Compact urban development, social demands and austerity measures are increasing pressures on urban greenspace. Meanwhile, active citizens, defined as voluntary individuals or groups who self-organize to contribute to urban green space development, provide ecological and social benefits to urban societies. This has inspired local governments to seek collaborations with non-state actors, including active citizens. However, the diverging aims, place-specific focus, and varying expertise of active citizenship may inhibit its contribution to ecological connectivity and upscaling beyond the local scale.

In this paper, we investigate how “mosaic governance” has potential as a framework for understanding active citizenship, its potential for upscaling and its relationship to strategic UGI planning. Using the policy arrangements approach, we analyse the role of discourse, resources, actors and rules of the game in the upscaling of active citizenship. Based on eight empirical cases from seven European cities, we analyse the diversity of collaborations between local governments and active citizens in greenspace development.

The cases show how active citizens can significantly contribute to UGI planning and implementation, for example by developing large parks with volunteers or designing a network of green corridors. The cases reveal multiple ways citizens and local governments benefit from collaborations, as well as different pathways for upscaling innovative discourses and practices from local communities to formal policy or to other cities. To enable upscaling, UGI planning needs to combine long-term, more formalized and higher-scale strategic approaches with more incremental approaches that correspond with localized, fragmented and informal efforts of local communities. While collaborations between municipalities and active citizenship is not without its difficulties, the examples of upscaling in our cases demonstrate the transformative power active citizens may have towards a more green, just and democratic city.