An Overview of Ecosystem Service Studies in a Tropical Biodiversity Hotspot, Sri Lanka: Key Perspectives for Future Research

Round 1

Reviewer 1 Report

After previous review, the manuscript was improved, but it still needs to be revised because some corrections were made in inappropriate way.

First that I found is the order of references in the list is alphabetical, while the numeration of references in the main text is consequent. As a result, the relations of the citations to the contents is inappropriate through the whole main text.

In addition, authors ignored my recommendations for inclusion some references. In particular, http://dx.doi.org/10.24189/ncr.2017.042, where key words “Sri Lanka*” and “biodiversity*” are present (thus this study fits the criteria used for sampling). Therefore, authors specially ignored this (and some others, too - e.g., https://dx.doi.org/10.24189/ncr.2020.029) reference from analysis. I don't know why, but authors don't want to use all of the publications, which are searchable using these key words. All this makes the sampling to be biased. Moreover, the sampling is unclear. I advice to add a scheme of sampling. For instance, I recommend authors to use the scheme(s) used in other systematic reviews (see https://doi.org/10.3389/fpls.2020.524969, https://dx.doi.org/10.24189/ncr.2020.019). Otherwise, the selection is considered as biased, and therefore thw results, too. Therefore, I don't see a need to comment results, because they will be changed during the revision according to my presented comments.

The section Introduction should be revised, too. 
So, In lines 52-53, sentence "Biodiversity loss and habitat degradation pose serious threats to natural habitats and ecosystem services" should be supported by most recent references. I recommend the following ones:
1. https://doi.org/10.1016/j.cub.2019.07.063 
2. https://doi.org/10.1007/s10531-020-02000-x 
3. https://doi.org/10.1111/cobi.13621 

Paragraph in lines 89-93 is without supporting by citations. Why? The section Introduction should serve to be background of the research. And all statements should be supported by references.

But the main problem concerns the sampling. Moreover, the use of Web of Science only is not enough to obtain the complete knowledge on the raised issue. I strongly recommend to use Scopus, too with the same key words. Finally, I wonder why there only 139 articles were analysed? Today, I used the same key words in WoS search. So, I have obtained the following results:
I. "Sri Lanka*" AND "ecosystem service*": 52 records taking into account 47 ARTICLE type and 5 REVIEW type.
II. "Sri Lanka*" AND "biodiversity*": 300 records taking into account 276 ARTICLE type and 24 REVIEW type.

So, it is unclear, how has sampling been conducted. Therefore, the results are questionable, too,

I recommend to revise the manuscript according to my comments.

Author Response

Reviewer 1

After previous review, the manuscript was improved, but it still needs to be revised because some corrections were made in inappropriate way.

References

First that I found is the order of references in the list is alphabetical, while the numeration of references in the main text is consequent. As a result, the relations of the citations to the contents is inappropriate through the whole main text.

We updated all the references and the list was corrected.

Introduction 

The section Introduction should be revised, too. 
So, In lines 52-53, sentence "Biodiversity loss and habitat degradation pose serious threats to natural habitats and ecosystem services" should be supported by most recent references. I recommend the following ones:
1. https://doi.org/10.1016/j.cub.2019.07.063 got it
2. https://doi.org/10.1007/s10531-020-02000-x 
3. https://doi.org/10.1111/cobi.13621 

Thank you for suggesting this literature. We improved the introduction with more citations and whole section of introduction was largely edited 

For the lines 52-53 - we added the new references as suggested by the reviewer as following “ Biodiversity loss and habitat degradation pose serious threats to natural habitats and ecosystem services [5]–[9]”

Paragraph in lines 89-93 is without supporting by citations. Why? The section Introduction should serve to be background of the research. And all statements should be supported by references.

We added the relevant citations as follows for the lines 89-93

“Habitable environments all over the island with favourable climatic conditions, relatively high rainfall, and yearlong sunshine along with fertile soils, historical and modern irrigation system have provided an abundant supply of food to the population which was later extended into various plantation agriculture [20][21]. Sri Lanka is also abundant in numerous natural resources such as graphite, gems, high purity silica Quartz, and marine resources [22][23]” 

Methods

In addition, authors ignored my recommendations for inclusion some references. In particular, http://dx.doi.org/10.24189/ncr.2017.042, where key words “Sri Lanka*” and “biodiversity*” are present (thus this study fits the criteria used for sampling). Therefore, authors specially ignored this (and some others, too - e.g., https://dx.doi.org/10.24189/ncr.2020.029) reference from analysis. I don't know why, but authors don't want to use all of the publications, which are searchable using these key words. All this makes the sampling to be biased.

