| The Sloping Land Conversion Program（SLCP）is the world’s largest investment,the strongest policy,the most extensive ecological protection and restoration project with the highest participation of the public.As an ecological protection and restoration project with the core objective of improving the ecological environment,how the ecological performance of SLCP has always been the focus of the public,government policy makers and scholars.There is no doubt that the established literature and reports point out that SLCP has achieved significant ecological effects and the regional ecological environment has been greatly improved.However,considering that SLCP is a complex project involving natural environment and socio-economy,it is difficult to attribute all the significant ecological effects and ecological improvements to SLCP.In addition,behind the implementation of SLCP is a huge financial,resource and manpower investment of over 500 billion yuan from the central government,and over 500 million mu1 of cultivation retreat in SLCP participating areas,involving over 40 million households.The scarcity of resources determines that China’s resource input to SLCP cannot grow infinitely,and economic effectiveness and ecological effectiveness are equally important under resource constraints.However,little has been reported in the literature on the eco-efficiency of SLCP.So,the issues that need attention are:What exactly are the significant ecological effects achieved by SLCP?The significant ecological effects achieved by SLCP are the result of a combination of natural conditions,socio-economics and SLCP,so how large is the net effect of SLCP on ecological effects?How eco-efficient is SLCP?What is the relationship between the ecological effects and eco-efficiency of SLCP?And what are the factors that influence the eco-efficiency of SLCP?This paper will focus on the above issues,aiming to provide targeted policy suggestions for consolidating and improving SLCP,provide theoretical references for evaluating other ecological protection and restoration projects,and provide reference guidance for the ecological protection and restoration projects to be implemented under the"carbon peaking and carbon neutrality"strategy.This dissertation takes the ecological performance evaluation of SLCP as the main line,and based on a systematic review of relevant domestic and foreign literature,defines the basic concepts of ecological performance,ecological effects and ecological efficiency of SLCP based on theories of economics,management and ecology,identifies the essential characteristics and characterization indexes of the core variables of the dissertation,constructs a general research framework for ecological performance evaluation of SLCP,and clarifies the scientific questions to be addressed by the dissertation.Following the logical line of"ecological effect evaluation-ecological effect influence factor-ecological efficiency measurement-ecological efficiency influence factor",the ecological performance of SLCP in Loess Plateau was evaluated based on the long-term panel data of 314 counties in Loess Plateau from 1990 to 2018 constructed by multi-source remote sensing,socio-economic and SLCP data.The brief summary is as follows:First,based on multi-source remote sensing data and biophysical models,the ecological effects of SLCP on the Loess Plateau were evaluated in terms of both vegetation cover and ecosystem services using GIS technology.Secondly,based on the counterfactual framework,SLCP was considered as a"quasi-natural experiment",and a multi-period DID model was used to analyze the factors influencing the ecological effects of SLCP,to obtain the net effect of SLCP implementation on ecological effects,and to test the persistence and heterogeneity of the effects of SLCP implementation on ecological effects.Thirdly,the SLCP eco-efficiency evaluation index system was constructed,the SLCP eco-efficiency was measured using the DEA-BCC model,and the spatial and temporal evolution of the SLCP eco-efficiency was portrayed using the Kernel density estimation and spatial statistical model,and the relationship between the SLCP ecological effects and efficiency was also analyzed.Fourth,based on the DEA-Tobit model,the factors influencing the eco-efficiency of SLCP on the Loess Plateau were analyzed from both controllable and uncontrollable aspects.Finally,based on the results of the above empirical analysis,targeted policy recommendations are proposed.The main conclusions of this dissertation are as follows.（1）The implementation of SLCP on Loess Plateau has achieved significant ecological effects,vegetation cover and ecosystem services have been significantly enhanced,and the ecological environment in the area has been greatly improved.In terms of time dimension,from 2000 to 2018,the average vegetation cover of Loess Plateau increased from 45.09%to64.15%,the average soil erosion modulus decreased from 21.84 t·hm-2·yr-1 to 13.86 t·hm-2·yr-1,the average vegetation carbon sequestration increased from 737.68 g C·m-2·yr-1 to 1296.35g C·m-2·yr-1,the average soil conservation increased from 224.11 t·hm-2·yr-1 to 232.08 t·hm-2·yr-1,the average water conservation service capacity index increased from 0.0763 to 0.1028,and the average biodiversity maintenance service index increased from 0.0597 to 0.0798.From the spatial dimension,the areas with significant ecological environment improvement are mainly concentrated in the loess plateau gully area in the southwest,the loess hill gully area in the central and northeastern part of the region,and the earth and stone mountain area in the east.Further from the response of vegetation cover change,soil erosion change and ecosystem service change to different slope ranges,it can be obtained that 6-25°is the range of slopes with significant ecological improvement.