Humanity currently faces an array of global challenges that cross national borders, including issues like food security, energy crises, climate change, and ecological degradation. Rail transit plays a crucial role in addressing these issues, leveraging its capacity for high passenger and freight throughput alongside operational efficiency to significantly contribute to economic growth and environmental conservation. Economically, the development of rail transit facilitates economic integration and optimizes resource allocation among regions¹. By connecting different cities and regions with convenient rail transit, regional connectivity can be strengthened, promoting the flow of industries and talents and forming a more complete economic system and value chain, thereby enhancing the economic benefits and competitiveness of the entire region². To realize its fullest efficiency, rail transit should effectively connect resources with markets. Strategic development in regions that are resource-rich, densely populated, and economically vibrant ensures that rail transit maximizes its operational efficiency and contributes positively to broader development objectives. Therefore, the strategic selection of rail transit routes is crucial, as it has a direct impact to meet economic goals effectively.

From an environmental standpoint, the establishment of rail transportation systems can influence land use patterns and local ecological environments. Laurance et al.³ underscored the adverse and enduring impacts of transportation networks on environmental protection. Specifically, the planning of rail routes and station locations should thoughtfully account for topography and environmental conservation to minimize disruptions. In response to the negative impacts of transportation on environmental factors like climate change and natural disasters, some scholars suggest employing comprehensive transport-land interaction assessments^4,5. The implementation of rail transportation infrastructure may perturb extant ecosystems, engendering negative ramifications such as biodiversity depletion and ecological fragmentation, thereby impinging upon the habitat integrity and migratory pathways of fauna⁶. Thus, the strategic planning of rail transportation routes necessitates a holistic consideration of the intricate interplay between transportation and the environment. Rigorous environmental impact assessments during site selection and construction phases are indispensable⁷.

Based on the aforementioned discussion and the imperatives of sustainable development, we argue that evaluating rail transportation routes necessitates careful consideration of rail transit’s impact on both the environment and the economy to optimize existing rail networks. The absence of forward-thinking transportation assessments may render many routes economically inefficient and ecologically unsustainable. Furthermore, without comprehensive and large-scale geographical evaluations, certain rail transit developments may only address overt and immediate impacts within delimited regional boundaries, neglecting potential and indirect global ramifications⁸. This oversight could endanger biodiversity and critical ecosystem services due to pollution and land degradation. To effectively utilize rail transit’s potential for boosting regional economic growth while prioritizing environmental conservation, it is essential to develop strategic approaches that integrate a holistic perspective. These strategies should optimize rail transit routes in alignment with sustainable development principles, ensuring that economic advancements do not compromise ecological integrity.

To achieve the maximum economic benefits with the minimal environmental cost, and in adherence to the principles of sustainable development, we have developed a global top-level strategic plan for rail transit through a comprehensive optimization and evaluation system. We also consider the varying stages of development across different countries, proposing corresponding policy tools. By adopting a global-scale perspective, we address the broader implications of rail transit projects. This comprehensive viewpoint allows us to assess the large-scale and long-term impacts of rail transit on economic development and environmental protection. We employ the Bivariate Choropleth-Multi-Criteria Decision Analysis (BC-MCDA) model to form our evaluation framework. This model enables us to effectively weigh and synthesize multiple criteria⁹, facilitating the assessment and integration of significant data from various domains. By leveraging this model, we aim to provide insights for data-driven decision-making processes in spatial planning and transportation policy formulation.

Global economic benefit layer

The construction of the economic benefit layer aims to comprehensively evaluate the impact of railway transportation construction on economic benefits, with the objective of identifying regions with higher economic potential for the construction or improvement of railway transportation systems. Specifically, considering the impact of rail transportation on economic development, based on the IEA report¹⁰ and the location theory¹¹, in terms of economic benefits, three indicators including freight volume¹⁰, passenger volume¹⁰, and intensity of economic activities¹², encompassing 11 sub-indicators layers such as crops, biofuel crops, coal, conventional oil, unconventional oil, gas resources, metallic minerals, non-metallic minerals, nighttime light, accessibility and global population density data^3,13. The preliminary distribution of these sub-indicators is illustrated in Fig. 1.