Suggested literature was added and search scheme was modified including Scopus as explain bellow.

Moreover, the sampling is unclear. I advice to add a scheme of sampling. For instance, I recommend authors to use the scheme(s) used in other systematic reviews (see https://doi.org/10.3389/fpls.2020.524969, https://dx.doi.org/10.24189/ncr.2020.019). Otherwise, the selection is considered as biased, and therefore the results, too. Therefore, I don't see a need to comment results, because they will be changed during the revision according to my presented comments.

But the main problem concerns the sampling. Moreover, the use of Web of Science only is not enough to obtain the complete knowledge on the raised issue. I strongly recommend to use Scopus, too with the same key words. Finally, I wonder why there only 139 articles were analysed? Today, I used the same key words in WoS search. So, I have obtained the following results:
I. "Sri Lanka*" AND "ecosystem service*": 52 records taking into account 47 ARTICLE type and 5 REVIEW type.
II. "Sri Lanka*" AND "biodiversity*": 300 records taking into account 276 ARTICLE type and 24 REVIEW type.

So, it is unclear, how has sampling been conducted. Therefore, the results are questionable, too,

We clarified the search under the subtitle “Literature collection, eligibility and exclusion criteria” and following text was added.

For identifying publications related to ecosystem services and related studies in Sri Lanka, we searched ISI Web of Science (WOS: Clarivate Analytics, USA) for the articles published between 1988 and 2020 and Scopus (https://www.scopus.com/) for the articles published between 1992 and 2020. We last accessed these databases in March 2021 and used the following search terms:

For all available databases of WOS (from 1988 to 2021),

1. TOPIC: (“Sri Lanka*” AND “ecosystem service*”) ➔ 79 results
2. TOPIC: (“Sri Lanka*” AND “biodiversity*”) ➔ 502 results

For Scopus database for title, abstract and keywords (from 1992 to 2021),

3. TITLE-ABS-KEY (“Sri Lanka*” AND “ecosystem service*”) ➔ 78 results
4. TITLE-ABS-KEY (“Sri Lanka*” AND “biodiversity*”) ➔ 355 results

We are aware that there might be publications covering similar issues that do not use the term “ecosystem services or biodiversity”. However, the keywords used in the search strings were designed to capture related articles as much as possible and to keep the study objectives straightforward.

We determined few inclusion and exclusion criteria regarding literature type, only journal articles were selected. We excluded book series, book, chapter in book and confer-ence proceedings. We retained publications that have quantified one or more ecosystem service and biodiversity studies related to any ecosystem type of Sri Lanka. As many Sri Lankan Ecosystem and biodiversity related research were unpublished and confined to thesis studies, we did not include them in this review as we couldn’t get access to them during the review period. For example, we found 156 of grey or secondary literature on Scopus database for the query no 4 above, which were not included in the analyses. Moreover, to avoid confusion and difficulty in translation we excluded the non-English publication and focused only on articles published in English. With regards to timeline, we tried to select articles published from 1988 as we wanted to see the evolution of research related to ecosystem services and biodiversity in Sri Lanka, however Scopus data-base is limited to publication information from 1992 onwards.

Further we updated all the sections according to the new results

Reviewer 2 Report

The paper is well organised. Have a good and documented introductions; high-quality graphs and maps. 

Author Response

Reviewer

The paper is well organised. Have a good and documented introductions; high-quality graphs and maps.

