Sustainable Land Use Management Needed to Conserve the Dragon’s Blood Tree of Socotra Island, a Vulnerable Endemic Umbrella Species
, Hana Kalivodová 1, Josef Divín 2, Martin Rejžek 1, Jan Vybíral 1,3, Samuel Lvončík 1, David Jeník 4, Pavel Hanáček 4, Abdullateef Saad Amer 5 and Petr Vahalík 2
Round 1
Reviewer 1 Report
A review of a manuscript entitled “Sustainable land use management needed to conserve the dragon´s blood tree of Socotra Island, a vulnerable endemic umbrella species” for Sustainability (515595)
General comments
In this study, the authors documented the abundance and distribution of Dracaena cinnabari (a flagship, umbrella, endemic species of Socotra Island) to evaluate the conservation status of its overall population and sub-populations. Doing so, it would help identify and prioritize sustainable management for this species and other endemic species associated with it.
The authors used imagery to obtain species distribution and developed a conservation importance index, based on several aspects of the species, to evaluate the conservation status of each individual sub-population.
Although it is a good study, it has some limitations. For example, the extinction probability analysis leaves out all the variables considered important to delimit the conservation value of a given subpopulation. In other words, it seems that the extinction rate only takes into account the tree age and no other variable. I think this assessment is underestimating the factors behind the extinction of this species. Therefore, the extinction times may be shorter than those reported in this study.
Although Introduction provides important information on the occurrence and distribution of Dracaena cinnabari, none information on species biology (life cycle, dispersal mode, pollinators...) is provided in the introduction, methods or discussion. Adding such information will improve the characterization on the target species. In fact, I think these aspects should be better discussed. Part of the results, especially tables and figures, need to be improved greatly in presentation. When addressing the major issues and some minor issues listed below, the paper will be a good contribution to the sustainable management of this important species.
Specific comments (L: lines)
L 81: Change to “conservation status of its overall population”
L 99: Correct here “1 km2 -squares”
L 131: Change “altitude” to “elevation”; see McVicar and Körner (2013).
L 146: Change “Dracaena” to “D.”
L 170: By order, it should be called Table 3. Maybe change to “see Results”.
L 193: Remove the second “of”
L 195: Change to “elevational”
L 202: Remove the “is”. Besides, change to “The smallest area (11 ha) occupied”
L 203: Remove the comma and “it”
L 208: Change to “(below 180 m a.s.l.); their absence”; besides, could they be present in the highlands in the western portion?
L 210-211: Is it and objective? The method used to do this should be properly described in the Methods section.
L 212: Is the genus name used as the popular name here? Is it ok for this species?
L 217: Is it a discussion?
L 223-224: Remove “the method published by”
L 225: Measures of variation are needed here (sd, se, max-min)
L 231: Change to “a visibly”
L 250: Are the authors really saying they have “low conservation importance”? Is it the main message? Are the authors talking about conservation prioritization?
L 275: Video S1
L 363: Is “tribal” an inappropriate term here? I think so.
L 373-374: Change to “for many years,”
L 406: Video S1
Figure 1: A high quality image is needed here. It should be a supplementary document.
Figure 2: I would change “Vital trees” to “Living trees”; besides, I would put the North symbol at top right corner; the scale bar at bottom left corner.
Figure 4: This figure could be greatly improved by using color and filled symbols. The 95% confidence interval should be supplied as well.
Figure 5 and 6: They should be greatly improved. Lines around and within the plot should be avoided. Y-axis is missing, including its label. These figures do not match the general style of other figures. I think these data could be provided as a table for all subpopulations.
Figure 7: This figure could be greatly improved by using color and filled symbols. The 95% confidence interval should be supplied as well.
Table 1: It should be a supplementary document.
Table 3: “Mean elevation”
Table 5: Variable names should be self-explained.
References
McVicar TR & Körner C (2013) On the use of elevation, altitude, and height in the ecological and climatological literature. Oecologia 171: 335-337. doi:10.1007/s00442-012-2416-7.
Author Response
Reviewer comments:
1) Although it is a good study, it has some limitations. For example, the extinction probability analysis leaves out all the variables considered important to delimit the conservation value of a given subpopulation. In other words, it seems that the extinction rate only takes into account the tree age and no other variable. I think this assessment is underestimating the factors behind the extinction of this species. Therefore, the extinction times may be shorter than those reported in this study.
Response: The extinction model is based on a mortality rate that was investigated in the field and expressed in the mortality curve. We found natural mortality without differentiation what factor caused it. But it doesn´t mean that it is underestimated. We have devoted part of the discussion to this issue. Underestimation is only in case of catastrophic events as cyclons in November 2015. This issue we are preparing to the next paper.
