Many cities are expanding rather fast. As a result several green areas vanished, while the remaining ones are getting more and more under urban pressure. Changes in the size and configuration of green urban areas will affect the liveability of a city for citizens, as well as the local survival probability of many plant and animal species. In order to keep the city liveable and healthy not only water, energy and waste flows should be managed properly, but also green urban areas. Area, connectivity and quality of habitat patches are crucial for the survival of many species. Therefore, biotope types should be maintained in a proper setting of a network, which makes the exchange of individuals of species with a poor dispersal capacity possible. For getting public support for the maintenance of nature quality of green areas a good communication between responsible authorities and citizens is conditional. Monitoring of nature quality is necessary in order to keep biodiversity at a high level. A monitoring programme can be part of an Ecological Policy Plan of the city.