Thank you for the comment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Despite two previous peer review stage and comments, authors didn't hear my suggestions. Without doubts, I see that they improved Introduction section by references (although formatting of the list of references doesn't meet requirements of the journal Forests). However, the basic problems are remained. These are as follows:

This is still unclear what exactly publication have been included in the analysis, This makes impossible to repeat the same study. In the systematic reviews, it is accepted to present lists of the analysed publications as an Electronic Supplement(s). Authors should do it. However, unfortunately (because I see that each time the work becomes better), I have one significant comment:

It is a pity that authors eliminated a considerable number of studies focused on taxonomic issues and new species introductions (I am sorry that I am not able to indicate the concrete place, but the lines are not numerated in the manuscript). Please, note that these studies are directly related to the biodiversity issues! So, taxonomic treatments of certain groups of plants/animals could increase or decrease the biological diversity in certain area. At the same time, species introduction (if I understand correctly, it is introduction of alien ornamental or domestic plants/animals) could increase the biological diversity, while if it is related to biological invasion (many invasive species were previously introduced plants or animals), it can decrease biological diversity of the studied area. Therefore, I suggest to leave these studies in the analysis.

This is important to add definition what do you understand under "ecosystem services" and what types are considered here? This should be added in the section Material and Methods. However, there is no such information. Moreover, in the first sentence of Materials and Methods, authors said "publications related to ecosystem services and related studies", i.e. while we (potential readers) don't know what do mean "ecosystem services", there are also "related studies".. What is included in these "related studies"? All these inconsistencies and ambiguous wording don't allow me to understand what exactly do authors want to study using the systematic review?

Additionally, please, note that the key words set of (“Sri Lanka*” AND “biodiversity*”) is not enough, if authors don't use abbreviation "biodiversity", by preferring the full wording "biological diversity". 

Also, you should not say about the literature, which was not defined in the search conditions. For example, I mean the sentence "For example, we found 156 of grey or secondary literature on Scopus database for the query no 4 above, which were not included in the analyses". If you didn't aim to analyse or check the secondary documents, you should leave these sources outside of the discussion and consideration.

In Results, you should not say that "majority of the articles were about biodiversity" because the difference is too small (50.9% vs. 49.1%). In addition, I suggest to compare the ONLY biodiversity-related studies vs. ONLY ecosystem services related studies by considering studies that measured both biodiversity and ecosystem services.

Figure 2: is these any correlation between climatic zone and number of certain ecosystem type? It would be interesting, I think. In relation to other calculation I would recommend trying to add statistical treatments, finding correlations between parameters. This should enlarge the audience of readers.

The main comment about Discussion: for uncertain reasons, in the section authors are focused on discussion of ecosystem service-related studies only. At the same time, data obtained from analysis of biodiversity studies and in general about biodiversity if Sri lanka are almost not mentioned. I advice to pay attention to the biodiversity-related studies.

Author Response

Response to Reviewer 1

Despite two previous peer review stage and comments, authors didn't hear my suggestions. Without doubts, I see that they improved Introduction section by references (although formatting of the list of references doesn't meet requirements of the journal Forests). However, the basic problems are remained. These are as follows:

This is still unclear what exactly publication have been included in the analysis, This makes impossible to repeat the same study. In the systematic reviews, it is accepted to present lists of the analysed publications as an Electronic Supplement(s). Authors should do it. However, unfortunately (because I see that each time the work becomes better), I have one significant comment:

It is a pity that authors eliminated a considerable number of studies focused on taxonomic issues and new species introductions (I am sorry that I am not able to indicate the concrete place, but the lines are not numerated in the manuscript). Please, note that these studies are directly related to the biodiversity issues! So, taxonomic treatments of certain groups of plants/animals could increase or decrease the biological diversity in certain area. At the same time, species introduction (if I understand correctly, it is introduction of alien ornamental or domestic plants/animals) could increase the biological diversity, while if it is related to biological invasion (many invasive species were previously introduced plants or animals), it can decrease biological diversity of the studied area. Therefore, I suggest to leave these studies in the analysis.

We now have provided the lists of the analyzed publications as two Electronic Supplement(s).

Though taxonomic issues and new species introductions papers are related to biodiversity issues if those papers didn’t mention or didn’t imply anything related to ecosystems services that is provisional, regulatory, cultural or aesthetic we eliminated such papers as the focus of our study is to explore the ecosystem service studies in sri Lanka.

