Politická ekonomie 2025, 74(5)  | DOI: 10.18267/j.polek.1510

Environmental Sustainability in Southeast Asia: Evidence from Linear and Nonlinear Unit Root Tests and Policy Implications

Sefa Özbek, Bahar Özbek
Sefa Özbek (corresponding author), Faculty of Applied Sciences, Tarsus University, Mersin, Turkey
Bahar Özbek, School of Graduate Studies, Tarsus University, Mersin, Turkey

This study focuses on Southeast Asian countries that have attracted attention with their recent economic growth performance. The validity of environmental sustainability is investigated through data for the period 1973-2022. For this purpose, ecological footprint data from Indonesia, the Philippines, Cambodia, Malaysia, Singapore, Thailand and Vietnam are used. Unit root tests with various power properties are used in the study. Firstly, we use ADF and PP unit root tests based on the Dickey-Fuller unit root test procedure. In addition, among the nonlinear unit root tests, those of Leybourne et al. (1998) and Harvey and Mills (2002) are used. On the other hand, we also perform the unit root test of Hepsağ (2021), which includes gradual structural breaks and is among the latest nonlinear unit root tests. The results vary depending on unit root tests of different strengths. In general, the validity of environmental sustainability, in other words, convergence, is concluded. These results mostly show the effectiveness of regional and global policies. Some of the results reveal that convergence is not valid in some countries, the invalidity of environmental sustainability and emphasize the effectiveness of national policies.

Keywords: Environmental sustainability, convergence, nonlinear unit root, Southeast Asian countries
JEL classification: C22, Q53, Q56

Received: June 15, 2024; Revised: April 24, 2025; Accepted: May 5, 2025; Prepublished online: December 12, 2025; Published: October 23, 2026  Show citation

ACS AIP APA ASA Harvard Chicago Chicago Notes IEEE ISO690 MLA NLM Turabian Vancouver
Özbek, S., & Özbek, B. (2026). Environmental Sustainability in Southeast Asia: Evidence from Linear and Nonlinear Unit Root Tests and Policy Implications. Politická ekonomie, 74(5), 941-970. doi: 10.18267/j.polek.1510
Download citation
  • BibTeX (.bib)
  • Bookends (.ris)
  • EasyBib (.ris)
  • EndNote (.enw)
  • EndNote 8 (.xml)
  • ISI WoS (.isi)
  • Medlars (.medlars)
  • Mendeley (.ris)
  • MODS (.xml)
  • Papers (.ris)
  • RefWorks (.txt)
  • RefManager (.ris)
  • RIS (.ris)
  • MS Word (.xml)
  • Zotero (.ris)
    • Open full article

