Sustainable Management of Carbon Sequestration Service in Areas with High Development Pressure: Considering Land Use Changes and Carbon Costs

Round 1

Reviewer 1 Report

This study analyzed changes in the carbon stocks and the economic values in 20 years in Korea due to changes in land use and land cover. The manuscript is well-written and straightforward. Here are some minor comments.

L58 affect=> affecting

L71 observe=> evaluate

L96 which are a major=> which is a major

L97 is occupying => occupies

L119 to maintain=> in maintaining

L351 add “and” before ‘forest land → grassland’.

L353 add , before “such as”

L405 add . after [43-45]

L411 remove “Firstly,”

Author Response

Response to reviewer

 

Line 58: affect=> affecting

(Answer) Reflecting the reviewer’s comment, we revised the text (line 72):

“Thus, the scale and type of LULC change and carbon prices are the factors that either directly or indirectly affecting the carbon sequestration service of the ecosystem.”

Line 71: observe=> evaluate

(Answer) Reflecting the reviewer’s comment, we revised the text (line 84):

“Moreover, it is also important to evaluate how the economic value of the carbon storage service alters when the market price of the carbon is applied.”

Line 96: which are a major=> which is a major

(Answer) Reflecting the reviewer’s comment, we revised the text (line 110):

“It has four distinct seasons and due to its abundant rainfall, it has well-developed vegetation including forests and agricultural land which is a major carbon storage (Figure 1a) in the country.”

Line 97: is occupying => occupies

(Answer) Reflecting the reviewer’s comment, we revised the text (line 111):

“The forest area occupies over 60% of the national land area and the mean stand volume density is 145.99m3 ha-1 in 2015 [17,18].”

Line 119: to maintain=> in maintaining

(Answer) Reflecting the reviewer’s comment, we revised the text (line 123-124):

“It also weakens the ability of ecosystems to adapt to the climate change and poses a great challenge in maintaining national and regional ecosystem services.”

Line 351: add “and” before ‘forest land → grassland’.

(Answer) Reflecting the reviewer’s comment, we revised the text (line 403):

“At regional level, the types of the LULC change which are the cause of the carbon stock changes also varied from 'forest land → agricultural land', 'forest land → urban land', 'agricultural land → urban land', and ‘forest land → grassland’.”

Line 353: add , before “such as”

(Answer) Reflecting the reviewer’s comment, we revised the text (line 405):

“Korea's carbon market is still in its infancy, and its market price is low, such as the prices in the carbon pricing mechanism of many other countries.”

Line 405: add . after [43-45]

(Answer) Reflecting the reviewer’s comment, we revised the text (line 445):

“Even after restoration, its ecological value is never the same [47-49].”

Line 411: remove “Firstly,”

(Answer) Reflecting the reviewer’s comment, we revised the text (line 451):

“The joint management policy can be suggested as follows.”

Author Response File: Author Response.docx

Reviewer 2 Report

In general the authors did good work on the data but the paper could be considerably improved in clarity and inconsistencies should be removed or explained. If you have an Korean version of the paper, try to have a fully bilingual professional check both texts, because I think some concepts may have been translated wrongly, by translating the word rather than the concept. see my comments in the attached file.

Comments for author File: Comments.pdf

Author Response

Response to reviewer

 

Line 36: Carbon storage capacity is one of the most essential ecosystem services. I am not too sure that the MEA classifies this service as such.

(Answer) Reflecting the reviewer’s comment, we checked the MEA (ref. 1) and have revised the original sentence as follows (line 36):

“The climate change regulation service provided by ecosystem through the carbon storage capacity is one of the important ecosystem services.”

Line 38: “Anthropocene” – what is this? Needs some clarification. Is it relevant here?

(Answer) The term "Anthropocene" means entering a new geological age due to the increased use of fossil fuels (ref. [2]). We used the term to emphasize the global environmental change mainly caused by humankind. But as the reviewer mentions, there is no direct linkage to land-use changes. Therefore, we revised the original text as follows (line 39).

“However, all kinds of man-made global environmental change are giving serious negative impacts on the carbon storage capacity.”