We clearly mentioned in the methods section which papers we considered in our overview including exclusion and inclusion criteria as follows

“ We determined few inclusion and exclusion criteria regarding literature type, only journal articles were selected. We excluded book series, book, chapter in book and confer-ence proceedings. We retained publications that have quantified one or more ecosystem services related to any ecosystem type of Sri Lanka.

Studies that only mentioned ecosystem benefits but that did not quantify, value them nor measured threats and pressures on ecosystems or biodiversity and didn’t discuss any issues related to ecosystem and biodiversity management were not included as we were interested in the body of literature that actively deems themselves as ecosystem service and related biodiversity research in Sri Lanka. We further removed papers that are not dealing with ecosystem services or ecosystem service-related biodiversity aspects and those only mentioned these two terms in their abstract or keywords and didn’t identify or discuss any type of ecosystem service or biodiversity studies in the full article”

This is important to add definition what do you understand under "ecosystem services" and what types are considered here? This should be added in the section Material and Methods. However, there is no such information. Moreover, in the first sentence of Materials and Methods, authors said "publications related to ecosystem services and related studies", i.e. while we (potential readers) don't know what do mean "ecosystem services", there are also "related studies". What is included in these "related studies"? All these inconsistencies and ambiguous wording don't allow me to understand what exactly do authors want to study using the systematic review?

We included a new paragraph in methods section with the definition on what we considered ecosystem services studies in this manuscript as foloows

“ Defining ecosystem services and terminology

For this study we defined ecosystem services as the benefits people receive from ecosystems, here we considered both direct and indirect services provided by ecosystems under the four categories of cultural ecosystem services (nonmaterial benefits such as recreational activities, the aesthetic values); provisioning ecosystem services (products obtained from ecosystems); regulating ecosystem services (the benefits obtained from the regulation of eco[1]system processes); and supporting ecosystem services [1]–[4]. Thus, if any paper considered:

• the importance of biodiversity in the delivery of ecosystem services
• impact of anthropogenic and natural drivers of change on ecosystem services
• market and non-market values of ecosystem services
• traditional knowledge, stakeholder perceptions on ecosystem services
• management of ecosystem services, we included them in our study.

Additionally, please, note that the key words set of (“Sri Lanka*” AND “biodiversity*”) is not enough, if authors don't use abbreviation "biodiversity", by preferring the full wording "biological diversity". 

Additionally, please, note that the key words set of (“Sri Lanka*” AND “biodiversity*”) is not enough, if authors don't use abbreviation "biodiversity", by preferring the full wording "biological diversity". 

We consider the key words we selected have covered the majority of published articles on ecosystem services in Sri Lanka

Also, you should not say about the literature, which was not defined in the search conditions. For example, I mean the sentence "For example, we found 156 of grey or secondary literature on Scopus database for the query no 4 above, which were not included in the analyses". If you didn't aim to analyse or check the secondary documents, you should leave these sources outside of the discussion and consideration.

We remove this section as suggested by the reviewer

In Results, you should not say that "majority of the articles were about biodiversity" because the difference is too small (50.9% vs. 49.1%). In addition, I suggest to compare the ONLY biodiversity-related studies vs. ONLY ecosystem services related studies by considering studies that measured both biodiversity and ecosystem services.

We changed this sentence as follows “The articles about biodiversity were (50.9%) and primarily related to species introduction, species abundance-richness, or changes in biodiversity while  ecosystem services studies were comprised of (49.1%) of considered articles”

Figure 2: is these any correlation between climatic zone and number of certain ecosystem type? It would be interesting, I think. In relation to other calculation I would recommend trying to add statistical treatments, finding correlations between parameters. This should enlarge the audience of readers.

The main comment about Discussion: for uncertain reasons, in the section authors are focused on discussion of ecosystem service-related studies only. At the same time, data obtained from analysis of biodiversity studies and in general about biodiversity if Sri lanka are almost not mentioned. I advice to pay attention to the biodiversity-related studies.

Our focus of this study is to discuss the status of ecosystem services studies in Sri Lanka as our title says and not the status of biodiversity studies in Sri Lanka.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

After preliminary reading the abstract, Introduction and Material and Methods sections, I clearly found that the present manuscript is out of the research scope of the journal Forests. This paper doesn't consider forest ecosystems as a specific habitat/ecosystem, but forests are being studied together with all other habitats here. I recommend authors to re-submit this manuscript to another journal, which is not so specialized.