Visualization of sub-indicators of global economic benefit layer.

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The overlaying of these multiple continuous sub-indicators subsequently forms the global economic benefits layer, excluding Antarctica and small island nations within the major oceans. This layer is represented on a scale of 0 to 1, with deeper shades of red indicating higher levels of economic benefits, as depicted in Fig. 2. According to the data provided in Table 1 below, a total area of 11.106 million square kilometers (7.42% of the global land area) is categorized as important economic benefit regions. Specifically, when analyzed by continent, the economic benefit areas span 1.877 million square kilometers in Africa, 1.5618 million square kilometers in Asia, 1.5786 million square kilometers in Europe, 4.3005 million square kilometers in North America, 0.5978 million square kilometers in Oceania, and 1.1909 million square kilometers in South America.

Global Economic benefit layer (0.05 degrees*0.05 degrees).

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Further regional analysis reveals that main economic benefit regions include areas such as the non-desert regions of the Western United States in North America, the Brazilian Plateau and the La Plata Plain in South America, the Indian Peninsula, North and Northeast Plains of China in Asia, the coastal areas of Southeast and Southwest Australia in Oceania, Eastern and Western European plains in Europe, and the East African Plateau. These regions, characterized by relatively high passenger flow, freight volume, and economic activity intensity, are considered to have higher economic potential and are suitable candidates for railway transportation system construction or improvement.

Global environmental conservation layer

Drawing on the research findings of Laurance et al.³ and the requirements of Sustainable Development Goals (SDGs)¹⁴, we have constructed an environmental conservation layer by integrating global datasets across seven first-level indicators: ecological importance, lakes and wetlands, protected areas, topography, natural disasters, climate, and carbon reserves. Moreover, the global distribution of values for sub-indicators of these first-level indicators is depicted in Fig. 3. Similarly, these sub-indicators were subsequently standardized and aggregated to generate the environmental conservation layer as illustrated in Fig. 4, which encompasses the entire globe except Antarctica and small island nations in the oceans. All values were normalized to a range between 0 and 1. Regions exhibiting higher scores in this layer primarily comprise humid tropical and subtropical rainforests, wildlife-rich savannahs in South America and Africa, mountain ranges in East Asia, Arctic glaciers, as well as islands and wetlands in South Asia.

Visualization of sub-indicators of global environmental conservation layer.

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Global environmental conservation layer (0.05 degrees*0.05 degrees).

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The results from Tables 1 and 2 indicate that the total area covered by the important environmental protection layer is 24.1431 million square kilometers, accounting for 16.14% of the global land area. The environmental protection layer spans across Africa, Asia, Europe, North America, Oceania, and South America, with respective total areas of 1.5612, 9.1154, 1.2129, 6.5043, 0.4563, and 5.2930 million square kilometers. The global distribution of environmental protection areas, as depicted in Fig. 5, demonstrates that darker shades of green, following standardization, signify higher environmental value, emphasizing the urgent need for environmental protection. Based on the visualizations presented in Figs. 2 and 4, several regions can be classified as having high environmental protection value but limited economic potential, such as the Amazon rainforest, the Tibetan Plateau in China, the Rocky Mountains of North America, Islands of Indonesia, Altay Mountains, and the glaciers of Greenland. Preserving these areas is crucial for conserving biodiversity and maintaining ecosystem integrity. Efforts to protect these environments can support global ecological balance and advance SDGs.

Overlaying process of economic and environmental layers.

