Ecological economists have vigorously debated the concept and consequences of de-growth since the first publication by Kallis et al. (2010) and a-growth since the first publication by Van den Bergh (2010), as well as their value as alternative sustainability paradigms. In particular, an ideological debate by these authors (i.e., Kallis, 2011; Van den Bergh, 2011) in Ecological Economics has led to a conceptual debate by (mainly) these authors and (some) other authors in (mainly) this journal and (some) other journals (e.g., Haapanen and Tapio, 2016; Cosme et al., 2017).

However, environmental sustainability is a practical issue. Indeed, the observed failures of international pacts on climate change (e.g., the Kyoto Protocol and the Paris Agreement) suggest that it is not enough for a technological improvement to be possible or a cultural change to be intended to move the world away from unsustainable practices; new technologies and values must also be feasible (i.e., both effective and practical) to achieve realistic equilibrium sustainability conditions.

The primary purpose of this study is to test whether there can be synergies between a-growth and de-growth to support the practical debate over how to achieve weak sustainability and strong sustainability as two theoretically distinct sustainability paradigms. To do so, I will conceptually characterize the four sustainability paradigms (section 2.1) by developing a single theoretical framework that depicts all these sustainability paradigms (section 2.2). I will then apply real-world data to this theoretical framework to test whether the conditions required only by a-growth (based on improvements in production technology), only by de-growth (based on changes in consumption preferences), and the combined requirements under a-growth and de-growth are unable to meet the conditions required by weak and strong sustainability (section 3). I discuss the previous results in the literature and the novel insights of my study, as well as the methodological weaknesses and strengths of my approach in section 4, and I summarize my conclusion in section 5.

Note that the public opinion on the growth versus environment dilemma has been properly evaluated (i.e., multi-level and cross-country models) by three recent articles: Gugushvili (2021) in 33 European countries by applying logistic regressions to data from the 2017 European Values Study; Lou et al. (2022) in 58 countries by applying random forest models to the World Values Survey data collected from 2010 to 2014; and Paulson and Büchs (2022) in 34 European countries by applying logistic regressions to data from the 2017 European Values Study. Indeed, other articles are limited to a single country (e.g., Drews et al., 2019; Savin et al., 2021; Böhmelt and Zhang, 2023) or they apply single-level models (e.g., Nadeau et al., 2022). In those three articles, the idea of sacrificing a certain level of growth for the sake of the environment turns out to have predictors at the country level (i.e., Gross Domestic Product growth rate, Gross Domestic Product per capita, and carbon dioxide productivity) and the individual level. In particular, post-materialists, politically left-leaning, better-off, and higher educated people with a larger sense of responsibility, self-expansion identity, concern for the environment, and a more favorable attitude toward science and technology prioritize environmental protection over growth; materialists, politically right-wing, and disadvantaged people prioritize growth over environmental protection.

However, combining economic perspectives with ecological perspectives means adopting an interdisciplinary approach.

The secondary purpose of this study is to highlight the main linkages and interactions between ethical assumptions and implications in alternative perspectives. In particular, ethical assumptions and implications of the four main sustainability paradigms are highlighted in section 2.1, whereas ethical assumptions and implications of the combined theoretical model are discussed in section 5.

Note that many articles have characterized de-growth and a-growth in terms of values (e.g., Gunderson, 2018; Hankammer and Kleer, 2018; Strunz and Bartkowski, 2018; Sandberg et al., 2019) and policies (e.g., Khmara and Kronenberg, 2020; Fitzpatrick et al., 2022). Moreover, some articles have compared de-growth and a-growth from the experts’ and researchers’ perspectives (e.g., D'Amato et al., 2019; Lehmann et al., 2022). Finally, few articles have characterized de-growth and a-growth with a theoretical approach (e.g., Heikkinen, 2020) or an empirical approach (e.g., O'Neill, 2015). However, to the best of my knowledge, no articles have characterized and compared de-growth and a-growth with a theoretical and empirical approach.

In this section, we rely on the following realistic assumptions to support the analytical results:

Note that technology improvements or value changes in current generations in developed and less-developed countries will affect the production technologies and consumption preferences of the future generation (Van den Bergh et al., 2019). Moreover, the equitable distribution of social and economic costs solves the problem created by referring to average representative individuals. Finally, nature has instrumental value in weak sustainability, a-growth, and de-growth, but intrinsic value in strong sustainability (Zagonari, 2021).

