How to hierarchise species to determine priorities for conservation action? A critical analysis

Hierarchisation and prioritisation methods represent a crucial step to determine priorities and implement actions in conservation biology: they are required to determine how to allocate available resources to the different components of biodiversity. However, they are very heterogeneous in terms of targets and goals. The main differences are presented with a focus on hierarchisation methods targeting species. This paper reviews 40 studies using 24 different point-scoring or rule-based methods aiming to determine conservation concerns for species. Only the hierarchisation methods targeting species were compared and their differences where highlighted in terms of study area, taxa, criteria assessment and summarisation. Then six different studies using the same hierarchisation method for species were compared as well. This study enables to analyse the different existing methods in order to perform more relevant methodological choices adapted to the objective and the context of each selection process. A consistent framework is designed to help managers to choose an appropriate method using well-defined goals, study areas and taxonomic targets, and take into account data availability.