Table 1 Evaluation of target and reference conditions setting methods, regarding different issues. Note that scores are high: 3, moderate: 2, and low: 1, except in the case of data needs, which are opposite (the lowest data need the highest score). BPJ: best professional judgment (note that it can be used both in setting reference conditions and targets); WFD: Water Framework Directive; HD: Habitats Directive; CWA: Clean Water Act; OSPAR: Oslo-Paris Convention. Based partially upon the discussions within the OSPAR/Marine Strategy Framework Directive Workshop on approaches to determining Good Environmental Status for biodiversity, held in Utrecht (Netherlands), 23-24 November 2010. based upon the data used for their creation may be inappropriate for predicting changes in Drivers-Pressures-States. In dynamic and highly variable marine environments our modelling capabilities are insufficient for defining reference conditions (Hering et al., 2010). This difficulty is overemphasized when natural oscillation occurs. Hence, this method scored the second value (Table 1). To achieve model predictions of high robustness, a large data set that is spa- tially and temporally intensive is required—in many eco-regions such data sets do not exist. The applicability of model predictions between eco-regions is of unknown validity. Most importantly, the complexities of this approach tend to make transparency and com- prehensibility for stakeholders and policy makers low. tion of the biological attributes representative of the aquatic biota expected to be found in the ecoregion or type, through quantitative models, i.e. using habitat suitability models, multiple regression models, etc. (CIS, 2003a). However, there are numerous issues in developing and applying such models: (i) selection of a con- ceptual ecological paradigm identifying the minimal number of dependent and independent variables of the model; (ii) identifi- cation and incorporation of linear and non-linear relationships; (iii) generalized models that are based primarily upon concep- tual relationships may produce predictions of little applicability to different ecoregions or at smaller spatial scales necessary for restoration decisions; and (iv) models that have robust predictions