Review Reports - Scientific Research for Amazonia: A Review on Key Trends and Gaps

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have presented an article that represents a thoughtful and ambitious attempt to synthesize scientific research on the Amazon conducted between 1977 and 2024. Its main strength is its broad coverage of the topic - from the natural sciences to the social sciences - and its attempt to identify key research areas for the future. The text is well-written, clear in language and coherent in content.

Introduction:
Some of the sentences in the Introduction are very long and repeatedly complex, which can make it difficult to read. Although the objectives of the paper are indicated (to assess the progress of science, to identify priorities), no clear hypothesis or specific research questions fall. In a scientific article, these should be clearly formulated.

Methods:

The application of bibliometric analysis using the Bibliometrix package in R is adequate and well described.
It was not explained how many articles were analyzed qualitatively or on what basis they were selected (randomly? by citations? by thematic relevance?). The authors should add a subsection or paragraph describing the criteria for selecting papers for qualitative analysis. The authors should also justify the selection of only two keywords (“AMAZON” and “RAINFOREST”).

Results and Discussion:

My comment is also that the authors could have discussed more broadly the reasons for the decline in publications after 2021 outside of the pandemic.

In addition, they suggest that the authors add comparisons with other megabiomes of the world (e.g., Congo, Borneo) in terms of scientific interest.

Author Response

Reviewer 1

Comments 1: The authors have presented an article that represents a thoughtful and ambitious attempt to synthesize scientific research on the Amazon conducted between 1977 and 2024. Its main strength is its broad coverage of the topic - from the natural sciences to the social sciences - and its attempt to identify key research areas for the future. The text is well-written, clear in language and coherent in content.

Response 1: We thank the reviewer for their positive evaluation and appreciation of the broad scope and clarity of our manuscript. We are pleased that the effort to cover both natural and social sciences and to outline key areas for future research was recognized as a major strength.

Introduction:
Comments 2: Some of the sentences in the Introduction are very long and repeatedly complex, which can make it difficult to read. Although the objectives of the paper are indicated (to assess the progress of science, to identify priorities), no clear hypothesis or specific research questions fall. In a scientific article, these should be clearly formulated.

Response 2: We appreciate this valuable suggestion. In the revised version, we have simplified the Introduction to make it more readable by reducing lengthy and complex sentences. Moreover, we have added clear research questions and a guiding hypothesis to sharpen the study’s focus, as recommended, as can be seen in the last two paragraphs of the Introduction section:

Key aspects within well-established scholarly trends can be highlighted as pathways to future governance practices. Additionally, the consolidation of the multidisciplinary approach for diverse and expanding academic inquiries is a key outcome of this review. Given this context, this paper aims to assess the evolution of scientific activity related to the Amazon at a global scale, with an emphasis on identifying priority research topics that align with key regional and international agendas for conservation and sustainable development. Specifically, the study aims to understand how scientific production has responded to major environmental and socio-political challenges over the past five decades and to what extent current research efforts address emerging knowledge gaps critical for informed policy-making.

To guide this investigation, we pose the following research question: How have thematic trends, institutional contributions, and international collaborations shaped the trajectory of Amazonian research between 1977 and 2024, and what gaps remain to be addressed in future studies? We hypothesize that while research output has increased substantially and diversified in scope, significant imbalances persist. By combining bibliometric mapping with a qualitative synthesis of key topics, this paper provides a comprehensive overview of past achievements, current gaps, and strategic directions for advancing Amazonian science in support of sustainable regional development.

Methods:

Comments 3: The application of bibliometric analysis using the Bibliometrix package in R is adequate and well described.
It was not explained how many articles were analyzed qualitatively or on what basis they were selected (randomly? by citations? by thematic relevance?). The authors should add a subsection or paragraph describing the criteria for selecting papers for qualitative analysis. The authors should also justify the selection of only two keywords (“AMAZON” and “RAINFOREST”).

Response 3:

We thank the reviewer for this important observation. The total number of articles included in the analysis is shown in Figure 3, which presents the 3,730 documents retrieved from the Scopus database between 1977 and 2024. These documents formed the basis for the bibliometric mapping. For the qualitative analysis, a subset of articles was examined in greater depth based on their thematic relevance. Specifically, we selected documents that clustered around key themes identified through bibliometric techniques (e.g., keyword co-occurrence and thematic mapping). These clusters were then explored qualitatively to capture contextual details, ongoing debates, and disciplinary nuances that are not discernible through bibliometric data alone. We have now clarified this selection strategy in the revised manuscript.

