Abstract: Urban biodiversity provides diverse ecosystem services for modern cities, and serves a fundamental role in maintaining sustainable urban development. However, potential threats to urban biodiversity have been increasing along with intensified human perturbations and the consequent transformation from natural landscape to artificial landscape. Naturalness assessment has been widely applied to identify the natural attributes or hemeroby, and to inform urban biodiversity conservation and ecosystem management. In this study, three naturalness assessment methods were summarized based on the concept of naturalness and its assessment. The three methods are indicator biology method, natural distance method, and multi-index comprehensive assessment method. The research progress of naturalness assessment applied in urban biodiversity conservation has been broadly reviewed from the aspects of urban habitat quality assessment, urban landscape dynamic monitoring, and urban ecological space planning. It is proposed that the naturalness assessment of urban ecosystems should be evaluated in a more comprehensive perspective by taking biodiversity status and changes, ecosystem integrity, human disturbance and management decision-making into consideration, and naturalness assessment should be further incorporated into the studies of land use, socio-economic and ecological effects, as well as to reveal the relationship between human activities and biodiversity in urban area.

Key words: naturalness, hemeroby, urban ecosystem, urban biodiversity