The first discussions in Rotterdam about the subject of urban ecology started less than ten years ago. It resulted in the publication and adoption of several Nature and Environmental Policy Plans. In the second Nature Policy Plan it was admitted that a proper knowledge about the actual situation concerning the presence of plant and animal species in the city is lacking. As a direct result of this reflection the Rotterdam Institute for Urban Nature or ‘bureau Stadsnatuur Rotterdam’ (bSR) was founded in September 1997. It immediately started to develop plans to collect data on the Rotterdam urban flora and fauna, not only for the sake of science, but certainly - and perhaps mostly - for the sake of urban welfare. Few cities in The Netherlands have conducted ecological research so far. Some cities have published a bird atlas, a flora atlas, or similar studies on the urban natural life, but a thorough ecological mapping has so far not been made. The process of biotope mapping is an unknown phenomenon in The Netherlands. German and other European cities, on the other hand, have a long tradition of scientifically thorough mapping activities and have inspired bSR to promote starting similar activities in Rotterdam, with the ultimate goal of increasing the ecological ánd esthetical value of the urban greenery.