Abstract: Ecological security is a concept with rich connotations,which operates across multiple scales from ecosystems and regions to the globe. Understanding the relevant scales of ecological security is the foundation for effective research and the construction of a comprehensive ecological security system. Ecological security includes regionality, spatial differences and spatial spillovers. Each scale of ecological security has its own characteristics but all the scales are interconnected. Global scale ecological security concerns the overall survival and development of humanity. Regional scale ecological security is easier to address through policies or projects because it corresponds with governance units. The ecosystem is the most important scale to understand the fundamental mechanisms of ecological security. Ecological security at different scales is affected by both natural and social factors. The global and regional scales pay more attention to the impact of social factors, while the ecosystem scale focuses more on natural factors. The changing characteristics and functions of different ecological media result in ecological security issues at different scales. The differences in scales could have influences on the main analysis methods. Global scale ecological security assessment commonly applies models, while regional scale research uses comprehensive evaluation, ecological models and landscape ecology methods. At the ecosystem scale, the main methods are ecological indexes and ecosystem models.

Key words: ecological security, multi-scale, characteristics, impact mechanism