Temporal heterogeneity of the coupling
From 2011 to 2020, the coupling coordination degree of digital economy and ecological efficiency showed some fluctuations, but it was almost a straight upward trend, and the overall situation was floating around 0.55 in China (Fig. 2). The interaction manifests itself as the evolution from a transitional state on the verge of dissonance to a coordinated development. And finally entered a collaborative state in 2019. In terms of cities, Guangzhou, Hangzhou, and Xiamen have the best coupling, with average values of 0.75, 0.74, and 0.73, respectively. Zhengzhou, Xiamen, Pingliang and other cities showed a faster growth rate, higher than 55%. This shows that under the Belt and Road strategy, international cooperation in digital technology has been carried out, the construction of digital infrastructure along the route has been accelerated, and cooperation in the field of digital interconnection has continued to deepen. As a result, the digital transformation of the industry has been promoted, and the digital economy and ecological efficiency of these cities have strengthened the penetration and interaction. During the study period, the number of cities in dysregulation decreased from 21 to 2; the number of cities in synergy increased from 1 to 156; the number of cities in the transition period decreased from 205 to 9, showing a significant decrease; the number of cities in the adaptation period increased from 48 to 108, and the synergy has emerged. As far as the difference among cities is concerned, the absolute difference shows a fluctuating upward trend, while the relative difference fluctuates steadily around 0.10. This reflects that the differences in the development of digital economy and ecological efficiency among cities continue to widen, resulting in significant temporal heterogeneity in the interaction between the two systems. This also shows that although the coupling between the digital economy and ecological efficiency of prefecture-level cities in China is increasing, there is still a lot of room for improvement.
From the perspective of geographical location, the coupling of digital economy and ecological efficiency in eastern, central and western cities of China has shown an upward trend from 2010 to 2020. Both the absolute difference and the relative difference are relatively stable, floating around 0.04. Relatively speaking, the coupling in the east continues to occupy a significant advantage, with an average value of 0.57, and has entered the ranks of coordinated development after 2018. The cities in the central region increased from 0.45 in the early stage to 0.60 in the late stage. Although they gradually evolved from a transitional state to a synergistic edge, their growth rate was the lowest in the early stage, only 32.85%. The coupling fluctuations in the western region are the most frequent, but the late stage also shows coordinated development, and the growth rate in the late stage is the highest compared with the initial stage, reaching 37.05%. This shows that with the in-depth development of policies such as the rise of the central region, the development of the western region, and the Belt and Road Initiative, the development of the center and west has gradually been influenced and helped by the eastern region. The coupling of digital economy and ecological efficiency in the three major regions of China has risen relatively synchronously, but the stable and coordinated development of each region has not yet been achieved.
In terms of resource types, during the study period, the coupling of digital economy and ecological efficiency in non-resource-based cities has an advantage, and it is always better than resource-based cities, with an average value of 0.56. Non-resource-based cities entered a state of coordinated development in 2018, while resource-based cities entered into synergy at the end. In addition, the difference between the two types of cities is relatively small and stable, with the absolute difference floating around 0.03. It can be seen that non-resource-based cities lack traditional energy and are more inclined to seek new driving forces for digital development. The rapid development of the digital economy and the improvement of ecological efficiency are more easily reflected, resulting in more active interaction between the two than resource-based cities.
Spatial heterogeneity of the coupling
From 2011 to 2020, the coupling of digital economy and ecological efficiency showed a clear spatial jump and linkage pattern. Fig. 3 shows that in the early stage, the coupling of most cities in China was dominated by transitional level, and the interaction between the two was on the verge of dysregulation. In detail, only Shenzhen was the first to step into the collaboration. Moreover, there are few cities where the coupling is in the adaptation period or barely coordinated, and the distribution is more fragmented. Cities at this coupling level are mostly on the east coast. Cities in the transition period are mostly distributed in clusters, and cities in dysregulation are mostly scattered in the central and western regions. The coupling in the east is obviously better than that in the center and the west. It can be seen that the spatial heterogeneity of coupling is obvious, and the development of the digital economy as a whole is not synchronized with the ecological efficiency. In the later stage, the coupling of digital economy and ecological efficiency in most cities has entered a coordinated level, and the number of cities at the coordinated level has increased significantly. In detail, cities in synergy are mostly distributed in bands, cities in adaptation are distributed in sheets, and cities in transition are distributed in points. Additionally, the diffusion path generally shows the characteristics of spreading from the developed areas in the east to the underdeveloped areas in the central and western regions, which reflects the driving effect of the east to a certain extent. Therefore, there is a certain spatial heterogeneity in the coupling between the digital economy and ecological efficiency during the study period. The significant coupling gap caused by the unequal development opportunities among regions still needs to be further filled, and the benign resonance pattern of the two systems needs to be further promoted.
