For years, ecologists who have been trying to understand the relationship between the organisms with each other and/or their environments, have carried out their researches sometimes far from civilization, sometimes on a desolate island or in a tropical rainforest. Today, about half of the world's population lives in urban areas. Therefore, most of the ecological problems have been brought to these areas. Nevertheless, in cities, preserving and maintaining natural habitats, providing a place not only to live but also to enjoy and to relax, are possible only by applying the principles and concepts of urban ecology in planning. This study presents the outcomes of unplanned urbanization and possible preventive measures, which could be taken in the Kartal District, Istanbul-Turkey. Moreover, in this study, different kinds of urban habitats within the frontiers of Kartal were described and an inventorial study containing native, exotic and cultivated plant taxa were realized. For this plant inventory of the Kartal District, all the greenery in the area were explored in different seasons. Plant samples were collected, dried, labelled and then determined according to standard herbarium procedures. In the present study, totally 576 plant taxa were determined, whereas 477 (395 species, 51 subspecies and 31 varieties) of them were natural and 99 were exotic and cultivated. The most native taxa were in the Asteraceae family (50 species), while the most found kind of exotic plant family was Rosaceae (16 species). The archaeophyte and neophyte plants in these taxa, endemic, rare, endangered, medicinal and poisonous species were also mentioned. Furthermore, the necessity of having ecological studies become widespread in urban areas, initially in Istanbul and later in other places was emphasized in the study.