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Considering the issue of nature in the city through its unlikely biodiversity could seem surprising. This article derives from a synthesis of French language and English language literatures. The state of art highlights the case study of the Lyon metropolis compared with others urban settlements in developed countries of North hemisphere. The three following themes are presented. The first part explores the uncertain, ambiguous and often contradictory characteristics of nature in the city, through questioning live objects, spaces, places and territories. The second part focuses on urban biodiversity as an amazing stock of nature, underlines the contradictions between desired and undesired species, and shows the deceptive certainty of modeling. The last part deals with public policies in terms of tension, action, management and manipulation, insofar as nature elements appear as stakes for knowledge, power and duties.