New Interpretation of Human–Land Relation: Differentiated Impacts of Global Demographic Transition on Carbon Emissions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I found the paper original and interesting, and most of my comments are formal, but not irrelevant.

The paper lacks protocol, description of data and data sources, and access to data. With 195 countries recognised by the UN, many of which lack reliable data, the figure of 208 countries seems surprising. Nothing is said about the reliability of data or missing values. After all, how many countries will ever reach an urbanisation rate of 83% (Figure 8)? Which year of analysis was taken into account? Some variables are not sufficiently described: by DT(1) do you mean the percentage of elderly or the growth rate of the percentage of elderly? By secondary and tertiary industry, do you mean industry and service sector?

While economic and environmental terms are used precisely and rigorously, demographic terms mean nothing. Demographic transition, as defined by the theory of demographic transition (originally by Notestein, Thompson, Dirk, later by AJ Coale and JC Chesnais) or the model of demographic transition, describes and explains the evolution of mortality, fertility and age structure due to (and during) economic modernisation (the latter including, inter alia, industrialisation and urbanisation). The beginning of the demographic transition is marked by population juvenalisation (due to decreasing infant mortality rates), and it is only when adult mortality changes and fertility declines that population ageing is observed. So I suggest replacing the term of demographic transition with population ageing and urbanisation, and using these precise and correct terms systematically in the paper, even if the modified title becomes longer and less catchy. BTW: what is the current demographic transition (line 383)? Is there another DT (apart from the Neolithic transition, but I don't think you want to refer to that)?

Some formulations point to causality between variables, which raises my concerns, especially in the case of ageing and urbanisation: do they drive economic growth (line 197), or do they simply remain correlated, because it was economic growth that triggered demographic transition and ageing, but today both economic and demographic phenomena remain interdependent? While the regression models do not aim to decide which came first: the egg or the chicken, I suggest replacing these formulations with a neutral interpretation pointing to correlation, association or contribution.

Regarding my allegation of inappropriate self-citation, at least 5 of the authors' papers are cited, if I am not wrong. This would not be allowed in a demographic journal that I edit (with a much lower IF than Sustainability).

Finally, a non-formal comment. I was initially surprised to find that ageing is positively correlated with GDP growth and GDP per capita (formulas in line 152), but table 5 indicates a reverse relation (ageing in the denominator, first formula). I was relieved to read the results (lines 374-377), which were in line with my intuition. Can you comment on that?

Comments on the Quality of English Language

Some typos, like lines 148 (reference), 149 and 102. Otherwise, the language is good. 

Author Response

Thank you for your valuable and practical comment.

We have revised the question you raised, please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article combines demographic studies with environmental metrics to illustrate how shifts in population structure can significantly influence carbon emissions across 208 countries. The use of robust regression models based on the Cobb-Douglas production function to quantify these impacts. I recommend accepting the manuscript with minor revisions, suggesting improvements in the following areas:

1) The abstract mentions that demographic transition has a "positive impact on per capita economic growth" while negatively impacting "overall economic output and economic growth," which might seem contradictory to those unfamiliar with these economic nuances. For instance, you can say, "Our study highlights that while demographic transition boosts per capita economic growth, it adversely affects overall economic output and aggregate economic growth, highlighting significant reductions in carbon emissions as a result of these demographic changes."

2)Dependent Variable Design: It may be beneficial to include more environmental and socio-economic variables, such as levels of education, accessibility of health services, energy prices, and policy shifts. These factors could significantly influence carbon emissions.

3) In-depth Analysis of Regional Differences: The document refers to data from 208 countries, which vary widely in geographic distribution and economic development levels. It is unclear whether the author has analyzed the specific performance and underlying reasons of different regions (such as Asia, Africa, and Europe) in terms of population and environmental dynamics. Is the relationship between population structure and carbon emissions similar across these regions?

4) Policy Recommendations: While the article provides some suggestions for policy formulation, more specific strategies are needed to address the impacts of aging populations and urbanization on carbon emissions. For instance, describing how policies can be adjusted in societies with high aging populations to reduce carbon emissions, including promoting green transportation and optimizing energy use structures. It is advisable to incorporate international case studies to analyze how different countries effectively address similar challenges through policy innovation. The article should also explore how socio-economic factors such as income levels, education, and technological development affect population transitions and the environment.

5) Conclusion: While effectively summarizing the study's outcomes, the conclusion would be enriched by incorporating a critical evaluation of the work. This section should highlight the strengths and weaknesses and suggest directions for future research, particularly in contexts where the findings may have broader impacts or applications.

6) Language Expression and Clarity: The language of the manuscript requires refinement. It often employs unnecessarily complex and passive constructions, making it verbose and indirect. For instance, the phrase "The Kyoto Protocol reached in 1997 established a legal requirement for developed countries to reduce their greenhouse gas emissions" can be shifted to an active voice: "In 1997, the Kyoto Protocol established a legal requirement for developed countries to reduce their greenhouse gas emissions." Moreover, it is imperative to elucidate the full form of acronyms upon their first appearance, such as “C-D” and “EKC.” If the text is abundant with acronyms, incorporating a glossary would facilitate reader comprehension.

Comments on the Quality of English Language

The language of the manuscript requires refinement. It often employs unnecessarily complex and passive constructions, making it verbose and indirect. For instance, the phrase "The Kyoto Protocol reached in 1997 established a legal requirement for developed countries to reduce their greenhouse gas emissions" can be shifted to an active voice: "In 1997, the Kyoto Protocol established a legal requirement for developed countries to reduce their greenhouse gas emissions." Moreover, it is imperative to elucidate the full form of acronyms upon their first appearance, such as “C-D” and “EKC.” If the text is abundant with acronyms, incorporating a glossary would facilitate reader comprehension.

Author Response

Thank you for your valuable and practical comment. We have revised the question you raised.

Please see the attachment.

Author Response File: Author Response.pdf