Anthropogenic and Climatic Factors Differentially Affect Waterbody Area and Connectivity in an Urbanizing Landscape: A Case Study in Zhengzhou, China

Round 1

Reviewer 1 Report

Authors have improved the manuscript taking into account all remarks and corrected them. Now, the paper is in a right form to publish. 

Author Response

Response to Reviewer 1 Comments

 

 

Comments and Suggestions for Authors

 

Authors have improved the manuscript taking into account all remarks and corrected them. Now, the paper is in a right form to publish. 

 

Response: Thank you very much for reading and commenting on our paper!

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments

   The author used Landsat satellite imagery to observe temporal and spatial changes in open water habitats in Zhengzhou, and used a model selection approach with linear regressions to ask which climate and anthropogenic drivers were associated with these changes. This is an interesting topic, but the writing of this article is disappointing, and there are many problems that need to be improved. In addition, I have doubts about the author’s results of dividing open water bodies into seven detailed categories through the Landsat images.The specific opinions are as follows:

• In the introduction, the author uses a lot of space to describe the various effects of urbanization on water bodies, and introduces too much background aspects, but there is almost no research progress on the research focus of the article, such as what are the research methods in this area? What are the advantages and disadvantages? What is the overall dilemma facing this aspect?
• The article lacks a good overview of current research progress, and also lacks the innovative points of the article. After reading the full manuscript, it is not clear how innovative the article is in the field.
• The clarity of the pictures in the article is too low, and the legends and fonts are small, and some of the drawings do not meet the specifications, and the amount of information that the pictures can provide is very limited.
• The author divides the open water bodies of Zhengzhou into seven waterbody types: perennial river, seasonal rivers and streams, lakes, canals, reservoirs, ponds, and aquaculture. The remote sensing image used in this article is the Landsat series of images. The resolution of this series of images is 30 meters. How did the author achieve such a detailed classification of open water bodies? I doubt the classification result.
• The author has few introductions in the research methods, and can't see the detailed introduction of extracting 7 types of water bodies, and the classification results of water body types are the focus of subsequent research.
• We all know that the Landsat series of images generally can only achieve the extraction of a large category of land use classification, but to achieve fine classification, especially the extraction of the 7 types of water body types mentioned in this study, complex extraction methods are required, and need a lot of inspection sample points obtained by actual research. In addition, the Landsat series of images have a large number of cloud coverage and chromatic aberration images at different time periods. The author failed to show the splicing results of remote sensing images from 1990 to 2020, and failed to explain the specific image details.
• The analysis of influencing factors in the article is too one-sided. For example, the influence of human factors is multifaceted, and local policies, breeding systems, living customs, irrigation conditions, etc. will all affect the distribution of regional water bodies. What factor is the most core influencing factor?
• The author said that the PC did not consistently decrease over time, connectivity was greatest at the beginning of the study period in 1990. Connectivity briefly increased in 2005 before dropping off again. But why? The article puts forward some more results, but lacks the analysis of the deep-seated reasons of the results.
• The article lacks the necessary conclusion summary chapters, it is very important for the article, the author failed to summarize and condense the main conclusions of this research.
• The discussion part is very poorly written. On the one hand, it fails to discuss in points. On the other hand, it fails to raise some problems in the study,Such as the insufficiency of classification methods, the internal mechanism of various types of water bodies, patterns and landscape changes. The whole discussion chapter is a long and long discussion, a lot of the content of the introduction and the result analysis part is repeated, which obviously does not conform to the writing standard of the article.

Author Response

Response to Reviewer 2 Comments

Comments to Authors

The author used Landsat satellite imagery to observe temporal and spatial changes in open water habitats in Zhengzhou, and used a model selection approach with linear regressions to ask which climate and anthropogenic drivers were associated with these changes. This is an interesting topic, but the writing of this article is disappointing, and there are many problems that need to be improved. In addition, I have doubts about the author’s results of dividing open water bodies into seven detailed categories through the Landsat images.The specific opinions are as follows:

 

Point 1: In the introduction, the author uses a lot of space to describe the various effects of urbanization on water bodies, and introduces too much background aspects, but there is almost no research progress on the research focus of the article, such as what are the research methods in this area? What are the advantages and disadvantages? What is the overall dilemma facing this aspect?

 

Response: Thank you very much for your patience in reading and commenting. Based on your suggestion, we have expanded the introduction and added multiple descriptions and citations related to the research progress.

 

Lines 44-45: “Wetlands in rapidly urbanizing areas face increasing degradation and loss [7–9].”

 

Lines 47-50: “A more recent study of 1,250 inland Ramsar wetlands around the world found that 47% of the sites experienced wetland loss between 1980 and 2014. The study predicted a net loss of at least 6,000 km² of wetland area by 2100 [11].”

 

Lines 53-56: “Construction, drainage, and reshaping of urban land may further influence the distribution and type of waterbodies present in cities [15]. This can result in dramatic changes to the surface water and hydrology of urban landscapes, as seen in the Ganga basin in India [16] and Shenzhen, China [17].”

 

Lines 64-68: “Development near wetlands appears to be altering hydrology, leading to habitat degradation and declining populations of several wetland-dependent bird species [27]. In one city, wetland birds declined faster than all other bird groups during a 10-year period of urbanization, due largely to loss of habitat and connectivity [28].”

 

Lines 69-71: “Artificial wetlands in Cyprus provided habitat for many, although not all, waterbird species found in natural wetlands, including 11 threatened and near-threatened species [29].”

 

Lines 78-79: “The drivers of this expansion are diverse and vary from one region of the country to another [36].”

 

Lines 83-86: “A different analysis showed a net wetland gain of 1,548 km² between 2000-2015, but this net change hid considerable complexities in the types of wetlands gained and lost. In particular, natural wetlands decreased by 7,562 km² during the study period [39].”

Point 2: The article lacks a good overview of current research progress, and also lacks the innovative points of the article. After reading the full manuscript, it is not clear how innovative the article is in the field.

 

Response: Thanks to your suggestion, as described in the previous comment, we have added research progress related content and relevant literature in several places in the introduction. We also have attempted to highlight the innovation of the article in the 5th paragraph of the discussion, on lines  463-473 of the discussion section.

 

Lines 463-473： “Although the importance of wetlands has been recognized for many decades [97], urban wetlands have been relatively neglected compared to more natural habitats. Previous urban water system planning has been largely focused on meeting hydrological functions such as water supply and flood control [98,99], and most studies on waterbird protection have focused on areas such as nature reserves, coastal wetland landscapes [100], or the creation of bird landscapes [101]. This paper provides a novel contribution by exploring urban waterbird protection—an understudied topic—from the perspective of changes in the connectivity of urban water bodies. We hope to provide a new perspective on regional water system planning and waterbird conservation in urbanized areas, and suggest that the overall landscape connectivity of the entire city or even region should be considered during planning.”

Point 3: The clarity of the pictures in the article is too low, and the legends and fonts are small, and some of the drawings do not meet the specifications, and the amount of information that the pictures can provide is very limited.