Line 45-46: LULC changes …..global scale.. What do you mean here with carbon fluxes from local to global scale?

(Answer) We refer to this section to emphasize that land-use change in forests does not only mean reductions in regional carbon stocks, but also impacts globally through the carbon cycle such as carbon flux.

Line 50: Cannot… this requires further explanation, thinking of what drives prices of carbon

(Answer) The original sentence can be interpreted as if the market price of carbon cannot contain environmental values not only now but also in the future. But it’s not true. We revised original sentence and added more explanation like below (line 49-58):

But, the current market prices of carbon cannot sufficiently reflect the environmental value as the natural capital. Generally carbon have stored in natural capital such as forests, farmland, wetland, etc., which have a role as a public goods or environmental goods. If public goods or environmental properties once destroyed, its effects are prolonged and recovery takes a long time. Therefore, the price of carbon including the future cost of environmental destruction and recovery must be taken into account in the decision making process. But, usually, the market price is determined by reflecting the current value thought by the participants in the market using known information. In point of carbon, globally the carbon price mechanism has a short history and is still a growing market. This means that participants in the carbon market can underestimate carbon prices due to lack of information.”

Line 52: Underestimated…. But also overestimated?

(Answer) Overestimating the value of carbon sequestration service is unlikely in a near future as the price of carbon is expected to rise continuously. Although parties have pledged to actively leverage carbon pricing mechanism through the Paris Agreement, the price of carbon traded in the carbon pricing mechanism in most of countries is still too low to achieve the purpose of limiting global warming to less than 2℃. In this sense, countries making efforts to raise the carbon price by introducing a carbon price floor and incorporating more sectors into the carbon pricing mechanism.

Line 52-53: This is particularly the case…..why? explain better.

(Answer) In the same vein as the explanation for line 50 and 52, the market price of carbon reflects only the value of transactions at the present time, but it does not reflect the cost of environmental destruction and recovery, which can be a long-term or permanent damage. Therefore, long-term or permanent changes or damages to ecosystem services should be estimated not at the current carbon price but at the future carbon price, which is not yet predictable but is likely to rise.

However, since we already added the above to the text (line 49-58) for the response to line 50, we deleted the sentence.

Line 54: As a result…. How is this a result of the previous sentence?

(Answer) As the reviewer mentions, the term “as a result” in context does not fit. We took the reviewer's opinion and modified it to “ In an effort to get a reasonable price of carbon” (line 61).

Line 55-57: In addition, ….verification. this needs to be better explained. How would this work?

(Answer) The text was revised as follows to reflect the reviewer's comment (line 62-70).

"That is, the price of carbon should reflect, as Michaelowa et al. (2003; ref. 9) argues, environmental and social costs so that the decision-making of development can be made based on the proper cost-benefit analysis. In addition, the appropriate price of carbon could be introduced by setting a clear policy objective and the scope of the carbon prices, and also by increasing the accuracy of the emission data collection and verification. For example, accurate measurement, reporting and verification should be in place for a specific operation or abatement technology of carbon emission so that the country operating the carbon pricing mechanism sets the accurate emission cap for the nation, sector, and company, which in turn affect carbon prices."

Line 58: Thus, the LULC change….. should this be the “desired” LULC change or the “scale of” or “type of” LULC change?

(Answer) Reflecting the reviewer’s comment, we have revised the original sentence as follows (line 71):

“Thus, the scale and type of LULC change and carbon prices are the factors that either directly or indirectly affect the carbon sequestration service of the ecosystem.”

Line 59-60: Developing…. Developed…under-developed… is this a correct classification? In particular, what is “under-developed”?

(Answer) As the reviewer mentioned, the terms ‘developing country’, ‘developed country’ and ‘underdeveloped country’ are not clearly classified. Reflecting reviewer’s comment, we have revised original sentence as below (line 72-74):

“The countries with high development pressure are experiencing many LULC changes, and they also tend to make economic growth-oriented policy decisions.”

Line 59-63: Is this a valid assumption? Is there a reference for this?

(Answer) As the reviewer mentioned, also as in the response to lines 59-60, the following changes were made to connect with the modified earlier part (line 74-76).

