A global review of urban blue-green planning tools

State, city and local governments use environmental planning policies to guide development outcomes. Their policies operate within an increasingly complex regulatory environment and have proliferated as they seek to address past, present, and emerging land use challenges and shifting socio-ecological expectations. The development of integrated urban water (blue) and biodiversity (green) policies represents an example of policy alignment to reduce policy duplication and administrative costs, and to recognise the complementary benefits of land use changes. This paper presents a review of 12 urban blue -green policies, tracking their evolution and comparing five shared categories: vegetation, green infrastructure, surface treatments, water, and habitat. Results indicate that most policies have an emphasis on increasing vegetation cover. Policies that have been in place for longer are more likely to be mandatory requirements in the development assessment process. Newer policies, and those focused on specific precincts, tend to be discretionary and take a guidance approach. When each of the 12 policies are viewed over time, they fall into one of two policy evolutionary pathways. The first group has maintained a relatively small number of development controls or attributes, similar to those established by Berlin's Biotope Area Factor tool. The others have significantly increased the number of attributes used, providing greater choice in how landscaping and water controls can be implemented, and so doing have increased their complexity. The specific attributes and their relative weighting within the policies vary, reflecting the prevailing regulatory systems and policy priorities of each city. Overall, each blue -green policy demonstrates the benefits of combining attributes to achieve mutually beneficial blue and green city outcomes. They also represent examples of policy integration.