Remote Sensing of Coastal Wetland Degradation Using the Landscape Directional Succession Model
Round 1
Reviewer 1 Report
Degradation of wetlands, which caused by geographical environmental changes and the transitional use of wetland resources by humans, poses a serious threat to regional socio-economic development and ecological security. The coastal wetlands in Jiangsu Province, China play an important role in protecting biodiversity. In the period of 1980−2020, some of the coastal wetlands have been degraded or lost due to the invasion of Spartina alterniflora, and the utilization of wetlands.
The spatial and temporal evolution characteristics of coastal wetland degradation in Jiangsu Province were quantitatively evaluated by using Landsat images and the improved landscape directional evolution model. The research will help researchers better understand the degradation of coastal wetlands of Jiangsu Province and thus promote the planning and conservation of coastal wetlands.
The manuscript is well written by authors, and the conclusions are believable. I recommend that the manuscript be accepted for publication with minor revision in Remote Sensing.
Some suggestions:
1) The adverse influences of coastal wetland degradation on ecological functions of coastal wetlands in Jiangsu Province, such as water purification, coastal protection, and biodiversity maintenance should be discussed briefly in the section of discussion. For example, the influences of
2) The coastal wetlands in Yancheng City, and Nantong City are located in the middle coast of Jiangsu Province, which between Lianyungang City and Suzhou City from north to south, the northern Jiangsu coastal wetlands is proposed to be expressed in the Jiangsu coastal wetlands.
3) Some figures, such as figure 3, figure 5, figure 6, and figure 8 should be enlarged for more clearly.
4) Some incorrect expressions of km2 should be changed into km2, such as the km2 in lines 202 and 203.
Author Response
Dear Sir or Madam
We are very grateful to Reviewer for reviewing the paper so carefully. In accordance with your comments and suggestions, this paper is revised as follows.
#Specific comments:
(1) English language and style are fine/minor spell check required
Response:
Our manuscripts have been edited using MDPI's English editing service.
(2)The adverse influences of coastal wetland degradation on ecological functions of coastal wetlands in Jiangsu Province, such as water purification, coastal protection, and biodiversity maintenance should be discussed briefly in the section of discussion.
Response: (See Lines 610 - 614)
Thank you very much for your comments. We have added a brief discussion on the impact of wetland degradation on ecological functions to the revised manuscript.
(3)The coastal wetlands in Yancheng City, and Nantong City are located in the middle coast of Jiangsu Province, which between Lianyungang City and Suzhou City from north to south, the northern Jiangsu coastal wetlands is proposed to be expressed in the Jiangsu coastal wetlands.
Response:
Thank you very much for your comments. Your suggestions are important. We have changed the coastal wetlands in northern Jiangsu to Jiangsu coastal wetlands in the revised manuscript.
(4)Some figures, such as figure 3, figure 5, figure 6, and figure 8 should be enlarged for more clearly.
Response:
Thanks. We will eventually send all the original 300dpi images in the paper to the editorial team to ensure that the diagrams in the paper are clearly displayed.
(5)Some incorrect expressions of km2 should be changed into km2, such as the km2 in lines 202 and 203.
Response:
Thank you very much, this is the result of our negligence. We have corrected all similar issues in the full text.
Finally, I would like to thank you once again for your valuable comments.
Kind regards,
Linlin Cui
Guosheng Li
Author Response File: 
Author Response.doc
Reviewer 2 Report
The paper shows an interesting proposal for assessing the degradation of coastal wetlands, but limits itself to quantifying the affected areas, but does not clearly explain the reasons for the transitions between the species used in the assessment. Is it a natural transition? What does it depend on? On the other hand, the discussion, although interesting and clarifies a little the sense of the results, does not seem a real discussion, and should be improved. Some of the text included in the discussion could be moved to the description of the study area. In addition, it is recommended to include a detailed description of the hydrodynamic and climatic conditions of the area, as well as the dynamic conditions of the coast. It would be interesting to explain how it determines the accuracy of Time-series landscape classification maps from 1980 to 2020 obtained with the visual interpretation method. It would also be interesting to quantify the uncertainty of the area estimated (error ranges) in Lines 248 to 256, in line 264 (the value of the area of wetland degradation), and in table 3. An important aspect to improve is the resolution and size of all figures.
Author Response
Dear Sir or Madam
We thank you for your valuable revision comments. In accordance with your comments and suggestions, this paper is revised as follows.