Some teleological ethics are based on duty to future generations (e.g., Aristotle and Harsanyi); some deontological ethics are based on duty to future generations (e.g., Kant and Rawls);

In this section, we rely on the following real parameter values for the numerical results (Footprint Network, 2023; World Bank, 2023):

Note that I have assumed perfect inter-generational equity for all sustainability paradigms and no intra-generational equity for weak sustainability and a-growth (i.e., these sustainability paradigms adopt the perspective of an average individual). Next, the subscript N (northern hemisphere) is used to label parameters for OECD countries, and the subscript S (southern hemisphere) is used for non-OECD countries, with full recognition that this approach ignores some exceptions.

In summary, strong sustainability refers to sustainability in terms of an individual’s use of Earth’s resources (i.e., E_N ≤ E_F, E_S ≤ E_F); de-growth refers to sustainability in terms of both individual welfare and use of Earth’s resources (i.e., E_N ≤ E_F, E_S ≤ E_F, U_N ≤ U_F, U_S ≤ U_F); a-growth refers to sustainability in terms of both average welfare and use of Earth’s resources (i.e., p_N E_N + p_S E_S = E_C ≤ E_F, p_N U_N + p_S U_S = U_C ≤ U_F); and weak sustainability refers to sustainability in terms of average welfare (i.e., U_C ≤ U_F). In other words, weak and strong sustainability differ to the greatest extent among the four paradigms.

Using these assumptions and data, sustainability is not achieved under a-growth, since U_F = 4.444 < U_C = 6.251 and E* = 1.7 < E_C = 2.788. A technology improvement in both developed and less-developed countries should be achieved to meet E*/θ_AG = E_C/θ and U_F,AG ≥ U_C,AG (i.e., E = E* is included in this condition).

In particular, from E*/θ_AG = E_C/θ (equality 2), the use of resources must decrease (i.e., technological improvement TI = 1 + ∆θ < 1) if (5)TI=EF/EC<1 Since E_F = E* = 1.7 and E_C = 2.788. Thus, environmental efficiency must increase. Numerically, ∆θ = −0.39 = 1.7/2.788–1 = 0.61–1. Next, from U_F,AG = U_C,AG (inequalities 1_cur and 1_fut), the level of consumption must decrease (i.e., TI = 1 + ∆θ > 1) if:

or

Thus, if technological improvement occurs in the current period, the current generation must decrease its consumption level to avoid achieving greater welfare than the future generation. In contrast, if technological improvement occurs in the future period, the current generation can increase its consumption level without achieving a larger welfare than the future generation. Numerically, ∆θ = +2.51 from Equation 6_cur and ∆θ = −0.16 from Equation 6_fut.

Note that consumption is more likely to decrease (i.e., ∆θ > 0) if the concern for nature is small (i.e., small β) and the production technology is environmentally efficient (i.e., small θ), the consumption preference is large (i.e., large α), the concern for the future generation is large (i.e., large γ), and the world’s population is small (large E_F). Moreover, U_F,AG = 6.483, U_C,AG (current implementation) = 7.593, U_C,AG (future implementation) = 5.204 (i.e., U_F,AG > U_C,AG only if the technological transition occurs in the future period). Finally, under weak sustainability, sustainability is not achieved since U_F = 4.444 < U_C = 6.251. Achieving weak sustainability will require a reduction of the current welfare by 29% since U_F = 0.71 U_C. This is larger than the 24% reduction required under a-growth, in which technological improvement is implemented.

Under de-growth, sustainability is not achieved, since U_N = 8.265 > U_F = 4.444, U_S = 5.808 > U_F = 4.444, E_N = 5.74 > E_F = 1.7, and E_S = 2.14 > E_F = 1.7. A change in consumption preferences in both developed and less-developed countries should be espoused to achieve U_N* = U_N and U_S* = U_S. That is, E_N = E_N* = E_F and E_S = E_S* = E_F are included under these conditions. In particular, from equality 4, consumption preferences must decrease in developed countries (i.e., value change of α in developed countries VCA_N = 1 + ∆α_N < 1) and in less-developed countries (i.e., value change of α in less-developed countries VCA_S = 1 + ∆α_S < 1) if:

Numerically, ∆α_N = −0.66 and ∆α_S = −0.87. Next, from inequality 3, consumption preferences must decrease in developed countries (i.e., value change of α in developed countries VCA_N = 1 + ∆α_N < 1) and in less-developed countries (i.e., value change of α in less-developed countries VCA_S = 1 + ∆α_S < 1) if:

Where VCB_S and VCB_S are the value changes of β in developed and less-developed countries, respectively, VCG_S and VCG_S are the value changes of γ in developed and less-developed countries, respectively, and W represents the world (global) value based on the weighted populations, with:

Numerically, ∆α_N = −0.56 and ∆α_S = −0.66.

