Can Famine Be Averted? A Spatiotemporal Assessment of The Impact of Climate Change on Food Security in The Luvuvhu River Catchment of South Africa
Round 1
Reviewer 1 Report
The work "Can famine be averted?: A spatiotemporal assessment of the impact of climate change on food security in Luvuvhu River Catchment of South Africa." deals with the very important issue of climate change and food security. In my opinion, the work is not suitable for publication in its current form.
Detailed comments:
Material and methods (Study area) is too long. I would put the description from lines 140 to 169 in the introduction. I did not understand why the Authors includes chart 1 in the paper. Nothing follows from it. Besides, I can't really locate the LRCA catchment on the African continent according to this drawing.
The methodology did not provide the formula for the correlation coefficient used. I am not sure if it is correct to use the Pearson correlation coefficient without checking the assumptions.
The explanation of the very important abbreviations SPI, VCI is only in the summary and how to calculate them only on page 6.
Line 272: "for ten randomly sampled years between 1980 and 2016" As is the case with the 36 years represented on the X axis.
Line 289: Graph is unreadable (x-axis).
Line 278-280: "The results of this study vary from those of an earlier 278 study by Nkuna and Odiyo (2016), which reported 1982/83 and 1991/92 years as severely dry years."
How does this relate to chart 2 where the SPI_3 index is almost zero.
Why is the data in Figure 3 not the same as in Figure 2? (SPI_3 low and high indicator)
line 305: "of 2.03, indicat-305 ing that 2006/7 was an extremely wet year" ???
Lines 310-312: "As indicated by NDVI values (Figure 3) the highest vegetation vigour was widely 310 recorded in 1996, 2002, 2007 and 2011," - this data is missing in Figure 3
lines 338-340: "As shown in the results of this study, vegetation type plays a pivotal role in the 338 ability of the ability of plants to respond to rainfall variability, especially in rain-fed ag-339 ricultural areas." - where is it shown ??
The authors often refer to the results of the NDVI index, but the work lacks its results. My suggestion is to include them in the table.
Rows 394-406: Why was only 10 years used to study the correlation? The results of the correlation coefficient are very strange here. I am particularly concerned about the result of 0.8166. I would suggest recalculating the data and using the rank correlation coefficient.
lines 408–479: discussion needs improvement. The authors omitted the results of their work in the discussion. In the discussion, the authors indicate what they would like to obtain or what others have obtained.
lines 480–494: The conclusion needs to be corrected. It has nothing to do with work as it stands.
The work requires careful checking.E.g:
line 397: -0.6172 no minus in the chart
line 404: r = 3673
line 513: 3139
Author Response
Response to Review Report 1
Responses are in italics
Open Review
(x) I would not like to sign my review report
( ) I would like to sign my review report
English language and style
( ) Extensive editing of English language and style required
( ) Moderate English changes required
( ) English language and style are fine/minor spell check required
(x) I don't feel qualified to judge about the English language and style
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Does the introduction provide sufficient background and include all relevant references? |
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Is the research design appropriate? |
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Are the methods adequately described? |
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Are the results clearly presented? |
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Are the conclusions supported by the results? |
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Comments and Suggestions for Authors
The work "Can famine be averted?: A spatiotemporal assessment of the impact of climate change on food security in Luvuvhu River Catchment of South Africa." deals with the very important issue of climate change and food security. In my opinion, the work is not suitable for publication in its current form.
Detailed comments:
Material and methods (Study area) is too long. I would put the description from lines 140 to 169 in the introduction. I did not understand why the Authors includes chart 1 in the paper. Nothing follows from it. Besides, I can't really locate the LRCA catchment on the African continent according to this drawing.
Response: The length of the “materials and methods” section has been reduced. The contents that were in lines 140 to 169 were moved to the introduction.
The methodology did not provide the formula for the correlation coefficient used. I am not sure if it is correct to use the Pearson correlation coefficient without checking the assumptions.
Response: The formula for calculating the Pearson Product Correlation Coefficient has been added and the assumptions stated.
The explanation of the very important abbreviations SPI, VCI is only in the summary and how to calculate them only on page 6.
Response: The terms SPI and VCI have been defined as recommended
Line 272: "for ten randomly sampled years between 1980 and 2016" As is the case with the 36 years represented on the X axis.
Response: The years that have been included in the analysis are those corresponding to drought. The argument behind the selection is that the frequency of drought is increasing, unlike that of severely and extremely wet conditions. However, we still note that the occurrence of drought exhibits an element of randomness.
Line 289: Graph is unreadable (x-axis).
