Regional Cooperation in Marine Plastic Waste Cleanup in the South China Sea Region

Round 1

Reviewer 1 Report

This paper deals with a concern of great and growing importance and focuses on an area (the South China Sea Region) that is critical from the point of view of addressing the problem. It makes use of a rigorous simulation to reach the conclusion that "regional cooperation of the cleanup system is feasible." For the most part, the presentation is straightforward.

This is a striking conclusion, especially given the fact that most observers see the South China Sea as a sea of conflict in which political tensions tend to preclude most forms of international cooperation. That makes the paper's conclusion all the more striking. BUT it also imposes a burden on the authors to explain the basis for their optimistic conclusion. My most important comment, then, is that there is a need in a revised version of the paper to explain this seeming paradox, even while retaining the rigor of the simulation.

I am not competent to critique the simulation model in any detail. However, I was struck by the facts that the authors have chosen to model the cleanup system as a noncooperative game and to focus on bilateral or pairwise cooperation. I can see that this makes the simulation model more tractable mathematically. But I think it also makes the model rather unrealistic. At the same time, my guess is that using more realistic assumptions would not lead to conclusions that are more pessimistic.

One solution would be to retain the current simulation model as the analytic heart of the paper but then to add a discussion of the likely consequences of adjusting the assumptions to make the model more realistic. This would not require building an alternative model. A discussion of such changes would be sufficient.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The paper aims at designing a cooperation model on investigating the “cleanup system” from the Ocean Cleanup initiative to reduce marine plastic pollution.

Here are several comments:

L31-38:

• To highlight the gravity of the investigated environmental problem, you should add in the Introduction section references to the projections of the increase of plastic pollution in the ocean.
• The problem of plastic pollution is complex and transboundary, and indeed, the existing global legal framework is unfit to tackle it. However, there are several initiatives (apart from what you included - International Convention for the Prevention of Pollution from Ships) that are worth mentioning (e.g., the resolution of the third session of the United Nations Environmental Assembly on Marine Litter and Microplastics, December 2017).

L 169-172 “In this article, whether there is a plastic waste trade relationship between any two countries is determined by whether the plastic waste trade volume between the two countries is high enough to effectively implement recycling processes after the waste cleanup.”  What is this level? Is the level different between countries? Does it depend on countries’ financial expectations from the recycling activity? Does it depend on the technology used?

L 176 “this article includes the re-export and re-import of the export and import data.” Please explain what re-export and re-import refer to in your study. 

L 178: Use “” for i and -i (countries).

Related to H1: It is true, that is easier to arrive at an agreement more easily within bilateral agreement/cooperation. However, are there concrete premises for promoting a spillover from cooperation at the bilateral level to the multilateral arena? You just mentioned, “…foundation for future multilateral cooperations” (line 227). In essence, success lies in a large number of states that are committed to solving the problem, given its transnational character.

The structure of the paper needs to be improved. You must include Materials & Methods and Results sections. The whole sections “3. The Game Model of Marine Plastic Waste Cleanup Cooperation” and “4. Game Simulation” must be reorganized. Right now, these two sections are a mixture of methods, results, and discussions.

The Discussion section must explain clearly how the results answer the three questions: “(i) What factors influence the regional cooperation on marine plastic cleanup? (ii) How do these factors influence such regional cooperation? (iii) How can policy be formulated to promote this regional cooperation?”

L 183-185: Pls. rephrase, it does not read well.

Miscellaneous: replace all over the text the word “article” with “study”/ “paper”/ “contribution”; Replace “we” with impersonal forms.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

1)  I have previously asked you to delimitate the Materials & Methods section from the other sections. Your answer for Comment 6 is " Section 3 now only includes Materials & Methods". However, there is no Materials & Methods named section in your paper. Therefore, please include the corresponding name of the section.

2) Sub-section "5.2. Discussion" should come before "5.1. Conclusion"

Author Response

Please see the attachment

Author Response File: Author Response.pdf