The Effects of Urbanization on Ecological Footprint in Developing Countries: A Smooth Transition Regression Model

Abstract
Introduction
The rapid pace of urbanization, depletion of environmental resources, and growing ecological concerns in developing countries have made sustainable urban development a crucial challenge. Urbanization, while essential for economic progress, can intensify environmental pressures unless managed in parallel with green development policies. This study investigates the effects of urbanization on the ecological footprint in 35 developing countries over the period 1990–2023. By applying the Panel Smooth Transition Regression (PSTR) model, the nonlinear and threshold-based relationship between urbanization and environmental degradation is analyzed. The findings indicate that, at the early stages of urbanization, the ecological footprint increases with a significant coefficient of 1.33. However, once the urban population surpasses the threshold of 50 million, the effect reverses, suggesting that urban maturity and better infrastructure may reduce ecological pressures. Additionally, GDP growth is positively associated with the ecological footprint (coefficient = 3.29), indicating increased consumption and emissions in the growth process. Trade openness demonstrates a slight negative impact (coefficient = –0.01), while the share of renewable energy significantly reduces the ecological footprint (coefficient = –0.67), highlighting its role in environmental protection. The interaction term between GDP and urbanization also reveals a negative coefficient, implying that integrated policies combining economic growth with urban environmental planning can effectively mitigate ecological degradation.
 
Introduction
With the urban population growing from 30% in 1950 to more than 55% in 2018—and projected to reach 68% by 2050—developing countries face mounting pressure on their ecosystems due to unplanned urban expansion. Urbanization affects ecological footprints through increased resource use, carbon emissions, and land-use change. Managing these dynamics requires understanding the complex and nonlinear relationship between urbanization and environmental sustainability. This study contributes to the literature by evaluating the ecological impact of urban expansion while accounting for economic, trade, and energy factors. By examining the threshold dynamics of urbanization, we aim to identify when and how urban growth transitions from being environmentally detrimental to potentially beneficial.
Methods and Materials
The empirical analysis uses data from 35 developing countries between 1990 and 2023. The ecological footprint is measured as the dependent variable, while explanatory variables include urbanization, GDP per capita, trade openness, renewable energy share, and an interaction term between GDP and urbanization. The Panel Smooth Transition Regression (PSTR) model is employed to capture nonlinear effects and transition dynamics. This model allows for smooth transitions between regimes, reflecting how the impact of urbanization varies at different levels of development and infrastructure.
Results and Discussion
The PSTR analysis confirms a nonlinear relationship between urbanization and the ecological footprint. In countries with an urban population below the 50-million threshold, increased urbanization intensifies environmental stress. However, beyond the threshold, urbanization contributes to ecological improvement, likely due to better infrastructure, planning, and technological adoption. GDP growth is consistently linked with higher ecological pressure, while trade openness slightly mitigates environmental impacts. Most notably, the use of renewable energy shows a robust negative effect on the ecological footprint, emphasizing the importance of energy transition strategies. The negative coefficient on the GDP–urbanization interaction term indicates that combining economic growth with sustainable urban planning can counterbalance environmental degradation.
Conclusion
The results of this study highlight the dual role of urbanization in developing countries. Urban growth initially increases ecological pressure, but after reaching a threshold, it can lead to environmental improvements. Thus, promoting compact cities, investing in green infrastructure, and increasing the share of renewable energy are essential for sustainable urban development. Policymakers must consider the complex interactions among economic growth, urbanization, and environmental sustainability. Integrated strategies that align urban expansion with environmental protection can help developing countries move toward a greener future and reduce their ecological footprint.