    References

    1. Ahmed, M., Khan, A. M., Bibi, S., et al. (2016). Convergence of per capita CO2 emissions across the globe: Insights via wavelet analysis. Renewable and Sustainable Energy Reviews, 75, 86-97. https://doi.org/10.1016/j.rser.2016.10.053 Go to original source...
    2. Ahmed, Z., Pata, U. K. (2025). Unveiling the influence of environmental taxes, socioeconomic conditions, renewable energy, and financial globalization on environmental sustainability. Natural Resources Forum, 49(2), 1037-1056. https://doi.org/10.1111/1477-8947.12425 Go to original source...
    3. Ali, M., Kirikkaleli, D., Altuntaş, M. (2024). The nexus between CO2 intensity of GDP and environmental degradation in South European countries. Environment, Development and Sustainability, 26(5), 11089-11100. https://doi.org/10.1007/s10668-023-03217-w Go to original source...
    4. Alola, A. A., Ozturk, I. (2021). Mirroring risk to investment within the EKC hypothesis in the United States. Journal of Environmental Management, 293, 112890. https://doi.org/10.1016/j.jenvman.2021.112890 Go to original source...
    5. Altintaş, H., Kassouri, Y. (2020). Is the environmental Kuznets Curve in Europe related to the per-capita ecological footprint or CO2 emissions? Ecological Indicators, 113, 106187. https://doi.org/10.1016/j.ecolind.2020.106187 Go to original source...
    6. Aslan, A., Ilhan, O., Usama, A. M., et al. (2024). Effect of economic policy uncertainty on CO2 with the discrimination of renewable and non-renewable energy consumption. Energy, 291, 130382. https://doi.org/10.1016/j.energy.2024.130382 Go to original source...
    7. Balsalobre-Lorente, D., Ibáñez-Luzón, L., Usman, M., et al. (2022). The environmental Kuznets curve, based on the economic complexity, and the pollution haven hypothesis in PIIGS countries. Renewable Energy, 185, 1441-1455. https://doi.org/10.1016/j.renene.2021.10.059 Go to original source...
    8. Bilgili, F., Ulucak, R. (2018). Is There Deterministic, Stochastic, and/or Club Convergence in Ecological Footprint Indicator among G20 Countries? Environmental Science and Pollution Research, 25(35), 35404-35419. https://doi.org/10.1007/s11356-018-3457-1 Go to original source...
    9. Cai, Y., Chang, T., Inglesi-Lotz, R. (2018). Asymmetric Persistence in Convergence for Carbon Dioxide Emissions Based on Quantile Unit Root Test with Fourier Function. Energy, 161, 470-481. https://doi.org/10.1016/j.energy.2018.07.125 Go to original source...
    10. D'Orazio, P., Schäfer, D., Stephan, A. (2024). Macro-financial policy at the crossroad: addressing climate change, biodiversity loss, and environmental degradation-introduction to the special issue. Eurasian Economic Review, 14(1), 1-11. https://doi.org/10.1007/s40822-024-00265-z Go to original source...
    11. Dickey, D. A., Fuller, W. A. (1979). Distribution of the estimators for autoregressive time series with a unit root. Journal of the American Statistical Association, 74(366a), 427-431. https://doi.org/10.1080/01621459.1979.10482531 Go to original source...
    12. Dickey, D. A., Fuller, W. A. (1981). Likelihood ratio statistics for autoregressive time series with a unit root. Econometrica: Journal of the Econometric Society, 49(4), 1057-1072. https://doi.org/10.2307/1912517 Go to original source...
    13. Erdogan, S., Ahmed, M. Y., Sarkodie, S. A. (2022). Analyzing asymmetric effects of cryptocurrency demand on environmental sustainability. Environmental Science and Pollution Research, 29(21), 31723-31733. https://doi.org/10.1007/s11356-021-17998-y Go to original source...
    14. Erdogan, S., Okumus, I. (2021). Stochastic and Club Convergence of Ecological Footprint: An Empirical Analysis for Different Income Group of Countries. Ecological Indicators, 121, 107123. https://doi.org/10.1016/j.ecolind.2020.107123 Go to original source...
    15. Gil-Alana, L. A., Solarin, S. A. (2018). Have US Environmental Policies been Effective in the Reduction of US Emissions? A new Approach Using Fractional Integration. Atmospheric Pollution Research, 9(1), 53-60. https://doi.org/10.1016/j.apr.2017.06.008 Go to original source...