Influencing factors
Model building
Based on all-round selection of influencing factors, we verified the heterogeneity of the effects of these factors on coupling. Specifically, the equation between the coupling of digital economy and ecological efficiency and its influencing factors is expressed as follows:
Table 2 Regression results of the factors influencing the coupling
|
Geographical location
|
Resource-based city or not
|
Overall
|
East
|
Centre
|
West
|
Yes
|
No
|
CXT
|
0.0294***
|
0.0342***
|
0.0164*
|
0.0433***
|
0.0241***
|
0.0350***
|
(-6.2002)
|
(4.2797)
|
(2.2851)
|
(4.3934)
|
(3.3382)
|
(5.4511)
|
JSC
|
0.0001
|
-0.000262
|
0.000375
|
0.000249
|
0.000468
|
-0.0000783
|
(0.2437)
|
(-0.3309)
|
(0.5139)
|
(0.2282)
|
(0.6372)
|
(-0.1204)
|
HJG
|
-0.0389***
|
-0.0652***
|
-0.0155
|
-0.00315
|
-0.0542***
|
-0.0174
|
(-4.2059)
|
(-4.3473)
|
(-1.0942)
|
(-0.1525)
|
(-3.8916)
|
(-1.4016)
|
GJH
|
0.0887***
|
0.0932***
|
0.112***
|
0.0784***
|
0.0988***
|
0.0753***
|
(14.7801)
|
(8.0245)
|
(12.2764)
|
(6.8871)
|
(12.4524)
|
(8.4153)
|
ZFL
|
0.419***
|
0.404***
|
0.349***
|
0.397***
|
0.393***
|
0.444***
|
(23.1616)
|
(9.2101)
|
(14.1768)
|
(10.8072)
|
(16.0560)
|
(16.4902)
|
JFZ
|
0.109***
|
0.126***
|
0.0757***
|
0.139***
|
0.0824***
|
0.131***
|
(29.6606)
|
(19.8140)
|
(13.6906)
|
(17.8252)
|
(15.5143)
|
(25.5706)
|
KJP
|
0.0026**
|
0.0076***
|
0.0012
|
0.0008
|
0.0016
|
0.0022*
|
(3.1475)
|
(3.5213)
|
(1.1544)
|
(0.5509)
|
(0.4029)
|
(2.4933)
|
R-squared
|
0.6390
|
0.6478
|
0.6380
|
0.6903
|
0.6093
|
0.6674
|
Obs
|
2750
|
1090
|
1070
|
590
|
1110
|
1640
|
Note: “ *, **, *** ” indicate the statistical significance level of 10%, 5% and 1% respectively.
Regression results
Using the above model, the study explores the heterogeneous effects of factors on the coupling between digital economy and ecological efficiency in China. The specific analysis is as follows.
Industrial collaboration. The overall regression coefficient of industrial collaboration on the coupling of digital economy and ecological efficiency is positive, and the P value is less than 0.01, which is significant at the 1% significance level. This shows that while the collaboration of producer services and manufacturing is enhanced with the help of the digital technology, it simultaneously promotes ecological efficiency. The synergy between industries permeates the interaction, which contributes to the synergy of the two systems. From the perspective of geographical location, although industrial synergistic agglomeration has an economic effect on the east, centre and west, it has the strongest positive effect on the west and the weakest in the centre. The reason is that the west is relatively backward, the dividends of the digital economy are relatively more significant, and the cleaning function of the producer service industry for the manufacturing industry has been significantly improved, resulting in a relatively prominent positive effect on coupling. While the central cities are actively accepting the transfer of traditional industries in the east, the role of industrial synergy has not been fully reflected. In terms of resource types, both resource-based cities and non-resource-based cities are significant at the 1% significance level, but the coefficients of non-resource-based cities are higher. It can be seen that without the constraints of resources, the industrial synergistic agglomeration of such cities has more advantages, so it is more conducive to coupling.
Technological innovation. The overall regression coefficient of technological innovation on coupling is positive, but the effect is not significant. As an indispensable factor affecting coupling, technological innovation has not effectively promoted the synchronous improvement. Innovation can accelerate the development of the digital economy through technological improvement. The growths of digital economy help to quickly transform science and technology into the production process, promote the improvement of resource utilization, and reduce pollutant emissions in the production process. Therefore, this factor should promote the simultaneous development of the digital economy and ecological efficiency. The reason is that digital economy is mainly on the basis of extensional expansion, and the effect of "learning by doing" is not obvious. The breakthrough process of the innovation possibility boundary is relatively slow, and the large-scale expansion of digital capital has not only failed to realize the effective replacement of factor innovation and energy demand, but has also solidified the existing energy consumption pattern and aggravated the energy rebound effect. Therefore, there is an urgent need to bridge the digital divide and technological deficiencies. This also reflects that green technology research and the development of the digital economy have not fully matched in China, and key technologies and green innovation are seriously lacking.
