Risk assessment of invasive alien species introductions via European inland waterways

European network of inland waterways facilitates the transfer of invasive alien species (IAS) across European inland waters and coastal ecosystems, which requires appropriate risk assessment-based management options to address risks posed by human-mediated introductions of these species. During the development of methods to assess the risks of IAS introductions via European inland waterways we considered the DPSIR framework (‘Driving forces’, ‘Pressure’, ‘State’, ‘Impact’, ‘Response’) to structure developed environmental indicators in the socio-economic context. In addition, considering the current gap in addressing IAS in the river basin management in Europe, our goal was to develop and test relevant risk assessment protocols and water quality indicators on IAS for possible consideration in the Common Implementation Strategy of the EC Water Framework Directive and as part of a holistic risk-based management of European river basins. Owing to the high degree of scientific uncertainty when dealing with such a global and complex ecological issue as large-scale intercontinental and intra-continental introductions of IAS, the qualitative model of risk assessment was selected for risk assessment of IAS introductions via European inland waterways. The present variant of this model of risk assessment of IAS introductions, tested for selected assessment units within the main inland water invasion corridors, includes seven main components: (1) Identification of main invasion gateways, routes and corridors in Europe; (2) Selection of ecosystems as assessment and management units (AUs) within invasions corridors/invasion network; (3) Identification and analysis of pathways of IAS introductions within the ecosystem AU – ‘Driving forces’ according to the DPSIR framework; (4) Assessment of inoculation rates within the ecosystem AU (propagule pressure) – DPSIR ‘Pressures’; (5) Assessment of biological contamination level of the ecosystem AU - DPSIR ‘State’; (6) Assessment of invasiveness of the established in the ecosystem AU alien species (potential biopollution risk) - DPSIR ‘Impacts’; (7) Development of an online Risk Assessment Toolkit with early warning service for reporting of environmental indicators and recommendations for risk management to stakeholders – DPSIR ‘Responses’.