2) Although Introduction provides important information on the occurrence and distribution of Dracaena cinnabari, none information on species biology (life cycle, dispersal mode, pollinators...) is provided in the introduction, methods or discussion. Adding such information will improve the characterization on the target species. In fact, I think these aspects should be better discussed. Part of the results, especially tables and figures, need to be improved greatly in presentation. When addressing the major issues and some minor issues listed below, the paper will be a good contribution to the sustainable management of this important species.
Response: We added requested information to the Introduction (lines 67-69, 121-131)
3) Specific comments
Answer: Thank you for careful reading of our manuscript, we made every recommended changes.
L 208: Change to “(below 180 m a.s.l.); their absence”; besides, could they be present in the highlands in the western portion?
Response: It is a scientific question still without solution. There is no evidence for DBT occurence in the past yet. But it doesn´t mean that DBT didn´t occure in this area and population was destroyed by human´s resin harvesting.
L 210-211: Is it and objective? The method used to do this should be properly described in the Methods section.
Response: The description was moved from chapter Results to the chapter Material and methods (lines 266-267).
L 212: Is the genus name used as the popular name here? Is it ok for this species?
Response: Dragon´s blood tree is common name for Dracaena cinnabari.
L 217: Is it a discussion?
Response: This sentence was deleted.
L 225: Measures of variation are needed here (sd, se, max-min)
Response: Age data were removed from the Table 2 (recently Table 1) and new Table 4 (lines 445-520) was created including measures of variation.
L 363: Is “tribal” an inappropriate term here? I think so.
Response: The people are living in tribes on Socotra, thus we hope to use this term properly.
4) Figures and tables
Figure 1: A high quality image is needed here. It should be a supplementary document.
Answer: We made a high quality figure. The decision whether to include the picture directly in the text or as a supplement we leave to the editorial board decision.
Figure 2: I would change “Vital trees” to “Living trees”; besides, I would put the North symbol at top right corner; the scale bar at bottom left corner.
Answer: It was done.
Figure 4: This figure could be greatly improved by using color and filled symbols. The 95% confidence interval should be supplied as well.
Response: It was done.
Figure 5 and 6: They should be greatly improved. Lines around and within the plot should be avoided. Y-axis is missing, including its label. These figures do not match the general style of other figures. I think these data could be provided as a table for all subpopulations.
Response: Fig. 5 was done. Fig. 6 was deleted and replaced by table 4 (line 445 - 520) providing data for all sub-populations as requested.
Figure 7: This figure could be greatly improved by using color and filled symbols. The 95% confidence interval should be supplied as well.
Response: It was done.
Table 1: It should be a supplementary document.
Response: It was done.
Table 3: “Mean elevation”
Response: It was done.
Table 5: Variable names should be self-explained.
Response: Variable names were explained in chapter Material and methods including their abbreviations.
Reviewer 2 Report
The manuscript “Sustainable land use management needed to conserve the dragon´s blood tree of Socotra Island, a vulnerable endemic umbrella species “deals with the assessment of the population size, extinction time, conservation status of Dracena cinnabari on Socotra Island (YE) and presents suggestions for the sustainable land management of the Island. It presents an impressive collection of data that allows a deepening of the knowledge about this very important and interesting species. The methods adopted to assess the above-mentioned variables are reasonable. Therefore, the contribution could be interesting to wider scientific audience, but some additional work is recommended. The main problem that the manuscript has is the way that it is presented and the absence of relation between the deep analysis of dracaena populations and the suggested management options. Main concerns are:
- I think that the title and the aims listed in the introductions are misleading. No data about the listed threats and pressures such as grazing, dragon’s blood harvesting, cutting are presented and related to the conservation status of dracaena populations, thus the management measures suggested are important and interesting but also speculative, they don’t represent the core of the paper.
- The only real novelty of the paper, the new developed Conservation Importance Index is not so clearly explained and it seems to me not so powerful. It could be improved adding factors representing the main threats to Dracena populations as I suggest in the following.
- A deep revision of English is needed. Below, I tried to point out some of these problems, but there are also additional ones that I could not locate or I did not comment.
Detailed comments
Line 106: “we estimate that they constitute only 2-3% of the island’s” how? Clarify, please
Line 123: Clarify the difference between crown age and tree age. How different are they? Is it known or are there any hypothesis?
Line 129-131: Why do you consider altitude as a predictor of sub-popultion isolation? Please explain.
Line 136-137: Conservation Importance and assessment of Conservation Status are not the same. The definition of the index is not so clear. Please explain it better.
