Linking freshwater ecotoxicity to damage on ecosystem services in life cycle assessment

Freshwater ecosystems provide major benefits to human wellbeing—so-called ecosystem services (ES)—but are currently threatened among others by ecotoxicological pressure from chemicals reaching the environment. There is an increased motivation to incorporate ES in quantification tools that support decision-making, such as life cycle assessment (LCA). However, mechanistic models and frameworks that can systematically translate ecotoxicity effect data from chemical tests into eventual damage on species diversity, functional diversity, and ES in the field are still missing. While current approaches focus on translating predicted ecotoxicity impacts to damage in terms of species loss, no approaches are available in LCA for linking ecotoxicity further to damage on ecosystem functioning or ES.

To overcome this challenge, this paper proposes a way forward based on reviewing available approaches to characterize damage of chemical pollution on freshwater ES for use in LCA. We first outline an overall framework for linking freshwater ecotoxicity effects to damage on related ES in compliance with the boundary conditions of LCA. Second, within the proposed framework, we present possible approaches for stepwise linking ecotoxicity effects to species loss, functional diversity loss, and damage on ES. Finally, we discuss strengths, limitations, and data availability of possible approaches for each step.

Although most approaches for directly deriving damage on ES from either species loss or damage to functional diversity have not been operationalized for LCA, there are some promising options to be developed. The Threshold Indicator Taxa ANalysis (TITAN) seems promising to translate predicted ecotoxicity effect to a metric of quantitative damage on species diversity. A Trait Probability Density Framework (TPD) approach that incorporates various functional diversity components and functional groups could be adapted to link species loss to functional diversity loss. An Ecological Production Function (EPF) approach seems most promising for further linking functional diversity loss to damage on ES flows for human wellbeing. However, to integrate the entire pathway from predicted freshwater ecotoxicity to damage on ES into LCA, the approaches adopted for each pathway step need to be harmonized in terms of assumptions, boundary conditions and consistent interfaces with each other.