3.1.1 Arable land constraints

For the countries along the B&R, ensuring the steady growth of arable land is one of the most important means of achieving food security. Overall, the countries along the B&R have large amounts of arable land, accounting for about half of the world’s total area of land under cultivation. However, the uneven distribution of this arable land has resulted in uneven levels of agricultural development in the various countries in the region. Further, from the per capita perspective, although the total area of arable land along the B&R is very large, the per capita cropland in this area is only 0.17 ha, which is below the world average of 0.214 ha (Liu, 2017). Therefore, the extensive arable land resources of the countries along the B&R have no advantages. With the rapid growth of the population along the B&R and rapid urbanization, the demands placed on the arable land resources in this area will only become more intense in the future.

Changes in the arable land area over the period from 2000 to 2014¹(¹ Arable land area is based on data published on the Food and Agriculture Organization website: http://www.fao.org/faostat/zh/#data.) showed a downward trend along the B&R. Although there was an increase after 2013, it was insignificant, as shown in Fig. 1. A comparison of the changes in the arable land area along the B&R between 2013 and 2014 showed that in most countries there was no change, and some countries even experienced a decline in the area of arable land. Only a few countries experienced an increase in arable land. Thus, most of the B&R countries are only maintaining the status quo in terms of arable land protection. In addition to the processes of industrialization and urbanization, land degradation and destruction, ecological conversion, agricultural restructuring and the absence of farmland management systems are among the other important factors for the reduction of arable land areas in B&R countries. Under the combined effects of these factors, it is very difficult for B&R countries to ensure that the arable land area will remain in a stable state, which will present a major challenge for the region in its efforts to ensure food security.

Improving the productivity of arable land is another important way of ensuring food security. However, in general, agricultural production in the countries along the B&R is still relatively extensive (Li, 2017), some arable land remains idle, the degree of agricultural mechanization is low, and the technology used in agricultural production is outdated (Zhao, 2016), resulting in low agricultural productivity.

3.1.2 Water resource constraints

From the point of view of food security, water resources are another important aspect of agricultural productivity. In general, the overall water resources along the B&R are relatively abundant. In 2014, the renewable inland freshwater resources along the B&R totaled 15.2 trillion cubic meters, accounting for about 35.6%²(² Data source: the Food and Agriculture Organization’s AQUASTAT database.) of the world’s total water resources. However, based on uneven distribution and per capita availability, the overall B&R region is extremely short of water. In terms of the proportions of regional water resources, West Asia has 1.88%, Central Asia has 1.21%, Central Europe has 2.02%, Western Europe has 1.70%, Southern Europe has 3.76%, East Africa has 0.51%, and North Africa has 0.28% of the total. Thus, it can be seen that the proportion of water resources in most countries in this region is extremely low, with the majority of the available water resources being concentrated in South Asia, Southeast Asia, and Eastern Europe, which account for 73.82% of the total (Zuo, 2018).

In terms of per capita availability, the water resources of the countries along the B&R averaged 3346.5 cubic meters per capita in 2014, which was below the world average (Liu, 2017). Moreover, the per capita water resources of all countries along the B&R declined by 38.2% from 1962 to 2014 as a result of population growth, representing an average annual decrease of about 3%.

Although the countries along the B&R are short of water, their utilization efficiency is very low (Li, 2017). From the perspective of water consumption, the proportion of total water consumption attributed to agriculture reached 80% in the countries along the B&R in 2014 (see Fig. 2), accounting for about 75% of the world’s total agricultural water consumption. However, in terms of water intensity, the water consumption per unit of added value of agriculture in the region was 1020.7 cubic meters in 2014, which was about 1.2 times the world average.

As the main production area for the world’s grain needs, the countries along the B&R are responsible for the basic sustenance of the 4.6 billion people who live in this region. FAO statistics show that in 2016, the region’s grain output accounted for 58.8% of the world’s total output, including 64.9% of all wheat, 39.1% of corn, 88.8% of rice, 42.8% of barley, 56.6% of rye, 50.3% of millet, 40.8% of oats, 14.5% of sorghum, 70.5% of potatoes, and 32.2% of cassava.