“Consequently, the carbon storage capacity provided by the ecosystem may have decreased greatly and the economic value of the carbon sequestration service may also have reduced.”

Line 64: Korea is the only country….is that true? What about countries in Latin America such as Costa Rica, Cuba, Uruguay?

(Answer) As the reviewer mentions, the expression that Korea is the world's only afforestation success country is not true. We revised the original sentence as follow (line 77-78):

“Korea is the country that has successfully achieved in afforestation after the Second World War and the Korean War.”

Line 108-116: Should this not be in the results section? The section on study area should describe the study area, now it seems to be a mixture of introduction, study area description and results.

(Answer) Reflecting the reviewer’s comment, we moved the line 108-116 to 4.1 section (370-378).

Line 127-165: For this study it seems to be of little relevance for the methodology what others do with carbon costs. I would have expected here more on what the carbon costs mean in Korea (why the 2010 carbon price, how was this determined, is there any difference according to carbon pool or sector?). also it would be useful here to indicate the differences between price, cost, social cost and value of carbon and carbon services.

(Answer) This part (line 127-165) of our study is to show that there are the significant differences (ranging from a minimum of $1 to $139; ref. 23) in market prices in different countries that runs carbon pricing mechanism, and that the social cost of carbon derived from the study also does not converge into certain meaningful value. We also wanted to point out that many governments and experts are agreeing that the current market price that we pay for carbon emissions is far too low to offset the damage that carbon emissions will cause. That is, the value of carbon sequestration service can be underestimated if we assume its value based on current market value.

As the reviewer pointed out, the part has many foreign cases little relevance for our study. As reflecting reviewer’s comment, we revised the ‘2.2 Cost of carbon’ section to ‘2.2 Price of carbon’ (line 132-185). Firstly, we mentioned the meaning of carbon price and carbon pricing mechanism of ETS and carbon tax. And we briefly summarize the efforts of countries to raise the carbon prices, including global carbon pricing mechanisms and social costs of carbon. Next, we describe Korea's carbon pricing mechanism, ETS, and the carbon prices traded during the first planning period of 2015-2017 (ref. 31).

We applied a specific market price, average trading price of all tradable units in the first planning period (2015-2017) in the Korean ETS market, to visualize the changes of land use and as one of monetary values. This specific value is adopted, among many existing market prices, as this is the first time that the unit of carbon in Korea is measured and priced. However, in order to find the price that is closest to the research year (2009) and convertible through the GDP deflator, it was converted as of 2010. Detail methods explained in the ‘2.4 methods’ section.

Also, we understand the reviewer's question is asking whether a particular carbon pool has a different carbon price. As mentioned in the ‘2.4 methods’ section, we calculated the amount of carbon (t C) per unit area stored in four carbon pools of each ecosystem type. Since we multiplied a specific market value by the amount of carbon to express in monetary term, the valuation does not differ by different carbon pools.

Line 164: Are the EU ETS quotes in USD? And why use USD here (rather than Euros) while in other parts you use won? Be consistent in using either USD for all, or local currencies for all, in the latter case also indicating the exchange rates into USD or Euro in a base year.

(Answer) The World Bank report we referenced (ref. 23) was originally in USD. Reflecting the reviewer's comment, we converted our estimation in KRW into USD in a base year (2010) for consistency and better understanding (line 25, 251, 256, 354, 357).As we mentioned on response for line 127-165, we delete other countries’ detail carbon cost part including line 155-165.

Line 191: Table A1… it took me a while to realize that this Table is in the Annex. First time you use the A reference in Table numbers, explain that it refers to Tables in the annex please.

(Answer) Reflecting the reviewer’s comment, we mentioned Table A1 in main text (line 207-208) as below:

“Carbon stocks per unit area stored in four carbon pools by ecosystem type show in Table A1”

Line 189-199: You discuss 20 ecosystems; in the tables you also have a set of 7 ecosystems. Explain in the text how they relate, why the difference, and what this may imply for the carbon-loss or gain estimates in this paper. It would also be useful to describe the different ecosystems in terms of criteria that make you classify a pixel into one or the other ecosystem. This information could be provided as complementary information or in the annex tables.

