Separate Versus Unified Ecological Networks: Validating a Dual Framework for Biodiversity Conservation in Anthropogenically Disturbed Freshwater–Terrestrial Ecosystems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Lines 34–46 clearly show the worldwide relevance of freshwater ecosystems and the special connectivity difficulties they encounter compared to terrestrial systems thanks to the extensive and well-referenced introduction. Lines 47–59 correctly point out the multi-scale vulnerability of freshwater habitats and the need of hydrological connectivity frameworks. Sometimes oversimplifying their interactions, the introduction follows a dichotomous perspective of terrestrial versus freshwater systems. Lines 39–46, for instance, contrast terrestrial and freshwater fragmentation without noting that many anthropogenic pressures—e.g., urbanization, pollution—also affect both systems and their interfaces. The writers should change line 39 to make clear that although the main processes vary, terrestrial and freshwater drivers of biodiversity loss have significant interaction and overlap.

The authors of lines 92–105 claim that most ecological network (EN) studies ignore hydrological processes and functional disturbances, but they do not sufficiently credit recent developments in integrated landscape approaches or cite recent literature trying to close these gaps. Underrepresenting the advancement in the field could cause bias in this regard. The authors should change lines 92–105 to incorporate more recent integrative studies and moderate the assertion that EN approaches are mainly insufficient for freshwater systems.

Leveraging established models (InVEST, MSPA, MCR, Linkage Mapper) and integrating several data sources (lines 144–154), the methods are thorough and open. Separately building freshwater and terrestrial networks before combining, the dual framework shows a methodological advance. Some methodological decisions, meanwhile, call for more explanation and justification.

First, when aggregating habitat quality indicators, the authors assign fixed weights (inVEST: 0.75, NDVI/NDWI: 0.25) in lines 181–182. Neither a sensitivity analysis to show robustness nor a justification for these particular weights exists. The writers have to defend the weighting system or, better still, do a sensitivity study to demonstrate how results vary depending on weighting.

Second, although applied uniformly, the resistance multipliers for sluices—1.5 for primary, 1.25 for secondary, lines 234–235—have no empirical basis. On line 234 the writers should clarify how these values were calculated—from literature, expert elicitation, or calibration—and address the consequences of these decisions for the outputs of the model.

Third, although the study area is delineated in great detail (lines 126–139), the justification for its choice is not expressed clearly. In line 126 the writers should include a sentence outlining why this area is especially fit for testing the dual EN framework (e.g., high degree of freshwater–terrestrial coupling, anthropogenic disturbance).

Finally, the approaches for corridor validation lack enough clarity. The writers note using citizen-science bird records (lines 415–416), but they do not specify the validation technique or its restrictions. Lines 415–416 should have a more thorough description including discussion of the possible bias resulting from corridor validation using just avian data.

With quantitative comparisons between freshwater and terrestrial networks (lines 271–333), the results are rather neatly presented. One can easily see and understand the spatial patterns and resistance analyses. Still, a few points call for explanation or development.

Although the authors say freshwater corridors are the "backbone" of regional connectivity (line 331), their conclusion is based more on corridor length and resistance values than on actual movement or genetic data. This could overstate the practical importance of modeled corridors. Line 331 should be changed by the writers to admit that the classification of "backbone" is based more on model outputs than on direct ecological validation.

Furthermore highlighted in the results are the significance of agroforestry-complex patches in terrestrial networks (lines 287–290), although their ecological purposes are not quantified statistically. The authors should include a disclaimer in line 290 stating that, although not directly measured in this work, the functional role of these mosaics is dedetermined from literature and model structure.

Emphasizing the need of separate freshwater and terrestrial ENs (lines 338–366), the debate essentially places the research in the larger framework of connectivity science. The writers rightly point out that unified models have limits in mixed environments. Nevertheless, the debate occasionally exaggerates the originality of the dual framework and neglects the limits of the present research or other strategies.

