1. Introduction
Structural changes not only brought substantial economic growth in the world but they also raised the issues of environmental degradation and sustainable development [
1]. At the earlier stage of development, economic activities shifted from agriculture to manufacturing in the world; however, later on, emergence of the service sector showed tremendous growth, becoming the largest sector of the world economy. The contribution of services to world gross domestic product (GDP) and employment level remarkably increased, while the value addition of the agriculture and manufacturing sector to GDP declined. The service sector not only provides the highest level of output and employment, but it also stimulates a substantial increase in foreign trade, investments, and service-related exports over the globe [
2]. Over the last two decades, the valued-added contribution of the service sector to GDP increased from 69% in 1997 to 74% in 2015 in high-income countries, and surged extraordinarily from 48% in 1997 to 57% in 2015 in developing countries [
3]. The provision of services mainly depends upon the building infrastructure, transportation system, and power generation mechanism. According to the International Energy Agency (IEA) [
4] report, the transport and building sector accounts for approximately one-half of CO
2 emissions from fossil-fuel burning in the world after redistributing emissions from power generation to sectors. The report further indicates that electricity power generation in Asia caused almost a 50% increase in global emission over the period of 2000–2017, and China and India alone are increasing such emissions by 200 metric tons per annum. These facts and figures highlight the increasing vitality of the service sector to economic growth, while simultaneously raising concerns for unprecedented energy demand and environmental degradation.
The idea of structural change was introduced by Kuznets [
5], who identified the shift in sectoral employment from agriculture to manufacturing and the service sector during the path of economic growth. Structural changes may significantly affect sustainable economic growth because of technological progress and the element of uncertainty [
6]. However, a higher level of energy consumption requirements, especially in emerging economies, may distort the notion of such sustainable growth [
7]. Structural change in the economy may influence the bell-shaped relationship, which we call the environmental Kuznets curve (EKC), between economic growth and environmental degradation [
8]. The EKC hypothesis holds that pollution increases at the initial stage of economic development due to industrialization and urban development. However, at the advanced stage of economy, when the service sector grows and technology improves, people get more concerned about environmental issues, they demand a better and more sustainable environment, and pollution consequently tends to decrease [
9,
10,
11].
A large number of studies investigated the EKC theory in empirical settings based upon different sample characteristics and time spans, as well as applying a variety of econometric approaches. For instance, many researchers confirmed the existence of an inverted U-shaped nexus between economic growth and pollution [
12,
13,
14,
15,
16]. The evidence on the EKC hypothesis in previous studies is quite controversial, and a large number of studies did not support an inverted U-shaped relationship between economic growth and CO
2 emissions [
17,
18,
19]. Another set of studies reported mixed evidence relating to the EKC hypothesis due to variations in country dynamics and the type of pollution measures taken [
20,
21]. Miah et al. [
22] argued that global literature on EKC hypothesis provides mixed results depending upon the type of greenhouse gas (GHG) emissions taken as a measure of environmental degradation in empirical research. Marsiglio, Ansuategi and Gallastegui [
8] argued that the negative relationship between pollution and income level, as suggested by the EKC hypothesis, is a short-term phenomenon, and that pollution may increase in the long run, generating an N-shaped curve.
Relatively few studies empirically tested the environmental Kuznets curve (EKC) hypothesis with respect to structural change theory; in particular, the role of the service sector in explaining the bell-shaped relationship between economic development and environmental degradation was overlooked in empirical research. The structural transition and growth of the service economy may decrease environmental degradation [
23]. Marsiglio et al. [
8] also pointed out that the negative effect of income on pollution may depend upon the nature of structural change in the economy. Structural shifts to the service sector could possibly explain the existence of the EKC hypothesis, particularly in developing economies, which are facing the issue of premature deindustrialization [
24]. The past literature on the role of services in affecting environmental degradation is not only highly inconclusive but it also did not explicitly test the EKC hypothesis. Some studies argued that services positively affect pollution. For instance, Suh [
25] reported that services in the household sector produce more than one-third of total industrial air pollution when both the household consumption of services and the supply-chain network are accounted for. Moreover, Ali et al. [
18] pointed out in their empirical research that the service sector is more efficient than the energy-intensive industrial sector in terms of reducing CO
2 emissions. The service sector, which was earlier considered immaterial with regard to consumption of energy, now heavily depends upon energy and material items, which cause pollution and raise concerns for climate change [
26]. This immateriality notion was also challenged by Piaggio et al. [
27] who explained the increasing role of the service sector in producing CO
2 emissions, as the provision of services produces both direct emissions (as caused by the transport sector) and indirect emissions (due to its inputs produced by other highly energy-intensive sectors). However, Zaman et al. [
28] evidenced that the service sector reduces pollution in the world, while the manufacturing sector increases global emissions. Sohag et al. [
1] showed the positive impact of the industrial and service sectors on environmental degradation in middle-income countries, which are undergoing massive structural transitions.
