Efficiency Of The Water-Energy-Food Nexus System And Influence Factor Analysis

Under the influence of global factors such as climate change,population growth and accelerated urbanization,the contradiction between supply and demand of water,energy and food resources worldwide has become increasingly acute,and their resource security and sustainability has become one of the key issues limiting the socio-economic development in China.Improving the utilization efficiency of these resources is an effective way to alleviate this dilemma.The complex relationship between water,energy and food resources is known as the "water-energy-food nexus",and a fragmented development strategy for a single resource sector may cause unpredictable harm to other resource sectors.Along with the high consumption of nexus resources,many environmental problems inevitably arise.Therefore,under the consideration of the dual constraints of resources and environment and the complex interrelationship of water-energy-food nexus,it is of great significance to achieve the improvement of resource utilization efficiency of the nexus system to guarantee the resource security and achieve sustainable development in China.Current research on the efficiency of the nexus system is difficult to consider the linkage within the nexus system and the uncertainty of data in the evaluation process,which affects the credibility of the efficiency measurement.To address that,this paper aims to construct an undesirable network SBM model to assess the efficiency of the water-energy-food nexus system in 30 provinces of China from 2010 to 2019 through opening the "black box" of the water-energy-food nexus system based on the correlations.Further,by considering the uncertainty of indicator data,an interval undesirable network SBM model is constructed to achieve the efficiency evaluation of the nexus system under uncertainty.Based on the efficiency results from network SBM model,the key influencing factors of the external environment are analyzed by a geographically weighted regression model,the Spearman rank correlation coefficient method is mainly used to explore the internal relationship of the water-energy-food nexus system,and suggestions are made to improve the efficiency of the nexus system.The main findings of this thesis are as follows:（1）The efficiency of the water-energy-food nexus system and its subsystems in China showed an overall increasing trend during the study period.Among them,the food subsystem has the largest efficiency increase and is the key sector contributing to the efficiency growth of the nexus system.In addition,the efficiency of the water-energy-food nexus system in the eastern,central,and western regions of China all increased year by year.Among them,the eastern region is the key region to promote the overall efficiency of the nexus system.（2）The redundant inputs of water,energy and food resources and the excess emissions of various environmental pollutants have caused the inefficiency of the water-energy-food nexus system.Among them,in terms of water,energy and arable land resources,the provinces with the highest saving potential are Xinjiang,Hebei and Henan,respectively.In terms of undesirable environmental output,Shandong,Hebei and Henan have the greatest potential for improvement in total emissions of wastewater,exhaust gas and agricultural non-point source pollution,respectively.（3）Compared with the traditional model,the undesirable network SBM model takes into account the correlations among the resource subsystems in the evaluation process,and make the evaluation results more reasonably and accurately,with higher differentiation in efficiency.The undesirable network SBM model can figure out the uncertainty data in the indicators,retain more information in the evaluation results.Compared with undesirable network SBM model,it has more robust evaluation results,which is conducive to risk management and has a superior efficiency differentiation.（4）Water resources per capita,foreign investment and urbanization rate have positive effects on the efficiency of water-energy-food nexus system,while energy self-sufficiency rate,environmental protection investment and environmental regulation intensity mainly have negative effects on the nexus system,and the share of tertiary industry has both positive and negative effects.Different efficiency has different index systems of influencing factors,and the common influencing factors have different directions and degrees of influence on different efficiency.（5）The water resources and food subsystems in China have a more significant efficiency homogeneity,and there is an uneven spatial distribution of efficiency groups.The water-energy-food nexus system and its subsystems show significant synergy,among which the energy subsystem has stronger synergy with the whole system,and the water resources and food subsystems show better synergy among the resource subsystems.Combining external influences and internal analysis of the water-energy-food nexus system,further improvement of the efficiency for the nexus system can be achieved in several ways,such as expanding available water sources,building a water-saving society,improving the quality of urbanization,optimizing the energy supply structure,moderately adjusting the intensity of environmental regulations,introducing advanced production technologies and management models from advanced demonstration areas,and formulating and prioritizing cross-sectoral policies,etc.These will help alleviate the resource dilemma of water,energy and food in various regions of China,as well as achieve the regional sustainable and green development.