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Overlaying economic and environmental layers

We have applied the Bivariate Choropleth (BC) method to overlay the economic and environmental layers, incorporating principles of multi-criteria decision analysis (MCDA)^15,16, as depicted in Fig. 5. Subsequently, Fig. 6 presents the resulting overlay, where dark shades represent high-conflict areas, indicating values above the median on both economic and environmental axes. This technique enables a comprehensive understanding of the spatial distribution of economic-environmental factors, as well as the degree of coordination and conflict between them, facilitating informed decision-making in regional development planning and environmental management.

Overlaying maps of economic and environmental layers (0.05 degrees * 0.05 degrees).

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High economic-environmental conflict zones

The global distribution resulting from overlaying economic benefit and environmental conservation layers is depicted in Fig. 3. Results from Tables 1 and 2 indicate that the total area of high-conflict regions globally amounts to 931,100 square kilometers, representing 0.62% of the world’s land area. Specifically, the distribution of high-conflict areas by continent includes 65,110 square kilometers in Africa, 240,190 square kilometers in Asia, 215,610 square kilometers in Europe, 196,510 square kilometers in North America, 26,730 square kilometers in Oceania, and 186,980 square kilometers in South America. High-conflict areas are characterized by both high economic and environmental values, notably in regions such as the Mexican Plateau, the vicinity of the Alps in Europe, the Indo-Gangetic Plain in Asia, and islands like Sulawesi in Oceania and Japan. These regions experience rapid population growth and possess abundant biodiversity and natural resources, rendering land use decisions complex and challenging. In these regions, balancing the dual values of environmental conservation and economic development poses a highly challenging task.

Low economic-environmental conflict zones

Low-conflict areas refers to regions where the degree of conflict between economic activities and environmental conservation is relatively low, characterized by both relatively low environmental and economic values. In Fig. 6, these areas are depicted with lighter shades, approaching white, with values below the median on both axes. According to the data compiled from Tables 1 and 2, approximately 75.81% of the global land area falls into the category of low-conflict areas, with a total area of approximately 113.4123 million square kilometers. These regions are characterized by relatively low levels of economic activity and correspondingly lower environmental value. Specifically, the low-conflict area in Africa, Asia, Europe, North America, Oceania, and South America measures 21.8237 million, 41.818 million, 10.7426 million, 24.0453 million, 6.4937 million, and 8.489 million square kilometers, respectively, with Asia having the most significant percentage of low conflict areas. From a geographical perspective, these low-conflict areas are primarily distributed in higher latitudes, as well as in the central regions of Africa and Oceania, where the climates are either extremely arid or excessively cold. In these areas, often influenced by extreme climate factors and sparsely populated, human activities have relatively less pronounced impacts on the local environment. Consequently, there is relatively less pressure for both environmental conservation and economic development.

Global rail transportation distribution

Our study involves downloading vector data globally, encompassing various types of rail transportation routes, including Rail, Subway, Light rail, Tram, Narrow Gauge, Monorail, Miniature, Turntable, Bridge, Embankment, Hyperloop to construct the global rail transportation layer. The specific visualization of these data is illustrated in Fig. 7. There is a concentration of railways in East Asia, South Asia, Europe, and North America, particularly in regions with very high economic benefits. Notably, in some high-conflict areas such as southern and western Europe, central part of North America and eastern part of Asia, the density of rail transportation is quite high.

Global rail transportation distribution.

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Rail transit development based on economic-environmental conflict analysis

Rail transit development in high-conflict areas presents significant ecological risks but also harbors substantial economic value. Countries like India, Mexico, and Indonesia, which face high population pressures and urgent needs for rapid economic development, require rail transit to stimulate economic growth. However, they also confront severe pressures for environmental conservation. This scenario presents a conundrum: the right of nations to pursue development must be balanced against the need to preserve ecological assets that benefit all humanity. Imposing conservation duties that hinder development rights is impractical, just as it is untenable to prioritize development at the environmental conservation’s expense. A balanced resolution to this challenge lies in the introduction of land development rights^17,18.