#Specific comments:
(1) English language and style
Response:
Our manuscripts have been edited using MDPI's English editing service.
(2) The paper shows an interesting proposal for assessing the degradation of coastal wetlands, but limits itself to quantifying the affected areas, but does not clearly explain the reasons for the transitions between the species used in the assessment. Is it a natural transition? What does it depend on?
Response: (See pages 6 and 7)
Thank you very much for your question. We have refined the description of the method and the degradation direction in the figure is labeled.
The direction of natural wetland degradation includes (1) the conversion of natural wetlands to artificial wetlands or non-wetlands due to wetland development and utilization, (2) natural community succession involving soil dewatering, (3) natural community succession involving soil salt accumulation, (4) the invasion of exotic species, and (5) the opposite direction of settlement of pioneer species. The degradation directions of artificial wetlands include (1) the conversion of artificial wetlands into non-wetlands and (2) the direction of the ecological service value reduction: paddy field→ aquafarm → salt field → pool (paddy field→ aquafarm indicates the conversion from paddy fields to aquafarms.) . Several articles have been published on this method, and a more complete description of the method has been provided. The following literature can be consulted.
- Cui L, Li G#, Chen Y, Li L. Response of Landscape Evolution to Human Disturbances in the Coastal Wetlands in Northern Jiangsu Province, China. Remote Sensing. 2021; 13(11):2030.
- Linlin Cui, Guosheng Li#, Huajun Liao, Ninglei Ouyang. Analyzing coastal wetland degradation and its key restoration technologies in the coastal area of Jiangsu, China. Wetlands, 2018 38(3):525-537.
- Linlin Cui, Guosheng Li#, Huajun Liao, Ninglei Ouyang, Yue Zhang. Integrated Approach Based on a Regional Habitat Succession Model to Assess Wetland Landscape Ecological Degradation. Wetlands, 2015, 35(2):281-289.
(3) On the other hand, the discussion, although interesting and clarifies a little the sense of the results, does not seem a real discussion, and should be improved. Some of the text included in the discussion could be moved to the description of the study area. In addition, it is recommended to include a detailed description of the hydrodynamic and climatic conditions of the area, as well as the dynamic conditions of the coast.
Response: (See pages 3, 18 and 19)
Thanks. We have revised the introduction and discussion sections by adding a detailed description of the hydrodynamic and coastal dynamic conditions in the region.
(4) It would be interesting to explain how it determines the accuracy of Time-series landscape classification maps from 1980 to 2020 obtained with the visual interpretation method. It would also be interesting to quantify the uncertainty of the area estimated (error ranges) in Lines 248 to 256, in line 264 (the value of the area of wetland degradation), and in table 3.
Response: (See pages 6 and 8)
Thanks. We added an accuracy evaluation section and modified the results.
(5) An important aspect to improve is the resolution and size of all figures.
Response:
Thanks. We will eventually send all the original 300dpi images in the paper to the editorial team to ensure that the figures in the paper are clearly displayed.
Finally, I would like to thank you once again for your valuable comments.
Kind regards,
Linlin Cui
Guosheng Li
Author Response File: Author Response.doc
Reviewer 3 Report
In the last 40 years, coastal wetland ecosystems have been seriously impacted by human activities with their structure, function, and diversity, and therefore it requires a rational planning of ecological restoration to limit wetland degradation. However, the challenge remains to quickly and accurately identify degraded wetland areas and their degradation levels. This study present the used of remote sensing interpretation data from 1980 to 2020 and the wetland degradation evaluation method based on a landscape directional succession model to quantify the spatial and temporal characteristics of wetland degradation in northern Jiangsu Province, China. Their results found that 3020.67 km2 of wetlands became degraded over the 40 years, accounting for 42.74% of the total area of coastal wetlands, and that the overall degradation was mild. This degradation showed a significant spatial difference, with the wetland degradation in Yancheng City observed to be more serious than that in Nantong City. Degradation mainly occurred in Sheyang County, Dafeng District, Dongtai City, and Rudong County, and the spatial distribution pattern of severe and moderate degradation, mild degradation, and non-degradation was observed from land to sea in that order. The degradation of wetlands was observed to have obvious stages, and the degradation of coastal wetlands in the study area from 1980 to 2020 showed a significant increasing trend. The comprehensive score of wetland degradation in 2020 (1.67) was 32 3.70 times that in 1985 (0.45), and the turning point occurred in 2000. The types of wetland degradation were dominated by the transformation of natural wetlands into construction land (coastal industry), fish farming, and arable land, as well as the invasion of exotic species. Although great efforts have been made in recent years to protect and restore coastal wetlands, the development and utilization of coastal wetland resources should be strictly controlled to achieve the goal of sustainable development in coastal areas.
