Potential Spread of Desert Locust Schistocerca gregagia (Orthoptera: Acrididae) under Climate Change Scenarios

Round 1

Reviewer 1 Report

This manuscript presents an interesting study about how the ongoing climate change will impact on the distribution of the desert locust.

In general, the paper is technically convincing, but there are many aspects that should be improved, especially in terms of clarity.

The English requires substantial revision.

 

MAJOR ISSUES

1 Title: I think the title is not very clear and appropriate. I would suggest a more direct and simple title, like: Forecasting the spread of the desert locust under climate change scenarios

2 At lines 123-125, and 125-130, the authors introduce two sets of variables in the same way: “For the future bioclimatic factors”. Please, explain the difference between these two categories of climatic factors.

3 Were the 8 land-use variables calculated for the two scenarios? Please, clarify.

4 Please, specify the source of the DEM

5 At line 150 the authors say that they removed some variables because of high correlation, but do not explain which were eliminated and which were retained. If A and B are strongly correlated, it is correct than one of them is deleted, but it is important to specify which of the two and the reasons for choosing to delete, say, B and not A. The total set of variables, those which were deleted and reasons for the choice, might be provided as supplementary materials.

6 The same for lines 167-9

7 Explain what the importance values are and how they were calculated

8 Explain how suitability was calculated and why a 0.54 threshold was used

9 It is not clear what the values of changes in suitability (e.g. 0.3 at line 244; values in Figure 5, et cetera) mean (are they proportions? percentages?) and how they were calculated. Please, explain.

10 The analysis of niche conservation is not clear. Is this based only on current data (as I assume) or does it use future scenarios?). Please, clarify. In the method section the sentence “we considered only the conservation of climate niche to reduce the interference produced by other factors” is obscure. Do the authors mean that they did not consider land use and topographical predictors? If no future scenario is used, why the authors use “will” in the results?

11 Results presented in Figure 6 should be better explained.

Explain the meaning of equivalence and similarity for generalist readers, the meaning of Schoener D and what is represented as frequencies (frequencies of what?)

Explain what the PCA represents and how it was performed. Explain what is represented by solid and broken lines and blue and pink areas

Explain the meaning of BN, Bi and BSim (they are explained in the text, but should be also given in the Figure caption)

12 I disagree with the interpretation of results given at lines 281-286- First, I disagree with the statement that unfilled niches have a negligeable area. This is true for annual precipitation, and partially for minimum temperature, but not for mean temperature, where the green area is very large. Also, I think incorrect to say that the niche overlap did not change (actually, a better world would be “differ”); the overlap is a measure of overlap between native and invasion niches, so I cannot see how it might change.

Thus, I propose the following formulation (if I have correctly interpreted the analyses):

However, the invasion niche of mean temperature of the driest quarter is narrower than the native niche (Figure 7C). In general, most parts of the niche remain unchanged (Figure 7, blue part). The niche expansion (Figure 7, red part) is substantial for minimum temperature of the coldest month (Figure 7A) and annual precipitation (Figure 7B), being smaller for the mean temperature of the driest quarter (Figure 7C). Finally, unfilled niches (Figure 7, green part) are extremely small for the annual precipitation (Figure 7B), relatively small for the minimum temperature of the coldest month (Figure 7A), and relatively large for the mean temperature of the driest quarter (Figure 7C).

13 Figure 8 is not very clear because of the use of a scale reporting only the two extremes. I suggest using a different colour scale with some intervals (see, for example, https://commons.wikimedia.org/wiki/File:Elevation_Zones,_Global_%287242987984%29.jpg)

 

MINOR ISSUES

Line 14: delete pattern

14: researchers -> studies

15 : it -> this species

27: invasive -> invasion

35 : locusts (Schistocerca gregaria) in May 2019, -> locusts Schistocerca gregaria (Forskål, 1775) in May 2019,

37: 80 million/km2 in which places/conditions?

39: The desert locust [This is just an example of a situation in which I think the article the should be sued before desert locust; please, check and introduce where appropriate)

42: migrate over

50: by applying species distribution models (SDM)

53: add references for these others (are these references # 6 and 10 cited in the subsequent sentence?)

55: Since to the migration of desert locust being is affected

58: revise, the sentence is not understandable because of language problems

61: are key -> is essential

66: in new habitats or niches -> in new areas

70: to preventive control -> for preventively controlling

85: help us to

Figure 1. Please, explain what is figured in the inset in panel B

120: I’m not sure what the authors want to say. Perhaps: “We used a 2.5 arc-minute (approximately 5 × 5 km) grid for both the baseline period and future projections using bioclimatic variables”

123: typical concentration pathways -> scenarios

155: platform -> package

164: under the two scenarios RCP2.6 and RCP8.5.

229 et cetera: replace ~ with –

235-8: It is not clear how “the distribution of habitat suitable for desert locust will be similar” and at the same time “the high-, moderate-, and low-suitability habitat areas will increase”. Please, clarify

263: tests), and the -> tests. The

264: The results showed that the niche expansion -> The niche expansion

282: niche. (Figure 7C). -> niche (Figure 7C).

