Nature-based solutions: new challenges for urban planning

Nature-based solutions (NBS) are broadly defined as the use of solutions based on nature and ecological functions to address societal challenges, such as climate change adaptation and mitigation, population health, food security, and natural disasters, through the delivery of multiple ecosystem services (ES). This paper aims to outline some of the main challenges associated to the development and mainstreaming of NBS in urban planning, providing valuable insights for the integration of NBS in urban planning processes and instruments. To this aim, five challenges are proposed and discussed in this paper, namely: to provide decision-makers with tools and methods for mapping and assessing ES that substantiate evidence of NBS effectiveness in providing multiple benefits; to use more flexible and qualitative planning approaches that can foster the implementation of NBS such as performance-based planning; to develop indicators that can be used to evaluate and compare possible NBS during strategic environmental assessment of urban plans; to include the assessment of ecosystem disservices that may emerge when considering and comparing NBS interventions; to develop adequate measures of progress for the monitoring of NBS effects over time to strengthen the evidence base for their benefits and co-benefits.