The study is very interesting, but there are a few points to be improved as below:
1) Validation should be mentioned in the results section;
2) In discussion, it should be compared with some other studies in the same coastal wetlands to show the difference or similarity with different methods, such as Chen C et al. Satellite-based monitoring of coastal wetlands in Yancheng, Jiangsu Province, China, J. Mar. Sci. Eng. 2022, 10, 829.
3) Some more latest references should also be updated if some of them are helpful or able to support part of your research work.
Author Response
Dear Sir or Madam
We thank you for your valuable revision comments. In accordance with your comments and suggestions, this paper is revised as follows.
#Specific comments:
(1) English language and style are fine/minor spell check required
Response:
Our manuscripts have been edited using MDPI's English editing service.
(2)Validation should be mentioned in the results section
Response: (See pages 6 and 8)
Thanks. We added an accuracy evaluation section and modified the results.
(3)In discussion, it should be compared with some other studies in the same coastal wetlands to show the difference or similarity with different methods, such as Chen C et al. Satellite-based monitoring of coastal wetlands in Yancheng, Jiangsu Province, China, J. Mar. Sci. Eng. 2022, 10, 829.
Response: (See the discussion section)
Thank you very much for this comment. Based on your comments, we have revised the discussion section and added comparative analysis with the results of other scholars' studies as appropriate.
(4)Some more latest references should also be updated if some of them are helpful or able to support part of your research work.
Response: (See the modification section in the revised manuscript)
Thank you very much for this comment. we have re-cited some recent papers in the revised manuscript that can support our research.
Finally, I would like to thank you once again for your valuable comments.
Kind regards,
Linlin Cui
Guosheng Li
Author Response File: Author Response.doc
Round 2
Reviewer 2 Report
The authors have improved the work, but, a detailed description of the hydrodynamic and climatic conditions of the area, as well as the dynamic conditions of the coast, is still lacking. It would be interesting to know how waves and currents affect the study area. Why is a seawall and a coastal defense line shown in Figure 1? Although a paragraph has been introduced in the discussion about this, it is in Figure 1 that the presence of a seawall and a coastal defense line is shown. Also, between lines 481 to 515 there is no discussion of results; this is the description of the study area. It is suggested to move this part to section 2.1
Author Response
Dear Sir or Madam
Thank you very much for your comments, which led to a great improvement in the quality of the manuscript. In accordance with your comments and suggestions, this paper is revised as follows.
#Specific comments:
(1) The authors have improved the work, but, a detailed description of the hydrodynamic and climatic conditions of the area, as well as the dynamic conditions of the coast, is still lacking. It would be interesting to know how waves and currents affect the study area.
Response: (See the last paragraph of introduction)
Thank you very much for your comments. We have added the description in the revised manuscript.
(2) Why is a seawall and a coastal defense line shown in Figure 1? Although a paragraph has been introduced in the discussion about this, it is in Figure 1 that the presence of a seawall and a coastal defense line is shown.
Response: (See 2.1 study area)
Thanks. The seawall is marked in Figure 1 to determine the western boundary of the study area. We have added a description of the study area boundaries to the revised manuscript.
(3) Also, between lines 481 to 515 there is no discussion of results; this is the description of the study area. It is suggested to move this part to section 2.1.
Response: (See the last paragraph of introduction and 4.1. Regional variability in wetland degradation)
Thanks. We have revised the introduction and discussion sections.
Finally, I would like to thank you once again for your valuable comments.
Kind regards,
Linlin Cui
Guosheng Li
Author Response File: 
Author Response.pdf
Reviewer 3 Report
The revised version has been improved to meet the requirement and all my comments were replied and updated. It is suggested to be accepted for publication.
Author Response
Dear Sir or Madam
Thank you very much for your comments, which led to a great improvement in the quality of the manuscript.
Kind regards,
Linlin Cui
Guosheng Li
Author Response File: Author Response.pdf
