Economic development and multiple air pollutant emissions from the industrial sector

Analysis of Worldwide Greenhouse and Carbon Monoxide Gas Emissions: Which Countries Exhibit a Special Pattern? A Closer Look via Twitter

There is significant global concern about the harmful effects of greenhouse gas and carbon monoxide emissions (deforestation, air pollution, global warming, etc.). The 2015 Paris Agreement on climate change aspires to reduce global warming by achieving a climate-neutral world. Research has been carried out to calculate and diminish the aforementioned emissions in waste, power industry, transport, building, in addition to other areas. The aim of this paper is to analyse the carbon and greenhouse gas emissions across countries around the globe in order to find patterns and correlate them to socio-economic indicators [gross national income (GNI), industrial production (IPI) and human development indexes (HDI)] as well as Twitter interactions regarding climate change. For this purpose, time series and socio-economic data have been downloaded from different repositories including EDGAR (Emissions Database for Global Atmospheric Research), World Bank and UNDP (United Nations Development Programme). Although classical clustering algorithms have already been used in the examination of some environmental issues, we use a non-parametric time series clustering method, which has been suggested in certain scientific literature as a more flexible approach, since any ad hoc parametric assumptions are required. The chosen socio-economic indicators have also demonstrated their relevance in pieces of research related to various fields. With respect to Twitter, which is one of the most popular social networks nowadays, significant analysis has also been performed on the basis of capturing citizens' perceptions on a multitude of matters. We found that several countries such as Brazil, India, China, Nigeria, Russia, United States, Spain, Andorra, Greece, and Qatar show differences in carbon and greenhouse gas emissions patterns. Besides, there does not seem to be a correlation between GNI, IPI and HDI as well as the above mentioned emissions ( correlation < 0.16 ) . Regarding Twitter interactions, a dissimilarity in the distribution of hashtags was detected between the aforementioned countries and the rest of the world. This research can help to identify countries in which more governmental measures are needed to reduce the type of emissions analysed in certain industrial sectors. In addition, it points out the topics related to climate change that seem to generate the most debate on Twitter for countries with an unusual pattern.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s41742-023-00510-4.

Interaction between Urbanization and Eco-Environment in Hebei Province, China

Understanding the complex interaction between urbanization and the eco-environment is necessary for rapid and quality urbanization, eco-environmental protection, and the harmonious coexistence of humans and nature within a region. Based on panel data from Hebei Province between 1985 and 2019, we suggested a symbiosis hypothesis of urbanization and the eco-environment (SHUE) and used the distance coordination coupling model, the Tapio decoupling model, and the symbiosis model to quantitatively determine the interaction relationship between urbanization and the eco-environment. We found that (1) the improved ‘Northam curve’ of urbanization in Hebei Province met the logistic equation. (2) During the study period, the coordinated coupling degree (CCD) of urbanization and eco-environment exhibited an overall upward trend, while the coupling type gradually changed from the endangered imbalance recession type to the coordinated development type. (3) The decoupling types showed strong and weak decoupling fluctuations, with a high frequency of strong decoupling; the growth rate of the urbanization index was higher than that of the eco-environment index; and there was a positive effect between urbanization and eco-environment indicating positive urbanization. (4) The research results verified SHUE. The symbiosis mode of urbanization and eco-environment was mainly asymmetric mutualism, with the two demonstrating mutual promotion and mutualism. However, in 2016–2019, the symbiosis mode became parasitic, urbanization development enforced upon the eco-environment. The study constructed a set of quantitative method to systematically discuss the interaction relationship from two dimensions: coupling and decoupling. The results provide reference for the coordinated development of urbanization and eco-environment in Hebei Province and consequentially enrich this research field.

Nexus between Agricultural Land Use, Economic Growth and N2O Emissions in Canada: Is There an Environmental Kuznets Curve?

