Guidance on the assessment of alien species pressures

The aim of this paper is to provide guidance on (a) the pressures from alien species on river, lake, transitional and coastal water bodies; (b) data required for carrying out risk assessments for Article 5 analyses; and (c) pressure thresholds at which water bodies are at risk of failing the environmental objectives of the Water Framework Directive (WFD). Specific guidance is given on the work required for the river basin characterisation exercise in 2013, but the paper is also intended to inform the further extension of this work beyond that date.