Ecological standards for eutrophication and desiccation: Perspectives for a risk assessment

This paper describes an assessment of ecological standards for eutrophication and desiccation using the ecotoxicological approach of standard setting. In ecotoxicological risk assessment single-species toxicity data, such as No Observed Effect Concentration (NOEC), are used to extrapolate maximum tolerable concentrations (MTC) which protect 95% of the ecosystem's species. In our approach single-species data consist of the species-response function for both nutrient availability and soil moisture. These data were used to calculate the maximum levels at which 95% of the plant species are protected. A case study, using data on 275 plant species of usable grasslands in the province of South Holland, has been carried out. Ecological standards are calculated for maximum nitrogen load and changes in groundwater level. The influence of nitrogen limitation and moisture shortage on the 95% species protection level is considered. Differences in methodology between our approach and the assessment of ecological standards for micro-pollutants and critical loads are evaluated.