Core themes for an urban green systems thinker: A review of complexity management in provisioning cultural ecosystem services

[Display omitted] •We reviewed 70 papers on cultural ecosystem services provided by green spaces.•Our co-occurrence map shows a lack of common language about complexity science.•The complexity of the urban green system in CES provision is understudied.•We define and discuss six core themes of urban green complex systems.•Themes are non-linearity, emergence, resilience, internal and external connections. The urban green system is complex because it comprises heterogeneous small and large areas and linear elements connected to each other and with the city system with variable and non-linear rules. Every action in a green area changes the equilibrium of the system and can activate unpredictable synergies or conflicts with internal or external variables. Therefore, every action in a green area also changes the ecosystem services it provides to citizens. This paper focuses on cultural services and aims to evaluate the use of complexity science in their design and strengthening. After revisiting the main characteristics of complex systems thinking, the study performs a systematic literature review following a five-step process. Starting from an initial sample of 395 papers, 70 significant studies were selected. A descriptive and thematic analysis was then conducted of these to search for scholars familiar with complexity science or with one or more of its properties. Our results indicate this approach is lacking in the evaluation and planning of cultural ecosystem services. However, we discuss how urban green scholars apply the proprieties of complex systems in their studies, namely interactions, internal connections, emergence, non-linearity, resilience, and self-organization.