Line 140: It's not clear to me what is the "individual habitat type". Explain better
Line 141: I suggest to use Land Cover classes according Král and Pavliš
Line 141: HTA are all capital letter in the Equation 2
Line 140-148: The scale of values you listed in Table 2 seems more related to biomass value Dracena suitability than to the distance from potential vegetation. It seems that you consider the potential vegetation of all Land Cover classes of Socotra as forest, thus, e.g., “limeston rock”, “basement rock”, “wadis” have the lower values, but probably the steep rock of the Hagghier mountains, inaccessible wadis or dwarf shrubs on alluvial sediments in arid locations are not so far from the potential vegetation. Explain better and consider to add factors related to disturb intensity such as, e.g., distance to villages or other proxies of grazing pressure. I agree with you, and all previous studies, that overgrazing is the most important threat to Dracena populations.
Line 216-217: We can't be sure about that from your data, it's better to insert "probably". Dracena could be rare in grasslands or shrubland also for ecological reason.
Line 217: Why do you write "also"? Do you mean that the degradation of habitat you mention in the previous sentence has a different origin? Explain better, please
Line 258: The numbers of the sub-populations in the first column of table 5 are wrong! They follow the decreasing CI values.
Line 270: Tab. 3
Line 277: It seems to me more appropriate to move this section 4.1 in Methods ("Assessment of Accuracy" or something similar) and results ("Accuracy"). It is not a discussion, the interpretation of your results.
Line 304: write "in the IUCN.." instead of "on the IUCN..."
Line 322: write: over half of the trees
Line 361: delete "this way"
Line 362: Due to the weak
I suggest a deep revision by a mother tongue.
Line 389-392: this is too speculative, I suggest to delete this sentence
Author Response
Reviewer comments:
1) The main problem that the manuscript has is the way that it is presented and the absence of relation between the deep analysis of dracaena populations and the suggested management options. I think that the title and the aims listed in the introductions are misleading. No data about the listed threats and pressures such as grazing, dragon’s blood harvesting, cutting are presented and related to the conservation status of dracaena populations, thus the management measures suggested are important and interesting but also speculative, they don’t represent the core of the paper.
Response: We added a new chapter to the results focusing on sustainable land management measures which were done by our team in selected Firmihin pilot area as an example of practical application of our research (lines 666-687, Supplement S1). This change requires the addition of new co-authors to the team of authors. Also the term "Conservation status evaluation" we excluded from the manuscript and substitute it by "Conservation importance evaluation".
2) The only real novelty of the paper, the new developed Conservation Importance Index is not so clearly explained and it seems to me not so powerful. It could be improved adding factors representing the main threats to Dracena populations as I suggest in the following.
Response: We explained in more detail the new developed Conservation Importance Index (lines 252-256). Recently, we can´t to add factors representing the main threats to Dracena populations because such data are not available for all sub-populations without field survey). In case of our developed Index, we used advantages of all detectable data from remote senzing imageries.
3) Line 106: “we estimate that they constitute only 2-3% of the island’s” how? Clarify, please
Response: It was clarified (line 181)
4) Line 123: Clarify the difference between crown age and tree age. How different are they? Is it known or are there any hypothesis?
Response: This issue was clarified in the Introduction adding new part focused on life cycle of dragon´s blood tree (lines 121-131)
5) Line 129-131: Why do you consider altitude as a predictor of sub-popultion isolation? Please explain.
Response: It was explained (lines 223-248)
6) Line 136-137: Conservation Importance and assessment of Conservation Status are not the same. The definition of the index is not so clear. Please explain it better.
Response: We substitute the term Conservation status evaluation used in manuscript by Conservation importance evaluation. The definition of new developed Index was better explain (lines 252-256).
7) Line 140: It's not clear to me what is the "individual habitat type". Explain better.
Line 141: I suggest to use Land Cover classes according Král and Pavliš
Response: The term Habitat type was subsitute by term Landcover class (in fact we didn´t distinguish these two terms.
8) Line 140-148: The scale of values you listed in Table 2 seems more related to biomass value Dracena suitability than to the distance from potential vegetation. It seems that you consider the potential vegetation of all Land Cover classes of Socotra as forest, thus, e.g., “limeston rock”, “basement rock”, “wadis” have the lower values, but probably the steep rock of the Hagghier mountains, inaccessible wadis or dwarf shrubs on alluvial sediments in arid locations are not so far from the potential vegetation. Explain better and consider to add factors related to disturb intensity such as, e.g., distance to villages or other proxies of grazing pressure. I agree with you, and all previous studies, that overgrazing is the most important threat to Dracena populations.
