Bridging policy targets and aquatic ecosystem responses

Aquatic ecosystems are deteriorated due to eutrophication and fragmentation as main causes. In response to degradation, policy targets were defined to prevent further biodiversity losses. The aim of this thesis was to bridge the gap between policy targets and ecosystem responses to environmental pressures and restoration measures. Therefore, methods were developed to describe the links in the Driver-Pressure-State-Impact-Response (DPSIR) framework quantitatively, to develop science-policy indicators, to analyze restoration measures and to analyze spatial and temporal scale aspects.
In this thesis, articles are presented from drivers to impacts and from large, global scale to regional scale. On a global scale, the emissions of nutrients from households to rivers were modelled. On a national scale, the algae concentrations in lakes were calculated with the nutrient load from households and agriculture in combination with hydrological characteristics. Spatial and hydromorphological measures also determine nature values; these effects were calculated for the impact for two case studies in Ijsselmeer and Markermeer. Indicators were developed for national trends of nutrient quality and biological quality in the Netherlands. Fragmentation of rivers was analysed on two scales, on European scale for large distance anadromous species and on regional scale for riverine species in tributaries in Noord-Brabant in the Netherlands.
I concluded that the DPSIR framework comprise a useful framework to communicate with policy makers, but needs to be extended with more specific elements and indicators. Responses could be distinguished in cause- or effect-oriented or even symbolic depending on the type and scale of responses.