Rationale for ranking potential impacts on habitats and ecosystem services

• This evaluation concerns the levels of exposure and likely impact of chemicals on ecosystem services. No consideration has been given to the beneficial effects, e.g. of applying nutrients in aqueous sewage and sewage sludge (biosolids) to agricultural land and pasture.
• The impact on SPUs is considered to be mainly driven by the overall level of exposure to the chemical(s).
• The chemical mode of action and characteristics, e.g. complexity and variability were considered when known, i.e. existing knowledge of chemical fate and effects were taken into account.
• Direct linking of specific chemical properties with impacts on SPUs (e.g. EDs potentially producing chronic effects on populations) will be possible only in exceptional cases.
• Chemical exposures are more problematic for certain ecosystem services due to:
  • secondary exposures e.g. via the food chain – chemical residues are more problematic in food (following non-lethal exposure) than in fibre and fuel,
  • lack of redundancy in the provision of some ecosystem services, e.g. less species are pollinators than are primary producers.

These factors were applied to two of the case studies (down the drain chemicals and oil dispersants) to illustrate the approach, see Tables 2.4 and 2.5. The outcome of this step for each of the 4 case studies is shown in Chapter 4, Tables 4.1 – 4.4. Explanatory comments on the potential impacts of chemicals on single ESs are provided in Appendix D.

Table 2.4: Analysis of factors determining the potential level of impact of chemicals on ecosystem services; Example: down the drain chemicals

Table 2.5: Ecosystem services likely to be affected by increases in chemical exposure levels versus additional chemical or ES-related factors; Example: oil dispersants