Environmental awareness and humanities for environmental sustainability in the 21st century: rethinking development through social science lenses in the nordic nations

Despite their reputation as global front-runners in environmental governance and institutional excellence, the Nordic countries are increasingly grappling with complex sustainability pressures—from rapid urbanization and cultural realignments to evolving educational landscapes and shifting socio-economic dynamics. This study explores the impact of economic growth (EG), urbanization (URB), humanities investment (HUM), social trust (SS), and environmental awareness potential (EAP) on environmental sustainability (ES), measured via biocapacity per capita. Using panel data from 2002 to 2023 across five Nordic nations, the analysis applies the Method of Moments Quantile Regression (MMQR) and Feasible Generalized Least Squares (FGLS) to capture heterogeneous effects and ensure robustness. The results show that HUM consistently enhances ES, EG contributes positively at higher sustainability levels, while URB increasingly undermines ES in more advanced contexts. SS has a persistent negative effect, and EAP exhibits a nonlinear U-shaped relationship—initially reducing ES before improving it after a threshold. This study makes a novel empirical contribution by systematically integrating educational and cultural dimensions—often treated as peripheral in sustainability modeling—into a rigorous econometric framework. Specifically, it operationalizes humanities investment and environmental awareness as core explanatory factors within a panel structure, addressing critical gaps in the literature that have historically prioritized economic and technological determinants. By doing so, the research advances an interdisciplinary understanding of sustainability transitions as culturally embedded and socially mediated processes. Findings offer actionable insights for policymakers, particularly in aligning environmental education, cultural investment, and urban planning with the Sustainable Development Goals (SDGs), to drive sustainable transitions in the 21st century.

1 Introduction

The Nordic nations—Denmark, Finland, Iceland, Norway, and Sweden—are globally recognized for their robust welfare systems, strong democratic institutions, and progressive environmental policies (Raphael et al., 2024). Their commitment to sustainability is evident in initiatives like Denmark’s goal for Copenhagen to become the world’s first carbon-neutral capital by 2025 and Sweden’s Stockholm Wood City project, aiming to construct the world’s largest wooden city to reduce carbon emissions (Kangas and PalmeSocial PolicyEconomic, 2005; Kvist et al., 2011). However, despite these advancements, these countries face persistent sustainability challenges. For instance, the concept of Earth Overshoot Day reveals that if everyone lived like the average Nordic citizen, humanity would exhaust Earth’s annual resources much earlier in the year, indicating high per capita ecological footprints (Landström et al., 2019).

Urbanization is a significant factor influencing environmental sustainability in the Nordic region. Rapid urban growth has led to increased energy consumption, waste generation, and pressure on natural resources (Clement et al., 2003). While urban areas can offer efficiencies and innovations, they also pose challenges in balancing development with ecological preservation (Neubauer et al., 2007; Xu et al., 2025). Cultural investment, particularly in the humanities, plays a crucial role in shaping societal values and behaviors towards the environment (Holm et al., 2015). The Nordic countries have a rich tradition of supporting cultural initiatives that promote environmental awareness and stewardship (Holmberg, 2020). However, the extent to which these investments translate into tangible environmental outcomes remains underexplored.

Social trust is another cornerstone of Nordic societies, facilitating collective action and policy implementation (Philip et al., 2024). High levels of trust can enhance compliance with environmental regulations and support for sustainability initiatives (Holmberg, 2020; Cai et al., 2025). Yet, the direct impact of social trust on environmental sustainability metrics requires further empirical investigation.

Environmental awareness potential (EAP) reflects the capacity of individuals and societies to understand and act upon environmental issues. In the Nordic context, where education systems are well-developed, EAP is presumed to be high (Gram-Hanssen et al., 2023). Nevertheless, the relationship between EAP and actual environmental outcomes is complex and warrants detailed analysis.

The Nordic countries—Denmark, Finland, Iceland, Norway, and Sweden—offer a uniquely fertile ground for examining the societal dimensions of environmental sustainability. Their advanced economies, strong institutional frameworks, and globally recognized environmental policies create an ideal empirical landscape to investigate how cultural, social, and educational systems intersect with ecological outcomes (Philip et al., 2024). Far from being incidental choices, these nations were selected as the analytical focus of this study due to their status as real-world laboratories of sustainability governance. With high levels of institutional trust, cohesive welfare systems, and vibrant civic cultures, the Nordic model embodies a holistic policy architecture where environmental goals are often pursued in synergy with cultural investment, social cohesion, and economic planning (Reichborn-Kjennerud, 2025).

Moreover, these countries consistently top global rankings on environmental performance, social equality, and democratic governance, reinforcing their global reputation as leaders in sustainable development (Wang et al., 2020; Duan, 2025). What distinguishes them further is their integrated policy ethos—an approach where investments in humanities, trust-building, and education are seen not merely as social goods but as foundational pillars for long-term ecological resilience (Häyrynen, 2018; Nassar et al., 2024). This makes the Nordic context particularly well-suited to exploring whether and how non-technological, human-centered variables—such as cultural engagement, social trust, and environmental awareness—serve as enablers or limitations in realizing sustainable environmental performance.

By investigating the interplay of these variables within this high-governance, high-capacity region, the study not only contributes to a more nuanced understanding of sustainability transitions but also offers insights that may be transferable to other regions aiming to balance socio-economic progress with ecological integrity.

This study advances the current literature by examining the multidimensional drivers of environmental sustainability in the Nordic countries, focusing specifically on the roles of economic growth, urbanization, cultural investment, social trust, and environmental awareness. Unlike prior research that tends to isolate economic or technological determinants, this study integrates socio-cultural and educational dimensions to uncover how human-centered variables influence ecological outcomes in high-governance contexts. Economic growth (EG) is included linearly, even though the Environmental Kuznets Curve (EKC) hypothesis posits a U-shaped relationship between income and environmental outcomes. This choice is justified because the Nordic countries are high-income, post-industrial economies that prior studies suggest already lie beyond the EKC turning point, where further economic growth tends to correlate with improved environmental outcomes rather than deterioration (Munir and Ameer, 2022). Modeling EG linearly in this context, therefore, reflects both the economic maturity of the region and the literature that identifies more stable positive effects at advanced stages of development.

Similarly, urbanization (URB) is treated as a linear control, although prior research highlights that its impact on emissions and land use often follows an inverted U-shaped trajectory (Munir and Ameer, 2022; Talib et al., 2022). The justification for linear specification in this study rests on the distinctive features of Nordic urbanization: advanced green infrastructure, integrated spatial planning, and compact city models that mitigate many of the environmental costs typically associated with urban growth. In such contexts, urbanization’s effects are more stable and monotonic, making a linear treatment both parsimonious and appropriate for the Nordic case.

