Modeling the Future Tree Distribution in a South African Savanna Ecosystem: An Agent-Based Model Approach

Round 1

Reviewer 1 Report

This is an important paper in a relatively poorly studied region. It is impressive in its scope and thorough in its analysis. It is well written and illustrated carefully. It has a detailed and considerate literature context covering previous work. While some results importantly confirm previous studies, this paper also uncovers new findings and detail that will be incredibly valuable to the science community.

A few suggested minor changes are listed below, but other than these small typos there is a lot to recommend publishing this paper and no doubt it will become an important reference point for future work.

- L 5: Add a name of country.

- Clearly add research gap, research question and objective(s) at the end of introduction. 

- L 44-50: Its related to study area, move it to appropriate place. 

- L 86: Add some geographical information about study areas, e.g., Latitude, Longitude, elevation above sea level, vegetation characteristics. 

- Please also briefly describe the limitation of the study, computational complexity, and future direction in the Conclusion part.

Author Response

Dear Reviewer,

Thank you very much for the thoughtful and positive feedback. Please find below the changes (highlighted in red) that we made based on your comments.

- L 5: Add a name of country.

Thanks, has been added.

- Clearly add research gap, research question and objective(s) at the end of introduction. 

Line 81 Thanks, we agree that these points should be stated more prominently in the text. We added the following to the end of the Introduction:

The research question of this contribution is whether a large-scale agent-based model (ABM) that is informed by spatio-temporal data from the pertinent geographic region is suitable for modeling and predicting future tree distributions. We argue that this approach complements previous efforts, which relied mainly on aggregations of AGB and/or up-scaling from an average value per ha. Using an ABM, we were able to model the life cycles of each single tree belonging to one of for three different tree species. This provides a greater level of detail and a potentially richer model output for further analysis. As such, the research objective is to develop a workflow that comprises a data-driven selection of agent types for the model, a literature-driven modeling behavior of each agent type, the specification of a range of scenarios to compare different tree distribution outcomes, the implementation of the designed model, and first analyses of model outputs.

- Ll. 44-50: Its related to study area, move it to appropriate place. 

Thanks, we thought about moving this paragraph to the Study Area. However, we elaborate on some aspects of the study design in the Introduction (e.g., the exclusion of fire as a potential tree disturber) that pertain specifically to the two study areas of interest. Therefore, we opted for not moving lines 44—50 because it serves as a brief introduction to the study sites before the elaborations on the study design. We feel that this is permissible, given that we provide more detail on the study sites in the Study Area.

- L 86: Add some geographical information about study areas, e.g., Latitude, Longitude, elevation above sea level, vegetation characteristics. 

Thanks, we added:

To model distributions of specific savanna tree species, we placed our research areas) in the Lowveld, one of the savanna biomes in South Africa with the vegetation type Granite Lowveld. Being in the Lowveld, both study sites are located within an altitude range of 150 -600 m above sea level. The vegetation characteristics of this region typically consist of a few trees in tall shrubland, up to dense thicket or open savanna {Rutherford2006}.

Additionally, we added the Lat/Long for the study site Skukuza in section 2.2.

- Please also briefly describe the limitation of the study, computational complexity, and future direction in the Conclusion part.

Thanks, in part, we touched in limitations in the Discussion. To complement this, we added the following to the Conclusion (this also improved the transition to planned future work):

One limitation of this contribution is that the analyzed data for each of the four scenarios are based on a single simulation run. The reason for this is that a time span of 40 years was modeled. Since the model captures daily behaviors of several thousand individual agents, the computational complexity is considerable. This results in long real-world execution durations of the model. Therefore, we limited our analysis to a single run of each climate scenario.

Once again, thank you kindly for the friendly review and insightful suggestions for improvement.

Best regards,

Ulfia Lenfers

Reviewer 2 Report

adjust to impersonal writing

Dear authors,

Congratulations, this is a great work, the results you present and the methodology are very interesting. Therefore, I think it is necessary to support some sections so that this research can be replicated.
Here are some comments

adjust to impersonal writing

In the introductory section, provide more data on the forest cover of the savanna and the study areas. Also provide general data on the consequences of the effects of the driving factors, e.g., how much forest cover is affected by the drivers included in the model (elephants, fuelwood). This gives the reader an overview of the problem and the rationale for conducting this research. A general analysis of the region, which provides the reason for selecting the study areas.

All!!! It is well told narrated, but it could be better explained
It is not clear where the information came from. It is mentioned that you have high-quality and georeferenced information, but the source, accuracy, quantity, and metadata in general needs to be detailed. It would be helpful if this was included at the beginning of Section 3.

It is necessary to include a framework as a picture that supports the understanding of the methodology, i.e. how information is managed, how MARS consumes all kinds of information and, in general, how it processes (layers, tree information), agents, etc... . In which part of the process Python, R and Kepler.gl are used.

The framework should outline how the results will be represented in general.
Section 3 can be restructured based on this framework. Section 3.2 should be well explained with this resource.

Geographic tools and geographic information are mentioned, but there is no representation of them.
I insist on how the spatial information was processed so that the ABM model can interpret it. It would be very interesting to include maps of the layers used (distribution of trees).

Land use and rural areas are mentioned in the discussion section and the results section, perhaps this should be covered in more detail. why land use was not a factor, since interesting scenarios are presented in these areas.

Something important is missing, the model validation section. How reliable the results are should be stated explicitly.

Author Response

Dear Reviewer, 
Thank you for the positive feedback. In the attached file, we take the liberty of making a few general remarks before going into each point individually. 
Best regards,

Ulfia Lenfers

Author Response File: Author Response.docx

Reviewer 3 Report

The paper"Modeling the Future Tree Distribution in a South African Savanna Ecosystem: An Agent-based Model Approach" presents a very vital topic.

The authors did a commendable job. The methodology and the results have been clearly presented. More so are the discussion and conclusions. Besides, the proposed model could save some of the endangered tree species.

I recommend acceptance of the paper in the current form

Author Response

Dear Reviewer,

Thank you very much for this kind of flattering review. Based on feedback from the other reviews, we did make some minor changes to the text.

Best regards,

Ulfia Lenfers

Reviewer 4 Report

Please avoid abbreviations. A list of abbreviations is not helpful in an online paper.

Author Response

Dear Reviewer,

Thank you for this feedback.

We double-checked all abbreviations to make sure that they are introduced at the appropriate place in the main text and that they are all included in the list of abbreviations at the end of the main document (before Appendix A). All abbreviations are introduced alongside the corresponding full version when it occurs for the first time in the text. The list of abbreviations is intended as an additional way of quickly finding the full version of an abbreviation, if needed by the reader.

Best regards,

Ulfia Lenfers