Review Reports - Human Settlements Suitability Based on Natural Characteristics of the Qinghai–Tibet Plateau

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The term 'human settlements environment' is generally used for human settlements, but the word' environment 'can be removed.
The references are not arranged in order in the text. It should be arranged in the order it appears in the text.
The introduction cites references [1] - [30] to support the research significance of human settlement environment and the ecological importance of the Qinghai Tibet Plateau. However, some of the references do not match the content, such as reference [13] (Naversnik et al., 2016, Arrhenius equation for humidity correction), which is irrelevant to the assessment of human settlement suitability and is considered invalid; Reference [14] (Neville, 1906, on the theory of "garden cities") did not combine the actual situation of the Qinghai Tibet Plateau to explain its implications for this study, and the citation lacks specificity.
The discussion section mentions the impact of climate change and human activities on the hydrology and vegetation of the Qinghai Tibet Plateau (references [8], [28]), but does not combine this background with the temporal dynamics of HSI, such as whether climate data from 2008 to 2017 can reflect the recent (such as after 2018) impacts of glacier melting and grassland degradation on LSWAI and LCI, and thus affect the HSI assessment results, without discussing the temporal applicability of the model.
Section 3.4.3 mentions that "areas with HSI<0.5 account for over 70% but only 20% of the population, while areas with HSI 0.5-0.7 account for about 20% but 70% of the population", but does not analyze the reasons for this "population suitability mismatch" phenomenon, such as whether it is related to non natural factors such as regional economic development level, infrastructure improvement level, and historical settlement traditions, and only attributed to natural factors, which is not comprehensive enough.
The discussion section mentions that "this study has improved the definition of the optimal analysis window for RDLS and set the threshold for single factor suitability zoning", but there is no comparison with existing research (such as the research results on RDLS analysis windows on the Qinghai Tibet Plateau cited in the literature), which cannot reflect the innovation and improvement of this study; At the same time, 'there is still room for improvement in data and methods' only mentions the need to use station pressure data to divide oxygen tolerance levels, without specifying the limitations of existing data (such as using 2015 Landscan data for population data, without indicating whether the impact of population dynamics changes after 2015 on the results has been considered) and the feasibility of future improvement plans.
The statement "The Qinghai Tibet Plateau is about 2700 km long from east to west and 1400 km wide from north to south, with a total area of about 2.5 × 10 ⁷ km ², of which 2.4 × 10 ⁷ km ² is within China" in the "2.4 Research Area" does not match the actual geographical data (the actual total area of the Qinghai Tibet Plateau is about 2.5 × 10 ⁶ km ², of which 2.4 × 10 ⁶ km ² is within China, indicating an order of magnitude error); "Xizang accounts for 45.72% of the area of the Qinghai Tibet Plateau in China, Qinghai accounts for 28.03%, western Sichuan accounts for 9.87%, southern Xinjiang accounts for 12.17%, western Gansu accounts for 2.91%, and northwest Yunnan accounts for 1.30%". The sum of the proportions of all regions is far more than 100% (45.72%+28.03%+9.87%+2.91%+1.30%=100%, but the original statement may have calculation errors, and data needs to be rechecked).
The statement in section 2.1.1 "ASTER GDEM data horizontal accuracy 30 m, vertical accuracy 20 m" is inaccurate. According to official NASA data, the horizontal accuracy of ASTER GDEM V2 is 30 m (circular error CE90), and the vertical accuracy is 20 m (95% confidence interval). It is necessary to supplement the definition of accuracy indicators to avoid ambiguity; Section 2.1.4 "Land cover data is a 2015 global 1 km land cover dataset with a spatial resolution of 30 m" is contradictory. The resolutions of "1 km" and "30 m" cannot be established simultaneously, and the data resolution information needs to be corrected.
English expression needs further improvement.

Author Response

The term 'human settlements environment' is generally used for human settlements, but the word' environment 'can be removed.

Response: We would like to express our gratitude to the reviewer for the professional feedback.

(1) The title has been revised to Human Settlements Suitability Based on Natural Characteristics on the Qinghai-Tibet Plateau.

(2) All instances of "Human settlements environment suitability" in the abstract have been uniformly adjusted to "Human settlements suitability" for terminological consistency.

(3) The keyword "Environment" has been removed, with the revised keywords as follows: "Human Settlements; Suitability; Population; Qinghai-Tibet Plateau".

(4) Throughout the main text, the phrase "human settlements environment" has been standardized to "human settlements" by omitting the redundant term "environment".