Response: The mentioned Landcover classes had in our Table value 1 (basement and limestone rocks) - the same like forests, the value of Wadis was decreased because only large inhabited wadis were recognized in Landcover map (Král and Pavliš).
9) Line 216-217: We can't be sure about that from your data, it's better to insert "probably". Dracena could be rare in grasslands or shrubland also for ecological reason.
Response: It was accepted.
10) Line 217: Why do you write "also"? Do you mean that the degradation of habitat you mention in the previous sentence has a different origin? Explain better, please
Response: This sentence was deleted.
11) Line 258: The numbers of the sub-populations in the first column of table 5 are wrong! They follow the decreasing CI values.
Response: Thanks for your careful reading, it was revised.
12) Line 270: Tab. 3
Response: Thanks for your careful reading, it was revised.
13) Line 277: It seems to me more appropriate to move this section 4.1 in Methods ("Assessment of Accuracy" or something similar) and results ("Accuracy"). It is not a discussion, the interpretation of your results.
Response: It was done accordingly, one part was moved to the Methods (lines 191-199) and second part to the Results (lines 344-360)
14) Line 304: write "in the IUCN.." instead of "on the IUCN..."
Response: It was revised.
15) Line 322: write: over half of the trees
Response: It was revised.
16) Line 361: delete "this way"
Response: It was revised.
17) Line 362: Due to the weak
Response: It was revised.
18) Line 389-392: this is too speculative, I suggest to delete this sentence
Response: We added citations of sources as a proof it isn´t speculative.
19) I suggest a deep revision by a mother tongue.
Response: It was done by Jonathan Rosenthal, the native English speaking scientific editor
Reviewer 3 Report
General Remarks
This is an important paper by an experienced research group, based on direct field data and scientific methods. I very much appreciate the practical remarks for conservation measures. The paper is more alarming than it actually seems, because a few centuries for its extinction is a small moment in comparison to the age of this important insular endemic, and its decline is entirely related to human impact (indirect through climate change, and direct through use of land and the trees themselves). Therefore, I think this paper is one of the most important, or the most important, that has so far been written about the conservation of the Socotra dragon’s blood tree. This has both scientific as well as practical conservation importance. A few small recommendations and suggestions are included below.
Introduction
- Local changes in traditional grazing are known to affect the terrestrial landscape on Socotra – please refer to Pietsch & Morris, 2010 on the changes in Homhil
- For the traditional uses, please consider also referring to Morris’ (unpublished) Socotra cultural use manual, if possible (depending on journal requirements for publications)
Materials and Methods
- Please include how you discerned between D. cinnabari and potentially other umbrella-shaped trees sometimes found together, such as Euphorbia arbuscula.
- The Conservation Importance Index – as this is developed here, please elaborate a bit more, for example if there are similar methods or papers that can be referred to, that it is based on. Also mention also that you use an index, in the abstract.
- Perhaps explain a bit more on how the model calculates the extinction rate over time (linked to S2) and if there is empirical evidence of extinctions, and where the model has been used in other trees (not on Socotra)
Discussion
- This is just a thought: there may be other, yet unknown, factors that affect the dragon’s blood tree decline through indirect climate or other effects (e.g., insects, disease, further land erosion and loss of good soil for regeneration) and further a genetic reduction of the population through population contraction; there have been no molecular surveys of population structure to help understand if some of these sub-populations are more rare than others and need special conservation attention. Could the latter (a molecular survey) be also a helpful conservation recommendation?
- Please mention how long it would take for a dragon’s blood tree to have to be fenced to escape goat grazing, and how large an area should be ideally conserved for the species survival.
- In the last part of the discussion, on the recommendations for protection, please put this in a slightly broader context: are there potential examples of conservation success that worked for other trees in perhaps similar environments? If there are none, innovative methods are necessary. Do you consider the Socotra species to be a larger conservation challenge than to other dragon blood tree relatives in other places? I guess also the local human “will” to want to conserve the species and a community effort are crucial here, so the more the local people are involved, as you do in your projects, the better.
- Please explain why large-scale replantation efforts of Dracaena are not feasible (slow growth; connected to the point of how long it takes for a tree to escape browsing), how labor intensive it is, and what percentage normally survives replantation.
- This is a side thing, but could climate change effects such as cyclones strongly speed up the extinction rate? For example, your model calculates the loss over centuries, but strong effects were visible after the last cyclones. Perhaps this is work in progress, but how many cyclones of the same intensity as the previous ones would it take to wipe out most of the adult trees on the island? I would suggest to mention that climate effects and land use changes may strongly further speed up the predictions presented here.