（2）SLCP implementation is indeed an important reason for the significant ecological improvement of the Loess Plateau,and this conclusion still holds when the effects of natural and socio-economic factors on the ecological environment are taken into account.SLCP has a continuous and heterogeneous effect on the improvement of the ecological environment of the Loess Plateau.The baseline regression results of multi-period DID showed that SLCP could contribute to 16.71%and 10.52%increase in vegetation cover and ecosystem services,respectively,considering only the effects of SLCP on vegetation cover and ecosystem services,and after considering the effects of SLCP,natural conditions and socio-economic factors together,SLCP could still increase vegetation cover and ecosystem services by 15.78%and9.68%,respectively.The results of the dynamism test showed that SLCP not only had a continuous significant effect on vegetation cover and ecosystem service enhancement,but also the effect gradually increased with time.The heterogeneity results of the climate partitions showed that the size of the impact of SLCP on vegetation cover in each region was ranked as follows:arid region>semi-arid region>semi-humid region;the size of the impact of SLCP on ecosystem services in each region was ranked as follows:semi-arid region>arid region>semi-humid region.（3）The overall eco-efficiency of SLCP on Loess Plateau is low,and there is still a large potential to improve eco-efficiency.The eco-efficiency of SLCP shows a fluctuating upward trend in time and significant spatial clustering and divergence characteristics in space.There is a mismatch between the ecological effects and eco-efficiency of SLCP.On the efficiency measurement,from 2002 to 2015,the average value of eco-efficiency of SLCP on Loess Plateau was only 0.492,and from the overall perspective SLCP implementation is still in a relatively inefficient state,and there is still much room for improving the eco-efficiency of SLCP.Nevertheless,the eco-efficiency of SLCP showed a fluctuating upward trend over time,from 0.254 in 2002 to 0.649 in 2015,shifting from a medium low-efficiency state to a medium high-efficiency state.On the spatial and temporal evolution of efficiency,the results of Kernel estimation found that the absolute difference of eco-efficiency of SLCP in Loess Plateau tended to decrease among counties,and the polarization of efficiency among counties improved.The eco-efficiency of SLCP in Loess Plateau has obvious spatial aggregation and divergence characteristics.In terms of spatial distribution and evolution,the overall distribution trend is decreasing from southeast to northwest,and the low-efficiency and medium low-efficiency range keeps shrinking to the northwest,while the high-efficiency and medium high-efficiency range keeps expanding to the northwest.In terms of spatial association,there are positive clustering and dependence characteristics of SLCP eco-efficiency among counties.In terms of spatial differentiation,the southeastern counties are mostly hotspots of SLCP eco-efficiency,with"high-high concentration",while the northwestern counties are mostly coldspots of SLCP eco-efficiency,with"low-low concentration".In terms of the relationship between effects and efficiency,there is a mismatch between the ecological effects and ecological efficiency of SLCP on the Loess Plateau.From a spatial point of view,"high effective-high efficiency"counties are 108,mainly located in the semi-humid areas in the southeastern part of the Loess Plateau;"low effective-low efficiency"counties are 126,mainly distributed in the northern and northwestern parts of the Loess Plateau,as well as the arid and semi-arid areas in the east;"high effective-low efficiency"counties are 70,mainly distributed in the central part of the Loess Plateau,the arid areas in the northeast and the semi-humid areas in the south;"low effective-high efficiency"counties are10,which are scattered in the Loess Plateau.（4）In terms of controllable factors influencing the eco-efficiency of SLCP on the Loess Plateau,the prevalence of input redundancy and output deficiency are important reasons for the low eco-efficiency of SLCP.In terms of the uncontrollable factors influencing the eco-efficiency of SLCP,rural labor transfer rate（ltrans）,per capita net income of farmers（income）,average annual precipitation（pre）,≥10°C average annual cumulative temperature（tem）,soil nitrogen content（snc）and average river network density（river）are all drivers of SLCP eco-efficiency,but there is heterogeneity in the effects of each factor on the SLCP eco-efficiency of the Loess Plateau and its climatic divisions.First,in terms of controllable factors,the redundancy of inputs and insufficient outputs prevalent in SLCP implementation are important reasons for the low eco-efficiency of SLCP.The relatively small input redundancy and output deficiency in the southeastern counties of the Loess Plateau are important reasons for the high eco-efficiency of SLCP and its clustered distribution,while the relatively large input redundancy and output deficiency in the northwestern counties are important reasons for the low eco-efficiency of SLCP and its clustered distribution in the region.Second,from the uncontrollable factors,both socio-economic and natural condition factors selected in this dissertation are the drivers of eco-efficiency of SLCP.However,the magnitude of the effects of each factor on the eco-efficiency of SLCP in the Loess Plateau and its climatic sub-regions were different.For the Loess Plateau as a whole:tem>income>ltrans>river>snc>pre;for semi-humid areas:tem>ltrans>income>snc>river>pre;for semi-arid areas:income>tem>snc>pre>river>ltrans;for arid areas:income>river>tem>ltrans.Synthesizing the above research findings,this dissertation puts forward the following four policy recommendations:Firstly,make top-level design and continue to implement SLCP;Secondly,the implementation of ecological protection and restoration projects should be based on the actual situation of each region,and the spatial scope of afforestation should be decided according to the carrying capacity of water resources in each region,and forest and grass vegetation should be restored scientifically;Thirdly,conduct regular evaluation of ecological performance of ecological protection and restoration programs to increase the match between effect and efficiency;Finally,adhere to the natural restoration-oriented,artificial restoration and natural restoration combined. |
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