**5. Discussion**

This paper first discusses the spatio-temporal evolution patterns of carbon emissions and land economic efficiency to form a basic understanding of the research content and preliminary conclusions. On this basis, this study further verifies and supplements the preliminary conclusions quantitatively by means of econometric models. By combining qualitative and quantitative methods, this study aims to conduct a more detailed study of the problem and draw more convincing conclusions. In addition, this study enriches the findings with the specificity of the entropy method of weight assignment. In this section, the findings of the study are analyzed and discussed in detail.

#### *5.1. Discussions of Spatio-Temporal Evolution*

### 5.1.1. Carbon Emissions

From spatial distribution patterns, the overall carbon emissions of coastal cities in eastern China are higher. In 2011, among the 84 prefecture cities in eastern China, there were 20 "low-emission" areas, 46 "medium-emission" areas and 18 "high-emission" areas. In 2014, the figures were 21, 43 and 20, respectively, and in 2017 they were 18, 46 and 20, respectively. It can be seen that the three categories of high-, medium- and low-emission regions do not obviously change, with "medium-emission" regions accounting for more than half of the overall distribution and the remaining two categories accounting for about a quarter each. When categorized by province and municipality, we can see that Beijing (12th), Shanghai (10th), Tianjin (23rd) and Hebei Province (13th) have higher carbon emissions, while Zhejiang Province (4th), Shandong Province and Jiangsu Province (2nd) have medium emissions, and Guangdong Province (1st) and Fujian Province (7th) have lower emissions, where the national ranking of the regional GDP is shown in brackets. It can be found that there is no strong positive correlation between carbon emissions and GDP. However, it cannot be denied that, with the exception of the special case of Guangdong Province, the rest of the regions that are economically developed are generally not low in carbon emissions. Among them, Beijing, Tianjin and Shanghai, which are the only municipalities directly under the central government, are ranked highly and therefore do not affect this conclusion.

From temporal trends, 77 regions, accounting for 91.67%, had unchanged carbon emission levels in 2011, 2014 and 2017, while only seven regions had changed their carbon emission levels. Of the seven regions that changed, only Beijing saw a decrease in carbon emissions. The decline in Beijing's carbon emissions is due to the relocation of a large number of factories from Beijing to Hebei Province in recent years. At the same time, in 2017, Beijing launched a "coal-to-gas" strategy, using natural gas, a clean energy source, to replace coal as the main source of energy for winter heating. The analysis in this paragraph shows that the distribution of carbon emissions in eastern China has not changed obviously over time.

#### 5.1.2. Land Economic Efficiency

From spatial distribution patterns, the land economic efficiency (Land\_EcoE) of coastal cities in eastern China is significantly higher than that of other regions, but there is no significant difference between the north and the south. In 2011, among 84 municipal areas in eastern China, there were 18 "high-efficiency" areas, 57 "medium-efficiency" areas and 9 "low-efficiency" areas. Similarly, in 2014, the number was 17, 57 and 10, respectively. In 2017, it was 16, 62 and 6, respectively. It can be observed that the number of "high-efficiency" areas is slowly decreasing, the number of "medium-efficiency" areas is significantly increasing and that of "low-efficiency" areas is decreasing. Overall, the number of medium-Land\_EcoE areas is higher, about 70%, and the number of "highefficiency" areas is also significantly higher than that of "low-efficiency" areas, which is in line with the expectation of this study when selecting the more economically developed region of eastern China as the research target.

From temporal evolution trends, 66 regions, or 78.57% of the total, had a constant Land\_EcoE level over the three time points 2011, 2014 and 2017. There were 18 regions where the level of efficiency changed, of which seven regions saw a decrease and 11 regions saw an increase. In addition, in 2017, for example, 12 of these 18 regions became "medium-efficiency" areas, while only two regions were downgraded. This indicates that the distribution of Land\_EcoE in eastern China has gradually converged over time (becoming a "medium-efficiency" region) as Land\_EcoE indicators in this study are relative indicators. This is in line with China's development strategy of "common prosperity", whereby some regions ge<sup>t</sup> rich first and then help others to ge<sup>t</sup> richer, thus achieving common prosperity.

#### *5.2. Discussion of the Empirical Results*

The aim of this study is to investigate whether the current economically developed regions of China can achieve synergistic environmental and economic development. Considering the current low land use efficiency in China [67], the purpose of the study is analyzing the correlation between land economic efficiency and environmental pollution (carbon emissions). Therefore, this study establishes the first hypothesis: there is a positive correlation between the increase in land economic efficiency and the improvement of environmental pollution in eastern China. However, the results of Table 3 show that there is no significant correlation between Land\_EcoE and carbon emissions in eastern China. This may be due to the fact that even in economically developed eastern China, there are still some economically underdeveloped municipal areas. Accordingly, this study sets up a second hypothesis: there is a positive relationship between the increase in land economic efficiency and the improvement of environmental pollution in the most economically developed group of cities in eastern China. The results in Table 3 clearly show that the eastern regions of China, as a whole, still do not show co-development of land economic efficiency and environmental pollution improvement. However, in the most economically developed cities of eastern China, there is an extremely significant negative correlation between Land\_EcoE and carbon emissions (Table 4). This indicates that these economically developed regions have achieved synergistic development in economy–land–environment, indirectly indicating the effectiveness of China's existing economic development plans.

In addition, the evaluation system of land economic efficiency (Table 1) shows that R&D intensity (24.41%) and industrial production intensity (22.62%) contribute the most to the composite indicator of land economic efficiency, while with tertiary industrial production intensity (13.40%) and employment density (12.71%), the total contribution reaches 74.14%. This figure does not reflect their "importance" for land economic efficiency, but rather implies the degree of variation between regions in the other four secondary indicators (GDP growth rate, share of tertiary output, GDP per capita and road density) is relatively low. Therefore, this study argues that there is a need for regions with low land economic efficiency to pay more attention to the economic content of the first four indicators.
