农业外部性识别、评价及其内部化

农业外部性包括外部经济性与不经济性两方面, 前者表现为农业在食物保障、经济、生 态、社会与文化等方面所具有的多元价值, 而后者主要体现在农业对环境造成的非点源污染。我 国农业在土壤、水、大气、生物多样性和景观五个方面均有外部性表现, 本文对其分别进行了识 别。目前对于农业外部性的定量评估, 由于农业外部性表现具有较强的地域性、评价方法缺乏标 准、评价者立场与视角不同而使结果不具可比性。由于无论是农业外部经济性或外部不经济性均 是资源的低效配置, 因此各国从外部性产生的根源———市场失灵或政策失灵入手, 努力促使农业 多元价值得到最优表现, 并对农业外部不经济性加以控制。各国技术实践表明, 可持续农业技术 体系成为农业外部成本内部化的可行手段之一。

Identification, Evaluation and Internalization of Externalities of Agriculture

Externality of agriculture includes both external economy and external diseconomy.The external economy implies multiple roles of agriculture in food security,economic,ecological,social and cultural aspects besides providing food and fiber for human beings,while the external diseconomy is mainly focused on negative environmental impacts of agriculture,such as soil erosion,depleting water resources,non-point source pollution and greenhouse gas emission,etc.Externalities of agriculture in China in aspects of soil,water,air,biodiversity and landscape are identified and explained in detail.Many researches have been carried out on valuing the ecosystem services and external cost of agriculture,including a few about environmental cost in China.Yet the results can not be compared with each other simply because of numbers of reasons: strong regional characteristics of externalities,shortage of standard evaluating methods and different stands of evaluators.As both external economy and diseconomy are low efficient in resource allocation,the source of externality,whether from market failure or policy failure,or both,is being internalized by policy reform or technology amelioration.Objectives of both domestic agricultural policy and international trade one are to optimize multi-values of agriculture and to control the diseconomy of agriculture.Therefore,sustainable development of agriculture becomes one of preconditions.Policies and regulations that can protect rural environment,ensure food security and promote rural development have been attempted by Japan,USA and EU,etc.,which have taken effects in different degrees.And sustainable agriculture technology has been proved to be one of feasible measures for internalizing external cost of agriculture,including: diversifying landscape,Integrated Pesticide Management,soil and water conservation,no tillage,and Best Management Practice,etc.