Food security and ecological security are strategic issues that are related to social and economic development, and must be addressed effectively by our government in order to improve people's quality of life and social stability. Because people interfere with ecosystem structure, function and ecological processes during food production, this leads to declining ecosystem service function and a decrease in its value. Therefore, theoretical analysis and loss assessment of the reduction in ecosystem service value caused by ensuring food security has important theoretical and real significance. This paper aims to carry out theoretical analysis for the ecosystem service value loss caused by ensuring food security, and to construct an evaluation model of value loss. First, the thesis reveals the theoretical mechanism that illustrates how ensuring food security affects ecosystem service value loss. Second, the thesis constructs a model for evaluating the loss of ecosystem service value caused by guaranteeing food security, based on theoretical analysis. Finally, and using Changwu County of Shaanxi Province as an example, we evaluate its loss of ecosystem service value in 2008 to verify the practicability of the model.
Theoretical research shows that ecosystem services value loss caused by ensuring food security is divided into direct loss and indirect loss. Direct loss includes two aspects: in the process of food production, adjustment of land use leads to ecosystem exchange, whereby the ecosystem value declines and causes the loss of ecosystem services value. In addition, food production has a negative impact on the ecosystem that surrounds the agro-ecosystem, and those negative impacts can also cause the loss of ecosystem services value. Indirect losses relate to land being used for grain production; if land being managed in such a way that its ecological service value is high is then used for grain production, then the overall loss to the ecosystem services value is correspondingly great.
This thesis estimates the ecosystem service value in Changwu County. Evaluation results show that in 2008 the county's total ecosystem service value for different land use types was 85503.32×10⁴ yuan, in which forest generated the largest ecosystem service value of 58136.70×10⁴ yuan, accounting for 67.99% of the total value. Farmland, water, grassland and unused land accounted for 18.09%, 11.68%, 1.55%, and 0.69% of the total value, respectively. Forest, farmland and water produced more than 97% of the total value.
The ecosystem services value loss evaluation resulting from guaranteeing food security in Changwu County in 2008 shows that the reasonable conversion between different ecosystems caused a loss of ecosystem service value of 22834.16×10⁴ yuan. If all the farmland used for food production now functioned as forest, grassland or water, it would provide greater ecosystem service value than before and the difference would be 21963.30×10⁴ yuan, 4095.04×10⁴ yuan and 40678.82×10⁴ yuan, respectively.
Theoretical analysis and evaluation of value loss shows, first, that guaranteeing food security causes a tremendous ecosystem service value loss. People also lose the bigger ecosystem service value produced by other ecological systems such as forest and water. Second, application of the model shows that it is simple, clear, straightforward and easy to operate, and case application proves its applicability and practicability.