In addition, the section Material and Methods should present the key search options for conducting this systematic review. However, authors wrongly selected the set of key words for searching (“Sri Lanka*” AND “ecosystem service*”, “Sri Lanka*” AND “biodiversity*.”). This set doesn't cover a large set of publications where this research topic is considered. At least, I know other publications (about 10 only in my mind) from WoS, which could (should) be included in this systematic review, where, instead of "biodiversity", authors used such words as "plants", "animals", "mammals", "biological diversity", etc.
No less important problem - authors used too short period for this search (between March 2020 and December 2020), as well as they ignored Scopus database that would provide more comprehensive data set.
I am nothing saying about Introduction and Discussion now, because the previous problems don't allow me to think that the manuscript contains reliable results and consequently their discussion. But I would recommend authors to pay more attention to the background overview in Introduction.

Author Response

We are grateful for the reviewer’s feedback, comments and suggestions for the improvement of our manuscript. Though the reviewer generously points out about key word selection our objective wasn’t to cover a large set of publications rather to capture the papers those directly related to what we want to present in this paper. Therefore, we don’t agree to use “plants", "animals", "mammals", "biological diversity", etc as the key words of our study as the focus of the manuscript is to evaluate the nature of the current ecosystem services and related studies in Sri Lanka. Furthermore we don’t agree with the statement that “authors used too short period for this search (between March 2020 and December 2020)” as we came across papers published from 1975 – 2020 and used in our manuscript. And as the reviewer pointed out we modified the introduction hope it conveys our message in a clearer way.

Author Response File: Author Response.docx

Reviewer 2 Report

This is a well-prepared paper discussing a significant subject regarding ecosystem services in Sri Lanka.

Great points of the paper:

1. great documentation for the review literature
2. map distribution of review papers included in this article.
3. two aspects presented in the discussion section: present and future focus on ecosystem services. 

Modification for Figure 3

It is hard to make difference between each category of ecosystem services. You can put an indicator for each category to be easier to understand. 

Author Response

We are grateful for the reviewer comments, suggestions for the improvement of the manuscript. We modified the figure 3 so that it will be clearer in conveying our message.

Author Response File: Author Response.docx

Reviewer 3 Report

The topic is very interesting. However the paper looks like a report. There is a just basic statistics in results. I feel that review should have the deep qualitative approaches with research frame and sophisticated quantities analysis. But the paper do not have both. More systematic reviews are needed such as the papers below.

Seppelt, R., Dormann, C. F., Eppink, F. V., Lautenbach, S., & Schmidt, S. (2011). A quantitative review of ecosystem service studies: approaches, shortcomings and the road ahead. Journal of applied Ecology, 48(3), 630-636.

Martínez-Harms, M. J., & Balvanera, P. (2012). Methods for mapping ecosystem service supply: a review. International Journal of Biodiversity Science, Ecosystem Services & Management, 8(1-2), 17-25.

Haase, D., Larondelle, N., Andersson, E., Artmann, M., Borgström, S., Breuste, J., ... & Elmqvist, T. (2014). A quantitative review of urban ecosystem service assessments: concepts, models, and implementation. Ambio, 43(4), 413-433.

Schwarz, N., Moretti, M., Bugalho, M. N., Davies, Z. G., Haase, D., Hack, J., ... & Knapp, S. (2017). Understanding biodiversity-ecosystem service relationships in urban areas: A comprehensive literature review. Ecosystem services, 27, 161-171.

And I feel the reasons author set Sri Lanka as study area are weak. Please explain the reason in detail with detail history and map as the journal is international journal.

Author Response

We are thankful for reviewer’s comments and suggestions for the improvement of our manuscript. Though we respect what the reviewer stated as “just basic statistics in results. I feel that review should have the deep qualitative approaches with research frame and sophisticated quantities analysis” we consider the analysis in this manuscript has captured all what we want to say in its simple way and is enough to convey our message about the current situation of Sri Lanka’s ecosystem services studies. Furthermore we modified the introduction and the location map as the reviewer suggested.

Author Response File: Author Response.docx