Method of cultivated land landscape ecological security evaluation and its application

Ecological security is very important for regional development and society stability, and it has become a hot topic currently. The concept of ecological security can be understood from two aspects, namely the broader sense and the narrower sense. In a broader sense, ecological security includes natural, economic, and social ecological security, while in a narrow sense, it means the security of natural and half natural ecological system, including ecological system and environment security. As special public resources, the quantity and quality of cultivated land are closely related to national food security and social stability, and has great significance in the maintenance of national security. In this study, taking the cultivated land in eastern low hills and coastal region of Qinhuangdao, China as the research area, a cultivated land landscape ecological security evaluation model was built based on the principles of landscape ecology and ecological security. The model contained five landscape pattern indexes including fragmentation, isolation, fractal dimension and shape factor, which could reflect production efficiency, stability and resilience of cultivated land. With three TM(ETM+) remote sensing images in 1990, 2000, and 2010 as well as GIS techniques, the landscape ecological security of cultivated land in the research area was comprehensively evaluated based on each town unit, and the evolution of landscape ecological security pattern and gravity center was analyzed using center of gravity method. At last, the driving factors of landscape ecological security evolution were discussed. The results showed that the landscape ecological security of cultivated land in the research area had been declining all the time with the value decreasing from 0.63 in 1993 to 0.5 in 2000. The fragmentation of cultivated land in low mountainous and hilly areas was more serious, so its landscape ecological security was lower than coastal area. The landscape ecological security was divided into three levels according to Natural Break grading result of three years includingIlevel when ecological security was equal or less than 0.3, IIlevel when ecological security was greater than 0.3 and equal or less than 0.65, and III level when ecological security was equal or greater than 0.65. In addition, this study demonstrated that the pattern of landscape ecological security changed obviously. From 1993 to 2000, the I level area had no noticeable change, but the II and III level area were converted to each another. From 2000 to 2010, theIand IIlevel area were expanded, which were converted from the III level area. In the past 20 years, the gravity center of landscape ecological security of cultivated land had transferred to the adjacent regions of Qinhuangdao city. It indicated that the landscape ecological security of coastal area had been increased obviously. The reduction of rainfall and runoff, with the rapid increase in economy and population, and governmental policy decision all had a profound effect on the landscape ecological security variation of cultivated land. This study applied landscape pattern index to describe the landscape structure of cultivated land in ecological security study. The studies on ecological security evaluation of cultivated land are conductive to protection of fragile ecological environment and local sustainable development of cultivated land resources.