Assessment of the green development level for participating countries in the Belt and Road initiative.

Green Belt and Road development has gradually become a global consensus, and the quantitative assessment of the green development level constitutes the basis for building a green Belt and Road high-quality development path in practice. In this paper, the Belt and Road Green development index (BRGI) was proposed in three dimensions, i.e., green nature, green economy and green society, to evaluate the green development spatial and temporal characteristics of the 80 participating countries in the Belt and Road Initiative from 2010 to 2018, and based on the quadrant method, green development cooperation model was established. The results showed: (1) In 2018,the average BRGI of participating countries is 54.38, and more than half of the countries have not reached the average level; From a regional perspective, the green development level in Europe is the highest, followed by Northeast Asia and Southeast Asia, and it is the lowest in South Asia and Africa. (2) At the considered time scale, the green development level in the Belt and Road participation countries has been increased from 2010 to 2018. (3) The green Belt and Road development cooperation modes can be divided into the all-round high-level energy attraction cooperation model, systematic win-win cooperation model for the whole field, three-dimensional refined empowerment cooperation model and multilevel high-trust cooperation. According to the different cooperation modes, the study also provides policy recommendations to promote for green development.

Introduction

In 2020, the COVID-19 outbreak notably impacted the global economy, and green and sustainable development has become a global consensus. Chinese leaders have mentioned key terms such as green, ecological, sustainable, high quality and destiny of the human community at the G20 Riyadh Summit and the 75th United Nations General Assembly, thereby conveying to the international community the direction and firm determination of the future development path of China. Moreover, China has issued a clear signal of high-quality and sustainable development. This is also a clear manifestation of the high-quality and sustainable development goals of China. The Belt and Road initiative originated in China but belongs to the world, and green is the color of Belt and Road construction. Promoting the green belt and road initiative is a critical step toward serving as well as forging society of similar goals, combined future besides shared responsibilities. Faced with progressively serious national and domestic eco-environmental concerns, governments require a suitable ecological environment in order to pursue growth of the economy. Preventing as well as mitigating air degradation besides ecological harm is a common duty for all governments across the world. Promotion of green Belt and Road construction and dissemination of the concepts of ecological civilization and green development are important practices for China to participate in global environmental governance and an inevitable trend toward ensuring the destiny of humans (Lei et al., 2021; Diaz et al., 2011). To this end, the Chinese government has issued a series of policy documents, including Guidance on Promoting Green Belt and Road, Belt and Road Ecological and Environmental Protection Cooperation Plan, and Belt and Road Green Investment Principles, to promote Belt and Road construction. Within this context, the analysis and comparison of the green development level of Belt and Road participation countries constitutes an important basis for the establishment of a green Belt and Road cooperation mode, in addition to satisfying the urgent need to build a green community in the future (Zhou et al., 2021).

In order to protect and improve the societal and ecological environments, green development has become a mainstream value orientation (Chiang et al., 2015; Skea & Nishioka, 2008). Within the context of green development, the study of the green Belt and Road has received attention from various disciplines, such as nature, economy and society (Tang et al., 2019; Harlan, 2020; Hussain et al., 2020; Pei et al., 2020). Among the studies, some have focused on the on the connotation of the green Belt and Road. Lan et al. (2020) noted that the green Belt and Road encompasses two major contradictions in the development of the international society and emphasized the core of the contradiction. Some proposed that the Belt and Road Green development process indicates that humans and nature comprise a living community (Xu, 2021). Some have investigated the impact of infrastructure construction project on regional resources and the environment, some studies evaluated the environmental impacts of the construction of Belt and Road infrastructure, such as railroads, highways, power facilities and oil and gas pipelines, on ecologically sensitive areas (Tracy et al., 2017; Lan et al., 2020). Low-carbon investments are currently concentrated in higher-income countries and regions, while risk mitigation activities are currently concentrated in lower-income countries and regions (Harlan, 2020). Some studies focused on environmental factors in countries along the route (Ascensão et al., 2018; Dan et al., 2018; Lechner et al., 2018; Leng et al., 2020; Li et al., 2020; Mao & Shi, 2020). Some studies focused on the the distribution characteristics of resources and impact of global climate change on the Belt and Road (Hughe et al., 2020; Han et al., 2020; Hou et al., 2020; Aung et al., 2020; Saha, 2020). Any large-scale growth brings with it potential ecological difficulties. Aside from the direct environmental effects, Belt and Road expenditures that lock nations into irresponsible construction, innovation, besides extractive industries will have long-term severe repercussions.

Some scholars also analyzed the characteristics of green investment and financing along the Belt and Road (Glazyrina, 2018; Atif & Imran, 2020; Cheng & Ge, 2020; Liu et al., 2020, Xie & Zhang, 2021).