The present study investigates the relationship between nitrous oxide emissions and economic growth using the ARDL bounds testing approach in Canada over the period of 1970–2020. The agricultural land use and exports are included in the estimated models as additional control variables. The empirical findings confirmed the environmental Kuznets curve hypothesis when total N2O emissions are used as a dependent variable in the case of Canada, and similar results are found when we used agricultural induced N2O emissions as a dependent variable. The results also indicate that Canada is already in the decreasing segment of the Kuznets curve, and the turning point of GDP per capita for the total N2O emissions is $41,718, while for agricultural induced N2O emissions, it is $38,825. Our empirical evidence confirms that agricultural land use had a positive and significant effect on total N2O emissions, while a negative but insignificant effect in the case of agricultural induced N2O emissions. However, Canadian exports are negatively associated with total N2O emissions as well as agricultural induced N2O emissions, but it requires more stringent laws to curb N2O emissions-oriented exports to keep the ecosystem in balance in the short-run and intends to meet its long-term target of reducing emissions as it progresses towards Canada’s 2050 net-zero ambition.

Investigating whether the environmental Kuznets curve hypothesis holds for sectoral CO2 emissions: evidence from developed and developing countries

Carbon dioxide (CO₂) emissions entail a key component of greenhouse gases (GHGs) and are crucial for global warming and climate change issues. Although the environmental Kuznets curve (EKC) pattern of the emissions-income nexus has intrigued many researchers for a long time, few studies cover a wide range of economic sectors and a large number of countries, which calls for the re-investigation of sector-wise EKC arguments. Thereby, we investigate the long-run equilibrium relationship between CO₂ emissions and per capita income in a panel of 86 developing and developed countries for the period from 1990 through 2015. Our findings show that the EKC holds for three sectors: the electricity and heat production sector, the commercial and public services sector, and the other energy industry own use sector with the turning points of approximately 21,000 USD, 3000 USD, and 5000 USD, respectively. Additionally, emissions decrease monotonically for the manufacturing industries and construction sector, the residential sector, and the agriculture, forestry, and fishing sector, whereas they increase monotonically with the development of the transport sector. Policymakers should consider adopting sector-specific environmental policies based on each sector's unique income-emission relationship, to mitigate CO₂ emissions effectively, and attain sustainable economic growth.

Identifying the Driving Factors of Food Nitrogen Footprint in China, 2000–2018: Econometric Analysis of Provincial Spatial Panel Data by the STIRPAT Model

This paper studies the EKC hypothesis and STIRPAT model. Based on the panel data of carbon emission intensity and other influencing factors of 30 provinces in China from 2000 to 2018, the spatial effect of per capita food nitrogen footprint (FNF) and the effect of different socio-economic factors in China were studied by using exploratory spatial data analysis and fixed effect spatial Durbin model for the first time. The results show that: (1) there is a spatial agglomeration effect and a positive spatial dependence relationship in China’s provincial per capita FNF (FNFP), which verifies that the relationship between China’s FNF and economy is in the early stage of EKC hypothesis curve. (2) The driving forces of China’s FNF were explored, including Engel’s coefficient of urban households (ECU), population density (PDEN), urbanization, nitrogen use efficiency (NUE) and technology. (3) The results show that there is a significant spatial spillover effect of FNFP. The ECU and NUE can reduce the regional FNFP, and can slow down the FNFP of surrounding provinces. (4) Policy makers need to formulate food nitrogen emission reduction policies from the food demand side, food consumption side and regional level.