However, this production was achieved at the expense of the environment. FAO statistics show that from 2002 to 2016, the input of agricultural production resources in the region maintained a relatively rapid growth rate that was higher than the average global growth rate during the same period. Among the various inputs, the average annual increase in the fertilizer application rate was 2.8%, including annual increases in the application of nitrogen (2.4%), phosphorus (3.2%), potassium (3.9%) and pesticides (2.2%) compared with average annual global increases of 2.3%, 2.1%, 2.5%, 2.7%, and 2.2%, respectively, during the same period. In terms of total application amounts, the application of nitrogen, phosphorus, potassium, and pesticides in agricultural production in the region accounted for 65.4%, 62.9%, 59.1%, and 54.1%, respectively, of the global totals in 2016. From the point of view of application intensity, the amount of chemical fertilizer applied per unit of agricultural added value is about 1.1 times the global average, and the amounts of chemical fertilizer and pesticide applied per unit of arable land are also higher than the global averages. Further, it is predicted that the amounts of chemical fertilizer and pesticide used per unit of arable land will increase significantly in the future.

Zhang (1983) found that the optimum level of fertilizer input per unit of arable land is about 22.5 kg/mu, or about 338 kg ha^-1. This was supported by the findings of Li (1984). Statistics on fertilizer input per unit area of grain cultivation in China from 1998 to 2014 showed that fertilizer inputs fluctuated between 300 kg ha^-1 and 400 kg ha^‒1 (Hou et al., 2017). Therefore, an input of 338 kg ha of fertilizer is acceptable. At present, the average fertilizer input per unit area of arable land along the B&R is about 180 kg ha^‒1, hence there is still considerable room for growth given the optimum level of 338 kg ha^‒1. Moreover, given the rapid population growth along the B&R and the difficulty of increasing the arable land area, it seems inevitable that inputs of chemical fertilizers and pesticides will increase in an attempt to ensure food security by increasing grain production. This will undoubtedly cause a range of problems such as soil acidification, salinization, soil compaction and pollution, and the pollution of groundwater, rivers, and lakes in the form of eutrophication, leading to further deterioration of the environment (Zhao, 2016).

The B&R strategy provides a rare opportunity for agricultural cooperation between the countries in the region. There are some cooperative dialogues and various bilateral cooperation mechanisms among the countries along the B&R, such as China and ASEAN (10+1), the Greater Mekong Subregion (GMS) cooperation, the BCIM economic corridor, the Asian Cooperation Dialogue (ACD), the Shanghai Cooperation Organization (SCO), the Central Asian Regional Economic Cooperation Mechanism (CAREC), and the China-Central and Eastern European Countries Agricultural Economic and Trade Forum. However, these cooperative bodies only involve agreements signed by the governments of the relevant countries, and they lack action plans and follow-up plans (Jiang, 2015), meaning that agricultural cooperation between the countries in the region has not made substantive progress.

The most critical cooperation problem among the countries along the B&R is the lack of non-governmental organizations that specialize in agricultural cooperation aimed at integrating agricultural resources in the region and coordinating actions among countries in relation to agriculture. There is mutual assistance available in relation to agricultural resources, including machinery and materials, the environment, and the labor force. However, numerous differences in terms of the political, economic, cultural, historical, religious, and linguistic features of the various countries hinder more in-depth and extensive cooperation among countries in the field of agriculture. Thus, it is necessary to develop a cooperation mechanism on the basis of previous intergovernmental dialogue and cooperation, in addition to various multilateral and bilateral cooperation mechanisms. It is also necessary to establish a cooperation platform across borders, government departments, cultures and religions. Only in this way is it truly possible to promote agricultural cooperation between the countries along the B&R and achieve the sustainable development of agriculture in the region.

