Intercalibrating classifications of ecological status: Europe's quest for common management objectives for aquatic ecosystems

- Ecological status of European surface waters is harmonised by intercalibration (IC).
- IC ensures greater parity in the funds invested to achieve good ecological status.
- Less than half of the required IC is currently accomplished.
- IC already yielded a unified vision of what constitutes good ecology across Europe.

Halting and reversing the deterioration of aquatic ecosystems requires concerted action across state boundaries and administrative barriers. However, the achievement of common management objectives is jeopardised by different national quality targets and ambitions. The European Water Framework Directive requires that quality classifications are harmonised via an intercalibration exercise, ensuring a consistent level of ambition in the protection and restoration of surface water bodies across the Member States of the European Union. We outline the key principles of the intercalibration methodology, review the achievements of intercalibration and discuss its benefits and drawbacks. Less than half of the required intercalibration has been completed, mostly due to a lack of national assessment methods. The process has fostered a scientific debate on ecological classification with important implications for environmental management. Despite a significant level of statistical abstraction, intercalibration yielded a fundamental and unified vision of what constitutes good ecology across Europe, in principle ensuring greater parity in the funds invested to achieve good ecological status.