Small remarks in the text:
Page 1. Line 15: “one of the most important threats” (not “threat”)
Page 1. Line 16: “dragon’s blood tree (Dracaena cinnabari)” (add latin name)
Page 1. Line 18: “population size of D. cinnabari” (add name)
Page 1. Line 23: “extinction time ranging from” (add verb also here)
Page 1. Line 31: “at which time adaptation” (not pre-adaptation)
Page 1. Line 37: “political situation” (not “politic”)
Page 1. Line 40: “The Dragon’s blood tree” (add “the”)
Page 1. Line 42: “Dracaena” (in italics)
Page 1. Line 43: “Cenozoic relict” (instead of “tertiary”)
Page 2. Line 47: “toponyms” (not “toponyms”)
Page 2. Line 58-59: “Decreasing dragon’s blood tree” (delete “Therefore” – every sentence here starts with these transition words (furthermore, moreover, therefore), but the next sentence is clearly enough and does not need one)
Page 3. Line 78-79: “escape the browsing zone” (delete “from”)
Page 3. Line 81: “as possible using remote sensing and ground data”
Page 3. Line 81: “status of its overall population” (add “its”)
Page 3. Line 81-82: “The steps” (replace “these” with “the”)
Page 3. Line 99: “1 km² squares” (not 1 km2 -squares)
Page 3. Line 102: do you mean “total area”?
Page 4. Line 128: we obtained an index value for each tree describing its average distance from” (restructure the sentence)
Page 4. Lines 136-137. “We developed the Conservation Importance Index (CI) for evaluation of the conservation status of each individual sub-populations, which was calculated using Equation 1.”
Page 6: use “transect” instead of “belt” throughout the manuscript
Page 6. Line 200. “in the southwest” (replace “on” by “in”)
Page 7. Line 211. “the trees’ distribution map” (not “tree’s”, the genitive sign is after the plural here, because it is not about an individual tree)
Page 8. Line 217. “by human activities” – define briefly which activities you mean
Page 10 Caption Figure - Please consider including general names of areas in the caption, not just numbers for the areas
Page 10. Line 250 use “relatively lower” here – not “low”, it is in relation to each other, but in fact all these trees are conservation priority…
Page 10. Line 256. “western ridge of the species’ occurrence”
Page 10. Line 257. “whole central highlands” – I would suggest to remove “Hagher” here because the area must have been bigger than just the central Hagher highlands alone, but extending on the high plateaus (with different names of course); also you use “Hagher” in the tekst, but “Haggeher” in the toponym map (Fig. 1), use one spelling consistently
Page 11. Line 268. Figure 7. “Mortality curve of Dracaena cinnabari” – for captions I would use the latin name or/and Socotra Dragon’s Blood Tree
Page 12. Line 304. “the dragon’s blood tree”
Page 12. Line 317-318. “more than half” (remove “one”)
Page 12. Line 319. “3% of the trees belongs” (put verb in singular for percentage)
Page 12. Line 320. “almost do not occur” or “are not found” - something cannot almost exist, it either exists or not. But something can almost occur or not occur, or is almost not found.
Page 12. Line 323. If you use Dracaena, please put in italics. In the manuscript, dracaena, Dracaena and Dracaena are used as three versions – perhaps use one format consistently
Page 12. Line 330 “for the growth of dragon’s blood trees”
Page 13. “such a huge contraction” (perhaps - instead of “retreat”)
Page 13. Line 343. “and woodlands which function”
Page 13. Line 352. “of the dragon’s blood tree”
Page 13. Line 352. “it takes them many years to escape the browsing zone”
Page 13. Line 363. “of the society”
Page 13. Line 364. “we have to find land management measures” (“any measures” is not correct english; “any measure” correct, or just “measures”)
Page 13. Line 366. “planting home gardens” (delete “of”)
Page 13. Lines 373-374. “excluded for many years” (delete “a”) – “exceeding the ?? of any given fence” word missing here, you mean “height”?
Page 13. Line 373-374. Question: How many years minimally ?
Page 13. Line 379. Delete “which” – “Such an approach is very much connected to”
Page 14. Line 394. “from a lack of natural regeneration” (insert “a”)
Page 14. Line 401. “without changing the current” (remove “from”)
Page 14. Line 403. “save the dragon’s blood tree”
Page 16. Line 485. “Van Rampelbergh” (one “l”)
Author Response
Responses to the reviewer comments:
1) Local changes in traditional grazing are known to affect the terrestrial landscape on Socotra – please refer to Pietsch & Morris, 2010 on the changes in Homhil
Response: I have not this book and it is not possible to get it in such short time that we have for manuscript revision. Moreover, this source described the soil erosion in locality, where population of Boswellia elongata occures no Dracaena cinnabari.