The authors present their hybrid framework as a complete solution in lines 389–401 but do not sufficiently address possible constraints, such the lack of species-specific movement data, the stationary character of resistance surfaces, or the difficulty of merging dynamic land use and hydrological changes. Lines 389–401 should be changed by the writers to clearly state these constraints and propose how next studies might solve them.

Although the section on limits (lines 403–428) is honest and helpful, the section on validation (lines 415–416) is far too short. The authors should go further on the restrictions of relying just on bird data for corridor validation and address how this might distort the evaluation of connectivity for other taxa.

Conclusions: Emphasizing the need of a dual-framework approach for biodiversity preservation in complex environments, the conclusions are usually well supported by the results (lines 430–455). Given the dependence on modeled outputs and limited validation, the authors overstate the empirical robustness of their results, though. The ending in line 451 should be changed to make clear that, although the framework offers a useful tool, its efficacy for directing conservation action depends on more empirical validation and refinement, particularly for non-avian taxa.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article emphasizes the importance of implementing a hydrological connectivity model that emphasizes the anthropogenic impact on aquatic habitats. It emphasizes that the reallocation of land-use permits in urbanized areas and the investment in restoring aquatic corridors will have a beneficial effect on the revitalization of degraded ecosystems. Finally, it highlights the importance of educating both local and government communities to raise awareness of the importance of ecological connectivity.

Although field validation is currently necessary, it sheds light on the dynamics of ecosystems facing the challenge of their conservation through the use of innovative tools.

There is a good balance in the weight applied to each topic developed: biodiversity conservation, connectivity, conservation planning, ecological networks, both aquatic and terrestrial ecosystems, and patch analysis. Emphasizing the relevance of each aspect in the conservation and improvement of ecosystems, I consider this a well-developed study.

The introduction is sufficient and clear, the elements well presented.

Although Figure 1 lacks a vanishing line from the general plane to the regional plane, it would be appreciated if the coordinates in Figure 1 could be bolded to make it easier to read.

Figure 3: Increase the font size in the coordinates and the image resolution.

The methods are well presented, the results are clear and based on the method presented.

Both the discussion and the conclusions are sufficient

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Freshwater ecosystems play a pivotal role in supporting biodiversity and are essential for various ecological processes. However, these habitats are facing significant threats due to factors such as changes in river morphology, the development of hydraulic infrastructure, and pollution, leading to alarming declines in biodiversity. Unfortunately, much of the existing research on ecological networks has concentrated mainly on terrestrial environments, leaving a gap in our understanding of hydrological connectivity and its implications for species movement amid human disturbances. The submitted manuscript addresses this challenge by introducing a novel dual ecological network framework tailored for the Yangtze River Delta’s Ecological Green Integration Demonstration Zone. The submitted manuscript emphasises the divergence in the characteristics of network patches and corridors between freshwater and terrestrial ecosystems, highlighting the limitations of unified models that often favour dominant ecosystems while neglecting smaller, yet ecologically valuable patches. Due to this innovative approach, well-grounded results, insightful discussion and conclusions and well-designed structure of the manuscript, it deserves to be published in the highly esteemed scientific journal Land after addressing a few minor faults:

Lines 39-40. Please add references to support the statement.

Lines 55-57. Please add references to support the statement.

Lines 78-80. Please add references to support the statement.

Lines 107-111. Please move the description of the study area to Chapter 2.1.

Lines 156-166. Please add references to indicate inspiration sources for the applied methodology.

Lines 167-268. Please add references to indicate the inspiration source for using the natural breakpoint method.

Results: Please summarise the key findings in a series of tables to achieve higher coherence with the illustrations.

Discussion: Please abbreviate the chapter and highlight any further research perspectives opened by the results of this investigation, as well as the limitations of the proposed novel approach.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Manuscript reference: land-3740620-peer-review-v1

Separate Versus Unified Ecological Networks: Validating a Dual Framework for Biodiversity Conservation in Anthropogenically Disturbed Freshwater–Terrestrial Ecosystems

Comments on the manuscript

This study explores the concept of connectivity in its two dimensions, the structural connectivity and the functional connectivity, in assemblage with hydrological connectivity, because the aim of the research is to apply a terrestrial – freshwater ecological network model to a mixed landscape – the Yangtze River Delta’s.  