Response: The font size has been increased and the text bolded to enhance legibility
Line 278-280: "The results of this study vary from those of an earlier 278 study by Nkuna and Odiyo (2016), which reported 1982/83 and 1991/92 years as severely dry years."
How does this relate to chart 2 where the SPI_3 index is almost zero.
Response: The error has been corrected
Why is the data in Figure 3 not the same as in Figure 2? (SPI_3 low and high indicator)
Response: Figure 2 reflects the average SPI values for the entire catchment. On the other hand Figure 3 depicts the spatial variability of SPI, NDVI and VCI from one location to another within the catchment. The localised spatial variability of these indices does not necessarily correspond with that reflected by the time series in Figure 2 due to conditions characterizing different locations within the catchment.
line 305: "of 2.03, indicat-305 ing that 2006/7 was an extremely wet year" ???
Response: The error has been corrected
Lines 310-312: "As indicated by NDVI values (Figure 3) the highest vegetation vigour was widely 310 recorded in 1996, 2002, 2007 and 2011," - this data is missing in Figure 3
Response: The error has been corrected. The section has been rewritten and the regrettable error eliminated.
lines 338-340: "As shown in the results of this study, vegetation type plays a pivotal role in the 338 ability of the ability of plants to respond to rainfall variability, especially in rain-fed ag-339 ricultural areas." - where is it shown ??
Response: The error has been corrected. The section has been rewritten and the regrettable error eliminated.
The authors often refer to the results of the NDVI index, but the work lacks its results. My suggestion is to include them in the table.
Response:The relevant section has been rewritten and the regrettable error eliminated.
Rows 394-406: Why was only 10 years used to study the correlation? The results of the correlation coefficient are very strange here. I am particularly concerned about the result of 0.8166. I would suggest recalculating the data and using the rank correlation coefficient.
Response: We decided to use the Pearson Product Moment Correlation because we first considered the fact that both SPI_3 and VCI are continuous variables which are measurable on a ratio scale. We also took into consideration that there were no outliers in the data while linearity was relatively high. Lastly, SPI_3 and VCI data were available for all the years that were included in the analysis.
lines 408–479: discussion needs improvement. The authors omitted the results of their work in the discussion. In the discussion, the authors indicate what they would like to obtain or what others have obtained.
Response: We have reworked the discussion section and given more attention to our results.
lines 480–494: The conclusion needs to be corrected. It has nothing to do with work as it stands.
Response: The conclusion section has been reworked in line with the reviewer’s recommendation
The work requires careful checking.E.g:
line 397: -0.6172 no minus in the chart
Response: Error corrected
line 404: r = 3673
Response: Error corrected
line 513: 3139
Response: Error corrected
Submission Date
31 March 2021
Date of this review
06 Apr 2021 21:41:20
Author Response File: 
Author Response.docx
Reviewer 2 Report
Good introduction and discussion. You do a good job distinguishing between the different types of drought and flood. You also cover a lot of ground in this manuscript, and do it relatively well. You include discussions of many important topics and have well thought-out discussion and conclusions section.
My main two comments are:
1. This study is not directly about climate change. You do a wonderful job connecting drought to vegetation indices in different land cover types, and you can contextualize that with the fact that we know South Africa is projected to dry with climate change, but we can’t use Figure 2 alone to conclude that. It is insufficient evidence. All this means is that you need to revise the language of some of your results and the title of the paper.
2. You may want to consider using the CHIRPS precipitation data, which is an order of magnitude higher resolution, better matches your other datasets and is available for the same time period, rather than CRU. You can download the Africa monthly data here: https://data.chc.ucsb.edu/products/CHIRPS-2.0/africa_monthly/. The CRU data, while valuable and a reliable data source, relies on fewer gauge stations than other products, such as GPCC (Global Precipitation Climatology Centre data) and doesn’t include satellite information, as does CHIRPS. Given the small-scale study domain used here, it is not really possible to disaggregate the 0.5 degree resolution data to the finer-scale NDVI and EVI data because you are interpolating between distant stations to get information on very fine resolutions, which is why your SPI data is so overly smooth.
Comments:
Change title - add the specific domain (Luvuhvu River Catchment Area, or Limpopo River Basin), remove climate change and famine refs. This study deals with drought and food production, or drought and vegetation, not with climate change and food security. Although the results are absolutely relevant to both climate change and food security!
L59 - Flood - floods can occur without a river overflowing, I’d remove that part of the sentence since you bring up specifically riverine floods later. Flash floods, for example, which you allude to, wouldn’t necessarily involve a river at all.
Don’t equate above-normal precipitation with floods necessarily. These are excess precipitation years and should be referred to as such. The 3-month SPI will not tell you whether that precipitation was well distributed and beneficial for crops, or concentrated in a single intense rainfall event that led to widespread flooding.
