面源污染下三峡库区农业生态环境效率及影子价格测算

农业的现代化进程产生了较为严重的农业面源污染,将农业的生态环境效应纳入农业生产效率评价框架是研究的新方向。采用非径向、非角度的SBM-DEA模型,结合方向性距离函数,考察了2003-2015年期间重庆三峡库区农业生态环境效率,引入影子价格测算了各区(县)农业面源污染的边际减排成本。研究结果表明:2003-2015年期间,重庆三峡库区农业生态环境效率趋于稳步提升态势,但整体水平较低,平均值仅为0.508,全样本期投入无效率和非期望产出无效率平均值分别为27.3%和24.7%。农业生态环境效率较高的地区集中在都市核心区和库尾都市外围区,江北和大渡口的农业生态环境效率值为0.7;而库尾低山丘陵区、库中平行岭谷区、腹地山地丘陵区和腹地外围山地区的农业生态环境效率相对较低,尤其是巫溪、万州与开县农业生态环境效率值仅为0.4左右。从效率损失的原因看,化肥、农药的过度投入及其相应的逆生态环境效应表现突出,在投入无效率的来源分解中贡献最大,达35.82%;大渡口、南岸、江北、北碚与渝北农业面源污染排放的影子价格居前,分别为3.503、3.478、3.370、3.317、3.302亿元/万t,污染减排空间较小;万州、丰都与开县农业面源污染排放影子价格较低,分别为2.167、2.321和2.492亿元/万t。在制定区域排放目标时,应考虑区域农业生态环境效率的空间异质性,针对不同区域的农业生态环境效率和影子价格制定具有针对性的减排策略,尤其应当把生态环境效率改进余地较大和边际减排成本相对较低的地区作为减排重点地区。

Agricultural eco-environment efficiency and shadow price measurement in Three Gorges Reservoir area under non-point source pollution constraints

The modernization process of agriculture has led to serious agricultural non-point source pollution. It is a new direction to study the evaluation framework of agricultural production efficiency by including the ecological environment effect of agriculture. Agricultural eco-environmental efficiency which combines both economic and ecological performance is a valid way for agricultural sustainability analysis. Based on the non-radial and non-angle SBM-DEA model and the directional distance function, the agricultural eco-environmental efficiency of the Three Gorges Reservoir area in Chongqing during the period from 2003 to 2015 was investigated. The marginal price of agricultural non-point source pollution was estimated by introducing the shadow price cost of emission reduction. The results showed that: 1) During the period of 2006 to 2015, the agro-ecological environment efficiency of the Three Gorges Reservoir area in Chongqing tended to increase steadily, but the overall level was low;2) The input and output of each district (county) were needed to change to optimize the efficiency of agro-ecological environment. The areas with high agro-ecological environment were concentrated in the urban core area and the urban fringe of the reservoir, while the eco-environmental efficiency of the low mountain and hill area, parallel ridge valley area, mountainous area in the hinterland and surrounding mountain area in the hinterland were relatively low; 3) From the reasons of the efficiency loss, the excessive use of chemical fertilizers and pesticides and their corresponding adverse ecological and environmental effects were outstanding, mainly due to the inefficiency of agricultural investment and the inefficiency of undesired output; 4) The shadow prices of agricultural non-point source pollution in Dadukou, Nan'an, Jiangbei, Beibei and Yubei area were at the forefront, and the pollution abatement space was small, therefor, the task of reducing agricultural non-point source pollution should be commissioned. Fengdu, Kaixian and Wanxian district's shadow prices of agricultural non-point source pollution emission were low, thus those three areas should be assigned to agricultural non-point source pollution reduction. Chongqing section of Three Gorges Reservoir Area had an enormous potential for reduction of agricultural non-point source pollution and for the decrease of resource inputs to enhance the agricultural eco-environmental efficiency. Agricultural eco-environmental efficiency evaluation plays an important role in promoting agriculture ecological and sustainable development. The eco-environmental efficiency optimization provides further implications on resource and environmental protection strategies in Chongqing section of Three Gorges Reservoir Area. Meanwhile, we should evaluate agricultural eco-environmental efficiency according to resources endowment, factor substitution, adverse impact on ecology and environment and consider the regional development and different stages, we should promote differently the development of ecological agriculture.