Spatial Assessment of Ecotourism Development Suitability Incorporating Carrying Capacity in the Yellow River Estuary National Park

Comments 1: The abstract is too similar to an introduction or summary. An abstract should focus on the research objective, the gap it fills, the methodology, and the type of data used.

Response 1: Thank the reviewer for pointing this out. We agree with this comment. Therefore, we have thoroughly revised the abstract to concisely highlight the research gap, methodology, data sources, and key findings, removing redundant background descriptions (line 16-32). We believed the revised abstract now aligned with journal standards and more effectively communicated the study’s novelty and rigor. The modifications can be found at abstract.

Comments 2: The introduction is weak because the authors mention many irrelevant details, such as "Quantitative assessment methodologies," which are not relevant to this section. I suggest the authors focus solely on the topic. Furthermore, it would be beneficial to add a paragraph at the end of the introduction outlining the paper's structure. This will help readers understand the paper's focus.

Response 2: Agree and thank the reviewer for this constructive suggestion. We have revised the introduction to remove the irrelevant methodological details and sharpen its focus on the research gap and objectives (third and fourth paragraph in Introduction section). Furthermore, as recommended, we have added a concluding paragraph to outline the paper's structure (last paragraph in Introduction, line 125-131). We believe this would provide a clearer and more professional roadmap for the reader.

Comments 3: Please describe the materials and methods used in the paper clearly. Additionally, specify the duration of the data collection period. Please also ensure that all references are carefully reviewed and cited, as some are currently missing.

Response 3:

We thank the reviewer for these critical observations. We agree. Details regarding normalization, the methodological workflow for calculating weights of marine and terrestrial indicators, weight sensitivity analysis, and Weighted Linear Combination (WLC) have been clearly and thoroughly described in the Methods section (line 221-258) to enhance the transparency of the paper's methodology. Moreover, we have added the threshold and classification methods for each indicator's specific grading standards (Appendix A, Table A2). Also, we have explicitly stated the temporal scope of our data (section 2.2., line 158), the specific year for each dataset was listed in Table A1. We have carefully reviewed and revised the references in the paper, and all references have been properly cited.

Comments 4: Figures 4 and 5 are not precise. Please improve their clarity, ensure the text is legible, and redraw them carefully in high resolution.

Response 4: We thank the reviewer for this suggestion. All figures, including Figures 4 and 5, have been redrawn in higher resolution to significantly improve clarity, precision, and text legibility. We hope the improved figures could effectively communicate the spatial evaluation results.

Comments 5: I have noted the use of "e.g.," in sentences like this one: "e.g., boardwalks obstructing flow and reducing sedimentation rates." However, its purpose is unclear here. Please either remove it or explain what the example is referring to, "e.g.," ? Thank you.

Response 5: Thank the reviewer for point this out. We have removed all the “e.g.,”s in the paper to make the expression clearer.

Comments 6: I suggest the author use subsections within the discussion part. The current discussion is unclear, making it difficult to distinguish the main points from supporting arguments. Please modify this section carefully to improve its clarity and organization.

Response 6: We sincerely thank the reviewer for this crucial suggestion. We agree that the previous structure of the Discussion section was unclear. We have thoroughly reorganized the Discussion section (page 15-18) by introducing four clearly defined subsections: 4.1. Core Findings and Significance of the assessment; 4.2. The Land-Sea Coordination Mechanism in Ecotourism Development; 4.3. Comparison with Previous Studies and innovations; 4.4. Management Implications and Study Limitations. Besides, we have also carefully revised key sections of the Discussion, ​​including but not limited to​​ limitations, management implications, and validation of results (section 4.1 and 4.4).

We believed this could enhance the clarity and readability of the Discussion. It now distinguished the main points and guided the reader through our work in a structured manner.

Comments 7: The Conclusions section should be revised and rewritten. It does not clearly highlight the main findings of the authors' work. The conclusions should present the novel contributions and innovations of this specific study.

Response 7: Agree and thank the reviewer for this essential feedback. We have rewritten the Conclusions section to address this concern. The revised version now explicitly stated the novel contributions and innovations of our work (Conclusion section, line 606-615). ​We believe the revised Conclusion demonstrates enhanced comprehensiveness compared to the original version.​​

Comments 8: I think the author should add a separate section on future research directions after the Conclusions. This would be beneficial for readers and could guide the authors' future studies. Thank you.

Response 8: We thank the reviewer for this suggestion. We have rewritten and reconstructed the Conclusion section by separating a new paragraph that focus on future research directions (last paragraph in Conclusion section, line 616-629). We believed this structural change could improve the manuscript by clearly distinguishing the conclusive summary from the prospective outlook.