L197 - You reference Dec-Feb as JFM, this is DJF. JFM is Jan - Mar
You can’t directly assume that the increase in drought is due to climate change. This may well be the case, but please provide a citation if you wish to say this.
Figure 2 - without tick marks it’s difficult to tell which bars are for what years.
L342-343 - you say all land use types were affected and had low NDVI in 1992 and 2016, but this looks to be true only in 2016. In 1992 all land use types had an NDVI that was average or above average, indicating little effect of the drought on vegetation greens.
In the following lines you talk about grasslands having low NDVI values, but they are the highest of all values in 2016, and in 1992, while they are lowest, they are still average (NDVI anomaly = 0)
It’s not clear that the you can tell the difference in the speed of the response between wetland vegetative health and grassland vegetative health using annual values. You only have one value per year, so you can’t differentiate based on timing, only based on the intensity of the drought (e.g. in a moderate drought year wetland areas may not be affected, while grassland or subsistence areas are)
Figure 3: please make the colorbars have the same range, and make them uniform around 0 for each variable. The colorbar can be different for different variables, but it needs to be the same for different years. It is impossible to compare across years or to tell where the 0 line is in the current figure.
In line 373 you say that “When the ground is submerged, wetland and irrigated areas record highest NDVI” but you just said (correctly, I believe) that open water gives negative NDVI values. So this high NDVI value is a result of the vegetation (as you say later) not a result of the submerged ground.
L420-421: you say “the results of this study confirm findings from earlier research which reported the Limpopo Province as getting drier as a result of increasing frequency of droughts”. Your study does not show anything related to climate change. To do this you’d need to show that the increasing frequency of droughts is statistically significant and related to anthropogenic activities rather than decadal variability or chance. It’s fine to refer to the results of your study in the context of past studies though, such as the one you cite.
L481-482: change to saying “differential effects of drought” rather than differential effects of climate change. As stated above, your study does a wonderful job analyzing drought, but it is not dealing directly with climate change. Provided that South Africa is projected to dry, it’s okay to say that these results of drought are relevant to climate change though. This may seem semantic, but it’s important that we not use short statistical records to indicate the effects of climate change, or else we’ll come to many incorrect conclusions.
Minor comments
- a number of hyphens in the middle of words where they shouldn’t be
Please check references for completeness. I only checked for the Kogan references, and they are missing.
Is the Barbieri reference correct? It looks unrelated
Author Response
Response to Review Report 2
Responses are in italics
Open Review
( ) I would not like to sign my review report
(x) I would like to sign my review report
English language and style
( ) Extensive editing of English language and style required
( ) Moderate English changes required
(x) English language and style are fine/minor spell check required
( ) I don't feel qualified to judge about the English language and style
|
Yes |
Can be improved |
Must be improved |
Not applicable |
|
|
Does the introduction provide sufficient background and include all relevant references? |
( ) |
(x) |
( ) |
( ) |
|
Is the research design appropriate? |
( ) |
(x) |
( ) |
( ) |
|
Are the methods adequately described? |
(x) |
( ) |
( ) |
( ) |
|
Are the results clearly presented? |
(x) |
( ) |
( ) |
( ) |
|
Are the conclusions supported by the results? |
( ) |
(x) |
( ) |
( ) |
Comments and Suggestions for Authors
The paper focuses on the analysis of climate change impacts in LRCA, South Africa. The topic is current and relevant, moreover, the spatial focus unquestionably defines a really vulnerable area. The paper is well-structured and follows the main formatting requirements, furthermore, it was written in quite good and easy-to-understand English. Besides these positive remarks, several modifications might be made before acceptance and publication to improve the quality of the paper; see my detailed comments below:
- Some abbreviations - such as SPI, SPI_3 and VCI - can be found in the Abstract. Please firstly clarify them before using these expressions;
Response: The terms, SPI, SPI_3 and VCI were explained
- A single sentence regarding the importance of the topic in South Africa might be added to the Abstract;
Response: The importance of the topic to South Africa has been stated
- line 54: "Stud-ies"; line 56: "intensi-ty"; line 62: "de-creasing" - please correct these typos;
Response: The typos have been corrected
- The Introduction section provides a comprehensive overview of drought and flood issues; however, it is nothing to do with the current trends regarding scientific focus. Please provide a solid literature review to prepare the ground for your further investigation and emphasize the importance of your study in the light of current and available other papers.
Response: The focus of the paper has been more clearly stated as that of filling an existing gap in literature regarding how local conditions determine the impact of climate change on the environment
- line 125-169: please consider adding some sentences to the existing paragraphs regarding the climatic conditions of the studied area, this aspect is slightly missing from the text. Moreover, please provide an overview map for illustrating the continental or even global location of the study area (Figure 1.). Otherwise, the description of Materials and methods is clear and correct.