(Answer) Reflecting the reviewer's opinion, we supplemented the main text (line-192-197) to explain the LULC maps used in the calculation of area by ecosystem type in 1989 and 2009.

“The 1989 LULC map has 7 categories but the 2009 LULC map has more detailed 22 categories. The 22 categories of 2009 LULC Map is a subdivision of the seven categories of the 1989 LULC Map (see Table A1). For the 2009yr carbon stocks calculation and validation, we used the 2009 LULC map and reclassified it to 19 categories (Table A1). For the changes of 1989-2009 carbon stocks, we used 1989 and 2009 LULC map. To match the ecosystem types of them, we reclassified the 19 categories of 2009 LULC map to 7 categories of 1989 LULC map.”

Line 200-209: Here you justify the use of InVEST based on its use in studies on adaptation and landuse prediction. The use of InVEST here is, however, different. No projections are made but differences in biomass are estimated between two points in time. There is other software that can be used for that as well. So why InVEST and none of the other software?

(Answer) As the reviewer's comment, it is true that not only InVEST but also other software can be used to identify land use changes in future scenarios and the resulting carbon stock changes. The reason for using InVEST is that it can reflect four carbon pools and it is possible to analyze spatially and easily the time series change of carbon stocks through land use change, which is the purpose of this study.

Many studies have also adopted InVEST carbon model based approaches to estimate carbon stocks due to land-use changes in various ecosystems. For example, Tomasso and Leighton (2014; ref. 11) used InVEST carbon model to analyze changes in forest-based carbon stocks due to the land use changes in Connecticut, USA. Zhang et al. (2015; ref. 13) used LULC maps of 1980, 1995, and 2010 to identify spatial-temporal changes in carbon stocks (vegetation carbon and soil organic carbon) due to land-use change at China's national and regional levels.

In addition, there are many cases where InVEST was applied to Korea in previous studies, and the results were well matched with various ecosystem types and ecosystem services in Korea. Han et al. (2018; ref. 12) used the LULC map and InVEST model to identify the changes in urban green space and carbon sequestration services due to the urban growth in Seoul, Korea. Chung et al. (2015; ref. 36) used InVEST models to assessment the coastal ecosystem services for conservation strategies in Korea. Roh et al. (2016; ref. 16) also used InVEST models to estimate carbon stocks changes by LULC changes in Jeju Special Self-Governing Province, and showed that there was little difference between estimated carbon stocks based on field survey and LULC map based estimates (error rate 1.2%). As these studies show, the InVEST carbon model based approach applied in this study is appropriate to simulate temporal and spatial carbon stock changes due to land cover changes. This study is different from previous researches in deriving carbon stock loss due to LULC change for 20 years on a national and regional basis for all ecosystem types across Korea.

Line 207-210: What is the relevance for your study? I do not see any spatial land use scenarios towards the future and to prepare such scenarios socio-economic development pathways and policy options would need to be discussed as well, or trends at least a third point in time would need to be evaluated to use more reliable projection estimates.

(Answer) As reviewer mentioned, this study does not consider changes in carbon stocks due to the future scenarios. This study focuses on land-use changes over the past 1989-2009, resulting carbon stock changes, and its economic value. However, in order to provide future policy implications, it was necessary to mention at least the trends since 2009. We therefore confirmed that LULC change is continuing between 2009 and 2014, and mentioned that carbon stocks may continue to decline (line 430-438). In addition, we proposed a future research topic on how future carbon sequestration services will change, taking into account future socio-economic scenarios (see 4.3 Future policy directions to sustain the carbon sequestration services).

Line 215: The first and second LULC change types were analyzed to investigate the causes…. This is not clear. How was this done if there was only one change between two points in time? And how was the cause determined? For example, changing from forest to agriculture: what is the cause? Economic policy? Market prices? Need for more income?

(Answer) Since the unit of analysis is municipalities/counties with various LULC types, there has never been a single type change between two time points. Reflecting the reviewer's comment, we added the causes of LULC change of the top three municipalities (Seogwipo, Jeju, and Hwaseong) which showed big changes in carbon stocks for 20 years (line 395-399).