Most of the countries along the B&R are developing countries in which agriculture is a pillar industry. Thus, achieving sustainable agricultural development is crucial for the region. However, the countries along the B&R are in the process of rapid population growth, as well as industrialization and urbanization. The evolution of the relationship between social economy and agricultural resources and environment, will play decisive roles in the sustainable development of agriculture in the region. To this end, it is necessary to predict the possible future development trends of the countries along the B&R in order to evaluate the sustainability of agriculture in this area.

In terms of population growth, the United Nations Population Division predicts that the total population of countries along the B&R will reach 5.1 billion by 2030, or 440 million more than in 2017, with an average annual growth rate of 0.7%³(³ Data from the official website of the United Nations Population Division: https://population.un.org.). In terms of urbanization, the report released by the United Nations Population Division titled “World Urbanization Prospects: The 2018 Revision,” predicts that the proportion of the population in the countries along the B&R engaged in non-agricultural production will reach 0.56 in 2030. In terms of economic growth, using data from the United Nations’ “World Economic Situation and Prospects 2018,” we can predict that the total GDP of B&R countries will reach USD 47.1 trillion by 2030⁴(⁴ From prediction results of CEBR (https://cebr.com/), the total GDP of B&R countries will reach $46.8 trillion US dollars by 2030. Therefore, the GDP forecast of the B&R in 2030 in this paper is credible.), and GDP per capita will reach approximately USD 9235, which is roughly the average level of middle-income economies.

Population growth, economic growth, and other measures of social and economic development cannot be separated from the increasing consumption of water resources. Using the water footprint formula proposed by Ercin (2014), we can predict the changes in water demand of the countries along the B&R that will occur along with population growth by 2030:

where W₂₀₃₀ is the total water demand in 2030, POP(n)₂₀₃₀ is the population in 2030; $Wpercapita{{(n)}_{2017}}$ is the per capita water consumption in 2017; $\alpha $ is the increase in labor productivity; and n represents each country.

Based on the per capita water consumption in 2017, total water consumption in the region is expected to reach 3027.03 billion cubic meters by 2030, an increase of 15.8% from the 2613 billion cubic meters consumed in 2017.

Similarly, using grain output, we can predict the total amount of agricultural water used by the countries along the B&R in 2030:

where Wagri₂₀₃₀ is the total water demand for agriculture in 20, $Yagri{{(n)}_{2030}}$ is the grain output in 2030,$Wy{{(n)}_{2017}}$ is the agricultural water consumption per unit of grain output in 2017, and β is the labor productivity.

Using data on grain output from the countries along the B&R in 2017, agricultural water consumption is predicted to reach 2200-2600 billion m³ by 2030⁵(⁵ Because of the uncertainty of policies relating to arable land and fertilizer input, the grain output in 2030 may be between 1.95 billion tons and 2.26 billion tons, so the forecast results are in the range between these two values.).

The impacts of social and economic development on changes in arable land area are complex, but some studies have shown that there is a quantitative relationship between the process of urbanization and the change in arable land area.

The results of data fitting show that there is a negative linear relationship between the urbanization process and the arable land area along the B&R (see Table 1). Thus, every percentage point increase in the proportion of the population engaged in non-agricultural production leads to a reduction in arable land of approximately 3.95 million hectares⁶(⁶ Data are from the Food and Agriculture Organization of the United Nations.). Hence, we can deduce that by 2030, the arable land in this area will be reduced by 31.59 million hectares as a result of urbanization.

In addition to water resources and arable land, the environment is also impacted by social and economic development. Conservative forecasts estimate that if the use of agricultural inputs such as fertilizers grow at a rate of 2.9%⁷(⁷ The average growth rate was calculated using historical fertilizer usage data for countries along the B&R.), then by 2030, inputs of fertilizer will reach 187 million tons, and the input of fertilizer per unit area of arable land will reach 269 kg ha^-1, or approximately double that in 2016.

The impacts of the development of B&R countries on agricultural resources and the environment in the future means that these countries are now faced with the problem of choosing the most suitable mode of agricultural development.