By contrast, environmental awareness (EAP) is explicitly modeled nonlinearly through a quadratic specification, as both theory and empirical findings suggest that awareness operates in a threshold-dependent manner. Increases in awareness may initially raise recognition of environmental challenges without delivering immediate improvements, but once a critical mass of cognitive and institutional capacity is achieved, the influence shifts toward positive sustainability outcomes (Hermansson, 2023). For cultural investment (HUM) and social trust (SS), the literature supports more monotonic relationships, and the empirical results consistently confirm positive (HUM) or negative but attenuating (SS) effects, justifying their treatment as linear (Yongsheng and Yingquan, 2025).

Methodologically, the study employs the Method of Moments Quantile Regression (MMQR) to analyze distributional effects across varying levels of sustainability performance, and Feasible Generalized Least Squares (FGLS) to ensure robustness in the presence of cross-sectional dependence and heteroskedasticity. These techniques allow for a refined understanding of how the influence of each variable shifts across different ecological contexts. The results yield robust empirical evidence on the effectiveness—and limits—of cultural and educational investments in shaping environmental outcomes, offering rich insights for both academic discourse and policy design. Importantly, the policy recommendations generated from this analysis are tailored to the Nordic governance model but hold broader relevance for regions seeking to align socio-economic development with environmental integrity in the 21st century.

Based on the study’s objectives, the following research inquiries are addressed: (i) How do economic growth and urbanization impact environmental sustainability in the Nordic countries? (ii) What is the role of cultural investment and social trust in shaping environmental outcomes? (iii) How does environmental awareness potentially influence sustainability metrics, and is there a nonlinear relationship? (iv) What policy interventions can enhance the positive effects of these variables on environmental sustainability? By exploring these questions, the study aims to deepen the understanding of the multifaceted drivers of environmental sustainability and inform effective policy-making in the 21st century.

The organization of this paper is as follows: Section 2 provides a review of the relevant literature, Section 3 details the data and methodological framework, Section 4 reports the empirical results, and Section 5 discusses policy implications along with recommendations for future research.

2 Literature review

This section integrates various empirical studies examining how urbanization, the humanities, social trust, and education contribute to environmental sustainability across different countries.

2.1 Urbanization and environmental sustainability

Urbanization is widely recognized as a complex driver of environmental change, functioning both as a source of ecological pressure and as a potential avenue for sustainability innovation. While rapid urban growth often contributes to increased energy demand, vehicular emissions, and land conversion—factors that collectively elevate carbon emissions and ecological stress—it can also foster environmental gains when guided by effective planning (Zhang et al., 2024). Transit-oriented development, compact urban forms, and energy-efficient infrastructure have been shown to reduce per capita environmental footprints when strategically implemented. A global study by (Toor et al., 2024) demonstrated that urban expansion significantly disrupts biodiversity and alters ecological equilibria, underscoring the need for interdisciplinary approaches to urban sustainability. Complementing this, a study by (Mengiste et al., 2024) found that unregulated urban sprawl not only reduces agricultural land but also intensifies environmental pressures, especially in peri-urban zones. A study by (Harms et al., 2024) further argues that the environmental consequences of urbanization can be mitigated by re-integrating natural ecosystems into urban planning. Their findings advocate for visionary, nature-sensitive planning models that reconnect cities with ecological systems, offering pathways to balance urban development with sustainability imperatives.

2.2 Humanities and ecological sustainability

The humanities encompass disciplines such as philosophy, history, literature, ethics, and the arts—fields that cultivate critical reflection, cultural expression, and normative inquiry. Cultural investment, in this context, refers to public and private expenditure directed toward these domains, including funding for museums, libraries, performing arts, heritage conservation, and educational programs in the humanities. These investments reflect societal valuation of cultural capital, creativity, and ethical reasoning—traits increasingly recognized as foundational to sustainability transformations (Routledge et al., 2018; Soini and Dessein, 2016).

While the link between cultural investment and social development is well established, its implications for environmental sustainability require deeper interrogation. Cultural engagement can foster ecological awareness, promote sustainability education, and reinforce social cohesion—all of which are essential for collective environmental action. However, recent scholarship complicates this narrative. (Pyykkönen, 2024). critiques the anthropocentric bias in cultural sustainability discourse, arguing that cultural policy must more explicitly integrate ecological values to avoid reinforcing human-centered paradigms that marginalize nature.

(Schmitz and Herrero-Jáuregui, 2021) offer a complementary perspective by demonstrating how humanities-based conservation—particularly of cultural landscapes and traditional ecological knowledge—contributes to biodiversity preservation and ecological resilience. Their findings underscore the role of cultural heritage in shaping sustainable resource use and environmental stewardship.

In the Nordic context, where cultural policy enjoys robust institutional support, this paradox is especially salient. High levels of public investment in the humanities coexist with strong environmental performance, yet the alignment between cultural funding and ecological objectives remains uneven. As (Häyrynen and Hämeenaho, 2020) argues, cultural policy frameworks must evolve to explicitly support sustainability transitions by embedding ecological ethics, interdisciplinary collaboration, and place-based cultural practices into their design.

Taken together, these insights suggest that the humanities can either advance or impede ecological sustainability depending on how they are institutionally framed, funded, and integrated into broader governance systems. Including cultural investment as a variable in sustainability analysis thus requires a nuanced understanding of its normative, educational, and ecological dimensions.

2.3 Environmental awareness and environmental sustainability

Education attainment is widely recognized as a fundamental driver of sustainable development, influencing economic growth, environmental awareness, and social equity. Recent studies highlight the transformative role of higher education and skill development in fostering sustainability across different regions. A study by (Tafese and Kopp, 2025) explores how higher education institutions are embedding sustainability principles into curricula, shaping future leaders with a strong environmental consciousness. The research emphasizes that education for sustainable development (ESD) has gained momentum, particularly in Europe and Asia, where universities are aligning their programs with global sustainability goals. A study by (Gra et al., 2025) suggests that higher environmental awareness enhances economic resilience, reducing inequalities and fostering sustainable urban development. So, the higher consciousness rates and specialized training about the environment contribute to the adoption of renewable energy technologies, circular economy models, and climate adaptation strategies.

2.4 Social sciences and environmental performance

Social factors, including constructs such as social trust, civic participation, and collective norms, are increasingly recognized as foundational to sustainability transitions. These elements, studied extensively within the social sciences, influence how communities engage with environmental governance, adopt sustainable behaviors, and respond to climate policies. It is important to distinguish between the epistemic role of the social sciences as fields of inquiry and the operational role of social dynamics as drivers of ecological outcomes.

Social trust, in particular, functions as a lubricant for environmental governance by enhancing public compliance with regulations, facilitating cooperative behavior, and bolstering societal support for climate action. However, its influence is context-dependent and shaped by institutional quality, cultural norms, and historical legacies. For instance, (Ghoddousi et al., 2022), found that high levels of community trust significantly improved conservation outcomes in protected areas by fostering local stewardship and reducing anthropogenic pressure. Their study underscores the importance of trust-based engagement in enhancing the effectiveness of environmental management.

