Research On The Structural Optimization And Benefits Of Grain Trade Networks In Countries Along The "Belt And Road"

With economic and industrial development,the water crisis has intensified,posing a great challenge to the security of world grain supply and demand.The grain trade of the countries along the“Belt and Road”shows the mismatch between the quantity and direction of grain flows and the actual demand,and the imbalance of economic development has exacerbated the complexity of this problem.Therefore,it is very meaningful and challenging to explore the optimization of grain trade network structure in countries along the“Belt and Road”.The studies that have been conducted on the rationality of grain trade network structure have mostly considered the transportation cost,while grain is also used to meet the needs of industrial and economic development.Therefore,a study that reconstructs the structure of grain trade network in terms of the economic value of grain can fill this gap.In this thesis,the economic value of industrial grain is considered as opportunity cost,and a linear programming model of grain trade network in countries along the“Belt and Road”is constructed to minimize the total cost of grain trade.This exploration can increase the understanding of the impact of grain supply and demand structure on economic and social development and help policy makers to formulate policies for grain supply security.Based on agricultural,meteorological,socio-economic and geographical distance data,this thesis first quantifies grain production and consumption in 40 countries along the“Belt and Road”in 2018 to assess the supply and demand balance of grain.Then,this thesis further quantify the virtual water content and water stress index in grain and assess the virtual water supply and demand balance.The results show that:(1)There is a high concentration of grain resources.Ukraine and Russia being the largest grain surpluses,which account for about 40%of the total grain surpluses.China,Egypt,Iran and Turkey are the main demand countries for grain trade,accounting for about 75%of the total grain demand.(2)By comparing the relationship between grain supply and demand balance,virtual water supply and demand balance and water stress index of each country,it is found that there is a contradiction between the flow pattern of virtual water for grain and the distribution of real water flow in the countries along the“Belt and Road”.Based on the above contradictions,this thesis applies complex network theory to build bipartite network model of grain trade in 2018 in countries along the“Belt and Road”,and uses linear programming theory to construct a network structure optimiza-tion model and obtain the optimal grain supply and demand configuration with the goal of minimizing transportation costs.The structural characteristics of the optimal configuration and its economic,resource and environmental benefits are studied.It is found that:(1)The optimized grain supply and demand structure reveals that trading countries follow geographical proximity in selecting partners and the network structure shows a long-tail distribution.In addition,the grain trade of countries along the“Belt and Road”also shows scale-free characteristics,reflecting the tendency of economies to cooperate with countries with high trade volume to ensure grain supply and demand security.(2)In terms of economic benefits,the total trade cost of the optimal con-figuration obtained with the objective of minimizing transportation costs is about 466billion US dollars,which is close to 1/4 of the total agricultural output.(3)In terms of resource benefits,the loss of water resources due to grain trade of countries along the“Belt and Road”is about 72×10~9cubic meters,i.e.,most of the virtual water flows implied in the grain trade are from countries with low water productivity to coun-tries with high water productivity,resulting in inefficient use of water resources.(4)In terms of environmental benefits,the implied increase of carbon emissions in grain trade in countries along the“Belt and Road”is about 28 million tonnes,i.e.,grain is mainly transferred from countries with relatively high carbon emission coefficients to countries with low carbon emission coefficients.Further,on the basis of the grain trade network considering transportation costs,opportunity costs(the potential economic value brought by the industrial use of grain)are introduced to minimize the total costs(transportation costs and opportunity costs),and a grain trade network structure optimization model is constructed for the countries along the“Belt and Road”in 2018 to obtain the optimal supply and demand configu-ration,and analyze its structural characteristics as well as the economic,resource and environmental benefits.It is found that:(1)The optimized grain supply and demand structure has the same selective preference,long-tail characteristics,and follows geo-graphical proximity as the optimization results considering only transportation costs.(2)In terms of economic benefits,the introduction of opportunity costs has a positive economic impact by limiting the flow of grain trade from low to high industrial value added.This makes the economic value of the optimal configuration not only cover transportation costs,but also generate additional economic benefits of about 130 tril-lion US dollars,which is nearly 65 times the total agricultural output of the countries along the“Belt and Road”.(3)In terms of resource benefits,the optimal grain supply and demand configuration considering opportunity costs generates positive water ben-efits,saving about 28×10~9cubic meters of water.Compared with the optimal result without considering opportunity cost,the water saving is about 100×10~9cubic meters.(4)In terms of environmental benefits,the carbon emission from each economy due to grain trade in the optimal supply and demand configuration considering opportunity cost is about 3 million tonnes.Compared with the optimal configuration of the grain network without considering opportunity costs,a total of about 25 million tonnes of carbon emissions are reduced.In conclusion,the introduction of opportunity cost can help countries along the“Belt and Road”to improve their economic development,for-mulate reasonable water management strategies,and actively promote the process of pollution and carbon reduction.Based on the bipartite network of grain trade among the countries along the“Belt and Road”,this thesis introduces opportunity cost to build a trade structure optimiza-tion model and compares the economic,resource and environmental benefits with the optimal configuration without considering opportunity cost.This thesis helps to for-mulate and adjust policies related to the“Belt and Road”initiative,so as to optimize the structure of grain trade network and alleviate the pressure of water scarcity,while maximizing environmental protection and economic benefits.