There are two options regarding the development of agriculture along the B&R: conservative development and radical development. Under the conservative development approach, the countries along the B&R do not adopt innova tive policies and measures in relation to arable land, water resources, and the environment to cope with the challenges of social and economic development in the future. Conversely, under the radical development approach, the countries along the B&R will strive to achieve self-sufficiency in terms of grain production, as well as exporting as much surplus grain as possible.

From the perspective of conservative development, the countries along the B&R have not yet introduced more innovative policies, including farmland protection policies. In an effort to increase grain production, the use of agricultural materials such as chemical fertilizers in crop production was increasing at an average annual growth rate of 2.9% in 2016. By 2030, the input of chemical fertilizers will reach 187 million tons, and grain output is expected to reach 3000 kg/ha, thus total grain output will reach 2.08 billion tons. However, as a result of the lack of farmland protection measures, the area of land that is sown for grain production will be reduced by 31.59 million hectares because of the urbanization process, and total output will be reduced by about 95 million tons. Based on the abovementioned predictions regarding social and economic development, the total population of the countries along the B&R will increase to 5.1 billion by 2030. Thus, using the estimated demand by 2030 of 440 kg of grain per capita, the total demand for grain in the region will reach 2.26 billion tons, leaving a gap between demand and supply of about 275 million tons. Despite the growing gap between food demand and supply, agricultural water consumption will still be increasing significantly. Based on the above calculations, agricultural water consumption in 2030 under the conservative development approach will reach 2281.2 billion m³, an increase of 9.6% from the 2017 level of consumption.

As for the radical development approach, there are at least two ways to achieve the goal of grain self-sufficiency and to be able to export of surplus production by all countries along the B&R. Firstly, inputs of chemical fertilizers can be significantly increased. If the area of land sown for grain crops is maintained at the 2017 level until 2030, grain output will need to increase to at least 3270 kg ha^-1 to meet the basic demand for 2.26 billion tons of grain. To achieve this, the input of fertilizers will need to increase to 233 million tons, a rate of 335 kg ha^-1 of arable land. In addition, the input of agricultural water will need to increase to 2597.3 billion m³, which is equivalent to the total amount of water resources used for all purposes in the region in 2017. Thus, the input of fertilizer and the consumption of water resources are both ahead of schedule. Another way to achieve the goal is to increase the area of land sown for grain, which would reduce the input of fertilizer and agricultural water as much as possible, thereby achieving a balance between the area of land under cultivation and the use of fertilizer and water resources.

Generally, although the conservative development approach can reduce the consumption of water resources to some extent and the input of agricultural resources such as fertilizers is not as great, this approach is not sustainable. First, one consequence of the conservative development approach is a significant gap between food supply and demand, and thus food self-sufficiency cannot be achieved and food security cannot be guaranteed. Further, the gap between food supply and demand will continue to increase over time, which will affect not only the food security of the region, but also global food security. Second, the conservative development approach does not mean low or no consumption of resources. Resource saving is a passive way to deal with the problems of resources and the environment, but it will not bring about any long-term solutions. Third, and most importantly, adopting a conservative approach to development will be an inevitable choice. The reason for this lies in the fact that all the countries along the B&R are independent and lack coordination. Therefore, the efficiency of resource use by the countries in the region is difficult to improve, resulting in extensive resource consumption and low productivity.

Although the radical development approach can solve the problem of food security, it will require a significant investment in agricultural resources and lead to further damage to the environment. This approach is also unsustainable. Therefore, the countries along the B&R urgently need to solve not only the problems of agricultural resources and the environment, but more importantly, through top-level design and strategic planning, the agricultural development community along the B&R must be constructed, which is the fundamental reason for the sustainable agriculture along the B&R.

