, Waterfield, Yelekçi, Yu and Zhou2021, Fig. TS.20). Of particular relevance here is CH4, which is the second most important GHG contributor to climate change, but which has a much shorter lifespan than CO2.
The low non-CO2 and agricultural intensification pathways reduce non-CO2 GHG emissions. This would also be the case if meat consumption overall were reduced, as in the lifestyle change scenario. The consequent atmospheric cooling effectively reduces the need for CDR to meet end of the century warming goals (Van Vuuren et al., Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018). By reducing non-CO2 GHG emissions from CH4, the radiative forcing of the non-CO2 GHGs is reduced, which allows for more warming by CO2. As a result, the cumulative CO2 emissions by the end of the century in these scenarios are higher (see Figure 1). This is especially evident for the low non-CO2 scenario, in which cumulative emissions until 2100 are about 50 Gt CO2 higher than in the energy and material efficiency or the renewable energy scenario (Van Vuuren et al., Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018). (In this paper, we do not discuss these additional scenarios of Van Vuuren et al. because they are less controversial.)
The long-term warming in scenarios with higher cumulative CO2 emissions will accordingly be higher, putting additional pressure on future generations that are already burdened substantially with climate risks, impacts, and realizing net zero emissions. Therefore, with a view to burden-sharing across generations, the low non-CO2 and agricultural intensification scenario are ethically less problematic if they are pursued in addition to reducing net CO2 emissions, rather than as a substitute for short-term CO2 reductions as assumed in the scenarios discussed here.
4. Conclusion
We have discussed the moral implications of four scenarios that would reduce GHG emissions and hence the need for large-scale tCDR in ambitious mitigation scenarios (for a summary see Table 1). Two of them, the lifestyle changes and the low-population scenarios, are very clearly linked to societal transformations and the need for different lifestyles at the individual level. This has led to them being met with substantial skepticism and largely tabooed in political debates (cf. Section 1). By contrast, the other two scenarios, the low non-CO2 and the agricultural intensification scenarios, are commonly perceived as less challenging, possibly because at first glance they seem to encompass less need for societal transformation.
Table 1. Outline of the main arguments of Section 2
Please note that the table only serves as guidance to the reader. Without the context provided in the above sections, it is not meaningful and should thus not be used in isolation.
We show that the latter two scenarios are in fact the ones that turn out to be in need of further scrutiny. In the Global South, where potential for agricultural intensification is highest, an intensification based on high inputs of capital, new technologies, and agrochemicals is associated with considerable negative social consequences. A low-input, pro-poor agricultural intensification is far more ambitions in terms of societal transformations (especially regarding land governance and equity issues) than those implied in the lifestyle change and low-population scenario. By contrast, the switch from conventional meat production to cultured meat as a measure within the low non-CO2 scenario is not so challenging and goes along with co-benefits for animal welfare, human and animal health. But we argued that reducing GHG emissions via an increase in production and consumption of cultured meat is inferior to doing so via dietary changes toward a more plant-based diet.
Regarding the lifestyle changes and low-population growth scenario, we find that these pathways do indeed constitute permissible, perhaps even preferable, alternative options for contributing to the 1.5 °C goal. Our discussion shows that the key argument against the promotion of less GHG-intensive lifestyles, that is, that it violates the key principle of state neutrality, fails. Furthermore, we have pointed out that the lifestyle changes assumed by Van Vuuren et al. (Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018) go along with significant co-benefits. To argue for CDR to be on par or preferable to such lifestyle changes therefore requires presenting other arguments against measures that enable, support, or demand lifestyle changes and/or showing that large-scale CDR measures can bring about a similar extent of co-benefits than those associated with less GHG-intensive lifestyles. Similarly, low-population growth scenarios that result from increasing the average level of education as assumed by Van Vuuren et al. (Reference Van Vuuren, Stehfest, Gernaat, van den Berg, Bijl, de Boer, Daioglou, Doelman, Edelenbosch, Harmsen, Hof and van Sluisveld2018) constitute a multiple-benefit strategy in that increasing the average level of education brings about several positive effects, of which reduced emissions stemming from lower population growth is only one. If these pathways are indeed ethically preferable, we should discuss how to increase their political and societal feasibility, rather than simply assuming that they are unviable.
An open-ended discussion of different alternative pathways that does not rule out certain options from the outset on account of their involving societal transformations broadens the horizon to include much-needed multiple-benefit strategies. Against this backdrop, we reject the assumption that in comparison to large-scale tCDR, the alternative pathways modeled by Van Vuuren et al. are ethically problematic. Rather, we encourage a broader critical discourse on the role the state should play and on the implicit assumptions made by scientists and policy-makers regarding the ethical permissibility of certain policy pathways, including those that have been seemingly ‘tabooed’.
Acknowledgments
We would like to acknowledge Denise Reubert for her help with the references and the audience at the 2nd International Conference on Negative CO2 Emissions in Gothenburg, June 14–17, 2022, for their helpful questions. We would also like to thank the two anonymous reviewers for their constructive comments, especially for bringing up the point of the importance of non-female education.
Author contributions
C. H. and N. M. conceived the study. N. M., L. V.-K., C. H., and C. B. designed the structure of the manuscript. D. V. V. advised on the details of the pathways and commented on the manuscript. L. V.-K., C. H., and C. B. provided the moral philosophical arguments of the manuscript. All authors wrote the article and revised it for resubmission.
Funding statement
Nadine Mengis is funded under the Emmy Noether scheme by the German Research Foundation ‘FOOTPRINTS – From carbOn remOval To achieving the PaRIs agreemeNt's goal: Temperature Stabilisation’ (ME 5746/1-1). Clare Heyward's contribution was supported by both CEMICS2 (Contextualising Climate Engineering, Mitigation, Illusion, Complement or Substitute) SPP 1689, German Research Foundation, and the Institute for Future Studies project: ‘Climate Ethics and Future Generations’, funded by Riksbankens Jubileumsfond (grant number M17-0372:1). Christian Baatz is funded via project ADJUST (01UU2001) that is part of the funding line ‘Social-Ecological Research’ within the framework strategy ‘Research for Sustainability’ (FONA) by the Federal Ministry of Education and Research of Germany (BMBF). Lieske Voget-Kleschin acknowledges the financial support by the Federal Ministry of Education and Research of Germany (BMBF) in the framework of ASMASYS (03F0898D), one of the six research consortia of the German Marine Research Alliance (DAM) research mission ‘Marine carbon sinks in decarbonisation pathways’ (CDRmare). Detlef Van Vuuren acknowledges funding support from the European Research Council (ERC) under the Horizon Europe program (PICASSO project; grant agreement ID 819566).
Competing interests
None.
Research transparency and reproducibility
No unpublished data or software has been used for the manuscript.
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