Mapping urban ecosystem services to design cost-effective purchase of development rights programs: The case of the Greater Paris metropolis

International audienceIt is increasingly recognised that the good quality of life of city dwellers depends on the provision of a variety of urban ecosystem services (UES) within cities. However, soil sealing, associated with urbanisation and densification policies, affects soil multifunctionality and compromises the supply of future UES delivered both by public and private land. Incentive-based instruments could provide additional means of action for urban open space protection. Yet, their ability to produce conservation patterns that are cost-effective has been questioned, especially when they rely on public funding. To address this concern, this paper argues that conservation return on investment (ROI) analysis can be applied to UES supply protection objectives. We present an application of this method to a purchase of development right program within the Greater Paris metropolitan area (France). We assess and map the supply variation of three urban ecosystem services in case of soil sealing using Urban InVEST. These assessments are synthesised in the form of an index that serves as an indicator of the benefits of conservation investments. Conservation investment costs are based on estimates of the value of development rights from land market data. Finally, we use an expected-benefit-cost targeting strategy to produce maps showing the distribution of open land cells according to their regulatory status and their UES supply ROI. Our findings suggest that such maps provide a valuable decision-making tool to improve the cost-effectiveness of incentive-based conservation instruments and better inform land use decision planning