Nature-based solutions for urban biodiversity: Spatial targeting of retrofits can multiply ecological connectivity benefits

Protecting and enhancing biodiversity in urban areas is critical for meeting international conservation commitments, and has a vital role to play in the health and wellbeing of city residents. Yet, urbanisation can have devastating impacts on biodiversity, with urban development typically delivering landscapes in which habitat remains only as small, fragmented patches, surrounded by an inhospitable urban matrix. As cities begin to plan for urban biodiversity alongside other land use considerations, planners can leverage ecological knowledge and conservation planning concepts to aid decision making to deliver benefits for nature and people. Here we demonstrate how targeted green infrastructure placement can potentially increase the delivery of landscape level benefits for biodiversity by improving connectivity for native species. We measure the change in ecological connectivity when parking spaces are converted to small green spaces across the City of Melbourne, Australia. We test three reallocation scenarios with varying levels of parking space conversion to green infrastructure and varying levels of spatial prioritisation to ecological connectivity. While the scenario that maximised the number of parking spaces converted performed best, we show that targeted greening delivered the strongest connectivity outcomes per unit of area converted. Improvements in connectivity were two times higher per unit effort when conversion was targeted towards locations identified as potentially important barriers to landscape-level movement. Our research emphasises the advantage of strategically targeted green infrastructure investment to support urban biodiversity.