Nexus between Nitrous Oxide Emissions and Agricultural Land Use in Agrarian Economy: An ARDL Bounds Testing Approach

This paper analyses the relationship between Nitrous Oxide emissions, agricultural land use, and economic growth in Pakistan. Agriculture largely contributes to Nitrous Oxide emissions. Hence, models of agriculture induced Nitrous Oxide emissions are estimated in addition to models of total Nitrous Oxide emissions. Estimated models accommodate more flexible forms of relationship between economic growth and emissions than those of the widely adopted models in testing the Environmental Kuznets Curve. The Auto-Regressive Distributed Lag (ARDL) bounds testing approach to co-integration and the vector error correction model approach is applied to test the Environmental Kuznets’s Curve hypothesis for Pakistan and to detect the directions of causality among variables using the time series data for the period 1971 to 2012. Results indicate that an N-shaped rather than an inverted U-shaped relationship exists in the case of Pakistan. The tipping values for total Nitrous Oxide emissions and agriculturally induced Nitrous Oxide emissions indicate that Pakistan passes through a phase of increasing environmental degradation. Increases in agricultural land use and per capita energy use will increase the level of Nitrous Oxide emissions. However, controlling Nitrous Oxide emissions from agricultural land use and per capita, energy use without adversely affecting economic development will be a serious policy challenge for Pakistan.

Does the environmental Kuznets curve reliably explain a developmental issue?

This study aims to achieve two main objectives; first, it provides a brief but critical description of the empirical literature on the environmental Kuznets curve (EKC) in terms of history, origin, micro-foundations, measurement of environmental degradation, methodologies and samples. Second, it examines the curious attraction of the EKC despite considerable criticism it has attracted over time. The motivation stems from the mixed results probably due to different econometric techniques, sample periods, country-specific factors and environmental indicators used to test EKC. The study concludes that of course, the EKC has attracted a great deal of criticism, but its survival power is undeniable. Different taxonomies of the approaches to explain income-environment nexus have been established by various commentators producing different results under different scenarios. It is still equally important among researchers to interpret the relationship between income and pollution due to its charismatic characteristics; therefore, the empirical literature on EKC continues to grow despite criticism on its validity and assumptions. However, we should not be convinced that economic growth on its own will solve environmental ills. The proposition that affluent countries will invest heavily to level off and gradually contain their environmental pollution should not be persuaded. Therefore, policymakers must not encourage unlimited economic growth to cure environmental problems.

Study on the spatial spillover effects of cement production on air pollution in China

Since 1985, China has become the largest cement producer and consumer in the world. The pollutants emitted from cement production and processing have aggravated China's pressure to conserve energy and reduce emissions. Considering the fact of cross regional transfer and capacity replacement of cement industry, this paper explores the influence of cement production on air pollution by using spatial econometric models. The results illustrate that the concentration of PM_2.5 is obviously spatially dependent and presents high-east and low-west agglomeration characteristic on a national scale. Moreover, the positive correlation between cement production and air pollution is quite obvious, the spatial spillover effects of cement production on air pollution increase progressively, and the indirect spillover effects are seven times greater than the direct spillover effects. The results also show that the phenomenon of cement industries obtaining benefits at the cost of hurting air quality in surrounding areas is the most severe in eastern China. Thus, rules should be based on local conditions when making policies in cement industries and the strong correlation between the pollution of adjacent areas should be fully considered.

Value addition in the services sector and its heterogeneous impacts on CO2 emissions: revisiting the EKC hypothesis for the OPEC using panel spatial estimation techniques

This study examines the Environmental Kuznets Curve (EKC) hypothesis in the context of 12 members of the OPEC by utilizing data on both the aggregate gross value added and the services' sectoral value-added between 1992 and 2015. This empirical work contributes to the literature by applying the panel spatial techniques which resulted in the findings as follows. Firstly, the results verify the authenticity of the EKC hypothesis for the aggregate level of gross value added as perceived from its inverted-U shaped association with CO2 emissions. Secondly, the disaggregated analysis affirms the heterogeneity of the validity of the EKC hypothesis across the subsectors within the services sector; this justifies the importance of analyzing the EKC hypothesis from a comprehensive (disaggregated) perspective for unearthing key sector-specific policy implications. The results reveal that the EKC hypothesis holds only in the context of construction services only but not for the cases of restaurant services, tourism and transportation services. These key findings call for effective measures to be undertaken to address the adverse environmental impacts that can be attributed to thse three sub-sectors for which the EKC did not hold. In line with the overall findings from the empirical exercises, it is recommended that the concerned OPEC members reduce their monotonic dependency on the consumption of fossil fuels, oil in particular, and gradually incorporate renewable energy resources into the energy-mix particularly within their respective services sector.

