Co-creating urban ecosystem accounting: Physical and monetary accounts of runoff retention service provided by urban green spaces

Urban ecosystem accounting can provide the structure for systematically integrating the value of urban green spaces into management and decision making to support urban resilience and sustainability. However, there are very few instructive examples of urban ecosystem accounting, particularly those created collaboratively with a municipality. Therefore, the aim of this study was to develop co-created urban ecosystem accounts using Tampere, Finland, as a case study. By discussing concrete political and planning-related needs, priorities, and data availability, this study identified urban flooding and the role of green spaces in alleviating this challenge as critical issues. An ecosystem extent account was compiled for accounting years 2012 and 2018 to quantify changes in the extent of ecosystem types. Additionally, an ecosystem service account (physical and monetary), for runoff retention, was compiled for the same years. The runoff retention service was quantified using the InVEST Urban Flood Risk Mitigation model, considering two precipitation events representative of rainstorms that trigger urban flooding. The runoff retention service was translated into service providing areas, which were used in conjunction with service demanding areas to estimate the physical terms of actual flows of retention service for accounting. The monetary value of the service was estimated using the avoided damage cost method. Between 2012 and 2018, the value of runoff mitigation service provided by green spaces increased by 7 % under the 24 mm scenario and by more than 40 % under the 50 mm scenario. The accounts showed concretely how important urban green spaces are in the City of Tampere, and provide an argument to preserve and even increase them in the urban structure. Our experiential ecosystem accounts for urban runoff retention service by green spaces also offer insights to other municipalities, encouraging them to take steps forward in ecosystem accounting.