The contribution of informal green space to urban biodiversity: a city-scale assessment using crowdsourced survey data

Abstract Cities are crucial for supporting biodiversity and are likely to play an important role in helping respond to the global biodiversity crisis. Understanding how plants and animals utilize various urban spaces is essential for designing cities that accommodate both human and ecological needs. Informal green spaces (IGS) have been historically overlooked in green space research and planning. However, there is growing interest in the potential benefit of IGS in supporting urban biodiversity. This study builds on previous research by examining the contribution of IGS to biodiversity at the metropolitan scale. We do this by mapping IGS across the entire urban landscape of Greater Melbourne, Australia, using crowdsourced ecological survey data to assess the role of IGS in supporting native bird and plant species richness. Our findings indicate that IGS contribute to urban species richness and can do so to a similar extent as formal green spaces. We found that utility easements and brownfield sites were particularly important types of IGS for supporting species richness. While formal green spaces like parks remain vital for urban biodiversity, IGS should be considered an integral part of urban greenspace networks. These findings underscore the need to more actively consider IGS in urban green space decision making in order to achieve positive urban biodiversity outcomes.