Conversely, in settings where trust is fragmented or eroded, governance efforts may falter, leading to poor enforcement and biodiversity loss. (Sánchez-García et al., 2025). extended this line of inquiry by demonstrating that social trust underpins equitable sustainability transitions across European regions. Their research revealed that trust enhances collaborative behavior in environmental policy implementation, while disparities in trust across social groups can inhibit collective ecological action and exacerbate environmental injustice.

These findings align with broader literature emphasizing the role of social norms and civic cohesion in shaping sustainability outcomes. (Yamin et al., 2019), in a systematic review of behavioral interventions, showed that leveraging social norms can effectively promote pro-environmental behavior in real-world contexts. Similarly, (Schulz, 2024), highlighted the positive correlation between civic knowledge, institutional trust, and youth engagement in sustainability-oriented citizenship across democratic societies.

Taken together, these studies affirm that while the social sciences provide the analytical tools to study human-environment interactions, it is the underlying social factors—trust, participation, and norms—that actively shape the trajectory of sustainability transitions. Embedding trust-building mechanisms and inclusive civic engagement within environmental institutions is therefore essential for fostering resilient and equitable ecological outcomes.

3 Data, model formulation, and methods

This study investigates the drivers of environmental sustainability across five Nordic countries—Denmark, Finland, Iceland, Norway, and Sweden—covering the period from 2002 to 2023. The panel dataset includes six key variables derived from internationally recognized databases, as summarized in Table 1. The dependent variable, environmental sustainability (ES), is proxied by biocapacity per capita (measured in global hectares per person), sourced from the Global Footprint Network (GFN Global Footprint Network, 2025). This metric reflects the ecological capacity of each country to support its population and resource demands without overshooting natural limits.

Table 1

Table 1. Data source and variables.

The selection of independent variables is guided by a multidimensional understanding of sustainability, which incorporates not only structural economic and demographic aspects but also deeper sociocultural and cognitive drivers. Three variables represent the socio-cultural dimension. Environmental Awareness Potential (EAP) is constructed using Principal Component Analysis (PCA) on enrollment rates at primary, secondary, and tertiary levels (Khoiri et al., 2021). This index serves as a proxy for population-wide ecological awareness, building on the premise that education is a primary channel through which environmental values are transmitted and internalized. In the Nordic context, where sustainability education is deeply embedded in curricula and pedagogical approaches, education levels are strongly correlated with environmentally responsible attitudes and behaviors (Seikkula-Leino et al., 2021).

Government expenditure on cultural sectors is used as a proxy for investment in the humanities (HUM), reflecting the societal value placed on cultural capital, creativity, and ethical reflection—traits increasingly recognized as foundational to sustainability transformations. The social sciences (SS) dimension is proxied by national-level trust indices, thereby operationalizing the role of civic cohesion and collective norms (Luonila et al., 2023). The selection of social trust over other potential indicators is particularly justified in the Nordic context, where generalized trust is exceptionally high compared to global averages and constitutes a distinctive socio-cultural attribute of the region. This embedded trust underpins institutional legitimacy, reduces transaction costs in governance, and enables more effective collective responses to environmental challenges. As (Ekström and Sörlin, 2022) noted, the strength of social trust in Nordic societies facilitates cooperation, enhances compliance with environmental regulations, and accelerates the uptake of shared sustainability goals. In this sense, social trust is not only an empirically robust indicator of social cohesion but also a uniquely relevant variable for understanding how socio-cultural dynamics shape sustainability trajectories in the Nordic countries.

To account for broader structural and behavioral determinants of sustainability, the study includes two additional variables: economic growth (EG) and urbanization (URB). Both are obtained from the World Development Indicators (WDI World Bank, 2024). Economic growth is measured by annual GDP per capita growth, reflecting the scale and dynamics of economic activity. Its inclusion is theoretically grounded in the Environmental Kuznets Curve (EKC) hypothesis, which posits a non-linear relationship between income and environmental pressure—whereby environmental degradation may initially rise with economic growth but decline beyond a certain income threshold (Georgescu et al., 2024). Recent studies have found this pattern to be particularly relevant in Nordic high-income contexts, such as Norway, where economic expansion has shown both enabling and constraining effects on sustainability outcomes (Soroudi et al., 2025).

Urbanization, measured through annual growth in the urban population, captures demographic and spatial restructuring processes. While urbanization is often associated with increased resource consumption and environmental stress, Nordic countries have demonstrated effective urban planning and green infrastructure policies that may decouple urban expansion from ecological degradation (Amorim et al., 2021; Fagerholm et al., 2022). Including urbanization as a control variable helps isolate the effect of socio-cultural factors from those of settlement patterns and infrastructure transitions (Sunding et al., 2025).

Together, the inclusion of economic growth, urbanization, and environmental awareness alongside socio-cultural variables reflects the need to model environmental sustainability as a complex outcome shaped by both material conditions and intangible cultural and cognitive dynamics. This approach is particularly suited to the Nordic context, where strong governance, cultural investments, high educational standards, and economic affluence interact to produce both opportunities and constraints for sustainability transitions.

Table 2 presents the descriptive statistics for the study variables based on 110 observations covering the years 2002–2023 across the Nordic countries. The ES indicator shows a moderate average value (mean = 9.652 gha/person) with considerable dispersion (SD = 3.831), indicating substantial variability in ecological capacity across countries and years. The minimum and maximum values (3.774–17.200) further highlight inter-country differences.

Table 2

Table 2. Results of descriptive statistics.

EG and URB show mean annual growth rates of approximately 1.0%, though EG exhibits higher variability (SD = 2.701) and a large negative outlier (−8.515%), likely reflecting post-crisis contractions. URB remains relatively stable (SD = 0.602), with modest growth trends across the region.

The humanities (HUM) indicator, capturing cultural expenditure, averages 1.863% of GDP, with a max of 4.5% and a standard deviation of 0.772, suggesting noticeable but bounded variation in cultural investment. SS, proxied by social trust, is tightly distributed (mean = 6.777, SD = 0.346), reflecting high and consistent trust levels typical of Nordic societies (Figure 1).

Figure 1

Figure 1. Yearly variations in social sciences across Nordic economies, 2002–2023. (Source: Authors’ findings).

EAP variable, standardized via PCA, has a mean near zero and a standard deviation of 1.0, as expected. Its wide range (from −0.636–3.589) underscores disparities in education-driven awareness potential across time and space (Figure 2).

Figure 2

Figure 2. Temporal dynamics environmental awareness potential in Nordic countries (2002–2023). (Source: Authors’ findings).

Notably, the Jarque-Bera (J-B) test for normality indicates significant non-normality (p < 0.01) in all variables except SS, suggesting the presence of skewness or kurtosis in the distribution, which may influence model assumptions and estimation strategies.