For a long time now, the countries along the B&R have been unable to guarantee food security. The fundamental reason for this is their low level of efficiency with respect to inputs of agricultural resources and the resulting outputs. However, a deeper reason is the lack of integration of the agricultural resources by the countries along the B&R. In other words, there is no middle-man overseeing the process of integration, no intermediary overseeing coordination among these countries. Therefore, to realize the complementary advantages in terms of agricultural resources that exist among countries along the B&R, there is an urgent need to build an international agricultural development cooperation platform across the national boundaries; that is, a committee for the sustainable development of agriculture. As a strategic sponsor of the B&R strategy, China is responsible for taking the lead in promoting the establishment of a sustainable agricultural development committee for the B&R region. The establishment of this committee should be based on the principles of equality and mutual benefit under the framework of international law, with the countries along the B&R regarded as member states. There should be an authorization-agency relationship between the member states and the committee, whereby each member state authorizes the committee to act as its agent in exercising its powers. The establishment of this committee will enable the collection and exchange of agricultural resources, funds, technology, and other resources and information, which will facilitate the sharing of agricultural resources among countries and improve efficiency in the use of agricultural resources.

Relying on the support of international organizations and financial institutions, taking the Silk Road Fund as a precedent, the committee should work with the countries along the B&R to set up a special fund to support the sustainable development of agriculture. Meanwhile, the committee should cooperate with the investment and financing platform of the Global Agricultural Green Development Fund to guide and drive the investment of social capital. Thus, it can provide investment and financing support to encourage the cooperation of B&R countries regarding a range of activities, including the development and utilization of arable land and water resources, mechanization, green technology research and development, environmental protection and management, high-yield breeding and cultivation, and the use of organic fertilizers.

The solution to the sustainable development of agriculture along the B&R lies in scientific and technological innovations that support the efficient utilization of agricultural resources, the improvement of the environment, and the achievement of food security in the B&R region. Therefore, the committee for the sustainable development of agriculture, with the help of the B&R agricultural development fund, will need to develop technologies to aid mechanization, unmanned intelligence gathering, soil testing and improvement, water saving and recycling, agricultural breeding and cultivation, intelligent planting, the use of bioorganic fertilizers and pesticides, and the training of people in the application and promotion of those technologies to achieve state-of-the-art intelligent and sustainable agricultural production in the B&R region.

The sustainable development of agriculture along the B&R depends on the integration of agricultural resources, the improvement of resource efficiency, and the decoupling of agricultural resource inputs and outputs. The complementarity of the various agricultural resources in the countries along the B&R provides an opportunity for the integration of agricultural resources in the region. Generally, the main factors preventing the sustainable development of agriculture along the B&R are the uneven distribution of arable land and water resources, the low degree of mechanization, the shortage of labor, and the low level of planting technology, all of which affect the efficiency of agricultural resource utilization in the region. However there is also a lack of deeper and broader cooperation in agriculture between the countries along the B&R, which is the more fundamental reason. Therefore, in the future, the direction of agricultural development along the B&R must be to achieve the best allocation of agricultural resources in the region through innovation and construction of a mode of agricultural cooperation in the B&R.

Firstly, using the platform of the sustainable agricultural development committee with the help of a market regulation mechanism involving the introduction of a “virtual water” trading system, better allocation of water resources between rich and poor areas can be achieved, and thus the efficiency of water resource usage can be improved. Secondly, in view of the reduction of arable land area, all countries in the region should work together to explore the governance mode of arable land protection by means of technology transfer, capital investment, and institutional innovation, in order to ensure that the supply of arable land is maintained in a stable range. Thirdly, using the sustainable agricultural development committee supported by the investment and financing channels of the B&R agricultural development fund, cooperation in relation to agricultural production in the B&R area can be achieved by means of arable land plus agricultural machinery. Finally, a grain-based free trade zone should be created in the B&R. Relying on the existing agricultural cooperation platform in the region, namely, the ASEAN-China Free Trade Area (ACFTA), and based on the principle of a mutually beneficial free trade zone construction, the establishment of a grain-based free trade area in the B&R region will facilitate the free trade of grain among all countries of the B&R and eventually the entire world, thereby providing food security for the B&R region.