Implementing a system of land development rights is essential for achieving Pareto improvements¹⁹. This system operates on the principle that in high-conflict zones, the owners—be they nations, organizations, or individuals—have the inherent right to develop their land. If they opt not to develop and instead conserve the ecological space, they should receive financial benefits through the transfer of these development rights. This not only provides an added layer of choice compared to the current situation but also enhances environmental protection. The financial underpinning for the transfer of land development rights could be aligned with Sustainable Development Goal 17.2²⁰, whereby developed countries fulfill their Official Development Assistance (ODA) commitments²¹. This approach helps mitigate the fairness issues arising from the varying developmental stages of countries. Moreover, there is a need to explore diversified mechanisms for ecological protection compensation, improve compensation standards, and mobilize broader participation from countries, organizations, and private sectors²². The operational mechanisms for purchasing land development rights might include ecological compensation, land consolidation fees, carbon trading, and development rights trading, with specific payments determined by the assessed development potential of designated land areas^23,24. Theoretically, the introduction of land development rights aims to synchronize economic, environmental, and social interests, fostering greater acceptance among all stakeholders. This strategy represents a thoughtful approach to balancing development with ecological stewardship in high-conflict areas.

We found that over 75% of the land is situated in regions with relatively low economic-environmental conflict, meaning both economic potential value and environmental value are below the median. These areas include regions such as the deserts of the Middle East and high-latitude areas with extremely cold climates. In fact, this finding aligns with the research results of Jacobson et al.²⁵ from the National Geographic Society, who found that currently more than half of the Earth’s land surface experiences minimal human influence. Similarly, Oakleaf et al.²⁶ also found that 76% of the land is considered natural. Furthermore, from an economic demand perspective, large-scale rail transit development in these low-conflict areas lacks economic viability. In regions with weak economic demand, both passenger flow and economic intensity are low, resulting in limited economic returns and development potential for rail transit. Considering the specific conditions in regions such as the central areas of Africa and Oceania, as well as the vast high-latitude regions in the Northern Hemisphere, where the human impact index is low, we believe that until significant technological breakthroughs occur, the most prudent approach is to maintain the status quo in these areas rather than further expanding rail transit.

It is evident that many economic-benefit regions, indicated by large areas of deep red on the map. These regions include the Indian Peninsula and eastern China in Asia, the majority of the United States except for its western regions in North America, the Brazilian and La Plata plains in South America, and the southeastern and southwestern coastal areas of Oceania. We posit that future development efforts could focus on improving existing rail routes and potentially developing multimodal rail transit systems. This strategic approach aims to foster regional synergy and maximize economic potential and spillover effects. However, simultaneously, there is still considerable potential for certain economic-benefit regions rich resources to enhance economic development level through rail transit routes. Due to the lagging transportation industry, these resource-rich regions, such as vast African plateau, remain isolated from each other, lacking a comprehensive transportation system. As a result, their economic potential remains largely untapped, leaving ample room for development of rail transit^27,28. For these regions, vigorous development of rail transit can facilitate the flow of resources and strengthen capital injection.

Conversely, in areas characterized by predominant ecological value (depicted by lush greenery), where limited passenger demand results from sparse populations, ecological conservation should take precedence. For instance, in regions such as the Amazon Basin and the Qinghai-Tibet Plateau, characterized by rich biodiversity and exceptional ecological significance, ecological environments are fragile, with high costs and challenges associated with ecological restoration. Traditional transportation scholars often propose various measures to mitigate the impacts of transportation, such as constructing underground passages to reduce species reduction. However, Laurance et al.²⁹ argued that such remedial measures these remedial measures are ineffective, likening them to “using band-aids to treat cancer.” Scholars contend that such measures fail to adequately consider the ecological impacts and long-term maintenance costs associated with transportation development^29,30. Looking ahead through the lens of sustainable development theory, we argue that rail transit development should be limited as much as possible in these regions to protect precious ecological resources.