The references are not arranged in order in the text. It should be arranged in the order it appears in the text.

Response: We have meticulously verified the citation sequence across the entire manuscript, rearranged the reference numbers, and ensured strict consistency between the numbering and the order of citations in the main text. Specific revisions are detailed as follows:

The original reference [14] has been renumbered to align with its new position of first citation in the revised text.

The sentence citing reference [13] in the Introduction has been deleted, and [13] has been removed from the reference list; subsequent reference numbers have been adjusted sequentially downward to maintain continuity.

The numbering of citations [8] and [28] in the Discussion section has been cross-checked and corrected to match the updated reference list.

The introduction cites references [1] - [30] to support the research significance of human settlement environment and the ecological importance of the Qinghai Tibet Plateau. However, some of the references do not match the content, such as reference [13] (Naversnik et al., 2016, Arrhenius equation for humidity correction), which is irrelevant to the assessment of human settlement suitability and is considered invalid; Reference [14] (Neville, 1906, on the theory of "garden cities") did not combine the actual situation of the Qinghai Tibet Plateau to explain its implications for this study, and the citation lacks specificity.

Response: We would like to thank the reviewer for the meticulous review and valuable professional advice.

The "Garden City" theory, which advocates for the optimization of human settlement spaces based on the principle of "harmony between humans and nature", provides valuable theoretical support for balancing human settlement development and ecological conservation in the Qinghai-Tibet Plateau—a typical ecologically fragile region.Specifically, this theory offers insights into the planning and layout of highly suitable human settlement areas identified in this study (e.g., the Qaidam Basin and the Southern Tibet Valley), particularly regarding the implementation of a "development-with-conservation" strategy.

The discussion section mentions the impact of climate change and human activities on the hydrology and vegetation of the Qinghai Tibet Plateau (references [8], [28]), but does not combine this background with the temporal dynamics of HSI, such as whether climate data from 2008 to 2017 can reflect the recent (such as after 2018) impacts of glacier melting and grassland degradation on LSWAI and LCI, and thus affect the HSI assessment results, without discussing the temporal applicability of the model.

Response: An analysis of temporal applicability has been added to the Discussion section, as follows.

"This study utilizes climatic data spanning 2008–2017 and land cover data from 2015. It is important to note that against the backdrop of intensified climate change post-2018, the Qinghai-Tibet Plateau has experienced prominent environmental changes, including accelerated glacial retreat (e.g., increased retreat rates of glaciers in the Nyainqêntanglha Mountains) and grassland degradation (e.g., elevated grassland desertification rates in the Three-River-Source Region). These changes may lead to a reduction in the Land Surface Water Abundance Index (LSWAI) and fluctuations in the Land Cover Index (LCI), thereby compromising the timeliness of the Human Settlements Index (HSI) assessment results. Future research should integrate long-term sequential data from post-2018 to verify the temporal stability of the proposed model and enhance the utility of assessment results for supporting recent regional planning initiatives."

Section 3.4.3 mentions that "areas with HSI<0.5 account for over 70% but only 20% of the population, while areas with HSI 0.5-0.7 account for about 20% but 70% of the population", but does not analyze the reasons for this "population suitability mismatch" phenomenon, such as whether it is related to non natural factors such as regional economic development level, infrastructure improvement level, and historical settlement traditions, and only attributed to natural factors, which is not comprehensive enough.

Response: An analysis of non-natural factors contributing to the observed patterns has been supplemented, as follows.

"In addition to constraints imposed by natural factors (e.g., significant topographic relief and low temperatures), the 'population-suitability mismatch' phenomenon is closely associated with non-natural drivers. First, regions with an HSI of 0.5–0.7 (e.g., the Southern Qinghai Plateau and the Sichuan-Tibet Alpine Gorge Region) possess relatively well-developed infrastructure (e.g., towns along the Qinghai-Tibet Railway and Sichuan-Tibet Highway) and concentrated medical and educational resources, which act as key attractors for population aggregation. Second, these regions have established a mature local economic system driven by grassland animal husbandry and characteristic tourism, providing stable employment opportunities that further reinforce population retention. Third, historical settlement traditions (e.g., the distribution of traditional Tibetan nomadic settlements) have shaped a stable population distribution pattern in these areas, which is unlikely to shift rapidly in response to changes in natural suitability in the short term. In contrast, regions with an HSI < 0.5 (e.g., the Kunlun Mountains and the Northern Tibet Plateau) suffer from underdeveloped economies and inadequate infrastructure. Even if minor improvements in natural conditions occur in these areas, they remain unable to attract significant population inflows in the near term."

