**5. Conclusions**

The methods of the CCD model, human activity intensity model, and synchronous development model were used in this paper. This paper calculated and analyzed the evolution characteristics of the CCD of the PLEFs and the intensity of human activities in Wanzhou District from 2000 to 2020, as well as the types of their development relations. The following conclusions can be obtained:


**Author Contributions:** The co-authors together contributed to the completion of this article. Specifically, their individual contributions are as follows: conceptualization, T.L., F.Y. and Y.L.; software, M.F., X.H. and F.Y.; methodology, T.L., X.H. and M.F.; validation, T.L., Y.L. and M.F.; formal analysis, T.L. and X.H.; resources, T.L.; data curation, X.H. and M.F.; writing—original draft preparation, T.L., X.H. and M.F.; writing—review and editing, T.L., F.Y. and Y.L.; visualization, T.L. and F.Y.; supervision, T.L., Z.Z., C.W. and X.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Key Program of the National Social Science Foundation of China (Grant No. 20&ZD095), the National Social Science Foundation of China (Grant No. 21BJY223), the 2020 General Project of Water Transport Economics Research Center, Key Research Base of Humanities and Social Sciences of Colleges and Universities of Sichuan Province (Grant No. SYJJ2020C02), the National Social Science Youth Foundation of China (Grant No. 21CJY044), the National Social Science Youth Foundation of China (Grant No. 18CJL031), the Science and Technology Research project of Chongqing Education Commission (Grant No. KJQN202102103), the Humanities and Social Sciences Research Project of Chongqing Education Commission (Grant No. 21SKGH308), and the Chongqing Social Science Planning Social Organization Project (Grant No. 2021SZ26).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the author.

**Conflicts of Interest:** The authors declare no conflict of interest.

### **References**