Line 234-237: Example of how you repeat in the text exactly the same information that we can read in the Table: make a choice: either present it in the table or in the text, but do not repeat.

(Answer) Reflecting the reviewer’s comment, we deleted line 234-237 in the main text.

Line 247: What do you mean with each cell of the ecosystem type? Is that a pixel? A cell of the table? This could be clarified if you describe the methodology to determine carbon stock in the section of the methodology.

(Answer) As the reviewer points out, the expression 'cell' can be confusing. We changed 'cell' into 'pixel (30x30m)' (line 279). Also, we added detail information how to spatialize the carbon stocks by each ecosystem type in 2.4 methods section (line 221-222; 237-242). In this study, as we showed in Table A1, firstly 2009yr carbon stocks per unit area (t C / ha) of 20 ecosystem types were calculated using carbon pool data. Then we spatialized the 2009yr carbon stocks by 20 ecosystem types in pixels (30m x 30m) using ecosystem type map derived from reclassified 2009yr LULC map.

Line 248-253: What does it add to the information already in the table? There is no clarification of the values found, just a repetition

(Answer) Reflecting the reviewer’s comment, we deleted the line 248-253 and explained the meaning of the numbers in Table A5 in the main text (line 280-282).

Line 256: Carbon stocks in each cell…….. Again, “cell”? and why are these values different from those in line 248?

(Answer) Reflecting reviewer’s comment, we changed the expression ‘cell’ into ‘pixel’. Also, we have added a description of how to spatialize carbon storage in pixels (line 288).

The 0-21.9 values, shown in line 248, are the calculated carbon stocks per pixels (30m x 30m) using the carbon stocks per unit area (t C/ha) of 19 ecosystem types in 2009 (Table A1). The 0-11.9 values, shown in line 256, are the carbon stocks per pixels calculated using the carbon stocks per unit area (t C/ha) of 7 ecosystem types in 1989 and 2009. The range of values changed by reclassifying carbon values from the 19 ecosystem types listed in Table A1 into seven ecosystem types.

Line 279: “changes in LULC” explain in foot note what you mean with this. Also explain some of the more unexpected changes. For example, water to forest.

(Answer) Reflecting the reviewer’s comment, we add footnote to explain the meaning of “changes in LULC” (line 321).

The 5.4 million t C represents the net increase of carbon stocks resulting from water to other LULC types. Water have been changed to forest, farmland, grassland, and barren land through the waterway change or the reclamation project. In Korea, reclamation projects have been active in the last 20 years (1989-2009), mainly in the west and south sea coastal areas (ref. 36, 43).

Line 279: Table 3: I am a little puzzled how urban land shows a positive change in carbonstock of 4.3 million t of C between 1989 and 2009, while the carbon stock in 2009 is 2.6 million t. It had a negative carbon stock in 1989? The same for barren land (see also Table 5). This type of information is what should be explained in the text, rather than repeating the figures already presented in the tables.

(Answer) In response to the reviewer's comments, we have added an additional explanation to the text about the increase in carbon stocks over the last two decades in urban land and barren land (line 309-318).

“The 4.3 million t C represents the net increase of carbon stocks resulting from all LULC changes from urban areas into forests, grassland (urban parks), and farmland (garden). The 5.9 million t C also means the net increase in carbon stocks that occurred over the last 20 years as the barren land changed to a different land type. Like urban areas, barren land has been transformed into parks and farmland.”

However, the carbon stocks of urban ecosystems in 2009 (2.6 million t C) in Table 5 and Table A5 are actually the carbon stocks of forest ecosystems. Of the 20 ecosystem types in Table A5, 2.6 million t C represents the carbon stocks of urban forest ecosystems, and urban forest ecosystems are same as forest ecosystems. However, according to the ecosystem classification system of Table A1 and Table A5, urban forest ecosystem is included in urban ecosystem among seven ecosystem types. But urban ecosystems actually mean built-up areas. Thus, we excluded urban forest ecosystems from urban ecosystems and integrated them into forest ecosystems. As a result, the 2009 LULC map ecosystem type was modified from 20 to 19.