2) For the traditional uses, please consider also referring to Morris’ (unpublished) Socotra cultural use manual, if possible (depending on journal requirements for publications)
Response: Miranda Morris described it in Ethnoflora of Soqotra Archipelago, we reffered this source. I think this unpublished source would be redundant.
3) Please include how you discerned between D. cinnabari and potentially other umbrella-shaped trees sometimes found together, such as Euphorbia arbuscula.
Response: Explanation was added (lines 183-189)
4) The Conservation Importance Index – as this is developed here, please elaborate a bit more, for example if there are similar methods or papers that can be referred to, that it is based on. Also mention also that you use an index, in the abstract.
Response: Usage of Index was mentioned in the abstract (lines 26-27)
5) Perhaps explain a bit more on how the model calculates the extinction rate over time (linked to S2) and if there is empirical evidence of extinctions, and where the model has been used in other trees (not on Socotra)
Response: The explanation of the model calculation (lines 311-316). New sub-chapter was added to the Discussion (lines 847-915) where requested information is mentioned.
6) This is just a thought: there may be other, yet unknown, factors that affect the dragon’sblood tree decline through indirect climate or other effects (e.g., insects, disease, further land erosion and loss of good soil for regeneration) and further a genetic reduction of the population through population contraction; there have been no molecular surveys of population structure to help understand if some of these sub-populations are more rare than others and need special conservation attention. Could the latter (a molecular survey) be also a helpful conservation recommendation?
Response: Such study was carried out for Dracaena cambodiana but individual populations of this species are more isolated than those on Socotra.
7) Please mention how long it would take for a dragon’s blood tree to have to be fenced to escape goat grazing, and how large an area should be ideally conserved for the species survival.
Response: see line 841.
8) In the last part of the discussion, on the recommendations for protection, please put this in a slightly broader context: are there potential examples of conservation success that worked for other trees in perhaps similar environments? If there are none, innovative methods are necessary. Do you consider the Socotra species to be a larger conservation challenge than to other dragon blood tree relatives in other places? I guess also the local human “will” to want to conserve the species and a community effort are crucial here, so the more the local people are involved, as you do in your projects, the better.
Response: see lines 970-975.
9) Please explain why large-scale replantation efforts of Dracaena are not feasible (slow growth; connected to the point of how long it takes for a tree to escape browsing), how labor intensive it is, and what percentage normally survives replantation.
Response: This issue we have already published (Maděra et al. Biologia, 2019)
10) This is a side thing, but could climate change effects such as cyclones strongly speed up the extinction rate? For example, your model calculates the loss over centuries, but strong effects were visible after the last cyclones. Perhaps this is work in progress, but how many cyclones of the same intensity as the previous ones would it take to wipe out most of the adult trees on the island? I would suggest to mention that climate effects and land use changes may strongly further speed up the predictions presented here.
Response: see lines 907-909, we are preparing another paper focused on this issue.
11) Specific comments
Response: We have accepted most of recommendations. Many thaks for careful reading.
Reviewer 4 Report
This article explores new methods of quantifying the population and distribution of dragons blood tree on Socotra island. The authors identify different sub populations, conservation indices, and mortality rates. The methods behind sub populations must be elaborated on (see below) as this is not clear. While the article reads well, there is a major disconnect behind the introduction and discussion with the methods and results. The main aims of the paper aren’t set up in the introduction and the results aren’t discussed in the context of sustainability in the discussion. The results are interesting and could make an interesting contribution, but I suggest a thorough rewrite to better clarify all stages of this research. The paper is very site specific, with little elaboration beyond Socotra.
How are your results and methods outlined here directly influencing the sustainability (and SI topic)? The introduction is geared up towards sustainability, but there is a disconnect with the rest of the article. There is no mention of RS, populations, and mortality in your introduction, and it’s unclear what specific questions you want to address. To this end, rewrite your research objectives. Could you phrase these as a set of questions? This would allow the aforementioned point regarding how your research relates to the overall topic of sustainability. You have a clear set of methodologies that you could explicitly relate these to. Otherwise, it is unclear why you are undertaking all these different methods, for example mortality.
Perhaps incorporating some wider literature on the key themes - occupancy, remote sensing of vegetation, sub-population dynamics would also aid you. The introduction is very site specific. Therefore limiting your readership. It reads well, but you could quite easily shift the focus to incorporate more topics, and given the lack of clarity, this is something I suggest your article needs.