 

Response: Thank you for your comment. We have modified several images and adjusted their resolution to 300dpi. We have standardized the fonts in Figure 1, Figure 4 (original figure 3), and Figure 8 (original figure 7). We have changed the DEM map in Figure 1 to an optical image to show more information about Zhengzhou City, and in Figure 1c we have marked the extent of the built-up area with a yellow line. In figure 3 (original figure 2), we have rearranged the x-axis dates so that they no longer overlap, and we replaced titles with abbreviations for longer words so that they are consistent with the rest of the font formatting. In figure 4 (original figure 3), we replaced the yellow in the graph with a more pronounced brown, where we can clearly see that the most pronounced changes occur in the built-up areas, and we modified the scale in Figure 8 (original figure 7) to an integer scale.

 

Point 4: The author divides the open water bodies of Zhengzhou into seven waterbody types: perennial river, seasonal rivers and streams, lakes, canals, reservoirs, ponds, and aquaculture. The remote sensing image used in this article is the Landsat series of images. The resolution of this series of images is 30 meters. How did the author achieve such a detailed classification of open water bodies? I doubt the classification result.

 

Response: Thank you for your comments. We describe our approach to classification and accuracy assessment in lines 163-167 and 171-177 of the manuscript. We also include the overall accuracy assessment as Table 3 in the manuscript, and we include a more detailed accuracy assessment for each waterbody type and each year in Appendix A, Supporting Information Table 3. Our overall accuracy ranges from 87 - 96%, which we believe is satisfactory although obviously not perfect. Therefore, we added some text about the limitations of the study to the discussion on lines 486-490.

 

Lines 163-167: “Manual classification relied largely on the map of wetland resources that was created during the aforementioned field survey of 2018; each identified waterbody was examined by eye, compared to the survey map, and then classified. When necessary, classification and interpretation of waterbodies was also aided by information provided by the Zhengzhou Bureaus of Forestry and Water Resources.”

 

Lines 171-177: “We tested the accuracy of the open water classification using stratified random sampling [61] with different waterbody types as the basis for stratification. We determined sample size based on a 95% confidence level (α=0.05) to create a confusion matrix [62,63]. We calculated overall accuracy and the kappa coefficient, as well as the true positive rate (sensitivity) and the true negative rate (specificity) of each waterbody type. Gaofen-2 satellite images with 0.8 meter resolution, and timelapse imagery in Google Earth, were the primary reference data sources.”

 

Lines 486-490: “Moreover, the use of satellite imagery with higher spatial resolution could prove useful for monitoring smaller waterbodies and subtle shoreline changes in larger waterbodies. Future studies could also validate the classification of key waterbodies by using high resolution GNSS receivers as well as more automated classification methods.”

Point 5: The author has few introductions in the research methods, and can't see the detailed introduction of extracting 7 types of water bodies, and the classification results of water body types are the focus of subsequent research.

 

Response: As we explained in response to comment 4, there is a detailed description of the waterbody classification and accuracy assessment in the methods section. We have also added a figure showing our overall workflow which includes our extraction methods. We are not sure what you mean by ‘introductions in the research methods’, but we briefly introduced our research methods in the final paragraph of the introduction section. If there is specific information that you would like to see added to the manuscript, please let us know and we would be happy to add it.

 

Point 6: We all know that the Landsat series of images generally can only achieve the extraction of a large category of land use classification, but to achieve fine classification, especially the extraction of the 7 types of water body types mentioned in this study, complex extraction methods are required, and need a lot of inspection sample points obtained by actual research. In addition, the Landsat series of images have a large number of cloud coverage and chromatic aberration images at different time periods. The author failed to show the splicing results of remote sensing images from 1990 to 2020, and failed to explain the specific image details.

 

Response: First of all, we appreciate and respect your comments. As mentioned in response to the previous two comments, we completed an accuracy assessment of our classification and believe that it meets or exceeds the current standards in the literature. As described in the methods, our classification was completed manually based on extensive information gathered from field surveys. Therefore the classification was supported by field research. 

 

We agree that we previously did not include enough information about the number of images we used for each year and how they were spliced. We have now added that to the text in lines 140-143:

“Seven Landsat satellite images were downloaded from EarthExplorer (USGS., https://earthexplorer.usgs.gov/), one for each year of the study (Figure 2). Landsat images have 30-m resolution; this resolution imagery has been previously used for water identification [51–53].”

 

 

Point 7: The analysis of influencing factors in the article is too one-sided. For example, the influence of human factors is multifaceted, and local policies, breeding systems, living customs, irrigation conditions, etc. will all affect the distribution of regional water bodies. What factor is the most core influencing factor?

 

Response: Thank you for your patience in reading and commenting. We selected seven potential driver variables that have been shown to be important in the literature, as described on lines 189-193, so we do not believe that it is fair to say that the analysis is one-sided. However, we recognize that many factors influence land cover and land-use changes, and these factors can interact in complex ways.  In response to your comment about this on the previous version of the manuscript (as submitted to the journal ‘Remote Sensing’), we previously added an entire paragraph to the discussion to acknowledge these complexities; we have now further expanded this paragraph to address your new comments (see the paragraph on lines 450-462). However, the factors that you mentioned, such as policies and customs, cannot be easily quantified or incorporated into a statistical analysis such as we have done, and we believe that an investigation of these qualitative factors is outside the scope of our paper. We also added a sentence in the discussion to suggest this as a future area of research (lines 492-495). If you have specific suggestions for quantitative measurements we can make to address these issues, please let us know.

 

lines 188-193: “To evaluate potential drivers of waterbody change, we gathered a series of climate and anthropogenic variables that have been linked to waterbody changes in other studies: temperature [11], precipitation [64], potential evapotranspiration [65], human population density [66], the extent of built-up area [67], and the length of water-supply piping [68]. Each variable was measured repeatedly, for each 5-year interval of the study.”

 

Lines 450-462: “Many of the changes we observed in Zhengzhou seem to be unique among urban areas. Some of these changes--in particular the addition of artificial waterbodies and associated increase in  connectivity in the most urban parts of Zhengzhou--can be attributed to specific local and regional planning and policies. For example, in 2000, an old military airport was removed from Zhengzhou and the municipal government proposed a new town in its place. A plan was developed by a Japanese architect that involved the creation of several new waterbodies in what is now the main urban area [96]. One of the new lakes became the waterbody with the greatest overall contribution to landscape connectivity in the region (Figure 8). Other changes in the landscape, particularly the canals, are attributed to the subsequent regional hydraulic projects [49]. Because development in Zhengzhou was specifically planned to include open water, the patterns we detected in this system may be different from those seen in cities that did not intentionally include open water in their design.”

 

Lines 492-495: “It would also be interesting to conduct a more qualitative analysis of the many complex social factors that affect land use and land cover change over time, as our variables did not explain the changes in all waterbody types.”

 

Point 8: The author said that the PC did not consistently decrease over time, connectivity was greatest at the beginning of the study period in 1990. Connectivity briefly increased in 2005 before dropping off again. But why? The article puts forward some more results, but lacks the analysis of the deep-seated reasons of the results.