Comparison of existing studies and this research

As global population and urbanization continue to accelerate, the demand for diverse land use and intensified economic activity has driven the expansion of transportation networks. This, in turn, has led to the reduction and fragmentation of natural ecological spaces, resulting in the degradation of ecosystem regulation and service functions. Wilson³¹ advocated for preserving “Half-Earth”—a proposal to protect half of the planet’s land for wildlife, and numerous studies have also supported this view. Jacobson, et al.²⁵ found that more than half of the Earth’s land falls within areas of low human impact. Similarly, Venter, et al.³² reported that around 49% of the Earth’s terrestrial surface remains in a state of low modification. Ellis, et al.³³ highlighted that approximately 17.7% of the land is occupied by urban areas and croplands, 55% is shared between humans and nature, while 26.5% remains in a more natural state. Ellis³⁴ further stressed that any region designated under the “Half-Earth” initiative must be identified through long-term, open, representative, and normative discussions that account for social processes, institutions, and strategies. Furthermore, Sanderson, et al.³⁵ provided a foundational study using thematic maps to illustrate the boundaries between human-impacted and natural areas. By examining factors such as population density, settlements, and roads, they categorized land into “human-dominated,” “partially disturbed,” and “undisturbed” regions, concluding that nearly three-quarters of habitable land has been impacted by human activity³⁵.

Although the aforementioned studies show some variation in their numerical findings, these differences primarily stem from variations in how key concepts—such as “natural,” “wilderness,” and “human impact”—are defined, as well as differences in the focus and methods of regional classification used in each study. However, both previous research and the current study emphasize the importance of exercising caution in developing low human-impact lands, considering the conflicts between economic development and environmental protection, and advocating for scientifically informed land use. As Rojstaczer et al.³⁶ pointed out that careful consideration should be given to the potential severe consequences of any action, with respect for regional, cultural, and biological differences. We need to approach the impact of transportation infrastructure on the environment from a holistic perspective, considering broader, long-term goals that align with the fundamental interests of human society—namely, SDGs. This approach can respect the objective demands of nature and also reflect the ideal of harmonious coexistence between humans and the environment¹⁴. In particular, both transportation networks and ecological systems share global, interconnected, and systemic characteristics, where a disturbance in one area can have widespread effects. This study seeks to promote a greater awareness of the indirect and external negative impacts of economic activities on the environment, ultimately encouraging more sustainable development practices.

We are also aware of several limitations. Firstly, while the study spans a global scope, significant disparities exist in development levels, resource allocation, and environmental policies across different regions. Consequently, applying our research findings to specific areas necessitates consideration of local social, political, and cultural factors. Further detailed investigations and discussions should be based on our research results³.

Furthermore, regarding the evaluation method, we assigned equal weights to each primary and sub-indicator, yet in reality, these indicators may have different levels of importance in various specific regions. Therefore, in future research, adopting a weighted evaluation method could more accurately reflect the influence of different factors on the development of rail transportation, thereby enhancing the credibility and reliability of the assessment results. Moreover, our evaluation factors need to be adjusted over time to account for changes in economic and environmental conditions, as well as technological advancements. Continuous updates and improvements are necessary to ensure the effectiveness and applicability of the evaluation system. Thus, future research efforts could focus on developing an extension of our proposed evaluation system, which comprehensively considers more factors, including social, political, and cultural factors, and develops more regionally adaptive evaluation methods tailored to the characteristics of different regions^10,28. Through ongoing optimization and updates to the evaluation system³⁷, more comprehensive and accurate guidance can be provided for the implementation and management of rail transportation projects.

Our comprehensive evaluation system for rail transportation is founded on principles of multi-criteria decision analysis (MCDA), integrating diverse spatial datasets to provide a comprehensive assessment. Our study is totally based on the following datasets, which encompass the dimensions of transportation, economy, and environment. The specific data content, description, sources and references are presented in Table 3.