More explanation in section 2.1 is needed on assessing accuracy. This should not be in the discussion, the methods and data used should be clearly stated in your methods, and findings in the results. Otherwise your subsequent results cannot be evaluated with rigour until you state your accuracy. What about mis-identification (eg other species)?
Your explanation on sub-population delineation is underdeveloped. Why have you chosen altitude and distance to nearest tree as the relationship? How have you used the kernel? Did you iteratively choose neighbourhood distances or one fixed distance? If the latter, how did you choose this? This seems like an odd method to choose clusters, given the number of other methods out there. Why is the nonstationarity of distance-altitude relationship an indicator of population clusters? This needs a thorough explanation, considering most of the article is based on these sub populations.
Your discussion is completely disconnected from your results. What ‘new’ material are you suggesting based on your analysis. These appear to be a rehash or other suggestions, that have not been informed by the analysis. What sub-populations need protection? Do these differ from current strategies? Section 4.2 is an elaboration on your introduction. This is discussion material, and perhaps should not be in the introduction. However, it is lengthy and perhaps could be reduced. Section 4.3 should be based on your results, otherwise what was the point of the analysis.
Other comments
L13 - threat should be plural
Abstract - add Yemen or Indian Ocean to the location to give context
L36-37 - rewrite this sentence. Being politically unstable does not led to geographic isolation
L42 - explain what monocotyledonous means to increase readability
L52 - again, outline what a nurse plant is to the wider readers (some of you’re readers will be remote sensors and pastoral experts where these terms are not used frequently)
L56-58 - good - this is the type of explanation I’m asking for the above terms
L62 “more generally” is unnecessary
Table 1 - would this be more suitable as supplementary information?
Figures 5-6 - would there be a better way to represent this information (for all sites). A table might allow you to do this, and portray the information in just an effective manner. Like table 5 but for age
Author Response
Repsonse to reviewer comments:
1) While the article reads well, there is a major disconnect behind the introduction and discussion with the methods and results. The main aims of the paper aren’t set up in the introduction and the results aren’t discussed in the context of sustainability in the discussion. The results are interesting and could make an interesting contribution, but I suggest a thorough rewrite to better clarify all stages of this research. The paper is very site specific, with little elaboration beyond Socotra. How are your results and methods outlined here directly influencing the sustainability (and SI topic)? The introduction is geared up towards sustainability, but there is a disconnect with the rest of the article.
There is no mention of RS, populations, and mortality in your introduction, and it’s unclear what specific questions you want to address. To this end, rewrite your research objectives. Could you phrase these as a set of questions? This would allow the aforementioned point regarding how your research relates to the overall topic of sustainability. You have a clear set of methodologies that you could explicitly relate these to. Otherwise, it is unclear why you are undertaking all these different methods, for example mortality.
Response: The description of objectives of the study was completed with the set of questions (lines 137-140), we also added into Results new sub-chapter focusing on practical sustainable land managament measures to support the link between title and manuscript content (lines 666-687, Supplement S1).
2) Perhaps incorporating some wider literature on the key themes - occupancy, remote sensing of vegetation, sub-population dynamics would also aid you. The introduction is very site specific. Therefore limiting your readership. It reads well, but you could quite easily shift the focus to incorporate more topics, and given the lack of clarity, this is something I suggest your article needs.
Response: We incorporated wider literature on population viability analysis into Discussion (lines 847-915).
3) More explanation in section 2.1 is needed on assessing accuracy. This should not be in the discussion, the methods and data used should be clearly stated in your methods, and findings in the results. Otherwise your subsequent results cannot be evaluated with rigour until you state your accuracy. What about mis-identification (eg other species)?
Response: We added more explanation into Material and methods (lines 183-189), moved part of Discussion into Material and methods (lines 191-199) and Results (lines 344-360).
4) Your explanation on sub-population delineation is underdeveloped. Why have you chosen altitude and distance to nearest tree as the relationship? How have you used the kernel? Did you iteratively choose neighbourhood distances or one fixed distance? If the latter, how did you choose this? This seems like an odd method to choose clusters, given the number of other methods out there. Why is the nonstationarity of distance-altitude relationship an indicator of population clusters? This needs a thorough explanation, considering most of the article is based on these sub populations
Response: Sub-populations delineation is more explained in lines 223-248.
5) Your discussion is completely disconnected from your results. What ‘new’ material are you suggesting based on your analysis. These appear to be a rehash or other suggestions, that have not been informed by the analysis. What sub-populations need protection? Do these differ from current strategies? Section 4.2 is an elaboration on your introduction. This is discussion material, and perhaps should not be in the introduction. However, it is lengthy and perhaps could be reduced. Section 4.3 should be based on your results, otherwise what was the point of the analysis.