Comments 1: In Figure 2 the variables previously listed between lines 176-178, are not obvious included in the flowchart construction. So, it is unclear whether ecosystem criticality could be identified with biodiversity conservation significance, or the later is the expression of ecological protection goals.

Response 1: We thank the reviewer for point this out. We agree with this comment. The terminology used in lines 176–178 (prior) lacked rigor and precision, as the Biodiversity Conservation Significance system layer incorporated an Ecosystem Significance indicator. This may cause conceptual misunderstandings in the original context. Therefore, we have revised the original expression, replacing “ecosystem criticality” by “biodiversity conservation significance” to ensure the clarity of the expression. The revision can be found in line174-176.

Comments 2: For Table 1 construction there were not explained:

1. Which was the method to determine the weights for each index. Reading further on, 2 pages later, there were presented explanations. It would be appropriate to include the explanations first, and afterwards to present the results of calculations.

2. Which is the difference between terrestrial and marine weights.

3. For tourism capacity how can be measured the marine weight, as long as they are available on soil, i.e. terrestrial? Moreover, in this particular case, the terrestrial weight has the same value with the marine weight.

Response 2: We thank the reviewer for this essential feedback.

1. We agreed that the weights determination method should be explained at the model construction section. We moved the content to 2.3.2. Construction of Evaluation Index System and added an explanation and features of the AHP method (line 213-217). The detailed process of deriving separate marine and terrestrial weights was also explained (line 234-246). We hope this modification would improve the clarity and readability of the manuscript.

2. Due to the differences in marine and terrestrial indicators, the weights for marine and terrestrial indicators were calculated separately. However, these indicators belong to the same subsystem layer. Thus, the weighting process followed a sequential approach: subsystem weights were first determined, followed by separate calculations for marine and terrestrial indicator weights. The detailed process of deriving separate marine and terrestrial weights was described (line 236-245). This method accounted for land-sea differences while maintaining the standardization, allowing the subsequent integrated overlay calculations.

3. Tourism resources capacity was determined by both tourism facilities and resources, which existed not only on land but also in coastal areas. Within the YRENP, coastlines and nearshore zones contained tourism infrastructure and attractions, thus allowing marine indicators weights to be quantified. For this particular case, all three indicators in the Tourism Resources subsystem applied to both marine and terrestrial areas, hence they shared the same weights (line 239-240).

Comments 3: The manuscript fail to include the limits for the research. Some elements were described as shortcomings.

Response 3: We thank the reviewer for raising this important point. We agree that the study's limitations are crucial for an academic paper. In our original manuscript, we had addressed some limitation points in the final paragraph of the Discussion section. However, we acknowledged that this section could be more prominently. Therefore, we have rewritten the paragraph and elevated the limitation discussion into a dedicated subsection within the Discussion, titled “4.4. Management Implications and Study Limitations” (line 565-579). We believed this revision provides a much clearer assessment of the study's boundaries. Thank you for suggesting this valuable improvement.

Comments 1: Clarify the EECC–EDS relationship (conceptual consistency).

You describe EECC as both a foundation for and a component within EDS. Please fix one logic and stick to it throughout (e.g., sequential: EECC first, then integrate as a required constraint in EDS). Update Figure 2 and the Results/Discussion accordingly.

Response 1: We are grateful to the reviewer for this insightful comment. We agree that the relationship between EECC and EDS needed to be presented with greater conceptual consistency. We have thoroughly revised the manuscript to follow the logic that the EECC serve as an integral dimension within the comprehensive EDS assessment. We have rewritten the Theoretical Framework (2.3.1) section to state the logical concept more clearly (line 179-187). The Figure 2 was also updated to visually represent the EECC is one of the dimensions of the integrated EDS assessment. Also, we have carefully revised the text in Discussion section to ensure the conceptual consistency (line 517-519, 530-531). We believe these revisions have resolved the conceptual inconsistency and now present a much clearer framework.

Comments 2: AHP transparency and reproducibility.

Add the pairwise comparison matrices, expert panel size/fields/selection, CR values for each level, and how marine vs. terrestrial weights were derived.

Provide a weight-sensitivity analysis (e.g., ±10–20% perturbation of key weights) showing how classed EECC/EDS areas change.

Response 2: We thank the reviewer for these critical suggestions to enhance the methodological rigor, transparency, and reproducibility of our AHP process.