Dow Jones Sustainability Indices, Do They Make a Difference? The U.S. and the European Union Companies

Sustainability and corporate social responsibility (CSR) strategies of companies delineate the health and the welfare of the communities across the globe. The two major goals of this study are (1) To explore the relationship between the environmental regulations, market value, and adoption of sustainability and CSR strategies of the publicly traded firms listed on the Dow Jones Sustainability Indices (DJSI) and (2) To examine the impact of being added to or deleted from DJSI per different market sectors for the firms in the U.S. and the European Union (EU). The selected starting window, the year 2015, for studying the impact of addition to or deletion from the DJS indices was the Paris Accord proposal by the EU and strict sustainability regulations of the EU versus the U.S. We used event study methodology and regression analyses to explain the cumulative abnormal returns utilizing firms’ characteristics and specific market sectors. In addition, the other focus of the study was on heavy (polluting) industries and investigating if the addition to or deletion of the firms in these industries from the sustainability indices had an impact on the market value. The findings of this study reveal no impact of the environmental rules and regulations on adopting sustainability and CSR strategies by either the EU or the U.S. firms. The novel findings of this study indicate a significant negative impact on the market value of firms in heavy industries, Energy, Basic Materials, and Utilities when added to the DJS indices. The study discusses the underlying reasons for these differences and proposes strategies to enhance the impact of addition to or deletion from the DISI to increase firms’ commitments to sustainability and CSR strategies and altering the attitudes of the investors.

Exploring the Relationship between Urbanization and Ecological Environment Using Remote Sensing Images and Statistical Data: A Case Study in the Yangtze River Delta, China

With the rapid urban development in China, urbanization has brought more and more pressure on the ecological environment. As one of the most dynamic, open, and innovative regions in China, the eco-environmental issues in the Yangtze River Delta have attracted much attention. This paper takes the central region of the Yangtze River Delta as the research object, through building the index system of urbanization and ecological environment based on statistical data and two new indicators (fraction of vegetation coverage and surface urban heat island intensity) extracted from remote sensing images, uses the Entropy-TOPSIS method to complete the comprehensive assessment, and then analyzes the coupling coordination degree between the urbanization and ecological environment and main obstacle factors. The results showed that the coupling coordination degree in the study region generally shows an upward trend from 0.604 in 2008 to 0.753 in 2017, generally changing from an imbalanced state towards a basically balanced state. However, regional imbalance of urbanization and ecological environment always exists, which is mainly affected by social urbanization, economic urbanization, landscape urbanization, pollution loading and resource consumption. Finally, on the basis of the obstacle factor analysis, some specific suggestions for promoting the coordinated development of the Yangtze River Delta are put forward.

Lead distribution in urban street dust and the relationship with mining, gross domestic product GDP and transportation and health risk assessment