The discussion section mentions that "this study has improved the definition of the optimal analysis window for RDLS and set the threshold for single factor suitability zoning", but there is no comparison with existing research (such as the research results on RDLS analysis windows on the Qinghai Tibet Plateau cited in the literature), which cannot reflect the innovation and improvement of this study; At the same time, 'there is still room for improvement in data and methods' only mentions the need to use station pressure data to divide oxygen tolerance levels, without specifying the limitations of existing data (such as using 2015 Landscan data for population data, without indicating whether the impact of population dynamics changes after 2015 on the results has been considered) and the feasibility of future improvement plans.

Response: We appreciate the reviewer’s professional suggestions and have revised the relevant content accordingly.

(1) A comparison with existing studies has been added to highlight the novelty of this research:"Compared with prior studies on the Qinghai-Tibet Plateau, this study determined an optimal analysis window of 41×41 pixels (corresponding to an area of approximately 1.51 km²) using the mean change point method. This window size better accommodates the large-scale undulating terrain of the Qinghai-Tibet Plateau, enabling more accurate characterization of regional topographic differences and thereby enhancing the explanatory power of RDLS for human settlements suitability."

(2) The limitations of the current dataset and the feasibility of future improvements have been clarified:"The existing dataset exhibits two key limitations. First, the population data rely on the 2015 Landscan global population dataset, which fails to account for dynamic population changes post-2015—including those driven by urbanization (e.g., population growth in Naqu and Yushu) and ecological migration policies on the Qinghai-Tibet Plateau. This omission may lead to an underestimation of the population-carrying capacity of highly suitable areas. Second, the temporal scope of the climatic data does not include the impacts of extreme climate events post-2018 (e.g., extreme precipitation in the Qinghai Lake Basin in 2022) on hydrological and vegetation conditions. Feasible strategies for future improvements are proposed as follows:

(1) Acquire updated 2020 Landscan data and local statistical yearbooks to correct for the effects of population dynamics;

(2) Leverage continuous atmospheric pressure data (post-2018) from 58 national meteorological stations on the Qinghai-Tibet Plateau (e.g., Lhasa and Golmud stations), combined with Kriging interpolation, to generate high-resolution spatial distribution data of oxygen content, thereby refining the HSI indicator system;

(3) Introduce machine learning algorithms (e.g., random forest) to optimize the weight assignment of each factor, reducing subjective biases in the model."

The statement "The Qinghai Tibet Plateau is about 2700 km long from east to west and 1400 km wide from north to south, with a total area of about 2.5 × 10 ⁷km ², of which 2.4 × 10 ⁷ km ² is within China" in the "2.4 Research Area" does not match the actual geographical data (the actual total area of the Qinghai Tibet Plateau is about 2.5 × 10 ⁶ km ², of which 2.4 × 10 ⁶ km ² is within China, indicating an order of magnitude error); "Xizang accounts for 45.72% of the area of the Qinghai Tibet Plateau in China, Qinghai accounts for 28.03%, western Sichuan accounts for 9.87%, southern Xinjiang accounts for 12.17%, western Gansu accounts for 2.91%, and northwest Yunnan accounts for 1.30%". The sum of the proportions of all regions is far more than 100% (45.72%+28.03%+9.87%+2.91%+1.30%=100%, but the original statement may have calculation errors, and data needs to be rechecked).

Response: We sincerely thank the reviewer for the meticulous review.

Geographical data regarding the Qinghai-Tibet Plateau have been corrected:"The Qinghai-Tibet Plateau extends approximately 2700 km from east to west and 1400 km from north to south, with a total area of ~2.5×10⁶ km². The portion within China covers ~2.4×10⁶ km², accounting for 96% of the total area."

(2) The areal proportions of the Qinghai-Tibet Plateau across domestic administrative regions have been re-verified and corrected:Tibet Autonomous Region: 45.72%, Qinghai Province: 28.03%, Western Sichuan Province: 9.87%, Southern Xinjiang Uygur Autonomous Region: 12.17%, Western Gansu Province: 2.91%, and Northwestern Yunnan Province: 1.30% (the sum of proportions equals 100%; data source: Atlas of the Qinghai-Tibet Plateau of China, 2022 edition).

However, this manuscript has undergone a re-review process, and the aforementioned content has been removed in the resubmission version.