The study is interesting and contributes knowledge in the field of freshwater ecosystems conservation and management. The methods used are common, but organised in an interesting research framework, that can be used by other researchers and decision-makers.

The manuscript is well organised and presents an easy flow along the sections. The introduction presents adequate background information necessary to follow the study described in the manuscript. The motivation and aim of the study are clearly presented. The major findings are presented and discussed in an objective mode, and appropriate tables and figures illustrate the presentation and discussion of the data.

I recommend the publication of the manuscript after minor revision, mainly related to typos in the text.

Author Response

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Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

Dear Authors, We have thoroughly reviewed your manuscript entitled: “Separate Versus Unified Ecological Networks: Validating a Dual Framework for Biodiversity Conservation in Anthropogenically Disturbed Freshwater–Terrestrial Ecosystems”. The study presents a dual-framework approach for ecological network design, independently modeling freshwater and terrestrial systems in the Yangtze River Delta. By integrating habitat quality, landscape resistance, and hydrological connectivity, the authors show that separate networks better capture species movement patterns than unified models. The methodology is technically robust and addresses a critical gap in conservation planning across hybrid landscapes. This contribution is highly relevant for publication in Land, offering practical guidance for biodiversity management in human-modified ecosystems

However, I see a strong need for the authors to be able to address several of my suggestions:

Introduction

I suggest that the authors highlight more clearly the ecological relevance of ecotones between freshwater and terrestrial ecosystems, especially in lowland deltas, where the interaction between systems creates unique conservation challenges.

It would be advisable to explain how anthropogenic pressures such as water infrastructure and land use changes affect structural and functional connectivity in both types of ecosystems, incorporating recent references

I recommend a more explicit justification for the need to apply a dual-network approach, highlighting why unified models may produce biased results in mixed landscapes.

It is important to expand the discussion of the concept of hydrological connectivity, noting its multidimensional nature (longitudinal, lateral, vertical) and how it differs from connectivity in terrestrial systems.

I suggest including references to previous studies that have applied ecological networks in aquatic systems, indicating their limitations and how this work overcomes those methodological barriers.

It would be beneficial to mention current gaps in the simultaneous integration of habitat quality indicators, resilience models and hydrological processes within ecological network approaches.

Finally, I recommend that the introduction more clearly articulates how this study represents a methodological advance for assessing ecological connectivity and conservation planning in landscapes subject to intense human transformation.

Materials and methods

It is suggested that the authors detail more precisely the rationale for the choice of the NDVI and NDWI indicators, including their comparative advantages over other available spectral indices, and their empirical validation in similar contexts.

It would be advisable to explain the calibration and validation criteria of the InVEST model used to estimate habitat quality, mentioning whether local adjustments were made or default parameters were used, and how these affect the robustness of the analysis.

Discussion

It is important to analyse more critically the functional differences between freshwater and terrestrial corridors, differentiating their roles in ecological connectivity, biological resilience and the support of ecosystem services in fragmented landscapes.

It is suggested to highlight the applicability of the findings in territorial and ecological planning, especially in regions where the coexistence of hydraulic infrastructure and ecological fragmentation generates bottlenecks for biodiversity conservation.

It is relevant to link the results of the study with China's conservation policies, ecological restoration plans at basin level and the commitments framed in the National Strategy for Ecological Security.

It is recommended to close the discussion by emphasising the strategic value of the dual network approach as a tool for designing functional landscapes, proposing a framework that combines conservation, active restoration and adaptive connectivity monitoring.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for addressing all the comments to improve the quality of the paper.

Reviewer 5 Report

Comments and Suggestions for Authors

Dear Authors.

I have reviewed in detail each of the responses. I consider that you have done an excellent scientific work and the manuscript has significantly improved its quality. 

For this reason, I consider that in its current state it can be considered for publication.

Best regards.