In addition, we used only the keyword “AMAZON”, but this search retrieved a significant number of irrelevant documents, particularly those related to the Amazon company. To refine the search and ensure that it accurately captured publications related to the Amazon rainforest, we added the keyword “RAINFOREST”. This combination was not intended to limit the scope but rather to improve the precision of the search by excluding unrelated content. Furthermore, we aimed to compile a comprehensive and multidisciplinary body of literature from various fields, including environmental sciences, social sciences, policy studies, and conservation, while maintaining a clear focus on the Amazon biome.

Results and Discussion:

Comments 4: My comment is also that the authors could have discussed more broadly the reasons for the decline in publications after 2021 outside of the pandemic. In addition, they suggest that the authors add comparisons with other megabiomes of the world (e.g., Congo, Borneo) in terms of scientific interest.

Response 4: We appreciate this insightful comment. In response, we have expanded the discussion in the Results and Discussion section to address additional factors that may have contributed to the decline in publications after 2021 beyond the immediate impacts of the COVID-19 pandemic. Specifically, we now highlight that significant budget cuts to science and technology in Brazil have reduced funding for environmental research, limiting fieldwork capacity, equipment maintenance, and scholarships. The weakening of key public institutions and environmental agencies (e.g., IBAMA, ICMBio, INPE) has further constrained monitoring efforts and data availability.

We also discuss how shifts in the global scientific agenda may have diverted funding and scholarly attention toward other priority regions (such as the Arctic, Africa, and Southeast Asia) and emerging topics like the energy transition, public health crises, and artificial intelligence. While the pandemic initially disrupted research activities, its residual logistical and institutional effects continued to delay the full resumption of fieldwork and collaborations. The revised paragraphs read as follows:

Several factors may explain the decline in scientific publications about the Amazon after 2021. First, significant budget cuts to science and technology, particularly in Brazil, reduced funding for environmental research, limiting fieldwork, equipment maintenance, and the support of scholarships. Additionally, the weakening of public institutions and environmental agencies such as IBAMA, ICMBio, and INPE led to reduced monitoring and data availability. A shift in the global scientific agenda may also have contributed, as funding agencies and journals increasingly focused on other critical regions (e.g., the Arctic, Africa, Southeast Asia) or emerging topics such as energy transition, public health, and artificial intelligence.

The COVID-19 pandemic may have contributed to this decline in production as once scholars and scientists had to contend/deal with new research deadlines, delays, and rescheduling of agendas due to the lockdown policies and restrictions. The increased work hours required to adapt to online agendas and teaching, as noted by Heo et al. [38], can also explain the observed data. Although the peak of the COVID-19 pandemic had passed, its residual effects persisted, with logistical and institutional challenges delaying the full resumption of scientific activities. Furthermore, some research areas may have experienced temporary saturation, particularly those related to deforestation and land-use change, resulting in a slowdown in new studies. Finally, growing political barriers, territorial conflicts, violence against environmental defenders and Indigenous peoples, and restricted access to protected areas have posed additional challenges to conducting research in the region.

Reviewer 2 Report

Comments and Suggestions for Authors

This is a very good and useful paper and it should be published. Furthermore, Conservation is an appropriate outlet for the work. My comments are mostly in the form of suggestions, since the work (as is) is well referenced, well written, highly useful, and contains a good number of illustrative figures that (all together) tell the story quite well. Here are my suggestions:

The authors include a map of S. America, outlining the Amazon Basin, major population centers and national borders.
The authors consider some brief information on human demography over the course of time in the Amazon, especially on population growth of non-native peoples who have immigrated into the region. It would also be interesting to use this as one of the study themes, but I don't wish to suggest they do further analysis. I would hope others in would take it up in future similar analyses.
Some discussion of the expansion of protected areas, research within those areas, and threats to them would be relevant here. They included a few indicators of this (e.g. illegal mining and other lands changes). Again, this would be an interesting additional theme to the trend analysis but I am not suggesting they do more such analyses.

Overall, this is an excellent look at research themes, trends and alliances over time and I find the approach is highly useful, interesting, and applicable to other tropical regions under similar or even greater conservation threats (e.g. tropical Asia).

Author Response

Comments 1: This is a very good and useful paper and it should be published. Furthermore, Conservation is an appropriate outlet for the work. My comments are mostly in the form of suggestions, since the work (as is) is well referenced, well written, highly useful, and contains a good number of illustrative figures that (all together) tell the story quite well. Here are my suggestions:

The authors include a map of S. America, outlining the Amazon Basin, major population centers and national borders.
The authors consider some brief information on human demography over the course of time in the Amazon, especially on population growth of non-native peoples who have immigrated into the region. It would also be interesting to use this as one of the study themes, but I don't wish to suggest they do further analysis. I would hope others in would take it up in future similar analyses.
Some discussion of the expansion of protected areas, research within those areas, and threats to them would be relevant here. They included a few indicators of this (e.g. illegal mining and other lands changes). Again, this would be an interesting additional theme to the trend analysis but I am not suggesting they do more such analyses.