Generally, there have been many studies focused on the resource and environmental issues in the Belt and Road participating countries. However, for the evaluation of the green development level in Belt and Road participating countries, to our knowledge, there are few studies that ever have analyzed. Therefore, based on the concept of the green Belt and Road, this paper establishes the Belt and Road Green development index to quantitatively assess and classify the green development level in Belt and Road construction countries from 2020 to 2018. This study aimed to (1) establishes the Belt and Road Green development index (BRGI) to measure the green development level, (2) quantifies and evaluating the level of national green development of 80 Belt and Road participating countries from 2020 to 2018, and (3) based on the green development level, systematic combines the green Belt and Road development cooperation model. This paper provides a theoretical and practical basis to improve the theoretical system of green Belt and Road development and promote high-quality Belt and Road Green development.

The Belt and Road Green development index system

The concept of the green Belt and Road Initiative

Guided by the philosophies of ecological civilization and green development, the green Belt and Road Initiative upholds the resource-efficient and environment-friendly principles and aims to enhance green development in policy coordination, infrastructure connectivity, unimpeded trade, financial integration and people-to-people bonds by incorporating environmental protection into all aspects and whole process of the Belt and Road construction (MEP, 2015). The green Belt and Road initiative fully considering the ecological environment of Belt and Road countries and regions, maintaining the concept of green development and the ideas of ecological civilization and sustainable and inclusive development, and the concept of green development is embedded into all aspects and the whole process of Belt and Road construction. Moreover, ecological and environmental governance strengthening and biodiversity protection are promoted and environmental pollution is combated largely via green policy communication, green infrastructure connection, green trade enhancement, green capital integration and green demonstration projects for people-to-people communication. The schematic of the concept of green Belt and Road framework was drawn in Fig. 1. Here, there are core and outer layer categories are appeared. In that, core philosophy consists of green development, ecological civilization, inclusiveness, and sustainability. Further, the outer layer includes policy coordination, financial integration, unimpeded trade, people-to-people-bonds and infrastructure connectivity.

Fig. 1

The schematic of the concept of green Belt and Road

Framework of the Belt and Road Green development index system

The core connotation of green Belt and Road construction is to embed the concept of green development into all aspects and the whole process of Belt and Road initiative to achieve a green development model involving the harmonious coexistence between humans and nature. The framework of the Belt and Road Green development index (BRGI) was drawn in Fig. 2. The green concept proposes the realization of the coordinated development of three systems: nature, economy and society. Therefore, the BRGI adopts the green core concept as a constraint and selects the three dimensions of green nature, green economy and green society in index construction.

Fig. 2

The framework of the Belt and Road Green development index

Firstly, the sustainable advancement of the natural system in the green Belt and Road development process includes two major parts, namely, green resource utilization and the green ecological environment. Natural resource management (NRM) is the long-term administration of key soil resources, groundwater, oxygen, mining, woodlands, aquaculture, and uncontrolled flora and fauna. These elements, when combined, produce environmental functions that increase the performance of humankind. Eco-friendly clearly translates kind to the ecosystem else not damaging to the environment. This word most generally relates to sustainable in addition to green items or else activities that help preserve freshwater resources as well as electricity. Its items also help to reduce pollutants, waterways, besides ground. Sustainable development of the natural system constitutes the foundation for sustainable economic and social development.

Secondly, the sustainable advancement of the economic system in the development process of the Belt and Road should be green. In the process of Belt and Road construction, facility connection, trade enhancement and financial integration are important areas of economic cooperation. The Belt and Road Initiative area accounts for 82% of the growth, with East Asia seeing the highest percentage gains. Second, the Belt and Road Initiative has the potential to move 8.7 million communities out of poverty as well as 34 million out of economically disadvantaged areas internationally. In Belt and Road infrastructure construction, trade and investment and financing cooperation, the essence is to consider the premise of minimizing the damage to the natural ecological environment and achieving the reasonable and optimal allocation reflecting the ecological value to continuously promote the development of green elements in the process of Belt and Road cooperation. In the Belt and Road cooperation process, green elements should be increased and accumulated. Therefore, the dimension of the green economy includes three themes: green infrastructure, green investment and financing, and green trade.

Moreover, the sustainable advancement of the social system in the green development process of the Belt and Road strives to strengthen green societal development, inherit and carry forward the spirit of friendship and cooperation of the Silk Road, and enhance the green social welfare level in Belt and Road countries to realize people-to-people relationships in Belt and Road construction.

Selection of the indicators

Based on the concept and the framework of the green Belt and Road, the Belt and Road Green development index system was build (Table 1), which contains 24 indicators under seven themes: green resource utilization, green ecological environment, green infrastructure construction, green investment and financing, green trade, green social development, and green social welfare. The indicators in each dimension are subjected to multiple cycles of data determination and replacement of indicators without data.

