The Sustainability of Rock Art: Preservation and Research

Round 1

Reviewer 1 Report

This article aims to act as a reference point for the study of an important type of immovable tangible heritage, rock art. To do so, they explore the potential of both non-invasive and invasive methods provided by the STEM disciplines

The introduction to the problem and the overview of the types of natural and human-induced damage is clear although sometimes verbose. The figures help to mitigate this effect and to follow the discussion. However, for the sake of coherence, it would be good to have a three-picture figure also for the caves, as the authors have done for both the rock shelters (Fig. 2) and the open-air contexts (Fig. 3).

The analysis of processes affecting rock stability is well structured. Its division into natural and human-induced helps to better orientate within the wide range of processes and their multiple effects.

Nevertheless, to make the wide range of processes even more clear and understandable, I suggest adding a table at the end of Chapter 3, structured in a similar way to the current Table 1 and including at least: 1. the scale (micro- , meso- and macro-), 2. Natural or human-related distinction, 3. Where they occur (caves, rock shelters etc), 4. The type of process and effect.

This would be extremely helpful for non-expert readers to get a clear and in-depth picture of the entire set of processes affecting rock stability.

A section that must be absolutely enriched is the one concerning sustainability. To fit in the scopes of a scientific journal named “Sustainability” and having the paper title "The sustainability of rock art", one expects something more from this side. Currently, the only aspect of sustainability properly addressed by the paper is that of research, while the conclusions only briefly and cursorily mention the impact of tourism, thus referring to a problem of sustainability and only providing rather vague solutions.

Authors must therefore better explain what strategies can be put in place to ensure the sustainability of rock art in terms of conservation techniques and tourism regulation.

Author Response

This article aims to act as a reference point for the study of an important type of immovable tangible heritage, rock art. To do so, they explore the potential of both non-invasive and invasive methods provided by the STEM disciplines

The introduction to the problem and the overview of the types of natural and human-induced damage is clear although sometimes verbose. The figures help to mitigate this effect and to follow the discussion. However, for the sake of coherence, it would be good to have a three-picture figure also for the caves, as the authors have done for both the rock shelters (Fig. 2) and the open-air contexts (Fig. 3).

- As suggested at the beginning of the section, our aim is investigating rock shelters and open-air rock because they have specific environmental settings. Also, our experience is on such contexts, and we do not have pictures of cave sites. Such pictures are available in most of the papers we cited in the relevant part of our manuscript.

The analysis of processes affecting rock stability is well structured. Its division into natural and human-induced helps to better orientate within the wide range of processes and their multiple effects. Nevertheless, to make the wide range of processes even more clear and understandable, I suggest adding a table at the end of Chapter 3, structured in a similar way to the current Table 1 and including at least: 1. the scale (micro- , meso- and macro-), 2. Natural or human-related distinction, 3. Where they occur (caves, rock shelters etc), 4. The type of process and effect.

This would be extremely helpful for non-expert readers to get a clear and in-depth picture of the entire set of processes affecting rock stability.

• As suggested, we added a table (Tab. 1) listing rock art sites decay processes.

A section that must be absolutely enriched is the one concerning sustainability. To fit in the scopes of a scientific journal named “Sustainability” and having the paper title "The sustainability of rock art", one expects something more from this side. Currently, the only aspect of sustainability properly addressed by the paper is that of research, while the conclusions only briefly and cursorily mention the impact of tourism, thus referring to a problem of sustainability and only providing rather vague solutions. Authors must therefore better explain what strategies can be put in place to ensure the sustainability of rock art in terms of conservation techniques and tourism regulation.

- We appreciate this comment, and we added some sentences to the last part of the revised manuscript discussing the possibility of sustainable tourism of rock art.

Reviewer 2 Report

Overall, this is a very interesting paper that gives a decent overview of (mostly invasive) rock art research. As a rock art researcher myself, I commend the authors on their other recent publications and research, as they represent an important component in the sustainability of rock art.

That said, there are several notes and suggestions I would like to offer which could benefit the paper.