 

Response: Thanks for your comments. We discuss the observed connectivity patterns in the third paragraph of the discussion (lines 435-440): “Overall landscape connectivity, as measured by the PC index, fluctuated in Zhengzhou over time. The temporal pattern in connectivity appears similar to the pattern for the total surface area of the perennial river. The perennial river, i.e., the Yellow River, contains the majority of the water in Zhengzhou and spans the entire city from east to west. For this reason, the perennial river plays a dominant role in overall connectivity of aquatic habitats.”

 

Point 9: The article lacks the necessary conclusion summary chapters, it is very important for the article, the author failed to summarize and condense the main conclusions of this research.

 

Response: As described in more detail in response to comment 10 below, we have now added a conclusion section to the end of the paper.

 

Point 10: The discussion part is very poorly written. On the one hand, it fails to discuss in points. On the other hand, it fails to raise some problems in the study, Such as the insufficiency of classification methods, the internal mechanism of various types of water bodies, patterns and landscape changes. The whole discussion chapter is a long and long discussion, a lot of the content of the introduction and the result analysis part is repeated, which obviously does not conform to the writing standard of the article.

 

Response: We apologize but we are having trouble understanding this comment, although we understand that the reviewer does not like the discussion section. We do not believe that the discussion is poorly written or too long and are unclear on what specific problems areas the reviewer has identified. However, we made a change to the discussion that we hope will improve this section and address the reviewer’s concerns noted here and in comment 9, as well as comment 16 from reviewer 3. We moved what used to be the first paragraph of the discussion to the end of the paper and now title it ‘conclusion’. We hope that this makes the discussion seem less repetitive and also provides the desired conclusion section.

 

The final paragraph of the discussion section addresses some limitations of the study as the reviewer requests, including the temporal and spatial scale of analysis and the lack of qualitative analysis (lines 480-500). As for the length, the discussion section has 1382 words and 6 short paragraphs, which we believe would not be considered lengthy.

 

We are happy to make other changes to the discussion if the reviewer could provide some more specific criticisms.

 

Lines 480-500: “Our results show both increases and decreases in aquatic habitat and connectivity over time, with changes driven by both anthropogenic and climatic factors. While we believe these results reflect real changes happening in Zhengzhou, they should be considered in light of some limitations of this study. In particular, we used only seven time periods for our analysis. A longer temporal extent might reveal when key changes in aquatic habitat began, and more frequent sampling periods could potentially reveal stronger relationships with climatic drivers. Moreover, the use of satellite imagery with higher spatial resolution could prove useful for monitoring smaller waterbodies and subtle shoreline changes in larger waterbodies. Future studies could also validate the classification of key waterbodies by using high resolution GNSS receivers as well as more automated classification methods. Additional studies could consider the impacts of redistributing water resources at a larger scale (e.g. across the entire country) and how best to maintain and improve urban surface-water landscape connectivity. It would also be interesting to conduct a more qualitative analysis of the many complex social factors that affect land use and land cover change over time, as our variables did not explain the changes in all waterbody types. Finally, we suggest that future research could validate our connectivity analyses with fieldwork (e.g, placing GPS trackers on mallards) and expand the focus to other waterfowl or other taxa that use urban waterbodies. The work presented here is a first step toward understanding changes in aquatic habitat in Zhengzhou and we hope that it can assist in informing future urban planning strategies that benefit both people and wildlife.”

 

Author Response File: Author Response.pdf

Reviewer 3 Report

The present article is focused on anthropogenic and climatic factors that affect 
waterbody area and connectivity in an urbanizing landscape.

The abstract is well structured and includes most of the required data. However, the abstract should be improved in terms of main conclusions.

Section 1 - Introduction - is very well developed and provides a good image on how the article is structured and which steps are followed to conclude the research.

Section 2 - Materials and Methods - regarding the classification of open waterbodies in six classes - please explain why do you select the limit of 8 ha for making a difference between lakes and ponds

Please check lines 239 and 240. There are potential typo errors.

The results are clearly presented.

Please add a section with the main conclusions, clearly structured and emphasized.

Overall, this is a very good article which requires a minor revision.

 

Author Response

Response to Reviewer 3 Comments

 

 

Comments and Suggestions for Authors
The present article is focused on anthropogenic and climatic factors that affect 
waterbody area and connectivity in an urbanizing landscape.

Point 1: The abstract is well structured and includes most of the required data. However, the abstract should be improved in terms of main conclusions.

 

Response: We have now added several details to the abstract, and added a sentence about the relevance of our results for wildlife.

 

lines 23-26: “lakes and canals were the only waterbody types to show statistically significant changes in surface area, increasing by 712% and 236%, respectively. Changes in lakes and canals were positively correlated with the length of water pipeline in the city.”

lines 30-32: “Our results show that urbanization can have unexpected effects—both positive and negative—on connectivity and area of open water habitat. These effects are likely to be important for waterfowl and other aquatic organisms.”

Point 2: Section 1 - Introduction - is very well developed and provides a good image on how the article is structured and which steps are followed to conclude the research.

 

Response: Thank you very much for reading and commenting on the introduction section!

 

Point 3: Section 2 - Materials and Methods - regarding the classification of open waterbodies in six classes - please explain why do you select the limit of 8 ha for making a difference between lakes and ponds.

 

Response: Thank you for your question. Here we followed the classification used in the "National Wetland Resources Survey Technical Regulations" (linked below), which uses 8 ha as the cut-off between lakes and ponds. This classification was also used during the wetland resource survey of Zhengzhou City, which we used as a resource in our manual classification of waterbody types. We felt it was best to be consistent and use the same classification, and have now added this information to the footnote of Table 1.

 

The the national wetland resources survey technical regulations can be accessed at the following links:

http://www.china.com.cn/zhibo/zhuanti/ch-xinwen/2014-01/13/content_31170323.htm

http://www.shidicn.com/sf_822E186D9DE944DA9642D98D46342F35_151_wuzi0.html

 

Point 4: Please check lines 239 and 240. There are potential typo errors.

 

Response: Thank you for your reminder, we have corrected the font formatting.

 

Point 5: The results are clearly presented.

 

Response: Thank you very much for reading and commenting on the results of this manuscript!

 

Point 6: Please add a section with the main conclusions, clearly structured and emphasized.

Response: Thank you for your advice. The conclusion section has been added.

 

Point 7: Overall, this is a very good article which requires a minor revision.

 

Response: Thank you for your comments on the manuscript, we will carefully revise the issues you raised!

 

Author Response File: Author Response.pdf

Reviewer 4 Report

The authors present a case study focused on Zhengzhou, China investigating how rapid urbanisation is contributing to changes in surface water and the potential correlation to waterfowl. This manuscript is a valuable piece of research that is relevant to many rapidly developing cities globally, where water resource management, water availability, and associated impacts of urbanisation are of high priority to city and regional planners. While the methods are robust, broad sweeping statements related to the positive effect of urban water expansion specifically related to waterfowl habitat is not supported. Several generalised summary statements are not well supported by the results of the study and should be addressed before consideration for publication. Conclusions need to be tempered related to the overall ‘positive effect’ urbanisation has on the waterbodies as to not give the impression that water resources and associated beneficial effects on wildlife habitat will increase due to rapid urbanisation.