Table 1

Weight assignment of each indicator

	Secondary indicators	Tertiary indicators	Indicator properties
Green nature	Green resource utilization	Forest cover	Positive
		Energy use per unit of the gross domestic product (GDP)	Reverse
		Renewable energy as a percentage of the total energy use	Positive
		Natural resource rent as a percentage of the GDP	Positive
	Green ecological environment	Fine particulate matter (PM2.5) air pollution, average annual exposure	Reverse
		CO2 emissions per capita	Reverse
		Number of threatened species	Reverse
		Land and marine protected area as a percentage of the national territory	Positive
Green economy	Green infrastructure	Emissions in the transport sector as a percentage of the total fuel combustion	Reverse
		Quality of trade- and transport-related infrastructure	Positive
		Renewable power output as a percentage of the total power output	Positive
		Total number of patent applications	Positive
	Green investment and financing	Investment openness	Positive
		Green investment	Positive
		Business registration start-up procedure	Reverse
	Green trade	High-tech exports as a percentage of all manufactured exports	Positive
		Ease of doing business index	Reverse
		Logistics performance index	Positive
Green society	Green social development	GDP per capita growth rate	Positive
		Higher education enrollment	Positive
		Unemployment rate	Reverse
	Green society well-being	Proportion of the population with access to improved water sources	Positive
		Proportion of the population with access to improved sanitation facilities	Positive
		Gini coefficient	Reverse

The Society Index, SI, assesses a country's or region's eco—efficiency. It addresses longevity in its broadest definition, which includes human well-being, ecological well-being, and socioeconomic well-being. The Green Economy Index (GEI) is an analytical instrument aimed to assist nations, intergovernmental groups, and businesses in improving their "environmental" marketing strategy.

Evaluation method

Data resources and analyses

To ensure that the data of each sample are complete, reliable, and compared in the same dimension, the relevant data designed in this paper are selected and sourced from the World Bank database Data Bank, and the data are selected in the time range from 2010 to 2018. The data are processed as follows: first, due to the lack of different data types, the data are complemented via the method of difference, and approximate function values are estimated at certain points based on the function value status at a finite number of points. Second, to eliminate variability in the data units and indicator attributes, the data of the different types, units, intervals and orders of magnitude are transformed into dimensionless data.

When a certain sample indicator is a positive indicator, i.e., the larger the indicator value is, the more positive its impact on the green development of Belt and Road countries, the dimensionless value of the jth tertiary indicator under the ith secondary indicator is calculated as follows:when the sample indicator is an inverse indicator, i.e., the smaller the indicator value is, the more positive its impact on the green development of Belt and Road countries, the dimensionless value of the jth tertiary indicator under the ith secondary indicator is calculated as follows:where denotes the dimensionless value of the jth tertiary indicator under the ith secondary indicator, is the original value of the indicator, is the maximum original value of the indicator, and is the minimum original value of the indicator.

Determination of indicator weights

At present, the weighting methods and values of various evaluation systems are not uniform, including the equal weighting method, the combination of principal component analysis and entropy method, and the hierarchical analysis method. A broad method to clustering identification in which the goal is to predefined categories or data that are near to each other collectively is termed as hierarchical cluster analysis else clustering. Techniques for hierarchical cluster analysis are classified into two types such as divisive approaches and fuzzy clustering techniques. On the other hand, it provides a single layered hierarchical clustering from which a partitioning may be determined for every feasible option of Due to this reason, it offers a simple framework for exploring links betwixt clusters that non-nested algorithms cannot. The principal component analysis, entropy and hierarchical analysis methods overly rely on objective data characteristics, thereby ignoring the nearly equal importance of each indicator under real natural, economic and social conditions, and in regard to representative in the process of green Belt and Road development, an over-reliance on the Belt and Road Green development index ensues. A global organization founded in 1961 with a goal of developing sensible plans for decent opportunities is named as organization for economic cooperation and development (OECD). Its responsibilities encompass developing initiatives that favor access, wealth, out well for everyone besides fairness. The equal-weighted index is one of the stock market indices which assigns or gives equivalent worth to several businesses in the indices, hence the overall value of the asset is influenced by the quality of every share as though they all bear similar significance in the indicator computation. The equal-weight assignment method is one of the most common assignment methods adopted by Chinese and foreign evaluation and research centers, such as the Organization for Economic Cooperation and Development (OECD) green growth index system, Moody's credit rating index system, Standard & Poor's commodity index and the human green development index (HGDI) in China. Therefore, this paper applies the equal-weight assignment method to assign values to the indicator system.

Sample country selection

As of January 30, 2021, China signed cooperation documents with 140 countries to build the Belt and Road, and these 140 countries were adopted as the sample pool. According to the availability and representative of the obtained data, 80 sample countries (including China) were selected as target countries (Table 2), which are distributed in Northeast Asia, Southeast Asia, South Asia, West Asia, Central Asia, Europe, Oceania, South America, North America and Africa, including various types of countries such as high-income countries, middle- and high-income countries and lower-middle-income countries, which can better represent and reflect the green development of the considered Belt and Road countries.