AHP Transparency: We have revised the Methods section (2.3.3) to include the details for methodology transparency: the expert panel size and fields were added (line 234-236). The detailed process of deriving separate marine and terrestrial weights was described (line 236-246). We also added a Supplementary Material which include the pairwise comparison matrices and CR values for each level.

Weight-Sensitivity Analysis: we conducted a weight-sensitivity analysis to address this concern. We perturbed (±10%) the weights of the most sensitive indicators (Density of Protected Species and River Network Density) and recalculated the EDS. A summary of these findings has been added to the main text (2.3.3 Methods section, line 247-251), with full detailed results available in Supplementary Material. The analysis confirmed that our conclusions are robust to weighting uncertainties.

We believe these additions have greatly strengthened the reliability of our work.

Comments 3: Thresholding / classification rules.

For each indicator, report threshold sources (standard, analogue region, or Jenks) and the exact break values. Where standards are absent, justify the chosen breaks (e.g., ecological reasoning or distribution diagnostics).

Response 3: We thank the reviewer for these critical suggestions. We have added the grading criteria (including exact break values) and threshold sources for each index that are shown in Table A2 in Appendix A. We hope this could make the research process more transparent.

Comments 4: Temporal and seasonal variability.

Suitability and carrying capacity in deltas are strongly seasonal (migratory birds, vegetation, visitation). At minimum:

Add a seasonal sensitivity appendix with NDVI and THI for a dry vs. wet/peak-bird month, and discuss how EDS tiers shift.

Clarify data years (Table A1) and reconcile mixed vintages (2019–2022) with your 2010–2020 narrative.

Response 4: We thank the reviewer for this crucial observation regarding the role of seasonal variability. We acknowledge that this represents a limitation of the current study, and we appreciate the opportunity to clarify our approach and outline future steps.

Addressing Seasonal Variability: We fully agree with the reviewer that incorporating seasonal dynamics (e.g., migratory bird presence, vegetation phenology, visitor fluxes) is vital for a robust assessment. The reviewer's suggestion for a comparative analysis of dry vs. wet/peak-bird months is valuable. While conducting a full seasonal sensitivity analysis with new data is beyond the scope of this current manuscript, we have discussed the current limitation in discussion section (line 568-571) and the future research directions regarding seasonal variability in conclusion section (line 618-621). We stated that our model presents a static representation based on annualized data, and we highlighted how key factors like NDVI and THI likely vary seasonally, which would cause shifts in EDS tiers.

Temporal Scope of Data: we have specified the temporal scope of our data in section 2.2., line 167. It is also cleared stated in the Table A1. We have carefully reviewed the entire manuscript to ensure consistency in the expression of the data years. We apologize for any confusion that may have arisen from our phrasing and have further revised the text to ensure absolute clarity on this point.

We have addressed the reviewer's concern by acknowledging this limitation, prioritizing seasonal analysis in future work, and clarifying the data timeline, thereby strengthening the manuscript.

Comments 5: Validation / ground-truthing.

Move beyond model-only results:

Compare high-EDS cells with observed tourism proxies (POI density changes, ticketing/visitation if available) or hotspot analysis.

For biodiversity constraints, overlay protected-species observations (from the Plan or monitoring) and report a hit-rate or confusion matrix for “low EDS” zones.

If field data are unavailable, state this and propose a monitoring plan.

Response 5: We thank the reviewer for the important suggestion to validate our model results against observed data. We have taken this advice seriously and have now incorporated a qualitative validation discussion into the manuscript. Specifically, we have revised the 4.1. Core Findings and Significance of the Assessment section (paragraph 2, line 442-451). We explicitly compared our modeling results with independent ground observations in terms of tourism facilities and protected species. This revision directly grounded our model findings in empirical observations, enhancing the study's credibility.

Comments 6: Scale, units, and processing details.

Specify the spatial resolution of all rasters, CRS, and fishnet/grid size; justify the DEM-catchment threshold (300 km²) and accessibility speeds (30 km/h).

Normalize units before WLC and state the standardization formula used for benefit/cost indicators.

Response 6: Thank the reviewer for this detailed suggestion, which is very helpful for the rigor of the paper.

We specified the spatial resolution of all raster, CRS, and grid size in subsection 2.3.3, line 222-225.

The selection of the 300 km² catchment threshold was based on the geographical features of the Yellow River Delta and the macroscopic focus of our study. This well-watered region has a very dense channel network. Through a trial-and-error comparison of results generated by different catchment thresholds, 300 km² was determined to be the most appropriate for effectively delineating and highlighting the river network density. This was annotated in Table 2.

