Abstract:

 Land is the foundation ofglobal survival and development Land ecological security is related to regional sustainable development The land ecosystem plays a very important role in socialeconomic progress at regional, national, and international scale The land ecosystems of Yancheng city have become highly stressed and dysfunctional due to the continuous, excessive exploitation and utilization of land resources In this regard, there is considerable need for methods and indicators to diagnose the state of land ecosystem for prompting ecological restoration, management and regulation A catastrophic model for land ecological security assessment combined with the pressurestateresponse （PSR） model framework was developed in this paper to overcome the disadvantages in subjectivity and complexity of the currently used assessment methods Based on the actual land use in Yancheng city, the paper established the ecological security of land index system from perspectives of economy, society and ecological environment The catastrophic assessment index system was divided into hierarchical subsystems under the pressurestateresponse framework The catastrophe model integrated multiple assessment indices of land ecological security according to the inherent contradictions and relative importance of indices without calculating weights Specifically, membership degree of higher level index was calculated based on the membership degrees of lower level indices that were subjective to suitable model, such as cusp, fold, swallowtail and butterfly model The purpose of this paper is to judge the degree of land ecological security in Yancheng city from 2002 to 2011 via catastrophic theory and PSR model and find the inherent issues to make sure of sustainable development of this region The results showed that among the ten years, the value of pressure, state, response and synthetic about land ecological security was evaluated as safe in the year of 2003 and 2007, then in the year of 2002 and during 2004-2006 was at middle level, then the degree of land ecological security during 2008-2009 was insecure and very insecure from 2011 to 2012, which showed that ecological security level and circumstance of land use in Yancheng city continually decreased During this period, the land use pattern of Yancheng was under the tremendous pressure from the conflict between the rapid urbanization, economic development and the conservation and rehabilitation of ecoenvironment All these imply that land ecosystem conditions are not optimistic for Yancheng city and such situation should draw the high attention of related government departments There are some factors that demographic, the invest ration to protect environment and urbanization rate has the most important influence on the land ecological security of Yancheng city Generally, The calculation procedure presented in this paper does not require a high level of technical expertise to determine the membership degree, making it simple and operational Being applicable to similar land ecosystems, the catastrophic model is thus believed to provide an alternative approach to land ecosecurity assessment This paper emphasized the impacts of human activity on land ecological security of Yancheng city and put forward suggestions concerning the adjustment or optimization of land use pattern and improvement of the technical system for ecosecurity assessment based on regional overall planning from 2011 to 2030, which would have wide application prospective in the future