Table 3 presents the Pearson correlation coefficients among the six study variables. The dependent variable, ES, shows its strongest positive correlation with HUM (r = 0.561, p < 0.01), suggesting that greater investment in cultural sectors is moderately associated with improved environmental sustainability outcomes in the Nordic context. A weaker but still significant correlation exists between ES and URB (r = 0.196, p < 0.05), implying a mild positive association between urban population growth and sustainability—possibly reflective of efficient urban planning or compact city benefits common in the region.

Table 3

Table 3. Correlation matrix.

Interestingly, ES exhibits no meaningful correlation with EG (r = 0.078) or SS (r = −0.087), indicating that variations in economic growth and social trust are not linearly associated with changes in environmental sustainability over the study period (Brunak et al., 2025).

Notably, EAP is negatively correlated with both SS (r = −0.501, p < 0.01) and HUM (r = −0.246, p < 0.01), which may suggest a divergence between formal educational expansion (used here as a proxy for environmental awareness) and traditional civic or cultural cohesion metrics. This inverse relationship may reflect generational shifts or differing policy emphases across the Nordic countries.

Correlations among the independent variables also highlight moderate associations, particularly between HUM and URB (r = 0.374, p < 0.01) and between HUM and SS (r = 0.332, p < 0.01), suggesting interconnected dynamics between cultural investment, urban development, and social trust.

Multicollinearity does not appear to be a significant concern, as no correlations among independent variables exceed 0.7. However, the inverse relationship between EAP and other social dimensions warrants further exploration in the modeling stage.

The empirical foundation of this study is constructed on a multivariate framework that investigates the relationship between environmental sustainability and a blend of economic, spatial, cultural, and educational variables. The baseline functional form is represented as:

$ES=f\left(EG,URB,HUM,SS,EAP\right)(1)$

To capture potential nonlinear effects of ecological awareness, a quadratic term for EAP is incorporated, yielding the extended model:

$ES=f\left(EG,URB,HUM,SS,EAP,{EAP}^2\right).(2)$

This functional relationship is operationalized using a panel regression approach across the five Nordic countries from 2002 to 2023 see Equations 1–4.

${ES}_{i,t}={\beta }_0+{\beta }_1{EG}_{i,t}+{\beta }_2{URB}_{i,t}+{{\beta }_{3}HUM}_{i,t}+{{\beta }_{4}SS}_{i,t}+{{\beta }_{5}EAP}_{i,t}+{\epsilon }_{i,t},(3)$

${ES}_{i,t}={\beta }_0+{\beta }_1{EG}_{i,t}+{\beta }_2{URB}_{i,t}+{{\beta }_{3}HUM}_{i,t}+{{\beta }_{4}SS}_{i,t}+{{\beta }_{5}EAP}_{i,t}+{\beta }_6{EAP}_{i,t}^2+{\epsilon }_{i,t},(4)$

here, i and t index countries and time, respectively. The term ϵ_i,t represents the stochastic error, and the β coefficients denote the marginal effects of the explanatory variables on environmental sustainability (ES).

This model is anchored in Ecological Modernization Theory, which posits that economic growth (EG) and urbanization (URB) can facilitate environmental improvements if coupled with institutional and technological advancements. The inclusion of HUM and SS is guided by Cultural Sociology and Environmental Behavior Theory, which emphasizes how cultural investment and social capital shape environmental norms and cooperative behavior.

To address the educational component, the study draws from Environmental Literacy Theory, which argues that higher educational attainment fosters greater ecological awareness and responsible environmental actions. The environmental awareness potential (EAP)—constructed via PCA from school enrollment ratios—is conceptualized as a proxy for the population’s cognitive readiness for ecological sustainability. The quadratic term EAP² allows for testing the presence of nonlinear (e.g., diminishing or threshold) effects of environmental education.

This composite framework integrates structural and societal dimensions of sustainability, tailored to the Nordic context’s socioeconomic heterogeneity.

To test parameter constancy across countries, (Pesaran and Yamagata, 2008), is applied. The relevant test statistics are:

${\widehat{\Delta }}_{S-HT}=\sqrt{N}\times \sqrt{2k}\times \left(\frac{1}{N}\widehat{S}-k\right),(5)$

$\widehat{\Delta }{\widehat{}}_{adj.S-HT}=\sqrt{N}\times \sqrt{\frac{T+1}{2k\left(T-k-1\right)}}\times \left(\frac{1}{N}\widehat{S}-2k\right).(6)$

where, $\widehat{\mathrm{S}}$ denotes Swamy’s test statistic, and k, T, and N represent the number of predictors, periods, and cross-sections, respectively.

Cross-sectional dependence is examined using (Pesaran, 2007) test:

${\delta }_{C-DP}=\frac{{\left(\left(T\times N\right)\left(N-1\right)\right)}^{\frac{1}{2}}}{2}{\widehat{\mathit{PR}}}_N.(7)$

Stationarity is assessed using the Pesaran Cross-sectional Augmented Dickey-Fuller (CADF) test:

${\Delta CS}_{i,t}={\phi }_i+{{\phi }_{i}CS}_{i,t-1}+\varrho {\overline{CS}}_{t-1}+{\displaystyle \sum _{l=0}^p}{\psi }_{i,l}\Delta {\overline{CS}}_{t-l}+{\displaystyle \sum _{l=1}^p}{\upsilon }_{i,l}\Delta {\overline{CS}}_{i,t-l}+{\mu }_{i,t}.(8)$

To account for panel heterogeneity and cross-dependence, the CIPS statistic (Im et al., 2003) is then computed:

${\widehat{CIPS}}_{UR}=\frac{1}{N}{\displaystyle \sum _{i=1}^N}{CADF}_i.(9)$

To explore how explanatory variables affect different quantiles of ES, the study employs Method of Moments Quantile Regression (MMQR), introduced by (Machado and Santos Silva, 2019):

$Y_{i,t}={\alpha }_i+\acute{X_{i,t}}\psi +\left({\delta }_i+\acute{Z_{i,t}}\vartheta \right)U_{i,t}.(10)$

The unidentified factors are indicated by $\left(\alpha ,\psi ,\delta ,\vartheta \right)$ , $\left({\alpha }_i,{\delta }_i\right)$ denotes the nation-specific fixed effects, and vector $\acute{Z}$ captures the interaction terms influencing the conditional quantile function.

$Z_l{=Z}_l\left(X_{i,t}\right), l=1,2,\dots .,k.(11)$

The quantile function for ES is given by:

$Q_y\left(\mathrm{\tau }|X_{i,t}\right)=\left({\alpha }_i+{\delta }_i\left(\mathrm{\tau }\right)\right)+\acute{X_{i,t}}\psi +\acute{Z_{i,t}}\vartheta q\left(\mathrm{\tau }\right),(12)$

where τ represents the quantile level. This formulation ensures that the country-specific effects and time-variant factors are accounted for across different quantiles. The MMQR estimator solves the optimization problem:

${\mathit{min}}_q{\displaystyle \sum _i}{\displaystyle \sum _t}{\rho }_{\mathrm{\tau }}\left(R_{i,t}-\left({\delta }_i+\acute{Z_{i,t}}\vartheta \right)q\right).(13)$

The check function is exemplified by ${\rho }_{\gamma }\left(R\right)=\left(\mathrm{\tau }-1\right)RI\left\{R\le 0\right\}+tRI\left\{R>0\right\}$ . This confirms robustness in the estimation process by minimizing quantile-specific residual deviations see Equations 5–13.