Lead (Pb) is an important pollutant and it is of significance to explore the Pb distribution, influencing factors and health risk. Pb concentration and mass load per unit area in 385 street dust samples collected from 19 cities in China were determined during 2011-2013. The results show that the Pb concentration are 68.8, 105.4, 41.7, 49.7, 75.6, 81.7, 131.9, 67.5, 109.3, 164.1, 74.8, 66.4, 99.8, 58.4, 114.0, 59.6, 103.7, 55.4 and 80.4 for Beijing, Chengdu, Daqing, Harbin, Jilin, Jinan, Kunming, Lanzhou, Luoyang, Panzhihua, Qingdao, Yinchuan, Guangzhou, Tangshan, Xi'an, Guangyuan, Nanjing, Taiyuan and Tianjin, respectively. The Pb pollution level of urban street dust varies among cities in the range of 1.72-5.56 times higher than soil background values. The allometric function can fit the change in Pb concentration with particle size well. The medium-sized (38-120 μm) particles contributed 60.2%-80.4% to the Pb load and should be highlighted when selecting street dust management techniques. Influenced by the distribution of Pb ore, the Pb concentration of urban street dust in China shows obvious regional differences, with value in the south 112% higher than that in the north. Among all kinds of mining types, metal-related mining activities discharge a large amount of Pb dust in the process of crushing and smelting, thus contributing most to the Pb load. The Pb load was also affected by transportation. The relationship between Pb load and gross domestic product (GDP) was described with the environmental Kuznets curve (EKC) model, which indicated that the Pb emissions of most cities were still increasing. Finally, the human health risk assessment model with adjusted parameters showed that the Pb risk of all cities was below the threshold. Despite all this, given the EKC law of Pb emission, long-term follow-up assessments are needed.

Investigating the Relationship between the Industrial Structure and Atmospheric Environment by an Integrated System: A Case Study of Zhejiang, China

Under the dual pressure of industrial structure upgrade and atmospheric environment improvement, China, in a transition period, is facing the challenge of coordinating the relationship between the industry and the environment system to promote the construction of a beautiful China. Based on system theory and coupling coordination model, the interaction analysis framework between industrial structure (IS) and atmospheric environment (AE) was constructed. An integrated system with 24 indicators was established by the pressure–state–response (PSR) model of IS and level–quality–innovation (LQI) model of AE. Then, we analyzed trends observed in coupling coordination degree (CCD) and dynamic coupling coordination degree (DCCD) for 11 cities in Zhejiang Province, China, using statistical panel data collected from 2006 to 2017. Conclusions were as follows: (1) the 11 cities’ comprehensive level of the IS system shows a trend of stable increase, yet the comprehensive level of AE demonstrated a trend of fluctuation and transition. There are significant spatial variations among cities; (2) The CCD analysis results found that Hangzhou, Ningbo, and Wenzhou take the lead in realizing the transformation from barely coordinated development to superior coordinated pattern, while other cities were still in the stage of barely coordinated development; (3) the DCCD phase of 11 cities can be roughly divided into three types: upgraded—utmost development type (only Hangzhou), stable—harmonious development type (Wenzhou, Lishui, and Zhoushan) and transitional—harmonious development type (the remaining seven cities). This means, for most cities, the contradiction between the transformation process of IS and the AE has become increasingly prominent and intensified. Finally, three necessary and sustainable strategies were proposed to environmental policy makers.

Exploring the link between environmental pollution and economic growth in EU-28 countries: Is there an environmental Kuznets curve?

This study examines the Environmental Kuznets Curve hypothesis (EKC), considering the primary energy consumption among other country-specific variables, for a panel of the EU-28 countries during the period 1990–2014. By estimating pooled OLS regressions with Driscoll-Kraay standard errors in order to account for cross-sectional dependence, the results confirm the EKC hypothesis in the case of emissions of sulfur oxides and emissions of non-methane volatile organic compounds. In addition to pooled estimations, the output of fixed-effects regressions with Driscoll-Kraay standard errors support the EKC hypothesis for greenhouse gas emissions, greenhouse gas emissions intensity of energy consumption, emissions of nitrogen oxides, emissions of non-methane volatile organic compounds and emissions of ammonia. Additionally, the empirical findings from panel vector error correction model reveal a short-run unidirectional causality from GDP per capita growth to greenhouse gas emissions, as well as a bidirectional causal link between primary energy consumption and greenhouse gas emissions. Furthermore, since there occurred no causal link between economic growth and primary energy consumption, the neo-classical view was confirmed, namely the neutrality hypothesis.