• Figure 1 is good. Reminiscent of Dorn et al. (2008). But, you mention the constraints of climate and changing climate a lot in the manuscript, yet nothing climate related is noted in your figure. That seems to be a very important concept.
• Figure 5. The use of "small scale" is misleading, since the authors use it in terms of geographic scale, which would mean a large area. It's a trifling item, but one that is misstated in science all the time. Quick fix, though: use the term area instead, as in , "over a small area".
• Line 184: no comma after "slope". Extra commas can also be found scattered throughout the paper, so editorially speaking, it is suggested the authors double-check the usage of commas throughout the manuscript as sometimes it leads to conveying something very different.
• You cite Hall et al.'s 2012 paper (ref no. 48) but miss the main point of the article. That article focuses on why NOT to use the term "weathering" more than components of weathering. It argues for using more appropriate terminology such as "decay", or "stone decay", or "rock decay" or "deterioration". Citing this article to explain "weathering" is an incorrect use of the article. There are several "weathering" articles which have come out since that time that advocate for the same thing: using terms such as "decay" or "rock decay" or "stone decay" or "deterioration". For example, see Dorn et al. 2013. The Role of Fieldwork in Rock-Decay Research: Case Studies from the Fringe. Geomorphology 200: 59-74. Groom et al. 2015. Defining Tafoni: Re-examining Terminological Ambiguity for Cavernous Rock Decay Phenomena. Progress in Physical Geography 39(6): 775-793. Wang et al. 2020. Evaluating the condition of sandstone rock-hewn cave-temple façade using in situ non-invasive techniques. Rock Mechanics and Rock Engineering, 53(6), pp.2915-2920. Coombes et al. 2018. Thermal blanketing by ivy (Hedera helix L.) can protect building stone from damaging frosts. Scientific Reports, 8(1), pp.1-11 (which you already cite).
• SABs represent an important component of the rock art ecosystem. The authors note a few studies that highlight it (refs 59-63), but there is also another Dorn et al. article from 2012 that outlines this across the entire western US: Case Hardening Vignettes from the Western USA: Convergence of Form by a Divergence of Hardening Processes. Association of Pacific Coast Geographers Yearbook 74: 53-75. It's an easily overlooked article, since it's in a regional journal, but it represents one of the most comprehensive overviews/reviews of case hardening (and therefore SABs) in North America.
• Since one of this article's goals centers on the "...multifaceted possibilities of scientific investigations – non-invasive or invasive..." attention should be paid to such techniques (there are more than two-dozen specific different techniques for assessing rock art panels that I'm aware of). But two glaring omissions are found in section 4 and Table 1: 3D photogrammetry and scientific indices -- both of which represent non-invasive techniques for rock art condition assessment. In fact, there is not much mention (and therefore less discussion) in the manuscript concerning non-invasive techniques/condition assessments. If such studies are not to be included, then perhaps removing the term "non-invasive" from this article -- or stating upfront that the authors are not utilizing (or place value on discussing) the non-invasive techniques available, would be prudent -- even though some of them have been in successful use for nearly two decades (for example, see your current reference no. 33 and Mol and Clarke's 2019 research: Integrating structure‐from‐motion photogrammetry into rock weathering field methodologies. Earth Surface Processes and Landforms, 44(13), pp.2671-2684). 
• Line 546, "...as explained in the previous section..." NO, it was not explained in the previous section. Nor in the subsequent section.
• Although section 5 is supposedly dedicated to "non-invasive" techniques, it discusses only specific "micro-invasive" techniques, and especially those used by the authors at sites in varying climates. That's fine. And I've read each of those research papers. They're very interesting and contribute greatly to the rock art assessment literature. But they are not strictly "non-invasive" as defined in this manuscript. So again, it is suggested that the authors either 1) remove the discussion of "non-invasive" (perhaps use "micro-invasive" only) or 2) include a paragraph outlining truly non-invasive techniques and condition assessments, or at least include mention of them in Table 1.
• I'm familiar with most of the citations in the article, but unsure why some of the citations are where they are. For example, to lump in the Cerveny 2005 article (dissertation) as part of the introductory discussion of "Natural processes" (beginning on line 149) seems odd, since that research centers on development of a (non-invasive) condition assessment technique for rock art. Yes, it includes natural processes in its assessment, but the way the authors cite it takes away the important contribution of that research which has led to at least two dozen articles and several book chapters regarding the specific condition assessment technique since its first use. Just citing articles because their titles seem relevant to a topic makes the reader wonder how many other citations have been thrown into the manuscript without proper understanding of them. Several other examples can be noted, but it is suggested the authors review each citation to make sure they are citing it correctly.
• Lines 590-592: "In many cases, there is little to do, and prevention is the most effective mitigation strategy, through education and training of local people, especially in areas where continuous monitoring is not possible." This is spot on. In fact, there is a new book coming out in July on open air rock art management (Global Perspectives for the Conservation and Management of Open Air Rock Art Sites, A.B. Fernandes, M. Marshall, and I.D. Sanz, eds. Routledge -- specifically, section 4 centers on "education and training of local people").