Table 2

Sample countries for green development index evaluation

Region	Quantity	Country
Northeast Asia	4	China, Korea, Mongolia, Russia
Southeast Asia	8	Singapore, Malaysia, Myanmar, Cambodia, Vietnam, Thailand, Indonesia, Philippines
South Asia	4	Pakistan, Sri Lanka, Bangladesh, Nepal
Western Asia	9	United Arab Emirates (UAE), Turkey, Saudi Arabia, Iran, Azerbaijan, Georgia, Armenia, Yemen, Cyprus
Central Asia	2	Kazakhstan, Kyrgyzstan, Uzbekistan
Europe	23	Ukraine, Belarus, Moldova, Greece, Poland, Serbia, Czech Republic, Bulgaria, Slovakia, Albania, Croatia, Estonia, Lithuania, Slovenia, Hungary, North Macedonia, Romania, Latvia, Austria, Montenegro, Luxembourg, Portugal, Italy
Oceania	1	New Zealand
South America	4	Chile, Uruguay, Ecuador, Peru
North America	5	Costa Rica, Panama, El Salvador, Dominica, Jamaica
Africa	20	Sudan, Morocco, Tunisia, Egypt, Ethiopia, Tanzania, South Africa, Zambia, Mozambique, Namibia, Angola, Zimbabwe, Senegal, Côte d'Ivoire, Ghana, Nigeria, Togo, Benin, Niger, Cameroon

Assessment of the green development level in the Belt and Road participating countries

Overall characteristics of the green development level in the Belt and Road participating countries

In 2018, the green development level in the Belt and Road countries varied, with an average green development index of 54.38. More than half of the countries did not reach the average level, and the difference between the highest and lowest scores was 37.76, with a very obvious gap. Among the countries, the top five countries in terms of their green development level were New Zealand, Austria, Korea, Slovenia and Singapore, with green development index values of 70.68, 70.22, 68.82, 68.71 and 66.59, respectively. The five countries with the lowest green development level were Namibia, Niger, Sudan, Angola and Yemen, with BRGI values of 41.10, 39.70, 38.54, 37.57 and 32.92, respectively. The green development index of China reached 60.28, thus ranking 21 out of 80 countries (Table 3).