From a technical remote sensing standpoint, discussion related to the coarse resolution of LANDSAT and resulting omission of many smaller hydrologically significant (habitat connectivity for example) wetlands should be clearly stated and discussed. Many current habitat studies use a minimum of 10m resolution data. Sentinel-2 data (open source) could be mentioned as a suitable sensor for any follow-up investigations that would potentially change the findings in the paper.

Much of the study follows work that is currently underway or is complimentary to regional planning in Zhengzhou by government agencies. There is insufficient context and reference provided related to the foundation for classification of the waterbodies. More contemporary water use and change studies, specifically related to expansion and associated effects on surface water could be included to strengthen the review of pertinent literature. 

Once the suggested revisions are addressed the manuscript should attract significant interest from researchers and planners involved in waterbody management if published given the unique topic and largely robust methods used in the paper. 

General Comments:

• Since the study only examines Zhengzhou, China, this should be stated in the title as it is currently could be misleading and could be thought to be applicable to all or other urbanising landscapes.
• Figures: In general the figures are adequate for displaying the results of the study. One major issues is consistency of map elements and font between figures. This includes north arrow, scale bar and legend elements. (Example Figure 1 and Figure 7). Figure font also needs to be consistent and changed to. Use whole scale numbers (eg. instead of 22.5 use 20 or 25km). Including an optical image of the Zhengzhou area would greatly aid in the description of the region in the text, most notably the urban area (built-up areas) that is repeatedly mentioned in the paper, as well as the and larger rivers going through the city.
• Introduction: Paragraphs could be combined or rearranged to better introduce the changes in rapid developing Chinese cities, then state and provide additional references to specific studies. Including reference to additional relevant recent wetland loss studies conducted in China or other rapid developing cities in the world would also strengthen this section.
• Table 1. Aquaculture is mentioned in the text as being in table 1, but is not in the table. Since aquaculture is not used in the study, just state water bodies have been classified into 6 types since it is not relevant to the study moving forward. Table 1. ‘waterbody type’ heading needs to be case sentence for consistency.
• Figure 2. Font in the figure needs to be changed to match font in the rest of the paper. Dates on the X-axis need to be modified so they do not overlap. Some headings run out of the table and are difficult to read.
• Figure 3. The yellow colour used for ponds is difficult to see, making it hard to visualise where changes have occurred. Considering this is the primary results visual the plates could be larger. Alternatively selecting an inset area where lots of change is occurring rather than the entire area would make it easier to see where changes are occurring.  Ensure font and map element consistency.
• While stylistic, the repeated use of ‘we’ used to describe the various steps taken in the methods section could be reduced to enhance readability. The workflow steps could simply be stated or built into a workflow figure.
• Since both lake and canal area changes are stated in the abstract, reservoirs could also be reported, regardless of how small the decreasing trend is.
• Suggest rounding area numbers for readability.
• The number of images used and resolution of the various Landsat sensors needs to be stated in the methods.
• Equation 2 is not mentioned in the text.

 

Specific Comments:

Line 40. Add more recent references describing wetland loss in rapid developing cities.

Line 42. Suggest also stating reports and loss numbers from Ramsar.

Line 54: Suggest switching or combining the paragraphs starting on line 54 and 64. There is mention of a ‘Chinese City’ in line 55 (simply name the city in the text), but there is no context for this until the next paragraph. It would flow better by first stating the rapid development in China, then the effects it is having.

Lines 62-63: Unclear if this refers to urban wetlands in China, or wetlands in general. These references are also quite dated. Newer studies should be included.

Line 67: If the overall percentage decrease associated with 2,883sq/km in China is known, it should also be stated.

Lines 68-69: Clarify whether this is a result of natural circumstances or anthropogenic related, and whether this is true of strictly wetlands.

Line 87: National Central Cities? This may not be well understood to many readers. Suggest removing or elaborating if this is of importance to the study.

Line 78: Change ‘and asked’ to ‘to investigate’ or something similar.

Line 100: Include reference to Yellow River Diversion project.

Line 119: provide reference to support the statement on 30 year climatic trends. Is this a measure of averages or analysis of trends compared to previous decades?

Line 126: Provide some indication of normal or expected precipitation during May or June. A few statements on conditions during this time will provide readers context for these months and why they were chosen in this region for the study.

Line 132: Provide reference and further justification for the use of these bands in urban areas. It is unclear what is meant by ‘diminishes built up features’.

Line 139: The documents used for classifying these waterbodies (Zhengzhou Bureaus of Forestry and Water Resources) into these 7 types of waterbodies needs to be referenced.   

Line 386-387: This is only supported for surface water and connectivity. Many variables such as water quality, habitat suitability related to vegetation, forage value etc. are not examined in this paper, therefore it is not appropriate to have such general statements. Revise this statement or remove.

Line 389-390: This study referenced focuses on biodiversity hot spots. I am not sure the urban nature of this paper is well supported by the reference. Revise with appropriate literature reference.

Line 394: Name of lake and location on a figure?

Line 398: Reference is needed to this document or study. Without data to back it up these types of statements. Again, increase in just surface water does not correlate to suitable and productive habitat that offsets the effects of losses associated with established natural wetlands.

Line 403-404: This is not true of all anthropenic variables. State specifically what variables (from the results) are correlated with an increase in surface area. ‘Positive or negative effect’ should be replaced with simply ‘increase’ or ‘decrease’ in surface area as this is highly subjective.  

Line 420-421: Unclear if this is due to increases in diversion or allocation, or if there is a storage reservoir that is being drawn from.

Lines 437-438: It was previously stated the changes in Zhengzhou are different than a study of 32 other cities in China, where a decrease was observed. This makes Zhengzhou unique compared to the other cities.

Line 448-451: RAMSAR is worth mentioning in this statement as a global initiative to establish and preserve important wetland habitat.

474-479: Extents of key waterbodies could also be determined using high resolution GNSS receivers, which is useful for validation of the derived waterbody products. This sort of high resolution validation along with the absence of more automated classification approaches (ie. training data) to determine waterbody class also needs to be acknowledged and discussed.

Author Response

Response to Reviewer 4 Comments

 

 

 

Comments and Suggestions for Authors

The authors present a case study focused on Zhengzhou, China investigating how rapid urbanisation is contributing to changes in surface water and the potential correlation to waterfowl. This manuscript is a valuable piece of research that is relevant to many rapidly developing cities globally, where water resource management, water availability, and associated impacts of urbanisation are of high priority to city and regional planners.

Point 1: While the methods are robust, broad sweeping statements related to the positive effect of urban water expansion specifically related to waterfowl habitat is not supported. Several generalised summary statements are not well supported by the results of the study and should be addressed before consideration for publication. Conclusions need to be tempered related to the overall ‘positive effect’ urbanisation has on the waterbodies as to not give the impression that water resources and associated beneficial effects on wildlife habitat will increase due to rapid urbanisation.

