13. Introduction to Ecological Risk Assessment

The topsoil is the most biologically diverse part of the earth, harbouring more than one billion organisms per square meter. These soil organisms live in extremely complex mutual interaction and, additionally, in similarly complex interactions with their physical and chemical environment. Although not always acknowledged by the general public, the soil ecosystems perform so-called Ecosystem Services which are very important for society. Some of these Ecosystem Services, described in detail in this chapter, are soil structuring, humus formation, nutrient supply, cleaning function, disease control, and – only recently recognised – energy-related processes. The conclusion to be drawn is that intensive communication about Ecological Risk Assessment is a necessity, both to guarantee that appropriate ecological protection is on the political agenda and to justify protection of the soil ecosystem and the costs involved for the tax payer. Soil contamination has a big impact on the soil ecosystem. Ecological Risk Assessment is an extremely useful process for supporting the decisions taken concerning contaminated sites. The general target for Ecological Risk Assessment is Ecological Health (the preferred state) rather than the Ecological Integrity (the unimpaired condition), and this ideally at the level of a whole ecosystem. The important factors that relate to ecological effects in soil will be introduced in this chapter, factors such as bioavailability, food supply, sealing, resilience and recovery, adaptation, land use, secondary poisoning, the food web approach, wildlife protection, scale and contaminant pattern, and spatial planning. Finally, insight will be provided as to how Ecological Risk Assessment actually works in practice.