Note that from U_N = U_F and U_S = U_F, we can also obtain unfeasible solutions: ∆α_N = −0.64 and ∆α_S = −0.78. Moreover, U_F,DG = 1.204, U_C,DG (developed countries) = 1.600, U_C,DG (less-developed countries) = 1.165 (i.e., U_F,DG > U_C,DG only in less-developed countries). Finally, under strong sustainability, sustainability is not achieved since E_N = 5.74 > E* = 1.7 and E_S = 2.14 > E* = 1.7. Achieving strong sustainability will require a reduction of current consumption of Earth’s resources by 71% in developed countries and by 21% in less-developed countries.

The main analytical and empirical results are summarized in Table 2. Note that, under a-growth, it is assumed that the maximum transition costs that the current generation is willing to pay (i.e., 22,880 billion US$ = 24% of world GDP) is enough to move from θ to θ_AG. For example, the Italian government funded an ecological transition with 10 billion € per year for the next 6 years, which amounts to around 0.6% of the yearly Italian GDP (i.e., 1/40 of 24%).

Under the combination of a-growth and de-growth, if the technological transition occurs in the current period (i.e., conditions in 6_cur, 8_N, and 8_S are combined), the following relationship between changes in the consumption preferences (VCA_cur) and technology improvement (TI) must be met (9_cur):

With ° = E_F/TI and where VCB is the value change of β in both developed and less-developed countries and VCG is the value changes of γ in both developed and less-developed countries.

Under the combination of a-growth and de-growth, if the technological transition occurs in the future period (i.e., conditions in 6_fut, 8_N, and 8_S are combined), the following relationship between the change in consumption preferences and technology improvement must be met (9_fut):

Where

Note that because condition 9_cur combines the conditions in inequalities 1 and 3, it allows cultural changes in the conditions for a-growth and technological changes in the conditions for de-growth.

Figure 1 depicts as curves the combinations of conditions for a-growth (inequality 1_cur) and for de-growth (inequality 3) to produce 9_cur. Figure 1 also depicts as points the solutions for a-growth (inequality 1_fut) and for de-growth (inequality 3) to produce 9_fut (i.e., ∆α = 0.602–1 at a given β and γ, but ∆α = 0.903–1 if β is increased by 50%, ∆α = 0.318–1 if γ is increased by 50%, while ∆θ = 0.901–1). Note that the conditions in equality 2 for a-growth and 4 for de-growth are depicted by values smaller than 1 for 1 + ∆θ and 1 + ∆α, respectively (i.e., a technology improvement if ∆θ < 0 for a-growth and a consumption preference change if ∆α < 0 for de-growth).

Note that, by mathematical continuity, if the technological transition is implemented between the current and the future periods, the required ∆α and ∆θ will lie between the curve for a given color and the corresponding colored point in each scenario. In particular, the condition for weak sustainability is met since U_C = 6.251 < 6.483 = U_F,AG if ∆α = 0 and ∆θ = −0.39, whereas the conditions for strong sustainability are met by definition. Moreover, a larger concern for the environment (i.e., with β increased by 50% in both developed and less-developed countries) favors the fulfillment of the conditions in equalities 4 and 2 (i.e., a smaller ∆α is allowed for a given ∆θ), whereas a larger concern for the future generation (i.e., with γ increased by 50% in both developed and less-developed countries) complicates the fulfillment of the conditions in equalities 4 and 2 (i.e., a larger ∆α is required for a given ∆θ). Finally, a current technological improvement lets us achieve sustainability at a smaller change in consumption preferences than a future technological improvement for any magnitude of technological improvement (i.e., the curve for a given color is above the corresponding colored point in each scenario). In particular, a trade-off between technological improvement and a change in consumption preferences is relevant only for a current technological improvement (i.e., the required ∆α for a future technological improvement can be read on alternative curves for ∆θ = 0).

In the introduction, environmental sustainability is argued to be a practical issue (i.e., the new technologies suggested by a-growth and the new values suggested by de-growth must be feasible). In addition, environmental sustainability is claimed to be an interdisciplinary issue (i.e., the achievement of a sustainable equilibrium requires a compromise between economic and ecological criteria).