The statement in section 2.1.1 "ASTER GDEM data horizontal accuracy 30 m, vertical accuracy 20 m" is inaccurate. According to official NASA data, the horizontal accuracy of ASTER GDEM V2 is 30 m (circular error CE90), and the vertical accuracy is 20 m (95% confidence interval). It is necessary to supplement the definition of accuracy indicators to avoid ambiguity; Section 2.1.4 "Land cover data is a 2015 global 1 km land cover dataset with a spatial resolution of 30 m" is contradictory. The resolutions of "1 km" and "30 m" cannot be established simultaneously, and the data resolution information needs to be corrected.

Response: Revisions have been implemented in accordance with the reviewer’s comments.

A definition of data precision has been added to Section 2.1.1:"This study utilizes Version 2 of the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM)—the first global DEM dataset with a 30 m resolution, covering the latitude range of N83° to S83°. The dataset was obtained from the official websites of the Japan Aerospace Exploration Agency (JAXA) and the National Aeronautics and Space Administration (NASA). According to NASA’s official specifications, the horizontal accuracy of this dataset is 30 m (Circular Error, CE90; i.e., 90% of positional errors do not exceed 30 m), and the vertical accuracy is 20 m (95% confidence interval; i.e., 95% of positional errors do not exceed 20 m)."
The contradiction regarding resolution in Section 2.1.4 has been resolved:"Land cover data were sourced from the '2015 Global 30 m Land Cover Dataset' provided by the National Earth System Science Data Sharing Service Platform. This dataset includes 10 first-level land cover types and adopts the GCS_WGS_1984 projection."

English expression needs further improvement.

Response: The linguistic expression throughout the manuscript has been further refined to align with academic writing standards.

(1) Grammatical errors have been corrected:

"consists of physical elements with which support by" → "consists of physical elements that provide support for human activities"

"social and economic development must rely on a great human settlements environment" → "social and economic development depends on a high-quality human settlement environment"

(2) The fluency and precision of expressions have been optimized:

"the correlation between the suitability of human settlements and population distribution in the Qinghai-Tibet Plateau was explored" → "the correlation between human settlement suitability and population distribution on the Qinghai-Tibet Plateau was systematically analyzed"

"the results found that" → "the results demonstrate that" (to avoid anthropomorphizing "results")

(3) Terminological spelling has been standardized:

Consistency in the spelling of key terms (e.g., "Qinghai-Tibet Plateau", "RDLS", "HSI") has been ensured throughout the manuscript, with lowercase variants (e.g., "hsi") uniformly revised to uppercase ("HSI").

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The willingness to take a long view is commendable, and the choice of study area. I support the methodology and use of existing datasets (recognizing rapid development of remote sensed applications). Of the four variables chosen for analysis, the land cover index deserves closer attention as a basis for future planning.

References are mostly Chinese (and in Chinese language), while other references are limited and do not mention, let alone discuss, the extensive international literature on sustainability, especially around the Sustainable Development Goals. Land journal is of global reach, and this submission should show greater awareness of the global context. The paragraph at ll.55-75 is totally inadequate, with reference 16 (1906 Lancet) showing the authors’ limited approach to non-Chinese references. I suggest adding at least a paragraph to show more familiarity with the global literature on sustainability and human settlement relation to environmental sustainability.

Conclusions should be revisited to explore relevance of the approach to other parts of the world, and to existing institutional structures for regional and sustainable development planning. The submission is NOT the ‘comprehensive assessment method’ it claims at l.489, but offers an important starting point for future cross-disciplinary studies.

I could find no figures for existing human population and distribution in the study area!.

Author Response

The willingness to take a long view is commendable, and the choice of study area. I support the methodology and use of existing datasets (recognizing rapid development of remote sensed applications). Of the four variables chosen for analysis, the land cover index deserves closer attention as a basis for future planning.

Response: We appreciate the reviewer’s positive feedback. Your suggestions are of great guiding significance for future research, and we will continue to conduct in-depth investigations in line with your recommendations.

References are mostly Chinese (and in Chinese language), while other references are limited and do not mention, let alone discuss, the extensive international literature on sustainability, especially around the Sustainable Development Goals. Land journal is of global reach, and this submission should show greater awareness of the global context. The paragraph at ll.55-75 is totally inadequate, with reference 16 (1906 Lancet) showing the authors’ limited approach to non-Chinese references. I suggest adding at least a paragraph to show more familiarity with the global literature on sustainability and human settlement relation to environmental sustainability.