Line 297-299: Positive correlation between stock of 1989 and change between 1989 and 2009: however, of the ten municipalities/counties with highest stock in 1989 only 1 also showed highest change. How do you explain that if there is a positive correlation?

(Answer) Table 4 of original text shows the top 10 municipalities of high carbon stocks in the 2009 year, not in the 1989 year. But as reflecting reviewer’s comment and to clarify the meaning, we revised the original text and Figure 6. We noticed that the x and y axes were swapped on Figure 6, so we corrected it. As shown in Figure 7 in revised text, the top 3 municipalities with high carbon stocks in 1989 are not the same as the top 3 municipalities with high changes of carbon stocks during 1989-2009. Since the linear regression analysis was derived for all 162 municipalities, there may be regional differences even if there was a positive correlation.

Line 316-318: Would be good to have information on how these regions relate to the municipalities/counties in Table 4.

(Answer) We did not analyze changes in economic value among the 162 municipalities/counties. The purpose of this study is mainly to understand the carbon stocks and its changes at the national and local levels. For the economic value of carbon, we visualize the economic value of carbon sequestration services and their changes at the national and regional levels. For the comparison between countries to use other purpose, we think the regional self-government level (16 provinces) would be better than the detailed local government (162 municipalities/counties) level.

Line 327: Ecosystem (land)…. Why is land between brackets?

(Answer) As reflecting reviewer’s comment, we delete line 327 and revise the main text to clarify the meaning (line 367-381).

Line 342: Changes in LULC influenced by changes in carbon stock? Should that not be the other way around?

(Answer) The English translation was incorrect. We revised the original text as follow (line 390-391):

“At the national level, land use changes from forests to agricultural land, urban land, and grasslands have had a significant impact on carbon stock changes.”

Line 345: Where development projects are actively promoted…. This is mentioned several times. But what is the evidence? Any references? And how is this done? What are the policies behind it?

(Answer) As reflecting reviewer’s comment, we identified which development projects occurred in the top three municipalities out of the ten municipalities that have had high carbon storage changes due to land use change over the past two decades. In Seogwipo, ranches, farms and recreational areas increased during this period. In Jeju, farms, ranches and golf courses increased. In Hwaseong, large-scale development projects constructing the residential, industrial and commercial areas were promoted due to the new town development policy of national government. This information added to main text (line 395-399).

Line 347-349: This would make it less probable that the correlation between high initial carbon stock and high level of change is positive. Either explain better or revise your statistical analysis.

(Answer) As shown in Figure 7 and response for line 297-299, not all municipalities, which had high carbon stocks in 1989, have seen significant changes in carbon stocks over 1989-2009. In the top 10 municipalities of Table 4, there are municipalities with relatively larger carbon stock changes (line 393-395) and relatively small carbon stock changes (line 399-401).

Line 360-361: Do you need all your data and analysis to make this type of prediction? What is really the added value of the figure here? What do the groups stand for?

(Answer) As the reviewer mentioned, this figure is not based on data and scenario. Therefore, line 360-367 and figure 7 in original text have been deleted. As mentioned in the response to the review of line 207-210, we added the necessity of future study to analyze how carbon storage will change according to changes in land use at local level by future socioeconomic scenarios (line 483-486).

Line 368-377: Should this not be in the methodology? And if it is there already, you can omit here.

As suggested by the reviewer, we have merged 368-370 into the line 145-148, 2. Materials and methods 2.2 Price of carbon. And we deleted the rest of the part.

Line 385-432: Revise conclusions. This should not be further discussion and not have further references nor new information. It should be clear what your conclusions are and not repeat any of the previous sections, but rather build on those previous sections and respond to the objectives/research questions of your paper.

(Answer) As with the reviewer's opinion, discussion and conclusion are mentioned together. Therefore, we have divided this section into section 4.3 Future policy directions to sustain the carbon sequestration services and 5. Conclusion. In section 4.3, we suggest policy directions to sustain the carbon sequestration services. In section 5, we  summarized the study and suggest future research.

Line 400-402: These urbanization…..wetlands. who says that development frequently occurs in high carbon storage areas? And more so than not?