 

Response: We agree that we might have unintentionally overemphasized the positive aspects of landscape change in the previous version of the manuscript. In response to this comment, we have modified some of the text to be clear that while urbanization might have increased the connectivity of waterbodies in some areas, other negative changes have occurred as well. For example, we added this sentence to the end of the first paragraph of the introduction (lines 414-416):

 

“Therefore, we want to caution that urbanization in general is unlikely to have net positive effects on waterfowl or other wildlife.”

 

We also added this sentence to the end of the conclusion:

 

“These results show that urbanization can have unexpected and potentially positive effects on connectivity of surface water, although these results might not translate directly to positive effects on wildlife.”

 

Point 2: From a technical remote sensing standpoint, discussion related to the coarse resolution of LANDSAT and resulting omission of many smaller hydrologically significant (habitat connectivity for example) wetlands should be clearly stated and discussed. Many current habitat studies use a minimum of 10m resolution data. Sentinel-2 data (open source) could be mentioned as a suitable sensor for any follow-up investigations that would potentially change the findings in the paper.

 

Response: We agree that this kind of study would benefit from the analysis of finer-resolution images, and have a sentence addressing this in the 486-490.

 

“Moreover, the use of satellite imagery with higher spatial resolution could prove useful for monitoring smaller waterbodies and subtle shoreline changes in larger waterbodies. Future studies could also validate the classification of key waterbodies by using high resolution GNSS receivers as well as more automated classification methods.”

 

Point 3: Much of the study follows work that is currently underway or is complimentary to regional planning in Zhengzhou by government agencies. There is insufficient context and reference provided related to the foundation for classification of the waterbodies. More contemporary water use and change studies, specifically related to expansion and associated effects on surface water could be included to strengthen the review of pertinent literature. 

 

Response: Thank you for your question. Here we followed the classification used in the "National Wetland Resources Survey Technical Regulations" (linked below),

http://www.china.com.cn/zhibo/zhuanti/ch-xinwen/2014-01/13/content_31170323.htm

http://www.shidicn.com/sf_822E186D9DE944DA9642D98D46342F35_151_wuzi0.html

According to your suggestion, we have added the following citations: [11][16][17][27][34][36][87][88][97]

 

Point 4: Once the suggested revisions are addressed the manuscript should attract significant interest from researchers and planners involved in waterbody management if published given the unique topic and largely robust methods used in the paper. 

 

Response: Thank you for your careful reading and patient comments on the article! We will revise it carefully as requested!

 

General Comments:

 

Point 5: Since the study only examines Zhengzhou, China, this should be stated in the title as it is currently could be misleading and could be thought to be applicable to all or other urbanising landscapes.

 

Response: Thanks to your suggestion, we have added the words "A Case Study in Zhengzhou, China" to the title.

 

Point 6: Figures: In general the figures are adequate for displaying the results of the study. One major issues is consistency of map elements and font between figures. This includes north arrow, scale bar and legend elements. (Example Figure 1 and Figure 7). Figure font also needs to be consistent and changed to. Use whole scale numbers (eg. instead of 22.5 use 20 or 25km). Including an optical image of the Zhengzhou area would greatly aid in the description of the region in the text, most notably the urban area (built-up areas) that is repeatedly mentioned in the paper, as well as the and larger rivers going through the city.

 

Response: Thank you for your comments! We have unified the fonts in figure 1, figure 4 (original figure 3), and figure 8 (original figure 8). We have changed the DEM map in Figure 1 to an optical image according to your suggestion, and we have marked the extent of the built-up area with the area of the yellow line, and we have modified the scale in Figure 8 (original figure 7) to an integer scale, as requested.

 

Point 7: Introduction: Paragraphs could be combined or rearranged to better introduce the changes in rapid developing Chinese cities, then state and provide additional references to specific studies. Including reference to additional relevant recent wetland loss studies conducted in China or other rapid developing cities in the world would also strengthen this section.

 

Response: Thank you very much for your comment. We see how things could have been confusing in the previous version of the manuscript. The third paragraph of the introduction was meant to be more general in nature and not about China specifically. Therefore, we removed the part about the Chinese city and kept this as a separate paragraph. As suggested, we have also added more references about urban wetland changes, as described in the following text.

 

Lines 47-50: “A more recent study of 1,250 inland Ramsar wetlands around the world found that 47% of the sites experienced wetland loss between 1980 and 2014. The study predicted a net loss of at least 6,000 km² of wetland area by 2100 [11].”

 

Lines 53-56: “Construction, drainage, and reshaping of urban land may further influence the distribution and type of waterbodies present in cities [15]. This can result in dramatic changes to the surface water and hydrology of urban landscapes, as seen in the Ganga basin in India [16] and Shenzhen, China [17].”

 

Lines 64-68: “Development near wetlands appears to be altering hydrology, leading to habitat degradation and declining populations of several wetland-dependent bird species [27].”

 

Lines 75: “Constructed wetlands can also contribute to landscape connectivity [34].”

 

Lines 78-79: “The drivers of this expansion are diverse and vary from one region of the country to another [36].”

 

Point 8: Table 1. Aquaculture is mentioned in the text as being in table 1, but is not in the table. Since aquaculture is not used in the study, just state water bodies have been classified into 6 types since it is not relevant to the study moving forward. Table 1. ‘waterbody type’ heading needs to be case sentence for consistency.

 

Response: Thank you very much for your suggestion; we understand why this might have been confusing. We did not want to omit the mention of aquaculture altogether, as we did classify them and then remove them from analysis rather than lump them with other waterbody types. We have changed the wording of this section slightly to hopefully make things more clearly, as seen on Lines 158-163 and below:

 

“All open water was then manually classified as one of the following seven waterbody types: perennial river, seasonal rivers and streams, lakes, canals, reservoirs, ponds, and aquaculture. Aquaculture sites were identified but excluded from further analysis because their value as bird habitat is hard to predict and can be negative [59,60],  leaving six waterbody types in our analysis (Table 1).”

 

 

 

Point 9: Figure 2. Font in the figure needs to be changed to match font in the rest of the paper. Dates on the X-axis need to be modified so they do not overlap. Some headings run out of the table and are difficult to read.

 

Response: Thank you for your great suggestion! In figure 3 ( original figure 2), we have rearranged the x-axis dates so that they no longer overlap, and we replaced titles with abbreviations for longer words so that they are consistent with the rest of the font formatting.

 

Point 10: Figure 3. The yellow colour used for ponds is difficult to see, making it hard to visualise where changes have occurred. Considering this is the primary results visual the plates could be larger. Alternatively selecting an inset area where lots of change is occurring rather than the entire area would make it easier to see where changes are occurring.  Ensure font and map element consistency.

 

Response: Thanks to your suggestion, we replaced the yellow in the graph with a more pronounced brown. We believe this more clearly shows the ponds and the changes that occurred in the built-up areas. As described previously, we also changed the figures to make the font and map elements more consistent.

 

Point 11: While stylistic, the repeated use of ‘we’ used to describe the various steps taken in the methods section could be reduced to enhance readability. The workflow steps could simply be stated or built into a workflow figure.