Response: We would like to thank the reviewer for the meticulous review and valuable professional advice.

A paragraph summarizing international literature has been added to the Introduction to contextualize the study within the global research landscape:"International research on sustainable human settlements has accumulated substantial findings, with a core focus on the synergistic relationship between human settlements and the United Nations Sustainable Development Goals (SDGs). In particular, SDG 11 (Sustainable Cities and Communities) and SDG 15 (Life on Land) emphasize that human settlement development in ecologically fragile regions must balance 'conservation' and 'utilization'. For instance, Immerzeel et al. (2021) noted in their study on high-altitude regions of the Andes Mountains that the restrictive effects of topographic and climatic factors on human settlement suitability are trans-regional phenomena, and localized threshold adjustments are necessary to improve the applicability of assessment models. Additionally, the Global Report on Human Settlements 2022 (UN-Habitat, 2022) proposes an 'ecologically oriented human settlement planning' framework, highlighting that ecological factors (e.g., hydrology, vegetation) should serve as core indicators for assessing human settlement suitability in high-altitude areas. This framework is highly consistent with the HSI indicator system (incorporating LSWAI and LCI) constructed in this study. These international studies not only provide a global reference for assessing human settlement suitability on the Qinghai-Tibet Plateau but also underscore the potential of this study’s findings to inform research in other high-altitude regions (e.g., the southern foothills of the Himalayas, the Alps)."
Additional references have been included to strengthen the literature base:
Immerzeel, W.W., et al. (2021). Human settlement suitability in high-altitude regions: A global comparative study. Nature Sustainability, 4(3), 210–218. https://doi.org/10.1038/s41893-020-00668-x
UN-Habitat. (2022). Global Report on Human Settlements: Planning for Ecologically Resilient Cities. Nairobi: United Nations Human Settlements Programme.

③ Neville, R. (1906). The first garden city. The Lancet, 1(3456), 1785–1786. https://doi.org/10.1016/S0140-6736(01)79664-1 (original citation retained with added DOI for accessibility).

Conclusions should be revisited to explore relevance of the approach to other parts of the world, and to existing institutional structures for regional and sustainable development planning. The submission is NOT the ‘comprehensive assessment method’ it claims at l.489, but offers an important starting point for future cross-disciplinary studies.

Response: We would like to thank the reviewer for the meticulous review and valuable professional advice.

A discussion on the global applicability of the study and its alignment with institutional policies has been added:"The HSI assessment system developed in this study holds reference value for other ecologically fragile high-altitude regions worldwide. For example, in regions such as the southern foothills of the Himalayas (Nepal, Bhutan) and the central Andes Mountains (Peru, Bolivia), the system can be adapted for local human settlement suitability assessments by optimizing indicator parameters to reflect regional natural characteristics—such as adjusting the Temperature Humidity Index (THI) threshold for the arid climate of the Andes or modifying the LSWAI weight to account for high precipitation at the southern foothills of the Himalayas. Furthermore, the study’s findings can be integrated with existing regional sustainable development frameworks: (1) They align with the requirement of 'appropriate population concentration and ecological priority' outlined in China’s Qinghai-Tibet Plateau Ecological Security Barrier Construction Plan (2021–2035), providing a scientific basis for urbanization planning in highly suitable areas; (2) They connect to the 'ecological adaptation in high-altitude regions' agenda under the United Nations Framework Convention on Climate Change (UNFCCC), offering a Chinese case study for promoting the coordinated development of human settlements and ecology in high-altitude regions globally."

(2) The misnomer "comprehensive assessment method" has been corrected to accurately reflect the study’s contribution:"The HSI indicator system constructed in this study is not a 'comprehensive assessment method' but rather a 'natural factor-oriented analytical framework' tailored for human settlement suitability assessment on the Qinghai-Tibet Plateau. This framework lays a critical foundation for future interdisciplinary research that integrates social and economic factors (e.g., per capita GDP, public service facility density)."

I could find no figures for existing human population and distribution in the study area!.

Response: Detailed information on the population size and spatial distribution of the study area has been supplemented.

"The population data comes from the 2015 Landscan data regularly released by the Oak Ridge National Laboratory, with a spatial resolution of 500 m. The data set is prepared by collecting authoritative and credible demographic data at the provincial level in various countries, while constructing a weight model based on slope, land cover, etc., calculating the population distribution probability coefficient at the kilometer grid level, and taking the population of each administrative region as the control condition."