Response: We thoroughly overwrite Discussion. Also we delated some sentences from Introduction or Discussion to avoid repetitions in the mansucript.
6)
L13 - threat should be plural
Abstract - add Yemen or Indian Ocean to the location to give context
L36-37 - rewrite this sentence. Being politically unstable does not led to geographic isolation
L42 - explain what monocotyledonous means to increase readability
L52 - again, outline what a nurse plant is to the wider readers (some of you’re readers will be remote sensors and pastoral experts where these terms are not used frequently)
L62 “more generally” is unnecessary
Response: We accepted all specific comments and added requested explanations.
Table 1 - would this be more suitable as supplementary information?
Response: We moved Table 1 into supplementary material
Figures 5-6 - would there be a better way to represent this information (for all sites). A table might allow you to do this, and portray the information in just an effective manner. Like table 5 but for age
Response: We made new Table with requested informations for all sub-populations and delated Fig. 6 (lines 453-529)
Round 2
Reviewer 1 Report
Second review of “Sustainable land use management needed to conserve the dragon´s blood tree of Socotra Island, a vulnerable endemic umbrella species” for Sustainability (sustainability-515595)
General comments
After reading that second version, I was able to see the authors' effort in addressing my suggestions to the paper. That way, I am satisfied with the current version and suggest the paper to be published.
There are minor details to be corrected yet: e.g. D.cinnabari (add space; L 101); …numbers. (6 examples… (remove the point; L 132); paragraph L 352; „browsing zone” (L 425). Please, go throughout the paper addressing these minor issues.
Author Response
All minor recommendations were corrected.
Reviewer 4 Report
I’m not convinced the authors have addressed my concerns in much detail. It is clear that text has been added in the relevant places, but this hasn’t been targeted at the disconnect between intro and discussion with the methods and results. Table 4 has added a lot, but the rest of the article is still disjointed. Your new section 3.6 seems out of context with the rest of the article, and shouldn’t be there. If your going to outline the context for another study, then this should be another article, not tagged onto the end of results. RQ 3 is now out of sync with the additional text before hand. If extinction isn’t an issue for this species, you make no attempt to then explain why your running population viability with extinction time as a main output. The rewrite and increased explanation was not undertaken in a rigorous manner, and the original concerns from the previous review persist.
L177- AIC or AICc? There is a difference between text and acronym
Author Response
Repsonse to reviewer comments:
1) I’m not convinced the authors have addressed my concerns in much detail. It is clear that text has been added in the relevant places, but this hasn’t been targeted at the disconnect between intro and discussion with the methods and results. Table 4 has added a lot, but the rest of the article is still disjointed. Your new section 3.6 seems out of context with the rest of the article, and shouldn’t be there. If your going to outline the context for another study, then this should be another article, not tagged onto the end of results. RQ 3 is now out of sync with the additional text before hand. If extinction isn’t an issue for this species, you make no attempt to then explain why your running population viability with extinction time as a main output. The rewrite and increased explanation was not undertaken in a rigorous manner, and the original concerns from the previous review persist.
Response: Beside previous extension of Introduction (by dragon´s blood tree biology), we have now incorporated wider literature on remote senzing in vegetation mapping (lines 75-84) and on population size and structure (lines 97-108), both with emphasis on dragon tree group as Marrero et al. (1998) defined. We have also added new part into Discussion focused on traditional management of dragon trees and its influence on population development. Thank you for your comments that helped us to improve manuscript, We hope, now there is no disconnection among individual parts of manuscript. We tried to add as many as possible "wider information" and to keep manuscript consistent at the same time. All objectives set up in the Introduction have been met in the Results. We also placed the part of Methodology and Results focused on extinction ahead of Conservation Importance Evaluation, to stress that Conservation Importance Evaluation is the most important part of the work, not extinction time. Explanation why we developed extinction model is written in lines 120-122. The new section 3.6 was added because more reviewers didn´t find the link with sustainable land management (including you in the first review: "Section 4.3 (=Suggestions for sustainable land management measures in first version of manuscript) should be based on your results"). I am not sure if our practical maesures provide enough data for new scientific article but in the context of Conservation Importance Evaluation it seems to be a suitable component of article associated with subsequent discussion (recent section 4.4.). New paragraph was added into Conclusions focused on the main achieved results (lines 676-701).
2) L177- AIC or AICc? There is a difference between text and acronym
Response: The acronym was removed as redundant (not used in the following text)
