中文摘要：

农地除了能够依靠其生产功能而具有经济产出价值外，在空气和水的净化、生物多样性的维持、景观的提供及社会保障与安全稳定等方面也发挥着重要的作用。但由于市场机制的自身缺陷，人们对农地价值缺乏充分认识，导致农地资源得不到应有的保护。本文在将农地功能划分为经济生产、社会保障和生态服务的基础上，以2009年为评估期．尝试构建柯布一道格拉斯生产函数（C—D函数）和用近似市场法对我国1994年-2009年30个省份农地资源的经济产出价值、社会保障价值和生态服务价值进行了动态估算。结果显示：无法通过市场价格表现的社会保障价值与生态服务价值均远远大于农地经济产出价值，农地的社会保障价值在农地总价值中占有相当大的比重，其比例呈现出逐年增加的趋势。因此，农地的社会保障价值和生态服务价值无疑是农地价值中不容忽视的重要组成部分，应当引起土地管理者和农地非农转用决策者的充分重视。

英文摘要：

In addition to the economic value of its production, agricultural land plays an important role in air and water purification, biodiversity maintenance, landscape exhibition, and social security and stability. However, the true value of agricultural land is obscured because of defective market mechanisms, leading to unprotected agricultural land resources. We suggest that functions of agricultural land should include economic production, social security and ecological services. Using 2009 as the appraisal year and using the cobb-douglas function and approximate market law, we dynamically estimated the comprehensive value of agricultural land by examining economic output values, ecological service values and social guarantee values of agricultural land resources for 30 provinces from 1994 to 2009. The results show that the social security and ecological service values are far greater than the economic output of agricultural land. The social security value of agricultural land accounts for a sizeable proportion of the total value of agricultural land, and this is rising. The fundamental cause of rural-urban land conversion is the lower return on land agricultural use, which inevitably leads to other uses that have higher benefits. In the process of conversion, economic benefits improve but social benefit and ecological benefits are lost, leading to a net loss in social welfare. In order to achieve the optimal allocation of resources, the opportunity cost of land conversion, including the economic cost, social cost and environmental cost should be evaluated from the perspective of sustainable development. There is no doubt that the ecological service value and social guarantee value of agricultural land are important portions of the overall value of agricultural land. Our analysis will be helpful to social policy-makers and improve the social and ecological objectives of land use.