Priorities for biodiversity monitoring in Europe: A review of supranational policies and a novel scheme for integrative prioritization

• We provide a review of monitoring requirements and priorities in supranational biodiversity policies.
• We quantify overlaps and gaps among policies.
• In terms of spatial priorities, guidelines are lacking in most policies.
• We suggest an overarching system for priority setting in biodiversity monitoring.
• Our suggested system could serve as a first step towards more systematic prioritization of monitoring.

Trends and status of species and habitats need to be measured to assess whether global biodiversity policy targets have been achieved. However, it is impossible to monitor all species and habitats with a justifiable effort. Therefore, it is critical to prioritize the monitoring of specific biodiversity components. Priorities must be linked to key nature conservation policies to ensure that monitoring efforts are relevant to policy needs, achieve maximum impact, and obtain governmental support. Here we discuss priority setting in biodiversity monitoring in view of monitoring obligations and priorities in supranational biodiversity legislation and policies in Europe and assess overlaps in priorities among policies. While most supranational biodiversity regulations require monitoring of biodiversity, obligations are legally enforceable only for the Nature Directives, the Water Framework Directive, and the Marine Strategy Framework Directive of the European Union. Of the assessed international conventions and other relevant policy instruments about 50% explicitly designate priority species and most focus on vertebrates. Lower emphasis is given to habitats and geographical priorities are even less pronounced. Also, an overarching system for monitoring prioritization is still missing. Our prioritization system is based on three main criteria: (1) legal requirement for reporting, (2) wording used to define priority or importance, and (3) inclusion in lists that indicate importance of monitoring due to e.g. threats or relevance of a region for a species. Our system contains five main priority levels, within which an additional division differentiates priorities according to national/European responsibility criteria. Based on this system, we provide recommendations for allocating species and habitats enlisted by the reviewed policy tools to explicit non-overlapping priority levels. Our approach will facilitate synergies between monitoring activities for different policy needs, and contribute to alleviate the notorious resource shortage for biodiversity monitoring.