Table 3

Level of green development in the Belt and Road participating countries in 2018

	Region	Country	Green Nature Index	Green Economy Index	Green Society Index	BRGI	BRGI ranking
1	Northeast Asia	China	41.78	64.62	74.43	60.28	21
2		Russia	56.36	48.85	75.92	60.37	20
3		Korea	51.99	72.74	81.73	68.82	3
4		Mongolia	57.00	37.65	63.48	52.71	50
5	Southeast Asia	Singapore	38.19	78.39	83.19	66.59	5
6		Malaysia	52.83	55.82	73.34	60.66	19
7		Thailand	52.57	54.81	77.25	61.54	15
8		Indonesia	51.97	38.37	63.44	51.26	51
9		Philippines	47.59	44.68	68.20	53.49	46
10		Vietnam	54.73	55.60	75.86	62.06	14
11		Cambodia	65.62	32.82	63.07	53.84	42
12		Myanmar	55.36	24.78	71.16	50.44	54
13	South Asia	Sri Lanka	47.81	35.70	68.09	50.54	53
14		Pakistan	46.58	29.30	65.39	47.09	66
15		Bangladesh	41.81	28.87	68.33	46.34	69
16		Nepal	56.66	39.77	64.97	53.80	43
17	West Asia	Cyprus	44.71	51.43	76.71	57.62	31
18		Azerbaijan	53.52	40.18	64.58	52.76	49
19		Turkey	38.18	49.14	75.33	54.22	40
20		Armenia	53.51	44.73	69.21	55.81	34
21		Georgia	56.03	48.50	71.97	58.83	26
22		UAE	39.67	60.30	75.97	58.65	28
23		Saudi Arabia	36.64	37.54	73.81	49.33	56
24		Iran	42.80	33.27	68.40	48.16	63
25		Yemen	37.83	24.86	36.06	32.92	80
26	Central Asia	Kazakhstan	48.51	40.99	76.96	55.49	35
27		Uzbekistan	52.44	43.92	64.82	53.72	44
28	Europe Region	Austria	60.06	69.19	81.40	70.22	2
29		Czech Republic	55.16	57.49	83.35	65.33	7
30		Estonia	57.80	58.98	82.33	66.37	6
31		Greece	51.89	53.28	77.81	60.99	17
32		Italy	49.67	57.10	71.16	59.31	25
33		Luxembourg	54.05	48.57	68.86	57.16	32
34		Poland	55.78	56.16	83.45	65.13	8
35		Portugal	55.19	55.54	76.95	62.56	10
36		Slovakia	59.34	48.29	79.95	62.52	11
37		Slovenia	68.40	53.12	84.61	68.71	4
38		Croatia	57.44	49.76	79.49	62.23	13
39		Lithuania	55.86	49.18	77.27	60.77	18
40		Latvia	61.31	50.87	80.01	64.06	9
41		Albania	53.48	43.58	72.47	56.51	33
42		Bulgaria	59.06	46.56	74.98	60.20	23
43		Belarus	54.21	41.61	84.83	60.22	22
44		Hungary	52.97	52.88	81.33	62.39	12
45		Macedonia	53.60	44.97	64.06	54.21	41
46		Black Mountain	59.28	45.42	71.70	58.80	27
47		Romania	54.60	50.39	74.57	59.85	24
48		Serbia	51.91	48.16	75.11	58.39	29
49		Moldova	51.50	37.92	76.05	55.16	36
50		Ukraine	51.22	41.10	81.38	57.90	30
51	Oceania	New Zealand	60.93	69.04	82.08	70.68	1
52	South America	Chile	60.29	49.11	75.07	61.49	16
53		Uruguay	51.74	42.29	70.55	54.86	37
54		Ecuador	46.78	37.55	60.36	48.23	62
55		Peru	54.05	40.30	66.53	53.63	45
56	North America	Costa Rica	54.78	43.29	64.70	54.26	39
57		Dominica	52.96	37.32	69.20	53.16	48
58		Jamaica	51.88	40.79	59.11	50.59	52
59		Panama	49.65	51.07	62.70	54.47	38
60		El Salvador	46.47	36.64	64.86	49.32	57
61	Africa Region	Tunisia	43.24	35.63	64.46	47.78	64
62		Egypt	36.42	38.77	72.17	49.12	59
63		Morocco	45.90	40.34	59.77	48.67	61
64		Angola	62.80	23.77	26.13	37.57	79
65		Namibia	50.73	40.59	31.98	41.10	76
66		South Africa	47.18	47.61	33.64	42.81	74
67		Côte d'Ivoire	62.06	38.08	50.76	50.30	55
68		Cameroon	53.12	36.49	48.07	45.89	72
69		Ghana	56.88	31.06	50.60	46.18	70
70		Nigeria	54.52	33.20	40.15	42.62	75
71		Sudan	62.50	27.38	25.74	38.54	78
72		Senegal	56.03	30.94	52.38	46.45	68
73		Zambia	83.03	44.90	31.82	53.25	47
74		Benin	62.19	29.30	46.87	46.12	71
75		Ethiopia	65.11	33.99	47.53	48.88	60
76		Mozambique	74.50	38.38	28.82	47.24	65
77		Niger	51.78	24.26	43.07	39.70	77
78		Togo	67.08	30.45	39.44	45.66	73
79		Tanzania	69.11	32.53	38.56	46.73	67
80		Zimbabwe	72.88	27.96	46.64	49.16	58

In the green nature dimension, the top five countries with the highest green nature index values are Zambia, Mozambique, Zimbabwe, Tanzania and Slovenia, which are all countries in the African region, except for Slovenia. The top four countries in the African region also rank among the top five countries in terms of the green resource utilization index. These countries are all developing countries and utilize and exploit green resources to a lesser degree, so their green nature index is higher. The bottom five countries in terms of the green nature index are Singapore, Turkey, Yemen, Saudi Arabia and Egypt, which are mainly countries in the West Asia region.

In the green economy dimension, the countries with higher green economy index values are largely located in Europe and Northeast Asia, which are mostly high-income and upper-middle-income countries. The countries with lower index values are mainly located in South Asia and Africa, which exhibit a relatively lower economic development level and are primarily low- and middle-income countries. Specifically, the top ten countries in terms of the green economy index are Singapore, South Korea, Austria, New Zealand, China, UAE, Estonia, Czech Republic, Italy and Poland, largely high-income and upper-middle-income countries, reflecting that these countries contain good green infrastructure, green trade and green investment environments. The bottom ten countries are Togo, Pakistan, Benin, Bangladesh, Zimbabwe, Sudan, Yemen, Myanmar, Niger and Angola, which are mainly located in the African region and largely include low- and middle-income countries, indicating that these countries are more interested in economic demands than green incentives and should improve their green infrastructure construction, green investment and trade environments.

In the green society dimension, the countries with higher index values are mainly concentrated in Europe, Northeast Asia and Southeast Asia, while the countries with lower index values are mostly concentrated in Africa. Specifically, the top ten countries in terms of the green society index are Belarus, Slovenia, Poland, the Czech Republic, Singapore, Estonia, New Zealand, South Korea and Austria, largely European countries, indicating that European countries are leading socioeconomic development and green social well-being. The bottom ten countries are Nigeria, Togo, Tanzania, Yemen, South Africa, Namibia, Zambia, Mozambique, Angola and Sudan, all of which belong to the African region except Yemen, reflecting the poor performance of social progress and green society in the African region.

