Good Environmental Status of marine ecosystems: What is it and how do we know when we have attained it?

The European Marine Strategy Framework Directive (MSFD) requires EU Member States (MS) to achieve the Good Environmental Status (GEnS) of their seas by 2020. This ambition can only be fulfilled if there is a common understanding of what GEnS entails. This paper addresses this question especially with regard to the level where targets are set (descriptors, criteria, and indicators), to scales for assessments (i.e. regional, sub-divisions, water bodies, sites specific), and to difficulties in putting into practice the GEnS concept. Accordingly, we propose a refined and more operational definition of GEnS and we indicate the data and information needs related to all parts of that definition. We then indicate the options for determining when GEnS has been met, acknowledge the data and information needs for each option, and recommend a combination of existing quantitative targets and expert judgement. We take the view that the implementation of the MSFD needs to be less-complex than shown for other similar directives, can be based largely on existing data and information and can be centred on the activities of the Regional Seas Conventions.JRC.H.1-Water Resource