Author Response

Overall, this is a very interesting paper that gives a decent overview of (mostly invasive) rock art research. As a rock art researcher myself, I commend the authors on their other recent publications and research, as they represent an important component in the sustainability of rock art.

That said, there are several notes and suggestions I would like to offer which could benefit the paper.

Figure 1 is good. Reminiscent of Dorn et al. (2008). But, you mention the constraints of climate and changing climate a lot in the manuscript, yet nothing climate related is noted in your figure. That seems to be a very important concept.

- True! We updated figure 1.

Figure 5. The use of "small scale" is misleading, since the authors use it in terms of geographic scale, which would mean a large area. It's a trifling item, but one that is misstated in science all the time. Quick fix, though: use the term area instead, as in, "over a small area".

- Yes, we acknowledge the tricky use of ‘small scale’ and we changed as suggested.

Line 184: no comma after "slope". Extra commas can also be found scattered throughout the paper, so editorially speaking, it is suggested the authors double-check the usage of commas throughout the manuscript as sometimes it leads to conveying something very different.

- Changed and checked throughout the manuscript.

You cite Hall et al.'s 2012 paper (ref no. 48) but miss the main point of the article. That article focuses on why NOT to use the term "weathering" more than components of weathering. It argues for using more appropriate terminology such as "decay", or "stone decay", or "rock decay" or "deterioration". Citing this article to explain "weathering" is an incorrect use of the article. There are several "weathering" articles which have come out since that time that advocate for the same thing: using terms such as "decay" or "rock decay" or "stone decay" or "deterioration". For example, see Dorn et al. 2013. The Role of Fieldwork in Rock-Decay Research: Case Studies from the Fringe. Geomorphology 200: 59-74. Groom et al. 2015. Defining Tafoni: Re-examining Terminological Ambiguity for Cavernous Rock Decay Phenomena. Progress in Physical Geography 39(6): 775-793. Wang et al. 2020. Evaluating the condition of sandstone rock-hewn cave-temple façade using in situ non-invasive techniques. Rock Mechanics and Rock Engineering, 53(6), pp.2915-2920. Coombes et al. 2018. Thermal blanketing by ivy (Hedera helix L.) can protect building stone from damaging frosts. Scientific Reports, 8(1), pp.1-11 (which you already cite).

- We got the point! And we reconsidered the term weathering along the manuscript.

SABs represent an important component of the rock art ecosystem. The authors note a few studies that highlight it (refs 59-63), but there is also another Dorn et al. article from 2012 that outlines this across the entire western US: Case Hardening Vignettes from the Western USA: Convergence of Form by a Divergence of Hardening Processes. Association of Pacific Coast Geographers Yearbook 74: 53-75. It's an easily overlooked article, since it's in a regional journal, but it represents one of the most comprehensive overviews/reviews of case hardening (and therefore SABs) in North America.

- Thanks for this suggestion concerning the case hardening effect of SABs; we added this reference to the revised version of the manuscript.

Since one of this article's goals centers on the "...multifaceted possibilities of scientific investigations – non-invasive or invasive..." attention should be paid to such techniques (there are more than two-dozen specific different techniques for assessing rock art panels that I'm aware of). But two glaring omissions are found in section 4 and Table 1: 3D photogrammetry and scientific indices -- both of which represent non-invasive techniques for rock art condition assessment. In fact, there is not much mention (and therefore less discussion) in the manuscript concerning non-invasive techniques/condition assessments. If such studies are not to be included, then perhaps removing the term "non-invasive" from this article -- or stating upfront that the authors are not utilizing (or place value on discussing) the non-invasive techniques available, would be prudent -- even though some of them have been in successful use for nearly two decades (for example, see your current reference no. 33 and Mol and Clarke's 2019 research: Integrating structure‐from‐motion photogrammetry into rock weathering field methodologies. Earth Surface Processes and Landforms, 44(13), pp.2671-2684).

- We appreciate this comment, and we agree that methods to assess the conditions of rock art are not fully discussed in our manuscript. But consider also that this is not a review paper. In any case, we added the use of SfM and scientific indexes among the non-invasive methods cited in the manuscript, including relevant references.

Line 546, "...as explained in the previous section..." NO, it was not explained in the previous section. Nor in the subsequent section.