Spatial characteristics of green development in the Belt and Road participating countries

The BRGI of the Belt and Road participating countries in 2018 is adopted as the research object to analyze the spatial characteristics of the green development level in the Belt and Road participating countries. For statistical development, evaluation, as well as assessment of imaging techniques, spatial features including GIFOV else GSI, as well as radiometric characteristics like as scaling factor or detection distortion, are necessary. They do not, though, link the state of the system to the activities intended to be accomplished by the images. Based on the geographical distribution, the dark gray color is mainly distributed in Europe, Northeast Asia and Southeast Asia, while the light gray color occurs in South Asia and Africa (Fig. 3). Based on the evaluation results of the green development level in each country in 2018, the green development level in Europe is the highest, followed by Northeast Asia, Southeast Asia and Central Asia, while the green development level in West Asia, South Asia and Africa is the lowest (Fig. 4).1

Fig. 3

Spatial distribution of BRGI in 2018. The darker the color, the higher the level of green development

Fig. 4

BRGI in the Belt and Road participating countries by region in 2018

The European region exhibits the highest level of green development. Europe is located in the northwestern part of the Eastern Hemisphere and is the only continent among all continents that does not experience a tropical climate, with a mild climate and a more even distribution of precipitation, which is one of the main reasons why the ecological environment in this region is better than that in other regions. Coal in European countries is mainly distributed in Donbass in Ukraine and Silesia in Poland. Hence, Ukraine and Poland occur at a lower level of green development among the evaluated European countries, which is related to the higher utilization of resources in both countries. European countries possess a high level of industrial production and agricultural mechanization and already contain a good environment for green infrastructure construction, green investment and green trade, and their residents enjoy a high level of green well-being.

The Northeast Asia region exhibits the second highest level of green development. The sample countries in the Northeast Asia region in this paper include four countries, namely, Korea, China, Mongolia and Russia. Mongolia and the Far East of Russia are rich in natural resources, of which the majority of Russia is situated in the northern temperate zone with a diverse climate, and its water resources are extremely abundant, ranking second in the world in terms of freshwater resources. As such, Russia attains a relatively high green nature index. Korea has accelerated the development of new green industries through the Green New Deal and has promoted the development of a green economy. As such, Korea ranks second in terms of the green economy index among the 80 sample countries and is the first country to explicitly propose a green recovery strategy. China has become a pioneer in the green economy, ranking fifth in terms of the green economy index among the 80 sample countries. China has promoted green economic transformation and development in various aspects, such as green infrastructure construction, green finance, green investment and green trade, and has especially focused on green finance. Notably, Chinese green bonds have rapidly expanded in recent years and have quickly become the second largest green bond market in the world, with the issuance scale of green bonds exceeding 1 trillion yuan from 2016 to 2020.

Africa exhibits the lowest level of green development, ranking 47–79 among the 80 sample countries, with a relatively lower development level, and the bottom ten African countries account for 90% of the total amount. The reasons for the low green development level in Africa mainly include the following: (1) Africa experiences a hot and arid climate and is known as the tropical continent. The climate is characterized by a high temperature, little rain and notable dryness, the annual average temperature across the continent above 20 ℃ accounts for approximately 95% of the continental area, more than half of which remains hot year round. In addition, nearly half of all areas experience hot warm seasons and warm cool seasons, thus facing ecological and environmental problems such as drought and biodiversity loss. (2) African countries are economically underdeveloped, mostly low- and middle-income countries and low-income countries, with mining and light industry as the main sectors of African industry. These countries have higher demands for economic development than for green development. (3) Poverty and the resulting livelihood problems are major obstacles to the development of a green society, especially with the increase in absolute poverty attributed to high fertility rates. This challenge will become increasingly severe. According to UN data, the African population is growing rapidly and is expected to double from the current total to 1.1 billion people by 2050, while the extreme poverty rate in Africa is 38%. Moreover, 86% of the world's extremely poor people will reside in sub-Saharan Africa by 2050 (Zhi, 2019). (4) Africa attains a low level of health development, contains only 3% of the global health workforce and lacks access to health services provided by trained medical personnel throughout the continent, with the most severe crisis encountered in sub-Saharan Africa.

Temporal change characteristics of BRGI

Overall, the green development level in the Belt and Road participating countries revealed a growing trend from 2010 to 2018, from 50.62 in 2010 to 54.38 in 2018, an increase of 7.4%, with an annual growth rate of 0.3%/year (Fig. 5). The green development level in all countries gradually increased, indicating that countries are continuously advancing their green and sustainable development goals under top-level designed green policies. The green development index of each region exhibited a major downward trend in 2016, followed by a slow increase. The main reason is that after several years of moderate and sustained growth in the world GDP, the global economy experienced a recession in 2016. In particular, Brazil and Russia suffered a severe recession, and the growth rates in many other emerging economies, such as China, fell to well below trend levels, thus constraining green development.