 

Response: Thanks to your suggestions, we have not only changed the writing of the methods section in several places such as line 134, line 140, line 194, and line 224, but also added a workflow figure (now figure 2).

 

Point 12: Since both lake and canal area changes are stated in the abstract, reservoirs could also be reported, regardless of how small the decreasing trend is.

 

Response: In the abstract, we only mention the statistically significant changes. Since there was not a statistically significant change in reservoirs, we fear it would be misleading to mention it in the abstract. Therefore, we respectfully decided not to make this change. Instead, we modified the abstract to indicate that only lakes and canals had statistically significant changes.

 

Point 13: Suggest rounding area numbers for readability.

 

Response: Thank you for your suggestion. We rounded the numbers in this manuscript to increase readability. The specific changes are below:

 

Line 105: “It has a total area of approximately 7446 km².”

Line 303: “The total surface area of lakes increased from 116 hectares in 1990 to 942 hectares in 2020.”

Line 306: “Total surface area of canals increased 236% over the same time period, from 310 to 1042 hectares.”

 

Point 14: The number of images used and resolution of the various Landsat sensors needs to be stated in the methods.

 

Response: Thanks for your suggestion, we have added a description of the number and resolution of images in line 140:

“Seven Landsat satellite images were downloaded from EarthExplorer (USGS., https://earthexplorer.usgs.gov/), one for each year of the study (Figure 2). Landsat images have 30-m resolution.”

 

Point 15: Equation 2 is not mentioned in the text.

 

Response: Thanks for the reminder.  We now refer to equation 2 on line 254. “PC represents the probability that two randomly placed points within the landscape are accessible from each other (i.e., interconnected), and  is calculated as follows in equation 2.”

 

 

Specific Comments:

 

Point 16: Line 40. Add more recent references describing wetland loss in rapid developing cities.

 

Response: We have added numerous recent references about wetland and other landscape changes.

 

Lines 44-45: “Wetlands in rapidly urbanizing areas face increasing degradation and loss [7–9].”

 

Lines 47-50: “A more recent study of 1,250 inland Ramsar wetlands around the world found that 47% of the sites experienced wetland loss between 1980 and 2014. The study predicted a net loss of at least 6,000 km² of wetland area by 2100 [11].”

 

Lines 53-56: “Construction, drainage, and reshaping of urban land may further influence the distribution and type of waterbodies present in cities [15]. This can result in dramatic changes to the surface water and hydrology of urban landscapes, as seen in the Ganga basin in India [16] and Shenzhen, China [17].”

 

Lines 64-68: “Development near wetlands appears to be altering hydrology, leading to habitat degradation and declining populations of several wetland-dependent bird species [27]. In one city, wetland birds declined faster than all other bird groups during a 10-year period of urbanization, due largely to loss of habitat and connectivity [28].”

 

Lines 69-71: “Artificial wetlands in Cyprus provided habitat for many, although not all, waterbird species found in natural wetlands, including 11 threatened and near-threatened species [29].”

 

Lines 78-79: “The drivers of this expansion are diverse and vary from one region of the country to another [36].”

 

Lines 83-86: “A different analysis showed a net wetland gain of 1,548 km² between 2000-2015, but this net change hid considerable complexities in the types of wetlands gained and lost. In particular, natural wetlands decreased by 7,562 km² during the study period [39].”

 

Point 17:  Line 42. Suggest also stating reports and loss numbers from Ramsar.

 

Response: We have added text related to the loss of the Ramsar wetlands and its references to lines 47-50:

“A more recent study of 1,250 inland Ramsar wetlands around the world found that 47% of the sites experienced wetland loss between 1980 and 2014. The study predicted a net loss of at least 6,000 km² of wetland area by 2100 [11].”

 

 

Point 18:  Line 54: Suggest switching or combining the paragraphs starting on lines 54 and 64. There is mention of a ‘Chinese City’ in line 55 (simply name the city in the text), but there is no context for this until the next paragraph. It would flow better by first stating the rapid development in China, then the effects it is having.

 

Response: We apologize for the confusion here. As described in our response to comment 24, we deleted "Chinese" from the text and hope the introduction now flows better.

 

Point 19:  Lines 62-63: Unclear if this refers to urban wetlands in China, or wetlands in general. These references are also quite dated. Newer studies should be included.

 

Response: As we explained above in response to comment 24, this paragraph is meant to be more general and not focused on China. We hope that our edits make this more clear. We added one recent reference (the year 2017) to the sentence, but please note that there is not much research on the impact of constructed wetlands on landscape connectivity and thus recent studies are scarce.

 

Point 20:  Line 67: If the overall percentage decrease associated with 2,883sq/km in China is known, it should also be stated.

 

Response: We added the overall percentage on lines 82-83.

“which accounts for a 6.0% loss of the total wetland area.”

 

Point 21:  Lines 68-69: Clarify whether this is a result of natural circumstances or anthropogenic related, and whether this is true of strictly wetlands.

 

Response: We have added relevant text and references in lines 86-87. What we want to express here is that water is especially precious to northern China because the north is more arid than the south for natural reasons.

 

“The ecological value of urban waterbodies is particularly significant in northern China, where the climate is arid and surface water is scarce [40].”

 

Point 22:  Line 87: National Central Cities? This may not be well understood to many readers. Suggest removing or elaborating if this is of importance to the study.

 

Response: The description of the “National Central City” has been removed.

 

Point 23:  Line 78: Change ‘and asked’ to ‘to investigate’ or something similar.

 

Response: Thank you for your suggestion, we have completed the change.

 

Point 24:  Line 100: Include reference to Yellow River Diversion project.

 

Response: Thanks to the suggestion; the reference was added on line 118.

 

Point 25:  Line 119: provide reference to support the statement on 30 year climatic trends. Is this a measure of averages or analysis of trends compared to previous decades?

 

Response: Thank you very much for this comment. We agreed that we had an error in expression here and have modified the sentence on lines 136-138:

 

“It is long enough to observe the effects of climate and anthropogenic factors on urban waterbodies.”

 

Point 26:  Line 126: Provide some indication of normal or expected precipitation during May or June. A few statements on conditions during this time will provide readers context for these months and why they were chosen in this region for the study.

 

Response: This is a good point. We now include the following sentence on lines 147-148:

“Zhengzhou receives approximately 6 cm of precipitation in May and 9 cm in June [55,56].”

 

Point 27:  Line 132: Provide reference and further justification for the use of these bands in urban areas. It is unclear what is meant by ‘diminishes built up features’.

 

Response: We have added references [53] and [58] in line 152. We also changed ‘diminishes’ to ‘is sensitive to’, which we hope expresses the idea more clearly.

 

Point 28:  Line 139: The documents used for classifying these waterbodies (Zhengzhou Bureaus of Forestry and Water Resources) into these 7 types of waterbodies needs to be referenced.   

