Urban nature provides local ecosystem services such as absorption of air pollutants, reduction of noise, and provision of places for recreation, and is therefore crucial to urban sustainable development. Nature conservation in cities is also part of the global effort to halt biodiversity decline. Urban landscapes, however, display     distinguishing social and ecological characteristics and therefore the implementation of nature conservation frameworks into cities, requires reconsideration of what nature to preserve, for whom and where. The aim of this thesis was to examine the current urban nature conservation with special focus on formally protected areas, and discuss their future role in the urban landscape. A social-ecological systems approach was used as framework and both quantitative and qualitative methods were applied. The studies were performed at local to regional scales in the southern part of Sweden. Four key questions were addressed: i) What are the characteristics of nature conservation in urban landscapes? ii) How does establishment of nature conservation areas affect the surrounding urban landscape? iii) In what ways are spatial and temporal scales recognized in practical management of nature conservation areas? and iv) How can the dichotomy of built up and nature conservation areas be overcome in urban planning? Nature reserves in urban, compared to rural landscapes were in general fewer, but larger and included a higher diversity of land covers. They were also based on a higher number and different kinds of objectives than rural nature reserves. Urbanisation adjacent to nature reserves followed the general urbanisation patterns in the cities and no additional increase in urban settlements could be detected. In general, there was a lack of social and ecological linkages between the nature conservation areas and the urban landscape and practical management showed a limited recognition of cross-scale interactions and meso-scales. Such conceptual and physical isolation risks decreasing the public support for nature conservation, cause biodiversity decline, and hence impact the generation of ecosystem services. A major future challenge is therefore to transform current conservation strategies to become a tool where urban nature is perceived, planned and managed as valuable and integrated parts of the city. To enable social-ecological synergies, future urban planning should address proactive approaches together with key components like active enhancement of multifunctional landscapes, cross-scale strategies and border zone management.