The BC-MCDA method, based on multiple-criteria decision analysis, takes advantage of the complementary advantages of MCDA and BC. A large number of different factors are mapped into two categories according to bivariate choropleth mapping, and the relevant data are integrated for multiple-criteria decision analysis to achieve the purpose of supporting system decision making. The principle of BC-MCDA is to use choropleth mapping (i.e., use color gradients to represent non-quantifiable dimension values) to create two intersecting “N × N” groups and display clearly distinguished primary colors between geographic units, where each primary color has different degrees of depth. Its main purpose is to accurately display the spatial relationship between two groups of variables by using a variety of strategies, such as different element colors, symbols, and shadow ratios. Variables can be any related theme pairing.

The specific steps of the BC-MCDA method³⁷ are as follows:

1. 1.

   Problem:

2. 2.

   First, the comprehensive decision-making problem is concretized according to the goal, defined and constructed into two different parts.

3. 3.

   Standardization: Since each parameter has its own physical unit and measurement scale, these values cannot be directly compared with each other. Therefore, standardization is required to convert the parameter value into an equal, dimension-less score, usually between 0 and 1, with values close to 1 indicating areas that fully meet the standard, and 0 on the contrary.

4. 4.

   Weight: Reflects the importance of each factor relative to the considered goal. Weights can be assigned using a variety of methods, such as the AHP method or the entropy method.

5. 5.

   Superposition: After each parameter is standardized and the weight is determined, a single mapping is performed first, and then a bivariate choropleth mapping is performed. By converting the original counts into ratios or proportions, complex spatial problems between two relationships can be evaluated, determined and solved.

We employ the BC-MCDA method to integrate relevant spatial data and establish the evaluation framework for rail transit development. Specifically, we have defined primary and sub-indicators for the economic and environmental layers based on the data above, as shown in Table 4. To ensure uniformity and comparability across indicators, we adopted an equal-weighting approach and conducted dimensionless standardization. In essence, regions with high economic benefits are suitable for expanding rail transportation infrastructure, while areas of extremely high environmental value should avoid excessive development of rail transportation to prioritize environmental protection. In areas characterized by high economic-environmental conflict, the construction of rail transportation demands careful consideration, striking a balance between economic development and environmental protection. Adopting cautious, fair, and equitable strategies is imperative in such contexts. Conversely, in regions where both economic and environmental values are relatively low, maintaining the existing land use pattern is advisable unless significant advancements occur in science and technology.

Within the economic layer, we drew upon urban economic theories, including Thünen’s agricultural location theory⁵⁵, Webber’s industrial location theory⁵⁶, and Calthorpe’s Transit-Oriented Development (TOD) theory⁵⁷, to formulate an economic benefit layer. This layer encompasses three primary indicators: freight volume, passenger volume, and economic activity intensity¹⁰. These first-level indicators serve to identify regions with substantial economic potential ripe for stimulation through rail transportation development. Specifically, regions characterized by high production of bulk commodities such as agriculture, fossil fuels, and minerals were targeted. According to the IEA report¹⁰, the freight volume of rail transportation primarily comprises fossil fuels, mining outputs, and agricultural products. Based on location theory, modifying or expanding rail transportation can enhance market accessibility. Based on location theory^11,58, modifying or expanding rail transportation can enhance market accessibility. Secondly, regions with dense populations are identified as potential areas for substantial passenger volume. Lastly, urban development zones exhibiting strong economic activities were prioritized, reflecting regions with high economic activity intensity. The level of economic development and intensity is reflected in brighter nighttime light data⁴². Overall, the criteria for identifying economic-benefit regions involve assessing large freight and passenger volumes alongside robust economic indicators.