To ensure robustness, the study employs Feasible Generalized Least Squares (FGLS), which accounts for heteroskedasticity and serial correlation across panel units. FGLS produces efficient estimates in the presence of cross-sectional dependence and model heterogeneity, enhancing confidence in the empirical results.

4 Empirical results

To assess whether the marginal effects of the explanatory variables are consistent across the Nordic countries, the study employed the slope heterogeneity test developed by (Pesaran and Yamagata, 2008). This test is particularly important in a panel context where country-specific institutional, cultural, or policy factors may cause differential impacts of the same variable on environmental outcomes.

For the baseline model, the test results in Table 4 indicate strong evidence against the null hypothesis of slope homogeneity. The computed statistics, ${\widehat{\Delta }}_{\mathit{S}-\mathit{H}\mathit{T}}$ = 3.231 (p = 0.001) and $\widehat{\Delta }{\widehat{}}_{\mathit{a}\mathit{d}\mathit{j}.\mathit{S}-\mathit{H}\mathit{T}}$ = 3.913 (p < 0.001), are both significant at the 1% level. This suggests that the relationship between the predictors and environmental sustainability varies substantially across countries.

Table 4

Table 4. Slope heterogeneity test (S-HT).

Similarly, when the model is extended to include the nonlinear term for ecological awareness (EAP²), the test continues to reject slope homogeneity. The adjusted and unadjusted statistics for the extended model, ${\widehat{\Delta }}_{\mathit{S}-\mathit{H}\mathit{T}}$ = 2.666 (p = 0.008) and $\widehat{\Delta }{\widehat{}}_{\mathit{a}\mathit{d}\mathit{j}.\mathit{S}-\mathit{H}\mathit{T}}$ = 3.341 (p = 0.001), remain statistically significant, reinforcing the conclusion that cross-sectional heterogeneity is present in both model specifications (see Table 4).

These results imply that the determinants of environmental sustainability are not uniform across the Nordic countries, likely reflecting differences in environmental governance, cultural emphasis on sustainability, or education systems. Consequently, the use of estimation strategies that account for heterogeneity—such as MMQR—is warranted to obtain more accurate and context-sensitive insights.

To evaluate whether the panel data exhibit interdependence across countries, the study applies (Pesaran, 2007) Cross-Section Dependence (CD) test. This diagnostic is essential for determining the appropriateness of panel unit root and cointegration tests, as failure to account for cross-sectional dependence can bias standard estimators and lead to incorrect inferences.

As shown in Table 5, the CD test results reveal significant dependence across countries for most of the variables. The dependent variable ES_i,t exhibits strong cross-sectional dependence, with a CD statistic of 11.470 (p < 0.001), indicating that environmental sustainability outcomes are highly correlated among the Nordic nations. This is consistent with the shared policy frameworks, geographical proximity, and environmental cooperation mechanisms in the region.

Table 5

Table 5. Cross-section dependence (CD).

Similarly, economic growth (EG_i,t) displays high cross-country dependence (CD = 10.900, p < 0.001), reflecting the interconnectedness of Nordic economies. Both urbanization (URB_i,t) and cultural expenditure (HUM_i,t) show moderate but significant dependence (CD = 2.140, p = 0.033 and CD = 2.300, p = 0.021, respectively), suggesting that urban trends and public cultural policies may follow similar trajectories across these countries.

In contrast, social sciences (SS_i,t) and environmental awareness potential (EAP_i,t) exhibit weaker or statistically marginal dependence, with CD values of 1.140 (p = 0.254) and 0.300 (p = 0.061), respectively. These findings may indicate more distinct national profiles in terms of civic values and education-related environmental engagement.

The overall pattern of results in Table 5 supports the presence of non-negligible cross-sectional interdependence, particularly in environmental, economic, and spatial dimensions. This justifies the application of the second-generation panel unit root that explicitly accounts for such dependencies, thereby enhancing the robustness of the empirical framework.

To evaluate the stationarity properties of the panel dataset while accounting for cross-sectional dependence, the study employs the Cross-sectional Im, Pesaran, and Shin (CIPS) unit root test. This second-generation panel unit root test is well-suited for datasets exhibiting cross-sectional correlation, as confirmed by the CD test (Table 5).

Table 6 presents the CIPS test statistics at levels I (0) and first differences I (1). The results indicate that most variables are non-stationary at levels but become stationary after first differencing, confirming they are integrated of order one.

Table 6

Table 6. Cross-sectional augmented IPS (CIPS) unit root test.

Specifically, ES and EAP are non-stationary at levels (CIPS = −2.120 and −2.054, respectively) but become highly stationary at the first difference (CIPS = −4.414 and −3.830, both p < 0.01), supporting the I (1) classification. Likewise, SS shows a borderline result at levels (CIPS = −2.629) but exhibits strong stationarity after differencing (CIPS = −5.629).

EG is a notable exception, as it appears stationary at both levels (CIPS = −5.017) and first difference (CIPS = −5.679), suggesting it is integrated of order zero, I (0). This may reflect the relatively volatile yet mean-reverting nature of economic growth in the region (Khosravi et al., 2025).

URB, however, does not exhibit significant stationarity at either level (CIPS = −0.917) or first difference (CIPS = −1.990), which may imply the presence of unit roots or structural breaks requiring further investigation through alternative specifications.

HUM shows weak stationarity at levels (CIPS = −2.804, p < 0.10) and strong stationarity at the first difference (CIPS = −4.974), suggesting an I (1) process with potential near-stationary behavior in level form.

The Method of Moments Quantile Regression (MMQR) results presented in Table 7 reveal important distributional dynamics in how the explanatory variables influence ES across different quantiles of the outcome distribution. In the first model, the effects of variables vary significantly along the ES distribution. EG displays a consistently positive relationship with ES across quantiles, with its magnitude increasing slightly from lower to higher quantiles. This suggests that the environmental returns to economic growth are more pronounced in countries already performing well in terms of sustainability, likely due to better institutional integration of green growth strategies (Brunak et al., 2025). This outcome is supported by (Khosravi et al., 2025). This pattern aligns with the Environmental Kuznets Curve (EKC) hypothesis, which posits that environmental quality tends to improve after a certain level of income is achieved, as wealthier societies can afford cleaner technologies and stronger environmental regulations. Hence, the rising marginal benefit of EG at higher quantiles reflects a developmental threshold where economic progress supports rather than undermines sustainability (Usenata, 2018; Balsalobre-Lorente and Shahbaz, 2019).