Fig. 5

Trends of the green development level in the Belt and Road participating countries from 2010 to 2018 a by region; b on average

The overall trend of green development change in each region also exhibits a growing trend, but the growth rate varies (Fig. 6). The average annual growth rates in descending order are encountered in Oceania, Europe, Southeast Asia, Northeast Asia, South Asia, North America, South America, West Asia, Central Asia, and Africa. Among these regions, Africa's green development index remains basically unchanged, with an average annual growth rate of 0.08%, which also highlights the practical necessity for China to promote green Belt and Road construction.

Fig. 6

Average annual growth rate of the green development index by region from 2010 to 2018

Green development cooperation model with the Belt and Road participating countries

The development of differentiated green development cooperation strategies can improve China's green cooperation guidance. Countries along the Belt and Road exhibit different natural endowments and green development capacity levels. Based on quantification of the green development level in the Belt and Road participating countries, unique green development modes can be classified according to the corresponding natural resources and green development capacity endowments. Moreover, differentiated green development strategies can be formulated according to the resource endowments and realistic conditions to promote green Belt and Road construction in China with a high precision and quality. It is important for China to promote the green Belt and Road with a high precision and quality. By constituent services such as market knowledge, system evaluation assistance, collaborative ability to negotiate, financial systems of bulk order, availability to goods and services, dependence on external businesses for participant offerings, and so on, the collaborative prototype of non-profit organization offers real benefit to its target audience else customers, collaborative participants.

The green nature index can reflect the current situation of the ecological environment and resource utilization and the production factors of a given country, while the green economy can reflect the green development ability of the country. The development level of green nature and green society jointly determine the green welfare of people. Therefore, based on the quadrant method, considering the green nature index as the horizontal coordinate and the green economy index as the vertical coordinate, the Belt and Road countries are divided into four development cooperation modes (Fig. 7; Table 4).

Fig. 7

Green development cooperation mode

Table 4

Green cooperation models of the Belt and Road countries

Type	Cooperation mode	Country
High natural endowment and high green development capacity	All-round high-level energy attraction cooperation model	New Zealand, Russia, Vietnam, Zambia, Chile, Austria, Estonia, Czech Republic, Poland, Portugal, Slovenia, Latvia, Romania, Croatia, Lithuania, Luxembourg, Slovakia, Bulgaria, Montenegro, Georgia
Low natural endowment but high capacity for green development	Systematic win–win cooperation model for the whole field	China, Korea, Singapore, Panama, Malaysia, Thailand, Philippines, South Africa, Italy, Greece, Hungary, Serbia, Macedonia, UAE, Cyprus, Turkey, Armenia, Uzbekistan
Low natural endowment and low green development capacity	A three-dimensional and refined model of empowering cooperation	Jamaica, Dominica, El Salvador, Indonesia, Namibia, Morocco, Cameroon, Tunisia, Niger, Egypt, Uruguay, Ecuador, Sri Lanka, Pakistan, Bangladesh, Albania, Ukraine, Moldova, Azerbaijan, Iran, Yemen, Saudi Arabia, Kazakhstan
High natural endowment but low green development capacity	Innovative cooperation model with multiple high-trust levels	Costa Rica, Mongolia, Cambodia, Myanmar, Mozambique, Côte d'Ivoire, Ethiopia, Nigeria, Tanzania, Ghana, Senegal, Togo, Benin, Zimbabwe, Sudan, Angola, Peru, Nepal, Belarus

All-round and high-level energy attraction cooperation model

The induced energy cooperation model targets cooperation countries with a high natural endowment and a high green development capacity. Compared to China, these countries with a higher green nature index value and higher green development capacity for cooperation include New Zealand, Russia, Vietnam, Zambia, Chile, Austria, Estonia, Czech Republic, Poland, Portugal, Slovenia, Latvia, Romania, Croatia, Lithuania, Luxembourg, Slovakia, Bulgaria, Montenegro and Georgia, New Zealand and Austria. In particular, the last two countries exhibit a higher green economy index value than that of China.

Within this type of cooperation model, partner countries attain advantages in green development capacity and a high level of development in green environmental protection policies, green technology, green finance and green trade. It is suggested that through the cooperation model of energy attraction, we can carry out all-round and high-level cooperation in ecological environmental protection, green infrastructure, green finance and green trade, draw on the green development achievements and experiences of the partner participating countries, complement each other's advantages and provide a demonstration role for the construction of the green Belt and Road.