Response: We thank the reviewer for their encouraging and supportive comments, as well as for recognizing the relevance and quality of our work. We greatly appreciate the constructive suggestions for further enhancing the manuscript.

In response:

We have added a new figure (the new Figure 1 in the revised manuscript) that presents a map of the Amazon biome, including major population centers and national borders, as recommended. This visual aid provides helpful geographical context for readers unfamiliar with the region’s extent and administrative divisions, as can be seen below:

Thank you for your thoughtful observation. In response, we have expanded the discussion and included a more elaborated paragraph suggesting that human demographic dynamics, particularly the influx of non-native populations and their implications for land use and conservation, is a relevant avenue for future research. While this aspect is beyond the scope of our current analysis, it holds significant potential for complementary studies.
We appreciate your insightful comment. Accordingly, we have addressed the topic of expanding protected areas, research within these areas, and their ongoing threats in the Future Research Directions section. We recognize this as an important area for further investigation and encourage future studies to explore it in greater depth.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors present an ambitious and timely review of scientific document production related to the Amazon. By analyzing a substantial corpus of 3,730 documents published between 1977 and 2024, the study explores thematic trends, temporal publication patterns, country of origin, key contributing authors, and collaborative networks, among other dimensions.

This work is valuable in its attempt to synthesize a large body of literature using contemporary bibliometric tools, and the visual representations of the data contribute to the accessibility and clarity of the findings. However, despite the overall interest of the topic, there are several substantive and structural issues that need to be addressed before the manuscript is suitable for publication in Conservation.

Major Comments:

Scope and Keywords:
The inclusion of 3,730 documents stems from the use of overly broad search terms (“Amazon” and “rainforest”), which may dilute the relevance of the dataset and lead to overly complex data management. The authors should consider refining the search terms to focus more narrowly on specific themes or regions within Amazonia. This would enhance the relevance and interpretability of the results and would also require an adjustment of the manuscript's title to more accurately reflect the refined scope.
Geographical Focus:
Given that a large proportion of the documents relate to Brazil, the current analysis appears skewed. It may be more appropriate to narrow the territorial focus to Brazilian Amazonia or to introduce stratified analyses by country to maintain regional balance and clarity.
Redundancy in Figures:
There is redundancy between Figure 3 and the figure showing publications by Amazonian countries. These could be merged into a single, clearer visualization that avoids repetition and improves narrative flow.
Collaboration and Funding Analysis:
While the discussion of international collaboration networks and funding sources is informative, it seems tangential to the core focus of this manuscript. These aspects could be better developed in a separate study focused on scientific cooperation and research funding in the Amazon.
Table 1 – Research Classification:
Table 1 appears unnecessary. The classification methodology could be adequately described in the text, streamlining the presentation of results.
Future Research Directions:
The manuscript lacks a substantive discussion on future research needs, which is especially important given the manuscript’s stated focus on “trends and gaps.” Section 4 (Final Remarks) briefly touches on this, but a more detailed and critical reflection on the gaps in Amazonian research and directions for future inquiry is needed.

Recommendation:

I recommend a major revision. The authors should focus on reorganizing the manuscript’s structure and refining its scope, both thematically and geographically. Narrowing the search parameters, reducing redundancy, and strengthening the critical discussion will greatly enhance the clarity and impact of the study.

Author Response

Response: We sincerely thank Reviewer 3 for their thoughtful and constructive feedback on our manuscript. We appreciate the recognition of the study’s scope, the value of synthesizing such a large body of literature, and the usefulness of the visual representations provided. We also acknowledge the reviewer’s concerns regarding substantive and structural aspects that require improvement to strengthen the manuscript and ensure its suitability for publication in Conservation. In response, we have carefully considered each point raised and have made revisions to refine the scope and focus of the paper, reduce redundancies, clarify methodological choices, and expand our critical discussion of gaps and future research directions. We believe that these changes address the reviewer’s concerns and significantly enhance the clarity, coherence, and impact of the study. Below, we provide detailed, point-by-point responses to each specific comment, outlining how we have revised the manuscript accordingly.

Major Comments:

Scope and Keywords:
The inclusion of 3,730 documents stems from the use of overly broad search terms (“Amazon” and “rainforest”), which may dilute the relevance of the dataset and lead to overly complex data management. The authors should consider refining the search terms to focus more narrowly on specific themes or regions within Amazonia. This would enhance the relevance and interpretability of the results and would also require an adjustment of the manuscript's title to more accurately reflect the refined scope.