Measuring the Dynamic Efficiency of Regional Industrial Green Transformation in China

The green concept has become one of the key demands of the current era of development in China. As an attempt to cope with climate change and constraints of resources and environment, the industrial green transformation is bound to have a dramatic impact on the whole society. This paper enriches the understanding of industrial green transformation by highlighting its social attributes. Combining a hybrid model with a window analysis, this paper measures the dynamic efficiency of regional industrial green transformation in China from 2006 to 2015. In general, Beijing, Tianjin, Shanghai, Jiangsu, Zhejiang, Fujian, Shandong and Guangdong obtain the best performance; industrial water use has the lowest and most unstable efficiency among various resources. Tobit regression model, thereafter, is used to analyze the impact of hypothetical factors on the efficiency of industrial green transformation. The findings demonstrate that reduction and lean management of state-owned property, promoting the development of the productive service industry, minimizing the proportion of fossil energy use and establishing an excellent economic basis can have nationally positive impacts on the regional industrial green transformation; the progress of the productive service industry is the key to industrial green transformation in Eastern China, while the internal optimization of the industrial sector should be paid more attention in other regions, especially in Western China. Finally, detailed discussions and policy suggestions at a regional level as well as research prospects are given.

A study on the causal effect of urban population growth and international trade on environmental pollution: evidence from China

This study seeks to contribute to the recent literature by empirically investigating the causal effect of urban population growth and international trade on environmental pollution of China, for the period 1980-2014. The Johansen cointegration confirmed a long-run cointegration association among the utilised variables for the case of China. The direction of causality among the variables was, consequently, investigated using the recent bootstrapped Granger causality test. This bootstrapped Granger causality approach is preferred as it provides robust and accurate critical values for statistical inferences. The findings from the causality analysis revealed the existence of a bi-directional causality between import and urban population. The three most paramount variables that explain the environmental pollution in China, according to the impulse response function, are imports, urbanisation and energy consumption. Our study further established the presence of an N-shaped environmental Kuznets curve relationship between economic growth and environmental pollution of China. Hence, our study recommends that China should adhere to stricter environmental regulations in international trade, as well as enforce policies that promote energy efficiency in the urban residential and commercial sector, in the quest to mitigate environmental pollution issues as the economy advances.

Retrospective and prospective analysis of water use and point source pollution from an economic perspective-a case study of Urumqi, China

Using the Environmental Kuznets Curve (EKC) hypothesis, this study explored the dynamic trends of water use and point source pollution in Urumqi (2000-2014) from an economic perspective. Retrospective analysis results indicated that total GDP and GDP per capita increased around tenfold and a fivefold since 2000. Total, municipal and industrial water use had average annual growth rates of 3.96, 7.01, and 3.69%, respectively. However, agricultural water use, emissions of COD and NH₃-N showed average annual decreases of 3.06, 12.40, and 4.74%. Regression models reveal that total water demand in Urumqi would keep monotonically increasing relationships with GDP and GDP per capita in the foreseeable years. However, the relations of specific water usage and economic growth showed diverse trends. In the future, the discharge of COD and NH₃-N would further reduce with economic growth. It could be concluded that Urumqi has almost passed the stage where economic growth had caused serious environment deterioration, but the increasing water demand in Urumqi is still an urgent problem. The obtained results would be helpful for water resources management and pollution control in the future.

Economic growth and environmental pollution in Myanmar: an analysis of environmental Kuznets curve

This empirical study examines the short- and long-run relationship between GDP as an economic growth indicator and CO₂ emissions as an environmental pollution indicator in Myanmar by using annual time series data over the period of 1970-2014. It also carefully considered other proxies, such as trade openness, financial openness and urbanization, and structural breaks in the country. The fundamental objective of this study is to test the validity of environmental Kuznets curve (EKC) in the context of Myanmar. The dynamic estimates of the long- and short-term relationship among greenhouse gases (CO₂, CH₄, N₂O), GDP, trade intensity, financial openness, and urbanization growth are built through an autoregressive distributed lag (ARDL) model. The empirical findings indicate that there is positive short- and long-run relationship between CO₂ and GDP and thus, no evidence of EKC hypothesis is found for CO₂ in Myanmar. Nevertheless, the existence of the EKC is observed for CH₄ and N₂O. On the other hand, trade and financial openness have inverse relationship with CO₂ emissions. These results demonstrate that trade liberalization and financial openness will improve the environment quality in Myanmar in the long run.