 

Response: Unfortunately, the reports and related documents of the wetland resources survey in Zhengzhou City are not publicly available online. If allowed by the journal, we can include a link to the webpage related to the technical regulations of the wetland resources survey:

http://www.shidicn.com/sf_822E186D9DE944DA9642D98D46342F35_151_wuzi0.html

 

Point 29:  Line 386-387: This is only supported for surface water and connectivity. Many variables such as water quality, habitat suitability related to vegetation, forage value etc. are not examined in this paper, therefore it is not appropriate to have such general statements. Revise this statement or remove.

 

Response: This is a good point. We changed this sentence on lines 513-516 to:

“These results show that urbanization can have unexpected and potentially positive effects on connectivity of surface water, although these results might not translate directly to positive effects on wildlife.”

 

Point 30:  Line 389-390: This study referenced focuses on biodiversity hot spots. I am not sure the urban nature of this paper is well supported by the reference. Revise with appropriate literature reference.

 

Response: Thanks to your suggestion, we replaced the previous reference with two new references [87-88] to support the statement in line 401.

 

Point 31:  Line 394: Name of lake and location on a figure?

 

Response: We have added a reference to Figure 4 in the text of line 407, as the location of the new lake can be observed very clearly from Figure 4.

 

Point 32:  Line 398: Reference is needed to this document or study. Without data to back it up these types of statements. Again, increase in just surface water does not correlate to suitable and productive habitat that offsets the effects of losses associated with established natural wetlands.

 

Response: We did not intend to suggest that wildlife will necessarily benefit from the observed wetland changes, and have made several additions to the discussion to hopefully make this more clear we added this sentence to the end of the first paragraph of the introduction (lines 414-416): “Therefore, we want to caution that urbanization in general is unlikely to have net positive effects on waterfowl or other wildlife.”

 

We also added this sentence to the end of the conclusion: “These results show that urbanization can have unexpected and potentially positive effects on connectivity of surface water, although these results might not translate directly to positive effects on wildlife.”

.

As for the reference, We also included citations to several local news stories about waterfowl using the constructed waterbodies, on lines 408-410: “The wetland resource surveys commissioned by the Zhengzhou government, as well as some local news reports [90,91] show that these constructed waterbodies are used by many wildlife species, including waterfowl (data not shown). ”

 

Point 33:  Line 403-404: This is not true of all anthropenic variables. State specifically what variables (from the results) are correlated with an increase in surface area. ‘Positive or negative effect’ should be replaced with simply ‘increase’ or ‘decrease’ in surface area as this is highly subjective.  

 

Response: Thank you very much for your suggestion, we have changed the sentence as you described, in lines 417-419:

“We found that length of water pipe was correlated with an increase in surface area of lakes and canals, and precipitation was correlated with an increase in surface area of seasonal rivers and streams.”

 

Point 34:  Line 420-421: Unclear if this is due to increases in diversion or allocation, or if there is a storage reservoir that is being drawn from.

 

Response: Yes, we state a similar point in lines 116-123: “Two different water diversion projects have directly affected Zhengzhou's waterbodies over the last 15 years: the South-to-North Water Diversion Project [46] and the Yellow River Diversion project [47]. The former project is the largest such project in Chinese history, and has the goal of transferring fresh water from southern China to northern China [48–50]. The latter project is much smaller in geographic scope and has the goal of drawing water from the Yellow River to enrich the Jialu River and Long Lake and Longzi Lake in Zhengzhou itself.”

 

Point 35:  Lines 437-438: It was previously stated the changes in Zhengzhou are different than a study of 32 other cities in China, where a decrease was observed. This makes Zhengzhou unique compared to the other cities.

 

Response: We are very sorry for the mistake here, we have removed this sentence from the original text and now begin the paragraph with the following sentence (lines 450-451): “Many of the changes we observed in Zhengzhou seem to be unique among urban areas.”

 

 

Point 36:  Line 448-451: RAMSAR is worth mentioning in this statement as a global initiative to establish and preserve important wetland habitat.

 

Response: Thanks to your valuable suggestions, We add the relevant reference to Ramsar in line 463(reference [97]), and to ensure a smoother statement, we use other statements to bridge the two paragraphs.

“Although the importance of wetlands has been recognized for many decades [97], urban wetlands have been relatively neglected compared to more natural habitats.”

 

Point 37:  474-479: Extents of key waterbodies could also be determined using high resolution GNSS receivers, which is useful for validation of the derived waterbody products. This sort of high resolution validation along with the absence of more automated classification approaches (ie. training data) to determine waterbody class also needs to be acknowledged and discussed.

 

Response: Thanks to your suggestion, we have added the following sentence to lines 488-490:

“Future studies could also validate the classification of key waterbodies by using high resolution GNSS receivers as well as more automated classification methods.”

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

In the last round of review, we have put forward many revisions to the author, but the author has not made improvements to the key issues. Although the author has made some revisions, the key issues have not been solve. Other reviewers also have similar opinions with me, such as whether the accuracy of water classification is credible? From the experience of remote sensing classification, it is difficult to classify Landsat series images into such detailed types. There are also many problems in the discussion of influencing factors. In addition, I don’t agree with the innovation of the study mentioned by the author (we explore urban waterbird protection—an understudied topic—from the perspective of changes in the connectivity of urban water bodies. ). There are also related scholars in this area, we advised authors to read the more latest international research. Therefore, I stick to the opinions of the previous review.

Author Response

Response to Reviewer 2 Comments

Round 2

 

Dear Editor,

Thank you for the opportunity to further revise our manuscript. Below we have copied the comments from Reviewer 2 and described our response.

Comments from reviewer 2

 

In the last round of review, we have put forward many revisions to the author, but the author has not made improvements to the key issues. Although the author has made some revisions, the key issues have not been solve. Other reviewers also have similar opinions with me, such as whether the accuracy of water classification is credible? From the experience of remote sensing classification, it is difficult to classify Landsat series images into such detailed types. There are also many problems in the discussion of influencing factors. In addition, I don’t agree with the innovation of the study mentioned by the author (we explore urban waterbird protection—an understudied topic—from the perspective of changes in the connectivity of urban water bodies. ). There are also related scholars in this area, we advised authors to read the more latest international research. Therefore, I stick to the opinions of the previous review.

 

We see three main points in this comment, which we list and respond to below.

 

Point 1: Whether the accuracy of water classification is credible

 

Response: We have provided multiple measures of classification accuracy in the body of the paper and the appendix, we agree that the classification is difficult; the manual classification represents a huge amount of time invested by the lead author. It was feasible because the study area is a city in Henan Province, China, which has a relatively small area. It was also feasible because the lead author became familiar with the waterbodies in this study area while conducting fieldwork in collaboration with the Zhengzhou Bureaus of Forestry and Water Resources. If our honesty is in doubt, we are happy to provide the classified images as supplementary material.

 

Furthermore, a large number of articles have been published on identifying and classifying waterbodies with the 30 m Landsat imagery, so we are not the only researchers to take this approach. We cite three of these papers in our article to support our current research (citations 51-53).