With regard to the primary purpose of this study (i.e., possible synergies between a-growth and de-growth to achieve weak and strong sustainability), the main results of this study support the following statements:

By combining the conditions for a-growth and de-growth, the present study achieved the following insights:

In other words, implementing both technology improvements and value changes makes a-growth rely on relative rather than absolute decoupling and makes de-growth require realistic rather than unrealistic changes in consumption preferences.

Note that sustainability as an ethical issue to a greater extent than a technological issue implies that sustainability is an institutional problem. Emphasis should be put on institutions that shape the rules of interactions (conventions, norms, and legal rules) and institutions that aggregate the values of societies (communication, treatment, and representation of complexity). Next, the ethical concern for nature as more favorable than the ethical concern for future generations implies that religious and secular institutions fostering any environmental sensitivity should be supported. Think of inter-religious dialog on environmental precepts, for example, a focus on trusteeship and parsimony in Islam, maintaining equilibrium for every single organism in Hinduism, and avoiding pain for sentient animals in Buddhism (Zagonari, 2020b; Zagonari, 2023). Similarly, think of education for environmental responsibility at different education levels (i.e., from elementary pupils to university students) and at different environmental scopes (i.e., from local to global problems), for example, education about the environment, education through the environment, and education for the environment (Kopnina, 2020; Rousell, 2020).

In addition, with regard to the secondary purpose of this study (i.e., possible linkages and interactions between ethical assumptions and implications), the main features of the theoretical model combining a-growth and de-growth can be summarized as follows: the objective unit is the average welfare (i.e., like in weak sustainability and a-growth); intra-generational efficiency is disregarded (i.e., like in de-growth and strong sustainability); intra-generational equity is disregarded (i.e., like in weak sustainability and a-growth); and the constraint unit is the per-capita environmental status (i.e., like in de-growth and strong sustainability).

The present study has the following methodological weaknesses:

The present study has the following methodological strengths:

Note that the lack of unconditional analytical solutions due to the many parameters that are involved is irrelevant since numerical solutions based on real data are essential to solve such a practical problem. Next, sensitivity analysis is not required since the analytical models are based on production and utility functions, which are continuous in both variables and parameters, while the numerical results are depicted in a graphical framework which is based on continuous changes in parameters.

The purpose of this study was to test whether synergies were possible between a-growth and de-growth to achieve weak sustainability and strong sustainability as two theoretically distinct sustainability paradigms. The results show that a-growth is impossible whether the technological improvement occurs in the current period or the future period (due to the inconsistent technological changes that are required), whereas de-growth is unfeasible (due to the huge change in consumption preferences that are required). However, a combination of a-growth and de-growth was feasible, and it brought the weak and strong sustainability solutions closer together. In other words, the practical similarities between a-growth and de-growth (e.g., reduced working hours) should be stressed rather than ideological differences (e.g., efficiency in a-growth and equity in de-growth).

In summary, a-growth and de-growth have two different goals (efficiency and equity, respectively) and two different units (welfare based on the instrumental value of nature and the environmental status based on the intrinsic value of nature, respectively), although they both refer to the duty to future generations. A-growth adds externalities with respect to weak sustainability, whereas de-growth defines equity in terms of the minimum individual’s welfare. In de-growth, value changes (∆α) enable the achievement of an ecological stable equilibrium (E(0)) at a smaller loss in terms of welfare by attaching a larger value to a good environmental status. This value change amounts to the internalization of the environmental status in a-growth, although it implies the loss of individual’s identity assumed by a-growth (i.e., each individual as a set of fixed preferences). In a-growth, technological changes (∆θ) attach a smaller value to consumption in terms of the environmental status by enabling the achievement of a given level of welfare from consumption at a better environmental status. This technological change favors the satisfaction of the relative decoupling assumption in de-growth, although it requires the presence of complete and perfect information assumed by a-growth (i.e., the types of capitals to be focused on are properly identified). In combining a-growth and de-growth, the present study achieves intergenerational efficiency in terms of welfare (i.e., W_FG (E(0)) ≥ W_CG (E(0))) and the intergenerational equity in terms of the environmental status (i.e., E = E(0)). Note that W_FG ≥ W_CG does not imply the social stability as defined in the economic models, whereas E = E(0) does not imply the ecological resilience as defined in the ecological models.

Publicly available datasets were analyzed in this study. This data can be found at: http://data.worldbank.org and http://www.footprintnetwork.org.

FZ: Writing – original draft, Writing – review & editing.