    16. Gil-Alana, L. A., Cunado, J., Gupta, R. (2017). Persistence, Mean-Reversion and Nonlinearities in CO2 Emissions: Evidence from the BRICS and G7 Countries. Environmental Resource Economics, 67(4), 869-883. https://doi.org/10.1007/s10640-016-0009-3 Go to original source...
    17. Global Footprint Network (2024). Ecological Footprint. [Retrieved 2024-03-02] Available at: https://www.footprintnetwork.org
    18. Guo, J., Zhou, Y., Ali, S., et al. (2021). Exploring the role of green innovation and investment in energy for environmental quality: An empirical appraisal from provincial data of China. Journal of Environmental Management, 292, 112779. https://doi.org/10.1016/j.jenvman.2021.112779 Go to original source...
    19. Güler, İ., Naimoğlu, M., Şimşek, O., et al. (2025). Analyzing the impact of economic growth and FDI on sustainable development goals in China: insights from ecological footprints and load capacity factors. Frontiers in Environmental Science, 13, 1513158. https://doi.org/10.3389/fenvs.2025.1513158 Go to original source...
    20. Güzel, A. E., Okumuş, İ. (2020). Revisiting the pollution haven hypothesis in ASEAN-5 countries: new insights from panel data analysis. Environmental Science and Pollution Research, 27, 18157-18167. https://doi.org/10.1007/s11356-020-08317-y Go to original source...
    21. Harvey, D. I., Leybourne, S. J. (2007). Testing for time series linearity. The Econometrics Journal, 10(1), 149-165. https://doi.org/10.1111/j.1368-423X.2007.00203.x Go to original source...
    22. Harvey, D. I., Mills, T. C. (2002). Unit roots and double smooth transitions. Journal of Applied Statistics, 29(5), 675-683. https://doi.org/10.1080/02664760120098739 Go to original source...
    23. Heil, M. T., Selden, T. M. (1999). Panel Stationarity with Structural Breaks: Carbon Emissions and GDP. Applied Economics Letters, 6(4), 223-225. https://doi.org/10.1080/135048599353384 Go to original source...
    24. Hepsağ, A. (2021). A unit root test based on smooth transitions and nonlinear adjustment. Communications in Statistics-Simulation and Computation, 50(3), 625-632. https://doi.org/10.1080/03610918.2018.1563154 Go to original source...
    25. IEA (2024). Data and statistics. [Retrieved 2024-03-02] Available at: https://www.iea.org/data-and-statistics
    26. IMF (2024). International Monetary Fund. [Retrieved 2024-03-02] Available at: https://www.imf.org/en/Home
    27. Işik, C., Ahmad, M., Ongan, S., et al. (2021). Convergence Analysis of The Ecological Footprint: Theory and Empirical Evidence from The USMCA Countries. Environmental Science and Pollution Research, 28, 32648-32659. https://doi.org/10.1007/s11356-021-12993-9 Go to original source...
    28. Kasahun, M. (2025). Quantifying deforestation drivers through multi-temporal LULC Analysis and population-forest correlation modeling: a case study of Dara Woreda, Ethiopia. Environmental Challenges, 19, 101163. https://doi.org/10.1016/j.envc.2025.101163 Go to original source...
    29. Kearsley, A., Riddel, M. (2010). A further inquiry into the pollution haven hypothesis and the environmental Kuznets curve. Ecological Economics, 69(4), 905-919. https://doi.org/10.1016/j.ecolecon.2009.11.014 Go to original source...
    30. Lee, C. C., Chang, C. P. (2009). Stochastic Convergence of Per Capita Carbon Dioxide Emissions and Multiple Structural Breaks in OECD countries. Economic Modelling, 26(6), 1375-1381. https://doi.org/10.1016/j.econmod.2009.07.003 Go to original source...
    31. Leybourne, S. J., Newbold, P., Vougas, D. (1998). Unit Roots and Smooth Transitions. Journal of Time Series Analysis, 19, 83-97. https://doi.org/10.1111/1467-9892.00078 Go to original source...
    32. List, J., Strazicich, M. (2003). Are CO2 Emission Levels Converging among Industrial Countries? Environmental and Resource Economics, 24, 263-271. https://link.springer.com/article/10.1023/A:1022910701857 Go to original source...