 

We acknowledge that our classification is not perfect--because no classification method can guarantee 100% accuracy--so we have acknowledged the limitations of the 30 m remote sensing imagery and our plans for future work in the discussion (lines 487-491):

 

“Moreover, the use of satellite imagery with higher spatial resolution could prove useful for monitoring smaller waterbodies and subtle shoreline changes in larger waterbodies. Future studies could also validate the classification of key waterbodies by using high resolution GNSS receivers as well as more automated classification methods.”

 

Point 2: There are also many problems in the discussion of influencing factors.

 

Response: Thank you for your comment, if by "influencing factors" you mean factors affect the water bodies in addition to the variables that we measured. We have acknowledged this in multiple places in the paper, as explained in our previous responses (e.g., lines 451-463, 491-496 in the manuscript). However, we would also like to point out that some of our models have quite high explanatory power, suggesting that we actually have identified the most important influencing factors for those waterbody types. In particular, the models for lakes, canals, and seasonal rivers and streams have an r² > 0.83, so it is unlikely that adding other variables would substantially improve those models.

 

If we have misunderstood the meaning of this criticism, could we invite the reviewer to provide specific examples of what issues they are referring to and the definition of "influencing factors" and we would be happy to address them.

 

Point 3: I don’t agree with the innovation of the study mentioned by the author (we explore urban waterbird protection—an understudied topic—from the perspective of changes in the connectivity of urban water bodies. ). There are also related scholars in this area, we advised authors to read the more latest international research. Therefore, I stick to the opinions of the previous review.

 

Response: We apologize for not being clear enough here, as we could have been more specific about the unique contribution of our paper. We have now rephrased the offending sentence, on lines 465-478 and copied below.

 

In response to this comment, we also conducted another literature search on ‘urban waterbird protection from the perspective of changes in the connectivity of urban water bodies.’ to see if we previously missed any papers on this topic. We found only one recent relevant paper that we had not previously cited, and added a reference to it on lines 246 and line 474. While we believe that we are familiar with this body of literature, we would be happy to read and incorporate the literature referred to by this reviewer if they provide specific examples of authors or papers they believe we are missing.

 

“Although the importance of wetlands has been recognized for many decades [98], urban wetlands have been relatively neglected compared to more natural habitats. Previous urban water system planning has been largely focused on meeting hydrological functions such as water supply and flood control [99,100], and most studies on waterbird protection have focused on areas such as nature reserves, coastal wetland landscapes [101], or the creation of bird landscapes [102]. One exception is a study of Beijing, China, that examined habitat suitability and connectivity for the mallard duck (along with two other bird species; [80]), although only a single time period was examined. Our paper provides a novel contribution by exploring urban waterbird protection from the perspective of changes in the connectivity of urban water bodies over time. We hope to provide a new perspective on regional water system planning and waterbird conservation in urbanized areas, and suggest that the overall landscape connectivity of the entire city or even region should be considered during planning.”

 

Finally, we would like to thank the reviewers for their time, and we believe that the current edited draft of our manuscript is greatly improved. We trust that this revised manuscript is acceptable for publication.

 

Author Response File: Author Response.docx

Round 3

Reviewer 2 Report

The author has revised the paper according to the reviewers' comments.  I suggest to accept the paper. 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The paper entitled Anthropogenic and climatic factors differentially affect waterbody area and connectivity in a rapidly urbanizing landscape aims to present temporal and spatial changes in of cities in China. Please indiciate any numerical facts in the abstract. Please add a set of inputs for the model. Please explain what is  Conefor 2.6. Please improve the quality of Figure 3 and Figure 7. Please describe the input data in particular.

After reading the manuscript, I find the topics covered in it interesting for a wide audience. It is important to know the factors influencing waterbodies. The research description has been prepared correctly. In addition, I would add another method to describe the accuracy of the classification. For binary classification models in addition to AUC, accuracy matrix and its derivatives (sensitivity, specificity, overall accuracy, kappa statistics) could be evaluated and applied. Articles have already been written on a similar topic, but using different classification methods. The article is well prepared and, after minor faults are corrected, ready for publication. The conclusions in the article are correctly formulated. It is also possible to add an answer to the question: How do you take obtained results to the next step in terms of ecological implications?

Reviewer 2 Report

Comments

This study used Landsat satellite imagery to observe temporal and spatial changes in open water habitats in Zhengzhou, and try to and measured the area of each kind of waterbody, and we asked which climate and anthropogenic drivers were associated with these changes. However, there are still many problems in the manuscript, especially for the extraction results of six open water bodiesMy specific comments are as follows.

• The rapid urbanization landscape in the title of the article is very strange. What does the author mean? Does it mean landscape connectivity?
• In the abstract, there is a lack of introduction to the research methods used in this study, such as methods for obtaining open water and evaluating anthropogenic and climatic impacts for waterbody in different periods.
• The introduction is very poor. The author spends a lot of space to introduce the current situation and background of China's waterbody and wetlands, but there is very little introduction to the research progress related to the research topic.
• The introduction part failed to clarify the innovative points of this research, and the research progress in this area has not been scientifically and reasonably summarized and reviewed.
• The overview of the research area is too long. Please condense the language and briefly explain the current status of the key areas closely related to the research topic.
• In the part of the classification and identification methods of the six waterbody, the author lacks the introduction of specific technical methods and implementation details, such as how to define and distinguish the types of these six water bodies. With the resolution of the Landsat series of images, it is difficult to supervise the classification. The water bodies in the area are distinguished in such detail, and a higher accuracy is obtained, which questioned the classification accuracy of the six water bodies.
• The method of studying the influence of anthropogenic and climatic factors on water bodies is unreasonable. On the one hand, the selected indicators are too subjective and one-sided, and may not necessarily reflect the anthropogenic or climatic influences in the region. On the other hand, the anthropogenic influence is a comprehensive The effect is not the influence of a single factor. How to evaluate the influence of different human factors, such as the influence of local policies and urban planning on the area of regional water bodies? In addition, the impact of climatic factors on water bodies is a long-term effect, and the evaluation based on five years as a time section is not reasonable.
• The figures in the article have low accuracy and lack of information. The author is asked to improve the readability, clarity and information of the figures.
• The discussion chapter in the article has only one summary and is very lengthy, and it is not divided into points for discussion. The whole discussion part is more repetitive on the research results, which makes the discussion part chaotic. It is recommended to start from the advantages and disadvantages of the methods used in this research compared with other methods, and the differences and connections of different authors' research methods etc.
• The article structure of the entire manuscript is unreasonable, and even the conclusion chapter is missing.

 

Reviewer 3 Report

The type of information produced by the manuscript is very relevant to the environmental and urban planning of cities that have experienced rapid population growth and the extension of the built area. The work carried out the mapping, measurement and characterization of the water bodies in Zhengzhou over a period of 30 years.

However, the work does not present innovation or contributions that are sufficiently relevant in the field of remote sensing or digital image processing to justify publication in a periodical specialized in remote sensing.

I recommend authors to resubmit the manuscript to a specialized journal in the field of urban and regional planning.

As a contribution to the authors regarding the presentation quality of the article, I suggest that they improve the resolution of the figures and that they increase the size of the maps presented. It was difficult for me to "read" the maps presented, due to the small size and low resolution of the figures.