Response: We thank the reviewer for this thoughtful and constructive comment. We fully understand the concerns regarding the potential complexity and breadth that may result from using the keywords “Amazon” and “rainforest.” However, our intention was precisely to provide a comprehensive bibliometric overview of scientific research related to the Amazon biome as a whole, across all disciplines and countries. To address this complexity without narrowing the thematic scope, we applied a temporal segmentation approach, dividing the analysis into five distinct periods (1977–2008, 2009–2015, 2016–2019, 2020–2022, and 2023–2024). This methodological choice allowed us to track the thematic evolution over time, revealing how research topics, priorities, and discourses have shifted in response to scientific, political, and environmental changes. We improved our discussions to house all the periods.

Geographical Focus:
Given that a large proportion of the documents relate to Brazil, the current analysis appears skewed. It may be more appropriate to narrow the territorial focus to Brazilian Amazonia or to introduce stratified analyses by country to maintain regional balance and clarity.

Response: We appreciate the reviewer's comment. We acknowledge that the Amazon rainforest spans nine countries (Brazil, Bolivia, Colombia, Ecuador, Peru, Venezuela, Guyana, Suriname, and French Guiana). The analysis did not exclude any literature from any particular construct. The approach of including all literature indicated by the bibliometric results allows us to explore, for instance, how research is distributed across countries, the levels of collaboration between nations, and to identify governance gaps, research asymmetries, and transboundary challenges.

Brazil is a leader in scientific papers in almost all research areas in South America. This is also true for Amazonian research. In response to the reviewer’s suggestion, we have clarified this point in the Introduction and Methods sections, explicitly stating that the scope of the study is the entire Amazon biome across all nine countries. Additionally, we have enriched the Results and Discussion section with observations on the geographical distribution of the identified papers. Stratifying the analysis by country was not the scope of this paper.

Redundancy in Figures:
There is redundancy between Figure 3 and the figure showing publications by Amazonian countries. These could be merged into a single, clearer visualization that avoids repetition and improves narrative flow.

Response: We recognize the reviewer’s observation regarding the redundancy between the previous Figure 3 and the figure depicting publications by Amazonian countries (Figure 6). We agree with this point and have addressed it by removing Figure 6 and retaining Figure 3, as it provides a more comprehensive and informative overview that combines both annual trends and country-specific publication data. This adjustment streamlines the visual presentation and improves the narrative flow of the results, as suggested.

Collaboration and Funding Analysis:
While the discussion of international collaboration networks and funding sources is informative, it seems tangential to the core focus of this manuscript. These aspects could be better developed in a separate study focused on scientific cooperation and research funding in the Amazon.

Response: We thank the reviewer for this observation and understand the concern about the potential for the discussion on international collaboration and funding to extend beyond the manuscript’s primary scope. However, we respectfully believe that this analysis contributes and is integral to the paper’s objectives. Examining collaboration patterns and funding sources is important to understanding why Brazil has emerged as the leading contributor to Amazon research in Latin America.

Table 1 – Research Classification:
Table 1 appears unnecessary. The classification methodology could be adequately described in the text, streamlining the presentation of results.

Response: Thank you for this helpful suggestion. In response, we have removed Table 1 from the revised manuscript, and the relevant methodological details have been retained in the main text, as recommended. We agree that this change streamlines the presentation and improves the overall clarity of the section.

Future Research Directions:
The manuscript lacks a substantive discussion on future research needs, which is especially important given the manuscript’s stated focus on “trends and gaps.” Section 4 (Final Remarks) briefly addresses this, but a more detailed and critical reflection on the gaps in Amazonian research and directions for future inquiry is necessary.

Response: We appreciate this vital reviewer’s observation regarding the need for a more substantial and critical reflection on future research needs. In response, we have added a dedicated section, named Section 4: Future Research Directions, which provides a more detailed and strategic discussion of key gaps and emerging priorities identified through our analysis.

Recommendation:

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have fully addressed the comments made in the first version of the review. They significantly improved the structure of the text, clarified the research questions and hypothesis, expanded the methodology, and comprehensively discussed the possible reasons for the decline in publications after 2021. The answers were factual and the changes made significantly enhance the clarity and scientific value of the paper.

I recommend acceptance of the article for publication as revised.

Author Response

We sincerely thank you for the revisions and comments, which greatly contributed to finalizing the manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

After reading your appropiate responses I think that now is ready to be a paper for conservation. Anyway I'll take out the section regarding international collaboration networks and funding sources but I respect your decision on keep on your ms.

Congratulations for this research.

Author Response

We sincerely thank you for the revisions and comments, which greatly contributed to finalizing the manuscript.