- Yes, we changed this part of the manuscript.

Although section 5 is supposedly dedicated to "non-invasive" techniques, it discusses only specific "micro-invasive" techniques, and especially those used by the authors at sites in varying climates. That's fine. And I've read each of those research papers. They're very interesting and contribute greatly to the rock art assessment literature. But they are not strictly "non-invasive" as defined in this manuscript. So again, it is suggested that the authors either 1) remove the discussion of "non-invasive" (perhaps use "micro-invasive" only) or 2) include a paragraph outlining truly non-invasive techniques and condition assessments, or at least include mention of them in Table 1.

- Section 5 is discuss the significance of non-invasive and invasive methods and explain our viewpoint on the reliability of poorly invasive methods and not only to non-invasive methods. Also considering the previous comment, we modified a bit this part of the manuscript.

I'm familiar with most of the citations in the article, but unsure why some of the citations are where they are. For example, to lump in the Cerveny 2005 article (dissertation) as part of the introductory discussion of "Natural processes" (beginning on line 149) seems odd, since that research centers on development of a (non-invasive) condition assessment technique for rock art. Yes, it includes natural processes in its assessment, but the way the authors cite it takes away the important contribution of that research which has led to at least two dozen articles and several book chapters regarding the specific condition assessment technique since its first use. Just citing articles because their titles seem relevant to a topic makes the reader wonder how many other citations have been thrown into the manuscript without proper understanding of them. Several other examples can be noted, but it is suggested the authors review each citation to make sure they are citing it correctly.

- We agree with this comment. In fact, this paper was erroneously coted at this position, but it will be cited elsewhere following other comments from the reviewer.

Lines 590-592: "In many cases, there is little to do, and prevention is the most effective mitigation strategy, through education and training of local people, especially in areas where continuous monitoring is not possible." This is spot on. In fact, there is a new book coming out in July on open air rock art management (Global Perspectives for the Conservation and Management of Open Air Rock Art Sites, A.B. Fernandes, M. Marshall, and I.D. Sanz, eds. Routledge -- specifically, section 4 centers on "education and training of local people").

- We appreciate the publication of this new volume, but unfortunately it seems not yet available and thus we are not able to have a look and properly cite it.

Round 2

Reviewer 1 Report

I wish to thank the authors for considering most of my comments. The article sounds clearer in the points indicated in my first review.

However, I disagree with the authors' response to my first comment. If they want their paper to become a reference point for the study of rock art, it must be organized as a stand-alone one. This is true for both text and images. My suggestion to add a three-picture figure also for the caves goes in this direction. Even if the authors do not have pictures of the caves and they already quoted papers on them, a non-expert reader would appreciate having a visual idea of them. 

Furthermore, my third comment has only been partially followed. The new paragraph in the conclusion remains very broad, repeating the advantages of the touristic use of the rock art places for the economic growth of local communities. Let me try to help the authors with a couple of suggestions:

For example, given the potential risks and human-made threats to this type of heritage largely discussed in the paper, it would be important that when proposing a solution for the sustainability of rock art places, the authors also consider the risks that these can bring and how they are mitigated. This last point can be easily solved by illustrating successful examples of rock art places accessible to tourists.

Author Response

I wish to thank the authors for considering most of my comments. The article sounds clearer in the points indicated in my first review.

However, I disagree with the authors' response to my first comment. If they want their paper to become a reference point for the study of rock art, it must be organized as a stand-alone one. This is true for both text and images. My suggestion to add a three-picture figure also for the caves goes in this direction. Even if the authors do not have pictures of the caves and they already quoted papers on them, a non-expert reader would appreciate having a visual idea of them.

- We understand the point raised by the reviewer and for that reason we added a figure (now fig. 2) illustrating the case of rock surfaces in caves and their potential deterioration.

Furthermore, my third comment has only been partially followed. The new paragraph in the conclusion remains very broad, repeating the advantages of the touristic use of the rock art places for the economic growth of local communities. Let me try to help the authors with a couple of suggestions: For example, given the potential risks and human-made threats to this type of heritage largely discussed in the paper, it would be important that when proposing a solution for the sustainability of rock art places, the authors also consider the risks that these can bring and how they are mitigated. This last point can be easily solved by illustrating successful examples of rock art places accessible to tourists.

- We understand these suggestions; we think that this may represent a single paper discussing the topic of tourism in rock art site. In any case, we added a few sentences giving some examples of successful strategies or rock art site management and accessibility for tourists.