The controversial and contradictory findings indicate that the relationship between the service sector and pollution varies across countries due to different levels of economic growth, rates of industrialization and technological advancement, scales of urban growth, and regional differences. Therefore, the results of these prior studies cannot be generalized, which motivates us to investigate the role of the service sector in affecting environmental degradation and whether it affects the inverted U-shaped relationship between income and pollution, so as to gain a deep understanding of this complex relationship. Therefore, the purpose of our study is to examine the non-linear effect of the service sector on carbon emissions over the time period of 1971–2014 using an autoregressive distributive lag (ARDL) model.
Our study contributes to the existing literature in many aspects. Firstly, our research investigates the long-term relationship between the service sector and environmental degradation in Pakistan. We selected the service sector because it is the largest sector, and it showed a tremendous growth of 6.43% over the last two years, which is larger than that of the agriculture and manufacturing sectors. Furthermore, it contributes to more than 50% of the GDP, and it offers major employment to the labor force [
29]. The service sector consists of retailing and wholesaling, financial services, transportation and storage, communication and information technology (IT), government services, housing, and other private services in Pakistan.
Figure 1 exhibits how the structural change in Pakistan caused splendid growth as compared to the agriculture and industrial sectors, which showed declining trends in the economy. Secondly, our research is original and innovative because we are the first to analyze the role of the service sector in inducing an inverted U-shaped relationship between economic growth and pollution, which was overlooked in previous studies, especially in Pakistan. Moreover, the contradictory results regarding the role of the service sector in mitigating emissions requires further investigation so as to gain further insight and implement policy formulation. Therefore, we investigate the non-linear effect of services on environmental degradation to clearly determine the pollution reduction role of service sector. Thirdly, we apply an autoregressive distributive lag (ARDL) model with structural break analysis to account for any economic shocks, which could have biased or skewed the previous findings on the EKC hypothesis. The major structural changes which occurred in the 1980s and 1990s in Pakistan due to liberalization and major economic reforms could have substantially affected EKC results under a traditional econometric approach. Fourthly, we also examine the inverted U-shaped effect of energy consumption on carbon emissions to support the pollution-mitigating role of services. Lastly, we apply fully modified ordinary least squares (FMOLS) and dynamic ordinary least squares (DOLS) to confirm our previous findings, and we utilize the Toda and Yamamoto (TY) causality approach as used by Ahmed et al. [
30] to investigate causal interactions between variables.
The rest of the paper is structured as follows: in the forthcoming section, we undertake a critical and systematic review of the literature to identify research gaps. The third section describes the methodology consisting of model construction, data collection and variable description, unit root and structural break testing, and econometric modeling. In the fourth section, we elaborate on the mainstream results and discuss important findings. In the fifth section, the robustness tests were applied in terms of DOLS and Toda and Yamamoto causality tests to confirm our baseline model. Lastly, we conclude the study with major findings, policy implications, and directions for the future.
5. Conclusions and Policy Implications
This study investigated the long-term relationships among energy consumption, income level, services, trade openness, and CO2 emissions in Pakistan over the time period 1971–2014 using ARDL with structural break analysis; we also applied DOLS and Toda-Yamamoto causality tests as robustness measures to confirm the findings of the baseline model. Our pioneer research confirmed the role of the service sector in inducing the EKC hypothesis in Pakistan. Our findings confirmed the inverted U-shaped relationship between income level and environmental degradation as measured by CO2 emissions. Income level caused pollution at the initial stage of economic development; however, after reaching a certain threshold, it tended to decline environmental degradation. The service sector exhibited an inverted U-shaped nexus with CO2 emissions. Moreover, energy consumption had a bell-shaped effect on carbon emissions in Pakistan, which resulted in certain energy efficiency measures and cleaner energy production. The application of the DOLS model, as an alternative specification, confirmed the findings of ARDL and supported the EKC hypothesis along with a U-shaped effect of services and energy consumption on environmental degradation. The results of the Toda and Yamamoto test indicated the unidirectional causality between energy consumption and pollution, and the feedback relationship between income level and the service sector and CO2 emissions. However, we did not find any causal relationship between trade openness and pollution in the case of Pakistan.