Environmental regulation. The overall regression coefficient of environmental regulation on coupling is negative, the P value is less than 0.01, it is significant at the 1% significance level, and there is a relatively obvious inhibitory effect. Furthermore, it also has a negative effect on the eastern and resource-based cities with developed industries and large energy consumption. This may be due to the fact that environmental regulations often cannot be adjusted in time with market changes. In the context of the digital economy, specific regulatory measures need to be further analyzed in detail, and the strength of regulation and spatial spillover effects must be accurately grasped. In addition, due to various constraints such as budget and investment use, the government may have certain limitations in the process of intervening in environmental governance. It can be seen that only appropriate environmental regulation policies can actually help companies or have obvious incentives, and can promote the benign interaction of economy and the ecosystem.
Industrial upgrading. The overall regression coefficient of industrial upgrading on the coupling of digital economy and ecological efficiency is positive, and the P value is less than 0.01, which is significant at the 1% significance level. This reflects that new business formats derived from digital technologies. For example, 5G, cloud computing and other digital technology accelerate the transformation of traditional manufacturing into mid-to-high-end industries, thereby contributing to the industrial upgrading. The dividends brought by industrial upgrading have improved the ecological quality while benefiting economic growth. For the geographical location, the implementation of policies such as the rise of central China has continuously improved the market environment, expanded the positive external effects of the digital economy, and created more room for ecological quality improvement. The digital industry in the west is relatively scarce, and the development level of the digital economy is far behind that in the east. As a result, the green efficiency improvement effect of the digital economy has not yet been exerted. From the perspective of resource types, in view of the development characteristics of resource-based cities, it is necessary to get rid of resource dependence and realize industrial optimization, so the trend of industrial upgrading is more significant. The positive effect on the coupling of the digital economy and ecological efficiency is also more significant. However, the dividends of industrial digitalization have yet to be tapped.
Government support. The overall regression coefficient of government support on the coupling is positive. In addition, the P value is less than 0.01, which is significant at the 1% significance level. Compared with other influencing factors, this factor has the most significant positive effect on coupling. This directly reflects the crucial role of the government's macro-control to ensure the high-quality development of China's economy. From the perspective of geographical location, the government in the east has relatively strong regulation and control, and the financial support is relatively good. This has led to the region being able to better enjoy the dividends of the digital economy, forming a stronger ecological advantage and promoting efficient interaction between systems. For non-resource-based cities, the government supports a diversified economy and the ecological pressure is relatively small. Therefore, the positive effect of government support on the coupling is more significant than that of resource-based cities.
Economic foundation. The overall regression coefficient of economic basis for coupling is positive, with the P-value less than 0.01, significant at the 1% significance level. Regardless of geographic location and resource type, it passed the significance test. Specifically, the coefficient in the west is the highest, which shows that for relatively backward regions to a certain extent, the technological progress brought by the new economic form of the digital economy has a stronger enabling effect. Consequently, this situation is more favorable for the This situation is more favorable for of green total factor productivity. The digital economy in the east has developed earlier and has a higher level, which has enabled the release of the digital economy dividends to be more sufficient, and can make better use of the development of the digital economy to transform the traditional high-polluting production model. The economy of resource-based cities is mostly dominated by the mining and processing industries of natural resources such as coal and oil, and the high-tech industry is still in its initial stage. This makes the adjustment of the industrial structure rigid, coupled with the problems of high resource development intensity and low utilization efficiency, resulting in a more prominent contradiction between economic development and ecology. Therefore, the promotion effect of such cities is relatively limited compared to non-resource-based cities.
Spatial quality. The overall regression coefficient of spatial quality for coupling is positive, with the P-value less than 0.05, significant at the 5% significance level. Compared with other influencing factors, the positive effect is weaker, which indicates that the current driving effect of space quality on the digital economy and ecological efficiency still needs to be improved. The reason is that both ecological protection and digital economy involve a large amount of infrastructure construction, such as solar power stations, high-speed railways, industrial Internet, etc. As a developing country, China's infrastructure construction still needs to be further expanded and improved. From the perspective of geographical location, except for the east, other locations are not significant, which is mainly due to the superior spatial quality of the east, which greatly promotes the synergy of the digital economy and ecological efficiency. From the perspective of resource types, the spatial quality of non-resource-based cities has a significant positive effect on coupling. For the specific reason, compared with resource-based cities, non-resource-based cities are more dominated by the tertiary industry, have superior spatial environment, and have a strong ability to gather talents, capital and other elements, thereby effectively improving the ability of the digital economy to maintain ecosystems.