Linking ecological footprints with ecosystem valuation in the provisioning of urban freshwater

Two prominent and alternate approaches, ecosystem service valuation and ecological footprints, link the production of ecosystem services with their consumption by societies. An overlapping goal of both approaches is to promote the sustainable use of ecosystem services such that their production rates are not compromised. Yet, little integration of these perspectives and their emphasis on distinct units, dollars and area, has been attempted. We combined these two approaches to better understand variation in the societal demand and production of freshwater, a critical ecosystem service, for 121 cities in the United States. The analysis linked previously compiled data on urban water use and the spatial distribution of run-off water throughout the conterminous United States. Incorporating the spatial distribution of water consumption and production, we computed heterogeneous urban water use footprints for all 121 cities. From the relationship between annual municipal utility expense and footprint area, the median monetary value for water footprint area was $88,808 km− 2 yr− 1 from all the cities we considered. The ratio between the footprint-estimated cost and the utility-observed cost was negatively related to the local availability of water, and was independent of population size. By linking ecosystem service valuation and ecological footprint analyses into a coherent framework, we developed an integrated metric for understanding the provisioning of ecosystem services, which could help inform sustainable pricing guidelines for renewable freshwater.