(Answer) As reflecting reviewer’s comment, we revised original sentence as follow:

“And these urbanization and development projects will frequently occur in natural areas, such as mangroves, rain forests, farmland with traditional knowledges, and tropical and temperate wetlands.”

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Significant improvements have been made

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

The authors present a paper titled "Sustainable Management of Carbon Sequestration Service in Areas with High Development Pressure: Considering Land Use Changes and Carbon Costs. The manuscript analyses the changes in carbon sequestration services made by land use changes in the period 1989-2009. The abstract is clear, the Introduction is sound, but the Methods section, in my opinion, should be improved. In the 9 lines of the paragraph 2.1, the authors underline how in 2015, the forest area in Korea occupies 64 % of the land area and how volume density and carbon stocks increased on 2012; they also mention the increase in the price of the ecosystem service provided by forests in the period 1987-2014. The information provided in the above-mentioned lines (104-112) surely present the situation in Korea and the importance of forest in this country but does not help to understand why the paper is focussed on the period 1989-2009 and on the land use changes occurred in that period. In detail, a decrease in forest areas occurred in the period 1989-2009 but how this decrease is linked to the increase registered in the period 1960-2015? What is the significance, the real importance of analysing this period not referring to the actual one, to the current year or to much more recent years? I suggest the authors to better clarify the motivation behind the choice of the period and the importance of it to guide sustainable policy decisions.

In paragraph 2.3 Methods, lines 171-187 describe the classification in categories and sub-categories for each ecosystem service and the calculation of carbon stocks but it’s not clear which is the land use map and year that calculations are referred to. Then, at line 186, the authors say that validation is referred to the data of 2010 provided by the Korea Forest Service: these data are referred to the year 2010 and land use of 2010? I suggest the authors to better clarify year and land use map used in calculations and elaborations in the text and also in the Tables (see e,g. Table A2, A3, A4, these tables do not specify year and land use map used).

Analogously, in Section 3. Results, paragraph 3.1 Carbon Storage and Validation is not clear about year and map from which they derive the obtained results. At line 233, they mention again the Korea Forest Service without specify year and characteristics of land use map produced by the Korea Forest Service.

For what concerns section 4. Discussion, I suggest the authors to rename or include paragraph 4.3 Sustainable carbon sequestration service management strategy: at national and regional level in section 5. Conclusion. Even with some general concepts, this paragraph provides some concrete indications for policy decisions that could help to move towards sustainability. I suggest to better focus the conclusion on the importance of the analysed period 1989-2009 for future policy decision since this period shows a picture of the country which is far (how much? What happened from 2009 to 2019?) from the actual situation.

Reviewer 2 Report

This manuscript by Chun et al employs some simple approaches to estimate the carbon storage changes in Korea during 1989-2009 and associated economic values. I find the methods to estimate both the carbon storage and associated economic values unreliable. Therefore, I cannot support the publication of this manuscript.

To estimate carbon storage for different ecosystem and land use types, the authors use a simple method that multiplies the area of a given ecosystem/land use type and some carbon density. For example, the aboveground biomass of coniferous forests is calculated as the area times a fixed stock density (130.33 m3/ha) times some fixed BEF values… This simple method is way too coarse, since parameters like forest growing stock per unit forest area and root-shoot ratio are known to change with site quality, stand age, etc.  In fact, there already exist studies that have used more sophisticated methods to investigate the carbon dynamics of Korean forests, for example, Lee et al. (2014, Biogeosciences) as cited in this manuscript. I would encourage the authors to apply more reasonable carbon accounting methods to estimate the carbon storage and its changes in Korea.

To estimate the economic values of carbon storage, the authors again simply multiply the fixed monetary value borrowed from other studies by the above estimated carbon storage. This shows that the authors perhaps do not understand carbon pricing or carbon tax. As CO2 is a public pollutant, the taxation of pricing of carbon is to use economic leverage to reduce CO2 emission. Therefore, the setting of the carbon tax needs to well consider the carbon emission reduction goal and the market margin value of each additional dollar of carbon tax, and if the tax is tradable, which trading market it applies to? It’s definitely not that simple to borrow from other studies which may have different socioeconomic settings.