Using state and trend analysis to assess ecological security for the vulnerable agricultural ecosystems of Pengyang County in the loess hilly region of China

In this study, the pressure–state–response (PSR) framework and analytic hierarchy process (AHP) approaches were integrated for index selection and determination of associated weights among ecological, social, or economic indices. Comprehensive methods, comprising a fuzzy model, state evaluation, and trend evaluation were developed to assess the ecological security of specific agricultural ecosystems. The fuzzy model was used to rank ecological security by linking the membership function and a set of four levels, namely insecure (I), lightly secure (LS), moderately secure (MS), and secure (S). State and trend evaluation approaches were used to assess the ecological security of an agricultural ecosystem in Pengyang County in the southern Ningxia Autonomous Region, China. The results show that ecological security in Pengyang County was insecure (I) from 1986 to 1995 and lightly secure (LS) from 2000 to 2004. Ecological security has generally improved recently, and the constraining factors for the present ecological security are soil erosion, water shortage, excess population growth, low forest cover, and irrational application of chemical fertilizers. Finally, advice for decision makers is proposed in order to achieve sustainability.