Table 7

Table 7. MMQR estimates.

URB, on the other hand, exhibits an increasingly negative and significant impact at higher quantiles. While its effect is less pronounced at lower sustainability levels, it becomes significantly detrimental in the upper quantiles (Q0.75 and Q0.90). This pattern may indicate that, although urban growth can foster development, it places disproportionate pressure on ecological systems in countries already striving to maintain high sustainability standards (Yasin et al., 2021). This effect resonates with urban ecological footprint theory, which suggests that beyond a certain point, urbanization contributes to unsustainable consumption, spatial expansion, and infrastructure stress. In advanced economies, the ecological costs of urbanization may outweigh its developmental benefits, explaining its intensifying negative impact at higher levels of ES (Ortega-Montoya and Johari, 2019).

HUM demonstrates a robust and statistically significant positive effect across all quantiles, affirming the role of cultural investment in promoting sustainable values and behaviors throughout the spectrum of environmental performance. Such investments generate shared cultural narratives, symbolic practices, and ethical frameworks that strengthen pro-environmental values (Lu et al., 2025). In line with recent scholarship, the humanities can serve as catalysts for cultivating an eco-surplus culture, in which cultural values are mobilized in ecologically aligned ways, enabling individuals and institutions to reimagine human–nature relations as mutually supportive rather than extractive (Nguyen, 2024; Vuong and Nguyen, 2024). This is consistent with the strong positive correlation observed between HUM and ES (r = 0.561, p < 0.01, Table 3). This consistency suggests that public support for arts and culture is not merely a social good but a contributor to environmental stewardship across varying national contexts. This finding is theoretically grounded in Bourdieu’s concept of symbolic capital, wherein cultural assets—such as investment in humanities—serve to embed sustainability values within public discourse and collective identity, thereby fostering long-term ecological responsibility (Bourdieu et al., 2013). These findings are undermined by (Hao et al., 2024).

SS yields a somewhat unexpected negative effect across the distribution, though its influence weakens toward higher quantiles. The stronger negative associations at lower quantiles may reflect a complex interaction where generalized trust does not immediately translate into environmental outcomes, particularly in contexts where institutional mechanisms or environmental awareness are underdeveloped (Ren and Zhu, 2025). These findings are in line with the study by (Tan et al., 2024).

EAP variable reveals a significant negative effect on ES across most quantiles. While counterintuitive at first glance, this result may reflect a lag between increased awareness (as proxied by educational indicators) and the realization of tangible sustainability benefits. High awareness may lead to heightened recognition of environmental problems, without necessarily ensuring immediate behavioral or policy shifts (Dioba et al., 2024).

In the second model, which includes the nonlinear term EAP², the dynamics shift considerably. While EG retains its positive trajectory and URB continues to negatively impact ES, the magnitude of HUM’s effect remains comparably strong and significant. SS still exerts a negative influence, though the intensity diminishes somewhat with the inclusion of nonlinear effects. The EAP variable, however, becomes more strongly negative, especially at the lower quantiles, indicating that initial levels of awareness may correlate with increased environmental strain or heightened problem identification.

Importantly, the inclusion of EAP² introduces a positive and statistically meaningful curvature across all quantiles. The positive sign of the squared term suggests a U-shaped relationship between environmental awareness and sustainability. This implies that at low to moderate levels, increases in EAP may not immediately result in environmental gains and may even correlate with declining ES. However, once a critical threshold of awareness is reached, its impact becomes positive—indicating that sustained investment in ecological literacy and education eventually pays off in terms of improved environmental outcomes (Figure 3).

Figure 3

Figure 3. Graphical representation of MMQR. (Reference: Authors’ findings).

At low to moderate levels, rising awareness may correspond with heightened recognition of environmental problems, leading to short-term declines in sustainability outcomes due to increased reporting or system stress. However, beyond a critical threshold, awareness begins to reinforce sustainability, supporting the idea of a progressive cognitive shift toward what (Vuong, 2025) describes as a “nature quotient.” This construct reflects the internalization of ecological responsibility as a habitual and cultural disposition rather than a temporary concern (Zhou et al., 2025). Mechanisms such as climate fiction (cli-fi) provide a practical channel for this transformation, fostering ecological awareness through relatable narratives that encourage voluntary and sustained engagement with environmental issues.

This nonlinear structure offers a nuanced understanding of the awareness-sustainability nexus. It emphasizes the need for not just promoting environmental education but ensuring it reaches a level of depth and societal saturation that enables behavioral change, innovation adoption, and policy responsiveness. Hence, the addition of the nonlinear term not only improves model fit but also deepens theoretical insight, revealing that the relationship between awareness and sustainability is not linear but follows a more complex trajectory shaped by thresholds and contextual factors.

To ensure the reliability of the panel regression findings, a Feasible Generalized Least Squares (FGLS) estimation was conducted, and the results are presented in Table 8. FGLS is particularly appropriate for panel data structures with cross-sectional dependence, heteroskedasticity, or serial correlation—conditions previously confirmed through diagnostic testing in this study. The aim here is to assess the consistency and stability of coefficient estimates obtained via MMQR across a more generalized estimation framework.

Table 8

Table 8. FGLS robustness test.

The FGLS results for the linear specification largely align with the distributional insights from the MMQR model. Economic growth shows a statistically significant positive relationship with environmental sustainability (p = 0.098), confirming the modest but supportive role of economic expansion in promoting ecological wellbeing observed across MMQR quantiles. This finding supports the Environmental Kuznets Curve (EKC) framework, which suggests that beyond a certain income threshold, further economic growth enables the adoption of cleaner technologies, stronger regulatory frameworks, and greener consumption patterns. Hence, even within a generalized model like FGLS, EG’s positive impact reflects the sustainability dividends of development in mature economies.

Urbanization, though negative in sign, is statistically insignificant in the linear FGLS model (p = 0.256), reflecting its variable impact across the ES distribution—stronger and more negative at upper quantiles in MMQR, but less stable when averaged across the panel. This inconsistency may stem from the nonlinear and context-dependent nature of urban development: while urbanization can concentrate innovation and infrastructure, it may also amplify ecological stress through densification, land-use changes, and consumption intensity. The ecological footprint model helps explain this variability, showing that aggregate measures often mask place-based trade-offs in urban growth.

The effect of humanities remains highly significant and consistently positive (coefficient = 3.427, p < 0.001), reinforcing the MMQR finding that cultural investment serves as a robust and uniformly beneficial driver of environmental outcomes. This relationship underscores Bourdieu’s theory of symbolic capital, where cultural endowments—such as public support for humanities—facilitate value alignment between societal aspirations and ecological responsibility. Cultural policies can embed environmental ethics within education, arts, and public discourse, thereby fostering behaviors conducive to long-term sustainability.