Attempts to minimize nitrogen oxide emission from diesel engine by using antioxidant-treated diesel-biodiesel blend

The study represents a comprehensive analysis of engine exhaust emission variation from a compression ignition (CI) diesel engine fueled with diesel-biodiesel blends. Biodiesel used in this investigation was produced through transesterification procedure from Moringa oleifera oil. A single cylinder, four-stroke, water-cooled, naturally aspirated diesel engine was used for this purpose. The pollutants from the exhaust of the engine that are monitored in this study are nitrogen oxide (NO), carbon monoxide (CO), hydrocarbon (HC), and smoke opacity. Engine combustion and performance parameters are also measured together with exhaust emission data. Some researchers have reported that the reason for higher NO emission of biodiesel is higher prompt NO formation. The use of antioxidant-treated biodiesel in a diesel engine is a promising approach because antioxidants reduce the formation of free radicals, which are responsible for the formation of prompt NO during combustion. Two different antioxidant additives namely 2,6-di-tert-butyl-4-methylphenol (BHT) and 2,2'-methylenebis(4-methyl-6-tert-butylphenol) (MBEBP) were individually dissolved at a concentration of 1% by volume in MB30 (30% moringa biodiesel with 70% diesel) fuel blend to investigate and compare NO as well as other emissions. The result shows that both antioxidants reduced NO emission significantly; however, HC, CO, and smoke were found slightly higher compared to pure biodiesel blends, but not more than the baseline fuel diesel. The result also shows that both antioxidants were quite effective in reducing peak heat release rate (HRR) and brake-specific fuel consumption (BSFC) as well as improving brake thermal efficiency (BTE) and oxidation stability. Based on this study, antioxidant-treated M. oleifera biodiesel blend (MB30) can be used as a very promising alternative source of fuel in diesel engine without any modifications.

Understanding the relation between urbanization and the eco-environment in China's Yangtze River Delta using an improved EKC model and coupling analysis

Better understanding the relationship between urbanization (U) and the eco-environment (E) is necessary to coordinate the development of them. Using a comprehensive index system for U and E with statistic data, and an improved environmental Kuznets curve (EKC) model and dynamic coordination coupling degree (CCD) model, this study addressed the relationship between U and E in the Yangtze River Delta (YRD) in the period 1980-2013. The main conclusions were as follows: (1) Economic urbanization and eco-environment endowment were the highest weighted factors in the U and E system respectively, and thus constitute the key factors. (2) Differentiated inverted-U curves were shown to exist in the relation between U and E across the cities studied, thereby confirming the improved EKC hypothesis. We further found economically developed areas to have higher urbanization levels than less developed areas at the point at which the curve inflects, less developed areas have higher eco-environmental pressure at inflection. Before the appearance of the inflection point, a striking positive correlation was observed between eco-environmental pressure and the urbanization level, while a negative correlation was found to follow it. (3) A dynamic coordination coupling relation was found to exist between U and E, which conforms to an S-shaped curve. The coordination coupling process in the YRD has gradually moved from a "low-grade symbiosis" stage into a "break-in development" stage, but the pattern of coordination belonging to the eco-environment part of the relation was found to always show some lag. The dynamic CCD model showed a difference in the spatial distribution of CCD, presenting higher values in the periphery of the region, and lower values in the center during the study period. The improved EKC and coupling analysis detailed in this study may help Chinese decision makers to formulate sustainable measures to balance urbanization development and eco-environment protection.