​The reason for selecting a speed of 30 km/h to calculate transportation accessibility is that, according to the Master Plan of the Yellow River Estuary National Park, the speed limit on roads within the park is set at 30 km/h. Furthermore, this speed could reflect the actual traffic conditions within the protected area.​​

The reviewer’s suggestion regarding data normalization prior to the Weighted Linear Combination (WLC) is highly important. In our study, we have already performed normalization of the indicators by dividing each indicator into five tiers and assigning scores ranging from 1 to 5. This process ensures that all indicators are uniformly transformed into a numerical scale of [1, 5], standardizing units to ensure comparable WLC calculations. This process was mentioned in section 2.3.3 on line 226-227 and 252-254 to enhance the transparency of the methodology.

We hope these revisions could significantly enhance the technical rigor and clarity of our study.

Comments 7: Marine–terrestrial indicators and directions of effect.

Provide ecological justification for each indicator’s sign (e.g., coastal erosion sensitivity lowers EDS) and note exceptions (e.g., artificial shoreline: high accessibility but potentially low ecological suitability). Consider an interaction term (e.g., Erosion Sensitivity × Tourism Facility Capacity) via a simple scenario test.

Response 7: We thank the reviewer for this valuable suggestion. We have added the directions of indicators in Table 1, which provide a concise justification for the expected positive or negative impact of each indicator.

We agree that understanding the non-linear relationships and potential conflicts (e.g., between high tourism capacity and high erosion sensitivity) is a crucial next step for advancing spatial assessment models. Therefore, we have integrated a discussion of this specific content into the Future Research Directions (last paragraph in Conclusion section, line 621-629). We emphasized the need to move towards a more dynamic framework that employs interaction terms and spatial conflict analysis, as suggested, to better quantify management trade-offs.

Comments 8: From maps to zoning guidance.

Translate maps into actionable zoning: identify named sub-areas recommended for (i) core protection, (ii) buffer/education, (iii) moderate ecotourism, with indicative use envelopes (e.g., boardwalks only; no permanent structures; seasonal access). A small table mapping EECC×EDS combinations → management rules would be helpful.

Response 8: We thank the reviewer for this excellent suggestion to enhance the practical applicability of our research. We agree that translating spatial modeling results into actionable management guidance is a crucial step. We have addressed the comment by expanding the discussion on how our findings directly inform zoning decisions. In the Discussion section (section 4.4, line 544-557), we added: How the cross-tabulation of EECC and EDS levels can be used by park managers to derive management rules for different zones. And specific examples of management actions (e.g., "core protection", "buffer and educational functions") that are appropriate for different combinations of capacity and suitability. This discussion offered a science-based framework for precise zoning guidelines, making management implications concrete and actionable.

Comments 9: Uncertainty and robustness.

Discuss uncertainties from weighting, data quality (e.g., VIIRS lights), and interpolation (e.g., kriging of N:P). Include a short robustness check (alternative accessibility speed, alternative AL/AM normalizations such as per-area or per-worker).

Response 9: We thank the reviewer for this critical suggestion to enhance the methodological rigor of our study. We agree and explicitly discuss the potential uncertainties arising from our key methodological choices in the last paragraph of Discussion section (line 571-579), including: the subjectivity of the AHP process, the limitations of using VIIRS nighttime light data, and the estimation errors associated with the spatial interpolation (Kriging) of N:P ratios. We also added a short robustness check for land transportation accessibility determination (section 3.1.3, line 300-303). This could demonstrate that the results were not overly sensitive to reasonable variations in this indicator and adds confidence to the model's robustness. We hope the revisions could strengthen the paper by transparently addressing uncertainties and demonstrating the stability of our conclusions.

Comments 10: Language and figures.

Light copy-edit (e.g., “interprets,” not “interpretates”; “unclear” not “uncleared”).

Ensure all figures have legible legends/scales, north arrows, and consistent class colors across comparable maps.

Harmonize equation notation (a, b, c, c′) and ensure all referenced figures/tables appear once and in order.

Response 10: We sincerely thank the reviewer for these valuable technical suggestions. We agree and conducted a thorough and careful review of the entire manuscript. We have corrected all typographical and grammatical errors identified, including the specific examples mentioned (e.g., “interprets” replaced “interpretates”; “unclear” replaced “uncleared”) in line 42 and 49. We have redrawn all the figures in higher resolution to improve clarity, precision, and text legibility. Each now includes a clear legend, a scale bar, and a north arrow. We also have standardized the color schemes across all comparable maps (ArcGIS figures) to ensure visual comparison between different figures. Also, we have harmonized the notation used in all equations throughout the manuscript. All figures and tables are cited in the correct numerical order within the text and appear only once.