292: world, its -> world, since its

296: use might influence-> use that might influence

299: also be the key factors -> also be important factors

300; delete: (e.g., desert locust is densely distributed along the western side of the Himalayas)

304: delete: (importance value: 0.285; Table 1).

305-6: We attribute this finding to a negative effect of low temperatures on the mating ability and fertilization probability of male locusts, thus affecting the oviposition probability of female locusts.

313: humid -> moist

328: toward -> to

345-6. This sentence is ill-formulated. Please, correct.

349: origins -> the main range

356: the Eurasian plate -> Eurasia

360, 361, Figure 8: altitude -> elevation

371: to study -> to investigate

374: delete pattern

The English requires substantial revision. I included some suggestions among the minor issues, but the entire manuscript should be carefully revised.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments of reviewer

 Probably the title of paper may be corrected as follow (to stress the Latin names of taxa):

 

Potential impacts and drivers of the desert locust Schistocerca gregagia (Orthoptera: Acrididae) on the present and future global food security framework

 

Page 1, line 12

 

Printed:

The desert locust is one of the most harmful migratory pests in the world, posing a major ...

 

Replace for:

 

The desert locust Schistocerca gregagia (Forskål, 1775) is one of the most harmful migratory pests in the world, posing a major ...

 

Page 1, lines 34-36

 

Printed:

With the large-scale outbreak of desert locusts (Schistocerca gregaria) in May 2019, the serious impact of desert locusts on agricultural production again attracted people's attention [3].

 

Replace for:

 

With the large-scale outbreak of the desert locusts Schistocerca gregaria (Forskål, 1775) in May 2019, the serious impact of desert locusts on agricultural production again attracted people's attention [3]

 

Note of reviewer to Conclusions:

 

There are 34 species in the genus Schistocerca Stål, 1873 (Cigliano, M.M.; Braun, H.; Eades, D.C.; Otte D. Orthoptera Species File Online. Version 5.0/5.0. 2020. Available online: http://Orthoptera Species File.org), of them S. gregagia (Forskål, 1775) is known from Africa and Asia, one species - from the Galapagos Islands, one species - from the Philippines, and the rest species are known from North, Central and South America. It should be taken into account that the modern habitat of the Desert Locust has developed historically, and depends not only on the climate, but also on the type of vegetation and on the human economic activity. A few invasions of the Desert Locust into America and Australia have been noted, but the ways of probable migration of S. gregagia through the vast expanses of the Atlantic and Pacific Oceans are very problematic, especially considering that this is a phytophage and lays eggs in egg pods in the soil. Moreover, the numerous native species of Schistocerca are known from America; they has no economic value, but may limit the successful naturalization of Desert Locust because similarity of niches. This fact may be discussed in “Conclusions”.

 

Minor editing of Enlish language required. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The manuscript has been improved, but there are some points that  need further work.

 

1) TITLE: Delete “drivers”. Drivers are for spread, not for species.

2) Supplementary material: Names of variables should be given in full (what is bio1, bio2, etc.?), also for consistence with Table 1.

3) Supplementary material: Correct caption to Table S1 as follows: “The importance values of all variables in this table from the first model construction. The importance values in the Table 1 were calculated by model from the last residual variables, so the importance values in Table S1 are different from Table 1.” -> “”Importance values of all variables from a first model construction using all variables. The importance values shown in this table differ from those of Table 1, which are based on a reduced set.

4) Supplementary material: Correct caption to Table S2 as follows: “Table S2. Correlation analysis of the climate, land use and topographical factors. The values are Pearson correlation coefficient. Pearson correlation coefficients >0.7 are bold. *, P<0.05; **, P<0.01; ***, P<0.001.” -> “Table S2. Correlation analysis of the climate, land use and topographical factors. The values are Pearson correlation coefficients. Pearson correlation coefficients >0.7 are in bold. *, P<0.05; **, P<0.01; ***, P<0.001.”

4) Supplementary material: The authors must explain which variables were retain and why.

For example, given that Bio1 and Bio10 are highly correlated, which was retained? Bio1 or Bio10? Why?

5) Main text: Lines 182-184: These lines are not clear. Do the authors mean that they did not consider land use and topographical predictors?

6) Figure 5. Please, explain better what values of changes in suitability (Figure 5, et cetera) are. Does 0.3 mean 0.3 % or 30%

7) Figure 6. Explain that, in panel B, the solid and dashed contour lines illustrate 100% and 50% of the available environmental space, respectively

 

Minor

41: Desert locust mainly reside -> The desert locust mainly resides

157: the species distribution model, and it indicates the impact of that variable on -> the species distribution model, and hence its impact on

The English is relatively good, but a further check might be useful.

See, for example:

line 41: Desert locust mainly reside -> The desert locust mainly resides

Author Response

Please see the attachment.

Author Response File: Author Response.pdf