The current study verified the existence of an EKC in Pakistan, and these findings are similar to previous studies of Kisswani et al. [
19] for Thailand and Usman et al. [
13] in the case of India, conducted in developing countries. Although our results confirmed the existence of an inverted U-shaped relationship between economic development and air pollution, the improvement in environmental quality had a very sluggish behavior after the turning point of the EKC. The government should not only accelerate the real economic growth, address the issues of hyperinflation and unemployment in the country, and implement social inclusion strategies to reduce income inequality; they should also initiate environmental awareness and protection campaigns to escalate the mitigating process of environmental damage. The bidirectional causality between income level and CO
2 emissions also connoted that any effort to reduce CO
2 emissions will occur at the cost of economic development because both variables are linked.
The growth of the service sector induced the EKC hypothesis in Pakistan because of a shift from manufacturing to services over the last few decades. Moreover, the inelastic effect of services on environmental degradation in the case of models 1 and 2 is not an alarming sign in the short term. The non-linearity of services was also tested using ARDL and robustness analysis, which exhibited an inverted U-shaped effect of services on CO2 emissions. The tremendous growth of the service sector and the development of less energy-intensive sub-systems of services such as the educational sector, financial institutions, retailing and wholesaling sectors, personal and professional services, government services, and the recreational industry reduced pollution in the country. This phenomenon was further supported by the existence of a bell-shaped effect of energy consumption on carbon emissions, as tested in our previous section of results. These findings indicated that there was a tight linkage between energy consumption and pollution in the early phase of economic development and industrial growth, causing environmental degradation at a higher rate. However, during the later phase of economic development and the structural shift to the service sector, this link loosened due to energy-efficient technologies and the adoption of renewable energy resources in Pakistan.
Our research findings have significant and vital implications for designing appropriate environmental policies to mitigate environmental degradation. Although our findings verified the pollution mitigating role of energy use in Pakistan, the impact was relatively inelastic, and further efforts are required by the government to adopt energy conservation and optimization policies as implemented in other developing countries. According to World Bank Development Indicators (WDIs), Pakistan was reported to have consumed approximately 60% fossil-fuel energy consisting of oil, natural gas, petroleum, and coal. Thus, the Pakistan economy is still heavily dependent upon fossil-fuel energy, which is excreting substantial environmental pressure by emitting a huge amount of CO2 emissions. Similar to energy conservation and cleaner production strategies adopted in China, the government should build new water reservoirs to produce electricity to meet the growing demand for household, commercial, and industrial consumption, they should also formulate and implement an energy conservative policy, as well as raise the share of renewable energy options such as solar, wind, hydropower, and biomass in the total energy mix. The government should invest more money in renewable energy projects to mitigate the issue of rising environmental degradation.
Although the overall impact of the service sector on environmental quality does not raise sustainability issues for Pakistan, the analysis of sub-systems of services is recommended for further investigation and policy formulation. For instance, some sub-sectors of the service sector also generate pollution in the long run because of their linkage with building infrastructure, transportation, and electric power generation. The rising population and urban development are also causing substantial demand for services such as transportation, electricity, and building materials. The transport and logistic systems are the major causes of direct CO2 emissions because of the fossil-fuel energy used to meet this ever-increasing demand. There is an urgent need to improve the transportation system by introducing an efficient public transportation system and infrastructure to mitigate the issues of traffic congestion and air pollution, especially in the largest cities of Pakistan. The government should also design and implement an effective urban planning mechanism to introduce energy-efficient buildings such as skyscrapers and the idea of a compact city. The service sector also heavily depends upon industrial sectors for provision of its input, which could indirectly cause pollution. This input–output linkage between the service sector and other industries should be comprehended to design an all-inclusive pollution mitigating strategy for long-term consequences. Since the service sector also demands electricity consumption for running its operations, more options based on renewable energy for power generation should be explored and implemented to reduce the overall level of pollution in the country.
The current study investigated the issue of structural change in detail, but we recommend future researchers to also include other sectors of the economy, as well as perform decomposition analysis. We only used total energy consumption to measure energy efficiency by taking its quadratic term, but the unavailability of renewable energy data (data are available only from 1990 onward from the World Bank) for the sample period constrained us to making a comparative assessment. Moreover, the time series models such as ARDL and cointegration tests allowed a limited number of variables. Therefore, additional factors such as urbanization, population growth, and financial development could be utilized in future research.