Similarly, social sciences yield a strong and negative coefficient (−4.671, p < 0.001), echoing the MMQR results where SS demonstrated a diminishing negative effect from lower to upper quantiles. This consistency across methods reinforces the complexity of social trust’s relationship with sustainability—potentially shaped by unobserved mediators or lagged responses in civic behavior. This indicates that while generalized trust is a hallmark of Nordic societies, it does not automatically translate into ecological gains. Instead, trust may initially foster institutional complacency, whereby citizens defer responsibility to trusted authorities rather than engage in proactive ecological action. However, the diminishing negative effect of SS at higher quantiles suggests that in more advanced sustainability contexts, trust can act as an enabling condition, supporting collective action when coupled with participatory governance and ecological literacy. This dynamic is theoretically consistent with Ostrom’s collective action theory, which emphasizes that trust must be embedded within feedback-rich institutional settings to convert into sustainable outcomes.

The environmental awareness proxy exhibits a significantly negative coefficient (−0.665, p = 0.037) in the linear FGLS model, consistent with MMQR’s evidence of initial negative or neutral effects of educational awareness on ES across most quantiles. This negative effect likely reflects a short-term or transitional stage where rising awareness leads to increased environmental scrutiny or pressure, but not yet to improved outcomes. In early stages, heightened awareness can surface latent environmental challenges, increase media attention, or stimulate critical evaluation of current practices, thus creating a lag before behavioral or institutional change materializes.

When the quadratic term EAP² is added to the extended FGLS model, the explanatory power and interpretability of the model significantly improve. The EAP coefficient becomes more strongly negative (−3.880, p = 0.001), while the squared term EAP² is positive and statistically significant (1.252, p = 0.005), clearly confirming the nonlinear U-shaped relationship previously identified in MMQR. These findings imply that while marginal increases in environmental awareness may initially reduce sustainability—perhaps due to increased consumption, reporting, or system stress—higher levels of awareness eventually foster more sustainable behaviors and institutional responses, producing net positive environmental effects. This aligns with transition theory, which argues that awareness and disruption are precursors to system change. Once a critical threshold of environmental literacy and civic engagement is reached, societies begin to reconfigure norms, institutions, and technologies in more sustainable directions.

Moreover, the statistical significance of the Wald test in both models (p < 0.001) supports the joint relevance of the independent variables and validates the model structure. Notably, the Wald statistic increases when the quadratic term is included (from 86.520 to 100.490), indicating improved model fit and explanatory strength in the nonlinear specification.

In summary, the FGLS results reinforce the central findings from MMQR: economic and cultural variables consistently support sustainability, while the influence of awareness is complex and nonlinear. The introduction of the squared term for EAP proves essential in capturing this dynamic, confirming that environmental awareness must reach a critical mass before translating into measurable sustainability gains. The cross-method consistency between FGLS and MMQR enhances the credibility and generalizability of the study’s conclusions.

The findings yield several strategic insights relevant to advancing sustainability in the 21st century. The persistent influence of HUM supports continued investment in cultural sectors as a lever for ecological values (Wang et al., 2020). The nonlinear effects of EAP emphasize the need for enhanced environmental literacy within education systems, especially at higher levels. The complex role of SS underlines the necessity of coupling social trust with participatory environmental governance. The adverse impacts of URB at higher sustainability levels call for resilient and ecologically responsive urban planning (Ta et al., 2023). Lastly, the positive but modest effect of EG suggests the importance of aligning economic growth with green innovation, enabling countries to achieve both prosperity and environmental goals in a rapidly evolving global context (Knutas, 2025).

5 Conclusion and future recommendations

This study investigated the determinants of environmental sustainability (ES) in the context of the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden) over the period 2002–2023, employing a panel dataset that integrated key economic, spatial, cultural, social, and educational indicators. By focusing specifically on this high-governance, ecologically progressive regional bloc, the research highlights the institutional, cultural, and policy factors that shape sustainability outcomes in mature welfare states.

The analysis centered on five explanatory variables. Economic growth (EG) was proxied through annual GDP per capita growth, reflecting how changes in national wealth levels influence ecological outcomes. Urbanization (URB) was captured via the annual urban population growth rate, serving as a spatial proxy for demographic concentration and infrastructure strain. Humanities investment (HUM) was operationalized using government expenditure on culture as a percentage of GDP, conceptualized as a proxy for national cultural capital and public engagement with symbolic systems that influence sustainability values. Social sciences (SS) were measured using indices of social trust, representing collective civic norms, perceived institutional reliability, and social cohesion—factors that can either enable or inhibit ecological action. Environmental awareness potential (EAP) was constructed through Principal Component Analysis (PCA) of gross enrollment rates at the primary, secondary, and tertiary levels. This composite measure served as an indirect yet multidimensional proxy for the educational foundations underlying environmental literacy and civic preparedness. The dependent variable, environmental sustainability, was measured using biocapacity per capita, a metric that reflects each country’s ecological carrying capacity in relation to human demand, thus grounding the study in an outcomes-based sustainability framework.

To rigorously examine the dynamic and potentially heterogeneous effects of these variables on ES, the study employed a suite of econometric techniques. These included slope heterogeneity testing, cross-sectional dependence diagnostics, and unit root testing via the CIPS method, ensuring the validity of the panel data structure. The main empirical tools consisted of the Method of Moments Quantile Regression (MMQR) to capture distributional effects across quantiles of ES, and Feasible Generalized Least Squares (FGLS) for robustness checking under heteroskedasticity and interdependence.

The results revealed that humanities investment consistently exerted a strong and positive influence on ES across all quantiles and specifications, affirming the critical role of cultural endowments in shaping collective ecological norms and long-term environmental behaviors. Economic growth displayed a modest but increasingly positive effect, particularly in higher-performing sustainability contexts, suggesting that economic gains translate into environmental benefits primarily when accompanied by institutional readiness and ecological governance. Urbanization, conversely, had a significantly negative impact at the upper quantiles, indicating that its environmental burdens intensify in more developed urban contexts, where spatial pressures and ecological thresholds become more acute.

The effect of social trust remained persistently negative across most specifications, highlighting its complex and context-dependent role in ecological governance. While high trust is typically viewed as a civic asset, in certain settings it may foster institutional complacency or reduce individual engagement with sustainability efforts. Most notably, environmental awareness potential (EAP) exhibited a nonlinear U-shaped relationship with ES. At early stages, increases in educational attainment were associated with reduced sustainability, possibly due to heightened scrutiny, systemic strain, or the lag between awareness and action. However, beyond a critical mass, the effect reversed, confirming that deeper, widespread educational foundations are essential for producing informed ecological behaviors and institutional innovation.

The study demonstrates that environmental sustainability in the Nordic region cannot be explained solely by economic or technological factors. Instead, it emerges from a constellation of structural, cultural, educational, and social conditions that interact in complex, often nonlinear ways. By embedding these dimensions within a robust panel framework, this research contributes an integrated empirical basis for rethinking sustainability transitions as multidimensional, culturally embedded, and institutionally mediated processes. In doing so, it lays the groundwork for more holistic, context-sensitive policy interventions in pursuit of the Sustainable Development Goals (SDGs).

