| Food security and ecological security is an important strategic issue which has relationship with social and economic development, social stability and improving of the people's living quality. Our government has always been paying high attention to this issue which needs to b e addressed effectively. If we only pay attention to the food security and ignore the ecological security, then the development of grain production will also be unsustainable. Because people interfere with the ecosystem structure, function and ecological processes during food production, which leads to declining ecosystem service function and its decreasing value. Therefore, as for theoretical analysis and loss assessment for the loss of ecosystem service value caused by ensuring food security, it has important theoretical and realistic significance. This paper aims to do theoretical analysis for the ecosystem service value loss caused by ensuring food security, and construct the evaluation model of value loss. Firstly, the thesis discusses the necessity to evaluate the value loss, and clarifies the connotation of ecosystem service value loss caused by ensuring food security, then theoretically reveals the mechanism about how the ensuring of food security affects ecosystem service value loss, using interference theories from the angle of Ecological Economics and based on the present research on domestic and international ecosystem service value evaluation. Secondly, this thesis constructs the model of evaluating the loss of ecosystem service value caused by guaranteeing food security, based on theoretical analysis. Then we set ChangWu county of Shaanxi province as an example and evaluate its loss of ecosystem service value in 2008 to verify the practicability of the model. The research results are as follows:(1) Theoretical research shows that ecosystem service value loss caused by ensuring food security can be divided into three parts: the loss of agro-ecosystem service value caused by the reasonable exchange among different ecosystems in the process of food production and land use structure adjustment; the loss of ecosystem services value caused by negative impacts exerted on the ecosystem surrounding agro-ecosystem during food production; the ecosystem services value loss caused by the land use as grain production land rather than the land use types (or ecosystem types) which can bigger ecological service value. (2) This thesis estimates the ecosystem service value in Changwu County, referenceing the existing research results for ecosystem services value evaluation model. Evaluation results show that: in 2008 the County's total ecosystem service value of different land use types was 85503.32×10~4 yuan, in which forest generates the largest ecosystem service value 58136.70×10~4 yuan, which accounts for 67.99% of the total value. Farmland, waters, grassland and unused land account for 18.09%, 11.68%, 1.55%, and 0.69% of the total value respectively. Forest, farmland and waters produce more than 97% of the total value. All kinds of ecosystem service function can be arranged in accordance with the service value Size as follows: water conservation>biological diversity protection>soil formation and protection>climate adjustment>gas regulation>waste treatment>raw material>entertainment culture>food production.(3) Based on theoretical analysis, the paper constructs the model of evaluate different types'ecosystem service value loss. In order to verify the feasibility and practicability of the model, this paper sets Changwu County in shaanxi province as an example, and evaluates its value loss of guaranteeing food security in 2008. The reasonable conversion between different ecosystems caused the loss of ecosystem service value 22834.16×10~4 yuan; If all the farmland used for food production now functions as forest, grassland or waters, it will provide greater ecosystem service value than before and the difference are: 21963.30×10~4 yuan, 4095.04×10~4 yuan and 40678.82×10~4 yuan. As for per unit area of ecosystem service value difference, waters is 19682.34yuan/hm~2 and forest is 10627.4yuan/hm~2, while grassland is 1981.37yuan/hm~2.(4) Through theoretical analysis and evaluation of value loss, the research shows: firstly, guaranteeing food security not only causes a tremendous ecosystem service value loss, and people also have to give up the bigger ecosystem service value which produced by other ecological system (such as forest, waters, etc.); secondly, application of the model shows that this model is simple and clear, straightforward and easy in operation, and case application proves the applicability and practicability of the model. |
