A shift from individual species to ecosystem services effect: Introducing the Eco-indicator Sensitivity Distribution (EcoSD) as an ecosystem services approach to redefining the Species Sensitivity Distribution (SSD) for soil ecological risk assessment.

Abstract

Incorporating the ecosystem services (ES) approach into soil ecological risk assessment (ERA) has been advocated over the years, but implementing the approach in ERA faces some challenges. However, several researchers have made significant efforts to the soil ERA, such as applying the Species Sensitivity Distribution (SSD) to discern chemical effects on the soil ecosystem. Despite the considerable contributions of SSD to ERA, SSD fails to relate chemical impact on individual species to ES and account for functional redundancy as well as soil ecosystem complexity. Here, we introduce the Eco-indicator Sensitivity Distribution (EcoSD). An EcoSD fits ecological functional groups and soil processes, termed "eco-indicators," instead of individual species responses to a statistical distribution. These eco-indicators are directly related to critical ecosystem functions that drive ES. We derived an EcoSD for Cadmium as a model chemical and estimated a Soil Ecosystem Protection Value (EcoPVSoil ) based on the eco-indicator data set for cadmium from the literature. The EcoSD identified nitrogen cycling as the critical process disrupted by cadmium. A key advantage of EcoSD is that it identified key ecological and chemical indicators of an ecosystem services effect. In so doing, it links chemical monitoring results to sensitive ecological functions. The estimated EcoPVSoil for Cadmium was slightly more protective of the soil ecosystem than most regional soil values derived from this study's data set and soil guideline values from the literature. Hence, EcoSD has proved to be a practical and valuable ES concept with the potential to serve as an initial step of the tiered ERA approach.