Response: More information has been provided about the climatic conditions of the study area.
- line 338-339: please correct the confusing sentence;
Response: The sentence has been corrected
- Please clearly define the main limitations of the study and the applied methodology in the Discussion section.
Response: The limitations of the study have been stated as that of finding high resolution satellite data for the study.
- The conclusion section does not include any information with regards to the results, please add a short summary of the main outputs to the section.
Response: The error has been corrected.
Submission Date
31 March 2021
Date of this review
16 Apr 2021 11:29:34
Author Response File: Author Response.docx
Reviewer 3 Report
The paper focuses on the analysis of climate change impacts in LRCA, South Africa. The topic is current and relevant, moreover, the spatial focus unquestionably defines a really vulnerable area. The paper is well-structured and follows the main formatting requirements, furthermore, it was written in quite good and easy-to-understand English. Besides these positive remarks, several modifications might be made before acceptance and publication to improve the quality of the paper; see my detailed comments below:
- Some abbreviations - such as SPI, SPI_3 and VCI - can be found in the Abstract. Please firstly clarify them before using these expressions;
- A single sentence regarding the importance of the topic in South Africa might be added to the Abstract;
- line 54: "Stud-ies"; line 56: "intensi-ty"; line 62: "de-creasing" - please correct these typos;
- The Introduction section provides a comprehensive overview of drought and flood issues; however, it is nothing to do with the current trends regarding scientific focus. Please provide a solid literature review to prepare the ground for your further investigation and emphasize the importance of your study in the light of current and available other papers.
- line 125-169: please consider adding some sentences to the existing paragraphs regarding the climatic conditions of the studied area, this aspect is slightly missing from the text. Moreover, please provide an overview map for illustrating the continental or even global location of the study area (Figure 1.). Otherwise, the description of Materials and methods is clear and correct.
- line 338-339: please correct the confusing sentence;
- Please clearly define the main limitations of the study and the applied methodology in the Discussion section.
- The conclusion section does not include any information with regards to the results, please add a short summary of the main outputs to the section.
Author Response
The paper focuses on the analysis of climate change impacts in LRCA, South Africa. The topic is current and relevant, moreover, the spatial focus unquestionably defines a really vulnerable area. The paper is well-structured and follows the main formatting requirements, furthermore, it was written in quite good and easy-to-understand English. Besides these positive remarks, several modifications might be made before acceptance and publication to improve the quality of the paper; see my detailed comments below:
- Some abbreviations - such as SPI, SPI_3 and VCI - can be found in the Abstract. Please firstly clarify them before using these expressions;
Response: The terms, SPI, SPI_3 and VCI were explained
- A single sentence regarding the importance of the topic in South Africa might be added to the Abstract;
Response: The importance of the topic to South Africa has been stated
- line 54: "Stud-ies"; line 56: "intensi-ty"; line 62: "de-creasing" - please correct these typos;
Response: The typos have been corrected
- The Introduction section provides a comprehensive overview of drought and flood issues; however, it is nothing to do with the current trends regarding scientific focus. Please provide a solid literature review to prepare the ground for your further investigation and emphasize the importance of your study in the light of current and available other papers.
Response: The focus of the paper has been more clearly stated as that of filling an existing gap in literature regarding how local conditions determine the impact of climate change on the environment
- line 125-169: please consider adding some sentences to the existing paragraphs regarding the climatic conditions of the studied area, this aspect is slightly missing from the text. Moreover, please provide an overview map for illustrating the continental or even global location of the study area (Figure 1.). Otherwise, the description of Materials and methods is clear and correct.
Response: More information has been provided about the climatic conditions of the study area.
- line 338-339: please correct the confusing sentence;
Response: The sentence has been corrected
- Please clearly define the main limitations of the study and the applied methodology in the Discussion section.
Response: The limitations of the study have been stated as that of finding high resolution satellite data for the study.
- The conclusion section does not include any information with regards to the results, please add a short summary of the main outputs to the section.
Response: The error has been corrected.
Submission Date
31 March 2021
Date of this review
16 Apr 2021 11:29:34
Author Response File: 
Author Response.pdf
Round 2
Reviewer 1 Report
Thank you for considering my comments. I believe that the work may be published in its current form.
Reviewer 3 Report
The authors have largely restructured their manuscript based on my previously suggested recommendations. However, the changes cannot be traced easily, since the authors did not use any highlighting technique in their paper. Nevertheless, the paper can be accepted in its present form.
