A novel method for plant species conservation prioritization at a local scale: the IDEA protocol and beyond

Efficient biodiversity conservation requires prioritizing species, but a policy gap persists: global Red Lists assess extinction risk at broad scales, yet seldom inform local planning where management decisions occur. Subregional priority lists are therefore essential, though limited by data gaps. To develop a vascular plant list for regional policy, we applied a multi-step evaluation. Starting from old lists of threatened Tuscan flora (Italy), 567 species were selected after excluding alien, widespread, or taxonomically uncertain taxa. Fifteen botanists scored them by four criteria: threat level, local rarity, phytogeographic relevance, and taxonomic distinctiveness. Scores were then reviewed with the IDEA protocol, a structured Delphi-type process designed to reduce disagreement and build consensus. Expert variation was measured with a dissension metric. Each species received a Conservation Priority (CP) value based on a management risk formula, allowing allocation into three classes. In total, 456 taxa were fully assessed: 62 reached the highest CP, 167 medium, and 227 low; 111 were excluded due to insufficient data or likely absence. Expert dialogue reduced score variance, improving transparency and reproducibility. This approach minimizes bias while accounting for regional specificities, bridging the gap between global assessments and local conservation needs, and guiding more effective allocation of limited resources.