Water related impacts on nature protection sites

Models for the prediction of impacts of water-related projects on nature protection areas are often based on the assumption that the involved sites are homogeneous with respect to the operational environment of spontaneously settled plant species. This is shown to be a false assumption. As a consequence, the site requirements for nature protection cannot be immediately derived from autecological records, as it is done in agricultural impact models. Both types of impact models are compared. In this contribution, the nature site is conceived as an ecological device, which itself requires a singular environment in order to safeguard the requisite internal variety. Impact models for nature protection should be based on the environmental requirements of such ecodevices, rather than those of the individual species. Current Dutch models are compared with regard to the description and the role of the sites.