    33. Makarov, I., Alataş, S. (2024). Production-and consumption-based emissions in carbon exporters and importers: A large panel data analysis for the EKC hypothesis. Applied Energy, 363, 123063. https://doi.org/10.1016/j.apenergy.2024.123063 Go to original source...
    34. Mert, M., Bölük, G. (2016). Do foreign direct investment and renewable energy consumption affect CO2 emissions? New evidence from a panel ARDL approach to Kyoto Annex countries. Environmental Science and Pollution Research, 23(19), 21669-21681. https://doi.org/10.1007/s11356-016-7413-7 Go to original source...
    35. Naimoğlu, M., Özbek, S. (2022). Testing The Environmental Kuznets Curve Hypothesis under Structural Breaks: The Case of Turkey. Alanya Akademik Bakiş, 6(3), 3069-3084. https://doi.org/10.29023/alanyaakademik.992079 Go to original source...
    36. Nguyen, T. T. H., Tu, Y. T., Diep, G. L., et al. (2023). Impact of natural resources extraction and energy consumption on environmental sustainability in ASEAN countries. Resources Policy, 85, 103713. https://doi.org/10.1016/j.resourpol.2023.103713 Go to original source...
    37. Ogunbode, C. A., Doran, R., Böhm, G. (2020). Exposure to the IPCC special report on 1.5 °C global warming is linked to perceived threat and increased concern about climate change. Climatic Change, 158, 361-375. https://doi.org/10.1007/s10584-019-02609-0 Go to original source...
    38. Oğul, B. (2023). Tarim Sektöründeki Gelişmeler Çevresel Kirliliğini Etkiliyor mu? Türkiye Üzerine Ampirik Bulgular. MANAS Sosyal Araştirmalar Dergisi, 12(3), 1016-1026. https://doi.org/10.33206/mjss.1063110 Go to original source...
    39. Ojogiwa, O. T. (2021). The crux of strategic leadership for a transformed public sector management in Nigeria. International Journal of Business and Management Studies, 13(1), 83-96. https://doi.org/10.48080/ijbms.20210105 Go to original source...
    40. Özbek, S., Naimoğlu, M. (2025). The effectiveness of renewable energy technology under the EKC hypothesis and the impact of fossil and nuclear energy investments on the UK's Ecological Footprint. Energy, 322, 135351. https://doi.org/10.1016/j.energy.2025.135351 Go to original source...
    41. Özbek, S., Naimoğlu, M. (2022). Çevre kalitesi-ekonomik karmaşiklik ilişkisi: Türkiye ekonomisi üzerine fourier eşbütünleşme analizi. İstanbul İktisat Dergisi, 72(1), 407-431. https://doi.org/10.26650/istjecon2022-1061837 Go to original source...
    42. Özcan, B., Ulucak, R., Doğan, E. (2019). Analyzing Long Lasting Effects of Environmental Policies: Evidence from Low-, Middle- and High-Income Economies. Sustainable Cities and Society, 44, 130-143. https://doi.org/10.1016/j.scs.2018.09.025 Go to original source...
    43. Panopoulou, E., Pantelidis, T. (2007). Club Convergence in Carbon Dioxide Emissions. The Institute for International Integration Studies Discussion Paper Series, 235. https://doi.org/10.1007/s10640-008-9260-6 Go to original source...
    44. Pata, U. K., Aydin, M. (2023). Persistence of CO2 emissions in G7 countries: a different outlook from wavelet-based linear and nonlinear unit root tests. Environmental Science and Pollution Research, 30(6), 15267-15281. https://doi.org/10.1007/s11356-022-23284-2 Go to original source...
    45. Pata, U. K., Yilanci, V. (2021). Investigating the persistence of shocks on the ecological balance: evidence from G10 and N11 countries. Sustainable Production and Consumption, 28, 624-636. https://doi.org/10.1016/j.spc.2021.06.027 Go to original source...
    46. Pata, U. K., Naimoglu, M., Karlilar, S., et al. (2024). Analyzing the EKC hypothesis for the top 10 energy-importing countries: a perspective for the COP27 targets. Air Quality, Atmosphere & Health, 17(5), 953-966. https://doi.org/10.1007/s11869-023-01490-2 Go to original source...
    47. Phillips, P. C., Perron, P. (1988). Testing for a unit root in time series regression. Biometrika, 75(2), 335-346. https://doi.org/10.1093/biomet/75.2.335 Go to original source...
    48. Phillips, P. C., Sul, D. (2007). Transition modeling and econometric convergence tests. Econometrica, 75(6), 1771-1855. https://doi.org/10.1111/j.1468-0262.2007.00811.x Go to original source...