5.1 Policy implications

The findings of this study imply several actionable directions for both national and global policy actors in advancing sustainability agendas in the 21st century. At the national level, governments, particularly in the Nordic region, should institutionalize environmental literacy within their educational systems, not only as subject matter but as a cross-cutting civic competence. This requires integrating ecological thinking into curricula, pedagogy, and extracurricular programs to foster long-term behavioral and attitudinal change. Such efforts directly contribute to SDG 4 (Quality Education), especially Target 4.7, which calls for education that promotes sustainable development and global citizenship.

Additionally, the demonstrated importance of cultural investment highlights the need for increased public funding for the humanities, particularly for projects that promote ecological awareness, environmental storytelling, and sustainability-themed cultural production. This aligns with SDG 11 (Sustainable Cities and Communities) and SDG 16 (Peace, Justice, and Strong Institutions) by reinforcing inclusive, participatory cultural spaces that strengthen civic engagement.

Governments should also enhance participatory governance mechanisms, ensuring that social trust is translated into collective environmental action. This could involve creating more inclusive platforms for citizens to engage in sustainability planning, climate budgeting, and environmental monitoring, supporting SDG 16.7, which promotes responsive, inclusive, participatory, and representative decision-making. Urban development policies must shift toward ecological resilience, with a focus on expanding green infrastructure, regulating urban sprawl, and ensuring that urbanization does not compromise ecological thresholds—advancing SDG 11.3 on sustainable urbanization.

Economic planning should be reoriented to decouple growth from environmental degradation, emphasizing the scaling of green innovation, clean technologies, and circular economic models. Fiscal instruments such as tax incentives, public-private green partnerships, and sustainable procurement should be strategically deployed to facilitate this transition, contributing directly to SDG 8.4 (resource efficiency in production and consumption) and SDG 9.4 (upgrading infrastructure and industries for sustainability).

At the global level, international organizations must support and coordinate sustainability efforts to ensure coherence and capacity building across nations. Agencies like UNESCO and UNEP should expand the global reach of environmental education frameworks, particularly in developing and transitional economies where awareness levels may be low but ecological vulnerability is high. Institutions such as the OECD and the World Bank can offer both financial and technical assistance to help governments mainstream sustainability into their policy architecture, including education, urban planning, and green economic reform.

Within the European Union, shared sustainability standards and coordinated cultural-educational initiatives aligned with the European Green Deal can enhance regional policy convergence and progress toward collective SDG achievement. Global civil society, including non-governmental organizations and advocacy networks, plays a critical role in linking local voices with international environmental agendas. Their capacity to mobilize communities, disseminate knowledge, and hold institutions accountable remains essential for reinforcing democratic, participatory, and culturally rooted pathways to sustainability.

Collectively, these strategies not only support national progress but also advance the broader objectives of the United Nations 2030 Agenda, particularly across SDGs 4, 8, 9, 11, 12, 13, and 16. They reinforce the study’s conclusion that sustainability in the 21st century must emerge from an integrated nexus of education, culture, trust, and adaptive policy institutions operating across local and global scales.

5.2 Limitations and future recommendations

While this study offers valuable insights into the determinants of environmental sustainability across the Nordic countries over the 2002–2023 period, several limitations must be acknowledged. First, the analysis is constrained by the regional focus on five high-income countries, which limits the generalizability of the findings to other regions, particularly those with different institutional, cultural, or socio-economic dynamics. The exclusive use of Nordic nations, though methodologically coherent, excludes potential comparative insights from other environmentally progressive or developing countries.

Second, although the constructed EAP variable innovatively captures educational drivers using PCA on enrollment rates, it remains an indirect proxy for ecological literacy and may not fully reflect the depth or quality of environmental education content. More nuanced measures—such as environmental knowledge assessments, attitudinal surveys, or sustainability-oriented curricula—could enhance future analyses. Similarly, variables such as SS and HUM are captured through singular proxies, which may oversimplify multidimensional constructs. Incorporating additional or composite indicators could enrich the explanatory depth. Also, both are modeled linearly here, yet their effects may not be strictly monotonic. Cultural investment could display threshold effects, where benefits emerge only beyond a certain level, while social trust may strengthen sustainability in participatory settings but weaken it if it fosters institutional complacency. Future research should test nonlinear or interaction effects to capture these complexities more fully.

Third, the annual panel structure of the dataset, while adequate for capturing medium-to long-term trends, may limit the study’s ability to detect short-term fluctuations or seasonal dynamics in environmental and socio-economic variables. Moreover, the study does not explicitly model structural breaks—such as the 2008 global financial crisis or the COVID-19 pandemic—which may have significantly influenced both economic trajectories and environmental outcomes during the observed period.

Methodologically, while MMQR and FGLS offer robust tools for dealing with heterogeneity and cross-sectional dependence, the analysis does not incorporate dynamic models that capture lagged effects or feedback loops, such as GMM or panel VAR techniques. Future research could benefit from exploring the temporal causality between awareness, trust, and sustainability outcomes, and from modeling environmental sustainability as part of a broader system of interconnected socio-ecological variables.

Lastly, while biocapacity per capita serves as a solid proxy for environmental sustainability, it may not fully capture all relevant ecological dimensions such as emissions intensity, biodiversity loss, or climate resilience. Future studies could adopt a multi-indicator sustainability index to broaden the analytical scope.

In sum, expanding the geographic scope, integrating more direct and diverse indicators, incorporating dynamic modeling techniques, and enhancing the ecological comprehensiveness of outcome measures are recommended pathways for future research aiming to better understand and inform sustainability transitions in the 21st century.

Data availability statement

Publicly available datasets were analyzed in this study. This data can be found here: https://data.worldbank.org/country.

Author contributions

CW: Data curation, Methodology, Conceptualization, Formal analysis, Investigation, Resources, Visualization, Writing – original draft, Writing – review and editing. LZ: Data curation, Methodology, Supervision, Project administration, Validation, Investigation, Funding acquisition, Resources, Visualization, Software, Writing – original draft, Writing – review and editing. XZ: Formal Analysis, Project administration, Methodology, Conceptualization, Visualization, Validation, Funding acquisition, Writing – review and editing, Writing – original draft, Resources, Investigation.

Funding

The author(s) declared that financial support was not received for this work and/or its publication.

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.

Publisher’s note

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Footnotes

^{Abbreviations:} MMQR, Method of Moments Quantile Regression; FGLS, Feasible Generalized Least Squares; SDGs, Sustainable Development Goals; ES, Environmental Sustainability; URB, Urbanization; EG, Economic Growth; HUM, Humanities; SS, Social Sciences; EAP, Environmental Awareness Potential.

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