When it comes to environmental considerations, our first principle is to avoid expanding and extensively constructing rail transportation in areas of significant biodiversity, ecological conservation, and carbon storage. Therefore, we overlay layers associated with ecological conservation to pinpoint regions with high environmental conservation value. Additionally, we overlay layers of different natural disasters and climate data to identify areas with a high likelihood of such events. We recognize these areas as environmentally fragile and advocate minimizing the arbitrary construction and operation of rail transportation systems to reduce local safety risks and property losses. Moreover, from a geological perspective, we incorporate DEM data to assess elevation and slope, identifying steep terrain and areas with excessively high elevations that are unsuitable for constructing and maintaining rail transportation infrastructure. After integrating all these factors, we advocate minimizing rail transportation construction in areas with high environmental conservation value.

Geo-based visualization analysis

The geo-analysis in this study was conducted using ArcGIS software. During the analysis process, vector layers representing different continents were overlaid within bivariate choropleth maps to generate specific datasets for each continent. Prior to this, various sub-layers were overlaid within ArcGIS to create comprehensive visualizations of global spatial datasets. The final presentation of these layers was carried out in QGIS, where maps were generated for visualization purposes.

Overlaying sub-layers to form the global economic benefit layer

Our approach begins with the amalgamation of multiple sub-layers, each assigned equal weights, culminating in the creation of an economic benefit layer. This composite layer facilitates a comprehensive evaluation of the potential advantages associated with railway transportation construction. Initially, our analysis focuses on regions characterized by high production volumes in sectors such as agriculture, fossil fuels, and mining. These areas typically experience significant freight volumes, primarily driven by the extraction and transportation of fossil fuels, mining activities, and agricultural produce, including biofuels. Additionally, we considered factors related to passenger volume, mainly derived from global population density data. Regions with higher population densities often require expanded passenger transport services. Furthermore, we incorporated data concerning the intensity of economic activity, as inferred from global nighttime light data. Lastly, employing the ArcGIS Spatial Analyst tool, we utilized fuzzy overlay techniques with equal weighting for the sub-layers, resulting in an index layer with values ranging from 0 to 1.

Overlaying sub-layers to form the global environmental conservation layer

Our research methodology involves integrating seven global datasets, encompassing both vector and raster data, to construct an environmental protection layer. The datasets encompass ecological importance, lakes and wetlands, protected areas, carbon storage, natural disasters, extreme climatic conditions, and topography. We standardized all sub-layers to adjust parameter ranges between 0 and 1. Employing the ArcGIS Spatial Analyst tool, we utilized fuzzy overlay techniques with equal weighting for the sub-layers, resulting in an index layer ranging from 0 to 1. Throughout this process, we carefully considered the necessity of protecting critical ecological environments, such as lakes and wetlands, protected areas, and carbon storage, during rail transportation project construction. Additionally, we evaluated the long-term negative impacts and risks posed by sensitive ecological environments, including natural disasters, extreme climatic conditions, and topography, on rail transportation construction and operation.

Forming the economic-environmental conflict layer

Overlaying economic and environmental layers to form the conflict layer is based on the application of the Multi-Criteria Decision Analysis (MCDA) method. This method facilitated the integration of the previously derived economic benefit layer with the environmental protection layer. Subsequently, using the Bivariate Choropleth (BC) method, both the economic benefit and environmental protection layers were categorized into 7 quantiles. This was followed by a cross-tabulation process to generate 49 distinct color combinations, as illustrated in Fig. 8. In the resulting chart, areas representing economic benefit zones (depicted in red) exhibited a higher potential for economic advancement, surpassing the median of the economic axis. Conversely, these zones demonstrated lower environmental protection value, falling below the median of the environmental axis. Conversely, environmental protection zones (depicted in green) necessitated relatively higher environmental costs, exceeding the median of the environmental axis, while showcasing lower potential economic benefits, below the median of the economic axis. Regions designated as high-conflict areas (depicted in black) exhibited values surpassing the median on both the economic and environmental axes, indicating significant conflicts between economic development and environmental conservation priorities. Conversely, low-conflict areas (depicted in white) demonstrated lower priority levels in both economic and environmental aspects, remaining below the median on both axes.

Economic-Environmental Conflict Layer Establishment.

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