    49. Qiu, J., Seah, S., Martinus, M. (2024). Examining climate ambition enhancement in ASEAN countries' nationally determined contributions. Environmental Development, 49, 100945. https://doi.org/10.1016/j.envdev.2023.100945 Go to original source...
    50. Smoot, L. D., Baxter, L. L. (2003). Fossil fuel power stations-coal utilization. In: Meyers, R. A. Encyclopedia of Physical Science and Technology, 3rd edition. New York: Academic Press. ISBN 978-0-12-227410-7. Go to original source...
    51. Solarin, S. A., Tiwari, A. K., Bello, M. O. (2019). A multi-country convergence analysis of ecological footprint and its components. Sustainable Cities and Society, 46, 101422. https://doi.org/10.1016/j.scs.2019.101422 Go to original source...
    52. Stegman, A. (2005). Convergence in Carbon Emissions Per Capita. Macquarie Economis Research Papers, 5, 1-31.
    53. Tatar, H. E. (2022). Asean-5 Ülkelerinde Ekolojik Ayak İzi Yansimasi: SURADF ve SURKSS Birim Kök Testi. Fiscaoeconomia, 6(3), 1018-1035. https://doi.org/10.25295/fsecon1071194 Go to original source...
    54. Tiwari, A. K., Kyophilavong, P., Albulescu, C. T. (2016). Testing the Stationarity of CO2 Emissions Series in Sub-Saharan African Countries by Incorporating Nonlinearity and Smooth Breaks. Research in International Business and Finance, 37, 527-540. https://doi.org/10.1016/j.ribaf.2016.01.005 Go to original source...
    55. Ullah, S., Lin, B. (2024). Harnessing the synergistic impacts of financial structure, industrialization, and ecological footprint through the lens of the EKC hypothesis. Insights from Pakistan. Energy, 307, 132540. https://doi.org/10.1016/j.energy.2024.132540 Go to original source...
    56. Ulucak, R. (2017). Çevre kalitesi açisindan yakinsama hipotezine yeni bir bakiş: ekolojik ayak izi ve kulüp yakinsamaya dayali ampirik bir analiz. Anadolu Üniversitesi Sosyal Bilimler Dergisi, 18(4), 29-38. https://doi.org/10.18037/ausbd.552674 Go to original source...
    57. Ursavaş, N., Apaydin, Ş. (2023). The Convergence in Greenhouse Gas Emissions Across G-7 Countries. Fiscaoeconomia, 7(1), 327-340. https://doi.org/10.25295/fsecon.1143345 Go to original source...
    58. Yilanci, V., Pata, U. K. (2020a). Convergence of Per Capita Ecological Footprint Among The ASEAN-5 Countries: Evidence from A Non-Linear Panel Unit Root Test. Ecological Indicators, 113, 106178. https://doi.org/10.1016/j.ecolind.2020.106178 Go to original source...
    59. Yilanci, V., Pata, U. K. (2020b). Are shocks to ecological balance permanent or temporary? Evidence from LM unit root tests. Journal of Cleaner Production, 276, 124294. https://doi.org/10.1016/j.jclepro.2020.124294 Go to original source...
    60. Yilanci, V., Görüş, M. S., Solarin, S. A. (2021). Convergence In Per Capita Carbon Footprint and Ecological Footprint For G7 Countries: Evidence From Panel Fourier Threshold Unit Root Test. Energy & Environment, 33(3), 0958305X211011461. https://doi.org/10.1177/0958305X211011461 Go to original source...
    61. Yurtkuran, S. (2020). N11 ülkelerinde ekolojik ayak izi yakinsamasi: Fourier durağanlik testinden yeni kanitlar. Uluslararasi Ekonomi ve Yenilik Dergisi, 6(2), 191-210. https://doi.org/10.20979/ueyd.681354 Go to original source...
    62. Zhang, J., Hao, X., Li, X., et al. (2024). Evaluation and regulation strategy for ecological security in the Tarim River Basin based on the ecological footprint. Journal of Cleaner Production, 435, 140488. https://doi.org/10.1016/j.jclepro.2023.140488 Go to original source...
    63. Zhang, J., Hao, X., Li, X., Fan, X., & Zhang, S. (2024). Evaluation and regulation strategy for ecological security in the Tarim River Basin based on the ecological footprint. Journal of Cleaner Production, 435, 140488. https://doi.org/10.1016/j.jclepro.2023.140488 Go to original source...

    This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY NC ND 4.0), which permits non-comercial use, distribution, and reproduction in any medium, provided the original publication is properly cited. No use, distribution or reproduction is permitted which does not comply with these terms.


    Return to the content