Systematic win–win cooperation model in the whole field

The win–win cooperation model targets partner countries with the same type of green development as that of China. These countries all possess low natural endowments but a high green development capacity. Cooperating countries include Korea, Singapore, Panama, Malaysia, Thailand, the Philippines, South Africa, Italy, Greece, Hungary, Serbia, Macedonia, the UAE, Cyprus, Turkey, Armenia, and Uzbekistan, which are mainly concentrated in the African region and Southeast Asia.

Within this type of cooperation model, ecological and environmental problems are also faced in many aspects. Through the win–win cooperation model, we can further promote the development of the green economy and green society by joining forces and systematize in-depth cooperation in the fields of policy, finance and trade to encourage green Belt and Road cooperation and jointly realize ecological and environmental protection.

Choosing Southeast Asia as an example, Southeast Asia is an important area for Chinese outward power infrastructure investment and plays a vital role in Belt and Road infrastructure interconnection. Although fossil energy is the most important energy resource for most countries in Southeast Asia at this stage, renewable energy resources exhibit a greater potential for development. Through a combination of policies and other initiatives, the flow of funds to construct more low-carbon and green renewable energy infrastructure is not only crucial to the green transformation of Southeast Asian energy resources and the achievement of sustainable development goals but is also the rightful embodiment of green Belt and Road construction, which can help enhance the green influence and leadership of China in international governance and achieve win–win cooperation.

Three-dimensional and refined empowerment cooperation model

The empowerment cooperation model targets partner countries with a low natural endowment and a low green development capacity. Compared to China, these countries exhibit a low green development capacity. Partner countries include Jamaica, Dominica, El Salvador, Indonesia, Namibia, Morocco, Cameroon, Tunisia, Niger, Egypt, Uruguay, Ecuador, Sri Lanka, Pakistan, Bangladesh, Albania, Ukraine, Moldova, Azerbaijan, Iran, Yemen, Saudi Arabia, Kazakhstan, etc., largely concentrated in West Asia, South Asia and Africa.

Within this type of cooperation model, the natural endowment of the partner countries is similar to that of China, but their green development capacity is lower than that of China. In comparison, China exhibits obvious advantages in green infrastructure construction, green finance and green trade, including the advantages of a national system, continuous improvement of financing mechanisms, and technical and personnel advantages. We can build a three-dimensional and refined cooperation model through the export of green technology and other advantageous elements and enable partner countries to enhance their green development capacity.

Innovative cooperation model with multiple high-trust levels

This innovative cooperation model targets partner countries with a high natural endowment but a low green development capacity. Compared to China, these countries exhibit a high natural endowment and higher green nature index value but a lower green development capacity. In the cooperation process, more attention should be paid to the protection of the ecological environment while enhancing the green economy and green social development capacity. Partner countries include Costa Rica, Mongolia, Cambodia, Myanmar, Mozambique, Côte d'Ivoire, Ethiopia, Nigeria, Tanzania, Ghana, Senegal, Togo, Benin, Zimbabwe, Sudan, Angola, Peru, Nepal, Belarus, etc., which are mostly located in Africa, South Asia, West Asia and Central Asia.

Within this type of cooperation model, the partner countries possess high natural endowments but low levels of green economic development. Similar to the empowerment cooperation model, China exhibits obvious advantages in green infrastructure construction, green finance and green trade. The difference is that the cooperation process should focus on maintaining the high natural endowment level in the partner countries, driven by green investment projects, and constantly exploring multilevel high-trust cooperation models such as technological innovation and investment and financing innovation.

Conclusion

As Belt and Road construction is vigorously promoted, the concept of green development will certainly be widely recognized and actively practiced by participating countries and regions. Based on the connotation of the Belt and Road, this paper constructs the Belt and Road Green development index and evaluates and analyzes the current situation of the green development level and its differences among the 80 considered Belt and Road participating countries. This study compensates for the relative shortage of current research on green Belt and Road construction and provides important policy inspiration for China to further promote green Belt and Road construction. The main conclusions are as follows: (1) in 2018, the green development level in the considered Belt and Road countries was low, with an average value of 54.38, and more than half of the countries did not attain the average level. (2) At the spatial scale, the green development level in the European region was the highest, followed by Northeast Asia, Southeast Asia and Central Asia. (3) At the time scale, the green development level in the Belt and Road countries revealed a trend of continuous improvement from 2010 to 2018, from 50.62 in 2010 to 54.38 in 2018, an increase of 7.4%, at an annual growth rate of 0.3%/year. With top-level designed green policies, countries are continuously promoting green and sustainable development goals while developing a green economy.

The development of differentiated green development cooperation strategies can improve green cooperation guidance. Countries along the Belt and Road possess different natural endowments and green development capacity levels. Based on the quantification of the green development level of the Belt and Road participating countries, China can classify varied green development models based on the differences in natural resources and green development capacity endowments and formulate custom green development strategies based on the actual resource endowments and realistic conditions.