ABSTRACT: The objective of this paper is to analyse the role of nature in urban areas. The presence of nature in cities is mainly reduced to urban open spaces. From an ecological point of view, parks, gardens and other green areas can be understood as urban ecosystems, which support different ecological processes. These processes are the source of a wide range of ecosystem services, which contribute to improve urban environmental quality standards in the city. The paper reviews the theoretical and methodological basis of study of this ecological functionality of open spaces, and tries to discern potential complementarities and synergies between urban ecology and the naturbanization theory.